Site-Specific Information 

in Support of 

Establishing Numeric Nutrient 

Criteria for the Springs Coast

Florida Department of Environmental Protection

Tallahassee, FL 32399

August 20, 2010 
Draft ii August 2010

Table of Contents

Executive Summary ............................................................................................................... 1

Geographic and Physical Description ..................................................................................... 4

Sources of Nutrients.............................................................................................................. 8

Ground Water, Springs, and Spring-fed Rivers.................................................................................8

Wetlands and Wildlife ..................................................................................................................10

Atmospheric Deposition................................................................................................................10

Offshore Spring Vents...................................................................................................................13

Coastal Currents...........................................................................................................................15

Biological Summary............................................................................................................. 16

Submersed Aquatic Vegetation and Species Composition ..............................................................16

Epiphyte Loads on Seagrass..........................................................................................................29

Phytoplankton Species Composition..............................................................................................29

Macroalgal Species Composition and Biomass (Including Calcareous Forms)..................................30

Depth to Seagrass Targets............................................................................................................30

Presence and Frequency of Harmful Algal Blooms .........................................................................30

Coral or Hardbottom Community Structure and Areal Extent.........................................................31

Shellfish Production and Frequency/Duration of Bed Closures........................................................34

Quantification of Landings from Commercial/Recreational Fisheries..............................................35

Existing Local Biological Indices ....................................................................................................37

Hypoxia .......................................................................................................................................37

Water Quality Studies ......................................................................................................... 37

Anclote River Estuary Studies 1970s..............................................................................................38

MML Study of Selected Rivers, 1984–85 ........................................................................................38

Project COAST, 1997–Present........................................................................................................41

MML Intensive Study of the Chassahowitzka NWR, 1996–2001......................................................52

Random Sampling by IMAP through the FWRI...............................................................................60

Waters on the 303(d) List..................................................................................................... 61

Proposed Numeric Nutrient Criteria..................................................................................... 63

References 68

Appendix A. Water Quality Data Plots from Entire Record of Project COAST Data................ 72

Appendix B. Annual Geometric Mean Chlorophyll a (Uncorrected) and TN from Project 

COAST ............................................................................................................. 80

Appendix C. Relationship between Salinity and Annual Geometric Mean TN per Site in 8 

Coastal Areas of Project COAST........................................................................ 93
Draft iii August 2010

Appendix D. Data Comparisons between Providers............................................................. 97
Draft iv August 2010

List of Tables

Table 1a. Checklist of nutrient enrichment symptoms in the Springs Coast................................................ 2

Table 1b. Checklist of additional factors in the Springs Coast ..................................................................... 3

Table 2. Land use in selected springsheds depicted in Figure 3 (SWFWMD 2007 land use)........................ 9

Table 3. Land use in the Pithlachascotee and Anclote River watersheds (SWFWMD 2004 and 

2007 land use)............................................................................................................................. 9

Table 4. Annual load estimates for TP and TN for two spring-fed rivers along the Springs Coast. 

Estimates were calculated based on annual mean nutrient concentrations from 

bimonthly sampling at 1 SWFWMD site on each river (site as indicated in table) and 

mean annual discharge at USGS gauge stations (SWFWMD).................................................... 9

Table 5. Estimates of seagrass coverage along the Springs Coast to approximately 15 miles 

offshore, from the interpretation of 2007 digital imagery (SWFWMD; Kolasa 2010). 

Shown are acres and percent of total area comprised by various bottom habitats 

within 4 regions. .......................................................................................................................16

Table 6. Comparison of seagrass acreage estimated for the Springs Coast in 1985 and 2007 

(from Kolasa and Craw 2009). ..................................................................................................17

Table 7. Summary of observations of seagrass species at 188 sampling locations in the Big Bend 

and Springs Coast regions. The depths represent the maximum depth at which each 

species was observed. The depths listed in the 1974–1980 column were determined 

from the depths measured in the 2000 study (from Hale et al. 2004). ....................................22

Table 8. Regional Braun-Blanquet statistics by sampling for the entire coastal study area in the 

MML study of the Chassahowitzka NWR (30 stations) (Table 5 in Toutant et al. 2004)..........24

Table 9. Macroalgal species occurrence in St. Martins Marsh, 1998–2009, sampled by Aquatic 

Preserve staff. Shown is the number of sampling quadrats in which that species was 

present, of 100 total quadrats sampled per year. The sampling program and 

methods are described in the section on SAV and species composition...................................31

Table 10. Summary water clarity data for estuarine sites sampled off three Springs Coast rivers 

by MML, 1984–85. Values presented at mean/standard deviation (from Dixon 1986)..........39

Table 11. Annual geometric mean TN and chlorophyll a (uncorrected) from the 1984–85 MML 

study of the Weeki Wachee and Crystal Rivers. .......................................................................39

Table 12. Summary of data analysis for coastal areas of Citrus and Hernando Counties combined 

(33 stations) and Pasco County (39 stations), 1997–2006. ......................................................49

Table 13. Summary of data analysis for Pasco County stations grouped by salinity, 1997–2006. 

“salinity<25” represents 13 stations, “salinity 25-30” represents 19 stations, and 

“salinity>30” represents 7 stations...........................................................................................50

Table 14. Sample sizes for sites and years for FDEP’s analysis of the MML study of the 

Chassahowitzka NWR...............................................................................................................56

Table 15. Summary of data analysis for coastal areas of the Chassahowitzka NWR, 1997–2004 

(12 stations). The first table contains only station years with at least 4 samples; the 

second table contains all station years (range 1 to 6 samples per station year; mean 

3.6 samples per station year). Data collected and analyzed by MML.....................................59

Table 16. Summary of data analysis for coastal areas of the Chassahowitzka NWR, 1997–2004, 

with stations divided by mean salinity (5 stations < 20 ppt; 7 stations > 20 ppt). Each 
Draft v August 2010

salinity category contains tables for which only station years with at least 4 samples 

were included, and tables for which all station years were included (range 1 to 6 

samples per station year; mean 3.6 samples per station year). Data collected and 

analyzed by MML......................................................................................................................60

Table 17. Mean values by area and year for IMAP sampling in the region of the Crystal River 

Estuary (data from FDEP IWR Run 40). Samples for chlorophyll a were depth 

integrated; others were surface grabs. ....................................................................................61

Table 18. Waterbody IDs within the marine portions of the Springs Coast region that are listed on 

the 303(d) list of impaired waters. ...........................................................................................61

Table 19. Mean and standard deviations of site annual geometric means, summarized by 

subregion and salinity range. Note that fewer than ten sites are reported for some 

subregions because freshwater sites were not included. N = sample size, SD = 

standard deviation....................................................................................................................63

Table 20. Proposed numeric nutrient criteria for all segments of Springs Coast, including TP, TN, 

and chlorophyll a. For compliance purposes, the long term geometric mean shall not 

exceed the long term limit nor shall the average of all stations in a segment exceed 

the network average more than twice in a 5 year period. The last column shows the 

value which single station shall not exceed, by segment, more than twice in a 5 year 

period........................................................................................................................................66

List of Figures

Figure 1. Map of the Springs Coast, showing managed areas (areas that are discussed are 

labeled) and mapped seagrass coverage (2007, limited to 15 miles offshore). ......................... 5

Figure 2. Springs Coast coastal WBIDs contained within USGS HUC 35. .................................................... 7

Figure 3. Aquatic features of the Springs Coast, including major waterways, springs, delineated 

springsheds, and coastal bathymetry. Note the very shallow nature of the nearshore 

area. Major springsheds delineated by the SWFWMD............................................................11

Figure 4. Aquifer vulnerability in spring areas (Figure 16 in Harrington et al. 2010) ................................12

Figure 5. Atmospheric deposition of inorganic N (nitrate and ammonium nitrogen) by quarter at 

the Chassahowitzka NWR (NADP FL05) (from Dixon and Estevez 2001)..................................13

Figure 6. Locations of potential offshore springs in the northern half of the SWFWMD (from 

DeWitt 2003) ............................................................................................................................14

Figure 7. The average surface CDOM absorption over the West Florida Shelf for the period from 

June 1 to July 17, 1998, shows the southward dispersal of the Suwannee River plume. 

At right, a time series (May 5 to July 29, 1998) for locations along a transect through 

the river plume shows the variability in the modeled surface CDOM normalized by the 

highest value modeled for that location during the period (red). Similarly, 7-day 

composite Sea-viewing Wide Field-of-view Sensor (SeaWiFS) chlorophyll a values for 

the corresponding pixel locations are presented (black) as values normalized by the 

highest value observed during that period. Values were interpolated when cloud 

cover obscured retrieval (from Jolliff et al. 2003).....................................................................15

Figure 8. Comparisons of 1985 and 2007 submersed aquatic vegetation (SAV) coverages for a) 

Crystal River region, b) Weeki Wachee region, c) Aripeka region, and d) Anclote 
Draft vi August 2010

region. 1985 coverage by Continental Shelf Associates (1985). 2007 coverage by 

Avineon Inc. and provided by SWFWMD. Dense Seagrass = 75-100% cover, SparseMedium Seagrass = 10-75% cover, and Patchy Seagrass polygons are areas with 

discontinuous patches of seagrass > 10% cover.......................................................................21

Figure 9. Locations along the Springs Coast where Thalassia testudinum was present in the 1985 

study, but replaced by Syringodium filiforme (S) or Halodule wrightii (H) or both 

species in the 2000 study. Dotted lines delineate the 6-meter (m) and 9-m isobaths 

(from Hale et al. 2004)..............................................................................................................23

Figure 10. Medians and quartiles of salinity of 12 routinely sampled coastal stations in the MML 

study of the Chassahowitzka NWR (Figure 9 in Dixon and Estevez 2001)................................25

Figure 11. Mean density for vascular SAV species by year, in the MML study of the 

Chassahowitzka NWR (Figure 5 in Toutant et al. 2004). .........................................................25

Figure 12. Mean density for rhizophytic algal species by year, in the MML study of the 

Chassahowitzka NWR (Figure 6 in Toutant et al. 2004). ..........................................................26

Figure 13. Fixed monitoring sites in St. Martins Marsh Aquatic Preserve. ................................................27

Figure 14. Frequency of occurrence of seagrass species in St. Martins Marsh Aquatic Preserve, 

1997–2009................................................................................................................................28

Figure 15. Average total seagrass coverage at St. Martins Marsh Aquatic Preserve, 2002–09. 

AVG B&B represents the average Braun-Blanquet ranking assigned at each of 100 

sampling quadrats per year. Ranks are abundance codes ranging from1 to 5.......................28

Figure 16. Average epiphyte ranking in St. Martins Marsh Aquatic Preserve, 2004–09. Shown 

are average epiphyte rankings of 100 sampled quadrats. Possible epiphyte ranks 

range from 1 to 4. The sampling is described in the section on submersed aquatic 

vegetation and species composition.........................................................................................29

Figure 17. Phytoplankton concentrations by major group and by sampling, from the 1996–2001 

MML study of the Chassahowitzka NWR (Figure 33 in Dixon and Estevez 2001). ...................30

Figure 18. Hardbottom habitat in St. Martins Marsh Aquatic Preserve (photo from St. Martins 

Marsh Aquatic Preserve staff). ................................................................................................. 32

Figure 19. Location and size of coral beds and coral reefs off the coast of a) Citrus County and b) 

Hernando County, generated from 2007 aerial photos (map courtesy of SWFWMD).............34

Figure 20. Commercial blue crab harvest (pounds per trip) per year in Citrus, Hernando, and 

Pasco Counties, for the period of survey record (1995–2008) (from FWCC). ...........................35

Figure 21. Commercial bait and food shrimp harvest (pounds per trip) per year in Citrus, 

Hernando, and Pasco Counties, for the period of survey record (1995–2008) (from 

FWCC). ......................................................................................................................................36

Figure 22. Commercial landings (pounds per trip) of grouper and mullet per year in Citrus, 

Hernando, and Pasco Counties, for the period of survey record (1995–2008) (from 

FWCC). ......................................................................................................................................36

Figure 23. Total commercial finfish harvest (pounds per trip) per year in Citrus, Hernando, and 

Pasco Counties, for the period of survey record (1995–2008) (from FWCC). ...........................37

Figure 24. TN data for one site in the Weeki Wachee Estuary and one site in the Crystal River 

Estuary, 1984–85, from the MML study. ..................................................................................40

Figure 25. Salinity as a predictor of TN for one site in the Weeki Wachee estuary and one site in 

the Crystal River Estuary, 1984–85, from MML study. .............................................................40
Draft vii August 2010

Figure 26. Project COAST sampling stations. Forty stations along the coast of Citrus and 

Hernando Counties have been sampled monthly from 1997 to the present, with 10 

stations each in the Weeki Wachee, Chassahowitzka, Homosassa, and Crystal River 

systems. Forty stations along the coast of Pasco County have been sampled monthly 

from 2000 to the present, with 10 stations each in the Aripeka, Hudson, 

Pithlachascotee, and Anclote River regions. Colored station markers represent the 

mean annual geometric mean of each station for 1996–2006, calculated by FDEP................42

Figure 27. Relationship between log10-transformed monthly mean chlorophyll and TN and TP 

concentrations from all estuarine systems along the Citrus, Hernando, and Pasco 

County coasts (from Jacoby et al. 2009a).................................................................................43

Figure 28. Trend analysis based on correlation of site data with time. Wet months were 

identified as June, July, August, and September (from Jacoby et al. 2009a)............................ 44

Figure 29. Trend analysis based on correlation of site data with time. Transitional months were 

identified as December, January, February, and March (from Jacoby et al. 2009a)................44

Figure 30. Trend analysis based on correlation of site data with time. Dry months were 

identified as April, May, October, and November (from Jacoby et al. 2009a). ........................45

Figure 31. Trend analysis based on correlation of site data with time. Wet months were 

identified as June, July, August, and September (from Jacoby et al. 2009b)............................45

Figure 32. Trend analysis based on correlation of site data with time. Transitional months were 

identified as December, January, February, and March (from Jacoby et al. 2009b)................46

Figure 33. Trend analysis based on correlation of site data with time. Dry months were 

identified as April, May, October, and November (from Jacoby et al. 2009b). ........................46

Figure 34. Geometric mean TN concentrations per station for the Weeki Wachee River and 

coastal sites. Sites 1 and 2 are in the river, Site 3 is at the river mouth, and Sites 4 

through 10 are in the coastal area. ..........................................................................................51

Figure 35. Location of the Weeki Wachee River and coastal sites in Project COAST. ................................52

Figure 36. Sampling stations in the Chassahowitzka NWR in the 1996–2001 MML study (from 

Dixon and Estevez 2001)...........................................................................................................53

Figure 37. DO (means and quartiles) for stations along the riverine transect. Stations 24, 26, 

and 44 are in the coastal areas (from Dixon and Estevez 2001). .............................................54

Figure 38. Mean TN, IN, and organic nitrogen (ON) along the riverine transect, illustrating the 

generally conservative net behavior downstream of Station R1.7; salinity 3.5 practical 

salinity units (PSU) (Figure 28 in Dixon and Estevez 2001).......................................................55

Figure 39. Water quality sampling sites from the MML study of the Chassahowitzka River and 

coast, used in FDEP’s data analysis. .........................................................................................56

Figure 40. Mean annual salinity is positively related to annual geometric mean TN. Salinity was 

depressed at all stations during 1998, a year of particularly high rainfall...............................57

Figure 41. Annual geometric mean corrected chlorophyll a at Chassahowitzka River sites (R4.0–

R0.0) and Bay sites (40C-3) collected by MML. Very high chlorophyll a levels were 

measured at the bay sites in 1998 (El Niño event); stable levels in the river indicate 

that the increase was due to input from coastal waters..........................................................57

Figure D-1. TP concentrations in the Weeki Wachee River, 1997–2009, sampled by FDEP and 

Project COAST. ..........................................................................................................................97
Draft viii August 2010

Figure D-2. Comparison of available data for Homosassa Head Springs, sampled by FDEP and 

Project COAST. ..........................................................................................................................98

Figure D-3. Comparison of COAST TN data and FDEP Trend Variability NO2+3 data from the Weeki 

Wachee River. Most TKN values from the FDEP data were nondetect, and thus FDEP 

NO2+3 and Project COAST TN data were compared.................................................................. 98

Figure D-4. Comparison of salinity values at sites that are located close to one another in the 

Chassahowitzka Estuary, from the COAST and Mote Marine Lab (MML) sampling 

programs...................................................................................................................................99

Figure D-5. Comparison of total phosphorus values at sites that are located close to one another 

in the Chassahowitzka Estuary, from the COAST and Mote Marine Lab (MML) 

sampling programs. The minimum detection limit (MDL) for the MML lab was 50 

μg/L; non-detects were plotted as 25 μg/L. .............................................................................99

Figure D-6. Comparison of chlorophyll a values at sites that are located close to one another in 

the Chassahowitzka Estuary, from the COAST and Mote Marine Lab (MML) sampling 

programs.................................................................................................................................100

Figure D-7. Comparison of total nitrogen values at sites that are located close to one another in 

the Chassahowitzka Estuary, from the COAST and Mote Marine Lab (MML) sampling 

programs.................................................................................................................................101

Figure D-8. Comparison of total phosphorus values at sites that are located close to one another 

in the Suwannee Estuary, from the COAST and Suwannee River Water Management 

District (SRWMD) sampling programs....................................................................................102

Figure D-9. Comparison of total nitrogen values at sites that are located close to one another in 

the Suwannee Estuary, from the COAST and Suwannee River Water Management 

District (SRWMD) sampling programs....................................................................................103
Draft 1 August 2010

Executive Summary

This report was prepared by the Florida Department of Environmental Protection (FDEP), in cooperation 

with local scientists, to support the development of numeric nutrient criteria for the Springs Coast. The 

primary purpose of the proposed numeric nutrient criteria is to protect healthy, well-balanced natural 

populations of flora and fauna from the effects of excess nutrient enrichment. 

The Springs Coast of Florida, encompassing the coastal areas of Citrus, Hernando, and Pasco Counties, is 

a low-energy coastline that functions like an estuary, despite the lack of physical barriers and 

enclosures. The region is characterized by extensive tidal marshes and swamps, with much of the 

coastline in conservation land, and a wide continuous seagrass bed that extends 15-30 miles offshore in 

some areas due to the very shallow and clear water of this coastline. Marine habitats in the area include 

extensive seagrass beds, patches of limestone hardbottom habitat that support macroalgal and coral 

communities, oyster reefs, and some mangrove areas. Submersed aquatic vegetation (SAV), which 

includes seagrass and macroalgae, is the most nutrient-sensitive biological endpoint in the Springs 

Coast, and SAV mapping conducted in 1985, 1999, and 2007 suggests that SAV acreage and the location 

of the deep edge has not been degraded during that interval. 

Although nitrogen (N) levels have been increasing and/or there has been ecological imbalance in recent 

decades in some inland spring runs in Springs Coast watersheds (Kings Bay, Homosassa, Weeki Wachee), 

N levels have been stable in the coastal area since the 1980s. The increased loading in freshwater 

systems has not been sufficient to exceed the capacity of the river and estuary to use those nutrients, 

and thus nutrient concentrations in the estuary have not increased. Total phosphorus (TP) 

concentrations have been stable or declining during that period. Nutrient limitation studies have shown 

that algal growth is either limited by phosphorus (P) or co-limited by N and P in this region. Therefore, 

limits for N and P are warranted. Biological data from the region suggest that the designated aquatic life 

use is currently being fully supported, and so the nutrient regime of the recent record (the past 15 

years) is protective of that use. 

Contributors

Dr. Kellie Dixon (Mote Marine Laboratory; Dr. Thomas K. Frazer and Dr. Chuck Jacoby (University of 

Florida); Chris Zajac, Keith Kolasa, Dr. Gary Williams, Veronica Craw (Southwest Florida Water 

Management District); Melissa Charbonneau (Big Bend Seagrasses and St. Martin Marsh Aquatic 

Preserves); Nia Wellendorf (FDEP) 
Draft 2 August 2010

Table 1a. Checklist of nutrient enrichment symptoms in the Springs Coast -= Empty cell/no data; N/A = Not available

Response Variable Observed 

Historically 

or Currently?

Explanation Source

Low dissolved oxygen 

(DO) (hypoxia/anoxia)

No None of the segments with waterbody identification numbers (WBIDs) within this region are listed 

for DO, and no reports of hypoxia or anoxia were found.

Florida 303(d) list

Reduced clarity No Plots of annual geometric mean Secchi depth from 6 to 10 years of Project COAST data show no 

trend. 

Project COAST data 

from STORET

Increased chlorophyll 

a concentrations

Yes, limited 

in space and 

time

No trend is visually apparent in the data overall (Appendix B). An increasing trend in chlorophyll a

was detected for wet season months at some Crystal and Homosassa Estuary sites only, in trend 

analyses conducted by Jacoby et al. 

Jacoby et al. 2009a; 

Project COAST data 

from STORET 

Phytoplankton 

blooms (nuisance or 

toxic)

Yes There was a sustained bloom in 1998 following large amounts of rainfall and water from the 

Suwannee River extending south along the Springs Coast. This bloom was not toxic, but temporarily 

increased chlorophyll a levels. 

Dixon and Estevez 2001

Problematic epiphyte 

growth 

No Epiphyte rank data from St. Martins Marsh Aquatic Preserve indicate no problematic growth and no 

change over the sampling period from 2004 to 2009. 

Analysis provided by 

M. Charbonneau

Problematic 

macroalgal growth

No An attendee at FDEP’s February 23, 2010 public meeting shared an anecdotal account of seeing more 

red algae (macroalgae) nearshore; however, that account has not been verified with data.

- 

Submerged aquatic 

vegetation (SAV) 

community changes 

or loss

Yes The 2000 study by J. Hale and colleagues found some areas near the deep edge off Citrus and 

Hernando Counties in which Halodule or Syringodium had replaced Thalassia, but no cause was 

identified. Subsequent studies of the 1998 El Niño event suggest that the colored plume from the 

Suwannee River could have shaded those areas and caused temporary community shifts. FDEP does

not think that this is an example of anthropogenic degradation caused by nutrients. Community 

changes were also observed along the coast of the Chassahowitzka National Wildlife Refuge (NWR), 

but those changes were attributed to an increase in fresh water in 1998 and resultant low salinity.

Hale et al. 2004; 

J. Hale, personal 

communication; 

Toutant et al. 2004; 

Jolliff et al. 2003

Emergent or shoreline 

vegetation 

community changes 

or loss 

No No such reports were found in the literature. Much of the shoreline is protected as conservation 

land.

- 

Coral/hardbottom 

community changes 

or loss 

Unknown No information on change or loss was found in the literature. There is currently a map of 

hardbottom communities along the Springs Coast (Figure 18), but no historical reference exists for 

comparison. 

- 

Impacts to benthic 

community

N/A No additional information was found other than the benthic communities listed above. - 

Fish kills No - - 
Draft 3 August 2010

Table 1b. Checklist of additional factors in the Springs Coast

- = Empty cell/no data

Nutrient Factors Observed? Explanation Source

Increased nutrient 

loading or 

concentrations

Yes There has been increased loading of N from some spring rivers, but loading estimates through 

time are not available. Trend analyses by Jacoby et al. (2009) detected some some increases in TN 

and TP during the wet months off the coast of Citrus County. See Appendix B for annual means.

Harrington et al. 2010; 

Jacoby et al. 2009a, 

2009b 

Difference between 

nearshore and 

offshore levels 

Yes In the northern Springs Coast, nutrient levels are often higher offshore due to external sources 

and relatively small freshwater inputs from coastal rivers. In the southern Springs Coast, there is 

an expected gradient of nutrient concentrations as terrestrial river water is diluted by lowernutrient Gulf water.

Appendix B; Figure 25

Mitigating factors 

that could 

prevent nutrient 

expression

No - - 

Other significant 

stressors 

to biological 

communities

No - - 

Natural highnutrient episodes 

(e.g., seasonal or 

event driven)

Yes During periods of extreme high rainfall (e.g., the El Niño event in 1998), water from the Suwannee 

River has been shown to travel along the Springs Coast and could reduce water clarity. 

- 
Draft 4 August 2010

Geographic and Physical Description 

(Adapted from http://www.protectingourwater.org/ and Wolfe 1990)

The Springs Coast watershed includes coastal areas off Citrus, Hernando, and Pasco Counties, from 

Crystal River south to the Anclote River (Figure 1). It is bound on the east by the Brooksville Ridge, a 

sandy remnant of previous higher sea levels that is characterized by porous limestone geology, with 

wetlands in low-lying areas and scattered sinkhole lakes. The whole region is contained in U.S. 

Geological Survey (USGS) Hydrologic Unit Code (HUC) 35, Crystal River to St. Petersburg, and is divided 

into many waterbody IDs (WBIDs) for assessment by FDEP (Figure 2). Major cities and towns in the 

watershed include Port Richey, New Port Richey, Weeki Wachee, Brooksville, and Crystal River. 

Much of the shoreline is preserved by local, state, or federal entities. From north to south, protected 

lands include the Marjorie Carr Cross Florida Greenway Trail State Recreation and Conservation Area, 

Crystal River Preserve State Park, St. Martins Marsh Aquatic Preserve, Chassahowitzka National Wildlife 

Refuge, Weeki Wachee Preserve, Werner-Boyce Salt Springs State Park, and Anclote Key Preserve State 

Park (Figure 1). Consequently, much of the coast contains intact salt marshes and mangrove forests that 

provide a buffer between uplands and the estuarine waters. 

The six major rivers in the watershed—Crystal, Homosassa, Chassahowitzka, Weeki Wachee, Anclote, 

and Pithlachascotee—their springs, and their associated coastal aquatic resources are dominant 

features. The watershed contains four major spring complexes, which occur because of the region's

karst geology. A spring complex is a group of springs, often spread out over several square miles. The 

springs are recharged mainly by rainfall.

The coastline has very low relief, so the nearshore areas are very shallow with low wave energy. The 

coast contains numerous tidal creeks and salt marshes, as well as isolated islands fringed with 

mangroves. There are very few natural sandy beaches. Most of the region functions like an estuary, 

with its shallow waters, abundant freshwater flows, and low-energy shoreline. Seagrass beds cover 

almost the entire nearshore area where depths are sufficient, and extensive oyster reefs are also 

present. Vast salt marshes up to ten miles wide provide a buffer between the upland land uses and the 

estuaries.

In the Springs Coast region, the nearshore estuarine area provides essential habitat for numerous fish 

and wildlife species, including nursery and juvenile habitats for many recreational and commercial fish 

species. The commercial seafood harvests on Florida's west coast consist of at least 95% estuarydependent species. 

Conservation lands include the following:

• The Crystal River NWR comprises 20 islands and several small parcels of land. Six 

hundred million gallons of fresh water flow daily from more than 30 natural springs 

in the refuge. The springs are a natural warmwater refuge for the endangered West 

Indian manatee and provide critical habitat for the Crystal River herd, which makes 

up about 25% of the United States's manatee population.
Draft 5 August 2010

Figure 1. Map of the Springs Coast, showing managed areas (areas that are discussed are labeled) 

and mapped seagrass coverage (2007, limited to 15 miles offshore).
Draft 6 August 2010

 

• The 23,000-acre St. Martins Marsh Aquatic Preserve, established in 1969, is the 

southern terminus for migratory waterfowl of the Atlantic and Mississippi flyways. 

St. Martins Marsh provides stopover and wintering areas for many migratory 

species. DeWitt (2003) describes this preserve as “a nearly pristine area of extensive 

needle rush islands, sea grass meadows, and mangrove keys.”

• The Chassahowitzka NWR, established in 1931, comprises 31,000 acres of shallow 

saltwater bays, estuaries, brackish marshes, and tidal streams, with a fringe of 

hardwood swamps. It is accessible only by boat. This NWR is the site of a whooping 

crane reintroduction program that has been ongoing since 2000. 

• Weeki Wachee Preserve contains the southernmost coastal hardwood hammock in 

western Florida. 

• Starkey Wilderness Park, an 8,069-acre tract, encompasses a portion of the 

headwaters of the Anclote River and a stretch of the Pithlachascotee River. 

• Anclote Key Preserve State Park is a barrier island at the southern end of this region. 

Just to the east of Anclote Key lies Anclote Anchorage, a shallow area containing 

seagrass beds that provides breeding habitat for numerous marine species. The 

Anclote NWR encompasses the waters between Anclote Key and the mainland.

A comprehensive description of the geology, hydrology, and ecology of the Springs Coast can be found 

in An Ecological Characterization of the Florida Springs Coast: Pithlachascotee to Waccasassa Rivers 

(Wolfe 1990). 
Draft 7 August 2010

Figure 2. Springs Coast coastal WBIDs contained within USGS HUC 35.
Draft 8 August 2010

Sources of Nutrients 

Ground Water, Springs, and Spring-fed Rivers 

The coasts of Citrus and Hernando Counties receive the majority of their freshwater input from ground 

water through the major spring-fed rivers and from diffuse ground water seeps from the karst 

landscape. Springs and spring runs carry ground water captured within the spring group’s springshed 

(Figure 3). The karst geology of this region makes the ground water very vulnerable to contamination 

from fertilizers, animal waste, and wastewater (Harrington et al. 2010). The landuse in the springsheds 

for area springs contain 23% to 45% urbanization, 9% to 25% agriculture, and 23% to 41% forest (Table 

2). It is notable that the percentage of wetlands in the springsheds ranges from 11% to 18%, which is 

low compared with neighboring watersheds to the north. The karst landscape is one reason for the low 

percentage of wetlands and the higher percentage of upland forests; soils are very well drained, and 

thus the water goes from land into ground water. That groundwater resurfaces as spring boils and 

within coastal marshes. Table 3 lists the land use distributions for the watersheds of the major rivers of 

Pasco County. 

In 2010, the Florida Springs Initiative reported on nutrient levels in Florida’s major springs and ground 

water (via wells) and the causes of elevated nitrate levels at selected sites (Harrington et al. 2010). They 

reported the following median nitrate concentrations (mg/L) from 2001 to 2006 for regularly monitored 

spring boils along the Springs Coast: Tarpon Hole Spring (0.185) and Hunter Spring (0.39) of Kings Bay, 

Homosassa Springs #1,2,3 (0.5-0.54), Chassahowitzka Main and #1 (0.53 and 0.575), and Weeki Wachee 

Main (0.765). 

Those nitrate levels are moderate compared with springs statewide, but almost all exceed the proposed 

nitrate criterion for clear streams and springs of 0.35 mg/L, and all are an order of magnitude greater 

than estimated background conditions. Orthophosphate concentrations in these spring boils are among 

the lowest statewide (Harrington et al. 2010). In their report, Harrington et al. (2010) reported N 

isotope studies indicating that the most significant sources of nitrate to Weeki Wachee Springs is 

inorganic fertilizer from residential lawns and golf courses, as well as septic tanks. Table 4 contains 

annual N and P loading estimates from the Homosassa and Weeki Wachee Rivers. These estimates are 

derived from water quality and flow estimates within the spring runs rather than at the spring boil. 

The only major freshwater inputs into the Pasco County coastal area are the Anclote and the 

Pithlachascotee Rivers, which originate in swamps and not springs. The shallow coastal area is not as 

wide as in the northern Springs Coast; seagrass beds extend approximately 15 miles offshore rather than 

the 30-mile extent in the northern areas (K. Kolasa, personal communication, SWFWMD). 

There are approximately 140 active wastewater treatment facilities in the vicinity of the Crystal, 

Homosassa, Chassahowitzka, Weeki Wachee, and Aripeka Spring Complexes (FDEP website 

www.protecingourwater.com, 2010). Most of these do not discharge to surface waters, but rather 

discharge into percolation ponds or are discharged via land application. The soils in this region are 

porous and the ground water is highly vulnerable to contamination from land activities, so any landbased wastewater disposal system potentially contributes nutrients to the ground water and ultimately 

the springs and coastal areas (Figure 4; Harrington et al. 2010; Kuhnman and DeHaven 2008). The 

coastal areas of Hernando and Pasco Counties are similarly vulnerable to ground water contamination 

(Harrington et al. 2010).
Draft 9 August 2010

Table 2. Land use in selected springsheds depicted in Figure 3 (SWFWMD 2007 land use) 

Springshed Springshed 

Area 

(square 

kilometers 

[km2])

Urban 

and 

BuiltUp

Agriculture Upland 

Nonforested

Upland 

Forests

Water Wetlands Barren 

Land

Transportation, Communications, and 

Utilities

Kings Bay 671 45.0% 10.7% 1.4% 27.4% 2.7% 11.2% 0.2% 1.4%

Homosassa 734 22.8% 14.9% 1.3% 40.8% 1.8% 17.5% 0.3% 0.5%

Chassahowitzka 439 35.6% 13.7% 1.1% 31.3% 0.8% 15.5% 0.1% 1.9%

Weeki Wachee 719 30.9% 24.9% 2.5% 24.4% 1.3% 13.7% 0.2% 2.0%

Aripeka 110 44.6% 9.6% 1.0% 23.0% 1.7% 16.6% 0.2% 3.3%

Table 3. Land use in the Pithlachascotee and Anclote River watersheds (SWFWMD 2004 and 2007 land 

use).

Land Use Anclote

2004 Land Use

Pithlachascotee

2007 Land Use

Urban 28.47% 22.76%

Citrus, orchards, nurseries 0.76% 1.74%

Pasture, rangeland, and other 

agriculture

24.69% 25.91%

Uplands 15.23% 28.37%

Wetlands 24.40% 17.07%

Water 5.74% 2.08%

Other 0.71% 2.06%

Table 4. Annual load estimates for TP and TN for two spring-fed rivers along the Springs Coast. 

Estimates were calculated based on annual mean nutrient concentrations from bimonthly sampling at 

1 SWFWMD site on each river (site as indicated in table) and mean annual discharge at USGS gauge 

stations (SWFWMD).

Parameter Homosassa River Weeki Wachee River

USGS gauge USGS 02310700 HOMOSASSA R AT 

HOMOSASSA FL

USGS 02310525 WEEKI WACHEE 

RIVER

Mean annual flow 

(cfs)

243 140

SWFWMD station Site HV-3 10/05-8/09 WEEKI WACHEE RIVER WW5

2/06 –2/09

Mean annual TN concentration 

(mg/L)

0.45 0.72

Mean annual TP concentration 

(mg/L)

0.027 0.011

Annual TN load 97,761 90,117
Draft 10 August 2010

(kg/yr)

Annual TP load 

(kg/yr)

5,866 1,377

cfs = Cubic feet per second

mg/L = Milligrams per liter

kg/yr = Kilograms per year

Wetlands and Wildlife

Citrus and Hernando Counties are developed along U.S. Highway 19 and along the rivers. There are, 

however, large areas of undeveloped salt marsh, river habitat, and low-lying islands on the western edge 

of the counties towards the Gulf of Mexico. The 23,000-acre St. Martins Marsh Aquatic Preserve, the 

32,000-acre Crystal River Preserve State Park, and the 31,000-acre Chassahowitzka NWR are large areas 

that support abundant wildlife and wetland flora. The West Indian (Florida) manatee, an endangered 

species, inhabits the area year-round. Bird communities are also present in the salt marshes. Migratory 

waterfowl and other more permanent bird residents are found in significant numbers throughout the 

area. Abundant wildlife along the shoreline has the potential to increase nutrients in nearshore waters, 

especially following rainfall and during coastal flood events. In addition, migratory waterfowl 

populations are seasonal and can be found in the uplands and marshes, and sometimes roosting on 

exposed sandbars and oyster reefs. The concentration and loading of organic N into an estuary is 

positively correlated with the percentage of wetlands in the watershed (FDEP stream studies). 

However, coastal wetlands can also uptake land-derived N before it reaches coastal waters (Valiela and 

Cole 2002). 

Atmospheric Deposition

Dixon and Estevez (2001) reported on the atmospheric deposition of inorganic nitrogen (IN) in rainfall, 

as measured by the National Atmospheric Deposition Program (NADP) at Chassahowitzka Site FL05 

(Figure 5). They reported that the atmospheric deposition of IN directly to the waters of the 

Chassahowitzka NWR is nearly double that contributed by riverine flow. 
Draft 11 August 2010

Figure 3. Aquatic features of the Springs Coast, including major waterways, springs, delineated 

springsheds, and coastal bathymetry. Note the very shallow nature of the nearshore area. Major 

springsheds delineated by the SWFWMD. 
Draft 12 August 2010

Figure 4. Aquifer vulnerability in spring areas (Figure 16 in Harrington et al. 2010)
Draft 13 August 2010

Figure 5. Atmospheric deposition of inorganic N (nitrate and ammonium nitrogen) by quarter at the 

Chassahowitzka NWR (NADP FL05) (from Dixon and Estevez 2001)

Offshore Spring Vents

Spring vents have been identified offshore of Citrus, Hernando, and Pasco Counties (Figure 6). DeWitt 

(2003) did not observe flow at the vents in Hernando and Pasco Counties. Flow was detected at the 

Maya Spring vent in Citrus County in April 2002, but high salinities and temperatures from the vent 

during subsequent deployments of YSI sondes suggested that very little ground water discharge is 

occurring at this site (DeWitt 2003). DeWitt (2003) reported a number of other sinkholes offshore (30 to 

50 miles) but indicated that ground water discharge was unlikely from most of these sinks.
Draft 14 August 2010

Figure 6. Locations of potential offshore springs in the northern half of the SWFWMD (from DeWitt 

2003)
Draft 15 August 2010

Coastal Currents 

Various currents within the Gulf of Mexico occasionally bring waters from the rivers to the north 

through the Springs Coast region. One such event occurred in 1998, when it was documented by 

ecologists (Dixon and Estevez 2001) and oceanographers (Jolliff et al. 2003; Weisberg et al. 2004) that 

the plume of colored dissolved organic matter (CDOM) from the Suwannee River extended past the 

nearshore areas of the Springs Coast (Figure 7). Jolliff et al. (2003) determined that the 1998 plume was 

from the Suwannee River, but other rivers may contribute as well (the Withlacoochee and Waccasassa 

are also colored rivers north of the Springs Coast).

Figure 7. The average surface CDOM absorption over the West Florida Shelf for the period from June 1 

to July 17, 1998, shows the southward dispersal of the Suwannee River plume. At right, a time series 

(May 5 to July 29, 1998) for locations along a transect through the river plume shows the variability in 

the modeled surface CDOM normalized by the highest value modeled for that location during the 

period (red). Similarly, 7-day composite Sea-viewing Wide Field-of-view Sensor (SeaWiFS) chlorophyll

a values for the corresponding pixel locations are presented (black) as values normalized by the 

highest value observed during that period. Values were interpolated when cloud cover obscured 

retrieval (from Jolliff et al. 2003). 
Draft 16 August 2010

Biological Summary 

Submersed Aquatic Vegetation and Species Composition

SAV, including seagrasses and associated macroalgae, is the marine aquatic community most sensitive to 

nutrient enrichment and potential resultant light reduction along the Springs Coast. The SAV 

community along this coastline is vast and valuable, providing habitat for fish, manatees, sea turtles, and 

other wildlife. Zieman and Zieman (1989) provide a comprehensive review of the character and value of 

the seagrass communities off the west coast of Florida, including the Springs Coast. They summarize the 

functions of seagrass communities as (1) high production and growth, (2) food and feeding pathways, (3) 

shelter, (4) habitat stabilization, and (5) nutrient effects (holding detritus onsite, hosting nitrogen-fixing 

organisms, and pumping nutrients from sediment to water).

Estimates of Submersed Aquatic Vegetation Coverage

Thalassia testudinum, Syringodium filiforme, Halodule wrightii, and Halophila spp. comprise the vascular 

component of the SAV community in this region. Kolasa and Craw (2009) interpreted aerial photos to 

determine seagrass coverage for the project area (Table 5; Figure 8). Seagrass cover was found within 

379,016 acres of 494,404 total acres mapped, or 77% of the total project area. In general, dense 

seagrass comprised 272,772 acres, or 63% of the 431,323 acres of submerged bottom mapped. 

Seagrass within the sparse-to-medium classification comprised 87,393 acres (20%), patchy seagrass 

comprised 18,851 acres (4%), and bare substrate comprised 52,305 acres (12%). Dense seagrass was 

the dominant seagrass cover type within all 4 segments, with the Aripeka and Weeki Wachee segments 

containing the largest area and percentage of dense seagrass (68% and 73%, respectively). In contrast, 

the Anclote and Homosassa segments contained larger areas of nonvegetated or bare substrate (24% 

and 21%, respectively). 

Table 5. Estimates of seagrass coverage along the Springs Coast to approximately 15 miles offshore, 

from the interpretation of 2007 digital imagery (SWFWMD; Kolasa 2010). Shown are acres and 

percent of total area comprised by various bottom habitats within 4 regions.

Habitat Type Anclote to 

Pithlachascotee 

(acres [%])

Aripeka to 

Hernando 

Beach 

(acres [%])

Weeki Wachee to 

Chassahowitzka 

(acres [%])

Homossasa to 

Crystal River 

(acres [%])

All Regions 

(acres [%])

Dense seagrass 36,221 (59%) 76,855 (68%) 100,825 (73%) 58,870 (50%) 272,772 (63%)

Patchy seagrass 5,903 (10%) 4,138 (3%) 4401 (4%) 4,408 (4%) 18,851 (4%)

Sparse to 

medium seagrass

4,201 (7%) 17,461 (25%) 36701 (17%) 29,026 (25%)) 87,393 (20%)

Other–

open water, tidal 

flats, shoals 

(nonvegetated)

14,575 (24%) 7,091 (4%) 5,759 (7%) 24,881 (21%) 52,305 (12%)

Total area of 

submerged 

bottom

60,902 (100%) 105,547 (100%) 147,688 (100%) 117,186 

(100%) 

431,323 (100%) 

Dense seagrass beds extend well beyond the western boundary (15 miles offshore) of this project’s 

study area. These offshore dense beds are primarily located within the shallow offshore zones of the 
Draft 17 August 2010

Aripeka and Weeki Wachee segments, where water depth increases at a gradual rate of 1 foot per mile. 

The shallow depth (less than 20 feet), good water clarity, and adequate light penetration support 

seagrass growth in these offshore waters (Zieman and Zieman 1989). 

The mapping of SAV by photo interpretation of aerial surveys was also conducted for the Springs Coast 

in 1985 (Continental Shelf Associates 1985) and 1999. Comparison in coverage between years is difficult 

due to different mapping techniques and different image resolution. The most comparable years were 

1985 and 2007, and Table 6 contains the comparison between those mapping efforts for the entire 

mapping region (from Kolasa and Craw 2009). The acreages are comparable, though the 2007 mapping 

shows a higher percentage of unvegetated area. However, the detail of line work and number of 

polygons were so different between the 2 years (e.g., the majority of dense seagrass was represented by 

2 polygons totaling 288,000 acres in 1985, compared with 1,900 polygons of dense seagrass in the 2007 

effort) that the authors do not conclude that there has been any loss in seagrass (Kolasa and Craw 

2009). Their analysis does not include a comparison of acreage for each region, but visual examination 

of 1985 and 2007 coverages in the four regions of their study indicate few areas of potential loss (Figure 

8). An area of “patchy seagrass” just east of Crystal River is present in 1985, but the 2007 map is devoid 

of seagrass in that area of roughly 6 miles by 1.5 miles (Figure 8a). Two isolated circle areas in the 

northern nearshore portion of the Aripeka region were mapped in 1985 but not in 2007 (Figure 8c). 

The recent efforts to map SAV in this region using digital imagery from 2007 showed that the deep edge 

of dense SAV coverage in Pasco County, at 11-13 feet deep, has not been reduced (Kolasa and Craw 

2009; Figures 8c, 8d), which suggests that water clarity in that area has not been degraded. The deep 

edge extends too far out into the Gulf in Citrus and Hernando Counties (about 30 miles) for this study 

(to 15 miles offshore) to make any judgment about that portion of the coast. 

Table 6. Comparison of seagrass acreage estimated for the Springs Coast in 1985 and 2007 (from 

Kolasa and Craw 2009). 
Draft 18 August 2010
Draft 19 August 2010
Draft 20 August 2010
Draft 21 August 2010

Figure 8. Comparisons of 1985 and 2007 submersed aquatic vegetation (SAV) coverages for a) Crystal 

River region, b) Weeki Wachee region, c) Aripeka region, and d) Anclote region. 1985 coverage by 

Continental Shelf Associates (1985). 2007 coverage by Avineon Inc. and provided by SWFWMD. Dense 

Seagrass = 75-100% cover, Sparse-Medium Seagrass = 10-75% cover, and Patchy Seagrass polygons 

are areas with discontinuous patches of seagrass > 10% cover.

2000 Field Survey Results 

Field SAV surveys of species composition were conducted from 1974 to 1980 (Iverson and Bittaker 1986) 

and repeated in 2000 (Hale et al. 2004; Table 7) in the Springs Coast and along the Big Bend Coast. 

There was some apparent replacement of T. testudinum with S. filiforme or H. wrightii at some deep 

sites between 1980 and 2000 (Figure 9; Hale et al. 2004). Hale et al. (2004) reported that there may 

have been a shift in species composition and maybe even a loss of seagrass at the deep edge, and 

hypothesized that those changes may have been due to increased light limitation and nutrients from 

rivers in the region. They note that effects are more likely from highly colored northern rivers (e.g., 

Suwannee) rather than small spring-fed rivers along the adjacent coast, but no water quality data were 

available at that distance from shore to confirm their hypothesis. They acknowledge the limitations of 

their comparison, including the fact that they only sampled each survey point once during one year, 

whereas Iverson and Bittaker visited each site six times and considered a species present if it was 

detected one time. Despite these limitations, the authors think that they may have detected some 

change in distribution, but that further sampling would be necessary to confirm their findings (J. Hale, 
Draft 22 August 2010

personal communication, May 14, 2010). The results of the 2007 mapping described previous;y, in 

which the deep edge in Pasco County had not changed, do not refute these authors’ conclusions of 

seagrass loss because they did not detect any change in Pasco County (Hale et al. 2004); most of their 

observed loss or change was in the areas far offshore of Citrus and Hernando Counties, beyond the 

reach of the 2007 mapping by SWFWMD. 

The replacement of T. testudinum with S. filiforme or H. wrightii is consistent with the hypothesis that 

some kind of stress occurred, likely light limitation, and the latter two species were able to recolonize 

the area first because of their life history (see the discussion in Hale et al. 2004). However, it is not clear 

if the increased light limitation was due to increased color, turbidity, or chlorophyll a in the water 

column, and if that increased limitation was part of a downward trend or sporadic event. The 2000 

sampling event followed closely behind a period of high flow from October 1997 to June 1998, an El 

Niño event, in which the freshwater discharge from the Suwannee River was nearly three times the 

long-term average (Carlson et al. 2010) and it was shown that the Suwannee River plume of CDOM 

extended south over the Springs Coast (Jolliff et al. 2003; Figure 7). 

Quinlan (2003) found that the light extinction coefficient in the estuarine areas (reef and nearshore) of 

the Suwannee River was most strongly correlated with tripton (nonalgal suspended solids), followed by 

CDOM and chlorophyll a. Only during very low-flow periods was light extinction highly correlated with 

chlorophyll a. These results indicate that phytoplankton biomass is not the major contributor to water 

clarity reductions in the Suwannee River but, rather, from the organic materials from swamp source 

waters in the Suwannee River watershed. Dr. T. Frazer (University of Florida) has measured light 

extinction coefficient in the nearshore region of the Springs Coast for 13 years, and he has found that it 

is poorly correlated with chlorophyll a (T. Frazer, personal communication at public meeting in Crystal 

River 2/23/10). However, the Florida Wildlife Research Institute (FWRI) of the Florida Fish and Wildlife 

Conservation Commission (FWCC) have preliminary results of a 5-year water clarity and SAV study in the 

region north of the Suwannee River that suggest that chlorophyll and turbidity explain the variation in 

water clarity greater than color (Paul Carlson, personal communication 7/31/10). FDEP has not obtained

light extinction data with which to perform independent analyses. 

Table 7. Summary of observations of seagrass species at 188 sampling locations in the Big Bend and 

Springs Coast regions. The depths represent the maximum depth at which each species was observed. 

The depths listed in the 1974–1980 column were determined from the depths measured in the 2000 

study (from Hale et al. 2004).
Draft 23 August 2010

Figure 9. Locations along the Springs Coast where Thalassia testudinum was present in the 1985 

study, but replaced by Syringodium filiforme (S) or Halodule wrightii (H) or both species in the 2000 

study. Dotted lines delineate the 6-meter (m) and 9-m isobaths (from Hale et al. 2004). 

Mote Marine Laboratory Studies in the Chassahowitzka NWR

Mote Marine Laboratory (MML) studied water chemistry, sediment, and SAV throughout the boundaries

of the Chassahowitzka NWR from 1996 to 2004. The purpose of the study was to establish the baseline 

condition for the community amid growing concerns over freshwater reductions and increased nitrate 

concentrations in the springs. Dixon and Estevez (1998) describe Chassahowitzka Bay as “a large, 

shallow (<2m), exposed mosaic of saltmarsh, seagrass beds, and algal assemblages growing on an 

extensive karstified limestone shelf.” Their studies showed a diverse SAV community, dominated by 

attached macroalga and Thalassia testudinum in the nearshore areas of Chassahowitzka Bay (see Table 

8, from Toutant et al. 2004). Dixon and Estevez (1998) characterized the system as healthy.

High rainfall in 1998 (an El Niño event) followed by an extensive algal bloom allowed MML to study the 

effects of reduced salinity and water clarity on the SAV community (Toutant et al. 2004). The 

chlorophyll a concentration in 1998 was greater than 20 micrograms per liter (μg/L) at some stations for 

6 months from May to October 1998, where levels were typically well below 5 μg/L (see Figure 41 in the 

section on water quality studies). There were high surface water flows during this time, and the salinity 

was less than 20 parts per thousand (ppt) for that 6-month period at stations where it typically ranges 

from about 25 to 30 ppt (Figure 10). Toutant et al. (2004) estimated that the bloom dominated at least 

50 km of the coastline and hypothesized that the excess nutrients originated from large rivers to the 

north (Withlacoochee and Suwannee), although excess fresh water originated all along the coast. SAV 

responses shown in Toutant et al. (2004) demonstrate that the SAV community is very dynamic along 
Draft 24 August 2010

this coastline and is driven by salinity as well as light (Figures 10 and 11). Acetabularia crenulata and 

Caulerpa paspaloides were the two most abundant rhizophytic algae at the beginning of the study 

(1996), were reduced during 1998, and rebounded by 2000 (Figure 12). These algae are not tolerant of 

fresh water; their abundance was likely reduced due to the decrease in salinity rather than algal blooms 

(Toutant et al. 2004). 

Table 8. Regional Braun-Blanquet statistics by sampling for the entire coastal study area in the MML

study of the Chassahowitzka NWR (30 stations) (Table 5 in Toutant et al. 2004). 

OBS = Number of quadrats in which species was observed

FREQ = frequency

ABUN = abundance

DENS = density
Draft 25 August 2010

Figure 10. Medians and quartiles of salinity of 12 routinely sampled coastal stations in the MML study 

of the Chassahowitzka NWR (Figure 9 in Dixon and Estevez 2001).

 

Figure 11. Mean density for vascular SAV species by year, in the MML study of the Chassahowitzka 

NWR (Figure 5 in Toutant et al. 2004). 

Note: Only a subset of sites was surveyed in 1998. 
Draft 26 August 2010

Figure 12. Mean density for rhizophytic algal species by year, in the MML study of the Chassahowitzka 

NWR (Figure 6 in Toutant et al. 2004). 

Note: Only a subset of sites was surveyed in 1998.

SAV in St. Martin’s Marsh Aquatic Preserve 

(text and figures provided by Big Bend Seagrass and St. Martins Marsh Aquatic Preserve staff) 

Aerial surveys are the most commonly used tool for estimating seagrass locations, acres, and broad 

scale changes over time. However, additional localized changes to seagrass species such as abundance 

and health are difficult to capture using traditional mapping methodologies. The St. Martins Marsh 

Aquatic Preserve’s seagrass monitoring program began in 1997, in the region between the 

Chassahowitzka and Homosassa Rivers in Citrus County. Sampling is conducted within a 25-mile grid 

consisting of 25 fixed sites that are 1 mile apart (Figure 13). At each site, 4 replicate quadrats are 

randomly thrown for a total of 100. Coverage estimates of seagrass, rooted macroalgae, and drift algae 

are made using Braun-Blanquet sampling methods. This involves identifying the percent coverage of all 

seagrass and algae species represented within a 1 square meter (m2

) “quadrat.” The preserve uses the 

following coverage abundance codes: 1 = <5% cover; 2 = 5%-25% cover; 3 = 25%-50% cover; 

4 = 50%-75% cover; 5 = 75%-100% cover (Figure 15). 

The type of data collected has been adjusted throughout the study period, but the site locations have

remained the same. The preserve continues to collect data on indicators that prove to be the most 

accessible and comparable, including seagrass and macroalgae abundance, seagrass species 

composition, canopy height, epiphyte density (1 = clean, 2 = light, 3 = moderate, 4 =heavy), water 

quality measurements (DO, pH, temperature, salinity, turbidity, color, photosynthetic active radiation 
Draft 27 August 2010

(PAR), sediment type/grain size, and the presence of other organisms present in the bed, such as bay 

scallops and sea urchins. The monitoring program provides information to resource managers to assess 

the status of this resource in and near the preserve, and is not representative of the entire Springs 

Coast. 

This area of Florida is extremely shallow and is characterized by exposed karst features, resulting in a 

mosaic of seagrass and hardbottom habitats. The dominant species within the hardbottom habitat are

Siderastrea radians (shallow-water starlet coral) and Spheciospongia vesparium (loggerhead sponge) 

(see Table 9 and Figure 18 in later sections). The dominant seagrasses species within the project 

location are Thalassia testudinum and Syringodium filiform (Figure 14). In 2002, the preserve began to 

assess total seagrass coverage, total macroalgal coverage, and total SAV coverage (Figure 15). Total 

seagrass coverage has ranged between 3.02 and 4.13 on the Braun-Blanquet scale of 1 to 5 

(approximately 25-55 percent cover SAV). Total epiphyte coverage density has been stable throughout 

the study period (Figure 16). The project area has a very diverse array of rooted macroalgae, and a total 

of 19 species occur within the study area (Table 8). The dominant macroalgal species within the study 

area are Penicillus capitatus and Caulerpa prolifera. 

Figure 13. Fixed monitoring sites in St. Martins Marsh Aquatic Preserve.
Draft 28 August 2010

Figure 14. Frequency of occurrence of seagrass species in St. Martins Marsh Aquatic Preserve, 1997–

2009. 

Figure 15. Average total seagrass coverage at St. Martins Marsh Aquatic Preserve, 2002–09. AVG 

B&B represents the average Braun-Blanquet ranking assigned at each of 100 sampling quadrats per 

year. Ranks are abundance codes ranging from1 to 5.
Draft 29 August 2010

Figure 16. Average epiphyte ranking in St. Martins Marsh Aquatic Preserve, 2004–09. Shown are 

average epiphyte rankings of 100 sampled quadrats. Possible epiphyte ranks range from 1 to 4. The 

sampling is described in the section on submersed aquatic vegetation and species composition. 

Epiphyte Loads on Seagrass

None of the studies reviewed mentioned problematic ephiphyte growth on seagrass. 

Phytoplankton Species Composition

Roger Johansson conducted a year-long study of water quality and primary productivity in three regions 

of the Anclote River estuary from 1973-1974 (Johansson 1975). The three regions he studies were the 

Anclote River (3 sites in tidal portions), Anclote Anchorage (5 sites between the river mouth and Anclote 

Key) and the Gulf of Mexico (3 sites on the seaward side of Anclote Key). Phytoplankton and benthic 

algae were collected at one site within each region. Phytoplankton were dominated by diatoms at all 

times of year, and they observed a bloom of the dinoflagellate Ceratium hircus in January. Diatoms 

were the only phytoplankton group of any importance in terms of biomass during the course of the 

study (Johansson 1975).

Mote Marine Lab studied phytoplankton in the Chassahowitzka NWR. In the 1996–2001 study, the 

phytoplankton community was dominated at all times by diatoms (Figure 17). The community 

experienced a large algal bloom during the 1998 El Niño event. Diatoms were still dominant then, but 

dinoflagellates were also very abundant.
Draft 30 August 2010

Figure 17. Phytoplankton concentrations by major group and by sampling, from the 1996–2001 MML 

study of the Chassahowitzka NWR (Figure 33 in Dixon and Estevez 2001). 

Macroalgal Species Composition and Biomass (Including Calcareous Forms)

Table 9 lists the types of macroalgal species found in St. Martin’s Marsh from 1998 to 2009.

Depth to Seagrass Targets

No seagrass depth targets have been established. Based on the 2007 mapping effort by the SWFMWD, 

dense beds occur up to 13 feet deep off Pasco County, the only area for which their mapping reached 

the deep edge. In 

Presence and Frequency of Harmful Algal Blooms

No harmful algal blooms (HABs) have been documented for the area. 
Draft 31 August 2010

Table 9. Macroalgal species occurrence in St. Martins Marsh, 1998–2009, sampled by Aquatic 

Preserve staff. Shown is the number of sampling quadrats in which that species was present, of 100 

total quadrats sampled per year. The sampling program and methods are described in the section on 

SAV and species composition. 

Macroalgal Species 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Acetabularia 

crenulata

15 5 4 15 9 10 3 5 2 5 1 4 

Avrainvillea levis 2 1 2 0 3 0 0 0 0 0 0 0 

Anadyomene stellata 3 1 0 9 5 1 2 1 1 1 0 0 

Caulerpa ashmeadii 7 11 4 11 11 16 7 10 7 7 4 4 

Caulerpa 

cupressoides

2 3 6 3 2 3 1 2 4 4 0 3 

Caulerpa langinosa 0 0 0 3 2 0 0 0 0 2 4 0 

Caulerpa mexicana 0 0 0 0 0 0 0 0 0 0 4 0 

Caulerpa paspaloides 0 2 0 3 1 7 1 5 5 0 6 4 

Caulerpa prolifera 67 52 48 62 54 71 19 51 32 22 17 41

Drift algae 40 74 57 40 22 39 25 35 45 29 7 8 

Digenia simplex 7 3 2 10 5 3 3 7 2 1 1 6 

Halimeda incrassata 30 44 33 48 42 44 33 33 26 22 18 30

Penicillus capitatus 57 61 63 63 63 46 52 52 47 39 16 41

Penicillus dumetosus 4 35 32 32 37 28 26 26 40 53 48 48

Padina vickersiae 4 0 0 0 0 0 0 0 0 0 0 0 

Rhipocephalus 

phoenix

3 6 7 6 9 2 5 2 3 5 0 0 

Sargassum sp. 1 4 2 15 6 0 3 5 0 0 3 8 

Udotea flabellum 21 21 25 38 31 27 15 21 30 26 15 4 

Unknown algae 0 0 0 0 0 2 0 0 3 0 0 0 

Coral or Hardbottom Community Structure and Areal Extent 

Dense areas of coral are found around the St. Martins Marsh Aquatic Preserve within water as shallow 

as 4 to 6 feet (Figure 18). These coral beds are flat areas of exposed limerock containing dense growth 

of small coral isolates. Only 1 to 2 species inhabit the shallow beds around the St. Martins Keys,

primarily Siderastrea radians (lesser starlet) and Siderastrea siderea (massive starlet). In addition, 

scattered coral is found growing on much of the hardbottom within 1 mile of the coastline. Again, these 

are primarily Siderastrea radians (lesser starlet) and Siderastrea siderea (massive starlet); however, 

other corals that are occasionally seen include Solenastrea hyades (knobby star) and Stephanocoenia 

intersepta (blushing star). Sponges such as the loggerhead sponge (Spheciospongia vespari) are also 

very common within 1 mile of the coastline, especially between the St. Martins Keys and 

Chassahowitzka River. They support a more diverse coral and sponge community than the flat-bottom 

coral beds. 

Within 6 to 8 miles of the coastline, there are a number of shallow reef systems and rock outcroppings 

that support up to 10 species of coral. These reefs are located in 12 to 15 feet of water and have 2- to 6-

foot relief. In addition to the 4 species listed above, common corals inhabiting these systems include 

Stephanocoenia intersepta (blushing star), Cladocora arbuscula (tube), Manicina areolata (rose), Oculina 
Draft 32 August 2010

robusta (robust ivory tree), and Solenastrea bournoni (smooth star) (description from K. Kolasa, 

SWFWMD). 

Unfortunately, little historical information is available on the reef systems for the Springs Coast. 

Continental Shelf Associates completed some work in 1985 at the same time the seagrass mapping was 

completed; however, no maps were generated. The 2007 seagrass imagery has provided the first 

images of these systems that are sufficiently detailed for reef mapping. Figure 19 shows the location 

and size of coral beds and coral reefs off the Springs Coast, generated from 2007 aerial photos. 

Figure 18. Hardbottom habitat in St. Martins Marsh Aquatic Preserve (photo from St. Martins Marsh 

Aquatic Preserve staff). 
Draft 33 August 2010

a.)
Draft 34 August 2010

b.)

Figure 19. Location and size of coral beds and coral reefs off the coast of a) Citrus County and b) 

Hernando County, generated from 2007 aerial photos (map courtesy of SWFWMD).

Shellfish Production and Frequency/Duration of Bed Closures

Citrus County is the only portion of the Springs Coast that is part of a Shellfish Harvesting Area 

monitored by the Florida Division of Aquaculture, and it is not a major shellfishing area compared with 

other regions. For the winter season, 64,472 acres are Conditionally Approved (<14 MPN/100 ml fecal 

coliforms) for shellfish harvesting, 4,004 acres are Conditionally Restricted (<88 MPN/100 ml fecal 

coliforms), and 7,380 acres are Prohibited. Closure in the winter season is dependent upon rainfall and 

associated fecal coliform concentrations (see discussion on relevance of fecal coliforms to nutrient 

criteria development later in this report). For the Spring/Fall season, 66,608 acres are Approved, 1,867 

acres are Restricted, and 7,380 acres are Prohibited. Closure during the Spring/Fall season occurs during 

emergency conditions such as red tides, hurricanes, and sewage spills. The prohibited areas are in the 

Crystal River and along the marshy coastline. Approved areas are the open water portions of Citrus 

County waters (Kuhman and DeHaven 2008). From 1995 through 2006, the annual reported commercial 

landings of shellfish in Citrus County averaged 546 pounds, with an annual dockside value of $1,289. 

This area accounted for 0.03% of shellfish landings in Florida and .03% of shellfish value in Florida

(Kuhman and DeHaven 2008). 
Draft 35 August 2010

The Florida Fish and Wildlife Conservation Commission (FWCC) conducts annual scallop surveys to 

monitor the status of representative scallop populations in Florida and to assess changes in population 

abundance that may occur in response to management and restoration efforts instituted by the state 

since 1994. FWCC (2009) described the results of 2008 bay scallop surveys in coastal areas of the 

Homosassa, Hernando, and Anclote segments. These surveys measured adult abundance and 

recruitment, and also reported on restoration efforts, at 20 sites within each area. For the 3 areas 

within the Springs Coast, adult abundance and recruitment indicated improving trends and good 

condition (FWCC 2009). No active restoration efforts were reported for this area, though the statewide 

harvesting regulations apply. Adult abundance declined in the Homosassa and Hernando study areas in 

2009 (FWCC 2010), but that decline is likely due to increases in fresh water (S. Geiger, FWCC, personal 

communication).

Quantification of Landings from Commercial/Recreational Fisheries

Data from the FWCC fish landings data by county illustrate that the Springs Coast region supports a 

range of fisheries (Figures 20 through 23). Changes in the fisheries cannot be attributed to nutrient 

effects; however, the presence of stable fisheries, especially shellfish, suggests healthy habitat 

conditions.

Figure 20. Commercial blue crab harvest (pounds per trip) per year in Citrus, Hernando, and Pasco 

Counties, for the period of survey record (1995–2008) (from FWCC).

0

50

100

150

200

250

300

350

400

450

Blue Crabs - Citrus Blue Crabs - Hernando Blue Crabs - Pasco

Commercial Blue Crab Harvest (pounds/trip)

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008
Draft 36 August 2010

Figure 21. Commercial bait and food shrimp harvest (pounds per trip) per year in Citrus, Hernando, 

and Pasco Counties, for the period of survey record (1995–2008) (from FWCC).

Figure 22. Commercial landings (pounds per trip) of grouper and mullet per year in Citrus, Hernando, 

and Pasco Counties, for the period of survey record (1995–2008) (from FWCC).

0

200

400

600

800

1000

1200

Shrimp, Bait -

Citrus

Shrimp, Bait -

Hernando

Shrimp, Bait -

Pasco

Shrimp, Food -

Citrus

Shrimp, Food -

Hernando

Shrimp, Food -

Pasco

Commercial Shrimp Harvest (pounds/trip)

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

0

200

400

600

800

1000

1200

1400

1600

Grouper, Total -

Citrus

Grouper, Total -

Hernando

Grouper, Total -

Pasco

Mullet, Total -

Citrus

Mullet, Total -

Hernando

Mullet, Total -

Pasco

Commercial Landings (pounds/trip) of Grouper and Mullet

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008
Draft 37 August 2010

Figure 23. Total commercial finfish harvest (pounds per trip) per year in Citrus, Hernando, and Pasco 

Counties, for the period of survey record (1995–2008) (from FWCC).

Existing Local Biological Indices

No local biological indices have been established.

Hypoxia

No hypoxic episodes are known to have occurred. 

Water Quality Studies

This section discusses the following studies: 

• Anclote River Estuary studies 1970s; 

• MML study of selected rivers in the Springs Coast area, 1984–85; 

• Project COAST, 1997–present; 

• MML intensive study of the Chassahowitzka NWR, 1996–2001; and

• Random sampling of the Springs Coast, 2000–04, by the Inshore Marine Monitoring 

and Assessment Program (IMAP) through the Fish and Wildlife Research Institute 

(FWRI).

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Finfish, Total - Citrus Finfish, Total - Hernando Finfish, Total - Pasco

Commercial Total Finfish Harvest (pounds/trip)

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008
Draft 38 August 2010

Anclote River Estuary Studies 1970s

Roger Johansson conducted a year-long study of water quality and primary productivity in three regions 

of the Anclote River estuary from 1973-1974 (Johansson 1975). The three regions he studies were the 

Anclote River (3 sites in tidal portions), Anclote Anchorage (5 sites between the river mouth and Anclote 

Key) and the Gulf of Mexico (3 sites on the seaward side of Anclote Key). He measured salinity, 

temperature, turbidity, orthophosphate, nitrate, ammonia, silica, primary productivity, chlorophyll a, 

and phaeopigments monthly at each site. 

Mean water chemistry values over the period of the study at the river sites were 0.079-0.154 mg/L 

orthophosphate, 0.015-0.045 mg/L ammonia, and 0.052-0.105 mg/L nitrate. Mean values for the 

Anchorage sites were 0.045-0.054 mg/L orthophosphate, 0.003-0.004 mg/L ammonia, and 0.009-0.036

mg/L nitrate. Mean values for the Gulf of Mexico sites were 0.048-0.057 mg/L orthophosphate, 0.002-

0.005 mg/L ammonia, and 0.008-0.027 mg/L nitrate.

Mean uncorrected chlorophyll a over the period of the study at the river sites ranged from 7.86-11.5 

mg/m3 (phaeopigments range 3.76-4.6 mg/m3

), and monthly averages of all sites ranged from a low of 

3.75 mg/m3 (phaeopigments 0.17 mg/m3

) in December to a high of 21.33 mg/m3 (phaeopigments 8.67

mg/m3

) in September. Mean uncorrected chlorophyll a over the period of the study at the Anchorage 

sites ranged from 4.55-7.0 mg/m3 (phaeopigments range 2.29-4.08 mg/m3

), and monthly averages of all 

sites ranged from a low of 1.7 mg/m3 (phaeopigments 1.53 mg/m3

) in March to a high of 10.91 mg/m3

(phaeopigments 5.29 mg/m3

) in August. Mean uncorrected chlorophyll a over the period of the study at 

the Gulf of Mexico sites ranged from 4.22-5.96 mg/m3 (phaeopigments range 2.91-3.58 mg/m3

), and 

monthly averages of all sites ranged from a low of 1.88 mg/m3 (phaeopigments 0.8 mg/m3

) in November 

to a high of 17.33 mg/m3 (phaeopigments 7.53 mg/m3

) in August.

MML Study of Selected Rivers, 1984–85 

MML conducted a 2-year study of water quality at river and estuary stations of the Waccasassa, 

Withlacoochee, Crystal, Weeki Wachee, and Aripeka Rivers, under contract with the SWFWMD for 

determining minimum flows and levels (MFLs). Except for the Aripeka sites, those data are in LEGACY 

STORET and in the Impaired Surface Waters Rule (IWR) database. Data are reported and analyzed in 

Dixon (1986). The systems discussed here are Crystal River, Weeki Wachee, and Aripeka. 

Metered parameters (salinity, pH, DO, and temperature) were recorded at 10 sites in the Crystal and

Weeki Wachee systems, with water chemistry (nutrients, turbidity, color, total suspended solids (TSS), 

chlorophyll a, phaeophytin a, and transparency) sampled at 5 stations. Only five sites were monitored 

for Aripeka because it is a much smaller system. The Crystal and Weeki Wachee River stations were 

sampled in 1984 and 1985, but Aripeka was only sampled in 1984. 

Water clarity was generally very good offshore from these spring-fed rivers, with 20% of surface light 

reaching as deep as 3.8 m (Table 10). Dixon (1986) conducted a correlation analysis to determine which 

light attenuation factor contributed most to the light extinction coefficient, and they found color to be 

most important for Weeki Wachee, color and turbidity for Crystal River, and chlorophyll a for Aripeka. 

Chlorophyll a values (uncorrected) were fairly low, at 3.3-3.6 μg/L on average for Crystal River estuary 

1.4 μg/L for Weeki Wachee, and 2.5 μg/L for Aripeka. Average dissolved oxygen (DO) levels were high, 

even on the bottom (Table 10), and minimum bottom DO concentrations were typically greater than 5 

mg/L for these sites (Dixon 1986). Note that their analyses included sites along each river reach, not just 

in the estuary, and so these results must be viewed with caution in the current context. 
Draft 39 August 2010

Table 10. Summary water clarity data for estuarine sites sampled off three Springs Coast rivers by 

MML, 1984–85. Values presented at mean/standard deviation (from Dixon 1986). 

PCU = Platinum cobalt unit

NTU = Nephelometric turbidity unit

mg/m3 = milligrams per cubic meter

Parameter Crystal River Crystal River Weeki Wachee Weeki Wachee Aripeka

River mile 0.00 -3.48 -0.15 -3.62 -0.4

Color (PCU) 10/4 9/5 15/5 7/3 15/3

TSS–Surface (mg/L) 5/2 7/3 3/1 5/4 3/1

TSS–Mid (mg/L) 6/2 8/3 3/1 5/3 3/1

TSS–Bottom (mg/L) 7/2 9/3 4/2 6/3 11/25

Turbidity (NTU) 3.6/1.7 2.9/1.2 1.1/0.3 1.0/0.3 ---

Chlorophyll a, 

uncorrected (mg/m3) 

3.6/3.3 3.3/1.9 1.4/0.7 1.4/0.9 2.5/1.9

Extinction coefficient 

(m-1) 

0.81/0.27 0.51/0.36 0.69/0.28 0.49/0.25 0.69/0.22

Depth receiving 20% 

light (m)

2.2 3.7 2.6 3.8 2.6

Bottom dissolved 

oxygen (mg/L)

7.7/1.5 7.3/1.1 8.0/1.8 7.7/1.1 8.0/1.4

FDEP Analysis of 1984–85 MML Study 

Two years of data at one site off Crystal River and one site off the Weeki Wachee River along the Springs 

Coast were available in Legacy STORET (Figures 24 and 25). These were normal or low-normal rainfall 

years (Dixon 1986). TN was calculated by adding total Kjeldahl nitrogen (TKN) and nitrate+nitrite

(NO2+3). Table 11 contains sample sizes and the results of those analyses. Phaeophytin a was analyzed 

but is not available in STORET. Annual geometric mean total nitrogen ranged from 0.472 mg/L to 0.504 

mg/L at Crystal River and was 0.611 mg/L for both years at Weeki Wachee (Table 11; Figure 24). There 

was not much relationship between total nitrogen and salinity (Figure 25). Annual geometric mean 

chlorophyll a (uncorrected) ranged from 0.62 to 3.19 μg/L. Total phosphorus data were not analyzed 

due to uncertainty of data comparability (Appendix D). 

Table 11. Annual geometric mean TN and chlorophyll a (uncorrected) from the 1984–85 MML study of 

the Weeki Wachee and Crystal Rivers.

Site Year Sample Size Annual Geometric 

Mean TN 

(mg/L)

Annual Geometric Mean 

Chlorophyll a

(uncorrected)

Crystal River-10 1984 10 0.504 3.19

Crystal River -10 1985 6 0.472 2.04

Weeki Wachee-10 1984 12 0.611 1.78

Weeki Wachee-10 1985 6 0.611 0.62
Draft 40 August 2010

Figure 24. TN data for one site in the Weeki Wachee Estuary and one site in the Crystal River Estuary, 

1984–85, from the MML study.

Figure 25. Salinity as a predictor of TN for one site in the Weeki Wachee estuary and one site in the 

Crystal River Estuary, 1984–85, from MML study.
Draft 41 August 2010

Project COAST, 1997–Present

Forty sites off the coast of Citrus and Hernando Counties have been sampled monthly since 1997, and 40

stations off the coast of Pasco County have been sampled monthly since 2000, as part of Project COAST, 

which is led by Principal Investigator Dr. Tom Frazer of the University of Florida and funded in 

cooperation with the SWFWMD (Figure 26). The project measures TN, TP, chlorophyll a, light extinction 

coefficient, Secchi depth, color, salinity, DO, and temperature at 10 sites within each of 8 river 

systems/areas along the coast. Water quality analyses are conducted at the University of Florida, 

Institute of Food and Agricultural Sciences (IFAS) School of Forest Resources and Conservation (SFRC) by 

the LakeWatch Program. At the time of this writing, data are available in STORET through 2006, and 

several reports of the results are available (Frazer et al. 1998; Frazer et al. 2002; Frazer et al. 2005; 

Frazer et al. 2006; Jacoby et al. 2009a; Jacoby et al. 2009b). This is the most extensive and 

comprehensive dataset available for the region. 

Appendix A summarizes the Project COAST data as mean concentrations for all estuary stations for each 

coastal segment. The results of FDEP analyses will be presented later in this report. Below is a summary 

of Dr. Frazer (and colleagues) interpretation of the data. 

The following text is excerpted from Jacoby et al. (2009a) and accompanies Figures 27-33: 

Chlorophyll concentrations are correlated with concentrations of total phosphorus and total nitrogen 

(Figure 27). The stronger empirical relationship between chlorophyll and total phosphorus pointed to 

phosphorus as a major driver of changes in chlorophyll. Across all stations in all systems, mean 

concentrations of total nitrogen, total phosphorus and chlorophyll increased in response to an El Niño 

event, which generated significant rainfall during 1998 (Appendix A). These changes decreased water 

clarity as shown by a reduction in the proportion of times a Secchi disc remained visible throughout the 

water column. The systems recovered, with “typical” values recorded after 6–8 months. Overall, these 

results illustrated how natural variation can confound identification of anthropogenic impacts, and they 

pointed to the value of sustained sampling. Trends were examined by correlating indicators with time. 

Total nitrogen concentrations increased significantly in the Crystal and Homosassa systems, especially 

during wet months (Figures 28–30). Significant increases in total phosphorus concentrations were not 

as widespread. As expected, chlorophyll concentrations in these systems increased in response to 

increased nutrients. In contrast, decreases in nutrient and chlorophyll concentrations were prevalent in 

the Chassahowitzka and Weeki Wachee systems. Further insights into causal relationships await 

collation of data on human activities and completion of diagnostic studies of key biological processes.

Data suggest that phosphorus is limiting along the Pasco County portion of the Springs 

Coast as well (Figure 27; Jacoby et al. 2009b). The analyses described above were 

conducted for Pasco County sites as for northern sites, in which data were divided into 

seasons and correlations over time were run to determine temporal trends over the 

period 2000-2008. Results showed no increase in TN, TP, or chlorophyll a concentrations 

over time in the coastal areas of Pasco County; concentrations actually declined in some 

cases (Figures 31–33; Jacoby et al. 2009b). 

Nutrient limitation studies conducted by Dr. Frazer on monthly samples collected during 2000–01 

showed that the Weeki Wachee, Chassahowitzka, and Homosassa coastal systems were limited by P in 

79%, 40%, and 51% of samples; limited by N in 0%, 4%, and 0% of samples; and co-limited by N and P in 

6%, 40%, and 32% of samples, respectively. For the Crystal River coastal area, 29% of samples were 
Draft 42 August 2010

limited by N and 29% by P, and 29% were co-limited. The remaining samples were undetermined. 

These results are important to support the theory of P-limitation in this region, as strong relationships 

between TP and chlorophyll a are not sufficient evidence to indicate P-limitation (Lewis and 

Wurtsbaugh 2008).

Figure 26. Project COAST sampling stations. Forty stations along the coast of Citrus and Hernando 

Counties have been sampled monthly from 1997 to the present, with 10 stations each in the Weeki 

Wachee, Chassahowitzka, Homosassa, and Crystal River systems. Forty stations along the coast of 

Pasco County have been sampled monthly from 2000 to the present, with 10 stations each in the 

Aripeka, Hudson, Pithlachascotee, and Anclote River regions. Colored station markers represent the 

mean annual geometric mean of each station for 1996–2006, calculated by FDEP. 

Notes: Maps made by N. Wellendorf with data pulled from Florida STORET in March 2010. This figure includes river/stream sites and 1 year of 

data (1996) that were not included in subsequent FDEP analyses.

Total Nitrogen

Geometric Mean

Total Phosphorus

Geometric Mean

Chlorophyll a (uncorrected)

Geometric Mean

Crystal River

Homosassa

Chassahowitzka

WeekiWachee

Aripeka

Hudson

Pithlachascotee

Anclote
Draft 43 August 2010

Figure 27. Relationship between log10-transformed monthly mean chlorophyll and TN and TP

concentrations from all estuarine systems along the Citrus, Hernando, and Pasco County coasts (from 

Jacoby et al. 2009a). 

Note: These figures include data from the Withlacoochee River, which is not considered part of the Springs Coast for the current effort.

Correlation coefficient = 0.84

p < 0.001

-1.0

0.0

1.0

2.0

0.0 0.5 1.0 1.5 2.0 2.5

log10[Chlorophyll (μg L-1)]

Log10[Total phosphorus (μgL-1)]

Correlation coefficient = 0.46

p < 0.001

-1.0

0.0

1.0

2.0

2.0 2.5 3.0 3.5

log10[Chlorophyll (μg L-1)]

Log10[Total nitrogen (μgL-1)]
Draft 44 August 2010

Figure 28. Trend analysis based on correlation of site data with time. Wet months were identified as 

June, July, August, and September (from Jacoby et al. 2009a). 

Figure 29. Trend analysis based on correlation of site data with time. Transitional months were 

identified as December, January, February, and March (from Jacoby et al. 2009a). 

Nitrogen Phosphorus Chlorophyll

= significant positive correlation = significant negative correlation

Temporal correlations with TN, TP and Chlorophyll

- Wet Months -

= significant positive correlation = significant negative correlation

Temporal correlations with TN, TP and Chlorophyll

- Transitional Months -

Nitrogen Phosphorus Chlorophyll
Draft 45 August 2010

Figure 30. Trend analysis based on correlation of site data with time. Dry months were identified as 

April, May, October, and November (from Jacoby et al. 2009a). 

Figure 31. Trend analysis based on correlation of site data with time. Wet months were identified as 

June, July, August, and September (from Jacoby et al. 2009b). 

Nitrogen Phosphorus Chlorophyll

= significant positive correlation = significant negative correlation

Temporal correlations with TN, TP and Chlorophyll

- Dry Months -

= significant positive correlation = significant negative correlation

Temporal correlations with TN, TP and Chlorophyll

- Wet Months -

Nitrogen Phosphorus Chlorophyll
Draft 46 August 2010

Figure 32. Trend analysis based on correlation of site data with time. Transitional months were 

identified as December, January, February, and March (from Jacoby et al. 2009b). 

Figure 33. Trend analysis based on correlation of site data with time. Dry months were identified as 

April, May, October, and November (from Jacoby et al. 2009b). 

= significant positive correlation = significant negative correlation

Temporal correlations with TN, TP and Chlorophyll

- Transitional Months -

Nitrogen Phosphorus Chlorophyll

= significant positive correlation = significant negative correlation

Temporal correlations with TN, TP and Chlorophyll

- Dry Months -

Nitrogen Phosphorus Chlorophyll
Draft 47 August 2010

FDEP Analysis of COAST Data

FDEP notes the following details about sample analysis methods used by Project COAST that require 

additional scrutiny before using the results of the data to support the development of water quality 

standards.

Chlorophyll a from Project COAST is reported without correction for phaeophytin. FDEP will propose 

water quality criteria for corrected chlorophyll a, and thus the uncorrected chlorophyll a data are 

expected to yield higher numbers than what FDEP will consider appropriate for the criteria. Project 

COAST reported corrected chlorophyll a data and phaeophytin concentrations for a few recent years of 

the project. This report contains comparisons of the corrected and uncorrected chlorophyll a data to 

inform the use of uncorrected values (the majority of the data record). The corrected and uncorrected 

values are highly correlated. 

The method used by COAST for determining TN in water samples is not an EPA-approved method, nor is 

it an approved method in FDEP’s Standard Operating Procedures (SOPs). Bachmann and Canfield (1996) 

describe this method and provide data that show that the method produces results comparable to EPAapproved methods for TN in fresh water. 

Water samples are frozen before analysis, an approach that also does not conform to FDEP SOPs. 

However, Bachmann and Canfield (1996) and Canfield et al. (2002) demonstrate that TN results are not 

significantly affected by freezing. Also, the Project COAST samples are not held frozen for very long 

before analysis, compared with citizen-collected samples described by Canfield et al. (2002), which may 

be held for three months before analysis. 

TP samples are also frozen, rather than acidified, before analysis. Canfield et al. (2002) showed that this 

preservation method did not significantly affect the analytical results. 

Due to these inconsistencies between Project COAST lab analyses and FDEP SOPs and EPA guidance, 

several analyses were conducted in which the water chemistry results from Project COAST were 

compared with the results from concurrent sampling by other entities that used labs certified by the 

National Environmental Laboratory Accreditation Conference (NELAC) and NELAC-approved methods. 

The results of these analyses suggest that it is appropriate to use the long-term Project COAST datasets, 

in conjunction with other data sources, to support proposed numeric nutrient criteria (see Appendix D 

for comparisons). 

Data were pulled from Florida STORET in April 2010, but only included data through 2006. Stations 

designated as river/stream in STORET (by data generators) and one additional station that is 

predominantly fresh were not included in this analysis (Chassahowitzka-1, -2, -10; Crystal-4; Homosassa5; Pithlachascotee-1; and Weeki Wachee-1, -2). Data from 1996 were not included due to small sample 

size, and so the data used included 1997 to 2006 (with no data available for 2005). For each station, 

annual geometric mean TN, TP, and chlorophyll a were calculated. 

The initial approach taken for pooling stations was to separate Pasco County sites from the northern 

Springs Coast, based on a recommendation by Dr. Tom Frazer. The annual geometric mean was 

calculated for each station-year, and then the distribution of those geometric means was described for 

each of the two large regions (Table 12). The long-term mean of the annual geometric means was 

calculated, and then a theoretical curve was fitted using a log normal distribution function to estimate 

the 75th and 90th percentile of the data. The long term means for TN were nearly identical (380 μg/L) for 
Draft 48 August 2010

the two regions, long term mean TP was higher for the northern region (12.1 μg/L) than for Pasco 

County (9.2 μg/L) but both were low, and the long term mean chlorophyll a (uncorrected) was very low 

for both regions (< 2 μg/L; Table 12). Appendix B contains plots of annual geometric means over time

for each site. 

The annual geometric mean TN for each station was then plotted against average salinity for each year

to determine if FDEP should pursue salinity-dependent criteria. Appendix C contains figures of salinity 

versus TN for all systems. In general, salinity had a weaker influence on TN in the northern systems of 

Crystal River, Homosassa, Chassahowitzka, and Weeki Wachee The relationships are weak and in some 

cases are positive, with increasing N as salinity increases. Positive relationships suggest that there are 

nonlocal inputs of nutrients to these coastal areas, and this is most likely due to transport from the 

rivers to the north. The relationship was strongest for 1998, in which the influence of the Suwannee 

River and possibly the Withlacoochee River on this region has been documented (Dixon and Estevez 

2001; Jolliff et al. 2003). There was a relationship between salinity and TN some years at Weeki 

Wachee, but it was not consistent. At Crystal River, TN peaks at midrange salinities, suggesting that 

something besides salinity is influencing TN concentrations there. Annual geometric means for each 

station are shown pictorially in Figure 26, and show a clear gradient of TN along the Pasco County coast, 

but not along the coasts of Citrus and Hernando Counties. Therefore, all sites in the Crystal, 

Homosassa, Chassahowitzka, and Weeki Wachee systems were not broken out into different salnity 

regimes. 

For the Pasco County stations, TN and salinity shifted somewhat from year to year, but there was a 

consistently negative relationship between salinity and TN in that region, indicating that the river 

systems along that part of the coast are controlling the coastal nutrient regime (Figure 26; Appendix C). 

Pasco County sites were pooled for 1 analysis, and then divided into 3 groups based on mean annual 

salinity over the course of the dataset: less than 25 ppt, 25 to 30 ppt, and greater than 30 ppt (Table

13). Pasco County sites were of higher salinity overall, probably because the farthest sites are farther 

from shore than the northern Project COAST sites, and possibly also because the coast has a slightly 

higher gradient off Pasco County; thus the farthest sites are in deeper water. Long term geometric 

mean TN was higher for the sites < 25 ppt (417 μg/L) than for sites of 25-30 ppt (466 μg/L) or > 30 ppt 

(456 μg/L; Table 13). Long term mean TP and Chlorophyll a (uncorrected) were higher for the sites >30 

ppt than for lower salinities, but that is probably due to the fact that most sites > 30 ppt are in the 

Anclote estuary, and higher nutrients there may be from anthropogenic origin. The tidal reaches of the 

Anclote River are on the 303(d) list for mean chlorophyll a values > 11 μg/L from 1999-2002, but a TMDL 

has not been established. Annual geometric mean TP and chlorophyll a are greater for the Anclote 

Estuary than the other coastal areas of Pasco County (Figure 26), and that could be due to natural 

factors such as a larger watershed with swamp drainage or less mixing with the Gulf due to barrier 

island, or due to anthropogenic input. 
Draft 49 August 2010

Table 12. Summary of data analysis for coastal areas of Citrus and Hernando Counties combined (33 

stations) and Pasco County (39 stations), 1997–2006. 

LN = Natural logarithm

GM = Geometric mean

C.I. = Confidence interval

Note: The long-term region annual geometric mean and 90th percentile of site annual geometric means within the region are shown in bold. 

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Mean LN 5.94 2.50 0.49

Std. Dev. LN 0.27 0.45 0.74

N 293 293 299

95% C.I. 0.03 0.05 0.08

Long-term GM 380.05 394.82 12.12 13.45 1.63 2.15

Lower 95% C.I. 368.39 11.52 1.50

Upper 95% C.I. 392.07 12.76 1.78

75th Percentile 456.26 444.12 16.37 18.23 2.69 3.06

90th Percentile 537.85 530.43 21.46 22.91 4.21 4.58

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Mean LN 5.94 2.22 0.01

Std. Dev. LN 0.18 0.42 0.63

N 234 234 234

95% C.I. 0.02 0.05 0.08

Long-term GM 380.31 386.38 9.19 10.14 1.01 1.25

Lower 95% C.I. 371.76 8.70 0.93

Upper 95% C.I. 389.07 9.71 1.10

75th Percentile 428.45 423.89 12.24 12.53 1.55 1.61

90th Percentile 476.97 486.61 15.83 15.58 2.28 2.34

CHLOROPHYLL A 

(uncorrected; μg/L)

TOTAL NITROGEN (μg/L) TOTAL PHOSPHORUS (μg/L) CHLOROPHYLL A 

(uncorrected; μg/L)

CITRUS & 

HERNANDO 

COUNTIES

PASCO COUNTY

TOTAL NITROGEN (μg/L) TOTAL PHOSPHORUS (μg/L)
Draft 50 August 2010

Table 13. Summary of data analysis for Pasco County stations grouped by salinity, 1997–2006. 

“salinity<25” represents 13 stations, “salinity 25-30” represents 19 stations, and “salinity>30” 

represents 7 stations. 

LN = Natural logarithm 

GM = Geometric mean 

C.I. = Confidence interval 

Note: The long-term region annual geometric mean and the 90th percentile of site annual geometric means within the region are shown in 

bold. 

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Mean LN 6.03 2.18 0.05

Std. Dev. LN 0.17 0.44 0.60

N 78 78 78

95% C.I. 0.04 0.10 0.14

Long-term GM 417.12 423.31 8.84 9.93 1.05 1.28

Lower 95% C.I. 401.39 8.00 0.92

Upper 95% C.I. 433.48 9.77 1.20

75th Percentile 467.98 467.06 11.92 10.43 1.58 1.49

90th Percentile 519.04 534.99 15.60 15.01 2.27 2.14

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Mean LN 5.90 2.09 -0.25

Std. Dev. LN 0.16 0.37 0.57

N 114 114 114

95% C.I. 0.03 0.07 0.11

Long-term GM 365.63 370.56 8.07 8.72 0.78 0.95

Lower 95% C.I. 354.71 7.53 0.70

Upper 95% C.I. 376.88 8.64 0.87

75th Percentile 408.22 409.46 10.36 9.74 1.15 1.05

90th Percentile 450.79 460.55 12.97 13.40 1.62 1.53

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Mean LN 5.88 2.65 0.65

Std. Dev. LN 0.16 0.19 0.32

N 42 42 42

95% C.I. 0.05 0.06 0.10

Long-term GM 356.49 360.71 14.10 14.35 1.92 2.01

Lower 95% C.I. 339.55 13.30 1.73

Upper 95% C.I. 374.27 14.96 2.12

75th Percentile 396.10 403.48 16.03 15.48 2.38 2.34

90th Percentile 435.51 433.13 17.98 17.71 2.89 2.82

PASCO COUNTY 

salinity >30 ppt

TOTAL NITROGEN (μg/L) TOTAL PHOSPHORUS (μg/L) CHLOROPHYLL A 

(uncorrected; μg/L)

PASCO COUNTY 

salinity < 25 ppt

TOTAL NITROGEN (μg/L) TOTAL PHOSPHORUS (μg/L) CHLOROPHYLL A 

(uncorrected; μg/L)

PASCO COUNTY 

salinity 25-30 

ppt

TOTAL NITROGEN (μg/L) TOTAL PHOSPHORUS (μg/L) CHLOROPHYLL A 

(uncorrected; μg/L)
Draft 51 August 2010

Portions of the Project COAST dataset provide an opportunity to compare trends over time in the 

freshwater sources and the receiving coastal waters. Figure 34 compares the annual geometric mean 

TN through the period collected by Project COAST for the Weeki Wachee River (Sites 1 and 2, with Site 3 

influenced by the river and Gulf; Figure 35) and coastal areas (Sites 4 through 10; Figure 35). 

As previously mentioned, TN (specifically nitrate) has increased in recent years in the Weeki Wachee 

river due to anthropogenic factors (Harrington et al. 2010), and that trend is evident at Sites 1 and 2 

(Figure 34). However, the coastal sites do not follow the same pattern. The year 1998 was very wet, 

and TN concentrations at the coastal sites were significantly higher in 1998 than during other study 

years; however, concentrations at the river sites did not increase as dramatically. These data suggest 

that the increased loading in the freshwater systems has not been sufficient to exceed the capacity of 

the river and estuary to use those nutrients, and thus the nutrient concentrations in the estuary have 

not increased. No further increase is anticipated due to the proposed nitrate criteria that will apply to 

these spring runs (<0.35 mg/L). 

Figure 34. Geometric mean TN concentrations per station for the Weeki Wachee River and coastal 

sites. Sites 1 and 2 are in the river, Site 3 is at the river mouth, and Sites 4 through 10 are in the 

coastal area.

0

100

200

300

400

500

600

700

800

900

1997 1998 1999 2000 2001 2002 2003 2004 2006

Total Nitrogen (μg/L)

Geometric Mean TN Concentration 

for Weeki Wachee Stations, COAST 

Weeki Wachee-1

Weeki Wachee-2

Weeki Wachee-3

Weeki Wachee-4

Weeki Wachee-5

Weeki Wachee-6

Weeki Wachee-7

Weeki Wachee-8

Weeki Wachee-9

Weeki Wachee-10
Draft 52 August 2010

Figure 35. Location of the Weeki Wachee River and coastal sites in Project COAST.

MML Intensive Study of the Chassahowitzka NWR, 1996–2001 

MML measured water chemistry and SAV within the boundaries of the Chassahowitzka NWR from 1996

to 2004. The purpose of the study was to establish a baseline condition for the refuge, but MML was

also able to document changes due to a major storm year. The study included a network of 30 coastal 

stations and eight riverine stations within the refuge (Figure 36), some sampled approximately 30 times 

during the study (3 to 5 times per year) and some only sampled a few times. MML collected water 

quality data and conducted SAV surveys. The results are available in MML reports (Dixon and Estevez 

1998; Dixon and Estevez 2001; Toutant et al. 2004), and are summarized here (additional data analyses

are provided in a later section). Water quality analyses included N species, TP, orthophosphate, 

chlorophyll a (corrected), and other water quality and clarity measurements. Analyses were conducted 

using EPA- and FDEP-approved methods at a NELAC-certified lab. MML also conducted studies of the 

invertebrate community along the length of the Chassahowitzka River, including some estuary areas 

(Leverone 2006). 

Dixon and Estevez (1998) reported on the first 2 years of the study, and Dixon and Estevez (2001) 

reported through 2001. They reported that the waters of Chassahowitska Bay are very well mixed and 

shallow, with strong tidal currents. Only 5% of observations at coastal stations were below 45 mg/L; 
Draft 53 August 2010

these were in the early morning at several stations, mainly in the northern part of the refuge (Figure 37). 

The long term mean at coastal stations was 6.8 mg/L (Dixon and Estevez 2001). 

Figure 36. Sampling stations in the Chassahowitzka NWR in the 1996–2001 MML study (from Dixon 

and Estevez 2001).
Draft 54 August 2010

Figure 37. DO (means and quartiles) for stations along the riverine transect. Stations 24, 26, and 44 

are in the coastal areas (from Dixon and Estevez 2001). 

Nitrate+nitrite concentrations in the Chassahowitzka River had increased in the years prior to this 

sampling program, but nearly all of that N is assimilated by algae before it reaches the coastal sites, 

rather than being converted to another form of nitrogen (Figure 38; Dixon and Estevez 2001) . TN 

concentrations increase with salinity and distance offshore, which is contrary to the expected pattern. 

Dixon and Estevez (2001) postulate that the Withlacoochee and/or Suwannee Rivers to the north 

generate a plume of high-nutrient water that travels over the offshore areas of the Springs Coast. They 

cited observations that peak flows in the Weeki Wachee River occurred between August 1997 and 

March 1998, but bloom conditions within that estuary did not become established until May–June 1998, 

implying a nutrient source other than the Weeki Wachee River (Dixon and Estevez 2001). 
Draft 55 August 2010

Figure 38. Mean TN, IN, and organic nitrogen (ON) along the riverine transect, illustrating the 

generally conservative net behavior downstream of Station R1.7; salinity 3.5 practical salinity units 

(PSU) (Figure 28 in Dixon and Estevez 2001). 

FDEP Analysis of MML Study Data

Statistical Analysis–MML graciously provided FDEP with the full dataset from its 1996–2004 study of the 

springs, rivers, and coastal area of the Chassahowitzka NWR. Most of the following analyses focused on 

the coastal sites (Figure 39). Comparisons of TP data from this study and available TP data from similar 

sites during the same periods revealed some discrepancies between the MML data and other sources. 

The MML results were consistently higher than results from the FDEP Tallahassee lab for the spring head 

or the LakeWatch lab for coastal stations (Appendix Figure D-5). Analytical methods differ between the 

organizations, and further investigation will be necessary to determine the cause of the difference. Due 

to the longer time span and broader spatial coverage of the Project COAST data, this report does not 

include MML TP data.

Sites sampled varied from year to year during the MML study, with some sites sampled for the duration 

of the study and other sites only sampled during one or two years. For the purposes of numeric nutrient 

criteria development, only data from sites sampled each year were included, and 1996 data were not 

included due to the small sample size that year. Table 14 lists the sample sizes for each site/year used. 

The years included were 1997 to 2004, and the sites included were 3, 4, 7, 18, 21, 23, 24, 26, 28, 30, 40C, 

and 44 (Figure 39). TN was calculated by adding the results for nitrate+nitrite (NO2+3–N) and total 

Kjeldahl nitrogen (TKN). If the result was below detection, then half the detection limit was used in the 

TN calculation.
Draft 56 August 2010

Figure 39. Water quality sampling sites from the MML study of the Chassahowitzka River and coast, 

used in FDEP’s data analysis.

Table 14. Sample sizes for sites and years for FDEP’s analysis of the MML study of the Chassahowitzka 

NWR.

Station 1996 1997 1998 1999 2000 2001 2002 2003 2004

18 1 3 4 5 4 4 4 3 2

21 1 3 3 5 4 4 4 3 2

23 1 2 5 5 4 4 4 3 2

24 2 3 4 5 4 4 4 3 2

26 1 2 4 5 5 4 4 3 2

28 1 2 4 5 4 4 4 3 2

3 1 2 4 5 4 4 4 3 2 

30 1 2 4 5 4 4 4 3 2

4 1 2 5 5 4 4 4 3 2 

40C 1 2 4 5 4 4 4 3 2

44 1 6 5 4 4 4 3 2

7 1 2 4 5 4 4 4 3 2
Draft 57 August 2010

Figure 40. Mean annual salinity is positively related to annual geometric mean TN. Salinity was 

depressed at all stations during 1998, a year of particularly high rainfall. 

Figure 41. Annual geometric mean corrected chlorophyll a at Chassahowitzka River sites (R4.0–R0.0) 

and Bay sites (40C-3) collected by MML. Very high chlorophyll a levels were measured at the bay sites 

in 1998 (El Niño event); stable levels in the river indicate that the increase was due to input from 

coastal waters. 

0

200

400

600

800

1000

1200

0 5 10 15 20 25 30 35

Annual Geometric Mean TN (μg/L)

Annual Mean Salinity (ppt)

Annual Mean Salinity vs. Annual Geometric Mean Total 

Nitrogen for 12 MML Chassahowitzka Estuary Sites

1997

1998

1999

2000

2001

2002

2003

2004

0

5

10

15

20

25

30

R4.0R3.0R2.5R2.0R1.7R1.3R1.0R0.0

40C

4430282624232118

743

Annual Geometric Mean Chlorophyll a (corrected, μg/L), 

Chassahowitzka River (R0.0-4.0) and Bay (3-40C) Sites, by MML

1997

1998

1999

2000

2001

2002

2003

2004
Draft 58 August 2010

Data were analyzed as described above for Project COAST data. There was a positive relationship 

between salinity and TN within years, though it was not consistent (Figure 40). This positive relationship 

for many years indicates that there is a frequent source of N to this estuary that is not related to the 

Chassahowitzka or Homosassa River discharge. The annual geometric mean for each station and year 

was calculated, and then the stations were pooled to describe the distribution of annual geometric 

means overall (Table 15). Stations were also separated into two salinity groups, with stations that had 

average salinity over the life of the project of less than 20 ppt in one group, and stations with average 

salinity greater than 20 ppt into a second group (Table 16). This division was exploratory, and results 

further indicate that N concentrations are generally higher in higher salinity areas, due to nutrient 

sources outside of the watershed. Note that chlorophyll a values are lower at high salinity, which may 

support Dr. Frazer’s conclusion that this part of the coast is phosphorus-limited.

As noted in Toutant et al. (2004) and all of the Project COAST reports (Frazer, Jacoby refs.), 1998 was an 

El Niño year with very high rainfall and higher nutrients and chlorophyll values in general. In the MML 

Chassahowitzka NWR study, the chlorophyll levels were nearly an order of magnitude higher in the 

coastal areas in 1998 than during other years, but were comparable among all years in the rivers that 

deliver fresh water to that part of the coast (Figure 41). This discrepancy suggests that the higher 

chlorophyll a in 1998 was due to far-field effects from rivers to the north, carried by a southerly current; 

this conclusion was reached by investigators through experience and modeling (Dixon and Estevez 2001; 

Jolliff et al. 2003; Weisberg et al. 2004).
Draft 59 August 2010

Table 15. Summary of data analysis for coastal areas of the Chassahowitzka NWR, 1997–2004 (12 

stations). The first table contains only station years with at least 4 samples; the second table contains 

all station years (range 1 to 6 samples per station year; mean 3.6 samples per station year). Data 

collected and analyzed by MML. 

LN = Natural logarithm

GM = Geometric mean

C.I. = Confidence interval

Note: Long-term region annual geometric mean and the 90th percentile of site annual geometric means within the region are shown in bold.

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Mean LN 6.21 0.27

Std. Dev. LN 0.31 1.04

N 60 59

95% C.I. 0.08 0.27

Long-term GM 495.75 522.51 1.32 2.51

Lower 95% C.I. 457.07 1.00

Upper 95% C.I. 537.71 1.72

75th Percentile 612.89 597.73 2.65 1.92

90th Percentile 741.81 802.97 4.96 8.54

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Mean LN 6.21 0.18

Std. Dev. LN 0.31 0.96

N 86 96

95% C.I. 0.07 0.19

Long-term GM 498.47 516.08 1.19 2.22

Lower 95% C.I. 466.27 0.98

Upper 95% C.I. 532.90 1.45

75th Percentile 615.01 596.78 2.27 1.51

90th Percentile 743.02 781.24 4.06 6.71

Chassahowitzka 

NWR (min 4 

samples/yr)

TOTAL NITROGEN (μg/L) CHLOROPHYLL A 

(Corrected; μg/L)

Chassahowitzka 

NWR (all years)

TOTAL NITROGEN (μg/L) CHLOROPHYLL A 

(Corrected; μg/L)
Draft 60 August 2010

Table 16. Summary of data analysis for coastal areas of the Chassahowitzka NWR, 1997–2004, with 

stations divided by mean salinity (5 stations < 20 ppt; 7 stations > 20 ppt). Each salinity category 

contains tables for which only station years with at least 4 samples were included, and tables for 

which all station years were included (range 1 to 6 samples per station year; mean 3.6 samples per 

station year). Data collected and analyzed by MML. 

LN = Natural logarithm

GM = Geometric mean

C.I. = Confidence interval

Note: Long-term region annual geometric mean and the 90th percentile of site annual geometric means within the region are shown in bold.

Random Sampling by IMAP through the FWRI

Florida’s IMAP was a probabilistic sampling program for Florida’s marine waters that sampled the whole 

state from 2000 to 2004. The program was conducted by the FWRI in cooperation with the EPA’s Gulf 

Breeze office. The Crystal River Estuary (west-central coast) was the only area of the Springs Coast 

included in the program. 

Table 17 contains summary water quality data as reported in FDEP’s IWR database Run 40 (2010). 

Although the IMAP reports indicate that TN was analyzed, the IWR database only contained 

nitrate+nitrite data. IMAP reports do not include a qualitative assessment of the study findings, but 

simply a report of some of the quantitative results. Nutrient and chlorophyll a concentrations were low 

and similar to other data sources. 

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Mean LN 6.11 0.70 6.08 0.59

Std. Dev. LN 0.25 0.85 0.25 0.72

N 25 25 40 40

95% C.I. 0.10 0.35 0.08 0.23

Long-term GM 449.40 464.44 2.01 3.12 435.86 449.78 1.81 2.56

Lower 95% C.I. 404.67 1.41 402.41 1.44

Upper 95% C.I. 499.09 2.86 472.09 2.28

75th Percentile 533.40 478.63 3.58 2.13 515.81 507.16 2.95 2.15

90th Percentile 622.34 665.54 6.02 9.10 600.23 654.83 4.57 7.17

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Log Normal 

Distibution

Empirical 

Percentile

Mean LN 6.28 -0.04 6.28 -0.12

Std. Dev. LN 0.34 1.06 0.32 1.00

N 35 34 56 56

95% C.I. 0.12 0.37 0.09 0.27

Long-term GM 531.76 414.93 0.96 2.05 534.42 563.43 0.89 1.97

Lower 95% C.I. 473.55 0.67 490.24 0.68

Upper 95% C.I. 597.13 1.39 582.58 1.16

75th Percentile 667.70 476.64 1.97 0.87 664.14 644.53 1.74 0.89

90th Percentile 819.53 662.93 3.73 7.13 807.61 857.15 3.18 6.23

TOTAL NITROGEN (μg/L) CHLOROPHYLL A 

(Corrected; μg/L)

TOTAL NITROGEN (μg/L) CHLOROPHYLL A 

Chassahowitzka NWR (min 4 samples/yr)

Salinity < 20 ppt 

(5 sites)

Chassahowitzka NWR (all years)

Salinity > 20 ppt 

(7 sites)

TOTAL NITROGEN (μg/L) CHLOROPHYLL A 

(Corrected; μg/L)

Chassahowitzka NWR (min 4 samples/yr)

TOTAL NITROGEN (μg/L) CHLOROPHYLL A 

Chassahowitzka NWR (all years)
Draft 61 August 2010

Table 17. Mean values by area and year for IMAP sampling in the region of the Crystal River Estuary

(data from FDEP IWR Run 40). Samples for chlorophyll a were depth integrated; others were surface 

grabs.

Geographic Area Year N Chlorophyll a

(corrected, μg/L)

Color 

(PCU)

Nitrate + 

Nitrite 

(mg/L)

TP 

(mg/L)

Salinity 

(ppt)

Crystal River 

Estuary

2003 8 2.09 15 0.002 0.019 20.3

Waters on the 303(d) List 

Only one marine area within the Springs Coast were listed for nutrients, chlorophyll a, or DO, and that 

area was the tidal portion of the Anclote River. The chlorophyll a impairment is based on annual 

average chlorophyll a values exceeding 11 ug/l in 1999, 2001, and 2002 (values of 13.48, 14.89, and 

12.26 ug/l, respectively). Nitrogen was determined to be the limiting nutrient based on a median TN/TP 

ratio of 8.2 (74 values). Verified period total nitrogen median = 0.77 mg/L (74 values), total phosphorus 

= 0.1 (87 values), and BOD median = 2 mg/l (82 values) for the assessed tidal WBID 1440A. Other areas 

are listed for mercury or for bacteria (Table 18). Mercury impairment is not related to nutrients, and it 

is possible to have bacteria impairments without nutrient pollution sources (see discussion below). 

Table 18. Waterbody IDs within the marine portions of the Springs Coast region that are listed on the 

303(d) list of impaired waters. 

Basin 

Group 

Name

Planning Unit Waterbody 

ID (WBID)

Water Segment 

Name

Parameters 

Assessed 

(IWR)

Concentration 

Causing Impairment

Springs 

Coast

Anclote River / 

Coastal Pinellas 

County

8044C ROBERT K REES 

PARK BEACH

Bacteria Beach advisories > 21 

days/yr

Springs 

Coast

Anclote River / 

Coastal Pinellas 

County

8045A GULF HARBORS 

BEACH

Bacteria Beach advisories > 21 

days/yr

Springs 

Coast

Crystal River / Kings 

Bay Planning Unit

8039A FORT ISLAND 

GULF BEACH

Bacteria Beach advisories > 21 

days/yr

Springs 

Coast

Middle Coastal 1409B OELSNER PARK 

BEACH

Bacteria Beach advisories > 21 

days/yr

Springs 

Coast

Middle Coastal 8042A PINE ISLAND 

BEACH

Bacteria Beach advisories > 21 

days/yr

Springs 

Coast

Middle Coastal 8044A ROBERT J 

STRICKLAND 

BEACH

Bacteria Beach advisories > 21 

days/yr

Springs 

Coast

Middle Coastal 8044B BRASHER PARK 

BEACH

Bacteria Beach advisories > 21 

days/yr

Springs 

Coast

Middle Coastal 8044D ENERGY AND 

MARINE CENTER

Bacteria Beach advisories > 21 

days/yr

Springs 

Coast

Anclote River / 

Coastal Pinellas 

County

1440A ANCLOTE RIVER 

BAYOU 

COMPLEX 

(SPRING BAYOU)

Dissolved 

Oxygen

< 4.0 mg/L

Springs 

Coast

Anclote River / 

Coastal Pinellas 

County

1440 ANCLOTE RIVER 

TIDAL

Mercury (in 

fish tissue)

Exceeds DoH 

threshold ( > 0.43 

mg/kg)

Springs 

Coast

Anclote River / 

Coastal Pinellas 

County

1440A ANCLOTE RIVER 

BAYOU 

COMPLEX 

(SPRING BAYOU)

Nutrients 

(chla)

Median TN = 0.77 

mg/L
Draft 62 August 2010

The use of fecal coliform as indicators of the presence of human pathogens has been under scrutiny in 

Florida for the past decade. One of the priorities of the Gulf of Mexico Alliance (GOMA) is the need to 

improve microbial source tracking (MST) and pathogen-detection methods for use under Gulf of Mexico 

conditions (GOMA 2009). The GOMA Pathogens Workgroup recently submitted comments regarding 

the status of EPA recreational water quality criteria (GOMA 2009). It expressed concern that the EPA 

recreational criteria were derived in places that do not represent Gulf of Mexico conditions, and that the 

use of fecal indicators was not appropriate for waters primarily influenced by animal sources. Areas in 

the Gulf of Mexico for which the group thought the EPA criteria might not be appropriate included lowpopulation-density coastal areas, areas of heavy rainfall, subtropical latitudes, and areas where waters 

contain a large amount of organic detritus and/or CDOM (GOMA 2009). 

Boehm et al. (2009) express similar concern about the current and proposed recreational criteria, and 

specifically call attention to the need for further research and revision in tropical waters and waters 

adversely impacted by urban runoff and animal feces. This is not to say that fecal coliform and 

enterococci bacteria cannot indicate human sources or cannot co-occur with nutrient inputs, but that 

there is ample evidence to caution against assuming that the presence of these bacteria automatically 

indicates the presence of anthropogenic nutrients.

The following text is taken from a review conducted by Dr. V.J. Harwood of the University of South 

Florida (USF) as part of an MST project she is conducting for FDEP: 

The main groups of indicator bacteria for recreational water quality assessment in use 

today include fecal coliforms, or a specific member of that group, Escherichia coli, in 

fresh water and the genus Enterococcus in both fresh and estuarine/marine waters. 

However, in order for the indicator concept to work optimally there are many 

assumptions that must hold true. One of the most important assumptions is that 

indicator bacteria must co-occur with human pathogens when pathogens are present 

and pose a human health risk. Unfortunately, recent research has indicated that this 

assumption is often false by showing that the presence of indicator bacteria do not 

always correlate well with the presence of pathogens such as Salmonella, 

Campylobacter, Cryptosporidium, Giardia, or enteric viruses (Anderson et al. 2005, 

Bonadonna et al. 2002, Harwood et al. 2005, Lemarchand and Lebaron 2003, Lund 1996, 

Rees et al. 1998).

One important reason for the lack of correlation between traditional fecal indicator 

bacteria and pathogens is that the indicator bacteria are not specific to humans, nor to 

other hosts known to shed human pathogens in their feces, but are present in the 

intestines of all warm-blooded animals and some cold-blooded animals (Souza et al. 

1999). Because not all animals are equally likely to carry human pathogens, 

contamination from all sources does not represent an equal health risk. Thus, some 

sources of fecal contamination in water are of greater concern than others. 

Furthermore, there is increasing evidence of naturalized or environmentally adapted 

strains indicator bacteria (both coliforms and enterococci) that are capable of persisting 

in a culturable form for extended periods, or even growing, in a wide variety of 

environmental matrices, including terrestrial soils, aquatic sediments, and attached to 

aquatic vegetation (Byappanahalli and Fujioka 1998, Byappanahalli et al. 2003, Ishii et 

al. 2006, Jeng et al. 2005, Ksoll et al. 2007, Solo-Gabriele et al. 2000, Topp et al. 2003, 

Whitman et al. 2003). If indicator bacteria are persisting in environmental matrices their 

reintroduction into the water column, such as might occur during storms or high 
Draft 63 August 2010

recreational activity, may lead to false positive indications regarding contamination and 

public health risk. As a result of these two confounding factors, it is now clear that 

simply measuring concentrations of waterborne indicator bacteria do not offer detailed 

enough information to properly determine health risks associated with recreational 

water use. Furthermore, this practice does not allow specific sources of contamination 

to be identified or targeted for remediation of water quality.

Proposed Numeric Nutrient Criteria 

The data and syntheses presented here show that the biological communities along the Springs Coast 

are meeting the designated aquatic life use. Some positive correlations with time were found for TN, 

TP, and chlorophyll a in coastal Citrus county during the wet months (Jacoby et al. 2009a, 2009b), but 

the coastal ecosystem has not shown detrimental effects and those trends are not apparent in the data

overall. Additionally, increased nitrate in some spring-fed rivers has not influenced the nutrient regime 

of the coastal area overall. It is possible that there has been some seagrass loss off the coast of Crystal 

River. The Anclote River Estuary is on the 303(d) list for chlorophyll a and dissolved oxygen and the 

coastal area adjacent to the Anclote has higher TP and chlorophyll a than coastal areas just north of it 

off the Pithlachascotee River. It has not been determined whether or not those values are higher due to 

anthropogenic activity. Chlorophyll a values measured in the Anclote Estuary by the COAST program 

from 2000-2006 are comparable to those measured in the estuary area in 1973-74 (Johansson 1975). 

[Feedback from the public welcome] FDEP recommends numeric nutrient criteria that will maintain the 

existing long-term nutrient regime and not allow increases, as determined by the available data, but 

excluding data from areas that have potentially been identified as nutrient enriched. 

The magnitude of nutrients is fairly consistent along this coast (Table 19), from the Crystal River to the 

Anclote River, but nutrients and chlorophyll a vary with salinity and the sources of the nutrients differ 

between the northern and southern areas of the region. Criteria could either be derived for each river 

system individually, or developed collectively for the whole region, taking salinity into account. Total 

phosphorus and chlorophyll a are generally higher in waters of lower salinity (Table 19), but total 

nitrogen levels do not decrease as much at higher salinities, likely due to nitrogen coming from larger 

rivers to the north (Suwannee, Withlacoochee). 

[FDEP is seeking input on appropriate regionalization or separation by salinity along the Springs Coast. 

Below we propose criteria based on mean annual site salinity.] 

Table 19. Mean and standard deviations of site annual geometric means, summarized by subregion 

and salinity range. Note that fewer than ten sites are reported for some subregions because 

freshwater sites were not included. N = sample size, SD = standard deviation

N

Mean 

Chlorophyll a, 

uncorrected

SD 

Chlorophyll a, 

uncorrected

Mean 

Total 

Nitrogen

SD Total 

Nitrogen

Mean Total 

Phosphorus

SD Total 

Phosphorus

Means by Subregion

Crystal 9 2.74 1.03 322 79.71 18.99 5.08

Homosassa 9 1.65 1.12 401 74.23 11.93 3.95

Chassahowitzka 7 1.96 1.18 379 8.72 11.63 3.92

Weeki Wachee 7 0.96 0.10 420 17.74 8.32 0.53

Aripeka 10 0.71 0.18 386 25.23 6.75 0.46

Hudson 10 0.74 0.23 368 39.33 7.03 0.86

Pithlachascotee 9 1.44 0.97 413 48.10 11.91 6.05
Draft 64 August 2010

Anclote 10 2.04 0.65 379 38.19 14.77 2.81

Means by Salinity Category

< 20 ppt 17 2.48 1.25 369 64.52 15.76 6.77

20-25 ppt 26 1.24 0.65 407 59.20 9.93 3.57

25-32 ppt 28 1.19 0.76 368 31.01 10.17 4.01

Methodology 

For consistent application and for providing an appropriate level of protection, water quality criteria 

need to include magnitude, frequency, and duration components. The magnitude is a measure of how 

much of a pollutant may be present in the water without an unacceptable adverse effect. Duration is a 

measure of how long the pollutant may be above the magnitude, and frequency relates to how often 

the magnitude may be exceeded without adverse effects. It is preferred to derive the magnitude 

component of a criterion through a cause-effect relationship (such as those measured through toxicity 

testing). The magnitude would then be set at a level that would protect a majority of the sensitive 

aquatic organisms inhabiting the system. Absent a demonstrated cause-effect relationship, the 

magnitude may be set at a level designed to maintain the current data distribution, accounting for 

natural temporal variability, when the current conditions are protective of the designated uses of the 

waterbody. Since a criterion derived based on the existing data distribution has no direct link to any 

observed cause and effect relationship, it is assumed that maintaining the current data distribution will 

preserve the uses associated with that distribution. 

The frequency and duration components of the criteria are best established as additional descriptors of 

the reference condition data distribution. Specifically, these components should be part of a statistical 

test designed to determine whether the long-term distribution of data has shifted upward ( or in some 

cases, downward) from the reference distribution. This test would then be used to determine whether 

future monitoring data are consistent with the magnitude (long-term average) defined by the reference 

dataset. It is critical to account for the natural variability surrounding the magnitude expression and to 

control for statistical errors. 

The derivation of the magnitude, frequency and duration components of the numeric nutrient criteria 

for Springs Coast is described briefly below. More details concerning the statistical approaches used can 

be found in the document “Overview of FDEP Approaches for Nutrient Criteria Development in Marine 

Waters” (FDEP 2010).

Magnitude 

The magnitude component can be set at a variety of values based on the frequency and duration that 

will be used to determine compliance. For the “healthy existing conditions” approach, FDEP established 

the magnitude at: a) an adjusted long-term central tendency (geometric mean) of the distribution, 

expressed as a long-term geometric mean never to be exceeded; and b) an annual geometric mean, not 

to be exceeded more than two times over a five- year period. The long-term average condition was 

adjusted to a level that represents an insignificant increase from the baseline. Allowing for an 

insignificant increase accounts for uncertainty in the estimate of the mean and partially addresses the 
Draft 65 August 2010

fact that the reference based approach fails to identify a threshold of imbalance, and thus is highly 

prone to excessive Type I error. For the purpose of antidegradation evaluations, EPA has established 

that a ten percent change in a water quality parameter represents an insignificant departure from the 

historical condition, known as a de minimus change (US Sixth Circuit Court 2008). Therefore, the longterm geometric mean limit was derived to allow for up to a ten percent increase in the long-term 

geometric mean, which was calculated as the geometric mean of the annual geometric means of the 

long-term dataset for each segment of the waterbody.

Because it is not always practical to assess compliance with the criteria on the same long-term basis, 

FDEP also developed criteria expressed as an annual geometric mean so that estuaries could be assessed 

on an annual basis. It should be noted that the duration and frequency components of the criteria must 

be linked to the response timeframe of the sensitive endpoint. Short-term averaging periods (e.g., 1 to 

30 days) might be appropriate for nutrient criteria where a sufficiently robust cause-effect relationship 

has demonstrated that a eutrophic response occurs over such timeframes. If however, such a shortterm response cannot be demonstrated, or there is no indication of use impairment, longer averaging 

periods should be used. 

Since the duration and frequency components of the criteria must be consistent with the derivation of 

the magnitude component, the long-term geometric mean target cannot simply be applied as an annual 

mean. Doing so would result in an unacceptability high Type I failure rate (identifying a healthy system 

as being impaired) since approximately 50 percent of the individual yearly means are expected to be 

above the long-term mean. Therefore, the long-term target must be adjusted to allow for the 

application to a shorter duration with an acceptable Type I error rate of no more than a 10 percent.

An annual criterion with an approximate 10 percent Type I error rate for a given frequency was derived 

by appropriately accounting for the annual variability above the mean. This annual target concentration 

was derived as an upper percentile of the distribution of the annual geometric mean concentrations. 

Previous proposals by EPA have utilized three-year assessment periods to express the duration nutrient 

criteria components. Although it is possible to construct a test that achieves the 10 percent Type I error 

rate target over a 3-year period, a slightly longer period (5 years) will provide better control for Type II 

error and will more fully capture climatic cycles (e.g., el nino, la nina), which tend to be longer than 

three years in Florida (and may actually be on a multi-decadal scale). Furthermore, a five year period is 

more consistent with both the State’s five year 303(d) assessment and NPDES permit renewal cycles.

Given a five year assessment period, FDEP derived criteria expressed as an annual geometric mean by 

using the 75th percentile of the annual geometric means from the long-term dataset. FDEP 

demonstrated that setting the criteria at this percentile results in a magnitude that, when expressed as 

an annual geometric mean not to be exceeded more than twice during a five-year period, will achieve 

the targeted 10 percent error rate. The magnitude component of the criteria (not to be exceeded more 

than twice in a 5 year period) was established to allow for two separate assessments:

• As an annual geometric mean for a network of stations in a specified segment of the waterbody; 

and 
Draft 66 August 2010

• As an annual geometric mean for a single station in a given segment. 

The two expressions of magnitude differ in the handling of within-segment spatial variability. The 

network average magnitude was calculated based on the distribution of spatially averaged annual 

geometric means, while the single site magnitude was calculated using the distribution of station annual 

geometric means. Use of the network average magnitude is appropriate for assessing overall segment 

status. However, a network average is only representative of overall segment status if it is relatively 

homogeneous. If the segment is not well mixed, is very large, or contains localized nutrient sources, 

then there is a potential that isolated areas of enrichment may be masked in the network spatial 

average. Therefore, the single station annual geometric mean has the benefit of assessing localized 

enrichment patterns. DEP has not decided whether both expressions of magnitude are needed in all 

cases, and we are seeking additional feedback from local experts and stakeholders.

Summary of the Proposed Criteria

FDEP proposes three sets of potential criteria: a) a long-term geometric mean concentration; b) an 

annual geometric mean of values from a network of stations over a given area, not to be exceeded more 

than twice in a five-year period; and c) an annual geometric mean of values from a single location, not to 

be exceeded more than twice in a five-year period. Data from Crystal and Anclote river estuaries were 

not included in the calculations for proposed criteria. 

The proposed long-term targets for the protection of a healthy, well-balanced aquatic community in 

Springs Coast, as well the annual limits for each segment, are provided in Table 20. Appropriate salinity 

zone is determined for a station based on the annual mean salinity. 

Table 20. Proposed numeric nutrient criteria for all segments of Springs Coast, including TP, TN, and 

chlorophyll a. For compliance purposes, the long term geometric mean shall not exceed the long term 

limit nor shall the average of all stations in a segment exceed the network average more than twice in 

a 5 year period. The last column shows the value which single station shall not exceed, by segment, 

more than twice in a 5 year period. 

TP (μg/L)

 Network Average Assessed as a Single Site GM

Salinity Zone LT_GM LT_Limit 2:5 Annual Limit 2:5 Annual Limit

<20 15.8 17.3 20.1 24.3

20-25 9.7 10.6 13.0 14.1

>25 8.6 9.4 12.0 12.6

TN (μg/L)

Network Average Assessed as a Single Site GM

Salinity Zone LT_GM LT_Limit 2:5 Annual Limit 2:5 Annual Limit

<20 381 419 468 500

20-25 432 476 550 586

>25 368 404 456 466

Chlorophyll a (μg/L)
Draft 67 August 2010

 Network Average Assessed as a Single Site GM

Salinity Zone LT_GM LT_Limit 2:5 Annual Limit 2:5 Annual Limit

<20 2.4 2.6 3.5 4.2

20-25 1.1 1.2 2.0 2.1

>25 0.8 0.9 1.4 1.5
Draft 68 August 2010

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Draft 72 August 2010

Appendix A. Water Quality Data Plots from Entire Record of Project COAST Data 

(from Frazer and Jacoby 2010) 

0

200

400

600

800

1000

1200

Mar-96 Aug-97 Dec-98 May-00 Sep-01 Jan-03 Jun-04 Oct-05 Mar-07 Jul-08

TN (ug/L)

Crystal Monthly Average Total Nitrogen (TN) 

1996 through 2008 Estuarine Stations

0

10

20

30

40

50

60

70

80

Mar-96 Aug-97 Dec-98 May-00 Sep-01 Jan-03 Jun-04 Oct-05 Mar-07 Jul-08

TP (ug/L)

Crystal Monthly Average Total Phosphorus (TP) 

1996 through 2008 Estuarine Stations

0

5

10

15

20

25

Mar-96 Aug-97 Dec-98 May-00 Sep-01 Jan-03 Jun-04 Oct-05 Mar-07 Jul-08

CHL-a (ug/L)

Crystal Average Chlorophyll-a (CHL-a)

1996 through 2008 Estuarine Stations 
Draft 73 August 2010

0

200

400

600

800

1000

1200

1400

1600

Mar-96 Aug-97 Dec-98 May-00 Sep-01 Jan-03 Jun-04 Oct-05 Mar-07 Jul-08

TN (ug/L)

Chassahowitzka Monthly Average Total Nitrogen (TN) 

1997 through 2008 Estuarine Stations 

0

5

10

15

20

25

30

35

40

45

Mar-96 Aug-97 Dec-98 May-00 Sep-01 Jan-03 Jun-04 Oct-05 Mar-07 Jul-08

TP (ug/L)

Chassahowitzka Monthly Average Total Phosphorus (TP) 

1997 through 2008 Estuarine Stations

0

5

10

15

20

25

Mar-96 Aug-97 Dec-98 May-00 Sep-01 Jan-03 Jun-04 Oct-05 Mar-07 Jul-08

CHL-a (ug/L)

Chassahowitzka Average Chlorophyll-a (CHL-a)

1997 through 2008 Estuarine Stations 
Draft 74 August 2010

0

200

400

600

800

1000

1200

Mar-96 Aug-97 Dec-98 May-00 Sep-01 Jan-03 Jun-04 Oct-05 Mar-07 Jul-08

TN (ug/L)

Weeki Wachee Monthly Average Total Nitrogen (TN) 

1997 through 2008 Estuarine Stations 

0

5

10

15

20

25

30

Mar-96 Aug-97 Dec-98 May-00 Sep-01 Jan-03 Jun-04 Oct-05 Mar-07 Jul-08

TP (ug/L)

Weeki Wachee Monthly Average Total Phosphorus (TP) 

1997 through 2008 Estuarine Stations

0

2

4

6

8

10

12

Mar-96 Aug-97 Dec-98 May-00 Sep-01 Jan-03 Jun-04 Oct-05 Mar-07 Jul-08

CHL-a (ug/L)

Weeki Wachee Average Chlorophyll-a (CHL-a)

1997 through 2008 Estuarine Stations 
Draft 75 August 2010

0

200

400

600

800

1000

1200

Mar-96 Aug-97 Dec-98 May-00 Sep-01 Jan-03 Jun-04 Oct-05 Mar-07 Jul-08

TN (ug/L)

Homosassa Monthly Average Total Nitrogen (TN) 

1996 through 2008 Estuarine Stations 

0

10

20

30

40

50

60

Mar-96 Aug-97 Dec-98 May-00 Sep-01 Jan-03 Jun-04 Oct-05 Mar-07 Jul-08

TP (ug/L)

Homosassa Monthly Average Total Phosphorus (TP) 

1996 through 2008 Estuarine Stations

0

5

10

15

20

25

Mar-96 Aug-97 Dec-98 May-00 Sep-01 Jan-03 Jun-04 Oct-05 Mar-07 Jul-08

CHL-a (ug/L)

Homosassa Average Chlorophyll-a (CHL-a)

1996 through 2008 Estuarine Stations 
Draft 76 August 2010

0

100

200

300

400

500

600

700

800

May-99 Oct-00 Feb-02 Jun-03 Nov-04 Mar-06 Aug-07 Dec-08

TN (ug/L)

Aripeka Monthly Average Total Nitrogen (TN) 

2000 through 2008 Estuarine Stations 

0

2

4

6

8

10

12

14

16

18

May-99 Oct-00 Feb-02 Jun-03 Nov-04 Mar-06 Aug-07 Dec-08

TP (ug/L)

Aripeka Monthly Average Total Phosphorus (TP) 

2000 through 2008 Estuarine Stations

0

1

2

3

4

5

6

7

May-99 Oct-00 Feb-02 Jun-03 Nov-04 Mar-06 Aug-07 Dec-08

CHL-a (ug/L)

Aripeka Average Chlorophyll-a (CHL-a)

2000 through 2008 Estuarine Stations 
Draft 77 August 2010

0

100

200

300

400

500

600

700

800

May-99 Oct-00 Feb-02 Jun-03 Nov-04 Mar-06 Aug-07 Dec-08

TN (ug/L)

Hudson Monthly Average Total Nitrogen (TN) 

2000 through 2008 Estuarine Stations 

0

5

10

15

20

25

May-99 Oct-00 Feb-02 Jun-03 Nov-04 Mar-06 Aug-07 Dec-08

TP (ug/L)

Hudson Monthly Average Total Phosphorus (TP) 

2000 through 2008 Estuarine Stations

0

1

2

3

4

5

6

7

8

9

10

May-99 Oct-00 Feb-02 Jun-03 Nov-04 Mar-06 Aug-07 Dec-08

CHL-a (ug/L)

Hudson Average Chlorophyll-a (CHL-a)

2000 through 2008 Estuarine Stations 
Draft 78 August 2010

0

100

200

300

400

500

600

700

800

900

1000

May-99 Oct-00 Feb-02 Jun-03 Nov-04 Mar-06 Aug-07 Dec-08

TN (ug/L)

Pithlachascotee Monthly Average Total Nitrogen (TN) 

2000 through 2008 Estuarine Stations 

0

5

10

15

20

25

30

35

40

May-99 Oct-00 Feb-02 Jun-03 Nov-04 Mar-06 Aug-07 Dec-08

TP (ug/L)

Pithlachascotee Monthly Average Total Phosphorus (TP) 

2000 through 2008 Estuarine Stations

0

2

4

6

8

10

12

14

16

18

20

May-99 Oct-00 Feb-02 Jun-03 Nov-04 Mar-06 Aug-07 Dec-08

CHL-a (ug/L)

Pithlachascotee Average Chlorophyll-a (CHL-a)

2000 through 2008 Estuarine Stations 
Draft 79 August 2010

0

100

200

300

400

500

600

700

800

May-99 Oct-00 Feb-02 Jun-03 Nov-04 Mar-06 Aug-07 Dec-08

TN (ug/L)

Anclote Monthly Average Total Nitrogen (TN) 

2000 through 2008 Estuarine Stations 

0

5

10

15

20

25

30

35

40

May-99 Oct-00 Feb-02 Jun-03 Nov-04 Mar-06 Aug-07 Dec-08

TP (ug/L)

Anclote Monthly Average Total Phosphorus (TP) 

2000 through 2008 Estuarine Stations

0

2

4

6

8

10

12

May-99 Oct-00 Feb-02 Jun-03 Nov-04 Mar-06 Aug-07 Dec-08

CHL-a (ug/L)

Anclote Average Chlorophyll-a (CHL-a)

2000 through 2008 Estuarine Stations 
Draft 80 August 2010

Appendix B. Annual Geometric Mean Chlorophyll a (Uncorrected) and TN from Project 

COAST 

Data are from Project COAST and include all sites. Freshwater sites removed from the statistical analyses are Chassahowitzka-1, -2, -10; Crystal4; Homosassa-5; Pithlachascotee-1; and Weeki Wachee-1, -2. 
Draft 81 August 2010
Draft 82 August 2010
Draft 83 August 2010
Draft 84 August 2010
Draft 85 August 2010
Draft 86 August 2010
Draft 87 August 2010
Draft 88 August 2010
Draft 89 August 2010
Draft 90 August 2010
Draft 91 August 2010
Draft 92 August 2010
Draft 93 August 2010

Appendix C. Relationship between Salinity and Annual Geometric Mean TN per Site in 8 

Coastal Areas of Project COAST. 

Notes: Plots do not include freshwater sites. Data pulled from STORET and analyzed by N. Wellendorf, FDEP. 

0

100

200

300

400

500

600

700

800

0 5 10 15 20 25 30

Annual Geometric Mean TN (mg/L)

Mean Annual Salinity

Crystal River Bay Salinity vs. TN (9 sites)

1997

1998

1999

2000

2001

2002

2003

2004

2006

0

100

200

300

400

500

600

700

0 5 10 15 20 25 30

Annual Geometric Mean TN (mg/L)

Mean Annual Salinity

Chassahowitzka (COAST) Salinity vs. TN

(7 sites)

1997

1998

1999

2000

2001

2002

2003

2004

2006
Draft 94 August 2010

0

100

200

300

400

500

600

700

800

900

1000

0 5 10 15 20 25 30 35

Annual Geometric Mean TN (mg/L)

Mean Annual Salinity

Homosassa Salinity vs. TN (9 sites)

1997

1998

1999

2000

2001

2002

2003

2004

2006

0

100

200

300

400

500

600

700

800

900

0 5 10 15 20 25 30

Annual Geometric Mean TN (mg/L)

Mean Annual Salinity

Weeki Wachee Salinity vs. TN (8 sites)

1997

1998

1999

2000

2001

2002

2003

2004

2006
Draft 95 August 2010

0

100

200

300

400

500

600

10 15 20 25 30 35

Annual Geometric Mean TN (mg/L)

Mean Annual Salinity

Aripeka Salinity vs. TN (10 sites)

2000

2001

2002

2003

2004

2006

0

100

200

300

400

500

600

700

10 15 20 25 30 35

Annual Geometric Mean TN (mg/L)

Mean Annual Salinity

Hudson Salinity vs. TN (10 sites)

2000

2001

2002

2003

2004

2006
Draft 96 August 2010

0

100

200

300

400

500

600

700

0 5 10 15 20 25 30 35

Annual Geometric Mean TN (mg/L)

Mean Annual Salinity

Pithlachascotee Salinity vs. TN 

(9 sites)

2000

2001

2002

2003

2004

2006

0

100

200

300

400

500

600

20 25 30 35 40

Annual Geometric Mean TN (mg/L)

Mean Annual Salinity

Anclote - Salinity vs. TN (10 sites)

2000

2001

2002

2003

2004

2006
Draft 97 August 2010

Appendix D. Data Comparisons between Providers

FDEP and SWFWMD Springs Studies

FDEP and SWFWMD have sampling programs that regularly monitor some springs and spring runs. 

Some of these data were plotted as an estimate of trends in loading to the estuarine system over time, 

and as a way to compare data that were collected and analyzed using different methods but from 

roughly the same sites.

Figure D-1. TP concentrations in the Weeki Wachee River, 1997–2009, sampled by FDEP and Project

COAST.

0

0.005

0.01

0.015

0.02

0.025

0.03

10/28/1995

3/11/19977/24/199812/6/19994/19/2001

9/1/2002

1/14/20045/28/2005

10/10/2006

2/22/2008

7/6/2009

11/18/2010

Total Phosphorus (mg/L)

TP - Weeki Wachee @ Brooksville TV site vs. 

COAST sites upstream and downstream w/in 1 mile

TV site - TP

COAST WW1-TP

COAST WW2-TP
Draft 98 August 2010

Figure D-2. Comparison of available data for Homosassa Head Springs, sampled by FDEP and Project 

COAST.

Figure D-3. Comparison of COAST TN data and FDEP Trend Variability NO2+3 data from the Weeki 

Wachee River. Most TKN values from the FDEP data were nondetect, and thus FDEP NO2+3 and Project 

COAST TN data were compared. 
Draft 99 August 2010

Figure D-4. Comparison of salinity values at sites that are located close to one another in the 

Chassahowitzka Estuary, from the COAST and Mote Marine Lab (MML) sampling programs.

Figure D-5. Comparison of total phosphorus values at sites that are located close to one another in the 

Chassahowitzka Estuary, from the COAST and Mote Marine Lab (MML) sampling programs. The 

minimum detection limit (MDL) for the MML lab was 50 μg/L; non-detects were plotted as 25 μg/L. 
Draft 100 August 2010

Figure D-6. Comparison of chlorophyll a values at sites that are located close to one another in the 

Chassahowitzka Estuary, from the COAST and Mote Marine Lab (MML) sampling programs. 
Draft 101 August 2010

Figure D-7. Comparison of total nitrogen values at sites that are located close to one another in the 

Chassahowitzka Estuary, from the COAST and Mote Marine Lab (MML) sampling programs. 
Draft 102 August 2010

Figure D-8. Comparison of total phosphorus values at sites that are located close to one another in the 

Suwannee Estuary, from the COAST and Suwannee River Water Management District (SRWMD) 

sampling programs. 
Draft 103 August 2010

Figure D-9. Comparison of total nitrogen values at sites that are located close to one another in the 

Suwannee Estuary, from the COAST and Suwannee River Water Management District (SRWMD) 

sampling programs.