An Ecological characterization of the Florida Springs Coast

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Material Information

Title:
An Ecological characterization of the Florida Springs Coast Pithlachascotee to Waccasassa Rivers
Series Title:
Biological report
Physical Description:
xiv, 334 p. : maps ; 28 cm.
Language:
English
Creator:
Wolfe, Steven H
Drew, Richard D
Handley, Larry
National Wetlands Research Center (U.S.)
United States -- Minerals Management Service
Florida -- Dept. of Environmental Regulation
Publisher:
U.S. Dept. of the Interior, Fish and Wildlife Service
Minerals Management Service
Place of Publication:
Washington D.C
New Orleans La
Publication Date:

Subjects

Subjects / Keywords:
Ecology -- Florida -- Tampa Bay Watershed   ( lcsh )
Natural history -- Florida   ( lcsh )
Tampa Bay Watershed (Fla.)   ( lcsh )
Genre:
non-fiction   ( marcgt )

Notes

Bibliography:
Bibliography: p. 254-279.
Statement of Responsibility:
edited by Steven H. Wolfe (State of Florida, Dept. of Environmental Regulation) ; project officer, Larry Handley (U.S. Fish and Wildlife Service, National Wetlands Research Center)
General Note:
"December 1990."
Funding:
Biological report (Washington, D.C.) ;

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
All rights reserved, Board of Trustees of the University of Florida
Resource Identifier:
aleph - 001852362
oclc - 26461542
notis - AJS6716
System ID:
UF00000130:00001

Related Items

Related Items:
Alternate version (PALMM)
PALMM Version

Table of Contents
    Title Page
        Page i
    Disclaimer
        Page ii
    Preface
        Page iii
    Table of Contents
        Page iv
        Page v
        Page vi
        Page vii
        Page viii
    List of Figures
        Page ix
        Page x
        Page xi
        Page xii
    List of Tables
        Page xiii
    Conversion factors
        Page xiv
    Acknowledgement
        Page xv
    Authors
        Page xvi
    Introduction
        Page 1
        Purpose and organization of the document
            Page 1
        The Florida springs coast
            Page 2
            Page 3
    Geology and physiography
        Page 4
        Introduction
            Page 4
        Physiography and geomorphology
            Page 5
            Page 6
            The Brooksville Ridge
                Page 7
            The Ocala Hills and the cotton plant ridge
                Page 7
                Page 8
            The Lake and Sumter Uplands
                Page 9
            The western valley and Tsala Apopka plain
                Page 9
            The Gulf Coastal Lowlands
                Page 10
        Surface and subsurface geological formations
            Page 11
            Exocene series
                Page 11
            Oligocene series
                Page 12
            Miocene series
                Page 13
            Pliocene series
                Page 14
            Pleistocene to Holocene (recent) series
                Page 14
        Marine geology
            Page 15
            Page 16
            Regional marine geology
                Page 15
            Local marine geology
                Page 17
                Page 18
                Page 19
                Page 20
        Economic geology
            Page 21
        Important natural geologic sites
            Page 22
            Chassahowitzka springs
                Page 22
            Homosassa springs
                Page 22
            Weeki Wachee Springs
                Page 22
            Diffluence of the Withlocoochee River, and Lake Tsala Apopka
                Page 23
        Problems affecting the coast
            Page 23
            Page 24
            Page 25
            Page 26
    Climate
        Page 27
        Introduction
            Page 27
        Climatological features
            Page 27
            Temperature
                Page 27
            Rainfall
                Page 27
                Page 28
                Page 29
                Page 30
                Page 31
            Winds
                Page 32
                Page 33
                Page 34
                Page 35
            Insolation
                Page 36
                Page 37
                Page 38
            Relative humidity
                Page 39
        Effects of climate on ecosystems
            Page 39
            Page 40
        Major influences on climate
            Page 41
            Natural influences on climate
                Page 41
            Anthropogenic influences
                Page 42
                Page 43
        Summary of climatic concerns
            Page 44
        Areas needing research
            Page 44
    Hydrology and water quality
        Page 45
        Hydrology
            Page 45
            Page 46
        Water quality
            Page 47
            Page 48
            Page 49
        Hydrology and water-quality regulation and management
            Page 51
            Page 52
            pH
                Page 54
            Dissolved solids
                Page 57
            Temperature
                Page 58
            Other contents
                Page 59
        Major influences on surface water
            Page 61
            Page 64
            Surface-water quality
                Page 65
        Major influences on ground water
            Page 66
            Ground-water hydrology
                Page 66
                Page 68
            Ground-water quality
                Page 69
                Page 70
        Area-wide surface-water hydrology and water quality
            Page 71
            Page 72
            Page 73
        Area-wide ground-water hydrology and water quality
            Page 74
        Basin hydrology and water quality
            Page 75
            Basin hydrology and water quality
                Page 75
                Page 76
                Page 77
                Page 78
                Page 79
                Page 80
                Page 81
                Page 82
                Page 83
                Page 84
            Withlacoochee River basin
                Page 85
                Page 86
                Page 87
                Page 88
                Page 89
                Page 90
        Hydrology and water-quality concerns
            Page 91
            Page 92
            Page 93
            Page 94
            Page 95
            Page 96
            Water-quality concerns
                Page 97
                Page 98
    Terrestrial and freshwater habitats
        Page 99
        Introduction
            Page 99
            Page 100
        Coastal strand
            Page 101
        Scrub
            Page 102
            Page 103
            General scrub information
                Page 104
            Sand pine scrub
                Page 105
                Page 106
            Oak scrub
                Page 107
            Rosemary scrub
                Page 108
        High pine forest (Sandhill)
            Page 109
            General high pine forest information
                Page 109
                Page 110
                Page 111
                Page 112
            Longleaf pine sandhill
                Page 113
            Turkey oak sandhill
                Page 114
            Longleaf pine-southern red oak forest
                Page 114
        Pine flatwoods
            Page 115
            General pine flatwoods information
                Page 116
                Page 117
                Page 118
            Pond pine flatwoods
                Page 119
            Wet flatwoods (slash pine flatwoods)
                Page 119
            Mesic flatwoods (longleaf pine flatwoods)
                Page 119
            Scrubby flatwoods
                Page 120
        Hammocks
            Page 120
            General hammock information
                Page 121
                Page 122
                Page 123
            Xeric hammock
                Page 124
            Mesic hammock
                Page 124
                Page 125
                Page 126
            Hydric hammock
                Page 127
            Pioneer hammock
                Page 128
        Sinkholes and terrestrial caves
            Page 129
        Pine plantations and old field forests
            Page 130
            Pine flatwoods plantation
                Page 130
                Page 131
            High pine plantations
                Page 132
            Hammock and old-field pine plantation
                Page 133
            Summary
                Page 133
        Cleared rural upland
            Page 133
            Page 134
        Developed areas
            Page 135
        Bayhead
            Page 136
            Page 137
            Page 138
        Mixed swamp
            Page 139
            Page 140
        Cypress dome
            Page 141
            Page 142
            Page 143
        Freshwater marshes and prairies
            Page 144
            Page 145
            Page 146
            Page 147
        Ponds
            Page 148
            Page 149
        Lakes
            Page 150
            Page 151
        Blackwater streams
            Page 152
            Page 153
        Springs, spring runs, and spring-fed rivers
            Page 154
            Page 155
        Aquatic caves
            Page 156
        Endangered and threatened species
            Page 157
    Saltwater wetland, estuarine, and marine habitats
        Page 158
        Introduction
            Page 158
            Estuarine system classification
                Page 158
            Tides and salinity ranges
                Page 159
        Estuarine habitats
            Page 160
            Brackish marshes
                Page 160
                Page 161
            Salt marshes
                Page 162
                Page 163
                Page 164
                Page 165
                Page 166
                Page 167
            Intertidal flats
                Page 168
                Page 169
            Oyster reefs
                Page 170
                Page 171
                Page 172
                Page 173
                Page 174
                Page 175
            Intertidal mangrove forests
                Page 176
                Page 177
                Page 178
                Page 179
                Page 180
                Page 181
                Page 182
                Page 183
                Page 184
            Marine algae
                Page 185
                Page 186
            Open water
                Page 187
                Page 188
                Page 189
            Subtidal soft bottoms
                Page 190
                Page 191
            Seagrass beds
                Page 192
                Page 193
                Page 194
                Page 195
                Page 196
                Page 197
                Page 198
                Page 199
                Page 200
                Page 201
                Page 202
                Page 203
                Page 204
                Page 205
        Marine habitats
            Page 206
            Marine open water
                Page 206
                Page 207
            Artificial reefs
                Page 208
                Page 209
            Subtidal soft bottoms
                Page 210
    Summary
        Page 211
        The springs coast in review
            Page 211
            Page 212
        Land-use planning and conservation
            Page 213
            Page 214
            Page 215
            Page 216
        The springs coast tomorrow
            Page 217
            Page 218
            Page 219
    Literature cited
        Page 220
        Page 221
        Page 222
        Page 223
        Page 224
        Page 225
        Page 226
        Page 227
        Page 228
        Page 229
        Page 230
        Page 231
        Page 232
        Page 233
        Page 234
        Page 235
        Page 236
        Page 237
        Page 238
        Page 239
        Page 240
    Apendix tables
        Page 241
        Page 242
        Selected U.S. geological surve maps for the Florida springs coast
            Page 241
        Common and characteristic animals of gulf-coast scrub communities
            Page 243
            Page 244
            Page 245
        Characteristic and common plants of the gulf coast scrub communities
            Page 246
            Page 247
        Animals common in or characteristic of high pine forest
            Page 248
            Page 249
        Common and characteristic plants of high pine forest
            Page 250
            Page 251
        Animals common in or characteristic of pine flatwoods
            Page 252
            Page 253
            Page 254
        Common and characteristic plants of the pine flatwoods
            Page 255
            Page 256
        Common and characteristic animals of hammocks
            Page 257
            Page 258
            Page 259
        Common and characteristic plants of hammocks
            Page 260
            Page 261
            Page 262
        Common and characteristic animals of cleared rural land
            Page 263
            Page 264
        Common and characteristic animals of developed areas
            Page 265
            Page 266
        Common and characteristic animals of bayheads
            Page 267
            Page 268
        Common and characteristic plants of bayheads
            Page 269
        Common and characteristic animals of mixed swamps
            Page 270
            Page 271
            Page 272
        Common and characteristic plants of mixed swamps
            Page 273
            Page 274
        Common and characteristic animals of cypress domes
            Page 275
            Page 276
            Page 277
        Common and characteristic plants of cypress domes
            Page 278
            Page 279
        Common and characteristic animals of freshwater marshes and wet prairies
            Page 280
            Page 281
            Page 282
            Page 283
        Common and typical plants of marshes and wet prairies
            Page 284
            Page 285
        Common and characteristic animals of ponds
            Page 286
            Page 287
            Page 288
        Common and characteristic animals of lakes
            Page 289
            Page 290
            Page 291
        Animals characteristic of blackwater streams
            Page 292
        Common and characteristic animals of spring runs and spring fed rivers
            Page 293
            Page 294
            Page 295
        Endangered and threatened species in the Springs Coast with watersheds and counties where they are found
            Page 296
            Page 297
            Page 298
            Page 299
        Common and and scientific names of fishes of Springs Coast brackish marshes
            Page 300
            Page 301
        Common and scientific names of macroinvertebrates from Springs Coast brackish marshes
            Page 302
        Common birds of Springs Coast salt marshes
            Page 303
            Page 304
        Common macroinvertebrates of Springs Coast intertidal flats
            Page 305
        Springs Coast oyster-associated fauna; phylogenetic species list
            Page 306
            Page 307
            Page 308
        Ten most abundant oyster fauna, with rank, at different Springs Coast estuary sites
            Page 309
        Rank order list of oyster associated fauna
            Page 310
            Page 311
        Macroalgae species present on Springs Coast oyster reefs
            Page 312
        Common macroalgae species from the springs coast region
            Page 312
        Common water-column-dwelling fishes of Springs Coast estuaries
            Page 313
        Common demersal fishes of Springs Coast estuaries
            Page 314
        Common demersal macroinvertebrates from springs coast estuaries
            Page 314
        Taxonomic listing the typical habitat of all insects, oligochaetes, and leeches found in Springs Coast estuaries
            Page 315
            Page 316
        Common benthic macroinvertebrate infauna of the offshore estuarine Springs Coast
            Page 317
        Common benthic macroinvertebrate infauna of the inshore fresh and occasionally estuarine
            Page 318
        Common benthic macroinvertebrate infauna of the intermediate mesohaline (moderate, fluctuating-salinity) springs coast
            Page 318
        Common marine fishes of the Springs Coast
            Page 319
        Federal, State, and local environmental control agencies and their responsibilities
            Page 320
            Page 321
        Springs Coast regulatory agency locations, addresses, and phone numbers
            Page 322
            Page 323
            Page 324
Full Text
,'l -1 ) 0 '


Biological Report 90(21)
December 1990


AN ECOLOGICAL CHARACTERIZATION
of the

FLORIDA SPRINGS COAST:
Pithlachascotee to Waccasassa Rivers


Fish and Wildlife Service and
Minerals Management Service
U.S. Department of the Interior


In cooperation with the
Southwest Florida
Water Management District


U~elirruI.















DISCLAIMER


The opinions, findings, conclusions, or recommendations expressed in this report are those of the
authors and do not necessarily reflect the views of the U.S Fish and Wildlife Service unless so desig-
nated by other authorized documents.




























This report may be cited:
Wolfe, S.H., ed. 1990. An ecological characterization of the Florida Springs Coast: Pithlachascotee to
Waccasassa Rivers. U.S. Fish Wildl. Serv. Biol. Rep. 90(21). 323 pp.















PREFACE


This report is one in a series that provides an ecological description of Florida's gulf coasts. The
watersheds described herein, with their myriad communities, produce many benefits. The maintenance
of this productivity through enlightened resource management is a major goal of this series. This report
will be useful to the many people who have to make decisions regarding the use of the natural resources
of the area.


Any questions or comments about or requests for this publication should be directed to:





Information Transfer Specialist
U.S. Fish and Wildlife Service
National Wetlands Research Center
NASA Slidell Computer Complex
1010 Gause Boulevard
Slidell, Louisiana 70458















CONTENTS




DISCLAIM ER ............................................................................................................................................ii
PREFACE ................................................................................... ............................... .......................iii
APPENDIX INDEX ..................... ............................................................................ ............................... ii
FIGURE INDEX ..................................................................................................................................ix
TABLE INDEX ......................................................................................................................... ....... ..xiii
CONVERSION FACTORS ................................................................................................................ xiv
ACK NOW LEDGM ENTS .................................................................................................................. v
AUTHORS ................................................................................................................................................ xvi
Chapter 1. INTRODUCTION
1.1 Purpose and Organization of the Docum ent..................................................... ............... 1
1.2 The Florida Springs Coast ...................................................................................................... 2
Chapter 2. GEOLOGY AND PHYSIOGRAPHY
2.1 Introduction ..................................................................................................................................4
2.2 Physiography and geomorphology ...............................................................................................5
2.2.1 The Brooksville Ridge ................................................................................................ 7
2.2.2 The Ocala Hills and the Cotton Plant Ridge.................................................................... 7
2.2.3 The Lake and Sum ter Uplands..........................................................................................9
2.2.4 The W western Valley and Tsala Apopka Plain............................................. .............. 9
2.2.5 The Gulf Coastal Lowlands ...................................................................................... 10
2.3 Surface and Subsurface Geological Form nations ................................................. ............... 11
2.3.1 Eocene Series ............................................................................................................ 11
2.3.2 Oligocene Series ....................................................................................................... 12
2.3.3 M iocene Series.......................................................................................................... 13
2.3.4 Pliocene Series .......................................................................................................... 14
2.3.5 Pleistocene to Holocene (Recent) Series ................................................. ............ 14
2.4 M marine Geology .......................................................................................................................... 15
2.4.1 Regional M marine Geology ......................................................................................... 15
2.4.2 Local M marine Geology ........................................................... ...................................... 17
2.5 Econom ic Geology ...............................................................................................................21
2.6 Im portant Natural Geologic Sites .........................................................................................22
2.6.1 Chassahowitzka Springs ...........................................................................................22
2.6.2 Homosassa Springs ...................................................................................................22
2.6.3 W eeki W achee Springs ............................................................................................. 22

Iv










Page
2.6.4 C hunky P ond ........................................ ............................................ ......................... 22
2.6.5 Diffluence of the Withlacoochee River, and Lake Tsala Apopka ................................23
2.7 Problems Affecting the Coast .................................... ................. .........23
Chapter 3. CLIMATE
3.1 Introduction ................................................................................................................................27
3.2 Climatological Features .......................................................................................27
3.2.1 Temperature .................................................. 27
3.2.2 R ainfall.................................................................................... ..................................27
3.2.3 W inds ........................................... .............................................................................32
3.2.4 Insolation .................................................................................... .............................. 36
3.2.5 Relative Humidity.............................................. .................................................39
3.3 Effects of Climate on Ecosystems ........................... ........................... ............................39
3.4 Major Influences on Climate ........................................... ...............................................41
3.4.1 Natural Influences on Climate ................................................. .................................41
3.4.2 Anthropogenic Influences ............................ ............................... .......................42
3.5 Summary of Climatic Concerns .......................... ............................. .............................44
3.6 A areas N feeding R research ......................................................................... .............................. 44
Chapter 4. HYDROLOGY AND WATER QUALITY
4.1 H ydrology ...................................................................................................................................45
4.2 Water Quality ............................................................................................................................47
4.3 Hydrology and Water-Quality Regulation and Management................................................ 51
4.4 Water-Quality Parameters ....................................................................................................53
4.4.1 Dissolved Oxygen...............................................................................................53
4 .4 .2 pH ............................................. .................................................................................54
4.4.3 Turbidity and Sediments .................................................................................55
4.4.4 Dissolved Solids .......................................................................................................56
4.4.5 Temperature ....................................................................... .............................58
4.4.6 Other Contents ............................................................................................................59
4.5 Major Influences on Surface Water ........................................ ........................................60
4.5.1 Surface-Water Hydrology............................................................................................60
4.5.2 Surface-Water Quality ........................................... .............................................65
4.6 Major Influences on Ground Water ...................................................................................... 66
4.6.1 Ground-Water Hydrology......................... ................................................. ....66
4.6.2 Ground-Water Quality ........................................ ................................................69
4.7 Area-wide Surface-Water Hydrology and Water Quality ......................... ................... 71
4.8 Area-wide Ground-Water Hydrology and Water Quality ........................... .................... 74
4.9 Basin Hydrology and Water Quality ...................................................... ........................75
4.9.1 Coastal Area between the Anclote and Withlacoochee Rivers.....................................75
4.9.2 Withlacoochee River Basin.......................................................................................... 85
4.9.3 Waccasassa River Basin and Coastal Area between Withlacoochee and Suwannee
R ivers .......................... .......................................................... 9 1
4.10 Hydrology and Water-Quality Concerns ...................... .. .. ...............................91
4.10.1 Hydrologic Concerns ........................................... ............................................91
4.10.2 Water-Quality Concerns ............................ ................. ........................................97

V








Page
Chapter 5. TERRESTRIAL AND FRESHWATER HABITATS
5.1 Introduction ............................................ ..............................................................................99
5.2 Coastal Strand ..................................................................................... ................................101
5.3 Scrub ...................................................................................................................................... 102
5.3.1 General Scrub Information .......................................... ................ 104
5.3.2 Sand Pine Scrub ...................................................................................................... 105
5.3.3 Oak Scrub ............................................................................... ................................ 107
5.3.4 Rosemary Scrub ............................................... ................................................. 108
5.4 High Pine Forest (Sandhill) ............................................ .............................................. 109
5.4.1 General High Pine Forest Information............................ .. ............... .......... 109
5.4.2 Longleaf Pine Sandhill........................ ....... ............... ........................ 113
5.4.3 Turkey Oak Sandhill ......................................... ............... .......... 114
5.4.4 Longleaf Pine-Southern Red Oak Forest .......................................... .............. .......... 114
5.5 Pine Flatwoods ............................................................. ................................................ 115
5.5.1 General Pine Flatwoods Information.......................... ... ........... .............. 116
5.5.2 Pond Pine Flatwoods ............................ .... ................ ........................... 119
5.5.3 W et Flatwoods (Slash Pine Flatwoods) .............................................. 119
5.5.4 Mesic Flatwoods (Longleaf Pine Flatwoods) ......................................................... 119
5.5.5 Scrubby Flatwoods .............................................. ............................................. 120
5.6 Hammocks ................................................................................................................................ 120
5.6.1 General Hammock Information .............................................. .......... .... 121
5.6.2 Xeric Hammock ......................................................................... ....................... 124
5.6.3 Mesic Hammock ............................................. ................................................. 124
5.6.4 Hydric Hammock.................................................................... ........... .............. 127
5.6.5 Pioneer Hammock..................................................................... ........................ 128
5.7 Sinkholes and Terrestrial Caves ....................................................... ............................ 129
5.8 Pine Plantations and Old Field Forests .......................................................... 130
5.8.1 Pine Flatwoods Plantations............................................................. 130
5.8.2 High Pine Plantations.................................................................................................... 132
5.8.3 Hammock and Old-Field Pine Plantations........................................................ ....... 133
5.8.4 Summary ................................................................................. .............................. 133
5.9 Cleared Rural Upland .............................. .... ................................................................. 133
5.10 Developed Areas............................................................................... .......................... 135
5.11 Bayhead .......................................................................................... ................................ 136
5.12 Mixed Swamp ................................................................................. .................................. 139
5.13 Cypress Dome................................................................................... ....................... 141
5.14 Freshwater M arshes and Prairies................................................................. 144
5.15 Ponds .................................................. ........................... ...... ...................... 148
5.16 Lakes ... ............................................................................................. ....... ................. 150
5.17 Blackwater Streams ................................................................................................................ 152
5.18 Springs, Spring Runs, and Spring-fed Rivers.......................... ....... .............. 154
5.19 Aquatic caves.......................................................................................................................... 156
5.20 Endangered and Threatened Species ..................................................... .......................... 157



vi









Page
Chapter 6. SALTWATER WETLAND, ESTUARINE, AND MARINE HABITATS
6.1 Introduction ......................................................................................................................... 158
6.1.1 Estuarine System Classification..................................................................................... 158
6.1.2 Tides and Salinity Ranges............................................................................................. 159
6.2 Estuarine Habitats............................................................................................................... 160
6.2.1 Brackish M arshes .......................................................................................................... 160
6.2.2 Salt M arshes ............................................................................................................ 162
6.2.3 Intertidal Flats ......................................................................................................... 168
6.2.4 Oyster Reefs............................................................................................................ 170
6.2.5 Intertidal M angrove Forests .......................................................................................... 176
6.2.6 M marine Algae .......................................................................................................... 185
6.2.7 Open W after ............................................................................................................. 187
6.2.8 Subtidal Soft Bottoms ................................................................................................... 190
6.2.9 Seagrass Beds ......................................................................................................... 192
6.3 M marine Habitats .................................................................................................................. 206
6.3.1 M arine Open W ater ......................................................................................................206
6.3.2 Artificial Reefs.................................................................................... .....................208
6.3.3 Subtidal Soft Bottoms ............................................................................................. 210
Chapter 7. SUMMARY
7.1 The Springs Coast in Review ...................................................................................................211
7.2 Land-Use Planning and Conservation .................................................... .......................... 213
7.3 The Springs Coast Tomorrow ............................................................................................. 217
LITERATURE CITED ................................................................. .................................................. 220
APPENDIX TABLES
A. Selected U.S. Geological Survey M aps for the Florida Springs Coast............................................ 241
B. Common and characteristic animals of gulf-coast scrub communities............................................ 243
C. Characteristic and common plants of the gulf coast scrub communities ......................................... 246
D. Animals common in or characteristic of high pine forest. ............................................................... 248
E. Common and characteristic plants of high pine forest..................................................................... 250
F. Animals common in or characteristic of pine flatwoods.......................................................... 252
G. Common and characteristic plants of the pine flatwoods. ............................................................... 255
H. Common and characteristic animals of hammocks.......................................................................... 257
I. Common and characteristic plants of hammocks............................................................................. 260
J. Common and characteristic animals of cleared rural land. .............................................................. 263
K. Common and characteristic animals of developed areas. .............................................................265
L. Common and characteristic animals of bayheads. .......................................................................... 267
M Common and characteristic plants of bayheads. ............................................................................... 269
N. Common and characteristic animals of mixed swamps ................ .................................................. 270
0. Common and characteristic plants of mixed swamps. ..................................................................... 273
P. Common and characteristic animals of cypress domes ................................................................ 275
Q. Common and characteristic plants of cypress domes.................................... .................................278
R. Common and characteristic animals of freshwater marshes and wet prairies....................................280
S. Common and typical plants of marshes and wet prairies...............................................................284

vii








Appendix Table Page
T. Common and characteristic animals of ponds. ..............................................................................286
U. Common and characteristic animals of lakes ................................................................................. 289
V. Animals characteristic of blackwater streams ................................................................................292
W. Common and characteristic animals of spring runs and spring fed rivers .....................................293
X. Endangered and threatened species in the Springs Coast with watersheds and counties where
they are found. ........................................... ........................................................... ...................... 296
Y. Common and scientific names of fishes of Springs Coast brackish marshes ................................300
Z. Common and scientific names of macroinvertebrates from Springs Coast brackish marshes. .......302
AA. Common birds of Springs Coast salt marshes. .............................................................................. 303
AB. Common macroinvertebrates of Springs Coast intertidal flats. .......................................................305
AC. Springs Coast oyster-associated fauna; phylogenetic species list ................................................. 306
AD. Ten most abundant oyster fauna, with rank, at different Springs Coast estuary sites.................... 309
AE. Rank order list of oyster associated fauna ...................................................................................... 310
AF. Macroalgae species present on Springs Coast oyster reefs............................................................ 312
AG. Common macroalgae species from the Springs Coast region..................................................312
AH. Common water-column-dwelling fishes of Springs Coast estuaries. ..............................................313
AI. Common demersal fishes of Springs Coast estuaries. .................................................................314
AJ. Common demersal macroinvertebrates from Springs Coast estuaries...........................................314
AK. Taxonomic listing the typical habitat of all insects, oligochaetes, and leeches found in Springs
Coast estuaries. ............................................................................................................................ 315
AL. Common benthic macroinvertebrate infauna of the offshore estuarine Springs Coast.................... 317
AM. Common benthic macroinvertebrate infauna of the inshore fresh and occasionally estuarine
Springs C oast ..................................................................................................................................318
AN. Common benthic macroinvertebrate infauna of the intermediate mesohaline (moderate,
fluctuating-salinity) Springs Coast......................................... .................................................... 318
AO. Common marine fishes of the Springs Coast ................................................................................. 319
AP. Federal, State, and local environmental control agencies and their responsibilities....................320
AQ. Springs Coast regulatory agency locations, addresses, and phone numbers. ................................322


viii















FIGURES




Figure Page
1. Drainage basins and features of the Springs Coast region of Florida .............................................. 3
2. The Floridan Plateau and its present day emergent part, Florida. The Ocala Uplift has an
important influence on spring occurrence in the state................................... .........................5
3. Terraces and shorelines of Florida ............................................................................................... 6
4. Major transpeninsular physiographic divisions of Florida; Springs Coast region shaded ................7
5. Physiography of the Florida Springs Coast and adjacent areas. ............................. .............. 8
6. Location of major geomorphological features in west-central Florida...............................................11
7. Cross-section across Hemando County illustrating low, flat gradient near the present coastline ....12
8. Distribution of the four main morphologic sectors in Citrus, Hemando, and Pasco Counties. ..........18
9. Diagrams showing the evolutionary stages of karstification. ............................................ .............. 20
10. Present shoreline and a predicted shoreline in the year 2100 in the Bayport area of Hemando
County, based on a 180-cm rise in sea level ............................................ ............................................24
11. Present shoreline and a predicted shoreline in the year 2100 in the Bayonet Point area of Pasco
County, based on a 180-cm rise in sea level ................................................................................25
12. Locations of NOAA climatological stations near the Florida Springs Coast. ..................................28
13. Isotherms for July temperatures in the Florida Springs Coast, 1959-1979.......................................29
14. Isotherms for January temperatures in the Florida Springs Coast, 1959-1979 .................................30
15. Seasonal rainfall variation at selected sites in the Florida Springs Coast .....................................31
16. Average annual rainfall in the Florida Springs Coast, 1951-1980. .................................................32
17. Springs Coast 12-month rainfall 1951-1980 (after Jordan 1984). ................................. .... 33
18. Percent of total daily rainfall during individual hours of the day at Orlando .................................34
19. Occurrence of extended dry periods at Orlando and Tampa, 1950-1980.........................................34
20. Low level (600-900 m ) winds. .................................................................................................... 35
21. Percentage of time wind blew from different directions at Tampa (nearest data site) during
different seasons, 1959-1979 average. ..........................................................................................36
22. Seasonal windspeed at Tampa (nearest data site). ..................................... ........36
23. Paths of hurricanes striking the Springs Coast 1885-1990. .........................................................37
24. Change in length of atmospheric light path with change in distance above or below orbital plane. ..38
25. Change in light intensity at Earth's surface with change in distance above or below orbital plane. ..38
26. M ean daytime sky cover at Lakeland ...........................................................................................39
27. Variations in insolation striking the atmosphere, depending on latitude and season .......................40
28. Monthly insolation at selected sites near the Florida Springs Coast ..................................................41
29. Percent of possible sunshine at Lakeland (nearest site to Springs Coast for which such data is
available). ............ .......................... ............................................................ 41









Figure Page
30. Increasing atmospheric carbon dioxide as measured atop Mauna Loa, Hawaii ...............................43
31. The basic hydrologic cycle..................................................................................................................46
32. The Florida hydrologic divide. ............................................................................................................47
33. Major drainage basins and surface-water features of the Springs Coast region of Florida. ...............48
34. Potentiometric surface of the Floridan aquifer in the Springs Coast in May 1980...........................49
35. Recharge areas to the Floridan aquifer in the Springs Coast region ..................................... ..50
36. Oxygen solubility as a function of temperature. ..............................................................................53
37. Oxygen solubility as a function of salinity........................................................................................ 53
38. General distribution of minimum pH in Springs Coast surface waters. ...........................................55
39. Estimated average dissolved solids concentrations in surface waters of the Florida Springs Coast. .56
40. Seasonal riverflow in the Springs Coast Withlacoochee River.................................... .............. 60
41. Locations and magnitudes of major springs in the Florida Springs Coast .............................. 62
42. River-mouth flow phenomena: a- Formation of a salt wedge and "stacking" of freshwater layer
to right of flow direction at river mouths; b-Coriolis and geostrophic forces affecting fresh water
flow ing from river m youths. .................................................................................................................63
43. Generalized relationship of surface water to ground water for springs and siphons ........................67
44. Location of limestone aquifers known to be within 50 ft of land surface and of surficial beds of
low w after perm ability. .......................................................................................................................70
45. Generalized land use and vegetation map of the Florida Springs Coast ..........................................72
46. Comparative average potential evapotranspiration in the middle gulf area as calculated by four
m models .................................................................................................................................... ............74
47. Coastal Area drainage basin-the area between the Anclote River and the Withlacoochee River. ...76
48. Hammock Creek estuary and sampling stations from SWFWMD study..........................................79
49. Hammock Creek: surface and bottom, high-tide isohaline positions; mean, standard deviation,
and m axim a of penetration during 1984. ............................................................................................80
50. Weeki Wachee River estuary showing sampling stations from SWFWMD study and results of
extensive dredge-and-fill activity..................................................................................................... 81
51. Weeki Wachee River: surface and bottom, high-tide isohaline positions; mean, standard deviation,
and maxima of penetration during 1984-1985. .............................................................. ................ 82
52. Crystal River estuary and sampling stations from SWFWMD study. ..............................................83
53. Crystal River: surface and bottom, high-tide isohaline positions; mean, standard deviation, and
maxima of penetration during 1984-1985. .............................................................................. .. 84
54. Withlacoochee River drainage basin .............................................................................................. 86
55. Withlacoochee River: surface and bottom, high-tide isohaline positions; mean, standard deviation,
and maxima of penetration during 1984-1985 ....................................................................................90
56. Waccasassa River Basin and coastal area between Withlacoochee and Suwannee Rivers ...............92
57. Waccasassa River estuary and sampling stations from SWFWMD study........................................93
58. Waccasassa River: surface and bottom, high-tide isohaline positions; mean, standard deviation,
and m axim a of penetration during 1985. ............................................................................................94
59. Projected sea-level rise using different scenarios. .........................................................................96
60. Diagram showing Bruun Rule for beach erosion following increase in sea level. ...........................96
61. Generalized successional and edaphic relationships among the main biological community types
of northern peninsular Florida including the Springs Coast. ..........................................................101
62. Approximate location of the largest areas of scrub in and near the Florida Springs Coast ......... 103








Figure Page
63. Mature sand pine scrub with sand pine overstory and understory of sand live oak, myrtle oak,
crooked-wood, and rosemary and a ground cover of deermoss......................................................106
64. Oak scrub, showing sand road through a thicket of myrtle oak, sand live oak, crooked-wood, and
saw-palmetto with one sand pine in right background.................................................................... 107
65. Rosemary scrub, showing pure stand of rosemary with no herbaceous ground cover. .................. 108
66. Major areas of high pine forest in the Florida Springs Coast. ........................................................ 110
67. Longleaf pine sandhill, showing longleaf pine, wiregrass, and occasional turkey oaks................. 113
68. Turkey oak sandhill, showing turkey oak and wiregrass with one young longleaf pine left of
center. .................................................................................................................... ......................115
69. Pine flatwoods, showing longleaf pine, saw-palmetto, and openings containing mix of herbs and
dw arf shrubs. ..................................................................................................................................... 116
70. Major areas of pine flatwoods in the Florida Springs Coast ........................................................... 117
71. Major areas containing hammock forest in the Florida Springs Coast. ............................................ 122
72. Xeric hammock with sand live oak, saw-palmetto, and Spanish moss............................................. 125
73. Mesic hammock, showing mixed hardwood forest with dense overstory and understory in
D ecem ber. ............................................................................................................................... .126
74. Hydric hammock (flooded), showing live oak and loblolly pine with some smaller sweetgum and
red m aple in the background. ............................................................................................................ 127
75. Coastal hydric hammock dominated by cabbage palm with some southern redcedar.................... 128
76. Pine plantation on flatwoods site, showing a 2-year-old slash pine plantation with grass-
dominated ground cover and a 20-year-old slash pine plantation with shrub understory................ 130
77. Bayhead, showing evergreen shrub layer and trunks of sweetbay, loblolly-bay, and swamp tupelo
in January ............................................................................................................................ ............ 137
78. Mixed swamp, showing mixed hardwoods, buttresses, cypress knees, one old cypress stump in
center background, and one baldcypress. .......................................................................................... 138
79. Cypress dome, showing a nearly pure stand of pondcypress surrounded by a young pine
plantation on a pine flatwoods site. ............................................................................................. 142
80. Cypress dome interior showing a dense ground cover of Virginia chain fern stalks in January...... 143
81. Freshwater marsh and prairie with cordgrass (Spartina bakeri, bluestem (Andropogon spp.), and
m aidencane (Panicum hemitomon). ............................................................................................ 145
82. Small, ephemeral pond less than half full of water ......................................................................... 148
83. M medium -sized lake ............................................................................................................................ 150
84. Medium-sized blackwater stream during a wet period. .................................................................. 153
85. Spring-fed river showing mixed hardwoods and baldcypress on the banks ................................... 155
86. Changes in macrophyte populations found along the marsh salinity gradient from fresh to salt ... 161
87. Generalized schematic view of gulf-coast salt marshes on protected low-energy shorelines. ......... 165
88. Horizontal distribution of macrofauna in a typical Springs Coast tidal marsh ............................... 166
89. Mangrove species found in the Springs Coast. ............................................................................... 178
90. Mangrove forest types represented in the Springs Coast. ............................................................... 179
91. Diagrammatic transect of the mangrove community from the pioneer red mangroves to the
tropical ham m ock forest .......................... ................................................. ........................... 181
92. Algal zonation on m angrove prop roots............................................................................................ 182
93. Yield of penaeid shrimp and vegetation coverage in an estuary..................................................... 193
94. Location of grassbeds along the Florida Big Bend and Springs Coast .......................................... 194
95. Composition of grassbeds along the Florida Big Bend and Springs Coast..................................... 195








Figure Page
96. Four common seagrass species present in Springs Coast waters.................................................. 196
97. A typical Thalassia shoot, showing oldest leaves to left and new growth on right .....................98
98. Typical depth distributions of three seagrass species and a common brackish species Ruppia
m aritim a .......................................................................................................................................... 199
99. Biomass versus water depth for four seagrasses .........................................................................200
100. Seasonal cycle of Thalassia testudinum leaf ash-free dry weight from stations at two locations .. 201
101. Ecosystem development in seagrasses. Without disturbance, a Thalassia climax is reached.......201
102. Idealized sequence of seagrass recolonization and growth after a large disturbance. ............... 202
103. Schematic view showing the numerous seagrass-epiphyte interactions that occur in a seagrass
bed and the important physical factors affecting the interactions................................................. 204
104. Seasonal phytoplankton abundances in the northeast Gulf of Mexico ..........................................207
105. Artificial reef locations in Springs Coast waters. .............................................. .................... 209
106. 1980 Florida Springs Coast population by county.......................................................................212
107. Florida Springs Coast projected population increase 1980-2000. ................................................213
108. Distribution of major areas with high densities of gopher tortoises .............................................215
109. Proposed statewide network of protected areas and corridors................................................218















TABLES



Table Page
1. Surface and near-surface geologic formations in the Florida Springs Coast ..................................... 13
2. Statistics for Florida Springs Coast rivers............................................................................................71
3. First-magnitude springs and spring groups of the gulf-coast region of north central Florida ......... 154
4. Animals exclusive to the aquatic caves in the Springs Coast region. ................................................ 157
5. Some mammals of Springs Coast salt marshes. ............................................................................... 167
6. Common birds of Springs Coast intertidal flats. .............................................................................. 169
7. Oyster-associated fauna collected from each of 13 oyster stations.................................................. 172
8. Common invertebrate species associated with Springs Coast oyster reefs ...................................... 173
9. Ten most abundant oyster-associated fauna by quarter, listed by rank............................................. 174
10. Percentage abundance of taxonomic groups of sedentary oyster-associated fauna......................... 174
11. Selected oyster-associated fauna which may be used as salinity indicators .................................... 175
12. General response of a mangrove ecosystem to severe oil spills. .....................................................185
13. Most abundant fish and invertebrates trawled from sampling stations in Springs Coast estuaries ... 188
14. Marine turtles with special status that occur in Springs Coast marine waters. ................................208










CONVERSION FACTORS


Metric to U.S. Customary
Multiply by To Obtain
millimeters (mm) ................................ 0.03937 ........................... inches (in.)
centimeters (cm) ................................. 0.3937 ............................. inches (in.)
meters (m) ........................................... 3.281 ............................... feet (ft)
kilometers (km) ................................... 0.6214 ............................. miles (mi)

square meters (m2) .............. ........... 10.76..................................square feet (ft2)
square kilometers (km2) ...................... 0.3861 ............................. square miles(mi2)
hectares (ha) ........................................2.471.................................acres

liters (1) ................................................ 0.2642 .............................. gallons (gal)
cubic meters (m3) .............................. 35.31 ................................. cubic feet (ft3)
cubic meters (m3) ..................................0.0008110 .........................acre-feet

milligrams (mg) .................................. 0.00003527 ....................... ounces (oz)
grams (g)...............................................0.03527 ............................. ounces (oz)
kilograms (kg).................2.......................2.205.................................pounds (Ib)
metric tons (t)................................ 2205.0................................... pounds (lb)
metric tons (t) ...................................... 1.102 ............................... short tons

kilocalories (kcal) .............. 3.....................3.968 ..................... British thermal units (BTU)
Celsius degrees (C) ........................... 1.8(C) + 32 .....................Fahrenheit degrees (F)


U.S. Customary to Metric
Multiply by To Obtain
inches...............................................25.40................................ millimeters
inches.................................................. 2.54 ...................................centimeters
feet (ft) ...............................................0.3048............................... meters
fathoms ................................................. 1.829 ................................. meters
miles (mi) ............................................. 1.609 ................................. kilometers
nautical miles (nmi) ............................ 1.852 ............................... kilometers

square feet........................................... 0.0929 ............................. square meters
acres...................................................... 0.4047...............................hectares
square miles .......................................... 2.590 ................................ square kilometers

gallons .................................................. 3.785 .................................liters
cubic feet ..............................................0.02831 .............................cubic meters
acre-feet ....................................... 1233.0 ..................................... cubic meters

ounces (oz)..........................................28.35 ................................grams
pounds (lb) ......................................... 0.4536 .............................kilograms
short tons (ton)...................................... 0.9072............................... metric tons

British thermal units ..............................0.2520 ...............................kilocalories
Fahrenheit degrees ................................0.5556(F -32) ..................Celsius degrees
















ACKNOWLEDGMENTS


The authors wish to acknowledge the assistance of the numerous people who contributed to the
preparation of this document. Many people were consulted during the preparation of this work, and
many more contributed knowledge over the years that enabled the authors to write these descriptions of
biological communities. Many public and private agency representatives cooperated with our search
for published and unpublished data sources. Noteworthy among these were the staffs and libraries of
the Southwest Florida Water Management District and the Florida Department of Natural Resources'
Marine Research Institute.
The final product was greatly improved by the generous reviewing efforts of: Eric Shaw and Mark
Friedemann, Florida Department of Environmental Regulation; Loma Patrick of the U.S. Fish and
Wildlife Service; Jim Buckner, David Hall, Paul Moler, and Barbara Muschlitz for review of the
terrestrial and fresh water chapter, as well as Loretta Wolfe and Bonnie Boynton for review and editing.
Extra thanks to the U.S. Fish and Wildlife Service's Beth Vairin for editing assistance and review and
Sue Lauritzen for review of and assistance with graphics.

We would especially like to thank Lawrence Handley and the late Millicent Quammen of the U.S.
Fish and Wildlife Service for review, review coordination, and general assistance...and persistence.












Conventional graphics by Carol Knox and Elizabeth Woodsmall
Computer graphics by Steve Wolfe
Photographs by Bob Simons
Layout by Loretta Wolfe
















AUTHORS


Steven H. Wolfe
Florida Department of Environmental Regulation
Biology Section
2600 Blair Stone Road
Tallahassee, Florida 32399-2400

Robert W. Simons
Consulting Ecologist
1122 SW 1llth Ave.
Gainesville, Florida 32601

Reed E. Noss
Landscape Ecologist
925 NW 31st St.
Corvallis, Oregon 97330

Jeffrey A. Reidenauer
Breedlove and Associates, Inc.
4301 Metric Dr.
Winter Park, Florida 32792

Michael S. Flannery
Southwest Florida Water Management District
2379 Broad St.
Brooksville, Florida 34609

Michael J. Bland
Florida Department of Environmental Regulation
Hazardous Waste Section
2600 Blair Stone Road
Tallahassee, Florida 32399-2400
















Chapter 1. INTRODUCTION


1.1 Purpose and Organization of the
Document

For many years, Florida has been experiencing
rapid growth that shows no signs of slowing. The
areas of the state that have received the main popula-
tion influx to date are experiencing severe problems
with environmental degradation and loss of the very
features that attracted the people in the first place.
Urbanization, draining of wetlands, sewage and
industrial-effluent discharges, contaminated surface
runoff, and alterations of the hydrologic regime
controlling the ground-water supplies all have caused
and are causing loss of wildlife habitat and wildlife
populations. In many areas, contamination of ground
water through seepage from surface contaminants
and saline intrusion cause water shortages that are
aggravated by prolonged dry spells. "Reclamation"
of wetlands has damaged nature's ability to keep the
ground-water aquifers full and may be affecting the
rainfall patterns themselves.
Many of the actions that have caused environmen-
tal damage were done out of ignorance. The people
of Florida are realizing that the expense to the
taxpayer of trying to undo past errors far exceeds the
cost of requiring that initial development take place
in such a way as to minimize damage. While contin-
ued growth may be inevitable, we can maintain much
of the physical and aesthetic natural attributes that
make Florida one of the finest areas in the country.
The authors have dubbed the area covered in this
document the Springs Coast because of the need to
refer to it in terms briefer than "the upper coast of
west-central Florida" or other similar descriptions.


This region includes the drainage basins and
nearshore waters of the west coast of Florida
between, but not including, the Anclote River basin
and the Suwannee River basin. The name Springs
Coast was chosen because this area of coast contains
a multitude of springs, both named and too small or
inaccessible to have been named. Much of the area is
karstic limestone where the Floridan aquifer is
flowing onto the surface of the land, helping to
provide the extensive marshlands along the coast.
Most recognizable among the springs are the famous
Crystal River, Weeki Wachee, and Homosassa
springs.
This document is a summary of the available
information on the Springs Coast area of Florida, for
use by planners, developers, regulatory authorities,
and other interested parties. An understanding of the
factors affecting their plans and the possibly unex-
pected impacts of their actions on others will, it is
hoped, promote intelligent development in areas
capable of supporting it. We have tried to provide a
clear, coherent picture of what is currently known
about how the physical, chemical, and biological
factors of the environment interact. Extensive refer-
ences are provided so that those wishing more detail
on any aspect will know where to find it. Many of
the sources cited are among the so-called "grey litera-
ture," studies and reports that are not published or are
not widely circulated. Much valuable information is
available in these documents. We have also tried to
identify those aspects of the local environment that
are most susceptible to damage or most likely to
cause damage. Finally, we have tried to identify the
direction of future development and locate those
areas needing study prior to developmental pressure.
















Chapter 1. INTRODUCTION


1.1 Purpose and Organization of the
Document

For many years, Florida has been experiencing
rapid growth that shows no signs of slowing. The
areas of the state that have received the main popula-
tion influx to date are experiencing severe problems
with environmental degradation and loss of the very
features that attracted the people in the first place.
Urbanization, draining of wetlands, sewage and
industrial-effluent discharges, contaminated surface
runoff, and alterations of the hydrologic regime
controlling the ground-water supplies all have caused
and are causing loss of wildlife habitat and wildlife
populations. In many areas, contamination of ground
water through seepage from surface contaminants
and saline intrusion cause water shortages that are
aggravated by prolonged dry spells. "Reclamation"
of wetlands has damaged nature's ability to keep the
ground-water aquifers full and may be affecting the
rainfall patterns themselves.
Many of the actions that have caused environmen-
tal damage were done out of ignorance. The people
of Florida are realizing that the expense to the
taxpayer of trying to undo past errors far exceeds the
cost of requiring that initial development take place
in such a way as to minimize damage. While contin-
ued growth may be inevitable, we can maintain much
of the physical and aesthetic natural attributes that
make Florida one of the finest areas in the country.
The authors have dubbed the area covered in this
document the Springs Coast because of the need to
refer to it in terms briefer than "the upper coast of
west-central Florida" or other similar descriptions.


This region includes the drainage basins and
nearshore waters of the west coast of Florida
between, but not including, the Anclote River basin
and the Suwannee River basin. The name Springs
Coast was chosen because this area of coast contains
a multitude of springs, both named and too small or
inaccessible to have been named. Much of the area is
karstic limestone where the Floridan aquifer is
flowing onto the surface of the land, helping to
provide the extensive marshlands along the coast.
Most recognizable among the springs are the famous
Crystal River, Weeki Wachee, and Homosassa
springs.
This document is a summary of the available
information on the Springs Coast area of Florida, for
use by planners, developers, regulatory authorities,
and other interested parties. An understanding of the
factors affecting their plans and the possibly unex-
pected impacts of their actions on others will, it is
hoped, promote intelligent development in areas
capable of supporting it. We have tried to provide a
clear, coherent picture of what is currently known
about how the physical, chemical, and biological
factors of the environment interact. Extensive refer-
ences are provided so that those wishing more detail
on any aspect will know where to find it. Many of
the sources cited are among the so-called "grey litera-
ture," studies and reports that are not published or are
not widely circulated. Much valuable information is
available in these documents. We have also tried to
identify those aspects of the local environment that
are most susceptible to damage or most likely to
cause damage. Finally, we have tried to identify the
direction of future development and locate those
areas needing study prior to developmental pressure.







Florida Springs Coast Ecological Characterization


The report is divided into two main sections.
Chapters 2-4 cover the geology and physiography,
the climate, and the many aspects of the surface- and
ground-water systems. These chapters provide the
physical and chemical background information
necessary to understand much of the environmental
pressure affecting the biological habitats. These
habitats and their inhabitants--terrestrial, freshwater,
and marine-are described in Chapters 5 and 6.
Chapter 7 summarizes the main points and identifies
present and potential problems.

1.2 The Florida Springs Coast

The Springs Coast of Florida as defined for this
report extends from the Pithlachascotee River basin
located north of Tampa Bay to the Waccasassa River
area south of the mouth of the Suwannee River
(Fig. 1). It includes one of Florida's largest rivers,
the Withlacoochee, as well as several of the state's
largest springs.
Within the Springs Coast are included the coastal
drainage basin between the Anclote and Withla-
coochee Rivers, the Withlacoochee River basin, and
the coastal area between the Withlacoochee and
Suwannee Rivers including the Waccasassa River
basin. This territory includes large expanses of
marsh and wetland and, along its shores, the southern


end of the largest area of seagrass beds in the state-
the Florida Big Bend Seagrass Beds Preserve. It also
possesses numerous spring-fed rivers and streams
along the coast, whose constant discharges provide
unique, relatively stable estuarine environments.
The northern half of the Springs Coast is just
beginning to feel growth pressures; the southern
portion along the coast has recently experienced
heavy development, but the area is still relatively
small. Virtually the entire coastline is low-energy,
i.e., mangrove and salt marsh. This enormous coastal
wetland, often extending kilometers inland, is the
primary reason for limited human inhabitation.
Though the population pressures from the more
popular southern areas of the state are now moving to
the north, the delay has allowed us to gain an under-
standing of the irreplaceable value of these areas.
The wetlands of the Big Bend and the Springs Coast
support much of the gulf fishery, acting as a nursery
and food source. In addition, many areas are impor-
tant for recharging the underground aquifers upon
which much of the state depends for its water
supplies.
The Springs Coast, which is beginning to receive
heavy development, stands a good chance of main-
taining its environmental and ecological quality
through that development. We hope this document
helps in achieving that result.







1. Introduction

84* 5, 83*
LAFAYETTE

lGILCHRIST L )

DIXIE
DIXIE (: ALACHUA



Sf ) -.i--t :-- .-
7-,




/ LEVY
EVY MARION


-9r-
e\

29 -
/k :- ( \.)
'- *- -. ) I


S CITRUS T.I
% ') t, .h (B *,"

o0

\ SUMMER
(A) Coastal area from Anclota River i
to Withlacoochee River \
I ER A DO I ,
(B) Wlthlacoochus River basin
(C) Waccasa River and oata
arsa between Withlacoochao _ee ._ .-_ I I-,- "
and Suwannae Rher. er s
IV
PASCO

..f I POLK
/ .""/ I --


IEL.
/ LA a 1-IIiLLSBOR9UGH U n
Figure 1. Drainage basins and features of the Springs Coast region of Florida.
















Chapter 2. GEOLOGY AND PHYSIOGRAPHY
by Reed E. Noss and Michael J. Bland


2.1 Introduction

The geology of any region determines to a great
extent the habitats available to plants and animals.
Rocks near the surface are the "parent material" from
which soils are formed, and plastics such as sands and
clays are the primary inorganic components of soils.
The chemical composition, texture, and other proper-
ties of a particular parent material and soil will favor
some plant species over others. Surface limestone,
for example, produces soils with abundant calcium
compared to most sandy soils or organic mucks.
Certain "calciphilous" plant species are found most
frequently, or perhaps only, where limestone out-
crops or is very near the surface.
Geology also determines landform. To the lay
person, the influence of landform on ecology might
be most obvious in mountainous regions, where
cliffs, screes, and climatic changes related to eleva-
tion and slope aspect have profound effects on
species distributions. In Florida, geological influ-
ences on habitat are more subtle, but just as impor-
tant. Variations in elevation in Florida, ranging from
0 to 105 m above sea level, are not enough to create
any noticeable differences in climate. But Florida's
modest slopes are extremely important in determin-
ing soil moisture levels. The slope moisture gradient,
interacting with fire and other abiotic factors,
produces a corresponding gradient in species compo-
sition. Xeric ecosystems with low soil-moisture
levels and high fire frequencies are found at the top of
the slope moisture gradient, and wetlands are found
at the bottom. In the middle are mesic habitats such
as mixed species hardwood forests.


A prominent landform of our study region, and
over much of Florida, is karst. Karst topography is a
regional landform that has been modified by the solu-
tion of subsurface limestone. Rainwater, charged
with carbonic acid from the solution of atmospheric
CO2, percolates through the crevices of limestone
and dissolves it, creating caves, sinkholes, many
solution valleys and depressions, and other karst
features. Karst features provide habitats that would
otherwise be absent from the regional landscape,
such as prairies, lakes, and poorly drained depres-
sions, that support diverse assemblages of species.
What we know as Florida is the emergent part of a
large peninsular platform called the Floridan Plateau
(Fig. 2) that extends southward from the continental
mass and separates the deep waters of the Atlantic
Ocean and the Gulf of Mexico. The Floridan Plateau
is composed of thousands of feet of sedimentary
rocks covered by plastic sediments (including sand,
clay, silt, shell marl, rock fragments, and other mate-
rials) of varying thickness (from 0 to several hundred
feet). Episodically, at times in the past, the entire
Floridan Plateau has been submerged beneath the
sea, while at other times it has been almost entirely
emergent. At one time of emergence the land area of
the peninsula was over twice its present size. The
limestone and dolomite bedrock that underlies all of
our study region was deposited in shallow seas from
about 58 to 25 million years ago (from middle
Eocene to Miocene epochs; still older sediments and
igneous rocks are found beneath these Tertiary sedi-
ments, but will not be considered further in this
report). The plastics that overlie the bedrock were
deposited from about 25 million years ago to the
present (from Miocene to Holocene epochs). Some
















Chapter 2. GEOLOGY AND PHYSIOGRAPHY
by Reed E. Noss and Michael J. Bland


2.1 Introduction

The geology of any region determines to a great
extent the habitats available to plants and animals.
Rocks near the surface are the "parent material" from
which soils are formed, and plastics such as sands and
clays are the primary inorganic components of soils.
The chemical composition, texture, and other proper-
ties of a particular parent material and soil will favor
some plant species over others. Surface limestone,
for example, produces soils with abundant calcium
compared to most sandy soils or organic mucks.
Certain "calciphilous" plant species are found most
frequently, or perhaps only, where limestone out-
crops or is very near the surface.
Geology also determines landform. To the lay
person, the influence of landform on ecology might
be most obvious in mountainous regions, where
cliffs, screes, and climatic changes related to eleva-
tion and slope aspect have profound effects on
species distributions. In Florida, geological influ-
ences on habitat are more subtle, but just as impor-
tant. Variations in elevation in Florida, ranging from
0 to 105 m above sea level, are not enough to create
any noticeable differences in climate. But Florida's
modest slopes are extremely important in determin-
ing soil moisture levels. The slope moisture gradient,
interacting with fire and other abiotic factors,
produces a corresponding gradient in species compo-
sition. Xeric ecosystems with low soil-moisture
levels and high fire frequencies are found at the top of
the slope moisture gradient, and wetlands are found
at the bottom. In the middle are mesic habitats such
as mixed species hardwood forests.


A prominent landform of our study region, and
over much of Florida, is karst. Karst topography is a
regional landform that has been modified by the solu-
tion of subsurface limestone. Rainwater, charged
with carbonic acid from the solution of atmospheric
CO2, percolates through the crevices of limestone
and dissolves it, creating caves, sinkholes, many
solution valleys and depressions, and other karst
features. Karst features provide habitats that would
otherwise be absent from the regional landscape,
such as prairies, lakes, and poorly drained depres-
sions, that support diverse assemblages of species.
What we know as Florida is the emergent part of a
large peninsular platform called the Floridan Plateau
(Fig. 2) that extends southward from the continental
mass and separates the deep waters of the Atlantic
Ocean and the Gulf of Mexico. The Floridan Plateau
is composed of thousands of feet of sedimentary
rocks covered by plastic sediments (including sand,
clay, silt, shell marl, rock fragments, and other mate-
rials) of varying thickness (from 0 to several hundred
feet). Episodically, at times in the past, the entire
Floridan Plateau has been submerged beneath the
sea, while at other times it has been almost entirely
emergent. At one time of emergence the land area of
the peninsula was over twice its present size. The
limestone and dolomite bedrock that underlies all of
our study region was deposited in shallow seas from
about 58 to 25 million years ago (from middle
Eocene to Miocene epochs; still older sediments and
igneous rocks are found beneath these Tertiary sedi-
ments, but will not be considered further in this
report). The plastics that overlie the bedrock were
deposited from about 25 million years ago to the
present (from Miocene to Holocene epochs). Some







2. Geology and Physiography


Figure 2. The Floridan Plateau and its present day
emergent part, Florida. The Ocala Uplift has an im-
portant influence on spring occurrence in the state.



of these clastics are sediments of near-shore marine
origin, some are fluvial deposits transported by
rivers, some are lacustrine (lake-bottom) deposits,
and some represent aeolian (wind-blown) sediments
such as dunes.
One of the most prominent geomorphological
features of Florida is the step-like series of terraces
that progress in elevation from the coast to the inte-
rior (Fig. 3). The interior (landward) edges of these
terraces, called scarps, represent the beach dunes and
ridges of ancient shorelines. Many of these scarps
are associated with variations in sea level that parallel
the glacial and interglacial periods of the Pleistocene
epoch (Walker and Coleman 1987). During glacial
maxima, when much of the earth's water was frozen
in glaciers and polar ice, sea level was as much as
41 m below its current level. During warm, moist
interglacial periods, seas rose to levels higher than
today's. Florida terrain higher than 30-52 m above
present sea level may not represent terrace deposits
associated with Pleistocene sea levels, but rather
older deposits of Pliocene and upper Miocene age


(Healy 1975a). In fact, some recent evidence
(reviewed by Clewell 1981) suggests that sea level
rose to a maximum height of only 8-11 m above
present mean sea level (m.s.l.) during Pleistocene
interglacial stages. If this is true, then with the excep-
tion of brief interglacial warm periods, Florida has
been continuously emerging from the sea since the
Miocene. Some recent authors still consider all
marine terraces as Pleistocene in age. Much of the
uncertainty about terrace age is due to the fact that
differential warping and subsidence of the land
surface, the latter due to solution weathering of lime-
stone, has resulted in terraces of the same age (same
shoreline) being found today at different heights in
different areas (Walker and Coleman 1987). Geolog-
ical change and climate-induced fluctuations in sea
level will undoubtedly continue to be important
processes in Florida's future.


2.2 Physiography and geomorphology

Physiography is the study of physical geography,
and geomorphology is the geological study of the
configuration and evolution of landforms. Together,
they refer to what commonly is called "the lay of the
land." All habitats and biological communities exist
in a physiographic and geomorphological context.
Because of Florida's low relief, delineation of
geomorphic features has not been as straightforward
as in mountainous areas. Although terraces created
during past high sea levels are often easily recog-
nized, higher terraces are older and have been
subjected to more erosion and sagging due to solution
of underlying limestones. Hence, contour lines
representing terrace scarps are not necessarily good
delineators of physiographic features (White 1970).
Rather, one must look directly to the landforms of the
region as they exist today.
White (1970) divided Florida into three general
physiographic zones (Fig. 4). All of our study region
is within the Central or Mid-Peninsular Zone. This
zone is characterized by discontinuous, subparallel
ridges separated by broad valleys. Broad, shallow
lakes are prominent features of the valley floors, and








Florida Springs Coast Ecological Characterization


840 .


83"






,-1.


29 -




(D


0


IF'
jI~-ln r, s l
n .L



~41 1J~ I





Figure 3. Terraces wid shorelines ofFlorida (aftcr Hcely 1975a).





2. Geology and Physiography


0,
0.


d


Figure 4. Major transpeninsular physiographic divi-
sions of Florida; Springs Coast region shaded (after
White 1970).



some deep lakes with complex geological histories
occur on the ridges (White 1970). The following is a
description of some of the most prominent physi-
ographic features of our study region. These features
can be identified on White's (1970) physiographic
map of North Peninsular Florida (Fig. 5).

2.2.1 The Brooksville Ridge
One of the most striking physiographic features of
this region is the Brooksville Ridge, which extends
some 177 km from eastern Lafayette County (north
of our study region) southward to the Zephyrhills
area of southern Pasco County. The Withlacoochee
River, flowing through the Dunnellon Gap between
the towns of Dunnellon and Inglis where Levy,
Marion, and Citrus Counties come together, divides
the ridge into two unequal parts. The larger southern
part is about 97 km long and from 16 to 24 km wide.
The smaller part to the north is about 80 km long and
varies in width from 6 to 10 km. In contrast to the
near sea-level elevations of the adjacent Gulf Coastal
Lowlands, the Brooksville Ridge ranges from about
21 m m.s.l. to over 75 m m.s.l.. The surface is highly


irregular, with elevations varying 30 m or more over
short distances. The Brooksville Ridge is often
considered a western part of a larger physiographic
region of Florida, the Central Highlands.
The deep sands of the Brooksville Ridge were
probably deposited as dunes at the Wicomico shore-
line at an elevation of about 30 m (Knapp 1978). The
elevations at the toe of this scarp are variable,
however, suggesting that certain parts of the scarp
have been shores at more than one sea level (White
1970). Underlying the surficial sands are clayey
phosphatic sands and sandy clays (mostly of the
Miocene Hawthorn Formation), which overlie lime-
stones and dolomites of Oligocene and Eocene age.
The higher elevations of the carbonate rock under the
Ridge, relative to the adjacent lowlands, has been
attributed to the less permeable overlying sands and
clays as compared to the more porous sands of the
lowlands (Vemon 1951). The clayey sands of the
Brooksville Ridge reduce downward percolation of
surface waters and resultant dissolution of the under-
lying carbonates. Hence, the Brooksville Ridge is a
relatively persistent landform which supports impor-
tant upland community types such as longleaf pine
sandhills and sand pine and oak scrub. Dependent on
these uplands are many threatened and endangered
species of our region, including the gopher tortoise
(which finds excellent burrow sites in the deep
sands), red-cockaded woodpecker, indigo snake, and
Sherman's fox squirrel.

2.2.2 The Ocala Hills and the Cotton Plant Ridge
Forming the western edge of the Central High-
lands, the Ocala Hills extend 9 mi southwestward
from the city of Ocala and range in elevation from 23
to 53 m above m.s.1.. These hills, at most 8 km wide,
are part of a series of uplands that separate the West-
em Valley from the Central Valley and form a line
paralleling other prominent ridge systems in Florida,
including Trail Ridge and the Lake Wales Ridge
(White 1970). Like the Brooksville Ridge, the Ocala
Hills are thought to be relict coastal features
composed of predominantly clayey sands that have
protected underlying carbonate rocks from solution.





2. Geology and Physiography


0,
0.


d


Figure 4. Major transpeninsular physiographic divi-
sions of Florida; Springs Coast region shaded (after
White 1970).



some deep lakes with complex geological histories
occur on the ridges (White 1970). The following is a
description of some of the most prominent physi-
ographic features of our study region. These features
can be identified on White's (1970) physiographic
map of North Peninsular Florida (Fig. 5).

2.2.1 The Brooksville Ridge
One of the most striking physiographic features of
this region is the Brooksville Ridge, which extends
some 177 km from eastern Lafayette County (north
of our study region) southward to the Zephyrhills
area of southern Pasco County. The Withlacoochee
River, flowing through the Dunnellon Gap between
the towns of Dunnellon and Inglis where Levy,
Marion, and Citrus Counties come together, divides
the ridge into two unequal parts. The larger southern
part is about 97 km long and from 16 to 24 km wide.
The smaller part to the north is about 80 km long and
varies in width from 6 to 10 km. In contrast to the
near sea-level elevations of the adjacent Gulf Coastal
Lowlands, the Brooksville Ridge ranges from about
21 m m.s.l. to over 75 m m.s.l.. The surface is highly


irregular, with elevations varying 30 m or more over
short distances. The Brooksville Ridge is often
considered a western part of a larger physiographic
region of Florida, the Central Highlands.
The deep sands of the Brooksville Ridge were
probably deposited as dunes at the Wicomico shore-
line at an elevation of about 30 m (Knapp 1978). The
elevations at the toe of this scarp are variable,
however, suggesting that certain parts of the scarp
have been shores at more than one sea level (White
1970). Underlying the surficial sands are clayey
phosphatic sands and sandy clays (mostly of the
Miocene Hawthorn Formation), which overlie lime-
stones and dolomites of Oligocene and Eocene age.
The higher elevations of the carbonate rock under the
Ridge, relative to the adjacent lowlands, has been
attributed to the less permeable overlying sands and
clays as compared to the more porous sands of the
lowlands (Vemon 1951). The clayey sands of the
Brooksville Ridge reduce downward percolation of
surface waters and resultant dissolution of the under-
lying carbonates. Hence, the Brooksville Ridge is a
relatively persistent landform which supports impor-
tant upland community types such as longleaf pine
sandhills and sand pine and oak scrub. Dependent on
these uplands are many threatened and endangered
species of our region, including the gopher tortoise
(which finds excellent burrow sites in the deep
sands), red-cockaded woodpecker, indigo snake, and
Sherman's fox squirrel.

2.2.2 The Ocala Hills and the Cotton Plant Ridge
Forming the western edge of the Central High-
lands, the Ocala Hills extend 9 mi southwestward
from the city of Ocala and range in elevation from 23
to 53 m above m.s.1.. These hills, at most 8 km wide,
are part of a series of uplands that separate the West-
em Valley from the Central Valley and form a line
paralleling other prominent ridge systems in Florida,
including Trail Ridge and the Lake Wales Ridge
(White 1970). Like the Brooksville Ridge, the Ocala
Hills are thought to be relict coastal features
composed of predominantly clayey sands that have
protected underlying carbonate rocks from solution.





Florida Springs Coast Ecological Characterization


Highlands


Springs COt
Baslnsoundary
Indistinct-feature ,-----
boundary
Escarpment


Gulf
of
Mexico


"" . '^ ^^ ^

Figure 5. Physiography of the Florida Springs Coast and adjacent areas (after White 1970).
8







2. Geology and Physlography


West of the Ocala Hills, and separated from them
by Martel Hill (which is just outside our study
region), is Cotton Plant Ridge. This sandy ridge is
about 26 km long and 8 km wide, with a distinct
northwest-southeast orientation relative to the other
ridges of the Central Highlands. Maximum elevation
is about 30 m m.s.l., and sediments are predomi-
nantly white sands. The unusual orientation of
Cotton Plant Ridge suggests a derivation different
from the supposed shoreline origin of other ridges in
this region (Knapp 1978). Superimposed on Cotton
Plant Ridge are hills with a surface pattern that
suggests an aeolian origin, which may explain their
orientation perpendicular to the dune-forming south-
west winds (White 1970).

2.2.3 The Lake and Sumter Uplands
The Lake and Sumter Uplands are two highland
areas named for Lake and Sumter Counties, respec-
tively, and separated by the Lake Harris Cross Valley
in the vicinity of Leesburg. Each of the two uplands
is about 56 km long and 24 km wide. They lie gener-
ally between the Western and Central Valleys, but are
partly bounded by higher lands such as the Lake
Wales Ridge on the eastern side of the Lake Upland
and the Ocala and Fairfield Hills and Cotton Plant
Ridge at the northern edge of the Sumter Upland.
The Lake and Sumter Uplands gradually decline in
elevation from north to south, from 38 to 45 m m.s.l.
at the southern end of the Lake Upland to 23-30 m at
the northern end of the Sumter Upland (White 1970).
The Lake and Sumter Uplands are similar in
composition to the Brooksville Ridge: sands and
clayey sands overlying limestone bedrock. The Lake
Upland is dominated by relict beach ridges with
limited but differential solution of the underlying
limestones. As the beach ridges and intervening
swales decline in elevation northward, a series of
many small lakes appears, which gives Lake County
its name (most of these lakes lie to the east of our
study region, however). With the exception of the
large Lake Weir (in Marion County, and just outside
our study region), the Sumter Uplands contain few
lakes.


2.2.4 The Western Valley and Tsala Apopka
Plain
The Western Valley is a large, irregularly shaped
area of low relief and poor drainage bounded on the
west by the Brooksville Ridge and on the east by the
Lake and Sumter Uplands and other highlands to the
north (including the Ocala Hills, Cotton Plant Ridge,
and Fairfield Hills). The Western Valley extends
about 225 km from the High Springs Gap in western
Alachua County (just north of our study region) to
the Zephyrhills Gap in Pasco and Hillsborough
Counties (just south of our study region). It is
connected to the Central Valley (east of our study
region) by the Lake Harris Cross Valley (which sepa-
rates the Lake and Sumter Uplands) and by the
Alachua Lake Cross Valley in southern Alachua
County (east of our study region).
With elevations ranging generally from about 15
to 30 m above m.s.l., the Western Valley contains
many swamps and lakes. The largest of the swamps,
the Green Swamp, lies in parts of Lake, Sumter, and
Polk Counties (Deuerling and MacGill 1981). The
Green Swamp is one of the most significant natural
landscapes of our region, although it is being increas-
ingly modified by human activities.
The Tsala Apopka Plain is a lower (from 12 to
23 m above m.s.l.) and flatter portion of the Western
Valley located in eastern Citrus, Hernando, and
Pasco Counties, and western Sumter County. It is
bounded on the east by the Withlacoochee River and
on the west by the Brooksville Ridge. The Tsala
Apopka Plain contains a number of lakes, including
present-day Lake Tsala Apopka, Lake Panasoffkee,
and many smaller lakes, all of which are believed to
be remnants of a much larger lake that once occupied
all of the Tsala Apopka Plain (White 1970). The
larger ancestral lake apparently found a new, lower
outlet through a solution opening (the Dunnellon
Gap) in the confining Brooksville Ridge to the west.
This escape seems to have reversed the flow of the
Withlacoochee River between Zephyr Hills and
Dunnellon, partially draining the ancestral lake and
leaving the smaller lakes we see today in lower areas.
These lower areas are probably old sinks dating back
to before the impounding of the ancestral lake







2. Geology and Physlography


West of the Ocala Hills, and separated from them
by Martel Hill (which is just outside our study
region), is Cotton Plant Ridge. This sandy ridge is
about 26 km long and 8 km wide, with a distinct
northwest-southeast orientation relative to the other
ridges of the Central Highlands. Maximum elevation
is about 30 m m.s.l., and sediments are predomi-
nantly white sands. The unusual orientation of
Cotton Plant Ridge suggests a derivation different
from the supposed shoreline origin of other ridges in
this region (Knapp 1978). Superimposed on Cotton
Plant Ridge are hills with a surface pattern that
suggests an aeolian origin, which may explain their
orientation perpendicular to the dune-forming south-
west winds (White 1970).

2.2.3 The Lake and Sumter Uplands
The Lake and Sumter Uplands are two highland
areas named for Lake and Sumter Counties, respec-
tively, and separated by the Lake Harris Cross Valley
in the vicinity of Leesburg. Each of the two uplands
is about 56 km long and 24 km wide. They lie gener-
ally between the Western and Central Valleys, but are
partly bounded by higher lands such as the Lake
Wales Ridge on the eastern side of the Lake Upland
and the Ocala and Fairfield Hills and Cotton Plant
Ridge at the northern edge of the Sumter Upland.
The Lake and Sumter Uplands gradually decline in
elevation from north to south, from 38 to 45 m m.s.l.
at the southern end of the Lake Upland to 23-30 m at
the northern end of the Sumter Upland (White 1970).
The Lake and Sumter Uplands are similar in
composition to the Brooksville Ridge: sands and
clayey sands overlying limestone bedrock. The Lake
Upland is dominated by relict beach ridges with
limited but differential solution of the underlying
limestones. As the beach ridges and intervening
swales decline in elevation northward, a series of
many small lakes appears, which gives Lake County
its name (most of these lakes lie to the east of our
study region, however). With the exception of the
large Lake Weir (in Marion County, and just outside
our study region), the Sumter Uplands contain few
lakes.


2.2.4 The Western Valley and Tsala Apopka
Plain
The Western Valley is a large, irregularly shaped
area of low relief and poor drainage bounded on the
west by the Brooksville Ridge and on the east by the
Lake and Sumter Uplands and other highlands to the
north (including the Ocala Hills, Cotton Plant Ridge,
and Fairfield Hills). The Western Valley extends
about 225 km from the High Springs Gap in western
Alachua County (just north of our study region) to
the Zephyrhills Gap in Pasco and Hillsborough
Counties (just south of our study region). It is
connected to the Central Valley (east of our study
region) by the Lake Harris Cross Valley (which sepa-
rates the Lake and Sumter Uplands) and by the
Alachua Lake Cross Valley in southern Alachua
County (east of our study region).
With elevations ranging generally from about 15
to 30 m above m.s.l., the Western Valley contains
many swamps and lakes. The largest of the swamps,
the Green Swamp, lies in parts of Lake, Sumter, and
Polk Counties (Deuerling and MacGill 1981). The
Green Swamp is one of the most significant natural
landscapes of our region, although it is being increas-
ingly modified by human activities.
The Tsala Apopka Plain is a lower (from 12 to
23 m above m.s.l.) and flatter portion of the Western
Valley located in eastern Citrus, Hernando, and
Pasco Counties, and western Sumter County. It is
bounded on the east by the Withlacoochee River and
on the west by the Brooksville Ridge. The Tsala
Apopka Plain contains a number of lakes, including
present-day Lake Tsala Apopka, Lake Panasoffkee,
and many smaller lakes, all of which are believed to
be remnants of a much larger lake that once occupied
all of the Tsala Apopka Plain (White 1970). The
larger ancestral lake apparently found a new, lower
outlet through a solution opening (the Dunnellon
Gap) in the confining Brooksville Ridge to the west.
This escape seems to have reversed the flow of the
Withlacoochee River between Zephyr Hills and
Dunnellon, partially draining the ancestral lake and
leaving the smaller lakes we see today in lower areas.
These lower areas are probably old sinks dating back
to before the impounding of the ancestral lake






Florida Springs Coast Ecological Characterization


(White 1981). Alluvial deposits of variable thickness
on the plain overlie limestone, and much of the local
relief is a highly irregular low topography that
resembles dunes (White 1970).

2.2.5 The Gulf Coastal Lowlands
The Gulf Coastal Lowlands is a poorly drained
area of low relief (from 0 to about 30 m above m.s.l.)
that extends inland from the Gulf of Mexico to the
Brooksville Ridge, throughout the length of our study
region. Located within the Gulf Coastal Lowlands
are coastal swamps, river valley lowlands, and
marine terraces of Pleistocene age (10,000-1.6 mil-
lion years ago) and possibly older. A marine terrace
is a gently sloping or nearly horizontal surface that
was formed by an ancient sea, the inland edge of
which is usually marked by a seaward-facing escarp-
ment representing ancient shoreline features such as
dunes. Terraces are usually covered by sands or
clayey sands. As mapped by Healy (1975a; see Fig.
3), seven marine terraces occur in our region. Start-
ing with the presumed oldest, they are the Coharie,
Sunderland (or Okefenokee), Wicomico, Penho-
loway, Talbot, Pamlico, and Silver Bluff Terraces.
The older three terraces extend above the Gulf
Coastal Lowlands as defined by White (1970), but
are discussed here for convenience.
The Coharie Terrace is found in our region only in
small areas of Pasco County. Standing at 52-65 m
above m.s.l., the Coharie Terrace was considered by
Cooke (1931) to have been formed when the Pleisto-
cene shoreline was at 65 m above m.s.l.. If, however,
Pleistocene seas were never this high (a more recent
view), then this terrace may be much older (of Plio-
cene or even Miocene age). The Sunderland Terrace,
which also may be older than Pleistocene times,
stands at 30-52 m above m.s.l. (with a shoreline at
52 m) in much of our study region. The other possi-
bly pre-Pleistocene terrace in our region is the
Wicomico, standing at 21-30 m above m.s.l. (shore-
line at 30 m). The Brooksville Ridge is associated
with this terrace over much of its area.
The four remaining terraces are within the Gulf
Coastal Lowlands, except for the Penholoway, which
extends from the lowlands through gaps into the


Western Valley. These four terraces (except possibly
the Penholoway) are generally agreed by modem
authors to represent Pleistocene deposits and shore-
lines. The Penholoway Terrace, at 13-30 m above
m.s.1. (shoreline at 30 m), occupies the most inland
portion of the Gulf Coastal Lowlands in much of our
region and also is found in the Tsala Apopka Plain
and surrounding lowlands. The Talbot Terrace, at 8-
13 m above m.s.l. (shoreline at 13 m), is not well
developed in our region, but occupies a strip of land
in Hernando and Pasco Counties between the
Penholoway and Pamlico Terraces.
The Pamlico Terrace is the best developed of the
Pleistocene Terraces in our region, and occupies
most of this part of the Gulf Coastal Lowlands at 2-
13 m above m.s.l. (shoreline at 13 m). Many dunes
are associated with the Pamlico Terrace, which
seems to indicate that much more sand was available
for the building of dunes and beaches than is present
today (Deuerling and MacGill 1981). The source of
these sands may have been the Brooksville Ridge
(White 1970). Signs of an ancient barrier island-
lagoon system in the Crystal River area also indicate
a greater supply of sand in the past than today
(Deuerling and MacGill 1981). Underlying the
Pamlico Terrace are a number of karst features,
including sinkholes and depressions that are masked
by a thin veneer of sand, marls, and coquina depos-
ited during the Pleistocene. The Waccasassa Flats,
which occupy the Pamlico Terrace in central Levy
County north of the town of Gulf Hammock, is a
swampy area composed of varying amounts of
clayey sands (4-5.5 m thick) overlying limestone.
The origin of the Waccasassa Flats is uncertain;
Vernon (1951) and White (1970) pointed to a fluvial
source, whereas Puri et al. (1967) thought marine
processes were responsible.
The Silver Bluff Terrace, at 0.3-3 m above m.s.l.
(shoreline at 3 m), is the most recent of the terraces,
and is found in the region only in Levy County and
extreme northwest Citrus County. The Silver Bluff
Terrace is associated with a coastal marsh belt and is
composed primarily of Pleistocene to Holocene
(Recent) marine sediments underlain by limestones
and dolomites quite close to the surface.







2. Geology and Physiography


Puri and Vemon (1964) and White (1970) desig-
nated the westernmost and lowest area of the Gulf
Coastal Lowlands, occupying much of the Pamlico
and Silver Bluff Terraces in the region, as a physi-
ographic subregion called the Coastal Swamps. This
area is recognized as a low-energy coast where there
is a dearth of sand for building beaches, and includes
many lagoons, salt marshes, freshwater swamps, and
hydric hammocks. Some of the most important natu-
ral areas of our region, such as the Chassahowitzka
Swamp and much of Gulf Hammock, fall into the
Coastal Swamps subregion.


2.3 Surface and Subsurface Geological
Formations

The surface and subsurface geologic formations of
our study region (Figs. 6 and 7, Table 1) are mostly
limestones and dolomites deposited in Tertiary seas
from the Eocene epoch (from 58-36 million years
ago) through the Oligocene epoch (36-25 million
years ago), overlain by clastics that include quartz
sands, silts, clayey sands, and clays. These clastics
were deposited from the Miocene epoch, through the
Pleistocene to the Holocene (from 25 million years
ago to the present). The study of rock strata, espe-
cially their distribution, deposition, and age, is called
stratigraphy. The following discussion will concern
only surface and near-surface stratigraphy, and not
the pre-Eocene sediments and igneous basement
rocks that occur in our area below about 1,200 m.
The surface and near-surface stratigraphy and
outcrop patterns of our region are controlled by a
dominant structural feature, the Ocala Uplift. Puri
and Vernon (1964) described the Ocala Uplift as "a
gentle anticlinal flexure about 230 miles long and
about 70 miles wide exposed near the surface in
west-central Florida." The Ocala Uplift is not
expressed topographically (i.e., it does not produce a
hill or ridge), but can be seen in the outcrop patterns
of the rocks. Rocks previously deposited and
lithified were uplifted relative to rocks of the same
strata in surrounding areas, so that a particular stra-
tum will occur at different elevations in different
parts of our study region.


Figure 6. Location of major geomorphological fea-
tures in west-central Florida (White 1970).


2.3.1 Eocene Series
The middle Eocene Avon Park limestone, which
was deposited about 45 million years ago, is the
oldest formation to outcrop in Florida. The Avon
Park limestone is present in the subsurface through-
out most of our study region, but is exposed only in
two small areas of Levy, Marion, and Citrus counties.
These two outcrops occur near Dunnellon and Leba-
non Station and along the Withlacoochee River, and
in the vicinity of the towns of Gulf Hammock and
Otter Creek. The Avon Park formation was depos-
ited in "shallow coastal bays, beaches, and marine
shelves where almost no plastic material was being
deposited" (Vernon 1951). The upper sediments of







2. Geology and Physiography


Puri and Vemon (1964) and White (1970) desig-
nated the westernmost and lowest area of the Gulf
Coastal Lowlands, occupying much of the Pamlico
and Silver Bluff Terraces in the region, as a physi-
ographic subregion called the Coastal Swamps. This
area is recognized as a low-energy coast where there
is a dearth of sand for building beaches, and includes
many lagoons, salt marshes, freshwater swamps, and
hydric hammocks. Some of the most important natu-
ral areas of our region, such as the Chassahowitzka
Swamp and much of Gulf Hammock, fall into the
Coastal Swamps subregion.


2.3 Surface and Subsurface Geological
Formations

The surface and subsurface geologic formations of
our study region (Figs. 6 and 7, Table 1) are mostly
limestones and dolomites deposited in Tertiary seas
from the Eocene epoch (from 58-36 million years
ago) through the Oligocene epoch (36-25 million
years ago), overlain by clastics that include quartz
sands, silts, clayey sands, and clays. These clastics
were deposited from the Miocene epoch, through the
Pleistocene to the Holocene (from 25 million years
ago to the present). The study of rock strata, espe-
cially their distribution, deposition, and age, is called
stratigraphy. The following discussion will concern
only surface and near-surface stratigraphy, and not
the pre-Eocene sediments and igneous basement
rocks that occur in our area below about 1,200 m.
The surface and near-surface stratigraphy and
outcrop patterns of our region are controlled by a
dominant structural feature, the Ocala Uplift. Puri
and Vernon (1964) described the Ocala Uplift as "a
gentle anticlinal flexure about 230 miles long and
about 70 miles wide exposed near the surface in
west-central Florida." The Ocala Uplift is not
expressed topographically (i.e., it does not produce a
hill or ridge), but can be seen in the outcrop patterns
of the rocks. Rocks previously deposited and
lithified were uplifted relative to rocks of the same
strata in surrounding areas, so that a particular stra-
tum will occur at different elevations in different
parts of our study region.


Figure 6. Location of major geomorphological fea-
tures in west-central Florida (White 1970).


2.3.1 Eocene Series
The middle Eocene Avon Park limestone, which
was deposited about 45 million years ago, is the
oldest formation to outcrop in Florida. The Avon
Park limestone is present in the subsurface through-
out most of our study region, but is exposed only in
two small areas of Levy, Marion, and Citrus counties.
These two outcrops occur near Dunnellon and Leba-
non Station and along the Withlacoochee River, and
in the vicinity of the towns of Gulf Hammock and
Otter Creek. The Avon Park formation was depos-
ited in "shallow coastal bays, beaches, and marine
shelves where almost no plastic material was being
deposited" (Vernon 1951). The upper sediments of







Florida Springs Coast Ecological Characterization


EXPLANATION
t' POST-SUWANNEE
--CRYSTALLINE LIMESTONE(SUWANNEE LIMESTONE)
i= PARTIALLY RECRYSTALLIZED Ls. (SUWANNEE LIMESTONE)
E CRYSTAL RIVER FORMATION 0 10km E
I--- BROOKSVILLE RIDGE
W PAMLICO QUARRY -60m
GULF OF MEXICO COASTLINE EOLIAN SCARP
+30m 3m DEPTH AT 20km OFFSHORE -30
GRADIENT= 1: 6666
S.L.
A


Figure 7. Cross-section across Hemando County (line "A" on Figure 6) illustrating low, flat gradient near the
present coastline. Also shown are the Pleistocene sands of the Pamlico Terrace deposited on the west flank of
the erosionally resistant limestones of the Brooksville Ridge (Hine and Belknap 1986).


the Avon Park limestone were apparently dolo-
mitized subsequent to deposition, thus making it
difficult to recognize fossils and other features indic-
ative of a particular environment (Knapp 1978). The
exposed sediments generally appear as a brown to
dark-brown to tan very fine-grained soft to relatively
hard dolomite containing numerous black carbonifer-
ous plant fossil impressions. Interbedded limestone
consists almost entirely of small foraminiferan
microfossils.
Overlying the Avon Park formation are late
Eocene limestones of the Ocala Group, named for
exposures of this limestone in quarries near the city
of Ocala. These limestones, which were deposited in
a shallow marine environment about 40 million years
ago, form the major surface and near-surface bedrock
over most of our study region. The limestones of the
Ocala Group were considered by Puri (1953) to
consist of three formations, which in ascending order
are the Inglis Formation, Williston Formation, and
Crystal River Formation. Puri's three formations
cannot be mapped or definitely recognized lithologi-
cally. As a result many modem authors have aban-
doned these terms (Miller 1986). The lower strata of
the Ocala Group consist of cream to white generally
fine-grained soft or semi-indurated micritic limestone


containing abundant miliolid remains and scattered
large foraminiferans.
The upper part of the Ocala Group, which is the
typical Crystal River Formation of the literature, is a
white, generally soft and somewhat-friable porous
coquina composed of large foraminiferans, bryozoan
fragments, and whole to broken echinoids, all loosely
bound by a matrix of micritic limestone (Miller
1986). The Ocala limestone is one of the most
permeable rock units in the Floridan aquifer system.
The surface of the formation is very irregular because
of solution of the limestone by acidic ground water.
This solution has resulted in a distinctive karst topog-
raphy over most of our region, with numerous caves,
sinkholes, and other features. The karst surface has
apparently been developing from Miocene to Holo-
cene times when the limestone surface was above sea
level and exposed to weathering and solution agents.


2.3.2 Oligocene Series
The Suwannee Limestone was deposited as
marine sediments during the Oligocene (about 30 to
37 million years ago). In our study region, the
Suwannee limestone is found at or near ground
surface in small parts of Citrus and Hernando


12









2. Geology and Physiography

Table 1. Surface and near-surface geologic formations in the Florida Springs Coast (all Quaternary-period).

Epoch Formation Years ago Characteristics

Holocene 0 to 10,000 Thin sand and gravel deposits; mostly adjacent to
present streams, estuaries, lagoons, and the coast.


Pleistocene


Pliocene


10,000 to 2.5 Sand and clayey sand on terraces and ancient
million shorelines, often in dunes.


2.5 to 7
million


Terrace deposits.


Alachua Formation


Bone Valley
Formation

Hawthorne Formation


Tampa Limestone


Oligocene Suwannee Limestone


Ocala Group (Crystal
River Formation,
Williston Formation,
Inglis Formation)

Avon Park Limestone


Gray to bluish-gray clayey sand; weathers red to
reddish brown.

Highly phosphatic sand and clay beds; mostly
fluvial origin.

7 to 25 Phosphatic clayey sand or sandy clay; dolomites
million or dolomitic limestones in lower beds.

White to light gray, sandy or locally clayey
limestone; fossiliferous.

30 to 37 Cream to tan-colored limestone, granular to
million chalky, hard, partially silicified; highly
fossiliferous.

40 to 45 White, generally soft, coquina limestone; highly
million fossiliferous; cream to white, soft to fairly hard
micritic limestone in lower beds.


Brown to dark brown to tan, very fine-grained
soft to relatively hard dolomite.


Counties, in the south-central region of the Brooks-
ville Ridge. The general lithology is a cream to tan-
colored limestone, granular to chalky, moderate to
well-indurated (hard), variably recrystallized,
partially silicificd (forming chert), and highly fossilif-
erous, containing many mollusks and several distinc-
tive foraminiferans. The Suwannee Limestone in this
region may be 36 m thick (Vernon 1951). The
Suwannee Limestone unconformably rests upon the
Ocala Group limestones (Crystal River Formation),


meaning that the stratigraphic record is incomplete
and intervening sediments may have been present
and subsequently eroded.


2.3.3 Miocene Series
The limestones of the Eocene and Oligocene
series in our region are commonly overlain by sedi-
ments of Miocene age. The oldest of these Miocene
sediments in our region, which occur at or near the


Miocene


Eocene







Florida Springs Coast Ecological Characterization


surface over much of Pasco County, compose the
Tampa Formation. The Tampa Limestone is a sandy
limestone of early Miocene age. It is a white to light-
gray sandy soft to hard locally clayey fossiliferous
(mostly pelecypod and gastropod casts and molds)
limestone with local occurrences of phosphate and
chert (Miller 1986).
Covering a major portion of our study region is the
Hawthorne Formation, the most widespread and
thickest Miocene unit in the southeastern United
States. The Hawthorne is a complexly interbedded,
highly variable sequence that consists primarily of
clay, silt, and sand beds containing little to abundant
phosphate. Fossils in the Hawthorne Formation
include sharks' teeth, ray dental plates, and silicified
heads of colonial corals (K.E. Williams et al. 1977).
Where it is present, the Hawthorne Formation
comprises most of the upper confining unit of the
Floridan Aquifer system. Although the upper
Hawthome sediments are entirely plastics or a vari-
able mixture of plastics and carbonate fragments, the
lower sediments are often phosphatic dolomites or
dolomitic limestone beds, usually brown but locally
cream to white (Miller 1986). Sediments of the
Hawthorne Formation are thought to have been
deposited in a near-shore marine environment, and
probably constitute residual sediments eroded from
the Brooksville Ridge. The phosphate minerals in
the Hawthorne were probably deposited from
upwelling cold marine waters (Miller 1986). The
Hawthorne Formation probably covered most of our
study region, but in places has been eroded away to
expose older sediments. Hawthome phosphorites are
mined over a large area in central Florida.

2.3.4 Pliocene Series
The Bone Valley Formation, a highly phosphatic
sequence of sand and clay beds containing vertebrate
remains of Pliocene Age (about 2.5-7 million years
ago), is at or near the surface in several parts of our
region, including portions of Levy, Gilchrist, Marion,
Hemando, Pasco, Sumter, Lake, and Polk Counties.
The Bone Valley Formation is mostly of fluvial
origin and is composed largely of material reworked
from underlying Miocene rocks (Puri and Vernon


1964). The extent and thickness of the Bone Valley
Formation is uncertain and difficult to distinguish
from the underlying Hawthorne Formation (Miller
1986). Some authors (e.g., Cooke 1945; Vernon
1951; X.E. Williams et al. 1977) identify a Middle
Pliocene deposit, the Alachua Formation, in parts of
our study area. This unit is a generally nonfossi-
liferous (but with local vertebrate fossils) gray to
bluish-gray clayey sand that weathers red to reddish
brown on exposure. It contains residual silicified
boulders of late Eocene, Oligocene, and Miocene age
and locally heavy concentrations of secondary hard-
rock phosphate (K.E. Williams et al. 1977). Later
authors generally consider these sediments to be
residual material of the Hawthorne group (Campbell
1984). The Alachua Formation was not mapped as a
separate unit by Brooks (1981).

2.3.5 Pleistocene to Holocene (Recent) Series
The Pleistocene epoch was the time of the glacial
advances and retreats, from about 2.5 million to
10,000 years ago. None of the Pleistocene glaciers
or their melt-water deposits came into Florida, but
Florida was greatly affected by fluctuating sea levels
during this epoch. Because of the uncertainty about
whether all the marine terraces of Florida represent
Pleistocene shorelines and associated dune systems
(e.g., the Brooksville Ridge), or whether all but the
lower three terraces are older than Pleistocene, it is
difficult to delineate Pleistocene deposits today. At
least some of the sand and clayey sand deposits on
the higher terraces and shorelines (such as the
Wicomico, including the Brooksville Ridge) may be
Pleistocene sediments. Brooks (1981) mapped Pleis-
tocene sand dunes in the Western Valley to the east of
the Tsala Apopka Plain and north of Lake Panasoff-
kee, and in portions of the Gulf Coastal Lowlands in
Pasco, Hemando, and southern Citrus Counties.
Localized examples of Pleistocene fossils (including
land vertebrates and marine and nonmarine inverte-
brates) occur throughout most of our study region.
The Holocene epoch began about 10,000 to
12,000 years ago and continues today. Holocene
deposits in our study region include thin sand and
gravel deposits that are mostly adjacent to present-







Florida Springs Coast Ecological Characterization


surface over much of Pasco County, compose the
Tampa Formation. The Tampa Limestone is a sandy
limestone of early Miocene age. It is a white to light-
gray sandy soft to hard locally clayey fossiliferous
(mostly pelecypod and gastropod casts and molds)
limestone with local occurrences of phosphate and
chert (Miller 1986).
Covering a major portion of our study region is the
Hawthorne Formation, the most widespread and
thickest Miocene unit in the southeastern United
States. The Hawthorne is a complexly interbedded,
highly variable sequence that consists primarily of
clay, silt, and sand beds containing little to abundant
phosphate. Fossils in the Hawthorne Formation
include sharks' teeth, ray dental plates, and silicified
heads of colonial corals (K.E. Williams et al. 1977).
Where it is present, the Hawthorne Formation
comprises most of the upper confining unit of the
Floridan Aquifer system. Although the upper
Hawthome sediments are entirely plastics or a vari-
able mixture of plastics and carbonate fragments, the
lower sediments are often phosphatic dolomites or
dolomitic limestone beds, usually brown but locally
cream to white (Miller 1986). Sediments of the
Hawthorne Formation are thought to have been
deposited in a near-shore marine environment, and
probably constitute residual sediments eroded from
the Brooksville Ridge. The phosphate minerals in
the Hawthorne were probably deposited from
upwelling cold marine waters (Miller 1986). The
Hawthorne Formation probably covered most of our
study region, but in places has been eroded away to
expose older sediments. Hawthome phosphorites are
mined over a large area in central Florida.

2.3.4 Pliocene Series
The Bone Valley Formation, a highly phosphatic
sequence of sand and clay beds containing vertebrate
remains of Pliocene Age (about 2.5-7 million years
ago), is at or near the surface in several parts of our
region, including portions of Levy, Gilchrist, Marion,
Hemando, Pasco, Sumter, Lake, and Polk Counties.
The Bone Valley Formation is mostly of fluvial
origin and is composed largely of material reworked
from underlying Miocene rocks (Puri and Vernon


1964). The extent and thickness of the Bone Valley
Formation is uncertain and difficult to distinguish
from the underlying Hawthorne Formation (Miller
1986). Some authors (e.g., Cooke 1945; Vernon
1951; X.E. Williams et al. 1977) identify a Middle
Pliocene deposit, the Alachua Formation, in parts of
our study area. This unit is a generally nonfossi-
liferous (but with local vertebrate fossils) gray to
bluish-gray clayey sand that weathers red to reddish
brown on exposure. It contains residual silicified
boulders of late Eocene, Oligocene, and Miocene age
and locally heavy concentrations of secondary hard-
rock phosphate (K.E. Williams et al. 1977). Later
authors generally consider these sediments to be
residual material of the Hawthorne group (Campbell
1984). The Alachua Formation was not mapped as a
separate unit by Brooks (1981).

2.3.5 Pleistocene to Holocene (Recent) Series
The Pleistocene epoch was the time of the glacial
advances and retreats, from about 2.5 million to
10,000 years ago. None of the Pleistocene glaciers
or their melt-water deposits came into Florida, but
Florida was greatly affected by fluctuating sea levels
during this epoch. Because of the uncertainty about
whether all the marine terraces of Florida represent
Pleistocene shorelines and associated dune systems
(e.g., the Brooksville Ridge), or whether all but the
lower three terraces are older than Pleistocene, it is
difficult to delineate Pleistocene deposits today. At
least some of the sand and clayey sand deposits on
the higher terraces and shorelines (such as the
Wicomico, including the Brooksville Ridge) may be
Pleistocene sediments. Brooks (1981) mapped Pleis-
tocene sand dunes in the Western Valley to the east of
the Tsala Apopka Plain and north of Lake Panasoff-
kee, and in portions of the Gulf Coastal Lowlands in
Pasco, Hemando, and southern Citrus Counties.
Localized examples of Pleistocene fossils (including
land vertebrates and marine and nonmarine inverte-
brates) occur throughout most of our study region.
The Holocene epoch began about 10,000 to
12,000 years ago and continues today. Holocene
deposits in our study region include thin sand and
gravel deposits that are mostly adjacent to present-







2. Geology and Physiography


day streams, and dune, estuarine, and lagoonal sedi-
ments next to the modem coast. Holocene deposits
also include residual materials from the weathering
of older sediments and local windblown sediments
(Miller 1986). Brooks (1981) did not map Holocene
deposits in our region.


2.4 Marine Geology

The Springs Coast comprises about 193 km of the
west coast of Florida and includes the coastal
portions of Levy, Citrus, Hemando, and Pasco Coun-
ties. This portion of the Florida coast is often termed
the "zero energy" coast (Tanner 1960) because of the
extremely low energy levels found here, with a mean
annual wave height of 30 cm and a spring tidal range
of 90 cm (Hine and Belknap 1986). The major
reasons for the low-energy conditions are (1) weaker
and less common extratropical storms; (2) the domi-
nant storm winds from the north and east, making
them offshore winds on this coast; (3) the wide, low-
gradient adjacent Continental Shelf, protecting the
coast from any large waves formed in the Gulf of
Mexico; and (4) the small fetch of the Gulf of Mexico
(Hine and Belknap 1986).
A complex area of salt marsh, mangrove swamp,
and oyster reefs with little to no natural sand accumu-
lations, this portion of the Florida coast has seen far
less real estate development than other parts of the
Florida coast. The only natural sandy beaches in the
study area are located on Seahorse and Cedar Keys;
however, several artificial beaches, such as those at
Pine Island-Bayport in Hemando County and at
Hudson and Floramar in Pasco County, are present.
These beaches are small, only 60-610 m long and
9 m wide, and need periodic nourishment (Bruun et
al. 1962). Several dredge-and-fill developments are
also present along the coast in the study area.
South from the Suwannee River, the marsh coast
is cut by numerous tidal creeks and extends into a
wide expanse of swamp with flooded topographic
highs, producing numerous isolated islands with
elevations of up to 4.5 m. The highest elevations
along the coast in this area are found on the islands in
the Cedar Keys group. Seahorse Key rises to 15.8 m.


Many of the islands have a mangrove fringe that
protects them from erosion. South from Cedar Keys
many communities are located in areas where eleva-
tions are less than 3 m or even 1.5 m in many places.
These low elevations make most of the coastal
portions of Levy, Citrus, Hemando, and Pasco
Counties unsuitable for development, as they are
prone to flooding during even a moderate storm event
(Doyle 1984).

2.4.1 Regional Marine Geology
Beginning in the lower Cretaceous and continuing
on up through late Oligocene time, the Florida plat-
form was the site of continuous carbonate deposition
(McKinney 1984). This formed a low-gradient car-
bonate platform separated by the Suwannee Channel
from terrigenous elastic input from the Appalachians
via the Apalachicola River (Chen 1965).
Extensive amounts of plastic material were depos-
ited as shore-parallel beach ridges during subsequent
high stands of sea level during the Miocene and Plio-
cene and several fluctuations in the Pleistocene
(Cooke 1945; Alt and Brooks 1965) (Figs. 3 and 6).
The Pleistocene shoreline at 7.6-9.1 m above present
sea level is believed to have been occupied repeatedly
and may represent the predominant interglacial stand
of sea level (Alt and Brooks 1965). The terrace
formed at this elevation is called the Pamlico Terrace
(Cooke 1945) and is present in Levy County and
along the coast in Citrus, Hemando, and Pasco Coun-
ties at elevations of 2.4-7.6 m above present sea level
(Healy 1975a). This terrace is the best developed
landform feature because it has been the least modi-
fied by erosion (Healy 1975a). The Pamlico Terrace
has its eastem edge at the Brooksville Ridge (Fig. 6),
while to the west the terrace extends into the Gulf of
Mexico to a submerged scarp at about 18.3 m below
sea level (Wetterhall 1964). This submerged portion
of the terrace is pocked by sinkholes and springs
which retain many of the features of those found on
land. A northward-flowing longshore current has
filled in many of these sinkholes and sluggish springs
with sand, but they can be seen from the air as
subrounded areas of different color or texture on the
gulf bottom (Wetterhall 1964).







Florida Springs Coast Ecological Characterization


The sand deposited during these Pleistocene high
stands of sea level was deposited well inland of the
present coastline (Fig. 7). Because there is no trans-
port of this material westward to the gulf, this portion
of the coast is sediment starved, and the bedrock
topography is the main factor controlling the shore-
line (Hutton et al. 1984). These sandy terraces are
located closer to shore farther south. The sand from
these terraces is transported to the gulf, helping in the
formation of the barrier islands in northern Pinellas
County (Hutton et al. 1984).
The landform development in the region is
controlled by several factors, according to Vernon
(1951) these are (1) a warm, humid climate with a
high annual rainfall; (2) a bedrock composed of
carbonates easily soluble in freshwater but highly
resistant to marine erosion; (3) low surface eleva-
tions; (4) flat to gently dipping porous rock covered
by limited porous sand and phosphatic beds;
(5) heavily charged phosphoric, humic, and carbonic
acid waters; (6) fracturing along the crest of the Ocala
Uplift; and (7) certain ground-water conditions.
The study area is underlain by a thick section of
Eocene, Oligocene, and Miocene limestones. The
upper few hundred feet of this section forms a gross
hydrologic unit called the Floridan aquifer, which
supplies almost all the freshwater to the area
(Wetterhall 1964). These limestones are near the
surface and exposed around the axis of the Ocala
Uplift, which is a broad flexure of these limestones of
uncertain origin (Vernon 1951; Winston 1976). The
axis of the Ocala Uplift trends northwest-southeast;
its crest is located in Citrus County (Vernon 1951).
This feature controls the outcrop pattern of the rocks
in this area, with older rocks to the north (the oldest
exposed rocks in Florida are Eocene in age and
located in Levy County) and younger rocks to the
south and southwest (Deuerling and MacGill 1981).
The Ocala Uplift caused a regional northwest-south-
east trending fracture system to develop, with fault-
ing along its crest and flanks (Yon and Hendry 1972)
establishing a secondary northeast-southwest fracture
system (Vernon 1951). These fracture systems have
served as loci of surficial karst topography through
the solution of the underlying limestone, leading to


the highly irregular limestone bedrock topography
found underlying the study area today (Hutton et al.
1984).
The larger rivers-the Waccasassa and Withla-
coochee, as well as the Suwannee at the northern
border of the Springs Coast-and smaller streams
and creeks in the study area carry no sediment other
than fine muds and dissolved solids to the Gulf of
Mexico (Vernon 1951). During floods the Suwannee
River does carry fine to medium sand reworked
along the river banks and deposited as sand bars
along the flood plain. Some of this sand reaches the
mouth, but the majority of sediments deposited at the
mouth and into the gulf are muds and dissolved solids
that precipitate as the river mixes with salt water
(Vemon 1951). The reason for this lack of sediment
load is that the rivers and streams cut through carbon-
ate rocks with only a thin veneer of plastic cover.
The Withlacoochee River is the largest in the
study area and discharges at the apex of a minor
salient in the coastline (White 1958). The lower
reach of the river seems to have escaped from its
former longer route parallel to the coast via the valley
of what was once a coast-perpendicular stream
(White 1958). West of the Brooksville ridge streams
tend to run perpendicular to the coast (Fig. 1) because
the land surface there was formed essentially by
simple emergence of the sea bottom. No structural
features, such as the offshore bars or beach ridges,
interpose there, because there are no large accumula-
tions of sand (White 1958). The Withlacoochee
River valley seems to have formed originally as a
lagoon behind an offshore bar at the level of the
Okefenokee Terrace, 45.7 m above present sea level
(MacNeil 1949). It has only lately acquired its
present course through the Brooksville Ridge as a
result of solution (White 1958).
The Waccasassa River reaches the coast at the
head of a bay, Waccasassa Bay. The river is believed
to have been an outlet for a much larger drainage area
than it now possesses (White 1958) and now drains a
broad area of delta plain (Vernon 1951), which
extends nearly to its headwaters and in which the
limestone is buried by a thin layer of fluvial sedi-
ments (White 1958).







2. Geology and Physiography


day streams, and dune, estuarine, and lagoonal sedi-
ments next to the modem coast. Holocene deposits
also include residual materials from the weathering
of older sediments and local windblown sediments
(Miller 1986). Brooks (1981) did not map Holocene
deposits in our region.


2.4 Marine Geology

The Springs Coast comprises about 193 km of the
west coast of Florida and includes the coastal
portions of Levy, Citrus, Hemando, and Pasco Coun-
ties. This portion of the Florida coast is often termed
the "zero energy" coast (Tanner 1960) because of the
extremely low energy levels found here, with a mean
annual wave height of 30 cm and a spring tidal range
of 90 cm (Hine and Belknap 1986). The major
reasons for the low-energy conditions are (1) weaker
and less common extratropical storms; (2) the domi-
nant storm winds from the north and east, making
them offshore winds on this coast; (3) the wide, low-
gradient adjacent Continental Shelf, protecting the
coast from any large waves formed in the Gulf of
Mexico; and (4) the small fetch of the Gulf of Mexico
(Hine and Belknap 1986).
A complex area of salt marsh, mangrove swamp,
and oyster reefs with little to no natural sand accumu-
lations, this portion of the Florida coast has seen far
less real estate development than other parts of the
Florida coast. The only natural sandy beaches in the
study area are located on Seahorse and Cedar Keys;
however, several artificial beaches, such as those at
Pine Island-Bayport in Hemando County and at
Hudson and Floramar in Pasco County, are present.
These beaches are small, only 60-610 m long and
9 m wide, and need periodic nourishment (Bruun et
al. 1962). Several dredge-and-fill developments are
also present along the coast in the study area.
South from the Suwannee River, the marsh coast
is cut by numerous tidal creeks and extends into a
wide expanse of swamp with flooded topographic
highs, producing numerous isolated islands with
elevations of up to 4.5 m. The highest elevations
along the coast in this area are found on the islands in
the Cedar Keys group. Seahorse Key rises to 15.8 m.


Many of the islands have a mangrove fringe that
protects them from erosion. South from Cedar Keys
many communities are located in areas where eleva-
tions are less than 3 m or even 1.5 m in many places.
These low elevations make most of the coastal
portions of Levy, Citrus, Hemando, and Pasco
Counties unsuitable for development, as they are
prone to flooding during even a moderate storm event
(Doyle 1984).

2.4.1 Regional Marine Geology
Beginning in the lower Cretaceous and continuing
on up through late Oligocene time, the Florida plat-
form was the site of continuous carbonate deposition
(McKinney 1984). This formed a low-gradient car-
bonate platform separated by the Suwannee Channel
from terrigenous elastic input from the Appalachians
via the Apalachicola River (Chen 1965).
Extensive amounts of plastic material were depos-
ited as shore-parallel beach ridges during subsequent
high stands of sea level during the Miocene and Plio-
cene and several fluctuations in the Pleistocene
(Cooke 1945; Alt and Brooks 1965) (Figs. 3 and 6).
The Pleistocene shoreline at 7.6-9.1 m above present
sea level is believed to have been occupied repeatedly
and may represent the predominant interglacial stand
of sea level (Alt and Brooks 1965). The terrace
formed at this elevation is called the Pamlico Terrace
(Cooke 1945) and is present in Levy County and
along the coast in Citrus, Hemando, and Pasco Coun-
ties at elevations of 2.4-7.6 m above present sea level
(Healy 1975a). This terrace is the best developed
landform feature because it has been the least modi-
fied by erosion (Healy 1975a). The Pamlico Terrace
has its eastem edge at the Brooksville Ridge (Fig. 6),
while to the west the terrace extends into the Gulf of
Mexico to a submerged scarp at about 18.3 m below
sea level (Wetterhall 1964). This submerged portion
of the terrace is pocked by sinkholes and springs
which retain many of the features of those found on
land. A northward-flowing longshore current has
filled in many of these sinkholes and sluggish springs
with sand, but they can be seen from the air as
subrounded areas of different color or texture on the
gulf bottom (Wetterhall 1964).







2. Geology and Physlography


The other smaller rivers and streams in the study
area, such as the Crystal, Halls, Homosassa, Weeki
Wachee, Mud, and Pithlachascotee Rivers all flow
over and drain a predominantly carbonate terrain. As
a result, these rivers carry very little, if any, sediment
to the gulf, and all have drowned and marshy mouths.


2.4.2 Local Marine Geology
This complex portion of the Florida coast is one of
the least studied areas in Florida, there having been
only one extensive study of the geologic history and
marine geology here. This study, conducted by Hine
and Belknap (1986), covered the coastal areas of
Citrus, Hemando, and Pasco Counties. From this
study they found that the area could be divided into
four coastal sectors (Fig. 8). Although Levy County
was not included in their study, the sectors discussed
below can be extended northward to include those
portions of Levy County that resemble the Hine and
Belknap coastal sectors. The remainder of this
discussion is based on the Hine and Belknap study.
The first sector Hine and Belknap discuss is their
Berm-Ridge Marsh sector, which is found in the
southern portion of the study area (Fig. 8). This area
lies closest to the ancient Pleistocene relict-shoreline
deposits located a few miles inland, but is still far
enough away from these sand deposits so that no
barrier islands or sandy beaches could form as they
did in northern Pinellas County, which has direct
access to these deposits. Because of this proximity to
these deposits and reduced influence of the bedrock
topography which increases to the north, however,
this area of the marsh coast is the least irregular. It is
essentially a slowly eroding marsh dominated by
Juncus roemerianus and supports a narrow sandy
beach and berm-ridge at the marsh-water interface.
A core through this sandy layer, which is only about
50 cm or less in thickness, reveals an organic-rich,
rooted mud-marsh deposit up to 1 m thick underlying
the sand. This mud in turn overlies an irregular lime-
stone weathering residuum up to i m thick. The
berm-ridge shoreline thins seaward as a result of
nearshore erosion. Offshore of the berm-ridge shore-
line, no more than 1 m of the marsh deposits-


beneath 10-30 cm of muddy, carbonate or quartz
sand-are preserved.
Hine and Belknap found a series of tidal creeks
criss-crossing this berm-ridge and marsh system.
The creeks are controlled by the underlying bedrock
topography and provide the drainage for the interior.
They started out as small ponds formed from solution
of the limestone. As sea level rose, these ponds
connected, forming the meandering tidal creeks.
Also present in this system are a large number of
hammocks, which are areas of topographic highs
that support a thin, sandy soil with less salt-tolerant
trees and shrubs.
Farther north, the berm-ridge marsh coast grades
into the Marsh Peninsula portion of this coast
(Fig. 8). Hine and Belknap describe this portion of
the coast as being more irregular due to the absence
of sand cover and the increased influence of the
underlying bedrock topography. The marsh peninsu-
las, points of land, promontories, or marsh headlands
are more common here and represent rock out-
croppings stranded as sea level rose. The same sort
of deposits as found in the berm-ridge marsh sector
are found her. However, the sand cover becomes
thinner and less continuous.
Continuing northward, we find the two most
complex portions of the marsh coast, according to
Hine and Belknap. The first of these are their Shelf
Embayment sectors (Fig. 8), which are microtidal,
low-wave energy, freshwater influenced shallow
depositional basins. These shelf estuarine systems
are rimmed by marshes and have been formed by
long-term exposure to mixed salt and fresh waters,
causing a lowering of the bedrock surface. The
cmbayments are all associated with large springs or
rivers, the magnitude and duration of whose freshwa-
ter flow determines their size. In Hine and Belknap's
study area, these embayments include the Bayport
embayment at the mouth of the Weeki Wachee and
Mud Rivers, Chassahowitzka Bay, Homosassa Bay,
and Crystal Bay. Withlacoochee Bay, Waccasassa
Bay, and Suwannec Sound in Levy County would
most likely fall into the shelf embayment category,
but further study in this area is needed to see if these
embayments display the same types of characteristics










Florida Springs Coast Ecological Characterization


55' 50' 45' 40'


-28*40'


28*20'N


82*35'W


Figure 8. Distribution of the four main morphologic sectors in Citrus, Hemando, and Pasco Counties (Hine and
Belknap 1986).


18







2. Geology and Physiography


found by Hine and Belknap farther south. Narrow
channels extending seaward under water represent
the river beds during lower stands of sea level.
Seaward of the rivers, such as Homosassa River, a
single row of sinkholes may be found aligned with
these channels within the shelf embayment. Off-
shore, a number of springs are present, indicating that
subterranean karstification is still going on.
Hine and Belknap divide their shelf embayment
into two sections, a nearshore section and an inner
shelf section. The nearshore section includes the
marshes, oyster bioherms, and interbioherm lows,
while the inner shelf consists of the area seaward of
the oyster bioherms. The division of these two
sections is one of wave energy caused by the shore-
parallel orientation of the oyster reefs.
Six sedimentary environments were found in the
shelf embayment system, these include (1) a lime-
stone weathering zone; (2) Pleistocene and eolian
sands; (3) marsh consisting of peat and peaty muds;
(4) interbioherm lows consisting of muddy, shelly
sands; (5) oyster bioherms consisting of the shells of
Crassostrea virginica; and (6) an inner shelf environ-
ment consisting of poorly sorted quartz and carbonate
sands.
The oyster reefs in the embayments were found to
flourish seaward in response to higher freshwater
flow. The reefs are associated with bedrock highs
and accumulate vertically with sea-level rise. The
oysters nucleate on local rocky knobs or drowned
hammocks and extend laterally into coast-parallel
features.
The final and most complex of the sectors
discussed by Hine and Belknap is their Marsh Archi-
pelago sector (Fig. 8). These are areas of partially
drowned and exposed karstic bedrock with numerous
rock-cored marsh islands separated by tidal creeks.
They found that these areas were so complex because
of several factors: (1) the age, lithology, and diage-
netic history of the bedrock; (2) the degree of fractur-
ing in the bedrock; (3) the volume of the freshwater
discharge; (4) lack of quartz sand veneer; and
(5) vegetative cover.
The marsh archipelagos are found bounding the
shelf embayments and are located just south of


Chassahowitzka Bay, at Chassahowitzka Point
between Homosassa and Chassahowitzka Bay,
and-the largest one-at Ozello. Outside of Hine
and Belknap's study area in Levy County, Turtle
Creek Point between Withlacoochee and Waccasassa
Bays most probably represents this type of coast.
Cedar Keys may also represent this type of coast in
part, but other things that will be discussed later also
affect this area. Again, further study in Levy County
and areas farther north is needed in order to better
characterize these areas.
Hine and Belknap found the marsh archipelago
sector to be divided into three subenvironments: (1) a
westward mangrove swamp, (2) an eastward salt
marsh, and (3) a north-south trending belt of hard-
wood hammocks. Overall, the marsh archipelago is
an area of regionally elevated bedrock located
between the lower shelf embayments. The reason for
the elevated conditions is that the archipelagos are
outside the influence of the freshwater from the rivers
and springs that Lead to the lowering of the shelf
embayments.
The controlling factor in this sector and the entire
Springs Coast is the development of karst in the
underlying bedrock. Hine and Belknap discuss three
orders of karst development present in the study area.
First-order karst operates on a regional scale, with
fracturing and solution of the carbonate strata
forming the major features of the area. Second-order
karst then relates to the solution and modification of
first-order features through corrosion by acid ground
water and other factors. Finally, third-order karst is
local, small-scale solution as a result of plant roots
and other biological, chemical, biochemical, and
physical degradation. Figure 9 displays the order of
events leading to the type of features found in the
study area. Where fractures are more numerous,
undersaturated ground waters dissolve more material
creating more topographic irregularities on the
surface and voids in the subsurface, which collapse to
form surface low areas. The low areas accumulate
acid-forming marsh sediments, which enhances the
process. The final diagram shows the modem
distribution of hammocks, marshes, and tidal creeks.
As stated earlier, Cedar Keys may represent a
marsh archipelago-type section of the coast, as it is










Florida Springs Coast Ecological Characterization


INITIAL FRACTURING OF LIMESTONE


500M


INCIPIENT KARSTIFICATION
MORE INTENSE LESS INTENSE


CONTINUING KARSTIFICATION


D CONTINUING KARSTIFICATION
WITH SEDIMENTARY
VENEER MARSH


HAMMOCKS


Figure 9. Diagrams showing the evolutionary stages of karstification (Hine and Belknap 1986).








2. Geology and Physiography


situated on a topographically high area between
Waccasassa Bay and Suwannee Sound, and many of
the islands are composed of limestone. The keys do
differ from the marsh archipelago coast in that many
of the islands are composed of quartz sand (Vemon
1951) and have natural sandy beaches. The sand for
the islands at Cedar Keys was supplied from a beach
that existed at a time when sea level was much lower.
These islands were once dunes formed by winds
blowing the sand landward from this ancient beach.
As sea level rose, these dunes were partially
submerged and modified into their present state by
wave and tidal action (White 1970). Sand shoals that
are several meters in relief and come within 50 cm of
the sea surface at low tide have also been found well
offshore of Hemando County in the St. Martins Reef
vicinity (Hine and Belknap 1986). Dune fields are
also found a short distance inland in Hemando and
Pasco Counties (White 1970) (Fig. 3) and, where
found, form an important local supply of sand and
provide higher elevations that help prevent coastal
flooding.


2.5 Economic Geology

The geologic deposits of our study region are
economically valuable in many ways. The useful
commodities include limestone, dolomite, phosphate,
sand, clayey sand, and a small amount of peat
(Vemon 1951; Knapp 1978; Deuerling and MacGill
1981).
Much of our region has large reserves of high-
quality limestone and dolomite, and all of the coun-
ties in our region where limestone is exposed have
had limestone quarrying (open pit) operations. Most
of the limestone is mined from the Avon Park Lime-
stone, the Ocala Group Limestones (Williston and
Crystal River Formations), and the Suwannee Lime-
stones. Some of the limestone found in the Crystal
River Formation is over 99.5% calcium carbonate
(Deuerling and MacGill 1981). Most of the mined
limestone is used as road-base material, and many
small quarries are adjacent to major highways. Other
uses include cement aggregate, soil conditioners,
asphalt filler material, solvents and neutralizers,


erosion control structures (rip-rap), and as a basic
ingredient of Portland cement. The dolomite in our
region, which contains about 36% magnesium
carbonate (Vernon 1951), is used primarily as a soil
conditioner. Quarrying of limestones and dolomites
is usually by the use of draglines and occasionally by
blasting (such as in the Suwannee Limestone, which
has interbedded hard and soft layers and requires
blasting to shatter the quarry face).
Sand and clayey sand are abundant in our region,
particularly near the coast and on the Brooksville
Ridge. These sediments are mined in many areas and
used for construction purposes, fill material, road
base materials, and in asphalt production. Clay,
present as fuller's earth, is mined in some areas for
use as absorbents and in other products.
Phosphate occurs as hard-rock phosphate, soft-
rock phosphate, and land-pebble phosphate. Hard-
rock phosphate deposits in our region are part of a
linear belt called the Hardrock Phosphate District,
which extends from eastern Hemando County north-
ward through Citrus, Levy, Marion, Gilchrist, and
Suwannee Counties. Hard-rock deposits consist of
boulders; pebbles; and small grains of phosphate,
clay, sand, chert, and silicified limestone lying upon a
limestone surface, which is irregular due to solution
(Vemon 1951). No hard-rock phosphate is being
mined in our region today, but it was mined exten-
sively between 1883 and 1966 (Deuerling and
MacGill 1981). Quartz sand and a tan-to-gray soft
phosphatic clay known as soft phosphate were sepa-
rated as waste products during the process of washing
hard-rock phosphate (Vernon 1943). The separated
waste clay and sand were discharged to settling areas
from which the clay is available for later recovery.
Soft-rock phosphate is now being recovered from old
settling areas in the Withlacoochee State Forest, and
is being used for direct application to soil and, if the
fluorine content is low enough, as an animal dietary
supplement.
Land-pebble phosphate is found in a large area
known as the Central Florida Phosphate District and
is mined from the Bone Valley, Hawthorne, and
Alachua Formations. This phosphate occurs as par-
ticles ranging from clay size to pebbles over an inch






Florida Springs Coast Ecological Characterlzation


in diameter. Florida phosphate production in 1978
supplied over 80% of the national output and 30% of
the world's output (Sweeney and Windham 1979).
Most of the phosphate is used in the production of
fertilizer. Phosphate is also an ingredient of deter-
gents, water softeners, and metal polishes (Deuerling
and MacGill 1981). Uranium is also separated as a
by-product of phosphate production (Sweeney and
Windham 1979).
Peat from Holocene-age deposits is being mined
in small boggy areas in Sumter County. Mining is
accomplished by clearing the surface of vegetation,
pumping to dewater the peat, then excavating the peat
by dragline. All of the peat produced from these
areas is utilized for horticultural purposes such as
landscaping and potting soils.
No oil or gas has been produced from any of the
exploratory wells in this region.


2.6 Important Natural Geologic Sites

Geologic features, in and of themselves, are as
much a part of our natural heritage as the biotic
communities which they underlie and help deter-
mine. Geologists customarily travel to human-
created sites such as quarries and road cuts to observe
exposed strata and fossils. But other natural features
are obviously of great interest as well. Knapp (1978)
and Deuerling and MacGill (1981) discussed
outcrops of interest in our study region, focusing on
stream cuts and river beds as well as mined areas.
White (1981) discussed a number of potential
Geological Natural Landmarks in Florida. These
sites are natural in origin, but unfortunately all have
been degraded to various extents by human activities.
The following is mostly a condensation of White's
(1981) descriptions of the Natural Landmark sites
proposed for our study region.

2.6.1 Chassahowitzka Springs
Located in southwestern Citrus County by the
town of Chassahowitzka, Chassahowitzka Springs is
a large spring complex with an average discharge of
201 X 106 L per day, comprising a cluster of large


springs separated enough to have branching spring
runs. Like all the springs in the region, water from
the Floridan aquifer is discharged. They are located
at the eastern edge of the Gulf Coastal Swamps
subregion of the Gulf Coastal Lowlands, at the foot
of a zone of relict coastal dunes of probable Pamlico
age. While the environs below the springs have not
yet been heavily developed, there is considerable
development at the springs themselves.

2.6.2 Homosassa Springs
Located in Citrus County at the southern edge of
the town of Homosassa Springs, Homosassa Springs
is a developed tourist facility but a good example of a
very large Florida spring. Its flow is 326 X 106 L per
day, emanating visibly from solution-enlarged
fissures in Eocene limestone bedrock (Ocala Group).
The head pool is some 24 m wide, and one of the
fissures has been measured at 13.3 m in depth.

2.6.3 Weeki Wachee Springs
Located in Hemando County 21 km west of the
city of Brooksvile, this very large spring has been
developed into a commercial attraction. There is also
some development on the lower part of the river,
much of it on canals off the river itself. Like Chassa-
howitzka and Homosassa Springs, Wccki Wachee
Springs lies along the western edge of a zone of relict
coastal dunes that were apparently deposited at the
Pamlico or Talbot shoreline when sea level was 9 to
12 m higher than it is today. The springs have a
headpool some 45 m in diameter, with a bottom slop-
ing downward to a depth of about 4 m, below which
it drops precipitously to 15 m. The deeper cavity is
about 15 m wide. Thus, the spring may be a relict
funnel-shaped sink that received surface drainage
during low glacial sea levels and is now discharging
artesian water during the present period of higher sea
level. The springs discharge up to 428 X 106 L per
day (Yobbi 1983).

2.6.4 Chunky Pond
Located in Levy County just south of the town of
Bronson, Chunky Pond is a series of small lakes and






Florida Springs Coast Ecological Characterlzation


in diameter. Florida phosphate production in 1978
supplied over 80% of the national output and 30% of
the world's output (Sweeney and Windham 1979).
Most of the phosphate is used in the production of
fertilizer. Phosphate is also an ingredient of deter-
gents, water softeners, and metal polishes (Deuerling
and MacGill 1981). Uranium is also separated as a
by-product of phosphate production (Sweeney and
Windham 1979).
Peat from Holocene-age deposits is being mined
in small boggy areas in Sumter County. Mining is
accomplished by clearing the surface of vegetation,
pumping to dewater the peat, then excavating the peat
by dragline. All of the peat produced from these
areas is utilized for horticultural purposes such as
landscaping and potting soils.
No oil or gas has been produced from any of the
exploratory wells in this region.


2.6 Important Natural Geologic Sites

Geologic features, in and of themselves, are as
much a part of our natural heritage as the biotic
communities which they underlie and help deter-
mine. Geologists customarily travel to human-
created sites such as quarries and road cuts to observe
exposed strata and fossils. But other natural features
are obviously of great interest as well. Knapp (1978)
and Deuerling and MacGill (1981) discussed
outcrops of interest in our study region, focusing on
stream cuts and river beds as well as mined areas.
White (1981) discussed a number of potential
Geological Natural Landmarks in Florida. These
sites are natural in origin, but unfortunately all have
been degraded to various extents by human activities.
The following is mostly a condensation of White's
(1981) descriptions of the Natural Landmark sites
proposed for our study region.

2.6.1 Chassahowitzka Springs
Located in southwestern Citrus County by the
town of Chassahowitzka, Chassahowitzka Springs is
a large spring complex with an average discharge of
201 X 106 L per day, comprising a cluster of large


springs separated enough to have branching spring
runs. Like all the springs in the region, water from
the Floridan aquifer is discharged. They are located
at the eastern edge of the Gulf Coastal Swamps
subregion of the Gulf Coastal Lowlands, at the foot
of a zone of relict coastal dunes of probable Pamlico
age. While the environs below the springs have not
yet been heavily developed, there is considerable
development at the springs themselves.

2.6.2 Homosassa Springs
Located in Citrus County at the southern edge of
the town of Homosassa Springs, Homosassa Springs
is a developed tourist facility but a good example of a
very large Florida spring. Its flow is 326 X 106 L per
day, emanating visibly from solution-enlarged
fissures in Eocene limestone bedrock (Ocala Group).
The head pool is some 24 m wide, and one of the
fissures has been measured at 13.3 m in depth.

2.6.3 Weeki Wachee Springs
Located in Hemando County 21 km west of the
city of Brooksvile, this very large spring has been
developed into a commercial attraction. There is also
some development on the lower part of the river,
much of it on canals off the river itself. Like Chassa-
howitzka and Homosassa Springs, Wccki Wachee
Springs lies along the western edge of a zone of relict
coastal dunes that were apparently deposited at the
Pamlico or Talbot shoreline when sea level was 9 to
12 m higher than it is today. The springs have a
headpool some 45 m in diameter, with a bottom slop-
ing downward to a depth of about 4 m, below which
it drops precipitously to 15 m. The deeper cavity is
about 15 m wide. Thus, the spring may be a relict
funnel-shaped sink that received surface drainage
during low glacial sea levels and is now discharging
artesian water during the present period of higher sea
level. The springs discharge up to 428 X 106 L per
day (Yobbi 1983).

2.6.4 Chunky Pond
Located in Levy County just south of the town of
Bronson, Chunky Pond is a series of small lakes and






Florida Springs Coast Ecological Characterlzation


in diameter. Florida phosphate production in 1978
supplied over 80% of the national output and 30% of
the world's output (Sweeney and Windham 1979).
Most of the phosphate is used in the production of
fertilizer. Phosphate is also an ingredient of deter-
gents, water softeners, and metal polishes (Deuerling
and MacGill 1981). Uranium is also separated as a
by-product of phosphate production (Sweeney and
Windham 1979).
Peat from Holocene-age deposits is being mined
in small boggy areas in Sumter County. Mining is
accomplished by clearing the surface of vegetation,
pumping to dewater the peat, then excavating the peat
by dragline. All of the peat produced from these
areas is utilized for horticultural purposes such as
landscaping and potting soils.
No oil or gas has been produced from any of the
exploratory wells in this region.


2.6 Important Natural Geologic Sites

Geologic features, in and of themselves, are as
much a part of our natural heritage as the biotic
communities which they underlie and help deter-
mine. Geologists customarily travel to human-
created sites such as quarries and road cuts to observe
exposed strata and fossils. But other natural features
are obviously of great interest as well. Knapp (1978)
and Deuerling and MacGill (1981) discussed
outcrops of interest in our study region, focusing on
stream cuts and river beds as well as mined areas.
White (1981) discussed a number of potential
Geological Natural Landmarks in Florida. These
sites are natural in origin, but unfortunately all have
been degraded to various extents by human activities.
The following is mostly a condensation of White's
(1981) descriptions of the Natural Landmark sites
proposed for our study region.

2.6.1 Chassahowitzka Springs
Located in southwestern Citrus County by the
town of Chassahowitzka, Chassahowitzka Springs is
a large spring complex with an average discharge of
201 X 106 L per day, comprising a cluster of large


springs separated enough to have branching spring
runs. Like all the springs in the region, water from
the Floridan aquifer is discharged. They are located
at the eastern edge of the Gulf Coastal Swamps
subregion of the Gulf Coastal Lowlands, at the foot
of a zone of relict coastal dunes of probable Pamlico
age. While the environs below the springs have not
yet been heavily developed, there is considerable
development at the springs themselves.

2.6.2 Homosassa Springs
Located in Citrus County at the southern edge of
the town of Homosassa Springs, Homosassa Springs
is a developed tourist facility but a good example of a
very large Florida spring. Its flow is 326 X 106 L per
day, emanating visibly from solution-enlarged
fissures in Eocene limestone bedrock (Ocala Group).
The head pool is some 24 m wide, and one of the
fissures has been measured at 13.3 m in depth.

2.6.3 Weeki Wachee Springs
Located in Hemando County 21 km west of the
city of Brooksvile, this very large spring has been
developed into a commercial attraction. There is also
some development on the lower part of the river,
much of it on canals off the river itself. Like Chassa-
howitzka and Homosassa Springs, Wccki Wachee
Springs lies along the western edge of a zone of relict
coastal dunes that were apparently deposited at the
Pamlico or Talbot shoreline when sea level was 9 to
12 m higher than it is today. The springs have a
headpool some 45 m in diameter, with a bottom slop-
ing downward to a depth of about 4 m, below which
it drops precipitously to 15 m. The deeper cavity is
about 15 m wide. Thus, the spring may be a relict
funnel-shaped sink that received surface drainage
during low glacial sea levels and is now discharging
artesian water during the present period of higher sea
level. The springs discharge up to 428 X 106 L per
day (Yobbi 1983).

2.6.4 Chunky Pond
Located in Levy County just south of the town of
Bronson, Chunky Pond is a series of small lakes and






Florida Springs Coast Ecological Characterlzation


in diameter. Florida phosphate production in 1978
supplied over 80% of the national output and 30% of
the world's output (Sweeney and Windham 1979).
Most of the phosphate is used in the production of
fertilizer. Phosphate is also an ingredient of deter-
gents, water softeners, and metal polishes (Deuerling
and MacGill 1981). Uranium is also separated as a
by-product of phosphate production (Sweeney and
Windham 1979).
Peat from Holocene-age deposits is being mined
in small boggy areas in Sumter County. Mining is
accomplished by clearing the surface of vegetation,
pumping to dewater the peat, then excavating the peat
by dragline. All of the peat produced from these
areas is utilized for horticultural purposes such as
landscaping and potting soils.
No oil or gas has been produced from any of the
exploratory wells in this region.


2.6 Important Natural Geologic Sites

Geologic features, in and of themselves, are as
much a part of our natural heritage as the biotic
communities which they underlie and help deter-
mine. Geologists customarily travel to human-
created sites such as quarries and road cuts to observe
exposed strata and fossils. But other natural features
are obviously of great interest as well. Knapp (1978)
and Deuerling and MacGill (1981) discussed
outcrops of interest in our study region, focusing on
stream cuts and river beds as well as mined areas.
White (1981) discussed a number of potential
Geological Natural Landmarks in Florida. These
sites are natural in origin, but unfortunately all have
been degraded to various extents by human activities.
The following is mostly a condensation of White's
(1981) descriptions of the Natural Landmark sites
proposed for our study region.

2.6.1 Chassahowitzka Springs
Located in southwestern Citrus County by the
town of Chassahowitzka, Chassahowitzka Springs is
a large spring complex with an average discharge of
201 X 106 L per day, comprising a cluster of large


springs separated enough to have branching spring
runs. Like all the springs in the region, water from
the Floridan aquifer is discharged. They are located
at the eastern edge of the Gulf Coastal Swamps
subregion of the Gulf Coastal Lowlands, at the foot
of a zone of relict coastal dunes of probable Pamlico
age. While the environs below the springs have not
yet been heavily developed, there is considerable
development at the springs themselves.

2.6.2 Homosassa Springs
Located in Citrus County at the southern edge of
the town of Homosassa Springs, Homosassa Springs
is a developed tourist facility but a good example of a
very large Florida spring. Its flow is 326 X 106 L per
day, emanating visibly from solution-enlarged
fissures in Eocene limestone bedrock (Ocala Group).
The head pool is some 24 m wide, and one of the
fissures has been measured at 13.3 m in depth.

2.6.3 Weeki Wachee Springs
Located in Hemando County 21 km west of the
city of Brooksvile, this very large spring has been
developed into a commercial attraction. There is also
some development on the lower part of the river,
much of it on canals off the river itself. Like Chassa-
howitzka and Homosassa Springs, Wccki Wachee
Springs lies along the western edge of a zone of relict
coastal dunes that were apparently deposited at the
Pamlico or Talbot shoreline when sea level was 9 to
12 m higher than it is today. The springs have a
headpool some 45 m in diameter, with a bottom slop-
ing downward to a depth of about 4 m, below which
it drops precipitously to 15 m. The deeper cavity is
about 15 m wide. Thus, the spring may be a relict
funnel-shaped sink that received surface drainage
during low glacial sea levels and is now discharging
artesian water during the present period of higher sea
level. The springs discharge up to 428 X 106 L per
day (Yobbi 1983).

2.6.4 Chunky Pond
Located in Levy County just south of the town of
Bronson, Chunky Pond is a series of small lakes and







2. Geology and Physiography


ponds at the foot of a relict marine-terrace (probably
Wicomico) scarp where soluble limestone underlies
the insoluble shoreline sands at the western edge of
the Brooksville Ridge. The slope of the water table
steepens behind the face of the scarp with the
increased gradient of water flow, bringing the water
table closer to the ground surface immediately below
the scarp. The increased water flow tends to dissolve
the buried surface of the limestone, creating sag
ponds along the toe of the scarp. The scarp is of
interest in itself as an example of a relict marine
shoreline formed by extensive shoreline erosion at
the crest of a marine transgression.

2.6.5 Diffluence of the Withlacoochee River, and
Lake Tsala Apopka
Whereas most fluvial diffluences result from
aggradation, as in deltas built of fluvial sediment or
upgrowth of peat, the diffluence of the upper Withla-
coochee River into the Hillsborough and lower With-
lacoochee Rivers apparently results from a reversal
of flow direction in the present lower Withlacoochee
River caused by stream piracy. The present Hillsbor-
ough River was probably the ancestral trunk stream
with two major tributaries: the present upper
Withlacoochee and a smaller stream arising in Rain-
bow (Blue) Springs and flowing southward along the
present Blue Spring River into the larger ancestral
Lake Tsala Apopka (see physiographic description,
above, of the Tsala Apopka Plain). Apparently this
stream system was disrupted by leakage of lake water
through cavernous openings in the limestone of the
Brooksville Ridge, at the present Dunnellon Gap near
the town of Inglis. This new outlet drained the ances-
tral Lake Tsala Apopka and reversed the flow of the
north branch of the ancestral river from southward to
northward.

2.7 Problems Affecting the Coast

The three most important factors affecting the
coast in the study area are sea-level rise, anthropo-
genic impacts, and severe storms such as hurricanes.
It is a fact that sea level is rising. The rate at which it
is rising, however, is the subject of much debate at


present. Scholl et al. (1969) have shown that sea
level has risen 40 cm/1000 years for the past 3,000
years. This equals alandward retreat of the shoreline
of 2.7 km/1,000 years (Hine and Belknap 1986).
Data indicate that sea level is rising much more
rapidly today than it was in the past few thousand
years. An 8.2-cm rise in sea level for the period from
1914 to 1980 is seen in the tide gauge records at
- Cedar Keys (Hicks et al. 1983). A sea-level rise of
4.8-17.1 cm by the year 2000 and 56-345 cm by the
year 2100 has been demonstrated to be a very good
possibility (Titus et al. 1984). More recent estimates
suggest a rise of 70-100 cm within the next 100 years
(Hine and Belknap 1986).
The cause for this expected acceleration in the rate
of sea-level rise is the greenhouse effect. Increasing
concentrations of carbon dioxide and other gases due
to the combustion of fossil fuels; deforestation;
cement manufacture; and the release of chlorofluom-
carbons from refrigerants, propellants, and other
sources are expected to warm the Earth several
degrees in the next century. This warming could
cause sea-level rise by expanding ocean water, melt-
ing mountain glaciers, and eventually, melting
substantial portions of the polar icecaps.
If sea level does rise the expected 70-100 cm, the
effects on this low-gradient portion of the Florida
coast would be drastic. Hine and Belknap (1986),
using a sea-level rise of 180 cm by the year 2100,
show in Figs. 10 and 11 what would happen to the
coastline. From this it is evident that much of the
coast could be submerged by the year 2100. The
coastal towns of Port Richey, Hudson, Aripeka,
Chassahowitzka, Paradise Point, Homosassa, Crystal
River, Ozello, Pine Island, and Bayonet Point may all
be under water, leaving Bayport a small island
surrounded by water (Hine and Belknap 1986).
With sea-level rise and landward retreat of the
shoreline, this portion of the coast will be exposed to
a sand source as it approaches the Brooksville Ridge
(Fig. 5). Hine and Belknap (1986) propose that this
exposure to a new source of sand would initiate the
formation of a beach, with straightening of the shore-
line occurring as the sand cover subdues the underly-
ing limestone bedrock surface. In time, a low-energy







2. Geology and Physiography


ponds at the foot of a relict marine-terrace (probably
Wicomico) scarp where soluble limestone underlies
the insoluble shoreline sands at the western edge of
the Brooksville Ridge. The slope of the water table
steepens behind the face of the scarp with the
increased gradient of water flow, bringing the water
table closer to the ground surface immediately below
the scarp. The increased water flow tends to dissolve
the buried surface of the limestone, creating sag
ponds along the toe of the scarp. The scarp is of
interest in itself as an example of a relict marine
shoreline formed by extensive shoreline erosion at
the crest of a marine transgression.

2.6.5 Diffluence of the Withlacoochee River, and
Lake Tsala Apopka
Whereas most fluvial diffluences result from
aggradation, as in deltas built of fluvial sediment or
upgrowth of peat, the diffluence of the upper Withla-
coochee River into the Hillsborough and lower With-
lacoochee Rivers apparently results from a reversal
of flow direction in the present lower Withlacoochee
River caused by stream piracy. The present Hillsbor-
ough River was probably the ancestral trunk stream
with two major tributaries: the present upper
Withlacoochee and a smaller stream arising in Rain-
bow (Blue) Springs and flowing southward along the
present Blue Spring River into the larger ancestral
Lake Tsala Apopka (see physiographic description,
above, of the Tsala Apopka Plain). Apparently this
stream system was disrupted by leakage of lake water
through cavernous openings in the limestone of the
Brooksville Ridge, at the present Dunnellon Gap near
the town of Inglis. This new outlet drained the ances-
tral Lake Tsala Apopka and reversed the flow of the
north branch of the ancestral river from southward to
northward.

2.7 Problems Affecting the Coast

The three most important factors affecting the
coast in the study area are sea-level rise, anthropo-
genic impacts, and severe storms such as hurricanes.
It is a fact that sea level is rising. The rate at which it
is rising, however, is the subject of much debate at


present. Scholl et al. (1969) have shown that sea
level has risen 40 cm/1000 years for the past 3,000
years. This equals alandward retreat of the shoreline
of 2.7 km/1,000 years (Hine and Belknap 1986).
Data indicate that sea level is rising much more
rapidly today than it was in the past few thousand
years. An 8.2-cm rise in sea level for the period from
1914 to 1980 is seen in the tide gauge records at
- Cedar Keys (Hicks et al. 1983). A sea-level rise of
4.8-17.1 cm by the year 2000 and 56-345 cm by the
year 2100 has been demonstrated to be a very good
possibility (Titus et al. 1984). More recent estimates
suggest a rise of 70-100 cm within the next 100 years
(Hine and Belknap 1986).
The cause for this expected acceleration in the rate
of sea-level rise is the greenhouse effect. Increasing
concentrations of carbon dioxide and other gases due
to the combustion of fossil fuels; deforestation;
cement manufacture; and the release of chlorofluom-
carbons from refrigerants, propellants, and other
sources are expected to warm the Earth several
degrees in the next century. This warming could
cause sea-level rise by expanding ocean water, melt-
ing mountain glaciers, and eventually, melting
substantial portions of the polar icecaps.
If sea level does rise the expected 70-100 cm, the
effects on this low-gradient portion of the Florida
coast would be drastic. Hine and Belknap (1986),
using a sea-level rise of 180 cm by the year 2100,
show in Figs. 10 and 11 what would happen to the
coastline. From this it is evident that much of the
coast could be submerged by the year 2100. The
coastal towns of Port Richey, Hudson, Aripeka,
Chassahowitzka, Paradise Point, Homosassa, Crystal
River, Ozello, Pine Island, and Bayonet Point may all
be under water, leaving Bayport a small island
surrounded by water (Hine and Belknap 1986).
With sea-level rise and landward retreat of the
shoreline, this portion of the coast will be exposed to
a sand source as it approaches the Brooksville Ridge
(Fig. 5). Hine and Belknap (1986) propose that this
exposure to a new source of sand would initiate the
formation of a beach, with straightening of the shore-
line occurring as the sand cover subdues the underly-
ing limestone bedrock surface. In time, a low-energy









Florida Springs Coast Ecological Characterization


82*38'


S28'"30'
32041-30- 32352'

Figure 10. Present shoreline and a predicted shoreline in the year 2100 in the Bayport area of Hemando County,
based on a 180-cm rise in sea level (Hine and Belknap 1986).


24











2. Geology and Physiography


620466.
28022'30 I


78937,381
---126*2'30'


28*5I1' 28-' "?el15
82*5*' 43*37 '5"

Figure 11. Present shoreline and a predicted shoreline in the year 2100 in the Bayonet Point area of Pasco
County, based on a 180-cm rise in sea level (Hine and Belknap 1986).


25









Florida Springs Coast Ecological Characterization


barrier-island coast similar to that found in northern
Pinellas County would develop. They also indicate
that because of the extremely low sedimentation
rates found in this area of the coast, the marshes are
barely able to keep up with the present 1.24 mm/year
rise in sea level and that any increase in this rate
would lead to widespread marsh drowning.
Coastal erosion in the study area is slow as
compared to other marsh areas in the United States
because of the rock underpinnings nearshore. How-
ever, several marsh islands have completely disappe-
ared in the period from 1944 to 1982 (Hine and
Belknap 1986). The most exposed outer islands and
areas exposed to boat traffic with resulting net
increases in wave energy (such as at Shell Island at
the mouth of the Crystal River) are the most prone to
shoreline instability (Hine and Belknap 1986).
The U.S. Army Corps of Engineers (1971) indi-
cate that no severe erosion occurs along the Springs
Coast, with the exception of a few areas such as the
beach at Pine island-Baypon in Hemrando County,
which has been stabilized with groins, and at
Seahorse Key in the Cedar Keys area of Levy
County, where severe beach erosion is occurring. In
areas where erosion is taking place, the rates are 33-
58 cm/year (Hine and Belknap 1986).
Several dredge-and-fill developments are taking
place along the coast in the study area. Hine and


Belknap (1986) indicate that, where present, these
dredge-and-fill operations equal or exceed natural
processes as causes of shoreline change.
Severe storms such as hurricanes are probably the
most important influences on the shoreline today.
Sea-level rise and changes brought on by human
activity take time to change the shoreline, but a single
hurricane can have disastrous effects over one or two
days. Because of the low gradient of this area and
because most of the development is on areas of low
elevation, a storm surge of 3-3.7 m during a
hurricane would flood most of the study area. Most
of the coastal portions of Levy, Citrus, Hemando, and
Pasco Counties have elevations below 3 m and are
the sites of developments or individual cottages and
houses. Thus, storm-surge flooding is the main threat
to this area (Doyle 1984).
Very little short-term coastal change is taking
place along this portion of the Florida coast. Except
for dredging activity or a severe storm causing
flooding, the low energy conditions and protected
nature of this marsh coast insure that it will change
very little. The long-term changes as a result of sea-
level rise and coastal subsidence from limestone
solution are what coastal planners in this area of the
Florida west coast should be concerned with as much
of this low-lying coastal area begins to disappear
under water.

















Chapter 3. CLIMATE
by Steven H. Wolfe


3.1 Introduction


The Florida Springs Coast experiences a mild,
subtropical climate as a result of its latitude (28010'-
29020' N) and the stabilizing effect of the adjacent
Gulf of Mexico (Bradley 1972). The waters of the
gulf moderate winter cold fronts by acting as a heat
source and minimize summer temperatures by
producing cooling sea breezes. Gulf influence is
strongest near the coast, weakening inland. Fairly
detailed long-term climatological summaries are
available only for sites just south and east of the
Springs Coast (e.g., Ocala, Lakeland, Tampa)
(Jordan 1973). More limited data are available for
Cedar Key to the north and certain other Springs
Coast locations where U.S. Weather Service stations
collecting less complete data are located (Fig. 12).


3.2 Climatological Features


3.2.1 Temperature
The Springs Coast encompasses an area of sub-
stantial climatic difference. The annual average of
the mean daily temperature is approximately 70 "F.
Mean summer temperatures are in the low 80's, and
mean winter temperatures are in the upper 50's.
Annual and seasonal temperatures vary widely (Figs.
13 and 14) with summer highs generally in the low to
mid 90's and infrequent occasions of 1000 or higher.
The summer heat is tempered by sea breezes along
the coast and up to 50 km inland, as well as the cool-
ing effect of frequent afternoon thundershowers.
Thundershowers occur on approximately half of the


days during summer and frequently cause 10- to 20-
degree drops in temperature (Bradley 1972).
Winter temperatures are quite variable due to the
frequent passage of cold fronts. The colder of these
fronts are of Arctic origin and may bring minimum
temperatures ranging from 25-30 F, with single-
digit lows almost unknown. Temperatures rarely
remain below freezing during the day anywhere
within the region, and the cold weather from a front
generally lasts only 2-3 days. Temperatures in the
60's and 70's F often separate the cold fronts. This
weather pattern results in average low temperatures
near 50 F during the coldest months (December
through February).

3.2.2 Rainfall
The Florida Springs Coast receives rainfall from
three types of systems: frontal, convective, and tropi-
cal cyclonic. The frontal systems dominate the
winter rainfall; convective showers and thunder-
storms are common during the remainder of the year.
The tropical storms, including hurricanes, resulting
from tropical cyclonic activity are more sporadic, and
years frequently occur with no activity.
The region experiences two peak rainfall periods:
a primary one during summer (June through Septem-
ber) and a secondary one during late winter and early
spring (February through April) (Fig. 15). The
Springs Coast lies in a transition zone between the
annual patterns of two wet/two dry seasons of north
Florida and one wet/one dry season of south Florida.
This transition results from the weakening of winter
cold fronts arriving from the north. Most of these
fronts stall out before reaching south Florida, or are

















Chapter 3. CLIMATE
by Steven H. Wolfe


3.1 Introduction


The Florida Springs Coast experiences a mild,
subtropical climate as a result of its latitude (28010'-
29020' N) and the stabilizing effect of the adjacent
Gulf of Mexico (Bradley 1972). The waters of the
gulf moderate winter cold fronts by acting as a heat
source and minimize summer temperatures by
producing cooling sea breezes. Gulf influence is
strongest near the coast, weakening inland. Fairly
detailed long-term climatological summaries are
available only for sites just south and east of the
Springs Coast (e.g., Ocala, Lakeland, Tampa)
(Jordan 1973). More limited data are available for
Cedar Key to the north and certain other Springs
Coast locations where U.S. Weather Service stations
collecting less complete data are located (Fig. 12).


3.2 Climatological Features


3.2.1 Temperature
The Springs Coast encompasses an area of sub-
stantial climatic difference. The annual average of
the mean daily temperature is approximately 70 "F.
Mean summer temperatures are in the low 80's, and
mean winter temperatures are in the upper 50's.
Annual and seasonal temperatures vary widely (Figs.
13 and 14) with summer highs generally in the low to
mid 90's and infrequent occasions of 1000 or higher.
The summer heat is tempered by sea breezes along
the coast and up to 50 km inland, as well as the cool-
ing effect of frequent afternoon thundershowers.
Thundershowers occur on approximately half of the


days during summer and frequently cause 10- to 20-
degree drops in temperature (Bradley 1972).
Winter temperatures are quite variable due to the
frequent passage of cold fronts. The colder of these
fronts are of Arctic origin and may bring minimum
temperatures ranging from 25-30 F, with single-
digit lows almost unknown. Temperatures rarely
remain below freezing during the day anywhere
within the region, and the cold weather from a front
generally lasts only 2-3 days. Temperatures in the
60's and 70's F often separate the cold fronts. This
weather pattern results in average low temperatures
near 50 F during the coldest months (December
through February).

3.2.2 Rainfall
The Florida Springs Coast receives rainfall from
three types of systems: frontal, convective, and tropi-
cal cyclonic. The frontal systems dominate the
winter rainfall; convective showers and thunder-
storms are common during the remainder of the year.
The tropical storms, including hurricanes, resulting
from tropical cyclonic activity are more sporadic, and
years frequently occur with no activity.
The region experiences two peak rainfall periods:
a primary one during summer (June through Septem-
ber) and a secondary one during late winter and early
spring (February through April) (Fig. 15). The
Springs Coast lies in a transition zone between the
annual patterns of two wet/two dry seasons of north
Florida and one wet/one dry season of south Florida.
This transition results from the weakening of winter
cold fronts arriving from the north. Most of these
fronts stall out before reaching south Florida, or are

















Chapter 3. CLIMATE
by Steven H. Wolfe


3.1 Introduction


The Florida Springs Coast experiences a mild,
subtropical climate as a result of its latitude (28010'-
29020' N) and the stabilizing effect of the adjacent
Gulf of Mexico (Bradley 1972). The waters of the
gulf moderate winter cold fronts by acting as a heat
source and minimize summer temperatures by
producing cooling sea breezes. Gulf influence is
strongest near the coast, weakening inland. Fairly
detailed long-term climatological summaries are
available only for sites just south and east of the
Springs Coast (e.g., Ocala, Lakeland, Tampa)
(Jordan 1973). More limited data are available for
Cedar Key to the north and certain other Springs
Coast locations where U.S. Weather Service stations
collecting less complete data are located (Fig. 12).


3.2 Climatological Features


3.2.1 Temperature
The Springs Coast encompasses an area of sub-
stantial climatic difference. The annual average of
the mean daily temperature is approximately 70 "F.
Mean summer temperatures are in the low 80's, and
mean winter temperatures are in the upper 50's.
Annual and seasonal temperatures vary widely (Figs.
13 and 14) with summer highs generally in the low to
mid 90's and infrequent occasions of 1000 or higher.
The summer heat is tempered by sea breezes along
the coast and up to 50 km inland, as well as the cool-
ing effect of frequent afternoon thundershowers.
Thundershowers occur on approximately half of the


days during summer and frequently cause 10- to 20-
degree drops in temperature (Bradley 1972).
Winter temperatures are quite variable due to the
frequent passage of cold fronts. The colder of these
fronts are of Arctic origin and may bring minimum
temperatures ranging from 25-30 F, with single-
digit lows almost unknown. Temperatures rarely
remain below freezing during the day anywhere
within the region, and the cold weather from a front
generally lasts only 2-3 days. Temperatures in the
60's and 70's F often separate the cold fronts. This
weather pattern results in average low temperatures
near 50 F during the coldest months (December
through February).

3.2.2 Rainfall
The Florida Springs Coast receives rainfall from
three types of systems: frontal, convective, and tropi-
cal cyclonic. The frontal systems dominate the
winter rainfall; convective showers and thunder-
storms are common during the remainder of the year.
The tropical storms, including hurricanes, resulting
from tropical cyclonic activity are more sporadic, and
years frequently occur with no activity.
The region experiences two peak rainfall periods:
a primary one during summer (June through Septem-
ber) and a secondary one during late winter and early
spring (February through April) (Fig. 15). The
Springs Coast lies in a transition zone between the
annual patterns of two wet/two dry seasons of north
Florida and one wet/one dry season of south Florida.
This transition results from the weakening of winter
cold fronts arriving from the north. Most of these
fronts stall out before reaching south Florida, or are

















Chapter 3. CLIMATE
by Steven H. Wolfe


3.1 Introduction


The Florida Springs Coast experiences a mild,
subtropical climate as a result of its latitude (28010'-
29020' N) and the stabilizing effect of the adjacent
Gulf of Mexico (Bradley 1972). The waters of the
gulf moderate winter cold fronts by acting as a heat
source and minimize summer temperatures by
producing cooling sea breezes. Gulf influence is
strongest near the coast, weakening inland. Fairly
detailed long-term climatological summaries are
available only for sites just south and east of the
Springs Coast (e.g., Ocala, Lakeland, Tampa)
(Jordan 1973). More limited data are available for
Cedar Key to the north and certain other Springs
Coast locations where U.S. Weather Service stations
collecting less complete data are located (Fig. 12).


3.2 Climatological Features


3.2.1 Temperature
The Springs Coast encompasses an area of sub-
stantial climatic difference. The annual average of
the mean daily temperature is approximately 70 "F.
Mean summer temperatures are in the low 80's, and
mean winter temperatures are in the upper 50's.
Annual and seasonal temperatures vary widely (Figs.
13 and 14) with summer highs generally in the low to
mid 90's and infrequent occasions of 1000 or higher.
The summer heat is tempered by sea breezes along
the coast and up to 50 km inland, as well as the cool-
ing effect of frequent afternoon thundershowers.
Thundershowers occur on approximately half of the


days during summer and frequently cause 10- to 20-
degree drops in temperature (Bradley 1972).
Winter temperatures are quite variable due to the
frequent passage of cold fronts. The colder of these
fronts are of Arctic origin and may bring minimum
temperatures ranging from 25-30 F, with single-
digit lows almost unknown. Temperatures rarely
remain below freezing during the day anywhere
within the region, and the cold weather from a front
generally lasts only 2-3 days. Temperatures in the
60's and 70's F often separate the cold fronts. This
weather pattern results in average low temperatures
near 50 F during the coldest months (December
through February).

3.2.2 Rainfall
The Florida Springs Coast receives rainfall from
three types of systems: frontal, convective, and tropi-
cal cyclonic. The frontal systems dominate the
winter rainfall; convective showers and thunder-
storms are common during the remainder of the year.
The tropical storms, including hurricanes, resulting
from tropical cyclonic activity are more sporadic, and
years frequently occur with no activity.
The region experiences two peak rainfall periods:
a primary one during summer (June through Septem-
ber) and a secondary one during late winter and early
spring (February through April) (Fig. 15). The
Springs Coast lies in a transition zone between the
annual patterns of two wet/two dry seasons of north
Florida and one wet/one dry season of south Florida.
This transition results from the weakening of winter
cold fronts arriving from the north. Most of these
fronts stall out before reaching south Florida, or are

















Chapter 3. CLIMATE
by Steven H. Wolfe


3.1 Introduction


The Florida Springs Coast experiences a mild,
subtropical climate as a result of its latitude (28010'-
29020' N) and the stabilizing effect of the adjacent
Gulf of Mexico (Bradley 1972). The waters of the
gulf moderate winter cold fronts by acting as a heat
source and minimize summer temperatures by
producing cooling sea breezes. Gulf influence is
strongest near the coast, weakening inland. Fairly
detailed long-term climatological summaries are
available only for sites just south and east of the
Springs Coast (e.g., Ocala, Lakeland, Tampa)
(Jordan 1973). More limited data are available for
Cedar Key to the north and certain other Springs
Coast locations where U.S. Weather Service stations
collecting less complete data are located (Fig. 12).


3.2 Climatological Features


3.2.1 Temperature
The Springs Coast encompasses an area of sub-
stantial climatic difference. The annual average of
the mean daily temperature is approximately 70 "F.
Mean summer temperatures are in the low 80's, and
mean winter temperatures are in the upper 50's.
Annual and seasonal temperatures vary widely (Figs.
13 and 14) with summer highs generally in the low to
mid 90's and infrequent occasions of 1000 or higher.
The summer heat is tempered by sea breezes along
the coast and up to 50 km inland, as well as the cool-
ing effect of frequent afternoon thundershowers.
Thundershowers occur on approximately half of the


days during summer and frequently cause 10- to 20-
degree drops in temperature (Bradley 1972).
Winter temperatures are quite variable due to the
frequent passage of cold fronts. The colder of these
fronts are of Arctic origin and may bring minimum
temperatures ranging from 25-30 F, with single-
digit lows almost unknown. Temperatures rarely
remain below freezing during the day anywhere
within the region, and the cold weather from a front
generally lasts only 2-3 days. Temperatures in the
60's and 70's F often separate the cold fronts. This
weather pattern results in average low temperatures
near 50 F during the coldest months (December
through February).

3.2.2 Rainfall
The Florida Springs Coast receives rainfall from
three types of systems: frontal, convective, and tropi-
cal cyclonic. The frontal systems dominate the
winter rainfall; convective showers and thunder-
storms are common during the remainder of the year.
The tropical storms, including hurricanes, resulting
from tropical cyclonic activity are more sporadic, and
years frequently occur with no activity.
The region experiences two peak rainfall periods:
a primary one during summer (June through Septem-
ber) and a secondary one during late winter and early
spring (February through April) (Fig. 15). The
Springs Coast lies in a transition zone between the
annual patterns of two wet/two dry seasons of north
Florida and one wet/one dry season of south Florida.
This transition results from the weakening of winter
cold fronts arriving from the north. Most of these
fronts stall out before reaching south Florida, or are








Florida Springs Coast Ecological Characterization


.@ High Springs


ALACHUA


.-.c^-.-^---





MARION
Ocala


0A


Brootsville
Chinsegut Hill
HERNANDO


I-


s HILL Oi UGH

Figure 12. Locations of NOAA climatological stations near the Florida Springs Coast (after Jordan 1984).


Cross City

DIXIE









840 ,
I GILCHRIST/l Y

DIXIE
-
I ", ) v
t


84v


SDIXE
ol.
< i


ALACHUA


I rJIj


ALACHUA

C .c .


s- --


-,' I- --/LE-- .I .-r, .-. '

/LEVY L L V
S.''- MARION MARION



29 0 29-


CITRUS 6-
o o CITRUS -

-O -- -A
(0 --M' -'- /LAKE 3
SUMTER LAKE (
o ', LAKE W I 1 0 "" '"
S IERNAND 0 HERNANDO "

) r'
-- -( ........ _. -( "-


I PASCO\ J PASCO\ Z
d. "< \- ^ V- ----" "" "
POLK POLK

a IIEL- I I O .I INEL-' '
SLAS HILLSBROUGH LAS HILL OROUGH

Mean maximum temp (F) Mean minimum temp (OF)
89 91 93 July 69 71 73 75



Figure 13. Isotherms for July temperatures in the Florida Springs Coast, 1959-1979 (after Femald 1981).


"1
' J




































Mean maximum temp (F)
65 67 69 71 73January


Figure 14. Isotherms for January temperatures in the Florida Springs Coast,


Mean minimum temp (OF)
39 41 43 45 47 49 51

1959-1979 (after Feald 1981).








3. Climate


0 i i - --- --------------------
Inverness
-o.- Saint Leo














Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month

Figure 15. Seasonal rainfall variation at selected sites in the Florida Springs Coast (data from Bradley 1972).


"rained-out" and reach south Florida as dry fronts,
resulting in cooler weather but little precipitation. As
a result, the dry seasons and the secondary wet season
are drier in the Springs Coast than to the north, but
because of the greater convective heating in the
south, the primary wet season is wetter (Fig. 15).
Average annual rainfall across the Springs Coast is
approximately 147 cm across the north of the region,
decreasing to approximately 137 cm in the south
(Jordan 1984) (Fig. 16). The average rainfall varies
widely and has ranged in any single 12-month period
since 1951 from less than 75 cm to 215 cm (Fig. 17).
Maximum annual rainfall values tend to be about 40
inches above the annual mean (Jordan 1984).
National Weather Service data compiled in Hafer and
Palmer (1978) show that while the eastern Springs
Coast edge can expect to receive the average rainfall
in any given year, the rest can expect only a 40%-
45% chance of receiving rainfall equal to or greater
than the average annual precipitation. In other words,
it is normal for the annual rainfall to be below


average. The occasional very wet years, which result
in the median rainfall values being significantly less
than the mean values, are probably the result of tropi-
cal storm activity.
During rainy years the maximum rainfall tends to
occur near the coast; however, during dry years the
rainfall maximum occurs farther inland. Rainfall pat-
tems tend to be more consistent approximately 25-
95 km inland (Jordan 1984). Rainfall gradients are
quite strong along some portions of the gulf coast;
annual totals are as much as 12-25 cm less at stations
very near the coastline than at those a few kilometers
inland (Jordan 1973).
Studies of the distribution of summer rainfall,
based on weather radar observations at Tampa and
with the results supported by corresponding studies at
Apalachicola, showed that showers within 160 km of
the radar installation were nearly as frequent over the
sea as over the land when averaged over a 24-hour
period (Smith 1970). This and similar studies in









Florida Springs Coast Ecological Characterization


Figure 16. Average annual rainfall in the Florida
Springs Coast, 1951-1980 (after Jordan 1984).



south Florida (Frank et al. 1967) found high numbers
of showers over land in the afternoon and low num-
bers in the early morning. They found a minimum
number over the sea in the afternoon and a maximum
during late night and early morning, especially within
50 km of the coast.
When interpreting the rainfall data, it is important
to note that the start and end of the rainy seasons may
vary by 6 or 7 weeks from year to year. On the aver-
age in Tampa (the nearest site with available data),
thunderstorms occur on 91% of days; 66% of the
storms occur in the summer (June-September), while
only 5% occur in winter (November-February).
Most of this summer rainfall occurs in the after-
noon in the form of often heavy local showers and
thunderstorms of short duration (1-2 hours) that are,
on rare occasions during the spring, accompanied by
hail. Summer rain that lasts for longer periods is


often associated with occasional tropical distur-
bances. Winter rains are associated with frontal
systems and are generally of longer duration than the
summer rains, but are fewer in number and have a
slower rate of rainfall accumulation. Hourly data
taken beginning in the 1940's and ending in the
1970's demonstrate these different diurnal patterns of
the summer and winter rains (Fig. 18). Few stations
collected this data, so data from Orlando are
presented, though it lies just outside the Springs
Coast area. Snowfall occurs at rare intervals across
the Springs Coast, approximately 1 year in 15 (U.S.
Dept. of Commerce 1980a,b,c).
Despite large average annual rainfalls, droughts
occur (Fig. 19). Even short periods of drought, when
combined with the reduced area of lakes and
wetlands and the low water table found during gener-
ally dry years, can cause extensive crop losses in the
agricultural areas, as well as increased damage from
forest fires. Fires during extended droughts can
cause severe damage even in the longleaf pine areas
adapted to seasonal fires, and result in the buying of
parched wetlands and other habitats normally
protected from fire. These areas, not adapted to the
normal periodic fires of the pine forest, may recover
very slowly (Means and Moler 1979).

3.2.3 Winds
a. Normal wind patterns. From March through
September, the Springs Coast is under the western
portion of the Bermuda high-pressure cell, which has
a general clockwise (anticyclonic) circulation of the
low-level winds (i.e., those measured at an altitude of
600-900 m) (Atkinson and Sadler 1970) (Fig. 20).
The latitude at which the wind shifts from out of the
southeast to out of the southwest (the "ridgeline,"
shown by the dashed lines in Fig. 20) changes
substantially during spring and summer. From Octo-
ber through February, a western anticyclonic cell
separates from the Bermuda anticyclone and estab-
lishes itself in the Gulf of Mexico (Fig. 20). The
center of the cell migrates somewhat as indicated by
the X's, but generally results in low-level winds from
a westerly direction over the Springs Coast.


32

























































Maximum Rainfall
over 12 consecutive months

Total Centimeters Recorded


178 191
f::::T


Minimum Rainfall
over 12 consecutive months

Total Centimeters Recorded
71 76 81 86 91 96
..:. .


203 216 229 241
Lq


Figure 17. Springs Coast 12-month rainfall 1951-1980 (after Jordan 1984).


I


IL a.







Florida Springs Coast Ecological Characterization


Dec-Mar
SJune-Sept

0 -



0'
12 6 12
Midnight AM Noon

Figure 18. Percent of total daily
individual hours of the day at Orlar
1984).


These circulatory patterns indicate that the
Springs Coast is primarily influenced by tropical air
masses in the spring and summer and by continental
(cold) air masses during the fall and winter. The
prevailing winds in the Florida Springs Coast are
from a southerly direction during the spring and
summer. Figure 21 shows seasonal windroses for
-- Tampa, the nearest site collecting this information.
6 12 Locally, wind directions may be determined by thun-
PM Midnight
derhead formation and thunderstorms. Wind direc-
Srainfall during tion changes with the passing of each cold front; most
ndo (after Jordan commonly these occur during the fall and winter
(September through March). As the front passes
through, the wind, which normally blows from a
southerly direction, rapidly changes direction with a
clockwise progression ("clocks") through the west,
then usually pauses out of the northwest quadrant for
approximately 1-3 days, blowing toward the front
receding to the south or southeast. After the front has
passed a sufficient distance to allow the "normal"
wind patterns to reassert themselves, the wind
-finishes clocking through the east and back to the
south. The directional orientation of the front and the
................... direction from which the wind blows immediately
following its passage depends upon the origin of the
front; the winds are from the north for fronts of Arctic
and Canadian origin, from the west to northwest for
r those of Pacific origin.


S28 40 43 43 27 0 0 16 26 54 38 39
Longest dry perod on record beginning In month indicated

25
Tampa [ 15-19days
20 ......................... ............. 0 20-24 da ......... .......................
*> 24 days


10

E L


Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
34 40 48 49 37 19 0 0 25 44 36 28
Longest dry period on record beginning In month indicated

Figure 19. Occurrence of extended dry periods at
Orlando and Tampa, 1950-1980 [no day over
0.25 cm] (after Jordan 1984).


This cycle is sometimes interrupted by the
approach of a new cold front closely following the
first. As a result, the most prevalent winds from
September through February (the season of frontal
passages) are out of the northern half of the compass
(following the fronts) with less frequent and weaker
winds from the southern half of the compass (before
the fronts) (Fig. 21). The annual average resultant
wind (i.e., the vector sum of the monthly wind speed
and direction) in the Springs Coast is from the north.
This is because the wind speeds that follow the
winter fronts are greater than those that blow during
the rest of the year. All of these wind patterns are
somewhat erratic due to convective forces inland and
because of the resulting land- and sea-breeze mecha-
nism near the coast.

The mean monthly wind strength is less in
summer than during the fall, winter, and spring

34







3. Climate


March-September


October-February


Figure 20. Low level (600-900 m) winds (after Atkinson and Sadler 1970).


(Fig. 22). Since no data from within the Springs
Coast is available, those for Tampa are given in the
figure to suggest the seasonal wind strength in the
Springs Coast. Inland stations exhibit somewhat
lower average speeds than those along the coast (Jor-
dan 1973). The highest 1-minute sustained wind
speed is seldom over 50 km/h, though sustained non-


hurricane-associated winds in the 85-95 km/h range
have been recorded (Bradley 1972).

b. Hurricanes, tornadoes, and waterspouts.
Hurricanes pose a major threat to the Florida Springs
Coast. A hurricane is a cyclonic storm (i.e., the
winds rotate counterclockwise in the northern





Florida Springs Coast Ecological Characterization


Fall (September-November) Winter (December-February)
Figure 21. Percentage of time wind blew from differ-
ent directions at Tampa (nearest data site) during dif-
ferent seasons, 1959-1979 average (after Fernald
1981).

hemisphere) with sustained wind speeds in excess of
120 km/h. Six hurricanes have come ashore in this
region from 1885 to 1985. Figure 23 shows the
tracks for hurricanes hitting near the Florida Springs
Coast during this period. Of 48 hurricanes and tropi-


12



a

It
C


46 -i--i--i--i----i- --

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan

Figure 22. Seasonal windspeed at Tampa (nearest
data site) (after Jordan 1973).


cal storms that struck or came within 150 miles of the
Florida coast from Tampa Bay to the Ochlockonee
River, including the Springs Coast, 5 were in June, 3
in July, 11 in August, 15 in September, 12 in October,
and 2 from November through May.
Much of the damage done by hurricanes is caused
by the local rise in sea level known as storm surge.
For hurricanes striking the Springs Coast from the
gulf, this rise occurs east of the "eye" (the storm's
center) as the counterclockwise wind circulation
about the eye pushes water ahead and traps it against
the coastline. Embayments help contain this water
and can increase storm-surge magnitudes substan-
tially when a hurricane strikes the northern or western
side. Tidal stage and phase, bottom topography,
coastline configuration, and especially wind strength
combine to determine the storm-surge magnitude.
The State of Florida addressed coastal safety, prop-
erty protection, and beach erosion during hurricanes
in Henningsen and Salmon (1981).
Tornadoes and waterspouts form infrequently.
They occur most commonly in the spring, associated
.with frontal weather systems, and in connection with
tropical storms and hurricanes. Tornado paths in
Florida are usually short, and historically, damage
has not been extensive. Waterspouts occasionally
come ashore, but dissipate quickly after reaching land
and, therefore, affect very small areas (Bradley
1972).

3.2.4 Insolation
The amount of sunlight insolationn) reaching the
Florida Springs Coast directly affects temperature as
well as photosynthesis. It indirectly affects processes
in which these factors play a role, including weather
patterns, rates of chemical reactions (e.g., metabo-
lism), productivity, and evapotranspiration (evapora-
tion and water transpired into the atmosphere by
plant foliage). The amount of insolation is controlled
by two factors: season and atmospheric screening.
a. Seasonal changes. Seasonal insolation is
controlled by five factors: (1) the changing distance
between the Sun and Earth as Earth follows its
elliptical orbit; (2) the increasing thickness of the








3. Climate


84*


LAFAYETTE


MARION D


1888 7
1896


-I


29* -


1950

Gulf
of
Mexico


1889


1968


280 -


1885 1921 -y / / \

Figure 23. Paths of hurricanes striking the Springs Coast 1885-1990 (after Jordan 1984; Case 1986).
37








Florida Springs Coast Ecological Characterization


atmosphere through which the solar rays must travel
to reach the Earth's surface at points north or south of
the orbital plane (Fig. 24); (3) the reduced density of
rays striking an area on Earth's surface north or south
of the orbital plane (Fig. 25); (4) the changes in cloud


Figure 24. Change in length of atmospheric light
path with change in distance above or below orbital
plane.







, "w. .. ", .. ,. v




E r %...
4. E^ r *? ^ *





Figure 25. Change in light intensity at Earth's
surface with change in distance above or below
orbital plane.


cover associated with the progression of the seasons;
and (5) seasonally induced changes in atmospheric
clarity due to particulates. Factors 2 and 3 are caused
by Earth's axial tilt relative to the orbital plane and
the resultant change in the angle at which solar rays
strike a point on the globe during Earth's year-long
trip around the sun. This change alters the distance
through the atmosphere that the rays must travel and,
therefore, changes the percentage of the rays reflect-
ed or absorbed by the atmosphere. Factors 4 and 5
are products of seasonal variations in insolation upon
circulation of air masses, hence the effects from
insolation affect the amount of it reaching the Earth's
surface. The concentration of screening particulates
in the atmosphere is further affected by seasonal
variations in emissions resulting from human activi-
ties (e.g., smoke from heating during winter) and by
the variations in the speed with which both natural
and anthropogenic particulates are removed by rain-
fall or diluted by atmospheric circulation.
b. Atmospheric screening. Absorption or reflec-
tion by water vapor, clouds, and atmospheric particu-
lates such as dust and smoke effectively reduce the
solar radiation penetrating to the Earth's surface. On
a clear day approximately 80% of the solar radiation
entering the atmosphere reaches the Earth's surface.
About 6% is lost because of scattering and reflection
and another 14% from absorption by atmospheric
molecules and dust. During cloudy weather, another
30%-60% may reflect off the upper surface of the
clouds and 5%-20% may be removed by absorption
within the clouds. This means that from 0 to 45%
may reach Earth's surface (Strahlcr 1975). Thus it is
clear that the single largest factor controlling short
term insolation is cloud cover.
The percentage of cloud cover, as well as its
patterns, varies seasonally (Fig. 26). The seasonal
patterns of cloudiness are controlled primarily by
extratropical cyclones and fronts in the winter, and by
localized convective weather patterns in the summer.
The types of clouds and rainfall patterns are different
under each of these systems. Daily cloud cover varia-
tions are considerably greater in summer than in
winter. That is, in summer many days have partial
cloud cover, while in winter the days tend to be







3. Climate


80

60

40

20

0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Figure 26. Mean daytime sky cover at Lakeland
(data from U.S. Dept. of Commerce 1980c).


entirely overcast or entirely clear. In the Springs
Coast and increasingly as one progresses into south
Florida, where winter cyclones and fronts are less fre-
quent, the amounts of cloud cover differ greatly in
winter and summer.
The maximum insolation striking Earth's atmo-
sphere at the latitude of Springs Coast Florida is
approximately 925 langleys/day (Strahler 1975).
Figure 27 shows the seasonal variation of the daily
insolation striking the atmosphere over the Springs
Coast region. The monthly average of the daily inso-
lation amounts actually received at several sites in the
Springs Coast are presented in Fig. 28. In addition,
the percent of possible sunshine measured at several
sites in the Springs Coast is presented in Fig. 29.
Atmospheric clarity over the Springs Coast is,
with the exception of clouds, generally very good.
Occasional atmospheric inversions during summer
months may result in "haze" as natural and anthropo-
genic aerosols are trapped near the surface and
concentrated, thereby reducing insolation.

3.2.5 Relative Humidity
The Florida Springs Coast is an area of high rela-
tive humidity. Relative humidity is the amount of
water vapor in the air, expressed as a percent of satu-
ration at any given temperature. Air incapable of
holding further water vapor (saturated) has a relative
humidity of 100%. The amount of water necessary to
saturate a volume of air depends upon temperature.


Air at a higher temperature is capable of holding
more water than that at a lower temperature; there-
fore, air near saturation will become oversaturated if
cooled. This oversaturation can produce dew, pre-
cipitation, or, when very near saturation, clouds or
fog. In the seasons when prevailing winds bring
moist air from the Gulf of Mexico (i.e., spring,
summer, fall), humidity is often 85%--95% during the
night and early morning, and 50%-65% during the
day (Bradley 1972).
High relative humidity can greatly accentuate the
discomfort of high summer temperatures. There are
several formulas commonly in use (e.g., Temperature
Humidity Index, Humidity Stress Index, Humiture)
that generate a "comfort" value based upon a combi-
nation of temperature and humidity. The afternoon
Springs Coast climate during June through Septem-
ber is usually well into the uncomfortable zone.
These indices are based on the effect of humidity
upon evaporation rates. The humid air flowing from
the Gulf of Mexico has minimal capacity to hold
further moisture. As a result, evaporative drying of
wetlands and other water bodies in the Springs Coast
is minimized, helping to maintain them between
rains. Summer rains and slow evaporation also
provide ideal conditions for many fungal and bacte-
rial diseases, prominent problems in area farming
(Shokes et al. 1982).
Fog is common at night and in the early morning
hours as the ability of the cooling air to hold water
decreases and the relative humidity rises over 100%.
Heavy fogs (visibility < 0.4 km) generally form in the
late fall, winter, and early spring. On the average,
they occur 35-40 days per year (Bradley 1972).
Little data on Springs Coast fog frequencies is avail-
able, but Tampa, just south of the Springs Coast,
experiences heavy fog on an average of 14% of days
in November through March, and 2% of the days
from April through October (Jordan 1973). Fogs
usually dissipate soon after sunrise.

3.3 Effects of Climate on Ecosystems

Climate influences the regional ecology through
two major mechanisms. The normal climate of the







3. Climate


80

60

40

20

0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Figure 26. Mean daytime sky cover at Lakeland
(data from U.S. Dept. of Commerce 1980c).


entirely overcast or entirely clear. In the Springs
Coast and increasingly as one progresses into south
Florida, where winter cyclones and fronts are less fre-
quent, the amounts of cloud cover differ greatly in
winter and summer.
The maximum insolation striking Earth's atmo-
sphere at the latitude of Springs Coast Florida is
approximately 925 langleys/day (Strahler 1975).
Figure 27 shows the seasonal variation of the daily
insolation striking the atmosphere over the Springs
Coast region. The monthly average of the daily inso-
lation amounts actually received at several sites in the
Springs Coast are presented in Fig. 28. In addition,
the percent of possible sunshine measured at several
sites in the Springs Coast is presented in Fig. 29.
Atmospheric clarity over the Springs Coast is,
with the exception of clouds, generally very good.
Occasional atmospheric inversions during summer
months may result in "haze" as natural and anthropo-
genic aerosols are trapped near the surface and
concentrated, thereby reducing insolation.

3.2.5 Relative Humidity
The Florida Springs Coast is an area of high rela-
tive humidity. Relative humidity is the amount of
water vapor in the air, expressed as a percent of satu-
ration at any given temperature. Air incapable of
holding further water vapor (saturated) has a relative
humidity of 100%. The amount of water necessary to
saturate a volume of air depends upon temperature.


Air at a higher temperature is capable of holding
more water than that at a lower temperature; there-
fore, air near saturation will become oversaturated if
cooled. This oversaturation can produce dew, pre-
cipitation, or, when very near saturation, clouds or
fog. In the seasons when prevailing winds bring
moist air from the Gulf of Mexico (i.e., spring,
summer, fall), humidity is often 85%--95% during the
night and early morning, and 50%-65% during the
day (Bradley 1972).
High relative humidity can greatly accentuate the
discomfort of high summer temperatures. There are
several formulas commonly in use (e.g., Temperature
Humidity Index, Humidity Stress Index, Humiture)
that generate a "comfort" value based upon a combi-
nation of temperature and humidity. The afternoon
Springs Coast climate during June through Septem-
ber is usually well into the uncomfortable zone.
These indices are based on the effect of humidity
upon evaporation rates. The humid air flowing from
the Gulf of Mexico has minimal capacity to hold
further moisture. As a result, evaporative drying of
wetlands and other water bodies in the Springs Coast
is minimized, helping to maintain them between
rains. Summer rains and slow evaporation also
provide ideal conditions for many fungal and bacte-
rial diseases, prominent problems in area farming
(Shokes et al. 1982).
Fog is common at night and in the early morning
hours as the ability of the cooling air to hold water
decreases and the relative humidity rises over 100%.
Heavy fogs (visibility < 0.4 km) generally form in the
late fall, winter, and early spring. On the average,
they occur 35-40 days per year (Bradley 1972).
Little data on Springs Coast fog frequencies is avail-
able, but Tampa, just south of the Springs Coast,
experiences heavy fog on an average of 14% of days
in November through March, and 2% of the days
from April through October (Jordan 1973). Fogs
usually dissipate soon after sunrise.

3.3 Effects of Climate on Ecosystems

Climate influences the regional ecology through
two major mechanisms. The normal climate of the









Florida Springs Coast Ecological Characterization


1100


spring
equinox


summer
solstice


winter
solstice


Figure 27. Variations in insolation striking the atmosphere, depending on latitude and season (after Strahler
1975).


Springs Coast establishes the basic conditions under
which all species must be able to live and compete if
they are to find a niche in the ecosystem. The occa-
sional abnormal or extreme climatic condition may
prevent establishment of a species that would other-
wise thrive by producing periodic local extinctions or
near-extinctions. The rarely-occurring severe or
prolonged freeze, heat wave, drought, or flood may
decimate a population so that years or decades are
required for its reestablishment.


No clear separation exists between conditions
constituting normal and extreme climatic conditions.
Regular events which are beyond a species' ability to
adapt may reduce what would otherwise be a domi-
nant organism to a minor position in the ecosystem or
prevent its establishment altogether. An example is
the mangrove. A dominant coastal species on the
southwest Florida coast, mangroves become increas-
ingly scarce as one progresses north along the
Springs Coast coast and are nearly nonexistent north








3. Climate


i 600 Lakeland
E 600 .. -.................... t......... .] Ta pa ..
o Tampa

cc 400, -- -- I I .. ..

.2 200
-l ,
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan

Figure 28. Monthly insolation at selected sites near
the Florida Springs Coast (data from Bradley 1972).



of Cedar Key. In conditions otherwise conducive to
mangrove growth, the occasional cold winters limit
their northward expansion. In contrast, an otherwise
minor organism may be dominant through its ability
to survive the climatic extreme and thereby out-
compete ecological rivals. Relatively small changes
in the "normal" extremes of climate may produce ef-
fects on ecosystem composition as large as those pro-
duced by changes in the average climate. An
example might be a situation where a slow-growing
and reproducing shrub species and a fast-growing
and reproducing shrub species compete for space in a
forest clearing commonly visited by foraging wild
pigs. All other factors being equal, the slow-growing
species might dominate, even though it would be
very slow to recolonize areas where it was dug up by


40
o













1980c).
20 20


Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan

Figure 29. Percent of possible sunshine at Lakeland
(nearest site to Springs Coast for which such data is
available) (data from U.S. Dept. of Commerce
1980c).


the pigs, because it could better tolerate the annual
dry summers. An increase in the normal summer
rainfall (a change in the "average climate") might
lead to dominance of the fast-growing species. The
same effect might result, however, if the area began
to experience previously unknown hard freezes
during occasional winters (a change in the climatic
extremes), and the slow-growing species was killed
by freezes while the fast-growing species was freeze
tolerant. Either change will have the greatest effect
upon those organisms living near their limits of toler-
ance.


3.4 Major Influences on Climate


3.4.1 Natural Influences on Climate
a. Long-term influences. Long-term changes
(over thousands to millions of years) in worldwide
climate are primarily a function of changes in the
concentration of atmospheric carbon dioxide (CO2)
(Revelle 1982). Carbon dioxide traps incoming solar
radiation (Hansen et al. 1981). This effect is
commonly known as the "greenhouse effect." The
resulting temperature increase allows the atmosphere
to hold more water vapor, itself an effective green-
house gas, which accentuates the warming. Other
gases (e.g., methane, nitrous oxide, chlorofluorocar-
bons) act similarly, but their effects are generally
subordinate to those of CO2 because of their rela-
tively low concentrations. The Sun "drives" Earth's
climate, since the wind and rain systems, as well as
the temperature regime, are products of varyinginso-
lation.
b. Short-term influences. Short-term (up to hun-
dreds of years) natural fluctuations in climate are
generally caused by changes in insolation screening.
The concentration of natural atmospheric particles
results from the balance between input from wind
scouring (particularly of desert and other arid
regions), volcanic dust output, smoke from forest
fires and volcanoes, and removal by gravitational
settling and atmospheric scrubbing during rainfall.
The Springs Coast, along with the rest of the
northern temperate lands, has experienced an








3. Climate


i 600 Lakeland
E 600 .. -.................... t......... .] Ta pa ..
o Tampa

cc 400, -- -- I I .. ..

.2 200
-l ,
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan

Figure 28. Monthly insolation at selected sites near
the Florida Springs Coast (data from Bradley 1972).



of Cedar Key. In conditions otherwise conducive to
mangrove growth, the occasional cold winters limit
their northward expansion. In contrast, an otherwise
minor organism may be dominant through its ability
to survive the climatic extreme and thereby out-
compete ecological rivals. Relatively small changes
in the "normal" extremes of climate may produce ef-
fects on ecosystem composition as large as those pro-
duced by changes in the average climate. An
example might be a situation where a slow-growing
and reproducing shrub species and a fast-growing
and reproducing shrub species compete for space in a
forest clearing commonly visited by foraging wild
pigs. All other factors being equal, the slow-growing
species might dominate, even though it would be
very slow to recolonize areas where it was dug up by


40
o













1980c).
20 20


Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan

Figure 29. Percent of possible sunshine at Lakeland
(nearest site to Springs Coast for which such data is
available) (data from U.S. Dept. of Commerce
1980c).


the pigs, because it could better tolerate the annual
dry summers. An increase in the normal summer
rainfall (a change in the "average climate") might
lead to dominance of the fast-growing species. The
same effect might result, however, if the area began
to experience previously unknown hard freezes
during occasional winters (a change in the climatic
extremes), and the slow-growing species was killed
by freezes while the fast-growing species was freeze
tolerant. Either change will have the greatest effect
upon those organisms living near their limits of toler-
ance.


3.4 Major Influences on Climate


3.4.1 Natural Influences on Climate
a. Long-term influences. Long-term changes
(over thousands to millions of years) in worldwide
climate are primarily a function of changes in the
concentration of atmospheric carbon dioxide (CO2)
(Revelle 1982). Carbon dioxide traps incoming solar
radiation (Hansen et al. 1981). This effect is
commonly known as the "greenhouse effect." The
resulting temperature increase allows the atmosphere
to hold more water vapor, itself an effective green-
house gas, which accentuates the warming. Other
gases (e.g., methane, nitrous oxide, chlorofluorocar-
bons) act similarly, but their effects are generally
subordinate to those of CO2 because of their rela-
tively low concentrations. The Sun "drives" Earth's
climate, since the wind and rain systems, as well as
the temperature regime, are products of varyinginso-
lation.
b. Short-term influences. Short-term (up to hun-
dreds of years) natural fluctuations in climate are
generally caused by changes in insolation screening.
The concentration of natural atmospheric particles
results from the balance between input from wind
scouring (particularly of desert and other arid
regions), volcanic dust output, smoke from forest
fires and volcanoes, and removal by gravitational
settling and atmospheric scrubbing during rainfall.
The Springs Coast, along with the rest of the
northern temperate lands, has experienced an








Florida Springs Coast Ecological Characterization


approximately 0.1 C reduction in average tempera-
ture over the last decade despite an increasing green-
house effect worldwide. It is probable that this is the
result of (1) the screening of insolation at these
latitudes by increased atmospheric smoke and dust
from recent increased volcanic activity and/or dust
from the expanding Sahara desert and drought areas
in North Africa, and /or (2) variation in the Sun's
output (Hoffman et al. 1983). These variations are
historically common and Titus and Barth (1984)
concluded that they were incapable of overwhelming
the overall greenhouse effect.
Periodic changes in climate and weather affecting
the Springs Coast and elsewhere have recently been
tied to the phenomenon known as El Niflo. Though
all the parameters of cause and effect are not yet
understood, a major current off the coast of Peru,
which drives the upwelling responsible for one of the
world's largest fisheries, apparently moves well
offshore and weakens because of changes in the wind
patterns driving it. Changes in equatorial wind
patterns that either cause the shift in water currents or
are caused by the shift (which factors are cause and
which are effect are not yet understood) affect world-
wide climate by altering patterns of rain, temperature,
and wind. The Springs Coast may have just recov-
ered from a period of weather in the early 1980's
influenced by an exceptionally strong El Nifio. The
hotter and drier summers and warmer winters
followed by a rebound period of spring flooding,
heavy summer rainfall, and colder winters that have
been experienced in the Springs Coast, and other
unusual weather patterns worldwide have been tenta-
tively identified as indirect effects of El Nifio.
Another mechanism controlling short-term
climate changes as well as being involved in long-
term variations is albedo, or the reflectance of a
surface. The higher the albedo, the more incoming
radiation is reflected and can pass through the "green-
house" gases and out of the atmosphere. The lower
the albedo, the more radiation is absorbed, reradiated
as heat and trapped in the atmosphere. Snow and ice
have a very high albedo; i.e., they are efficient reflec-
tors of solar energy (45%-85%). Bare ground, fields,
and forests have intermediate albedos ranging from


3%/-25%. Unlike land, the oceans (and water in gen-
eral) have a variable albedo;-very low (2%) for
radiation striking from low angles of incidence (i.e.,
with the sun high in the sky), but high for that striking
from high angles (i.e., with the sun low on the hori-
zon). This is caused by the growing proportion of the
light that is transmitted into the water at decreasing
angles of incidence. Thus, the equatorial seas at
midday are good absorbers of solar energy, but the
arctic seas are not. The significance of this in the
Springs Coast is that coastal waters are heated more
through insolation in summer, not only because of
the increase in sunlit hours from the longer day, but
also from an even greater increase of the time the
radiation strikes from high angles. Other local effects
of albcdo differences are common, as anyone who
has stood on an asphalt parking lot on a clear summer
day can attest.
Another difference between the effects of insola-
tion on land and water is caused by the difference in
the specific heat of dry soil or rock and that of water.
Water requires nearly five times as much heat energy
as rock to raise its temperature the same amount.
This, coupled with the increased evaporative cooling
found at the surface of water bodies, explains the
more extreme diurnal and seasonal temperature
regimens found over land as compared to that over or
near large bodies of water.

3.4.2 Anthropogenic Influences
Human activities increasingly influence climate,
although the line dividing natural and anthropogenic
influences is not always clear. Global warming due
to changes in the atmospheric greenhouse effect is
one of the most notable results of human activities
(Hansen et al. 1981; Weiss et al. 1981; Broecker and
Peng 1982; Edmonds and Reilly 1982). This change
is primarily a result of increasing concentrations of
atmospheric carbon dioxide from combustion of
fossil fuels, as well as from the logging of enormous
areas of forest, with the resultant release of CO2
through the burning or decomposition of the carbon
bound up in the organic matter (Chamey 1979); of
atmospheric methane (Rasmussen and Khalil
1981a,b; Kerr 1984); of atmospheric nitrous oxides







3. Climate


(Donner and Ramanathan 1980); and of chlorofluo-
rocarbons (Ramanathan 1975). There was a 9%
increase in atmospheric carbon dioxide between
1958 and 1985 (Fig. 30).
A conference was held in 1982 in response to
articles in popular literature (Boyle and Mechum
1982) concerning a theory ascribing recently reduced
rainfall and increased temperature in south Florida to
reduced albedo and evapotranspiration resulting from
the draining of area wetlands. The results of this
conference are summarized in Gannon (1982).
Though evapotranspiration from land masses may
account for only 5% of the precipitation in south
Florida (the bulk arriving with air masses off the
Atlantic), evapotranspiration increases the buoyancy
of the continental air masses. This probably in-
creases mass convergence, bringing in more moisture
from the adjacent oceans, thereby acting as a trigger
to increase convection and convection-induced rains.
Rainfall of this nature is found year round but is espe-
cially common in the summer. A 70-inch rainfall



350-
I300-------------
300


8340 .. 8 200 -------
Q
0 0 ---------------
S100 -------- --

00
0 330 58 62 66 70 74 78 82



S320




310
1958 1962 1966 19


deficit that accumulated between 1962 and 1982
along the St. Johns River in northeast Florida has also
been attributed to the draining by 1972 of approxi-
mately 72% of the once-vast wetlands through which
the river flowed (Barada 1982). If this relationship
between evapotranspiration and rainfall is confirmed,
a similar mechanism probably exists in the Springs
Coast, where similar pattems of convective rainfall
are found. Future development that reduces wetland
and vegetated areas might induce similar reductions
in summer rainfall.
Short-term cooling trends have been attributed to
insolation screening by dust, smoke, and debris
thrown into the upper atmosphere by large volcanic
eruptions such as Krakatoa in 1883 (Humphries
1940) and Mount St. Helens in 1980 (Searc and Kelly
1980). Smaller eruptions have a weaker cooling
effect. It is thought that this short-term cooling may
be partially masking the long-term global warming
caused by increasing concentrations of atmospheric
CO2 (Bell 1980).


)70 1974 1978 1982


Figure 30. Increasing atmospheric carbon dioxide as measured atop Mauna Loa, Hawaii (data from Charles
Keeling, Scripps Inst. of Oceanography).







Florida Springs Coast Ecological Characterization


3.5 Summary of Climatic Concerns

The Florida Springs Coast has three present and
near-future climatological concerns. Two of these
result from the present global warming trend. While
all effects of this warming are not predictable with
our present understanding of the ecosystem, certain
effects in the Springs Coast are probable. A major
impact resulting from global wanning is a predicted
substantial rise in sea level, significant effects of
which are expected within 25 years. This impact is
discussed more fully in section 4.8. The second
concern relating to atmospheric warming is a prob-
able change in weather patterns. A possible 5 F
increase in the mean global temperature by the latter
part of the next century is projected to yield a similar
increase in mean Springs Coast temperature and a
few percent increase in local precipitation (Revelle
1982; National Research Council 1983). The present
understanding of meteorology is not, however, suffi-
cient to permit reliable prediction of these changes.
This is particularly true of climate changes over a
relatively small area the size of the Springs Coast.
A final climatic concern for the future is the possi-
bility of reduced summer convectivee) rainfall.
Unlike the previous two problems, the causes have
not yet been widely initiated and are preventable.
Convective summer thundershowers provide the
majority of summer rainfall, which, in turn, supplies
the majority of the total annual rainfall (Fig. 15). The
convective mechanism causing these rains is similar
to that found in south and east Florida. Since the
"rain machine" in these regions may have been
weakened by extensive wetland draining, it is
possible that future terrain alteration in the Springs
Coast-including drainage and development of large
wetland areas-could cause a similar effect.


Predicting the occurrence and effect of climate
changes is very difficult, since the understanding of
the meteorological and oceanographic systems that
provide climatic feedback and checks and balances is
incomplete. With these constraints, even the sea-
level predictions, which are based on an intensive
program of study, include necessarily wide margins
for error. Unexpected or unexpectedly strong
feedback mechanisms may exist to damp the
warming trend. One possible example of such feed-
back is that the increase in size taking place in our
deserts (especially the Sahara) may be a result of
global warming; however, the increased dust blown
into the atmosphere from the larger desert area may
be increasing insolation screening and therefore
tending to reduce that warming. The possible
existence and "strength" of similar feedback mecha-
nisms make accurate prediction of future climate
difficult, although the National Academy of Sciences
(Chamey 1979) was unable to find any overlooked
physical effect that could reduce the estimated
temperature increase to negligible proportions. The
accuracy of the predictions is increasing through
research into the major climatic factors.


3.6 Areas Needing Research

Research on numerous aspects of the Springs
Coast climate is needed concerning questions which,
of course, affect much wider areas, but are applicable
to this area, especially the changing greenhouse
effect; the effects of increasing world-wide average
temperatures on area climate; the mechanisms
controlling coastal convective rainfall; and rates of
evapotranspiration and their connection to rainfall
and runoff.







Florida Springs Coast Ecological Characterization


3.5 Summary of Climatic Concerns

The Florida Springs Coast has three present and
near-future climatological concerns. Two of these
result from the present global warming trend. While
all effects of this warming are not predictable with
our present understanding of the ecosystem, certain
effects in the Springs Coast are probable. A major
impact resulting from global wanning is a predicted
substantial rise in sea level, significant effects of
which are expected within 25 years. This impact is
discussed more fully in section 4.8. The second
concern relating to atmospheric warming is a prob-
able change in weather patterns. A possible 5 F
increase in the mean global temperature by the latter
part of the next century is projected to yield a similar
increase in mean Springs Coast temperature and a
few percent increase in local precipitation (Revelle
1982; National Research Council 1983). The present
understanding of meteorology is not, however, suffi-
cient to permit reliable prediction of these changes.
This is particularly true of climate changes over a
relatively small area the size of the Springs Coast.
A final climatic concern for the future is the possi-
bility of reduced summer convectivee) rainfall.
Unlike the previous two problems, the causes have
not yet been widely initiated and are preventable.
Convective summer thundershowers provide the
majority of summer rainfall, which, in turn, supplies
the majority of the total annual rainfall (Fig. 15). The
convective mechanism causing these rains is similar
to that found in south and east Florida. Since the
"rain machine" in these regions may have been
weakened by extensive wetland draining, it is
possible that future terrain alteration in the Springs
Coast-including drainage and development of large
wetland areas-could cause a similar effect.


Predicting the occurrence and effect of climate
changes is very difficult, since the understanding of
the meteorological and oceanographic systems that
provide climatic feedback and checks and balances is
incomplete. With these constraints, even the sea-
level predictions, which are based on an intensive
program of study, include necessarily wide margins
for error. Unexpected or unexpectedly strong
feedback mechanisms may exist to damp the
warming trend. One possible example of such feed-
back is that the increase in size taking place in our
deserts (especially the Sahara) may be a result of
global warming; however, the increased dust blown
into the atmosphere from the larger desert area may
be increasing insolation screening and therefore
tending to reduce that warming. The possible
existence and "strength" of similar feedback mecha-
nisms make accurate prediction of future climate
difficult, although the National Academy of Sciences
(Chamey 1979) was unable to find any overlooked
physical effect that could reduce the estimated
temperature increase to negligible proportions. The
accuracy of the predictions is increasing through
research into the major climatic factors.


3.6 Areas Needing Research

Research on numerous aspects of the Springs
Coast climate is needed concerning questions which,
of course, affect much wider areas, but are applicable
to this area, especially the changing greenhouse
effect; the effects of increasing world-wide average
temperatures on area climate; the mechanisms
controlling coastal convective rainfall; and rates of
evapotranspiration and their connection to rainfall
and runoff.















Chapter 4. HYDROLOGY AND WATER QUALITY
by Steven H. Wolfe


Water quality is, in many ways, dependent on
hydrology, and often the forces affecting one also
affect the other. This chapter will discuss each of
these areas, their interrelationships, and their status in
the Florida Springs Coast. Excellent sources of infor-
mation on the water resources of the Springs Coast
are Rivers of Florida (Livingston 1991) and Water
Resources Atlas of Florida (Femald and Patton
1984). The Hydrologic Almanac of Florida (Heath
and Conover 1981) has very good discussions of
different hydrologic and water quality factors as well
as containing good, if occasionally dated, records on
Florida.
The Springs Coast surface-water and ground-
water supplies are normally inseparable. In many
places water flows from the surface into the ground
and back again many times as it makes its way to the
coast. Any changes in the hydrology or the quality of
one is likely to affect the other. The entire supply of
potable ground water in Florida floats on deeper
layers of saline ground water that are connected with
the Atlantic Ocean and the Gulf of Mexico. This
layer of freshwater floats because it is ~2.5% less
dense than the salt water. As water is removed from
the freshwater aquifer, the pressure of the underlying
salt water tends to push the salt/freshwater interface
higher, while nearly maintaining the level of the
upper surface of the freshwater aquifer. As a result,
"permanently" lowering the upper surface of the
freshwater aquifer by 1 ft over a broad area requires
withdrawing a volume of water equal to nearly 40 ft
of the aquifer thickness (1 ft = 2.5% of 40 ft). Thus,
simplistically, every foot by which our pumping of
the freshwater aquifers lowers the upper surface and
which is not replaced in a reasonable period of time


by rainwater, results in a 40-ft rise in the deeper
saline layers. The Florida Springs Coast, and all of
Florida, has tremendous volumes of freshwater
stored beneath the ground; however, it cannot be used
at a rate greater than the average rate at which it is
replaced by rainfall. Otherwise, salt-water intrusion
will render the coastal wells useless because the
underlying saline layer is much closer to the surface
nearer the oceans.


4.1 Hydrology

Hydrology is the study of the water cycle, includ-
ing atmospheric, surface, and ground waters. The
basic hydrologic cycle (Fig. 31) includes water vapor
entering the atmosphere as a result of evaporation,
transpiration, and sublimation. This vapor condenses
to form fog, clouds, and, eventually, precipitation.
Along the Florida Springs Coast, precipitation
normally reaches the ground in the form of rain.
Snow and hail occur infrequently. Upon reaching the
ground, the water either evaporates, soaks into the
soil and thence into the groundwater system, or (if the
ground is saturated or the rate of rainfall exceeds the
ground's ability to absorb it) runs off or pools,
forming streams, rivers, lakes, and other wetlands.
The surface and ground water of Florida is divided
into two distinct areas delineated by a line crossing
the state along the northern edge of the Springs Coast
(Fig. 32). There is almost no net movement of
surface water or ground water across this line; rainfall
north of the line recharges the northern part of the
area, and that south of the line recharges the southern
portion. The southern region in particular needs to















Chapter 4. HYDROLOGY AND WATER QUALITY
by Steven H. Wolfe


Water quality is, in many ways, dependent on
hydrology, and often the forces affecting one also
affect the other. This chapter will discuss each of
these areas, their interrelationships, and their status in
the Florida Springs Coast. Excellent sources of infor-
mation on the water resources of the Springs Coast
are Rivers of Florida (Livingston 1991) and Water
Resources Atlas of Florida (Femald and Patton
1984). The Hydrologic Almanac of Florida (Heath
and Conover 1981) has very good discussions of
different hydrologic and water quality factors as well
as containing good, if occasionally dated, records on
Florida.
The Springs Coast surface-water and ground-
water supplies are normally inseparable. In many
places water flows from the surface into the ground
and back again many times as it makes its way to the
coast. Any changes in the hydrology or the quality of
one is likely to affect the other. The entire supply of
potable ground water in Florida floats on deeper
layers of saline ground water that are connected with
the Atlantic Ocean and the Gulf of Mexico. This
layer of freshwater floats because it is ~2.5% less
dense than the salt water. As water is removed from
the freshwater aquifer, the pressure of the underlying
salt water tends to push the salt/freshwater interface
higher, while nearly maintaining the level of the
upper surface of the freshwater aquifer. As a result,
"permanently" lowering the upper surface of the
freshwater aquifer by 1 ft over a broad area requires
withdrawing a volume of water equal to nearly 40 ft
of the aquifer thickness (1 ft = 2.5% of 40 ft). Thus,
simplistically, every foot by which our pumping of
the freshwater aquifers lowers the upper surface and
which is not replaced in a reasonable period of time


by rainwater, results in a 40-ft rise in the deeper
saline layers. The Florida Springs Coast, and all of
Florida, has tremendous volumes of freshwater
stored beneath the ground; however, it cannot be used
at a rate greater than the average rate at which it is
replaced by rainfall. Otherwise, salt-water intrusion
will render the coastal wells useless because the
underlying saline layer is much closer to the surface
nearer the oceans.


4.1 Hydrology

Hydrology is the study of the water cycle, includ-
ing atmospheric, surface, and ground waters. The
basic hydrologic cycle (Fig. 31) includes water vapor
entering the atmosphere as a result of evaporation,
transpiration, and sublimation. This vapor condenses
to form fog, clouds, and, eventually, precipitation.
Along the Florida Springs Coast, precipitation
normally reaches the ground in the form of rain.
Snow and hail occur infrequently. Upon reaching the
ground, the water either evaporates, soaks into the
soil and thence into the groundwater system, or (if the
ground is saturated or the rate of rainfall exceeds the
ground's ability to absorb it) runs off or pools,
forming streams, rivers, lakes, and other wetlands.
The surface and ground water of Florida is divided
into two distinct areas delineated by a line crossing
the state along the northern edge of the Springs Coast
(Fig. 32). There is almost no net movement of
surface water or ground water across this line; rainfall
north of the line recharges the northern part of the
area, and that south of the line recharges the southern
portion. The southern region in particular needs to











AXpl
tQ,
/"~ 5,-~i-~
/ *f


Figure 31. The basic hydrologic cycle.








4. Hydrology and Water Quality


0


Figure 32. The Florida hydrologic divide (after Heath
and Conover 1981).

manage its water budget based upon the rainfall it
receives since there is no potential for recharge of the
aquifers from ground-water supplies or rainfall to the
north.
The fundamental organizational unit of surface
hydrology is the drainage basin. In its most basic
form, a drainage basin, or watershed, consists of that
area which drains surface runoff to a given point.
Thus the mouth of a river has a drainage basin that
includes the basins of its tributaries. The drainage
areas discussed in this document are based upon the
basins described by the U.S. Geological Survey
(Conover and Leach 1975) (Fig. 33). Most of these
consist of the Florida portion of the drainage basin of
a single coastal river. Some, however, represent
coastal drainage areas where lands drain to coastal
streams and marshes on a broad front rather than to a
single discharge point.
Ground water in the Springs Coast is contained
primarily within the Floridan aquifer, which under-
lies the entire region. This aquifer is found in a char-
acteristic limestone matrix. A shallow surficial
aquifer contained in sand beds overlying the Floridan
may be found in much of the Springs Coast.
Additionally, small but usable quantities of water


exist in some areas within the clay and sandy clay
confining layer separating the aquifers; however,
except for rural areas with small requirements, these
are little utilized because of the larger volumes avail-
able in the Floridan.
Local areas of aquifers in the Springs Coast are
recharged by five means: (1) drainage of surface
runoff into areas where the aquifer is unconfined (i.e.,
not overlain with a low-permeability stratum) and
located at or near the ground surface; (2) drainage of
surface runoff into sinkholes and other natural
breaches into the aquifer, (3) percolation of rainfall
and surface water through the upper confining beds;
(4) percolation through the confining layers of water
from aquifers overlying or underlying the one in
question but with a greater potentiometric surface
("pressure"); and (5) lateral transport from areas
within the aquifer with a higher potentiometric
surface (Fig. 34). Areas within the Springs Coast
recharging the Floridan aquifer are presented in
Fig. 35.

4.2 Water Quality

The availability of water has always been an
important factor in selection of sites for human activi-
ties. The primary concern of the past-securing
needed quantities of water-has, in recent years,
increasingly been replaced by concerns about the
quality of that water. Water quality affects people
directly by influencing water's suitability for drink-
ing, cooking, bathing, and recreation, and indirectly
by its effect upon the ecosystem within which
humanity exists. Factors affecting water quality
include the physical makeup of the local ecosystem
(e.g., the presence of limestone generally prevents
acidic water), seasonal changes in that ecosystem,
direct discharges from human sources, and indirect
discharges from human sources (e.g., acid rain).
Society judges water quality based upon its useful-
ness to people and those animals and plants it values.
Since our society has come to recognize the value of
a healthy ecosystem, we try to measure this health in
addition to the physical and chemical water-quality
parameters. Increasingly, this is done by examining








Florida Springs Coast Ecological Characterization


840 r


DIXIE 7,


ALACHUA







MARION


2- ^ 4 C--__ -- -" ......
290


CITRUS r "L--,



USGS.
Basin I i
Number 07 SUMMER I LAKE
(207) Coastal area from Anclote River \
to Withlacoochee River ( HERN DO
(208) Withlacoochee River basin i
(101) Waccasassa River and coastal
area between Withlacoochee I
and Suwannee Rivers. ... f

PASCO

A-. POLK

SLAS HILLSBOR UGH ,

Figure 33. Major drainage basins and surface-water features of the Springs Coast region of Florida.








4. Hydrology and Water Quality


Units in feet above NGDV
(formerly called
mean sea level)


Figure 34. Potentiometric surface of the Floridan aquifer in the Springs Coast in May 1980 (after Healy 1982).








4. Hydrology and Water Quality


the number and diversity of the species and individu-
als present in the water body. Various indices have
been developed and used, including numerous
species-diversity indices and what are known as
biotic indices, which measure the presence of key
species judged to be indicators of high water quality.
Combinations of these indices aid in quantifying the
degree of ecological health, but results from any one
index must be viewed with caution. Each method,
because of the manner with which it weighs different
factors, generally has situations in which it gives a
poor representation of the actual conditions.
a. Direct importance. The first concerns about
water quality were directed toward the transmission
of disease through drinking water. Even this concern
is relatively new. The desirability of separating
human wastes from sources of water for drinking and
food preparation was not understood in western
civilizations until the mid-1800's, and this separation
was not effected on a wide scale until the early
1900's.
Until the early 1970's, drinking water was
routinely examined and treated primarily for disease
pathogens. Only recently has an awareness of the
health and environmental impacts of toxicants
become widespread. The majority of these sub-
stances are metals or synthetic organic compounds.
Metals from natural sources in sufficient concentra-
tions to cause problems are uncommon. Few of the
organic hydrocarbons contaminating waters occur
naturally. The vast majority of toxic substances
found in the planet's waters are anthropogenic,
products of modem industrialized society.
Efforts to locate, identify, and remove these
substances from our waters are greatly hindered by
their enormous number and variety, their difficult
detection, and the lack of knowledge concerning both
their short- and long-term effects. Some are toxic at
levels below which their concentrations can be
reliably measured. Increasing the problem of con-
trolling these hazards is the daily discovery or synthe-
sis of additional chemical compounds, many of
which are a potential threat to water supplies. In
addition to exposure through contaminated drinking
water, some of these substances are being found in


human foods following uptake by food plants or
animals.
A secondary problem is the need for water of
sufficiently high quality to meet industrial needs.
Though most industrial water uses are for cooling,
steam generation, material transportation, and similar
tasks not requiring potable water, preventing scale
buildup in steam and cooling equipment and using
water for product makeup and certain chemical
processes may require that specific aspects of the
water quality be high.
b. Indirect importance. The quality of water,
both the physical characteristics and the presence or
absence of toxic components, is a factor controlling
ecosystem constituents (e.g., productivity, species
diversity). Just as climate and water availability exert
control upon floral and faunal composition, so does
the quality of the available water. An area of poor
water quality may support little or no life or, alterna-
tively, populations of undesirable species.
Humanity is at the apex of a food-web pyramid
and is, therefore, dependent upon the soundness of
the base of that pyramid for existence. If pressed, we
may be capable of treating sufficient quantities of
contaminated water to supply humanity's direct
water needs; however, water of the quality necessary
to support all levels of the ecosystem must be avail-
able, otherwise the food-web pyramid may erode
from beneath us.


4.3 Hydrology and Water-Quality Regula-
tion and Management.

Though attempts are being made to treat drinking
waters for contaminants, the removal of contami-
nants from the natural surface waters to which people
are exposed during work or recreation is much more
difficult to manage. It is impractical to treat surface
waters to remove contaminants or alter physical
parameters; rather, contaminant removal and physi-
cal changes must be performed prior to discharge of
domestic or industrial effluents. To this end, State
and Federal regulations have been enacted in an
attempt to control effluent discharges into surface







Florida Springs Coast Ecological Characterization


waters. Under the Federal Clean Water Act, point-
source discharges into surface waters of the United
States are regulated by the National Pollutant
Discharge Elimination System (NPDES). Under this
system dischargers are given permits to discharge
effluents meeting certain standards based upon the
types of waste generated. The discharger is required
to monitor the effluents and report periodically. In
Florida, all NPDES permit applications and reports
are reviewed by the Florida Department of Environ-
mental Regulation (FDER). Under NPDES regula-
tions, effluents should meet State water quality
standards. The NPDES program, however, does not
regulate dischargers in such a way that cumulative
impacts are controlled. Hence, while a river may
have numerous discharges into it, each meeting wa-
ter-quality standards, the cumulative effect of all the
discharges upon the river may cause its water quality
to fail to meet standards. The NPDES program
primarily is aimed at conventional pollutants, includ-
ing bacteria, nutrients, and materials decreasing dis-
solved oxygen (DO) concentrations.
The responsibility for management of the water
resources on a regional level is held by two agencies
within the Springs Coast. The Southwest Florida
Water Management District (SWFWMD) is respon-
sible for the coastal drainage basins south of and in-
cluding the Withlacoochee River basin (there are two
Withlacoochee Rivers within the state of Florida; the
other one is in north central Florida and is a tributary
of the Suwannee River). The Suwannee River Water
Management District (SRWMD) is responsible for
the coastal drainage basins north of the Withla-
coochee River basin, including the "other" Withla-
coochee River which flows to the Suwannee River!
Surface waters have been monitored by the FDER
since 1973 using Permanent Network Stations
(PNS), though this monitoring network has been
substantially reduced in recent years. The responsi-
bility for management of regional water resources is
held by the Southwest Florida Water Management
District (SWFWMD). This responsibility includes
regulation of water consumption and long-range
planning to help ensure the continuing availability of
high quality water.


Waste-load allocation studies have been per-
formed by the FDER and, in earlier years, the U.S.
Geological Survey to attempt to determine the
amount of effluent discharges, including those of
sewage treatment plants and private sources, that can
be discharged into water bodies without degrading
them. It should be pointed out that present methods
of waste-load allocation rely primarily on models of
DO and nutrient concentrations, are aimed at alloca-
tion of nutrient loads from public and private sources
to maintain DO levels necessary for a healthy aquatic
system, and are therefore incapable of predicting or
allowing for effects from toxic discharges. The
FDER conducts a program of acute and chronic tox-
icity bioassay testing on selected private and munici-
pal effluent discharges that are recommended to
them. Results of the tests are available as reports
from the FDER Biology Section, Tallahassee.
Primarily because of cost considerations, most
data collected from the various monitoring networks
and stations is physical or chemical in nature. The
biological baseline studies and monitoring needed to
enable accurate determination of the overall "good-
ness" of the water quality of a particular water body
is generally lacking. Data limitations due to chang-
ing sampling methods and uncharacterized ambient
conditions have prevented long-term trend analysis in
these river basins (FDER 1986a). Lack of baseline
data in most instances and lack of continuing data
collection in many instances prevents accurate detec-
tion of changes in surface-water quality and hinders
interpretation of data gathered in short-term studies
and laboratory simulations performed to predict
effects on area ecology (e.g., chronic toxicity bioas-
says) (FDER 1985a; Livingston 1986).
Following the discovery in the early 1980's of the
toxic pesticides aldicarb (Temik) and ethylene
dibromide (EDB) in Florida ground waters, the
Florida Legislature passed the Water Quality Assur-
ance Act of 1983, which included steps to address the
ground-water contamination problem. One major
aspect of this act was the institution of a ground-
water quality monitoring network administered by
the FDER. This consists of a network of existing
wells plus new wells where existing ones were






Florida Springs Coast Ecological Characterization


The problem of the reduced oxygen capacity of
warm water is compounded by two factors: algal
respiration and biochemical oxygen demand (BOD).
"Fish kills" caused by low DO (which may include
many organisms other than fish) generally occur at
night or during periods of cloudy weather. The net
oxygen production by the algal population during
sunlit hours changes to a net oxygen consumption
during dark hours when algal photosynthesis ceases
but respiration by the algae and other sources
continues.
c. Oxygen uptake-Biochemical Oxygen De-
mand (BOD). Biochemical oxygen demand results
from microbial and chemical consumption of oxygen
during the degradation of organic compounds in the
water column and bottom sediments; it becomes a
problem when excessive organic wastes enter an
aquatic system. Oxygen uptake from high BOD can
reduce DO levels to near zero. Even relatively low
levels of BOD can contribute significantly towards
low DO levels and resulting problems if that BOD
combines with floral and faunal respiration and
temperature-salinity interactions. As a result, fish
and invertebrate kills from low DO are not uncom-
mon, especially during summer months. Most of the
oxygen dissolved in water results from gas exchange
with the atmosphere except during periods of heavy
algal growth. The rate at which a water body absorbs
oxygen from the atmosphere is influenced by its
circulation. If the oxygen must diffuse through the
entire water column to reoxygenate depleted bottom
waters (i.e., the water body is stagnant) then this rate
is very slow. Bottom waters in canals and other
enclosed water bodies, particularly those with a high
ratio of depth to width and having organic bottom
sediments, are especially vulnerable to oxygen deple-
tion. If the depleted waters are circulated to the
surface, the rate of oxygen uptake from the atmo-
sphere is greatly enhanced and pockets of anaerobic
water are less likely to develop.

4.4.2 pH
The concentration of hydrogen ions in water is
measured in pH units. Waters of low pH (<7) are
acidic, those with pH = 7 are neutral,and those with


high pH (>7) are basic. The pH scale is inverse (in
terms of H+ ions) and logarithmic; hence water of
pH 6 has 100 times as many H+ ions as does that of
pH 8. The pH of water is important biologically and
chemically. Below a pH of approximately 6, harm-
ful biological effects may be felt, especially in sensi-
tive life stages such as eggs. Below a pH of about 4,
only a few specialized species can survive.
The biological effects of low pH are strongly
linked to other factors, particularly the nonhydrogen
ionic content of the water, since pH exerts a strong
effect on the form of many of the other contents in the
water. Ammonia, for instance, is found in the form
of ionized ammonia (NH4) and un-ionized ammonia
(NH3). The ionized form in which most ammonia is
found in acidic waters is several orders of magnitude
less toxic than the un-ionized form found in basic
water. This is the reverse of the general rule of thumb
that the ionic forms of substances (which often form
in low pH waters) tend to be more toxic (Cairns et al.
1975).
Biologically, most of the direct effects of low pH
upon aquatic fauna appear to be related to problems
with disruption of osmoregulation (regulating blood
and tissue fluids) and control of the ionic balance of
blood and vascular fluids (Leivestad et al. 1976,1980;
McWilliams and Potts 1978). The pH of blood (as
well as plant vascular fluids) exerts strong effects on
the ionic speciation of its components (that is, the
form in which the ion is found-for example, CO2
may be found in solution as CO2 gas, carbonic acid,
carbonate, and/or bicarbonate, depending upon
several factors, the major one being pH). Since pH
exerts strong effects on metabolic chemistry, blood
and vascular pH must be maintained within relatively
narrow ranges. The blood of aquatic fauna is typi-
cally separated from the surrounding water by a thin
semipermeable cell wall in their gills. Species or life
stages that have a high ratio of gill (or in the case of
eggs, chorion) surface area to body volume generally
have the most difficulty compensating for ambient
pH outside the nominal range for their blood chemis-
try (Lee and Gerking 1980).
In the Florida Springs Coast, surface waters of low
pH are generally found in swamps and swamp








4. Hydrology and Water Quality


as bicarbonate) and sulfate. These components are
generally the result of the dissolution of the limestone
matrix with which the water has been in contact. The
ready solubility of limestone and the frequent input of
ground water (which has generally had significant
contact with limestone) to the surface waters tends to
result in Springs Coast surface waters of at least
moderate alkalinity.
As mentioned in the discussion of pH, alkalinity in
Springs Coast water is very highly correlated to pH.
The various forms of carbonate found in the waters
are by far the predominant pH-buffering agent;
sulfate and other buffering ions are substantially less
common (Kaufman 1975a,b; Shampine 1975a).
Since the alkalinity of Springs Coast waters is
overwhelmingly a function of the carbonate concen-
trations, many studies (particularly of ground water)
do not measure alkalinity as such, but rather record
bicarbonate concentrations. In surface waters, total
alkalinity is more commonly measured because of
the increased likelihood that they may contain addi-
tional buffering ions caused by surface drainage and
input of human effluents. Alkalinity is not a water-
quality factor of importance in marine waters
because, though high, it is constant.
b. Hardness. The hardness of water, like the alka-
linity, is generally of concern in freshwater only.
Hardness is a measure of the cation (positive ion)
content of water. In the Springs Coast the major
freshwater cation is Ca++, with Mg++ a distant
second. Since calcium carbonate (limestone)
supplies most of the dissolved ions in surface and
ground waters, total dissolved solids, alkalinity, and
hardness are often highly correlated. The hardness of
natural Springs Coast waters can be reliably esti-
mated from the total dissolved-solid values (Fig. 39).
Hardness is usually reported as equivalent concentra-
tions of calcium carbonate (e.g., 120 mg/L as
CaCO3). High levels of hardness (> approximately
2,000 mg/L) are unpalatable but not generally harm-
ful, except for a laxative effect in first-time users
(Shampine 1975c). One aspect of hardness that is of
interest is its relationship to soap and detergent usage.
Soap combines with and precipitates hardness ions
until they are removed. Only then do lathering and


cleansing occur. Harder water, therefore, requires
use of more soap than does soft water. Hard water
also increases the rate of lime formation within
plumbing and heating equipment and, where high,
may necessitate the use of chemical softening tech-
niques to minimize maintenance.
c. Salinity. Salinity is the concentration of"salts"
dissolved in water. This term is generally used to
describe estuarine and marine waters, though very
low concentrations of salts are present in freshwaters.
Sodium (Na+) and chloride (C1-) ions provide about
86% of the measured salinity; magnesium (Mg+)
and sulfate (SO4=) account for another 11%, with the
remaining 3% consisting of various minor salts
(Quinby-Hunt and Turekian 1983). Technically, the
measurement of salinity has been defined based upon
the chlorinity, or chloride (C1-) content of seawater.
This was done because of the ease and accuracy with
which Cl- concentrations can be measured, and
because the proportions of all the different salts
present in seawater are very constant. The total
concentrations of these salts are approximately 103 to
104 times those found in freshwaters. As a result, the
chemistry of the freshwater flowing into an estuary
does not significantly affect the proportions of the
salts in the estuarine waters.
Salinity is a factor in water quality since salinity
tolerance can limit the species found in a given salin-
ity regime. Additionally, sudden or large changes in
salinity can be stressful or fatal to the biota. The
salinity tolerances of aquatic biota separate them into
three main groupings: freshwater (salinities below
0.5 ppt), estuarine (0.5 to 30 ppt), and marine (greater
than 30 ppt) (Cowardin et al. 1979).
In general, the freshwater and marine species have
narrow salinity tolerances, while estuarine species are
characterized by their tolerance to changing environ-
mental conditions, including salinity. Estuaries,
where fresh river waters mix with saltwater, regularly
present rapidly changing salinity conditions. As a
result, this habitat has lower species diversity than
more stable ones, although this does not imply fewer
individuals. Despite the harsh physical regime, abun-
dant dissolved nutrients promote high primary
productivity that can support a large number of








Florida Springs Coast Ecological Characterization


individuals of tolerant species. Separation of popula-
tions based on salinity tolerance applies equally to
coastal wetlands.
The salinity of Springs Coast coastal and estuarine
waters is extremely variable. These waters function
as a mixing zone for freshwater runoff from surface
and ground waters (0 salinity) and the offshore
marine waters (35 ppt). In general, estuarine salini-
ties range from near 0 throughout the estuary during
high river stages, to near 30 ppt within the estuary
(but away from the river mouth) during periods of
low river discharge. The coastal waters between the
estuaries often receive some freshwater runoff during
rainy periods; however, the salinity regime is much
more stable than that of the estuaries, and diumal
salinity changes are minimal or nonexistent.
d. Nutrients. The nutrient content of water affects
water quality primarily when high concentrations
promote excessive growth of algae and higher plants.
Too much eutrophication (i.e., nutrient enrichment)
causes excessive plant growth and the resulting
increased organic load depletes dissolved oxygen,
rendering the water less suitable for species consid-
ered desirable to people. The primary limiting nutri-
ents (i.e., those that, when lacking, commonly limit
algal and plant growth) are nitrogen (as ammonia,
nitrite, and nitrate), phosphate, and, for diatoms
(which often constitute the majority of fresh- and
salt-water phytoplankton), silica. There are many
more required nutrients; however, their availability is
normally such that they do not limit growth. In addi-
tion to excessive plant and algal growth, high concen-
trations of nitrates in drinking water also cause a
serious and occasionally fatal poisoning of infants
called methemoglobinemia (Slack and Goolsby
1976; Phelps 1978a).
In a natural surface-water system, nitrogen as a
nutrient is derived from organic debris that is carried
by runoff from surrounding terrain and from aquatic
species of nitrogen-fixing plants and bacteria, and is
regenerated within the system through the decay of
dead plants and animals. These sources are often
augmented, sometimes heavily, by human effluent
discharges. The most common of these are sewage
treatment plants, septic tanks, and runoff from fertil-
ized fields.


Phosphate and silica are derived, in an undisturbed
system, from the weathering of continental rock.
They are both recycled repeatedly through the cycle
of death, decay, and subsequent uptake. Florida has
extensive areas of phosphorus-rich limestone matrix
deposited during periods when the State was covered
by shallow seas. The dissolution of this rock and its
transport into both ground and surface waters provide
a ready source of this nutrient in many Florida
waters. The major anthropogenic contributors
include municipal sewage treatment discharges,
runoff from fertilized agricultural fields, and effluent
from phosphate mining operations. There is little
input of anthropogenic silica.
The limiting nutrients are not needed by algae and
plants in equal proportions. While the proportions
used vary widely between species and depend upon
environmental conditions, an average ratio of N:P =
10:1 for higher plants and algae and N:P:Si = 15:1:50
for diatoms can be used.

4.4.5 Temperature
Temperature affects water quality by acting as a
limiting factor if too high or too low for survival of a
specific organism, and by influencing the rate of
many biological and chemical processes, including
metabolism. In general, higher temperatures increase
the rate of metabolic functions (including growth)
and the speed of other chemical reactions. This tends
to increase the toxicity and rate of metabolic uptake
of toxicants (Cairns et al. 1975). Therefore, for those
toxicants which are bioconcentrated (accumulated
within the tissues), higher temperatures will result in
higher concentrations in living organisms.
Depending upon the size of the water body and
how well mixed it is, the water temperature may take
minutes or weeks to adjust to the average air
temperature. This lag time damps water temperature
fluctuations relative to air temperature fluctuations
and helps minimize the stress on aquatic lifeforms.
In addition to the seasonal fluctuations, there are
often diural fluctuations, particularly where turbid
or dark, tannic swamp waters are exposed to sunlight.
When the angle of incidence is small, water, as well
as many of its contents, absorbs solar energy very








4. Hydrology and Water Quality


efficiently. Dark coloration improves the efficiency
slightly, but restricts light penetration, and therefore
heating of the water, to near the surface. As a result,
surface water can become quite warm, while much
cooler water may exist below a shallow thermocline.
Freshwater surface temperatures vary depending
upon season and the volume, depth, and location of
the water body. Estuarine areas show the most com-
plex and rapid variations in water temperatures. The
dynamics of freshwater inflow temperatures, coastal
marine water temperatures, density stratification,
tide, and wind determine the proportions of freshwa-
ter and saltwater present at a site within an estuary
and may expose the inhabitants to very rapid
temperature fluctuations.
Locally, surface-water temperatures may be
strongly influenced by ground-water input. Ground-
water temperatures tend to remain very near the mean
annual temperature of the above-ground climate.
This is another example of temperature damping on a
larger scale, the result of the low rate at which the
earth changes temperature. Where ground water
flows into surface waters, the temperature of the
water near the ground-water input will be relatively
stable.
Temperature becomes a water-quality problem
when it is too cold or warm to support a normal
ecosystem. Low-temperature kills are almost exclu-
sively a natural product of winter cold spells and are
of short duration and temporary effect. High
temperatures, however, can become a long-term
problem when large quantities of water used to cool
power plants and other industrial operations are
discharged into surface waters. It is not uncommon
for thermal effects to be felt over a large area where
substantial quantities of heated water are discharged.
In the Springs Coast, the most notable instance of
hot-water effluent is the cooling water discharge
from the nuclear power plant at Crystal River.

4.4.6 Other Contents
This catchall grouping includes many materials of
great concern. Among these are toxic substances
such as ammonia, pesticides, and metals (e.g., lead,


mercury); carcinogens (cancer-causing agents),
mutagens (DNA-altering agents), and teratogens
(agents causing abnormal growth or structure); and
infectious agents (bacteria and viruses). Many
substances fall within two or more of these catego-
ries.
Metals and many of the toxic compounds in water
are often found in ionic forms. Most pesticides and
toxic organic compounds, however, do not require
ionization to be toxic. Many toxicants, ionic or not,
interfere with normal metabolic processes by displac-
ing critical metabolites and thereby blocking reac-
tions necessary for the maintenance of life.
While many ions are not toxic (at least at the
concentrations at which they are normally found), the
ionic forms of many elements and compounds are
generally more reactive than are the nonionic forms.
Additionally, different ions of the same substance
may vary in their toxicity. Generally, the higher the
valence number (i.e., the number of charges on the
ion), the more toxic the ion. As a rule, low pH
increases ionization and, therefore, the toxicity of
many substances.
The total concentration of the subject compound,
along with other factors such as pH, temperature,
ionic strength (i.e., the concentration of all ionic
forms present), and the presence of natural (and
anthropogenic) chelating agents such as tannins and
lignins, combine to determine the concentrations at
which the various ionic and nonionic forms of a
compound will be found. Since the toxicity (if any)
of that compound is affected by its exact form and
availability for uptake, and since the mode of that
uptake varies widely between species, predicting the
toxicity of effluents being discharged to surface and
ground waters is very difficult. The conditions found
in the area of each discharge play an important role in
determining the effect of an effluent on area ecology.
This is further complicated by the long period after
exposure which may elapse before the onset of symp-
toms, especially common in the carcinogens, terato-
gens, and mutagens. Since these conditions typically
fluctuate, sometimes widely, during the year, it can
be seen that predicting pollutant impacts can be very
difficult.







4. Hydrology and Water Quality


streamflow ("base flow") when surface runoff is
minimal. This moderating tendency is less notice-
able during periods of high runoff and streamflow.
Springs can become siphons under these conditions
and carry surface water directly to the aquifers
(Ceryak et al. 1983), thereby reducing the peak
streamflow somewhat. However, the relatively high
potentiometric pressures of the springs in most of this
region, coupled with the flat terrain that minimizes
changes in river stage, probably minimize or prevent
siphoning in much of the region. First- and second-
magnitude springs (>30 m3/s and 3-30 m3/s, respec-
tively) are clustered primarily in coastal Citrus and
Hernando County (Fig. 41). Third-magnitude
springs (<3 m3/s) also tend to cluster about these
areas but are found throughout the region.
Springs of Florida (Rosenau et al. 1977) includes
flow data for the springs and An index to springs of
Florida (Rosenau and Faulkner 1975) shows the
locations of those springs in the Springs Coast. The
USGS (1970) reported on the large springs of Citrus
and Hemando Counties.
b. Natural factors affecting coastal surface-wa-
ter hydrology. Coastal waters are affected by
several forces that have little affect on the freshwaters
inland. In shallow nearshore areas, such as those
common along the eastern Springs Coast coast and in
estuaries, wind is the major factor driving water
circulation (J. Williams et al. 1977; Livingston 1983).
This results in a net long-term movement of coastal
waters north and west during the late spring, summer,
and early fall, and south and east during the winter
months. Short-term currents are quite variable and
depend primarily upon (1) local wind direction,
(2) tide-induced currents, (3) proximity to river
mouths and the estuarine currents resulting from the
density differences of the mixing fresh and salt water,
and (4) the possible presence of eddies spun off the
Loop Current in the Gulf of Mexico.
(1) During much of the year, local wind direction
is affected by the convective phenomenon driving the
land breeze and sea breeze. Wind strength and direc-
tion and the resulting force exerted on the surface
waters often changes over short periods of time.
Chapter 3 contains more information on seasonal
changes in wind strength and direction,


(2) The Springs Coast coast experiences unequal
semidiumal tides, i.e., two high and two low tides
daily, each of different magnitude. This patten is the
result of a complex combination of forces, the gravi-
tational pull of the Moon and the Sun being the
primary ones. The period of the tides is such that
they are approximately 40 minutes later each day. In
research carried out along the west coast of Florida,
tides on the Springs Coast coastal shelf were found to
generate modest primarily onshore and offshore
currents (averaging 0.16 m/s) which, because of the
shallow topography, are stronger than those found
along the southern gulf coast of Florida (Battisti and
Clarke 1982). This wide, shallow coastal shelf was
also found to be resonant with the principal lunar tide,
adding a shelf-induced cycle of amplification and
damping to this portion of the tidal cycle (Battisti and
Clarke 1982). Of more importance to the nearshore
hydrology, the (normally) four-times-daily change of
direction of this movement of water induces substan-
tial mixing of the near-shore and offshore waters.
(3) A number of current-producing and -affecting
forces are in action at the mouths of rivers. Among
them are (a) the friction of the river flow upon the
saltwater it enters, (b) salt-wedge circulation, and
(c) geostrophic forces. The friction of the flow exit-
ing the river mouth attempts to "drag" adjacent salt-
water along with the body of river water, inducing
eddies along the transition zone between the two
water masses. A salt wedge forms because freshwa-
ter flowing out of the rivers is less dense than the
saltwater into which it flows; thus the freshwater
tends to form a layer flowing over the top of the
denser saltwater (Fig. 42a). This underlying layer of
saltwater is called a salt wedge, and since the
upstream end of this wedge has a lower salinity (is
less dense) from mixing with the overlying river
water, pressure from the denser saltwater behind it
forces the wedge upstream. In shallow, so-called
well-mixed estuaries (the type found along the
Springs Coast coast), turbulence and other mixing
forces tend to minimize the distance over which these
two water masses remain unmixed. However, the
mechanism is still functioning and an important part
of estuarine hydraulics. As the saltwater mixes with
the overlying freshwater at their interface, the






Florida Springs Coast Ecological Characterization


brackish water formed, less dense than the saltwater,
is caught up in the outward flow of freshwater and
carried out toward the gulf. This loss of saltwater
from the wedge induces a flow of saltwater from the
gulf to replace it. Thus the estuary experiences a net
outflow in the surface waters, and a net inflow in the
bottom waters. This inflow can be several times the
volume of the riverflow before it enters the estuary
(Knauss 1978). What are perceived as small changes
in river flow can result in large changes in estuarine
and nearshore circulation.
Others factors in estuarine circulation are those
caused by Coriolis and geostrophic forces. The
Coriolis "force" in the northem hemisphere is felt as
a force directed to the right of the direction of water
flow. The result of this force, when applied to an
estuary exhibiting stratified salinity, is that inflowing
fresh surface water tends to collect on the right side
(relative to the direction of flow) of the estuary
(Fig. 42b). In the Springs Coast, the resulting thicker
layer of freshwater is then forced west along the coast
by geostrophic forces caused by the pressure from the
denser, more saline waters to the south or east. These
two forces, in the absence of strong coastal currents,
cause the outflow of rivers in the Springs Coast to
tend to curve to the right once they reach the ocean
(Knauss 1978). Once free of the river banks, these
forces will tend to keep the surface layer of
freshwater "pinned" to the coast and force it west
along the coast until mixing destroys the stratifica-
tion. The magnitude of the effect of these forces on
coastal and estuarine circulation depends strongly on
the presence or absence of mixing forces at the time;
thus they are continuously in a state of flux.
A final influence on coastal hydrology is wave
mixing and erosion. Wave motion does not result in
significant lateral movement of water; however,
vertical mixing takes place to a depth approximately
-' twice the wave height. In shallow areas such as the
eastern Springs Coast nearshore region, large storm-
induced waves caused the waters to be well mixed
top to bottom. During periods of wave heights
greater than approximately 1 m, therefore, the eastern
Springs Coast coastal waters would be expected to
exhibit very little temperature or salinity stratifica-
tion.


c. Anthropogenic factors affecting inland sur-
face-water hydrology. Development often substan-
tially alters surface drainage. In the Springs Coast
these alterations include river damming, streamflow
diversion, river channelization, dredge-and-fill
activities, terraformingg," increasing runoff (e.g.,
stormwater drainage), wetland draining, floodplain
development, and extensive land-clearing activities.
The most common results of these alterations is
increased magnitude and duration of flooding and the
decreased water quality of runoff. Undeveloped
uplands in drainage basins act as a buffer to runoff,
absorbing the initial rainfall and impeding the rate at
which excess water runs off. Developed lands gener-
ally have a much reduced ability to absorb rainfall
due to the reduced amount of absorptive "litter,"
reduced permeability of the land surface, and reduced
evapotranspiration due to lower foliage densities. In
addition, most development includes measures such
as regrading of the terrain and installation of drainage
ditches and culverts, all aimed at speeding the rate of
runoff. As a result, the streamflow in developed
basins following periods of rainfall tends to peak
rapidly and at a much higher level than it does in
undeveloped basins. The problem is further exacer-
bated by the tendency of developed drainage basins
to restrict the area through which the stream or river
flows during high-water conditions. This area, the
floodplain, is the width of river channel required to
carry the runoff during periods of heavy rainfall in
the basin. After this floodplain is developed, which
commonly includes reducing its width by dumping
fill along its borders, the increased runoff resulting
from the development must now flow through a more
restricted channel, increasing the height of flooding
even more. The increased rate of runoff in developed
basins also increases erosion, which further reduces
landcover and retention of rainwater.
d. Anthropogenic factors affecting coastal sur-
face-water hydrology. Human alteration of fresh-
water input can also alter coastal estuarine systems.
Diversion of surface waters to different drainage
basins and alteration of the dynamics of the hydro-
logic cycle by anthropogenic activities (e.g.,
consumptive water use) can cause profound changes
in patterns of freshwater flow to estuaries and coastal








4. Hydrology and Water Quality


marshes, with potentially devastating results. Since
river outflow induces circulation and mixing in water
masses many times greater than the volume of water
discharged, the size of an estuary is controlled by the
volume of freshwater inflow, but any decrease of
inflow causes a much larger decrease in the volume
of the estuary. If average flow into an estuary is
reduced, then decreases in estuarine productivity
disproportionate to the volume of freshwater diverted
can be expected.

4.5.2 Surface-Water Quality
a. Natural factors affecting inland surface-wa-
ter quality. The major natural influence governing
surface-water quality is the progression of the
seasons. Surface waters are commonly composed of
some mixture of excess rainwater drained from
surrounding lands, flow from the surficial aquifer,
and artesian flow from the Floridan aquifer. Seasonal
factors that affect surface water quality include
rainfall, air temperature, and nutrient sources.
"Normal" rainwater is slightly acidic with a very
low concentration of dissolved minerals (i.e., soft
water). The water is poorly buffered and the pH is
easily changed by the materials it contacts. During
the rainy seasons, surface streams, rivers, and lakes
are composed primarily of rainfall runoff, with
ground water constituting a relatively small propor-
tion. The rainwater picks up tannic and other organic
acids through contact with organic debris during
runoff, particularly that encountered during the rela-
tively long periods of retention provided by swamps
and marshes. This swamp runoff is acidic (pH 4-5)
and highly colored, with a relatively low DO and a
very low concentration of dissolved minerals.
During periods of low rainfall, ground water
makes up an increased proportion of most surface
waters. Since ground waters are frequently highly
filtered and have spent time in contact with the
minerals composing the aquifer matrix (primarily
limestone), they are generally colorless, moderately
alkaline, and contain moderate to high levels of
dissolved minerals. Since surface runoff often has
weak organic acids acting as buffers, the pH of
surface water mixed with a small amount of ground


water can change radically. As a result of these
factors, surface-water chemistry (especially pH)
tends to reflect seasonal rainfall patterns.
In addition to the direct correlation between air
temperature and water temperature, air temperature
has many indirect influences on surface water. As
discussed previously, ambient temperatures affect
chemical reaction rates and equilibrium reactions in
water. As a result, rates of bioconcentration of toxics
are higher in warmer water, as are rates of nutrient
production and utilization. Another factor influenced
by air temperature is plant growth.
Seasonal change in ambient temperature is one of
the primary factors controlling plant and often animal
growth and reproduction, both in the drainage basin
and within water bodies. The growth and death of
biota are major factors in nutrient cycling and in the
levels of dissolved nutrients found in surface waters.
Dissolved nutrient levels tend to decrease during
periods of maximal population growth and increase
during periods when deaths (and therefore nutrient
regeneration) exceed reproduction and growth.
Surface runoff leaches nutrients from upland litter,
which are then carried to downstream water bodies.
Additionally, some of the litter is carried into the wa-
ter, where it settles to the bottom and decays, provid-
ing shelter and food for detrital feeders as well as
nutrients for primary production.
b. Natural factors affecting coastal surface-wa-
ter quality. The water quality of nearshore waters is
subject to many of the same climate-induced changes
that affect inland waters; however, by virtue of their
volume, the coastal waters are more resistant to
change. Nearshore water quality is primarily deter-
mined by the mixing dynamics resulting from the
previously discussed hydrologic factors. These
factors control the mixing of the freshwater draining
off the land and the marine waters offshore. One
relatively common event that is harmful to the
ecology occurs when conditions encourage plankton
blooms. The exact conditions triggering these
blooms are not fully understood; however, the dense
blooms introduce metabolic byproducts that are toxic
to many species and can produce fish kills. The BOD
from these kills, along with the enormous respiratory






Florida Springs Coast Ecological Characterization


oxygen demand of the plankton at night and during
overcast periods, can result in low levels of dissolved
oxygen, increasing the kill. These problems are
worst in constricted waters near shore.
c. Anthropogenic factors affecting inland sur-
face-water quality. Until recently, point-source
pollutant discharges have been the major human-
induced cause of water quality changes. In the
Springs Coast, much of which is relatively undevel-
oped, private and municipal sewage and discharges
are the most common point-source effluents.
Sources that are fewer in number but which may have
substantial local impact include discharges from
powerplants and mining operations. Discharges
from powerplants are primarily in the form of
thermal effluents; i.e., water that has been used to
cool the generators. The only power plant in the
Springs Coast is located at Crystal River (Crystal
River Nuclear Power Plant) in Citrus County.
Nonpoint-source pollution is considered by the
FDER to be a major, but largely uncontrolled, cause
of surface-water degradation. It is estimated from
studies that nonpoint sources contribute 450 times as
much suspended solids, 9 times as much oxygen-
depleting materials, and 3.5 times as much nitrogen
as point sources (FDER 1986a). The major non-
point-source pollutants in Springs Coast rivers are
pesticides, animal wastes, nutrients, and sediments.
The major sources of nonpoint-source pollution in
southeastern U.S. river basins are agriculture (affect-
ing 62% of basins) and urban storm-water runoff
(affecting 57% of basins), with silviculture (tree
farming), landfills, and septic tanks affecting 33% of
the basins (U.S. EPA 1977). Nonpoint-source
pollution is expanding and has the potential to nullify
water-quality gains being made through the reduction
of point-source emissions.
d. Anthropogenic factors affecting coastal sur-
face-water quality. The primary impact of human
activities on coastal water quality results from the
restriction of water circulation in dredged or other-
wise altered areas. This may result in high tempera-
tures, low DO, and salinity alterations. One of the
greatest effects of human activities results from salin-
ity alterations caused by the changes in hydrology


previously described. The factors affecting inland
surface-water quality may affect local coastal-water
quality, particularly in the estuaries.

4.6 Major Influences on Ground Water

4.6.1 Ground-Water Hydrology
a. Natural factors affecting ground-water hy-
drology. In the absence of cultural impacts, ground-
water levels are a function of rainfall. Ground-water
levels respond to area-wide rainfall with a lag time of
up to several weeks (Ceryak 1981). Since substantial
lateral transport is possible, levels tend to follow fluc-
tuations in rainfall averaged over substantial areas
(up to thousands of square kilometers). Ground-
water movement is from areas of high to those of low
potentiometric surface (Fig. 34).
Recharge of the Floridan aquifer from rains and
infiltration of surface water depends on the perme-
ability and thickness of the overlying strata and,
where there is a surficial aquifer, depends upon the
difference in head pressure between this overlying
aquifer and the Floridan aquifer as well as on the
permeability of the confining layer separating them.
During periods when the Floridan aquifer's potentio-
metric surface is locally low, rains may cause the
surficial aquifer's pressure to be greater than that of
the Floridan, with subsequent downward percolation
to the Floridan. At other times, however, the poten-
tiometric surface of the Floridan may be greater than
that of the surficial aquifer and no recharge to the
Floridan takes place. In this situation, water from the
Floridan aquifer may seep upward into the surficial
aquifer. In instances where the Floridan aquifer is
confined and its potentiometric surface is above the
land surface or above the level of overlying surface
water, springs and seeps may flow from the aquifer
and find their way into surface waters. High surface
water levels (i.e., floods) and/or low ground-water
levels can convert springs into siphons, thereby
draining surface waters directly into the aquifer
(Ceryak et al. 1983) (Fig. 43). This is common for
the springs along many rivers in the state and, in the
instances of springs flowing through large under-
ground passages, may allow substantial volumes of






Florida Springs Coast Ecological Characterization


oxygen demand of the plankton at night and during
overcast periods, can result in low levels of dissolved
oxygen, increasing the kill. These problems are
worst in constricted waters near shore.
c. Anthropogenic factors affecting inland sur-
face-water quality. Until recently, point-source
pollutant discharges have been the major human-
induced cause of water quality changes. In the
Springs Coast, much of which is relatively undevel-
oped, private and municipal sewage and discharges
are the most common point-source effluents.
Sources that are fewer in number but which may have
substantial local impact include discharges from
powerplants and mining operations. Discharges
from powerplants are primarily in the form of
thermal effluents; i.e., water that has been used to
cool the generators. The only power plant in the
Springs Coast is located at Crystal River (Crystal
River Nuclear Power Plant) in Citrus County.
Nonpoint-source pollution is considered by the
FDER to be a major, but largely uncontrolled, cause
of surface-water degradation. It is estimated from
studies that nonpoint sources contribute 450 times as
much suspended solids, 9 times as much oxygen-
depleting materials, and 3.5 times as much nitrogen
as point sources (FDER 1986a). The major non-
point-source pollutants in Springs Coast rivers are
pesticides, animal wastes, nutrients, and sediments.
The major sources of nonpoint-source pollution in
southeastern U.S. river basins are agriculture (affect-
ing 62% of basins) and urban storm-water runoff
(affecting 57% of basins), with silviculture (tree
farming), landfills, and septic tanks affecting 33% of
the basins (U.S. EPA 1977). Nonpoint-source
pollution is expanding and has the potential to nullify
water-quality gains being made through the reduction
of point-source emissions.
d. Anthropogenic factors affecting coastal sur-
face-water quality. The primary impact of human
activities on coastal water quality results from the
restriction of water circulation in dredged or other-
wise altered areas. This may result in high tempera-
tures, low DO, and salinity alterations. One of the
greatest effects of human activities results from salin-
ity alterations caused by the changes in hydrology


previously described. The factors affecting inland
surface-water quality may affect local coastal-water
quality, particularly in the estuaries.

4.6 Major Influences on Ground Water

4.6.1 Ground-Water Hydrology
a. Natural factors affecting ground-water hy-
drology. In the absence of cultural impacts, ground-
water levels are a function of rainfall. Ground-water
levels respond to area-wide rainfall with a lag time of
up to several weeks (Ceryak 1981). Since substantial
lateral transport is possible, levels tend to follow fluc-
tuations in rainfall averaged over substantial areas
(up to thousands of square kilometers). Ground-
water movement is from areas of high to those of low
potentiometric surface (Fig. 34).
Recharge of the Floridan aquifer from rains and
infiltration of surface water depends on the perme-
ability and thickness of the overlying strata and,
where there is a surficial aquifer, depends upon the
difference in head pressure between this overlying
aquifer and the Floridan aquifer as well as on the
permeability of the confining layer separating them.
During periods when the Floridan aquifer's potentio-
metric surface is locally low, rains may cause the
surficial aquifer's pressure to be greater than that of
the Floridan, with subsequent downward percolation
to the Floridan. At other times, however, the poten-
tiometric surface of the Floridan may be greater than
that of the surficial aquifer and no recharge to the
Floridan takes place. In this situation, water from the
Floridan aquifer may seep upward into the surficial
aquifer. In instances where the Floridan aquifer is
confined and its potentiometric surface is above the
land surface or above the level of overlying surface
water, springs and seeps may flow from the aquifer
and find their way into surface waters. High surface
water levels (i.e., floods) and/or low ground-water
levels can convert springs into siphons, thereby
draining surface waters directly into the aquifer
(Ceryak et al. 1983) (Fig. 43). This is common for
the springs along many rivers in the state and, in the
instances of springs flowing through large under-
ground passages, may allow substantial volumes of






Florida Springs Coast Ecological Characterization


surface water to mix with ground waters, increasing
the opportunity for large-scale contamination of
ground waters with surface pollutants. The existence
of siphons in Springs Coast rivers is undocumented.
However, the combination of high potentiometric
pressure springs and low-relief terrain (minimizing
changes in river stage) may minimize or prevent
conditions causing siphoning. The Pithlachascotee
River is the most likely to have siphons form, since it
is known that the river frequently loses water to the
underlying aquifer,
b. Anthropogenic factors affecting ground-wa-
ter hydrology. Ground-water levels are affected,
often extensively, by human activities. Three major
impacts presently exist in the Springs Coast:
(1) ground water withdrawal; (2) drainage wells; (3)
and surface hydrology alterations.
(1) Ground-water withdrawal tends to lower the
potentiometric surface in the immediate vicinity of a
well. As a result, ground water tends to flow laterally
toward the pumped well to fill the potentiometric
"hole," or cone of depression. The rate of this flow
depends upon the local permeability of the aquifer
and the pressure gradient between the well and the
surrounding aquifer. Another factor affected by
ground-water pumping is the depth to the saline layer
underlying the freshwater aquifers. Especially near
the coast, excessive pumping of ground water results
in saline intrusion into the potable aquifer. Because
the density difference between the freshwater aqui-
fers and the deeper saline ground water is minimal,
the permanent lowering by 1 ft of the upper surface of
the Floridan freshwater indicates that approximately
40 ft of the freshwater was removed and that the
upper surface of the underlying saline aquifer rose
nearly 40 ft. Investigations of seawater intrusion
along the Springs Coast have been carried out,
including that of Reichenbaugh (1972).
(2) Drainage wells have been used extensively in
some areas to drain perennially wet or flood-prone
areas. These wells are drilled into an aquifer and the
boreholes left open. "Excess" surface drainage is
then directed to the holes. It is also common, in suit-
able areas, that sink holes connecting to ground water
are used in place of drilled wells. The use of drainage


wells has decreased markedly because of concerns
about the poor quality of water draining into the aqui-
fers. Attempts by the water management districts to
locate these wells to help in water management plan-
ning have been hindered by the age of many of them
and by poor records of their existence. At the time of
this writing, the USGS is preparing a map of known
drainage wells (Kimrey 1990). Most of the drainage
wells in the Springs Coast and in the state will prob-
ably not be located.
(3) The surface hydrology of aquifer recharge
areas serves to channel water to or away from
recharge areas (Fig. 35). Recharge through sinkholes
and other breaches of the confining layer and by
percolation through porous soils can be easily altered
by human activities. Wetlands may serve to hold
water over areas of low porosity, thereby increasing
the amount of water percolating to the aquifer.
Diversion of surface drainage to, or away from,
sinkholes and wetlands, as well as speeding surface
drainage away from recharge areas as a flood
prevention measure, affects the amount and quality
of water recharging the aquifer. Development activi-
ties, especially in recharge areas, must be managed
carefully to ensure protection of ground-water
supplies.
In addition, while not presently used in the Springs
Coast, pressure-injection wells are used in various
locations throughout the state as a means of waste-
water and storm-water disposal. These techniques,
when used with storm water and with appropriate
caution towards their potential for ground-water
contamination, may help recharge the aquifer with
water that would otherwise evaporate or run off.
Pressure-injection wells are of two primary types,
those injecting into the freshwater aquifers and those
injecting into the saline-water aquifers. Injection into
many potable-water zones yields little increase in
storage, since the artesian aquifers are already full, so
this type of injection well is little used.
Liquid wastes are being injected into saline waters
in the deeper zones of the Floridan aquifer as a stor-
age and disposal method. This use is expanding,
especially in storing or disposing of secondarily
treated sewage effluent (Hickey 1984). The USGS







4. Hydrology and Water Quality


has mapped the general locations of deep saline aqui-
fers that might be suitable for liquid-waste disposal
(Miller 1979). Waste water is also injected into
nonpotable areas of saline intrusion to create a back
pressure and slow further intrusion (Stewart 1980).
Because of concern over its long-term effects, the
USGS is involved in extensive investigations into
this practice (e.g., Kaufman 1973; Pascale 1976;
Pascale and Martin 1978; Ehrlich et al. 1979; Hull
and Martin 1982; Vecchioli et al. 1984; Merritt
1984), and chemical changes in the wastes following
injection. Temporary storage of freshwater (storm
water) in saline aquifers is being evaluated by the
USGS in south Florida.

4.6.2 Ground-Water Quality
a. Natural factors affecting ground-water qual-
ity. Large areas in the Springs Coast function as
recharge areas for the Floridan aquifer (Fig. 35).
There is often a perception that surface water contacts
ground water only after it has very slowly percolated
through purifying layers of soil and rock. In Florida,
including the Springs Coast, this perception is often
incorrect. In many ground-water recharge areas, the
surface bodies of water and surface runoff are
directly connected to the ground water by channels
through the intervening rock. Below the surface of
the land, Florida is largely a sponge of karstic lime-
stone penetrated by innumerable solution channels
and sand beds. Though these porous layers of lime-
stone are often separated by confining layers of clay
and rock, their connections to the surface and to
surface waters is evident in the numerous springs and
sinkholes that dot Florida's landscape. Many sink-
holes act as drainage gutters, providing direct contact
between surface runoff and the ground-water aqui-
fers. The surficial aquifer, where it exists, is just a
layer of permeable strata laying on top of a confining
layer and exposed at the ground surface. Percolation
of surface waters into this aquifer is fast and rela-
tively unobstructed. Springs of Florida (Rosenau et
al. 1977) includes representative water quality data
from the springs and An Index to Springs of Florida
(Rosenau and Faulkner 1975) shows the locations of
those springs in the Springs Coast.


Ground water from the Floridan aquifer is charac-
terized by high pH, alkalinity, and hardness, resulting
from contact with the limestone within which the
Floridan is found. Water from the sand and gravel
aquifer is acidic and has low concentrations of
dissolved solids. The normal ground-water charac-
teristics in the shallower aquifers are affected by
surface-water hydrology. During periods of high
surface water, substantial quantities of often-dark,
acidic swamp runoff find their way into and mix with
(or replace) the ground water, rendering the quality of
water from shallow wells similar to that of the surface
waters.
b. Anthropogenic factors affecting ground-wa-
ter quality. Anthropogenic effects on ground-water
quality take three forms: (1) contamination by
surface waters and leaching of surface contaminants;
(2) contamination by direct means, i.e., drainage
wells and injection wells; and (3) increasing intru-
sion of saline waters into potable aquifers through
excessive pumping of ground waters. These effects
are further explained below.
(1) The surficial aquifer and the Floridan aquifer
where it is unconfined (not covered by a stratum of
low permeability) are often at or near the surface and
are by their proximity easily contaminated. Even
where beds of low permeability overlie the aquifer
(Fig. 44), surface contaminants are relatively easily
introduced. The terms "confining beds" and "low
permeability" were drafted by hydrologists describ-
ing the movement of ground water. For purposes of
water consumption, an overlying or surrounding
stratum of low permeability may slow local ground-
water recharge sufficiently to prevent large with-
drawals of water from an area. Percolation rates
measured in inches per day are very slow in terms of
aquifer recharge, but all too fast in terms of move-
ment of contaminants toward potable aquifers.
(2) Drainage wells have been in use for some
time, sometimes for the disposal of sewage and other
effluents, usually for the disposal of unwanted
surface water. Concerns have been raised over the
possible health effects of such activities, and their use
is being actively discouraged. Injection wells are
relatively new and, as discussed above, their effects








Florida Springs Coast Ecological Characterization


CHRIS


,I


0
29-

0.


SBeds 10 ft or more in thickness with low
hydraulic conductivity are absent within
50 ft of land surface.
-- Beds 10 ft or more in thickness with low
hydraulic conductivity occur within
50 ft of land surface.
SInsufficient data available.


Limestone aquifers known to be
within 50 ft of land surface.


Figure 44. Location of limestone aquifers known to be within 50 ft of land surface and of surficial beds of
low water permeability (after Healy and Hunn 1984).

70


ACHUA


r







4. Hydrology and Water Quality


are being studied intensively by the USGS and they
are heavily regulated by the U.S. Environmental
Protection Agency (EPA) and the FDER.
(3) Saltwater intrusion is becoming an increasing
problem, especially in coastal areas. One aspect of
this that is often overlooked is that intrusion of saline
waters into the shallow ground waters along the
coasts (where the potable aquifers are thinnest) can
change the makeup of overlying vegetation by killing
species that are not salt tolerant.


4.7 Area-wide Surface-Water Hydrology
and Water Quality

The Springs Coast contains one of Florida's major
coastal rivers, the Withlacoochee and six first-
magnitude springs. Table 2 gives major drainage
basin and waterbody sizes as well as streamflows for
Springs Coast lakes and rivers. Foose (1980) gives
drainage basin, river, and lake areas for Florida
including the Springs Coast. His later work (Foose


1983) includes further statistics concerning flow
characteristics of Florida rivers. Figure-45 shows the
general land usage in the Springs Coast, which
affects runoff and the water-quality characteristics of
downstream water bodies. Surface waters have been
monitored by the Florida Department of Environ-
mental Regulation (FDER) since 1973, using Perma-
nent Network Stations (PNS), though this monitoring
network has been substantially reduced in recent
years.
Primarily because of cost considerations, most
data collected from the various monitoring networks
and stations is physical or chemical in nature. The
biological baseline studies and monitoring needed to
enable accurate determination of the overall "good-
ness" of the water quality of a particular water body
is generally lacking. Data limitations due to chang-
ing sampling methods and uncharacterized ambient
conditions have prevented long-term trend analysis in
Florida river basins (FDER 1986a). Lack of baseline
data in most instances, and absence of continuing
data collection in many instances, prevents accurate


Table 2. Statisticsfor Florida Springs Coast rivers (data from Foose 1980, 1983; Rosenau et al. 1977).

Drainage Discharge gauging Mean annual
Major Length area site and distance discharge
Main rivers tributaries (km) (km2) above mouth (km) (m3/s)
Pithlachascotee River 29 507 near New Port Richey-15 0.88
Weeki Wachee River 11 spring run below Weeki Wachee Springs-10 4.98
Chassahowitzka River -8 spring run below springs cluster-1 3.92
Homosassa River Halls River 10 spring run below junction of SE fork 4.96
Crystal River 11 spring run town of Crystal River-6.4 27.6
Withlacoochee River Little Withlacoochee River 260 5,230 near Holder-61 31.01
Jumper Creek Canal at Inglis Dama-18 11.97
Lake Panasoffkee through Bypass channelb-18 32.05
Rainbow Springs
Waccasassa River Wekiva River 35 1,580 near Gulf Hammock-5.8 8.92
Otter Creek
a flow at Inglis Dam (below Lake Rousseau) is directed to the Cross Florida Barge Canal
b flow through Bypass channel (also below Lake Rousseau) is directed to lower Withlacoochee River






Florida Springs Coast Ecological Characterization


Gulf 4-
of
Mexico




Urban
Barren Land Transition
P Range
Wetlands

W Forest -.

Agriculture
Water Body




Figure 45. Generalized land use and vegetation map of the Florida Springs Coast (after SWFWMD 1978).
72