LOWER ST. MARKS RIVER/WAKULLA RIVER/APALACHEE BAY

RESOURCE CHARACTERIZATION

With a Discussion of Freshwater-dependent Habitats and Species

By F. Graham Lewis, Ph.D.

Nicholas D. Wooten

Ronald L. Bartel

Northwest Florida Water Management District

Water Resources Special Report 2009-01
NORTHWEST FLORIDA WATER MANAGEMENT DISTRICT

________________________________________________________________________________________________________________

GOVERNING BOARD

George Roberts, Chair

Panama City

Philip McMillan, Vice Chair

Blountstown

Steve Ghazvini, Secretary/Treasurer

Tallahassee

Peter Antonacci Stephanie Bloyd Joyce Estes

Tallahassee Panama City Beach Eastpoint

Tim Norris Jerry Pate Ralph Rish

Santa Rosa Beach Pensacola Port St. Joe

Douglas E. Barr

Executive Director

For additional information, write or call:

Northwest Florida Water Management District

81 Water Management Drive

Havana, Florida 32333-4712

(850) 539-5999
Acknowledgements

_____________________________________________________________________________________________________________________

The authors gratefully acknowledge the assistance of NWFWMD staff and other researchers that 

provided information and guidance during the development of this report. The contributions of the 

following NWFWMD staff are appreciatively acknowledged: Kris Barrios, Leigh Brooks, Linda 

Chaisson, Carlos Colon, John Crowe, Elaine McKinnon, Chris Richards, Jerrick Saquibal and Paul 

Thorpe. 

The authors also acknowledge the researchers and individuals that provided information and 

technical data that were referenced in this report. Among those, special thanks go to Scott Savery 

(FDEP) for providing much valuable information on wildlife resources in the Edward Ball Wakulla 

Springs State Park, Ted Hoehn and Richard Cailteux (FFWCC) for information on freshwater fish 

distributions in the Wakulla and adjacent rivers, Diane Eggeman (FFWCC) for waterfowl census 

data, and Terri Calleson (FFWCC) for manatee surveys. In addition, we acknowledge the valuable 

work and public outreach of the Wakulla Springs Working Group participants that strive to protect 

and restore Wakulla Springs and water resources in the St. Marks River Watershed.

Cover and Geographical Information Systems: John Crowe, NWFWMD
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TABLE OF CONTENTS

_____________________________________________________________________________

1.0 INTRODUCTION............................................................................................................................... 1

1.1 Purpose and Scope......................................................................................................................... 1

1.2 Watershed Research and Evaluations............................................................................................ 1

1.3 Watershed Protection and Preservation.......................................................................................... 1

2.0 ST. MARKS RIVER WATERSHED.................................................................................................... 3

2.1 Hydrogeology of Watershed........................................................................................................... 3

2.2 Woodville Karst Plain ................................................................................................................... 5

2.3 Sensitive Karst Areas...................................................................................................................... 5

2.4 Non-Point Source Runoff............................................................................................................. 10

3.0 LAND USE AND LAND COVER...................................................................................................... 11

3.1 Hydrologic Impacts of Land Use.................................................................................................. 11

3.2 Conservation Lands...................................................................................................................... 12

4.0 ST. MARKS RIVER HYDROLOGY ................................................................................................. 15

4.1 Lake Lafayette Sub-Basin ............................................................................................................ 15

4.2 Lower St. Marks Basin ................................................................................................................. 15

5.0 WAKULLA RIVER HYDROLOGY .................................................................................................. 20

5.1 Sinking Streams............................................................................................................................ 20

6.0 ST. MARKS WATERSHED DISCHARGE ........................................................................................ 22

6.1 St. Marks River Flow.................................................................................................................... 22

6.2 Rainfall and Flow ......................................................................................................................... 25

6.3 St. Marks River Low-Flow Analyses........................................................................................... 27

6.4 St. Marks River High-Flow Analyses........................................................................................... 29

6.5 St. Marks and Wakulla River Flood Model.................................................................................. 30

6.6 Wakulla Springs Flow .................................................................................................................. 32

6.7 Wakulla Spring Low-Flow Analyses ........................................................................................... 35

6.8 Wakulla Springs High-Flow Analyses......................................................................................... 36

6.9 St. Marks River and Wakulla River Discussion ........................................................................... 37

7.0 LOWER ST. MARKS AND APALACHEE BAY WATER AND SEDIMENT QUALITY ....................... 39

7.1 Water Quality Classifications....................................................................................................... 40

7.2 Water Quality Characteristics....................................................................................................... 41

7.3 Sediment Characteristics .............................................................................................................. 57

8.0 ST. MARKS/APALACHEE BAY HABITATS.................................................................................... 58
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8.1 Palustrine Forest ........................................................................................................................... 58

8.2 Freshwater and Brackish Wetlands .............................................................................................. 59

8.3 Tidal Salt Marsh ........................................................................................................................... 63

8.4 Submerged Aquatic Vegetation.................................................................................................... 64

8.5 Seagrass........................................................................................................................................ 66

8.6 Soft-Bottom Habitat ..................................................................................................................... 67

8.7 Hard-Bottom Habitat.................................................................................................................... 70

9.0 FAUNAL COMMUNITIES OF THE LOWER RIVERS AND APALACHEE BAY SYSTEM.................. 71

9.1 Riverine Communities.................................................................................................................. 71

9.1.1 Benthic and Epifaunal Invertebrates......................................................................................... 71

9.1.2 Fishes......................................................................................................................................... 72

9.1.3 Amphibians and Reptiles........................................................................................................... 75

9.1.4 Birds .......................................................................................................................................... 76

9.1.5 Mammals ................................................................................................................................... 79

9.2 Estuarine Communities................................................................................................................. 80

9.2.1 Salt Marshes.............................................................................................................................. 80

9.2.1.1 Benthic Infauna....................................................................................................................... 80

9.2.1.2 Macroinvertebrate Community............................................................................................... 81

9.2.1.3 Fish Abundance ...................................................................................................................... 82

9.2.2 Seagrass Beds............................................................................................................................ 83

9.2.2.1 Benthic Macrofauna (infauna and epifauna) ......................................................................... 83

9.2.2.2 Macroinvertebrate Abundance ............................................................................................... 84

9.2.2.3 Fish Abundance ...................................................................................................................... 86

9.2.2.4 Trophic Structure.................................................................................................................... 88

9.3 Commercial Landings................................................................................................................... 89

9.4 Threatened and Endangered Species............................................................................................ 91

10.0 IMPORTANCE OF FRESHWATER TO THE LOWER RIVERS AND APALACHEE BAY SYSTEM ..... 92

10.1 Species and Habitats with Freshwater Dependence ................................................................... 92

10.2 Flow Dependence and Salinity Tolerance .................................................................................. 94

10.2.1 Palustrine Forests.................................................................................................................... 95

10.2.2 Freshwater/Brackish Marshes................................................................................................. 96

10.2.3 Tidal Salt Marsh ...................................................................................................................... 97

10.2.4 Submerged Aquatic Vegetation (SAV)..................................................................................... 98

10.2.5 Seagrassses.............................................................................................................................. 98
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10.2.6 Oyster Reefs............................................................................................................................. 99

10.2.7 Faunal Abundance and Distribution ..................................................................................... 100

11.0 REFERENCES CITED ................................................................................................................... 102

12.0 APPENDICES................................................................................................................................ 117

Appendix A ....................................................................................................................................... 117

Appendix B........................................................................................................................................ 118

Appendix C........................................................................................................................................ 122

Appendix D ....................................................................................................................................... 123
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LIST OF FIGURES

_____________________________________________________________________________

Figure 1 St. Marks River & Apalachee Bay Watershed ................................................................... 4

Figure 2 Surface Water and Identified Karst Features of the St. Marks River Watershed ............... 6

Figure 3 Digital Elevation Map of the St. Marks River Watershed.................................................. 7

Figure 4 Digital Elevation Map of River Sink Area in North Wakulla County................................ 8

Figure 5 Sensitive Karst Areas of St. Marks River Watershed......................................................... 9

Figure 6 St. Marks Watershed Land Use By Category ................................................................... 11

Figure 7 Land Use and Land Cover in the St. Marks River Watershed.......................................... 13

Figure 8 Conservation Land in the St. Marks River Watershed ..................................................... 14

Figure 9 St. Marks River Watershed Sub-Basins............................................................................ 16

Figure 10 St. Marks River and Lafayette Outfall Flows................................................................... 17

Figure 11 Discharge Measurements at St. Marks River Rise............................................................ 18

Figure 12 Baseflow Estimation at St. Marks River Rise................................................................... 19

Figure 13 Cumulative Baseflow (Ground water Storage) and Surface Discharge at

St. Marks River Rise (Oct. 1956 – June, 2009)................................................................ 19

Figure 14 Wakulla River Digital Elevation Map .............................................................................. 21

Figure 15 Freshwater Inflows to Apalachee Bay.............................................................................. 22

Figure 16 Monitoring Stations in the Lower St. Marks River Watershed ........................................ 23

Figure 17 Daily Mean Discharge – St. Marks River (1957-June, 2009)........................................... 24

Figure 18 Tallahassee Normal Monthly Rainfall.............................................................................. 25

Figure.19 Tallahassee Annual Rainfall............................................................................................. 25

Figure.20 Tallahassee Normal Seasonal Rainfall ............................................................................. 25

Figure 21 Daily Mean Discharge – Ochlockonee and St. Marks Rivers (2004 - 2008).................... 26

Figure 22 Daily Flow Characteristics – St. Marks Rivers (1957 - 2008).......................................... 27

Figure 23 Low Flow Recurrence – St. Marks River at Newport ...................................................... 28

Figure 24 High Flow Recurrence – St. Marks River at Newport...................................................... 29

Figure 25 St. Marks and Wakulla Riverine Flood Inundation .......................................................... 31

Figure 26 Daily Mean Discharge – Wakulla Springs (May 1997 - June 2009)................................ 33

Figure 27 Periodic Wakulla River Discharge Measurements (1907 to 1987) .................................. 34

Figure 28 Daily Flow Characteristics – Wakulla Springs (May 1997 to June 2009)........................ 34

Figure 29 Low Flow Recurrence – Wakulla Springs........................................................................ 35

Figure 30 High Flow Recurrence – Wakulla Springs....................................................................... 36

Figure 31 Mean Daily Flows - St. Marks River and Wakulla Springs ............................................ 37

Figure 32 Combined Daily Flows St. Marks River and Wakulla Springs........................................ 38

Figure 33 Bathymetry of Apalachee Bay and Adjacent Waters ....................................................... 39

Figure 34 Shellfish Harvesting Areas in Western Apalachee Bay for Winter Months..................... 40

Figure 35 Water Quality Stations in the Lower St. Marks Watershed and Apalachee Bay.............. 43

Figure 36 Wakulla River Water Quality Stations ............................................................................. 44

Figure 37 Specific Conductance in the Wakulla and St. Marks Rivers............................................ 46

Figure 38 Long-term Salinity Inshore and Offshore in Apalachee Bay............................................ 47

Figure 39 Long-term Water Temperature in the Wakulla and St. Marks Rivers.............................. 47

Figure 40 Long-term Water Temperature Inshore and Offshore in Apalachee Bay......................... 48

Figure 41 Dissolved Oxygen in the Wakulla and St. Marks Rivers.................................................. 48

Figure 42 Dissolved Oxygen at Inshore and Offshore Sites in Apalachee Bay................................ 49

Figure 43 Nitrogen and Phosphorus in the St. Marks River ............................................................. 50

Figure 44 Nitrogen and Phosphorus in the Wakulla River ............................................................... 51

Figure 45 Specific Conductance at Upper and Lower Sites in the Wakulla River ........................... 52

Figure 46 Water Temperature at Upper and Lower Sites in the Wakulla River............................... 53

Figure 47 Dissolved Oxygen in the Upper and Lower Wakulla River ............................................. 53

Figure 48 Nitrate+Nitrate in the Upper and Lower Wakulla River .................................................. 54
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Figure 49 Nitrate+Nitrate vs Discharge at Wakulla Springs............................................................. 55

Figure 50 Soluble Phosphate (Ortho-phosphate) in the Upper and Lower Wakulla River .............. 55

Figure 51 Mean Total Nitrogen in the Wakulla River by Reach ...................................................... 56

Figure 52 Mean Total Phosphorus in the Wakulla River by Reach.................................................. 56

Figure 53 Wetland and Aquatic Habitats in the St. Marks/Apalachee Bay Watershed .................... 60

Figure 54 Coastal Wetlands in St. Marks/Apalachee Bay Area (1995 NWI)................................... 64

Figure 55 Seagrass Coverage (1992) in the Nearshore Area of Apalachee Bay............................... 69

Figure 56 Seagrass Coverage (2001) in the Nearshore Area of Apalachee Bay............................... 69

Figure 57 Annual Mid-winter Waterfowl Inventory on the Wakulla River From

Headwaters to U.S.98 ....................................................................................................... 77

Figure 58 Dominant Waterfowl Observed During Annual Mid-winter Waterfowl

Inventory on the Wakulla River........................................................................................ 77

Figure 59 Annual Mid-winter Waterfowl Inventory on the Lower St. Marks River ........................ 78

Figure 60 Dominant Waterfowl Observed During Annual Mid-winter Waterfowl

Inventory on the Lower St. Marks River.......................................................................... 78
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LIST OF TABLES

_____________________________________________________________________________

Table 1 St. Marks River at Newport - Low Flow Frequency Analysis............................................. 29

Table 2 St. Marks River at Newport - High Flow Frequency Analysis............................................ 30

Table 3 Wakulla Springs - Low Flow Frequency Analysis.............................................................. 36

Table 4 Wakulla Springs - High Flow Frequency Analysis.............................................................. 37

Table 5 Water Quality Site Summary For Tidal Reaches of the St. Marks and Apalachee Bay ...... 45

Table 6 Summary of Wakulla River Water Quality Sites ................................................................ 45

Table 7 Summary of Selected Water Quality Characteristics in the St. Marks and

Wakulla Rivers and Apalachee Bay..................................................................................... 46

Table 8 Summary of Selected Water Quality Characteristics in the Wakulla River System............ 52

Table 9 Mean Relative Abundance of Marsh Macrophytes in the Wakulla and Lower 

St. Marks Rivers................................................................................................................... 62

Table 10 Mean Dry Weight Biomass of Submerged and Intertidal Macrophytes

in the Wakulla and Lower St. Marks Rivers........................................................................ 65

Table 11 Biomass of Macrophytes in Apalachee Bay Offshore of Econfina River............................ 68

Table 12 Fishes Collected in Wakulla Springs State Park and Adjacent Reaches.............................. 73

Table 13 Fishes Collected from Six Sites in the Wakulla River......................................................... 74

Table 14 Mean Catch per Unit of Effort of Sportfish in the Wakulla, St. Marks, Aucilla 

and Wacissa Rivers.............................................................................................................. 75

Table 15 Ranking of Most Important Salt Marsh Macroinvertebrate Species in Three

Marsh Zones at St. Marks and Wakulla Sites...................................................................... 81

Table 16 Ranking of Most Important Tidal Creek Fish Species at High and Low Tides................... 82

Table 17 Ten Dominant Species Collected from Pooled Econfina and Fenholloway

Estuarine Sites from 1972 to 1979....................................................................................... 85

Table 18 Macroinvertebrate-habitat Associations in Apalachee Bay ................................................. 85

Table 19 Total and Relative Abundance of Dominant Macroinvertebrate Species From

Pooled Apalachee Bay Estuarine Stations........................................................................... 86

Table 20 Rank and Relative Abundance of Fishes Collected in Apalachee Bay Offshore of

Econfina and Fenholloway Rivers....................................................................................... 87

Table 21 Recent Commercial Harvests (2000 to 2002) of Selected Fish and Shellfish

Landed in Wakulla County ...................................................................................... 90

Table 22 Recent Commercial Harvests (2003 to 2005) of Selected Fish and Shellfish

Landed in Wakulla County .................................................................................................. 90
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ACRONYMS AND ABBREVIATIONS

BMP Best Management Practice

cfs Cubic feet per second. 

CPUE Catch Per Unit Effort

DACS Florida Department of Agriculture and Consumer Services

DO Dissolved oxygen in water

FAC Florida Administrative Code

FDEP Florida Department of Environmental Protection

FDOT Florida Department of Transportation

FFWCC Florida Fish and Wildlife Conservation Commission

FLMNH Florida Museum of Natural History

FMRI Florida Marine Research Institute

FNAI Florida Natural Areas Inventory

LIDAR Light Detection and Ranging

mgd Million gallons per day

NFF National Flood Frequency program

NPS Non Point Source Pollution

NWFWMD Northwest Florida Water Management District

NWI National Wetlands Inventory

NWR St. Marks National Wildlife Refuge

NWS National Weather Service

OFW Outstanding Florida Water

ppt Parts per thousand

SAV Submerged Aquatic Vegetation

SKA Sensitive Karst Area Designation

SRWMD Suwannee River Water Management District

STORET U.S. EPA’s Storage and Retrieval water quality database

SCI Stream Condition Index

SWIM Surface Water Improvement and Management Program

TMDL Total Maximum Daily Load

TKN Total Kjeldahl Nitrogen in water

TN Total Nitrogen in water

TP Total Phosphorus in water

USEPA United States Environmental Protection Agency

USGS United States Geological Survey

WBID Water body Identification Number
1

LOWER ST. MARKS RIVER/WAKULLA RIVER/APALACHEE BAY

RESOURCE CHARACTERIZATION

1.0 INTRODUCTION

1.1 Purpose and Scope

The St. Marks River Watershed was included by the Northwest Florida Water Management District 

(NWFWMD) as one of its priority water bodies in the Surface Water Improvement and 

Management (SWIM) Program in an effort to preserve and protect this area from further 

degradation. The SWIM Program was initiated by the Florida legislature in 1987 to prioritize 

surface waters of the state and to develop and implement plans to improve the quality of these 

waters and their associated resources. The five water management districts were directed to carry 

out the SWIM Program under the aegis of the Florida Department of Environmental Regulation 

(now the Florida Department of Environmental Protection). The SWIM Plan for the St. Marks 

River Watershed was approved in 1997 and a draft revision of the plan (2009) was presented at a 

public workshop in August 2009 to incorporate input from the community and stakeholders prior to 

final adoption. The plan provides a framework to address strategic priorities of water quality, 

natural systems, and flood protection with the goal of long-term sustainability of the watershed 

ecosystem. The current programs and initiatives of the NWFWMD supportive of the SWIM 

Program are provided in the SWIM Update (2009) plan and include a broad range of activities to 

manage and protect ground water and surface water resources. The cumulative effect of these 

efforts results in significant protection and improvement in the watershed.

1.2 Watershed Research and Evaluations

Numerous studies and evaluations related to the St. Marks watershed provide a broad range of 

information including ground water quality (Madonia 1977; Clemens 1988; FDEP 2003; Barrios 

and DeFosset 2005, 2006), springs inventory (Scott et al. 2004; Barrios 2006), and karst/geological 

features (Johnston and Bush 1988; Davis 1996; Pratt et al. 1996; Benoit et al. 1992). Other studies 

have focused on urban stormwater management (Bartel et al. 1991) and nutrient loading to the 

watershed (Chelette et al. 2002; Davis and Katz 2007). The primary focus of this study is to 

provide a detailed characterization and description of the water resources and natural systems of the 

lower St. Marks River and Wakulla River. For the purpose of this resource characterization, 

operational boundaries of the study area are restricted to the Wakulla River, St. Marks River from 

the rise near the border between Leon and Wakulla Counties to the mouth near the St. Marks 

Lighthouse, and adjacent portions of Apalachee Bay.

1.3 Watershed Protection and Preservation

The NWFWMD uses a variety of management strategies and tactics that are identified in the SWIM 

Update (2009) plan to restore, protect and preserve the water resources in the watershed. The goal 

as provided in the plan: “The St. Marks River watershed shall be managed to ensure the long-term 

sustainability of watershed resources, values, and functions. This shall encompass preservation 

and, where necessary, restoration of ecosystem health and integrity”. Some of the ongoing 
2

activities undertaken by the NWFWMD include: hydrologic data collection and monitoring, 

freshwater needs assessment, local stormwater planning assistance, construction of stormwater 

retrofit facilities and implementation of BMPs, integration of the Flood Hazard Map Modernization 

Program, preservation of critical lands and habitats, ecological restoration, public education and 

outreach, and reuse of reclaimed water. The implementation of these activities is outlined in the 

SWIM plan.

In addition to these activities, the NWFWMD initiated a program of water quality protection in the 

watershed through less-than-fee land acquisition. In “less-than-fee” purchases, the NWFWMD 

acquires only those rights in the property (i.e., development and land use conversion rights) that are 

needed to accomplish specific resource and environmental protection goals. This method enables 

the protection of more land with limited funds and the property remains in private ownership and 

thus remains on the local property tax rolls. As of 2007, the NWFWMD had approximately 1,181 

acres under less-than-fee acquisition. Nearly 45,650 acres have been identified for possible lessthan-fee acquisition (NWFWMD 2009). In 2003, the NWFWMD and the City of Tallahassee-Leon 

County BluePrint 2000 Intergovernmental Agency developed a five-year Memorandum of 

Agreement (MOA) to work cooperatively to acquire property in the St. Marks basin in Leon 

County. The overall goal of the MOA is to protect and preserve water resources of the basin.

Public lands are prominent in the basin and consist of portions of the Apalachicola National Forest, 

the Wakulla State Forest, the Edward Ball Wakulla Springs State Park, the St. Marks River State 

Park and the St. Marks National Wildlife Refuge. The Tallahassee-St. Marks Historic Railroad 

State Trail (bicycle trail from Tallahassee to St. Marks), the San Marcos de Apalachee Historic 

State Park (old Spanish fort at St. Marks), Tall Timbers Nature Conservancy, The Nature 

Conservancy, the City of Tallahassee and Leon County also have conservation land in the basin. A 

significant portion of the lower St. Marks basin and adjacent lands lie within the St. Marks National 

Wildlife Refuge. This refuge was established in 1931 to provide wintering grounds for migratory 

bird species. The refuge occupies nearly 68,000 acres in Jefferson, Wakulla, and Taylor counties 

and includes 32,000 acres of aquatic habitat in Apalachee Bay. 

Freshwater inflows are a dominant influence on habitat and biological resources within the St. 

Marks/Wakulla/Apalachee Bay system. The quantity, quality and timing of these discharges are 

important to maintaining the riverine and estuarine conditions found here. Activities in the drainage 

basin (e.g., the City of Tallahassee’s wastewater treatment spray field in SE Leon County and future 

development in the watershed) have the potential to significantly affect aquatic resources in the 

watershed. The following report describes these natural resources within the system potentially at 

risk for impacts arising from modifications to the quality and quantity of freshwater inflow.
3

2.0 ST. MARKS RIVER WATERSHED

The St. Marks River watershed (Figure 1) covers an area of about 1,170 square miles (748,800 

acres). The northern boundary of the watershed starts near Thomasville Georgia and extends 

approximately 52 miles to the south terminating at Apalachee Bay. The majority of the watershed 

(about 91 percent) is in three Florida counties, Leon (~ 40% of the watershed), Wakulla (~ 30% of 

the watershed) and Jefferson (~ 21% of the watershed). A watershed is the geographic area of land 

that drains to a common destination, in this case the St. Marks River and Apalachee Bay. The 

watershed has two rivers, the St. Marks River and Wakulla River (which is a tributary of the lower 

St. Marks River), that capture the majority of the surface drainage in the basin. Other major surface 

water features within the watershed are lakes Miccosukee, Lafayette, and Munson, and the coastal 

receiving waters of Apalachee Bay. In addition to surface water drainage in the watershed, ground

water provides a significant amount of the flow into both rivers and Apalachee Bay. The regional 

ground water contribution zone is represented in Figure 1 and includes an area of approximately 

1,963 square miles (1,256,061 acres) which is about 68% larger in area than the surface watershed. 

The estimated ground water contribution zone for the St. Marks River watershed was delineated 

using the potentiometric surface altitude of the Floridan Aquifer to develop ground water contours 

and contribution zone boundaries (Chelette et al. 2002; Barrios 2006). This contribution zone may 

change slightly depending on climatic variability that effects recharge, pumping and the 

potentiometric surface. The hydrogeology of the watershed is characterized by the complex 

interaction between surface water and ground water due to the limestone bedrock below the region.

2.1 Hydrogeology of Watershed

The Floridan Aquifer is a thick sequence of carbonate rocks and forms one of the most productive 

ground water supplies in the United States due to the its highly porous structure. The Floridan 

Aquifer underlies the entire St. Marks River Watershed. The watershed encompasses two main 

physiographic regions: the Tallahassee Hills subdivision of the Northern Highlands in the north, 

and the coastal lowlands in the southern portion of the watershed (Pratt et al. 1996). The watershed 

is described as a karst topography, which is a term commonly used to describe this type of 

carbonate geological formation and is characterized by dissolution features such as sinkholes, 

swallets, springs, disappearing streams, and underground drainage channels. These dissolution 

features provide pathways for pollutants from stormwater runoff and other anthropogenic sources to 

be rapidly transported into the ground water.

The topographic feature that separates the Tallahassee Hills and the coastal plain is an escarpment 

(Cody Scarp) that runs east-west across southern Leon County (Figure 1). The Cody Scarp marks 

the northern encroachment of the sea in the Pleistocene epoch and is identified by a significant drop 

in elevation between the Tallahassee Hills and coastal plain that removed Miocene and Pliocene 

sediments exposing carbonates of the St. Marks Formation and Suwannee limestone (Pratt et al. 

1996). The Upper Floridan Aquifer in the Tallahassee Hills region of the watershed is considered to 

be semi-confined due to clay soils overlaying the aquifer that become thicker to the north. The 

layer of sediments overlaying the aquifer in the Tallahassee Hills slows recharge as it moves 

downward to the water table providing filtering in combination with biological and chemical

 
4

Figure 1 – St. Marks River & Apalachee Bay Watershed
5

processes that remove contaminants as it slowly migrates downward. Much of the surface drainage 

north of the Cody Scarp drains to lakes that have outlet channels that intermittently discharge 

downstream depending on rainfall. Most of the lakes have one or more sinkholes that breach the 

confining layer and discharge into the water table. 

2.2 Woodville Karst Plain

The Woodville Karst Plain is an area that has been designated south of the Cody Scarp starting in 

southern Leon County and extending to the coast in Wakulla County and including a portion of 

southwest Jefferson County (Figure 2). This is an area where the top of the Floridan Aquifer is at or 

near land surface and is considered unconfined due to a thin or absent layer of soil that slows 

recharge to the aquifer (Pratt et al. 1996). The occurrence of karst features in the landscape 

increases dramatically below the Cody Scarp in the Woodville Karst Plain as shown in Figure 2. 

The proximity of the Floridan Aquifer to the surface increases the erosive processes on the 

limestone and accelerates the formation of dissolution features by slightly acidic surface water as it 

moves downward. Approximately 42 sinkholes north of the Cody Scarp have been identified and 

mapped by state and local agencies with about 232 sinkholes and 66 springs mapped below the 

scarp. There are likely many more sinkholes and springs that have yet to be mapped.

A digital elevation model of the watershed (Figure 3) was developed by the NWFWMD using Light 

Detection and Ranging (LIDAR) data to accurately measure bare earth elevations and map 

topographic features of landscape. Close examination of this map indicates that the landscape has 

many more sinkholes and karst features, particularly in the Woodville Karts Plain, than the karstic 

features currently identified. This new mapping technique provides a new tool to help locate and 

map karst features and identify areas that may require additional measures to protect the Floridan 

Aquifer and ground water resources from contamination. 

An area in northern Wakulla County along U.S. Highway 319 that has a high concentration of sink 

holes and karst features is shown in the digital elevation map in Figure 4. This elevation map was 

created using 2008 LiDAR data with a resolution of about ± 0.5 feet; previous topographic maps of 

this area had 5 foot contours. The red circles on the map indicate sink holes that have previously 

been indentified and mapped in the Future Land Use Mapping (FLUM) database. LiDAR data 

provides a valuable tool to accurately map the landscape and locate karst features that have not 

previously been identified as shown in Figure 4. The small blue circular features in the figure

indicate numerous sinkholes and dissolution karst features that have not been mapped and may have 

a hydraulic connection with the Upper Floridan Aquifer. Identification and protection of sink holes 

and karst features will be an increasingly important responsibility for state and local governments to

protect the Floridan Aquifer from future contamination and degradation.

2.3 Sensitive Karst Areas

The NWFWMD and the Florida Department of Environmental Protection (FDEP) have recognized 

the potential for contamination to ground water resources in karst regions of the panhandle and have

developed new rules to minimize contamination of the Floridan Aquifer by stormwater runoff from 

new development. The Environmental Resource Permitting Handbook (FDEP and NWFWMD

2007) designated several areas of the panhandle as Sensitive Karst Areas (SKAs) which include
6

Figure 2 – Surface Water and Identified Karst Features of the St. Marks River Watershed
7

Figure 3 – Digital Elevation Map of the St. Marks River Watershed
8

Figure 4 – Digital Elevation Map of River Sink Area in North Wakulla County

(Numerous Unmapped Karst Features Indicated On Map)
9

the St. Marks River Watershed (Figure 5). The requirements for new stormwater management 

systems in these sensitive areas include additional design criteria that are intended to prevent the 

direct discharge of stormwater runoff from new development into the Floridan Aquifer.

Figure 5 – Sensitive Karst Areas of St. Marks River Watershed
10

2.4 Non-Point Source Runoff

Non-point source (NPS) pollution originates from the general landscape with no single source and 

is transported in stormwater runoff. It is considered one of the most significant sources of 

contamination to surface and ground water resources in Florida. FDEP, water management districts 

and local governments regulate the discharge of stormwater in the state. Stormwater management 

and pollutant load reduction criteria are outlined in the Florida Administrative Code (FAC) 62-40. 

This rule establishes that stormwater design criteria provide at least 80 percent reduction of the 

average annual load of pollutants that cause or contribute to violations of State Water Quality 

Standards. When the stormwater system discharges to an Outstanding Florida Water (OFW), the 

design and performance criteria increase to 95 percent reduction (Harper and Baker 2007).

Urban land use has been shown to have the highest stormwater-generated NPS pollution per acre 

due to increased impervious surface area that increases runoff. Urban areas also typically have less 

vegetation and wetland areas that moderate flows and provide recharge, storage and treatment for 

runoff. In urban areas, lawns, roadways, buildings, commercial and institutional properties all 

contribute to NPS pollution. The pollutants include nutrients (primarily nitrogen and phosphorus), 

heavy metals, pesticides, petroleum products (oil, gas, grease, etc.), sediment and other 

contaminants that degrade water resources and natural systems. In the St. Marks River Watershed, 

a large percentage of the stormwater runoff that carries NPS pollution enters the Floridan Aquifer 

through sinks and swallets.

Many stormwater improvement projects are directed at correcting existing flooding problems. 

These projects typically also improve water quality by providing additional treatment, storage and 

reduction of nutrient loads by aquatic vegetation. The City of Tallahassee and Leon County have 

stormwater utility fees to help pay for stormwater improvements along with additional funding 

provided by NWFWMD, FDEP and federal grants. The City and County have jointly spent about 

$183,775,877 on completed or ongoing stormwater improvements in the Lake Lafayette and Lake 

Munson sub-basins that drain to the St. Marks River watershed (Tallahassee-Leon County 

Watershed Protection Initiative web site).

Agricultural land use, including silviculture, also contributes to NPS pollution. The use of best 

management practices (BMPs) including proper use of fertilizer and pesticides, erosion control 

measures, proper irrigation practices and providing buffers near wetlands and other water resources 

can minimize NPS pollution from agriculture.

The population of Leon County increased from 148,655 in 1980 to 272,497 in 2006 and almost 

tripled in Wakulla County from 10,887 in 1980 to 28,393 in 2006 (University of Florida, Bureau of 

Economic and Business Research). The additional wastewater generated from this population 

increase has been identified as a growing source of nutrients and other contaminants in the 

watershed. The City of Tallahassee southeast wastewater spray field has been identified as a source 

of pollution (primarily nutrients) in the basin. The City is completing a waste water reuse facility in 

southeast Tallahassee that will reduce nutrient loads into the ground water. Septic tanks have also 

been identified as an increasing source of nutrient pollution particularly in the watershed. Proper 

maintenance of existing septic systems and installation of performance-based systems to reduce 

nutrient loads to the ground water will be necessary to protect water resources.
11

3.0 LAND USE AND LAND COVER

Land use and land cover have a significant effect on the function and hydrologic characteristics of 

watersheds. Land use changes and urbanization affect peak flow characteristics, changes in total 

runoff and changes in the quality of water (Leopold 1968). In urban areas and medium to high 

density residential and commercial land use areas, impervious surfaces (primarily buildings and 

paved surfaces) allow stormwater to flow unimpeded downhill transporting pollutants such as 

sediment, oil, pesticides, fertilizers and other contaminants into streams, lakes and ground water. In 

the St. Marks Watershed a significant amount of the stormwater runoff is eventually transported 

into the ground water through sinkholes.

The major land use/land cover in the St. 

Marks River Watershed is upland forest 

which covers about 550 square miles 

(352,133 acres). The upland forests in the 

watershed primarily include natural 

forested land and silviculture (Figure 6). 

Wetlands are the next largest land cover 

and include about 302 square miles 

(192,988 acres). Agricultural land use and 

developed land use cover roughly equal 

areas of the basin, 147 square miles 

(94,369 acres) and 142 square miles 

(91,036 acres), respectively. The 

developed land use category includes a 

combination of residential, commercial and 

industrial land uses. Open water covers 

only about 16 square miles (10,017 acres) 

in the watershed and primarily includes 

lakes, rivers, streams and ponds. 

Institutional land use (educational, 

religious, health and military facilities) 

encompasses about 8 square miles (5,197 acres). Recreational and open land accounts for the 

remaining land use; these categories include about 3 square miles (1773 acres) and 2 square miles 

(1,286 acres), respectively.

3.1 Hydrologic Impacts of Land Use

Land uses that have the greatest impact on the hydrology of the watershed are the developed and 

institutional uses due to the significant alteration of flow and diminished recharge created by 

landscape changes and impervious surfaces. Land cover and uses associated with forested land, 

wetlands and agriculture (that use best management practices) typically allow for more absorption 

of rainfall and runoff. Limited impervious surface allows greater recharge in these areas and the 

presence of vegetation results in increased transpiration, both of which contribute to a reduction in 

the quantity and rate at which water runs off the land.

Figure 6 - St. Marks Watershed Land Use By Category

13%

12%

1%

0.2%

0.2%

47%

1%

26%

Agriculture

Developed Areas

Institutional

Open Land

Recreational

Upland Forests

Water

Wetlands
12

The two most developed sub-basins in the St. Marks River Watershed are the Lake Lafayette and 

Lake Munson sub-basins. These two basins include a large proportion of the developed land use 

areas in Leon County. The Lake Lafayette sub-basin is about 53,956 acres with about 46 percent of 

the land use developed and institutional. The Lake Munson sub-basin is about 43,494 acres with 

about 55 percent of the land use developed and institutional. The land area of these two sub-basins 

combined (97,090 acres) is only about 13 percent of the entire St. Marks River Watershed (748,800 

acres) yet it accounts for 51% of the developed and institutional acreage in the watershed (Figure 7).

The northern-most area of the watershed in Georgia is 108 square miles (69,308 acres) or about 9% 

of the watershed. The predominant land cover is upland forest (75%) with agriculture (12%), 

wetlands (7%), developed (5%) and water (1%) making up the remaining land use/land cover.

3.2 Conservation Lands

Conservation lands cover a significant portion (about 33%) of the basin and include federal, state, 

local government and private land (Figure 8). Conservation lands provide many benefits including 

protection of natural systems, recharge in the watershed, flood control, recreation and protection of 

historical and environmentally sensitive areas. Conservation lands also provide direct economic 

benefits for local communities by attracting visitors that spend money on goods and services. 

Forest and natural lands also provide the resource base for other economically beneficial activities 

such as timbering and recreational related businesses.

The Apalachicola National Forest is the largest national forest in Florida covering 571,088 acres, of 

which 106,944 acres are in the St. Marks River watershed. The management strategy for the 

national forest includes a sustainable multi-use concept that includes a diverse array of activities 

that provide economic value and manage and protect the natural environment. Recreational 

activities in the national forest and surrounding public lands include: camping, hiking, hunting, 

fishing, boating, bird and wildlife watching, swimming, horseback riding, mountain biking, off-road 

vehicle use and visiting natural and historic landmarks. Visitors to the national forest stimulate the 

local economy with the goods and services they purchase which include food, gas, lodging, supplies 

and services of guides and eco-tourism related businesses. The forest is also managed for timber 

production that provides additional economic benefits to local communities.

The St. Marks National Wildlife Refuge is the next largest conservation area in the watershed and 

encompasses the majority of the land along the coast in the lower St. Marks River Watershed. The 

wildlife refuge includes 50,184 acres in the lower St. Marks Watershed and provides valuable 

resource protection, wildlife habitat and recreational opportunities. Wakulla Springs State Park 

covers 2,860 acres and protects the area surrounding the main spring and the first three miles of the 

Wakulla River. An economic impact study was completed for four Florida spring state parks in 

2003 by the Florida State University (Bonn and Bell 2003). The report concluded that 180,793 

people visited Wakulla Springs in 2002 and about 70 % of these visitors were from outside Wakulla 

County. The report estimated that Wakulla Springs-related visitors spent about $22.19 million in 

Wakulla County on food, lodging, admission fees, entertainment, transportation, and associated 

expenditures in 2002 (Bonn and Bell 2003). This clearly demonstrates the positive economic 

impacts of conservation lands for local communities along with the resource protection provided by 

this type of land use.
13

Figure 7 - Land Use and Land Cover in the St. Marks River Watershed
14

Figure 8 – Conservation Land in the St. Marks River Watershed
15

4.0 ST. MARKS RIVER HYDROLOGY

The St. Marks River originates in eastern Leon County near an area of connected wetlands and 

travels south about 35 miles to Apalachee Bay. The upper portion of the river is primarily 

comprised of a combination of wetlands, intermittent streams and sinking streams. The main 

defined portion of the river arises in the Tallahassee Hills of northeastern Leon County as little 

more than a collection of connected wetlands (Barrios and DeFosset 2006). The upper St. Marks 

River receives intermittent surface flow from four sub-basins in the upper watershed, Lake 

Miccosukee, Patty Sink Drain, Black Creek (upper) and Lake Lafayette sub-basins (Figure 9). 

These sub-basins function as closed basins much of the time and drain to sinkholes or wetlands 

without direct surface discharge to the St. Marks River. The surface topography shown in Figure 3

(Digital Elevation Map of the St. Marks River Watershed) indicates that these sub-basins 

discharged to the Upper St. Marks River in the past before sinkholes captured the stream flow 

diverting it underground. During wet periods, high stream flows exceed the drainage capacity of 

sinkholes and streams in the upper basin flow directly into the St. Marks River or into wetlands that 

contribute flow to the upper river.

4.1 Lake Lafayette Sub-Basin

During high flow periods the river can pick up significant flow from the Lake Lafayette sub-basin 

which has a high percentage of development and impervious surface area. Lake Lafayette is a 

shallow depressional lake typical of lakes in the area. It has three distinct sections: Upper Lake 

Lafayette, Piney Z Lake (created by impoundments and situated between the upper and lower lake)

and Lower Lake Lafayette. A large sinkhole in the northwest corner of Upper Lake Lafayette 

typically swallows a significant amount of the runoff from the sub-basin during low to moderate 

flow periods. During higher flow periods surface drainage flows through Piney Z Lake into Lower 

Lake Lafayette and combines with runoff from the Alford Arm Tributary and flows east under 

Chaires Cross Road and into the St. Marks River.

There is a strong correlation between the river flow at the U.S. Geological Survey (USGS) station 

near Natural Bridge and the NWFWMD stage recorder on the Lake Lafayette Outfall channel 

(Figure 10). There is an 80 percent correlation between the outfall stage level (during periods of 

discharge to the river) and the river flow indicating a significant contribution of discharge from the 

Lake Lafayette sub-basin to the river during moderate to high flow periods. The flat periods on the 

bottom of the Lake Lafayette graph are periods when the outfall channel is dry and is not 

discharging to the river.

4.2 Lower St. Marks Basin

The river continues to pick up additional flow from wetland areas, intermittent streams and small 

seeps and springs as it crosses the Cody Scarp and flows south. Two second-order springs, Chicken 

Branch Spring and Horn Springs, contribute flow to the river above Natural Bridge in southeast 

Leon County. At Natural Bridge in southeast Leon County the entire river disappears underground 

into sinks and reemerges a half mile downstream at St. Marks Rise. A series of 17 synoptic 

discharge measurements were completed between 2003 and 2009 by NWFWMD above and below
16

Figure 9 – St. Marks River Watershed Sub-Basins
17

Figure 10 – St. Marks River and Lake Lafayette Outfall Flows

the St. Marks Rise to quantify the additional contribution of ground water to the river below the 

rise. The upstream and downstream measurements were completed within a few hours of each 

other to provide an accurate comparison of river flow above and below the rise. The river flow 

increased between 53 to 87 percent below the river rise (Figure 11) with an average increase of 80 

percent for the 17 instantaneous measurements completed to date. These measurements indicate the 

majority of the river flow below the rise is additional ground water flow as it re-emerges, under the

measured flow conditions. The measurements completed to date have all been during moderate to 

low flow periods, the percentage of ground and surface water contribution to the river below the rise 

likely has a different ground water/surface water ratio under high flow conditions.

A baseflow separation analysis was performed on the daily flow record for the St. Marks River 

below the rise to estimate the baseflow (ground water storage) component of the river flow. This 

analysis provides an estimate of the proportion of flow from direct surface runoff and baseflow 

derived from ground water storage. The results of three baseflow separation methods were 

analyzed and included Eckhardt, BFlow and local minimum methods (Lim et al. 2005). The final 

baseflow separation analysis was performed using a combination of the Eckhardt and local 

minimum (modified HYSEP) to develop a conservative result that does not over estimate the 

baseflow component. These results combined with discharge measurements completed above and 

below the rise confirm that the St. Marks River Rise is a first magnitude spring with average 

discharge above 100 cfs.

42.00

44.00

46.00

48.00

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60.00

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01/01/8807/01/8801/01/8907/01/8901/01/9007/01/9001/01/9107/01/9101/01/9207/01/9201/01/9307/01/9301/01/9407/01/9401/01/9507/01/9501/01/9607/01/9601/01/9707/01/9701/01/9807/01/9801/01/9907/01/9901/01/0007/01/0001/01/0107/01/0101/01/0207/01/0201/01/0307/01/0301/01/0407/01/0401/01/0507/01/0501/01/0607/01/0601/01/0707/01/0701/01/0807/01/0801/01/09

Outfall Level (Feet, NGVD 1929)

St. Marks Discharge (cfs)

St. Marks River Discharge 

Lake Lafayette Outfall Stage
18

Figure 12 shows the river flow at the USGS station below the river rise and the estimated baseflow 

(ground water contribution) using the baseflow separation analysis. The differences in flow 

between the paired instantaneous measurements above and below the rise (Figure 12) indicate the 

amount of additional ground water contribution to the river from the spring at the rise. The 

instantaneous discharge measurements below the rise may be different than the mean daily river 

flow (represented by the solid blue line) due to tidal influence, backwater and other factors. The 

instantaneous measurements above the rise are represented by blue circles and during low flow 

periods include a significant amount of ground water from springs above the rise.

The estimated baseflow contribution to the St. Marks River below the rise is about 77 percent of the 

river flow on average for the 51-year mean daily flow period of record using the baseflow 

separation analysis. The cumulative ground water and surface water contribution to the river for 

period of record is provided in Figure 13. The cumulative flow distribution indicates the influence 

of the ground water storage component of the aquifer and the importance of ground water flow to 

the lower St. Marks River system.

Figure 11 – Discharge Measurements at St. Marks River Rise

When the river re-emerges below Natural Bridge it flows south about 11.4 miles to the confluence 

with the Wakulla River at the town of St. Marks. The majority of the St. Marks River Watershed 

(93 percent of the watershed) lies above Natural Bridge Rise. While the river continues to pick up 

inflow in the lower reaches, the majority of the input to the river above the confluence with the 

Wakulla River is from the drainage area (both surface and ground water flow contribution) above 

the rise. After joining with the Wakulla River, the St. Marks River flows about 4 miles south 

through coastal estuarine habitat and empties into Apalachee Bay near the St. Marks Lighthouse.

60.4%

52.8%

86.0%

83.1%

87.4% 86.0%

81.4% 80.0%

55.5%

86.4% 85.5%

87.4% 86.2%

82.0%

86.4%

82.5%

86.0%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

0

100

200

300

400

500

600

700

800

04/09/0307/16/0310/07/0301/06/0404/07/0408/03/0411/02/0402/04/0504/25/0511/01/0501/09/0804/08/0807/31/0810/01/0801/29/0906/22/0908/05/09

Discharge (cfs)

Discharge Measurements

River Flow Above Rise

River Flow Below Rise

Flow Increase Below Rise
19

Figure 12 – Baseflow Estimation at St. Marks River Rise

Figure 13 – Cumulative Baseflow (Ground Water Storage) and Surface

Discharge at St. Marks Rise (1957 – June 2009)

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01/01/0303/01/0305/01/0307/01/0309/01/0311/01/0301/01/0403/01/0405/01/0407/01/0409/01/0411/01/0401/01/0503/01/0505/01/0507/01/0509/01/0511/01/0501/01/0603/01/0605/01/0607/01/0609/01/0611/01/0601/01/0703/01/0705/01/0707/01/0709/01/0711/01/0701/01/0803/01/0805/01/0807/01/0809/01/0811/01/0801/01/0903/01/0905/01/09

Discharge (cfs)

Streamflow Below Rise

Estimated Baseflow Below Rise

Measured Flow Below Rise

Measured Flow Above Rise
20

5.0 WAKULLA RIVER HYDROLOGY

The main tributary of the St. Marks River is the Wakulla River, which originates in northern 

Wakulla County at Wakulla Springs and flows south approximately ten miles before joining the St. 

Marks River at the City of St. Marks. The Wakulla River is a classic spring run and receives most

of the freshwater flow from springs or small spring runs that discharge into the river. The subbasins that contribute flow to the Wakulla River include: Munson/McBride Slough, Bradford 

Brook, Fischer Creek, Black Creek and Wakulla River (Figure 9). The majority of the flow into the 

Wakulla River is discharged through the main spring vent at Edward Ball Wakulla Springs State 

Park.

In addition to the main spring vent that discharges on average about 450 cfs (about 291 mgd), 28

additional springs have been identified in close proximity to the river that discharge directly or 

through spring runs into the river (Barrios 2006). The combined discharge of these smaller springs 

represents a small percentage of the Wakulla River flow. Sally Ward Spring had the next highest 

flow after Wakulla Springs with a measured discharge of 12.5 cfs (Second Magnitude). Five 

additional springs had flows from 1 to 6 cfs (Third Magnitude) with the remaining springs 

discharging less than 1 cfs. 

5.1 Sinking Streams

Excluding the Wakulla River, all major streams in the Wakulla River Watershed eventually drain to 

sinkholes and become sub-surface flow. Portions of the drainage from these sinking streams

reappear throughout the Woodville Karst Plain contributing to the outflows of the numerous springs 

such as Wakulla Spring and vents at Spring Creek.

The Munson/McBride sub-basin of the Wakulla River Watershed collects the majority of 

stormwater from the west and south side of the City of Tallahassee. Much of this stormwater runoff 

flows through Lake Munson and continues flowing south about eight miles in Munson Slough to 

Ames Sink where it flows underground. Dye trace studies conducted in 2005 by Hazlett-Kincaid 

indicated that a portion of the runoff entering Ames Sink from Munson Slough emerges from 

Indian, Sally Ward and Wakulla Springs within 14-22 days (Kincaid et al. 2007a). Cave divers 

have also mapped underground tunnels that connect Fisher Creek and Black Creek (sinking streams 

near the Leon/Wakulla county line in the Leon Sinks Geological Area) to Indian Springs and 

Wakulla Springs.

The surface topography (Figure 14) indicates that sinking streams like Munson Slough, Fisher 

Creek and Black Creek were surface streams in the past and drained directly to the Wakulla River. 

The erosive processes on the limestone in the upper Floridan Aquifer, particularly in the Woodville 

Karst Plain with little or no confinement, created sinkholes and other dissolution features creating 

the numerous sinking streams and springs we see today in the watershed.

One of the challenges today is to recognize the highly interactive connection between surface and 

ground water resources and the direct impacts our activities in the watershed have on the water 

resources. Best management practices (including stormwater, wastewater treatment and disposal, 

agricultural activities and public education to reduce non-point pollution) will need to continue to 

be implemented to improve and protect both surface and ground water resources. The City of 
21

Tallahassee and Leon County have completed numerous stormwater retrofit projects in the 

Munson/McBride sub-basin in recent years that provide flood attenuation and improve water 

quality. These ongoing efforts continue to improve water quality and reduce the impairment of 

downstream water resources that include streams, lakes, springs and the Wakulla and St. Marks 

Rivers.

Figure 14 – Wakulla River Digital Elevation Map
22

6.0 ST. MARKS WATERSHED DISCHARGE 

The primary freshwater inflows to the lower reaches of the St. Marks River Watershed are from the 

St. Marks River and its tributary the Wakulla River. As previously discussed, a significant portion 

the flow in both rivers is spring flow into the rivers. The St. Marks River flows directly into 

Apalachee Bay; freshwater also enters the bay from the Ochlocknee River on its western side as 

well as through a number of adjacent small tidal creeks and springs, particularly the Spring Creek 

Springs Group and several offshore vents (Scott et al. 2004). Further to the east, the Aucilla, 

Econfina and Fenholloway Rivers provide freshwater inflows to the bay. The comparative annual 

discharge for the rivers that flow into Apalachee Bay is shown in Figure 15. The St. Marks and 

Wakulla Rivers receive a large proportion of their flow from ground water and have less annual 

flow variability than the other major rivers discharging to the bay. 

Figure 15 – Freshwater Inflows to Apalachee Bay

6.1 St. Marks River Flow

In the lower St. Marks River Watershed there are two continuous flow monitoring stations operated 

by the USGS on the St. Marks River, one located below the river rise (St. Marks River near 

Newport) and the other on the Wakulla River at CR 365 (Wakulla River near Crawfordville) at the 

south end of the Wakulla Springs State Park. In addition, there are continuous monitoring stations 

0

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2001 2002 2003 2004 2005 2006 2007 2008

Mean Annual Discharge (cfs)

Year

Ochlockonee River @ Smith Crk

St. Marks & Wakulla rivers

Aucilla River near mouth

Econfina River near Perry

Fenholloway River near Perry
23

operated by the NWFWMD that collect discharge, river stage, rainfall, and other environmental 

data (Figure 16). The USGS also operates a monitoring station in the estuary at Spring Creek that 

collects discharge, tidal, and other environmental data.

Figure 16 - Monitoring Stations in the Lower St. Marks River Watershed
24

The St. Marks River (Newport) station is located about 0.6 miles south of the Natural Bridge Rise 

where the river re-emerges after flowing below ground. This station has been in operation since 

October 1956 with a 20-month break of record between October 1994 and June 1996. The surface 

drainage area for this station is about 561 square miles (359,308 acres) which is approximately 93 

percent of the surface drainage for the river. The river picks up additional flow below the USGS 

station before it is joined by the Wakulla River; but this percentage is small relative to total river 

flow because the majority of the surface drainage and ground water contribution area is above the

gauging station.

The mean daily discharge at the Newport station has a wide range of flows as shown in Figure 17. 

The daily mean flow for the period of record ranged from a high of 5,820 cfs in August 2008, when 

Tropical Storm Fay generated over 20 inches of rainfall in parts of the watershed over a 3-day

period, to a low of 251cfs during a severe drought in October 2001. The mean discharge for the 51-

year period of record is 695 cfs (449 mgd). Rainfall distribution and intensity in the watershed is 

the primary factor influencing the magnitude and timing of flows on the St. Marks and Wakulla 

rivers.

Figure 17 - Daily Mean Discharge – St. Marks River (1957-June 2009)

(Missing Record Period: 10/24/1994 - 06/30/1996)

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01/01/5701/01/5901/01/6101/01/6301/01/6501/01/6701/01/6901/01/7101/01/7301/01/7501/01/7701/01/7901/01/8101/01/8301/01/8501/01/8701/01/8901/01/9101/01/9301/01/9501/01/9701/01/9901/01/0101/01/0301/01/0501/01/0701/01/09

Discharge (cfs)

Mean Daily Flow

Mean (1957-June 2009)
25

6.2 Rainfall and Flow

The National Weather Service 

(NWS) operates a rainfall station in 

Tallahassee that reflects the longterm average precipitation in the St. 

Marks Watershed. Rainfall 

distribution can be highly variable for 

individual rainfall events across small 

geographic areas but long-term 

precipitation records are 

representative of rainfall in the 

watershed.

The St. Marks River Watershed 

typically receives abundant rainfall 

throughout the year. The current 

long-term average annual rainfall in 

Tallahassee for the years 1971 

through 2000 (National Weather 

Service) is 63.21 inches (Figure 18). 

During the last 61 years the highest 

annual rainfall in Tallahassee was 

104.18 inches in 1964 and the lowest 

annual amount was 30.98 inches in 

1954; the next two lowest years were 

2007 and 2000 (44.47 inches and 

44.51 inches respectively).

Rainfall can be highly variable from 

year to year depending climatic 

conditions and storm systems 

affecting the region (Figure 19). The 

long-term rainfall record indicates 

summer months (June - August) are 

typically the wettest season of the 

year receiving on average about 22

inches of rainfall (Figure 20). This is 

due to tropical storm systems and 

convective thunderstorm activity 

which occur most frequently during 

the summer months. The fall months 

in the panhandle usually receive the 

lowest rainfall, with October 

normally receiving the least monthly 

precipitation during the year followed 

by April (Figure 18). 

Figure 18 – Tallahassee Normal Monthly Rainfall

Figure 19 – Tallahassee Annual Rainfall (1948-2008)

Figure 20 – Tallahassee Normal Seasonal Rainfall

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Rainfall (inches)

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194819511954195719601963196619691972197519781981198419871990199319961999200220052008

Annual Rainfall (inches)

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Winter Spring Summer Fall

Rainfall (inches)

Mean Annual Rainfall = 63.21 inches
26

Flow variability in the St. Marks River is significantly less than other Florida panhandle rivers that 

are primarily fed by surface runoff. In Figure 21 a comparison of the daily mean flows for the 

Ochlockonee River (Havana) and the St. Marks River (Newport) for the 2004 – 2008 illustrates the 

variability of daily flows for the two rivers. The surface drainage area for the Ochlockonee River at 

Havana (1,140 square miles) is about twice the size of the St. Marks at Newport (561 square miles). 

The peak flow in August 2008 (runoff from Tropical Storm Fay) on the Ochlockonee River was 

34,300 cfs compared with a peak of discharge of 5,820 on the St. Mark River. The lowest flow on 

the Ochlockonee River for this record period was 26 cfs in October 2007 and the lowest flow on the 

St. Marks River was 333 cfs in November 2007. The St. Marks River has a significant baseflow 

contribution from ground water.

Figure 21 - Daily Mean Discharge – Ochlockonee and St. Marks Rivers

(2004 - 2008)

The range of observed flows for each calendar day (maximum, mean and minimum for complete 

years) is provided in Figure 22 for the St. Marks River at Newport. The highest flows for the period 

of record were observed in the summer and spring months, the lowest flows occurred during the 

fall. 

The high recharge rate and sinking streams in the Woodville Karst Plain contribute to the ground 

water inflow to the river and provide a significant proportion of the total flow. Travel time for 

precipitation to recharge the aquifer and re-emerge in the St. Marks watershed is highly variable and

20

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01/01/0403/01/0405/01/0407/01/0409/01/0411/01/0401/01/0503/01/0505/01/0507/01/0509/01/0511/01/0501/01/0603/01/0605/01/0607/01/0609/01/0611/01/0601/01/0703/01/0705/01/0707/01/0709/01/0711/01/0701/01/0803/01/0805/01/0807/01/0809/01/0811/01/08

Discharge (cfs)

Ochlockonee River @ Havana

St. Marks River @ Newport
27

Figure 22 - Daily Flow Characteristics – St. Marks River (1957 - 2008)

can be days, weeks or years depending on where the recharge occurs in the watershed. The USGS 

analyzed the relative age or resident time for ground water from four City of Tallahassee public 

water supply wells (Davis and Katz 2007). These wells were drilled to depths of 200 feet in 

southern Leon County to 450 feet in northern Leon County. The estimate age of ground water 

ranged from 7 to 31 years for these Floridan wells. The results also showed a consistent trend 

indicating relative age decreases from north to south in the watershed. Dye trace studies completed 

in 2006 and 2007 by Hazlett-Kincaid demonstrated that it took 45 – 60 days for ground water to 

travel from the two wells in southern Leon County to Wakulla Springs (Kincaid et al. 2007b).

6.3 St. Marks River Low-Flow Analyses

Analysis of the mean daily flows for the St. Marks River at Newport was completed using a LogPearson Type III probability distribution. This type of analysis provides probabilistic estimates of 

low and high flow frequencies and is typically used for stations with at least ten years of continuous 

flow record. The Newport station has a 51-year period of record from 1957 – 2008 with a period of 

missing data from October 1994 – June 1996. The low-flow statistics for the Newport station are 

provided in Figure 23 and Table 1. The low-flow recurrence (Figure 23) shows a convergence of 

flows for the 50- and 100-year recurrence intervals. This indicates a significant ground water 

contribution during low-flow conditions.

200

400

800

1600

3200

6400

Jan1

Jan15Jan29

Feb12Feb26

Mar11Mar25

Apr8

Apr22

May6

May20

Jun3

Jun17

Jul 1

Jul15Jul29

Aug12Aug26

Sep9

Sep23

Oct7

Oct21

Nov4

Nov18

Dec2

Dec16Dec30

Discharge (cfs)

Date

Calendar Day Peak Flow

Calendar Day Mean Flow

Calendar Day Low Flow
28

The lowest observed mean daily flow for the 51-year Newport record was 251 cfs in October 2001. 

This flow is equal to the 1Q100 which is the lowest one-day flow expected to occur in 100 years. 

This record low flow occurred after two significant drought years in 1999 and 2000 when the 

cumulative rainfall for the two years was 31.84 below normal. This record low flow occurred in 

October 2001 despite two tropical storms (Allison and Barry) bringing very high rainfall and wide 

spread flooding to the watershed in June and August of 2001, respectively. This delayed low flow 

response on the St. Marks River demonstrates the slow recharge rate of the aquifer in comparison 

with the rapid surface water response after rainfall events.

A widely used low-flow statistic is the 7Q10 which is defined as the lowest stream flow for seven 

consecutive days expected to occur once in 10 years. The 7Q10 statistic is used for regulatory 

purposes for stormwater and wastewater allocation, Total Maximum Daily Loads (TMDLs) and 

biological assessments. The 7Q10 for the Newport station on the St. Marks is 321 cfs (Table 1).

The 7Q10 for the Ochlockonee River at Havana is 31 cfs (Rumenik and Grubbs 1996) which is 

about one-tenth of the flow on the St. Marks. The Havana station has twice the contributing basin 

area as the Newport station which further illustrates the significant ground water influence on low 

flows on the St. Marks River.

Figure 23 - Low Flow Recurrence – St. Marks River at Newport

250

300

350

400

450

500

0.5 (2 Yr) 0.2 (5 Yr) 0.1 (10 Yr) 0.05 (20 Yr) 0.02 (50 Yr) .01 (100 Yr)

Discharge (cfs)

Probability (Recurrence Interval In Years)

90 Day 60 Day

30 Day 10 Day

7 Day 1 Day

Lowest Average Flow For Consecutive Days
29

Recurrence Lowest Average Flow for Indicated Consecutive Days (cubic feet per second)

Interval 1-day 2-day 3-day 7-day 10-day 30-day 60-day 90-day 183-day 365-day

100 Years 257 258 258 262 263 270 280 285 318 360

50 Years 271 272 272 276 278 286 297 304 342 388

20 Years 293 294 295 299 301 313 325 335 381 435

10 Years 315 316 317 321 324 338 352 365 418 480

5 Years 344 346 347 351 354 371 387 405 468 539

3 years 375 376 377 381 385 405 423 447 518 599

2 Years 410 412 413 417 421 443 465 496 577 668

1.01 Years 687 689 690 693 693 708 776 875 998 1157

Table 1 – St. Marks River at Newport - Low Flow Frequency Analysis

6.4 St. Marks River High-Flow Analyses

The high-flow probabilities for the St. Marks at Newport are provided in Figure 24 and Table 2. 

High-flow statistics are typically used to predict recurrence frequencies for stormwater design and 

flood frequency analyses. The range of high flow increases significantly with the increasing 

recurrence interval in years. A mean one-day peak flow of 5,927 cfs would only be expected to 

occur once every 100 years. The peak daily mean observed flow for the 51-year Newport record 

was 5,820 cfs in August 2008 after record rainfall in the basin from Tropical Storm Fay. The peak 

two-day mean flow was 5,760 cfs following T.S. Fay. The peak one-day and two-day mean flows 

were just below the 100-year recurrence high flow.

Figure 24 - High Flow Recurrence – St. Marks River at Newport 

750

1000

1250

1500

1750

2000

2250

2500

2750

3000

3250

3500

3750

4000

4250

4500

4750

5000

5250

5500

5750

6000

0.5 (2 Yr) 0.2 (5 Yr) 0.1 (10 Yr) 0.04 (25 Yr) 0.02 (50 Yr) .01 (100 Yr)

Discharge (cfs)

Probability (Recurrence Interval In Years)

90 Day 60 Day

30 Day 10 Day

7 Day 1 Day

Highest Average Flow For Consecutive Days
30

Recurrence Highest Average Flow for Indicated Consecutive Days (cubic feet per second)

Interval 1-day 2-day 3-day 7-day 10-day 30-day 60-day 90-day 183-day 365-day

100 Years 5927 5895 5742 5118 4777 3193 2242 1876 1498 1157

50 Years 5137 5095 4961 4407 4093 2793 2026 1719 1390 1089

25 Years 4383 4335 4219 3740 3460 2416 1813 1560 1279 1017

10 Years 3431 3379 3288 2914 2688 1946 1529 1344 1123 912

5 Years 2729 2677 2607 2318 2139 1602 1308 1169 991 822

3 years 2210 2161 2106 1884 1744 1348 1134 1029 882 744

2 Years 1766 1721 1680 1517 1412 1129 976 899 778 668

1.01 Years 539 518 513 514 518 498 457 442 386 360

Table 2 – St. Marks River at Newport - High Flow Frequency Analysis

6.5 St. Marks and Wakulla River Flood Model

A riverine flood analysis was completed for the lower St. Marks River below the rise and the 

Wakulla River to estimate flood inundation for 10-, 50- and 100-year flood events. A frequency 

analysis was performed using NWFWMD and USGS continuous gage records. Results of this 

analysis were fit to a log-Pearson Type III distribution to obtain the desired discharge frequency 

relationship to be used in the regression analysis. The analysis was performed using the National 

Flood Frequency (NFF) program and results were used in the hydraulic analysis. 

The HEC-RAS 3.1.3 model (U.S. Army Corps of Engineers) was used to estimate flood elevations 

and floodplain boundaries. The analysis was a one-dimensional model run to calculate the steady 

flow water surface profiles. The model schematic was developed using HEC GeoRAS version 4.0, 

Wakulla County LiDAR data, ortho-aerial photography, USGS 7.5 minute quadrangles, field 

inspections and surveyed cross-sections of the river channel. Bridge data from Florida Department 

of Transportation (FDOT) plans were used in the model. The CR 365 Bridge was surveyed and 

referenced using LiDAR. Finally, the mean high tide measured at the Wakulla and St. Marks 

Rivers was used as the boundary condition of the model. The results of this model analysis were 

overlayed on a digital elevation map (Figure 25) to show the extent of flooding for the 10- and 100-

year flood events. The flood zones depicted in the map represent flooding from river flow only and 

do not include coastal flooding from storm surge. The NWFWMD is currently in the process of 

restudying the 100-year flood boundary that would be caused by coastal flooding from hurricanes.

The flood plain area inundated by flood events on spring fed rivers like the St.Marks and Wakulla 

rivers is typically less extensive than for rivers primarily fed by surface runoff. In the Woodville 

Karst Plain the sinking streams provide an additional storage mechanism for runoff which reduces 

the peak flows discharging from the springs into the rivers. This is illustrated by comparing the 

peak flows from a flood event in August 2008 caused by intense rainfall in north Florida and south 

Georgia from Tropical Storm Fay. This storm generated over 20 inches of rainfall during a threeday period in parts of the St. Marks River watershed. The St. Marks River and the Ochlockonee 

River both experienced significant flooding from this event but the impacts on the St. Marks River 

were primarily confined to the flood plain in the immediate vicinity of the river. The drainage area

contributing to the Ochlockonee River at Havana is about twice the size of the St. Marks River 

above the river rise. The peak flows resulting from the storm were over 6 times higher on the 
31

Ochlockonee River at Havana than the St. Marks River. Mean daily flow on the Ochlockonee River 

at Havana preceding T.S. Fay was 85 cfs rising to 37,400 cfs on 08/25/09 after the storm. Mean 

daily flow on the St. Marks River was 569 cfs before the event increasing to 5,890 cfs after storm 

passage (Figure 21). Peak flow on the Wakulla River after T.S. Fay was about 2,510 cfs with no 

reports of riverine flooding.

Figure 25 - St. Marks and Wakulla Riverine Flood Inundation
32

6.6 Wakulla Springs Flow

The Wakulla River is the main tributary to the St. Marks River and contributes a significant 

proportion of the flow to the lower St. Marks. The two rivers join near the City of St. Marks in 

Wakulla County about 9.3 miles south of the main spring vent that forms the Wakulla River which 

is located in the Edward Ball Wakulla Springs State Park. The Wakulla River receives most if its 

flow from the main spring vent with additional flow from spring runs and submerged springs in the 

river. Twenty-eight small springs have been identified in close proximity to the Wakulla River and

contribute flow through spring runs or direct discharge into the river (Barrios 2006). Sixteen 

springs that contribute flow to the Wakulla River below the main spring vent were measured in 

2005 and 2006; the combined flow from these springs was about 36 cfs. The average discharge 

from Wakulla Spring for the period from May 1997 – June 2009 was 450 cfs. The minor springs 

that were measured contribute about 8% in additional flow to the river compared with the average 

flow of the main spring vent. The flow from the main spring fluctuates significantly depending on 

recharge in the basin; a similar large fluctuation in flow is likely with the minor springs contributing 

flow to the river. The main spring vent is the dominant source of fresh water discharge to the 

Wakulla River.

The NWFWMD operated a continuous discharge meter in the main vent of Wakulla Springs from 

May 1997 to July 2006. In order to calibrate and verify the flow data in the main spring vent, 24 

sets of discharge measurements were completed on the Wakulla River, Sally Ward Spring and the 

McBride Springs between 1997 and 2006. Sally Ward and McBride Springs provide the largest 

flow into the river between the main spring vent and the bridge at CR 365. The combined discharge 

of Sally Ward and McBride Springs was subtracted from the Wakulla River at CR 365 discharge to 

estimate the main spring vent discharge. River discharge was measured at the CR 365 Bridge rather 

than upstream due to heavy aquatic vegetation in the river downstream of the main spring vent that 

interferes with accurate measurements across the river.

In February 2004 the river was relatively clear of aquatic vegetation. Discharge measurements were

completed below the main spring vent, the CR 365 Bridge, Sally Ward Spring and McBride Springs

on the same morning. The main spring vent discharge and CR 365 discharge were 778 and 776 cfs,

respectively, after subtracting Sally Ward and McBride Spring from the flow at the CR 365 site. 

This confirmed the procedure of estimating the main spring vent discharge.

The USGS installed a continuous flow station on the Wakulla River at the CR 365 Bridge over the 

Wakulla River that has been providing data since October 2004. The USGS station is located about 

three miles downstream of the main spring vent. The USGS record for the period from August 

2006 to June 2009 was normalized using the mean combined discharge of Sally Ward Spring and 

the McBride Springs to estimate the main spring vent discharge. A continuous record was 

generated for the main spring discharge for the May 1997 to June 2009 period. The Wakulla 

Springs daily mean flow for the period of record ranged from a high of 2,195 cfs in August 2008 

(rainfall from Tropical Storm Fay) to a low of 56 cfs during a severe drought period in May 2000

(Figure 26); mean discharge for the 11-year period of record was 450 cfs (291 mgd).
33

Figure 26 - Daily Mean Discharge – Wakulla Springs (May 1997 - June, 2009)

(Missing Record Periods: 11/12/98 - 06/18/99 and 11/03/01 - 04/13/02)

A series of 297 periodic discharge measurements were completed on the Wakulla River at CR 365 

by the USGS from 1907 to 1987 (Figure 27). The measurements were too infrequent to provide a 

good flow record for this period but they do indicate the range of flows that were observed during 

this 80-year period. Highest flow measured during this period was 1,766 cfs in April 1973 and the 

lowest measurement was 23 cfs in June 1931. The annual rainfall in 1931 in Tallahassee was 

reported as 37.99 inches, the lowest annual rainfall on record (1886 to present). A series of 13 

monthly or bi-monthly measurements were completed between February 1931 and June 1932. 

These measurements indicate that this was one of the lowest flow periods on record for the Wakulla 

River; lowest discharge measured during this period was 23 cfs and the highest was 237 cfs. Flows 

on the Wakulla River are affected by tides, wind and other factors that can influence discharge 

measurements particularly during low flow periods.

There were no measurements completed between the years 1933 to 1940. Measurements resumed 

in July 1941 and 268 measurements were made monthly or bi-monthly for over the next 36 years 

until April 1976. Periodic measurements with this frequency do not capture the peak flows and 

minimum flows on dynamic systems like the Wakulla River but they do provide a relative 

indication of the range and average flows during the period. The highest flow measured during this 

36-year period (1941-1976) was 1,766 cfs (April 1973) and the lowest flow was 89 cfs (May 1955). 

The average flow for this series of measurements was 377 cfs. 

0

250

500

750

1000

1250

1500

1750

2000

2250

05/10/199709/10/199701/10/199805/10/199809/10/199801/10/199905/10/199909/10/199901/10/200005/10/200009/10/200001/10/200105/10/200109/10/200101/10/200205/10/200209/10/200201/10/200305/10/200309/10/200301/10/200405/10/200409/10/200401/10/200505/10/200509/10/200501/10/200605/10/200609/10/200601/10/200705/10/200709/10/200701/10/200805/10/200809/10/200801/10/200905/10/2009

Discharge (cfs)

Mean Daily Flow

Mean Flow (May '97 - Jun '09)
34

Figure 27 - Periodic Wakulla River Discharge Measurements

(1907 to 1987)

The range of observed flows for each calendar day (maximum, mean and minimum) for the 11 

years of continuous record for Wakulla Springs (May 1997 to June 2009) is provided in Figure 28. 

The highest flows for the period of record were observed in the summer and spring months. The 

calendar day mean and low flows exhibit little seasonal variability.

Figure 28 - Daily Flow Characteristics – Wakulla Springs 

(May 1997 to June 2009)

0

200

400

600

800

1000

1200

1400

1600

1800

02/01/190702/01/190902/01/191102/01/191302/01/191502/01/191702/01/191902/01/192102/01/192302/01/192502/01/192702/01/192902/01/193102/01/193302/01/193502/01/193702/01/193902/01/194102/01/194302/01/194502/01/194702/01/194902/01/195102/01/195302/01/195502/01/195702/01/195902/01/196102/01/196302/01/196502/01/196702/01/196902/01/197102/01/197302/01/197502/01/197702/01/197902/01/198102/01/198302/01/198502/01/1987

Discharge (cfs)

Instantaneous Discharge Measurements

0

125

250

375

500

625

750

875

1000

1125

1250

1375

1500

1625

1750

1875

2000

2125

2250

Jan1

Jan15Jan29

Feb12Feb26

Mar12Mar26

Apr9

Apr23

May7

May21

Jun4

Jun18

Jul2

Jul16Jul30

Aug13Aug27

Sep10Sep24

Oct8

Oct22

Nov5

Nov19

Dec3

Dec17Dec31

Discharge (cfs)

Date

Calendar Day Peak Flow

Calendar Day Mean Flow

Calendar Day Low Flow
35

6.7 Wakulla Spring Low-Flow Analyses

The low flow statistics for Wakulla Springs (Log-Pearson Type III probability distribution) are 

provided in Figure 29 and Table 3. The eleven-year record period was used for the Wakulla 

Springs analysis. The lowest daily mean flow measured during the 11-year continuous record for 

Wakulla Springs was 56 cfs in May 2000. This flow is slightly lower than the estimated one-day 

20-year (1Q20) low flow recurrence. A low flow measurement of 23 cfs was made by the USGS in 

June 1931 on the Wakulla River at the CR 365 bridge below the spring. This instantaneous 

measurement may not represent the mean daily flow for that day but a flow of 23 cfs is equivalent 

to the one-day 100-year daily mean low flow for Wakulla Springs (Table 3).

The observed and estimated low flows are lower for Wakulla Springs than the St. Marks River at 

Newport. The mean daily flow measured for Wakulla Springs was 56 cfs and the lowest St. Marks 

River flow was 251 cfs, about 4.5 times higher than the Wakulla Springs flow. The 100-year daily 

mean low flow is 23 cfs for Wakulla Springs and 257 cfs for the St. Marks River (Newport).The 

7Q10 low flow (lowest stream flow for seven consecutive days expected to occur once in 10 years) 

for Wakulla Springs is 108 cfs and 321 cfs for the St. Marks River.

Figure 29 - Low Flow Recurrence – Wakulla Springs

0

50

100

150

200

250

300

350

400

0.5 (2 Yr) 0.2 (5 Yr) 0.1 (10 Yr) 0.05 (20 Yr) 0.02 (50 Yr) .01 (100 Yr)

Discharge (cfs)

Probability (Recurrence Interval In Years)

90 Day 60 Day

30 Day 10 Day

7 Day 1 Day

Lowest Average Flow For Consecutive Days
36

Recurrence Lowest Average Flow for Indicated Consecutive Days (cubic feet per second)

Interval 1-day 2-day 3-day 7-day 10-day 30-day 60-day 90-day 183-day 365-day

100 Years 23 23 25 30 32 63 81 89 92 159

50 Years 36 36 39 44 46 81 102 111 120 195

20 Years 63 64 68 73 76 113 138 151 174 258

10 Years 96 98 102 108 111 147 176 192 230 320

5 Years 146 149 153 158 163 194 226 249 307 399

3 years 194 199 202 209 214 239 275 304 381 471

2 Years 244 251 253 263 270 288 329 366 460 543

1.01 Years 329 340 342 381 397 449 517 596 678 730

Table 3 – Wakulla Springs - Low Flow Frequency Analysis

6.8 Wakulla Springs High-Flow Analyses

The high flow probabilities for Wakulla Springs are provided in Figure 30 and Table 4. The range 

of high flows increases significantly with the increasing recurrence interval in years. The peak 

daily mean observed flow for the 11-year Wakulla Springs record was 2,195 cfs in August 2008 

after record rainfall in the basin from Tropical Storm Fay. This peak observed flow exceeds the 

estimated mean one-day 10-year flow (2,039 cfs) but is less than the estimated mean one-day 25-

year flow (2,606 cfs). 

Figure 30 - High Flow Recurrence – Wakulla Springs

500

750

1000

1250

1500

1750

2000

2250

2500

2750

0.5 (2 Yr) 0.2 (5 Yr) 0.1 (10 Yr) 0.04 (25 Yr)

Discharge (cfs)

Recurrence Interval In Years

90 Day 60 Day

30 Day 10 Day

7 Day 1 Day

Highest Average Flow For Consecutive 
37

Recurrence Highest Average Flow for Indicated Consecutive Days (cubic feet per second)

Interval 1-day 2-day 3-day 7-day 10-day 30-day 60-day 90-day 183-day 365-day

25 Years 2607 2596 2540 2267 2066 1395 1060 950 817 714

10 Years 2039 2012 1963 1752 1612 1161 964 888 787 689

5 Years 1652 1621 1578 1415 1314 998 879 823 746 652

3 years 1385 1354 1317 1190 1116 882 804 760 694 604

2 Years 1165 1137 1106 1011 958 786 730 690 627 543

1.01 Years 612 609 599 607 609 548 407 326 206 159

Table 4 – Wakulla Springs - High Flow Frequency Analysis

6.9 St. Marks River and Wakulla River Discussion

The flows measured on the St. Marks River at the rise and Wakulla Springs comprise most of the 

freshwater flow to the lower St. Marks River. A graph of the mean daily flows for the St. Marks 

River and Wakulla Springs (Figure 31) illustrates the flow contribution from these two river 

systems. The continuous record for Wakulla Springs starts in May 1997. The St. Marks River has 

higher baseflow for the majority of the record and higher peak flows than Wakulla Springs. 

Rainfall distribution in the watershed can have a significant effect on the timing and magnitude of 

flows on the two rivers. The peak flows on the St. Marks River are consistently about 2 times 

higher than Wakulla Spring with a few exceptions that may be due to differences in rainfall 

distribution in the watershed.

Figure 31 - Mean Daily Flows - St. Marks River and Wakulla Springs 

(Missing Wakulla Record: 11/12/98 - 06/18/99 and 11/03/01 - 04/13/02)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

05/10/9709/10/9701/10/9805/10/9809/10/9801/10/9905/10/9909/10/9901/10/0005/10/0009/10/0001/10/0105/10/0109/10/0101/10/0205/10/0209/10/0201/10/0305/10/0309/10/0301/10/0405/10/0409/10/0401/10/0505/10/0509/10/0501/10/0605/10/0609/10/0601/10/0705/10/0709/10/0701/10/0805/10/0809/10/0801/10/0905/10/09

Discharge (cfs)

Wakulla Springs Flow

St. Marks River Flow
38

The lowest mean daily flow for this record period for Wakulla Springs was 56 cfs in May 2000;

flow in the St. Marks for that day was 420 cfs. The lowest mean daily flow for this record period on 

the St. Marks was 251 cfs in October 2001; flow for Wakulla Springs on that day was 117 cfs. The 

average daily flow in the St. Marks and Wakulla rivers was 618 cfs and 450 cfs, respectively, for 

this period (May 1997 to June 2009). The observed record indicates that the flow on the St. Marks 

River is consistently higher than Wakulla Springs for all ranges of flows. These latest 

measurements and the estimated ground water contribution to the discharge at the St Marks River 

Rise confirm the spring at the rise is a first-magnitude spring with a greater discharge than Wakulla 

Springs. This data indicates the St. Marks River Rise is the largest spring in the watershed. 

The combined flow for the St. Marks River at Newport and Wakulla Springs approximates the fresh 

water flow discharging into Apalachee Bay from the lower St. Marks River (Figure 32). The 

combined mean daily discharge for the rivers for the 11 years of combined record was 1,097 cfs. 

The lowest flow was 354 cfs in October 2001 and the peak flow was 8,060 cfs following Tropical 

Storm Fay.

The St. Marks and Wakulla rivers pick up additional flow in the lower reaches of the rivers 

downstream of the monitoring stations but this addition is estimated to be a small percentage of the 

total flow. Numerous small springs flowing into the Wakulla River downstream of the main spring

vent were measured in 2005 and 2006 and contributed only about 8% additional flow to the river 

compared with the average flow of the main spring vent (Barrios 2006). Only four springs have 

been indentified on the St. Marks River downstream of the Newport station; they contribute less 

than one percent of the average flow at Newport.

Figure 32 - Combined Daily Flows St. Marks River and Wakulla Springs

(May 1997 to June 2009)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

7500

8000

8500

05/10/9709/10/9701/10/9805/10/9809/10/9801/10/9905/10/9909/10/9901/10/0005/10/0009/10/0001/10/0105/10/0109/10/0101/10/0205/10/0209/10/0201/10/0305/10/0309/10/0301/10/0405/10/0409/10/0401/10/0505/10/0509/10/0501/10/0605/10/0609/10/0601/10/0705/10/0709/10/0701/10/0805/10/0809/10/0801/10/0905/10/09

Discharge (cfs)

Date

Combined Daily Discharge

St. Marks Discharge Only 8060 cfs, 08/26/2008 (T.S. Fay)
39

7.0 WATER AND SEDIMENT QUALITY IN THE ST. MARKS

WATERSHED AND APALACHEE BAY

The St. Marks River estuarine complex is a relatively small shallow estuarine embayment located in 

the western portion of Apalachee Bay system. The bay system consists of a relatively shallow shelf 

gradually grading into deeper water (Figure 33); the slope of the bottom is so slight that depths are 

only 15 feet up to 6-8 miles offshore. Fresh water from the lower St. Marks River (downstream of 

the confluence with the Wakulla River) discharges through the estuarine complex into the 

Apalachee Bay system.

Figure 33 - Bathymetry of Apalachee Bay and Adjacent Waters
40

7.1 Water Quality Classifications

Surface waters within the St. Mark River/Apalachee Bay are classified by the State of Florida 

(Florida Department of Environmental Protection) as either Class II or III. These classifications are 

based on use, not by the actual quality of the water. 

Class II waters are designated as Shellfish Propagation or Harvest areas. These areas have water 

quality standards focusing on particular components that affect the quality of the shellfish harvested 

to protect consumers from possible diseases associated with their consumption. Shellfish harvesting 

areas within the Wakulla County portion of Apalachee Bay (Area #22) are shown in Figure 34 for 

the winter months; spring harvesting areas are identical. Currently, commercial harvesting is 

Figure 34 - Shellfish Harvesting Areas in Western Apalachee Bay

for Winter Months (October-March, DACS 2004)
41

prohibited in areas east of Live Oak Island, including the mouth of the St. Marks River and adjacent 

offshore waters. No approved harvesting areas are found to the east until reaching Horseshoe 

Beach in Dixie County. This designation does not apply to scallop harvesting which is a major 

recreational activity in the seagrass beds in Apalachee Bay. Scallops may be taken in season (July 1 

to September 10) from all bay areas (west bank of the Mexico Beach Canal in Bay County to the 

Pasco-Hernando County line) with a valid saltwater fishing license.

The majority of western Apalachee Bay is conditionally approved during both seasons with 

relatively small scattered portions of bottom conditionally restricted. Harvesting is prohibited in 

portions of Dickerson Bay, two areas near Spring Creek and an inshore triangle between Shell Point 

and Live Oak Island. Conditionally approved waters are open for harvest during the winter months 

(October to March) unless rainfall at the Ochlockonee River State Park exceeds 1.08 and 2.24 

inches, respectively, for Zones 1 and 2. Conditionally approved waters are harvestable during the 

spring/fall months (April, May and September) unless rainfall, measured at the State Park, exceeds 

2.35 and 3.78 inches for Zones 1 and 2, respectively. A portion of the waters are conditionally 

restricted when rainfall exceeds 4.02 inches (winter) and 4.75 inches (spring/fall). In all cases 

waters are temporary closed when the above conditions occur and are reopened when 

bacteriological levels meet the standards described in Rule 5L-1.003 (DACS) and fecal coliform 

levels in shellfish return to normal background levels. Closure and reopening is administered 

through the Division of Aquaculture, Department of Agriculture and Consumer Services.

All surface waters in St. Marks/Apalachee Bay not specifically listed as Class II are designated as 

Class III. Class III waters are designated to provide Recreation and Propagation of Healthy, Wellbalanced Populations of Fish and Wildlife. Standards for these waters are not as stringent for most 

parameters as for Class II and are directed to maintaining biodiversity and water quality sufficient 

for human contact such as swimming (hence the name Fishable/Swimable waters). All waters in 

the St. Marks River (except those in the City of St. Marks), the Wakulla River and waters within the 

Big Bend Seagrasses Aquatic Preserve are Outstanding Florida Waters and receive additional 

protection to maintain ambient conditions with no degradation.

7.2 Water Quality Characteristics

Considerable water quality data have been collected in the St. Marks/Apalachee Bay System over 

the last 30 years; yet, most has been restricted to waters near the upstream extent of tidal influence, 

particular in and around the City of St. Marks and its docking terminals for offloading petroleum 

products and bulk chemicals (FDEP 2003). Numerous oil spills have been documented over the 

years, including a sizeable spill in 1978, that have contaminated bottom sediments in the river. 

Limited amounts of water quality data have been collected in the Wakulla Springs and River 

system, despite the present location of the State Park. This is likely because much of the upper river 

reach was in private ownership before it was purchased by the state in 1986. Some collections have 

been made in and around Big Boggy Branch, a tributary in the lower reach of the Wakulla River, 

associated with the discharge from Primex Technologies (formally Olin Corporation), a 

manufacturer of small and intermediate arms propellants. LakeWatch has sampled several locations 

in the river since the mid-1990s. 
42

Existing water quality data for the estuarine portion of the St. Marks and adjacent Apalachee Bay is 

relatively sparse and generally restricted to short-term collections associated with larger sampling 

efforts focused on other portions of the system. Bacteriological collections are made routinely by 

the Division of Aquaculture (DACS) in association with shellfish harvesting areas and by the 

county health department to assess the status of local beaches (e.g., Shell Point Beach, Mashes 

Sands). While several nearby areas (near Panacea and offshore waters of the Econfina/Fenholloway

rivers) have had greater sampling efforts over the past 25 years, no comprehensive, long-term, water 

quality monitoring program is being carried out currently in either the St. Marks estuary or adjacent 

Apalachee Bay. 

As part of the FDEP’s watershed management approach for protecting water resources and 

addressing Total Maximum Daily Load (TMDL) requirements, a water quality assessment was 

developed for the Ochlockonee and St. Marks system (FDEP 2003). Recent water quality data were 

obtained from FDEP’s Florida Storage and Retrieval (STORET) databases, new data collected as 

necessary, and all information was assessed according to methodologies prescribed in the 1972 

federal Clean Water Act and the 1999 Florida Watershed Restoration Act. From this assessment a 

verified list of water bodies not meeting state water quality standards (impaired waters) was 

developed; TMDLs are under development for these water bodies.

Several portions of the St. Marks estuary and adjacent Apalachee Bay were placed on the verified 

list as not meeting water quality standards (FDEP 2003). Three water body segments in western 

Apalachee Bay (Apalachee Bay-west, Marshes Island and Shell Point) were listed for bacteria in 

shellfish and beach advisories, as well as all Florida Gulf Coast segments for excessive mercury in 

fish tissue.

Two segments in the St. Marks River basin (low dissolved oxygen) and one segment of the Wakulla 

River (biological imbalance due to excessive nutrients) were included on the verified impaired list. 

St. Marks River sub-basins, Black Creek (WBID 628) and Lake Weeks (WBID 971B), were 

verified as impaired for dissolved oxygen (DO) resulting from high nutrients. The northern portion 

of the St. Marks River (WBID 793B) is potentially impaired for DO as are two springs (St. Marks 

Spring WBID 971 and Horn Spring WBID 793Z). DO is typically naturally low in spring waters. 

The Wakulla River (WBID 1006) was placed on the verified list because of a biological imbalance 

attributable to nutrients discharges from the springs. Some waters, including Sally Ward Spring and 

McBride Slough, are potentially impaired for DO; however, as in the St. Marks springs, the low DO 

appears to be naturally occurring. The report (FDEP 2003) cites trend data for Wakulla Springs 

(WBID 1006X) and Wakulla River (WBID 1006) indicating a decrease in total phosphorus since 

1970, but an increase in total nitrogen (TN) and alkalinity. Big Boggy Branch (WBID 1124), a 

tributary of the river, has shown increasing trends for TN and fecal coliform.

Water quality data from a variety of sites representative of the St. Marks and Wakulla Rivers as 

well as adjacent areas of Apalachee Bay were retrieved from the Florida STORET database and are 

summarized here. Collections were taken by various agencies and organizations (e.g., FMRI, 

FDEP, LakeWatch) with varying characteristics, sampling procedures and analytical methods. 

These are combined and presented here only to provide an overview of environmental 

characteristics in the various reaches of the system.

Data were retrieved from 44 sites scattered throughout the Wakulla and St. Marks Rivers and the 

adjacent waters of Apalachee Bay. Twenty-nine sites were examined from the lower tidal reaches 
43

of both rivers along with sites in Apalachee Bay (Figure 35) to evaluate inputs to the estuarine 

portion of the system. Twenty-four sites were examined from the Wakulla River (Figure 36) to 

assess downstream water quality trends from the head springs to the confluence with the St. Marks. 

Nine sites were common to both analyses. Sites were chosen where collections spanned a range of 

sampling dates; single sample collections were avoided when possible. Information concerning the 

agencies responsible for sampling and dates of collection are given in Tables 5 and 6 for each site.

Figure 35 - Water Quality Stations in the Lower St. Marks Watershed

and Apalachee Bay (Boxes indicate station groups)

For the estuarine comparison, stations were combined into four groups representing the upper reach 

of tidal influence, middle and lower reach of the estuary, and Apalachee Bay (including adjacent 

embayments such as Dickerson and Oyster Bays). Water quality characteristics varied spatially and 
44

temporally throughout the collection sites with specific conductance/salinity increasing and most of 

the other characteristics generally decreasing with movement downstream (Table 7). 

Figure 36 - Wakulla River Water Quality Stations

(Boxes indicate station groups)

Specific conductance was low in the upper portions of both rivers with values in the Wakulla River 

(mean = 429 mho/cm) higher than in the St. Marks (mean = 250 mho/cm); salinities 

corresponding to these specific conductance are less than 0.2 ppt. Variation in conductance also 

appeared greater on the Wakulla (272-824 mho/cm) compared to the St. Marks River (92-300 

mho/cm). No seasonal variation was noted at either site (Figure 37).

Mean salinity increased with distance from the upper reach of the St. Marks and Wakulla Rivers to 

Apalachee Bay (Table 7). Salinity averaged 3.5 ppt near the confluence of the St. Marks and 

Wakulla Rivers, 14.8 ppt near the mouth of the St. Marks River and over 25 ppt offshore in 

Apalachee Bay. Salinity offshore in Apalachee Bay (e.g., Station 105) was relatively stable with 

occasional precipitous declines (Figure 38), presumably associated with increased freshwater runoff 

from localized storm events. Generally, salinity returned fairly quickly to pre-event conditions. 

Salinity declined and variability increased significantly closer to shore (e.g., Station 100) in greater 

proximity to freshwater sources. No pronounced seasonality was noted in either inshore or offshore 

salinity at the sites selected. 
45

Station ID

Agency Responsible 

For Collection Collection Period

Upper Tidal Reach

St. Marks @ Newport (3528) NWFWMD/FDEP 10/12/98 - 08/09/06

Wakulla @ Highway 98 (S292) NWFWMD/FDEP 02/28/00 - 01/31/02

1006V-A/B FDEP 04/11/06 - 09/12/06

1006W-A/B FDEP 04/11/06 - 09/12/06

WAK-WA-Lower-1/2/3 Florida LakeWatch 03/27/99 - 03/13/06

Middle Tidal Reach

WAK-ST-Lower-1/2/3 Florida LakeWatch 04/22/01 - 06/30/02

2350 FDEP 10/03/01

2059 FDEP 10/03/01

2465 FDEP 10/03/01 & 02/28/06

1593 FDEP 1/26/06 - 09/27/06

Lower Tidal Reach

WAK-ST-Lower-4 Florida LakeWatch 4/22/01-6/30/02

1373 FDEP 1/26/06-9/27/06

WAK-WAK4 Florida LakeWatch 01/10/01 - 05/17/01

Apalachee Bay

WAK-WAK1-3 Florida LakeWatch 01/10/01 - 05/17/01

WAK-WAK5-6 Florida LakeWatch 01/10/01 - 05/17/01

S081 FDEP 08/30/89 - 05/25/05

S090 FDEP 07/19/79 - 05/25/05

S100 FDEP 07/19/79 - 05/25/05

S105 FDEP 01/12/95 - 05/25/05

Table 5 – Water Quality Site Summary for Tidal Reaches of the

St. Marks River and Apalachee Bay

Station ID

Agency Responsible 

For Collection Collection Period

Head Springs

9695 FDEP 09/27/01 - 12/06/05

1006X-A/B FDEP 04/10/06 - 11/28/06

WAK-WA-River-1/2/3 Florida LakeWatch 04/26/96 - 02/27/06

Upper Reach

S570 NWFWMD/FDEP 02/28/00 - 01/31/02

1006-A/B/C FDEP 04/10/06 - 12/06/06

Middle Reach

S266 (Highway 365) NWFWMD/FDEP 02/13/92 - 08/11/92

WAK-WA-Middle-1/2/3 Florida LakeWatch 01/03/96 - 01/11/06

Lower Reach

S292 (Highway 98) NWFWMD/FDEP 02/28/00 - 01/31/02

1006V-A/B FDEP 04/11/06 - 09/12/06

1006W-A/B FDEP 04/11/06 - 09/12/06

WAK-WA-Lower-1/2/3 Florida LakeWatch 03/27/99 - 03/13/06

WAK-ST-Lower-1 Florida LakeWatch 04/22/01 - 06/30/02

300917708412465 FDEP 10/3/01 - 02/28/06

Table 6 – Summary of Wakulla River Water Quality Sites 
46

Figure 37 - Specific Conductance in the Wakulla and St. Marks Rivers

(FL STORET 2007)

STATION

Specific 

Cond.

Salinity Temp DO NH3 NO2+ 

NO3

TKN TN PO4 TP CHL-A

Upper Tidal Reach

St. Marks @ Newport 

(3528) 250 20.4 6.0 0.011 0.12 0.20 0.34 0.033 0.043

Wakulla @ Highway 98 

(S292) 414 21.0 8.1 0.013 0.38 0.16 0.55 0.018 0.031

1006 451 0.2 22.3 7.7 0.35 0.16 0.014 0.025 2.0

WAK-WA-Lower-1/2/3 0.53 0.025 2.5

Middle Tidal Reach

WAK-ST-Lower-1/2/3 0.39 0.031 5.1

2350/2059/2465/1593 3.5 21.2 7.6 0.027 0.13 0.38 0.020 0.037 0.85

Lower Tidal Reach

WAK-ST-Lower-4 0.31 0.026 6.1

1373/1010 14.8 22.0 7.1 0.040 0.06 0.53 0.009 0.028 1.0

WAK-WAK4 0.28 0.015 2.9

Apalachee Bay

WAK-WAK1-3 0.24 0.013 2.0

WAK-WAK5-6 0.24 0.012 1.4

S081 19.0 21.1 8.7

S090 22.1 20.7 8.4

S100 17.0 21.1 8.2

S105 25.3 22.3 8.1

Abbreviations/units of measure: Specific conductance ( mho/cm), Salinity (ppt), Temperature (oC), DO-dissolved oxygen (mg/l),

NH3-ammonia (mg/l), NO2+NO3-nitrate+nitrite (mg/l), TKN-total Kjeldahl nitrogen (mg/l), TN-total nitrogen (mg/l),

PO4-ortho-phosphate (mg/l), TP-total phosphorus (mg/l), CHL-A, chlorophyll a ( g/l)

Table 7 – Summary of Selected Water Quality Characteristics in the St. Marks

and Wakulla Rivers and Apalachee Bay (FL STORET 2007)

Specific Conductance recorded in the 

St. Marks River @ Newport and Wakulla River @ Highway 98

0

100

200

300

400

500

600

700

10/12/98 10/12/99 10/12/00 10/12/01 10/12/02 10/12/03 10/12/04 10/12/05

Date Conductance ( mho cm-1

)

St Marks

Wakulla
47

Figure 38 - Long-term Salinity at Inshore (Station 100) and Offshore (Station 105)

Sites in Apalachee Bay (FL STORET 2007)

Temperature varied seasonally both in the rivers (Figure 39) and offshore in Apalachee Bay (Figure 

40). The Wakulla River appeared significantly warmer in summer and cooler in winter than the St. 

Marks with slight differences in timing of seasonal peaks. Temperature varied from 11.8 to 26.7 oC 

on the Wakulla while only ranging between 14.5 and 24.3 oC on the St. Marks. This trend appears 

counterintuitive given the spring-fed origin of the Wakulla River. Water temperature in Apalachee 

Bay exhibited a wider range of values (8.2-35.3 oC) than those observed in the rivers. Winter lows 

tended to vary more among years than summer highs both in the rivers and offshore.

Figure 39 - Long-term Water Temperature in the Wakulla and

St. Marks Rivers (FL STORET 2007)

Salinity recorded at two sites in Apalachee Bay 

0

5

10

15

20

25

30

35

40

7/17/79 7/17/82 7/17/85 7/17/88 7/17/91 7/17/94 7/17/97 7/17/00 7/17/03

Date

Salinity (ppt)

St. 100

St. 105

Water Temperature recorded in the

St. Marks River @ Newport and Wakulla River @ Highway 98

10

12

14

16

18

20

22

24

26

28

10/12/98 10/12/99 10/12/00 10/12/01 10/12/02 10/12/03 10/12/04 10/12/05

Date Temperature ( 

oC)

St Marks

Wakulla
48

Figure 40 - Long-term Water Temperature at Inshore (Station 100) and

Offshore (Station 105) Sites in Apalachee Bay (FL STORET 2007)

Dissolved oxygen (DO) was relatively high with surface values averaging greater than 7.0 mg/l at 

all water quality collection sites except the St. Marks at Newport site which had a mean value of 

only 6.0 mg/l (Table 7). Values ranged between 4.9 and 10.7 mg/l on the Wakulla River and 

between 3.4 and 9.4 mg/l on the St. Marks (Figure 41). In Apalachee Bay, DO was slightly higher 

than in the rivers with mean values greater than 8 mg/l (Table 7); however, variability was also 

greater with several observations below 5 mg/l (range at Stations 100 and 105 was 3.1-13.8 mg/l; 

see Figure 42). DO was generally related to water temperature with higher values in colder months, 

but differences were noted.

Figure 41 - Dissolved Oxygen in the Wakulla and St. Marks Rivers

(FL STORET 2007)

Water Temperature recorded at two sites in Apalachee Bay

0

5

10

15

20

25

30

35

40

7/17/79 7/17/82 7/17/85 7/17/88 7/17/91 7/17/94 7/17/97 7/17/00 7/17/03

Date Temperature ( 

oC)

St. 100

St. 105

Dissolved Oxygen recorded in the

St. Marks River @ Newport and Wakulla River @ Highway 98

0

2

4

6

8

10

12

10/12/98 10/12/99 10/12/00 10/12/01 10/12/02 10/12/03 10/12/04 10/12/05

Date

Dissolved oxygen (mg l -1

)

St Marks

Wakulla
49

Figure 42 - Dissolved Oxygen at Inshore (Station 100) and Offshore

(Station 105) Sites in Apalachee Bay (FL STORET 2007)

Nutrient concentrations (both nitrogen and phosphorus) were generally low throughout the St. 

Marks/Apalachee Bay system, except in the upper reach of the Wakulla River (i.e., Wakulla Spring 

where higher levels of nitrates have resulted in increased density of nuisance aquatic plants). 

Nitrate+nitrite concentrations in the upper tidal reach of the Wakulla River (US98 bridge) averaged 

three times greater than that observed on the St. Marks River at Newport (US98 bridge) (Table 7). 

Orthophosphate concentrations in the Wakulla, on the other hand, were only about one-half that 

noted for the St. Marks (Table 7). Ammonium values were low in the upper tidal reach of both 

rivers. Ammonium and total Kjeldahl nitrogen generally increased with distance downstream while 

nitrate+nitrite and orthophosphate generally decreased (Table 7). Total nitrogen and total 

phosphorus were lower in Apalachee Bay than in the rivers. Some seasonality was noted in levels 

of nitrate+nitrite in the upper tidal reaches of both rivers (Figures 43 and 44) but not in 

orthophosphate.

Chlorophyll concentrations were generally low throughout much of the system with sporadic peaks 

in the rivers, particularly in the middle and lower tidal reaches (Table 7) where levels averaged 5.1 

and 6.1 g/l, respectively. Values in these reaches were observed to exceed 10 g/l on several 

occasions.

To examine downstream trends in water quality on the Wakulla River, stations were combined into 

four groups representing the head springs, the upper, middle, and lower reaches of the river as 

shown in Figure 36. Water quality characteristics varied spatially and temporally throughout the 

collection sites with specific conductance/salinity, dissolved oxygen and chlorophyll generally 

increasing and most of the other characteristics decreasing with movement downstream (Table 8).

Specific conductance was low in the upper reaches of the Wakulla with mean values ranging from 

269 to 310 mho/cm; salinities corresponding to these specific conductance are less than 0.1 ppt. 

Substantial variation in specific conductance was noted in the lower reach of the river with mean 

0

2

4

6

8

10

12

14

10/1/82 10/1/85 10/1/88 10/1/91 10/1/94 10/1/97 10/1/00 10/1/03

Dissolved oxygen (mg l

-1

)

Date

Dissolved Oxygen recorded at two sites in Apalachee Bay

St. 100

St. 105
50

values increasing from 414-474 mho/cm near the U.S. 98 bridge to over 8,600 mho/cm near the 

confluence with the St. Marks. Conductance was seasonally stable (Figure 45) in the upper reach 

near the main spring (site S570) yet varied noticeably in the lower reach (site S292). Fluctuations at 

the lower site likely reflect inputs from tributaries and, more importantly, tidal influence.

Figure 43 - Nitrogen (upper) and Phosphorus (lower) Concentrations

in the St. Marks River (FL STORET 2007)

St. Marks River @ Newport

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

10/12/98 10/12/99 10/12/00 10/12/01 10/12/02 10/12/03 10/12/04 10/12/05

Date

Nitrogen (mg l -1

)

NO2+NO3

NH3

TKN

St. Marks River @ Newport

0

0.01

0.02

0.03

0.04

0.05

0.06

10/12/98 10/12/99 10/12/00 10/12/01 10/12/02 10/12/03 10/12/04 10/12/05

Date

Phosphorus (mg l -1

)

Total Phosphorus

Ortho-PO4
51

Figure 44 - Nitrogen (upper) and Phosphorus (lower) Concentrations

in the Wakulla River (FL STORET 2007)

Mean salinity values were retrieved only from sites in the lower reach and ranged from 0.2 ppt near 

the U.S. 98 bridge to 4.9 ppt near the St. Marks confluence (Table 8). As noted previously, salinity 

increases with distance downstream in the St. Marks to Apalachee Bay (see Table 7). The lower 

reach of the Wakulla River appears to encompass the upper limit of salt intrusion under most 

conditions and as such is an area that is relatively sensitive to modifications in river flow and 

salinity distribution. Large changes in floral and faunal assemblages might be expected in this 

reach with changes in the salinity regime. 

Wakulla River @ Highway 98

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

2/28/00 6/28/00 10/28/00 2/28/01 6/28/01 10/28/01

Date

Nitrogen (mg l -1

)

NH3

TKN

NO2+NO3

Wakulla River @ Highway 98

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

2/28/00 6/28/00 10/28/00 2/28/01 6/28/01 10/28/01

Date

Phosphorus (mg l -1

)

Total Phosphorus

Ortho-PO4
52

STATION

Specific 

Cond. Salinity DO NH3

NO2+ 

NO3 TKN TN PO4 TP CHL-A

Head Spring

9695 307 2.2 0.005 0.71 0.05 0.75 0.028 0.030

1006X-A/B 310 2.4 1.28 0.14 1.42 0.023 0.026 0.9

WAK-WA-River 1/2/3 0.76 0.028 0.05

Upper Reach

570 300 7.6 0.010 0.72 0.06 0.78 0.026 0.033

1006 A/B/C 309 4.8 0.52 0.10 0.62 0.024 0.029 1.1

Middle Reach

S266 (Hwy 365) 269 7.9 0.017 0.61 0.46 1.07 0.032

WAK-WA-Middle-1/2/3 0.58 0.025 1.5

Lower Reach

S292 (Hwy 98) 414 8.1 0.013 0.38 0.16 0.54 0.018 0.031

1006 W/V 474 0.2 8.0 0.34 0.17 0.51 0.013 0.025 2.1

WAK-WA-Lower-1/2/3 0.50 0.024 2.5

WAK-ST-Lower-1 0.47 0.026 5.2

300917708412465 8666 4.9 8.1 0.013 0.17 0.53 0.70 0.020 0.024

Abbreviations/units of measure: Specific conductance ( mho/cm), Salinity (ppt), Temperature (C), DO-dissolved oxygen (mg/l),

NH3-ammonia (mg/l), NO2+NO3-nitrate+nitrite (mg/l), TKN-total Kjeldahl nitrogen (mg/l), TN-total nitrogen (mg/l),

PO4-ortho-phosphate (mg/l), TP-total phosphorus (mg/l), CHL-A, chlorophyll a ( g/l)

Table 8 – Summary of Selected Water Quality Characteristics in the

Wakulla River System (FL STORET 2007)

Figure 45 - Specific Conductance at Upper (S570) and Lower (S292) Sites

in the Wakulla River (FL STORET 2007)

Temperature varied seasonally (Figure 46) in the Wakulla River with lowest values in NovemberDecember and highest values varying from April to July depending on location. Temperatures in 

the upper reach (14.2-23.6 oC) varied less than downstream (11.8-26.7 oC), indicating the buffer 

effect of the spring. Dissolved oxygen (DO) was relatively low near the head springs with 

increasing values downstream (Table 8). Mean DO at the springs was 2.3 mg/l while most 

0

100

200

300

400

500

600

700

2/28/00 6/22/00 9/26/00 1/10/01 6/6/01 9/27/01 1/31/02

Specific Conductance ( mho cm-1

)

Date

Specific Conductance recorded at two sites in the Upper and Lower 

Reaches of the Wakulla River

S570

S292
53

locations downstream averaged over 7 mg/l. Some seasonality was observed, primarily at lower 

reach sites (Figure 47). DO was generally related to water temperature with higher values in colder 

months, but differences were noted (see site S570, Figure 47).

Figure 46 - Water Temperature at Upper (S570) and Lower (S292)

Sites in the Wakulla River (FL STORET 2007)

Figure 47 - Dissolved Oxygen at Upper (S570) and Lower (S292)

Sites in the Wakulla River (FL STORET 2007)

Nutrient concentrations (both nitrogen and phosphorus) were moderately high throughout the 

Wakulla River system (Table 8). Ammonia and total Kjeldahl nitrogen (TKN) were low at the head 

Water Temperature recorded at two sites in the Upper and Lower

 Reaches of the Wakulla River

0.0

5.0

10.0

15.0

20.0

25.0

30.0

2/28/00 6/28/00 10/28/00 2/28/01 6/28/01 10/28/01

Date Temperature ( 

oC)

S570

S292

Dissolved Oxygen recorded at two sites in the Upper and Lower

Reaches of the Wakulla River

0

2

4

6

8

10

12

2/28/00 6/28/00 10/28/00 2/28/01 6/28/01 10/28/01

Date

Dissolved Oxygen (mgL-1

)

S570

S292
54

springs and generally increased downstream, although several lower reach sites had low TKN. 

This generally low TKN was indicative of the spring-run character of the river which receives little 

organic inputs; the majority of the total nitrogen (TN) is in the dissolved inorganic form (i.e., 

nitrate+nitrite-N). Unlike the previous nutrient trends, nitrate+nitrite-N was relatively high at the 

head springs (e.g., 1.28 mg/l at sites 1006X) and decreased downstream; however, moderate levels 

were maintained through much of the lower reach (e.g., 0.38 mg/l at site S292). Concentrations fell 

to relatively low levels near the confluence with the St. Marks River (0.17 mg/l at site 

300917708412465). No apparent seasonality was observed in nitrate+nitrite-N at either upper or 

lower reach sites (Figure 48) The concentration of nitrate+nitrite versus discharge at the main 

spring vent of Wakulla Springs for the period from July 1997 to July 2009 is shown in Figure 49. 

This data indicates nitrate + nitrite concentrations are higher during low flow periods when ground 

water provides the majority of the flow to the spring. Nitrate+nitrite concentration decreases as 

flow increases indicating surface water discharging to the spring has lower nitrate+nitrite than 

ground water. 

Figure 48 - Nitrate+Nitrate at Upper (S570) and Lower (S292)

Sites in the Wakulla River (FL STORET 2007)

Soluble reactive phosphate (orthophosphate) concentrations were moderate to low throughout all 

reaches of the river; a slight decline in concentrations was observed with distance downstream 

(Table 8). No seasonality was noted in levels at either upper or lower reach sites (Figure 50).

As with nitrogen, the bulk of the total phosphorus (TP) was in the dissolved inorganic form 

indicating little organic input (Table 8). Some long-term nutrient trends were observed at 

LakeWatch stations, monitored for the last 10 years. TN appears to have declined slightly at upper 

reach stations (Figure 51), while TP has increased at middle and lower reach sites (Figure 52). 

Since TN and TP in this system primarily consist of inorganic forms of nitrogen and phosphate, it is 

likely that similar trends occur in nitrate+nitrite and soluble reactive phosphate as well. 

Nitrate+nitrite concentrations in the lower reach of the Wakulla River (U.S. 98 bridge) averaged

three times greater (0.38 mg/l) than that observed on the St. Marks River at Newport-U.S. 98 bridge 

Nitrate+Nitrite Concentrations at two sites in the Upper and Lower

Reaches of the Wakulla River

0

0.2

0.4

0.6

0.8

1

1.2

2/28/00 6/28/00 10/28/00 2/28/01 6/28/01 10/28/01

Date

Nitrate+Nitrite-N (mgL-1

)

S570

S292
55

(0.12 mg/l). Orthophosphate concentrations in the Wakulla River (0.018 mg/l), on the other hand, 

were only about one-half that noted for the St. Marks (0.033 mg/l). Chlorophyll concentrations 

were generally low throughout much of the system (Table 8) with occasional peaks at lower reach 

sites where levels averaged 5.2 g/l at one station (WAK-ST-Lower-1).

Figure 49 - Nitrate+Nitrite vs. Discharge at Wakulla Springs (Main Vent)

(July 1997 - July 2009, NWFWMD)

Figure 50 - Soluble Reactive Phosphate (Ortho-phosphate) at Upper (S570

and Lower (S292) Sites in the Wakulla River (FL STORET 2007)

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

1.10

0 100 200 300 400 500 600 700 800 900

Nitrogen, Nitrate (NO3) + Nitrite (NO2) as N (mg/L)

Discharge (cfs)

Soluble Reactive Phosphate Concentrations at two sites in the Upper and 

Lower Reaches of the Wakulla River

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

2/28/00 6/28/00 10/28/00 2/28/01 6/28/01 10/28/01

Date

Soluble Reactive Phosphate (mgL-1

)

S570

S292
56

Figure 51 - Mean Total Nitrogen in the Wakulla River by Reach

(LakeWatch Stations, FL STORET 2007)

Figure 52- Mean Total Phosphorus in the Wakulla River by Reach

(LakeWatch Stations, FL STORET 2007)

0

200

400

600

800

1000

1200

1400

1/1/96 1/1/98 1/1/00 1/1/02 1/1/04 1/1/06

Total Nitrogen ( gL

-1

)

Date

Mean Total Nitrogen at LakeWatch Stations averaged by Reach

in the Wakulla River 

Upper

Middle

Lower

0

10

20

30

40

50

60

1/1/96 1/1/98 1/1/00 1/1/02 1/1/04 1/1/06 Total Phosphorus ( gL

-1

)

Date

Mean Total Phosphorus at LakeWatch Stations averaged by Reach

in the Wakulla River 

Upper

Middle

Lower
57

In addition to the above analysis, FDEP Environmental Assessment Section, in conjunction with 

NWFWMD, has collected water quality and biological data at a site on the upper Wakulla River just 

below the turning basin in the State Park. These data, while included in the above discussion, are 

reported separately in the EcoSummary section on the FDEP website. Information on water quality 

and Stream Condition Index (SCI) has been provided from quarterly sampling since February 2000. 

According to these summaries, stream health has ranged from healthy to impaired. High nitratenitrite concentrations have been consistently observed along with a highly variable SCI. SCI values 

ranged from very poor to excellent (most in the poor and very poor categories) and were in part 

influenced by the presence of the exotic weed hydrilla (see latter section on submerged aquatic 

vegetation).

7.3 Sediment Characteristics

A sediment survey was conducted by the U.S. Fish and Wildlife Service in 1988 (Hemming and 

Brim 2002) to examine sediment quality in and around the St. Marks National Wildlife Refuge 

(NWR). Thirty-two sites (14 within and 18 north of the NWR) were sampled for grain size, metals, 

polycyclic aromatic hydrocarbons (PAH), aliphatic hydrocarbons, and organochlorine pesticides. 

Analytical results were compared to sediment quality guidelines (Long et al. 1995) and risks were 

assigned based on these numeric recommendations.

Sediments were generally sandy throughout the survey area with localized patches of finer material. 

Sand ranged from 12.3 to 94.6%, silt from 2.3 to 49.6% and clay from 2.9 to 51.9%. Areas with 

greater percentages of silts and clays were associated with human activity such as the lighthouse 

boat basin, and the fuel docks, power plant intake and marinas in the City of St. Marks. Total 

organic carbon was generally low ranging from 0.2 to 4.9% dry weight.

Sediment contamination was relatively low throughout the NWR but was noted occasionally at sites 

outside the refuge. Metals (copper and mercury) exceeded the Effects Range Low (ERL; Long et 

al. 1995) at several sites outside the NWR but were not found in the NWR. PAHs and 

organochlorine pesticide concentrations in the NWR did not exceed guidelines; however, PAH 

contamination was noted in the industrial area of the St. Marks associated with fuel docks and 

marinas. Aliphatic hydrocarbons and oils and grease residues were the only contaminants observed 

in sediments within the NWR; these were thought to be associated with motor vessel traffic in the 

refuge. 
58

8.0 ST. MARKS/APALACHEE BAY HABITATS

The lower St. Marks and Wakulla Rivers/Apalachee Bay system supports a variety of wetland 

habitats and biotic communities, and maintains a high level of biodiversity. Those habitats directly 

associated with surface waters of the springs, rivers and nearshore areas include: palustrine forests, 

fresh and brackish wetlands, tidal salt marshes, submerged aquatic vegetation, seagrasses, soft and 

hard bottom.

8.1 Palustrine Forest

Few investigations have focused on the wetland forests of the Wakulla and lower St. Marks basins. 

Based on forest community studies in the Ochlockonee, Wakulla/St. Marks and Suwannee rivers 

(Clewell 1986; Leitman et al. 1991; Light et al. 1993; Light et al. 2002), palustrine forests in this 

area are composed of at least three major vegetation types: bottomland hardwoods, cypress swamps 

and coastal tidal swamps. The distribution of these forests types are heavily influenced by 

elevation, the degree and type of inundation, and proximity to the coast (i.e., salt water). 

Bottomland hardwood forests occupy wet-mesic to nearly hydric habitats that are usually associated 

with stream and river floodplains (Clewell 1986). Habitats in these forests are generally inundated, 

sometimes briefly but occasionally for prolonged periods annually. During the dry season, the root 

zone is usually well aerated. In areas where flooding is more pronounced, cypress-tupelo swamps 

dominate. These swamps are characterized by prolonged hydroperiods in which the soils are 

inundated at least several weeks every year and often for as long as six months (Clewell 1986). 

Clewell (1986) described a variant of the cypress-tupelo swamp from the Wakulla River in which 

tupelos were generally absent leaving bald cypress as the dominant vegetation. Coastal swamps 

occur along river floodplains within the zone of tidal influence and along the inland margins of tidal 

marshes (Clewell 1986). While freshwater conditions generally prevail, coastal swamps are subject 

to tidal fluctuations and can tolerate some salt water inundation. Proximity to the coast results in 

rapid dissipation of flood waters precluding lengthy or prolonged inundation during seasonal 

flooding. Generally uniform hydrological conditions and occasional salinity shock likely limit the 

species present.

The vegetation community along the Wakulla River was divided into three zones roughly parallel to 

the river (Clewell 1986). A cypress swamp consisting primarily of bald cypress (Taxodium 

distichum), pop and pumpkin ash (Fraxinus carolina and F. profunda), and red maple (Acer 

rubrum) was noted along the river bank. Bottomland hardwoods comprised the adjacent terrace and 

slope leading to the uplands. Terrace trees were dominated by pumpkin ash, red maple, swamp 

laurel oak (Quercus laurifolia), planer-tree (Planera aquatica), and swamp red bay (Persea 

palustris), while the drier slope was inhabited by swamp laurel oak, sweetbay (Magnolia 

virginiana) and ironwood (Carpinus caroliniana). A bottomland hardwood site along the St. Marks 

River south of Natural Bridge (Clewell 1986) was dominated by ironwood (Carpinus carolina), 

green ash (Fraxinus pennsylvanica), sweet gum (Liquidambar styraciflua) and hackberry (Celtis 

laevigata). Other relatively abundant trees included loblolly pine (Pinus taeda), red maple and bald 

cypress. Another site about 1 km below Natural Bridge was examined by Light et al. (1993); they 

described three relatively distinct floodplain vegetation zones, similar to Clewell (1986), that

included the low plain and the lower and upper slopes. Ironwood and sweet gum dominated all 
59

zones with sweetbay, swamp dogwood (Cornus foemina) and bald cypress common in the lower 

regions. Loblolly pine was the most abundant tree on the upper slope. 

Although not examined in detail in the Wakulla/St. Marks area by Clewell (1986), coastal swamps 

have been described by Light et al. (2002) for the lower Suwannee River and are expected to be 

similar to those in the St. Marks. Canopy composition in these lower tidal swamps was dominated 

by pumpkin ash, bald cypress, swamp tupelo (Nyssa biflora), with pumpkin ash, swamp tupelo, 

sweet bay, cabbage palm (Sabal palmetto) and loblolly pine (Pinus taeda) dominating in the lower 

tidal mixed bottomland and hammocks. Cabbage palms were found in all tidal communities as both 

canopy and subcanopy trees. Lower tidal hammocks, as described by Light et al. (2002), vary in 

elevation and in distance from the Gulf, thus in exposure to river flooding, tidal surge, and salinity. 

Hammocks closest to the Gulf tended to have the largest proportion of cabbage palms.

Light et al. (2002) defined three major and 14 specific forest types in the ten-year floodplain of the 

lower Suwannee River. General forest types were divided into riverine, upper tidal and lower tidal 

components. These forest types are similar to those described by Clewell (1986) from limited 

sampling in the Wakulla/St. Marks vicinity. Dominant canopy species, primary soil texture in the 

root zone, and typical hydrological conditions are summarized for the specific wetland forest types 

(Light et al. 2002). Riverine bottomland hardwoods and riverine swamps comprise the riverine 

habitats. These forest types vary in inundation levels ranging from durations of 1-2 months every 3 

years to 4-7 months annually. Dominant trees included live oak (Quercus virginiana), sweet gum 

(Liquidambar styraciflua), swamp laurel oak, river birch (Betula nigra), bald cypress, overcup oak 

(Quercus lyrata) and planer-trees. Upper tidal habitats were dominated by swamp laurel oak, 

cabbage palm, bald cypress, pumpkin ash and water tupelo (Nyssa aquatica). Flooding in upper 

tidal habitats ranged from once every 2 years, with rapid soil drying after flood recession, to 

monthly by high tides or high river flow with continuously saturated soils. Lower tidal hammocks 

and swamps ranged in inundation from every 1-2 years to daily or several times monthly. In most 

cases, soils are saturated continuously, at least in the lowest areas. Lower tidal forests consist of 

cabbage palm and loblolly pine on the higher sites and pumpkin ash, swamp tupelo, sweetbay and 

bald cypress in the wetter sites.

Approximately 39,500 acres of palustrine forests (both forested and scrub-shrub wetlands) are 

found in the St. Marks and Wakulla basins (Figure 53; NWI coverage) with the majority (78%) 

found in the St. Marks. The bulk of the St. Marks palustrine forest is found in the upper portion of 

the basin. Of the nearly 8,800 acres of wetland forests in the Wakulla basin, most are located in the 

lower, tidal portion just upstream of its confluence with the St. Marks River. A relatively narrow 

fringe of forested habitat extends upriver and includes the areas around the main and secondary 

springs (e.g., Sally Ward and McBride).

8.2 Freshwater and Brackish Wetlands

The fresh and brackish wetlands include both emergent and submergent plant forms and result in a 

floral continuum from the headwaters/springs to the estuary. A riparian marsh habitat is found in 

the freshwater portion of the system with the brackish marsh extending downstream through the 

oligohaline region of the estuary where salinities range from 0 to 15 ppt. Marsh species 

composition is likely influenced by a combination of salinity tolerance and differences in soil type, 

elevations and competitive interactions.
60

Figure 53- Wetland and Aquatic Habitats in the St. Marks/Apalachee

Bay Watershed (NWI 1994)
61

Often the emergent portions of these fresh/brackish marshes are dominated by sawgrass (Cladium 

jamaicense), maidencane (Panicum hemitomon), giant cutgrass (Zizaniopsis miliacea) and cattails 

(Typha spp.), but may contain large interspersed patches of black needlerush (Juncus roemerianus). 

In the underwater areas, various species of submerged aquatic vegetation often proliferate. While 

numerous freshwater marshes are evident scattered throughout the coastal region, none were noted 

in the National Wetlands Inventory (NWI) coverage along either of the river corridors (Figure 53).

Riparian freshwater and brackish marshes were examined in the Wakulla River by Thompson 

(1977). Five locations were studied from the U.S. 98 bridge (transect I) to a point about halfway 

between the lighthouse and the confluence of the Wakulla and St. Marks rivers (transect V) with 

three sites upstream of the confluence and two downstream. Ninety-four species of plants were 

identified consisting of 74 emergent marsh species, 10 permanently submerged aquatics, 8 intertidal 

aquatics and 2 floating species. Overall, clearly defined communities were not observed at each site 

rather an intergrading of species between locations; gradual changes in dominance of individual 

species were noted between adjacent locations (Table 9).

A riparian freshwater marsh exists at the upper site (transect I) and is dominated by dwarf 

arrowhead (Sagittaria subulata), needle rush (Juncus polycephalus), pickerelweed (Pontederia 

cordata), and obedient plant (Dracocephalum purpureum). No appreciable salinity was measured 

at this site (salinity range: 0.0-0.3 ppt). Sites along the middle and lower river were brackish in 

nature with mean salinities ranging from 1 ppt (transect II) to 8 ppt (transect V). Middle river 

stations (transects II and III) were dominated by black needle rush (Juncus roemerianus), sawgrass 

(Cladium jamaicense), dwarf arrowhead, spiked loosestrife (Lythrum lineare), and climbing 

hempweed (Mikania scandens). These sites had higher mean salinities (1-2 ppt) with significantly 

greater salinity ranges (11-13 ppt). Lower river locations (transects IV and V) were inhabited by 

black needlerush, sawgrass, dwarf arrowhead, false loosestrife (Ludwigia repens), marsh fimbry

(Lilaeopsis chinensis), and eastern grasswort (Fimbristylis castanea). Salinitiy ranged up to nearly 

25 ppt at these lower sites even though mean values were only 3 and 8 ppt, respectively. Upper site 

(I) vegetation was more distinctly limnetic and displayed differences between east and west river 

banks, probably a result of differences in bank slope and degree of inundation. Lower sites (IV and

V) had some salt marsh characteristics (see tidal salt marsh section) but were more heterogenous in 

species composition. In contrast with more coastal salt marshes, these sites lack the extensive salt 

flats of salt grass (Distichlis spicata) and glasswort (Salicornia spp.) and salt barrens. Thompson 

(1977) suggested that their absence resulted from low tidal inundation that was either too fresh (not 

sufficient salt) or too infrequent to allow the development of these flats and barrens.

Limited information is available on the extent of fresh and brackish marsh in the system. 

Freshwater wetlands were found in the NWI coverage of the watershed (Figure 53), but were not 

mapped along the river corridor proper, possibly because of the small amount of habitat existing or 

their intergrading with the narrow fringing palustrine forest. Freshwater and brackish wetlands 

were not differentiated for mapping purposes in the NWI coverages, but were readily distinguished 

from the tidal salt marshes (see below).
62

Transects

I II III IV V

River Mile (from Mouth) 15 12 10 8 5

Species

Sagittaria subulata

(dwarf arrowhead) 32 16 1 13 1

Juncus polycephalus

(needle rush) 34

Cladium jamaicense

(sawgrass) 9 13 8 <1

Pontederia cordata

(pickerelweed) 6 2

Dracocephalum purpureum

(obedient plant) 7

Juncus roemerianus

(black needlerush) 55 79 63 82

Lythrum lineare

(spiked loosestrife) 5

Mikania scanden s

(climbing hempweed) 4

Saurus cernuus

(lizard’s tail) 1

Scirpus americanus

(bull rush) 1

Ludwigia repens

(false loosestrife) 1 4

Fimbristylis castanea

(marsh fimbry) 2 1

Lilaeopsis chinensis

(eastern grasswort) 2 12

Other species 21 8 6 7 3

Mean salinity (top/bottom) 0/0 0/1 1/2 2/3 4/8

Max. salinity (top/bottom) 0/0 2/12 4/13 7/24 13/25

Table 9 – Mean Relative Abundance of Marsh Macrophytes in the

Wakulla and Lower St. Marks Rivers (Thompson 1977)
63

8.3 Tidal Salt Marsh

Salt marshes are similar to brackish marshes in that they serve as a transition between terrestrial and 

marine systems. Generally, salt marshes are intertidal and develop along relatively low energy 

shorelines. Unlike brackish marshes, they may be found under significantly more saline conditions. 

Salt marshes in the Florida panhandle are usually characterized by large, fairly homogeneous 

expanses of dense black needlerush (Juncus roemerianus). Often they are accompanied on the 

water ward side by smooth cord grass (Spartina alterniflora). The Juncus and Spartina zones are 

very distinctive and can be separated easily by elevation, with Spartina inhabiting the lower, 

regularly flooded zone, and Juncus found in higher, less flooded area. Frequently, additional 

species of cord grass (Spartina spp.), salt grass (Distichlis spicata), glasswort (Salicornia virginica), 

various sedges (Scirpus spp.) and the common cane (Phragmites australis) occur.

Generally, tidal salt marshes can be divided into four ecological zones governed by elevation and 

extent of inundation: Spartina alterniflora zone, Juncus marsh, salt flats, and barrens (Wolfe et al. 

1988). The Spartina zone typically fringes tidal creeks and channels. A small landward increase in 

elevation permits development of lush Juncus stands that are by far the most extensive and 

conspicuous feature of the tidal marsh. Juncus plants may grow to 6-7 feet in height throughout the 

majority of the marsh declining to about one-half this height at the landward edge of the marsh near 

the flatwoods where they merge with the salt flats. Stunted plants of several genera typify the flats, 

especially Salicornia, Batis, Borrichia and Aster. The barrens are landward of the flats and consist 

of bare ground flooded by high tides for only brief periods. This infrequent tidal inundation 

coupled with long exposure to sunlight results in such high salt content of the soil that excludes 

most plants. True salt marshes appear limited to the higher salinity regions of the St. 

Marks/Apalachee Bay complex with an expansive area noted all along the coastal region.

Salt marsh production and zonation were examined in the vicinity of the East River, a small tidal 

creek along the eastern side of the St. Marks River mouth (Krucznski et al. 1978). The study site 

was dominated by black needlerush, followed by smooth cord grass and salt grass. Productivity 

was greatest in the low marsh (i.e., closest zone to the water) and decreased landward for both 

needlerush and cord grass; salt grass was found primarily in the high marsh. Needlerush production 

was significantly greater than cord grass in all zones examined; salt grass production, however, 

exceeded both needlerush and cord grass in the high marsh (the only zone in which it was noted in 

appreciable abundance).

Early estimates of salt marsh habitat in the vicinity of the St. Marks River were provided for a larger 

section of Apalachee Bay (McNulty et al. 1972) and included the area from Alligator Harbor 

eastward to the Econfina River (shown in Figure 18 of the above cited report). Within this larger 

area, approximately 137,600 acres of tidal marsh were mapped. More recent information, available 

from the NWI mapping, indicated about 22,300 acres of tidal marsh and 5,350 acres of salt flats 

within the basin adjacent to the mouth of the St. Marks River (Figure 54). This acreage represents 

only a small fraction of the tidal marsh habitat located along the shoreline of Apalachee Bay, as 

indicated in both Figure 54 and McNulty et al. (1972). Approximately 3,200 acres of salt marsh/salt 

flats were noted in the lower St. Marks basin proper with only 218 acres of marsh and flats in the 

lower portion of the Wakulla basin just upstream of the confluence of the Wakulla and the St. 

Marks Rivers. 
64

Figure 54- Coastal Wetlands in the St. Marks/Apalachee Bay Area (1995 NWI data)

8.4 Submerged Aquatic Vegetation

Submerged aquatic vegetation (SAV), including seagrass, represents one of the most important and 

productive habitats in freshwater, estuarine and nearshore environments. SAV beds support highly 

diverse and abundant floral and faunal communities and provide spawning, feeding, nursery and 

protective refugia for a wide array of aquatic organisms including many of recreational and 

commercial value.

Submerged and intertidal vegetation has been characterized in the Wakulla River by Thompson 

(1977) at the same transect locations described previously for riparian and brackish marshes. Nine 

species were collected with SAV biomass varying noticeably between locations from 63 to 759 g 

per m

2

(Table 10). Upper, less saline sites (I and II) were dominated by tape grass (Vallisneria 

americana), strap-leaf sag (Sagittaria kurziana), dwarf arrowhead (S. subulata), southern naiad 

(Najas guadalupensis), coontail (Ceratophyllum demersum), and Illinois pondweed (Potamogeton 

illinoensis). Strap-leaf sag, Illinois pondweed and small pondweed (Potamogeton pusillus) were 

found only at these upper sites. Although not shown in Table 10, dwarf arrowhead made up nearly 

65% of the intertidal marsh vegetation on the west bank of site I. Total plant biomass was greatest 

at upper sites and least at the lower site. Eight of the nine species decreased in biomass with 

distance downstream and increasing salinity. Widgeon grass (Ruppia maritima) was the only 
65

species to increase in biomass from sites I to IV and was the only SAV collected at the downstream, 

most saline station (V). Despite its presence at this lower site, biomass declined from the values 

noted at the two adjacent upstream locations. This suggests that while widgeon grass is the most 

salt tolerant of the riverine SAV it cannot tolerate the wide salinity range at the lower site. Red 

pondweed (Potamogeton perfoliatus) was noted only at site IV and showed no distribution trends. 

Thompson (1977) suggested that salinity is a major influence on SAV distribution throughout these 

sections of the river. Thompson cited anecdotal claims by local residents that Hurricane Agnes in 

1972 virtually eliminated all aquatic vegetation from at least the brackish portions of the Wakulla 

River; Clewell (1986) questioned whether this defoliation resulted from salinity intrusion or 

uprooting. 

 Transects

I II III IV V

River Mile (from Mouth) 15 12 10 8 5

Species

Ceratophyllum demersum 

(coontail) 0 189 1 0 0

Najas guadalupensis 

(southern naiad) 44 154 2 0 0

Potamogeton illinoensis 

(Illinois pondweed) 79 0 0 0 0

Potamogeton perfoliatus 

(red pondweed) 0 0 0 68 0

Potamogeton pusillus 

(small pondweed) 2 1 0 0 0

Ruppia maritima

(widgeon grass) 0 52 92 144 63

Sagittaria kurziana

(strap-leaf sag) 204 1 0 0 0

Sagittaria subulata

(dwarf arrowhead) 0 154 29 1 0

Vallisneria americana 

(tape grass) 242 209 143 111 0

TOTAL 571 759 267 324 63

Mean salinity (top/bottom) 0/0 0/1 1/2 2/3 4/8

Max. salinity (top/bottom) 0/0 2/12 4/13 7/24 13/25

Table 10 – Mean Dry Weight Biomass (g/m

2

) of Submerged and Intertidal

Macrophytes in the Wakulla and Lower St. Marks Rivers (Thompson 1977)

Birkitt (1981) reported considerably higher SAV biomass from three vegetation transects taken near 

the U.S. 98 bridge (near Thompson’s (1977) transect I). Four macrophyte species were noted 

yielding a total biomass of about 1545 g per m2. Strap-leaf sag dominated the sites making up 

88.6% of the total plant biomass; tapegrass and Illinois pondweed contributed 8.5% and 2.9%, 
66

respectively. Trace amounts of southern naiad were observed. Birkitt reported significant 

heterogeneity (i.e., patchiness) in vegetation distribution that was particularly noticeable with dense 

patches of tapegrass interspersed within dense areas of strap-leaf sag yielding a mosaic pattern. 

Strap-leaf sag biomass increased upstream while tapegrass biomass increased downstream within 

the river reach examined. Birkitt suggested this pattern was related in part to the distribution of 

chlorinity/salinity within the river with tapegrass having the greater tolerance. Plant biomass was 

uncorrelated with most of the sediment characteristics collected (i.e., grain size, skewness, or 

percent silt/clay); total biomass was correlated with the degree of sediment sorting and as such was 

likely related to current velocity.

Additional qualitative investigations of SAV have been made in the upper portion of the river, from 

the head springs (within the State Park) to the U.S. 98 bridge, primarily to examine results of an

exotic weed eradication program initiated there. The accidental introduction of hydrilla (Hydrilla 

verticillata) in 1997 to the Wakulla Springs system, fueled by high nutrient concentrations, led to 

explosive nuisance plant growth and prompted the State of Florida to begin herbicide application in 

2002. Excessive hydrilla growth degrades the river by physical smothering of native habitats and 

water quality degradation (e.g., low dissolved oxygen levels and extensive organic silt buildup 

resulting from decomposition of dead plant tissue). An herbicide overdose in April 2002 damaged 

native vegetation and lead to sediment scouring in portions of the river; partial recovery followed 

relatively quickly over the next growing season. A tapegrass transplanting program was initiated 

by State Park staff in 2004 to aid in the re-vegetation of native species (S. Savery, FDEP, personal 

communication).

Limited information exists on the acreages of submerged and intertidal vegetation in the system; the 

areas of SAV mapped in the NWI wetlands coverage (Figure 53) are found scattered in the upper 

reaches of the basins and are not related to the river corridors.

8.5 Seagrass

Seagrasses represent one of the most important and productive habitats in estuarine and nearshore 

environments. Seagrass beds support highly diverse and abundant floral and faunal communities 

and provide spawning, feeding, nursery and protective refugia for a wide array of aquatic organisms 

including many of recreational and commercial value. Seagrass beds in the St. Marks/Apalachee 

Bay system are dominated by turtle grass (Thalassia testudinum) and shoal grass (Halodule 

wrightii). Other species include manatee grass (Syringodium filiforme), star grass (Halophila 

engelmanni) and widgeon grass (Ruppia maritima).

Vertical zonation of seagrasses generally correlates with tidal level in most shallow estuarine waters 

(Zieman 1987). Halodule wrightii and Ruppia maritima are abundant intertidally, with Ruppia

preferring a somewhat lower level than Halodule; Thalassia, Syringodium and Halophila are found 

only below low water levels. Low or unusually high salinity may restrict or eliminate Thalassia and 

Syringodium. Thalassia and Syringodium are usually associated with stable, near-marine salinities 

(20-36 ppt), open coastal water, and subtropical to tropical temperatures. Halodule is generally 

found in more estuarine conditions (10-25 ppt), but also forms dense stands in open coastal, highsalinity regions, in areas of high water movement or in tidal flats where it is subject to exposure. 

Ruppia is most common in very brackish water (1-5 ppt), with meadows extending into the mouths 

of rivers (Dawes 1987).
67

Grass beds in Apalachee Bay are comprised of a variety of rooted seagrasses and attached and 

drifting macroalgae. In an adjacent area of Apalachee Bay (off the Econfina and Fenholloway 

Rivers), Zimmerman and Livingston (1976a, b, 1979) collected a total of 39 species of benthic 

macrophytes; red algae dominated the list with 17 species. These studies focused on a comparison 

of plant assemblages in the relatively unpolluted Econfina River and the heavily polluted 

Fenholloway River (receiving effluent from a pulp mill). Grass beds in the unpolluted Econfina 

area are likely very similar to those off the mouth of the St. Marks River, about 15 miles to the west. 

Examining only those stations directly off the mouth of the Econfina River (seven sites), 30 species 

were observed (Table 11); the calcareous green alga Halimeda incrassata was the most prevalent 

macrophyte in the area in terms of biomass, followed by turtle grass and manatee grass. Widgeon 

grass and shoal grass were present but in less abundance. Overall biomass of macrophytes was 

highly seasonal with maximum standing stock noted during the warm summer months.

Seagrass in Apalachee Bay was estimated to occupy about 58,100 acres in the early 1970s 

(McNulty et al. 1972). These acreages were mapped in the above cited report and included the area 

from Alligator Harbor eastward to the Econfina River. Later mapping by the NWI (Figure 53)

indicated approximately 29,630 acres (classified as estuarine algal beds) along the Apalachee Bay 

coastline (see discussion of Wakulla County beds in Sargent et al. 1995). These mapped beds 

appear limited in size and spatial extent and likely do not depict total seagrass coverage in the area. 

More recent surveys, including one by FDEP in 1992 (statewide) and one by SRWMD in 2001 (Big 

Bend only), were carried out in the area but are not directly comparable because of differences in 

photography and mapping techniques. Despite these differences, the recent maps can be evaluated 

by examining overlapping mapped portions of the coverages and estimating seagrass acreages for 

each survey within the overlap zone. In this way we can estimate possible differences over the time 

period between surveys. Given the above caveats, seagrasses were estimated to cover about 89,350 

acres (Figure 55) and 68,300 acres (Figure 56), respectively, during the 1992 and 2001 surveys. 

While this difference may reflect artifacts of the sampling, if real, this would be a loss of almost 

25% of the seagrass in the compared area.

On a larger scale, seagrass declines have been observed for the Big Bend area, defined as the five 

counties from the Apalachicola to the Withlacoochee Rivers (Handley et al. 2007). Investigators

cited total seagrass acreage (continuous and patchy cover) to have been 817,528 acres in 1984, 

267,639 acres in 1992 and 447,251 acres in 1995. While it is unclear if the 1995 estimate is a 

reversal of a downward trend or if the 1992 values were low, seagrass habitat covers less acreage 

now than historically.

8.6 Soft-Bottom Habitat

Unvegetated sand and mud make up sizeable portion of both rivers, adjacent tributary and tidal 

creek channels, and bay bottom in the St. Marks/Apalachee Bay system. These bottom areas, 

although devoid of most structure, can be quite productive in terms of infaunal organisms and the 

communities they support. While the most conspicuous habitats are tidal marsh, oyster reef and 

SAV/seagrass, soft bottom areas can serve as significant feeding grounds for a variety of fin and 

shellfish of recreational and commercial value. The extent of the soft-bottom habitat is unclear 

having not been mapped to date in the area.
68

Species Plant Phylum

Total Dry

Weight (g)

Halimeda incrassata Chlorophyta 20648

Thalassia testudinum Spermatophyta 18335

Syringodium filiforme Spermatophyta 3969

Digenia simplex Rhodophyta 2330

Ruppia maritima Spermatophyta 687

Laurencia poitei Rhodophyta 466

Penicillus capitatus Chlorophyta 365

Halodule wrightii Spermatophyta 337

Polysiphonia harveyi Rhodophyta 278

Caulerpa prolifera Chlorophyta 125

Halophila engelmanni Spermatophyta 100

Anadyomene stellata Chlorophyta 82

Gracilaria verrucosa Rhodophyta 59

Padina vickersiae Phaeophyta 51

Spyridia filamentosa Rhodophyta 35

Sargassum pteropleuron Phaeophyta 26

Udotea flabellum Chlorophyta 25

Gracilaria cervicornis Rhodophyta 24

Laurencia intricata Rhodophyta 15

Sargassum filipendula Phaeophyta 7

Gracilaria foliifera Rhodophyta 6

Udotea conglutinata Chlorophyta 4

Caulerpa paspaloides Chlorophyta 4

Codium isthmocladum Chlorophyta 4

Cladophoropsis membranacea Chlorophyta <1

Laurencia papillosa Rhodophyta <1

Cladophora sp. Chlorophyta <1

Chondria tenuissima Rhodophyta <1

Polysiphonia subtilissima Rhodophyta <1

Chaetomorpha linum Chlorophyta <1

Table 11 – Biomass of Macrophytes in Apalachee Bay Offshore of Econfina River 

(Zimmerman and Livingston 1976)
69

Figure 55- Seagrass Coverage (1992) in the Nearshore Area of Apalachee Bay

Figure 56- Seagrass Coverage (2001) in the Nearshore Area of Apalachee Bay
70

8.7 Hard-Bottom Habitat

Much of the hard substrate habitat in panhandle estuaries is artificial, comprised of structures such 

as jetties, bridges, and pier pilings. Of the naturally occurring hard substrate habitats in this area, 

oyster reefs are the most abundant as well as being ecologically and economically important. 

Natural oyster reefs are extensive in the lower St. Marks River and adjacent tidal marshes, but are 

restricted in the lower Wakulla River because of low salinity.

The biology of the oyster has been extensively studied worldwide because of its economic value

(see summaries by Galtsoff 1964; Kennedy et al. 1996). Oysters are typically reef building 

organisms, growing on the shell substrate accumulated from generations of oysters. They may 

occur in both intertidal and sub-tidal environments. The primary reef-building commercial oyster in 

the panhandle is the Eastern or American oyster (Crassostrea virginica). This species grows in a 

wide salinity range (10-30 ppt) with optimal growth occurring at water temperature of about 25oC. 

Frequently reefs also contain large numbers of other bivalve mollusks such as horse oysters (Ostrea 

equestris) and hooked mussels (Ischadium recurvum).

The location and distribution of oyster reefs depend on many interacting factors which include 

complex combinations of geological, physical, chemical and biological processes. Reef oysters, 

although tolerant of broad ranges of important habitat variables such as temperature and salinity, are 

susceptible to various forms of physical disturbance that can adversely affect or destroy reef 

structures. Success of the eastern oyster depends on factors that influence spawning, planktonic 

larval development, metamorphosis of the spat stage, and longevity of the sexually mature adult. 

Commercial harvesting, predation, disease and physical processes such as sedimentation (burial) are 

major causes of mortality in the developing oyster reefs. Water circulation is important for larval 

transport and settlement, delivery of food (phytoplankton), and removal of waste. Salinity is a key 

factor in the incidence of predation and disease, both increasing with increasing salinity.

McNulty et al. (1972) attempted to estimate oyster habitat in Apalachee Bay from Alligator Harbor 

to Econfina River (see Figure 18 in above cited report) but likely underestimated the coverage. 

They noted approximately 2,700 acres of beds, of which nearly 90% were closed to shell fishing. 

Currently shellfish harvesting is allowed in some western parts of Apalachee Bay but not in the 

immediate vicinity of the St. Marks (see previous section on water quality classifications). No 

recent oyster bar location mapping is available for the area.

In addition to living hard bottom, limestone outcroppings appear throughout the river and nearshore 

area and undoubtedly provide habitat and shelter for a variety of aquatic organisms. These 

structures, however, have not been mapped and little is known about their influence on floral and 

faunal assemblages.
71

9.0 FAUNAL COMMUNITIES OF THE LOWER ST. MARKS/WAKULLA 

RIVERS AND APALACHEE BAY SYSTEM

The St. Marks watershed and nearshore Apalachee Bay provide a diversity of habitats supporting a 

wide range of riverine and estuarine biological communities. Interestingly, considerably more 

information has been gathered over the years on the less accessible estuarine assemblages than on 

the relatively easily observed freshwater plant and animal communities. This noted difference is 

probably more a function of specific interests of nearby university researchers than accessibility to 

sampling sites.

9.1 Riverine Communities

Much of the information available concerning riverine animal communities in the watershed are

derived from studies in the Wakulla River. The Wakulla Springs and River system supports a 

variety of biotic communities and maintains a relatively high level of biodiversity. As a spring-fed 

stream, the Wakulla River differs from other types of panhandle streams in several important ways 

(Wolf et al. 1988), all of which influence the floral and faunal assemblages present. Spring waters 

are generally clear and as such can support lush plant growth. These waters also have a relatively 

constant temperature that persists to a certain extent downstream, making them thermally buffered. 

Because they travel through subterranean limestone sediments/caverns, spring waters have 

relatively high concentrations of calcium, magnesium, iron and other minerals and are notably less 

acidic than non-spring streams. These characteristics influence the types and abundances of 

animals present.

9.1.1 Benthic and Epifaunal Invertebrates

Studies examining the invertebrate communities in the river are few, including those of Birkitt 

(1981), Walsh and Williams (2003) and ongoing investigations by FDEP and NWFWMD of 

environmental conditions at Edward Ball Wakulla Springs State Park. Additionally, long-term 

monitoring has occurred in the vicinity of Big Boggy Branch, a tributary to the lower Wakulla River 

that receives treated industrial discharge from Primex Technologies, Inc. (aka. Olin Corporation). 

Birkitt (1981) examined benthic and epifaunal communities associated with submerged aquatic 

macrophytes at three transects in the lower reach of the Wakulla River near the U.S. 98 bridge. The 

study site was co-located with that of Thompson (1977) and near the upper limit of salinity in the 

system under all but extreme conditions (e.g., above normal tides, hurricanes). Twenty-six 

epifaunal and 29 benthic taxa were collected from a seasonally limited sampling program. Density 

of epifaunal invertebrates was three times greater at the upstream transect relative to the two 

downstream ones, ranging from 296 to 845 individuals per 0.25m2over the three locations. 

Number of individuals per gram of plant was also greatest upstream. Number of taxa was similar 

among the sampling sites, ranging from 16 to 18. The upstream transect was dominated by the 

caddisflies Orthotricha sp. and Agraylea sp., and the oligochaete Nais sp.; downstream transects 

had high numbers of Nais sp. and the chironomid midge Orthocladius sp. Epifaunal abundance was 

significantly correlated with the biomass of strap-leaf sag (Sagittaria kurziana), the dominant SAV 

in the river at this location. Density and number of taxa of benthic invertebrates was also greatest at 

the upstream transect. All three locations were dominated by unidentified oligochaete worms and 

gammarid amphipods; chironomid midges represented a sizable fraction of the individuals collected 
72

at the upper two sites. Benthic abundance was correlated with percent silt/clay in the sediments; 

number of benthic taxa was associated with total SAV biomass, decreased sorting of sediments and 

greater percent silt/clay. Overall, Birkitt noted that salinity, macrophyte biomass and species, and 

various sediment characteristics (i.e., degree of sorting and percent silt/clay) appeared to influence 

aquatic community structure.

Freshwater mussels were surveyed in a brief investigation within the boundaries of the State Park 

(Walsh and Williams 2003). Only four species of native unionids were collected: variable spike 

(Elliptio icterina, 86.6%), peninsular floater (Utterbackia peggyae, 7.3%), Florida pondhorn 

(Uniomerus carolinianus, 3.7%), and southern rainbow (Villosa vibex, 2.4%). Several specimens of 

the nonindigenous Asian clam (Corbicula fluminea) were also found. The authors suggested that 

the Wakulla River likely supports a native mussel fauna relatively depauperate in species richness, 

but that may have moderately large populations, especially of the variable spike, a species widely 

occurring in springs and spring-fed rivers throughout north central Florida.

The apple snail (Pomacea paludosa) was a common inhabitant of the springs and upper river

historically; however, its abundance has dwindled in recent years (S. Savery FDEP, personal 

communication). Apple snails are a primary food of the limpkin (Aramus guarauna) (Bryan 1981), 

a protected wading bird once common on the Wakulla River but now rarely seen. Apple snails 

generally live in slow flowing, relatively shallow water, and require SAV for grazing and egg 

laying. They prefer broad-leafed emergent plants that grow more than 10 cm above the water 

surface. Because of the dramatic declines in numbers of apple snails (and limpkins) in the Wakulla 

River, the State Park initiated a snail release program in 2003 to restore population levels. To date 

over 3,000 snails have been released, averaging about 600 per year (S. Savery FDEP, personal 

communication); nearly 2,000 snails were released in 2005. In addition, an egg cluster survey was 

begun in the upper reach of the river within the park. Numbers of egg clusters have increased from 

86 in 2005, 753 in 2006, to 1826 in 2007 (S. Savery FDEP, personal communication), perhaps 

indicating the success of the snail release program. Recent reports cite the presence of the exotic 

island apple snail (P. insularum) within park boundaries yet little is known about its current 

distribution. This species has invaded a number of panhandle water bodies with devastating effects 

on native vegetation.

9.1.2 Fishes

Fish assemblages in the river and springs have been sampled for a number of years primarily 

through collections by Yerger and students at Florida State University; considerable material from 

these collections resides in the Florida Museum of Natural History (FLMNH) but was only recently 

summarized along with results of new collections (Walsh and Williams 2003). In addition, sport 

fishes have been compared from several Big Bend coastal streams by the Florida Fish and Wildlife 

Conservation Commission (Cailteux et al. 2004, 2005).

A total of 43 species representing 20 families and 31 genera were located in FLMNH collections; 

these represented collections made in the head springs, downstream sections of the river and

McBride Slough (a tributary entering the river downstream of the head springs). Twenty-three 

species from 13 families and 21 genera were recently collected, restricted to areas from the main 

spring pool downstream to the mouth of McBride Slough, and results were compared with museum 

specimens (Walsh and Williams 2003). Both sets of collections were combined and are shown in 
73

Table 12; forty-seven species have been recorded from these studies. Recent collections were 

dominated by redeye chub (Notropis harperi), coastal shiner (Notropis petersoni) and spotted

Family Species

USGS FLMNH

Number Percent Spring Adjacent Percent

Lepisosteidae Lepisosteus osseus 9 0.9 3 0.05

Lepisosteus platyrhincus 4 0.4

Amiidae Amia calva 6 0.6

Anguillidae Anguilla rostrata 8 0.8 9 0.15

Cyprinidae Notropis cummingsae 355 5.84

Notropis harperi 273 28.1 841 72 15.01

Notropis petersoni 154 15.9 436 36 7.76

Opsopoeodus emiliae 82 1.35

Pteronotropis hypselopterus 1 0.1 252 51 4.98

Catostomidae Erimyzon sucetta 39 4.0 17 1 0.3

Minytrema melanops 3 0.3 6 0.1

Ictaluridae Ameiurus catus 1 0.02

Noturus gyrinus 24 2 0.43

Noturus leptacanthus 10 0.16

Esocidae Esox americanus 11 4 0.25

Esox niger 2 0.03

Aphredoderidae Aphredoderus sayanus 18 1.9 69 3 1.18

Mugilidae Mugil cephalus 3 0.3

Atherinopsidae Labidesthes sicculus 4 0.4 195 3.21

Belondiae Strongylura timucu 1 0.02

Fundulidae Fundulus confluentus 28 0.46

Fundulus escambiae 1 0.02

Fundulus grandis 1 0.02

Fundulus seminolis 43 4.4 426 7.0

Lucania goodei 78 8.0 734 27 12.5

Lucania parva 67 1.10

Poeciliidae Gambusia holbrooki 61 6.3 524 22 8.98

Heterandria formosa 43 4.4 142 32 2.86

Poecilia latipinna 7 0.7 145 2.38

Syngnathidae Syngnathus scovelli 1 0.02

Centrarchidae Lepomis auritus 2 0.2 143 2.35

Lepomis gulosus 3 0.05

Lepomis marginatus 5 0.08

Lepomis microlophus 4 0.07

Lepomis punctatus 167 17.2 188 3.09

Micropterus notius 5 0.5

Micropterus salmoides 35 3.6 44 1 0.74

Percidae Percina nigrofasciata 47 0.77

Gerreidae Eucinostomus argenteus 72 1.18

Sparidae Lagodon rhomboides 21 0.35

Sciaenidae Bairdiella chrysoura 8 0.13

Leiostomus xanthurus 6 0.10

Elassomatidae Elassoma okefenokee 5 0.5 500 9 8.37

Elassoma zonatum 5 4 0.15

Gobiidae Gobiosoma bosc 4 0.07

Microgobius gulosus 1 0.02

Achiridae Trinectes maculatus 3 0.3 384 6.31

Total number of species 23 42 14

Total number of individuals 971 5817 265

Table 12 – Fishes Collected in Edward Ball Wakulla Springs State Park

and Adjacent Reaches (Walsh and Williams 2003)
74

sunfish (Lepomis punctatus). Museum collections were dominated by redeye chub, coastal shiner, 

Seminole killifish (Fundulus seminolis), bluefin killifish (Lucania goodei), eastern mosquitofish

(Gambusia holbrooki), and Okefenokee pygmy sunfish (Elassoma okefenokee). Differences in 

sampling effort, locations and methods between the various collections preclude discussion of 

population or species trends over time. However, the combined data set results in a good 

representation of the fish fauna in the springs and upper river. An interesting observation drawn 

from these comparisons is the current presence of Suwannee bass (Micropterus notius); Suwannee 

bass were absent from earlier collections. This species is not native to the St. Marks/Wakulla 

drainage and was likely introduced from an adjacent or nearby system (Walsh and Williams 2003). 

The Suwannee bass is a State of Florida recognized Species of Special Concern (FFWCC 2007). 

Recent collections by the FFWCC (Table 13; T. Hoehn, unpublished data) suggest that Suwannee

Species Common Name Number

Percent

Composition

Micropterus notius Suwannee bass 162 11.7

Micropterus salmoides Largemouth bass 99 7.2

Lepomis auritus Redbreast sunfish 23 1.7

Lepomis microlophus Redear sunfish 5 0.4

Lepomis punctatus Spotted sunfish 266 19.2

Lepomis macrochirus Bluegill 1 0.1

Lepomis gulosus Warmouth 2 0.1

Erimyzon sucetta Lake chubsucker 35 2.5

Minetrema melanops Spotted sucker 14 1.0

Lepisosteus oculatus Spotted gar 4 0.3

Lepisosteus osseus Longnose gar 9 0.7

Mugil cephalus Striped mullet 2 0.1

Fundulus seminolis Seminole killifish 9 0.7

Lucania goodei Bluefin killifish 10 0.7

Gambusia holbrooki Gambusia 11 0.8

Labidesthes sicculus Brook silverside 32 2.3

Notropis petersoni Coastal shiner 486 35.1

Notemigonus crysoleucas Golden shiner 2 0.1

Notropis cummingsae Dusky shiner 202 14.6

Pteronotropic hypselopterus Sailfin shiner 1 0.1

Anguilla rostrata American eel 2 0.1

Esox niger Chain pickerel 1 0.1

Aphredoderus sayanus Pirate perch 1 0.1

Noturus gyrinus Tadpole madtom 1 0.1

Percins nigrofasciata Blackbanded darter 3 0.2

Total (24 species) 1383

Table 13 – Fishes Collected from Six Sites in the Wakulla River

(T. Hoehn – FFWCC, unpublished data)
75

bass are now one of the dominant species throughout much of the river, comprising nearly 12% of 

samples. As with previous samples, FFWCC collections also contained relatively high numbers of 

spotted sunfish, and coastal and dusky (Notropis cummingsae) shiners.

Sportfish populations have been examined in several Big Bend coastal rivers (Cailtreux et al. 2004, 

2005). The Wakulla River had the highest overall catch per unit effort (CPUE) of the four rivers 

examined (Table 14) with collections in the St. Marks a close second. Sportfish catch, like that 

observed in general collections (e.g., Walsh and Williams 2003), were dominated by spotted 

sunfish; Suwannee and largemouth (M. salmoides) bass made up a sizeable percentage of the catch.

Overall, the fish assemblage in the Wakulla River appears relatively depauperate in species number, 

as is typical of spring runs, with dominance by common riverine species. The downstream extent 

that many of these species travel is likely determined in large part by the upstream movement of 

salinity in the river; many of these freshwater species are salinity intolerant. Several species, on the 

other hand, are typical inhabitants of the estuary and are frequently found upstream in oligohaline 

and fresh areas. These estuarine species include striped mullet (Mugil cephalus), timucu 

(Strongylura timucu), Gulf pipefish (Syngnathus scovelli), pinfish (Lagodon rhomboides), silver 

perch (Bairdiella chrysoura), spot (Leiostomus xanthurus) and hogchoker (Trinectes maculatus) 

(Walsh and Williams 2003). Relatively high concentrations of calcium ions in the upper reaches of 

the river likely influence these species ability to live in this region.

Species

Wakulla

(N=16)

St. Marks

(N=10)

Wacissa

(N=12)

Aucilla

(N=12)

Largemouth bass 1.55 0.94 1.38 0.54

Suwannee bass 2.25 2.65 2.46 0.01

Redbreast sunfish 0.72 0.90 0.22 2.45

Bluegill 0.01 0.09 0.02 0.07

Redear sunfish 0.38 0.43 0.03 0.13

Black crappie NC 0.10 NC 0.02

Spotted sunfish 4.31 3.67 2.92 1.08

Warmouth 0.13 0.36 0.01 0.11

Flier NC NC NC 0.18

Total Sport fish 9.35 9.14 7.04 4.59

Table 14 – Mean Catch per Unit Effort (CPUE) of Sportfish in the Wakulla,

St. Marks, Aucilla and Wacissa Rivers (Cailtreux et al. 2004, 2005)

9.1.3 Amphibians and Reptiles

Limited information is available on the distribution of herptofauna in the St. Marks/Wakulla River 

system. Fifteen species of amphibians and 39 species of reptiles have been recorded within the 

Edward Ball Wakulla Springs State Park (S. Savery, FDEP, personal communication). Of these, 

nine amphibians and 21 reptiles (Appendix A) are thought to use habitats directly associated with 

the river (e.g., floodplain marshes). 
76

Amphibians are unable to reproduce under strictly terrestrial conditions and most species must 

return to water to lay their eggs. Eggs usually develop into aquatic larvae with external gills, 

muscular tails and a free-living lifestyle. Varying amounts of time are necessary before 

metamorphosis into adults occurs, thus requiring specific minimum periods of inundation. 

Metamorphosis will not occur in habitats inundated for less than the required period. Reptiles, on 

the other hand, do not require water for reproduction; most lay eggs with protective coverings on 

land. As such, they depend on water levels only as sources of drinking water.

9.1.4 Birds

Over 190 species of birds (Appendix B) have been observed within the Edward Ball Wakulla 

Springs State Park (S. Savery, FDEP, personal communication). While many of these species are 

found strictly in terrestrial habitats, an abundance of water fowl, wading birds and other species use 

the river, the fringing marshes and swamps, and are dependent indirectly on water level 

maintenance. At least 75 species use habitats directly associated with the river (e.g., floodplain 

marshes).

Numerous species, including a variety of waterfowl and wading birds, rely on inundated habitats for 

food, either submerged aquatic vegetation or the abundant benthic invertebrates and fishes 

associated with it. Food limitation can lead to local extinctions, as has been noted in Wakulla 

Springs with the limpkin (Aramus guarauna). Limpkins are limited in geographic range by their 

diet of large aquatic snails (Bryan 1981), chiefly the apple snail (Pomacea paludosa). While 

smaller snails and bivalves may be consumed, an abundance of Pomacea is usually required. Bryan 

(1981) cites varying numbers of limpkins on the Wakulla River from fewer than 20 in 1949 to 65 on 

average between 1968 and 1972 declining back to 17-19 over the 1976-1980 period. A resident 

population has not been present since the late 1990s. Surveys in recent years by State Park 

personnel documented few if any birds observed; sporadic sightings have been made, the most 

recent in April 2007. Their decline was coincident with the near extirpation of apple snails from the 

area. 

Waterfowl are common in the Wakulla and lower St. Marks rivers and the St. Marks National 

Wildlife Refuge, a federally operated sanctuary set up to provide habitat for over-wintering 

waterfowl. Annual mid-winter inventories of waterfowl have been conducted throughout this area 

as part of a nationwide effort to survey waterfowl in major concentration areas (D. Eggeman, 

FFWCC, personal communication). The survey is useful in documenting the distribution of 

waterfowl on their wintering grounds and in assessing habitat use. Surveys are conducted primarily 

by fixed-wing aircraft with specific sampling procedures undefined. Instead, an aerial crew 

determines the best and most practical means to count all waterfowl seen within a predefined unit 

area. The exact means of coverage may vary from year to year; however, the objective is to count 

all waterfowl within the survey unit. The survey is conducted annually beginning in early January. 

Two flight tracks (#105 St. Marks; #120 Wakulla) are surveyed in this area.

Annual abundances of waterfowl observed in the Wakulla River during the mid-winter inventory 

are shown in Figure 57; number of birds varied from year to year with peak observances in 1974, 

1982 and 1986. Except for these peaks, numbers have remained relatively stable throughout the 

period of observation. Fewer birds, however, were seen in the most recent year of the compilation 

(2003). American widgeon and scaup made up 75% of the waterfowl observed over the 30-year 

period (Figure 58); ring-necked ducks (14%), American coot (9%) and ten other species (2%) 
77

comprised the remainder of the inventory. Similar abundances of waterfowl observed in the lower 

St. Marks River during the mid-winter inventory are shown in Figure 59. Number of birds varied 

significantly from year to year with peak observances in 1972, 1973, 1984, 1992 and 1996; greater

Figure 57- Annual Mid-winter Waterfowl Inventory on the Wakulla River

from the Headwaters to U.S. 98 (FFWCC 2007)

Figure 58 - Dominant Waterfowl Observed During Annual Mid-winter

Waterfowl Inventory on the Wakulla River (FFWCC 2007)

Mid-Winter Waterfowl Inventory

Summary for the Wakulla River

0

1000

2000

3000

4000

5000

6000

7000

8000

197419761978198019821984198619881990199219941996199820002002

Year of Survey Number of birds observed

Most Common Species observed on the Wakulla River during Mid-winter 

Inventory (1973-2003)

Ring-necked duck

14%

Scaup

31%

American coot

9%

Miscell

2%

American 

widgeon

44%
78

than 35,000 birds per survey were estimated for these peak years. Few birds were seen during the 

period from 1974 to 1982. Redhead ducks made up 45% of the waterfowl observed over the 30-

year period (Figure 60); American coots (13%), scaups (12%), American green-winged teal (6%), 

northern pintail (6%) and 16 other species (18%) comprised the remainder of the inventory. 

Figure 59 – Annual Mid-winter Waterfowl Inventory on the lower

St. Marks River (FFWCC 2007)

Figure 60 - Dominant Waterfowl Observed During Annual Mid-winter

Waterfowl Inventory on the lower St. Marks River (FFWCC 2007)

Mid-Winter Waterfowl Inventory

Summary for the Lower St. Marks River

0

10000

20000

30000

40000

50000

1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000

Year of Survey Number of Birds Observed

Most Common Species observed on the Lower St. Marks River River

 during Mid-winter Inventory (1972-2000)

American greenwinged teal

6%

American coot

13%

American wigeon

5%

Northern pintail

6%

Redhead

45%

Scaup

12%

Miscellaneous

13%
79

Differences in abundance and species composition between birds observed in the Wakulla and St. 

Marks areas are likely due to size and habitat differences between the two systems, especially the

extensive marshes along the lower St. Marks River and the adjacent, shallow diked ponds 

maintained in the St. Marks Wildlife Refuge. These areas provide significantly more aquatic 

habitat for overwintering waterfowl than that found along the riverine corridor of the Wakulla.

9.1.5 Mammals

Twenty-two species of mammals (Appendix C) have been recorded from the Edward Ball Wakulla 

Springs State Park (S. Savery, FDEP, personal communication). While most of these species rely 

on aquatic habitats to only a limited extent, others like the West Indian manatee (Trichechus 

manatus latirostris) live in and depend heavily on maintenance of river flows and levels. Manatees 

are a protected species both at the federal and state level (i.e., listed as endangered by both, although 

the state is considering downgrading their listing to threatened) and have been observed with 

increasing frequency in panhandle estuaries (T. Calleson, FFWCC, personal communication).

Florida manatees are habitat generalists living in a wide variety of environments, from urban canal 

systems to pristine mangroves (Haubold et al. 2006). They can tolerate a wide range of salinities 

from freshwater to marine conditions. Manatees are herbivores requiring relatively large expanses 

of submerged aquatic vegetation for feeding. Manatees are particularly susceptible to cold-related 

stress, generally seeking warmer waters when temperatures drop below 20oC; they cannot withstand 

prolonged exposure to temperatures below 16oC. In the northern portion of their distributional 

range, winter aggregations are observed in springs, spring-run rivers and in warm-water outfalls 

from power plants and other industrial facilities.

Few documented sightings of manatees had been made in Wakulla County (either the Wakulla or 

St. Marks River) prior to the early-1980s (Powell and Rathbun 1984); the Suwannee River appeared 

to be the northern limit to their year-round range on the Gulf coast. By the mid-1980s, however, the 

number of manatee sightings had increased during the warm months. Sightings west of the 

Suwannee River were considered outside the normal range and were likely animals moving from 

their winter aggregations in Crystal and Homosassa rivers. The Big Bend and panhandle coasts 

contain highly suitable habitat with abundant submerged aquatic vegetation (SAV) and less boat 

traffic than peninsular Florida (Morris 2007). Increasing numbers of sightings and increasing 

human usage during the mid-1990s prompted the FFWCC to conduct an aerial survey of the area to 

document habitat usage (Morris 2007). Two hundred sixty-six manatees were observed on 46 

monthly flights between 1994 and 1996, averaging about six individuals per survey. Twenty-eight 

of these individuals were calves. A high count of 24 animals was sighted in June 1996. Distinct 

seasonal usage was noted with higher numbers found during the warm season (April-October); June 

had the highest number of observations. During summer, most individuals were sighted on the 

Wakulla River between the U.S. 98 bridge and just downstream of the confluence with the St. 

Marks. All of these sites had abundant SAV. During winter, most manatees were seen in the St. 

Marks River within or near the discharge canal of the Purdom power plant. Little evidence to date 

supports over-wintering west of the Suwannee River. Despite more sightings within the basin at 

Wakulla Springs, no individuals had been observed to over-winter in either the Wakulla or St. 

Marks system (Morris 2007) until 2008 when at least ten individuals were noted in and around 

Wakulla Spring. 
80

Recent counts by State Park personnel in and around the spring basin indicated 39 manatee 

sightings in 2003, 8 in 2004, 104 in 2005, 225 in 2006, and 38 as of August 2007 (S. Savery, FDEP, 

personal communication). Most observances were single individuals or pairs; however, on two 

occasions in 2005 as many as nine animals were noted together.

9.2 Estuarine Communities

Ecological information on invertebrate and fish communities in the immediate vicinity of the St. 

Marks estuary appears limited to a handful of studies carried out in the St. Marks National Wildlife 

Refuge to examine zonation patterns in salt marsh communities (Subrahmanyam and coworkers) 

and the influence of food web structure on overwintering migratory waterfowl in nearshore seagrass 

beds (Baird et al. 1998; Christian and Luczkovich 1999). However, Livingston and coworkers have 

amassed considerable information on the ecology of seagrass beds in adjacent areas of Apalachee 

Bay (i.e., offshore of the Econfina and Fenholloway Rivers to the east of St. Marks). The areas 

examined by the Livingston group are very similar to those in the nearshore regions of the St. 

Marks with comparable floral and faunal assemblages and dynamics. The majority of this work (in 

both salt marsh and seagrass communities) was conducted during the 1970’s and 1980’s, with little 

follow up investigations. Despite the lack of recent data, these works provide an excellent 

characterization of the area. Information gleaned from these studies is summarized in the 

following sections. 

9.2.1 Salt Marshes

Tidal salt marshes are the most visible habitat along the shoreline of the lower St. Marks River and 

adjacent coastline of Apalachee Bay. These marshes are drained by a series of small tidal creeks, 

usually with very limited watersheds, and provide refuge for a variety of macroinvertebrates and 

fishes. The following sections summarize a series of studies conducted in the marshes of the lower 

St. Marks (Subrahmanyam and coworkers).

9.2.1.1 Benthic Infauna

Horlick and Subrahmanyam (1983) examined the macroinvertebrate infauna in a small tidal creek 

near the St. Marks Lighthouse. Four sampling sites were established along the length of creek 

beginning at the mouth and ending at the origin. A total of 111 species was collected with the 

number of species at each site positively related to the distance from the creek mouth; greatest 

number of species was noted near the mouth with least number at the creek origin. Densities of 

organisms varied spatially and temporally ranging from 979 to 43,343 individuals per m2. 

Generally, densities followed the gradient described for species with greatest densities usually 

observed near the creek mouth. Dominant species varied with creek location and included 

Ampelisca abdita (amphipod), Hargeria rapax (tanaid), unidentified oligochaetes, Xenathura 

brevitelson (isopod), unidentified hydrobid snail, and the polychaetes Aricidea sp., Laeonereis 

culveri, and Haploscoloplos foliosus. As expected, species composition at the creek mouth more 

closely resembled open estuarine assemblages while faunal composition at the upper creek site was 

more similar to adjacent salt marsh assemblages. Distinct seasonal patterns of abundance were seen 

with peaks in spring and fall thought to be related to breeding and recruitment, while midsummer 

declines were related to increased numbers of predatory fish.
81

9.2.1.2 Macroinvertebrate Community

Species composition, abundance and spatial distribution of macroinvertebrates were examined in 

two tidal marshes near the mouth of the St. Marks River, one located on the western side of the river 

along Goose Creek Bay and the other adjacent to the East River just north of the lighthouse 

(Subrahmanyam et al. 1976; Kruczynski and Subrahmanyam 1978; Subrahmanyam and Coultas 

1980). A total of 22,814 organisms representing 51 species were collected from the two sites with 

mollusks accounting for 31%, annelids 24%, crustaceans 44% and insect larvae 1% of the total 

numbers. Overall mean density from the sites was 475 individuals per m2 with significantly higher 

density in the low marsh (540 individuals per m2) relative to the high marsh (381 individuals per 

m

2

). Seasonal mean density tended to be greater in winter (578 individuals per m2) than summer 

(375 individuals per m2); similarly, greater number of species was noted in winter. In contrast, 

biomass was highest in summer; the gastropod Littorina irrorata accounted for 81% of summer 

biomass.

Species composition varied with distance from the creeks (Table 15), with certain species found in 

greater abundance in specific zones. The lower marsh zone was dominated by the gastropod 

Littorina irrorata, the isopod Cyathura polita, and the tanaid Apseudes sp., while the upper zone 

had high numbers of Littorina, Cyathura and unidentified fiddler crabs (Uca spp.). The high marsh 

zone, located above the salt flats, was characterized by the fiddler crab Uca pugilator and the 

mollusks Melampus bidentatus and Cyrenoidea floridana.

Species Phylum

Marsh Zones

Lower Upper High Marsh

Littorina irrorata M 1 1 7

Cyathura polita C 2 2 10

Apseudes sp. C 3 10

Scoloplos fragilis A 4 5

Leptochelia sp. C 5 4

Uca longsignalis C 6 10

Sesarma reticulatum C 7 9

Eurytium limnosum C 8

Laeonereis culveri A 9

Lycastopsis pontica A 10

Uca spp. C 3 8

Polymesoda caroliniana M 6 6

Modiolus demissus M 7

Oligochaetes (unidentified) A 8 5

Uca pugilator C 9 1

Cyrenoidea floridana M 10 3

Melampus bidentatus M 2

Cerithidea scalariformis M 4

Table 15 – Ranking of Most Important Salt Marsh Macroinvertebrate Species in

Three Marsh Zones in the lower St. Marks (Subrahmanyam et al. 1976)

(Phylum ID: A = Annelida, C = Crustacea, M = Mollusca)
82

9.2.1.3 Fish Abundance

Subrahmanyam and Drake (1975) and Subrahmanyam and Coultas (1980) examined the fish 

community inhabiting tidal creeks in two marshes near the mouth of the St. Marks River (same 

locations as described above under Macroinvertebrate Community). Fifty-five species were 

collected during the year of the study. The community was dominated by five species of killifish 

(Fundulus similis, F. grandis, F. confluentes, Adinia xenica, and Lucania parva), sheepshead 

minnow (Cyprinodon variegatus), sailfin molly (Poecilia latipinna), tidewater silverside (Menidia 

beryllina), spot (Leiostomus xanthurus), spotfin mojarra (Eucinostomus argenteus), and pinfish 

(Lagodon rhomboides). Although distinct seasonal patterns were not evident, higher numbers of 

fish were generally collected during the cooler months at high tide, and in warmer months at low 

tide. Overall, average numerical abundance and biomass were greater during low tides when fish 

were concentrated in the tidal creeks; at high tide individuals could move out of the creeks into the 

salt marsh and forage with the tidal flooding. Abundance rankings of the numerically dominant 

species are shown for the two marshes over high and low tides (Table 16).

Species

 St. Marks Marsh Wakulla Marsh

Low Tide High Tide Low Tide High Tide

Fundulus similis 1 1 12

Menidia beryllina 2 1 5 2

Fundulus grandis 3 10 3 5

Cyprinodon variegates 4 4

Leiostomus xanthurus 5 2 2 1

Adenia xenica 6 6

Eucinostomus argenteus 7 6 9 4

Poecillia latipinna 8 10

Lagodon rhomboides 9 3 7 6

Anchoa mitchelli 10 5 8 3

Fundulus confluentes 11 11

Paralichthys albigutta 12

Lucania parva 13 11

Strongylura notata 11

Strongylura marina 7 7

Polydactylus octonemus 4 12 8

Anchoa hepsetus 8

Oligoplites saurus 9 9

Mugil cephalus 12 10

Cynoscion arenarius 13

Dorosoma petenense 13

Harengula jaguana 13

Table 16 – Ranking of Most Abundant Tidal Creek Fish Species at High

and Low Tides (Subrahmanyam and Drake 1975)

Fish species were placed into four categories according to gut content, occurrence at low or high 

tides, and monthly length frequencies; groups included permanent residents, species using the 

marshes as nursery grounds, foraging species, and sporadic visitors. Those fishes collected as both 

young and adults on high and low tides were considered permanent residents. In this group, 
83

Fundulus similis, F. grandis and Cyprinodon variegatus were the most common, Adenia xenica and 

Poecillia latipinna less common, and Lucania parva and F. confluentes were least common. While 

juveniles of these species predominated, adults were relatively common. The second category 

contained primarily juveniles caught on both tides; adults were either not collected or were 

collected only on high tides. Included in this group were Menidia beryllina, Leiostomus xanthurus, 

Eucinostomus argenteus, Mugil cephalus, Lagodon rhomboides, Oligoplites saurus, Anchoa 

mitchelli and A. hepsetus, Syngnathus scovelli, Synodus foetens, Gobiosoma bosci, Gobionellus 

boleosoma and others. These species were considered to utilize the marsh as nurseries. A third 

category included those species caught only on high tides and included numerous adults; these 

species were considered to be foraging species using the marshes as feeding grounds on the 

flooding tide. This group contained such species as Bairdiella chrysoura, Brevoortia patronus, 

Cynoscion arenarius, Harengula jaguana, Hyporhamphus unifasciatus, Orthopristis chrysoptera

and Scianops ocellata. These species are common inhabitants of the nearby offshore grass beds and 

move inshore to feed. The fourth category is the sporadic visitor and includes such species as 

Polydactylus octenemus, a relatively uncommon species along the northern Gulf that appears 

occasionally in high numbers. Its movements are erratic and it inhabits a variety of habitats.

Livingston (1975) recorded 36 species of fishes inhabiting a marsh tidal creek in the Econfina River 

about 12 miles east of the St. Marks River. His collections were dominated by Brevoortia patronus, 

Menidia beryllina, Leiostomus xanthurus, Fundulus grandis, Anchoa mitchelli and Poecilia 

latipinna. The overall species list was similar to that observed in the St. Marks marsh by 

Subrahmanyam and Drake (1975) and Subrahmanyam and Coultas (1980).

The marsh fish community is highly dynamic with various species entering the marshes in different 

seasons. Feeding migrations, recruitment of juveniles and movement of resident species generally 

account for the temporal variations in abundance, biomass and species composition in the marshes.

9.2.2 Seagrass Beds

Seagrass meadows are the most conspicuous habitat in the nearshore waters of Apalachee Bay. 

These beds are highly productive areas and provide food and habitat for a diverse array of species. 

While limited data are available for the portions of Apalachee Bay directly influenced by the St. 

Marks River, the following sections summarize information gathered from a variety of studies 

(Livingston and coworkers) in the shallow grass beds in the eastern sections of the bay (i.e., the 

areas offshore of the Econfina and Fenholloway rivers). 

9.2.2.1 Benthic Macrofauna (infauna and epifauna)

A variety of small organisms are found associated with seagrass and macroalgae in Apalachee Bay, 

including a diverse array of polychaetes, mollusks and crustaceans (e.g., amphipods, isopods, 

tanaids, decapods). Stoner (1980) noted 170 species of macrofauna associated with seagrass beds in 

Apalachee Bay, including 75 polychaetes, 31 amphipods, 21 mollusks, 10 shrimp, 6 crabs and 5 

isopods; the fauna were dominated by amphipods (37%) and polychaetes (45%). Mean 

macrofaunal density was 2,827 individuals per m2 with values ranging from 833 to 8,301 per m2. 

Density of animals generally peaked between April and May with declines in the late summer and 

fall. Numbers began to increase in November associated with a sharp decline in fish populations. 

This observation was attributed to a decrease in predation pressure with fewer fish predators on the 
84

beds in late fall and winter. Overall, macrofaunal abundance was positively correlated with plant 

biomass; the greater the plant biomass at a site, the greater the macrofaunal density (Stoner 1980).

Within the seagrass beds, animals are not distributed randomly, rather preferences have been noted 

among microhabitats/seagrass species (Lewis 1984, 1987). Eighty-two crustacean species were 

collected from a variety of microhabitats within the grass beds (Lewis 1982). Vegetated habitats 

consistently supported greater numbers of individuals and species that did unvegetated zones, either 

large bare patches or small sandy areas among the grass shoots (Lewis 1984). Distribution of 

crustaceans among seagrass microhabitats was thought to be a complex function involving faunal 

habitat choice and predation pressure, both of which are affected by the amount and kind of 

seagrass present.

Comparing the crustacean epifauna of turtle grass with that on the dominant macroalgae in the grass 

beds, a similar suite of species was noted despite significant differences in shape or architecture 

among plant species; however, relative abundances of many species varied among plant hosts 

(Lewis 1987). Species richness was generally higher on turtle grass than on any of the macroalgae. 

Abundances of crustaceans per plant biomass or per plant surface area, on the other hand, were 

greater on all macroalgal species compared to seagrass. Although abundances per plant biomass 

and plant surface area were greater on macroalgae relative to turtle grass, densities (individuals per 

meter square of bottom) of animals associated with turtle grass were significantly greater than those 

associated with macroalgae, primarily because of the greater abundance of turtle grass in the grass 

bed. These observed abundance differences can be influenced by several factors, including: (1) 

morphological constraints of individual species based on body size and shape, (2) differences in 

food availability, especially epiphytes and detritus, (3) competitive interactions and territorial 

behavior, and (4) differential susceptibility to predation. 

The picture of crustacean abundance (as well as other organisms) that emerges from these and other 

studies is one of a spatial and temporal mosaic within the grass beds. First, greater abundance and 

species richness are associated with vegetated than with unvegetated areas in the beds. Second, 

animals do not occur in equal numbers on all macrophytes. The most common plant, Thalassia 

testudinum, had the lowest number of associated individuals of any of the macrophytes examined. 

Crustaceans are, in fact, concentrated on small, isolated “islands” of macroalgae scattered 

throughout the grass bed. As seagrass and macroalgal biomass change diurnally and seasonally, 

densities of associated animals are affected (Lewis 1987). 

9.2.2.2 Macroinvertebrate Abundance 

A variety of larger organisms are also found associated with seagrass and macroalgae in Apalachee 

Bay, including an assortment of mollusks, crustaceans (e.g., shrimp, crabs) and echinoderms 

(Hooks 1973; Heck 1976; Hooks et al. 1976; Dugan and Livingston 1982; Greening and Livingston 

1982). Dugan and Livingston (1982) recorded 112 epibenthic macroinvertebrate species from trawl 

samples collected in Apalachee Bay from 1972 to 1979; 85 species were collected in the Econfina 

estuary, 95 in the Fenholloway. Decapod crustaceans accounted for 95% of the total number of 

individuals, followed by mollusks (4%) and echinoderms (1%). Nearly twice as many animals were 

collected from Econfina relative to Fenholloway stations; abundances were related to the amount of 

vegetation present (which was related to the presence of pulp mill pollution in the Fenholloway). 

The 10 dominant species for each estuary are shown in Table 17; these species made up over 92% 

and 80% of the fauna in the Econfina and Fenholloway, respectively, and consisted of small shrimp 
85

and crabs. Arrow shrimp (Tozeuma carolinense) and hermit crabs (Pagurus maclaughlinae) 

dominated the fauna in the Econfina while the hippolytid shrimp (Hippolyte pleuracanthus) and 

hermit crabs (P. maclaughlinae) were most abundant in the Fenholloway. Seven of the top ten 

species in each area were found in common. Dugan and Livingston (1982) categorized the 

dominant species by habitat associations (Table 18). They noted that despite high seasonal 

variability, macrofaunal abundance and species numbers were relatively constant from year to year. 

Reduced numbers of species tended to coincide with periods of climatological stress (e.g., low 

winter temperature, reduced salinities).

Econfina Species Abundance Percent Fenholloway Species Abundance Percent

Tozeuma carolinense 13974 22.6 Hippolyte zostericola 4925 16.3

Pagurus maclaughlinae 11712 18.9 Pagurus maclaughlinae 3925 13.0

Palaemonetes intermedius 7133 11.5 Periclimenes longicaudatus 3338 11.0

Palaemon floridanus 7011 11.3 Palaemon floridanus 3064 10.1

Hippolyte zostericola 5180 8.4 Tozeuma carolinense 2983 9.9

Neopanope texana 4634 7.5 Neopanope texana 2894 9.6

Periclimenes longicaudatus 3435 5.6 Neopanope packardii 1163 3.8

Thor dobkini 1634 2.6 Farfantepenaeus duorarum 842 2.6

Neopanope packardii 1264 2.0 Palaemonetes intermedius 686 2.3

Farfantepenaeus duorarum 1046 1.7 Callinectes sapidus 514 1.6

Table 17 – Ten Dominant Species Collected from Pooled Econfina and Fenholloway

Estuarine Sites from 1972 to 1979 (Dugan and Livingston 1982)

Low Salinity Oyster Bar Red Algae Seagrass

Palaemonetes intermedius Ophiothrix angulata Hippolyte zostericola Echinaster sentus

P. pugio Ophioderma brevispinum Periclimenes longicaudatus Argopectin irradians

Callinectes sapidus Ophiolepis elegans P. americanus Columbella rusticoides

Farfantepenaeus duorarum Brachiodontes exustus Lysmata wurdemanni Modulus modulus

Rhithropanopeus harrisii Menippe mercenaria Thor dobkini Podochela riisei

Panopeus herbstii Portunus gibbesii Anachis avara Tozeuma carolinense

Eurypanopeus depressus Rhithropanopeus harrisii Urosalpinx perrugata

Panopeus herbstii

Eurypanopeus depressus

Table 18 – Macroinvertebrate-habitat Associations in Apalachee Bay

(Dugan and Livingston 1982)

In addition to seasonal and inter-annual variability, Greening and Livingston (1982) observed a 

significant amount of diurnal (day/night) variation in macroinvertebrate distributions (Table 19). Of 

the 34 species comprising greater than 0.1% of their catch, eight were more abundant during the day 

and 11 were more prevalent at night; 15 showed no preference. Habitat differences in the grass bed 

(e.g., presence of red algae clumps) appeared to influence the degree of variation between the 

sampled day and night communities. 
86

Species Phylum D/N Abundance

Percent of 

Total

Hippolyte zostericola C D 20526 14.0

Pagurus maclaughlinae C D 18558 12.7

Anachis avara M D 15200 10.4

Farfantepenaeus duorarum C N 11636 7.9

Periclimenes longicaudatus C D 11548 7.9

Tozeuma carolinense C D 10007 6.8

Palaemon floridanus C O 8472 5.8

Thor dobkini C O 6981 4.8

Neopanope texana C N 6951 4.7

Argopectin irradians M O 3721 2.5

Ambidexter symmetricus C N 3706 2.5

Turbo castanea M N 3467 2.4

Urosalpinx perrugata M D 2873 1.9

Modulus modulus M O 2710 1.8

Alpheus normanni C N 2096 1.4

Columbella rusticoides M D 2095 1.4

Neopanope packardii C N 2049 1.4

Echinaster sp. E O 1793 1.2

Libinia dubia C O 1583 1.1

Nassarius vibex M O 1554 1.1

Ophioderma brevispinum E D 1464 1.0

Cerithium muscarum M O 1083 0.7

Latreutes fucorum C O 785 0.5

Epialtus dilatatus C O 637 0.4

Palaemonetes intermedius C O 627 0.4

Prunum apicinum M O 496 0.3

Ophiothrix angulata E O 415 0.3

Metaporhapsis calcerata C N 395 0.3

Podochela riisei C O 383 0.3

Callinectes sapidus C N 366 0.2

Bulla striata M N 190 0.1

Portunus gibbesii C N 188 0.1

Sicyonia laevigata C N 166 0.1

Pagurus pollicaris C O 149 0.1

Table 19 – Total and Relative Abundance of Dominant Macroinvertebrate Species from

Pooled Apalachee Bay Estuarine Stations (Greening and Livingston 1982)

(Only those organisms comprising >0.1% of total catch are included. Phylum id: C=Crustacea, 

E= Echinodermata, M=Mollusca. D/N: D=day catch greater, N=night catch greater, O=no 

difference between day and night catch)

9.2.2.3 Fish Abundance 

Over one hundred species of fishes were collected from the seagrass beds of Apalachee Bay 

offshore of the Econfina and Fenholloway Rivers between 1971 and 1979 (Livingston 1984a, b). 

Total and relative abundance of dominant fishes collected are summarized for the multiyear 

sampling effort (Table 20). Both areas were dominated by pinfish (Lagodon rhomboides), probably 
87

the most common grassbed species in the northern Gulf of Mexico. Other abundant species 

included spot (Leiostomus xanthurus), filefish (Monocanthus ciliatus and Stephanolepis hispidus), 

silver perch (Bairiedella chrysoura), black sea bass (Centropristis striata), spottail pinfish 

(Diplodus holbrooki), dusky pipefish (Syngnathus floridae), pigfish (Orthopristis chrysopterus) and 

silver jenny (Eucinostomus gula). These ten species comprised 85% of the fishes caught in the 

Econfina estuary, and along with the bay anchovy (Anchoa mitchelli) made up 78% of the 

Fenholloway estuarine fish catch. Bay anchovies, not typically a grassbed species, were found in 

abundance in the Fenholloway estuary at sites relatively devoid of vegetation. Fish collections 

taken near the mouth of the Econfina River (Station 7), a site with conditions very similar to the 

lower St. Marks estuary, were dominated by spot, pinfish, silver perch, threadfin (Polydactylus 

octonemus), and silver jenny.

Species

Econfina Fenholloway

Rank Abundance Percent Rank Abundance Percent

Lagodon rhomboids (pinfish) 1 44463 54.1 1 8661 23.1

Leiostomus xanthurus (spot) 2 7747 9.4 2 5997 16.0

Bairidella chrysoura (silver perch) 3 5084 6.2 4 3694 9.8

Monocanthus ciliates (fringed filefish) 4 3435 4.2 6 1246 3.3

Diplodus holbrooki (spottail pinfish) 5 3164 3.9 11 650 1.7

Syngnathus floridae (dusky pipefish) 6 1982 2.4 12 521 1.4

Orthopristis chrysoptera (pigfish) 7 1965 2.4 5 2044 5.4

Eucinostomus gula (silver jenny) 8 1530 1.9 10 765 2.0

Centropristis striata (black sea bass) 10 1356 1.7 8 903 2.4

Stephanolepis hispidus (planehead filefish) 11 1218 1.5 7 928 2.5

Opsanus beta (Gulf toadfish) 12 1015 1.2 22 209 0.6

Eucinostomus argenteus (spotfin mojarra) 14 833 1.0 14 499 1.3

Paraclinus fasciatus (banded blenny) 15 605 0.7 16 379 1.0

Syngnathus scovelli (Gulf pipefish) 17 497 0.6 19 288 0.9

Chilomycterus schoepfi (striped burrfish) 18 467 0.6 13 510 1.4

Cynoscion nebulosus (spotted seatrout) 21 372 0.5 21 231 0.6

Anchoa mitchelli (bay anchovy) 26 184 0.2 3 5337 14.2

Synodus foetens (inshore lizardfish) 29 136 0.2 28 120 0.3

Total number of individuals 82241 37582

Total number of species 94 99

Table 20 – Rank and Relative Abundance of Dominant Fishes Collected in Apalachee

Bay Offshore of the Econfina and Fenholloway Rivers (Livingston 1984)

(Collections were taken monthly at seven sites in each system between 1971 and 1979.

Abundances were pooled for the collection period over all stations in each area.)

Total number of fishes was lowest in winter months (December to February) and highest between 

May and August; number of fish species was highest in July and August, concurrent with peaks in 

abundance. Both total fish number and number of the dominant species, Lagodon rhomboides, 

were highly correlated with the abundance of seagrass (Stoner 1983). These significant 

relationships likely result from increased food and shelter provided by seagrass. 
88

9.2.2.4 Trophic Structure 

Several studies focused on the feeding ecology of invertebrates (Leber 1983, 1985) and fishes 

(Stoner 1980; Stoner and Livingston 1980; Ryan 1981; Livingston 1982; Livingston 1984a, b; 

Clements and Livingston 1984) associated with Apalachee Bay seagrass beds. Decapod crustaceans 

and fish are among the principal macrofaunal predators in the Apalachee Bay grass beds; both 

groups have been found to be important links between primary production and higher consumers.

Leber (1983) examined feeding patterns of the dominant decapods, noting that they fell into two 

major subgroups: herbivores (largely brachyuran crabs) and carnivores (penaeid and caridean 

shrimps). Both subgroups included some strongly omnivorous trophic groups; however, within the 

carnivorous subgroup, plant material was limited and consumption may have been primarily 

incidental. Seagrasses were a major food item only in diets of brachyuran crabs (Neopanope 

packardii, N. texana, Epialtus dilatatus, Pitho anisodon, Podochela riisei and Libinia dubia) and an 

alpheid shrimp (Alpheus normanni). Considerable overlap in diet was noted among the feeding 

groups with nine dominant food categories observed: (1) crabs, (2) shrimp-amphipods, (3) 

polychaetes-amphipods, (4) amphipods, (5) amphipods-copepods-filamentous epiphytes, (6) 

Thalassia-detritus-encrusting algae-crustaceans, (7) encrusting algae-Thalassia, (8) filamentous 

epiphytes-Thalassia, and (9) Thalassia. The pink shrimp, Farfantepenaeus duorarum, was the 

dominant invertebrate predator on most animal prey types, feeding heavily on copepods, 

amphipods, bivalves, gastropods, and shrimp. The caridean shrimps, Processa bermudensis and 

Ambidexter symmetricus, were the dominant polychaete predators. Callinectes sapidus, Palaemon 

floridanus, Metaporhaphis calcerata were also highly predatory on grassbed epifauna. Previously 

thought to be predominantly opportunistic feeders, Leber (1983) found these decapods to be 

differentially restrictive in feeding mode with consumer selectivity of food types likely a function of 

prey accessibility, predator preferences and morphological constraints on consumers.

In addition to documenting dietary patterns of dominant decapods, Leber (1983, 1985) noted their 

influence in grassbed community dynamics. In a series of predator inclusion/exclusion 

experiments, he found predaceous pink shrimp (F. duorarum) were an important organizing force 

in faunal distribution and abundance patterns. Predation by pink shrimp strongly affected 

abundances of prey groups known to be important in its diet. The intense predation effects in his 

“simple” experimental habitat (clipped seagrass treatment) demonstrated the potential for shrimp to 

significantly depress prey population densities in sparsely vegetated microhabitats. As microhabitat 

structural complexity increased (intermediate and high plant biomass treatments) predation effects 

on prey densities were reduced for some prey species. For other prey species, however, predation 

effects remained relatively constant across the vegetation gradient. Amphipods and larger mollusks 

were most affected, with predation on these taxa significantly reduced in more complex habitats. 

Plant biomass appeared less important in reducing predation on decapods and polychaetes. Leber 

concluded that strong natural associations of epifauna with seagrass and macroalgae appear to be 

the net result of predation, refuge and habitat selection/preference.

Trophic relationships of fishes have been extensively examined in the Apalachee Bay grass beds by 

Livingston and coworkers. These beds serve as nursery areas for juvenile stages of many fishes 

migrating from offshore during varying seasons of the year. These species undergo seasonal 

progressions of feeding habits that follow specific size-related patterns including various trophic 

levels from herbivory to carnivory (Livingston 1982; 1984a, b). Using a nine-year data base of 

stomach analysis and food preferences, Livingston (1982) identified size-specific feeding classes 
89

within the dominant grassbed fishes according to similar dietary habits. Similar “ontogenetic 

trophic units” could be grouped together resulting in three major categories of trophic organization: 

planktivorous feeders, benthic omnivores and carnivores, and crustacean specialists. The 

planktivorous group fed primarily on copepods, amphipods and some plant remains, with 

polychaetes constituting a significant portion for some species; this group included bay anchovy 

(Anchoa mitchelli), spot (Leiostomus xanthurus) and the mojarras (Eucinostomus gula and E. 

argenteus). Benthic omnivores and carnivores fed on harpacticoid copepods, invertebrate eggs, 

benthic crustaceans and plant remains during the early stages, followed by increasing dependence 

on plant material and hydroids in more mature fish. Some members of this group fed on 

combinations of plant remains and small invertebrates such as amphipods, copepods, polychaetes 

and bivalves mollusks. The benthic omnivore/carnivore group included: pinfish (Lagodon 

rhomboides), spottail pinfish (Diplodus holbrooki), fringed and planehead filefish (Monacanthus 

ciliatus and Stephanolepis hispidus), striped burrfish (Chilomycterus schoepfi), Gulf toadfish 

(Opsanus beta), sea catfish (Arius felis), inshore lizardfish (Synodus foetens) and cownose rays 

(Rhinoptera bonasus). The final group specialized on crustaceans such as crabs, shrimp and 

amphipods and included dusky and Gulf pipefish (Syngnathus floridae and S. scovelli), pigfish 

(Orthopristis chrysoptera), silver perch (Bairdiella chrysoura), black sea bass (Centropristis 

striata), and banded blenny (Paraclinus fasciatus). Overall trophic organization of seagrass fishes 

appeared largely dependent on interactions of individual feeding aggregations with seasonal 

progressions of key habitat features and productivity cycles (Livingston 1982). Despite 

considerable seasonal and annual variability in physical conditions, general ontogenetic feeding 

patterns remained relatively stable over the period of observation (Livingston 1984b).

Additionally, the food web structure of inshore Halodule wrightii beds in the St. Marks National 

Wildlife Refuge was examined with particular emphasis on the role of overwintering migratory 

waterfowl (Baird et al. 1998; Christian and Luczkovitch 1999). Based on productivity, several taxa 

were noted to be potentially important to energy flow relative to their trophic position. These 

included protozoans in the water column and sediments, spot, predatory polychaetes, Gulf flounder 

and needlefish, and fish-eating birds. Through their analysis, detritus and benthic microalgae were 

important sources of food in the extended diets of many consumers. Energy flow through the 

winter Halodule community was dominated by detritus and benthic microalgae at the bottom and by 

waterfowl and piscivorous fish at the top. This pattern changed seasonally as seagrass productivity 

increased and many of the birds emigrated in summer.

9.3 Commercial Landings

Commercial harvests of several estuarine species have been reported for the Apalachee Bay area. 

Landings are reported by the county in which they are sold to a wholesale seafood establishment 

and do not necessarily reflect the actual location of capture. Landings shown here are those 

reported for Wakulla County and are expected to account for those harvests in the immediate 

vicinity of the St. Marks River as well as adjacent waters. While overall county landings include 

such offshore finfish as grouper, many commercial species are caught entirely or in part in the 

estuarine portions of the system. Blue crabs, oysters and mullet fall into the inshore group, having 

been harvested in more estuarine waters; shrimp, stone crab, grouper and sea bass are more marine.

Of the inshore species, blue crabs and mullet clearly dominated the Wakulla County harvest over 

the last six years (Table 21 and 22); relatively small catches were reported for oysters. Blue crabs 

made up over 85% of the invertebrate catch with mullet comprising nearly half of the finfish catch. 
90

Invertebrates

Year

2000 Trips 2001 Trips 2002 Trips

Blue crab 939,535 2160 67,6191 2145 838,472 2215

Stone crab 76,619 767 69,810 508 107,244 610

Shrimp (Total) 34,445 63 48,102 99 38,588 59

Oysters 24,567 211 71,155 599 55,465 436

All Invertebrates 1,081,256 3096 878,760 3262 1,046,751 3287

Fish

Mullet (Total) 320,223 961 395,528 939 365,679 826

Grouper

Gag 142,978 537 179,185 643 151,872 602

Red 138,823 402 186,763 572 163,498 569

Sea bass 32,462 88 77,623 176 74,712 205

All Finfish 765,032 1708 963,714 1791 888,212 1812

Table 21 – Recent Commercial Harvests (in pounds) of Selected Fish and Shellfish

Landed in Wakulla County (Fish and Wildlife Research Institute 2007)

Invertebrates

Year

2003 Trips 2004 Trips 2005 Trips

Blue crab 1,377,151 2494 1,591,136 2388 1,621,968 2520

Stone crab 73,949 551 74,845 422 75,317 489

Shrimp (Total) 42,177 66 24,483 44 18,523 28

Oysters 33,742 187 19,931 112 27,473 260

All Invertebrates 1,534,153 3286 1,714,619 2828 1,750,129 3065

Fish

Mullet (Total) 382,300 862 358,354 836 295,834 862

Grouper

Gag 96,645 408 114,790 365 103,495 324

Red 64,802 352 84,062 351 82,648 303

Sea bass 96,966 223 5610 56 24,842 105

All Finfish 763,463 1601 659,965 1411 594,569 1392

Table 22 – Recent Commercial Harvests (in pounds) of Selected Fish and Shellfish

Landed in Wakulla County (Fish and Wildlife Research Institute 2007)

Overall, commercial landings appear to have increased slightly during the latter three years with a 

noticeable portion of that increase due to blue crabs. Grouper made up the majority of the offshore 

species, comprising about a third of the finfish catch. Stone crab and shrimp harvests, although an 

order-of-magnitude smaller than blue crab, contribute significantly to the area’s commercial 

fisheries.
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9.4 Threatened and Endangered Species

The St. Marks watershed supports about 32 species of plants and 74 species of animals designated 

by the federal government or the State of Florida as either threatened, endangered, species of special 

concern or rare (see Appendix A in NWFWMD 1997). Florida Natural Areas Inventory (FNAI 

2008) includes 92 element occurrences of rare and endangered plants (31) and animals (61) within 

the basin. From these combined lists, only a limited number have been sighted or have the potential 

for inhabiting the submerged portions of St. Marks estuary and adjacent Apalachee Bay; these 

include gulf sturgeon (Acipenser oxyrinchus desotoi), West Indian manatee (Trichechus manatus 

latirostris) and three species of sea turtles (Atlantic loggerhead, Caretta caretta; Atlantic green 

turtle, Chelonia guttata; Kemp’s ridley, Lepidochelys kempii).

Of these, West Indian manatees are one of the most frequent inhabitants of the area. Manatees are a 

protected species both at the federal and state level (i.e., listed as endangered by both, although the 

state is considering downgrading their listing to threatened) and have been observed with increasing 

frequency in panhandle estuaries (T. Calleson, FFWCC, personal communication). A detailed 

description of manatee sightings in the area is given in the previous section on Riverine 

Communities-Mammals.

Hoehn (1998) cited no references to rare and imperiled fishes in the St. Marks and Wakulla Rivers. 

He stated that Alabama shad (Alosa alabamae), gulf sturgeon, and Suwannee bass (Micropterus 

notius) have been observed in the Ochlockonee River and the blackbanded sunfish (Enneacanthus 

chaetodon) were found in the Aucilla and Econfina; however, none had been collected in the St. 

Marks system. Recent collections, however, have noted relatively large numbers of Suwannee bass 

in both the Wakulla and St. Marks Rivers (Walsh and Williams 2003; Cailteux 2004, 2005; T. 

Hoehn, FFWCC, pers. comm.). The western portion of Apalachee Bay was not included in the 

recent gulf sturgeon critical habitat designation (USFWS 2003) despite having collections from the 

Apalachicola, Ochlockonee and Suwannee Rivers (Wakeford 2001). Any gulf sturgeon found in 

the St. Marks River and adjacent waters are likely transients.

Beck et al. (2000) listed occurrence records of five “imperiled” species in the northeastern 

Apalachee Bay region (Ochlockonee Bay to Econfina River). These included one record of gulf 

sturgeon, one of manatee, three occurrences of Kemp’s ridley, four observations of dwarf seahorse 

(Hippocampus zosterae) and six of fringed pipefish (Anarchopterus criniger). These latter two 

species were considered imperiled, primarily because of their declining habitat (high salinity 

seagrass beds), but are neither state nor federally listed. 
92

10.0 IMPORTANCE OF FRESHWATER TO THE LOWER ST. MARKS

AND WAKULLA RIVERS AND APALACHEE BAY SYSTEM

Freshwater inflow is thought to be one of the most important variables influencing riverine 

ecosystem components (e.g., fish populations, floodplain forest composition, nutrient cycling) both 

directly and indirectly (Poff et al. 1997; Richter et al. 1997; Richter et al. 2003). A river’s flow 

regime has been described as the “master variable” governing many other parts of the riverine 

system (Richter et al. 2003) and includes characteristics of magnitude, frequency, duration, timing 

and rate of change (Poff et al. 1997). Increased natural variability of these characteristics generally 

results in greater diversity and complexity of riverine habitats and is essential to successful lifecycle completion for many aquatic, riparian and wetland species (Richter et al. 1996). Variation in 

hydrologic conditions frequently influences population dynamics of these species by affecting 

reproductive success, natural disturbance, biotic competition and predator-prey relationships (Poff 

and Ward 1989). Modifications to the hydrologic regime can result in alterations to the species 

composition, structure and function of these systems primarily through changes in the physical 

habitat (Richter et al. 1996).

The role of freshwater input in determining the productivity of river-dominated estuaries has been 

extensively discussed (Snedaker et al. 1977; Schroeder 1978; Cross and Williams 1981; Longley 

1994; Livingston et al. 1997; Estuarine Research Federation 2002). Under natural river inflow 

conditions, the combination of generally high levels of primary production together with reduced 

predator activities by marine organisms have established conditions favoring rapid growth and 

enhanced productivity of estuarine populations that are adapted to rapidly changing environmental 

conditions (Livingston 1984c, 1991). This is particularly noticeable in systems with moderate to 

large riverine input and near the head of estuaries with relatively small freshwater inflow.

A key component of the estuarine environment is its dynamic nature, which in part is a function of 

an ever-changing, non-uniform freshwater input. This freshwater input is modified by basin 

morphology, winds and tides to produce highly variable conditions both spatially and temporally. 

The seasonal timing and magnitude of inflows are important, particularly during the critical periods 

of reproduction and growth. Relatively few organisms have evolved the physiological and 

behavioral adaptations to tolerate these widely fluctuating conditions; yet, those that have may be 

found in high numbers. These organisms have evolved life history strategies to maximize the 

benefits provided by the estuary. Despite the seasonal and inter-annual variation, inflows to 

panhandle estuaries display a recurrent pattern of winter peaks and summer-fall lows. This pattern 

is reflected in the seasonality of individual estuarine organisms that display species-specific phaselagged relationships to flow (Livingston 1991).

10.1 Species and Habitats with Freshwater Dependence

Several species and habitats identified in this resource characterization appear dependent on 

freshwater flow to varying extents. While little long-term quantitative data exist on the abundance 

of species and habitats in the Wakulla and lower St. Marks Rivers and Apalachee Bay relative to 

river discharge, inferences can be made based on studies in nearby water bodies and the 

comparative amounts of freshwater entering the system. Based on the similarity of species 

composition between the St. Marks/Wakulla fauna and that collected in these neighboring areas, it 
93

seems reasonable to assume similar general relationships exist here with environmental 

characteristics.

Studies carried out recently in Apalachicola Bay (summarized in Lewis et al. 1997) indicated that 

the abundance and distribution of dominant estuarine organisms were associated with various 

environmental factors such as river flow, rainfall, salinity and temperature. These associations, 

however, were highly variable and differed for each species (or taxonomic group) and for each bay 

region. While some consistency across bay regions was noted for some species (or taxonomic 

groups), no single large-scale pattern was observed across the range of organisms examined. Flow 

and salinity were significant contributors to infaunal variance while salinity (and occasionally flow) 

was influential for catch of some shrimp. Temperature was the most frequently noted characteristic 

influencing the dominant fishes. Similar findings were noted for the dominant fishes and 

invertebrates in the Suwannee River estuary (Tsou and Matheson 2002). Salinity was an important 

covariate, along with bottom vegetation, affecting recruitment in nine of 13 species; water 

temperature was associated with abundances of six species. The lower St. Marks and inshore 

Apalachee Bay share many of the same dominant species with Apalachicola Bay and the Suwannee 

River estuary; presumably similar relationships with environmental variables exist.

In addition, significant correlations were found between annual fisheries catch and Apalachicola 

River flow (Wilber 1992, 1994). As with fisheries-independent data, commercial harvests of blue 

crabs and oysters were related to flow in different ways. Annual blue crab landings from both 

Franklin and Wakulla counties (Wilber 1994) were positively related to river flows during the 

previous years grow out period (September to May). Annual commercial oyster landings were 

related positively to flows two years before (Wilber 1992). Both relationships suggest mechanisms 

related to the physical conditions in the bay during the early life history stages of the organisms 

which may be coupled to either increased food or decreased predation (both of which are provided 

by increased river flows). Increased oyster mortality (from both predation and disease) was 

associated with increased salinity in Apalachicola Bay (Livingston et al. 1999, 2000). Blue crabs, 

and to a lesser degree oysters, make up a significant fraction of the commercial landings in the 

Wakulla County area and may be affected by changes in freshwater discharges. 

Overall ecological system function in estuaries may also depend on freshwater inflows. Primary 

productivity is intimately linked to riverine input of dissolved inorganic nutrients. This relationship, 

however, is mediated by the residence time of freshwater in the estuary, which is clearly a function 

of freshwater inflow (primarily) and winds and tides (secondarily). In Apalachicola Bay about 75% 

of the estuarine phytoplankton production occurs during the warm, low-flow months of May to 

November (Mortazavi et al. 2000). Phytoplankton standing stock during this time, as estimated by 

chlorophyll concentrations, is relatively low and a function of phytoplankton growth rate, 

zooplankton grazing, nutrient limitation (primarily nitrogen), sedimentation, and export from the 

bay. The latter three factors are significantly affected by freshwater discharge.

Recent studies (Chanton and Lewis 1999, 2002) provide evidence that the bulk of the secondary 

production in large alluvial river estuaries (i.e., Apalachicola Bay) is fueled from in situ

phytoplankton productivity. Zooplankton grazing can clearly result in substantial reductions in 

plankton biomass and provide a primary trophic transfer for phytoplankton primary production to 

upper level consumers in the estuary (Putland and Iverson 2007a, b). In addition, phytoplankton 

production can enter the food web through deposition to bottom sediments and subsequent 

incorporation into higher trophic levels through deposit-feeding infauna and epifauna. Organisms 
94

inhabiting areas closest to the mouth of the river and its distributaries appear more reliant on riverborne detritus than those living in areas more distant. However, even for these organisms, 

phytoplankton productivity plays a major role in faunal diets, making up at least half of the carbon 

transferred on average. Mid- and outer-bay organisms rely heavily on plankton production for 

subsistence (Chanton and Lewis 2002).

The lower St. Marks River and inshore Apalachee Bay estuary differ significantly from 

Apalachicola Bay in several important ways that influence primary production: significantly lower 

freshwater inflows, low nutrient loading (despite relatively high concentrations from Wakulla 

Spring) resulting in lower overall phytoplankton productivity, and the presence of large tidal 

marshes and seagrass beds in close proximity. Without more information on nutrient loading and 

primary productivity in this system, it is difficult to predict production dynamics. It is likely, 

however, that phytoplankton productivity provides at least a portion of the base of the food web in 

the St. Marks system and it is reasonable to expect similar trophic organization and transfers given a 

similar suite of organisms present. Seagrass and, more importantly, epiphytic algae growing on 

seagrass blades, are also important links to higher trophic levels in these seagrass-dominated 

systems (Moncrieff and Sullivan 2001), but at present their contribution is unknown. Direct feeding 

on seagrass blades, however, is limited to only a few species (Livingston 1982, 1984a; Leber 1983; 

Stoner and Livingston 1984).

The emerging picture of the structure and function of faunal assemblages in estuaries is one of 

overall stability amid and dependent upon a high level of variability and productivity in the system. 

Relatively few species inhabit estuaries, but those that do are physiologically and behaviorally 

adapted to the highly fluctuating conditions. These species are found in high numbers and biomass 

in response to high levels of primary production (both autochthonous and allochthonous). While 

individual species respond in different ways to changes in flow and its associated characteristics, the 

overall function (e.g., trophic organization) of the system is relatively constant within normal flow 

ranges. Deviations in river discharge, at both low- and high-flow ends of the flow spectrum, may 

be reflected in faunal changes that last several years (Livingston et al. 1997). Permanent flow 

modifications could be accompanied by important changes in estuarine productivity, related 

changes in faunal representation within the food web, and the potential reduction and loss of 

specific estuarine populations.

This discussion points to the complexity of estuarine systems and supports an adherence to the 

natural flow paradigm (Richter et al. 1997) which states: the full range of natural intra- and interannual variation of hydrological regimes, and associated characteristics of timing, duration, 

frequency and rate of change, are critical in sustaining the full native biodiversity and integrity of 

aquatic ecosystems. Modifications in flow characteristics may be accompanied by subtle changes 

in estuarine faunal assemblages. Some populations will benefit while others will be negatively 

affected. Maintenance of overall system integrity requires minimizing departures from historical 

flows.

10.2 Flow Dependence and Salinity Tolerance

Habitats potentially vulnerable to changes in freshwater inflow in the Wakulla and lower St. Marks 

Rivers and Apalachee Bay include palustrine forests, fresh, brackish and salt marshes, submerged 

aquatic vegetation and seagrass beds, and oyster reefs. Species living in these habitats have varying 

abilities to tolerate salt and could be impacted adversely by long-term declines in freshwater inputs 
95

with subsequent intrusion of saline water. To assess this potential vulnerability, salinity tolerance 

ranges were compiled from the literature for the dominant organisms observed in both riverine and 

estuarine portions of the system (Appendix Tables D-1 for flora and D-2 for fauna). Ranges are 

provided for different life history stages, where available. In general, estuarine species have wide 

salinity tolerances to cope with the dynamic, highly variable environment; food is often the limiting 

factor. Freshwater species, on the other hand, are less tolerant (often intolerant) of saline conditions 

and the amount of inundation is more influential in determining habitat and species distributions; 

salinity may determine the downstream limit of their distribution.

10.2.1 Palustrine Forests

Floodplain and coastal hammock forests of the Wakulla River are composed of a variety of species 

with varying tolerances to salinity (Appendix Table D-1). The two dominant species in the lower 

reaches of the Wakulla, bald cypress and cabbage palm, display moderate salinity tolerance. Bald 

cypress exhibited significant reductions in photosynthesis and gas conductance at salinities between 

2 and 8 ppt (Pezeshki et al. 1990; McLeod et al. 1996; Allen et al. 1997) with reduction in growth at 

salinities as low as 2 ppt (Conner et al. 1997). Mortality of 100% was noted at 10 ppt (Conner and 

Askew 1992). Cabbage palms exhibited significant declines in photosynthesis at salinities between 

8 and 15 ppt (Perry and Williams 1996) with only 35% survival of seedlings at 8 ppt (Williams et 

al. 1998). Other less common species appear less tolerant and may be impacted more severely with 

reduction in freshwater inflow (see tolerances in Appendix Table D-1).

Light et al. (2002) examined the structure of the floodplain vegetation community in the lower 

Suwannee River basin and projected changes with varying amounts of freshwater depletions. 

Fourteen specific forest types were described within the riverine, upper tidal and lower tidal reaches 

of the river. They suggested that floodplain forest composition was primarily determined by 

duration of inundation and saturation, depth and frequency of floods, and salinity. Each forest type 

is associated with a specific range of durations of inundation and saturation and characteristic flood 

depths. Permanent long-term reductions in flow would result in decreases in duration of flooding 

and soil saturation which in turn lead to changes toward drier forest types and a movement upstream 

of forest species restricted by flood depths. Additionally, the boundary between forest and marsh 

(i.e., tree line) will shift upstream as salinity intrudes further upriver. Salt-intolerant species will 

retreat upstream as tidal movement extends further from the Gulf and forest species composition 

will be altered to include a greater percentage of salt-tolerant forms. Flow reductions will also 

result in decreases in the amount of inundated floodplain area affecting not only forest composition 

but also reducing habitat for a variety of floodplain animals, including fishes, reptiles and 

amphibians, birds and mammals. Similar findings were noted for the floodplain ground-cover 

vegetation (Darst et al. 2002). They suggested lower flows will result in changes in the understory 

species composition as some plants retreat upstream, decline in abundance or disappear altogether 

due to inundation requirements (i.e., flood depth and duration) and/or salt intolerance.

A variety of ecological consequences may result from these floodplain vegetation changes (Light et 

al. 2002). As changes occur in forest composition (i.e., movement toward drier forest types) there is 

an increased possibility of exotic invasion, an increased risk of human disturbance, a decrease in 

concomitant biological diversity because of vertical structure and microhabitat loss as forests are 

converted to marsh, a decrease in area of the wettest swamps and important swamp species such as 

cypress, and a decrease in canopy basal area, species richness and associated wildlife. A loss of 

saturated soils may result in a decrease in soil water retention and subsequent soil oxidation, 
96

decrease in soil denitrification, and an increased vulnerability to fire. Finally, a loss of inundated 

areas will be accompanied by decreases in aquatic habitat used by a variety of both floodplain 

dependent and main channel species that use the floodplain for feeding, shelter and reproduction.

Examining sea-level rise and the retreat of coastal forests, Williams et al. (1999) observed that 

zonation among tree species along the Florida Gulf coast was related to tidal-flooding frequency. 

Tree species number correlated negatively with frequency of flooding. Only cabbage palm (Sabal 

palmetto) and southern red cedar (Juniperus virginiana) were present on the most frequently 

flooded plots with cabbage palms the only living tree on the wettest sites. Live oaks (Quercus 

virginiana) occurred in areas with intermittent tidal flooding. Loss of tree species with inundation 

appeared the result of cessation of regeneration caused by exposure to salt. Forest understory 

replacement by salt marsh species appeared to follow, rather than cause, failure of regeneration. 

Field zonation patterns appeared consistent with greenhouse studies examining the relative salt 

tolerance of seedlings (Williams et al. 1998). Of the species examined, cabbage palm and southern 

red cedar were best able to maintain green leaves under experimental salt exposure; live oak 

survived high salt concentrations by dying back and re-sprouting. While their study focused on the 

effects of sea-level rise, the authors noted that coastal forest retreat as described could be 

accelerated by drought or upstream consumptive water use by humans (Williams et al. 1999).

Other authors have similarly addressed this retreat, discussing transitions in forested wetlands along 

gradients of salinity (Brinson et al. 1985; Brinson et al. 1995). With upstream movement of saline 

waters, forest changes are more pronounced at the transitions between wetland types. Freshwater 

forested wetlands tend to give way to brackish herbaceous wetlands. Two phases of transition are 

described in which the first appears to be the death of trees dominating the upper canopy and their 

replacement by mixed shrubs and herbaceous plants which are in turn replaced by herbaceous 

brackish marsh during the second phase (Brinson et al. 1985). The intrusion of salt water not only 

results in osmotic stress (and reduced water availability) to the trees but also is accompanied by 

abundant sulfate and the increased potential for anaerobic respiration. Toxicity to a variety of tree 

species often results under these conditions with sulfide accumulation in the surrounding sediments 

(Brinson et al. 1995). If high salinities are wide spread and persistent, swamp forests may be 

replaced by brackish marsh as was observed at the mouth of the Santee River, South Carolina 

(Kjerfve 1979). Some movement of the tree line with subsequent encroachment by marsh may 

occur in the lower Wakulla River floodplain depending on the magnitude of upstream flow 

reductions.

10.2.2 Freshwater/Brackish Marshes

Freshwater and brackish marshes are found through much of the Wakulla River and may be 

subjected to some impacts from salt intrusion in the lower reach of the basin. Marshes in the 

Wakulla are dominated by needlerush, sawgrass, pickerelweed, bull rush and a variety of other 

emergent and submergent species with varying degrees of salt tolerance (Appendix Table D-1). 

Some species like duck potato and pickerelweed have been observed in salinities up to nearly 9 ppt, 

while bull rush was recorded up to nearly 17 ppt (Penfound and Hathaway 1939). On the other 

hand, needlerush has a wide range of tolerance (see salt marsh section). Most other species found in 

the area displayed either significant declines in germination, growth, and photosynthesis or 

increases in mortality at salinities in the range of 2-6 ppt (Appendix Table D-1). These species may 

be affected by reductions in freshwater inflows and salinity increases.
97

Tidal marshes and their response to external variables were examined in the Suwannee River delta 

(Clewell et al. 1999). They found no relationships between individual marsh species abundance 

from shoreline transect sites and any of the environmental variables measured, particularly salinity 

or salinity maximum. There was a strong negative relationship, however, between the CladiumJuncus (i.e., sawgrass-needlerush) abundance ratio and several variables, particularly mean salinity 

(R2=0.85) and salinity maximum (R2=0.91). Cladium is more prominent in freshwater areas while 

Juncus is more salt tolerant. For vegetation in the marsh interior, electrical conductivity/salinity 

was the single most important variable influencing plant abundance and species composition. 

Marsh vegetation was very heterogeneous with species composition and dominance highly variable 

spatially. Patchiness was likely caused in part by storm-related disturbances like erosion, knocked 

over plants, salt-kill and storm wrack deposition. These disturbances kill or destroy sizeable areas 

of live vegetation (particularly the dominant sawgrass and needlerush) and open up bare space for 

colonizing species. Over time sawgrass and needlerush grow into these areas and regain 

dominance.

Clewell et al. (1999) suggested that long-term low flows may be accompanied by several changes in 

the tidal marshes. It is likely that no change will occur in the hydroperiod because of the proximity 

to the Gulf and the influence of tides; however, marsh inundation is likely to be more saline. 

Higher salinity may cause no harm to salt tolerant species such as Juncus (needlerush), Phragmites

(giant cane), Spartina (cord grass), Scirpus (bull rush) and Typha (cattail) but less tolerant species 

will likely not persist. Less tolerant species will retreat upstream ahead of the migration of more 

salt tolerant species. Significant ecological harm may be visible upstream in riverbank marshes 

where mesohaline (mid-salinity range) marshes may replace oligohaline (low-salinity range)

marshes which in turn may expand into the freshwater zone. Some tidal river swamps may become 

salt stressed and be replaced by tidal salt marsh. Some upstream retreat and conversion of these 

fresh/brackish marshes may be expected in the Wakulla River depending upon the magnitude of 

flow and salinity change experienced.

10.2.3 Tidal Salt Marsh

Salt marsh contributes only a small fraction of the overall wetlands acreage in the lower Wakulla 

basin being restricted to the downstream-most portion near the confluence with the St. Marks River. 

Its expanse is significantly greater in the lower St. Marks River where salt marsh is the predominant 

habitat bordering most of the lower river and estuary. These marshes are dominated by black 

needlerush (Juncus roemerianus) and smooth cord grass (Spartina alterniflora), both of which 

display wide tolerance to salt (Appendix Table D-1). Needlerush has been observed growing in 

salinities up to 60 ppt (Eleuterius 1984). Growth was noted, however, to be inversely related to 

salinity with greatest production actually observed in freshwater. Similarly, cord grass is found in 

environments with salinities ranging from near fresh to almost full sea water (Mendelssohn and 

Marcellus 1976; Pulich 1990); greatest production, again, was noted at salinities less than 19 ppt 

(Mendelssohn and Marcellus 1976). Needlerush and cord grass, because of their salt tolerance, are 

able to compete favorably and dominate in areas where less salt tolerant vegetation cannot survive. 

Some upstream expansion of these marshes into the lower Wakulla River may be expected 

depending upon the magnitude of flow and salinity change. No effects are anticipated in the more 

broadly distributed salt marshes throughout the lower St. Marks River with their high tolerance for 

moderate to high salinities.
98

10.2.4 Submerged Aquatic Vegetation (SAV)

Salinity intrusion will likely affect SAV negatively in the lower reaches of the Wakulla and St. 

Marks Rivers. Tapegrass (Vallisneria americana), for example, is a salt-tolerant freshwater 

angiosperm that occurs in fresh, oligohaline, and mesohaline reaches of estuaries in the eastern 

United States and Gulf of Mexico; it is one of several species found in SAV beds throughout the 

Wakulla River. Published salt tolerances (Appendix Table D-1) vary with growth cessation 

reported to occur from 6.6 (Haller et al. 1974) to 15 ppt (Doering et al. 1999); other work suggested 

mortality at salinities greater than 15 ppt (Kraemer et al. 1999). Doering et al. (2001) noted that 

while significant mortality occurred at 18 ppt, the degree of mortality was proportional to the 

duration of exposure. Recovery could be achieved with return to low salinity. They suggested that 

a 70-day intrusion of 18 ppt is near the upper limit of what might be tolerated without a net 

population reduction. This degree of intrusion would result in an approximate 80% reduction in 

shoot density, but with return to low salinity, recovery to pre-intrusion density was estimated in 

about 115 days. Multiple, repeated salinity intrusions, however, were not examined and could be 

expected to have more serious and perhaps unrecoverable consequences. Tapegrass has been 

observed in the lower St. Marks in areas with mean bottom salinity of 3 ppt and maximum values of 

24 pp; some impacts may be sustained depending on the magnitude of flow reduction. Other 

species such as dwarf arrowhead, southern naiad, coontail and false loosestrife are primarily 

freshwater species with slight salt tolerances (Appendix Table D-1); these species are generally 

found at salinities below 3 to 6 ppt. Some impacts are likely even with moderate freshwater 

reductions. Exotic species such as Eurasian watermilfoil and hydrilla have relatively low salinity 

tolerances (exception: Twilley and Barko (1990) observed highest biomass of watermilfoil at 12 

ppt) and may be affected in the lower reaches of the system.

Examining SAV beds in the lower tidal portion of the Suwannee River, Estevez and Sprinkel (1999) 

suggested that reduced flows will increase salinity in the lower river and cause an up-stream retreat 

and overall reduction of SAV beds. These consequences likely result from specific river-bed 

morphology (i.e., narrow to nonexistent shorelines upstream in the Suwannee) and lack of potential 

colonizing estuarine or marine grasses at the river mouth and in Suwannee Sound. They further 

suggested that as the SAV beds retreat upstream the overall community assemblage will be 

simplified by loss of sensitive species. Total bed area, cover or biomass might not be reduced, but 

habitat diversity would be negatively affected by species loss. Further down the Gulf coast in the 

Chassahowitzka, Homosassa and Crystal rivers, SAV biomass approached zero at sites where 

annual average salinity was greater than 3.5 ppt (Hoyer et al. 2004). While similar upstream 

movement of SAV beds might occur in the Wakulla system it is unlikely that the lower portion of 

the river would be left devoid of grasses because of the presence of potentially colonizing estuarine 

species in the lower St. Marks. Both widgeon grass (Ruppia maritima) and shoal grass (Halodule 

wrightii) are present in the lower reach of the system, have wide salinity tolerances (Appendix 

Table D-1) and will likely expand upstream with salt water intrusion. The replacement of the 

diverse and abundant SAV with fewer estuarine-tolerant species would likely result in a decrease in 

habitat structure with subsequent declines in associated fauna.

10.2.5 Seagrasses

Near and offshore grass beds in Apalachee Bay are unlikely to experience any change caused by 

minor modifications in freshwater flow. These beds are dominated by widgeon and shoal grasses 

inshore with shoal, manatee and turtle grass offshore. Widgeon and shoal grass have broad salinity 
99

tolerances (Appendix Table D-1) ranging from near fresh to hypersaline conditions while turtle

grass is most abundant at intermediate to high salinities (Appendix Table D-1). Based on a series of 

stress indicators such as shoot decline, growth rate and photosynthetic efficiency, these species were 

able to tolerate salinities up to 55 ppt, with turtle grass (60 ppt) and shoal grass (65 ppt) having 

slightly higher thresholds than widgeon grass (55 ppt) when salinities were gradually increased 

(Koch et al. 2007). Stress threshold levels dropped noticeably for turtle grass (45 ppt) when salinity 

was pulsed without a slow osmotic adjustment period; no pulsed tests were run for the other species. 

In addition, turtle grass seedlings were observed to survive 50 ppt when exposed to slow increases 

in salinity, yet all died at this level in pulsed experiments (Kahn and Durako 2006). It is interesting 

to note that while widgeon grass is highly tolerant of high salinity (up to 390 ppt in review by 

Kantrud 1991) and is able to produce reproductive shoots across a wide salinity range, it is often 

found dominating the low salinity freshwater-marine interface community (Koch et al. 2007). At 

the other end of the salinity range, widgeon grass is the only species capable of surviving extended 

periods in freshwater (McMillan 1974). Shoal grass does not survive salinity less than about 3.5 ppt 

for six weeks (McMahan 1968) and turtle grass dies between 5 and 10 ppt (McMillan 1974). 

Interestingly, while widgeon grass survives well in low salinity waters, maximum photosynthetic 

efficiency has been observed between 10 and 20 ppt (Murphy et al. 2003). Because of the wide 

salinity tolerances of widgeon and shoal grass, and the preference of turtle grass for moderate to 

high salinity, little change in seagrass bed distribution and dynamics is likely in Apalachee Bay with 

small declines in freshwater inflows.

10.2.6 Oyster Reefs

Oyster reefs occur throughout the lower reach of the St. Marks River where they become a 

conspicuous feature, especially during low tides. While these reefs do not support a commercial 

fishery (an existing fishery is located in the western sections of Apalachee Bay in Dickerson and 

Oyster bays), they provide important habitat for organisms seeking food and shelter. The large reef 

expanse is located in the areas of significant tidal mixing and is likely limited to a certain degree by 

the amount of freshwater inflow. Salinities average 3.5 and 14.8 at middle and lower tidal reaches, 

respectively, with significant variation (see Water Quality section Table 3). Changing freshwater 

inflows may modify the salinity structure somewhat in this reach with subsequent effects on oysters.

The eastern oyster (Crassostrea virginica) is an estuarine resident and as such tolerates the dynamic 

conditions found there; salinity tolerances for various life history stages are shown in Appendix 

Table D-2. Adult oysters can survive in salinities from freshwater to 45 ppt with optimal conditions 

for growth between 10 and 30 ppt (Longley 1994; Pattillo et al. 1997). While capable of surviving 

at low salinities for short periods of time, oysters generally close their shells and do not feed below 

about 3 ppt (Loosanoff 1953). Eggs and larvae prefer moderate salinities (10-29 ppt) with optimal 

growth of spat occurring from 13 to 30 ppt (Pattillo et al. 1997). Predation and disease, as 

contributors to mortality, affect oyster population dynamics and are directly related to salinity; both 

are higher in high salinity waters. A variety of predators feed on oysters including gastropod 

mollusks (Thais haemastoma and Melongena corona), crabs (Callinectes sapidus and Mennippe 

mercenaria) and fishes (Pogonias cromis and Archosargus probatocephalus). The southern oyster 

drill (T. haemastoma) is thought to be one of the major predators along the Gulf coast and is limited 

by average salinity below 15 ppt (Butler 1953). Crown conch (M. corona), while preferring 

salinities between 20 and 29 ppt, have been found in waters as low as 8.5 ppt (Hathaway and 

Woodburn 1961). High levels of mortality on some reefs have been attributed to the sporozoan 

parasite Perkinsus marinus, also called “dermo”. Incidence of Perkinsus infection is correlated with 
100

temperature and salinity (Soniat 1996) with mortality suppressed at low salinity. Infection intensity 

increases as salinity increases with 9 to 12 ppt as a minimum threshold (Ragone and Burreson 

1993). Little is known concerning the occurrence of predators and disease on lower St. 

Marks/Apalachee Bay reefs. Declining freshwater inflows may increase the incidence of both on 

the reefs with subsequent influence on oyster population dynamics dependent on the amount of 

change. Bergquist et al. (2006) found oyster percent cover and density in the Suwannee River 

estuary to be negatively related to salinity.

10.2.7 Faunal Abundance and Distribution

Information on the epibenthic invertebrate and fish assemblages in the Wakulla River is limited to 

the studies of Birkett (1981), Walsh and Williams (2003), and continuing collections by FDEP, 

FFWCC and NWFWMD. Other efforts, by both the academic and governmental community, have 

involved primarily terrestrial assemblages and are beyond the scope of this characterization. 

Epifaunal and benthic invertebrate communities were dominated by caddisfly and chironomid 

larvae and oligochaete worms (Birkett 1981). In addition, variable spikes and other unionid 

mollusks were most abundant in the upper reach of the river (Walsh and Williams 2003). These 

species are typical of freshwater systems and generally exhibit intolerance to salt. Similarly, apple 

snails once abundant in the upper river but now with declining numbers, are also salt intolerant; 

adequate water levels, however, are required for egg laying on emergent vegetation. Birkett (1981) 

noted a significant correlation between epifaunal invertebrate abundance and diversity and plant 

biomass. Thus many of these species not only are directly susceptible to salinity intrusion from a 

physiological perspective but also indirectly influenced by a loss of habitat as many of the 

freshwater macrophytes on which they live have limited tolerance to salt.

Many of the fishes documented from the collections of Walsh and Williams (2003) and the FFWCC 

(Cailteux et al. 2004, 2005) are freshwater species with limited range of salinity. These species will 

retreat upstream with salinity encroachment. Some of these species, however, have the ability to 

invade the oligohaline (low salinity) and mesohaline (moderate salinity) zones and have been 

collected at salinities as high as 15 to 20 ppt. Swingle and Bland (1974) recorded several of these 

latter species in Alabama water which are listed here along with the maximum salinity recorded: 

longnose gar (Lepisosteus osseus) 21.7, chain pickerel (Esox niger) 7.5, coastal shiner (Notropis 

petersoni) 7.4, lake chubsucker (Erimyzon sucetta) 14.4, spotted sunfish (Lepomis punctatus) 17.5, 

and largemouth bass (Micropterus salmoides) 17.5. No salinity information was found for the listed 

Suwannee bass (M. notius).

Little impact will be felt from slight salinity intrusions by most of the remaining fauna, including 

amphibians, reptiles, birds and mammals. Some loss of submerged aquatic vegetation may limit 

feeding by some water fowl and manatees from the downstream-most portions of the river, but this 

limitation should be relatively small given the abundance of SAV throughout the system.

Invertebrates and fishes inhabiting the downstream salt marshes will be little affected by salinity 

intrusion; these species, in fact, may expand their habitat if the fresh-salt marsh line retreats 

upstream. Common marsh invertebrates include marsh periwinkle (Littorina irrorata) and fiddler 

crabs (Uca spp.); blue crabs are frequent migrants into the tidal creeks. The marsh fish community 

is dominated by a number of resident (longnose killifish Fundulus similis, Gulf killifish F. grandis, 

sheepshead minnow Cyprinodon variegatus, sailfin molly Poecilia latipinna and tidewater 

silverside Menidia beryllina) and migrant species (bay anchovy Anchoa mitchelli, Gulf menhaden 
101

Brevoortia patronus, pinfish Lagodon rhomboides, spot Leiostomus xanthurus). These species 

dominate many Gulf coastal marshes and estuaries and display wide tolerances for environmental 

conditions, including salinity. Salinity ranges for dominant salt marsh organisms, where available, 

are shown in Appendix Table D-2.

Seagrass invertebrates consist predominantly of small cryptic species including palaemonetid 

(Palaemonetes spp.) and hippolytid shrimp (Tozeuma carolinense, Thor spp., Latreutes spp.) and 

xanthid (Neopanope spp., Panopeus spp.) and hermit crabs (Pagurus maclaughlinae). Pink shrimp 

(Farfantepenaeus duorarum) and blue crab (Callinectes sapidus) are the most abundant larger 

seagrass invertebrates. Common seagrass fishes include pinfish (Lagodon rhomboides), spot 

(Leiostomus xanthurus), filefish (Monocanthus ciliatus and Stephanolepis hispidus), silver perch 

(Bairiedella chrysoura), black sea bass (Centropristis striata), spottail pinfish (Diplodus holbrooki), 

dusky pipefish (Syngnathus floridae), pigfish (Orthopristis chrysopterus) and silver jenny 

(Eucinostomus gula). Many of these species, while having broad tolerances, prefer moderate to 

high salinities (Appendix Table D-2).

In general, these species are typical estuarine inhabitants with broad environmental tolerances 

(Appendix Table D-2). Marsh and inshore resident are adapted for highly fluctuating and variable 

conditions. Many of the migrant species spawn in nearshore Gulf waters (penaeid shrimp spawn 

offshore) such that their eggs and larvae are found predominantly in high salinity. Larvae move 

into marshes and estuaries where they reside as juveniles and grow before emigration again to the 

Gulf. As adults most have been recorded in salinities from near freshwater to >35 ppt; some are 

frequent inhabitants of hypersaline lagoons with salinities >45 ppt. Despite their high tolerance, 

greatest abundance is often found in mesohaline conditions (5-18 ppt); pink shrimp and many of the 

seagrass fishes (especially those preferring turtle grass) have generally higher abundance in waters 

>18 ppt. Because of these wide salinity tolerances, little change in distribution and population 

dynamics of these species is likely with small declines in freshwater inflows.
102

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117

12.0 APPENDICES
118
119
120
121
122
123

Appendix D – Salinity Tolerances for Selected Organisms

Table D-1. Representative salinity tolerance ranges for the dominant plants (riverine forest, emergent marsh - fresh 

and salt, submerged aquatic vegetation and seagrasses) found in portions of Wakulla and lower St. Marks rivers and 

Apalachee Bay, Florida. Tolerances are given along with the source of information. Table entries are salinity 

values given in parts per thousand.

Species Salinity Range References

Riverine Forest

Bald cypress 0-8.9 Penfound and Hathaway (1938)

 (Taxodium distichum) 2-7 (58-84% reduction in photosynthesis) Pezeshki et al. (1990)

100% mortality of seedlings at 30 for >2 days (flooded) Conner and Askew (1992)

73% mortality at 8; leaf area reduction at >4 Allen et al. (1994)

100% mortality of seedlings at 10 (flooded); decreased McLeod et al. (1996)

 photosynthesis at 2 (flooded), unaffected at 2 (watered)

2-8 (significant reductions in photosynthesis and stomatal Allen et al. (1997)

 conductance in seedlings)

Seedling growth (height) reduced at 2, no reduction in Conner et al. (1997

 diameter or biomass

Cabbage palm 8-15 photosynthesis declined nearly 65%; none observed Perry and Williams (1996)

 (Sabal palmetto) at 15; seed and seedlings survival greater at low (avg 3)

 vs. high (avg 23) salinity sites in field

<5% survival of seedlings at 22, 25% at 15, 35% at 8, Williams et al. (1998)

 65% at 4, >80% at 2; 25% green leaves at 15, 65% at 4

Green ash 0.8-8 (48-88% reduction in photosynthesis) Pezeshki et al. (1990)

 (Fraxinus pennsylvanica) 100% mortality of seedlings at 10 (flooded); severly McLeod et al. (1996)

 decreased photosynthesis at 2 (flooded), unaffected at 2

 (watered)

Seedling growth (height, diameter, biomass) reduced at 2 Conner et al. (1997)

Loblolly pine 100% mortality of seedlings at 30 for >2 days (flooded) Conner and Askew (1992)

 (Pinus taeda)

Live oak <10% survival of seedlings at 22, 50% at 15, 75% at 8, Williams et al. (1998)

 (Quercus virginiana) >75% at 4; <25% green leaves at 8, 25% at 4

Sweet gum No survival of seedlings at >8, <5% at 4, 50% at 2; no Williams et al. (1998)

 (Liquidambar styraciflua) green leaves at >8, <5% at 4, 50% at 2

Red maple 80% mortality of seedlings after 1-day exposure to 27, Conner and Askew (1993)

 (Acer rubrum) 100% >2 days; greatly reduced growth after 1-day

 exposure
124

Species Salinity Range References

Emergent Marsh (Fresh)

Duck potato 0.0-8.9 Penfound and Hathaway (1938)

 (Sagittaria lancifolia) 2.9 (37-45% decrease in photosynthesis; 34-67% decrease Pezeshki et al. (1987)

 in stomatal conductance)

4.8 (tissue damage); 15 100% mortality McKee and Mendelssohn (1989)

>2 significantly reduced germination Baldwin et al. (1996)

4.6 (increased biomass relative to control at 2.3, in field) Webb and Mendelssohn (1996)

>6 (tissue damage); 12 (low mortality) Howard and Mendelssohn (1999)

>6 (reduced growth) Spalding and Hester (2007)

Common arrowhead 2 (decreased survival, growth and time to emergence); Delesalle and Blum (1994)

 (Sagittaria latifolia) 4 (reduced germination)

Pickerelweed 0-8.9 Penfound and Hathaway (1938)

 (Pontederia cordata) 2.5 (highest recorded) Clewell et al. (1999)

Maidencane 0.0 Penfound and Hathaway (1938)

 (Panicum hemitomon) 9.4 (growth reduction); 15 100% mortality McKee and Mendelssohn (1989)

7.6-10 lethal limits in lab experiments Hester et al. (1998)

>6 (growth reduction); 12 (significant mortality) Howard and Mendelssohn (1999)

>4 (reduced growth, increased mortality) Spalding and Hester (2007)

Bullrush 5.5-16.8 Penfound and Hathaway (1938)

 (Scirpus americanus) 6 (highest recorded) Clewell et al. (1999)

>6 (some growth reduction); 12 (no mortality) Howard and Mendelssohn (1999)

Sawgrass 0-2 Penfound and Hathaway (1938)

 (Cladium jamaicense) 4+3 (LA statewide) Chabreck (1972) cited in Clewell et al. (1999)

8 (highest recorded) Clewell et al. (1999)

Emergent Marsh (Salt)

Smooth cordgrass 5.5-49.7 Penfound and Hathaway (1938)

 (Spartina alterniflora) 15.2+7.8 mean (LA statewide) Chabreck (1972) cited in Longley (1994)

0.6-33.0 (<19 higher production) Mendelssohn and Marcellus (1976)

6-34 (20+8 mean) Pulich (1990) cited in Longley (1994)

2-28 (12+7 mean)

83-115 lethal limits in lab experiments Hester et al. (1998)

Black needlerush 1.2-44.3 Penfound and Hathaway (1938)

 (Juncus roemerianus) 13.9+8.3 mean (LA statewide) Chabreck (1972) cited in Longley (1994)

0-60 growth decreasing with salinity (max in freshwater) Eleuterius (1984)

0-20 Clewell (1986)

0.5-38 (mean 17.3+9.3) Woerner and Hackney (1997)

0->40 Touchette (2006)
125

Species Salinity Range References

Submerged Aquatic Vegetation (SAV)

Tapegrass <10 survived (0.2-3.3 growth; 6.7 no growth) Haller et al. (1974)

 (Vallisneria americana) 0-12.8 present (5.3 mean); 2.2-13.9 absent (7.6 mean) Davis and Brinson (1976)

<12 growth unaffected Twilley and Barko (1990)

<15 survival (higher growth <3 in dry, <9 in wet season) Doering et al. (1999)

>ca. 15 upper limit to survival Kraemer et al. (1999)

18 upper limit with mortality proportional to exposure Doering et al. (2001)

 time up to 70 days

>15 increased mortality Frazer et al. (2006)

Dwarf arrowhead 6 (highest recorded) Clewell et al. (1999)

 (Sagittaria subulata)

Southern naiad >10 no survival (0.2-6.7 highest growth; 6.7-10 growth Haller et al. (1974)

 (Najas guadalupensis) very low)

1.73 (mean) observed in field Hoyer et al. (2004)

Coontail 1.92 (mean) observed in field Hoyer et al. (2004)

 (Ceratophyllum demersum)

Claspingleaf pondweed >4 biomass and flower production decline Twilley and Barko (1990)

 (Potamogeton perfoliatus)

False loosestrife 3 (highest recorded) Clewell et al. (1999)

 (Ludwigia repens)

Eurasian watermilfoil 4 highest net photosynthesis, declines at >16; >16 P:R McGahee and Davis (1971)

 (Myriophyllum spicatum) ratio declines

>13.3 no survival (0.2-6.7 highest growth; 6.7-13.3 Haller et al. (1974)

 growth decline)

12 highest biomass Twilley and Barko (1990)

2.04 (mean) observed in field Hoyer et al. (2004)

>15 increased mortality, decreased growth Frazer et al. (2006)

Hydrilla >6.7 no survival (0.2-3.3 highest growth; 3.3-6.7 growth Haller et al. (1974)

 (Hydrilla verticillata) decline)

>4 biomass decline; >6 stem density and length decline Twilley and Barko (1990)

1.48 (mean) observed in field Hoyer et al. (2004)

>15 no survival Frazer et al. (2006)
126

Species Salinity Range References

Seagrasses

Widgeon grass <28 to set seed Bourn (1935) cited in Longley (1994)

 (Ruppia maritima) 0-33.2 (<25 ma) Phillips (1960)

<74 lab survival (>46 no growth) McMillan and Moseley (1967)

16-24 in field Zimmerman and Livingston (1976)

0->60 (up to 390) in field Kantrud (1991) summary table

0-40 (10-20 optimal) Murphy et al. (2003)

0-30 (growth lower in pulsed salinity) La Peyre and Rowe (2003)

36-70 (>55 stress threshold) Koch et al. (2007)

Shoal grass 1-60 (dwarfing at high salinity); 25-34 abundant Phillips (1960)

 (Halodule wrightii) <74 lab growth McMillan and Moseley (1967)

3.5-52.5 lab survival McMahan (1968)

23-37 lab survival McMillan (1974)

17(6 min)-36 in field Zimmerman and Livingston (1976)

May-55 Dunton (1996)

5-45 blade growth (10-35 max) Lirman and Cropper (2003)

35-62 in field Cotner et al. (2004)

36-70 (>65 stress threshold) Koch et al. (2007)

Turtle grass 10-48 (25-38.5 optimal) Phillips (1960)

 (Thalassia testudinum) <74 lab survival (>60 no growth) McMillan and Moseley (1967)

10-50 lab survival McMillan (1974)

15-40 in field (24-35 optimal) Zieman (1975)

17(6 min)-36 in field Zimmerman and Livingston (1976)

6-35 lab survival (growth least at 6); 22-36 field optimal Doering and Chamberlain (2000)

5-45 blade growth (15-40 max) Lirman and Cropper (2003)

10-50 (30-40 optimal for photosynthetic efficiency) Kahn and Durako (2006)

36-70 (>60 stress threshold) Koch et al. (2007)
127

Table D-2. Representative salinity ranges for the dominant animals (invertebrates and fishes) found in 

portions of lower St. Marks River and Apalachee Bay, Florida. Salinity ranges are given for different life 

history stages, where available, along with the source of information. Table entries are salinity values 

given in parts per thousand; ma = most abundant in stated range.

Species Eggs and Larvae Juveniles Adults References

Invertebrates

Eastern oyster <3 no feeding Loosanoff (1953)

 (Crassostrea virginica) 5-30 Galtsoff (1964)

3-44 Copeland and Hoese (1966)

16-22 setting Chatry et al. (1983)

 abundant

17-24 optimal-spat 0-45 (10-30 best after Longley (1994)

 survival; 10-24 ma)

7.5-34 (10-22 5.6-35 (13-30 optimal)- 2-43.5 (14-30 optimal after Pattillo et al. (1997)

 optimal)-eggs spat for growth)

5-39 (25-29

 optimal)-larvae

2-35 Livingston et al. (2000)

11-29 (means per site; Bergquist et al. (2006)

 4-24 mean lows)

Blue crab 0-30+ (2.0-4.9 ma) Swingle (1971)

 (Callinectes sapidus) 0-28.5 Swingle and Bland (1974)

0-40 (<13 optimal) 0.1-60.0 (lit review) Copeland & Bechtel (1974)

23-30 for hatching 6-25 ma 0-60 after Longley (1994)

10-33 (23-28 2-21 ma <10 ma (males) after Pattillo et al. (1997)

 optimal)-eggs 23-33 ma (egg-

>5 (16-36 highest bearing females)

survival)-larvae

Grass shrimp 0-21.3 (10-15 ma) Swingle (1971)

 (Palaemonetes pugio) 0-25.4 (15-20 ma) Swingle and Bland (1974)

20-25 optimal- 0-55 (2-36 ma) after Pattillo et al. (1997)

 larvae
128

Species Eggs and Larvae Juveniles Adults References

White shrimp <10 ma Gunter et al. (1964)

 (Litopenaeus setiferus) 8-34 Perez Farfante (1969)

1.3-30+ (5-10 & 25-30 Swingle (1971)

 ma)

2.7-35.0 ma Stokes (1974)

0-38 (no optimal) 0.2-45.3 (lit review) Copeland & Bechtel (1974)

1.1-28.5 Swingle and Bland (1974)

5-15 (optimal)- 1-20 ma 0-48 after Longley (1994)

 postlarvae

0.4-37 postlarvae 0.3-41 (<10 ma) >27 offshore-usually after Pattillo et al. (1997)

Pink shrimp >20 Hildebrand (1955)

 (Farfantepenaeus duorarum) 12-43 5-47 25-45 Tabb et al. (1962)

>18 ma Gunter et al. (1964)

15.5-37.7 ma Stokes (1974)

8-36 (20-35 optimal) 0.6-65 (lit review) Copeland & Bechtel (1974)

12-43 postlarvae <1-47 (>20 preferred) 1-69 (25-45 ma) after Pattillo et al. (1997)

Fishes

Bay anchovy 2.3-36.9 (<15 ma) Gunter (1945)

 (Anchoa mitchelli) 5-35 Springer and Woodburn (1960)

0-30 Tabb and Manning (1961)

0-34 (20-30 ma) Swingle (1971)

0-34 (25-30 ma) Swingle and Bland (1974)

0.5-1, 20-25 0-40 1-32 after Pattillo et al. (1997)

0-30 (10-20 ma): 0-30 (<15 ma): means 0-30 (<15 ma): means Peebles et al. (2007)

 means

Gulf menhaden 2-33.7 Gunter (1945)

 (Brevoortia patronus) 6.6-34.2 Springer and Woodburn (1960)

6.6-33.2 larvae 0.1-31.6 (10-15 & >30 Swingle (1971)

 ma)

0-26 (<12 optimal) 0.0-54.3 (lit review) Copeland & Bechtel (1974)

0-40+ (<12 ma) Longley (1994)

>29 eggs & early 0-67 (20-25 ma) after Pattillo et al. (1997)

 larvae

5-30 postlarvae
129

Species Eggs and Larvae Juveniles Adults References

Gulf killifish 2-37.1 (5-15 ma) Gunter (1945)

 (Fundulus grandis) 0.8-35.6 (15-30 ma) Kilby (1955)

0.8-16.2 (<15 ma)

3.7-29.8 (13-20 ma) Springer and Woodburn (1960)

0-5 & 20-25 Swingle (1971)

0-25 Swingle and Bland (1974)

5-40 (5-18.3 0-76.1 after Pattillo et al. (1997)

 optimal)-larvae

Longnose killifish 2-37.1 (20-30 ma) Gunter (1945)

 (Fundulus similis) 0.8-37.6 (15-30 ma) Kilby (1955)

3.2-32.3 Springer and Woodburn (1960)

5-30 (10-25 ma) Swingle (1971)

4.7-30 (>10 ma) Swingle and Bland (1974)

Sheepshead minnow 2-35.7 (10-25 ma), one Gunter (1945)

 (Cyprinodon variegatus) collection at 71.5

0.8-35.6 (15-30 ma) Kilby (1955)

0-26.1 (<15 ma)

0-35 Tabb and Manning (1961)

10-25 (20-25 ma) Swingle (1971)

0.9-25 Swingle and Bland (1974)

0-142 (10-30 ma) after Pattillo et al. (1997)

Tidewater silverside 0-34.9 (15-20 ma), one Gunter (1945)

 (Menidia beryllina) collection at 71.3

3.5-37.6 (15-30 ma) Kilby (1955)

0-26.1 (<15 ma)

17-26 Tabb and Manning (1961)

0-5 & 15-20 ma Swingle (1971)

0-23.8 Swingle and Bland (1974)

0-30 (2-8 optimal)- 0-34.5 (2-28 optimal) 0-120 (<45 ma) after Pattillo et al. (1997)

 larvae

Pinfish 2.1-37.2 Gunter (1945)

 (Lagodon rhomboides) 3.7-35.1 Springer and Woodburn (1960)

8-37 Tabb and Manning (1961)

2-30+ (>20 ma) Swingle (1971)

0-43.8 Pattillo et al. (1997)
130

Species Eggs and Larvae Juveniles Adults References

Atlantic croaker 2-36.7 (<15 ma) Gunter (1945)

 (Micropogonias undulatus) 5-29.8 Springer and Woodburn (1960)

19-32 Tabb and Manning (1961)

0-30+ (5-15 ma) Swingle (1971)

0-29.1 Swingle and Bland (1974)

25-35 (optimal)- 0-37 (6-15 optimal) 0->60 after Longley (1994)

 eggs

15-35 (optimal)-

 larvae

15-36 larvae 0-36.7 (10-20 ma) 0-70 (15-20 ma) after Pattillo et al. (1997)

Spot 2-36.7 (>15 ma) Gunter (1945)

 (Leiostomus xanthurus) 5-34.2 Springer and Woodburn (1960)

9-48 Tabb and Manning (1961)

0.1-30+ (5-20 & >30 ma) Swingle (1971)

0-28.5 Swingle and Bland (1974)

30-35 eggs 0-36.2 (>10 ma) 0-60 (15-30 ma) after Pattillo et al. (1997)

6-36 larvae

Silver perch 2.1-33.7 (<25 ma) Gunter (1945)

 (Bairdiella chrysoura) 3.7-35 (>20 ma) Springer and Woodburn (1960)

9-48 Tabb and Manning (1961)

0.2-30 (>10 ma) Swingle (1971)

3.5-28.5 (>15 ma) Swingle and Bland (1974)

14.3-26 eggs 0-35.5 (>20 ma) 0-48 after Pattillo et al. (1997)

<1-37.4 (>10 ma)

 larvae