Front Cover
 Title Page
 Table of Contents
 List of Figures
 List of Tables
 Surface hydrology and water...
 Terrestrial and freshwater...
 Estuarine and saltwater wetlan...
 Florida bay and mangrove islan...
 The Florida Keys
 Back Cover

Title: Ecological characterization of the lower Everglades, Florida Bay and the Florida Keys
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Permanent Link: http://ufdc.ufl.edu/UF00000099/00001
 Material Information
Title: Ecological characterization of the lower Everglades, Florida Bay and the Florida Keys
Series Title: Ecological characterization of the lower Everglades, Florida Bay and the Florida Keys
Physical Description: Book
Creator: Schomer, N. Scott
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Bibliographic ID: UF00000099
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
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Resource Identifier: ltqf - AAA0261
ltuf - AME7135
alephbibnum - 002441922
 Related Items
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PALMM Version

Table of Contents
    Front Cover
        Front Cover 1
        Front Cover 2
    Title Page
        Page i
        Page ii
        Page iii
        Page iv
    Table of Contents
        Page v
        Page vi
        Page vii
    List of Figures
        Page viii
        Page ix
        Page x
        Page xi
    List of Tables
        Page xii
        Page xiii
        Page xiv
        Page xv
        Page xvi
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        Page 69
        Page 70
    Surface hydrology and water quality
        Page 71
        Page 72
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    Terrestrial and freshwater wetlands
        Page 109
        Page 110
        Page 111
        Page 112
        Page 113
        Page 114
        Page 115
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        Page 143
        Page 144
    Estuarine and saltwater wetlands
        Page 145
        Page 146
        Page 147
        Page 148
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    Florida bay and mangrove islands
        Page 165
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    The Florida Keys
        Page 175
        Page 176
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    Back Cover
        Page 248
        Page 249
Full Text

Biological Services Program
September 1982







A 0
yl- j




Bureau of Land Management
Fish and Wildlife Service

U.S. Department of the Interior


The Biological Services Program was established within the U.S. Fish
and Wildlife Service to supply scientific information and methodologies on
key environmental issues that impact fish and wildlife resources and their
supporting ecosystems. The mission of the program is as follows:

To strengthen the Fish and Wildlife Service in its role as
a primary source of information on national fish and wild-
life resources, particularly in respect to environmental
impact assessment.

To gather, analyze, and present information that will aid
decisionmakers in the identification and resolution of
problems associated with major changes in land and water

To provide better ecological information and evaluation
for Department of the Interior development programs, such
as those relating to energy development.

Information developed by the Biological Services Program is intended
for use in the planning and decisionmaking process to prevent or minimize
the impact of development on fish and wildlife. Research activities and
technical assistance services are based on an analysis of the issues, a
determination of the decisionmakers involved and their information needs,
and an evaluation of the state of the art to identify information gaps
and to determine priorities. This is a strategy that will ensure that
the products produced and disseminated are timely and useful.

Projects have been initiated in the following areas: coal extraction
and conversion; power plants; geothermal, mineral and oil shale develop-
ment; water resource analysis, including stream alterations and western
water allocation; coastal ecosystems and Outer Continental Shelf develop-
ment; and systems inventory, including National Wetland Inventory,
habitat classification and analysis, and information transfer.

The Biological Services Program consists of the Office of Biological
Services in Washington, D.C., which is responsible for overall planning and
management; National Teams, which provide the Program's central scientific
and technical expertise and arrange for contracting biological services
studies with states, universities, consulting firms, and others; Regional
Staffs, who provide a link to problems at the operating level;and staffs at
certain Fish and Wildlife Service research facilities, who conduct in-house
research studies.

September 1982



N. Scott Schomer
Richard D. Drew

State of Florida
Department of Environmental Regulation
2600 Blair Stone Road
Tallahassee, Florida 32301

Cooperative Agreement 14-16-009-80-999

Project Officer
Ken Adams
National Coastal Ecosystems Team
U.S. Fish and Wildlife Service
1010 Cause Boulevard
Slidell, Louisiana 70458

Performed for
National Coastal Ecosystems Team
Office of Biological Services
U.S. Fish and Wildlife Service
U.S. Department of the Interior
Washington, D.C. 20240


New Orleans OCS Office
Bureau of Land Management
U.S. Department of the Interior
New Orleans, Louisiana 70130



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 designated by other
authorized documents.

Library of Congress Card Number 82-600623

This report should be cited:

Schomer, N.S. and R.D. Drew. 1982. An Ecological Characterization
of the Lower Everglades, Florida Bay and the Florida Keys. U.S. Fish
and Wildlife Service, Office of Biological Services, Washington, D.C.
FWS/OBS-82/58.1. 246 pp.


This report is one In a series that provides an ecological description
of Florida's gulf coast. The region treated herein, with its myriad trop-
ical and subtropical communities, produces many benefits to man. The
maintenance of this productivity through enlightened resource management is
a major goal of this series. This report will be useful to the many parti-
cipants in the democratic process that governs the use of the natural
resources of this region.

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

Information Transfer Specialist
National Coastal Ecosystems Team
U.S. Fish and Wildlife Service
NASA Slidell Computer Complex
1010 Gause Boulevard
Slidell, Louisiana 70458



A conceptual model of the study area identifies four major ecological
zones; 1) terrestrial and freshwater wetlands, 2) estuarine and saltwater
wetlands, 3) Florida Bay and mangrove islands and 4) the Florida Keys.
These are geographically delineated from one another by a combination of
elevation gradient and positioning relative to one another and to major
outside influences such as upstream watersheds, the continental shelf and
major ocean current systems. These zones are delineated by differences in
basic physical-chemical background factors such as substrate, climate,
hydrology and water chemistry which in turn promote characteristic ecologi-
cal communities. Many of these communities are similar between zones but
localized differences do exist, as do significant shifts in relative
abundance of community types. The terrestrial and freshwater wetlands
support pinelands, sawgrass marshes, wet prairies, sloughs and occasional
tree islands on freshwater peat, marl and limestone soils. The estuarine
and saltwater wetlands support mangrove forests, salt marshes and oscillat-
ing salinity systems on mangrove peat, marine marl, sand or "liver mud"
substrates. Florida Bay exhibits oscillating meso-to hypersaline waters
over grassbeds on marine lime mud sediments. These mud banks form an
anastomosing pattern surrounding deeper "lake" areas having only a thin
veneer of sediment. The exposed tips of the mud banks frequently support
mangrove or salt prairie vegetation. The Florida Keys support almost all
of the above communities to some small degree but are more prominently
characterized by extensive offshore coral reefs. The upper keys are them-
selves a relict reef exposed by global lowering of sea level. The lower
keys are composed of rock hardened Miami oolite, a limestone formed via
chemical precipitation rather than biological deposition. The productivity
of these communities with regard to fish and wildlife reflects 1) the
diversity and type of habitats available to species that are potentially
capable of exploiting them, 2) the degree of alteration of these habitats
by man and natural forces, and 3) historical, biogeographic and random
factors that restrict organisms to specific environments or prohibit them
from exploiting a potential habitat.

r' I


PREFACE . . . . . . ..... . . . . ... iii
SUMMARY . . . . . . . . . . . . . ... iv
LIST OF FIGURES .................... .... viii
LIST OF TABLES ............................ xii
ACKNOWLEDGEMENTS ................... .... xv


1.1 Purpose and Organization of the Report. ......... 1
1.2 The Study Area. .. .................... 1
1.3 Energy and Materials Flow Through the Coastal Watershed .. 3
1.4 Conceptual Model of Regional Ecological Processes . . . 5


2.1 The Lower Everglades. . . . . . . . . . 13
2.2 Taylor Slough/Florida Bay . . . . . . . ... .17
2.3 The Florida Keys ........ .......... .... 21


3.1 Introduction. ..... . . . . . . .... 25
3.2 Rainfall. . . . . . . . . . . . . . 25
3.3 Winds . . . . . . .... . . . . 31
3.4 Temperature ...................... 34
3.5 Relative Humidity . . . . . . . . . . 35
3.6 Solar Radiation ................ ..... 36
3.7 Hurricanes. ...... . . . . . . . . . 38
3.8 Air Pollution .................... .. .. 42


4.1 Structure and Geologic Setting. . . . . . . . 47
4.2 Tertiary Stratigraphy . . . . . . . . ... .49
4.3 Pleistocene Sediments . . . . . . . . ... .49
4.4 Holocene Sediments ...... . . . . . 56
4.41 Everglades and Southwest Coast. . . . . 56
4.42 Taylor Slough/Florida Bay . . . . . . . .61
4.43 Florida Keys. . . . . . . . . . . 64


5.1 Historical Perspective. . . . . . . . . . 71
5.2 Conservation Area 3 . ........ ....... .. 72
5.3 Shark River Slough and Associated Estuaries ...... 77
5.4 Whitewater Bay ................... ....80
5.5 Taylor Slough .. .......... ... .. .. .. .. 81
5.6 Florida Bay .... ... ........ ... ..... 83
5.7 Florida Keys ......... .......... .... 86


6.1 Habitat Zonation . . . . . . . . . . 109
6.11 Pinelands. . . . . . .. . . 111
6.12 Hammocks . . . . . . . . . . . 112
6.13 Prairies ................ ..... 113
6.14 Cypress. ....... ........... 114
6.15 Thickets . . . . . . . . . . . 114
6.16 Marshes . . . . . . . . . . .117
6.17 Disturbed Habitats . . . . . . . . 118
6.2 Habitat Partitioning for Fish & Wildlife Production. . . 127
6.21 Energy Flow .................... 127
6.22 Invertebrates. . . . . . . . . 132
6.23 Fish . . . . . . . . . . . 133
6.24 Amphibians and Reptiles. . . . . . . . .135
6.25 Birds. ....... . . . . . . . . 137
6.26 Mammals . . . . . . . . . . .142


7.1 Previous Literature Reviews and Syntheses . . . 145
7.2 Habitat Zonation. . . . . . . . . ... . 145
7.21 Mangrove Forests . . . . . . . .. 145
7.22 Salt Prairies, Marshes and Transitional Habitats. . 147
7.23 Open Waters .................. .. 149
7.3 Habitat Partitioning for Fish & Wildlife Production . .. 150
7.31 Energy Flow .................. .. 150
7.32 Invertebrates . . . . . . . . ... .154
7.33 Fish . . .. . .. . .. . . .. .. .156
7.34 Amphibians and Reptiles ............... 159
7.35 Birds ..... . . . . . . . . 161
7.36 Mammals . . . . . . . ..... 163


8.1 Previous Literature Reviews and Syntheses . . . 165
8.2 Habitat Zonation .......................165
8.3 Habitat Partitioning for Fish 6 Wildlife Production . . 166
8.31 Energy Flow .................. .. 166
8.32 Invertebrates . . . . . . . . ... .169
8.33 Fish. . . ...... .... ....... 170
8.34 Amphibians and Reptiles ............... 171
8.35 Birds .... . . . . . . . . 172
8.36 Mammals . . . . . . . . .... 173



9.1 Previous Literature Reviews and Syntheses . . . 175
9.2 Habitat Zonation .................. ... 175
9.21 Terrestrial Habitats . . . . . . . . 178
9.22 Intertidal/Shoreline Habitats. . . . . . .. 181
9.23 Marine Habitats. . . . . . . . . .. 188
9.3 Habitat Partitioning for Fish & Wildlife Production. . . 198
9.31 Energy Flow .................... 198
9.32 Invertebrates. . . . . . . . . 201
9.33 Fish . ........ . . . . . 209
9.34 Amphibians and Reptiles. . . . . . . . 213
9.35 Birds. . . . . . . . .... 215
9.36 Mammals .. .................. 218

REFERENCES .. . ...... .... .... . . . ... 221

List of Figures

Figure Title Page

1 Map of study area identifying subunits. 2

2 Conceptual model of Keys ecosystem. 7

3 Conceptual model of ecosystem influenced by man. 9

4 Conceptual model of lower Everglades/Florida Bay
and the Florida Keys. 10

5 Map of lower Everglades physiographic zones. 14

6 Coastline types of lower Everglades. 17

7 Map of Taylor Slough/Florida Bay physiographic
zones. 18

8 Map of physiographic zones of the Florida Keys. 22

9 Florida climatic divisions. 25

10 Average monthly rainfall for three representative
stations in the study area. 28

11 Annual mean, total wet season, and total dry season
rainfall patterns in the study area. 29

12 Average annual maximum for one day rainfall. 30

13 Streamlines and isotachs at the 950 mb sublevel for
1957 to 1965. 32

14 Mean monthly divergence curves for June through
August 1963 over the Florida Peninsula. 33

15 Isotherms for study area annually, and in January
and August. 35

16 Diurnal patterns in relative humidity over south
Florida in April and September. 37

17 Points of entry and probabilities of hurricanes at
selected coastal locations. 41

18 Tracks of major hurricanes passing over the Dry
Tortugas since 1871. 41

19 Location of precipitation sampling sites in study
area, and average chemical concentrations. 43

List of Figures

Figure Title Page

20 The Floridan Plateau. 47

21 Stratigraphic nomenclature of Pre-Cenozoic
strata in the Florida peninsula. 50

22 Distribution of surface exposed Pleistocene
formations. 52

23 Distribution of the Miami Limestone. 54

24 Cypress head/bay head sedimentary profiles. 58

25 Sectional profile through Florida Bay, Flamingo,
Whitewater Bay, and the Everglades. 61

26 Taylor Slough sedimentary zones and core types. 62

27 Cross section of Cross Bank in Florida Bay. 64

28 Summary of Holocene sediments of the south
Florida shelf margin. 65

29 Depositional environments in the lower Keys. 67

30 Schematic drawing of mechanisms involved in
forming subaerial crusts in the Florida Keys. 69

31 Hydrologic cycle model modified from Figure 4
conceptual model of regional ecological processes. 73

32 Map of Conservation Area 3 and control structures. 74

33 a. Hydrograph of monthly mean discharge through
Tamiami Trail. 78

b. Monthly distance traveled by sheet flow under
varying conditions. 78

34 Relationships between salinity in Whitewater Bay
and freshwater runoff across Tamiami Trail. 82

35 Representative isohalines in Whitewater Bay
during wet and dry seasons. 82

36 Distribution of subenvironments in Florida Bay
defined by mollusks. 84

37 Isohalines in Florida Bay. 86

38 Schematic of mixed and semidiurnal tides. 87


List of Figures

Figure Title Page

39 Delineation of tide types in the Florida Keys. 87

40 Water level fluctuations in Florida Bay at
Tavernier. 92

41 Pathlines of the 220 isotherm at 100 meters
depth in the Gulf of Mexico from August 1972 to
September 1973. 94

42 Conductivity and chloride concentration in
relation to geology on Big Pine Key, Florida. 96

43 Summary of physical/chemical conditions along
the south Florida shelf margin in the Florida Keys. 101

44 Schematic diagram of water budget in canals of
the Florida Keys. 108

45 Terrestrial and freshwater wetlands in the lower
Everglades and Taylor Slough. 109

46 Summary diagram of successional relationships
among south Florida vegetation communities. 111

47 Summary diagram of energy flow through the terrestrial
and freshwater wetland ecosystem in the lower
Everglades. 128

48 Estuarine and saltwater wetlands in the lower
Everglades and Taylor Slough. 146

49 Mangrove community associations and forest types 147
along the southwest coast of Florida. 148

50 Physical/chemical factors in relation to plant
distributions in Whitewater Bay. 150

51 Summary diagram of energy flow through the mangrove
zone community. 151

52 Diagramatic representation of protein enrichment of
mangrove detritus during degradation. 153

53 Distribution of 15 zooplankters in relation to
salinity In the Shark River estuary. 155

54 Continuum of mangrove environments and associated
fish communities. 157

List of Figures

Figure Title Page

55 Summary diagram of energy flow through the Florida
Bay/mangrove island ecosystem. 168

56 Habitat zonation in the Florida Keys. 176

57 Profile of marine habitats off the Florida Keys. 189

58 Summary diagram of energy flow through the Florida
Keys ecosystem. 199

59 Simplified model of shrimp migratory patterns
in south Florida. 203

60 Seasonal abundance of post larval shrimp at
Whale Harbor Channel in the upper Keys. 204

61 Length frequency distributions of Panulirus
argus in three areas of the Keys. 208

62 Geographical distribution of representative
Florida Keys fish fauna for day and nighttime
hours. 214

List of Tables

Table Title Page

1 Explanation of energy circuit language symbols utilized
in the conceptual models. 6

2 Habitats corresponding to conceptual model zonations. 11

3 Wet season, dry season, and total annual precipi-
tation for the study area. 27

4 a.) Mean number of days with rainfall greater than
0.01 Inch. 30
b.) Mean number of days with rainfall greater than
0.10 inch. 30

5 Most common wind direction and speed by month
for selected first-order weather stations. 34

6 Mean monthly relative humidities (%) for 0100,0700,1300,
1900 hours, and 24 hour average from south Florida first
order weather stations. 36

7 Solar radiation and related climatological data for Key
West, Miami, and Ft. Myers first-order weather stations. 38

8 Seasonal averages of nutrient species contained
in rainwater at Tamiami Trail 40-mile bend. 44

9 Reference chart for discussion of geology. 48

10 Recognized sea level fluctuations of the
Pleistocene in Florida. 51

11 Mean sea level oscillations during the last 6,000 years. 59

12 Mappable habitat communities of the south Florida
reef and shelf. 66

13 Average concentrations of major Inorganic ions and
color for wet and dry seasons in Conservation Area 3. 76

14 Average, minimum, and maximum concentrations of
trace metals in surface waters of Conservation Area 3. 77

15 Selected water quality parameter concentrations in
Shark River Slough. 79

16 Tidal ranges along the shallow shelf break. 87

17 Profile of tidal range from shallow slope break
to inner shelf Florida Bay. 88


List of Tables

Table Title Page

18 Summary of wind data from the Florida Keys. 90

19 Average salinity of open sea nearshore water
associated with the Florida Keys. 100

20 Salinities for the Florida reef tract and vicinity. 100

21 Concentration (ppb) of heavy metals mercury, chromium,
cobalt, and zinc in corals from the upper Keys reef
tract. 105

22 Concentration of pesticides (ppb, dry weight) in
canal sediments from the Florida Keys. 108

23 Habitats, vegetation communities, and hydroperiods
in the freshwater lower Everglades. 110

24 Synopsis of disturbed vegetation community types
occurring on abandoned farmlands in the east
Everglades. 123

25 Habitat use by lower Everglades fishes. 134

26 Habitat use by lower Everglades amphibians and
reptiles. 136

27 Habitat use by lower Everglades birds. 138

28 Endangered, threatened, or rare bird species and
species of special concern that utilize terrestrial
and freshwater wetlands of the lower Everglades. 141

29 Habitat use by lower Everglades mammals. 142

30 Leaf litter production rates of mangrove ecosystems. 152

31 Reported spawning seasons of migratory estuarine
fishes in Whitewater Bay. 160

32 Trophic relations of amphibians and reptiles in the
mangrove zone. 160

33 Trophic relations of surface and diving birds in the
mangrove zone. 162

34 Endangered, threatened, or rare bird species, and
species of special concern that utilize the mangrove
zone. 163


List of Tables

Table Title Page

35 Trophic relations of mammals in the mangrove zone. 164

36 Physical, chemical, and biological conditions in
subenvironments of Florida Bay. 167

37 Distribution of breeding wading and swimming
birds in the four ecosytems of the study area. 173

38 Shorelines types in the Florida Keys. 177

39 Habitat subzonation in Florida Keys wetlands. 179

40 Bank reef zonation. 195

41 Size range distribution of pink shrimp in the
controlled area of Key West, Florida. 202

42 Seasonal variation in the relative distribution
of pink shrimp post larvae with depth. 204

43 Common continental, insular, and mixed fish faunal
associations for the Florida Keys. 210

44 Common diurnal and nocturnal fish fauna of the
Florida Keys. 213

45 Florida Keys fish fauna which are endangered,
threatened, or species of special concern. 214

46 Amphibians and reptiles from the Florida Keys. 215

47 Endangered, threatened or rare reptiles and
species of special concern from the Florida Keys. 215

48 Estimated breeding pairs of wading birds in
the lower Keys. 216

49 Breeding land birds in the Florida Keys. 218

50 Land mammals occurring in the Florida Keys. 219

51 Cetaceans occurring in or near the Florida Keys. 219


The authors wish to acknowledge the assistance of a number of people
who contributed to the preparation of this document. Many public and
private agency representatives cooperated with our search for published and
unpublished data sources. Noteworthy among these were the staffs of Ever-
glades National Park, the South Florida Water Management District, the
National Marine Fisheries Service, the South Florida Regional Planning
Council, the University of Florida's Center for Wetlands, and the Univer-
sity of Miami Rosenstiel Institute. Two individuals in particular, Alison
Lewis and Carol Knox provided continual and invaluable support to the
completion of this work. Ms. Lewis's persistence and efficiency in manag-
ing a virtual mountain of computerized bibliographic information greatly
simplified our task. Ms. Knox's patient revision and completion of the
tables and figures was carried out in an expert and timely manner. Valu-
able editorial review and comment was provided by Mr. Joe Carroll of the
U.S. Fish and Wildlife Service, Ms. Mimi Drew and Mr. Eric Livingston of
the Florida Department of Environmental Regulation. Grateful appreciation
is extended to Ruth Gray, Alisa Gregory, and Tish Elliott, who prepared
draft manuscripts of the synthesis paper and the bibliography, and to
Francie Stoutamire who prepared the final manuscript. Finally the authors
wish to express special thanks to our project officer, Mr. Ken Adams, for
his constant support and expert guidance in directing our efforts and
bringing this document to publication.




In recent years man's cultural
and economic development have accel-
erated at an unprecedented pace.
Inevitably this development precipi-
tates rapid change in the environ-
mental conditions to which plants
and animals have adapted. Wide-
spread habitat destruction, sewage
and industrial effluent discharge,
ground and surface water diversion,
and urban and agricultural runoff
are but a few of the inevitable by-
products of development that exert
acute as well as chronic effects on
the land, water, and biota.

Particularly within the highly
developed and rapidly changing
coastal zone, a fine line is emerg-
ing between what is considered
healthy economic development and
what must be conserved to insure a
healthy and productive balance
between man and nature. Often, in
deciding where this line lies, there
is much confusion as well as uncer-
tainty over exactly what natural
resources exist in an area, and how
they function. This report is an
attempt to alleviate this confusion
and uncertainty.

This document is the culmina-
tion of an extensive review of
published and unpublished literature
on pertinent ecological processes
within the study area. In contrast
to conventional literature reviews
and syntheses, the present document
deliberately crosses disciplinary
boundaries in an effort to focus on
how the watershed functions as an
integrated ecological system. At
the core of this focus is the basic
question, "How do energies and

materials flow through the lower
Everglades, Florida Bay, and Florida
Keys watershed?"

In answering this question, the
document is divided into two parts,
one on physical/chemical background
conditions, and the other on struc-
tural and functional ecological
patterns of energy utilization. The
first part identifies spatial and
temporal patterns in the distribu-
tion of physical/chemical forces
which drive the metabolism of the
study area. In this regard chapters
2 through 5 are presented, covering
the physiography of the study area,
its climate, its geology, and char-
acteristics of hydrology and water
quality. The second part describes
the overall habitat zonations that
develop in response to physical/
chemical controls, as well as perti-
nent patterns of resource partition-
ing (e.g., productivity, species
utilization and dependence, succes-
sion, etc.) between and within
individual habitats. Our treatment
of these patterns is divided into
four chapters (6 through 9) corre-
sponding to major ecological zones
as explained in Section 1.4.


The study area includes three
major subunits: (1) the lower Ever-
glades; (2) Taylor Slough/Florida
Bay; and (3) the Florida Keys
(Figure 1). The central component
of the lower Everglades is Shark
River Slough, a broad expanse of
sawgrass marsh studded with occa-
sional tree islands, or hammocks.
The lower Everglades sub-area is
bounded on the northeast by the
intersection of Tamiami Trail and
South Florida Water Management

820 SP CAK

Figure 1. Map of study area identifying subunits.


I- -~iiT~--l_~. il--l~~-i"e -

District (SFWMD) canal-levee L-31.
The area is bounded on the northwest
by the delineation of a hydrologic
boundary between the lower Ever-
glades and the Big Cypress Basin.
The southwestern boundary begins
approximately 13 km (8 mi) south of
Tamiami Trail on SFWMD canal-levee
L-31 and runs southwest to the vi-
cinity of Flamingo on Florida Bay.
This somewhat hazy line follows
State Road 27.

The Taylor Slough/Florida Bay
segment is bounded on the east by
SFWMD canal-levee L-31 W and on the
southeast by U.S. Highway 1. To the
south the intracoastal waterway,
which doubles as the southern bound-
ary of Everglades National Park,
forms a convenient physiographic
marker between the present segment
and the Florida Keys. The park
boundary from Long Key northwest to
East Cape Sable forms the gulf-side
boundary of this segment.

The third segment, the Florida
Keys, forms a gradually arching
chain of islands extending from the
southeastern tip of the Florida
peninsula (Soldiers Key just south
of Miami Beach) southwestward to the
Dry Tortugas, a distance of approxi-
mately 376 km (234 mi). The arc is
bounded on the convex side by the
Atlantic Ocean and the Straits of
Florida, and on the concave side by
Florida Bay and the Gulf of Mexico.

Throughout this report the
study area in Figure 1 is often
referred to as a "watershed" though
it does not readily conform to the
classic model of a distinct hydro-
logic unit. Historically, this
watershed once incorporated the
entire 22,500 km2 (8,688 mi2) of
the Kissimmee River Basin north of
Lake Okeechobee. The effective
drainage area of the watershed has
decreased significantly, however, as

a result of hydrologic modifications
of the Kissimmee, the drainage of
the Everglades south of the lake,
and the construction of dikes and
levees surrounding the lake. The
drainage area from Lake Okeechobee
to the Gulf of Mexico is now esti-
mated to be around 2,059 km2
(795 mi2) (Browder and Moore
1980). For our purposes, however,
we consider the "watershed" to be
only that portion which is relative-
ly untouched by direct physical
modifications. The boundaries of
this area correspond in large part
to those of the Everglades National
Park. In addition, the fact that
much of the freshwater used on the
Florida Keys originates from the
hydrologic budget of the lower Ever-
glades necessitates that the keys
also be considered a part of the


The hydrologic boundaries of
watersheds form distinct, though
somewhat amorphous "membranes"
across which considerable energy and
materials flow. Within these bound-
aries, various forms of energy and
matter are constantly being tapped,
transformed, and modified to yield a
wide range of products including
fish and wildlife as well as indus-
trial and agricultural goods. These
processes and pathways of production
and consumption within the watershed
are collectively responsible for
what we call "watershed metabolism."

In addressing watersheds as
living metabolic units, we concern
ourselves with two broad categories
of work being performed within their
boundaries: (1) inorganically medi-
ated work; and (2) biologically
mediated work.

Inorganically mediated work
refers to the forces attendant to
basic physical/chemical background
conditions, such as climate, which
affect all aspects of watershed
metabolism. Forces such as sun-
light, winds, tidal fluctuations,
heat flux, rainfall, atmospheric
chemical fallout, and osmotic gradi-
ents form the basic energy sources,
or forcing functions, that drive the
metabolism of the watershed. These
naturally occurring energy sources
"work" for the watershed in the
sense that they both force and allow
changes to occur in the composition
of the biota, soils, and water.

Biologically mediated work
refers to the processes involved in
the transformation and storage of
energy and matter into plant and
animal biomass, and its subsequent
degradation. In the context of
watershed metabolism, organisms form
sites at which complex energy and
material processing occurs, such as
the uptake of nutrients from the
soil and water, the evolution of
oxygen or carbon dioxide, or the
transformation of fish biomass into
bird feathers.

Within the boundaries of a
watershed, these two forms of work
are integrated at every ecological
level of organization. At the spe-
cies level, individual populations
are continually fine-tuned to their
environment through adaptations in
behavior, physiology, and anatomy.
Simultaneously, species also develop
interdependencies that promote
mutual survival and exploitation of
physical/chemical energies. This
process results in the formation of
characteristic environments referred
to as habitats, or communities.

At higher ecological levels
("higher" meaning greater spatial
and temporal coverage), this inte-

gration becomes increasingly com-
plex. The linkage may be direct as
in very specific reproductive needs;
or indirect as in trophic web rela-
tionships between producers and con-
sumers in widely separated habitats.
When these factors are superimposed
onto natural fluctuations in cli-
mate, invasions of species into new
environments, and continual habitat
alteration, it becomes necessary to
focus on integration at the ecosys-
tem level.

For our purposes the term "eco-
system" refers to any series of
interrelated habitats. An "estu-
arine ecosystem", for instance,
encompasses numerous habitats such
as mud flats, grass beds, oyster
reefs, sand bottoms, muck bottoms,
open waters, salt marshes, and man-
groves. These habitats are inter-
connected by wind and tidal mixing,
freshwater flushing, and by a broad-
ly tolerant and wide ranging variety
of resident and seasonal species,
each with their own adaptive strat-
egy for survival. In an upland
ecosystem setting, the movements of
birds, mammals, and insects (beyond
the boundaries of vegetation types),
as well as massive resource move-
ments such as seed dispersion and
runoff, results in the overlapping
of terrestrial habitats.

Although one could legitimately
look at many levels of ecological
organization for important patterns
of integration between organisms and
their environment, the watershed is
a particularly fundamental unit.
The hydrologic integrity of a water-
shed provides a fairly stable tem-
plate around which interconnected
habitats can become organized into
an ecosystem. Background geology,
soils, and latitude of the watershed
strongly influence the plants and
animals that inhabit the drainage
basin. These "habitats" in turn


influence soil development, erosion,
and solution of the substrate, and
consequently affect the physical and
chemical nature of other habitats
within the basin. The net structure
and function of these terrestrial
and freshwater habitats influence
the delivery rates and loadings of
water and chemical energy to the
downstream estuary. Here too,
geology and long-term patterns of
hydrologic input serve as evolution-
ary guidelines around which species
can organize into habitats.


In this section, we apply the
above concepts to the development of
a "model" of the lower Everglades,
Florida Bay, and Florida Keys water-
shed. Through this model we present
a simplified flow diagram of how the
various components of the watershed
(its meteorological setting, its
hydrologic cycle, its soils, and its
biological resources) interact to
create and maintain a living unit.

In some respects, the concep-
tual model is similar to a painting
of a coastal marsh: if one concen-
trates on a blade of grass, the de-
tail Is lost, and the blade, or what
appears to be the blade, becomes no
more than a stroke of paint. The
artist's intention is not to accu-
rately portray every blade of grass
but to catch the essence of the
marsh as a whole. This approach
underlies the perspective sought in
a conceptual model; that is, to
sacrifice the minutiae, in order to
identify the overriding controls,
forces, sinks, and pathways of the
system. It is hoped that through
this perspective the viewer may see
the forest in spite of the trees.

Symbols used throughout this

section in constructing the concep-
tual model of energy and materials
flow are presented in Table 1. A
brief explanation of the meaning and
general use of each of these symbols
is also given.

Figure 2 presents a conceptual
model of energy and materials flow
through a selected ecological system
(i.e., a number of closely related
habitats). The Florida Keys eco-
system is chosen for illustration.
Within Figure 2, an attempt is made
to ground-truth each of the symbols
and the lines interconnecting them
with an explanation. Not all the
possible connections and lines are
presented since this unduly compli-
cates the visualization process and
eventually compromises the simplify-
ing purpose of the model. Only the
major forcing functions and internal
metabolic processes are explicitly
diagrammed. To the right of the
model, a dashed line leads off to an
abbreviated list of the overlapping
habitats which this ecosystem encom-

In addition to the forcing
functions listed as "Incoming Ener-
gies", the Florida Keys ecosystem is
intricately linked to a series of
additional "ecosystems", such as
Florida Bay, the estuarine and salt-
water wetlands of the mainland, the
shallow coastal and continental
shelf of the Gulf of Mexico, and the
blue-water Straits of Florida.
These interconnections are symbol-
ized in the general model as double
directional arrows between the Keys
and the respective ecosystems, sig-
nifying that energy and matter flow
in both directions.

In keeping with the initial
purpose of this document, it is
essential that we also incorporate
man's role in watershed metabolism.
As agriculture, industry, and















a. Passive Storage

The passive storage symbol shows the location in a
system for passive storage such as moving potatoes into
a grocery store or fuel into a tank. NO new potential
energy is generated and some work must be done in the
process of moving the potential energy in and out of the
storage by sore other unit. It is used to represent the
storage of materials or biomass in systems.

b. Wr kgatU

The workgate module indicates a flow of energy (con-
trol factor) which makes possible another flow of energy
(input-output). It is used to show the multiplier
inter action of two system components.

c. Self-aintaining consumer population

The self-maintaining acnsuer population symbol re-
presents a combination of "active storage" and a 'mlti-
plier by which potential energy stored in one or more
sites in a subsystem is fed back to do work on the suc-
cessful processing and ork of that unit.

d. Primary producer

The primary producer symbol is a combination of a
"consumer unit" and a "pure energy receptor". Energy
captured by a cycling receptor unit is passed to a self-
maintaining unit that also keeps the cycling receptor
machinery working, and returns necessary materials to
it. The green plant is an example.

reservoir. A full description of this source would
require supplementary description indicating if the
source were constant force, constant flux, or programmed
in a particular sequence.

f. Logic Switch

The logic switch signifies that the distribution of
an energy flow is controlled at sone points) within the
ecosystem by a decision criteria. Where or when or how
mch of the energy flow is taking a given output pathway
is determined by a logic control function. Examples
include the control of pumping schedules and directions
in response to water supply. The cost of maintaining
and operating the combination of control structures and
decision making pathways also follows the second law of

g. Two-way workgate

The twOo-ay workgate or forced diffusion module
represents the movement of materials in two directions
as in the vertical movement of minerals and plankton in
the sea. The movement is in proportion to a concentra-
tion gradient or a casual force shown operating the
gate. The heat sink shows the action to follow the
second law of thermodynamics.

Table 1. Explanation of energy circuit language symbols utilized in the
conceptual models (adapted from Snedaker and Lugo 1974).


Growth medium contained
in surface waters:
Water & Chemical Energy
contained in biota, roots,
leaves ,cytoplasm, atmosphere

Primary & Heterotrophic


Recycle of Nutrients
through microbial decomposition
& mineralization


Recycle of Detritus
excretion, fecal matter,
mechanical mixing &breakdown
f of plant and animal matter
by consumers

Trophic Web

Tropical Hammocks Terrestial
Scrub Mangrove Intertidal
Rocky Shores Jntert
High velocity channels
Sea grasses
Coral reefs
Back reefs Marine
Patch reefs
Fore reefs J

Nutrient & water
Uptake from soils.
groundwater recharge
& sedimentation

Secondary Productivity '
Growth of consumer
Reproduction o biomass
Maintinence )

Figure 2. Conceptual model of keys ecosystem.


government expand, their management
functions increasingly become na-
ture's management functions as well.
The private control of vast acreages
of land for timber or agricultural
production, the designation and man-
agement of public lands for parks,
wildlife refuges, and conservation
areas, and the spread of urban and
suburban development, are not only
competing interests within man's
economy; they are also competing
with, and dependent upon, nature's
ability to self-regulate. To accu-
rately perceive the relationships
between man and nature in south-
western Florida it is essential to
understand that man himself is a
function of natural processes rather
than a force separate from them.

With this in mind, the general
model in Figure 3 is constructed to
include the activities of man as an
integral part of watershed metabo-
lism. Curiously enough, man's
activities do not bring any new
principles to bear upon energy and
material flow through natural eco-
systems. Rather, his major impacts
(1) The selected conversion of
natural lands into agricul-
tural and timber production;
(2) The funneling of natural and
manufactured resources into
the production and support
of complex cultural structu-
res (e.g., buildings, roads,
and industrial goods).

A total conceptual model of the
present study area is presented in
Figure 4. This model identifies the
primary ecological zonations of the
watershed, namely:
(1) The terrestrial and fresh-
water wetlands ecosystem;
(2) The saltwater wetlands and
estuarine ecosystem;
(3) The Florida Bay and mangrove

island ecosystem; and
(4) The Florida Keys ecosystem.
For each of these zones or "ecosys-
tems", the habitats which they
incorporate are listed in Table 2.
Major forcing functions are shown
entering the model from the left
side of the figure. Chemical and
physical energy inputs are augmented
by imported goods and services which
support the activities of man, par-
ticularly in the Florida Keys and in
the East Everglades Agricultural
Area. Energy and materials are
exported from the watershed via (1)
evapotranspiration, (2) the emigra-
tion of species, (3) fisheries
industries, (4) tidal flushing and
runoff of chemical energy and sedi-
ment, and (5) export of agricultural
and manufactured goods. Within each
ecosystem the work of the plants and
animals is symbolized by the com-
bination of symbols presented in
Figure 2. Two major oceanic ecosys-
tems associated with the Florida
Straits and the southeastern Gulf of
Mexico, regularly influence the
watershed. They are also shown in
the model. The double-headed arrows
that run between major ecosystem
zones signify that energy and matter
flow between the respective subsys-
tems. These connections may take
the form of physical/chemical energy
transfers such as those effected by
runoff, hurricanes, or tidal mixing;
or biological energy transfers such
as those effected through the active
migrations of organisms.

Man's role in watershed metab-
olism is represented by three some-
what distinct consumer, or manage-
ment, functions:
(1) Urban/industrial structure,
primarily located on the
eastern margin of the Ever-
glades and in the Keys. This
includes the activities of
agriculture, commercial and
sport fishing industries,

~ I I_


Agriculture a natural system

Air & Surface Water Pollution:
By-Products of Urban-

Hunting &

SUrban &

Ground Water &
Mineral Storage

Figure 3. Conceptual model of ecosystem influenced by man.


to southeast
coast consumers

to Keys




Figure 4.

Conceptual model of lower
Florida Keys.

tourism, residents, and var-
ious cultural and economic
support facilities;
(2) The Everglades National Park
Service (ENP) which monitors
(and to some extent con-
trols) the vast majority of
the study area;

Everglades/Florida Bay and the

(3) The South Florida Water
Management District (SFWMD)
which essentially controls
the upstream watershed and
is responsible for distribu-
ting water throughout south

Terrestrial & Freshwater Estuarine & Saltwater Florida Bay & Florida Keys &
Wetlands Wetlands Mangrove Islands Reefs

1. Pinelands 1. Salt marshes 1. Seagrasses 1. Tropical hammocks
2. Hammocks 2. Salt prairies 2. Intertidal shoals 2. Pinelands
3. Prairies 3. Beaches & dunes 3. "Lakes" 3. Disturbed habitats
4. Cypress 4. Mangrove forests 4. Mangrove islands 4. Rocky shores
& blue green
5. Thickets 5. Oscillating salinity algal mats 5. Mangroves
open waters
6. Marshes 6. Canals
a) Mangrove ponds
7. Ponds b) Tidal streams 7. High velocity
c) Estuarine bays channels
8. Disturbed habitats d) Oceanic bays
8. Seagrasses
9. Coral reefs
a) Back reefs
b) Patch reefs
c) Fore reefs

Table 2. Habitats corresponding to conceptual model zonations.

The remainder of this document
is devoted to a detailed discussion
of the ecological characteristics of
the lower Everglades, Florida Bay,
and Florida Keys. We hope that as
the details of watershed metabolism
unfold, the reader will be able to
visualize where the information
presented may be "plugged-in" to the
conceptual model. We also hope that
in so doing, the reader will gain
some useful insights into the mecha-
nisms that govern the quiet, persis-
tent evolution of this fascinating

_ I~____~



Figure 5 presents a map of the
major physiographic delineations
within the lower Everglades drainage
basin. These delineations, as well
as those in subsequent sections for
Taylor Slough/Florida Bay and the
Florida Keys, are based upon pre-
viously published accounts (e.g.,
Davis 1943, Puri and Vernon 1964,
White 1970, Craighead 1971), as well
as biological and hydrological fac-
tors such as dominant vegetation
types, hydroperiod, surface drain-
age, and circulation. The term
hydroperiod refers to that portion
of the year when the water table is
at or above the land surface.

The lower Everglades subunit
can be further broken down into six
distinct physiographic areas:
(1) Shark River Slough
(2) Rocky Glades
(3) Broad River/Lostmans River
(4) Coastal Swamps and Lagoons
(5) Cape Sable

Shark River Slough
The Shark River Slough refers
to that portion of the Everglades
that is more or less synonymous with
Douglas' (1947) "river of grass".
Within the present study area the
slough is a broad southwesterly
trending arc of continuous wetland,
dotted throughout with numerous tree
islands. It is distinguished on its
northwestern and southeastern bound-
aries by expansive transitional
areas of slightly higher bedrock
elevation, and a consequently short-
er hydroperiod. The slough occupies
the center of the Everglades trough,
a wide, slightly concave depression
in the underlying limestone (White

Rocky Glades
To the south of Shark River
Slough lies a transitional area
known as the Rocky Glades or Rock-
lands (Davis 1943, DERM 1980). The
name "Rocky Glades" is derived from
the character of the limestone rock
that lies exposed at the surface of
this area. The limestone, which is
often called pinnacle rock, occurs
in craggy masses made of rock hard-
ened bryozoan colonies. These colo-
nies were laid down when the area
lay beneath sea level during the
late Pleistocene.

The Rocky Glades form a thin
transitional area between the Shark
and Taylor Sloughs. Geologically,
the Fort Thompson Formation under-
lies the Everglades trough as a
surface bedrock feature, while the
back slope of the Atlantic Coastal
Ridge (Miami Limestone) forms the
surface rock for the areas farther
east. Consequently, these bedrock
features also make the Rocky Glades
a hydrologic transition zone between
the Shark River Slough drainage to
the southeast and the Taylor Slough
drainage to the south.

Broad River/Lostmans River
To the northwest of Shark River
Slough the bedrock of the Everglades
trough again rises gradually in ele-
vation toward the Big Cypress Spur,
which is a southerly extension of
the Immokalee Rise, and the south-
western slope (Puri and Vernon 1964,
White 1970). These latter features
more or less define the Big Cypress
Basin. The freshwater wetland and
upland area between the Everglades
trough and the Big Cypress Basin is
labeled the Broad River/Lostmans
River Drainage.


Figure 5. Map of lower Everglades physiographic zones
(adapted from USDI 1979).


Like the Rocky Glades, this
area is distinguished from Shark
River Slough by subtle differences
in hydrology (hydroperiod) and geol-
ogy. In this area the Miami Lime-
stone all but disappears while the
Fort Thompson Formation, a bedrock
feature of the Everglades trough, is
gradually encroached upon by a thin
veneer of Pamlico sands of late
Pleistocene age (Cooke 1945).
Farther northwest, the dissected
Tamiami formation of the earlier
Miocene age lies exposed at the sur-
face, only thinly covered by more
recent strata (Schroeder and Klein
1954, McCoy 1962).

Coastal Swamps and Lagoons
To the southwest of these three
areas lies the low mangrove and salt
marsh dominated zone referred to by
Purl and Vernon (1964) as the retic-
ulate coastal swamps. These coastal
swamps and lagoons extend from the
upland limit of periodic saltwater
influence to the Gulf of Mexico, a
distance of about 16 to 40 km (10 to
25 mi). Prominent features that
delineate the area are:
(1) the salt marshes which lie
relatively upland;
(2) the mangrove forests which
grow in vast wetland ex-
panses and along the shore-
lines; and
(3) the "back bays" or lagoons.
The back bays represent a
distinct physiographic fea-
ture of the area which be-
comes more prominent as one
moves north along the coast.

The coastal swamps and lagoons
receive the major bulk of surface
runoff from the Everglades. When
sea level was lower, prior to the
recent Flandrian sea level rise of
the Holocene epoch, the area inun-
dated by freshwater was relatively
larger than it is today. As surface
waters flowed over this area, dif-
ferential solution of the less re-

sistant bedrock limestone resulted.
in the formation of freshwater chan-
nels. The freshwater runoff also
influenced the relative preponder-
ance of various peat and/or marl
forming environments.

As sea level subsequently rose
to its present level, the more sus-
ceptible areas of underlying peat
eroded and oxidized leaving anasto-
mosing lagoons and "back bays"
(Spackman et al. 1964, White 1970).
The area is now characterized by
fluctuating fresh and saltwater

The largest and most conspic-
uous of these lagoons is Whitewater
Bay. Along its northern boundary
the drainage pattern into Whitewater
Bay distinctly follows numerous
southeasterly trending channels such
as the Watson River, North River,
and Robertson River. Throughout the
bay are numerous islands whose
southwest/northeast orientation sug-
gest historical erosion of their
underlying marl along relict fresh-
water channels. To the southeast
the bay is confined by a degenerate
extension of the Atlantic Coastal
Ridge that terminates in the "Cape
Sable High" (White 1970). Prior to
construction of the Buttonwood
Canal, which directly connects
Whitewater Bay with Florida Bay,
flushing was toward the northwest.
The Joe River, which runs parallel
to the axis of the bay on its south-
western boundary, reflects this re-
cent drainage pattern. Both White-
water Bay and the Shark River Slough
flush to the Gulf of Mexico in the
vicinity of Ponce de Leon Bay.

Where the main thrust of the
lower Everglades drainage enters the
gulf, conditions are less favorable
for the formation of lagoons or back
bays (White 1970). Consequently,
there is a wide area of coastline
north of Whitewater Bay in which


only one small lagoon-like body of
water appears, i.e., Tarpon Bay in
the Harney River. Farther north,
however, beginning at Lostmans
River, back bays become a prominent
feature of the landscape. This
feature continues and expands to the
north within the Big Cypress drain-
age basin culminating in the Ten
Thousand Islands area south of Cape

Cape Sable
One of the most distinctive
features of the southwestern tip of
Florida is Cape Sable. White (1970)
claims that the cape overlies a de-
generate westerly extension of Miami
Limestone of the Atlantic Coastal
Ridge. He refers to the terminal
end of this extension as the "Cape
Sable High". The forefront of the
cape actually exhibits three dis-
tinct capes: the Northwest Cape and
the Middle Cape, which are quartz
sand covered capes; and the East
Cape, which contains relatively more
marl (Craighead 1971).

The present beaches are surface
exposures of buried coquinoid ridges
which constitute a major portion of
the underlying strata of the seaward
cape. Behind these beaches and
beach ridges, the cape is separated
from the nearest surface bedrock by
a broad expanse of marl and peat,
and Whitewater Bay. These marl and
peat areas are vegetated with salt
marshes, mangroves, salt prairies,
and tropical hardwood hammocks
(Craighead 1971, Browder et al.

It is believed that the beaches
at Cape Sable first formed as a
result of a shallow submarine scarp
cut into the bedrock (White 1970).
This wave-cut notch allowed local-
ized wave breaking long enough for
a bar to be built and a barrier to
be formed. The subsequent growth
of shellfish offshore continued
to feed the beach with shell and

sand, particularly during hurricanes
(Craighead 1971).

The coastal prairies behind the
beaches of Cape Sable are composed
of a succession of troughs and low
dunes (Craighead and Gilbert 1962).
On the upland side of these prai-
ries, the highest elevations support
a continuous ridge of hammocks
(Craighead 1971, Browder et al.
1973). A series of shallow ponds,
the largest of which is Lake
Ingraham, extend from the north of
the Middle Cape east to Flamingo.
Craighead considers these ponds to
be remmants of former open waters
that have not been completely filled
by surrounding marl and peat. Water,
when present in these troughs, can
be either fresh or saline depending
on local hydrologic conditions.
White (1970) characterizes inland
Cape Sable as an isolated pocosin
sloping gradually down from a peat
dome toward the Joe River and White-
water Bay.

North of the Northwest Cape,
beach sand is less apparent owing to
the more gradually sloping submarine
topography and the increased influ-
ence of freshwater glades runoff.
Craighead (1971) singles out Big
Sable Creek as an area where the
creek delta and beach are actively
receding with rising sea level. The
erosion forces which are believed to
be at work in forming the Big Sable
Creek coastline environment are as
(1) Shoreline mangroves are kil-
led by deposits of hurricane
(2) Storm tides gradually erode
unconsolidated sediment;
(3) Trees are toppled and car-
ried back to sea by hurri-
cane backwash.
The types of shorelines that border
the lower Everglades coast and their
approximate geographic extent are
summarized in Figure 6 (Spackman
et al. 1964).

Figure 6. Coastline types of
the lower Everglades
(adapted from Spackman
et al. 1964).


Figure 7 presents a stylized
map of the major physiographic
delineations of the Taylor Slough/
Florida Bay drainage basin. For our
purposes the area is further broken
down into a total of 8 physiographic
subzones as follows:
(1) Taylor Slough Headwaters
(2) Upper, Middle, & Lower
Taylor Slough
(3) Taylor Slough Coastal Drain-
(4) Coastal Swamps & Lagoons
(5) Florida Bay
Northern Subenvironment
Interior Subenvironment
Gulf Subenvironment
Atlantic Subenvironment

Taylor Slough Headwaters
The central component of the
Florida Bay drainage basin is Taylor
Slough. It occupies a more or less
distinct surface drainage area
formed by an extension of the Miami
Coastal Ridge south and a southwest/
northeast trending offshoot of this
ridge known as Long Pine Key. Puri
and Vernon (1964) show this as a
continuous connection which forms
the upper boundary of what they
refer to as the "southern slope",
while Davis (1943) refers to these
areas as the "Southern Coast and

Nonetheless, a hydrologic
bridge does exist at the confluence
of the Miami Rock Ridge and the
Everglades Keys (Davis 1943) con-
necting the southern slope and the
area to the north. This northern
area is known as the Taylor Slough
headwaters (Waller 1979). It lies
partially within the boundaries of
Everglades National Park. Most of
its approximately 250 km2 (97
mi2) area lies within a privately
owned tract of land known as the
East Everglades (DERM 1980). Land
use in this area reflects the grow-
ing pressure of urban and agricul-
tural interest.

The headwaters of Taylor Slough
are separated from the Shark River
Slough on the north by a narrow
strip of land, the Rocky Glades,
which is considered to be in the
main stem of the Everglades sheet
flow from Lake Okeechobee south to
Whitewater Bay (Parker et al. 1955,
McPherson et al. 1976, DERM 1980).
Surface relief in the Taylor Slough
headwaters, is extremely limited.
The area is perched at an elevation
of approximately 2.3 m (7 ft) above
mean sea level. Both Shark River
Slough to the north and Taylor
Slough to the south are slightly
lower in elevation.



Figure 7. Map of Taylor SloughlFlorida Bay physiographic zones
(adapted from USDI 1979).


Historically, sheet flow from
Lake Okeechobee through the Ever-
glades has followed a south by
southwest curve as outlined by the
arc of Shark River Slough. Some of
this sheet flow, however, has been
transverse to the main axis of the
Miami Rock Ridge, the Everglades
Keys, and the Rocky Glades. This
causes erosion of the thin layer of
overlying marl soils and solution of
the underlying Miami oolite, leading
to a solution riddled topography.
These erosional surfaces cut across
the limestone toward Taylor Slough
and the southern slope. This nat-
ural evolution of morphology is com-
plicated by vegetational patterns,
peat deposition, marl formation, and
rock plowing for agricultural pur-
poses. (Rock plowing refers to an
agricultural practice in which marl
soils are dug up and crushed to
facilitate planting and drainage).

Upper, Middle, and Lower Taylor
The northern boundary of this
segment is located where SFWMD
Canal 31-W intersects the main chan-
nel of Taylor Slough (Olmstead
et al. 1980). This area is referred
to by Olmstead et al. (1980) as
upper Taylor Slough, a rather well
defined, 5.5 km (3.4 mi) long seg-
ment running from the intersection
of the slough and the canal levee
structure L-31 W south to State Road
27, Anhinga Trail. Middle Taylor
Slough refers to that segment of the
slough from State Road 27 south 7 km
(4 mi) (Olmsted et al. 1980). The
slough is joined in this segment by
a large arm from the east. Lower
Taylor Slough refers to the segment
lying south of this point to Florida

The bedrock of Taylor Slough is
broadly concave with the central
portion averaging only 90 to 120 cm
(3 to 4 feet) lower than the mar-
gins. The center of this broad

depression in the Miami oolite var-
ies from 0.2 to 2.0 m (8 in. to 6.5
ft) below the margins. However,
marl soils and peat deposits tend to
obscure and smooth over the under-
lying variations in bedrock.

The slough itself is charac-
terized by comparatively dry areas
in the north that are dominated by
muhly prairies (Muhlenbergia
filipes) (Hilsenbeck et al. 1979).
Interspersed in the upper part of
the slough are limestone outcrop-
pings (the Everglades Keys), which
are colonized by pines and tropical
hardwoods. A small but significant
portion of the land is former agri-
cultural land, now in the hands of
Everglades National Park. The cen-
tral portion of the upper slough is
a relatively wetter area dominated
by sawgrass (Cladium jamaicensis)
and spike rush (Eleocharis cellu-
losa) marshes.

Farther south, middle Taylor
Slough broadens and becomes vegeta-
tionally dominated by sawgrass,
spike rush, and willow (Salix caro-
liniana) marshes (Olmstead et al.
1980). Toward Florida Bay the
freshwater slough vegetation is
gradually replaced by buttonwood
(Conocarpus erecta), mangrove for-
ests, salt barrens, and tropical
hardwood hammocks.

Southeast Coastal Glades
Lying to the east and south of
the main stem of Taylor Slough is
another band of what Purl and Vernon
(1964) refer to as gulf coastal
lagoons. Upland of this band are
freshwater marl prairies referred to
in Figure 7 as the coastal drainage
region, which serves as the only
source of fresh water outside of
direct rainfall to extreme upper
Florida Bay. Farther east and north
these marl prairies drain into the
series of sounds that separate
Florida Bay from Biscayne Bay.


This area roughly corresponds
to what some call the southeast
saline Everglades (Egler 1952, DERM
1980). A considerable chunk of this
area (approximately 30%) lies within
the privately owned East Everglades
Agricultural Area. For our pur-
poses, the northeast and eastern
boundaries of this province corre-
spond to SFWMD Canal 111 (C-111),
also known as the Aerojet Canal,
which runs from just east of the
park entrance southeast to U.S.
Highway 1 and then south to Florida
Bay. This is considered to be the
extent of the southeast coastal
glades drainage system that directly
affects Florida Bay. The remainder
of the southeast coastal glades
drains into Long, Barnes, and Card
Sounds to the northeast.

Taylor Slough Coastal Drainage
That portion of the southern
slope north of the coastal swamps
and lagoons, and west of Taylor
Slough is referred to as the Taylor
Slough Coastal Drainage. To the
north, the area extends to include
Long Pine Key and the Everglades
Keys. To the west, the area is
bounded by State Road 27 (Anhinga

The elevated limestone ridges
that run west/southwest from the
upper Taylor Slough (Long Pine Key
and the Everglades Keys) form a
barrier inhibiting sheet flow from
Shark River and the lower Rocky
Glades, as outlined in Figure 1. As
such they represent the northern
boundary of the drainage basin from
which surface waters flow south
either into Taylor Slough or direct-
ly into Florida Bay. The Park High-
way is chosen as the western bound-
ary of this province though some
surface drainage does occur, espe-
cially in the wet season, through
culverts underneath the road.

South of the Everglades Keys
this segment is largely dominated by
muhly prairies. Almost directly in
the middle of the area is a large
oblong area of scattered dwarf
cypress, known as "hatrack" cypress.
Although most of the segment is
clearly dominated by natural commu-
nities, a significant area of former
agricultural lands is also present
on the southeastern fringe of Long
Pine Key. This area, which was
recently acquired by the National
Park, is referred to as the Hole-

Coastal Swamps and Lagoons
To the west of Taylor Slough,
Puri and Vernon (1964) distinguish
two physiographic provinces, aside
from the southern slope, lying with-
in the Taylor Slough drainage basin.
The first of these, the gulf coastal
lagoons, refers to the series of
lagoons from Seven Palm Lake to West
Lake. A broad continuous strip of
land covered by coastal prairie
occupies the area north of these
lagoons, running southeast to the
mangroves bordering Madiera Bay.
The northern border of the gulf
coastal lagoons roughly corresponds
to a partial barrier between fresh
and saline waters known as the
Buttonwood Embankment (Craighead
1971). A distinct band of pioneer
red mangrove (Rhizophora mangle)
occurs 3 to 8 km (2 to 5 mi) inland
of this barrier. The second prov-
ince distinguished by Purl and
Vernon (1964) in this region is the
reticulate coastal swamps which
correspond to the more saline black
mangrove (Avicennia germinans) and
white mangrove (Laguncularia race-
mosa) communities which occupy the
area south of the gulf coastal
lagoons to Florida Bay.

To the west of lower Taylor
Slough the coastal swamps and la-
goons are characterized by a series

of lakes (or lagoons) fringed by
mangroves and some tropical hard-
woods toward the eastern end. South
of these lagoons toward Florida Bay
the area is dominated by buttonwood,
and red, black, and white mangroves,
and prairies of salt tolerant (halo-
phytic) herbaceous vegetation (Rus-
sell et al. 1980). On the eastern
side of lower Taylor Slough the
coastal lagoons are conspicuously
absent, and surface drainage is
better defined. This hydrologic
structuring leads to a vegetation
and land form pattern that generally
follows and radiates out from the
surface drainage pattern. Also less
prevalent on the eastern side of
Taylor Slough are the broad plains
of buttonwood and halophytes.

Florida Bay
Florida Bay is a triangularly
shaped body of water extending from
about U.S. Highway 1 on the north-
east to Long Key on the extreme
southwest to East Cape Sable, lying
north and west of Long Key. For
purposes of this report the north-
eastern boundary of the bay follows
U.S. Highway 1 down to Key Largo.
The progressively restricted circu-
lation and exchange of water in Card
Sound and Barnes Sound act as a
barrier inhibiting hydrologic and
ecologic exchange between Biscayne
and Florida Bays (Tabb et al. 1962,
Lee and Rooth 1972). As such the
sounds collectively represent a dis-
tinct physiographic transition zone
between the two bay systems.

Florida Bay is characterized by
numerous mangrove covered islands
that represent the above-water pin-
nacles of a nearly continuous series
of shoals. Fleece (1962) comments
that these shoals often seem to
occur at roughly right angles to one
another. Many of the shoals sur-
round areas of deeper water ( > 2 m
or 7 ft) which are locally referred
to as "lakes".

The complex topography of the
bay system is an important factor in
determining the distribution of
physical and chemical conditions,
and thus subenvironments. As men-
tioned earlier, the upper most part
of the bay is actually a series of
semienclosed sounds which are fairly
well isolated from one another
hydrologically. Beginning just
southwest of Blackwater and Little
Blackwater Sounds, the mud shoals
and islands are not as numerous or
continuous, and the area is uniform-
ly shallow (0 to 2 m or 0 to 7 ft).
Moving toward the Gulf of Mexico on
the mainland side, the width and
length of the mud banks increases,
though the number of islands and
their area above water does not.
Toward the Keys side, the mud banks
are thinner and tend to encircle
deeper "lake" areas.

Turney and Perkins (1972)
divide the bay into four distinct
subenvironments based on dominant
molluskan faunas and physical/chemi-
cal factors. The northern subenvi-
ronment lies along the northern
shoreline toward the Gulf of Mexico.
The interior subenviroment is the
broad central expanse of the bay
which these and other authors (Gins-
burg 1956, Gorsline 1963) believe is
subject to little or no regular
tidal flushing. The Gulf and Atlan-
tic subenvironments correspond to
those areas influenced by tidal
exchange with the Gulf of Mexico
and the Florida Keys area, respec-


Figure 8 presents a map of the
major physiographic features of the
Florida Keys. Extensive exposed and
sheltered mangrove shorelines domi-
nate the surface vegetation of the
Keys, particularly on the Gulf of
Mexico and Florida Bay side, and on
the peripheral keys (e.g., Rodriguez

After US.C. G.S. Charts 112,113 (After Ginsberg,1956) C.AK

Figure 8. Map of physiographic zones of the Florida Keys (adapted from Ginsburg 1956).

-- -""E-"-LII~~L ~ _gl~i~sTii

Key, Johnson Keys). Over the past
50 to 70 years, development through
dredge and fill activities has
converted many of these mangrove
community areas into more habitable
environments for man, as evidenced
by changes in shoreline habitats
(Griswold 1965). The new shorelines
are generally characterized by
riprap/gravel beaches, mixed sand
and gravel beaches, and exposed and
sheltered rocky shores and seawalls
(Getter et al. 1981). Natural sand
beaches are remarkably few and lim-
ited in size. Inland, the mangrove
communities give way to tropical
hardwood hammocks (primarily on the
northern Keys and Big Pine Key), and
Caribbean slash pine stands (Pinus
eliottii var. densa) on islands sur-
rounding and including Big Pine Key
(Alexander and Dickson 1972, CZM

As evidenced by the extent of
mangrove vegetation on the islands,
much of the Florida Keys land area
lies only .6 to 1 m (2 to 3 ft)
above high tide. At only two loca-
tions in the island chain (both in
the upper Keys) does the elevation
reach or exceed 5 m (18 ft) (Hoff-
meister and Multer 1968). Where
these maximum elevations occur, the
island's shape departs from the
typically flat character of the
majority; of the Keys, exhibiting a
slightly raised, centrally-elongated
axis with the southeast and north-
west sides sloping gradually to the-
Atlantic Ocean and Florida Bay, re-
spectively. Beyond the shorelines,
intertidal flats border both sides
of the islands. These are generally
shallow water areas, barely covered
at low tide, which gently slope into
the deeper water of the surrounding
platform. In some places the flats
are exposed at low tide and are cov-
ered by soft laminated algal crusts
(Multer 1977). Florida Bay lies
beyond the flats to the northwest of
the upper Keys.

Farther southwest of Florida
Bay, a great expanse of carbonate
sediments exist under a shallow sea
with a depth rarely exceeding 18 km
(60 ft). This platform bounds the
lower and middle Keys to the gulf
side and is built upon the south-
western submarine extension of the
Floridan Plateau (Brooks 1973).
Stockman et al. (1967) labeled this
current-swept region "The Sluiceway"
as it exhibits a scoured seascape
with only a thin veneer of recent
carbonate sediments a few centi-
meters thick.

Seaward toward the Straits of
Florida and paralleling the Keys is
an arcuate band of living reefs,
linear shoals and depressions de-
scribed as the Florida Reef Tract by
Vaughn (1916). Living reefs that
locally reach to the low water mark
are concentrated on the seaward side
of this band to form a discontinuous
barrier (see Figure 8), e.g., Ameri-
can Shoal, Carysfort Reef, Alligator
Reef. These are also referred to as
the Outer reefs (Ginsburg 1956) or
Bank reefs (Shinn 1963). The area
between them and the Keys is 4.8 to
11 km (3 to 7 ml) wide, and is re-
ferred to as the back reef (Glnsburg
1956) or inner shelf (Enos 1977).
The back reef is characterized by
patch reefs (Ginsburg 1956) or reef
knolls (Turmel and Swanson 1976),
(e.g., Hen and Chickens Keys, Mos-
quito Bank), linear shoals, (e.g.,
White Bank, Washer Woman Shoal) and
areas of deeper water, exceeding
5.5 m (18 ft) (e.g., Hawk Channel)
ranging in depth from 5.5 to 9 m
(18 to 30 ft) off Key Largo to 6 to
15 m (20 to 50 ft) off Key West
(USDC 1962, USGS 1971, Enos 1977).

The Florida Keys are divided
into at least three physiographic
zones distinguished by differences
in their shape, orientation and li-
thology. These are, as illustrated
in Figure 8, the upper Keys (Soldier

Key southwest to New Found Harbor
Keys), the lower Keys (East Bahia
Honda Key to Key West), and the dis-
tal atolls, including the Boca Gran-
de Key Group, the Marquesas Keys,
and the Dry Tortugas (White 1970).

The northernmost zone, the up-
per Keys, is characterized by long
narrow islands, elongated in a
northeast to southwest direction
that roughly parallels the reef
tract described earlier. Based on
the slope and orientation to the
reef tract, the origin and composi-
tion of the upper Keys is easily
understood. Named and described by
Sanford (1909), the Key Largo Lime-
stone is a typical organic reef
composed of wave resistant elements,
the most important of which are
hermatypic corals. These form the
framework of the structure and are
responsible for trapping large
amounts of calcarenite in which they
are now embedded (Krawiec 1977).

The lower Keys form a roughly
triangular group of islands which
generally elongate at right angles
to the northeast-southwesterly ori-
entation of the upper Keys. The
exposed rock formation here is an
extension of the Miami Limestone
Formation, oolitic facies, upon
which Miami and other southeastern
Florida cities have been built
(Hoffmeister and Multer 1968). The
northwest-southeast elongation of
the lower Keys is caused primarily
by the direction of movement of the
tidal scour produced by differences
in time and height of the tides in
the Gulf of Mexico and the Straits
of Florida.

The distal atolls form the
third physiographic region of the
Florida Keys (Puri and Vernon 1964,
White 1970). This designation is
based, it appears, on little more
than the isolated nature of the
islands west of Key West, and their
general shape. Davis (1942) re-

ferred to these "atolls" and the
scattered islands to the west of Key
West as the Sand Keys after an
earlier description by Millspaugh
(1907). The thirty islands of the
Sand Keys fall into three primary
groups: two atoll-like groups, the
Marquesas and Dry Tortugas Keys, and
a loose cluster of small islands
just west of Key West, referred to
by Millspaugh (1907) as the Boca
Grande group. All of these islands
fall within an area extending 112 km
(70 mi) east and west, and 14.4 km
(9 mi) north and south. The Boca
Grande group of 14 islands extends
17.6 km (11 mi) west of Key West;
the elliptical shaped Marquesas Keys
lie 27.2 to 32 km (17 to 20 mi) west
of Key West; and, the Dry Tortugas
are clustered between 104 to 112 km
(65 to 70 mi) west of Key West.
Davis (1942) concluded that the
coarse calcareous sand found in the
three island groups are an accumula-
ted matrix of unconsolidated detri-
tal material of various origins in-
cluding calcareous algae, mollusks,
foraminifera, echinoids, nullipores
(coralline algae Shrock and Twen-
hofel 1953) and coral reef rubble
(Dry Tortugas only]. The two more
easterly groups, the Marquesas Keys
and the Boca Grande group, are built
up from oolitic limestone banks of
the Miami formation and are domina-
ted vegetatively by mangrove and
beach dune strand communities (Davis
1942). Their nearshore marine envi-
ronment is distinguished by flat
bare and grass covered calcareous
sand bottoms, with a notable absence
of coral reefs. Seaward of the Boca
Grande group's southernmost islands,
the Florida Keys reef tract termi-
nates. The Dry Tortugas exhibit
primarily beach-dune strand communi-
ties with the mangroves representing
a very small man-introduced percent-
age of the land cover. Rockbottoms,
shoals, and reefs characterize the
nearshore and lagoonal waters
(Multer 1977).



A classification system devised
by the National Weather Service
divides Florida into seven climatic
divisions, three of which influence
the study area (Figure 9). Each
zone encompasses an area within
which basic climatic variables, pri-
marily temperature and rainfall, are
generally consistent when averaged
over extended periods of record.
The boundary lines between climatic
divisions approximate lines of
change and do not depict radical
changes in climatic patterns. Like-
wise, station to station differences
occur within any one division, espe-
cially where coastal boundary influ-
ences are significant. In spite of
these limitations, the climatic
divisions offer a ready means of
organizing statewide and basin-wide
descriptions, and will be used in
much of the discussion to follow.

Many meteorological measure-
ments are available from the three
first-order weather stations opera-
ted by the National Weather Service
that triangulate the study area
(Ft. Myers, Key West, and Miami).
An additional, more limited selec-
tion is available from numerous
other government agencies. These
measurements are collected for a
variety of applications, agriculture
and aviation being two of the more
important. Detailed meteorological
information is restricted to a few
of the available stations in the
basin, including Key West (Inter-
national Airport), Homestead AFB,
and the Key West Naval Air Station
(NAS). In addition to the Key West
station, two additional, primary
NOAA weather stations (Miami and
Ft. Myers) are included to complete

the measurement of the basin. For a
more in-depth discussion of weather
stations adjacent to and within
the study areas see Parker et al.
(1955), Thomas (1970), Bradley
(1972), Thomas (1974), and MacVicar


US Daaortment of Commerce. 1972.

Figure 9. Florida climatic divisions
(adapted from USDC 1972).


The Everglades/Bay/Keys basin
has a tropical savanna climate char-
acterized by a relatively long and
severe dry season, and a wet season
(Hela 1952). The dry season, last-
ing from November to April (Riebsame
et al. 1974), generates between
18% to 33% of the annual, rainfall
(Thomas 1974), primarily from large
scale (synoptic) winter frontal

- - Study Are


storms (Echternacht 1975). Table 3
shows the relationship between wet
season, dry season, and total annual
rainfall. The table illustrates two
important qualities of rainfall
distribution which are related to
latitude and maritime influence
(Thomas 1974). First, there is a
noticeable decrease of annual preci-
pitation from north to south. Sec-
ond, the wet-dry season differences
in precipitation become less pro-
nounced from north (mainland) to
south (lower Keys). Two of the 14
stations (denoted by asterisks)
report data based on six or less
years of record. These values prob-
ably do not represent the actual or
"true" annual averages because of
the brief recording period. The
questionable validity of these two
stations is further supported by a
five year cyclic pattern observed by
both Thomas (1970, 1974) and Sass
(1967) for the eastern coastal ridge
and the Florida Keys region. With
the stations in these two areas
removed from the data set, the two
trends described previously become
more pronounced. The probable cause
for the differences in these two
areas is the geographical placement
of the Keys and coastal islands in
relation to the prevailing easter-
lies, and the consequent effect on
the land-seabreeze convective pro-
cess. MacVicar (1981) reports that
the predominance of convective type
rainfall in south Florida during the
wet season results in much higher
rainfall totals on the mainland than
along the shore or on the coastal
islands. The distance of 1.6 km
(1 mi) inland from the coast can
mean a difference of 15% to 25% of
the wet season and annual rainfall
values. For example, the coopera-
tive station on Miami Beach, at
the water's edge, has a normal an-
nual rainfall of about 117 cm (46
inches). Seventeen (17) kilometers
(9 mi) inland, at the National

Weather Service Office, the annual
average rainfall is 150 cm (59
inches) (USDC 1981a). The decrease
of convective influenced rainfall
decreases annual average rainfall,
and increases the percentage of dry
season precipitation (see Table 3)
to total precipitation.

Synoptic processes (cold
fronts) dominate the basin's dry
season (Echternacht 1975). They
occur in the area an average of once
every seven days (Warzeski 1976),
although the frequency decreases
equatorially (Thomas 1970). Rain-
fall related to these events has a
characteristic distribution pattern
distinct from that observed in con-
vective-type thundershowers. Synop-
tic rains typically fall over a more
uniform area of the front and are
dependent only on the temporary
passage of the system (Echternacht
1975). Data reported during its
passage would be expected to come
from a number of meteorological
stations simultaneously (Gruber
1969) and would be independent of
diurnal cycles reported for convec-
tive storms (Asplidin 1967).

Wet season daily rainfall
patterns, which are dominated by
convective storms, exhibit large
differences in precipitation from
station to station (Bradley 1972,
Woodley et al. 1974, Echternacht
1975). Woodley (1970) estimates the
natural variability of rainfall from
a single cumulonimbus cloud in south
Florida to range from 200 to 2000
acre-feet; 90% of the 60 to 80 thun-
derstorms occurring annually in the
basin occur during the wet season
(Bradley 1972). These storms are
brief and usually intense, with
some strong winds. Day-long wet
season storms occur infrequently
and are associated with tropical
disturbances (Bradley 1972). The
short duration, high intensity


Years Dry Season (%) Wet Season (%)
Station Location Record PPTN(a) PPTN(a)

Tamiami Trail 40 mi 26 10.1 18% 47.0 82%
Main- Everglades 43 10.3 19% 44.6 81%
land Homestead Exp. Stat. 55 12.5 20% 50.2 80%
Royal Palm Rang. Stat. 20 11.0 19% 46.4 81%
Flamingo 20 9.7 20% 40.0 80%

Tavernier 32 12.5 26% 35.5 74%
Upper Lignumvitae Key 4 8.9 24% 28.0 70%
Keys Long Key 20 10.3 24% 33.5 76%
Marathon Shores 19 11.3 27% 30.6 73%

Big Pine Key 6 9.3 24% 29.0 76%
Lower Key West WSD 127 10.7 28% 27.9 72%
Keys Key West Airp. 27 12.1 30% 27.6 70%
Dry Tortugas 17 11.3 32% 24.2 68%
Sand Key 11 9.6 33% 19.1 67%





*N < 10, see text
(a) measurements given in inches

Table 3. Wet season, dry season, and total annual precipitation for the
Everglades/BaylKeys basin (adapted from Thomas 1974).

thundershowers are related to cyclic
land-seabreeze convection patterns
and result in the majority of rain
occurring during the mid to late
afternoon hours, or when the peak
convergence is observed (Gruber
1969, Echternacht 1975). A temporal
shift in these diurnal patterns has
been noted along the eastern shore
and the coastal islands, including
the Florida Keys. Here, where the
convective activity is initiated
prior to moving inland, the daily
rainfall occurs during the early
morning hours (USDC 1981a, 1981b).

Distribution of rainfall over
southern Florida during the wet
season follows a bimodal pattern
shown in Figure 10. The first of

two peaks occurs in May or June and
the second during September and
October (Thomas 1974). This bimodal
seasonal distribution of rainfall is
associated with an upper air trough
which extends southwards from the
middle latitudes centering itself
over southern Florida during June.
It is displaced westwards into the
Gulf of Mexico during July and
August and returns again in Septem-
ber/October (Gruber 1969, Thomas
1970). Periods of heaviest rainfall
occur when this trough is overhead
(Riehl 1954). Although this bimodal
quality is characteristic of all the
basin stations, the late spring/
early summer peak is less pronounced
in the Keys (Thomas 19701.









SKey West
ORoyal Palm
Ranger Station



A---A--- -A-^

Jan Feb Mar Apr May June July Aug Sep Oct Nov Dec

Figure 10. Average monthly rainfall for three representative stations in
the study area (adapted from USDC 1981a, 1981b, 1981c).

Thomas' (1970, 1974) analysis
of the average annual rainfall
distribution for the Everglades/Bay/
Keys basin is presented in Figure
11a. Annual (and monthly) rainfall
varies considerably from year to
year; ranges in excess of 102 cm
(40 in) for an individual station
are commonplace. For example, Key
West reported 160 cm (62.92 in)
during 1969 and 51 cm (19.99 in) in
1974 (USDC 1981b). Figures 11b and
11c illustrate the mean total wet
season and dry season rainfall,

respectively, for the study area.
These two figures highlight the dif-
ferences between the mainland and
the keys' annual rainfalls.

A precipitation characteristic
commonly reported and of interest
for air pollution and ecological
work is the number of days on which
certain size classes of rainfall oc-
cur, i.e., rainfall greater than or
equal to .254 cm (0.10 in). Table 4
presents a summary of mean number
of days per month with rainfall


--- -- I


1 60(6

Figure 11. Annual mean, total
Figure 11. Annual mean, total
wet season, and total
dry season rainfall
patterns in the study
area (adapted from
Thomas 1974, MacVicar

greater than or equal to .0254 cm
(0.01 in), for first order stations,
and .254 cm (0.10 in), for second-
order stations, within or adjacent
to the Everglades/Bay/Keys basin.
The distribution of rainfall fre-
quency displays a fairly uniform
pattern both monthly and seasonally.
The lower east coast exhibits a

greater number of high rainfall days
over the summer/wet season than
either the Keys or the southwest
coast. The mean annual rainfall
amounts, and number of days with
rainfall greater than or equal to
1.27 and 2.54 cm (0.5 and 1.0 in)
for the climatic divisions covering
the Everglades/Bay/Keys basin also
support the trends mentioned above.

Comparing the rainfall size
classes presented for these events
yields a ratio of 7:5:2:1; that is,
there are roughly 7 times more days
recording rainfall greater than or
equal to .0254 cm (0.01 in) than
.254 cm (1.0 in). Also, the major-
ity of the rainfall events (75%)
in the basin contribute less than
1.27 cm (0.50 in).

The SFWMD has recently com-
pleted the first phase of a project
which provides an important addition
to the rainfall data base. MacVicar
(1981) has produced a series of
rainfall-frequency maps summarizing
the predicted maximum precipitation
for durations ranging from one to
five days, and wet, dry, and annual
series for 1, 3, 5, 10, 25, 50, and
100 year return periods. Figure 12
presents his results for average
annual maximum for 1 day rainfall.
These rainfall-frequency maps cover
the entire south Florida region,
considering data from all rainfall
gages with at least 20 years of
daily records available. The Fla-
mingo Ranger Station at the south-
west corner of the mainland, near
Cape Sable, was omitted from con-
sideration even though more than
20 years of records exist (Thomas
1974). This omission seriously
hampers the contours' accuracy in
much of the southwestern mainland
area of the Everglades/Bay/Keys
basin. This should be kept in mind
when comparing mean annual and
seasonal contours between Thomas
(1970, 1974) and MacVicar (1981).


Station Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Everglades and SW
Fort Myers 5 6 5 5 8 15 18 18 16 8 4 5
Lower East Coast
Miami 7 6 6 6 10 15 16 17 18 15 8 6
Key West 7 6 5 4 8 13 13 15 16 12 7 7
Source: U.S. Department of Commerce, 1975.
Period of Record: Variable (Minimum length of record, 11 years. Length of record at all but two stations greater
than 25 years.)

Everglades and SW
Belle Glade
Lower East Coast

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

3 3

5 9 8 8 11 9


4 4 4 4 6 12 12 12 12 8 3 3 84
3 3 3 3 6 10 13 12 12 6 2 3 76
3 4 4 4 8 12 12 13 13 10 4 3 90

Source: U.S. Department of Commerce, August 1976.
Period of Record: 1951-1974.

Table 4. (adapted from Dames and Moore 1978).



Figure 12. Average annual maximum
for one day rainfall
(adapted from MacVicar

Drought is occasionally experi-
enced even during the "wet" season
(Bradley 1972). The effect of
drought is aggravated or ameliorated
by variations of temperature which
affect transpiration, evaporation,
and soil moisture. One of the more

noteworthy studies in this regard is
that of Gannon (1978). In attempt-
ing to model the daily sea breeze
circulation over the south Florida
peninsula, Gannon (1978) concludes
that developments on the land sur-
face such as urbanization and wet-
land drainage inadvertently modify
weather patterns by redistributing
rainfall via changes in the overall
daily heat budget. Soil moisture
and surface albedo (the ratio of
reflected radiation to total radia-
tion) are the two most important
factors influencing the strength of
the daily sea breeze circulation in
Gannon's model. Surface albedo in
turn is inversely related to soil
moisture; thus wetland drainage may
exert something of a self-accelerat-
ing effect on the daily hydrologic
cycle through: (1) lowering soil
moisture which itself changes the
heat budget and provides less mois-
ture for evapotranspiration; and
(2) increasing surface albedo which
even further increases daytime heat-
ing. The total removal of wetlands



I~----- ---- -------

from the weather cycle through pav-
ing and other urban development
further amplifies the shift toward
higher temperatures.

The insidious implications of
this situation for fish and wild-
life, as well as for the human
population of south Florida, have
recently been noted by Arthur Mar-
shall (Boyle and Mechum 1982).
His hypothesis is that development
and drainage have slowly replaced
Florida's wet season "rain machine"
with a relatively drier "heat ma-
chine" during summer months. Thus
wet season rains which are so vital
to south Florida's ecosystems occur
less frequently due to massive
changes in the daily heat budget.


Wind patterns in south Florida
are determined by the interaction of
prevailing easterly tradewinds and
localized diurnal factors produced
by land-sea convection patterns
(during the wet season), or synoptic
scale cold fronts (during the dry
season) (Echternacht 1975). In a
comprehensive examination of season-
al differences in the large scale
wind fields for the Florida penin-
sula, Gruber (1969) described the
seasonal streamlines at three ver-
tical levels: 950 millibars (mb)
occurring at 0 to 610 m (0 to 2000
ft); 500 mb, occurring at 5,486 to
6,096 m (18,000 to 20,000 ft); and
200 mb, occurring at approximately
12,192 m (40,000 ft). His work was
summarized by Echternacht (1975) in
an attempt to apply the wind field
patterns to potential air pollution
problems affecting south Florida.
Figure 13 illustrates the four sea-
sonal wind field patterns adapted by
Echternacht (1975) at the 950 mb
level (i.e., for low-level winds).
For the Everglades/Bay/Keys basin
Figure 13 shows a dominant easterly

influence varying from due east in
fall and winter seasons, to east
southeast in spring and summer.

This prevailing easterly flow
interacts with the two seasonal wind
patterns described previously. Dur-
ing the wet season (May to October),
convective scale winds initiated by
thermal gradients at the land-sea
interface find support from the
prevailing southeasterly winds
(Pielke 1973). The heating of the
land surface promotes seabreeze cir-
culation during the day resulting in
the convergence of warm moist air
over the peninsula (Dames and Moore
1978, Gannon 1978). At night the
process reverses, the land cools
faster than the ocean, and air tends
to diverge away from the peninsula.
The recurrent wind cycle and mari-
time influence is significant to the
area's wet season climate due to the
flat terrain and proximity to the
water ( < 40 m or 25 mi) (Bradley
1972, Echternacht 1975). Frank
et al. (1967) monitored the daily
changes in divergence over the
Florida peninsula for the summer
months of June through August. As
illustrated in Figure 14, a pro-
nounced diurnal pattern was recorded
showing very strong convergence
(i.e., negative divergence) during
the day (peaking around 12:00 to
2:00 E.S.T.). Therefore, the con-
vective scale is the fundamental
scale of motion during the basin's
wet season (Echternacht 1975).

In the dry season (November to
April) the convective influence
diminishes as the sun's angle of
incidence decreases, reducing the
radiant heating of the land's sur-
face during the day and thus mini-
mizing the thermal gradient between
the land-sea surfaces (Blair and
Fite 1965). During this time the
wind patterns are influenced by
synoptic scale systems or winter


Figure 13. Streamlines and isotachs at the 950 mb sublevel for 1957 to 1965
(adapted from Echternacht 1975).


Im*a~o~ '

<- June... ,..-.. \ . .....
July ," / '-
, . . . . " \ / "- J u l y
o \. / ..**

30- .. \ .
= \ ". *

S-20o \:

-30-\ .. .."


1:00 4:00 7:00 10:00 13:00 16:00 19:00 22:00 1:00 4:00


Figure 14. Mean monthly divergence curves for June through August 1963
over the Florida peninsula (adapted from Frank et al. 1967).

frontals moving cold air masses
southward. Although the south Flor-
ida basin lies far enough to the
south to remain under the influence
of the easterlies year round (see
Figure 13; winter), a northerly
component, related to the synoptic
scale systems, affects the daily
weather patterns (Echternacht 1975).
Winter cold fronts pass over the
basin approximately once a week dur-
ing this dry season (Warzeski 1976).
Warzeski (1976) describes the cold
front in the Biscayne Bay region as
follows :

"An average cold front affects wind
patterns in the Biscayne Bay region
for 4 to 5 days, involving a slow
3600 clockwise rotation of wind

direction (direction from which the
wind is blowing). Winds rise above
ambient throughout this period,
reaching maxima roughly half a day
before and after passage of the
front itself. Maximum winds ahead
of the front are from the southwest
and reach 8 m/sec. Maximum winds
during an exceptional cold front can
reach 20 to 26 m/sec."

Monthly wind speed and direc-
tion for the three first-order
weather stations triangulating the
basin (Ft. Myers, Miami, Key West)
are presented in Table 5 (USDC
1981a, 1981b, 1981c). The reported
wind directions are those most fre-
quently occurring during each month.
This method of comparison does not


give an adequate depiction of diur-
nal shifts in wind direction and
speed resulting from the differen-
tial heating of air and water sur-
faces or the passage of individual
winter frontal systems. It does,
however, indicate the predominance
of different seasonal factors con-
trolling wind. On a seasonal basis,
highest average wind speeds tend to
occur in late winter and early
spring, and lowest speeds during the
summer. High localized winds of
short duration occur occasionally in
connection with summer thundershow-
ers and with cold fronts moving
across the state during other sea-
sons (Bradley 1972). Wind speeds
associated with convective systems
follow a diurnal pattern. On a
typical day, wind speeds are lowest
in the nightime, increase during the
daylight hours to a peak in the af-
ternoon, and then decrease again in
the evening (Dames and Moore 1978).

Synoptic scale influences are
associated with the passage of the
front, as previously described,
rather than with diurnal patterns
(Warzeski 1977). The influence of
synoptic scale systems on prevailing
wind direction is evidenced by the
northerly component of the prevail-
ing wind directions for the months
of October through January in
Table 5.

Wind direction and speed tend
to vary with height above the
ground. The variation of wind di-
rection with height is not always
uniform, but wind speed generally
increases with height over the flat
terrain of the Everglades/Bay/Keys
basin (Dames and Moore 1978). Sea-
sonal variations of wind speed and
direction at the 950 mb level (0 to
610 m or 0 to 2000 ft) are presented
in Figure 13. Dames and Moore
(1978) examined the low-level wind
patterns at 150m, 300m, and 500m
(492, 984, and 1640 ft) at Miami.

They concluded that:

"During both the morning and evening
at all three levels, winds are pre-
dominantly from the east and south-
east. Furthermore, the mean wind
speeds of the prevalent wind direc-
tions are greater than at Tampa and
Jacksonville. Certainly this is not
the case on each day of the year,
but it appears to be the most common

Month S












Ft. Myers Key West
nternat. Airport Internat. Airport
ind (mph) Prevail. Wind (mph) Prevail.
peed Direct. Speed Direct.
(8.5) (12.1)
8.6 E 12.2 NE
(9.1) (12.2)
9.2 E 12.3 SE
9.6 SW 12.6 SE
(9.0) (12.8)
8.9 E 12.7 ESE
8.2 E 11.1 ESE
7.4 E 9.9 SE
(6.8) (9.9)
6.9 ESE 10.1 ESE
(6.8) (9.6)
6.9 E 9.4 ESE
(7.7) (10.1)
7.9 E 10.3 ESE
8.5 NE 11.4 ENE
8.3 NE 12.0 ENE
(8.2) (12.1)
8.3 NE 12.0 NE

8.2 E 11.3 ESE

Internat. Airport
Wind (mph) Prevail.
Speed Direct.
9.4 NNW

10.1 ESE
10.3 SE
10.4 ESE
9.4 ESE
8.1 SE
7.8 SE
7.6 SE

Table 5. Most common wind direction
and speed by month for
selected first order weather
stations (adapted from
USDC 1981a, 1981b, 1981c).


The southern latitude and mari-
time influences are the primary con-
trols on the temperature regime in
the Everglades/Bay/Keys basin. The
climate is basically subtropical/
marine characterized by a long, warm
summer followed by a mild, dry win-
ter (Bradley 1972).


Illustrated in Figure 15 are
isotherms developed for south Flor-
ida (Thomas 1970) describing mean
annual temperature (Figure 15a), and
the mean monthly temperature for
the coolest month (January, Figure
15b) and the warmest month (August,
Figure 15c). Differences between
coastal/keys areas and inland re-
gions are highlighted by the fact
that the isotherm contours follow
the coastline (Figure 15). The

coastal/keys areas reflect a mari-
time influence, exhibiting low daily
ranges of temperature and rapid
warming of cold air masses which
pass to the east of the state (USDC
1981a, 1981b). Inland locations
generally display a greater range of
temperatures due to the more rapid
heating and cooling of ground sur-
faces (Gerrish 1973, Dames and Moore
1978). For example, the average
daily range of temperature is 5.50C
(100F) at Miami Beach and Key West,
while well inland in the Everglades
the average daily range is near 100C
(180F) (USDC 1981a, 1981b). Another
example of this temperature differ-
ential between coastal and inland
areas appears in the annual number
of days with temperatures reaching
320C (900F) or above. Miami Beach
reports less than 15 days per year
as compared to inland stations re-
porting approximately 60 days per
year (USDC 1981a). The minimum tem-
peratures reported for coastal/keys
and inland sites repeat this trend.


Tortugaos go



Figure 15. Isotherms for study
area annually, and in
January and August
(adapted from Thomas

A simple statistical represen-
tation of relative humidity is dif-
ficult for many locations because of
large diurnal and seasonal varia-
tions (USDC 1981a, 1981b, 1981c).
In Florida, and more so in south
Florida, the situation is less com-
plex because of the abundance of
moisture throughout the year (Dames
C and Moore 1978). Table 6 summarizes
the mean monthly relative humidity
for 0100, 0700, 1300, 1900 hours at
the Miami, Ft. Myers, and Key West
first-order weather stations.

Combining all hours of the day
and all months into a single aver-
age, the mean annual relative humid-
ity is quite uniform throughout the
basin, averaging about 75% (USDC
1981a, 1981b, 1981c). Relative
humidities are generally highest
during the early morning hours,


Key West Airport (N=32)
0100 0700 1300 1900 x

81 82 69 77 7;

78 80 67 75 75

77 79 66 73 74

76 77 64 71 72

77 77 65 72 7;

78 78 68 73 74

77 76 66 71 73
78 78 67 73 74

79 81 70 76 7;

80 82 69 76 7;

80 83 69 76 7;

81 83 70 78 7E

YEAR 78 80 68 74 75

Miami Intern. Airport (N=16)
0100 0700 1300 1900 x

81 84 60 69 74

79 83 57 66 71

78 82 57 65 71

75 79 55 64 68

80 82 61 70 73
84 86 67 75 78

82 86 64 72 76
83 87 66 74 78

85 89 68 78 80

83 87 65 74 77

81 85 62 71 75

79 84 59 70 73

81 84 62 71 75

Ft. Myers, Page Field (N
0100 0700 1300 1900

86 88 58 73

84 88 55 70
84 89 52 68

84 88 48 65

85 88 51 67

88 88 59 74
88 88 60 75

88 89 61 77

88 90 62 78

86 88 57 73
87 89 56 74

87 89 56 75

86 89 56 72 76

Table 6. Mean monthly relative humidities (%) for 0100, 0700, 1300, 1900
hours, and 24 hour average from south Florida first order weather
stations (adapted from USDC 1981a, 1981b, 1981c).

typically on the order of 75% to
90%, and generally lowest in the
afternoon hours, averaging from 50%
to 70%. On a seasonal basis, mean
relative humidities tend to be
lowest in the spring months (April)
and highest in the summer and fall
months, although seasonal differ-
ences are not great. The Florida
Keys, reflecting a dominant maritime
influence, show even less daily and
seasonal variation. Also, the sea-
sonal peak for the Keys appears more
in the fall as opposed to the summer
as observed in Miami (USDC 1981a,
1981b). Figure 16 illustrates the
more stable relative humidity exhib-
ited in the Keys compared to main-
land stations.


Throughout the year, incoming
solar radiation varies little within
the latitudinal constraints of the

Everglades/Bay/Keys basin (Dames
and Moore 1978). What does vary
are factors such as cloud cover, air
pollution (particulate load or dust-
iness), and relative humidity, which
modify the transmission, absorption
and reflection of solar energy
(Blair and Fite 1965, Bamburg 1980).
These factors result in temporal and
spatial variations in the amount of
solar radiation reaching the land
and water surfaces.

Miami is the only first-order
weather station to collect solar
radiation data in or near the study
area (Bradley 1972). From 20 years
of records, the average daily solar
radiation reported is 447 langleys
(gm-cal/cm2). Monthly variation
ranges from 319 langleys in December
to 572 langleys in April (Bradley
1972). The higher values are re-
ported during middle to late spring
rather than during the summer

87 89 56 75




'""~ L'



MIAMI A-- ----A

80- A


: 60- /A

55- \ A

50- V

45- -- --- i --- ---
01:00 07:00 13:00 19:00

Hours (EST)

01:00 07:00 13:00 19:00

Hours (EST)

Figure 16. Diurnal patterns in relative humidity over south Florida in
April and September (adapted from USDC 1981a, 1981b, 1981c).

solstice (when the angle of inci-
dence is least) because of increased
precipitation and cloud cover asso-
ciated with the beginning of south
Florida's wet season.

As stated previously, the po-
tential incoming solar radiation is
approximately the same throughout
the basin. However, the insolation
(radiation reaching the ground/water
surface) varies in relation to local
atmospheric differences (Bamburg
1980). Table 7 shows climatic data
collected at Ft. Myers, Miami, and
Key West first-order stations. This
data represents either a direct

measurement of incoming solar radia-
tion or observations which measure
the factors affecting the solar
energy's passage through the atmo-
sphere (Bradley 1972, USDC 1981a,
1981b, 1981c). The Miami Station is
located some 15 km (9 mi) inland,
thus it is assumed that this station
represents the characteristics of
the study area's more inland envi-
ronment (USDC 1981a). It is also
assumed that Ft. Myers and Key West
represent the coastal and island
environments, respectively, of the
basin. The coastal/island areas
within the basin exhibit less cloud
cover and more clear days than


Key West Internat. Airport
Month (1) (2) (3) (4) (5) (6)

Miami Internat. Airport
(1) (2) (3) (4) (5) (6) (7)

JAN 73 5.1 11 12 8 0 61 5.3 10 12 9
FEB 76 4.7 11 10 7 0 61 5.3 9 11 8
MAR 83 4.6 13 12 6 0 78 5.4 8 15 8
APR 84 4.5 13 12 5 0 80 5.4 8 15 7
MAY 81 5.2 9 14 8 0 66 6.0 6 15 10

JUN 74 6.2 4 16 10 0 76 6.8 3 14 13
JUL 77 6.3 3 18 10 0 78 6.6 2 17 12
AUG 77 6.3 3 18 10 0 74 6.6 2 18 11
SEP 71 6.6 3 15 12 0 73 6.8 2 15 13
OCT 70 5.7 8 13 10 0 70 6.0 6 14 11
NOV 71 5.1 10 12 8 0 63 5.4 8 14 8
DEC 72 5.1 11 12 8 0 60 5.3 9 13 9
YEAR 76 5.5 99 164 102 1 70 5.9 73 173 119

1 334
1 397
1 475
1 572
* 540

0 506
* 539
* 510
* 440
* 387

1 350
1 319
9 447

Ft. Myers Page Field
(1) (2) (3) (4) (5) (6)
5.0 11 12 8 5
4.9 11 10 7 3
4.9 12 11 8 3
4.6 11 13 6 2
5.0 9 15 7 1
6.1 5 15 10 *
6.5 2 18 11 *
6.3 3 18 10 *
6.2 4 15 11 *
5.0 11 12 8 1
4.7 12 11 7 2
4.9 12 11 8 4
5.3 103 151 101 21

(1) Percent of possible sunshine
(2) Mean sky cover sunrise to sunset (tenths)
(3) Mean number of days, sunrise to sunset to be clear
(4) Mean number of days, sunrise to sunset to be partly cloudy
(5) Mean number of days, sunrise to sunset to be cloudy
(6) Mean number of days with heavy fog (* = trace)
(7) Average daily solar radiation in langleys

Table 7. Solar radiation and related climatological data for Key West,
Miami, and Ft. Myers first order weather stations (adapted
from USDC 1981a, 1981b, 1981c).

inland areas. This quality is most
apparent in the dry season months
(November through April), during
which the highest number of clear
days are reported for all three sta-
tions. The number of days of heavy
fog increases from south to north,
and from east to west. During the
dry season the fog is usually an
early morning or late night phenome-
non which generally dissipates or
thins soon after sunrise (USDC
1981a, 1981b, 1981c). Heavy daytime
fog is seldom observed in south
Florida (Bradley 1972). The mean
annual total hours of sunshine for

the basin ranges from approximately
3000 hours inland to nearly 3300
hours at Key West (Dames and Moore


Warzeski (1976) divides the
climatic conditions of south Florida
into three energy levels or intensi-
ties. These are: (1) prevailing
mild southeast and east winds; (2)
winter cold fronts; and (3) tropical
storms and hurricanes. The first
two were previously discussed in
the sections on wind and rainfall.

-- I I.

Tropical storms and hurricanes,
because of their Infrequent occur-
rence, significance as an ecological
force, and unique climatic charac-
teristics, are treated here as a
separate climatic element.

In summer and fall, occasional
low-pressure areas are observed
which originate in the warm, moist
air of the equatorial trough. The
winds are light and usually drift
from east to west. Then an atmo-
spheric wave appears in the easterly
flow and proceeds westward at 16 to
24 km per hr (10 to 15 mph) (Blair
and Fite 1965). These easterly
waves usually form between 5 and
200 north of the equator. From this
point the easterly wave development
may go through one or all four
stages of a tropical cyclone as
described by Riehl (1954):
(1) Formative stage. Winds usu-
ally remain below hurricane
force with the strongest
winds generally occurring in
one quadrant, poleward and
east of the center of a
deepening of the barometric
trough. Areas of weak wind
circulation (less than 61 km
per hr or 38 mph) are refer-
red to as "tropical depres-
sions" or "tropical distur-
bances". These disturbances
move in a very rough coun-
terclockwise direction and
may travel great distances
organized as such (Gentry
(2) Immature stage. If the
shallow depressions inten-
sify with winds exceeding
61 km per hour (38 mph) the
"tropical depression" has
become a "tropical storm"
characterized by barometric
pressures dropping to 1000
mb and below, and winds
forming tighter concentric
bands around the center or
eye. The cloud and rain

patterns also change from
disorganized squalls to nar-
row organized bands spiral-
ing inward (Riehl 1954).
If the winds intensify to
119 km per hr (74 mph) or
more, a tropical cyclone or
hurricane is born (Gentry
1974). Still only a rela-
tively small area is invol-
ved, i.e., hurricane force
wind radius of 32 to 48 km
(20 to 30 mi) (Riehl 1954).
(3) Mature stage. The surface
pressure at the center is no
longer falling and the maxi-
mum wind speed no longer
increases (Riehl 1954). In-
stead, the circulation ex-
pands, extending the radius
of hurricane force winds.
(4) Decaying stage. Tropical
cyclones, both mature and
immature, generally move
westward in the prevailing
westward drift of the east-
erlies. They enter the de-
caying stage as they recurve
from the tropics and enter
the belt of westerlies,
usually decreasing in size
(Riehl 1954, Blair and Fite

During the immature and mature
stages the general westward movement
ranges from 16 to 48 km per hr (10
to 30 mph). The typical path is
parabolic, although the actual path
of any given storm is governed by
the winds existing above it, result-
ing in a multitude of speed and
directional changes (Blair and Fite
1965). Blair and Fite (1965) pro-
vide a concise description of the
passage of a hurricane over the
Everglades/Bay/Keys basin:

"As such a storm approaches, the
barometer beings falling, slowly at
first and then more and more rapid-
ly, while the wind increases from a
gentle breeze to hurricane force,


and the clouds thicken from cirrus
and cirrostratus to dense cumulonim-
bus, attended by thunder and light-
ning and excessive rain. These con-
ditions continue for several hours,
spreading destruction in their
course. Then suddenly the eye of
the storm arrives, the wind and the
rain cease, the sky clears, or part-
ly so, and the pressure no longer
falls but remains at its lowest.
This phase may last thirty minutes
or longer, and then the storm begins
again in all its severity, as be-
fore, except that the wind is from
the opposite direction and the pres-
sure is rising rapidly. As this
continues, the wind gradually de-
creases in violence until the tem-
pest is passed and the tropical
oceans resume their normal repose.
The violent portion of the storm
may last from twelve to twenty-four

South Florida has the dubious
honor of being visited more often by
hurricanes and tropical storms than
any other equal-sized area of the
United States (Gentry 1974). The
Everglades/Bay/Keys basin is exposed
to both Atlantic and Carribean hur-
ricanes. Tropical cyclones general-
ly strike the east coast of south
Florida from an ESE direction--a
predominant direction for Atlantic
hurricanes before recurvature (Jor-
dan 1973, Ho et al. 1975). The west
coast of south Florida is vulnerable
to late-season tropical cyclones
moving in a northeastward direction
after recurvature (Cry 1965, Bradley
1972). Figure 17 illustrates the
frequency of hurricane occurrences
along the Atlantic coastline for
five of 58 coastal segments delin-
eated by Simpson and Lawrence
(1971). Points-of-entry in south
Florida of tropical storms and hur-
ricanes also appear in Figure 17.
Major hurricane tracks passing
through the Dry Tortugas appear in
Figure 18. The average forward
speed for hurricanes affecting the

basin is 10 knots with a radius of
maximum winds extending an average
of 20 nautical miles from the center
(Ho et al. 1975). Detailed descrip-
tions of the passage of specific
hurricanes and tropical storms
through the basin exist in litera-
ture such as the U. S. Department of
Commerce's "Monthly Weather Review".
This journal summarizes all meteoro-
logical data associated with the
passage of tropical waves, distur-
bances, storms, and hurricanes for
each year's hurricane season.

The three primary forces asso-
ciated with the passage of a hurri-
cane are wind, storm surge, and
rain. As discussed previously, sus-
tained winds greater than 119 km per
hr (74 mph) must exist prior to a
tropical storm's graduation to hur-
ricane status. Sustained winds over
200 km per hr (125 mph) must be
present for a hurricane to be clas-
sified a "Great Hurricane". Ball et
al. (1967), Pray (1966), and Perkins
and Enos (1968) describe the pas-
sages of two "Great Hurricanes",
Donna (Sept. 1960) and Betsy (Sept.
1965), through the Florida Keys.
Winds over 200 km per hour (125 mph)
have occurred in the study area on
several occasions during the last
century (Sugg et al. 1971, see Fig-
ure 17). The most notable was the
"Labor Day" hurricane in 1935 which
passed over Long Key with winds
estimated between 322 to 402 km per
hr (200 to 250 mph) (Bradley 1972).

One can best appreciate the
ecological significance of hurri-
canes when it is understood that the
wind force increases by the square
of the wind speed. In other words,
a 150 km per hr (93 mph) wind exerts
four times as much force' as a 75 km
per hr (47 mph) wind. When hurri-
cane winds exceed 400 km per hr
(249 mph, as was estimated for the
"Labor Day" hurricane by Gentry
1974) their strength becomes almost

I)lllllll~R~------ -*


24- TC GH\ 16 12 5 CYCLONES
19 13 4 26 GH-GREAT
18 13 2 values in %

Figure 17. Points of entry and probabilities of hurricanes at selected
coastal locations (adapted from Jordan 1973).

Figure 18. Tracks of major hurricanes passing over the Dry Tortugas
since 1871 (adapted from Jordan 1973).



Storm surge, resulting in an
increase in high tides and rough
seas, is caused by a complex inter-
action of storm wind, minimum pres-
sure, and the slope of the bottom
topography of waters adjacent to the
land (Gentry 1974). The effects are
of course more pronounced when the
storm moves onshore, as opposed to
moving along the coastline. Since
1873, 8 hurricanes have caused
record storm tides in sbuth Florida,
2 of them within the study area
(Simpson et al. 1969). There ap-
pears to be no discernible pattern
in the occurence of these great
storms all areas of the coast have
been equally affected. Record storm
surge tides range between 2.9 and
5.5 meters (9.5 and 18 feet) above
undisturbed or still water levels
(Simpson et al. 1969). In addition,
coastal areas are also subject to
strong wave action which causes
waters to reach even further inland
than indicated by tide heights alone
(Gentry 1974).

The amount of rainfall associ-
ated with tropical storms varies
greatly depending on several fac-
tors, the more obvious ones being
the intensity of rainfall, the for-
ward movement, and the size of the
storm (Gentry 1974). Because of the
violent nature of the storm, the
error in the rainfall measurements
may be as high as 50%. Usually
12.5 to 25 centimeters (5 to 10
inches) of rain are recorded during
the passage of a tropical storm
(Gentry 1974).


Three general types of atmo-
spheric contaminants (related to
both natural and man-made sources)
affect the south Florida environment
(Echternacht 1975). These are: (1)
sources for small particulate matter
that can form condensation nuclei,
(2) sources for particulate matter

suspended in the air that can be
scavenged by falling raindrops, and
(3) sources of solutes which are
dissolved in condensation particles
(cloud droplets). The sources for
all three and their geographic dis-
tributions are dependent on the
basin weather patterns. For the
Everglades/Bay/Keys basin this means
the wet-dry season variation. Pas-
sage of large scale synoptic systems
during the dry season (November-
April) may contain pollutants from
sources far removed from the state
(Echternacht 1975), in addition to
localized sources (Holle 1971). Wet
season convective systems exhibit
diurnal activity related to land-sea
breeze interactions. These systems
convey atmospheric contaminants
primarily from local sources, i.e.,
automobile emissions, stack gases,
fertilizer and pesticide dusts, and
ash from burned marsh grasses and
sugar cane residue (Holle 1971,
Echternacht 1975).

Two mechanisms are involved in
the movement of air-borne contami-
nants from the atmosphere to the
land and water surfaces. The mate-
rial, inorganic and organic, is
transported either by (1) wet or
(2) dry fallout (Irwin and Kirkland
1980). Material associated with dry
fallout is in a continuous flux of
suspension and deposition, e.g.,
wind generated dust, car emissions.
Those materials deposited during wet
fallout or rainfall, either in a
dissolved or particulate form, are
affected by two processes referred
to as rainout and washout (Echter-
nacht 1975). Semonim and Adams
(1971) describe rainout as the re-
moval of aerosols in the rainmaking
process and washout as the process
of falling rain scavenging air-borne
particulates. For instance, in
south Florida Echternacht (1975)
concluded that with nutrient fallout
total phosphate (TPO4) in the par-
ticulate form is subject to the

_~ ~

washout process, i.e., scavenging of
particulate TPO4 by falling rain
and as dry fallout year round. In
contrast, nitrogen as NOx occurs
primarily in the solute form and is
therefore removed in the rainout
process. Total atmospheric fallout,
wet plus dry, is commonly reported
as bulk precipitation. It consists
of three fractions: (1) dissolved
materials in aqueous precipitation,
(2) the water-soluble component of
dry precipitation, and (3) the
water-insoluble component of either
wet or dry precipitation (Irwin and
Kirkland 1980). Irwin and Kirkland
(1980) summarized qualitative rain-
fall characteristics at selected
USGS study sites in Florida includ-

*4 Station location and number

No+ a-K CI


0.2 0.1 0 0.1 0.2

Diagrams show general chemical
character of bulk precipitation.
The ionic concentrations are
plotted for sodium and potassium
(Na+K), calcium (Ca), magnesium
(Mg), chloride (Cl), bicarbonate
(HC03), and sulfate (S04). Anions
are plotted to the right of the
centerline and cations to the left.
The area of a diagram is an in-
dication of the dissolved-solids
concentration--larger areas reflect
greater dissolved solids concentration.

0 20 40 60 Miles
i l l i II

ing six sites within or adjacent to
the Everglades/Bay/Keys basin. Fig-
ure 19 illustrates the mean chemical
composition of the more common inor-
ganic ions in rainfall. Within the
basin, particularly at stations 3
and 4, calcium (Ca) and bicarbonate
(HCO3) are dominant ions while
magnesium (Mg) and sulfate (SO4)
are least significant. At Station 5
(40 Mile Bend Tamiami Trail) sodium
plus potassium (Na + K) and chloride
(CI) dominate and continue to do so
up to Lake Okeechobee. Waller and
Earle (1975) suggest that the ele-
vated sodium and chloride concentra-
tions are a function of the proxi-
mity of ocean waters, although a
decrease observed in stations within

Figure 19. Location of precipitation sampling sites in study area, and
average chemical concentrations (adapted from Irwin and
Kirland 1980).

rl II I

the Everglades National Park (1, 3,
4) further south and closer to the
coast do not support this supposi-
tion. Higher calcium/bicarbonate
levels observed in this basin
(sites 1, 3, 4) are believed to be
derived from fine rock and marl
soils (Waller and Earle 1975).

Waller (1975) reports that bulk
precipitation comprises as much as
78% of the total annual input of
nitrogen and 90% of the input of
phosphorus to the conservation areas
north of the Everglades National
Park. The majority of the total
loading occurs during the wet season
due to the increased quantity of
rainfall. Concentrations in dry
fallout, however, tend to increase
during the dry season (Echternacht
1975, Waller and Earle 1975).
Echternacht (1975), reviewing the
South Florida Water Management Dis-
trict's rainwater data, illustrated
this seasonal difference of nitrogen
and phosphorus concentrations. Peak
concentrations occur during spring
months, which are characterized by
high winds and low rainfall and,
therefore, high dry fallout condi-
tions (Table 8). Summer months,
during peak rainfall and maximum
dilution, show the lowest concen-
trations. Dilution, soil drying,
increased wind activity, and con-
tamination of collecting devices by
animals are believed to be the pri-
mary causes of the obscured season-
ality. Fire is also believed to be
a factor in enhancing the concentra-
tion of dry fallout in the dry sea-
son (Holle 1971, Waller and Earle

The mean nutrient values for
total nitrogen as "N" are fairly
uniform for all sites; however,
phosphorus as "P" reported at sites
1 and 3 are the highest recorded in
the state's USGS monitoring network
(Irwin and Kirkland 1980; see Figure
19). These two sites are monitored

monthly and are located close to
"natural" settings at the Everglades
National Park Research Center and at
Grossman Hammock in Shark River
Slough. Therefore it is suggested
that local biota, such as birds and
frogs, may be contaminating the
samples (Waller and Earle 1975,
Irwin and Kirkland 1980). Bulk pre-
cipitation data collected by the
South Florida Water Management Dis-
trict support the idea of contamina-
tion at sites 1 and 3 (Echternacht
1975). Davis and Wisniewski (1975)
reported nitrogen as "NOx" and
phosphorus (ortho as "P") at sites
in Homestead, Tamiami Trail (40 Mile
Bend), and the Everglades. The
values reported are much lower than
reported at sites 1 and 3 by Irwin
and Kirkland (1980).

Ammonium Nitrate Nitrite Orthophosphate Total Phosphate

PP Ppm
Summer 0.30 0.28
Fall 0.61 0.26
Winter 1.91 0.27
Spring 2.30 0.49

ppm ppm ppm
0.01 0.03 0.04
0.02 0.06 0.07
0.02 0.08 0.09
0.06 0.13 0.30

Table 8. Seasonal averages of nu-
trient species contained in
rainwater at Tamiami Trail
40 mile bend (adapted from
Echternacht 1975).

Most trace metals in bulk pre-
cipitation are derived from dry
soils and fine rock material wafted
into the air by winds. Mercury and
arsenic, however, are believed
related to pesticide use on nearby
agricultural operations (Waller and
Earle 1975). Lead and iron are
attributed to motor vehicle activity
(Irwin and Kirkland 1980). Site 4
(Tamiami Trail, 40 Mile Bend) is the
only site in the basin monitored for
trace metals in bulk precipitation.
Of all trace metals, cadmium and
zinc show up in the most potentially
hazardous concentrations; however,

C- -

these concentrations are believed to
result from contamination by nearby
galvanized metals (Waller and Earle
1975). All trace metal sampling
sites are located near highways
and/or located with the objective
of measuring some local phenomena,
and thus very likely do not portray
regional conditions (Irwin and
Kirkland 1980).

The pH of rainfall reported at
sites 1, 3, 4, and 5 within the
basin ranged from pH 5.2 to pH 8.7
(Irwin and Kirkland 1980). This
data should be viewed as only ap-
proximate due to the holding times

Data on selected pesticides and
industrial compounds monitored are
rather limited for the basin. Trace
amounts of PCB were reported at
sites 1 and 3, and malathion and
diazinon were just detectable at
site 4. Site 2 monitored at a camp-
ground near Florida City just south
of Homestead reported the presence
of a variety of pesticides, highest
of which were diazinon (mean concen-
tration = 0.26 ppb) and malathion
(mean = 0.47 ppb). The sampling
site is located to the east of the
Everglades National Park and sand-
wiched in between two major farming
areas dealing mainly in truck crops,
i.e., vegetables. Application of
pesticides in this area is usually
done by aerial sprayers, providing
ample opportunity for atmospheric
contamination over the sampling
site. The values reported should be
considered conservative because of
the rapid breakdown of the organo-
phosphate compounds reported in
highest concentrations, such as

Dames and Moore (1978) studied
sulfur dioxides in the state of
Florida, concentrating their efforts
in Hillsborough, Duval, and Escambia

Counties. The results were applied
to other counties including Dade and
Monroe. Their review of historical
data for Miami and Homestead showed
very low values, with most readings
below the official detection thresh-
old of 0.01 ppm. Dade County's
projected 1980 rate of emissions
(1,164 grams/sec.) was the highest
of any south Florida county and
ranked ninth in the state. Dames
and Moore (1978) concluded, however,
that the 24-hour maximum concentra-
tions of SO2 are presently, and
will continue to be, far below
Florida and national air quality
standards, even at locations where
the maximum combined effects are

Inversions occur when warm air
becomes caught below colder air, re-
sulting in the trapping of a stable
air column and thereby preventing
mixing or dilution of air pollutants
immediately above the ground. By
monitoring towers in and adjacent to
the basin, Cerrish (1973) concluded
that inland inversions form almost
every night, are much stronger than
those on the coast of south Florida,
and are strongest in the dry season.
Because of the diurnal nature of the
inversions, significant atmospheric
pollutant buildup seldom occurs; the
daily inversions are quickly dis-
persed by the dynamic wind and rain
patterns that exist over the basin
(Dames and Moore 1978).

I I I ~a~ I



The Floridan Plateau (Figure
20), originally named by Vaughan
(1910), represents the great projec-
tion of the North American continent
that separates the Gulf of Mexico
from the Atlantic Ocean. It
includes not only the state of Flor-
ida, but an equal area beneath water
less than 50 fathoms (91.4 m or
300 ft) deep. The plateau underlies
all of the Everglades, Florida Bay,
and the Florida Keys, as well as a
large area of the Gulf of Mexico.
In the gulf, the plateau's bottom

slopes gently away from the west
coast of Florida, but it drops off
sharply just south of the Keys into
the Straits of Florida. The median
axis of the plateau passes through
Key West, Bradenton, Sarasota, Cedar
Key, and Madison, Florida (Cooke

Table 9 is a reference chart
for the ensuing discussion of geo-
logic structure and stratigraphy.
More detailed tables correlating
specific rock formations and facies
in Florida with geologic periods may
be found in Cooke (1945) and Puri
and Vernon (1964).

Figure 20. The Floridan Plateau (adapted from Perkins and Enos 1968).

I I I II I I ------ I li~ IIPIA 38~81 111





















Paleocene 70,000,000
Lower birds cereals







2 ?nn non nN













spores of

Table 9. Reference chart for discussion of geology.



Structurally, the area under
consideration in this report lies
within what Pressler (1947) refers
to as the Florida peninsula sedimen-
tary province. The peninsula sedi-
mentary province is characterized by
nonclastic (chemically or biologi-
cally produced as opposed to erosion
produced) sediments, primarily car-
bonates and anhydrites. Of parti-
cular significance to the present
study area are two structural fea-
tures of the peninsula. The first
is the south Florida embayment of
the Gulf of Mexico, whose center of
deposition passes through Florida
Bay and the Keys, paralleling the
lower southwest coast (Puri and
Vernon 1964). The second is the
south Florida shelf, a term applied
by Applin and Applin (1964) to a
shallow shelf generally paralleling
and leeward of the south Florida

Pressler (1947) believes that
anticlinal folds are the most preva-
lent type of structures within the
south Florida embayment. Although
probably occurring as secondary
structural features, faults should
also be prevalent within this area.
Based on the configuration of the
surface of the submerged areas,
Pressler and others believe the
Florida peninsula is bounded on the
south and east by major fault zones.
These faults are probably due to
continental movements in addition to
settling, compacting, and continuous
downwarping of the sedimentary fill.
The latter factors are also likely
to contribute localized structural
features significant to the accumu-
lation of oil.

According to Applin and Applin
(1964), the floor of the coastal
plain in the Florida peninsula is
the truncated surface of a variety
of igneous and sedimentary rocks
that are chiefly Precambrian and
early Paleozoic in age. Unfortu-

nately, most of the work conducted
on underlying Pre-Mesozoic rocks in
Florida is restricted to north and
central portions of the peninsula.
One of the primary reasons for this
is the volume of sedimentary fill
overlying the coastal plain floor in
southern Florida. A number of in-
vestigators (Pressler 1947, Antoine
and Harding 1963, Applin and Applin
1964) place the Pre-Mesozoic floor
at 3,658 to 6,096 m (12,000 to
20,000 ft) below mean sea level.
Figure 21 (from Puri and Vernon
1964), summarizes the stratigraphic
relationships of the Pre-Cenozoic
Florida peninsula.


The oldest rock layer of the
Tertiary beneath the Everglades,
Taylor Slough, and Florida Keys is
the Avon Park Limestone, a cream
colored chalky limestone of marine
origin belonging to the Clairborne
group of the Eocene series (Cooke
1945). Above this, the Crystal
River Formation thins from east to
west beneath Taylor Slough headwa-
ters, and remains thinly represented
farther south. Suwannee Limestone
(Cooke and Mansfield 1936), of late
Oligocene age, and the Hawthorn
faces, of the Alum Bluff stage of
the Miocene series, overlie these
older strata. Pliocene rocks under-
lying the Everglades, Florida Bay,
and the Florida Keys are represented
by the contemporaneous Caloosahat-
chee and Tamiami Formations (Parker
and Cooke 1944). To the north, to-
ward the Big Cypress, the dissected
Tamiami Formation is thinly covered
by Pleistocene sands and occasional-
ly even outcrops at the surface.


The cessation of the deforma-
tion that warped the Citronelle For-
mation to the north of the present
study area is a convenient beginning


__ BEDS OF NAVARRO AGE (?) (ABSENT IN PART)............LAWSON LIMESTONE.....................

BEDS OF TAYLOR AGE.................................BEDS OF TAYLOR AGE.......................

BEDS OF AUSTIN AGE.................................BEDS OF AUSTIN AGE.......................

(0 "{ J UPPER BEDS OF EAGLE FORD AGE...................
0 0




BEDS OF TPINITY AF............
0 Punta Gorda Anhydrite
0 Sunniland Limestone


S(I Well)


C CL <

z a


-1 Z 0

0 0





Figure 21. Stratigraphic nomenclature of Pre-Cenozoic strata in the Florida
peninsula (adapted from Puri and Vernon 1964).


date for the Pleistocene epoch in
Florida (Cooke 1945). Subsequent
oscillations of sea level in re-
sponse to glacial formation and
melting are primary factors in
determining Pleistocene rock forma-
tions underneath the Everglades,
Taylor Slough, and Florida Bay.
Much of the area is underlain by
marine sedimentary sequences punctu-
ated by fresh water limestones and
subaerial exposure surfaces (Perkins
1977). The wedge of overlying
Pleistocene sediment, which attains
a thickness of approximately 61
meters (200 ft) in the lower Keys,
pinches out northward against topo-
graphically higher Miocene and
Pliocene sediments, such as the
Tamiami and Caloosahatchee Forma-
tions mentioned earlier (Perkins

Sea level prior to the initial
Pleistocene glacial melt lay at
approximately 82.3 meters (270 ft)
above the present shore line. Dry
land on the Floridan Plateau was
restricted to a few small islands
lying In what is now Polk County,
and another group in the vicinity of
the Trail Ridge area near Jackson-
ville. Subsequent sea level fluctu-
ations gradually left more and more
of the Floridan Plateau exposed. As
Cooke (1945) explains, this succes-
sive dampening of sea level rise is
probably the result of sea floor
spreading which concurrently in-
creased the global volume of the
oceans. Table 10 lists the names
of recognizable sea level fluctu-
ations of the Pleistocene in Florida
and the respective heights to which
they extended above present day sea

The most ancient of the Pleis-
tocene rock layers in south Florida
is the Fort Thompson Formation.
Sellards (1919) first applied this

Name Height Above Present Sea Level (ft)
Brandywine 270
Coharle 215
Sunderland 170
Wlcomico 10oo
Penholoway 70
Talbot 42
Pamico 25
Silver B suff (tentative)

Table 10. Recognized sea level fluc-
tuations of the Pleistocene
in Florida (adapted from
Cooke 1945).

name to the formation, which con-
sists of beds of fresh water marl
and limestone alternating with beds
of marine shell marl, in the vicin-
ity of Fort Thompson on the Caloosa-
hatchee River (Cooke 1945). The
Fort Thompson includes three sepa-
rate and distinct marine shell beds,
the youngest of which is the Coffee
Mill Hammock marl. The three marine
beds are separated by two thin beds
of soft marl containing shells of
fresh water snails. The tops of the
fresh water beds have been hardened
into brittle limestone, but are per-
forated by solution holes which are
filled with marine shells from suc-
ceeding strata. The Fort Thompson
Formation is of special importance
to the human population of the
southeast coast for it forms part of
what is commonly referred to as the
Biscayne Aquifer, the sole drinking
water source for much of the south-
east coast. Figure 22 from Dubar
(1974) shows the Fort Thompson For-
mation in relation to more recent
Pleistocene strata in south Florida.
Toward the east coast the formation
is relatively thicker than toward
the west coast, where it thins out
about half way across the peninsula.

Figure 22. Distribution of sur-
face exposed Pleis-
tocene formations
(adapted from Dubar

Of the major formations laid
down during the Pleistocene, the
Miami Limestone is by far the most
prominent surface exposed formation
within the lower Everglades, Florida
Bay, and to some extent the Keys.
Miami Limestone, first named Miami
Oolite by Sanford (1909), refers to
the generally soft white limestone
that extends over much of the south-
ern tip of Florida and the terminal
Keys. To the northeast the forma-
tion gradually increases in sand
content until it merges, in the
vicinity of Palm Beach, with the
sandy Anastasia Formation also of
the Pleistocene Epoch (Cooke 1945).
In the lower Keys the formation
again gradually increases in sand
content, a fact which led Sanford
(1909) to name the formation the
"Key West Oolite" in the vicinity of
the Keys. However, more current re-
search on the origins and relation-
ships within the Miami Limestone
have led to general abandonment of
the term "Key West Oolite".

Hoffmeister et al. (1967) de-
scribe the "Miami Limestone" as com-
posed of two distinguishable facies,
an upper oolitic faces and a lower
bryozoan faces. The upper oolite
facies began forming in the late
Pleistocene epoch when sea level
conditions favored the formation of
unstable oolite sand belts just back
from the outer edge of the Florida
platform. The constituent particles
of the oolitic facies are ooids,
pellets, and skeletal sand. Ooids
are concentrically laminated, spher-
ical to subspherical grains which
formed as a result of the unique
physical and chemical conditions
which occurred on shallow sand belts
along the southeast coast. The
nuclei of ooids may be composed of
any type of rock fragment, such as
calcite, shell, or quartz sand. As
deep water from the Gulf Stream
rushed over the shallow bank, the
temperature and salinity of the
water increased, thus decreasing the
solubility of calcium carbonate.
The water became increasingly turbu-
lent and agitated, causing excess
carbon dioxide to be driven off,
further reducing the calcium carbon-
ate solubility. Together these
actions resulted in the precipita-
tion of calcium carbonate around
tiny rock fragments leading to the
formation of typical ooids (Hoff-
meister 1974). As would be expected
on a relict oolite sand belt, ooids
comprise the major rock type found
in the Atlantic Coastal Ridge. West
and northwest of the ridge (into the
Everglades and Taylor Slough headwa-
ters) ooids decrease to approximate-
ly 10% of the rock. The pelletal
component of the oolite refers to
grains which are ellipsoidal in
shape and carry no implication of
their origin, while the skeletal
sand component originates from the
remains of numerous shallow water
mollusks and bryozoans.

L I rI.

The oolite faces contains
localized layers of calcite which
generally increase in crystalline
structure with depth (Ginsburg
1954). As one proceeds down in the
oolite, many of the aragonitic ooids
and pellets have been entirely or
partially replaced by calcite. In
the lower levels beneath the water
table, many of the ooids and pellets
have themselves been completely dis-
solved, leaving only cavities in the
calcitic cement. Hoffmeister et al.
(1967) refer to the character of
this cavity ridden limestone rock as

In physical appearance the
oolitic faces may often be cross-
bedded, I.e., exhibit longitudinal
ridges oriented at varying angles to
one another. These are more promi-
nent on the seaward side than on the
Everglades side of the Atlantic
Coastal Ridge. The crossbeds are
believed to have formed as a result
of the complex tidal and wave action
to which the ridge was exposed.

On the western side of the
coastal ridge the oolitic faces
slopes gradually down toward the
Everglades, slowly decreasing in
thickness over the distance of a few
miles. In its place the underlying
bryozoan faces of the Miami Lime-
stone is exposed at the surface
(Figure 23).

The bryozoan facies, which
averages 3 m (10 ft) in thickness,
consists of large numbers of massive
tubular cheilostome bryozoan com-
pound colonies, primarily Schizo-
porella floridana. Many of these
colonies are 30 cm (1 ft) or more in
diameter. As outlined in Figure 23,
the bryozoan faces underlies the
oolitic faces beneath all but the
southern tip of Taylor Slough. Here
and southward to the upper Keys the
oolite appears to be continuous down

to, or contemporaneous with, the Key
Largo Limestone. A fair number of
fossil corals, especially branching
Porites sp., are found along this
strip in place of the bryozoans.

Hoffmeister et al. (1974) de-
scribe the occurrence of two main
growth forms of bryozoan colonies:
(1) those that are rough irreg-
ular masses with knobby
subcylindrical projections
that vary greatly in size;
these are the more numerous
group as well as generally
larger in size; and
(2) a smaller size form, 10 to
13 cm (4 to 5 in) at most,
also irregular with crooked
branches emanating from a
bumpy base. The tubes have
a tendency to flange out
near the tops.
In their present environment, bryo-
zoans in Florida Bay are often found
encrusting around gorgonians, blades
of sea grasses, and green algae.
This same growth form is evident in
the geologic record of the "Miami

As the shallow seas slowly
retreated, the submerged oolitic bar
(now the Atlantic Coastal Ridge)
gradually emerged as dry land.
During this slow retreat tidal chan-
nels were cut through the unstable
oolite, connecting the shallow sea
that lay over the present Everglades
with the Atlantic Ocean to the east.
These tidal channels can be seen
today in the Atlantic Coastal Ridge
as complete or partial transverse
cuts and valleys often called
"Transverse Glades" (Davis 1943).
Some of these contain major fresh
water streams and canals, while
others are overlain by sand or shell
deposits. One of the larger of
these relict tidal channels connects
Taylor Slough head waters with upper
Taylor Slough.



Atlantic Coastal Ridge EAST
sea 20 FT
Qolitic Focies *Vol -

Bryozoon Facies

Figure 23. Distribution of the Miami Limestone (adapted from Hoffmeister
et al. 1964).

According to Hoffmeister et al.
(1967), ecologic conditions behind
the coastal ridge during periods of
the Pleistocene were ideal for the
encrusting bryozoan Schizoporella
floridana to flourish. Some poly-
chaetes and mollusks such as Strom-
bus sp., also found the shallow sea
environment relatively hospitable.
On the southeast facing forefront
of the ridge, tidal flushing of a

migrating sand shoal/patch reef com-
plex made it possible for corals to
encroach upon the bryozoan community
(Perkins 1977). This accounts for
the lack of underlying bryozoans at
the southern tip of Taylor Slough
and beneath Florida Bay, and their
relative replacement there with
Porites corals and Key Largo Lime-




m ......

Key Largo Limestone, first
named and described by Sanford
(1909), represents a typical organic
reef composed of in situ, wave re-
sistant elements, the most important
of which are hermatypic corals.
These form the framework of the
structure and are responsible for
the trapping of large amounts of
calcarenite in which they are now
embedded (Multer 1977). Hoffmeister
and Multer (1964) summarize the
spatial distribution, community com-
position, chemical composition, and
additional qualities of the Key
Largo Limestone as follows:

"The Key Largo is an elevated
coral reef of Pleistocene age. Its
horizontal extent is now fairly well
known by aerial examination and core
borings. It underlies Miami Beach
in the north, comes to the surface
at Soldier Key and is again submer-
ged beneath the Miami Oolite from
Big Pine through Key West. In
addition it has recently been found
a few feet beneath sea level along
the eastern shore of the Florida
mainland from Miami southward for at
least 40 miles.

"It varies considerably in
thickness throughout. At Key West
and Big Pine Key it is at least 180
feet thick, at Grassy Key 170 feet,
at middle Key Largo 70 feet, and at
the northern tip of Key Largo 145
feet. Wherever its base has been
located it rests on an unconsoli-
dated quartz and calcareous sand.

"Its composition is that of a
typical coral reef with large, mas-
sive coral heads, many in place,
surrounded by smaller coral colo-
nies, shells and shell fragments of
all sizes of common marine organ-
isms. Reef building corals are
found from top to near the bottom
of the formation, but, in general,
are more prolific in the upper two-

thirds than in the lower third. An
indurated calcarenite of varied
organic components is probably the
most important rock by volume.

"Probably the dominant coral
species of the formation are Mon-
tastrea annularis, Diploria clivosa,
P. Strigosa, D. labrinthiformis and
several species of Porites. In
addition Acropora cervicornis is
prolific at several localities.
Practically all the coral species
found living today on the Florida
reef tract can be recognized in the
Key Largo. One notable exception is
Acropora palmata. This species,
commonly known as the Elkhorn coral,
is one of the most prolific in the
living reefs and as yet has never
been located in the Key Largo.

"...The great bulk of the Key
Largo Limestone is greatly altered
and recrystallized. Some excellent
specimens of well-preserved corals
can be found here. From these it
has been determined, on the basis of
the Thorium-Uranium ratio that the
apparent age of the upper part of
the Key Largo Formation is about
100,000 years.

"One of the most interesting
types of lithology of the Key Largo
is what has been called for want of
a better name "holey limestone".
This rock displays an unusual frame-
work structure in which numerous
large and irregularly shaped holes,
which comprise 40 to 60 percent of
the total volume, are present. The
rock is found chiefly a few feet
below sea level and is brought to
the surface in large quantities by
dredges engaged in making cuts for
boat slips and canals.

"The origin of this rock has
posed a difficult problem.. Although
it is believed to have been formed
in more than one way, it is now


known that the accumulation of tre-
mendous amounts of fragments of a
thin branched Porites accounts for
much of it.

"The stratigraphic relation
between the Key Largo Limestone and
Miami Oolite can be seen at a con-
tact at the southeastern point of
Big Pine Key. Here the Miami Oolite
gently overlaps the old coral reef
in a southern direction. The con-
tact appears to be of a transitional
character. No other surface contact
has been seen in the lower Keys.
However it is known that the oolite
cover of these Keys is relatively
thin, particularly along their
southern borders. For example at
Boca Chico and Stock Island it has
a thickness of only 3 to 6 feet.
The oolite cover appears to thicken
gradually to the north; at the
center of Key West is reaches 20

Multer (1977), with more recent
coring data, reports an expanded
range of the Key Largo Limestone to
occupy an area up to or exceeding a
20 km (12.4 ft) width (extending
both seaward and into the Florida
Bay) and extending at least 376 km
(235 miles) in a continuous band
from North Miami Beach to the Dry
Tortugas (Multer and Hoffmeister
1968). The interface of the Key
Largo Limestone with the Miami Lime-
stone Formation on the southeast
Atlantic Coastal Ridge is illustra-
ted in Figure 23. The Key Largo
Limestone Intermingles with the
bryozoan faces of the Miami Lime-
stone Formation, tapering off in a
westerly and northerly direction.
The maximum elevation for the forma-
tion is +5.5 m (18 ft) on Windley
Key in the upper Florida Keys (Dubar
1974). The core borings, besides
establishing the formation range,
led Multer and Hoffmeister (1968) to
divide it petrologically into three
major faces:

"(1) an outer reef faces (2 to
4 miles seaward of the present Keys)
containing 4 common rock types, in-
cluding encrustate Acropora palmata
boundstone, (2) a back-reef faces
(2 miles seaward and approximately
1 mile lagoonward of the Keys) con-
taining 6 common rock types, and (3)
a lagoonal faces in the approximate
site of modern Florida Boy contain-
ing five common rock types.

"Vertical persistence of major
faces and similarity of each with
overlying Holocene sediments indi-
cate a general continuity of envi-
ronments for at least the last
100,000 years."


Holocene sediments in the lower
Everglades and Taylor Slough are the
result of a seasonal abundance of
rainfall and a warm subtropical cli-
mate which have, over the last 5,000
years, stimulated both luxuriant
plant growth and case hardening of
periodically exposed limestone rock.
The case hardening has, in time,
made surface penetration of the
Everglades trough caprock difficult,
thus promoting retention of water
and the growth of wetland vegeta-
tion. Together these conditions
lead to an ideal setting for the
production of alternating layers of
organic peat and calcitic mud in
recent sediments. Holocene sedi-
ments in the Keys reflect a much
more pervasive marine influence.


Gleason et al. (1974) consider
all Holocene sediments and soils of
the south Florida mainland to be of
the Lake Flirt Formation. Sellards
(1919) first named this formation
the Lake Flirt Marl based on geo-
logic cross sections exposed in old
Lake Flirt to the west of Lake


Okeechobee. However, Brooks (1968)
later renamed it the Lake Flirt
Formation to include muck layers
sandwiched in between the distinct
marl beds. Due to the low relief of
the area and its recent emergence
from the sea, erosional soils are
generally non-existent or poorly
developed (Davis 1943).

It is generally agreed (Davis
1943, Parker and Cooke 1944, Davis
1946, Gleason et al. 1974) that the
distribution of surface sediments
and soils in south Florida closely
follows bedrock geology and hydrol-
ogy. Underlying bedrock topography
is characterized by two troughs
corresponding to Shark River and
Taylor Sloughs. In contrast, these
distinctive features of the bedrock
topography are nearly obliterated in
the surface topography. Due to peat
accumulation and/or the deposition
of fresh or brackish water calcium
carbonates, surface relief tends to
become flattened out.

Within the lower Everglades and
Taylor Slough study area, there are
two major divisions of Holocene
sedimentary sequences:
(1) that area in which cores to
Pleistocene bedrock reveal
no brackish water sequences
of marl or peat and
(2) that area in which cores
indicate (primarily through
the presence of Rhizophora
peat) an inundation by
brackish, marine conditions
at some time in the recent

The Everglades are character-
istically dominated by herb covered
marshes and forested swamps. Saw-
grass (Cladium jaimaicenis), a
sedge, generally prevails over the
majority of the landscape, often to
the apparent exclusion of all else.
Interrupting this river of grass are

numerous, relatively small forested
areas that may be elliptical, round,
or tear-dropped in shape. These
are variously referred to as tree
islands, heads, keys, cones, or ham-
mocks (Craighead 1971). The shape
of individual islands is believed to
be a function of surface hydrology
(Davis 1943, Loveless 1959). Ellip-
tical islands are prominent in the
relatively fast flowing Shark River
Slough, while rounder islands are
more characteristic of the drier
areas north of Florida Bay. The
"tails" of tree islands are often
found to be growing in furrows of
the bedrock (Craighead 1971).

There are different types of
islands, and many are successionally
related to one another. Some origi-
nate on bedrock highs where the
slight elevation difference allows
colonization by true terrestrial
vegetation. Subsequent deposition
and trapping of organic matter re-
tains this initial elevation advan-
tage. Other islands such as the
"bay head" are usually found in
bedrock depressions which are built
up to a low mound of organic soils
above the surrounding marsh. Still
others, such as the cypress and wil-
low heads, exhibit little or no peat
buildup above average high water.
Spackman et al. (1964) describe a
sequence of events whereby cypress
initially colonizes a wet area and
gradually succeeds into a bayhead.
Figure 24 presents cross sectional
profiles of these two types of tree

In the cypress island, the un-
derlying veneer of fresh water marl
suggests that the area was once a
spikerush (Eleocharis dominated)
marsh where deposition of calcium
carbonate by the marl producing
algal mat was once very active.
Note that the marl appears perfora-
ted by the peat, a characteristic



Moat Moat
r 1o

WatertE Algal MatS Fresh Water MarlSS PeatMZ BedrockM In Feet
0 50

Figure 24. Cypress head/bay head sedimentary profiles (adapted from
Spackman et al. 1964).

which suggests to Craighead (1971)
that peat accumulation may actually
"dissolve" the underlying limestone
and thus contribute to the mainte-
nance of the islands. In the bay-
head, freshwater marl beneath the
island is absent, elevation above
the water level is higher, and the
characteristic moat of the cypress
head is much less conspicious.

As the last glacial ice sheets

of the Pleistocene retreated, sea
level gradually rose to the vicinity
of where it now stands. However,
oscillations of sea level did not
stop with the passing of the Ice
Age; rather they became relatively
smaller and more frequent. Fair-
bridge (1974) presents a general
model of recent sea level changes
(Table 11) but warns that the south
Florida sequence is not well docu-

(1) (2) (3)
200 0 ------- ----- 20th C. Submergence
600 200 -1*C -0.5m Paria Emergence
1,000 600 +0.5*C +0.3m Gotland Emergence
1,200 1,000 -0.5C -0.5m ----

+1*C +0.6m Rottnest Submergence


-2m Florida Emergence

+1C +2m Abrolhos Submergence
-1IC -lm Pelham Bay Emergence
+2C +3m Younger Peron Submergence

4,700 4,300 -0.5C
6,000 4,700 +2.5C

-im Bahama Emergence
+4m Older Peron Submergence

Viking (Dunkerquian III)
"Dark Ages"
Carolingian (Dunkerquian II)
Iron Age (Dunkerquian II)
Bronze Age
Neolithic (Calaisian II)

Mesolithic (Calaisian I)

(1) Years expressed B.P., "before present" (A.D. 1950) in uncorrected radiocarbon years
(6,000 B.P. = approximately 6,900 B.P. sidereal years).
(2) Temperature, world average departures for mid-latitudes, at peak stage.
(3) Maximum sea level departure from present M.S.L. (extreme departures probably lasted only a few
centuries or less; note that changing tidal characteristics may considerably vary these figures).
(4) Cultural labels are, for general interest, those of northern Europe, with chronostratigraphic terms
from the Flandrian area.

Table 11. Mean sea level oscillations during the last 6,000 years (present-
ed in stratigraphic order from top to bottom; to perceive the

Concurrent with sea level fluc-
tuations, climatic conditions (i.e.
temperature and rainfall) also os-
cillated. These latter oscillations
in turn exerted rather dramatic
effects on surface and ground water
tables, salt water intrusion, hydro-
periods, and consequently on sedi-
mentary environments and rates in
southern Florida. Some of the
record of these fluctuations lies
buried beneath the swamps, while the
rest is either totally eroded or
less conspicuously preserved beneath
the continental shelf.

Early opinions (Davis 1940)
that the growth of the southwest
Florida shoreline was regressive,

from bottom to top) (adapted from

i.e. sea level was receding, due to
sediment accumulation and land
building by mangroves, were at least
partially founded on an error in the
assigning of a marine origin to the
basal carbonate sediment (Gleason et
al. 1974). From historical accounts
of red mangroves growing inland from
their present distribution, it was
suggested by Davis (1940) that the
mangrove forest might be moving sea-
ward. Today it is generally agreed
that mangroves may well act as sedi-
ment traps and shoreline stabi-
lizers; however, major shifts in
shoreline features are more likely
dominated by sea level fluctuations,
longshore drifts of sediment, tidal
scouring, erosion, and fluctuations

1,600 1,200
2,000 1,600
2,800 2,000
3,400 2,800
4,300 3,400

historic sequence, read table
Fairbridge 1974).


in climate and water table. Figure
6 identifies the shoreline types
occurring along the mangrove coast
of the Everglades. These are parti-
cularly important zones to remember
since they more or less define the
forces that shape the southwest
coast environment.

In the cape sector of Figure 6
the Holocene record is dominated
by interfingering beach, marl, and
peat. Behind the aggrading bar-
rier beach on the forefront of the
cape are hardwood hammocks, salt
marshes, salt barrens, and shallow
lakes which in places overlie a
continuous peat layer as much as
2.7 to 4 m (9 to 13 ft) thick
(Spackman et al. 1964, Smith 1968).
To the north of the cape sector
lies a dissected section of coast-
line known as the tidal scour sec-
tor. As mentioned earlier, the
mangrove forest and underlying peat
in this section of the coast are
being actively eroded and swept out
to sea.

Recent sediments within White-
water Bay itself are gradational in
a northeast to southwest direction
going from predominantly fresh water
to predominantly brackish (Spackman
et al. 1964). Bedrock contours in
Whitewater Bay reveal a slight ridge
(2 m or 6 ft contour) just behind
the mouth of the slough entry sec-
tor. Islands in Whitewater Bay,
which vary from a few square yards
to many hectares in area, are gener-
ally steep, two-sided sequences of
peat overlying a thin veneer of
freshwater marl. Within the open
water of Whitewater Bay and espe-
cially in the mangrove ponds to the
northeast, a sediment called "liver
mud" (Davis 1940) abounds. This
jellolike sediment is believed to
result from the mixing of eroded
peat with freshwater marl brought in
by surface runoff.

To the south of Whitewater Bay
toward Flamingo, recent sediments
form a slightly elevated bank of ma-
rine marl known as the Flamingo Marl
(Davis 1943). This bank is believed
to have been heaped upon the shore-
line by storm waves (Craighead and
Gilbert 1962). Figure 25 presents a
general profile of recent sediments
from Florida Bay at Flamingo, north
through Whitewater Bay.

The slough entry sector of Fig-
ure 6 refers to the area where Shark
River Slough and Whitewater Bay
enter the Gulf of Mexico. Numerous
steeply sloping islands, often cov-
ered with straight boled red man-
groves 15 to 23 m (50 to 75 ft)
tall, dominate the coastline. The
islands, like those of Whitewater
Bay, are essentially blocks of peat
resting on bedrock or thin marl.
Occasionally, the upper half of the
block may be composed of carbona-
ceous mud. Island surfaces are com-
monly higher on their gulf or tidal
channel exposed sides, thus forming
a sort of marl levee. Sediments of
the levee are composed of calcareous
and siliceous muds which have been
heaped up by storms. Some of the
mud carries over the island margins
and mixes with the accumulating
organic matter to form the upper
carbonaceous mud layer of the peat

To the north of the slough
entry sector the coastline is rela-
tively smooth, and black mangroves
(Avicennia qerminans) may extend all
the way to the shore. This is known
as the river sector portion of the
coast. Cross sections from cores at
the mouth of the Harney River show a
buried peat layer extending nearly
3.2 km (2 mi) out into the gulf
beneath surface marine sediments.
These cores provide very convincing
evidence of a transgressing sea
(Spackman et al. 1964).

_ 11-1-----11~


# ->
0 GO


Figure 25. Sectional profile through Florida Bay, Flamingo, Whitewater Bay,
and the Everglades (adapted from Spackman et al. 1964).

For a detailed account of re-
cent sedimentary sequences and a
general historical picture of the
fresh to saltwater transition zones
of the southwest coast during the
Holocene, the reader should consult
Smith (1968) and Cohen (1968).
These authors outline the sedimen-
tary patterns of marl and peat along
the lower Everglades from Flamingo
and Cape Sable to just north of
Lostman's River.


The most extensive work on the
distribution, origin, and strati-
graphic relationships of Holocene
sediments in the southern Everglades
(particularly Taylor Slough) is
presented by Gleason (1972), and
summarized by Gleason et al. (1974).
Representative cores of six distinct
stratigraphic groups and a map of
their distribution in Taylor Slough
appear in Figure 26.

Group A, located in the deep-
est central portion of the slough,
is composed exclusively of peat.
Alternating layers of water lily
(Nymphaea odorata) and sawgrass
peats reflect changes in the surface
environment due to climatic and sea
level fluctuations. Gleason et al.
(1974) believe the entire central
depression of Taylor Slough is prob-
ably underlain by this continuous
peat substrate down to the oolitic
bedrock. The alternating but con-
tinuous record of peat suggests that
this portion of the slough has
always been wet, variations have
occurred in mean depth and hydro-
period due to Holocene climatic

Group B, located on both the
western and eastern margins of the
slough, is composed entirely of
calcite. The calcite is produced
through the action of the blue green
algal mat that extends over much of
the exposed limestone and is common













`'*. .

::: -:--:



Mine-ology and
P.at Type
mar i scus

rMr iscus
Transit-ionfa (60)

Transit onal (M)
M@r iscu$

ter Lily

Water Lily

Minerology and
Peat Type
tr. Quartz

tr. Quartz


Minerology and
Peat Type


tr. Quartz

tr. Ar4gomi9h

CORE Minerology and
2 Peat Type
Rh zophora
y a frit o
12 l ih hizophora
is V,;-.7 Calcite

Transitional Peat
S- Water lily
M- Mariscus
R Rhizophora

RE Minerology and
P2 Peat Type

86 Calcite

Transiti.jn ai (M)


41 : ter Lily


Water Lily

Minerology and
Peat Type



Figure 26.

Taylor Slough
Gleason et al.

sedimentary zones and core types

(adapted from

in the "marl
the east and

west of

communities to
Taylor Slough.

This ongoing deposition of calcite
is believed analogous of the condi-
tions which produced the strata of
the Lake Flirt Formation. The con-
tinuous calcite strata in these
cores suggests the recent environ-
ment has remained fairly constant in
these vicinities.

Group C, located on the eastern
margin of the slough and running
parallel to its axis, consists of an
upper layer of calcite underlain by
alternating layers of peat. Gleason
et al. (1974) interpret this struc-
ture as a "filling up" of the basin
with sediments. Deep water peats
gradually build up, then transi-
tional peats, and finally, as the
hydroperiod shortens, calcareous
periphyton begin depositing a calci-
tic mud layer.

margin of t


located on
upper slou



of a peat layer sandwiched in
tween two calcite layers. Glea:
interprets this structure to rep
sent an historical shift in hyd
period allowing peat to build up
a relatively wetter area. A sub
quent drop in water level forced
return of a calcite producing, re
tively drier environment.


Group E, located along the
upper fringe zone between Taylor
Slough and Florida Bay, represents a
transitional environment reflecting
the oscillations of Holocene sea
level. The many alternating layers
of red mangrove peat and calcitic
mud indicate that neither marine nor
freshwater conditions have dominated
during recent time.




Group F, located along the
southern lip of the slough consists
of red mangrove peat overlying a
layer of calcitic mud. This ar-
rangement supports the theory of a
general transgression of the sea
over south and southwestern Florida
(Scholl et al. 1969).

In Florida Bay, Holocene sedi-
ments range in thickness from 15 cm
(6 in) in the lake areas to 3 to
3.7 m (10 to 12 ft) near Cape Sable.
Radiocarbon dating indicates that
deposition of these largely uncon-
solidated, fine grained calcareous
muds began about 4,000 years ago
(Scholl 1966), during the Flandrian
transgression (rise in sea level)
that accompanied the melting of the
last continental ice sheets.

Prior to this time, the bedrock
of Florida Bay had been invaded by
wetland and terrestial vegetation
similar to that of the present day
Everglades. The surface was also
exposed to the same forces of ero-
sion and solution from freshwater
rains and runoff. As sea level
rose, the gradually encroaching
marine waters encountered conditions
that were similar to those now
existing in the southern Everglades.
Scholl (1966) believes that bank
formation (the keys of Florida Bay)
began early in the bay's history,
presumably where slack water condi-
tions existed due to converging cur-
rents. Hoffmeister (1974) believes
the keys and shoals provide a rough
tracing of former freshwater drain-
age patterns that have been greatly
altered by current action, especial-
ly near the Coral Keys and the open
gulf. Sediment trapping and further
vegetational stabilization from man-
groves and sea grasses as sea level
continued to rise resulted in the
present day configuration of man-
grove keys. Ball et al. (1967)

demonstrate that the exposed keys
and submerged banks may in fact
increase in area due to sediments
heaped up during hurricanes.

Figure 27 presents a cross
section of cores from Cross Bank in
Florida Bay (near Upper Matecumbe
Key). These cores outline the three
major strata of the Holocene sedi-
mentary record that occur in Florida
Bay: (1) the very few or no shells
layer (corresponding to the carbon-
ate mud of Fleece 1962); (2) the
slightly and moderately shelly layer
(corresponding to the shelly sand of
Fleece 1962); and (3) the peat lay-
er. Peat layering is reported from
cores beneath keys (Fleece 1962) and
shoals (Turney and Perkins 1972),
but is not found elsewhere in Flor-
ida Bay away from these structures.

The carbonate mud layer arises
primarily from the action of encrus-
ting green algae such as Halimeda
sp., Udotea sp., and Penicillus sp.,
which secrete fragile skeletons of
tiny aragonite crystals (Stockman
et al. 1967). These same authors
estimate that the Penicillus popula-
tion alone could account for one
third of the lime mud production in
Florida Bay. Numerous other species
of calcareous algae are believed to
make up the difference, in addition
to some import from the gulf (Hoff-
meister 1974).

Ginsburg (1956) reports that
51% of the sediments by weight in
Florida Bay have a mean grain size
greater than 1/8 mm as opposed to
83% in the nearby Florida Key reef
tract. Of this relatively smaller
proportion, 87% is of molluskan
(76%) and foraminiferan (11%) ori-
gin. In contrast to these bay sedi-
ments, the shelly sands near the
keys contain a considerably greater
amount of algal and coral remains.




I -

. 6-

and PLOerkins 1972)

Figure 27. Cross section of Cross Bank in Florida Bay (adapted from Turney
and Perkins 1972).


Our discussion of Holocene
sediments in the Florida Keys is
presented in two sections: (1) sedi-
ments of the marine environment; and
(2) sediments of the terrestrial and
freshwater environment. Based on
surface area alone, it is obvious
that the former of the two dominates
in sediment contribution to the

Recent marine sediments of the
Keys are produced in what amounts to
a vast, multifaceted carbonate fac-
tory (Enos 1977). These bioclastic
sediments are produced by organisms
restricted geographically by bottom
morphology, circulation, and most
importantly by the very substrate
the organisms themselves have pro-
duced. Figure 28 illustrates and
summarizes the Holocene sediments of
the south Florida shelf margin in
the vicinity of the lower Keys.

Enos (1977) describes three
natural subdivisions of the seaward
shelf off of the lower Keys:
(1) the slightly restricted in-
ner shelf margin;
(2) the outer shelf margin where
circulation and turbulence
are maximum; and
(3) the shallow slope seaward of
the shelf break.
The primary controls on sediment
distribution patterns are skeletal
productivity, mechanical redistri-
bution, pre-existing rock topo-
graphy, and contemporary sediment

Sediment accumulations in the
inner shelf margin are generally
less thick and muddier than those on
the outer margin. Wedges of sedi-
ment piled against the Pleistocene
rock of the Keys reach more than 5 m
(15 ft) in thickness. These wedges
are elongate parallel to the shelf
edge. Patch-reef banks of the inner












PEREABILITY 5,00 TO 34,00) MA 60 TO 325 B EPBAILITY 0.9g--80 N o.

Figure 28. Summary of Holocene sediments of the south Florida shelf margin (adapted from Enos 1977).





=; TO 41 FFFT


0 1 TO 15 FEET


5 TO 20 F~eat l



O T5 1 3 FEET

O T1 12 FEET

O T1 8 F

shelf margin also tend to be elon-
gate parallel to the shelf edge,
but most are small, less than 2 km
(1.2 mi) long. Tidal deltas, ori-
ented perpendicular to the shelf
edge, develop where passes between
rockfloor highs enter restricted
basins of the inner shelf. Most of
the sediment in tidal deltas is gen-
erally less than 5 m (15 ft) thick.

Changes in sediment thickness
and total volume along the lower
Keys are most closely tied to the
amount of tidal exchange with the
restricted shelf. Where water from
the inner shelf and the broad Gulf
of Mexico shelf flows across the
shelf margin, sediment acurnulation
is reduced, probably owing to de-
creased productivity. Tidal deltas
and inner shelf-margin sediment
wedges are lacking here, too, be-
cause they are dependent on current
constriction by the Florida Keys.

The outer margin, ( > 3 km or
2 mi) is the site of the thickest
(typically 8 m (26 ft) or more) and
most permeable (up to 35 darcys)
sediments in the Holocene package.
The thickest sediment accumulations
lie in belts parallel to the shelf
edge. The trends of these belts are
quite predictable, but the sediment
thickness and physical properties
vary along the axis of the coast.
The outer reef belt is the most
nearly continuous and the thickest.
It is 1 to 2 km (about 1 mi) wide
and located immediately behind the
shelf break.

The shallow-slope sediment
blanket is thickest within a kilo-
meter of the shelf break at a water
depth of about 30 m (100 ft). Shelf-
edge sands form prisms of thick
sediment 1 to 2 km (.6 to 1.2 mi)
wide, 2 to 3 km (1.2 to 1.9 mi) be-
hind the slope break. The largest
sand shoal is 40 km (25 mi) long and

as much as 9 m (30 ft) thick. Where
sand shoals are lacking, a belt of
discontinuous patch-reef banks may
occupy the same position. The
patch-reef belt is also 1 to 2 km
(.6 to 1.2 ft) wide, trends parallel
to the shelf, and may be more than
8 m (25 ft) thick, but continuity is
poor and the sediments are generally
muddy. A bed-rock depression with a
thin layer of muddy sediment isola-
tes the patch reef belt of the lower
Keys from the outer reef belt.

Enos (1977) states that the
Holocene sedimentary sequence dif-
fers from the Pleistocene in that it
contains little quartz or nonskele-
tal carbonate, and the distribution
of grainstone is less widespread.
He attributes these differences to
the relatively small degree of
submergence in recent time and
the low supply of terrigeosus ma-
terial from the Florida mainland.
Table 12 summarizes the existing
sediment producing communities off
the lower Keys and their relative

1. Rock or dead reef
a. open marine--mainly encrusting and boring organisms
b. restricted circulation--mainly encrusters and borers
2. Mud
a. grass covered--turtle grass (Thalassia), green algae
(Halimeda, Penicillus) miliolid foraminifera, browsing
gatropods, burrowing pelecypods and shrimp (Calianassa)
b. bare--a few green algae, foraminifera
3. Sand
a. grass covered--Thalassia, Halimeda, peneroplid
foraminifera, browsing gastropods, burrowing pelecypods
b. bare--burrowing echinoids
4. Patch reef--head corals
5. Outer reef--corals (Acropora, Montastrea, Diploria, Porites),
Millepora, Halimeda opuntia
6. Forereef muddy sand--pelagic foraminifera
7. Shoal fringe, restricted--finger coral (Porites), red algae
(Goniolithon), Halimeda opuntia
8. Reef rubble--few organisms
Relative skeletal productivity by the habitat communities is estimated
5 > 4 > 7 > 2a > 3a > la > Ib > 6 > 2b > 3b > 8.

Table 12. Mappable habitat communi-
ties of the south Florida
reef and shelf (adapted
from Enos 1977).

1 I;lff' ~n~Ulllli~E~~I_~I_ _ ____ __ __ __ _____~___

Jindrich (1969) and Basan (1973)
provide more specific discussion of
the Holocene sediment environments
in the lower Keys gulf side, an area
only briefly discussed by Enos

(1977). Figure 29
depositional enviroi
by Jindrich (1969).
carbonate sediment
due to the sediment-
of the marine grass
dinum and the calca
Halimeda opuntia.
consists primarily o
lusks, foraminifera,

Illustrates the
nments outlined
The majority of
accumulation is
-trapping effects
Thalassia testu-
reous green alga
The sediment
f Halimeda, mol-
and Pleistocene

1969). I
the ENE
and still
lower Key



rock fragments (Jindrich
n the Barracuda Keys, to
of Jindrich's study area
to the gulf side of the
s, Basan (1973) identified
* pattern of carbonate
tion containing the same
r components described by
(1969) and in the same

relative abundance. Studies by
Landon (1975) and Kissling (1977)
contain more recent and supplemental
research on carbonate sediments in

the lower Key
to and include
















0 I 2 KM

I I I I IV I I I I I I 1

I -

Carbonate ooze
Medium Sand
Coarse Sand

After Jndrich,1969

Depositional environments in the lower
Jindrich 1969).


(adapted from

Holocene sediment
in the distal islan
of Key West (Boca Gran

d groups
de Group,

Marquesas Keys, and Dry Tortugas)
are rather scarce. For the area
including the Marquesas and Boca
Grande groups the only study found
which addresses recent sediments was
Davis' (1942) work describing the
general topography of the Sand Keys

island groups)
scribes these
low, calcareous


of th
ar to


nd and

(1942) de-
groups as
marl ridges

from a shallow limestone
esenting an extension of
Keys oolitic facies of
Limestone. The composi-
te calcareous sediment is
banks on the lower Keys'
as previously discussed



to all three




, Basan 1973).



ion, out


* 6m

Figure 29.






I- I Il l I I 1 -1 1 1 I -1 I '. I r -, I I




a 1 ,

- - - - - - - - - - - - -



i 1 I I I I I I I I


Compared to the Marquesas Keys,
corals play a much more significant
role in the composition of recent
sediments in the Dry Tortugas. The
Dry Tortugas represent a drowned
Pleistocene platform 17 to 21 m (56
to 69 ft) below sea level which is
comprised of three biogenic buildups
(facies): (1) detrital lagoonal
bank, (2) Montastrea reef bank, and
(3) Acropora palmata reef (Jindrich
1972). These faces lie adjacent to
one another and are also present in
vertical succession as individual
growth stages that vary in thickness
and lateral extent. A zone of
Acropora cervicornis develops as a
transition between the Montastrea
and A. palmata growth stages. The
present reef assemblages and bottom
topography have been strongly influ-
enced by cumulative storm effects
that are linked to the slow sea
level rise over the past several
millenia (Jindrich 1972).

Storm degradation is manifes-
ted by (1) continuous removal of
A. palmata and its replacement by
storm-resistant coralline algae and
Millepora sp. to produce truncated
rocky surfaces, (2) abundant reef
rubble, (3) erosion of spur-grooves,
and (4) development of intertidal
rubbly reef flats.

Noncoralline sediments range in
size from cobble-sized algae to
foraminifera. Variations in texture
and particle composition are mainly
a result of sediment transport and
grain shape. In general, three
modes of sediment transport produce
three characteristic assemblages of
constituent particles:
(1) a gravel sized population;
(2) a sand sized population;
(3) a fine sand to silt sized

Strong mixing occurs between the
gravel and sand population on the
storm degraded shoals, and between
the sand and silt population on the
lagoon bottom. Sands generally
flank the reefs and reef banks and
show minimum mixing. Lagoonal bank
sediments, stabilized by seagrass
and coral growth, are composed of an
incongruous mixture of the in-place
fraction and varying proportions of
transported sediments.

During a low sea-level stand
created by a period of Pleistocene
glaciation, organic acid solutions
created numerous pits or holes in
the surface of the Keys' limestone
(Krawiec 1963). These pits (geo-
logically referred to as breccias)
became, and still act as, storage
tanks for coral debris, organic
soils from mangrove swamps and hard-
wood hammocks, and loose material of
all available types generated by the
hurricanes and lesser tropical
storms. These result today in an
exposed karst topography over the
Florida Keys (Kissling 1968, Seimers
and Dodd 1969, Dodd and Seimers
1971, Multer 1977), Florida Bay
(Gray 1974), and the seaward lagoon-
al environment (Turmel and Swanson
1964). The karst topography affects
the localized drainage and concen-
tration of soils on the Keys. This
concentration in turn influences the
terrestrial floral and faunal dis-
tribution (Multer 1977). Immediate-
ly over the bedrock in the Keys are
laminated crusts which are either
exposed, covered by thin soils, or
covered, in the case of solution
holes, by thicker miscellaneous
debris described above. Multer and
Hoffmeister (1968) describe three
types of indurated crusts coating
the Florida Keys: (1) porous lamina-
ted crust characterized by horizon-
tal root tubes: (2) dense laminated


crust, smoother and less permeable
than the porous crust and marked
by the absence of root tubes;
and (3) microcrystalline rind, a
thin, dense, tan microcrystaline

calcite mosaic. Figure 30 illustra-
tes the mechanisms responsible for
forming subaerial crusts formed on
the Florida Keys.

(1) rising capillary CaCO waters,
(2) ponded meteoric solutions
REPRECIPITATION OF: Dissolved containing CaCO3 leached from
CaCO to form laminae &/or bedrock and
lateral migration of fluid (3) gravity and wind driven drain-
over crust surface age from soil patches (rich
in CaCO3 and organic material.

_ Organic Matter
o O,* oO Carbonate Particles in Soil
. CoCO3 Saturated Water

Figure 30. Schematic drawing of mechanisms involved in forming
subaerial crusts in the Florida Keys (adapted from
Multer and Hoffmeister 1968).

No studies have been found
describing the origin and formation
of existing freshwater marl areas
observed by Alexander and Dickson
(1970, 1972) in the Key Deer Wild-
life Refuge. Whether these are of
marine or freshwater origin is un-
known. Davis (1940) describes the
succession of mangrove species to
climax coastal hammock forests as an
accumulation of mangrove and other

humus with a marl clay, of marine
origin, until it becomes granular
and loamy and supports the vegeta-
tion of the hammock forests. Obser-
vations on the soils associated with
the Caribbean pine and hardwood ham-
mock communities included in more
recent studies concur with Davis
(1940) (Alexander 1953, Alexander
and Dickson 1970, 1972).

El s



The quantity, distribution, and
quality of freshwater within the
Everglades, more than any other en-
vironmental characteristic, influ-
ences the capacity of this area to
support its unique fish and wildlife
resources. Before man's influence,
the terminal Everglades received a
seasonal pulse of surface sheetflow.
It began in June or July, spread
slowly toward the coast, and reached
peak flow and stage around October.
As Lake Okeechobee filled with fresh
water from direct rainfall and
Kissimmee River runoff, it eventual-
ly spilled over at points in its
southern boundary and began filling
the 64.4 km (40 mi) wide river of
grass. As the lake continued to
rise due to heavy summer rainfall,
the entire southern lip of the lake
would gradually become obscured by a
continuous connection between the
open water to the north and the saw-
grass plains to the south.

Water levels in the pre-drain-
age Everglades were on the average
much higher than today, occasionally
leading early investigators to refer
to it as a "lake" (Parker 1974).
The Atlantic Coastal Ridge acted as
a partial dam on the Everglades
eastern boundary. Water periodical-
ly spilled over this dam through the
lower transverse glades, through
falls eroded in the porous lime-
stone, or over the top of the ridge
when waters were especially high.
The relative hydraulic head (ap-
proximately 3 m or 10 ft during low
water) resulted in numerous artesian
springs in downstream Biscayne Bay;
apparently outflow occurred through
subterranean solution channels.
Toward the southwest the predrainage

river of grass flowed slowly in a
southwesterly trending arc through
luxuriant sawgrass marshes, open
water sloughs, and mangrove covered

Beginning in the early 1900's
this pattern of water abundance
began to change significantly.
In 1882 the construction of the
Caloosahatchee Canal signified the
beginnings of a physical alteration
process in the hydrologic regime
that continues today. The period
1905 to 1913 saw the North New River
and Miami Canals completed and
placed into operation. By 1921 the
Hillsboro and West Palm Beach Canals
were added. At the same time (1916-
1924), the St. Lucie Canal was dug
in order to provide drainage for
Lake Okeechobee. However, a hurri-
cane in 1926 set back the usefulness
of the St. Lucle Canal for this
purpose by overloading it with sedi-
ment. In 1935 redigging of the
canal restored it to its original
design conditions. Several other
major canals in the Miami area,
mainly the Tamiami, were also con-
structed during the 1920's.

Also in the 1920's, construc-
tion of a levee, the Hoover Dike,
around the south and east of Lake
Okeechobee was begun. Continual
expansion of this structure for
flood purposes has resulted in a
levee some 136.8 km (85 mi) long
around the entire southeast portion
of the lake, beginning north of the
Caloosahatchee Canal. Most of these
major structures were in place by
the mid to late 1930's.

Beginning in the late 30's it
became apparent that the uncontrol-
led drainage of the Everglades


opened up the potential problem of
salt water Intrusion along the
southeast coast. The drought of
1943 through 1945 amplified the
potential for this problem and
started the search for a long term

In 1949 the Florida Legislature
authorized the formation of the Cen-
tral and Southern Florida Flood
Control District (CSFFCD). The
purpose of this agency was to de-
velop a comprehensive, coordinated
means by which to regulate both
flood waters and salt water intru-

By 1953 the CSFFCD had con-
structed a system of levees along
the eastern boundary of the Ever-
glades to retain freshwater runoff
during the dry season. By 1960 the
levees had been expanded to enclose
what are now referred to as Conser-
vation Areas 1 and 2 in the northern
Everglades. By 1962 a levee running
parallel to the Tamiami Canal was
completed, giving partial enclosure
to Conservation Area 3. By 1967 all
but a 11.4 km (7.1 mi) gap along the
latter's western boundary was com-
pleted, thus allowing regulation of
flow to the present study area.

In 1967 canal C-111 was con-
structed along the southeastern
boundary of the study area as part
of CSFFCD's South Dade County Area
Plan of Improvement (Barnes et al.
1968). The canal, an extension of
canal-levee L-31W along the Atlantic
Coastal Ridge, was intended to pro-
vide flood control, drainage, and
navigation benefits for the area
from Florida Bay on the south to
Tamiami Trail on the north. This
area is now known as the East Ever-
glades. A salinity barrier (S-197
of CSFFCD) was constructed and be-
came operational near the confluence
of the canal with U.S. Highway 1 in
1968 (Meyer and Hull 1969).

Working from our initial con-
ceptual model of regional ecological
processes, Figure 31 presents a
modified version which emphasizes
and summarizes the major pathways of
the hydrologic cycle as it occurs
within the study area. Each of the
storage in Figure 31, or groups of
closely associated storage, is
discussed somewhat in sequence with
the natural flow of water, and the
chemical energy contained within it.
Some of these pathways have been
discussed in the section on climatic
factors. In this section we focus
primarily on patterns in the ground
related pathways of the hydrologic
cycle, such as spatial and temporal
variations in flow through and
storage of water, and fresh and
saltwater fluctuations.


Conservation Area 3 is divided
into two areas, 3A and 3B, having
surface areas of 2,037.2 and 331.2
km2 (786.6 and 127.9 mi2) re-
spectively (Figure 32). Regulation
of the area varies from 2.9 to 3.2 m
(9.5 to 10.5 ft) providing a maximum
total storage capacity of 380,000
acre-feet. Due to the sloping topo-
graphy (4 m or 13 ft on the north to
2.1 m or 7 ft on the south), most of
the storage is at the lower end.
High evapotranspiration losses due
to dense vegetation cover tend to
restrict the area's utility as a
storage reservoir. In addition to
receiving input from upstream pump-
age (Canal 123) and direct rainfall,
Conservation Area 3A also receives
some runoff from the Big Cypress
Basin via the L-28 tieback canal
(SFWMD 1977).

Prior to the construction of
the levees on the south of Conserva-
tion Area 3, flow out of the area
occurred via numerous bridges be-
neath Tamiami Trail. In general,
the flow was then intercepted and

From all storage

S To southwest

Keys aqueduct

G.W Groundwater

Figure 31. Hydrologic cycle model modified from Figure 4 conceptual model
of regional ecological processes.

II "~Ra~uaR~~~~a~:.i r -~- ~~~a~~-nnnr~ru.-_,.~.

Figure 32. Map of Conservation
Area 3 and control
structures (adapted
from SFWMD 1977).

redistributed by Tamiami Canal
southward through numerous stub
canals into Everglades National Park
(ENP) and the East Everglades
(Parker et al. 1955). When levees
29 and 67A were constructed in 1962
and 1963 the pattern and magnitudes
of flow delivered to ENP on the
south changed dramatically (Leach
et al. 1972). Figure 32 outlines
the structures and flow patterns
involved in the transmission of
waters through the Tamiami Canal
south to ENP and the East Ever-
glades. Flow patterns across the
canal are divided into 3 sections,
the western section from Monroe to
40-mile bend, the middle section
from 40-mile bend to L-67A, and the
eastern section between L67A and

In the westernmost section
beyond Conservation Area 3, Leach
et al. (1972) found that flow con-
tinued in much the same pattern
after levee construction as prior to
construction. In the middle section
flow was routed through four spill-
ways (S-12, A-D) and down the Levee
67A extension canal, while in the
easternmost section flow was re-
stricted to seepage across and under
levee L-29. Prior to construction
of L-29 the eastern section provided
considerably more water to the south
Dade, East Everglades area than it
does today. Peak flows to the south
were highest in the eastern section
before levee 67-A directed water to
the middle section and levee 29
acted to retain most of the water
within Conservation Area 3B. In the
middle section peak flows have been
augmented due to storage and diver-
sion. In summary, Leach et al.
(1972) identify two major changes
that have occurred in terms of water
input to lower Shark River Slough
over the past 40 years:
(1) A general increase in the
flow of water to the Ever-
glades resulting from the
deflection of water south by
levee 30 along the coastal
ridge; and
(2) redistribution of the major-
ity of flow through the
spillways below area 3A away
from the East Everglades due
to construction of levee
67-A and levee 29.

Because hydroperiod plays such
as important role in the ecology of
the Everglades, considerable atten-
tion has been fixed on determining a
minimum water input requirement for
Everglades National Park. This in-
put is to be delivered and regulated
by SFWMD, the regional water man-
agement agency. Dealing strictly
with the runoff component of this
input, Leopold et al. (1969) estima-
ted an annual minimum requirement of

rl.~nu~rl*lplirXu~LDCIIVYI~~- ---- I I I II


315,000 acre-feet, including input
from the Big Cypress, to maintain
the Everglades National Park. Of
this total, 260,000 acre-feet was
considered to be the average annual
flow required from Conservation Area
3A. This was just slightly less
than the 273,000 acre-feet estimate
of Van V. Dunn (1961). The latter's
estimate was a median value rather
than an absolute minimum [Tabb

Klein et al. (1975) calculates
that the total annual inflow to the
park prior to conservation area
construction (1941-1962) was 947,000
acre-feet. Bear in mind that this
estimate includes rainfall and run-
off, and it reflects a relatively
low water condition compared to the
pre-drainage Everglades. As of 1941
Lake Okeechobee was diked and much
of what used to be Everglades sheet
flow was being bled off through
major drainage canals to the east
and west. After conservation area
construction (1963-1970) Klein esti-
mates average annual inflows to the
park at 1,384,000 acre-feet. Of the
437,000 acre-feet increase, approxi-
mately 250,000 was due to the water
control structures and the rest to
increased rainfall.

Since 1972, the U.S. Geological
Survey (USGS) has been monitoring
the quality of surface waters and
sediment within the conservation
areas to the north of Tamiami Canal.
Moving south through the conserva-
tion areas, water quality character-
istics change significantly. In
particular, specific conductance, a
measure of the total ionic content
of water, decreases in a southerly
direction (Waller and Earle 1975,
Goolsby et al. 1976). A distinct
gradient of increasing specific con-
ductance also exists in the direc-
tion of the urbanized east coast
within Conservation Area 3 (Waller
and Earle 1975).

Mineralization of Everglades
surface waters is due primarily to
the closeness of highly soluble
calcium carbonate rock and leaching
from organic soils. Additionally,
groundwater to the south of Lake
Okeechobee is highly mineralized due
to contact with connate (entrapped)
seawater from ancient marine sedi-
ments (Parker et al. 1955). As
rainfall and runoff oscillate sea-
sonally, concentrations of major
inorganic ions respond accordingly.
Wet season concentrations are gener-
ally lower than dry season concen-
trations, due to relative dilution
(Table 13).

Notable exceptions to the gen-
eral seasonal trend are color and
sulfate in both groups of stations
and calcium at the marsh sites. All
of these increase in concentration
with increased rainfall/runoff.
Excess color in the marshes arises
from washout of organic tannins and
lignins, which are higher in concen-
tration during the wet season than
during the dry season. Sulfate
concentrations decrease during the
dry season presumably because of
anaerobic reduction to sulfide
(Waller and Earle 1975). Calcium
concentrations decrease during the
wet season probably because of
enhanced precipitation under pH
conditions greater than 8.3.

In contrast to the general sea-
sonal pattern, Lutz (1977) reports
no particular seasonal trends in the
major individual inorganic ions in
the Tamiami Canal to the east of the
study area; however, specific con-
ductance does show an increasing
trend during the dry season as well
as a slight increase with depth.

Nitrogen, phosphorous, and
organic carbon are fairly high in
the conservation areas due to the
highly organic soils and productive
marsh environment. As with the

Season (PCS)1/ Ca Mg Na K HCO3 SO4 C1 DS2/ H3/
D 85 41 20 130 7.0 218 4.5 200 520 180
Marsh sites W 72 43 10 48 2.3 166 12 67 270 120

Southern canal D 49 74 12 52 3.0 270 1.8 80 370 230
sites W 56 57 5.8 27 1.7 190 3.1 44 240 155

Dry season samplings April 1973 and 1974.
Wet season samplings October 1972 and 1973.
1/ Platinum cobalt standard.
2/ Dissolved solids.
3/ Hardness.

Table 13. Average concentrations of major inorganic ions and color for
wet and dry seasons in Conservation Area 3 (in milligrams per
liter except where noted) (adapted from Waller and Earle 1975).

major inorganic ions, nutrient con-
centrations tend to decrease toward
the south as agricultural runoff is
assimilated or trapped within the
marshes. Median total nitrogen
values range between 0.6 and 1.8
mg/l toward the south end of Conser-
vation Area 3. Total phosphorous is
fairly low throughout Conservation
Area 3 and in Tamiami Canal ranging
between 0.00 and 0.02 mg/ll (Waller
and Earle 1975). Nitrogen at the
marsh sites in the lower end of WCA
3 tends to increase toward the end
of the dry season as water levels
drop and ponding concentrates re-
maining nutrients. In Tamiami Canal
little seasonality is evident in
total nitrogen concentrations.
Phosphorous concentrations show
little seasonal variation in both
the canal and at the marsh sites.

Trace metal concentrations at
marsh stations and in Tamiami Canal
are presented in Table 14. Of all
the trace metals only iron occa-
sionally exceeds water quality stan-

dards, but this is typical of the
soils in this area. No particular
seasonal or spatial trends are obvi-
ous in trace metal occurrence and

Organic pesticides and their
breakdown products seldom remain in
detectable concentrations within the
surface waters of the conservation
areas, although they are detected in
71% of rainfall samples at concen-
trations of 0.01 mg/l to 0.9 mg/l
(Waller and Earle 1975). Concentra-
tions were lowest at the northern
boundary of ENP, probably because of
its distance from agricultural lands
to the north.

Due to their physical, chemi-
cal, and biological properties, many
pesticides (as well as trace metals
and nutrients) tend to accumulate in
organic sediments. Consequently,
sediments generally exhibit higher
concentrations of these materials
than the waters above them. The
building of organic peat soils by

As Cd Co Cr Cu Fe
i v a i v a i v a i v a i v a i v a
n q x n l 0 n g f n x n g X n 9 x
Marsh Total 1 10 17 0 1 9 0 1 6 0 1 10 0 2 10 10 220 1400
Sites Dissolved 0 10 17 0 1 8 0 1 5 0 1 10 0 2 10 10 80 180

Southern Total 0 12 40
Canal Sites Dissolved 0 6 14

0 2 10 0 1 5 0 3 30 0 6 130 50 250 950
0 2 7 0 1 4 0 3 10 0 5 10 20 10 310

Pb Mn Zn Hg Sr
i v a i v a i v a i v a i v a
n q n x 0 n g 0 n 9 x n 9 .

Marsh Total 0 5 22
Sites Dissolved 0 5 22
Southern Total 0 6 25
Canal Sites Dissolved 0 3 25

0 36 300 0 28 150 0.0 0.1 0.8
0 26 280 0 46 40
0 14 30 0 34 250 0.0 0.1 1.0
0 9 25 0 20 40

Table 14. Average, minimum, and maximum concentrations of trace metals
in surface waters of Conservation Area 3 (in micrograms per liter)
(adapted from Waller and Earle 1975).

sawgrass, wet prairies, and other
Everglades communities indicates
that the sediments act as a sink for
these materials entering the system
either in solution or in particulate
form. As water, sediment, and de-
tritus move through the glades, some
of this material may be recycled.

In general, canals which cut
through and drain the organic soils
disrupt their function as a nutrient
and pesticide sink. Lowering water
levels exposes the soils to oxida-
tion causing the release of bound
nutrients, organic moities, inorgan-
ic ions, and trace metals which
remained tied up under the reducing
conditions necessary for peat accu-
mulation. Waller and Earle (1975)
report relatively higher concentra-
tions of nutrients in the marsh
soils than in the canal sediments;
and higher concentrations of trace
metals in canal sediments than in
marsh soils. Pesticide concentra-
tions in all sediments declined with

distance away from agricultural
operations. Apparently the canals
serve as a mechanism for hastening
the export of trace metals and
organic matter, as well as water,
from the conservation areas. Unfor-
tunately, they are exported to
urbanized areas and estuaries where
they are not necessarily wanted.


Flow through the Tamiami Canal
spillways generally peaks in October
due to the corresponding peak in
rainfall (Leach et al. 1972), while
minimum flows occur in April and May
just prior to the onset of the wet
season. Considerable variation in
this general pattern occurs from
year to year, however, as evidenced
in Figure 33a of monthly average
flows from a variety of years.

As expected, water movement
through Shark River Slough, in any

30 780 2500

90 740 1400

I .....N


Hydrograph of monthly mean discharge
through Tamiami Trail (adapted from
Leach et al. 1972).

year or sequence of years, depends
on the timing, duration, and magni-
tude of flood and drought condi-
tions. Once inside the park, water
flows slowly southward as a broad
sheet. Under high flow conditions
the rate of sheetflow migration may
reach 426.7 to 487.7 m (1,400 to
1,600 ft) per day or about 80.5 km
(50 mi) per year. Under low flow,
rates may drop to zero as the water
table falls below ground level
(Figure 33b). Superimposed onto
this slow movement of sheetflow, the
constant background forces of evap-
oration and transpiration act to
remove as much as 85% of the average

Monthly distance traveled by sheet
flows under varying conditions
(adapted from Leach et al. 1972).

total input of rainfall
1974, Parker et al. 1955).


Thus the picture emerges, not
so much of a continuous "river of
grass" flowing from Tamiami Canal to
Whitewater Bay, Florida Bay, and the
Gulf of Mexico, but rather of a
series of sheetflow pulses, each
from a different runoff year. These
are connected to one another to form
a continuous but oscillating gra-
dient of flow through the Shark
River Slough. Seasonal pulses from
Tamiami Canal are augmented by local
rainfall and diminished by evapo-
transpiration. As the seasonal


50 ..
/ / _--
S1944 65 Miles
1947 425 Miles
35 --1959 503Miles /
----1960 452 Mile /
NOTE:Runoff year(April-March) /


/ ,

1 //-

5- /.

J I-

Figure 33.

j F M

pulse of rainfall/runoff recedes and
the rate of flow decreases, so too
do losses to transpiration and evap-
oration. The pulse may travel as
little as 8 to 10 km (5 to 6 mi) in
a year or as much as 32 km (20 mi)
depending on specific conditions.
Then, as the subsequent year's pulse
begins, what remains of the previous
year's pulse (usually below ground
by then) becomes replenished with
local rainfall and upstream drain-
age. Increased upstream flow from
the current year's pulse pushes last
year's even farther downstream,
eventually into the estuarine zone.

The open water estuarine zone
of the western Everglades National
Park begins about 24 to 32 km (15 to
20 mi) southwest of the 40-Mile Bend
in Tamiami Canal. Beginning with
the numerous small creeks that form
the headwaters of the Shark River
estuary, the tidally affected brack-
ish water zone extends southwesterly
for approximately 32 km (20 mi) to
Ponce de Leon Bay. To the south of
the Shark River estuary, coastal
drainage into Whitewater Bay occurs
through a diffuse network of smaller
rivers, most notably the Watson,
North, and Roberts Rivers. To the
north of Shark River estuary, drain-
age to the gulf through the Harney
and Broad Rivers is not only local
but in part derives from the Shark
River Slough. North of the Broad
River, Lostman's Bay signifies the
beginnings of the "back bay" zone
(White 1970) that extends northward
along the coast eventually grading
seaward into the Ten Thousand Is-
lands. This area is characterized
by a line of bays set back and sepa-
rated from the coast by a 3 to 8 km
(2 to 5 mi) wide strip of mangrove
swamp. Drainage into Lostman's Bay
and the Gulf of Mexico arises pri-
marily from the drainage area north
of Shark River Slough and adjacent
to the Big Cypress Basin.

The upper end of Shark River
estuary, known as Rookery Branch,
exhibits wide seasonal fluctuations
in water level and salinity. As
local rainfall and upstream flow
increase during June to October,
water level rises and salinity
falls. Seasonal salinity variation
in the Shark River estuary is great-
est at Rookery Branch and gradually
decreases toward Ponce de Leon Bay.
The relatively shallow depth, low
channel slope, strong wind, and
constant tidal flux results in a
generally well-mixed, homogeneous
water column in Shark River and
nearby estuaries. Tidal velocities
approaching 6.4 km per hr (4 mph)
have been observed in the lower
Shark River (McPherson 1971).

Kolipinski and Higer (1969)
characterize Shark River Slough
within the National Park as rela-
tively unpolluted with respect to
nitrate, sulfate, calcium, dissolved
solids, and iron. Median values and
ranges for these parameters from 65
samples collected between December
1959 and September 1967 appear in
Table 15.






0-7.7 0.4
40-173 54

Dissolved solids 24-1152



Table 15. Selected water quality
parameter concentrations
in Shark River Slough
(adapted from Kolipinski
and Higer 1969).

In the upper slough, still
within the park, Kolipinski and
Higer (1969) studied the dissolved
oxygen dynamics of an alligator hole
within a willowhead, and the sur-
rounding sawgrass marsh. Under high
water conditions, diurnal oxygen
levels in the hole and marsh were
very similar, ranging from about
3.0 mg/I in early morning to as much
as 9.0 mg/I during early afternoon.
As water levels dropped below ground
level, respiration in the alligator
hole increased. At low water levels
diurnal fluctuations remained small,
and concentrations seldom reached
greater than 2.0 mg/l. Similar
conditions were reported for the
Tamiami Canal waters.

Pesticide concentrations in
surface waters from both the upper
Shark Slough and the lower estuary
are reported to be uniformly low
(Kolipinski and Higer 1969, McPher-
son 1971). Concentrations of DDT
within sediments, however, are as
much as 1000 times greater than in
surface waters in the upper slough.

Recently Flora and Rosendahle
(1981) documented an ominous but
confusing change in the inorganic
chemistry of Shark Slough surface
waters. Prior to construction of
L-29 on the north boundary of the
park, specific conductance in the
slough averaged 272 uohms/cm. The
sodium to chloride ratio (Na:CI)
averaged 0.34 for the same period.
After construction (1962 to present)
specific conductance averages 652
uohms/cm and the Na:CI ratio aver-
ages 0.88. This increased minerali-
zation of surface waters is believed
to be the result of increased drain-
age by canals, thereby removing the
buffering action of marsh filtra-
tion. Rainfall in the area is much
less mineralized and therefore tends
to improve the water quality. This
change is ominous because of its

magnitude yet confusing because its
effects on marsh productivity and
ultimately the food web are not
easily predicted.

McPherson (1971) reports an
expected seaward increase in the
concentration of inorganic ions
toward the mouth of the Shark River
estuary. Silica (SiO2), tannins,
and lignins occur in higher concen-
trations at the freshwater end of
the estuary. Nutrients, trace met-
als, and pesticides vary widely,
exhibiting no regular seasonal or
spatial trends.

Information on changes in the
long term, overall water quality of
the Shark River estuaries are re-
ported by Davis and Hilsenbeck
(1974). These authors document the
gradual inland migration of saline
waters in response to upstream
diversion and management activities.
Their findings are particularly
important in that they point out an
insidious change in the availability
of habitat for estuarine organisms,
whose survival and growth depend on
a certain timing and range of fluc-
tuating salinity conditions.


Previous discussions of geology
and geomorphology have established
that Whitewater Bay is an eroded
depression lying just north of a
southeasterly extending ridge of
Miami Oolite. The relatively well
defined drainage pattern to the
northeast of the bay (the Watson,
North, and Roberts Rivers) suggests
that historical Shark Slough drain-
age at lower sea level conditions
traversed its present boundaries and
flowed directly into Whitewater Bay
(White 1970). The general north-
east/southwest orientation of the
many islands within the bay strongly
reinforces this conclusion (Spackman

et al. 1964). Dominant molluskan
fauna in recent sediments (Scholl
1963) also confirms that a definite
fresh to brackish to marine environ-
ment has prevailed along this same
axis in the bay over the past 5000

As the bay was gradually sub-
merging to form an open water estu-
ary, inundation by tides, primarily
through the Shark River Slough to
the north, modified the historical
drainage pattern. Thus a seasonally
oscillating "double" gradient was
established; one dominating during
the wet season in the northeast/
southwest direction representing the
historical freshwater flow influ-
ence; the other dominating the dry
season in the northwest/southeast
direction representing the effect of
tidal inundation and flushing.

In 1957 the situation was even
further modified by the opening of
the Buttonwood Canal which connected
Whitewater Bay to Florida Bay by way
of Coot Bay. Under the pre-canal
conditions, Coot Bay and southeast-
ern Whitewater Bay were extremely
sensitive to the effects of wind,
particularly along the southeast/
northwest axis. With southeast
winds, water was effectively drained
through Tarpon Creek into Whitewater
Bay, while during sustained north-
west winds, water "piled up" in the
small bay. It is significant to
note also, that under both condi-
tions daily tidal fluctuations were
nearly obliterated by wind action.

After the Buttonwood Canal
opened, the piling up of water in
Coot Bay under northwest winds was
all but eliminated. Flow constric-
tion by Tarpon Creek continued to
allow some build up in Whitewater
Bay, but Coot Bay was essentially
well flushed. The hydrologic con-
nection between Coot Ray and Florida

Bay disrupted the seasonal cycle of
water supply to the small lakes
south of Coot Bay. These had pre-
viously received input from the
overflow of waters in Coot Bay
(Tabb et al. 1962), especially dur-
ing the dry season when northwest
winds are most frequent. Presently
the Buttonwood Canal is being closed
in an effort to reestablish the
historical conditions.

The timing of the wet and dry
seasons in Whitewater Bay, as re-
flected in minimum and maximum
salinities, has been shown to be
approximately 3 months out of phase
with flow from the Tamiami Canal to
the north (Figure 34). As fresh-
water inflow peaks, the salinities
line up in a distinct southwest-
northeast gradient consistent with
the orientation of the water supply
(Figure 35). As freshwater inflow
subsides, salinity gradients tend to
reorient along the bay's southeast
to northwest axis consistent with
the main direction of tidal flows.
Extreme losses to evapotranspiration
often lead to salinities greater
than in open sea water as evidenced
in Figure 35. Especially intense
localized conditions of rainfall or
drought can, however, produce con-
siderable variation in these general
seasonal patterns (Clark 1971).


Surface discharge from Taylor
Slough arises from two sources:
(1) local rainfall; and
(2) overland sheetflow origi-
nating from Shark River
overflow and Tamiami Canal
between levees 30 and 67A.

As presented earlier, rainfall
in Taylor Slough averages around
150 cm (59 in) annually, with a peak
in September and a low in December
(Earle and Hartwell 1973). Likewise,


- 170-
LL 150-
C 130-
m 90-



, 10-

(Miami to 40-mile Bend)
Averages of three months of
flow data in acre feet.

/ -

1955 1956 1957 / 1958 1959
Bottom salinity in ppt (Averages
of three months, set back three.
months to account for lag.
Salinity graph inverted
so that low values show
\ / / as peaks.

1956 1957 1958 1959

Figure 34. Relationships between
salinity in Whitewater
Bay and freshwater
runoff across Tamiami
Trail (adapted from
Tabb et al. 1962).

. ^ '



C. E ." ,s
z.a* SABLE

-^ MARCH 1962
a1 I '' TIDE
o MI.. --so-s
L -' Y

Figure 35. Representative iso-
halines in Whitewater
Bay during wet and dry
seasons (adapted from
Tabb et al. 1962).

seepage discharge from the Tamiami
Canal between levees 30 and 67A
generally peaks in August through
October and bottoms out in March or

April. As mentioned in the discus-
sion of Conservation Area 3A, a
marked decrease in flow across this
section of Tamiami Trail occurred
after 1960 as the result of increas-
ed water retention behind levee 29
and diversion of flow to the west by
levee 67A.

Schneider and Waller (1980)
claim that surface water levels in
the Taylor Slough headwaters display
a relatively smaller range of fluc-
tuation than in areas to the north
(Shark River Slough) and south
(canal C-111). Apparently, surface
water levels in the Taylor Slough
headwaters are less strongly impact-
ed by drainage controls than are the
other two areas.

However, groundwater records in
the same area suggest that changes
have occurred in the below ground
water levels subsequent to the canal
and levee construction of the
1960's. Specifically, groundwater
tables exhibit less seasonal vari-
ability, with some indication that
seasonal lows are now lower than
prior to water level control. In
the wells close to canal C-111 this
is particularly obvious. Control
structure S-18C on C-111 opens auto-
matically when upstream stage reach-
es 0.6 meters (2 ft), effectively
dampening the peak of "average" high
water levels.

Surface flow from upper Taylor
Slough is measured as it passes
under a 12.1 km (7.5 mi) stretch of
Context Road through no less than 80
culverts. Downstream, near Home-
stead, flow is again measured
beneath a 4.8 km (3 mi) stretch of
State Road 27. Schneider and Waller
(1980) present flow duration curves
for these two stations that show the
upper slough effectively drying up
for much of the average year. Dif-
ferences in flow durations during


& 10-
z -
- 20-
. 30-


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