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Group Title: Guide for prescribed fire in southern forests
Title: The ecology of the Apalachicola Bay system
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 Material Information
Title: The ecology of the Apalachicola Bay system an estuarine profile
Series Title: FWS/OBS-82/05
Physical Description: Book
Language: English
Creator: Livingston, Robert J.
Kitchens, Wiley M.
National Coastal Ecosystems Team, Division of Biological Services, Fish and Wildlife Service, U. S. Dept. of the Interior
Affiliation: Florida State University -- Tallahassee -- Department of Biological Sciences
Publisher: Fish and Wildlife Service, U. S. Dept. of the Interior
Place of Publication: Washington, D. C.
Publication Date: 1984
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Bibliographic ID: UF00000100
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
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ltuf - AME7133
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Table of Contents
    Front Cover
        Page 1
        Page 2
    Main
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HUME LIBRARY
INSTITUTE OF FOOD AND
AGRICULTURAL SCIENCES
UNIVERSITY OF FLORIDA
Cainemu le


-p










FWS/OBS-82/05
September 1984


THE ECOLOGY OF THE APALACHICOLA BAY SYSTEM:
AN ESTUARINE PROFILE






by

Robert J. Livingston
Department of Biological Science
Florida State University
Tallahassee, FL 32306


Project Officer


Wiley M. Kitchens
National Coastal Ecosystems Team
U.S. Fish and Wildlife Service
1010 Gause Blvd.
Slidell, LA 70458


Prepared for


National Coastal Ecosystems Team
Division of Biological Services
Research and Development
Fish and Wildlife Service
U.S. Department of the Interior
Washington, DC 20240



























































Library of Congress Card No. 84-601077


This report should be cited as:

Livingston, R.J. 1984. The ecology of the Apalachicola Bay system: an estuarine
profile. U.S. Fish Wildl. Serv. FWS/OBS 82/05. 148 pp.

















PREFACE


This paper represents a synthesis of
knowledge concerning the Apalachicola
drainage system, which is located in
Florida, Georgia, and Alabama. The
Apalachicola Bay complex is only one part
of a major drainage area that includes the
Apalachicola, Chattahoochee, and Flint
River systems on one side and the
northeastern Gulf of Mexico on the other.
The boundaries that separate various
components (i.e., the river and its
associated wetlands, the bay system, and
the open gulf) are artificial in an
ecological sense. Likewise, the
traditional boundaries that have separated
various scientific disciplines--such as
physics, chemistry, meteorology, and
biology--are somewhat arbitrary when a
systems approach is used to determine the
functional interactions among interacting
subsystems. Thus various boundaries must
be crossed when the investigator attempts
to understand an entire aquatic ecosystem.

Over the past 12 years, researchers
in the Apalachicola system have carried
out a series of multidisciplinary and
interdisciplinary studies to determine the
response of the Apalachicola estuary to a
series of environmental variables. Such
an effort can be likened to the growth of
concentric layers of a snowball as it
rolls down a hill. The solution of each
problem forms the foundation for a new
question, which, in turn, serves as the
template for new hypotheses and tests.
The combination of background field
analyses and experiments in the laboratory
and the field have been used as the basis
of this effort. Eventually, we can view
the overall picture by cutting through the
snowball of ideas, hypotheses, and
resolutions to form models of how the
ecosystem works. As of this writing, 12
years of continuous field and experimental


data hav
computerizE
used to
Apalachico
comparison
southeastei
The
Apalachicol
step in
functions.
having an
aquatic
industrial
activities
destruction
restriction
turn, can
socioeconon
area is
According
progressive
carried ou
objective
information
established
and Bay Na


fe
ed f
dev
la
wit
rn Ui


been transformed
'iles, which are now b
elop models of how
Bay system works
h other such systems in
united States.


into
einq
the
in
the


scientific work on the
a estuary is only the first
our understanding of system
Increasingly, humans are
important influence on natural
systems. Urbanization,
ization, and agricultural
can lead to habitat
i, pollution, and severe
is on productivity, which, in
be translated into very real
nic problems. The Apalachicola
a multiple-use system.
I, sound land planning and
resource management are best
t with a comprehensive base of
scientific and economic
i. With the recent
nt of the Apalachicola River
tional Estuarine Sanctuary--the


largest such sanctuary in the nation--the
Apalachicola drainage system has been
designated by law as a special area, a
place of refuge and shelter for important
aquatic species as well as humans as
integral parts of the ecosystem. As one
of the last relatively natural big river


areas in
productive
enough to
scientific
enough to
other such
is current
determine
translated
management


the United States, the highly
Apalachicola system is small
analyze in a comprehensive
fashion while being extensive
be used as a natural model for
areas. The Apalachicola valley
ly part of a major experiment to
whether scientific data can be
into a comprehensive resource
program that will accommodate


economic development while perpetuating
the natural resources of the region.

















SUMMARY


The results of 12 years of continuous
field studies and experiments in the
Apalachicola Ray system are reviewed and
summarized in this paper. Included are
data concerning the geography, hydrology,
chemistry, geology, and biology of the
Apalachicola drainage system with particu-
lar emphasis on the estuary and associated
waters.

The Apalachicola Bay system is part of
a major drainage area that includes four
rivers and their associated wetlands in
Georgia, Alabama, and Florida. The Bay is
a shallow coastal lagoon fringed by
barrier islands and dominated by wind
effects and tidal currents. River bottom-
lands that include the channels, sloughs,
swamps and backwaters, and periodically
flooded lowlands are important components
of the system. Principal influences on
the biological processes in the estuary
are the physiography of the basin, river
flow, nutrient input, and salinity dis-
tribution in space and time. Water
quality is affected by periodic wind and
tidal influences and freshwater inflows.

Compared to most of the estuaries in
the United States, the Apalachicola Bay
system is in a relatively natural state,
although hardly pristine. However,
economic development and population growth
are beginning to put pressure upon the
region, threatening it with destructive
changes. The economic and ecological
importance of the area as a producer of
food and as shelter for diverse species is
such that it has inspired a movement to
protect its natural resources. Broadening
the economic base of the region while
maintaining its biological productivity
will require the development of a
comprehensive management plan based on the
deepest possible understanding of the


basis for that productivity, supported by
ongoing study, close monitoring, and
continued cooperation from local
interests.

Research efforts to acquire the
necessary understanding are not yet com-
plete, but have nonetheless given rise to
one of the most extensive computerized
data bases so far assembled on an estu-
arine system. Powerful programs for
working with these data have also been
developed; because of the extreme com-
plexity of their interplay, computer
analysis has been and will continue to be
a primary tool in understanding how
physical and biological processes work in
the estuary.

Rased upon the data obtained thus
far, some efforts have been initiated to
preserve and protect important freshwater
and estuarine wetlands. Included in these
efforts are the following:


State and federal land-purchase
programs

Integration of local (county) land-
use regulations into a comprehensive
plan for new and existing
development

Creation of the Apalachicola River
and Bay National Estuarine Sanctuary,
the largest such sanctuary in the
country.

The effort to manage the Apalachicola
Bay system is an ambitious one; only time
will tell whether it will be successful in
its effort to protect important wildlife
values as the region undergoes economic
development.

























CONTENTS


PREFACE
SUMMARY


FIGURES ........
TABLES .........
CONVERSION TABLE
ACKNOWLEDGMENTS


1. INTRODUCTION (HISTORICAL PERSPECTIVE AND OVERVIEW)
1.1. Geographic Setting and Classification ......
1.2. Driving Forces and Human Influence .........


2. ENVIRONMENTAL SETTING ....................
2.1. Origin and Evolution of the Estuary


2.1.1.
2.1.2.
2.1.3.
2.1.4.
2.2. Climat
2.2.1.
2.2.2.
2.2.3.
2.3. Hydrol
2.3.1.
2.3.2.
2.4 Physic
2.4.1.
2.4.2.
2.4.3.
2.4.4.
2.5 Biolog
2.5.1.
2.5.2.
2.5.3.
2.5.4.
2.5.5.


Geological Time.Frame ....
Geomorphology and Regional
Watershed Characterization
Barrier Islands ..........
e ............................
Temperature .............
Precipitation ............
Wind .....................
ogy .........................
Freshwater Input .........
Tides and Currents .......
al/Chemical Habitat .........
Temperature and Salinity .
Dissolved Oxygen .........
pH .......................
Water Color and Turbidity
ical Habitats ................
Wetlands .................
Seagrass Beds ............
Soft-Bottom Substrates ...
Oyster Bars ..............
Nearshore Gulf Environment


2.6 Natural Resources of the Apalachicola


3. PRIMARY PRODUCTIVITY AND NUTRIENT CYCLING ..
3.1. Primary Producers ...................
3.1.1. Allochthonous Sources ......
3.1.2. Autochthonous Sources ......
3.2. Detritus Flux and Nutrient Dynamics ..
3.3. Microbial Ecology ....................


4. SECONDARY PRODUCERS ........................
4.1. Zooplankton ..........................
4.2. Larval Fishes ........................


.......
........
........
Geology

.,,...o
..,....
......,
,.......
........,
..... .
....o..,,
...o.,,
.......,
.... ..,,
........
,,,.o..,
.... ....
.......,
.........
....,,
......,
,,,....
..,...
....,..


Drainac


................ .. .
......... ....... .. ......
.......... .. .. ...... ...


......... .. ...... .......
.............. ... ... ....
.......... ... .... ........
......... ........ .. .....
................ ... ....
......... ....... .........
.......... ...... ... ......
......... .. .............
....................... .
......... ........ .......
.... .... .. .... ..... .. .. ,
..................... ...
.........
.......... ..............
......... .... ........ ..
...,.. ........ ........ ..
.......
........ .... ... ..... ....
..... ..... .......... .....
................ .. ......
...........
......... .......... ... ...
.....,, .I .. ...... ..
.......... ... ...........
ge System ...............


........................ ........
.,,. ...........................
................................


.............................. ........... .... .... ............
................ ........... ....... .


............................ ....
............................. ..
.......,. .....................
..................... ..... .... .










4.3. Benthos
4.4. Oysters


4.5. Nekton ................


5. NICHE
5.1


DIVERSITY, TROPHIC INTERACTIONS, AND COMMUNITY STRUCTURE .


Habitat-Specific Associations ..


5.1.1. Marshes ...............................
5.1.2. Seagrass Beds .......................
5.1.3. Litter Associations ...................
5.1.4. Oyster Bars ..........................
5.1.5. Subtidal (Soft-Sediment) Communities ..
5.2 Physical Control of Biological Processes ........
5.3. Trophic Relationships and Food-Web Structure ....
5.4. Predator-Prey Interactions and Community Response

6. LONG-TERM ECOLOGICAL RELATIONSHIPS ....................

7. THE ESTUARY AS A RESOURCE .........................
7.1. Fisheries .....................................
7.2. Socioeconomic Factors ...........................
7.3. Existing and Projected Impact by Man ............
7.3.1. Physical Alterations ..................
7.3.2. Toxic Substances ......................
7.3.3. Municipal Development ...............
7.4. Land Planning and Resource'Management ...........
7.4.1. Public Land Investment ................
7.4.2. The Apalachicola Estuarine Sanctuary ..


7.4.3. Local Planning Efforts and Integrated Management
7.4.4. Integration of Management Efforts ...............

8. COMPARISON WITH OTHER ESTUARIES ..............................

LITERATURE CITED ............................... ...............


APPENDICES


A. Overview of Sampling Program in North Florida Coastal Areas ........
1. Apalachicola Bay System ......................................
2. Apalachee Bay System .......................................
B. Computer Programs for Analyzing Field and Laboratory Data ..........
1. Special Program for Ecological Science (SPECS):
System Overview ...............................................
2. "MATRIX" Program System: Summary of Capabilities .............
C. Review of Ongoing Research Programs of the Center for Aquatic
Research and Resource Management (Florida State University) .......
1. Overall Scope of the Program ...............................
2. Center for Aquatic Research and Resource Management:
Personnel (1984) ............................................


................... 90


....... 112


............................................................. 131


........ .... .......................... .. 0..... .. ... ... ... ..
S..... ..................... ......................... ,. ......


.. . . .


""""'


,


















FIGURES
Number Page

1 The tri-river drainage area ............................................ 1

2 Location of the tri-river drainage system in the southeastern
United States ..................................................... 2

3 Important features of the Apalachicola Bay system, the major
contributing drainages, and the barrier island complex ................. 3

4 Impoundments along the tri-river system ............................... 4

5 The Apalachicola estuary ............................................... 6

6 Geological features of the Apalachicola drainage system ................ 7

7 Natural areas of the Apalachicola basin ............................... 9

8 Aerial view of St. Vincent Island .................................... 11

9 Seasonal averages of Apalachicola River flow and rainfall from
Columbus, GA, and Apalachicola, FL .................................... 11

10 Six-month and thirty-six month moving averages of Apalachicola River
flow and Apalachicola rainfall ........................................ 12

11 Net water current patterns in the Apalachicola estuary as indicated
by flow models ............................. .......................... 14

12 Apalachicola River flow and monthly average minimum air temperature .... 15

13 SYNMAP projections of average levels of salinity, dissolved oxygen,
turbidity, and color at permanent stations in the Apalachicola
estuary .................. ......................................... 16
14 Surface salinity at stations 1 and 5 in the Apalachicola estuary from
1972 through 1982 ..................................... .. ............ 17

15 Surface dissolved oxygen at stations 1 and 5 in the Apalachicola
estuary from 1972 through 1982 ........................................ 18

16 Water color at stations 1 and 5 in the Apalachicola estuary from
1972 through 1982 ............................................ ........ 19

17 Turbidity at stations 1 and 5 in the Apalachicola estuary from
1972 through 1982 .................................... ... ... .... 19

18 Frequently flooded areas and soil associations in the Apalachicola
River Basin ........................................................ 23

vit









Number Page

19 Distribution of the marshes and submergent vegetation in the
Apalachicola estuary ...................... ............................. 24

20 Distribution of oyster bars and sediments in the Apalachicola
estuary ........... ... ........................... .................. 26

21 Nutrient/detritus transport mechanisms and long-term fluctuations in
detrital yield to Apalachicola River flow .............................. 28

22 Regression analysis of microdetritus and Apalachicola River flow by
season ................................................................ 31

23 Average seasonal variation in phytoplankton productivity for the
Apalachicola estuary ................................................... 36

24 Monthly averages of daily litterfall on intensive transect plots across
the Apalachicola wetlands ............................................. 38

25 Tentative model of microbial interactions with various physical and
biological processes in the Apalachicola River estuary ................... 42

26 Seasonal distribution of total zooplankton biomass in the Apalachicola
estuary and associated coastal-areas during 1974 ......................... 45

27 Summed numerical abundance and number of species of benthic
infauna and epibenthic fishes and invertebrates taken in the
Apalachicola estuary ............................................. .. 59

28 Life cycle of the blue crab along the gulf coast of Florida .............. 65

29 Average monthly distribution of anchovies in the Apalachicola estuary
from 1972 through 1979 .................... ......................... . 69

30 Average monthly distribution of croaker in the Apalachicola estuary
from 1972 through 1979 .............................................. 70

31 Average monthly distribution of sand seatrout in the Apalachicola
estuary from 1972 through 1979 ........ ................................... 71

32 Average monthly distribution of spot in the Apalachicola estuary
from 1972 through 1979 ............................ ................... 72

33 Average monthly distribution of penaeid shrimp in the Apalachicola
estuary from 1972 through 1979 .......................................... 73

34 Average monthly distribution of blue crabs in the Apalachicola
estuary from 1972 through 1979 ........................................ 74

35 Numerical abundance and species richness of invertebrates taken
in leaf-litter baskets at various permanent sampling sites in
the Apalachicola estuary ............................................. 78

36 Regression of numbers of species of litter-associated macroinvertebrates
on salinity at three stations in the Apalachicola estuary ................ 78









Number Page

37 Simplified feeding associations of four dominant fishes (bay anchovy,
sand seatrout, Atlantic croaker, spot) and blue crabs in the
Apalachicola estuary ................................................ 85

38 Generalized simplified model of seasonal relationships of the dominant
macroinvertebraes and fishes in the Apalachicola Bay system .............. 86

39 Long-term fluctuations of squid abundance, salinity and temperature
taken in the Apalachicola estuary from June 1972 through March 1979 ..... 91

40 Monthly frequencies of blue crabs and variations in key physico-chemical
parameters at the 10 day-time stations in the Apalachicola estuary
from March 1972 through March 1978 ........................................ 92

41 Long-term abundance patterns in the dominant trawlable fish populations
in the Apalachicola estuary from March 1972 through February 4, 1982 ..... 95

42 Relative importance of four dominant species of invertebrates and
fishes taken in the Apalachicola Bay System from March 1972 through
February 1975 ........................................................... 96

43 Temporal associations of fishes taken in Apalachicola estuary from
March 1972 to February 1976 ...:................. ....... ..... ....... 98

44 Dredge spoil bank along the Apalachicola River ......................... 100

45 Ditching and diking associated with agricultural activities in the
lower Apalachicola floodplain ............................................ 105

46 The extent of diking by agricultural interests along the western
bank of the lower Apalachicola River .................................... 105

47 Portions of St. George Island showing housing development on the
Gulf side and dredging on the bay side ................................. 106

48 Major public investments and specially designated areas in the
Apalachicola basin ................................................... 108

49 Boundaries of the Apalachicola River and Bay Estuarine Sanctuary
with inclusion of real and proposed purchases according to the
Environmentally Endangered Land (EEL) Program (state) and
current federal holdings ................................. .......... 110

















TABLES



Number Page

1 Distribution and area of major bodies of water along the coast of
Franklin County (north Florida) with relative area of oysters,
grassbeds, and contiguous marshes ........................................ 15

2 Bottom salinities at stations in the Apalachicola estuary ................. 17

3 Terrestrial habitats and land-use patterns in the immediate watershed
of the Apalachicola Bay system ........................................... 20

4A Tree species found within the Apalachicola floodplain ..................... 21

4B Areas of each mapping category for five reaches of the
Apalachicola River .................................................... 22

5 Linear regression of total microdetritus and river flow by month/year by
season (August 1975-April 1980) ........................................... 30

6 Net above-ground primary production of marsh plants in various
salt marshes .............................................................. 32

7 Presence/absence information for net phytoplankton taken from the
Apalachicola estuary by month from October 1972 through September 1973 .... 33

8 Physical, chemical, and productivity data taken from locations along the
northwest gulf coast of Florida ........................................... 37

9 Total annual net productivity and net input to the Apalachicola estuary
and the Apalachicola Bay system .......................................... 38

10 Nutrient yields for various drainage areas in the Apalachicola-
Chattahoochee-Flint River system .......................................... 39

11 Nutrient values for stations in the Apalachicola estuary and River ........ 40

12 Distribution of the major zooplankton groups in the Apalachicola estuary
and associated coastal areas ............................................ 44

13 Pearson correlation coefficients for significant zooplankton relationships
in East Bay, Apalachicola Bay, and coastal areas .......................... 46

14 Distribution of ichthyoplankton in the Apalachicola estuary as indicated
by the presence of eggs and larvae ...................................... 47

x









Number Page

15 Numbers of ichthyoplankton taken at various stations within the
Apalachicola estuary .............................................. 48

16 Invertebrates taken in cores, leaf-baskets, dredge nets, and otter
trawls in the Apalachicola Bay system (1975-1983) ...................... 50

17 General abundance information and natural history notes for the
dominant organisms in the Apalachicola estuary ........................ 56

18 Fishes and invertebrates commonly taken with seines in oligohaline and
mesohaline marshes of the Apalachicola estuary ......................... 61

19 Epibenthic fishes and invertebrates in the Apalachicola estuary from
1972 through 1982 ........... .................................... 63

20 Epibenthic fishes and invertebrates in the Apalachicola estuary from
June 1972 to May 1977 .................................. ..... ...... 66

21 Factor analysis of physico-chemical variables in the Apalachicola system
taken monthly from March 1972 to February 1976 ........................ 81

22 Correlation coefficients of linear regressions of nitrate,
orthophosphate, silicate, and'ammonia on salinity ...................... 82

23 Results of a stepwise regression analysis of various independent
parameters and species (population) occurrence in the Apalachicola
estuary from March 1972 to February 1975 .............................. 84

24 Parametric and nonparametric correlations of seasonal variations of
blue crab frequencies and abiotic variables ........................... 93

25 Multiple stepwise regression of seasonal variations of frequencies of
blue crabs of three size groups and selected abiotic variables ......... 93

26 Land use inventory of the Apalachicola River basin ..................... 102

27 Approximate dimensions of selected estuarine systems ................... 113

28 Estimates of particulate primary production in various estuaries in
the United States ...................................... . .......... 113

29 Approximate land use distribution and population density surrounding the
estuarine study areas ....................................................... 114

30A Approximate annual input from land drainage and point source discharge
of dissolved inorganic nitrogen per unit area and per unit volume in
various estuaries ....................................... .. ....... 115

308 Approximate annual input from land drainage and point source discharges
of dissolved inorganic phosphate per unit area and per unit volume in
the study areas ....................................................... 116

31 Total numbers of fishes per trawl sample taken at permanent stations in
the Apalachicola estuary, the Econfina estuary, and the Fenholloway
estuary ..... ......................................................... 117

xi













CONVERSION TABLE


Metric to U.S. Customary


Mul tiply

millimeters (mm)
centimeters (cm)
meters (m)
kilometers (Ian)

square meters (m ) 2
square kilometers (km )
hectares (ha)

liters (1)
cubic meters (m3)
cubic meters

milligrams (mg)
grams (g)
kilograms (kg)
metric tons (t)
metric tons
kilocalories (kcal)

Celsius degrees


To Obtain


0.03937
0.3937
3.281
0.6214

10.76
0.3861
2.471


inches
inches
feet
miles

square
square
acres


0.2642
35.31
0.0008110

0.00003527
0.03527
2.205
2205.0
1.102
3.968

1.8(oC) + 32


feet
miles


gallons
cubic feet
acre-feet

ounces
ounces
pounds
pounds
short tons
British thermal units

Fahrenheit degrees


U.S. Customary to Metric


inches
inches
feet (ft)
fathoms
miles (mi)
nautical miles (nmi)

square feet (ft2)
acres
square miles (mi )

gallons (gal)
cubic feet (ft3)
acre-feet


ounces (oz)
pounds (lb)
short tons (ton)
British thermal units (Btu)


25.40
2.54
0.3048
1.829
1.609
1.852

0.0929
0.4047
2.590


3.785
0.02831
1233.0


28.35
0.4536
0.9072
0.2520


Fahrenheit degrees


millimeters
centimeters
meters
meters
kilometers
kilometers

square meters
hectares
square kilometers

liters
cubic meters
cubic meters

grams
kilograms
metric tons
kilocalories

Celsius degrees


0.5556(F 32)

















ACKNOWLEDGMENTS


The research on which this paper is
based began as a modest monitoring project
in Apalachicola Bay in March 1972. Since
that time, more than 1000 people--
scientists, research aides, graduate and
undergraduate students, and professional
staff people--have participated in a
series of projects carried out within a
broad spectrum of disciplines. The
research effort has included chemistry,
hydrological engineering, physical
oceanography, biology, geology, geography,
fisheries, computer programming,
statistics, resource planning and
management, and economics. Many of the
data have been retained and organized into
a series of computer files, which T am
currently holding at the Florida State
University Computer Center. A complete
list of this information is given in the
appendices to this paper.

Although funding for this program has
come from various sources, the maior
contributions have been made by the
Florida Sea Grant College (National
Oceanic and Atmospheric Administration)
and the Franklin County Board of
Commissioners. Supplementary funds have
been provided by private industry and
state and federal agencies. The list
includes local developers, forestry
interests, the Florida Department of
Environmental Regulation, the Florida
Department of Community Affairs, the


Coastal Plains Regional Commission, the
U.S. Environmental Protection Agency, the
National Science Foundation, the Florida
Department of Natural Resources, the
Northwest Florida Water Management
District, the U.S. Geological Survey, the
Florida Game and Fresh Water Fish
Commission, the U.S. Fish and Wildlife
Service, and the Man in the Biosphere
Program of the U.S. Department of State.
Special credit should be given to the
Department of Biological Science (Florida
State University) for its long-running
support of the research. It is somehow
consistent that the main impetus for the
research effort has come from local
concerns (the fishermen of Franklin
County, Florida) and a federal agency (the
Florida Sea Grant College, NOAA) that has
always sought to apply basic scientific
knowledge to practical problems. The
people of Franklin County, depending on
the sea for their livelihood, recognized
early that, as land development
accelerates in Florida, a forward-looking
management program will be necessary to
protect the resource that has been at the
center of their way of life for
generations. The combination of basic and
applied science, local, state, and federal
involvement, and a multidisciplinary,
long-term research program has led to a
series of resource management/planning
actions that are unprecedented in the
nation.



















CHAPTER 1
INTRODUCTION (HISTORICAL PERSPECTIVE AND OVERVIEW)


1.1. GEOGRAPHIC SETTING AND
CLASSIFICATION

The Apalachicola estuary (Figures
1-3) is part of a tri-river system that
includes the Apalachicola River in Florida
and the Chattahoochee and Flint Rivers in
Georgia and Alabama. The Chattahoochee
River originates at the base of the
Appalachian Mountains in the Piedmont
upland, and traverses three geologic
provinces: the Piedmont, the Appalachian,
and the Coastal Plain. The Flint River
begins in the lower Piedmont Plateau just
north of the fall line and flows through
the Coastal Plain.

The Apalachicola-Chattahoochee-Flint
(ACF) drainage basin includes an estimated
48,484 km2 (19,200 mi2) in western
Georgia, southeastern Alabama, and
northern Florida (Figure 1). The
Chattahoochee River drains approximately


TRI-RIVER
SYSTEM


21,840 km2 (8,650 mi2) and the Flint River
drains an estimated 21,444 km2 (8,494
mi2). The Jim Woodruff dam, which forms
Lake Seminole at the confluence of the
Flint and Chattahoochee rivers,
constitutes the headwaters of the
Apalachicola River. The Apalachicola
River is approximately 171 km (108 mi)
long, with a fairly uniform slope of 0.15
m/km (0.5 ft/mi); it falls approximately
12 m in its course from Lake Seminole to
the Gulf of Mexico. The Apalachicola
River drains an area of about 2,600 km2
(1,030 mi2). The Chipola River, which
joins the Apalachicola River near its
southern terminus (Figure 1), has a
watershed equal to that of the
Apalachicola. About 3% of the ACF basin
is in the Blue Ridge mountains, 38% in the
Piedmont Plateau, and 59% in the coastal
plain below the fall line (Figure 2). The
lower coastal plain is nearly flat, with
extensive wetlands development.


Figure 1. The tri-river (Apalachicola, Chattahoochee, Flint) drainage area showing
the distribution of the important habitats and the position of key cities and
municipalities within the Apalachicola-Chipola drainage system.












Fall


GULF
OF
MEXICO


Figure 2. Location of the tri-river
drainage system in the southeastern United
States showing the relative positions of
upland features and the Apalachicola
estuary.


A detailed review of the dimensions
of the Apalachicola Bay system (29035'N to
29055'N; 84o20'W to 85020'W) (Figure 3) is
given by Livingston (1980a). This system
is composed of six major subdivisions:

East Bay 3,981 ha (9,837 acres)
Apalachicola Bay 20,959 ha
(51,792 acres)
St. Vincent Sound 5,540 ha
(13,689 acres)
West St. George Sound (to Dog Island)
14,747 ha (36,440 acres)
East St. George Sound
16,016 ha (39,576 acres)
Alligator Harbor 1,637 ha
(4,045 acres)

The entire area totals 62,879 ha (155,374
acres). A natural shoal forms a submerged
boundary between Apalachicola Bay and
St. George Sound. The bay is bounded on
its extreme southern end by three barrier
islands: St. Vincent, St. George, and Dog
Island. There are four natural openings
to the gulf: Indian Pass, West Pass, East
Pass, and a pass between Dog Island and
Alligator Harbor. A man-made opening
(Sike's Cut) was established in the
western portion of St. George Island. The


3.6-m- (12-ft-) deep Intracoastal Waterway
extends northwestward from St. George
Sound through Apalachicola Bay, up the
Apalachicola River to Lake Wimico and then
along an artificial channel to St. Andrews
Bay to the west.

The Apalachicola estuary is a lagoon
and barrier island complex. It has been
classified as a shallow coastal plain
estuary oriented in an east-west direction
(Dawson 1955). Because of the placement
of the barrier island complex, it could be
called a coastal lagoon. The average
depth is between 2 and 3 m at mean low
tide (Gorsline 1963).

In terms of Pritchard's (1967)
estuarine classification scheme, the
Apalachicola Bay system is a width-
dominated estuary controlled by lunar
tides and wind currents. As such, it is a
type D estuary (Conner et al. 1981) in
that it is dominated by physical forces
(i.e., tidal currents, wind) as a function
of its shallow depths. As a result, the
bay system is relatively well mixed,
although various portions of the estuary
are periodically (seasonally) stratified
(Livingston 1984a).

1.2. DRIVING FORCES AND HUMAN INFLUENCE

The principal driving forces that
determine the habitat structure and
biological processes of the estuary are
river flow, physiography of the basin,
seasonal changes of nutrients, and
salinity as modified by wind, tidal
influences, and freshwater inflows. Tidal
influence extends approximately 40 km (25
miles) up the river. As a biological
entity (Odum et al. 1974), the estuary
(which includes East Bay, Apalachicola
Bay, St. Vincent Sound, and western
portions of St. George Sound), is
characterized by upland marshes that grade
into soft-sediment areas, vegetated
shallow bottoms, and oyster reefs. The
oligohaline East Bay merges with
mesohaline and polyhaline portions of
Apalachicola Bay, St. Vincent Sound, and
St. George Sound.

The Apalachicola River, the largest
in Florida in terms of flow, is the
principal source of fresh water to the
estuary. The average flow rate is about









665 m3 sec-1 (23,500 ft3 sec-1) measured
at Blountstown, Florida. Maximum and
minimum discharges over the past 15 years
are 4,600 m3 sec-1 (162,500 cfs) and 178
m3 sec-1 (6,280 cfs), respectively. The
river and, secondarily, local rainfall
determine the distribution of salinity in
the estuary. The placement of the barrier
islands also has a maior influence on the
salinity regime of the estuary (Livinqston
1979, 1984a). The islands limit the
outflow of the low-salinity water to the
outer Gulf of Mexico.

The Aoalachicola basin occupies the
last sparsely inhabited and undeveloped
drainage system and coastal region in
Florida (Livingston 1983a, b, c).
Franklin County, with a population of only
8,403 in 1979, encompasses the lower river
and bay system. Forested uplands,
wetlands, and aquatic habitats comprise
most of the land area in Franklin County.
The local economy is based largely on the


sport and commercial fisheries of the
Apalachicola River and Bay system.
According to recent estimates (Florida
Department of Administration 1977),
commercial fishing, recreation, forestry
and timber processing, agriculture, and
light manufacturing characterize the
regional economy of the entire
Apalachicola basin. The human population
of the six counties along the river has
grown slowly since 1960, increasing only
7% (from 101,782 to 109,254) from 1969 to
1974. State government is a major
employer in the region, while industrial
or commercial land use is confined to only
0.2% of the basin area.

The Apalachicola drainage system is
one of the least polluted in the country
(Livingston 1974a, b, 1977a-d, 1978, 1979,
1980a-c; Livingston and Thompson 1975;
Livingston and Duncan 1979; Livingston et
al. 1974, 1976a, b, 1977, 1978). Some
problems, however, have emerged in recent
years (Livingston 1983d).


0 10 20
KM.


Figure 3. Detailed features of the Apalachicola Bay system including the major contri-
buting drainages, the barrier island complex, and the major passes in the bay complex.









1. A 13,352-ha (33,000-acre) cattle
ranch was established in the Apalachicola
River floodplain about Q-10 km (6 mi)
above the bay. Much of the area was
cleared, ditched, and drained, while waste
water was pumped over the dikes into the
river system. The potential impact of
this operation is under study and review,
although farming has continued, and water
quality has deteriorated in some of the
upland creeks.

?. Portions of the drainage system
have historically been subjected to
forestry operations, which include
ditching, draining, clearcutting, and
reforestation. These activities have been
associated with local changes in water
quality and short-term adverse effects on
aquatic biological associations
(Livingston 1978). A long-term
multidisciplinary study has just been
completed by the Florida Sea Grant College
(Livingston 1983c) along with proposed
management practices which are designed.to
mitigate adverse impacts.

3. Recent population increases along
the north Florida coast have stressed
regional coastal counties in terms of
municipal development, sewage disposal,
and storm water runoff (Livingston 1983d).
The recognition of such potential impact
has led to the development of relatively
advanced local land use plans such as that
adopted by Franklin County in 1981
(Livingston 1980a, b, 1983c).
Implementation of the comprehensive plan
has not been carried out, however. During
1984, sewage spills closed down the
Apalachicola oyster industry for prolonged
periods. Meanwhile, proposals to bring
high-density construction projects to
coastal areas of Franklin County have
proliferated.

4. A continuing problem in the
region involves proposals to either
channelize or dam the Apalachicola River
to make a corridor for barge traffic and
industrial development. These
developments would serve as a north-south
link between upriver ports on the
Chattahoochee and Flint Rivers in Alabama
and Georgia and the Gulf of Mexico.
Authorization for a maintained channel
(30.5 m or 100 ft wide, 2.7 m or 8.8 ft
deep) by the U.S. Army Corps of Engineers


(USACE) was part of the amended Rivers and
Harbor Act of 1946. A system of 13 dams
is already in place on the Chattahoochee
River and three dams are currently in use
on the Flint River (Figure 4). Associated
with these activities are a series of
barge terminal facilities and offloadinq
systems. Rock outcrops in the
Apalachicola River have been removed as
part of ongoing, extensive dredging and
channelization of the river. Superimposed
over these activities is the increasing
municipal water use in areas such as
Atlanta, Georgia, where sustained
population growth could reduce water flow
in the tri-river system in the near
future.


* Federal
o Other


0 60
km


GULF
OF
MEXICO


Figure 4. Distribution of impoundments
along the tri-river system (after
information provided by the U.S. Army
Corps of Engineers).
















CHAPTER 2
ENVIRONMENTAL SETTING


?.1. ORIGIN AND EVOLUTION OF THE ESTUARY

2.1.1. Geological Time Frame

The physiographic structures of most
estuaries are ephemeral in terms of
geological time. Climatological forces
are continuously at work shaping and
reshaping the basin features.
Characteristics of the Apalachicol-a
estuary are dependent on the interaction
of an upland drainage system with offshore
marine conditions. The estuary is, in
effect, an extension of the upland river
or drainage area, and its origin and
evolution are inextricably linked to the
dynamic geological history of the land/sea
interaction.

The Aoalachicola River is the only
drainage area in Florida that has its
origin in the Piedmont, which, as will be
explained later, is of biological
importance to the region. The geological
history of this area is well known in
general terms. By the Cretaceous period
(about 135 million years ago), most of the
tri-river valley was submerged under
ancient seas (Tanner 1962). The origin of
the Apalachicola River or its antecedents
occurred some time in the Miocene epoch
about 25 million years ago (W. F. Tanner,
Florida State University, pers. comm.).
There has been a gradual decline in sea
level through Cenozoic time (70 million
years ago to present); sea level has
dropped an estimated 70-100 m from the
middle of the Miocene (Tanner 1968).
Olsen (1968) gives evidence that the upper
Apalachicola River basin (the area around
Blountstown, Florida; Figure 1) was a
deltaic or coastal environment during the
Miocene. By the Pleistocene epoch (1
million years ago), there was evidence of
an arcuate chain of barrier islands


approximately 22.5 km (14 mi) northeast of
Apalachicola, Florida. These islands were
located in what is now the Tate's Hell
Swamp (Figure 1). The general dimensions
of the Apalachicola valley as we see them
today were established in the Pleistocene.

The maior drainages of the Florida
panhandle (which includes the Apalachicola
drainage system) are alluvial in that they
carry sediment loads that eventually end
up in the coastal estuaries (Figures 1,
5). The geological structure of the
Apalachicola River estuary is of Recent
and Pleistocene origin. Marine sediments
comprise a major physical feature of the
region. The Apalachicola estuary is
bounded by well-developed beach-ridge





I9
J IL















Figure 5. The Apalachicola estuary with
details of upland drainage areas and the
placement of permanent sampling sites for
". .. .." ,















the long-term field studies of the Florida
State University research team (after
Livingston et al. 1974).









plains of late Holocene origin (Fernald
1981). The linear, gently curving beach
ridges of the area attest to the changes
in orientation of the estuary through
geological time in response to wide
fluctuations of sea level. The
Apalachicola estuary is part of a broad,
sandy shore plain, which is constantly
being changed by a combination of
climatological elements such as wind,
rainfall and sea level alterations. The
present structure of the bay is around
10,000 years old (Tanner 1983). Sea level
reached its modern position about 5000
years ago when the construction of the
present barrier island chain was underway.
Except for the southward migration of the
delta front, the general outline of the
bay system was established at this time
(Tanner 1983).

2.1.2. Geomorphology and Regional Geology

a. Upland areas. The major
formations in the upper Chattahoochee
River system are underlain by igneous
rocks and crystalline schists. The area
is characterized by Tertiary limestone
outcroppings, which add to the habitat
diversity of the region (Figure 6). The
lower division of Piedmont upland, defined
as the Opelika Plateau, is underlain by
Archean (i.e., Precambrian) rocks.
Tributaries of the Chattahoochee River
have subsequently eroded these formations
with some valleys cut approximately 62 m
(200 ft) below the general surface. The
rocks of the Appalachian province pass
under the Coastal Plain formations. Along
the border between the Appalachian
province and the Coastal Plain,
Appalachian rocks are overlain by
Cretaceous formations. These rocks are
more deeply buried by Tertiary and
Quaternary sediments further north. The
Coastal Plain is covered with a thick
layer of plastic (erosion produced)
sediments as well as limestone
(nonclastic) sediments, some of which may
be crystalline.

Adams et al. (1926) have presented a
detailed account of the Paleozoic,
Mesozoic, and Cenozoic formations in
Alabama, which is generally applicable to
the Apalachicola valley. The Cenozoic
formations are confined to the Coastal
Plain and represent deposits at the bottom


of an ancient sea, which consist of sand,
clay, mud, or calcareous ooze. Fossil
marine mollusks and echinoderms are
interspersed with remnants of fossil
plants from flood plains, marshes, and
swamps. Pleistocene marine sands and
clays overlie older formations along the
coast, and estuarine and fluvial deposits
extend up the main river valley. Swamps
immediately upland of the Apalachicola
estuary are underlain by quartz sand
(Brenneman and Tanner 1958).


Figure 6. Geological features of the
Apalachicola drainage system showing (A) a
line north and west of which there are
thin patches of Tertiary limestone near
the land surface and (B) a line beyond
which the limestone thickens and is more
deeply buried. The top of the Tertiary
limestone is shown in feet below sea
level, while Tertiary limestone that
occurs in or near the land surface is also
outlined (modified from Means 1977).









The coastal geomorphology of the
Apalachicola region is extremely complex;
major features are developed from wind and
current modified beach ridges (Clewell
1977). These formations are complicated
by considerable Pleistocene sea-level
fluctuations. The northern gulf coastal
lowlands are dominated by Pliocene epoch
marine sands. The flood plain of Holocene
(recent) sediment reaches depths
approximating 24.3 m (80 ft) near the
river mouth and 13.7 m (45 ft) near
Blountstown, Florida (Figure 1). These
sediments lie directly on Miocene strata
because much of the Pliocene and
Pleistocene sediments were eroded during
periods when sea level was lower and river
flow was greater. The sea level
approximately 20,000 years ago was over
125 m (410 ft) lower than that found
today, and the coastline was considerably
seaward of its current position.

The Florida panhandle is an uneven
platform of carbonate bedrock (limestone
with dolomite) overlain by one or more
layers of less consolidated clastics
(Figure 6, Puri and Vernon 1964; Clewell
1978). Superficial strata are of Eocene,
Oligocene or early Miocene origin.
Considerable solution activity has led to
the formation of sinks, caves and other
karst features (Means 1977). The clastics
consist of Fuller's earth (primarily the
clays montmorillinite and attapulgite),
phosphatic matrix, sand, silt, clay, shell
marl, gravel, rock fragments, and fossil
remains. The clastics with shell marl are
sediments of ancient shallow seas and
estuaries. Various plastic strata were
deposited during the early Miocene, while
others were fluvial and aeolian deposits
or sediments in lake bottoms. These
clastics form terraces sloping toward the
Gulf. Such terraces are altered by
erosion and dissection by streams and
rivers. In spite of various
post-Pleistocene sea-level fluctuations,
elevations in this area have changed less
than 10 m as a result of erosion,
deposition, and sedimentation. Dunes,
spits, bars, and beach ridges became
stranded inland as the sea receded.

b. Soils and sediments. The
Apalachicola River floodplain lies wholly
within the Florida Coastal Plain and is in
contact with Tampa Limestone (early


Miocene). The river just below the Jim
Woodruff Dam flows through the Citronelle
formation (Pliocene) that borders the
western edge of the Pleistocene bed from
16 to 20 km below the dam to Blountstown.
The eastern portion of the river is
influenced by the Hawthorn formation
(Fuller's earth and phosphatic limestone)
and Duplin marl (sandy marine and clayey,
micaceous shell marl). The clays in
particular and fine sands cause
considerable turbidity. The river bed is
composed primarily of remnants of
Pleistocene deposits (sand to coarse
gravel) that are covered by fine clay
sediments. The lower river valley is
composed largely of Plio-Pleistocene
marine sands, which lie over the Aucilla
Karst Plain, the Jackson Bluff formation,
and the lower part of the Citronelle
formation.

Upland soil composition reflects the
geological history of the Apalachicola
valley. Soils in the titi swamps and
savannahs of the Apalachicola National
Forest are strongly acidic and low in
extractable cations (Mooney and Patrick
1915; Coultas 1976, 1977, 1980). Total
phosphorus is low in all soils of the
basin. Cypress and gum swamps are also
highly acidic and low in extractable
bases, while more alluvial soils are less
acidic. Estuarine marsh soils are rela-
tively high in organic matter, especially
at the river mouth. These soils are
derived largely from the erosion of the
northern Piedmont-Appalachian soils, which
have been deposited on the sea floor and,
at times, have been uplifted above sea
level. Floodplain soils are composed of a
broad range of textures and colors. They
are predominantly clay with some silty
clay and minor clay loams (Leitman, 1978).
Point bars in the river bed are composed
largely of fine and very fine sands.

Soils in wetlands directly associated
with the Apalachicola River have been
analyzed. Swamp soils are wet, moderately
acidic, high in clay content, and low in
salinity (Coultas in press). The princi-
pal clay-sized minerals include kaolinite,
vermiculite, quartz, and mica. These
areas are poorly drained and contain
considerable amounts of clay and organic
matter. The soils are formed from recent
accumulations of sediments deposited in









stream channels and estuarine meanders.
The pH values range from 4.q to 6.6.

Studies of the marshes above East Bay
(Coultas 1980; Coultas and Gross 1975)
indicate that the deltaic soils are
slightly acidic and become alkaline with
depth. The dense mats of roots and
rhizomes from the predominant sawgrass
(Cladium jamaicense) and needlerush
(Juncus roemerianus) along the eastern
portions of the estuary tend to hold the
soils in place. The soils are composed of
thin organic deposits mixed with clay and
overlie loamy sands of fine-textured
materials. Considerable amounts of silt
occur in some soils, and most have poor
load-bearing capacity because of the high
organic content and high field moisture
levels. Vegetation differences are
attributed to soil salt content. Sawqrass
is dominant in areas most affected by
river flow (i.e., with low salinity), and
needlerush is predominant in tidal areas
(i.e., those with higher salinity)
(Coultas 1980).

Sediments in the estuary are
characterized by mixtures of sand, silt,
and shell components (Livinqston 1q78).
Present sediments are accumulating over
tertiary limestones and marls that outcrop


in the scoi
Pass and In
and norther
are silty a
and shell gq
The thickne
(Gorsline
erosion of
periods of
composed of
Areas near
quantities


ured
Idian
n por
reas
ravel


central channels of West
Pass. St. Vincent Sound
tions of Apalachicola Bay
that grade into sand/silt
toward St. George Island.


ss of these sediments (10-?0 m)
1963) may be the result of
older deltaic deposits during
higher sea level. East Ray is
silty sand and sandy shell.
the river mouth have varying
of woody debris and leaf


matter, especially during winter and
spring months of heavy river flooding
(Livingston et al. 1976a). The floor of
the bay is thus formed largely of quartz
sand with a thin (but varying) cover of
silt, clay, and debris depending on the
proximity to land runoff.

The estuarine sediments originated in
the southern Appalachians and have
undergone a complex history of deposition
and reworking in the coastal plain
deposits, coastal marshes, beaches, and
dunes. Fine sediments flow out of the bay


into
moved
at the


the Gulf
by tidal
e mouths


of Mexico while sand
currents within the bay
of the western inlets.


cusp of the Aoalachicola Bay coastline has
been built by river sediments deposited
during Tertiary and Pleistocene times with
modification by waves and long-shore
drift. Puri and Vernon (1964) and Clewell
(1978) have made a detailed review of the
geological formations and soil
distribution in the region.

2.1.3. Watershed Characterization

Numerous physiographic, geological,
and biogeographic features contribute to
the biotic richness of the Apalachicola
drainage system (Clewell 1977; Means
1977). While the Apalachicola basin
(Figure 7) lies entirely within the
Coastal Plain, it is subdivided into upper
and lower regions; the Marianna lowlands,
New Hope Ridge, Tallahassee Hills and


MARIANNA


WESTERN
RED HIL


RIVER
BOTTOM-
LANDS


Figure 7. Natural areas
Apalachicola basin based
physiography, vegetation types,
geography, and distribution of
(after Means 1977).


of the
on the
regional
organisms









Beacon Slope are part of the Gulf-Atlantic
rolling plain, while the lower coastal
lowlands are part of the Gulf-Atlantic
Coastal Flats (H. M. Leitman et al. 1982).
The drainage system contains streams of
various types, which range from first-
order ravine streams (Means 1977) to the
higher order low-gradient, meandering
types. The latter contain high organic
acid levels in the flatwoods or are
calcareous and clear in the Marianna
Lowlands karst plain. Extensive lake
systems are lacking in the valley;
Ocheesee Pond is located in an abandoned
bed of the Apalachicola River, and two
other natural lakes (Lake Wimico, Dean
Lake) occur in the basin. The upper river
region, cutting through Miocene sediments,
has a flood plain 1.5-3 km (0.9-1.9 mi)
wide. This floodplain widens to 3-5 km
(1.9-3.1 mi) along middle portions of the
river, with the lower river having the
widest floodplain (7 km; 4.4 mi). The
upstream tidal influence in the floodplain
does not extend above km 40 (mi 25). -The
Chipola River joins the Apalachicola at km
45 (river mi 28). The delta is about 16
km (10 mi) wide and is surrounded by a
broad marsh.

The previously described geological
processes have led to high physical
diversity of the land forms in the
Apalachicola basin. "Steepheads" or
amphitheatre-shaped valley heads with very
steep walls (Means 1977) occur in small
drainages that dissect the eastern
escarpment between Bristol and Torreya
State Park within a narrow east-to-west
alignment through the Florida panhandle.
These constant environments are important
habitats for various species. The
Apalachicola Ravines (Fiqure 7) (Hubbell
et al. 1956) are drainages that form
another unique habitat associated with the
river basin. These ravines include small-
order stream bottoms and steep valley
slopes; the vegetation grades upward from
hydric plant communities near the bottom
to xeric vegetation at the top of small
divides between ravines. The Marianna
lowlands form a karst plain containing
more vadose (i.e., above water table) cave
ecosystems than any other part of the
coastal plain (Means 1977). The
Apalachicola lowlands, a flatwoods region
with little relief, is a low, slightly
inclined plain with extensive swamplands.


The eastern portion of the Apalachicola
lowlands contains parts of the Tate's Hell
Swamp, which is undergoing extensive
changes due to forestry operations. The
western lowlands are part of a cattle
ranch and farming operation. The Western
Red Hills are separated from the other
natural areas by the Chipola River valley.
This area is high in elevation but not as
deeply dissected as the Apalachicola
Ravines. Grand Ridge (Figure 7) is a
wedge-shaped area bounded by the Chipola
and Apalachicola Rivers. While originally
part of the same upland mass that extended
from the Apalachicola Ravines westward,
Grand Ridge has been eroded. This area is
associated with springs, caves, and
troglodyte (i.e., subterranean) fauna.
The river bottomlands represent a
floodplain habitat characterized by the
river channel, sloughs, swamps and
backwaters, and the periodically flooded
lowlands. Many springs and aquatic cave
systems empty directly into the river
bottomlands.

2.1.4. Barrier Islands

At the mouth of the Apalachicola
River is a well developed barrier-island
system composed of three islands (St.
Vincent, St. George, Dog) (Figure 3).
These islands roughly parallel the
coastline and are characterized by sets of
sand dunes of differing geological ages.
While the shore system is based on dunes
that date back some 3000 to 6000 years,
the barrier islands are no older than 3000
years. They consist of quartz sand that
has been transported from the southern
Appalachian Piedmont by the river system
and that currently rests on an eroded
Pleistocene surface (Zeh 1980). On St.
Vincent Island, for example, gently
curving lines of beach ridges (Figure 8)
up to 1 m (3 ft) high serve as the base
for small dunes; such ridges represent the
geological history of sand deposition in
the region, with the oldest (northernmost)
ridges indicating where sea level achieved
its earliest position.

St. George Island is about 48 km (30
mi) long and averages less than 0.5 km
(1/3 mi) in width. It consists of 2,973
ha (7,340 acres) of land and 486 ha (1,200
acres) of marshes. The medium to fine
grain sands provide for relatively poor


























Figure 8. Aerial view of St. Vincent
Island.


aquifer conditions; all fresh water is
derived from rainfall. Silty clay
sediments at depths between 7.6 and 9.2 m
(25-30 ft) below the sandy surface create
an impermeable barrier to separate rain-
derived fresh water from the surrounding
salt water. There is a shallow lens of
fresh water beneath the island. Some of
this fresh water, modified by
transpiration and evaporation, is
eventually discharged into the Gulf and
lagoonal marine systems.

2.2. CLIMATE

2.2.1. Temperature

The climate in the Apalachicola basin
is mild, with a mean annual temperature of
200 C (680 F). Temperature varies with
elevation and proximity to the coast. The
mean annual number of days with
temperatures at or below freezing is 20 at
Lake Seminole and 5 along the Gulf Coast
(National Oceanic and Atmospheric
Administration, unpublished data; Clewell
1977). Livinqston (unpublished
manuscript), working with long-term
(40-year) climatological data, found that
temperatures usually peak in August with
lows from December to February, at which
time monthly variance is maximal. While
peak summer temperatures are similar from
year to year, winter minima vary. A time-
series (spectral) analysis indicates that
there is a long-term period of recurring
low winter temperatures of 118 months (9.8


yr). Periodic low winter monthly minima
occurred in 1940, 1948, 1958, 1968, and
1977. Thus, in addition to a strong
seasonal component, there may be a long-
term periodicity to temperature
fluctuations in the Apalachicola region.

2.2.2. Precipitation

Mean annual rainfall in the
Apalachicola River basin is approximately
150 cm (59 inches). There are, however,
considerable local differences in monthly
precipitation totals. In the Apalachicola
delta, areas west of the river receive
almost one-third less rainfall than those
east of the river (i.e., Tate's Hell
Swamp). Rainfall in the Georgia portion
of the watershed is 130 cm/yr (51
inches/yr).

The rainfall patterns of Florida and
Georgia (Fiqure 9; Meeter et al. 1979) are
basically similar except for the timing of
rainfall peaks. Georgia rainfall has two


1200-


r 1000

0
J eoo.
LU
IJ
W
> oo00


400


200


E
.20 Z

15

-10

.5


J FMAMJ J A SON D
MONTHS
Figure 9. Seasonal averages of
Apalachicola River flow (Blountstown,
Fla.) and rainfall from Columbus, Georgia,
and Apalachicola, Florida. Standard
deviations (S.D.) are given for selected
months (after Meeter et al. 1979).










peaks: one in March and another of equal
magnitude in July. The Florida rainfall
peak in March is not as great as that of
Georgia, but the primary difference is the
much larger, sustained rainfall peak in
summer and early fall in Florida. In both
areas, there are drought periods during
mid to late fall. Spectral analysis of
long-term trends (Figure 10) indicate
that, while rainfall is highly variable,
there are certain long-term trends.
Florida (Apalachicola) rainfall has
80-month (6.7-yr) cycles in peak reoccur-
rence, while Georgia rainfall has a
slightly different spectrum.


2.?.3. Wind

Wind direction is predominantly from
the southeast during the spring
(March-May) and southwest to west during
the summer (June-August). Winds come from
the north or northeast during the rest of
the year. However, analysis of long-term
wind data indicates that there is wide
variability of wind velocity and direction
over the Apalachicola watershed at any
given time. In the shallow estuary, winds
can cause rapid changes in the normal
tidal current patterns. Southerly winds
tend to augment astronomical tides and


6 MONTH -
36 MONTH -----


RAINFALL


I I I I I I I I I I I
10 1925 1930 1935 1940 1945 1950 1955 1960 1965 1970 1975
YEARS


C,
-400 Cr
.LJ

-300 Co

z Li



-100 0,

(D




O
2-200
I








I-
z






(D
w






0


0

10


Figure 10. Six-month and 36-month moving averages of Apalachicola River flow
(cfs; 1920-1977) and Apalachicola rainfall (1937-1977). Data are taken from Meeter
et al. (1979).









cause abnormally high water without the
usual ebb.

The air circulation over the Gulf of
Mexico is primarily anticyclonic (clock-
wise around an atmospheric high-pressure
region) during much of the year. However,
strong air masses of continental origin
often move through the northern Florida
area, especially during the winter. From
November to March, an average of 30 to 40
polar air masses penetrate the Gulf each
year. Storms are usually formed along
slow-moving cold fronts in winter.
Tropical storms or hurricanes may occur in
summer and early fall. Lesser storms
often occur as extratropical cyclones,
which tend to move across the Gulf from
west to northeast during winter periods
(Jordan 1973). Winter storms tend to be
more pervasive in a geographic sense,
while summer storms are often intensive,
short-lived, localized events. The
likelihood of the occurrence of a
hurricane in the northeast Gulf is about
once every 17 years with fringe effects
about once every 5 years (Clewell 1978).
The last hurricane to hit Apalachicola,
Hurricane Agnes, occurred in June 1972.
Overland (1975) showed that basin
orientation (relative to wind direction,
headlands, and marsh areas) can produce
variations in surge heights, which are
responsible for much damage. Livingston
(unpublished data) found that Hurricane
Agnes had no sustained effect on water
quality or the biota of the Apalachicola
estuary.

2.3. HYDROLOGY

2.3.1. Freshwater Input

The Apalachicola River has the
highest flow rate (690 m3 sec-1 at
Chattahoochee, Florida; 1958-1980) and
broadest flood plain (450 km2 of bottom-
land hardwood and tupelo-cypress forests)
of any river in Florida (H. M. Leitman et
al. 1982). Apalachicola River discharge
accounts for 35% of the total freshwater
runoff on the west coast of Florida
(McNulty et al. 1972). Seasonal variation
(Figure 9) is high, with peak flows from
January through April and low flows from
September through November. The absence
of a summer river-flow peak (despite rain-
fall peaks in the basin at this time) may


be related to higher evapotranspiration
rates in the vegetation of the watershed
(Livingston and Loucks 1978). A spectral
analysis using data from 1920 to 1977
(Figure 10) indicated river-flow cycles on
the order of 6-7 years (Meeter et al.
1979). Indications of longer-term cycles
were shown along with the abnormally low
river flow during the mid-1950's.

In a cross-spectral analysis of
Georgia rainfall with river flow, the two
patterns were in phase (Meeter et al.
1979; Figure 9). The analysis indicated
that the Apalachicola River flow patterns
more closely resembled cycles of Georgia
rainfall than they did those of Florida
rainfall. This pattern should be expected
since only 11.6% of the drainage basin is
in Florida, and the remainder is in
Georgia. Stage fluctuations vary greatly
from upper to lower river with the
narrowest ranges (from peak to low) at
downstream stations (H. M. Leitman et al.
1982). Such flooding patterns are
essential to elements of the hydrology of
the estuary.

Floodplain inundation varies with
location on the river and reflects the
influence of natural riverbank levees
(H. M. Leitman et al. 1982). Natural
levees within the flood plain are
inundated only at high stages of river
flow. The level of the water table also
depends on river stage. Fluctuations are
damped by water movement through flood-
plain soils. The levees of the upper
river, where there is a greater range of
water fluctuation, are higher than those
in the lower river where the flood plain
is quite flat. Flood depths tend to
decrease from the upper to the lower river
and rates of flow in the upper river
floodplain are generally less than those
along the middle and lower reaches of the
river. The height of the natural levees
and the size and distribution of breaks in
the levees all control the hydrological
conditions of the river flood plain. Such
hydrological conditions, in turn, control
the form and distribution of floodplain
vegetation (H. M. Leitman et al. 1982).

2.3.2. Tides and Currents

Franklin County straddles a region of
transition between the diurnal tides of









west Florida and the semidiurnal tides on
the Gulf peninsula. Tides at Analachicola
are diurnal to semidiurnal, with
"uncertainties" concerning the selection
of a "typical" tide pattern for each month
(Conner et al. 1981). Tides in the
Apalachicola estuary are influenced by the
main entrances and smaller passes. Tidal
ranges vary from 0.13 m (0.43 ft) at Dog
Island near the eastern end of the estuary
to 0.23 m (0.75 ft) at East Pass.
Gorsline (1963) classified this estuary as
unsymmetricall and semidiurnal except
during periods of strong wind effect."
While currents in the Apalachicola estuary
are tide-dominated, they are also
dependent on local physiographic
conditions and wind speed and direction
(Livingston 1q78). River discharge has
little influence on the hydrodynamics of
the partially stratified estuary (Conner
et al. 1981). Shallow estuaries such as
the Apalachicola are wind dominated in
terms of flushing and current movement.
The wind can be up to three times more
important than the tidal input in the
determination of current strength and
direction (Conner et al. 1981).
Net flows tend to move to the west
from St. George Sound; East Bay water
merges with the westward flow (Fiqure 11).
West Pass appears to be a major outlet for
the discharge of estuarine water to the
Gulf, especially when influenced by long-
term or high velocity winds from the east.
Water movement through Indian Pass also
occurs in a net westward direction,
although the Picoline Bar may retard
passage (Dawson 1955). Estuarine currents







'O z



Figure 11. Net water current patterns in
the Apalachicola estuary as indicated by
flow models developed by B. A. Christensen
and colleagues. (A detailed analysis of
such currents can be found in Conner et
al. (1981).)


may be affected by excessive land runoff
or high velocity winds from the east or
west. Strong north to northeast winds
deflect water downwind and to the west.

Gorsline (1963) estimated a tidal
prism equal to about 20% of the bay water
volume, and he suggested that the
residence time of river water in the
estuary ranges from a few days to a month.
The two western passes account for over
66% of the total bay discharge, even
though they account for only 10% of the
inlet area (Gorsline 1963). The bulk of
river flow exits through these passes, and
the effects of river flow on salinity can
be felt 265 km (165 miles) offshore in the
gulf. Tidal deltas extend seaward from
Indian Pass, West Pass, and East Pass,
indicating appreciable sediment transport
through these areas. Current velocities
in the bay rarely exceed 0.5 m sec-1,
while velocities in the passes may reach
2-3 m sec-1i
2.4. PHYSICAL/CHEMICAL HABITAT
Important habitat features of the
Apalachicola Bay system include physio-
graphic, climatic, and river-flow
conditions. While marshes (emergent
vegetation), oyster beds, and grassheds
(submergent vegetation) represent
important biological habitats of the
estuary. the primary physical habitat in
terms of areal extent is the shallow,
unvegetated soft sediment bottom (Table
1). Within the myriad of rapidly changing
gradients of physical and chemical
features of the estuary, there are certain
recurrent patterns and general trends that
remain more or less constant in soace and
over time. Such water-quality features
and nutrient distributions are important
determinants of the habitat conditions in
the Apalachicola Bay system.
2.4.1. Temperature and Salinity

Because of the shallowness of the bay
system and wind-mixing of the water
column, there is little thermal
stratification in the estuary. Water
temperature is highly correlated (r =
0.00, p < 0.00001) with air temperature
(Livingston 1983c), which indicates rapid
mixing. Summer temperature peaks are
similar from year to year, with seasonal
highs usually in August. Water









Table 1. Distribution and area of major bodies of water along the coast of Franklin
County (north Florida) with areas of oysters, grassbeds, and contiguous marshes.


Area Oysters Grassbeds Marshes
Water body (ha) (ha) (ha) (ha)

St. Vincent Sound 5,539.6 1,096.5 --- 1,806.9
Bay 20,959.8 1,658.5 1,124.7 703.4
East Bay 3,980.6 66.6 1,433.5 4,606.1
St. George Sound (West) 14,746.8 1,488.8 624.3 751.9
St. George Sound (East) 16,015.5 2.6 2,767.3 810.8
Alligator Harbor 1,637.0 36.7 261.3 144.3
Total 62,879.3 4,349.7 6,211.1 8,850.4
Percent of total water area 100 7 10 14


temperature minima occur from December to
February; monthly variance is highest
during winter. Whereas peak summer
temperatures are comparable from year to
year, winter minima vary annually (Figure
12). During years of extreme cold,
temperature ranged from 50 C to a maximum
of 330 C over a 12-month period. In
addition to strong seasonal components of
changes in water temperature, periodic
winter lows occurred at relatively regular
(8-11 yr) intervals. In recent times, the
winter of 1976-77 was particularly cold.
The seasonal temperature cycles are
evidently superimposed over long-term
temperature trends.

The distribution of salinity in the
bay at any given time is affected
primarily by river flow, local rainfall,
basin configuration, wind speed and
direction, and water currents. The
principal source of fresh water for the
estuary is the Apalachicola River,
although there is evidence that local
runoff and ground water flows affect the
habitat characteristics of the bay system
in local areas (Livingston unpublished
data). In terms of salinity, the bay
system may be divided into two main
provinces: the open Gulf waters of
eastern St. George Sound and the brackish
(river-diluted) portions of western St.
George Sound, Apalachicola Bay, East Bay,
and St. Vincent Sound.


972 197 9 19, 9 7 97 1 979 .8


30



s -
u
LJ
> 12

I 6
S


TIME
Figure 12. Apalachicola River flow and
average minimum air temperature data
provided by U.S. Army Corps of Engineers
and the NOAA Environmental Data Service,
Apalachicola, Fla.









Sound vary from polyhaline to euhaline (>
30 ppt) conditions. Gorsline (1963)
alluded to the vertical isohaline
conditions of the estuary except for areas
that are deep or near the inlets.
Livingston (1978, 1984a), however, has
documented seasonal vertical salinity
stratification in various parts of the
estuary, especially in areas affected most
directly by the river. Differences of
surface and bottom salinities of as much
as 5-10 ppt during periods of
stratification further complicate the
exact dimensions of the salinity regime in
a given area of the bay system through
time. However, by most statistical
measures, river flow is the chief
determinant of the salinity structure of
the estuary (Meeter and Livingston 1978).

There are persistent seasonal
patterns of salinity in the Apalachicola
estuary, although such patterns are
modified by annual variation of river flow
and fluctuations of local rainfall. Low
bay salinities coincide with high river
flows during winter and spring periods;
secondary salinity reductions occur in the
bay system during late summer-early fall

Table 2. Bottom salinities in parts per
thousand at stations in the Apalachicola
estuary. All data represent 5-year means
(1972-77) with maxima and minima for this
period. A cluster analysis was made to
group the stations according to salinity
type.
Bottom salinities (ppt)
Apalachicola Sta- Mini- Maxi- 5-yr
estuary areas tion mum mum mean
1 0.0 33.7 15.7
1A 3.0 35.6 22.1
Outer Bay 1E 6.9 31.6 15.7
1C 1.4 33.7 20.4
IX 0.0 32.0 17.8
2 0.0 28.1 10.4
River dominated 3 0.0 22.0 4.8
4 0.0 31.8 9.6


4A 0.0
5 0.0
Upper (East) bay--- 5 0.0
-5B 0.0
5C 0.0
-6 0.0
Sike's Cut--- 1B 10.6


26.2 3.6
28.0 7.4
27.3 5.1
25.7 3.8
27.8 4.3
23.0 3.6
35.5 28.6


periods of high local precipitation
(Figure 14). Salinity generally peaks
during the fall drought
(October-November). Long-term salinity
trends follow river flow fluctuations; low
salinity was noted for a prolonged period
throughout the estuary during the heavy
river flow conditions of the winter of
1972-73, although various factors combine
to shape the long-term (multiyear)
salinity trends in the estuary. Various
statistical analyses (Meeter and
Livingston 1978; Meeter et al. 1079) have
made a strong association of Apalachicola
River flow with the spatial/temporal
distribution of salinity throughout the
bay system.


30-


Staton 1


0 ,,,, ,,,, i.. ... ... ,l ,,,,,,, .. ,,,,rl, ........... llll l . . .
1972 1973 1974 1975 1976 1977 1978 1979 1990 1961 1982

30
Station 2

24
5.





5 Is-
I-



1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982
YEAR and MONTH

Figure 14. Surface salinity (5-month
moving averages) at stations 1 and 5
(Apalachicola Bay, East Bay) taken monthly
from 1972 through 1982.










2.4.2. Dissolved Oxygen

Diurnal and seasonal variations of
dissolved oxygen (Figure 15) reflect
biological and physical processes in the
system. Maximum levels usually occur
during winter and spring months because of
low water temperature and, to a lesser
degree, low salinity. During summer and
fall periods, vertical stratification of
dissolved oxygen is evident in various
parts of the estuary. Spatial
distribution of mean dissolved oxygen
values (Figure 13) is not uniform; the
highest values occur in the upper reaches
of East Bay (i.e., Round Bay), just off
St. George Island (i.e., Nick's Hole), and
along the eastern side of St. Vincent
Island. Concentrations of dissolved
oxygen in most of the estuary during the
10-vr period of observation are sufficient
to support most forms of estuarine biota
(Figure 15). No sign of cultural
eutrophication is evident. The long-term
pattern of dissolved oxygen maxima
followed the long-term temperature trends,
with dissolved oxygen peaking during the
cold winters from 1976 to 1978. Such
changes represent an indirect effect of
temperature on long-term habitat variation
in the estuary.

9.4.3. .pH

From 1972 to 1Q82, the pH throughout
most of the bay system ranged between 6
and 9 (Livingston 1983c, unpublished-
data). However, relatively low pH levels
(4-5) were observed in upper portions of
East Bay during periods of heavy local
rainfall and runoff from newly cleared
lands in Tate's Hell Swamp (Livingston
1978). Such changes were temporary and,
overall, the pH of the Apalachicola Bay
system remains within a range that is not
limiting to most life forms.

2.4.4. Water Color and Turbidity

Light transmission, as determined by
color (measured in platinum-cobalt units)
and turbidity (in Jackson Turbidity
Units), is a key variable in the timing
and distribution of primary and secondary
productivity in the estuary. The spatial
and temporal distributions of water color
and turbidity (Figures 13, 16, 17) are
related to patterns of fresh-water flow


into the bay system. The highest levels
of both factors are found at the mouth of
the river and throughout upper East Bay
with clear-cut gulfward gradients. Both
color and turbidity reach seasonal high
levels during winter and early spring
periods of high river flow and overland
runoff. During the major flooding in the
winter of 1972-73, turbidity and color in
the estuary reached a 10-yr high point at
most stations. While the general pattern
of color in the estuary follows river flow
fluctuations, the highest levels occurred
in eastern East Bay. The color was
directly associated with forestry
activities and runoff from the Tate's Hell
Swamp (Livingston 1978). Various
compounds such as tannins, lignins, and


E
> -

z

a 75
WJ
0

m,
Q


Station






j^niAAM.


1972 1973 1974 1975 176 1977 197 197199 1981 1982

Staton 2

125-
z

0
n 75-
a

(')


1972 1973 74 1975 1976 1977 1978 1979 1980 1981 1982
YEAR and MONTH

Figure 15. Surface dissolved oxygen
(5-month moving averages) at stations 1
and 5 in the Apalachicola estuary taken
monthly from 1972 through 1982.









fulvic acid complexes, which occur
naturally in the upland swamps, are washed
into the estuary during periods of high
local precipitation. Such water-quality
changes, associated with river flow and
local rainfall, affect the biological
organization of the bay system in terms of
primary productivity and food web
structure (Livingston 1983b-d).

?.5. BIOLOGICAL HABITATS

The Apalachicola drainage system as a
whole is an almost unbroken series of
natural habitats, which include upland
vegetation, swamps, marshes, and flood
plain wetlands. Much of the basin
vegetation has the appearance of a mature
forest because of rapid regrowth. Slash
and longleaf pine are abundant in upland





300- Station I




I?
0


1972 173 1974 975 1976 1977 1978 79 190 191 1982


areas. Although several municipalities
are located near or within the
Apalachicola and Chipola flood plains.
none is a major urban center; there is
little industrialization in the basin.
The dimensions of the biological habitats
within the bay system and its associated
watershed (i.e., Franklin County) are
given in Tables 1 and 3. Aquatic areas,
together with forested and nonforested
wetlands, comprise about 42% of the total
area of Franklin County. As noted
previously, aquatic areas are dominated by
unvegetated soft-bottom substrates.

2.5.1. Wetlands


a. Bottomland hardwoods.
Apalachicola flood plain (Figure
the upper river is relatively


175

140
EE

s 05
^70

3 5


The
18) of
narrow


Station I










i A\ _


1972 1973 1974 1975 976 977 1978 1979 1980 1981 1982


300-

= 240-


r;
0 0
o


06


Station 2


4n 140

Q a

O
t- o
I-0
o 9


ii


1972 1973 1974 1975 1976 197 79 99 1979 1980 981 19B2
YEAR and MONTH

Figure 16. Color (5-month moving
averages) at stations 1 and 5 in the
Apalachicola estuary taken monthly from
1972 through 1982.


StLion 2









4AJJVAu


1972 1973 1974 1975 1976 1977 176 1979 1980 198 1982
YEAR and MONTH

Figure 17. Turbidity (5-month moving
averages) at stations 1 and 5 in the
Apalachicola estuary taken monthly from
1972 through 1982.








Table 3. Terrestrial habitats and land-use patterns in the immediate watershed of the
Apalachicola Bay system (Florida Bureau of Land and Water Management 1977).


Category Total area (ha) % of total


Residential
Commercial, services
Transportation, utilities
Mixed urban or built-up areas
Other urban or built-up areas
All urban or built-up areas


Cropland and pasture
Other agriculture
All agricultural land


Herbaceous rangeland
Rangeland


Evergreen forest land
Mixed forest land
All forest land


Streams and canals
Lakes
Reservoirs
Bays and estuaries
All water


Forested wetland
Nonforested wetland
All wetlands


Beaches
Quarries and pits
Transitional areas
All barren land

Total area of Franklin County:


2,461
178
218
27
39
2,922


68,598
36,396
104,994


1,469
452
10
62,879
64,810


25,562
8,465
34,027


1,441
25
110
1,575

198,398


(1.5-3.0 km or 0.9-1.q mi wide). The
forested flood plain broadens along the
lower river (up to 7 km or 11.1 mi wide),
with most of the flood-plain wetlands
located in the lower delta (H. M. Leitman
et al. 1982). The forested flood plain of
the Apalachicola basin is the largest in
Florida (450 km2, 173 mi?; Wharton et al.
1977), and 60 of the 711 tree species in
north Florida are found there (Table 4).


The predominant species in terms of cover
include water tupelo, ogeechee tupelo,
baldcypress, carolina ash, swamp tupelo,
sweetgum, and overcuo oak. These species
are typical of southeastern alluvial flood
plains and occur in such areas partially
because of their adaptive response to
restricted availability of oxygen in
saturated and inundated soils. Despite
continuous logging for over a century, the









Table 4. A. Tree species found in the Apalachicola floodplain (from Leitman 1983 and
H. M. Leitman et al. 1982). Included is the relative basal area (in percent) of the
top 25 species. B. Area, in acres, of each mapping category for five reaches of the
Apalachicola River (from Leitman 1983).


A. Common name

Ash, Carolina
Green
Pumpkin
Baldcypress
Birch, river
Box elder
Bumelia, buckthorn
Buttonbush
Chinaberry
Cottonwood, swamp
Cypress
Dogwood, stiffcornell
(swamp dogwoodb)
Elm, American
Slippery
Winged
Grape
Hawthord, green
Parsley
Hickory, water
Hornbeam, American
Locust, water
Maple, red
Mulberry, red
Oak, cherrybark
diamond-leaf
laurel

overcup
swamp chestnut
water
Palmetto, cabbage
Persimmon, common
Pine, loblolly
spruce
Planertree (water-elmb)
Possumhaw holly
Silverbell, little
Sugarberry (hackberry)
Swamp-privet
Sweetbay
Sweetgum
Sycamore, American
Titi


Scientific name

Fraxinus caroliniana Mill. (5.4)
Fraxinus pennsylvanica Marsh. (2.9
Fraxus profunda (Bush.) Bush. (1.9)
Taxodium distichum (L.) Rich. (10.6)
Betula nira L. (0.8)
Acer negundo L. (0.3)
Bumelia lycioides (L.) Pers.
Cephalanthus occidentalis L.
Melia azedarach L.a
Populus heterophylla L. (0.4)
see badcypress
Cornus foemina Mill.
(Cornus stricta Lam.b)
Ulmus americana L. (2.4)
TmusT rubra Muhl.
Ulmus alata Michx.
Vitis spp.C
Crataequs viridis L.
Crataegus marshallii Egqle.
Carya aquatica (Michx. f.) Nutt. (2.9)
Carpinus caroliniana Walt. (2.0)
Gleditsia aquatica Marsh.
Acer rubrum L. (1.5)
Morus rubra L.
Quercus falcata Michx., var. pagodaefolia Ell.
Quercus laurifolia Michx. (2.5)
Quercus emisphaerica Bartr. (0. laurifolia
Michx.d)
Quercus lyrata Walt. (3.2)
Quercus prinus L. (0. michauxii Nutt.b) (0.3)
Quercus nigra L. (1.8)
Sabal palmetto (Walt.) Lodd.
Diospyros virginiana L.
Pinus taeda L.
Pnus qlabra Walt.
Planera aquatica Gmel. (2.9)
Ilex decidua Walt. (0.8)
Halesia tetraptera Ellis. (H. parviflora Michx.b)
Celtis laevigata Willd. (2.8)
Forestiera acuminata (Michx.) Poir.
Magnolia virginiana L. (1.0)
quidambar styraciflua L. (4.8)
Platanus occidentalis L. (0.6)
Cyrilla racemiflora L.


(continued)








Table 4. (Concluded.)


Common name Scientific name

Tupelo, Ogeechee Nyssa ogeche Bartr. (11.0)
water Nyssa aquatica L. (29.9)
swamp (blackgum) Nyssa biflora Walt. (N. sylvatica var. biflora
(Walt.) Sarg.b) T5.0)
black (sourgum) Nyssa sulvatica Marsh. (N. sylvatica Marsh.
var. sylvaticab)
Viburnum, withered Viburnum cassinoides L.
Walnut, black Juqansnigra L.
Willow, black Salix nigra Marsh. (0.4)




alntroduced exotic species.
bAccording to Little (1979).
cRadford and others (1968).
dLittle (1979) does not recognize Quercus hemisphaerica as a separate
species.






Acres
B. Lower Lower Lower
river from river from river from
Mapping Upper Middle Wewahitchka Sumatra mile 10
category river river to Sumatra to mile 10 to mouth Total

Pine 136 672 0 204 0 1,010
Sweetgum-
Sugarberry-
Water oak-
Loblolly Pine 642 1,440 154 474 0 2,710
Water hickory-
Sweetgum-
Overcup oak-
Green ash-
Sugarberry 12,500 32,200 15,800 1,770 48.0 62,300
Tupelo-cypress
with mixed
hardwoods 1,170 1,860 8,310 15,800 6,920 34,100
Tupelo-cypress 2,420 2,270 6,240 10,300 456 21,700
Pioneer 0 150 19.2 0 0 169
Marsh 0 0 0 0 9,030 9,030
Open water 2,730 3,110 1,540 2,010 1,260 10,700
Unidentified 1,020 748 81.3 76.8 19.2 1,950
Total 20,600 42,500 32,100 30,600 17,700 144,000









total water area (Table 1). Except for
certain areas along the eastern portions
of St. George Sound, submerged vegetation
in the Apalachicola estuary is light-
limited by high turbidity and water color.
High sedimentation and resuspension of
sediments in the estuary may also affect
the seagrass bed distribution. Seagrasses
and algal associations are largely
confined to fringes of the estuary at
depths of less than 1 m. The largest
concentration of these submerged grassbeds
is in eastern St. George Sound; such
seagrass beds also occur in upper East
Bay, inside St. George Island in
Apalachicola Bay, and in western St.
George Sound. In East Bay, freshwater and
brackish-water species (Vallisneria
americana, Ruppia maritima, and
Potamogeton sp.) are predominant. Grass
beds along the mainland east of the river
are dominated by Halodule wrightii,
Syringodium filiforme, and Thalassia
testudinum. The shallow laqoonal flats of
Alligator Point, Dog Island, and St.
George Island are populated by Halodule
wrightii, Gracilaria spp., and Syringodium
filiforme. Few if any grassbeds are found
in St. Vincent Sound.

As a habitat, seagrass beds provide
organic matter and shelter for various
infaunal and epibenthic invertebrates and
fishes.

2.5.3. Soft-Bottom Substrates

Muddy, soft bottom substrates
comprise about 78% of the open water zone
of the Apalachicola Bay system and are
thus the dominant habitat form in the
area. The relative composition of the
sand, silt, clay and shell fractions of
the sediments depends on proximity to
land, runoff conditions, water currents,
and trends of biological productivity.
Sediment type and associated water-quality
conditions in the benthic habitat
determine the composition of infaunal and
epifaunal biological components.
Recruitment and community composition of
the benthic invertebrates (meiofauna and
macrofauna) may depend on the distribution
of flocculent resuspended sediments and
bedload transport. The unvegetated, soft-
bottom habitat in the Apalachicola Bay
system represents the basis for important
food web relationships in the estuary.


2.5.4. Oyster Bars

The Apalachicola estuary is an ideal
environment for the growth and culture of
the oyster (Crassostrea virginica). The
oyster bars that cover about 7% of the
aquatic area of the bay system (Table 1)
are an important habitat for various
assemblages of estuarine organisms. Major
oyster beds are located in St. Vincent
Sound, west St. George Sound, and the East
Bay-Apalachicola Bay complex (Figure 20).
New (constructed or artificial) oyster
reefs are located in eastern portions of
St. Vincent Sound. The highly productive
natural oyster bars of St. Vincent Sound
and western St. George Sound represent the
primary concentrations of commercial
oysters in the estuary. The waters of
both areas are well circulated by the
prevailing currents and are characterized
by salinity conditions optimal for oyster
propagation and growth (Livingston 1983c,
d). The reefs near the seaward edge of
the bay thrive when the river is high
while those near the river mouth do well
during conditions of low water.

Whitfield and Beaumariage (1977)
estimate that about 40% of Apalachicola
Bay is suitable for growing oysters but
that substrate type is a major limiting
factor. Rapid oyster growth due to
favorable environmental conditions
accounts for the fact that over 90% of
Florida's oysters (8%-10% nationally) come
from the Apalachicola estuary.

2.5.5. Nearshore Gulf Environment

The shallow nearshore gulf is a
drowned alluvial plain grading into a
limestone plateau to the east and south
(McNulty et al. 1972). The eastern Gulf
of Mexico is characterized by moderately
high-energy sand beaches. The north gulf
coast sedimentary province contains relict
sand west of the Apalachicola delta. The
Miocene relict sands and clays off the
Apalachicola embayment grade into quartz
sand and mud over limestone characteristic
of the extreme eastern gulf region. Much
of the water motion along the shallow West
Florida Shelf is due to tides, although
wind effects are evident, especially in
winter when cold fronts move through the
area. The high-salinity coastal waters
are well mixed except during warmer months








temperate systems that have been studied
(Mattraw and Elder 1980).

3. Nutrient levels are higher in the
Apalachicola wetlands than in most
comparable systems throughout the northern
hemisphere. The ADalachicola wetlands
contribute significant quantities of
nutrients and organic matter to river and
bay areas. Regular seasonal flooding by
the currently free-flowing river is
necessary for mobilization of particulate
organic matter (POM) and nutrients out of
the floodplain (Mattraw and Elder 1980).

4. The Apalachicola drainage system
includes a grouo of ecological regions
that contribute to speciose and unique
plant associations. The flora comprises
117 plant species, of which 17 are
endangered, 28 are threatened, and 30 are
rare. Nine species are narrowly endemic
while 27 are endemic to the general
Apalachicola area (Means 1977).

5. The Apalachicola wetlands provide
habitat for rich faunal assemblages. The
basin receives biotic exchanges and input
from the Piedmont, the Atlantic Coastal
Plain, the Gulf Coastal Plain, and
peninsular Florida. The floodplain
forest, with over ?50 species of
vertebrates, is one of the most important
animal habitats of the Southeast (Means
1977).

6. Of the drainages of the
Apalachicolan and West Floridian molluscan
province (from the Escambia River to the
Suwannee River), the Apalachicola River
contains the largest total number of
species of freshwater gastropod and
bivalve mollusks. The river contains the
greatest proportion of endemics to the
total fauna in the province, with at least
six rare and endangered species (two
Amblemids, four Unionids) (Heard 1977).

7. The tri-river valley is
characterized by a rich fish fauna (116
species) (Yerger 1977). The Apalachicola
basin contains more fish species (85) than
any other Florida river. Three, species
(Notrpis callitaenia, N. zonistius,
Moxostoma sp.) are restricted to the
Apalachicola River and its major
tributaries, while a fourth species (the
"handpaint" bluegill, Lepomis macrochirus)


originated in the system. Existing
freshwater sport and commercial fisheries
are diverse and rich. The Apalachicola
River is the only river on the Florida
gulf coast that supports a striped bass
(Morone saxatilis) fishery (Livingston and
Joyce 1977). This fishery is based on a
population that is endemic to the river
and considered a separate race from the
Atlantic coast striped bass.
8. Excluding fishes, the
Apalachicola River system contains over
250 species of vertebrates. The highest
species density of amphibians and reptiles
in North America (north of Mexico) occurs
in the upper Apalachicola basin (Means
1977). The abundant and diverse bird
fauna is concentrated in the floodplain
forests. Two species considered extinct,
the ivory-billed woodpecker (Campephilus
rincipalis) and Bachman's sparrow
Aimophila aestivalis), were last sighted
in the Apalachicola system. These species
are part of a growing list of approxi-
mately fifty soecies of amphibians,
reptiles, birds, and mammals that are
considered endangered, threatened, rare,
of special concern, or of undetermined
status.

9. The Apalachicola estuary, with
its barrier islands, represents a major
flvway for gulf migratory bird species.
The estuary has the highest density of
nesting ospreys (Pandion haliaetus) along
the northeast Florida gulf coast (Eichholz
1980).

10. The Apalachicola Ray system is
one of the richest and least polluted such
areas in the United States. The estuary
now provides over 90% of Florida's oysters
and is part of a major spawning ground for
blue crabs along the Florida gulf coast
(Livingston and Joyce 1977). The bay
serves as an important nursery for penaeid
shrimp and finfishes and is characterized
by some of the highest densities of
infaunal invertebrates of any comparable
area in the United States.
11. The highly profitable
Aoalachicola oyster industry and various
sport and commercial fisheries directly
and indirectly provide the economic and
cultural basis for a high proportion of
the people in the region (Livinaston
1983c).

















CHAPTER 3
PRIMARY PRODUCTIVITY AND NUTRIENT CYCLING


Most aquatic systems such as rivers
and estuaries depend on sources of organic
matter outside the system (i.e.,
allochthonous: dissolved and particulate
organic matter from associated wetlands)
and within the system (i.e., autoch-
thonous: phytoplankton, benthic plants).
Inorganic nutrients (phosphorus, nitrogen)
and organic matter (dissolved, particu-
late) are swept into aquatic systems by
rainfall, overland runoff, and river
flooding. The extremely complex chemical
processes involved in the transformation
of nutrients into plant and animal biomass
are not well understood and are intri-
cately related to microbiological
activity. One important generalization
based on the long-term field studies is
that the Apalachicola estuary is
inextricably linked to the river in terms
of freshwater input and the movement of
dissolved and particulate organic material
into the estuary. River input is sea-
sonally and annually pulsed, and such
influx of materials has an important
influence on allochthonous and
autochthonous sources of organic matter
throughout the Apalachicola estuary.

Nutrient fluxes and primary
productivity of the river-estuary system
have been studied for over a decade; the
following is a review of the available
information concerning the Apalachicola
system.

3.1. PRIMARY PRODUCERS

3.1.1. Allochthor.ous Sources

a. Freshwater wetlands. The
production and decomposition of organic
matter in the floodplain wetlands
represents one facet of estuarine
productivity (Livingston 1981a; Livingston


et al. 1977; Elder and Cairns 1982; Elder
and Mattraw 1982; Mattraw and Elder 1980,
1982). Over time, the Apalachicola River
has meandered in broad curves through the
flood plain. Erosional and depositional
processes have led to the development of
shoals, backswamps, channels, sloughs,
levees, and oxbow lakes. The dynamics of
the Apalachicola River affect the
transport of dissolved and particulate
substances into receiving aquatic areas.
However, such transport of allochthonous
substances depends on complex interactions
of river flooding with factors such as
wetland productivity, decomposition
processes, the timing and relative heights
of the flood stage, the heights of
surrounding lands, soil types, and
drainage characteristics of the flood
plain. The unifying characteristics of
the wetland inputs are the distribution
and environmental functions of the
bottomland hardwood forests of the
Apalachicola floodplain (Figure 21).




EVAPO-TRANSPIRATION
RAIN--DISCHARGE
STAGE FLOODPLAIN
ELEVATIOSAN I POSITION ATMOSPHERE
SOILSj 1) KEAF i l
PRODUCTION
TREE NUTRIENTS
DISTRIBUTION DETRITUS

RIVER- TRANSPORTr--
RIVER-0
BAY
Figure 21. Nutrient/detritus transport
mechanisms and long-term fluctuations in
detrital yield to the Apalachicola River
flow (modified from Mattraw and Elder 1980
and Livingston unpubl.).









General plant distribution in the
riverine wetlands is associated with
topographic features of the flood plain
and surrounding forested lowlands (Clewell
1978). H. M. Leitman et al. (1982) showed
that the height of natural riverbank
levees and the size and distribution of
levee breaks control floodplain hydroloqic
conditions. Vegetative composition is
highly correlated with depth of water,
duration of inundation and saturation, and
water level. Leitman (1978, 1983) and
Leitman and Sohm (1981) described in
detail the distribution of floodplain
trees in the Apalachicola drainage.
According to these studies, pine flatwoods
and loblolly pine-sweetgum associations
are often found on elevated slopes while
more mesic hardwoods inhabit the levees.
River banks are occupied by willows and
birches. Terraces or basin depressions
are inhabited by hardwood swamp species.
Cypress-tupelo associations are often
located in sloughs. Backswamps are
characterized by blackgum and sweetbay
associations.

The bottomland hardwood community of
the Apalachicola floodplain produces large
amounts of potentially exportable material
(Elder and Cairns 1982). The weighted
mean of litterfall was 800 grams m-2 with
overall annual deposition within the 454
km2 bottomland hardwood flood plain of
360,000 metric tons (mt) (396,720 tons) of
organic matter. These production levels
are similar to those observed in equa-
torial forests but are higher than those
noted in cool temperate forests and most
warm-temperate forests. Levee vegetation
produced more litterfall per ground
surface area than did the swamp
vegetation. The seasonal distribution of
litterfall was characterized by a sharp
late autumn peak. The three most abundant
flood plain tree species (tupelo, cypress
and ash) accounted for over 50% of the
total leaf-fall, even though these species
were the least productive of those
analyzed on the basis of mass-per-stem
biomass.

Annual flooding is a major factor for
mobilization of substances out of the
flood plain. Flooding leads to immersion
of litter material, enhanced decomposition
rates, and transfer of the breakdown,
products (nutrients and detritus) to


associated aquatic systems (Cairns 1981,
Elder and Cairns 1982). The river is thus
closely associated with the rich
productivity of the Apalachicola wetlands
and is the primary agent for movement of
organic matter out of the floodplain. In
this way, the forested Apalachicola River
flood plain is an important source of
organic carbon for the estuary. Spring
floods during March and April of 1980
deposited 35,000 mt (38,570 tons) of
detritus derived from litterfall into the
Apalachicola estuary (Mattraw and Elder
1982). During one year of observation,
total organic carbon deposits in the bay
amounted to 214,000 mt (235,830 tons).
Total nitrogen and total phosphorus inputs
to the river during the same period were
21,400 (23,593) and 1,650 mt (1,818 tons),
respectively (Mattraw and Elder 1982).
The annual detrital organic carbon input
was 30,000 metric tons (Mattraw and Elder
1982). Mattraw and Elder (1982) estimated
that an 86-day period of winter and spring
flooding accounted for 53, 60, 48, and 56
percent of the annual total organic
carbon, particulate organic carbon, total
nitrogen, and total phosphorus transport,
respectively. Flood characteristics are
important determinants of the amounts and
forms of transported materials. While
there was an annual net export of
nutrients to the estuary, it is likely
that the wetland system acted as a
nutrient sink during certain periods of
the year. Although nutrients are released
to the river by flood-plain vegetation,
such compounds are subject to active
recycling within the receiving aquatic
systems.

The considerable export of
particulate matter from the flood plain is
consistent with previous findings.
Livingston (1981a) and Livingston et al.
(1976a) found a direct relationship
between river flooding and the appearance
of micro- and macroparticulate matter in
the estuary. Results of long-term studies
of the significance of river-derived
particulate organic matter to the estuary
(Livingston 1981a, b) indicate that the
exact timing of the peak river flows and
the seasonal changes in the productivity
of wetlands vegetation are key
determinants of short-term fluctuations
and long-term trends of the input of
allochthonous organic matter Into the









Apalachicola estuary (Figure 21). A
linear regression of microdetritus and
river flow by season (Table 5; Figure 22)
showed seasonal differences in the
relationship of detrital concentration and
river flow (Livingston 1981a). During
summer periods, there was no direct
correlation of river flow and detritus in
the estuary. By the fall, there was still
no significant relationship although there
were occasional influxes of detritus with
minor peaks in the river flow. By winter,
however, a strong direct relationship was
apparent between microdetrital loading and


Table 5. Linear regression (log/log) of tot
river flow (m3 sec-i) by month/year by seas
located at the mouth of the Apalachicol
(1981a). r = Pearson correlation coefficient


river-flow peaks. The winter regression
differed from that of the spring detrital
loading, which, though significantly
associated with river-flow levels,
required higher river levels for
comparable concentrations and loading of
detritus. This analysis indicates that
the degree and timing of river flooding on
a seasonal basis affects the level of
detrital loading to the estuary.

There are various additional sources
of allochthonous nutrients and detritus
for the Apalachicola River and estuary


al microdetritus (ash-free dry weight) and
on (August 1975-April 1980), at station 7,
a River. Data are taken from Livingston


Station/month r r2 (Significance of r)


Station 7 (Surface)

June-August

September-November

December-February

March-May


Station 7 (Mid-depth)

June-August

September-November

December-February

March-May


Station 7 (Bottom)

June-August

September-November

December-February

March-May


0.39863

0.03469

0.00188

0.00057




0.11809

0.25542

0.00570

0.00397



0.40243

0.22867

0.00037

0.02253









* JUNE-AUG. 0 DEC.-FEB
SSEPT-NOV, MAR-MAY


o
S , *


o I
o .
. .I *
.-" l o


2.5 3.0
*Ash free dry weight log river flow (cfs)

Figure 22. Regression analysis of the
relationship of microdetritus to
Apalachicola River flow by season (totals
taken from station 7, surface) (after
Livingston 1981a).

systems (Mattraw and Elder 1982). These
include headwater inflow, tributary and
ground-water inflow, upland productivity,
atmospheric fallout, and productivity
within the aquatic system itself. The
hydrological characteristics of the river
system influence both the type of detritus
produced and the quantity transported,
since the wetland distribution is
determined by patterns of flooding, and
the same flooding provides an energy input
as a transport medium. The Jim Woodruff
Dam removes practically all the
particulate matter from the Flint and
Chattahoochee drainages (Mattraw and Elder
1982), so the Chipola-Apalachicola wetland
area is the primary contributor of organic
detritus to the bay system.

b. Coastal marshes. The primary
nonforested area in the bay system
consists of freshwater and brackish
marshes in the Apalachicola delta just
above East Bay (Figure 19). In parts of
East Bay, marshes are dominated by
bullrushes (Scirpus spp.), cattails (Typha
domingensis), and other freshwater species
such as sawgrass (Cladium iamaicense).
Brackish-water species such as cordqrass
and needle rush are also found. The


northeast section of St. Vincent Island
has a well-developed brackish-water marsh.

Kruczynski (1978) and Kruczynski et
al. (1978a, b) have analyzed the primary
production of tidal marshes dominated by
Juncus roemerianus in the St. Marks
National Wildlife Refuge just east of the
Apalachicola estuary. The authors
considered such marshes representative of
undeveloped wetlands in northwest Florida.
Aboveground production was measured in
each of three zones based on soil
characteristics, elevation, and species
assemblages. The high marsh areas were
located approximately 600 m (1,969 ft)
inland; middle marsh areas were located
approximately 240-360 m (787-1,181 ft)
from the bay; and low marsh areas were
placed 0-120 m (0-394 ft) from the bay.
Based on carbon-14 methods, the authors
found that total aboveground production of
a north Florida Juncus marsh is 8.5 t C
ha-1 yr-1 (3.8 tons/acre/yr) (low marsh),
5.7 t C ha-1 yr-1 (2.5 tons/acre/yr)
(upper marsh), and 1.8 t C ha-1 yr-1 (0.8
tons/acre/yr) (high marsh). Using average
figures weighted by area for an
extrapolated estimate of marsh
productivity in the Apalachicola marshes
(Table 1), there is an estimated net
production of 37,714 t yr-1 (41,561
t/yr-I) in the Apalachicola estuary (East
Bay, Apalachicola Bay, St. Vincent Sound)
and 46,905 t yr-I (51,689 tons/year) in
the entire bay system.

A comparison of these figures with
those from other areas (Table 6) indicates
that production of Juncus and Spartina
systems along the northeast Gulf coast is
comparable to that in other marsh areas.
According to Kruczynski et al. (1978b),
Spartina decomposes faster than Juncus, so
nutrients from the former may be more
readily available to associated estuarine
systems.

3.1.2. Autochthonous Sources

a. Phytoplankton. Phytoplankton are
ubiquitous in rivers, estuaries, and
coastal systems. The phytoplankton
community represents an important part of
aquatic ecosystems both from the
standpoint of primary production and as a
key element in food webs. Diatoms are
dominant in the net phytoplankton taken in









the Apalachicola estuary throughout the
year (Table 7) (Estabrook 1973). In East
Bay, Melosira granulata is the dominant
species; Chaetoceros lorenzianus is
dominant in Apalachicola Bay. Species
such as Chaetoceros lorenzianus,
Bacteriastrum delicatulum, and
Thalassiothrix frauenfeldii are


predominant in the spring, while
Skeletonema costatum, Rhizosolenia alata
and Coscinodiscus radiatus prevail during
fall and winter months. Although the
phytoplankton standing crop is quite low
at any given time, phytoplankton
productivity is often quite high in areas
such as the Apalachicola Bay system.


Table 6. Net above-ground primary production of marsh plants
(Kruczynski et al. 1978b).


in various salt marshes


Marsh plant and Net primary productivity g/m2/yr
location LM UM HM Authors


Spartina alterniflora
FL
NJ
DE
NY
GA
New England
GA
MD
NC
NC
LA
GA
LA
VA
DE
NC
VA
GA
GA


Juncus roemerianus
FL+
MS
NC
NC
NC
NC
NC
NC
MS


700


827
985
800-1300
1158
1207
1296
1300
1410
2000
2960








949
_--_


335


508

200-300


329
610
1005

1484
500







595


130
300
445










445
550
1332
2883
3000



243
390
560
754
796
849
895
870-1900
2106


Kruczynski et al. 1978a
Good 1965
Morgan 1961
Udell et al. 1969
Smalley 1959
Shea et al. 1975
Teal 1962
Johnson 1970
Stroud & Cooper 1968
Marshall 1970
Day et al. 1973
Schelske & Odum 1961
Kirby 1971
Keefe & Boynton 1973
Morgan 1961
Williams & Murdoch 1972
Wass & Wright 1969
Odum & Fanning 1973
Odum 1971



Kruczynski et al. 1978a
Gabriel & de la Cruz 197,
Foster 1968
Williams & Murdoch 1972
Stroud & Cooper 1968
Heald 1969
Waits 1967
Kuenzler & Marshall 1973
Willingham et al. 1975


LM = low marsh.
UM = upper marsh.
HM = high marsh.
+ = estimate by change in biomass method.










Table 7. Presence/absence information for net phytoplankton
Apalachicola estuary by month from October 1972 through September
1973). x = presence.

1 = 10/14/72 3 = 01/06/73 5 = 04/22/73 7 = 06/11/73
2 = 12/02/72 4 = 03/19/73 6 = 05/19/73 8 = 07/12/73


taken from the
1973 (Estabrook


9 = 08/22/73
10 = 09/10/73


Phytoplankter 1 2 3 4 5 6 7 8 9 10


PHYLUM CHRYSOPHYTA


Melosira sulcata
Melosira ranulata
Melosira nummuloides
Melosira dubia
Melosira varians
Skeletonema costatum
Coscinodiscus radiatus
Coscinodiscus spp.
Coscinodiscus apiculatus
Coscinodiscus wailessi
Coscinodiscus excentricus
Coscinodiscus marginatus
Coscinodiscus centralis
Coscinodiscus oculus iridis
Coscinodiscus nitidus
Coscinodiscus concinnus
Actinocyclus chrenbergii
Actinocyclus undulatus
Biddulphia sinensis
Biddulphia rhombus
Biddulphia aurita
Biddulphia alternans
Biddulphia longicruris
Eupodiscus radiatus
Bellarochia maleus
Triceratium favus
Triceratium reticulum
Hemiaulus hauckii
Chaetoceros spp.
Chaetoceros lorenzianum
Chaetoceros decipiens
Chaetoceros didymus
Chaetoceros curvisetus
Chaetoceros coarctatus
Chaetoceros bravis
Chaetoceros affinis
Chaetoceros compressus
Chaetoceros peruvianum
Chaetoceros glandazii
Chaetoceros pelaqicus
Chaetoceros danicum
Chaetoceros constrictum
Bacteriastrum delicatulum


x x
x x
x
x

x x

x x
x
x
x
x
S


X X x


x x x x
x x
x


x x


x


x
x
x
x

x
S



X


x x x


x
x x
x x


x x
x


x x
x
x
x
x
X


X


x x
x
x
S
X


x X X

(continued)

33


x
x x x x
x x
x
x x
x
x


x
x x x x x x


x
x x x x
x x x x
S Sx
x x x


x x x x x
x x


x x x x
x
x x
xS S


x x
x
x x x x x x x










Table 7. (Continued.)


Phytoplankter 1 2 3 4 5 6 7 8 9 10


Bacteriastrum elongatum
Rhizosolenia alata
Rhizosolenia imbricata
Rhizosolenia setigera
Rhizosolenia bergonii
Rhizosolenia spp.
Rhizosolenia robusta
Rhizosolenia stotterfothii
Rhizosolenia calcar-avis
Rhizosolenia hebetata
Guirardia flaccida
Asterionela formosa
Thalassiothrix frauenfeldii
Thalassiothrix mediterranea
Thalassiothrix longissima
Thalassiothrix nitzschioides
Licmophora abbreviata
Rhabdonema adriaticum
Pleurosigma spp.
Gyrosigma spp.
Amphiprora paludosa
Navicula lyra
Navicula spp.
Lithodesmium undulatum
Fragilaria spp.
Diatoma spp.
Nitzschia pungens
Nitzschia spp.
Nitzschia sigmoidea
Nitzschia closterium
Nitzschia paradox
Grammatophora marina
Cymbella tumida
Cymatosira belgica
Pinnularia spp.
Synedra spp.
Surirella fastuosa
Cocooneis disculoides
Schroederella delicatula
Eucampia cornuta

PHYLUM PYRROPHYTA

Ceratium furca
Ceratium tripos
Ceratium massiliense
Ceratum fuses
Ceratium concilians
Ceratium trichoceros
Peridi-mium spp.
Peridimium grande(?)


x


x x x
x x
x x
x


x
x x
x


x
x
x

x x x
x
x x x x x
x x x x
x
x x x x x

x
x


x
X X X
x x
x x
x

x
a


x x
x
x
a
a


x x
x x
x x

x


x


x

x
x x
x
x x
x x

x x
x


x
x x
x


x
x x x x x x

x
x x x x x
x
a a a a a X
X X a


x x x x
x x x x x x x
x x x x x
x x x x
x

x x
x
(continued)


x x x
x x
x
x x
x x x

x
x x

x x


x x
x


X X X




x
x x








Table 7. (Concluded.)

Phytoplankter 1 2 3 4 5 6 7 8 9 10

Dinophysis caudata x x
Dinophysis diagenesis(?)
Dinophysls tros x

PHYLUM CHLOROPHYTA

Pediastrum simplex x x
Pediastrum duplex x x
Pediastrum tetras var. tetraodon x
Scenedesmus quadricauda x


Studies by R. L. Iverson and his
students indicate that phytoplankton
productivity is an important source of
organic matter in the Apalachicola
estuary. In general, phytoplankton growth
depends on temperature, light, and
available nutrients (nitrogen, phosphorus)
(Figure 23). Temperature is the primary
limiting factor for phytoplankton
productivity in the estuary during the
winter months. Nutrient concentrations
and possibly predation pressure control
phytoplankton production from late spring
to the fall. The usually low levels of
phytoplankton productivity during the
winter give way to peaks in April.
Secondary peaks are noted during summer
and fall months.

The average C14 phytoplankton
productivity (Figure 23) ranged from 63 to
1,694 mg C m- day-1 (Estabrook 1973;
Livingston et al. 1974). The relationship
of phytoplankton productivity and
predation pressure from zooplankton has
not been determined. However, since river
discharge is strongly associated with
nutrient concentrations in the estuary
(Livingston et al. 1974), such factors as
river flow and nutrients, together with
the general ecological conditions in the
estuary, combine to control the phyto-
olankton productivity of the bay system.

Despite considerable spatial and
temporal variability of phytoplankton
productivity, Eastabrook (1973) estimated
an annual productivity value of 371 g C


m-2 for the Apalachicola estuary. This
figure was taken from averaged data (five
bay stations) sampled monthly over a
12-month period. Based on these figures,
the phytoplankton productivity from the
bay system approximates 233,284 t C yr-1
(257,079 tons C yr-1); for the immediate
estuary (East Bay, Apalachicola Bay), this
figure is 103,080 t C yr-1 (113,594 tons C
yr-1). When compared to production values
in other estuaries of the region (Table
8), the phytoplankton productivity and
chlorophyll a levels in the Apalachicola
estuary are relatively high.

b. Submerged vegetation. The
relatively high levels of color,
turbidity, and sedimentation tend to limit
submerged macrophytes to the shallowest
portions of the Apalachicola estuary
(Livinqston 1980c, 1I83c). Species
composition and distribution of seagrass
beds are given by Livingston (1980c,
1983c). A major concentration of
seagrasses occurs in eastern St. George
Sound, which remains outside of the
influence of river drainage (Table 1,
Figure 19). Such areas are dominated by
turtle grass (Thalassia testudinum), shoal
grass (Halodule wrighti, and manatee
grass (Syrinqodium filiforme). Seagrass
beds are also located in upper portions of
East Bay. Such assemblages are dominated
by tape weed (Vallisneria americana),
widgeon grass (Ruppia maritima), and sago
pondweed (Potamogeton sp.). Since the
early 1980's Eurasian watermilfoil
(Myriophyllum spicatum) has taken over










2000



1000


ONDJ FMAMJ JAS
Month

Figure 23. Average seasonal variation in
daily phytoplankton productivity for the
Apalachicola estuary (taken from Estabrook
1973; Livingston et al. 1974).




various bayous along the northeastern
margin of the bay (Livingston, unpublished
data). There is little or no submerged
vegetation in St. Vincent Sound. Seagrass
beds in Apalachicola Bay and western St.
George Sound are restricted to shallow
lagoonal portions of Dog Island and St.
George Island and are dominated by
Halodule wrightii, Gracilaria spp., and
Syringodium filiforme. Thus the
distribution of submerged vegetation
generally reflects previously described
depth characteristics, water-quality
features, drainage and current patterns,
and salinity distribution.

Seagrass beds undergo regular sea-
sonal cycles of productivity and standing
crop. The ecology of the East Bay
Vallisneria beds has been well studied
(Livingston and Duncan 1979; Purcell 1977;
Sheridan 1978, 1979; Sheridan and
Livinqston 1979, 1983). Net annual
production of Vallisneria varies from 320
g C m-2 yr-1 to 350 g C m-2 yr-1. This
species undergoes sharp reductions of
standing crop biomass during winter
months. After a period of rapid spring
growth, maximum leaf development is
maintained from May through July. By
August, considerable degeneration of the
plant standing crop occurs and is followed
by new growth during September and


October. Similar cycles of growth occur
in the Thalassia-dominated qrassheds in
areas of higher salinity (Bittaker 1975;
Livingston 1982a; Zimmerman and Livinqston
1976a, b, 1979). Net annual production
has been estimated to be 500 g C
m-2 yr-1 (Iverson unpublished data).
Rapid growth occurs during scoring and
early summer. Standing crop biomass
usually peaks during summer months with
rapid degeneration as water temperature
falls (November, December). during winter
months, productivity and standing crop are
relatively low in the various types of
seagrass beds in shallow coastal areas of
the northeast Gulf coast of Florida.

Based on the productivity figures and
the seagrass distribution (Table 1), the
grassbeds in the East Bay-Apalachicola Bay
area produce 8,Q53 t C yr-1 (9,866 tons C
yr-1). Grassbed production in the
remaining portions of the Apalachicola Bay
system approximates 18,260 t C yr-1
(20,122 tons C vr-1). Total production
for the entire system is 27,213 t C y-1
(29,989 C y-1).

3.2. DETRITUS FLUX AND NUTRIENT DYNAMICS

Availability of organic matter does
not explain the processes involved in
transformation of energy as it moves
through the complex food webs of the
river-estuary system. Since relatively
few organisms feed directly on living
macrophytes, the degradation processes,
which include mechanical fragmentation,
chemical leaching, autolysis, hydrolysis,
oxidation, and microbial activity, are
important in the dynamic transfer of
estuarine nutrients from available organic
matter. Input to the immediate estuary
and the bay system as a whole is
seasonally timed to specific
meteorological factors (Table Q). Most of
the river input occurs during winter and
spring periods, while major phytoplankton
blooms take place in the spring and fall.
Input of organic matter from the seagrass
beds occurs during the summer and fall.
The transfer of organic materials from the
coastal marshes is not as well understood
as that of the other sources. In general,
the contribution of plant detritus to the
nutrient dynamics of the estuary is ex-
tremely complex in terms of timing and









Table 8. Physical, chemical, and productivity data taken from locations along the
northwest gulf coast of Florida (from R. L. Iverson and his students, unpublished data,
Myers 1977). Standard deviations () are also given.

Station Temp. Salin. Turb. Liqht N10 N02 PO0 Pri. prod. Chl-a
oC 0/oo JTU ly hr-1 q atm 1-1 mo C m-1 hr-1 mq m-3

Econfina 28.4 26.2 3.15 26.5 0.32 0.01 0.04 6.00 0.51
estuary (1.01) (2.48) (0.35) (5.60) (0.14) (0.03) (0.01) (1.951 (0.17)
F.S.U. Marine 27.8 20.7 3.15 37.8 0.55 0.02 0.19 9..0 0.5?
Laboratory (1.78) (3.53) (0.49) (3.73) (0.10) (0.02) (0.04) (0.58) (0.21)
Ochlockonee 28.2 4.20 4.97 37.q 1.q3 0.05 0.37 30.8 2.14
River estuary (1) (0.90) (1.06) (0.78) (7.22) (0.37) (0.01) (0.07) (?.57) (0.41)
Ochlockonee 28.7 10.3 4.93 37.Q 2.24 0.17 0.36 26.4 3.00
River estuary (2) (0.80) (0.70) (0.61) (7.22) (0.83) (0.05) (1.09) (4.74) (1.51)
Apalachicola 27.5 3.74 16.5 33.9 1.08 0.15 0.3a 40.9 5.13
estuary (5) (1.19) (2.58) (3.06) (q.17) (2.63) (0.16) (3.08) (10.7) (1.12)
Apalachicola 77.5 11.7 11.7 36.9 3.55 0.21 0.40 36.7 4.11
estuary (2) (1.34) (3.26) (6.88) (3.50) (3.69) (0.16) (0.00) (5.81) (0.84)


Heald 1972; Odum et


Among the major litter producers of
the Apalachicola flood plain, Cairns
(1981) and Elder and Cairns (1082) found
decomposition rates of floodplain leaf
matter to be species-specific. Tupelo
(Nyssa spp.) and sweetgum (Liquidambar
styraciflua) leaves decomposed completely
in 6 months. Leaves of baldcypress
(Taxodium distichum) and diamond-leaf oak
(Quercus laurifolia) were more resistant.
Water hickory Cara auatica) had
intermediate decomposition rates. Rates
of carbon and biomass loss were linear
over a 6-month period, but phosphorus and
nitrogen leaching was nearly complete
within a month. Periods of river flooding
were particularly important for
mobilization of the litterfall into the
aquatic system. Flooding immerses litter
material, increases decomposition rates,
and provides a transport medium. Because
of the high diversity of floodplain tree
species, the autumn peak of leaf fall is
relatively prolonged (September-December)
(Figure 24). Compared to the ACF system
as a whole, the Apalachicola flood plain
is extremely high in nutrient yield per
unit "area, especially for carbon and
phosphorus (Table 10). Mattraw and Elder


(1982) postulated that the upper
ChattahoocheeFlint watersheds yielded
fewer nutrients because the 16 reservoirs
act as nutrient retention ponds. Although
headwater inflow provides substantial
loads of dissolved nutrients to the
estuary, particulate matter delivered from
the river is derived almost exclusively
from the Apalachicola/Chipola wetlands.
Approximately 16% of the organic carbon
delivered to the estuary is derived from
less than 1% of the ACF basin (Mattraw and
Elder 1982).

Particulate organic matter is
transferred from the river to the estuary
primarily during winter/spring floods,
although there is no direct correlation
between microdetritus in the estuary and
river flow by season (Table 5).
Microdetritus flow is generally low during
summer and fall periods and highest during
the first river floods of winter (Figure
22). In the estuary, surface dissolved
nitrogen and phosphorus concentrations
peak during periods of high river flow
(Estabrook 1973; Livingston et al. 1974,
1976a; Table 11). Thus, the degree and
timing of river flooding on a seasonal
basis determines the form and level of
nutrient fluxes into the estuary from the
river wetlands.


processing (Odum and
al. 1979).








Table 9. Total annual net productivity and net input to the Apalachicola estuary (East
Bay, Apalachicola Bay, St. Vincent Sound) and the Apalachicola Bay system (Aoalachicola
estuary, St. George Sound, Alligator Harbor). Productivity includes (metric tons)
organic carbon produced by the Apalachicola River wetlands, coastal marshes, phyto-
plankton, and seagrass beds.


Apalachicola estuary Apalachicola Bay system

Net in situ Net input Net in situ Net input Season of
Vegetation productivity mt C yr-1 productivity mt C yr-1 maximum input
mt C yr-1 mt -C yr-1

Freshwater 360,000 30,000 360,000 30,000 winter/spring
wetlands

Coastal 37,714 37,714(?) 46,905 46,905(?) late summer,
marshes fall(?)

Phyto- 103,080 103,080 233,284(?) 233,284(?) spring and
plankton fall

Seagrass 8,953 8,953 27,213 27,213 summer-fall
beds


A review of the phytoplankton ecology
of the Apalachicola estuary (Estabrook
1973; Livingston et al. 1974, 1976a; Myers
and Iverson 1977) indicates that Dhyto-
plankton productivity is relatively
restricted to conditions of optimum
temperature and ample (available)
nutrients. Such conditions occur
principally in the spring, summer, and
fall. Multiple regression analysis (Myers
and Iverson 1977) indicated that river
discharge explained 20%-50% of the
variability of chlorophyll a and phyto-
plankton productivity. Nutrients were
positively correlated with river
discharge. Temperature accounted for 26%
to 49% of the variability in phytoplankton
productivity. Water temperature was also
positively correlated with phytoplankton
productivity. Wind speed was positively
correlated with suspended sediments and
phosphate concentrations, increases in
which were followed by increases in ohyto-
plankton productivity. Nutrient
enrichment experiments indicated that
nutrients are limiting only during summer
and fall (Estabrook 1973) and that
phosphate is the primary nutrient that
limits phytoplankton productivity in East
Bay and Apalachicola Bay (Myers and


Iverson 1977), although both nitrates and
phosphates may be limiting in summer
(Livingston et al. 1974).


S N J F M A M J J A
MONTH


Figure 24. Monthly averages of
litterfall on intensive transect
across the Apalachicola wetlands
Elder and Cairns 1982).


daily
plots
(after








Recently, certain revisions have been
proposed of early concepts of detritus
outwelling from coastal marshes (Haines
1979). There is evidence of no net export
of particulate organic matter (POM) from
salt marshes under certain conditions
(Woodwell et al. 1977). Odum et al.
(1979) have hypothesized that net fluxes
of POM from coastal marshes depend on the
geomorphology of the wetland basin, the
magnitude of the tidal range, and upland
freshwater input. In the Apalachicola
estuary, the tidal range is relatively
small. Marsh distribution is limited
largely to the delta area (East Bay) and
lagoonal portions of the barrier islands.
The considerable river runoff and the
associated export of organic matter due to
flooding would amplify the importance of
the East Ray marshes according to the Odum
model (Odum et al. 1979).

The salt marshes of the bay system
contribute only a small fraction of the
particulate organic loading to the bay
system (Livingston et al. 1974), although
such areas are important nurseries for
estuarine fishes and invertebrates


(Livingston 1980c). However, the marshes
may play a role in the export of organic
material to the bay system. Ribelin and
Collier (1979) showed that local marshes
export detrital aggregates or films that
average 25-50 m in thickness and are
produced by benthic algae rather than by
microbial decomposition of the marsh
plants. Tidal action lifts these films of
algae out of the marshes, especially
during late summer ebb flows. Thus, while
the vascular tissue of the marsh grasses
is decomposed beneath a layer of benthic
algae, it is essentially retained within
the marsh proper. Amorphous aggregates of
"nanodetritus" composed of microalgae may
play a more important role in the nutrient
budget of the bay system than previously
thought, especially during late summer and
early fall periods.

The seasonal abundance and spatial
distribution of nutrients and detritus in
the Apalachicola Bay system result from a
combination of forces, some of which are
quite localized and specific in nature.
For example, the timing and magnitude of
localized hydrologic events such as


Table 10. Nutrient yields for various drainage areas in the Apalachicola-
Chattahoochee-Flint River system. Data are presented on an areal basis (adapted from
Mattraw and Elder 1982).


Annual output minus input Areal yield
(metric tons) (g m-2 yr-1)

Area Phos- Phos-
Drainage basin (km2) Carbon Nitrogen phorus Carbon Nitrogen phorus

Apalachicola-
Chattahoochee-
Flint 50,800 213,800 21,480 1,652 4 0.4 0.03

Chattahoochee-
Flint 44,600 142,700 17,860 1.340 3 0.4 0.03

Apalachicola-
Chipola 6,200 71,100 3,620 312 12 0.6 0.05

Apalachicola 3,100 41,500 1,060 237 13 0.3 0.08

Chipola 3,100 29,600 2,560 75 10 0.8 0.02

Apalachicola
flood plain 393 34,300 674 206 87 1.7 0.52








passing thunderstorms, wind effects, and
tidal actions are superimposed over basin
characteristics such as depth and bottom
morphology. These, in turn, may
significantly influence larger-scale
conditions such as temperature, salinity,
and light penetration. The large-scale
seasonal fluctuations of important
climatic features, in combination with the
influence of local habitat distribution
and basin configuration, produce an array
of processes whereby organic matter is
incorporated into the estuarine food webs.

The seasonal cycle of nutrient-
detritus flux in the Apalachicola estuary
has been well established (Livingston et
al. 1976a; Livingston and Loucks 1978).
During winter and spring periods of high
river flow, dissolved nutrients and


particulate organic matter are washed into
the estuary. The influx is concurrent
with salinity reductions. Peak levels of
leaf matter are present during these
periods. One to two months later, wood
debris and other forms of particulates
appear in the bay system. In the spring,
as river flow diminishes, temperature
increases, and the water becomes clearer,
the spring phytoplankton blooms occur. As
nutrients, principally phosphorus, become
limiting during summer/fall months,
phytoplankton productivity becomes
dependent on wind-mixed transfers of
nutrients from the sediments into the
water column. During the summer and early
fall, local rainfall enhances nutrient
enrichment. At this time, benthic
macrophytes begin to die off. The peak
levels of macrophyte organic debris and


Table 11. Nutrient values (winter and summer) for stations in the Apalachicola estuary
(means + one standard deviation of five stations) and River (Station 2) (Livingston et
al. 1974).


Nutrient values ( g/1)

Nutrient Site 17 February 1973 12 July 1973

NO3 Bay T 179.53 + 13.11 2.25 + 2.84

B 186.79 + 19.48 4.24 1 2.25

River 232.90 219.54


NH4 Bay T 26.13 + 18.53 8.05 + 3.30

B 38.15 30.61 14.261 4.40

River 7.81 7.57


Oq4 Bay T 6.92 + 1.17 4.03 1 .76
B 6.931 1.29 5.78 1.69

River 12.63 9.53


Silicate (Si04) Bay T 2,531.80 57.59 1,939.66 + 413.15

B 2,534.08 + 62.88 1,216.67 1 802.98

River 2,632.55 3,109.12








microaggregates from the marshes occur
during the fall as river flow and rainfall
are minimal. By late fall (November),
temperature drops and salinity
coincidentally increases to an annual
maximum throughout the estuary. By
winter, temperature is low as river flow
once again rises.

Even though the input from various
sources is variable in terms of magnitude
over time, the input of particulate
organic matter to the estuary from all
sources is fairly constant. Thus, there
is a generally continuous influx of
dissolved and particulate organic and
inorganic matter to the estuary throughout
the year; this matter is then subject to
various processes, physical and
biological, which are dependent on
specific spatial-temporal habitat
conditions.

3.3. MICROBIAL ECOLOGY

In the Apalachicola estuary,
approximately 0.005% of the sediment dry
weight is composed of bacterial biomass
(organic carbon) and 0.00% is composed of
extracellular carbohydrates (0. C. White,
Florida State University; pers. comm.).
Usually, these microbes are concentrated
on particulate surfaces as morphologically
diverse prokaryotic and microeukaryotic
assemblages (White 1983). The ecological
importance of microbes to the estuary is
defined by microbial biomass (which forms
the basis of food webs) and microbial
metabolic activity (which contributes to
various bioqeochemical and recycling
processes). White and his coworkers have
quantified the biochemical "signature"
components of specific microbial community
associations. These components include
phospholipids, adenine-containing
components, muramic acid, and hydroxy
fatty acids, which provide biomass
estimates. Community composition has been
evaluated by analysis of phospholipid
alkyl fatty acids prokaryotess
microeukaryotes) and "signature" lipids
(anaerobic-aerobic bacteria). Fatty acids
are an excellent measure of algae, and
other groups of microeukaryotes can be
characterized by the polyenoic fatty acid
composition (Federle et al. 1983).
Nutritional status was analyzed by
measurement of poly-beta-hydroxy alkonates


(PHA), extracellular glycolalyn, and other
microbial byproducts (White 1983). These
methods were used to analyze microbial
activity in the Apalachicola estuary.

A series of experiments have been
carried out to learn the fate of
particulate organic matter deposited in
the estuary as a result of river flooding.
Morrison et al. (1977) demonstrated a
succession of microbiota that colonized
oak leaves deposited in the estuary.
Initially, colonization is by bacteria
with a high ratio of muramic acid to ATP.
These bacteria are succeeded by diatoms
and fungal mycelia that do not contain
muramic acid. Thus, initial bacterial
colonization is succeeded by a community
of fungi and microeukaryotes. Bobbie et
al. (1978) found that microbial
communities on biodegradable substrates
such as leaf matter are biochemically and
morphologically more diverse than those on
biologically inert substrates. A 10-fold
increase in biomass on the biological sub-
strates was also noted. Grazing amphipods
removed microbiota without affecting the
morphology of oak leaves (Morrison and
White 1980). The colonization of mixed
hardwood leaves from the Apalachicola
flood plain in the estuary varied more as
a function of leaf surface than of
location (White et al. 1977, 1979a, h).
However, macroorganisms were attracted to
the litter baskets as a function of
location rather than microbial biomass
(Livingston unpublished data).

The activities of microbes are
inextricably linked with organisms at
higher levels of the estuarine food web
(Figure 25). Amphipod distribution was
significantly correlated with concentra-
tions of certain bacterial fatty acids
(White et al. 1979a, b). Amphipods
grazing at natural densities induced
increases in microbial biomass, oxygen
utilization, PHB synthesis, lipid syn-
thesis, and 14C02 release from simple sub-
stances by microbes (Morrison and White
1980). These changes caused grazing
shifts in community structure from diatom-
fungal-bacterial associations to
bacterially dominated ones. Within
limits, grazing thus stimulates microbial
growth and alters the microbial community.
Indications are that organisms graze on
detrital and sedimentary microbiota and









substantially affect the microbial
associations. Studies of microbes in the
absence of their predators are not
sufficient if comparisons with natural
functions are intended (White 1983).

Recent studies indicate that
estuarine microbial associations in
polyhaline areas of the bay are actually
controlled by epibenthic predators
(Federle et al. 1983). Replicate areas (4
m2) of mud-flat sediment were caged in the
field to confine and exclude predators.
Uncaged areas were used as controls. The
microbiota of the sediments was
characterized at weeks 0, 2, and 6 by
measurement of the concentrations of
phospholipid and analysis of the fatty
acids of the microbial lipids extracted
from the sediments. The data were
analyzed using an analysis of variance and
step-wise discriminant analysis. After 2
weeks, the microbiota of the predator-
exclusion area was significantly different
from that in the control and predator
inclusion areas. After 6 weeks, these
differences became more pronounced. There
were no demonstrable caging effects that
could account for the treatment
differences. The results indicated that
removal of predators had a profound effect
on the microbial communities in estuarine
sediments. Thus, we see that the
intermediate trophic levels (epibenthic
predators) of the estuarine food webs are
part of the control mechanism that defines
the structure and level of productivity of
the microbial communities.

Sediments and particulate matter
deposited in the estuary form a substrate
for microbial productivity, which is
stimulated by dissolved nutrients in
various forms (Fiqure 25). The
transformation of dissolved substances
into living particulate matter produces
the food of important groups of grazing
organisms, which, in turn, represent the
base of the detrital food webs in the
estuary. Grazing and other physical
disturbances enhance microbial
productivity and alter the qualitative
composition and succession of the
microbial community. The periodic input
of particulate organic matter and


RIVER FLOW
RUNOFF LOW SALINITY
DISSOLVED NUTRIENTS
% Wf; DETRITUS u

PRIMARY strte
PRODUCTION
MICROBIAL
o .SUCCESSION
GRAZING
ORGANISMS

INCREASED MICROBIAL
BIOMASS



TIDAL SUBSIDY ncre II
WIND PHB/LIPIDS
DISTURBANCE 14CO, RELEASE
02 UTILIZATION





BASE, DETRITAL FOOD WEBS

Figure 25. Tentative model of microbial
interactions with various physical and
biological processes in the Apalachicola
River estuary (Livingston 1983c).


dissolved nutrients into a shallow bay
ecosystem characterized by gradients of
salinity is seen to provide the appro-
priate components for a highly productive
system. Tidal and wind-induced currents,
periodic flooding, and predation all
provide a series of disturbances that,
together with the periodic enrichment of
the system from upland runoff, increase
microbial productivity. River flow and
fresh water runoff from associated
wetlands, together with the shallowness of
the system and tidal/wind energy
subsidies, all contribute to the observed
high productivity of the estuary.
Considering their immense biomass and
their role as processors of nutrients into
biologically active material, the microbes
are an important component in the energy
transformations within the system.

















CHAPTER 4
SECONDARY PRODUCERS


4.1. ZOOPLANKTON

The diverse zooplankton represent an
important link between the phytoplankton
and higher levels of the estuarine food
webs. Almost every major group of
organisms is represented in the
zooplankton, either as larvae or as
adults; great variety is also evident in
the relatively extensive size range of
individuals. Zooplankton have marked
differences in swimming ability and are
often dispersed in patchy, somewhat
irregular spatial distributions.
Zooplankton repackage organic matter
produced by phytoplankton into larger
particles, thereby concentrating energy
into forms more useful to higher
predators. At the same time, they excrete
nutrients that may again contribute to
phytoplankton productivity.

Zooplankton (Table 12) are among the
least known assemblages in the
Apalachicola estuary. While the
dimensions and interrelationships of the
zooplankton community are relatively
poorly understood in the Apalachicola
estuary, certain factors such as
temperature, salinity, wind, nutrients,
primary (phytoplankton) productivity, and
predator-prey relationships are known to
contribute to processes involving this
group of organisms. Net zooplankton are
composed largely of holoplankton (plankton
for entire life cycle; about 90%), while
meroplankton (temporary plankton)
constitute less than 10% of the total
(Table 12; Edmisten 1979). The
holoplankton are composed mainly of
copepods, cladocerans, larvaceans, and
chaetognaths. Copepods, notably Acartia
tonsa, are dominant throughout the
estuary. Apalachicola Bay supports higher
numbers of cooepods than any other portion


of the estuary (Figure 26). Overall
seasonal peaks of copepods in Apalachicola
Bay are noted from March to August with
minimum densities in January and February.
Optimal salinities for the dominant
species, Acartia tonsa, range from 16 to
22 ppt. East Bay, characterized by low
but variable salinity, has the highest
variability in zooplankton numbers over
time. Coastal waters have been most
stable in terms of seasonal changes in
zooplankton abundance. Apalachicola Bay
also has the highest species richness of
the three areas studied. Cladocerans and
chaetognaths are located primarily in
coastal waters. Decapod larvae throughout
the estuary are primarily crab zoeae;
other zooplankton include polychaete
larvae, ostracods, amphipods, isopods,
mysids, echinoderms, ctenophores, and
coelenterates.

The zooplankton mean standing crop
(dry weight) in East Bay approximates 4.0
mq m-3 annually; in Apalachicola Bay, 32.1
mg m-3 yr-1; in coastal areas, 16.7 mq
m-3 yr-1. Peak dry-weight biomass occurs
in May throughout most of the study area
with secondary increases during July and
August (Figure 26). Zooplankton
distribution is influenced by changes of
temperature and salinity through time
(Table 13). Edmisten (1979), using
analysis of covariance with temperature
and salinity as covariates for factors
such as Acartia numbers, percent abundance
(of Acartiaa, total zooplankton numbers,
zooplankton biomass, and Shannon
diversity, found significant station and
month differences in all cases (p < 0.02).
Temperature significantly influenced
numbers of Acartia, total zooplankton
numbers (p < 0.01, and biomass. Salinity
significantly affected zooplankton
numbers, biomass, and diversity (p < 0.01)









Table 12. Distribution of the major zooplankton groups in the Apalachicola estuaryand
associated coastal areas (after Edmisten, 1979). Average values are given from 1973
through 1974. The symbol (+) means 1/m3 or less than 0.1%.


Average 1973-1974 values

East Bay Apalachicola Bay Coastal
(1 station) (6 stations) (1 station)
Zooplankton groups No./m3 % No./m3 % No./m3 %


Copepods

Acartia tonsa

Paracalanus
crossirostris

Paracalanus parvus

Temora turbinata

Oithona nana

Oirhona colcarva

Pseudodiaptomus
coronatus

Centropagestus

Centropagestus hamatus

Euterpina actifrons

Corycaeus americanus

Carycaeus amazonicus

Labidocera aestiva

Other copepods

Cirripedia larvae

Decapod larvae

Cladocerans

Molluscan larvae

Larvaceans


1696 94.1

1666 92.5


6522 80.2

5546 68.2


2286 71.4

635 19.8


(continued)









Table 12. (Concluded.)


Average 1973-74 values

East Bay Apalachicola Bay Coastal
(1 station) (6 stations) (1 station
Zooplankton groups No./m3 % No./m3 % No./m %


Chaetognaths 0 0.0 27 0.3 52 1.6

Polychaete larvae 1 + 92 1.1 10 0.3

Fish eggs & larvae 1 + 92 1.1 10 0.3

Other zooplankton 2 0.1 35 0.4 16 0.5


(Table 13). Although direct correlations
were lacking, there was a strong positive
relationship between salinity and
diversity. Temperature and salinity had
no significant effect (at the 0.05 level)
on the various dependent variables in East
Bay or coastal areas.

The general lack of definitive
statistical relationships between
individual zooplankton indicators or
indices and dominant physical variables
such as temperature and salinity reflects
the considerable diel, seasonal, and
annual variability in the distribution of
zooplankton in the estuary. Other factors
are almost certainly important to such
distribution during various periods of the
year. Peaks of zooplankton biomass tend
to be associated in some way with
phytoplankton peaks, especially in
Apalachicola Bay and coastal areas (Fiqure
26). Predator-prey relationships may play
an important role in zooplankton
distribution and abundance throughout the
year. Such trends are obviously affected
by habitat differences, however. The
relatively small East Bay is characterized
by low salinity and high sedimentation and
turbidity. Salinity changes, derived
largely from river flow and storm-water
runoff, are rapid. Most of the peaks of
zooplankton abundance correspond to
salinity increases in this area. The
copepod Acartia tonsa has a major
influence on abundance curves and
diversity indices in East Ray; it averages
92% of the zooplankton taken throughout
the year.


Coastal areas are physically stable
when compared to the estuary; salinity
varies little throughout the year in the
offshore systems. In such areas,
zooplankton standing crop is generally
higher than that in East Bay. Diversity
tends to increase because Acartia averages

W PHYTOPLANKTON
PEAKS
-- EAST BAY
~ e--0 cOAST
E .-. APALACHICOLA
I BAY
E 80

< | \

0 60 -

0
I-



z 40 -/V
-J







NDJ FMAM JJ ASOND
MONTH
Figure 26. Seasonal distribution of
zooplankton biomass in the Apalachicola
estuary and associated coastal areas
during 1974 (after Edmisten 1979).









Table 13. Pearson correlation coefficients (r) for significant (p < 0.05) zooplankton
relationships in East Bay, Apalachicola Bay, and coastal areas (Edmisten 1979).


Variable East Bay Apalachicola Bay Coastal areas

Temperature vs.
Acartia tonsa -- 0.45
Total zooplankton -- 0.58
Zooplankton biomass -- 0.58 0.46a
Salinity vs.
Acartia tonsa 0.45
% Acartia tonsa -- -0.30
Total zooplankton -- 0.31
Zooplankton biomass 0.50a 0.40
Zooplankton diversity -- 0.51


aSignificant at p < 0.10.


less than 20% of the overall abundance.
The evenness factor is higher in the more
stable marine environment with increased
representation by cladocerans, decapod
larvae, and other copepods (i.e., Temora
turbinata, Paraclinus arvus, P.
crassirostris, Oithona nana) Edmisten
1979). Zooplankton biomass in coastal
waters is correlated with temperature (r =
0.46).

Zooplankton in Apalachicola Bay has
characteristics of both the inshore and
offshore components (Edmisten 1979).
Overall numerical abundance was highest in
Apalachicola Bay (Figure 26). Numbers of
Acartia tonsa and total zooplankton
abundance and biomass follow general
seasonal trends of water temperature.
Salinity affects the spatial distribution
of zooplankton in Apalachicola Bay at any
given time. Salinity increases appear to
be associated with decreased relative
abundance of Acartia tonsa. At low
salinities, lower numbers of Acartia are
taken although this species still comprise
a higher percentage of the overall zoo-
plankton assemblage at such times. Thus,
while temperature influences overall
trends of abundance through time, salinity
is associated with the spatial
distribution and relative abundances of
zooplankton in Apalachicola Bay at any
given time.


4.2. LARVAL FISHES

Planktonic fish larvae, derived from
either demersal or planktonic eggs, are
common among various marine teleost
species. While it is well known that
estuaries have relatively high levels of
phytoplankton productivity and that such
levels are necessary for feeding
aggregations of zooplankton (Mann 1982),
the relationship of such high productivity
to developing stages of marine fishes is
not quite as well known. Lasker (1975)
has shown that larvae of the northern
anchovy (Engraulis mordax) feed on
phytoplankton and that there is a direct
association between feeding activity and
phytoplankton concentration. Thus, there
may be close relationships between the
highly productive inshore waters of the
Gulf and developing stages of various
teleost fishes.


The relatively high numbers of
ichthyoplankton in the Apalachicola
estuary indicate the importance of this
system as a nursery for fishes. The most
abundant planktonic form is the bay
anchovy (Anchoa mitchilli), which accounts
for 92% of the eggs and 75% of the larvae
taken during a year-long survey (Tables
14, 15; Blanchet 1978). Other relatively
abundant larvae include silversides









Table 14. Distribution of ichthyoplankton in the Apalachicola estuary as
indicated by the presence of eggs and larvae. Dotted lines indicate
sparse breeding activity. Solid lines indicate widespread and/or inten-
sive breeding as indicated by large numbers of eggs or larvae. Data are
taken from Blanchet (1978).


Month
Species N D J F M A M J J A S 0 N D

Brevoorita sp. ...._ ...
Haren jaguana .....
Anchoa mitchili .. .........
Anchoa hepsetus .....
Gobiesox strumosus ...... ..
Atherinidae ..............
Syngnathus scovelli ... .. ........... ...........
Syngnathus isanae ...... ....... ....
Chloroscombrus chrysura .........
Laodon rhomboides ..
ard iella chrysura _____
Cynoscion arenarius ..... ...........
Cynoscion nebulosus
Leiostomus xanthurus
Menticirrhus sp......
Micropogonias undulatus

Pogonias chromis ...............
cae s oceTTata .......
ypleurochilus eminatus .........................
Hypsoblennius hentzi .............
Gobiosoma sp. ....
Prionotus sp. .... ......... .....
Trinectes maculatus ...... ....................


(Atherinidae), skilletfish (Gobiesox
strumosus), gobies (Gobiosoma spp.), and
various warm-season spawners. Winter to
early spring types are dominated by
Atlantic croaker (Micropogonias
undulatus), spot (Leiostomus xanthurus),
and Gulf menhaden (Brevoortia patronss.
Various other sciaenid larvae are taken,
including red drum (Sciaenops ocellatus),
southern kingfish T Menticirrhus
americanus), and the sand seatrout
(Cynoscion arenarius). The abundance of
total larvae is highest in western
portions of Apalachicola Bay, largely
because of the high numbers of Anchoa
mitchilli.

Eggs of most species (except
anchovies) are generally found offshore,
indicating that few species actually spawn
within the estuary. The developing stages


of fishes usually appear within the bay
system at different times of the year.
Areas in the estuary away from the passes
are characterized by the presence of
species that spawn within the bay
(anchovies, atherinids, blennies and
gobies). Relatively large numbers of goby
larvae are found at West Pass.

With the exception of the gulf
pipefish (Syngnathus scovelli), which
appears to breed throughout the year, most
species have specific breeding seasons
extending from one to several months.
Anchovies have an extended breeding season
although they are considered warm-season
spawners. Two peaks in total larval
abundance (April-May and July-September)
occur (Table 15). Larval abundance and
species richness are higher during spring
months, however. Peak numbers of









Table 15. Numbers
parenthesis) taken
Blanchet 1978).


of ichthyoplankton with larvae and without anchovy larvae (in
at various stations within the Apalachicola estuary (after


Station __e
Inshore
Little
Date 3 1C 2 offshore 1B St. George 1A 1


0.8 8.4
(0.8) (8.4)
0.7
(0.7)


2.7 0.8
(2.7) (0.8)

1.4
(1.4)


4.1 1.5 6.2 1.7
(4.1) (1.5) (6.2) (1.7)

1.9 3.4 4.3 0.7
(1.9) (3.4) (4.3) (0.7)


0.3 1.3 1.0 11.3 12.0
(0.3) (1.3) (1.0) (11.3) (12.0)

3.0
(3.0)


0.4 0.7
(0.4) (0.7)


12/27

1/5/74

1/12

2/26

2/27

3/28

4/20

4/26

5/17

6/18

7/18

8/22

9/12


11/21/73


0.3 -- -- 12.3
(0.3) -- -- (12.3)

6.8 1.2 4.7 0.4 3.1 2.2
(0.4) (0.7) (4.2) (0.0) (1.2) (2.0)

0.5 0.8 0.2 2.5 7.1 1.4 0.5
(0.5) (0.8) (0.2) (2.2) (7.1) (1.4) (0.3)

14.3 61.3 115.1 10.1 47.7 265.2 222.6 298.4
(1.8) (40.3) (0.9) (6.1) (7.3) (3.0) (33.2) (10.2)
S 90.4 -- -- -- 41.5
S (15.8) -- -- (24.1)

13.4 163.0 171.0 2.4 84.0 2580.8 1010.6 108.0
(8.4) (7.8) (25.3) (1.7) (7.7) (11.5) (25.4) (8.4)

98.9 70.5 8.3 62.8 241.5 1325.2 1234.5 54.0
(52.8) (51.0) (0.0) (52.7) (50.6) (31.2) (283.8) (12.2)

34.7 3.5 32.4 55.5 16.1 136.7 2.3 5.3
(1.6) (0.4) (4.0) (50.6) (0.7) (16.1) (1.7) (1.3)

0.5 3.5 9.5 20.3 1119.4 61.0
(0.0) -- -- (3.5) (2.4) (5.1) (38.7) (0.0)

16.4 150.7 72.8 16.2 141.1 75.5 18.1
(9.9) (4.1) (23.3) -- (1.6) (9.7) (10.3) (0.7)

5.5 194.9 99.2 746.6 217.8 51.1 1032.6 46.6
(3.7) (92.0) (2.1) (738.2) (75.1) (6.9) (20.6) (0.0)


(continued)


I









Table 15. (Concluded.)


Station
Inshore
Little
Date 3 1C 2 Offshore 18 St. George 1A 1

10/17 5.1 4.1 2.5 7.8 2.4 4.2 3.5 3.8
(4.1) (4.1) (1.4) (7.8) (2.4) (4.2) (3.2) (0.8)
11/7 0.6 0.5 0.2 0.2
(0.6) (0.5) (0.2) (0.2)
12/3 2.8 0.5 2.5 0.7 1.6 7.0 10.1
(2.8) (0.5) (2.5) (0.7) (1.6) (7.0) (9.8)


ichthyoplankton (25.8 m-3) are found just
beyond Sike's Cut in April.

Fishes that live in a given estuary
can be organized into various categories
according to their life history (McHugh
1967). Estuarine-dependent forms include
truly estuarine species, anadromous and
catadromous species, marine species that
live and often spawn offshore but use the
estuary as a nursery, and marine species
that enter the estuary seasonally as
adults but remain offshore as juveniles.
In the Apalachicola estuary, the estuarine
eggs and larvae are dominated by one
estuarine species, the bay anchovy. At
stations that are not near the passes (3,
2, 1; Table 15) numbers of larvae of
species other than anchovies are usually
low. Such areas tend to be dominated by
species that spawn within the estuary
(i.e., atherinids, blennies, skilletfish).
Blanchet (1978) attributed the low number
of eggs in the estuary to the flushing of
the bay system. It is also possible that
the generally low salinities within the
estuary prevented spawning by most
species. Overall, the pattern and
distribution of the fish larvae within the
bay system would indicate that, while
specific causative factors remain unknown,
the primary function of the bay is its use
as a nursery by true estuarine species and
marine species that spawn offshore.

4.3. BENTHOS

Considerable information is available
concerning benthic macroinvertebrates in


estuarine and coastal systems (Mann 1982).
Benthic infauna, which live within the
sediments, are usually separated according
to size into macrobenthos, meiobenthos,
and microbenthos. Although there are
differing opinions as to the exact
dimensions of each size category, most
workers agree that the macrobenthos
includes those organisms taken in 250-500
micrometer ( m) sieves. Meiobenthic
organisms are those taken between 62 m
and 250 m, and organisms smaller than 62
m are classified as microbenthos.
Macroinvertebrates living just above the
sediments or at the sediment-water
interface are called epifauna or
epibenthic invertebrates. These organisms
will be treated as nekton in this review.

The relative composition of any given
benthic macroinvertebrate collection
depends to a considerable degree on the
form of sampling gear. In the
Apalachicola Bay system, benthic
macroinvertebrates have been taken by
cores and ponars (McLane 1980; Mahoney and
Livingston 1982), leaf packs (Livingston
et al. 1977), otter trawls (Livingston
1976a, b; Livingston et al. 1976b), and
dredge-nets and seines (Purcell 1977).
The benthic macroinvertebrates in the
Apalachicola Bay system represent a
diverse fauna (Table 16) with distinct
patterns of temporal and spatial
distribution (Livingston et al. 1977).
Although considerable seasonal and year-
to-year variation in species composition
and relative abundance is found at any
given sampling area, certain trends are









Table 16. Invertebrates taken in cores, leaf-baskets, dredge nets, and otter trawls in
the Apalachicola Bay system (1975-1983). Data are derived from Livingston et al.
(1976c, 1977), McLane (1980), Purcell (1977), Mahoney (1982), and Sheridan (1978,
1979). Recent taxonomic updates are noted in Livingston et al. (1983).


Phylum Mollusca
Class Gastropoda
Subclass Prosobranchia
Order Archaeogastropoda
Family Neritidae
Neritina reclivata
Order Mesogastropoda
Family Calyptraeidae
Crepidula fornicata
Crepidula pana
Family Naticidae
Polinices duplicatus
Family Epitoniidae
Epitonium rupicola
Family Hydrobiidae
Texadina
sphinctostoma
Family Cerithiidae
Bittium varium
Order Neogastropoda
Family Fasciolariidae
Fasciolaria tulipa
Family Melongenidae
Busycon contrarium
Busycon spiratum
Melongena corona
Family Muricidae
Urosalpinx perrugata
Family Columbellidae
Anachis avara
Mitrella lunata
Family Olividae
Olivella sp.
Family Thaididae
Thais haemastoma
Family Marginellidae
Prunum apicinum
Subclass Opisthobranchia
Order Cephalaspidea
Family Bullidae
Bulla striata
Family Retusiaae
Retusa canaliculata
Family Pyramidellidae
Odostomia laevigata
Order Anaspidea
Family Aplysiidae
Aplysia willcoxi
Order Nudibranchia
Nudibranch sp.


Class Bivalvia
Bivalve sp. 2
Bivalve sp. x
Order Mytiloida
Family Mytilidae
Amygdalum papyria
Brachidontes exustus
Brachidontes sp.
Order Arcacea
Family Arcidae
Anadara brasiliana
Anadara sp.
Anadara transversa
Order Ostreoida
Family Ostreiidae
Crassostrea virginica
Order Veneroida
Family Cyrenoididae
Pseudocyrena floridana
Family Mactridae
Mactra fragilis
Mulina lateralis
Rangia cuneata
Family Solenidae
Ensis minor
Family Tellinidae
Macoma balthica
Macoma mitchelli
Tellina texana
Family SemelTdae
Abra aequalis
Family Solecurtidae
Tagelus plebeius
Family Dreissenidae
Mytilopsis leucophaeta
Family Corbiculidae
Polymesoda caroliniana
Family Cardiidae
Dinocardium robustum
Class Cephalopoda
Order Teuthoidea (= Decapoda)
Family Loliginidae
Lolliquncula brevis
Class Polyplacophora
Family Chitonidae
Chiton tuberculatus
Phylum Annelida
Class Polychaeta
Polychaete (unident.)


(continued)

50









Table 16. (Continued.)


Order Orbiniida
Family Orbiniidae
Haploscoloplos
foliosus
Ha loscopllos
fragilis
Scoloplos rubra
Family Paraonidae
Paraonis sp.
Order Spionida
Family Spionidae
Carazziella hobsonae
Paraprionospio
innata
Soanes bombyx
Streblospio benedicti
Scololepis texana
Family Magelonidae
Magelona polydentata
Magelona sp.
Family Cirratul idae
Chaetozone sp.
Order Capitellida
Family Capitellidae
Capitella capitata
Capitella sp.
Capitellides jonesi
Heteromastus
filiformis
Mediomastus ambiseta
Notomastus hemipodus
Pol dora lignin
[old7ora socialist
Poldora websteri
Family Arenicoli dae
Arenicola cristata
Family Maldanidae
Branchioasychis
americana
Clymenella sp.
Order Phyllodocida
Family Phyllodocidae
Eteone heteropoda
Paranaitis speciosa
Phyllodoce Tragilis
Family Hesionidae
Gyptis brevioalpa
0phiodromus abscura
Podarke sp.


Family Pilarqiidae
Ancistrosyllis
hartmanae
Ancistrosyllis sp.
Parandalia americana
Sigambra bassi
Family Syllidae
Pionosyllis sp.
Syllidae sp.
Family Nereididae
Laeonereis culveri
Nereid sp. A
Nereis succinea
Stenoninereis martini
Family Glyceridae
Glcera americana
Family Goniadidae
Glycinde solitaria
Order Amphinomida
Family Amphinomidae
Amphinome rostrata
Order Terebellida
Family Amphictenidae
Cistena gouldi
Family Ampharetidae
Hobsonia florida
Melinna maculata
Order Eunicida
Family Onuphidae
Diopatra cuprea
Family Eunicidae
Mar physa sanguinea
Family Lumbrineridae
Lumbrineris sp.
Lumbrineris tenuis
Order Sabellida
Family Sabellidae
Fabricia sp.
Class Oligochaeta
Oligochaeta spp.
Order Haplotaxida
Family Tubificidae
Limnodriloides sp.
Peloscolex benedeni
Phallodrilus sp.
Tubificoides
heterochaetus
Tubificoides sp.
Family Naididae
Paranais litoralis


(continued)

51









Table 16. (Continued.)


Phylum Arthropoda
Subphylum Crustacea
Class Malacostraca
Superorder Peracarida
Order Mysidacea
Mysidopsis almyra
Mysidopsis bahia
Mysidopsis ~Tigeow
Taphromysis bowman
Taphromysis
louisianae
Order Tanaidacea
Hargeria rapax
Order Cumacea
Cumacea sp.
Order Isopoda
Family Anthuridae
C athura polita
Xenanthura
brevitelson
Family Sphaeromatidae
Cassidinidea ovalis
Sphaeroma
quadridentatum
Sphaeroma terebrans
Family Idoteidae
Edotea montosa
Edotea sp.
(cf. montosa)
ErichsoneTTa sp.
(cf. filiformis)
Family Munnidae
Munna reynoldsi
Order Amphipoda
Suborder Caprellidea
Family Caprellidae
Paracaprella
tenuis
Suborder Gammaridea
Family Haustoridae
Lepidactylus sp.
Haustoridae sp.
Family Gammaridae
Gammarus
macromucronatus
Gammarus
mucronatus
Gammarus sp.
Family Bateidae
Batea
catharinensis
Carinobatea sp.


Family Ampeliscidae
Ampelisca abdita
Ampelisca vadorum
Ampelisca
verrll i
Family Melitidae
Melita
appendiculata
Melita elongata
Melita fresnelii
MeTi-ta-
intermedius
Melita
loi isetosa
Melita nitida
Melita sp.
Family Ischyroceridae
Cerapus sp.
cf. tubularis)
Erichthonius
brasiliensis
Erichthonius sp. 2
Family Aoridae
Grandidierella
bonnieroides
Grandidierella
sp.
Lembos sp.
Microdeutopus sp.
Family Corophiidae
Corophium
louisianum
Corophium sp.
Family Crangonyctidae
Crangonyx
richmondensis
Family Amphilochidae
Gitanopsis sp.
Family Ampithoidae
Cmadusa compta
Cadusa sp.
Family Talitridae
Orchestia grillus
Orchestia uhleri


(continued)









Table 16. (Continued.)


Superorder Eucarida
Order Decapoda
Family Penaeidae
Penaeus aztecus
Penaeus duorarum
Penaeus setiferus
Trachypenaeus
constrictus
Trachypenaeus
similis
Xiphopenaeus
kroyeri
Sicyonia
brevirostris
Sicyonia dorsalis
Family Sergestidae
Acetes americanus
Family Palaemonidae
Leander
tenuicornis
Macrobrachium
ohi one
Palaemonetes
intermedius
Palaemonetes
pugio
Palaemonetes
vulgaris
Periclimenes
americanus
Periclimenes
Tongicaudatus
Family Alpheidae
Alpheus
armillatus
Alpheus formosus
Alpheus
heterochaelis
Alpheus normanni
Family Ogyrididae
Ogyrides limicola
Family Hippolytiae
Hippolyte
zostericola
Latreutes
parvulus
Lysmata
wurdemanni
Thor dobkini
Tozeuma
carolinense


Family Processidae
Ambidexter
symmetricus
Process
fimbriata
Process
hemphilli
Process sp.
Family Cambaridae
Procambarus
penaensalanus
Family Callianassidae
Callianassa
atlantica
CalTianassa
jamaicense
Family Paguridae
Pagurus
bonairensis
Pa urus
longicarpus
Pagurus
pollicaris
Family Majidae
Libinia dubia
Libinia
emarginata
Metaporhaphis
calcarata
Podochela riisei
Family Portunidae
Callinectes
sapidus
Callinectes
similis
Ovalipes
guadulpensis
Portunus gibbesii
Family Xanthidae
Eurypanopeus
depressus
Hexapanopeus
angustifrons
Menippe
mercenaria
Neopanope
packardii
Neopanope texana
Panopeus herbstii
Rhithropanopeus
harrisii
Family Grapsidae
Sesarma cinereum
Family Ocypodidae
Uca minax









Table 16. (Concluded.)


Family Porcellanidae
Petrolisthes
armatus
Clibanarius
vittatus
Family Leucosidae
Persephona
mediterranea
Superorder Hoplocarida
Order Stomatopoda
Family Squillidae
Squilla empusa
Class Ostracoda
Ostracoda sp.
Class Branchiura
Argulus sp.
Subphylum Hexapoda
Class Insecta
Insect larvae
(several unident.)
Order Diptera
Family Chironomidae
Chironomidae
Ablabesmia sp.
Chironomus sp.
Cadotanytarsus so.
Clinotanypus so.
Coelotanypus sp.
Cryptochironomus
fulvus
Cryptochironomus
sp.
Dicrotendipes sp.
Glyptotendipes sp.


Nanocadius sp.
Orthocladius sp.
Parachironomus sp.
Polypedilum sp.
Procladius sp.
Procladius sp.
anypus sp.
Tanytarsus sp.
Family Heleidae
Bezzia sp.
Order Odonata
Suborder Anisoptera
2 unident. spp.
Suborder Zygoptera
1 unident. sp.
Order Ephemeroptera
Family Caenidae
Caenis sp.


Family Heptageniidae
1 unident. sp.
Family Baetidae
Callibaetis sp.
Order Plecoptera
1 unident. sp.
Order Hemiptera
Family Corixidae
1 unident. sp.
Order Lepidoptera
Family Pyralidae
Nymphula sp.

Phylum Echinodermata
Echinarachinus
parma
Echinaster sp.
Hemipholus
elongata
Luidia clathrata
Ophiothrix
angulata








evident. Infaunal numerical abundance and
dry weight biomass (Figure 27) in East
Bay, Apalachicola Bay, and St. George
Sound usually peak during winter and early
spring months (Mahoney and Livingston
1982; Livingston 1983b, c; Livingston et
al. 1983). Numbers of infaunal species
reach the highest levels during winter and
spring months (Figure 27). Monthly
variance follows the trends of numerical
abundance and species richness. Sheridan
and Livingston (1983), working in shoal
grass (Halodule wri htii) meadows on the
north shore of St. George Island, found
infaunal densities exceeding 104,000
individuals m-2 in April 1975.

Spatial gradients of salinity,
productivity, and sediment types influence
the infaunal community composition
(Livingston et al. 1983). While physical
factors appear to predominate in the
infaunal community relationships in the
upper estuary near the river mouth, other
factors such as predation pressure and
competition may be important determinants
of such interspecific interactions in
polyhaline portions of the bay system
(Livingston et al. 1983).

Overall, infaunal species fall into
four general categories: crustaceans,
polychaetes, mollusks, and a miscellaneous
group that includes insect larvae and
oliqochaete worms. Predominant species in
East Bay include Mediomastus ambiseta,
Steblospio benedicti, Heteromastus
filiformis, Ampelisca vadorum, Hobsonia
florida, Hargeria rapax, and
Grandidierella bonnieroides. The tanaid
Hargeria raDax is most abundant in or near
grass beds in Apalachicola Bay from
February to April. Other dominant grass-
bed species include Heteromastus
filiformis and Hobsonia florida. The
amphipod Grandidierella bonnieroides
ranges throughout the East
Bay-Apalachicola Bay complex, with peak
abundances during early spring and late
summer. Soft-sediment polyhaline
assemblages are dominated by Mediomastus
ambiseta, Paraprionospio pinnata, and
immature tubificid worms (ivingston et
al. 1983). The sedentary polychaete
Heteromastus filiformis is largely
restricted to grass beds and is most
abundant during April. The amphipod
Ampelisca vadorum occurs primarily in the


Apalachicola Bay seagrass meadows during
winter and early fall months. The poly-
chaete Mediomastus ambiseta is found in
fine mud bottoms throughout the bay, with
peaks of abundance in March. The
ubiquitous polychaete Streblospio
benedicti utilizes a variety of habitats
throughout the estuary, with peak
abundance during winter months. The
polychaete Hobsonia florida is found
throughout the bay from grass beds to soft
sediment (unvegetated areas). Peak
abundance is noted during early fall
months. In general, the polychaete
species are eurythermal and euryhaline and
include selective and nonselective deposit
feeders. Sheridan and Livingston (1983)
noted that the dominant tanaids and
amphipods are detritivores and deposit
feeders.

Because considerable amounts of
detrital matter are usually swept into the
estuary by the Apalachicola River during
winter-spring periods, the organic litter
forms an important habitat for various
macroinvertebrates. Organisms associated
with leaf litter and detritus have been
described by Livingston (1978) and
Livingston et al. (1976b, 1977). Litter
fauna is dominated by isopods, amphipods,
and decapods, which utilize particulate
matter and litter-associated microbes for
food and/or shelter. Dominant species in
East Bay and Apalachicola Bay include
Neritina reclivata, Palaemonetes spp.,
Corophium louisianum, Gammarus spp.,
Grandidierella bonnieroides, Melita spo.,
and Munna reynoldsi. Salinity appears to
be an important organizing feature of
litter associations (Livingston unpubl.).

Life-history strategies of dominant
infaunal and litter-associated
macroinvertebrate populations are dictated
by substrate type, temperature, salinity,
and biological factors (Table 17). Most
dominant infaunal populations reach peaks
of numerical abundance during late winter
and spring periods of low salinity and
increasing temperature. Most such species
are euryhaline and eurvthermal.
Reproduction of some infaunal populations
occurs throughout the year while others
reproduce only between spring and fall.
Individual species have different patterns
of distribution within the estuary depen-
ding on recruitment patterns and response











Table 17. General abundance information and natural history notes for the dominant organisms (infauna,
epibenthic fishes, and invertebrates) in the Apalachicola estuary. A comparison of species character-
istics with observations in other gulf estuaries is also given. References for such notes are listed.


Peak
abundance
in gulf
estuaries


Peak
abundance
Apalachicola
system


Reproductive Reproductive
Salinity patterns in patterns in
and temperature gulf Apalachicola
tolerance estuaries system_


References


Spring and Summer and High; prefer low
fall fall salinity. Direct
relationship of
size with salinity


Penaeus duorarum Late summer, July -
(Pink shTip7- fall November


Penaeus aztecus
(Brown shrimp)



Palaemonetes pug
(Grass shrirnp]



Callinectes sapidus





Lolliguncula brevis
T7BTef squid)


BENTHIC INVERTEBRATES

Hargeria rapax
{tanaid)


Hiph; prefer high
salinity, usually
dominant at
salnities 18 ppt


Spawn in gulf in
early spring and
fall. Postlarvae
and juveniles enter
bays in spring





Spring and summer
spawning; post
larval peaks,
August September


Late spring, Late spring, High; prefer low Postlarvae enter
summer early summer salinities bays late winter-
10-20 ppt spring; juveniles
early summer


February,
March


February High; prefer low
April salinities
10-20 ppt


Large crabs Winter ? High; direct


Varied, early
spring to late


Summer, fall


Spawn in summer
and fall



Spring, summer


Prefer high Suggested estuarine
salinity, 15 ppt spawning throughout
the year


February Salinity range
April 6.3-26.8 ppt
Temperature range
11.5-32.50C


Hermaphroditic


Juveniles enter Gunter 1950; Linder and
bay in spring, Anderson 1956; Ingle 1957;
summer Loesch 1965; Williams 1956;
Copeland and Truitt 1966;
Christmas et al. 1966; Perez
Farfante 1969; Perret 1971;
Gaidry and White 1973; Copeland
and Bechtel 1971, 1974; Stokes
1974; Swingle and Bland 1974.

Juvenile stages
enter bay during
summer


Juveniles in bay
during early summer


Hoese and Jones 1963; Wood
1967; Rouse 1969; Perret 1971;
Single and Bland 1974.


Young enter bay Gunter 1950; Hedgepeth 1050;
narnell 1959; Tagatz 1968;
More 1969; King 1971; Lyons et
al. 1971; Copeland and Rechtel
1974.

Perret 1971; Swinele
1971; Swingle and Bland 1974;
Laughlin 1979; Laughlin and
Livingston 1981.


Hermaphroditic;
ovigerous females
noted throughout
the year


Livinaston 1978; Livingston et
al. 1976b, 1977; McLane 1980;
Sheridan and Livingston 1983.


Ovigerous females Livingston 1978; Livingston et
noted from al. 1976b, 1977; McLane 1980;
November Sheridan and Livingston 1983.


_ _Species


NEKTONIC INVERTEBRATES

Penaeus setiferus
(White shrimp


Grandidierella
bonnieroides
Tamphipod)


March -
August


Salinity range
0-26.8 ppt
Temperature range
6.0-32.5C .









Heteromastus
fi'liformim
TpoTychaete)

Mediomastus
amIseta
(polychaete)



Am elisca vadorum
tamphipoad



Streblospio benedicti
(po ychaete)



Hyaneola florida
polychaetiY



Cerapus sp.
amphipod)
s-4

Dicrontendipes sp.
dipterann


Aricidea fragilis
TpaTychaeTeT



Melita nitida
Tih iodT-



Melita eloniata
TamTOphio_


April Salinity range
6.3-26.8 ppt
Temperature range
11.5-32.50C

March Salinity range
0-18.8 ppt
Temperature range
6-310C


February Salinity range
6.3-26.8 ppt
Temperature range
6-32.50C

August Salinity range
November 0-26.8 ppt
Temperature range
6-32.5oC

September Salinity range
0-26.8 ppt
Temperature range
6-32.50C

Late spring Salinity range
0-10 ppt
Temperature range
10-300C

Late fall, Salinity range
winter 0-10 ppt
Temperature range
6-310C


April


Late spring,
early winter



Spring


Year-round
reproduction


Salinity range
6.3-26.8 ppt
Temperature range
11.5-32.50C

Salinity range
20-33 ppt
Temperature range
21-320C

Salinity range Long spawning
O0-32 ppt season with
Temperature range juvenile recruit-
20-320C ment throughout
year



(continued)


Ovigerous females
noted all months
except August
with peaks in
February

Year-round
reproduction


Ovigerous females
noted May-July



Ovigerous females
noted July -
September


Ovigerous females
noted Aoril,
August, October


Ovigerous females
noted in Spring



Ovigerous females
noted in May,
October




Ovigerous females
noted in Spring



Compatible with
previous studies


Ljvingston 1978; Livingston et
al. 1976b, 1977; McLane 1980;
Sheridan and Livingston 1983.


Livingston 1978; Livingston et
al. 1976b, 1977; McLane 1980;
Sheridan and Livingston 1983.



Livingston 1978; Livingston et
al. 1976b, 1977; McLane 1980;
Sheridan and Livingston 1983.

Livingston 1078; Livingston et
al. 1976b, 1977; McLane 1980;
Sheridan and Livingston 1983.


Livingston 1978; Livingston et
al. 1976h, 1977; McLane 1980;
Sheridan and Livingston 1983.


Livingston 1978; Livingston et
al., 1976b 1977; McLane 1980;
Sheridan and Livinqston 1983;
Sheridan 1979.

Sheridan 1976; Livingston 1978;
Livingston et al. 1976b, 1977;
McLane 1980; Sheridan and
Livingston 1983.

Sheridan 1979; Livingston 1978;
Livingston et al. 1976b, 1977;
McLane 1980; Sheridan and
Livingston 1983.

Sheridan 1979; Livingston 1978;
Livingston et al. 1976b, 1977;
McLane 1980; Sheridan and
Livingston 1983.


Sheridan !979; Livinqston 1978;
Livingston et al. 1976b, 1977;
McLane 1O80; Sheridan and
Livingston 1983.

Gunter 1945; Reid 1954;
Springer and Woodburn 1960;
Gunter and Hall 1965; Fox and
Mock 1968; Perret 1071.
















Species


Mel ta interned ia
amphi-l-p ...... .












FISHES

Anchoa mitchilli
Tay anchovyY




Micropogon ras
unduljatus
TA-lantic croaker)



Cynoscion arenarius
(Sana seatrou5tT





Leiostomus xanthurus
TSnc1tY _




Bairdiella chrysura
(Siver perti)




Chloroscombrus
chrysrbus
TAtTIntic bumper)


Peak
abundance
in gulf
estuaries


Peak
abundance
Apalachicola
system


Table 17 (Concluded.)


Reproducti ve
Salinity patterns in
and temperature gulf
tolerance estuaries


Aoril Salinity ranqe Spawning in
Jjnp 1-17 pot oasses during
Temperature range late fall and
10-320C early winter;
juveniles in
estuaries
Ictober-April

Late summer, Salinity ranqe Spring spawning
early fall 0-'4 pot with juveniles in
Temperature range estuaries April -
2?r-2oC September


Summer and Summer, 'all Hiqh; dIrect
fall and early relationship of
winter size with saliniv


Spring and
summer




May-July






April-July


Summer-early
fall


Januarv-Aoril Hiqh


Spawn near passes
late winter, earlv
spring; juveniles
in bays December -
May

Soawn in estJarles
Aoril-June with
iuveniles appearing
'rom May to September


March-Auqust Even distribution
over salinity;
caught between
2n and 350C



January-April High; highest Spawn near passes
catches, 10-1 late winter, early
o/oo spring; juveniles
in bays December-
May

Fall-early High; direct Spawn in estuaries
winter relationship of April-June with
size with salinity juveniles appearing
from May to
September


Summer and July-
fall October


Abundant in high
salinity with direct
relationship of
size with salinity


Reproductive
patterns i1
Apal chicola
System .---


Juveniles in bI
around October -
November. Arult
miqralion, .1ne
to nctober


Reference,


Gunter 1945; Reid 1954; Kilby
1955; Springer and Woodburn
1960; Bechtel and Copeland
1970; Perret 1971; Copeland and
Bechtel 1974; Swingle and Bland
1974.


J;uvnilos in bay hunter 1i45; Reid 1I54; Kilbv
April-May 1qA5; Sorinqer and Woodhurn
160; lechtel and Cooeland 1971;
Perret 1l71; Cooeland and Bechtel
1974; Swinqle and 31and 1074.



Juveniles in bay Dearson 1920; hunter 1Q4t ;
January Joseph and Yerqer lq15; Norden
February 1966; Svkes and Finucane ayS;
Nelson 1169; ferret 1971;
Swinale and Rland 1q74.

,uveniles in bayv hunter 1945; Killv 19i5;
summer months Soringer and Woorhurn 160;
Gunter and Hall lQ6,; Nnrden
1Q66; Fox and 'nck 190o; Perret
1071; Swingle ani Rland 1q74.

Gunter 1945; Reid 1954; Kilby
1955; Joseph and Yerger 1956;
Springer and Woodburn 1960;
Gunter and Hall 1965; Norden
1966; Perret and Calllouet
1974.

Juveniles in bay Pearson 1929; Gunter 1945;
January- Joseph and Yerger 1956; Norden
February 1966; Sykes and Finucane 1966;
Nelson 1969; Perret 1971;
Swingle and Bland 1974.

Juveniles in bay Gunter 1945; Kilby 1955;
summer months Springer and Woodburn 1960;
Gunter and Hall 1965; Norden
1966; Fox and Mock 1968; Perret
1971.

Gunter 1945; Reid 1954; Kilby
1955; Joseph and Yerger 1956;
Springer and Woodburn 1960;
Gunter and Hall 1965; Norden
1966; Perret and Caillouet
1974.


~_~












































j M A j J JA S D N


o2














E 6
aJ









IN 0


o 0
ImE
I I :


if


It


Month
Based on 40 core samples token monthly in East Boy 1975 1982


Month


2Bosed on 48 2-man otter trial tows token monthly in Apolachlcola Estuary 1972 1982
Bosed on 48 2 mn otter trawl tows taken monthly in Apalchilcolo Estuary 1972 1982

Figure 27. Summed numerical abundance and number
of species of benthic infauna and epibenthic fishes
and invertebrates in East Bay and Apalachicola Bay
from 1972 to 1982 (from Livingston unpubl.). Data
are presented as monthly means +1 standard devia-
tion of the mean.








to stress. However, there is relatively
little in the way of detailed life-history
information concerning these invertebrate
species.

4.4. OYSTERS
Oysters (Crassostrea virginica)
represent an important part of the biota
of the Apalachicola estuary (Figure 20).
Such factors as temperature, rainfall/
river flow (and hence salinity),
productivity (allochthonous and
autochthonous), bottom type, and predation
define the life history of oysters in the
Apalachicola estuary. Ingle and Dawson
(1951, 1952) noted that temperature is
rarely limiting and that the spawning
season is one of the longest in the United
States (April through November). The
free-swimming larval stage persists for
two weeks. Ingle and Dawson (1952) found
that oyster growth in Apalachicola Bay is
the fastest in the United States and is
continuous throughout the year because of
the relatively high year-round
temperatures. Successful oyster
development depends on an appropriate
substrate such as oyster shells, which can
be planted throughout the estuary as
cultch to enhance growth. Whitfield and
Beaumariage (1977) estimate that nearly
40% of Apalachicola Bay is suitable for
growing oysters. The ample nutrients and
primary production of the bay also enhance
oyster growth.

Oyster-bar associations also include
various organisms that prey on oysters
(Menzel et al. 1958, 1966). These include
boring sponges, polychaete worms,
gastropod mollusks (such as Thais
haemastoma and Melongena corona), and
crustaceans (Menippe mercenaria).
Salinity is the most important limiting
factor for oyster populations, but it has
been hypothesized that such influence is
indirect in that low salinity limits
predation by excluding important species
such as Thais and Menippe. During periods
of high salinity, oyster predation is
enhanced and can be considerable.
Experiments have shown that oysters over
50 mm in length are rare in unprotected
areas of high salinity relative to areas
where oysters are shielded from predation
by baskets at similar salinities (Menzel
et al. 1966).


4.5. NEKTON
Nekton are those organisms that are
strong enough swimmers that they can move
through the water column, even against
water currents. In the Apalachicola Bay
system, the nekton comprise the bulk of
the sport and commercial fisheries and are
among the more conspicuous biological
components of the estuary. Eoibenthic
fishes and invertebrates in the
Apalachicola marshes (Table 18) and ooen
water areas (Table Q1) are characterized
by high numbers of predominant species,
with the top three species of each group
accounting for 70%-80% of the total
numbers taken throughout the year. The
relatively low number of fish and
invertebrate species in the bay system at
any given time, together with the high
dominance of a relatively few extremely
successful species, contribute to the low
species diversity throughout the estuary
(Livingston 1q76b).

In a given year, peak numbers of
fishes tend to occur from February through
April (Fiqure 27). This situation is due
largely to the presence of juvenile spot
and Atlantic croaker. Species numbers, on
the other hand, tend to oeak during
October. Epibenthic invertebrates reach
abundance peaks from August through
October, largely because of high numbers
of penaeid shrimp and, secondarily, blue
crabs (Figure 27). Seasonal patterns of
invertebrate species richness tend to
follow those of the fishes. The highest
numbers of invertebrate soecies usually
occur in October. The peaks of abundance
and species richness of fishes and
invertebrates are characterized by monthly
high variances.

Various organisms appearing in the
estuary may not be estuarine dependent
throughout their life histories. Many
such organisms are migratory. The
anadromous species in the Apalachicola
drainage system include the Atlantic
sturgeon (Acipenser oxvrhynchus), Alabama
shad (Alosa alabamae), and striped bass
(Morone saxatilis) (Yerger 1077). The
skipjack herring (Alosa chrysochloris) is
another possible anadromous species.
Other species, such as the Atlantic
needlefish (Strongylura marina) may be
diadromous. Catadromous species include








Table 18. Fishes and invertebrates commonly taken
with seines in oligohaline (East Bay) and mesohaline
(Apalachicola Bay) marshes of the Apalachicola estuary
(from Livingston and Thompson 1975).


Species
Scientific name Common name


East Bay
Fishes

Ictalurus natalis
Micropterus saTmoides
Lepomis microlophus
Lepomis punctatus
Poecilia latipinna
Adinia xenica
Cyprinodon variegatus
Fundulus grandis
Fundulus confluentus
Fudulu sdimnilis
Notemigonus crysoleucas
Lucania parva
Lucania goodei
Notropis sp.
Lepisosteus osseus
yprinus carpio
u a rostrata
Pomoxis nigromaculatus
Menidia beryllina
Anchoa mitchilli
Brevoortia patrons
Mugi curema
Muqi ceiphaTus
Micropogonias undulatus
Bairdiela chrysoura
Stellifer lanceolatus
Cynoscion arenarius
Para ichthys 1ethostigma
Trinectes maculatus
Eucinostomus gua
Lutanus griseus
Gobiosoma bosci
Microgobius gulosus
Archosargus probatocephalus

Invertebrates


Callinectes sapidus
Palaemonetes pugio
Penaeus setiferus
Penaeus aztecus


yellow bullhead
largemouth bass
redear sunfish
spotted sunfish
sailfin molly
diamond killifish
sheepshead minnow
gulf killifish
marsh killifish
longnose killifish
golden shiner
rainwater killifish
bluefin killifish
shiners
longnose gar
common carp
American eel
black crappie
inland silverside
bay anchovy
gulf menhaden
white mullet
striped mullet
Atlantic croaker
silver perch
star drum
sand seatrout
southern flounder
hog choker
silver jenny
gray snapper
naked goby
clown goby
sheepshead


blue crab
grass shrimp
white shrimp
brown shrimp


(continued)








Table 18. (Concluded.)


Species
Scientific name Common name

Aoalachicola Bay
Fishes

Anchoa mitchilli bay anchovy
Anchoa hepsetus striped anchovy
IMenidTia --er-yTina inland silverside
Eucinostomus gula silver jenny
Synodus foetens inshore lizardfish
Strongylura marina Atlantic needlefish
Lucania parva rainwater killifish
Fundulus similis longnose killifish
Synnathus floridae dusky pipefish
Lagodon rhomboides pinfish
Leiostomus xanthurus spot
Bairdiella chrysoura silver perch
Cynoscion nebulosus spotted seatrout
Muil cehalus striped mullet
rtoprsts chrysoptera pig fish
Opsanus beta gulf toad fish
Invertebrates

Callinectes sapidus blue crab
Palaemonetes pugio grass shrimp
Palaemonetes vulgaris grass shrimp
Palaemonetes intermedium grass shrimp
Penaeus setiferus white shrimp
Penaeus duorarum pink shrimp
Penaeus aztecus brown shrimp
Neopanope texana mud crab


the American eel (Anguilla rostrata),
hogchoker (Trinectes maculatus), and
mountain mullet (Agonostomus monitcola).
Various other freshwater species and some
marine forms, such as striped mullet
(Mugil cephalus) and the southern flounder
(Paralichthys lethostigma), occur in the
lower river and estuary although they do
not make true migrations.

The estuarine dominants such as
sciaenid fishes, oenaeid shrimp, and blue
crabs have annual migrations during which
the adults spawn offshore, the larval and
juvenile stages move into the estuarine
nursery, and finally the subadults return
to the open gulf to spawn as adults. Most
such species are either marine-estuarine
or estuarine. Oesterling and Evink (1977)


studied migratory habits of blue crabs
along the Gulf coast of Florida (Figure
28). Adult blue crabs spawn offshore and
the larvae, after going through a series
of zoeal planktonicc) stages, metamorphose
into a single megalops stage that has both
planktonic and benthic features (Figure
28). The megalops eventually molts into
the first crab stage, which develops
mainly within the estuarine nursery
grounds. The authors found that female
crabs move northward along the gulf coast
of Florida, some as far as 500 km. Few
males move more than 40 or 50 km. Such
migrations appear to be linked to spawning
within the Apalachicola offshore area
(from the Ochlockonee River drainage to
the Apalachicola River drainage). Large
numbers of egg-bearing females are









Table 19. Epibenthic fishes and invertebrates taken in otter trawls and
trammel nets at various stations in the Apalachicola estuary from 1972
through 1982 (Livingston unpublished data). Species are listed in order of
numerical abundance.


Species


A. Fishes
Anchoa mitchilli 41.
Micropogonias undulatus 42.
Cynoscion arenarius 43.
eiostmus xanturus 44.
Polydactylus octonemus 45.
Arius felis 46.
Chloroscombrus chrysurus 47.
Menticirrhus americanus 48.
Smphuru plagusa 49.
Bairdie5la chrysura 50.
Etropus crossotus 51.
Trinectes maculatus 52.
Prionotus tribulus 53.
Stellifer lanceolatus 54.
Anchoa hepsetus 55.
Pon~Tcthys porosissimus 56.
Prionotus scitulus 57.
Eucinostomus gula 58.
Paralichthys lethostigma 60.
Synodus foetens 60.
Eucinostomus argenteus 61.
Dasyatis sabina 62.
Cynoscion nebuTosus 63.
Microgobius thalassinus 64.
Urophycis flordanus 65.
Lagodon rhomboides 66.
Gobiosoma bosci 67.
Chaetodipterus faber 68.
Orthopristis chrysoptera 69.
Brevoortia patrons 70.
Dorosoma petenense 71.
Peprilus burti 72.
Pepr paru 73.
Stephanolepis hispidus 74.
phaeroides nephelus 75.
Ophichthus gome 76.
Synqnaths ouisianae 77.
Syngnathus sco 78.
Gobionellus boleosoma 79.
Harengula pensacolae
B. Invertebrates
Penaeus setiferus 4.
Callinectes sapidus 5.
Palaemonetes pugo 6.


Archosargus probatocephalus
Microgobius gulosus
Bagre marinus
Menidia berylina
Monacanthus ciliatus
Caranx hippos
Centropristis melana
Syngnathus floridae
Ancyclopsetta quadrocellata
Chilo ycterus schoepfi
Diplectrum formosum
Ictalurus catus
Sciaenops ocellata
Astroscpus y-graecum
Hippocampus erectus
Lepisosteus osseus
Lucanis parva
Lutjanus griseus
Tpsanus beta
Paralichth s albigutta
Ohidion beani
uterus schoepfi
D iTpodus iolbrooki
Gobionellus hastatus
Hypsoblennius hentzi
Menticirrhus saxatijis
Myrophis unctatus
Ogi1bia cayorum
Oligoplites saurus
Pomatomus saltatrix
Rhinoptera bonasus
Scomberomorus maculatus
Selene vomer
Sphyraena borealis
Shrna tiburo
Sardinella anchovia
Caranx bartholomaei
ugil sp.
Gymnura micrura


Penaeus duorarum
Trachypenaeus constrictus
Chrysaora quinquecirrha


(continued)

63








Table 19. (Concluded.)


Species

B. Invertebrates (continued)

7. Lolliguncula brevis 36. Brachiodontes exustus
8. Penaeus aztecus 37. Hexapanopeus angustifrons
9. Palaemonetes vulgaris 38. Luidia clathrata
10. Portunus gbbesii 39. Persephona mediterranea
11. Stooophys melegris 40. Clibanariusvittatus
12. Neritina reclivata 41. Libinia dubia
13. SquiT a empusa 42. Periclimenes americanus
14. Calinectes similis 43. Ambidexter symmetricus
15. Rhithropanopeus harrisii 44. Busycon spiratum
16. Neopanope texana 45. Procabarus paeninsulanus
17. Polinices duplicatus 46. Eupleura sulcidentata
18. Neopanope ackardii 47. Hemipholus elonata
19. Mulinia laterais 48. Alheus normanni
20. Acetes americanus 49. ury opeu epressus
21. Pagurus pollicaris 50. Lysmata wurdemanni
22. Rangia cuneata 51. Pentacta sp.
23. Menippe mercenaria 52. Petrolisthes armatus
24. Xiphopeneus kroerl 53. Podochela riisei
25. Alpheus heterochaTeis 54. Tozeuma carolinense
26. Latreutes parvulus 55. Nubranch sp.
27. Palaemonetes intermedius 56. Alpheus armillatus
28. Metoporhaphis calcarata 57. Sesarma cinereum
29. Crassostrea virginica 58. Sicyona dorsais
30. Palaemon floridanus 59. Anadara brasiliana
31. Periclimenes longicaudatus 60. Dinocardium robustum
32. Ogyrides limicola 61. Cantharus cancelaria
33. Trachypenaeus similis 62. Urosalpinx perrugata
34. Busycon contrarium 63. valipes quadulpensis
35. Branchiosychis americana 64. Pagurus longicarpus


concentrated in this area in winter. The
authors hypothesized that larval dispersal
from the Apalachicola area takes place
along clockwise (Looo) currents that
eventually wash onto the Florida Shelf
(Figure 28). 7oea larvae then disperse
along the coast, with the megalops stage
settling into the coastal estuaries.
Livingston et al. (1077) used daytime
trawling to estimate winter populations of
juvenile blue crabs in the Apalachicola
estuary of approximately 30,000,000
individuals. Migration of spawning
females appears to coincide with flooding
of the north Florida drainage system,
which makes particulate organic matter
available as food to the young crabs
(Laughlin 1979). Thus, the migration of


blue crabs along the gulf coast could be
tied to both the reproductive
characteristics of the species and the
trophic organization of the Apalachicola
estuary.

Life-history features of the dominant
epibenthic species in the Apalachicola
estuary have the same patterns as
elsewhere in the northern Gulf of Mexico
(Table 17). Spawning and recruitment
generally vary from species to species
according to different combinations of
seasonal physical factors. The bay
anchovy is the most abundant fish and is
one of the few fish species that does not
show regular seasonal recruitment
progressions. In contrast, the Atlantic


























/
firstt crab'


Figure 28. Life cycle of the blue crab
along the gulf coast of Florida.
Ovigerous females move toward the
Apalachicola estuary. It is hypothesized
that developing stages move back down the
gulf coast of Florida with offshore
currents (after Oesterling and Evink
1977).



croaker spawn near passes during fall and
early winter; the juveniles occupy the
estuary in peak numbers during late winter
and early spring when salinities are
usually less than 10-15 ppt. Spot also
spawn near passes, and peaks of abundance
in the estuary generally coincide with
those of the Atlantic croaker. Sand
seatrout are usually most abundant during
summer months after spawning offshore
during the spring. This species is taken
at various salinities, but temperature
appears to be limiting; high catches are
generally taken in 200-350-C water.

White shrimp are dominant from August
to November, with spring spawning and
recruitment. Other penaeids usually reach
peak numbers during late spring (brown
shrimp: Penaeus aztecus) or late summer
(pink shrimp: P. duorarum). The blue
crab shows a Timodal annual peak of
recruitment; numbers peak during winter
and summer periods. Depth and specific
microhabitat conditions are the principal
determinants of blue crab distribution at


any given time (Laughlin 1979; Livingston
unpubl.). The brief squid (Lolli uncula
brevis), is limited in spatial/temporal
distribution by salinity (20-30 ppt) and
other habitat characteristics and complex
trophic relationships (Laughlin and
Livingston 1982). In summary, these
species-specific responses to multifactor
complexes demonstrate the difficulty of
trying to design linear models to explain
and predict spatial/temporal patterns of
occurrence.

The spatial distributions of nektonic
fishes and invertebrates in the
Apalachicola estuary (Table 20) tend to be
associated with freshwater runoff into the
system. Relative dominance at a given
station varied according to salinity
gradients and habitat type. Regular
seasonal changes in distributions are
evident for most of the dominant nektonic
species. For example, anchovies are
relatively uniformly distributed within
the estuary during January and February
(Figure 20). By the spring, anchovies are
concentrated in upper portions of East
Bay. During the early summer, there are
minor population peaks with primary
concentrations in eastern portions of East
Bay. By the fall, the anchovies
concentrate around the mouth of the
Apalachicola River as well as in portions
of East Bay, and during early winter, the
anchovies become uniformly distributed
throughout East Bay and Apalachicola Ray.

In January, Atlantic croaker tend to
congregate at the mouth of the
Apalachicola River and upper portions of
East Bay (Figure 30). By February, this
distribution is more uniform throughout
East Bay and northern Apalachicola Bay, a
situation that appears to hold during
ensuing winter and spring months until,
by May or June, the croakers move out of
the bay.

The spatial distribution of sand
seatrout through a given seasonal cycle is
quite regular (Figure 31). As the young
seatrout move into the bay system in May,
they concentrate in upper portions of East
Bay and just off the mouth of the
Apalachicola River. Secondary concentra-
tions are found throughout East Bay and
northern portions of Apalachicola Bay.
The distribution changes little in June,









Table 20. E:pibenthic fishes and invertebrates taken in otter trawls at permanent
stations in thne Apalachicola estuary from June 1072 to May 1977. Stations have been
nrderpd_ by, cluster analysis according to relative abundance of fishes and
invertebrates. Data are given concerning numbers/sample, dry weight biomass/sample,
percent dominance (by numbers), and Margalef richness. Dominant species are also
enumerated by station.


Number Biomass per % Domin-
per sample (a, ance (by
Station sample dry weight) numbers)


Dominant species


OUTER BAY-


2

RIVER - 3
DOMINATED

4


UPPER
(EAST) BAY


A.
- 1 43.4 46.2


- 1A 18.0 47.5



- 1E 55.9 53.9

- 1C 51.6 75.1


- 1X 73.2 171.8


96.4 65.6


44.5 31.3


100.9



64.6

74.3


-- 5A 101.4 60.Q


S5B


S5C

--6


74.1


90.8

109.9


FISHES


39 MICROPOGONIAS UNDULATUS
ANCHOA MITCHILLI

41 ANCHOA MITCHILLI
MICROPOGONIAS UNDULATUS
LEIOSTOMUS XANTHURUS

77 LEIOSTOMUS XANTHURUS

43 MICROPOGONIAS UNDULATUS
ANCHOA MITCHILLI

34 LAGODON RHOMBOIDES
BAIRDIELLA CHRYSURA
ORTHOPRISTIS CHRYSOPTERA

46 ANCHOA MITCHILLI
MICROPOGONIAS UNDULATUS

44 ANCHOA MITCHILLI
LEIOSTOMUS XANTHURUS

49 ANCHOA MITCHILLI
MICROPOGONIAS UNDULATUS
BREVOORTIA PATRONS

47 LETOSTOMUS XANTHURUS

44 ANCHOA MITCHILLI
MICROPOGONIAS UNDULATUS
LEIOSTOMUS XANTHURUS

47 ANCHOA MITCHILLI
LEIOSTOMUS XANTHURUS
MICROPOGONIAS UNDULATUS

47 ANCHOA MITCHILLI
LETOSTOMUS XANTHURUS

47 LEIOSTOMUS XANTHURUS

33 ANCHOA MITCHILLI
LEIOSTOMUS XANTHURUS
MICROPOGONIAS UNDULATUS
BREVOORTIA PATRONS


Margalef
richness


3.77


3.43



3.54

3.48


3.55



2.88


3.82


3.14



3.30

3.90

3.01





2.99


3.09

3.98


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


I~---










Table 20. (Continued.)


Number Biomass per % Domin-
per sample (g, ance (by Margalef
Station sample dry weight) numbers) Dominant species richness


A. FISHES (continued)


SIKE'S CUT-- 1B


129.3


36 ANCHOA MITCHILLI
CYNOSCION ARENARIUS
ETROPUS CROSSOTUS


B. INVERTEBRATES


7.0 7.2


5.5 5.3


OUTER BAY--- 1E


- 1C


6.4 9.5


- 1X 16.3


2

RIVER 3
DOMINATED

4


47 CALLINECTES SAPIDUS
PENAEUS SETIFERUS

38 PENAEUS SETIFERUS
CALLINECTES SAPIDUS
LOLLIGUNCULA BREVIS
TRACHYPENAEUS CONSTRICTUS

48 CALLINECTES SAPIDUS
PENAEUS AZTECUS

27 PENAEUS DUORARUM
LOLLIGUNCULA BREVIS
CALLINECTES SAPIDUS

57 ACETES AMERICANUS
CALLINECTES SAPIDUS
PENAEUS DUORARUM

70 PENAEUS SETIFERUS

49 CALLINECTES SAPIDUS
PENAEUS SETIFERUS

52 PENAEUS SETIFERUS
CALLINECTES SAPIDUS


(continued)









Table 20. (Concluded.)


Number Biomass per % Domin-
per sample (g, ance (by Margalef
Station sample dry weight) numbers) Dominant species richness


B. INVERTEBRATES (continued)
--4A 13.0 16.0 67 PENAEUS SETIFERUS 1.24
PALAEMONETES PUGIO
-5 12.2 9.9 57 PENAEUS SETIFERUS 1.45
CALLINECTES SAPIDUS
UPPER -5A 13.7 3.9 65 PENAEUS SETIFERUS 1.18
(EAST) BAY CALLINECTES SAPIDUS

5B 6.8 5.1 53 CALLINECTES SAPIDUS 1.39
PENAEUS SETIFERUS
5C 12.5 5.2 54 CALLINECTES SAPIDUS 1.11
PENAEUS SETIFERUS
-6 45.8 11.1 50 PALAEMONETES PUGIO 1.17
PENAEUS SETIFERUS
SIKE'S CUT---B 10.0 8.4 41 LOLLIGUNCULA BREVIS 3.28
CALLINECTES SAPIDUS
PORTUNUS GIBBESI
ACETES AMERICANUS


but in July, the highest concentrations of
the sand seatrout are found at the mouth
of the Apalachicola River. Distribution
usually remains relatively unchanged
during August and September. The
remaining fish, dwindling in numbers
during the fall months, spread out
throughout East Bay and northern
Apalachicola Bay. By winter or early
spring, as noted above, no sand seatrout
are taken.

Spot have a different pattern of
distribution (Figure 32). As they move
into the estuary in Jaunary, spot tend to
congregate in upper East Bay and around
Nick's Hole drainage off St. George
Island. This distribution broadens
throughout eastern portions of East Bay
and Apalachicola Bay during February and
March. Concentrations of spot appear in
areas of the bay that receive freshwater


runoff from upland areas. East Bay is a
particularly important nursery area for
this species. By summer, remnants of the
population are found off St. George
Island.

The spatial distribution of
postlarval penaeid shrimp in the
Apalachicola estuary illustrates the
summer and fall dominance of these species
(Figure 33). During early summer, they
are concentrated in East Bay. However,
during July and August, high numbers of
penaeids are located at the mouth of the
Apalachicola River. By fall, although
still concentrated in East Bay, they tend
to be more evenly distributed throughout
the estuary as they move into the open
gulf to spawn. Few shrimp are taken
during the winter months. As with other
dominant (and commercially important)
species in the bay, the penaeids appear to

















































October



Anchovies


EL~


Ca

January









April


Individuals per Two-Minute Trawl Tow by Month
0.0 5.0 = 20.0 50.0
5.0 10.0 50.0 90.0
10.0 20.0 90.0 200.0


Figure 29. Average monthly distribution of anchovies (Anchoa mitchilli) in the
Apalachicolaestuary from 1972 to 1979.


February


November


ULAMB :

June






tat
-1



September









December



























OTI


October


Atlantic

Croaker


November I December
Individuals per Two-Minute Trawl Tow by Month
0.0- 5.0 20.0 -30.0
5.0 10.0 30.0 50.0
10.0-20.0 50.0- 90.0


Figure 30., Average monthly distribution of Atlantic croaker (Micropogonias
undulatus) from 1972 to 1979.


August


Septe


i TARN.

March

































































San Individuals per Two-Minute Trawl Tow b) Month

Sand 0.0 -.0 1 10.0 15.0
2.0 5.0 15.0 25.0
Seatrout 5.0-10.0 m 25.0-3.0

Figure 31. Average monthly distribution of sand seatrout (Cynoscion arenarius)
in the Apalachicola estuary from 1972 to 1979.


February


T lrr~%------- ----;-
-- ---- -- --;"-" -- -
- ---


April


October


srT


CUT
November


December





























































V l ----- --- s
t~ Q'~-;----- ---- ----- ~- -- ~ I I s
- - =----- -------

%&A -----------
------ --- ---- -" -

November December
Individuals per Two-Minute Trawl Tow b3 Month


Spot


0.0 -

10.0 -
[ 20.0 -


S 40.0 90.0

S 90.0 250.0
250.0 500.0


Figure 32. Average monthly distribution of spot (Leiostomus xanthurus) in the
Apalachicola estuary from 1972 to 1979.


CUT
sam.


April




APlE~


nT





CUT
July


May


BUCUT

June


August


October


4L.

















































































Individuals per Two-Minute Trawl Tow by Month


W'W T's*,Aj 11


w mhte nrmp o0.0 2. 10.0- 20.0
S2.0 5.0o 2o.o-30o.o

s5.0- 1o.o 3o.o 7o.o


Figure 33. Average monthly distribution of penaeid shrimp (Penaeus spp.) in
the Apalachicola estuary from 1972 to 1979.


February


ST. --- -----



PAR
March


April


May





4PALACMICOLA
RNS EASI BAV
APALAC" OA


ST aI
ISLISN
..- 1 UOR41A
WES t
m KCul
August


June


STW I


IVul
WES
CUT
July


ST VmIC
tslwl


September


October


-1-9


-11-14











I


Blue Crabs


Individuals per Two-Minute Trawl Tow by Month

[ 0.0 1.0 4.0 6.0

1.0 -2.0 6.0 9.0

2.0 4.0 9.0 13.0


Figure 34. Average monthly distribution of blue crabs (Callinectes sapidus)
in the Apalathicola estuary from 1972 to 1979.


March I


Septembere


"mm-%


m


m-m""


---I


I
:.5~
.








be attracted to the upper freshwater
portions in the estuary.

Although the major peaks in numbers
of juvenile blue crabs occur during the
winter, secondary increases are often
noted during the summer and fall (Figure
34). As the young blue crabs enter the
Aoalachicola estuary during the winter
months, they concentrate in East Bay and
off the Nick's Hole drainage (St. George
Island). During May and June, peaks in
the number of blue crabs occur in these
areas. By the summer and fall months, the
blue crabs are concentrated in East Bay.
Blue crabs appear to be attracted to areas


that receive overland runoff although they
are not attracted by direct river flow.

While there is a general pattern of
concentration of the dominant epibenthic
fishes and invertebrates in areas that
receive direct input of freshwater runoff
from upland areas, it is simplistic to
assume that runoff per se is the primary
factor that influences the temporal and
soatial aspects of the distribution of
such organisms in the estuary. There are,
in fact, a complex of species-specific
limiting factors that are associated with
the trophic organization of the bay
system.
















CHAPTER 5
NICHE DIVERSITY, TROPHIC INTERACTIONS, AND COMMUNITY STRUCTURE


5.1. HABITAT-SPECIFIC ASSOCIATIONS

The Apalachicola estuary, as an
ecosystem, can be defined as a series of
habitats with associated assemblages of
organisms. Such assemblages (or communi-
ties) live in the same general habitat,
compete for space and food, and are part
of the highly complex trophic structure of
the river-bay system. The dimensions of a
given community are difficult to define
precisely because the component
populations vary considerably in their
distribution and community function in
space and time. However, selected factors
can be used to characterize the various
estuarine assemblages. Sources of primary
productivity, habitat features, the
physical and chemical environment
(including pollutants), modes of
reproduction and recruitment, feeding
interactions, predator-prey relations, and
competition are some of the features that
shape the estuarine communities.

The distribution of most of the
estuarine assemblages may be partitioned
into the following habitats: marshes,
seagrass beds, litter associations, oyster
bars, and subtidal unvegetated (soft-
sediment) areas. Many of the long-term
biological studies in the Apalachicola
estuary have concentrated on the macro-
invertebrates benthicc, epibenthic) and
fishes that are found in these areas.

5.1.1. Marshes

The marshes, which include complex
patterns of tidal channels and small
creeks, provide food and habitat for a
number of organisms in the Apalachicola
estuary (Table 18). Marsh complexes
include insects, mollusks, crustaceans,
fishes, birds, and mammals. Topminnows of


various species are dominant in such
areas. Many species that are important to
the sports and commercial fisheries of the
region spend at least part of their life
histories in the estuarine marshes. Such
species include blue crabs, penaeid
shrimp, large-mouth bass, lepomids,
striped mullet, spotted and sand seatrout,
and anchovies. Few species spend their
entire lives within the marshes, however,
and the marsh habitat is best
characterized as a nursery for migratory
species during summer and fall months.

5.1.2. Seagrass Beds

The distribution of grassbeds in the
Apalachicola estuary (Figure 19) is the
result of a number of environmental
controlling factors. Even though it is
limited to only about 10% of the aquatic
area by the high turbidity and
sedimentation associated with the river,
this habitat's productivity is high.
Grassbed productivity is also limited by
water temperature, salinity, and the
activity of certain invertebrates.
However, grassbeds also have an effect on
certain water quality indices. Various
studies in East Bay (Livingston 1978;
Purcell 1977) indicate that water quality
factors such as dissolved oxygen and pH
are higher in the grassbeds than in
associated mudflats.

The oligohaline grassbeds of East Bay
are dominated by tapeweed (Valisneria
americana), a freshwater species. Other
species found in conjunction with tapeweed
are Potamogeton pusillus, Ruppia maritima
(locally dominant in western bayous of
East Bay), Cladophora sp., and Halophila
engelmanni. In recent years, some parts
of East Bay are being taken over by the
Eurasian watermilfoil (Myriophyllum








spicatum). During the period 1980-1981,
this introduced species became dominant in
Round Bay, one of the eastern bayous. By
1982-1983, the Myriophyllum had become
rooted throughout the upper East Bay area
(Livingston unpubl.). It is unclear how
spread of Eurasian watermilfoil will
affect the distribution of plants and
animals in the East Bay seagrass beds.

Currently, the oligohaline seagrass
beds serve as a nursery for benthic
species such as the snail Neritina
reclivata (a major dominant) and
epibenthic species (Odostomia sp.,
Gammarus macromucronatus and Taphromysis
bowmani. Infaunal assemblages are
dominated by polychaetes (Loandalia
americana, Mediomastus ambiseta),
amphipods (Grandidierella bonnieroides)
and chironomid larvae (Dicrontendipes
sp.). Fish populations are dominated by
rainwater killifish (Lucania parva),
pipefish (Syngnathus scoveli),
silversides (Menidia beryin, gobies
(Microgobius guosus), and centrarchids.
Many species utilize these areas (Duncan
1977; Livingston and Duncan 1979; Purcell
1977). Of the 28 dominant benthic species
of fishes that comprised over 98% of the
abundance in the area, most consumed
detritus, small mollusks, crustaceans,
epiphytes, and insect larvae. Most of the
penaeid shrimp, insect larvae, and fishes
that are found here are seasonally
abundant at early stages of their
reproductive cycles, which indicates the
use of these areas as primary nursery
grounds. Peaks of abundance are staggered
throughout the year.

The predominant macrophyte species in
mesohaline or higher-salinity areas off
St. George Island in Apalachicola Bay is
Halodule wrightii (Sheridan and Livingston
1983). Infaunal macroinvertebrates,
dominated by Hargaria rapax, Heteromastus
filiformis, Ampelisca vadorum and various
oligochaetes, reach peaks of abundance
during early spring. Predominant fishes
include silver perch (Bairdiella
chrysoura), pigfish (Orthopristis
chrysoptera), pinfish (Lagodon rhomboides)
and spotted seatrout (Cynoscion
nebulosus). These species are abundant
from May through September. Blue crabs
(Callinectes sapidus), pink shrimp
(Penaeus duorarum) and grass shrimp


(Palaemonetes vulgaris) are the dominant
invertebrates. Their densities are
bimodal, peaking in the winter and summer
months. These areas are also
characterized by the year-round presence
of larval and juvenile nekton.

5.1.3. Litter Associations

Leaf litter associations are
dominated by omnivores and detritivores.
The fraction of particulate organic matter
(POM) large enough to be identified as
litter is populated with gastropod
mollusks (Neritina reclivata), amphipods
(Gammarus mucronatus, Melita spp.,
Grandidierella bonnieroides, Corophium
louisianum, Gitanopsis sp.), isopods
(Munna reynoldsi), and decapods
(Palaemonetes pugio, P. vularis, Penaeus
setiferus, Callinectes sapidus).

Species richness of the litter-
associated fauna in upper East Bay
(station 5A), the river mouth (station 3),
and the shoal grassbeds off St. George
Island (station 1X) peaks during August
and September (Figure 35). Such peaks are
strongly associated with salinity levels
at the respective study sites (Figure 36).
Dominant species vary from location to
location. The level and timing of peaks
of abundance also vary spatially (Figure
35). Upper East Bay, which is outside of
the direct influence of the Apalachicola
River, appears to be the least productive
part of the estuary in terms of litter-
associated macroinvertebrates. Areas rich
in detritus, such as station 3, are most
highly populated during March and
September, periods when the river is
flooding or macrophytes are dying off.
The highest numbers of litter-associated
macroinvertebrates occur in the Halodule
beds off St. George Island from April to
June, a period of high macrophyte
productivity. These data indicate that
while species richness may be strongly
influenced by salinity, the numerical
abundance of the litter associations is
more strongly aligned with the
availability of detritus.

While physical factors such as
salinity and temperature are important
determinants of the distribution of
litter-associated organisms in the
estuary, recent experiments by Florida











Z) 25-


02
i,






[L
1.
LL.
S 15-
a:
w

z
5-
w
S2,oo000-
z

Z
S15,000-

-j 10,000-
4

w 5000-

z


Stations


S20

. 15
. -
o-
CL 10


*\ *

c^=-c--^ ^-
I I I I I I I I I I I
J F M A M J J AS OND
TIME


Figure 35. Numerical abundance and
sopcies richness of invertebrates taken in
leaf-litter baskets at various permanent
sampling sites in the Apalachicola
estuary, monthly from January, 1976,
through December, 1976. After Livingston
(1978) and Livingston et al. (1977).



State University researchers indicate that
biological associations are also
important. Macroinvertebrates appear to
utilize the detritus as shelter and a
source of food (White in press). In a
series of experiments with the leaf litter
community, White et al. (1979a) found
that, whereas the biomass (as measured
by lipid phosphate and
poly-beta-hydroxybutyrate), nutritional
history, and respiratory activity of
microbes are correlated with substrate
type, the macrofaunal populations are more
often associated with specific water
quality features such as salinity.
Numbers, biomass, and species richness of
detritus-associated microfauna are
associated with the mass and community
structure of the macrofaunal food web.
These macroinvertebrates apparently seek
out microbial populations rich in


* Station 5A (oligohaline)
* Station 3 (oligohline)
o Station IX ( mesohaline)


I- 0


!r.r

:?\
,,


0 5 10 15 20 25 30 35

SALINITY
Figure 36. Regression of numbers of
species of litter-associated
macroinvertebrates on salinity at three
stations in the Apalachicola estuary.
Samples were taken over a 12-month period
in oliqohaline (stations 5A, 3) and
mesohaline (station 1X) areas.


anaerobic or microaerophilic bacteria.
The data suggest that distinct populations
may choose different microbes. The
component energy linkages are poorly
understood, however. Little is known
concerning the protozoan components of
litter associations, although preliminary
analyses in East Bay indicate that
ciliates constitute the dominant protozoan
inhabitants of the litter assemblages (D.
Cairns, pers. comm.).

In summary, physical/chemical
features such as temperature and salinity
influence the spatial-temporal
distribution of litter-associated
macroinvertebrates in the estuary. Such
distribution is also determined by
productivity trends and the biochemical
features of the microbial communities.
The detritivorous macroinvertebrates serve
as a link between the microbial producers
and important estuarine fishes and
invertebrates that feed on these species
(Laughlin 1979; Livingston et al. 1977;
Sheridan 1978, 1979; Sheridan and
Livingston 1979).


0 o
00 0 *
. 0

C -TSav'r~


i


KJ









5.1.4. Oyster Bars


Oyster bars represent a relatively
significant habitat in the estuary (Table
1). The main concentrations of oysters
(Crassostrea virginica) (Figure 20) lie in
St. Vincent Sound and western portions of
St. George Sound. Oyster distribution is
dependent upon substrate, temperature,
salinity, and available food. Oyster
bars, themselves, provide habitat and food
for a variety of organisms. The oyster
associated community includes sponges
(Cliona vastifica), bryozoans
(Membranipora sp.), flatworms (Stylochus
frontalis), annelids (Neanthes succinea,
Polydora websteri), various arthropod
crustaceans Cainectes sapidus, Menippe
mercenaria, Neopanop spp., Petrolisthes
armatus), gastropods (Crepidula plan,
Melongena corona, Thais haemastroma), and
pelecypods Brachidontes exusta, Chione
cancellata) (Menzel etal.1966. Fishes
include blennies (Hypsoblennius spp.) and
toadfish (Opsanus beta). These organisms
use the reef for shelter and/or feeding.


Salinity controls oyster-bar
community organization. When salinities
are high, various stenohaline gulf species
are able to move into the oyster-rich
areas and feed on the oysters. Low
salinity limits such predation by acting
as a barrier to those organisms. Species
richness and diversity of the oyster-
associated populations vary directly with
seasonal increases in salinity. During
warmer months, extensive oyster mortality
in the Apalachicola estuary has been
attributed to infestation by the pathogen
Perkinsus marinus (formerly called
Dermocyctidium marinum) (Menzel 1983).
Young oysters are unaffected by this
disease, although up to 50% of adult
oysters may be killed annually. The
relatively long period of high water
temperature in the gulf estuaries
contributes to such mortality. A long-
term study is currently under way to
determine the response of the Apalachicola
oyster associations to various stimuli
including habitat features (water quality,
substrate), predation, competition,
disease, and possible over-fishing
(Livingston et al., unpubl.).


5.1.5. Subtidal (Soft-Sediment)
Communities

Almost 70% of the Apalachicola Bay
system can be characterized as a subtidal,
unvegetated, soft-sediment area (Table 1).
The muddy bottom substrate is inhabited
primarily by polychaetes (Mediomastus
ambiseta, Streblospio benedict) and
amphipods (Grandidierella bonnieroides).
The polychaetes are deposit and suspension
feeders with a high reproductive capacity
and considerable tolerance for low
salinity and variable environmental
conditions. Productivity trends, habitat
type, and the ecological characteristics
of the various populations contribute to
what is a temporally variable but highly
persistent assemblage of organisms in
terms of species richness, relative
abundance, and recruitment. In
oligohaline areas of the estuary, the
benthic macroinvertebrate assemblages are
characterized by high dominance, low
species richness, low diversity, and
varying standing-crop biomass and
numerical abundance (Livingston 1983c, d).
Areas around the mouth of the river have
much higher numbers of infaunal
macroinvertebrates than areas outside of
the region of general flow. Such
differences have been attributed
(Livingston 1983c, d) to the deposition of
nutrients and detritus by the river during
periods \of flooding (Figure 9) and
increased activity and abundance of the
benthic macroinvertebrates (Figure 27).

The general community characteristics
of the soft-bottom assemblages change as
salinities increase temporally and
spatially. In mesohaline and polyhaline
portions of the system, overall numerical
abundance is lower than in oligohaline
areas, but species richness and diversity
increase significantly (Livingston et al.
1983). Such trends are evident in the
associations of epibenthic fishes and
invertebrates, which are an important part
of the soft-sediment communities.
Dominant populations such as Atlantic
croaker, spot, penaeid shrimp, and blue
crabs feed extensively on organisms within
the muddy bottom of the estuary.

The soft-sediment community
(invertebrates and fishes) of the









Apalachicola estuary reflects the response
of hundreds of species to a complex
combination of physical, chemical, and
biological factors. Physical control,
together with productivity features,
recruitment patterns, predator-prey
interactions, and competition for various
resources determine to a considerable
degree the form and functions of the soft-
sediment communities in the Apalachicola
Bay system. Because the majority of the
research in the Apalachicola Bay system
has been carried out with the fishes and
macroinvertebrates of the soft-sediment
estuarine habitat, the interrelationships
of the dominant features of these
biological systems will be treated in a
more detailed fashion below.

5.2. PHYSICAL CONTROL OF BIOLOGICAL
PROCESSES

For some time, ecologists have argued
about the relative importance of physical
and biological control of aquatic
populations and communities. Clearly, the
problem is extremely complex, based on the
fact that each species is a product of a
given habitat while also having an input,
through predation and competition, to the
community. It is generally agreed that
temperate estuaries such as the
Apalachicola system are highly productive
and physically unstable in space and time.
Temperature and salinity have a major
influence on the form and processes of the
estuarine biota in such a system. At the
same time, various populations interact
with each other and their environment with
almost continuous feed-back to the system
as a whole.

The timed interactions of multiple
physical and biological components of an
estuarine system are difficult to
differentiate for a variety of reasons.
Individual physical events follow
different temporal patterns. Often such
phenomena are essentially cyclic although
"cycle" does not necessarily imply that
there is a complete return to a previous
condition. Biological responses are not
that simple and often follow nonlinear or
curvilinear patterns of response to
varying controlling factors. Analysis of
biological responses requires the initial
delineation of key dependent and
independent variables. Experimental


evaluation of hypotheses derived from
observational data can then be used to
determine the processes that define and
ultimately control the observed structural
components of the system.

Various attempts have been made to
delineate the relationships of physical
and biological variables in the
Apalachicola estuary (Livingston 1975,
1976b, 1979, 1982b; Livingston and Loucks
1978; Livingston et al. 1974, 1976b, c,
1978; Mahoney and Livingston 1982; Meeter
and Livingston 1978; Meeter et al. 1979).
Most analyses indicate that Apalachicola
River flow has a major influence on the
physical and biological relationships in
the estuary. For example, statistical
analysis of the principal physico-chemical
variables (Table 21) indicates that the
main factor or component could be called
"river flow." This river flow is
associated with low salinity, increased
color and turbidity (and reduced Secchi
readings), and reduced chlorophyll a.
River flow alone explained 32% of the
total variance and about half of the
variance explained by the four factors.
Average bay values of major nutrients vary
seasonally; high nutrient concentrations
are found during high (winter) river
discharge and low salinity conditions
(Table 22). The Apalachicola River
controls to a considerable degree various
factors such as nutrient and detritus
concentrations, salinity, color and
turbidity, and other water quality
factors. In turn, these conditions
control the level and pattern of
productivity fluctuations in the bay
system.


Studies of temperate estuaries
indicate that the combination of high
primary productivity and extremely
variable environmental conditions is often
associated with relatively low species
richness and diversity and high secondary
productivity of a few dominant species.
No matter which group of organisms is
considered, from phytoplankton to fishes,
salinity appears to be the primary
regulator of species numbers at a given
location in the estuary. Dominants are
able to adapt to low or highly variable
salinity conditions. Salinity is a major
determinant of species richness (S) of








Table 21. Factor analysis of physico-chemical variables in the Apalachicola system
taken monthly from March 1972 to February 1976. Color (Pt-Co units), turbidity
(J.T.U.), Secchi readings (m), salinity (ppt), temperature (OC), and chlorophyll a (mg
1-1) were noted at Station 1. Tidal data included stages of the tide on the ay of
collection while the wind variable was represented by two vector components (speed,
direction) (from Meeter and Livingston 1978).


Factor 1 Factor 2 Factor 3 Factor 4
(49.0% of (22.3% of (17.9% of (10.8% of
Variable variance) variance) variance) variance)


River flow -0.82 -0.08 -0.07 -0.08

Local rainfall -0.04 -0.30 -0.09 0.20

Tide (incoming or outgoing) 0.26 0.61 -0.68 0.06

Tide (high or low) 0.09 0.39 0.61 -0.37

Wind direction (E-W) -0.02 0.09 0.36 0.37

Wind direction (N-S) 0.10 -0.20 0.22 0.31

Secchi 0.57 -0.07 -0.17 0.24

Color -0.80 0.33 0.01 0.07

Turbidity -0.73 0.54 0.08 0.23

Temperature 0.38 0.15 0.02 -0.18

Salinity 0.68 0.21 0.23 -0.02

Chlorophyll a 0.47 0.51 0.09 0.31


benthic macroinvertebrates taken
(seasonally) in litter baskets at
different stations (3, 5A, 1X) along a
salinity gradient (Figure 36) (F = 30.4,
r2 = 0.45, with S as the dependent
variable). Numbers of species taken
during a season vary directly with
salinity rather than with station-specific
characteristics. Similarity coefficients
of species composition at the sampled
stations are closest during fall periods
of high salinity. These results indicate
that quantitative and qualitative species
representation, regardless of location,
are closely related to salinity.

Similar trends are found for phyto-
plankton (Estabrook 1973), zooplankton
(Edmisten 1979), infaunal


macroinvertebrates (Livingston unpublished
data), and epibenthic fishes and
invertebrates (Livingston 1979).
Livingston (1979) showed that salinity is
directly related to species richness and
diversity of estuarine nekton. Stations
characterized by low salinity are
associated with high numbers of
individuals, high relative dominance, and
low species richness (Table 20). Outer
bay stations, with higher salinities, are
defined by relatively low dominance, high
species richness and low numerical
abundance. High densities of organisms
that use the bay as a nursery, such as
penaeid shrimp, blue crabs and various
finfishes are not usually found in areas
having stable patterns of relatively high
salinity (Livingston 1984a).








Table 22. Correlation coefficients of linear regressions of nitrate,
silicate, and ammonia on salinity (from Livingston et al. 1974).


orthophosphate,


Date NO3 PO4 Si03 NH3


Oct. 14 1972 T -0.70 -0.73
B +0.12 -0.14

Dec. 2 1972 T -0.88 -0.20 -0.98
B -0.75 -0.55 -0.85

Jan. 6 1973 T -0.55 -0.89 -0.99
B -0.84 -0.82 -0.87

Feb. 17 1973 T +0.00 -0.95 -0.33 -0.02
B +0.58 -0.11 -0.002 -0.15

Mar. 19 1973 T -0.95 -0.78 -0.98 -0.85
B -0.97 -0.60 -0.998 -0.45

Apr. 22 1973 T -0.76 -0.77 -0.93 -0.67
B -0.62 -0.62 -0.80 -0.93

May 19 1973 T -0.88 -0.54 -0.998 -0.48
B -0.96 -0.65 -0.99 -0.81

Jun. 11 1973 T -0.60 -0.01 -0.995 -0.55
B -0.94 -0.61 -0.93 +0.06

Jul. 12 1973 T -0.82 -0.10 -0.97 -0.82
B -0.80 +0.42 -0.93 +0.03

Aug. 22 1973 T -0.90 +0.04 -0.95 -0.50
B -0.91 -0.84 -0.94 -0.91

Sep. 10 1973 T -0.99 -0.29 -0.995 -0.83
B -0.98 +0.15 -0.99 -0.98


Species richness and diversity of
nekton are directly associated with areas
of high environmental stability but low
secondary productivity. Infaunal
macroinvertebrates show the same general
response to salinity (Livingston 1983d).
Within a given area of low salinity,
however, species richness may increase in
areas of relatively high primary
productivity and detritus availability.
In this way, the influence of salinity may
be modified by ambient habitat conditions.

In low-salinity estuaries, species
diversity indices tend to reflect the
effects of salinity on recruitment of


dominant populations. Within a given
habitat (such as an oyster bar,
unvegetated soft-sediment area, or
seagrass bed), the spatial distribution of
organisms at any given time may depend on
gradients of productivity and salinity.
The regulating features may change their
relative importance through any given
seasonal succession. Temperature and
other physical features seasonally modify
the productivity-salinity association.
Among the phytoplankton, water temperature
is the primary limiting factor, although
river discharge, nutrients (mainly phos-
phorus), turbidity, and light inhibition
may control phytoplankton productivity at









different times of the year. Estabrook
(1973) noted that grazing zooplankton also
may control phytoplankton productivity
since experiments removing zooplankton and
net plankton enhanced nannoplankton
productivity greatly. The possibility
exists that competition for nutrients
among various species also is an important
determinant of relative phytoplankton
dominance.

Among the zooplankton, copepods are
dominant. The copepod Acartia tonsa
constitutes 95.5% of total zooplankton in
East Bay, 68.2% in Apalachicola Bay and
19.8% in coastal waters (Edmisten 1979).
Salinity and temperature control the
composition of zooplankton communities in
the estuary. Populations of Acartia vary
inversely with distance from the mouth of
the Apalachicola River and are
concentrated in Apalachicola Bay.
Temperature is associated with significant
(p < 0.01) differences in Acartia numbers.
Salinity significantly (p < 0.01) affects
the overall relative abundance of the
dominant populations. Edmisten (1979)
showed that temperature, salinity, station
and month had a multiple r value of 0.775.
In East Bay, Acartia numbers (as well as
zooplankton numbers and biomass) peak
during periods of high salinity. Thus,
temperature usually determines overall
numbers in the bay system, while salinity
determines their spatial distribution at
any given time. The response to midrange
salinities explains the nonlinear
(parabolic) relationship of Acartia with
salinity,. It appears that other
organisms can successfully complete with
Acartia at higher and lower salinities.

Life history strategies of various
nektonic estuarine species depend to some
degree on spatial/temporal gradients of
substrate type, salinity, food
availability, and energy flow. The
spatial distribution and abundance of
brief squid (Lolliguncula brevis) is
determined to a considerable degree by
salinity and temperature (Laughlin and
Livingston 1982). Optimal salinities
range between 25 and 30 ppt. Squid tend
to congregate near the passes during
summer and fall periods of high salinity.
Distribution within the estuary is
associated with the distribution of
zooplankton in the bay. Population trends


of squid followed long-term (9-year)
salinity trends that, in turn, were
associated with climatic features. There
were sharp decines in squid abundance
during periods of low salinity.

Overall, attempts to correlate
patterns of species abundance with
individual physical, chemical, and
productivity variables have not been
entirely successful. A multiple
regression analysis of individual
population densities with combinations of
independent variables indicates that such
components accounted for less than 50% of
the population variability (Table 23). No
single set of physical conditions
explained population variation through
time. While factors such as temperature,
salinity, productivity, and water quality
characteristics are important determinants
of general habitat availability, it is
clear that other factors, presumably
biological in nature, may be important to
our understanding of the processes that
determine the community structure of the
Apalachicola Bay system.

5.3. TROPHIC RELATIONSHIPS AND FOOD-WEB
STRUCTURE

Community structure is determined in
part by predator-prey interactions,
especially among dominant estuarine
populations. Comprehensive studies of the
feeding habits of dominant fishes
(Sheridan 1978; Sheridan and Livingston
1979) and invertebrates (Laughlin 1979)
have been carried out (Figure 37).
Pelagic anchovies feed primarily on
calanoid copepods throughout their lives.
Seventy percent of the diet of young
anchovies (standard length (SL), 10-39 mm)
is composed of these copeoods. Larger
fish (SL 40-69 mm) eat mysids, insect
larvae and juvenile fishes. A seasonal
progression of food item consumption
follows trends of available prey species.
The Atlantic croakers progress through a
series of distinct ontogenetic trophic
stages. Young fish (SL 10-30 mm) eat
insect larvae, calanoid copepods, and
harpacticoid copepods. Midrange fish (SL
40-99 mm) consume detritus, mysids, and
isopods; larger fish (SL 100-159 mm) eat a
high proportion of juvenile fishes, crabs,
and infaunal shrimp. Croaker at all
stages eat polychaete worms. Spot, which









Table 23. Results of a stepwise regression analysis of various independent parameters
and species (numerical abundance) in the Apalachicola estuary from March 1972 to
February 1975. Independent variables are listed by order of importance with R2
expressed as a cumulative function of the given parameters (from Livingston et al.
1976b). Independent variables were run with and without lag periods of 1-3 months.


Species Independent variables R2


Anchoa mitchilli Chlorophyll a, Secchi 0.38
Micropogonias undulatus River flow (Tag), Secchi (lag) 0.46
Cynoscion arenarius Chlorophyll a, wind, Secchi (lag) temp. 0.83
Polydactylus octonemus Chlorophyll a (lag), salinity, Secchi 0.58
Arius felis Temp., wind 0.30
Leiostomus xanthurus Turbidity (lag), Secchi, salinity, temp. 0.85
Chloroscombrus chrysurus Temp. (lag), temp., salinity 0.44
Menticirrhus americanus Temp. (lag) 0.19
Syphurus plaqiusa Color (lan), color, Secchi 0.63
BairdieTa chrysura Wind, temp., color 0.40
Penaeus setiferus Wind, chlorophyll a, incoming tide, color 0.48
Palaemonetes uo Turbidity 0.49
Callinectes sapidus Secchi, incoming tide 0.43
Penaeus duorarum Chlorophyll a, Secchi 0.41
Lolliguncula brevis Chlorophyll a (lag), temp. 0.43
Portunus gibbesii Chlorophyll i (lag), Secchi 0.39
Palaemonetes vularis Turbidity 0.32
Rhithropanopeus harrisii Wind 0.18
Callinectes similis Chlorophyll a, temp. 0.34


are also benthic omnivores, consume poly-
chaetes, harpacticoid copepods, bivalves,
and nematodes. Spot have a more diverse
diet than croaker and do not concentrate
on single prey types. Trends across size
classes are not as clearcut, although
there is decreased specialization with
growth. The sand seatrout is a water-
column predator of fishes and mysid shrimp
(Mysidopsis bahia). Small trout (SL 10-29
mm) tend to eat mysids and calanoid
copepods, while larger fish (SL 30-89 mm)
consume more juvenile fishes. Anchovies
(Anchoa mitchilli) comprise 70% of all
fishes taken.

Fishes regularly undergo ontogenetic
dietary shifts encompassing planktivory,
carnivory, omnivory, and herbivory within
the same species (Sheridan 1978; Sheridan
and Livingston 1979; Livingston 1979,
1982). Sheridan and Livingston (1979)
indicated that temporal differences in
feeding progressions were a major factor
in the lack of overlap in food types among
species. Laughlin (1979) found that blue


crabs also undergo trophic progressions.
Juveniles, abundant during winter months,
feed largely on plant matter, detritus,
and bivalve mollusks such as Rangia
cuneata, Brachidontes exustus, and
Crassostrea virginica. As the crab grows,
bivalves and fishes become progressively
more important in the diet. Larger blue
crabs feed primarily on bivalves, fishes,
and crabs (i.e., blue crabs, mud crabs
such as rhithropanopeus harrisi, and
xanthid crabs of the genus Neopanope).
Cannibalism is a significant mode of
foraging in the older blue crabs. Diet
generally reflects seasonal shifts of prey
abundance.

Although the distinctive nutrient
sources for the estuary have been
identified, the rate functions of energy
movement through the system are little
understood. The periodic inputs of
nutrients and detritus into the estuary
are transformed into biological matter.
Such integrative processes continuously
smooth out the episodic nature of energy
















/ H \ / \

n MY c Cynoaclo
S---- --
Po 2 J1
Callinectes
36 NE -
\1 / / Micropogonlas
\ \- HC // '


MB / /s
u '
\ 7812 j/
---J/DE Y Leiostomus
s

Figure 37. Simplified feeding
associations of four dominant fishes--bay
anchovy, sand seatrout, Atlantic croaker,
spot--and blue crabs in the Apalachicola
estuary. Four food compartments are
shown: phytoplankton (P), holoplankton
(H), meroplankton and benthos (MB), and
sediments (S). Major food items in the
compartments are: DE=detritus,
BI=bivalves, HC=harpacticoid copepods,
NE=nematodes, IN=insects, PO=polychaetes,
SH=shrimp, MY=mysids, CR=crabs, FS=fishes,
CC=calanoid copepods, DI=diatoms. Numbers
indicate dry-weight contribution of
particular food items (within boxes) and
food contributions of major food
compartments (after Laughlin 1979 and
Sheridan 1978).


transfer from upland systems. The
planktonic and detrital pathways come
together at the sediment level through
repackaging of fecal material and the
activity of the microorganisms. The
microbes transform dissolved nutrients
into available particulate matter. Over
2% of the dry-weight mass of the sediments
is composed of organic carbon, bacterial
biomass, and extracellular polysaccharides
(D. C. White personal communication). The
sediment organic matrix and POM form the


basis of the benthic (detrital) food webs.
The grazing of detritus and its microbial
populations enhances nutrient quality for
subsequent microbial development by
stimulating further microbial productivity
and enhancing the nitrogen and phosphorus
content of the POM. Physical disturbance,
through wind and tidal action and active
predation and biological activity, is one
of the reasons why the Apalachicola
estuary is such a productive system.

Seasonal relationships among the
various physical and biological factors in
the bay system have been developed (Figure
38). Although the biological response to
a given event usually follows a nonlinear
or curvilinear pattern, certain relation-
ships have become evident after many years
of observation. Seasonal variations of
temperature and the pulsed river flow are
usually out of phase. Local rainfall
(Florida) peaks during summer months.
Salinity in the estuary is highest during
summer and fall months. The timing of the
river flow, and the resultant loading of
nutrients and POM, is critical to the
seasonal biological successions in the
estuary, especially during winter and
early spring. During such periods of low
winter temperature and salinity and high
river flow and detrital movement into the
estuary, benthic infaunal abundance is
high. Epibenthic organisms (especially
fishes) reach peak levels during late
winter as temperature starts to increase
and macroinvertebrates available for food
are abundant. Benthic omnivores such as
spot and the Atlantic croaker are favored
by such conditions. Although these
sciaenids overlap in their temporal dis-
tribution, food size partitioning by these
two bottom-feeding fishes results in
distinctive differences in prey type and
size (Sheridan 1978). A larger apparatus
allows croaker to penetrate deeper into
the substrate and consume larger poly-
chaetes, shrimp, and crabs. Spot tend to
exploit smaller organisms, such as nema-
todes, harpacticoid copepods, juvenile
bivalves, and smaller forms of poly-
chaetes. There is enough dietary overlap,
however, to allow the potential for
competition between these two species.

Benthic macroinvertebrates occupy an
important trophic link between the primary
producers (and microbes) and the upper

















Le
F


REGIONAL EVAPOTRANSPIRATION
RAINFALL

Soil Composition
Floodplain Inundation MICROBIAL LOCAL RAINFALL
-/ ~SUCCESSION
VEGETATION DISTRIBUTION I Emergent V station \Nutents
of Production RIVER PEAKS wind
ragmenaon l/ o Ds'ta SUBMERGED VEGETATION: PRODUCTIVITY
Nutrient,' Detrlius Floe Dlsturbonce
Salimty Gradients
J \A '1| PHYTOPLANKTON PRODUCTIVITY
Conditioning Particulate Oranc M er Wind Subsidy-- ---- - -- -
Si I Detritus Productn
S MICROBJS-DETRTUS W
,,^-^1 T ER OCAE AEFD V |DETRITLS-FEEDINO
L I TRAKSi OCIAT INEDERTkRRATES
^r \ 1INVERTE ATES r INVER k


ANCH VIES


NOV


MONTH


Figure 38. Generalized, simplified model of seasonal relationships of the dominant
macroinvertebrates and fishes in the Apalachicola Bay system. The model associates
population distribution with seasonal changes in key physical variables, productivity
features, and the predator-prey relationships of the estuary.


trophic levels of the estuary. Of the 10
numerically dominant infaunal species
(representing over 83% of the total
number), five are detrital feeders, four
are deposit feeders (surface and subsur-
face), and one is a filter feeder. Of the
entire infaunal assemblage, there are
fifteen omnivore/carnivore types, seven
subsurface deposit feeders, eleven surface
deposit feeders, twelve (generalized)
deposit feeders, and seven filter feeders.
There are high numbers of the various
filter-feeding mollusks such as Rangia
cuneata and Crassostrea virginica.

The important role of detritus and
its associated microbial components is


indicated by the predominance of the
detritivore/omnivore feeders in the
macroinvertebrate assemblages. Of the
dominant litter-associated organisms, the
polychaetes are generally omnivorous,
consuming fine detritus, microalgae,
copepods, and amphipods. The gastropods
in the litter include omnivores, filter
feeders, scavengers, suspension feeders,
and carnivores. The herbivorous snail
Neritina reclivata is a major species in
the grassbeds of East Bay. The amphipods
found among the litter assemblages include
omnivores, detritus feeders (or leaf
scavengers) and, in the case of some
gammarids, filter feeders. A few species
such as Hyalella azteca, Gammarus









lacustris, and Melita spp. are known to be
leaf shredders (i.e., herbivores),
although other amphipods are predaceous,
feeding on hydroids, bryozoans, and
(possibly) zooplankton. Crustaceans such
as the tanaid Hargeria rapax are generally
omnivores, but some are shredders or
parasites. Mysid shrimp generally feed on
fine detritus and diatoms. Decapod
crustaceans found in the litter
associations are largely omnivores and
detritus feeders, although certain
dominants, such as penaeid shrimp and blue
crabs, are predominately carnivorous
during certain life stages.

During the spring months, river flow
discharge decreases, salinity increases,
and the water clears. These conditions
trigger the late spring phytoplankton
blooms and associated zooplankton
increases. The spring plankton peaks are
concurrent with increased relative
abundances of planktivorous fishes such as
anchovies and menhaden. As the
temperature increases and river flow
falls, the high numbers of infaunal
macroinvertebrates fall precipitously. As
a result, by the end of spring there are
few spot and Atlantic croaker in the bay,
and the sand seatrout, feeding on
anchovies, becomes the dominant scianid.
Sheridan (1978) postulated that the summer
anchovy peaks are truncated by sand
seatrout. There is little trophic
interaction of the sand seatrout with
other dominant fish predators; likewise,
there is little dietary overlap of these
species during their concurrent periods in
the estuary (May-August). During such
periods, predation pressure on penaeid
shrimp and crabs is low. By fall, most of
the sand seatrout have moved out of the
estuary and anchovies become dominant.

As temperature peaks during the
summer, the numbers of invertebrates
(penaeid shrimp, blue crabs) increase
(Figure 27). During this time, local
rainfall reaches seasonally high levels.
Benthic macrophytes attain peak
productivity and standing crop. By the
end of summer, macrophytes start to die
off, and estuarine detritus levels
increase as the temperature begins to
decline and salinity increases throughout
the estuary. By early fall, the numbers
of species of fishes and invertebrate


species reach high levels. One
explanation for this situation
those species limited by low
during most of the year are able
the shallow portions of the es
this time. Other factors th
enhance the observed high nu
species during the fall could b(
temperatures (to optimal levels)
availability of detritus
detritivorous invertebrates as fo


possible
is that
salinity
to enter
tuary at
at could
mbers of
e falling
and the
and/or
od.


An overwhelming majority of the
estuarine nekton is omnivorous at some
life-history stage, and detritus forms an
important component of stomach contents at
any given time (Sheridan 1978; Sheridan
and Livingston 1979; Livingston 1982b).
Of the seven dominant macroinvertebrates,
representing over 90% of the trawl-
susceptible catch, five (Peaneus
setiferus, Palaemonetes pugio, Callinectes
sapidus, Penaeus aztecus and Lolliguncula
brevisT are omnivore/carnivore types;
NeriaTna reclivata is an herbivore, and
Lolliguncula brevis is a zooplanktivore.
While the nutritional importance of the
detritus remains in doubt, omnivory
appears to be an important characteristic
of the predominant feeding patterns at
intermediate levels of the estuarine food
webs.

Top predators, feeding largely on
decapod crustaceans and fishes during the
fall, include spotted seatrout (Cynoscion
nebulosus), flatfishes (Paralichthys
spp.), adult silver perch Bairdiela
chrysoura), searobins (Prionotus spp.),
and various shark types.

During November, as the temperature
drops rapidly, epibenthic organisms
decrease and various migratory species
leave the estuary for nearshore gulf
waters as part of their annual migration.
Penaeid shrimp are an example of this type
of population behavior. River flow starts
to increase during the early winter, and
salinity goes down. Benthic infaunal
species richness and abundance increase as
winter progresses (Figure 27).

The seasonal succession of habitat
change, energy distribution, soecies-
specific recruitment patterns, predator-
prey relationships, and the resulting food
web configurations contribute to the









biological organization of the estuary.
Infaunal macroinvertebrates reach maximum
abundance from November through March,
although species richness is highest in
May. As indicated previously,
phytoplankton and zooplankton are abundant
during spring months and summer periods.
Fish abundance peaks during winter and
early spring although fish and
invertebrate species richness indices
reach their highest level in October.
Epibenthic invertebrate abundance, on the
other hand, is high during August when
penaeid shrimp and blue crabs are
prevalent. In general, the dominant fish
species, while overlapping in abundance to
some degree, tend to predominate during
different times of the year; high croaker
and spot abundance occurs in winter and
early spring, sand seatrout in summer, and
anchovies in the fall and early winter.
Water column feeders such as anchovies are
linked to plankton outbursts and predation
pressure from species such as sand
seatrout. Benthic feeders occur primarily
during periods of detritus/
macroinvertebrate abundance. Croakers and
spot feed largely on polychaetes, while
blue crabs concentrate on bivalves.
Directly or indirectly, most such species
take advantage of the detritus that is
brought into the estuary by the river.
The combination of low salinity, high POM,
and low predation pressure contributes to
the observed high relative abundance of
these species.

5.4. PREDATOR-PREY INTERACTIONS AND
COMMUNITY RESPONSE

Although productivity trends and
habitat characteristics are important
factors in the development and control of
food web and -ommunity structure,
biological features such as predator-prey
relationships and competition for
resources can be extremely important in
affecting the biological organization of
the estuary. Predation within aquatic
associations can lead to changes in
relative abundance, species diversity, and
other important community indices.
Peterson (1979) reviewed factors that
relate the impact of predation and
competitive exclusion to the response of
benthic macroinvertebrates in unvegetated,
soft-sediment estuarine habitats.
Previous work with various marine assem-


blages (largely
communities) has i
from predation


rocky
indicated
(through


processes such as cagin
increased total density,


richness, and
exclusion by p;
(Peterson 1979).
manipulative p
cause simplified
as a result of
increased popul
authors have


restricti
particular
SAccord
redator
action of
enhanced


intertidal
that isolation
manipulative


g) should lead to
increased species
on of competitive
dominant species
ing to this model,
exclusion should
the prey community
competition due to


action densities. Various
found that soft-bottom


associations of benthic macroinvertebrates
do not always follow such a paradigm
(Peterson 1979). A series of tests of
this basic hypothesis has been carried out
in the Apalachicola Bay system over the
past 3 years.

Inverse correlations between predator
and prey population do exist in the
Apalachicola estuary (Sheridan and
Livingston 1983). Macroinfaunal abundance
often declines precipitously during
periods of peak abundance of the chief
sciaenid predators (Mahoney and Livingston
1982). Such correlative results suggest
that fishes may have a direct influence on
the infaunal assemblages through
predation. In grassbed areas, however,
infaunal biomass is not affected because
larger species (burrowing deeper in the
sediments) are not influenced by such
predation. Also, recent experiments
indicate that macroinvertebrate
assemblages in East Bay remain largely
unaffected by predation pressure from
fishes in the late winter and spring and
by motile invertebrates (penaeid shrimp,
blue crabs) in the summer/fall (Mahoney
and Livingston 1982; Livingston unpubl.).
Thus, predation does not appear to play a
decisive role in the regulation of prey
density or macroinvertebrate community
structure in oligohaline portions of the
estuary during periods of peak predation
pressure.

One possible explanation of the
apparent contradiction of the predation
paradigm could lie in the recruitment
potential of the dominant infaunal
species. In a series of experiments with
azoic sediments (i.e., devoid of
macroinvertebrates), Mahoney (1982) found
that infaunal larval recruitment was a
deciding factor in the population dynamics


%









of various macroinvertebrate species such
as Streblospio benedicti and Capitella
capitata. Such organisms are
characterized by extremely short life
cycles. Rapid reproduction and larval
settlement could mask the impact of
physical and biological disturbances,
which are often important features of
temperate estuaries. Heavy larval
recruitment is not always followed by
predominance of a given species, however.
Other factors such as habitat suitability
and competition could also be implicated
in the determination of community
structure.

At various levels of biological
organization in the estuary, the dominant
macroinvertebrate populations are
opportunistic and are influenced to
varying degrees by the high productivity
and physical instability of the system.
Such populations have adapted well to
habitat instability and variability.
Response time to disturbance remains
little understood, however. Recent
experiments in polyhaline portions of the
bay system (Livingston et al. 1983)
indicate that salinity could be a factor
in the influence of predation on benthic
infaunal associations. Infaunal


macroinvertebrates in the
manipulated using a series


field were
of treatments


that involved exclusion cages (i.e.,
predators were kept out), inclusion cages
(i.e., predators were returned to
exclusion cages), and field controls.
These treatments were compared to
laboratory microcosms taken from the
field. Preliminary results indicate that,
over a 6-week period of observation, there
were increased numbers of
macroinvertebrates in the laboratory
microcosms and exclusion cages. Species
diversity was reduced in such treatments
relative to field controls and inclusion
cages. Thus predation in polyhaline areas
of high macroinvertebrate diversity and
low dominance may affect infaunal
macroinvertebrate community structure.
The influence of salinity on species
diversity and relative dominance could
thus be a factor in the relative influence
of predation pressure on dominant
populations in various portions of the
estuary. In areas of low dominance, the
influence of predation may be enhanced
relative to oligohaline areas where
dominance is naturally high. In any case,
few generalizations of predation effects
can be made without due consideration to
local habitat conditions.




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