Wekiva River and Rock Springs Run 

Pollutant Load Reduction Goals 

Report to the 

Florida Department of Environmental Protection 

August, 2006

Prepared by: 

Robert A. Mattson, Edgar F. Lowe, Ph.D., 

Carol L. Lippincott, Ph.D., Jian Di, 

Larry Battoe, Ph.D. 

St. Johns River Water Management District 

4049 Reid Street 

Palatka, FL 32177 
Executive Summary 

The Wekiva Parkway and Protection Act of 2004 (Chapter 369, Part III, FS) required the 

St. Johns River Water Management District (SJRWMD) to develop Pollutant Load 

Reduction Goals (PLRGs) for the Wekiva Study Area (WSA, Figure 1). The major 

spring-fed ecosystems within the WSA are Wekiwa Springs, the Wekiva River, Rock 

Springs, and Rock Springs Run. It is for these systems that the SJRWMD developed 

PLRG recommendations. PLRGs are the reductions in pollutant loadings needed to 

meet water quality standards or goals. The development of a PLRG is a four-step 

process: 1) determine the nature and degree of impairment, 2) identify the causative 

pollutant(s), 3) determine the acceptable concentration of each causative pollutant, and 

4) determine the reduction in loading required to achieve the acceptable concentration 

of each causative pollutant. 

The SJRWMD designed a project to develop multiple lines of evidence for the PLRG: 

relevant information in the scientific literature; biological, chemical, and physical data for 

the Wekiva River and Rock Springs Run and reference (less impacted) streams; 

mesocosm studies in the Wekiva River and Rock Springs Run and reference streams; 

and data for other spring-fed streams in Florida. Two reference streams were used to 

aid the assessment of impairment: Alexander Spring Creek Run and Juniper Creek 

(Figure 2). This work indicates potential impairment of the Wekiva River and Rock 

Springs Run in terms of ecosystem processes, overgrowth of periphytic algae, 

dominance of the periphyton by Cyanobacteria (blue-green algae), and toxic effects on 

larvae of nitrate-sensitive aquatic organisms. Two causative pollutants create these 

potential effects: nitrate and total phosphorus (TP). 

Two water quality standards apply to these effects: nutrients and toxicity. The standard 

for nutrients requires that they not cause an imbalance in flora and fauna (Chapter 62-

302.530[48][b], FAC), such as algal blooms, changes in algal species richness or 

taxonomic composition, or presence of nuisance algal mats. State and Federal water 

quality standards require that any pollutant shall not be present at toxic levels (Chapter 

62-302.530[62], FAC). Using these standards, there are several lines of evidence that 

the concentrations of nitrate and TP in the Wekiva River and Rock Springs Run are too 

high: 

 

1) They are higher than in the reference streams and other less-impacted Florida 

springs and spring-run streams; 

2) They are higher than historical data for springs and spring-run stream; 

3) Various measures of ecosystem metabolism are altered in the Wekiva River and 

Rock Springs Run, as compared to the reference streams and these changes are 

correlated with higher concentrations of nitrate and TP; 

4) In laboratory studies the growth of filamentous Cyanobacteria is accelerated by 

nitrate; 

5) In field studies of other springs, the abundance and growth of epiphytes was 

correlated with TP; 

i 
Figure 1 (Executive Summary). The Wekiva River basin, spring recharge area, and 

2004 Wekiva Study Area. Source: SJRWMD data. 

ii 
Figure 2 (Executive Summary). Location map showing the Wekiva River System 

(including the Wekiva River and Rock Springs Run) and the two reference spring-run 

streams; Alexander Spring Creek and Juniper Creek. Source: WSI, 2005 (Appendix 

C). 

iii 
6) In the Wekiva River and Rock Springs Run , the relative abundance of 

Cyanobacteria and Chlorophyta (algae which are generally considered 

“nuisance” taxa) was higher in sites with higher TP; 

7) Data from studies reported in the scientific literature indicate that nitrate is toxic 

to larvae of sensitive aquatic insects and amphibians at concentrations that have 

occurred in the Wekiva River and Rock Springs Run . Nitrate concentrations in 

the Wekiva River and Rock Springs Run have commonly exceeded estimated 

no-effects levels for these nitrate-sensitive aquatic organisms. 

These observations lead to a variety of potential target concentrations for nutrients 

(Tables 1 and 2; Figures 3 and 4). 

To reduce the potential for violation of water quality standards, the SJRWMD 

recommends that mean concentrations of nitrate and TP be reduced to 216 μg/L nitrate 

and 59 μg/L total phosphorus in the Wekiva River and 221 μg/L nitrate and 61 μg/L total 

phosphorus in Rock Springs Run. These concentrations include a margin-of-safety and 

were derived using statistical techniques that ensure a very low probability of exceeding 

thresholds that promote excessive or nuisance algal growth. 

Impairment was also demonstrated for total coliform bacteria, which exceeded the state 

water quality standard. The SJRWMD recommends the state water quality standard of 

< 2,400 colonies/100 ml as the target concentration for total coliform bacteria. 

In order to calculate PLRGs as percent reductions, pollutant concentrations were 

assumed to vary in direct proportion to the variation in pollutant loads. Thus, percent 

load reductions were assumed equivalent to the required percent reduction in 

concentrations: 

 

PLRG(%) = [(cmc – tmc) / cmc] x 100, 

 

Where cmc is the current mean concentration of the pollutant and tmc is the target 

mean concentration of the pollutant. This method yields load reductions for nitrate and 

TP ranging from 44 – 89% (Table 3). Reductions in total coliform counts were 

calculated based on EPA’s percent-reduction method (Lehmensiek, 2005). 

 

Spatial and temporal trends were considered in the calculation of PLRGs. Where there 

was a decreasing temporal trend, the cmc only reflected the recent period when there 

was no significant trend (i.e. data extending back from the present to that time when a 

non-significant trend became statistically significant). Spatial trends were also 

examined (from headspring to confluence with the next downstream system), and 

where appropriate, concentration reductions were applied to specific segments of each 

spring-run stream or to the entire stream. 

iv 
Table 1 (Executive Summary). Potential nitrate-nitrite (NOx) concentration targets based on various lin

Reference Basis for Target N

Ecosystem metabolism in the Wekiva River and Rock Springs Run (WSI 2005) 

Comparison to metabolism in less-impacted spring-run streams (Juniper & Alexander) Comparison to other springs in SJRWMD 

Nitrate toxicity to aquatic animals (Mattson et al. 2005) 

90% probability of <1,400 μg/L (lowest toxicity threshold for caddisflies) 

Wekiwa Spring

Rock Spring New thresholds after application of uncertainty factors 90% probability of <125 μg/L (lowest threshold with uncertainty factor): 

Wekiwa Spring Rock Spring

Rainbow River algal bioassays (Cowell and Dawes 2004) 

Lyngbya wollei biomass 90% probability of < threshold of 250 μg/L: 

Wekiva River Rock Springs Run 

Suwannee River periphytic algae and nitrate levels (Hornsby et al. 2000) 

Algal biomass Algal cell density 

Nutrients in Florida springs (WSI and DEP databases) 

130 Florida springs, including impacted springs Juniper Spring, Fern Hammock Spring Alexander Spring 

Nutrients in less-impacted spring-run streams in Florida (STORET database) 

Juniper Creek Alexander Spring Creek Wacissa River 

Nutrients in undeveloped streams In the United States (Binkley et al., 2004; Clark et al. 2000) 

Forested stream basins in the southeastern U.S. Undeveloped watersheds in the U.S. 

EPA proposed TMDL for Wekiwa Spring and Rock Springs Run (USEPA 2005) 

Comparison to Juniper Spring 

FDEP wastewater treatment criteria in the Wekiva Study Area (FDEP 2004) 

Comparison to less-impacted Florida springs 

v 
Table 2 (Executive Summary). Potential total phosphorus (TP) concentration targets based on various 

investigation. 

Reference Basis for Target TP 

Ecosystem metabolism in the Wekiva River and Rock Springs Run (WSI 2005) 

Comparison to metabolism in less-impacted spring-run streams (Juniper & Alexander) Comparison to springs in SJRWMD 

5

% Cyanobacteria and Chlorophyta in attached algae in Wekiva River and Rock Springs Run (analysis of data from GreenWater Labs 2005) 

90% probability of < 90 μg /L (threshold for increased levels of 

cyanobacteria and chlorophyta in attached algal community): 

Wekiva River Rock Springs Run 

Mapping and monitoring of submerged aquatic vegetation in the Ichetucknee River headsprings (PBS&J 2004) 

Epiphytic algal biomass 

Phosphorus in selected Florida springs in the 1950s (Odum 1953) 

Springs outside of phosphatic areas Springs within phosphatic areas 

Nutrients in Florida springs (WSI and DEP databases) 

130 Florida springs, including impacted springs Juniper Spring, Fern Hammock Spring Alexander Spring 

3

Nutrients in less-impacted spring-run streams in Florida (STORET database) 

Juniper Creek Alexander Spring Creek Wacissa River 

Nutrients in undeveloped streams in the United States (Clark et al. 2000) 

Undeveloped watersheds in the U.S. 

vi 
0

100200300400500600

Alexander Spring Creek Alexander spring Wacissa River Juniper Creek Juniper spring US watersheds Fern Hammock spring ecosystem metabolism - lower NITRATE TOXICITY - WEKIWA SPRING EPA TMDL NITRATE TOXICITY - ROCK SPRING SE US streams ecosystem metabolism - upper SJRWMD springs DEP wastewater criteria Suwannee River algae - lower ALGAL GROWTH - WEKIVA RIVER ALGAL GROWTH - ROCK SPRINGS RUN Suwannee River algae - up

Rainbow River 

Potential NOx target concentration (ug/L) proposed target concentration means

Figure 3 (Executive Summary). Potential and proposed nitrate targets based on Table 1.

vii 
0

102030405060708090

US watersheds Juniper Creek

Fern Hammock spring Juniper spring 130 Florida springs Alexander Spring Creek Wacissa River Alexander spring 1950s P in FL springs not in phosphatic areas ecosystem metabolism - lower SJRWMD springs epiphytic algae in Ichetucknee springs ATTACHED ALGAE IN THE WEKIVA RIVER ATTACHED ALGAE IN ROCK SPRINGS RUN 1950s P in FL springs in ph

e

Potential TP target concentration (ug/L)

proposed target 

concentration means

Figure 4 (Executive Summary). Potential and proposed total phosphorus targets based on Table 2.

viii 
Table 3 (Executive Summary). Recommended percent reductions in loading of nitrate, 

TP, and total coliform bacteria for the Wekiva River and Rock Springs Run. 

Nitrate 

Total 

Phosphorus 

Total Coliform 

Bacteria 

Wekiwa Spring 82% - - - - - - 

Upper Wekiva River 

(to Little Wekiva River) 

69% 50% 49% 

Lower Wekiva River 

(to Blackwater Creek) 

36% 50% 30% 

Rock Spring 85% - - - - - - 

Rock Springs Run 52% 29% 50% 

The recommended PLRGs are based on the best information available within the time 

frame required by the Wekiva Parkway and Protection Act. There was insufficient time 

to delineate seasonal and yearly fluctuations in biological conditions. Algal surveys and 

ecosystem metabolism studies in the Wekiva River and Rock Springs Run were 

conducted when there were significant impacts from the unusually strong hurricane 

season of 2004. Sediments had been eroded and deposited in new areas, vegetation 

had been buried and removed by scouring, and water quality was atypical. In addition 

to the problems associated with the short time frame for the work, an understanding of 

the influence of nutrient concentrations on the structure and function of spring-fed 

streams is still developing. These ecosystems have not been extensively studied, and 

much additional research is needed before they are as well understood as are lakes 

and wetlands. The potential for nitrate toxicity is also poorly known. Additional 

research is needed to decrease the uncertainty associated with the recommended 

PLRGs. 

In recognition of the numerous sources of uncertainty, these PLRG recommendations 

should be considered provisional. Large safety margins were employed to ensure that 

the PLRGs will be protective. Additional research may allow these safety margins to be 

reduced, resulting in higher concentration targets than those currently proposed. This 

will reduce the pollutant load reductions required to meet these higher targets. 

ix
TABLE OF CONTENTS 

Executive Summary i

TABLE OF CONTENTS x

LIST OF FIGURES xiii

LIST OF TABLES xv

LIST OF ACRONYMS AND ABBREVIATIONS xvi

1 INTRODUCTION 1

1.1 Wekiva River Protection Area ........................................................................... 1

1.2 Wekiva Parkway and Protection Act ................................................................. 1

1.3 Other Protective Designations .......................................................................... 3

1.3.1 Surface Water Improvement and Management Program........................... 3

1.3.2 Outstanding Florida Waters ....................................................................... 3

1.3.3 Aquatic Preserve ....................................................................................... 3

1.3.4 National Wild and Scenic River.................................................................. 4

1.4 Pollutant Load Reduction Goals........................................................................ 4

2 WEKIVA RIVER SYSTEM DESCRIPTION 6

2.1 Physiography and Geology............................................................................... 6

2.2 Climate and Hydrology...................................................................................... 8

2.3 Water Quality – Description, Status, and Trends ............................................ 10

2.3.1 Water Quality Description ........................................................................ 10

Analyte....................................................................................................................... 13

2.3.2 Water Quality Status and Trends............................................................. 13

2.3.3 Water Quality Issues................................................................................ 15

2.4 Ecological Overview........................................................................................ 15

2.5 Surrounding Land Use .................................................................................... 28

3 DISTRICT STUDIES CONDUCTED FOR PLRG DEVELOPMENT 29

3.1 Ecosystem Metabolism in the Wekiva River, Rock Springs Run, and in 

Reference Spring-run Streams .................................................................................. 29

3.2 Attached Algae in the Wekiva River and Rock Springs Run ........................... 30

3.3 SJRWMD Review of Literature and Data........................................................ 31

3.3.1 Nitrate Toxicity to Aquatic Animals .......................................................... 31

3.3.2 Coliform Bacteria Impairment .................................................................. 31

3.3.3 Total Phosphorus Thresholds for Attached Algae Growth ....................... 31

3.3.4 Rainbow River Algal Bioassays ............................................................... 32

3.3.5 Suwannee River Algae and Nutrients ...................................................... 32

3.3.6 Nutrients in Less-Impacted Spring-Run Streams and in 130 Florida 

Springs ................................................................................................................. 32

3.3.7 Nutrients in Undeveloped Streams in the United States .......................... 32

3.3.8 Nitrate Targets for EPA’s TMDL .............................................................. 32

3.3.9 Total Phosphorus and Epiphytic Algae in Ichetucknee Springs ............... 33

3.3.10 Phosphorus in Florida Springs in the 1950’s............................................ 33

x
3.3.11 Nitrate Targets for FDEP’s Wastewater Treatment Criteria ..................... 33

4 PLRG DEVELOPMENT 34

4.1 Determining Impairment.................................................................................. 34

4.1.1 FDEP Assessment of Impairment............................................................ 35

4.1.2 SJRWMD Analysis of Impairment............................................................ 35

4.2 Defining Nuisance Algae................................................................................. 38

4.3 Results of PLRG Investigations ...................................................................... 39

4.3.1 Ecosystem Metabolism in the Wekiva River, Rock Springs Run, and in 

Reference Spring-run Streams............................................................................... 39

4.3.2 Attached Algae in the Wekiva River and Rock Springs Run.................... 42

4.3.3 Nitrate Toxicity to Aquatic Animals .......................................................... 42

4.3.4 Coliform Bacteria Impairment .................................................................. 45

4.3.5 Total Phosphorus Thresholds for Attached Algae Growth ....................... 46

4.3.6 Rainbow River Algal Bioassays ............................................................... 46

4.3.7 Suwannee River Algae and Nutrients ...................................................... 46

4.3.8 Nutrients in Less-Impacted Spring-Run Streams and in 130 Florida 

Springs ................................................................................................................. 49

4.3.9 Nutrients in Undeveloped Streams in the United States .......................... 49

4.3.10 Nitrate Targets for EPA’s TMDL .............................................................. 49

4.3.11 Total Phosphorus and Epiphytic Algae in Ichetucknee Springs ............... 49

4.3.12 Phosphorus in Florida Springs in the 1950’s............................................ 50

4.3.13 Nitrate Targets for FDEP’s Wastewater Treatment Criteria ..................... 50

4.4 Evidence of Impairment and Causative Pollutants.......................................... 50

4.4.1 Nutrients - Imbalance of Flora and Fauna................................................ 50

4.4.2 Nitrate - Potential for chronic toxicity........................................................ 50

4.4.3 Nutrients - Non-compliance with OFW designation ................................. 51

4.4.4 Total Coliform Impairment........................................................................ 51

4.5 Pollutant Target Concentrations...................................................................... 51

4.5.1 Nutrients .................................................................................................. 51

4.5.2 Nitrate ...................................................................................................... 51

4.5.3 Total Phosphorus..................................................................................... 54

4.5.4 Total Coliform Bacteria ............................................................................ 57

4.6 Pollutant Load Reduction Goals...................................................................... 57

4.6.1 Nutrients .................................................................................................. 57

4.6.2 Total Coliform Bacteria ............................................................................ 61

4.7 Discussion and Conclusions ........................................................................... 61

5 LITERATURE CITED 64

6 APPENDICES 70

APPENDIX A. Descriptions of Natural Community Types found within the Wekiva 

River Basin. 

APPENDIX B. Work Plan - Pollutant Load Reduction Goal (PLRG) Analysis 

for the Wekiva River and Rock Springs Run. Final Report from Wetland Solutions 

Inc. (2004). 

xi
APPENDIX C. Pollutant Load Reduction Goal (PLRG) Analysis for the Wekiva River 

and Rock Springs Run, Florida. Final Report from Wetland Solutions Inc. (2005). 

APPENDIX D. Attached Algae Survey on the Wekiva River and Rock Springs Run. 

Final Report from GreenWater Labs (2005). 

APPENDIX E. Potential Nitrate Toxicity to Aquatic Animals in the Wekiva River and 

Rock Springs Run. 

APPENDIX F. Coliform Analysis in the Wekiva River and Rock Springs Run. 

APPENDIX G. Total Phosphorus Thresholds and Concentration Targets for Growth 

of Cyanobacteria and Chlorophyta in the Attached Algal Community. Additional 

Analysis of Greenwater Labs Data. 

APPENDIX H. Analysis of Periphyton and Nitrate Levels in the Suwannee River. 

Excerpted from: Hornsby, D., R. A. Mattson, and T. Mirti. 2000. Surfacewater 

Quality and Biological Monitoring. Annual Report. 1999. Suwannee River Water 

Management District Technical Report WR-00-04. iv, 148 pp. (.pdf file) 

APPENDIX I. Nutrients in Less Impacted Spring-Run Streams and in 130 Florida 

Springs. 

APPENDIX J. Epiphytes on Submerged Aquatic Vegetation in Headsprings 

of the Ichetucknee River, Florida. Excerpted from: PBS&J. 2004. Mapping and 

Monitoring Submerged Aquatic Vegetation in Ichetucknee Springs – 2004. Report 

submitted to the Suwannee River Water Management District, Live Oak, FL. Pp. 

variously numbered; 6 Appendices. 

xii
LIST OF FIGURES 

Figure 1-1. The Wekiva River system, showing major tributaries and 30 contributing 

springs. ....................................................................................................... 2 

Figure 2-1. The Wekiva River basin, spring recharge area, and 2004 Wekiva Study 

Area. .......................................................................................................... 7 

Figure 2-2. Potentiometric surface of the Floridan Aquifer in the Wekiva Study area. .. 9 

Figure 2-3. Location of springs and flow gaging stations in the Wekiva River system. 11 

Figure 2-4. Mean daily flows in the Wekiva River prior to and during the studies 

conducted for the PLRG effort, showing median flows for the period of record (1935-

2005), for the study period (Sept. 2004 to Aug. 2005), and dates of passage of 

hurricanes. ................................................................................................ 12 

Figure 2-5. Temporal trends in nitrate and total phosphorus in the Wekiva River for the 

period of record. . ......................................................................................... 16 

Figure 2-6. Temporal trends in nitrate and total phosphorus in Rock Springs Run for the 

period of record. ......................................................................................... 17 

Figure 2-7. Spatial trends in nitrate and total phosphorus in the Wekiva River for the 

period of record. .......................................................................................... 18 

Figure 2-8. Spatial trends in nitrate and total phosphorus in Rock Springs Run for the 

period of record. .......................................................................................... 19 

Figure 2-9. 2000 land use and land cover, showing forest and wetland areas in the 

Wekiva Study Area. ...................................................................................... 20 

Figure 4-1. Mean nitrate and total phosphorus concentration in intensive-study 

segments of the Wekiva River, Rock Springs Run, Alexander Spring Creek and Juniper 

Creek (from WSI, 2005). ................................................................................ 40 

Figure 4-2. Mean gross primary productivity and ecological efficiency in the Wekiva 

River, Rock Springs Run, Alexander Spring Creek, and Juniper Creek (from WSI, 

2005). ..................................................................................................... 41 

Figure 4-3. Nitrate concentration in the Wekiva River and Rock Springs Run, showing 

selected toxicity thresholds for aquatic insects, amphibians, and mosquitofish. ....... 44 

xiii
Figure 4-4. Plot of percent Cyanobacteria (= ”BG algae”) and Chlorophyta (= ”G algae”) 

versus total phosphorus concentrations in the attached algal community in the Wekiva 

River and Rock Springs Run. ....................................................................... 47 

Figure 4-5. Plots showing relationships between mean nitrate concentration and mean 

periphyton cell density and biomass from long term monitoring stations on the 

Suwannee River. ....................................................................................... 48 

Figure 4-6. Chart showing nitrate concentration targets that were considered and mean 

concentration targets proposed for the Wekiva River and Rock Springs Run. ........... 55 

Figure 4-7. Chart showing total phosphorus concentration targets that were considered 

and mean concentration targets proposed for the Wekiva River and Rock Springs 

Run. ........................................................................................................ 56 

Figure 4-8. Map showing Wekiva River system segments and current conditions for 

Nitrate (NOx) and total phosphorus (TP). ........................................................ 59 

xiv
LIST OF TABLES 

Table 2-1. Hydrogeologic framework for the Wekiva region.. .................................. 8 

Table 2-2. Summary of stream-flow characteristics for the Wekiva River and Rock 

Springs Run. ................................................................................................10 

Table 2-3. Summary of water quality data from the Wekiva River and Rock Springs 

Run. Values are means of available data for the period of record indicated. ........... 13 

Table 2-4. Results of SJRWMD 2004 water quality analyses. ............................... 14 

Table 2-5. Taxa primarily associated with, or that reach high abundance in, spring-run 

streams. .................................................................................................... 23 

Table 2-6. Listed and endemic taxa largely dependent upon aquatic and wetland 

habitats that occur in the Wekiva River system. ................................................. 26 

Table 2-7. Urban and developed land use in the surface drainage area of the Wekiva 

River and Rock Springs Run. ......................................................................... 28 

Table 4-1. Issues that were considered in determining impairment of the Wekiva River 

and Rock Springs Run. ................................................................................. 36

Table 4-2. Potential nitrate-nitrite (NOx) concentration targets based on various lines of 

investigation.. .............................................................................................. 52 

Table 4-3. Potential total phosphorus (TP) concentration targets based on various lines 

of investigation. ........................................................................................... 53 

Table 4-4. Segments in the Wekiva River and Rock Springs Run used for determination 

of nutrient load reductions. .. .......................................................................... 60 

Table 4-5. Percent load reduction in nitrate, total phosphorus, and total coliform 

bacteria required to meet target mean concentrations proposed and applicable water 

quality standards in the Wekiva River and Rock Springs Run. ............................... 60 

xv
LIST OF ACRONYMS AND ABBREVIATIONS 

AFDW - ash free dry weight 

cfs - cubic feet per second 

EOG - Executive Office of the Governor 

FAC - Florida Administrative Code 

FCREPA - Florida Committee on Rare and Endangered Plants 

 and Animals 

FDEP - Florida Department of Environmental Protection 

FNAI - Florida Natural Areas Inventory 

FS - Florida Statutes 

g - grams 

IWR - Impaired Waters Rule 

m2 - square meters 

mi2 - square miles 

MFL - Minimum Flows and Levels 

mg/L - milligrams per liter 

mgd - million gallons per day 

MSJRB - Middle St. Johns River Basin 

MSL - mean sea level 

NOx - Nitrate-nitrite (NO3/NO2) – nitrogen 

N - Nitrogen 

P - Phosphorus 

PLRG - Pollutant Load Reduction Goal 

SCI - Stream Condition Index 

SJRWMD - St. Johns River Water Management District 

SR - State Road 

SWFWMD - Southwest Florida Water Management District 

SWIM - Surface Water Improvement and Management 

TMDL - Total Maximum Daily Load 

TP - Total Phosphorus 

USEPA - U.S. Environmental Protection Agency 

WBID - Water Body Identification 

WQI - Water Quality Index 

WRBCC - Wekiva River Basin Coordinating Committee 

WSA - Wekiva Study Area 

xvi
1 INTRODUCTION 

The Wekiva River, its main tributaries (Rocks Springs Run, Little Wekiva River, and 

Blackwater Creek) and their 30 contributing groundwater springs (Figure 1-1) are 

resources of regional and statewide significance (Wekiva River Basin Coordinating 

Committee, 2004). Public conservation lands in the Wekiva River basin are some of the 

last remaining large natural areas in central Florida, a rapidly urbanizing region. The 

Wekiva River and its primary upstream tributary, Rock Springs Run, are classified by 

the Florida Natural Areas Inventory as spring-run streams and are considered imperiled 

in Florida. 

1.1 Wekiva River Protection Area 

Efforts to protect the Wekiva River basin began in 1988 when Governor Bob Martinez 

appointed the Wekiva River Task Force to recommend strategies to protect the Wekiva 

River basin (EOG #88-26). As a result of this group’s work, the Florida Legislature 

passed the Wekiva River Protection Act (Chapter 369, Part II, Florida Statutes [FS]). 

The purpose of this Act was to protect the ground and surface water resources of the 

Wekiva River basin through establishment of a “Wekiva River Protection Area” within 

which local governments were required to meet additional criteria in their 

comprehensive land-use plans (established in the statute). The Legislature also 

amended the Water Resources Act (Chapter 373, Florida Statutes [FS]) to require 

development of Minimum Flows and Levels (MFL) for the river and development of a 

scientifically defensible buffer adjacent to the river and its tributaries (Chapter 373.415, 

FS). The Wekiva River Protection Act of 1988 also required development of basinspecific criteria for surface water management permits issued in the basin. Basinspecific criteria addressed drawdown of surface water, erosion control, riparian habitat 

protection zones, and local government authorization within the Wekiva River Protection 

Area. 

1.2 Wekiva Parkway and Protection Act 

In 2002, Governor Jeb Bush appointed the Wekiva Basin Area Task Force (EOG 

#2002-259) to make recommendations on the best route for a limited-access 

expressway to connect State Road (SR) 429 and Interstate 4 in Seminole and Orange 

Counties. The Task Force was directed to make protection of the Wekiva River 

ecosystem a priority. This group submitted a report to the Governor in January 2003. 

Governor Bush then appointed the Wekiva River Basin Coordinating Committee 

(WRBCC) to expand on the Task Force recommendations and develop implementation 

strategies (EOG #2003-112). 

As a result of the recommendations of the WRBCC, the Florida Legislature passed the 

Wekiva Parkway and Protection Act in 2004 (Chapter 369, Part III, FS). One element 

instructed the St. Johns River Water Management District (SJRWMD) to develop 

Pollutant Load Reduction Goals (PLRGs) for the Wekiva Study Area: 

1
Figure 1-1. The Wekiva River system showing major tributaries and 30 contributing 

springs.

2
 “By December 1, 2005, the St. Johns River Water Management District shall establish 

pollution load reduction goals for the Wekiva Study Area to assist the Department of 

Environmental Protection in adopting total maximum daily loads for impaired waters 

within the Wekiva Study Area by December 1, 2006” (Chapter 369.318 [8], FS) 

The WRBCC identified the Wekiva River and its primary upstream tributary, Rock 

Springs Run, as high-priority for protection. Consequently, SJRWMD focused its initial 

efforts, beginning in the summer of 2004, on development of PLRGs for these two 

important spring-run streams. This report and its recommendations were prepared to 

address the PLRG requirements of the Wekiva Parkway and Protection Act. 

1.3 Other Protective Designations 

1.3.1 Surface Water Improvement and Management Program 

The Wekiva River basin is part of SJRWMD’s Surface Water Improvement and 

Management (SWIM) Program for the Middle St. Johns River Basin. The primary goal of 

the SWIM program is protection and restoration of aquatic resources of the Middle St. 

Johns River Basin (SJRWMD, 2002). Specific goals set forth in the Middle Basin SWIM 

plan include: 

• To preserve natural and functional components of the ecosystem while restoring, 

where feasible, such conditions to the degraded portions of the system; 

• To preserve, or where necessary restore, the quantity and quality of water 

necessary to support thriving biological communities, containing appropriate 

diversities of native species within the riverine and lacustrine systems of the St. 

Johns River Middle Basin; 

• To pursue the development and implementation of stormwater management 

plans. 

Developing PLRGs for the Wekiva River and Rock Springs Run implements goals 

stated in the Middle St. Johns River Basin SWIM Plan. 

1.3.2 Outstanding Florida Waters 

The Wekiva River is designated an Outstanding Florida Water (OFW; Chapter 62-

302.700, Florida Administrative Code [FAC]). This designation is conferred on water 

bodies within state and federal conservation areas and that have exceptional 

recreational or ecological significance (Chapter 62-302.700 [5], FAC). An important rule 

requirement is that discharges to OFWs cause no degradation of water quality (Chapter 

62-302.700[1], FAC). 

1.3.3 Aquatic Preserve 

The Wekiva River is in the Wekiva River Aquatic Preserve, first designated in June 

1975 by the Florida Legislature. The Preserve includes the Wekiva River, Rock Springs 

3
Run, portions of the Little Wekiva River and Blackwater Creek, and a portion of the 

Middle St. Johns River (added in 1985). Aquatic Preserves are areas of submerged 

land with exceptional biological, aesthetic, and scientific value (Chapter 258.36, FS). 

They are established and managed “for the purpose of being preserved in an essentially 

natural or existing condition so that their aesthetic, biological and scientific values may 

endure for the enjoyment of future generations” (Chapter 18-20.001 [2], FAC). 

1.3.4 National Wild and Scenic River 

Most recently, the Wekiva River and portions of its major tributaries were designated 

Florida’s third National Wild and Scenic River system (U.S. House of Representatives 

Bill H.R. 3155). This is a federal designation applied to rivers considered worthy of 

protection due to their ecological and aesthetic attributes and recreational value. The 

Wild and Scenic designation imposes additional requirements for federal activity that 

may affect the river and is an additional designation that recognizes the environmental 

and recreational value of this river system. 

1.4 Pollutant Load Reduction Goals 

Pollutant Load Reduction Goals are defined as “the estimated numeric reductions in 

pollutant loadings needed to preserve or restore designated uses of receiving bodies of 

water and maintain water quality consistent with applicable state water quality 

standards” (Chapter 62-40.210 [20], FAC). The legal basis for PLRGs is found in state 

law. 

• Chapter 373.016 (FS) indicates that it is state policy to “minimize degradation of 

water resources caused by the discharge of stormwater; and to preserve natural 

resources, fish, and wildlife . . .” 

• The State Water Resource Implementation Rule (Chapter 62-40, FAC) indicates 

that it is state policy to “Restore and protect the quality of ground and surface 

water by solving current problems and ensuring high quality treatment for 

stormwater and wastewater.” (Chapter 62-40.310 [2][a], FAC). 

PLRGs are part of the Surface Water Improvement and Management (SWIM) planning 

process. They may also be developed as part of a watershed management plan or may 

be adopted as part of a basin-specific rule (Chapter 62-40.430 [5][d], FAC). For the 

Wekiva River and Rock Springs Run, PLRGs were developed as required by the 

Wekiva Parkway and Protection Act. 

The PLRG process involves several steps: 

1. Determine the nature and extent of impairments, if any. 

4
Collect and analyze data to determine if the stream’s designated-use is impaired 

because of a violation of water-quality standards and/or because of an imbalance of 

flora and fauna. 

2. Identify the causative pollutants, if any. 

Assess the degree to which pollutant(s) such as nutrients are the cause of 

impairment. Impairments may stem from factors other than pollutants, such as 

altered hydrology, physical damage to biota, exotic species, species losses, and 

altered bathymetry. Impairments such as these cannot be addressed by PLRGs. 

3. Determine concentration of causative pollutants that will not result in 

impairments. 

Identify concentrations of pollutants that are safely below the levels associated with 

impairment. 

4. Calculate necessary pollutant load reductions. 

Relate acceptable pollutant targets to pollutant concentrations, and where feasible 

calculate pollutant load reductions needed to meet the target concentration. 

5
2 WEKIVA RIVER SYSTEM DESCRIPTION 

The Wekiva River Study Area (“WSA”; Figure 2-1) was delineated by the WRBCC 

(2004) and encompasses 473 square miles. The word Wekiva (alternate spelling 

Wekiwa – which is applied to the spring itself) derives from the Seminole/Creek for 

“spring” or “spring of water” (Morris 1995). Human use of the river dates back about 

12,000 years before present (Weisman 1993) when small groups of hunter-gatherers 

obtained freshwater, game, and fish from the river and its headspring, called Wekiwa 

Spring. Over the past century the river floodplain has served as a source of timber, and 

its springs as a respite for their “healing waters”, with various resorts and spas nearby. 

The Wekiva River and Rock Springs Run and their headsprings currently provide a 

variety of recreational opportunities including canoeing, swimming, snorkeling, tubing, 

boating, and fishing.

2.1 Physiography and Geology 

Physiography. The area that includes the Wekiva River surface water basin and 

“springshed” (the groundwater contributing area; Figure 2-1) lies within portions of the 

Marion Upland, Orlando Ridge, and Osceola Plain physiographic regions (Schmidt 

1997). Land elevations range from a high of 175 feet above mean sea level (MSL) in 

the western part of the region to a low of 10 feet above MSL at the confluence of the 

Wekiva River and Blackwater Creek (WSI 2004). Five marine terraces in the region 

were formed by sediment deposition and reworking during periods of higher sea level 

(Schmidt 1997). Wekiwa Spring and Rock Springs appear to emerge at the base of the 

Penholloway Terrace, which exhibits about 40 feet of relief. In the western and 

southern portions of the region, the land is a series of high (>75 feet above MSL) 

terraces and ridges with well-draining sandy soils. In the eastern and northeastern 

portions of the region, land elevations are generally < 25 feet above MSL with poorly 

draining wetland and flatwoods soils. 

The region also lies within the Southern Coastal Plain ecoregion (Berndt et al. 1996) 

and encompasses two stream-type subecoregions (Griffith et al. 1994); the Eastern 

Florida Flatwoods and Central Florida Ridges and Uplands. The Eastern Flatwoods 

subregion is characterized by variable soils, ranging from moderately draining sandy 

soils of the flatwoods to poorly draining clay or muck soils of wetlands. The Central 

Ridges subregion is characterized by deep, moderate- to well-draining sands supporting 

sandhill, scrubby flatwoods, or scrub ecosystems. 

Geology and Hydrogeology. The Wekiva River basin and springshed lie in a karstinfluenced landscape. The top of the limestone unit bearing the Floridan Aquifer 

(‘Floridan’) lies 50 to 100 feet beneath land surface (Osburn et al. 2002). A generalized 

hydrogeologic framework of the region is presented in Table 2-1. This region of the 

SJRWMD is where the Floridan is at or near land surface (Osburn, et al. 2002). Many 

of the lakes in the region were likely formed from solution (sinkhole) processes. The 

karst nature of the area means that there is a high degree of interconnection between 

surface water and groundwater. 

6
Figure 2-1. The Wekiva River basin, spring recharge area, and 2004 Wekiva Study 

Area. Source: SJRWMD data. 

7
Table 2-1. Hydrogeologic framework for the Wekiva region (adapted from Osburn et al. 

2002). 

Hydrogeologic Unit Epoch Stratigraphic Unit 

Surficial Aquifer System Holocene and 

Pleistocene 

Surficial sands and 

marine terrace deposits 

Intermediate Aquifer 

System (or intermediate 

confining unit) 

Pliocene Undifferentiated deposits 

Miocene Hawthorne Group 

Floridan Aquifer System Oligocene Suwannee Limestone 

Eocene Ocala Limestone 

Avon Park Formation 

Oldsmar Formation 

The Floridan Aquifer is the main water source for springs that discharge to the Wekiva 

River and its tributaries (Toth and Fortich 2002; Osburn et al. 2002). Figure 2-2 shows 

the potentiometric surface of the Floridan Aquifer in the Wekiva region in 2002. Water 

flow is perpendicular to the contours of the potentiometric surface. The principal areas 

of rainfall recharge to the Floridan are in the western and southern portions of the region 

(Osburn et al. 2002), with recharge of up to 12” of rainfall annually. Much of the lengths 

of the Wekiva River and Rock Springs Run lie within the discharge zone of the Floridan 

Aquifer, resulting in a predominance of spring flow in these streams. 

Water quality of the Floridan Aquifer in the Wekiva region is generally hard and high in 

dissolved calcium bicarbonate, reflecting the limestone matrix of the aquifer. Toth and 

Fortich (2002) identified areas of the Floridan aquifer in the region with elevated levels 

of nitrate, which they defined as >0.2 mg/L nitrate-nitrogen. Other sources (e.g., Scott 

et al. 2004 and references therein) define “natural background” for nitrate in the Floridan 

Aquifer as <0.05 mg/L.

2.2 Climate and Hydrology 

Climate Characteristics. Climate in the region is subtropical. Mean annual air 

temperature is 72 degrees F, ranging from an average monthly high of 90-95 degrees F 

during the summer (August/September) to an average monthly low of 59-60 degrees F 

in winter (December/January). Rainfall across the region averages 51.5 inches 

annually (WSI 2004). The highest annual rainfall in the period of record is 75 inches 

and the lowest annual total is 30 inches (WSI 2004). The majority of the rainfall occurs 

between June and September in association with convectional thunderstorms. Highest 

monthly total rainfall in the region is about 7-8 inches, typically in August, and lowest is 

about 2-3 inches in April (Fernald and Purdum, 1998). WSI (2004) found no apparent 

long-term temporal trend in rainfall based on data from seven stations in or near the 

Wekiva River. 

8
Figure 2-2. Potentiometric surface of the Floridan Aquifer in the Wekiva Study Area. 

Source: SJRWMD data.

9
Hydrology of the Wekiva River and Rock Springs Run . Stream flows in the Wekiva 

River basin are derived from surface drainage from the watershed and groundwater 

inflow from the Floridan Aquifer. Location of springs and stream flow-gaging stations in 

the basin are shown in Figure 2-3. A summary of stream-flow characteristics for the 

Wekiva River and Rock Springs Run are shown in Table 2-2.

Spring inflow appears to account for a majority of base flow in the Wekiva River. Thirty 

springs have been identified in the Wekiva River basin (Figure 2-3). Mean flows in 

these springs range from 67.1 cfs (Wekiwa Spring) to <1cfs in a number of the smaller 

springs. All appear to be fed by the Floridan Aquifer (Toth and Fortich 2002; WSI 

2004). Average flow of Wekiwa Spring, Rock Spring and Miami Spring total about 135 

cfs (Hupalo et al. 1994). Using the 2-year/30-day low flow of 202 cfs as typical base flow 

in the river at SR 46 (10 miles downstream of Wekiwa Spring), spring flow represents at 

least 67% of the base flow of the Wekiva River. This figure is probably low because it 

does not include groundwater inflow from other springs and other base flow sources. 

FDEP (2003) stated that spring inflow accounted for 64% of the base flow of the Wekiva 

River. Because of the predominance of spring flow in these streams, water quality in 

the springs exerts a major influence on water quality in the spring-run streams. 

Three tropical storm systems (Hurricanes Charley, Frances, and Jeanne) crossed the 

Wekiva basin in 2004, increasing flows in the Wekiva River (Figure 2-4) and Rock 

Springs Run. This caused atypically high flows and resulted in scouring of vegetation, 

higher water color due to leaching of tannins from the floodplain forests, and transfer of 

sediment. 

Table 2-2. Summary of stream-flow characteristics for the Wekiva River and Rock 

Springs Run. 

Mean 

Flow 

(cfs) 

Median 

Flow 

(cfs) 

Minimum 

Flow 

(cfs) 

Maximum 

Flow 

(cfs) 

Wekiva River 

(at State Road 46) 

290.7 253 105 2,060 

Rock Springs 

(in Kelly Park) 

60.1 59.2 48.2 72.1 

2.3 Water Quality – Description, Status, and Trends 

2.3.1 Water Quality Description 

The Wekiva River and Rock Springs Run are hardwater streams with relatively high 

conductivity and alkalinity, indicating water rich in dissolved minerals (Table 2.3). Color 

increases downstream in the Wekiva River and Rock Springs Run due to inflow of 

surface water from the adjacent drainage area. During the course of these studies, 

10
Figure 2-3. Location of springs and flow gaging stations in the Wekiva River system. 

11
Wekiva River at SR 46

0

200400600800

1000120014001600

7/1/2004

7/15/2004

7/29/2004

8/12/2004

8/26/2004

9/9/2004

9/23/2004

10/7/2004

10/21/2004

11/4/2004

11/18/2004

12/2/2004

12/16/2004

12/30/2004

1/13/2005

1/27/2005

2/10/2005

2/24/2005

3/10/2005

3/24/2005

4/7/2005

4/21/2005

5/5/2005

5/19/2005

6/2/2005

6/16/2005

Flow (cfs)

Mean Daily Flow POR Median Median Sep04 to Aug05

Charley Frances Jeanne

Figure 2-4. Mean daily flows in the Wekiva River prior to and during the studies conducted for the PLRmedian flows for the period of record (1935-2005), for the study period (Sept. 2004 to Aug. 2005), and of hurricanes.

12
Table 2-3. Summary of water quality data from the Wekiva River and Rock Springs 

Run. Values are means of available data for the period of record indicated. Source: 

WSI 2004. e = estimated by adding TKN and NOx-N. 

Analyte Wekiva River @ SR 46 

Rock Springs Run 

above Wekiva River 

Period of Record 1954-2003 1973-2003 

Conductivity (ųmhos/cm) 624 244 

pH (units) 7.42 7.31 

Alkalinity (mg/L as CaCO3) 94.9 86.6 

Color (pcu) 61.5 203 

Turbidity (NTU) 3.34 1.60 

Dissolved O2 (mg/L) 7.10 5.84 

Total Organic Carbon (mg/L) 8.31 21.9 

Total Nitrogen (mg/L) 1.25 1.68 e 

Total Kjeldahl Nitrogen (mg/L) 0.632 0.896 

NO3/NO2-N (mg/L) 0.578 0.784 

Ammonia (mg/L) 0.045 0.047 

Orthophosphorus (mg/L) 0.108 0.084 

Total Phosphorus (mg/L) 0.141 0.118 

Chlorophyll a - corrected (ųg/L) 1.70 2.90 

Fecal Coliform (#/100ml) 100 54.2 

Total Coliform (#/100 ml) 1,351 1,649 

water levels were high and subsequently color was high due to contribution of tannins 

from the floodplain forests. Nitrate levels in the headsprings are relatively high (1.4-1.5 

mg/L) but decline downstream, probably due to a combination of dilution and biological 

uptake (WSI 2004). Rock Springs Run exhibits higher color and total organic carbon 

than the Wekiva River. 

2.3.2 Water Quality Status and Trends 

FDEP Bioassessment. FDEP conducted habitat assessments, water quality sampling, 

and macroinvertebrate and algal assessments for the Wekiva River and Rock Springs 

Run in 1999 as part of their Statewide Stream Bioassessment Program (FDEP 2000). 

Results indicated nitrate enrichment in both streams because nitrate concentrations 

exceeded those found in 95% of other Florida streams. Ammonia, total Kjeldahl nitrogen 

and total phosphorus levels approximated the statewide stream median. 

Habitat Assessment scores at all sites in both streams fell within the optimum range for 

peninsular streams. Macroinvertebrate Stream Condition Index scores were all in the 

good or excellent range based on reference levels for peninsular streams (FDEP 2000). 

Average Algal Growth Potential (AGP) scores exceeded the “problem threshold”, 

13
indicating that nutrient levels were high enough to potentially support high levels of algal 

growth in both streams. 

SJRWMD Water Quality Analysis. In 2004, SJRWMD staff analyzed water quality 

status and trends for the Wekiva River and Rock Springs Run using data from stations 

located in the spring-run streams. Water quality variables examined were water clarity 

(turbidity or Secchi depth), bacteria (total and fecal coliform), oxygen demand, dissolved 

oxygen levels, and nutrients. Water quality in the Wekiva River and Rock Springs Run 

was also compared to about 50 other springs in the SJRWMD. 

For both the Wekiva River and Rock Springs Run, nitrate (NOx), and total phosphorus 

(TP) were high relative to springs in the SJRWMD, status was poor for nitrate and total 

coliform bacteria (based on FDEP criteria), and there was a degrading trend in total 

coliform bacteria in both streams (Table 2-4). Since the Outstanding Florida Waters 

designation for both streams, total coliform bacteria levels had degraded (=increased). 

For Rock Springs Run, nitrate had also degraded since OFW designation. 

Table 2-4. Results of SJRWMD 2004 water quality analyses. 

Nitrate Total Phosphorus Total Coliform 

Bacteria 

Wekiva River high relative to 

springs in SJRWMD 

poor status 

high relative to 

springs in SJRWMD 

poor status 

degraded since OFW 

designation 

degrading trend 

Rock 

Springs Run 

high levels relative to 

springs in SJRWMD 

poor status 

degraded since OFW 

designation 

high relative to 

springs in SJRWMD 

poor status 

degraded since OFW 

designation 

degrading trend 

14
SJRWMD staff conducted additional statistical analyses of water quality trends in 2005 

with a more comprehensive data set than used in 2004. Total phosphorus decreased in 

both the Wekiva River and Rock Springs Run since 1974 (Figures 2-5 and 2-6), with 

decreases in both wet and dry seasons. Nitrate concentration decreased in the Wekiva 

River since 1984 (Figure 2-5) due to wet season decreases. Nitrate did not decrease in 

Rock Springs Run since 1984 (Figure 2-6) except during the wet season. 

There were statistically significant decreasing downstream trends in nitrate 

concentration in both the Wekiva River and Rock Springs Run (Figures 2-7 and 2-8), 

which was evident in both the wet and dry seasons. These decreasing downstream 

trends in nitrate are partly due to dilution, but they also suggest that a considerable 

fraction of the nitrate load from the headsprings is being assimilated in the spring-run 

streams, with lesser amounts exported downstream to the St. Johns River. There was 

no downstream trend in total phosphorus in either stream (Figures 2-7 and 2-8), 

although Rock Springs Run showed an increasing downstream trend in total 

phosphorus during the wet season. 

 

2.3.3 Water Quality Issues 

Nitrate concentrations are elevated in many springs throughout Florida due to urban 

and agricultural development in the spring recharge areas (Florida Springs Task Force 

2000; Scott et al. 2004; Osburn et al. 2002; Toth and Fortich 2002). Consequently, 

spring-run streams receive unnaturally high loads of nitrate, causing concern about 

potential impacts to aquatic flora and fauna. Recent observations of large amounts of 

algal growth in springs and spring-run streams, and perceptions that large amounts of 

algae constitute a “nuisance,” have led to speculation that elevated nitrate levels cause 

excessive algae growth, with possible detrimental impacts associated with this algal 

growth. 

As a result of these concerns, the Wekiva Parkway and Protection Act directed FDEP to 

study and, if appropriate, initiate rulemaking for enhanced water quality and central 

wastewater treatment standards to achieve nitrogen reductions in surface water and 

groundwater. The Florida Department of Health was directed to study the effects of onsite waste disposal systems in the Wekiva Study Area, and if necessary to institute 

rulemaking to develop criteria to reduce nitrogen loading to surface and ground water 

from on-site systems. For these reasons, SJRWMD emphasized investigations into 

nitrates and algae growth in the PLRG development process. 

2.4 Ecological Overview 

Natural Community Types. Large portions of the Wekiva River basin are public 

conservation lands containing high quality natural communities. These are listed here 

and briefly described in Appendix A, using the Florida Natural Areas Inventory (FNAI) 

classification system (FNAI and FDNR 1990). Figure 2-9 shows natural community 

types based on the Florida Land Use, Cover and Forms Classification System 

(FLUCFCS). Natural community types include: 

15
0

200

400

600

800

1000

1200

1400

1600

1800

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

NOx (μg/L)

2000

0

100

200

300

400

500

600

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

Figure 2-5. Temporal trends in nitrate and total phosphorus in the Wekiva River for the 

period of record. Line indicates statistically significant decreasing trend. Total P (μg/L)

16
0

200

400

600

800

1000

1200

1400

1600

1800

2000

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

NOx (μg/L)

0

100

200

300

400

500

600

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

Total P (μg/L)

Figure 2-6. Temporal trends in nitrate and total phosphorus in Rock Springs Run for the 

period of record. Line indicates statistically significant decreasing trend. 

17
0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 5000 10000 15000 20000 25000

Distance from headspring (m)

NOx (μg/L)

0

100

200

300

400

500

600

0 5000 10000 15000 20000 25000

Distance from headspring (m)

Total P (μg/L)

Figure 2-7. Spatial trends in nitrate and total phosphorus in the Wekiva River for the 

period of record. Line indicates statistically significant decreasing trend. 

18
0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 3000 6000 9000 12000 15000

Distance from headspring (m)

NOx (μg/L)

0

100

200

300

400

500

600

0 3000 6000 9000 12000 15000

Distance from headspring (m)

g/L)

Figure 2-8. Spatial trends in nitrate and total phosphorus in Rock Springs Run for the 

period of record. Line indicates statistically significant decreasing trend Total P (μ

19
Figure 2-9. 2000 land use and land cover, showing forest and wetland areas in the 

Wekiva Study area. 

20
Upland Communities (FLUCFCS ‘4000 – Forest’)

Mesic Flatwoods 

Scrubby Flatwoods 

Sandhill 

Scrub 

Xeric hammock. 

Upland hardwood or Upland mixed forest 

Wetland Communities (FLUCFCS ‘6000 – Wetland’) 

Wet flatwoods 

Floodplain swamp 

Hydric hammock 

Baygall 

Freshwater marsh 

Aquatic Communities (FLUCFCS ‘5000 – Water’) 

Spring-run stream 

Blackwater stream 

Clastic upland lake 

Sandhill upland lake 

Aquatic Habitats. Aquatic habitats in the Wekiva River and Rock Springs Run were 

described in FDNR (1987), Hupalo, et al. (1994) and the National Park Service (1999). 

Overall, there have been few detailed biological studies of these two spring-run 

streams, and currently there is no regular program of biological monitoring. 

One of the principal aquatic habitats of the Wekiva River and Rock Springs Run are 

beds of submerged aquatic vegetation (SAV), primarily dominated by eelgrass, 

Vallisneria americana (WSI 2004; Canfield and Hoyer 1988). Other taxa of SAV 

present include spring-tape (Sagittaria kurziana), Brazilian elodea (Egeria densa), 

hydrilla (Hydrilla verticillata), variable-leaf milfoil (Myriophyllum heterophyllum), and 

sago pondweed (Potamogeton pectinatus). Associated with the SAV is a community of 

epiphytic algae growing attached to the leaves, which is a natural component of this 

habitat (Whitford 1956; Odum 1957). SAV beds provide important fish and 

macroinvertebrate habitat. Warren, et al. (2000) conducted macroinvertebrate surveys 

in SAV beds in the Wekiva River and found 127 taxa of invertebrates in these habitats. 

VanGenechten (1999) similarly found that SAV beds supported high fish densities 

compared to other habitats in the Wekiva River. 

Submerged wood debris, generally referred to as “snag habitat”, is a second important 

aquatic habitat. Studies in other southeastern coastal plain streams have documented 

the importance of wood snag habitat to macroinvertebrates and fishes (Benke et al. 

1984; Benke et al. 1985). Warren et al. (2000) found a total of 163 taxa of 

macroinvertebrates on snag habitat in the Wekiva River. Many of these taxa are 

important components of the diet of redbreast and spotted sunfish (Benke et al. 1985), 

two important sportfish on the river. 

21
Bare sediment (mud or sand) is a third major aquatic habitat type in the streams, and 

supports a diverse assemblage of macroinvertebrates. Warren et al. (2000) found 

highest total invertebrate taxa richness in this habitat in the Wekiva River (166 taxa). 

Invertebrate densities (#/m2

) were also high in this habitat. A number of fish taxa 

(catfish, sucker, and minnows) generally prefer to forage on bare sediments as opposed 

to vegetated habitats. 

Areas of floating and emergent aquatic vegetation are a fourth aquatic habitat. Areas of 

floating vegetation (primarily pennywort, Hydrocotyle spp.) support diverse 

macroinvertebrate and abundant fish populations (Warren et al. 2000). However other 

areas of this habitat, particularly monospecific beds of cattail (Typha sp.), are poor 

habitat for invertebrates and fish. 

Aquatic Fauna. Major groups of fauna on the Wekiva River and Rock Springs Run are 

benthic macroinvertebrates, fishes, herpetofauna (reptiles and amphibians) birds and 

mammals. Some of these taxa are, or tend to be, most associated with spring-run 

streams (Table 2-5). 

Benthic macroinvertebrates include aquatic insects, mollusks, worms and crustaceans 

associated with aquatic habitats. Warren et al. (2000) collected a total of 268 

invertebrate taxa in the Wekiva River, in 39 major taxonomic groups. Generally, the 

non-biting midges (Chironomidae) dominated the invertebrate diversity and abundance 

in most habitats. Mayflies (Ephemeroptera), caddisflies (Trichoptera), aquatic beetles 

(Coleoptera) and amphipods were the other abundant groups in the river. Eight taxa of 

hydrobiid snails (a group most frequently associated with springs and spring-run 

streams, with many endemics) were collected in this survey. 

A total of 51 species of fishes are known to occur in the river. Dominant taxa, by 

abundance, include sunfish, shiners, and killifish (Walsh and Williams 2003; 

VanGenechten 1999; Canfield and Hoyer 1988). VanGenechten (1999) determined 

that mats of floating vegetation and SAV beds constituted some of the best fish habitat 

in the Wekiva River in terms of fish taxa richness or abundance. Water depth and 

velocity appeared to be more important than water temperature and dissolved oxygen in 

explaining fish community structure. VanGenechten (1999) compared his fish data to 

those collected by Canfield and Hoyer (1988) about 10 years earlier and found no major 

changes in fish communities of the Wekiva River. 

We found few quantitative studies of other vertebrates (herpetofauna, birds and 

mammals) on the Wekiva River or Rock Springs Run. Aquatic Preserve staff have 

recently begun coordinating bird surveys in conjunction with volunteers (D. Shelley, 

Wekiva River Aquatic Preserve, personal communication). 

Species of Conservation Interest. Four federally-listed species occur in the basin along 

with many state-listed species and other rare and endemic species (Table 2-6). 

Additionally, searches for ivory-billed woodpeckers from 1987-1992 included the Wekiva 

22
Table 2-5. Taxa primarily associated with, or that reach high abundance in, spring-run streams. Adapt

(1990) and Mattson et al. (1995). All taxa listed here are known to occur in the Wekiva River basin exclikely to occur in the basin. 

Spring-run Stream 

“Best Habitat” 

Plants 

Eelgrass Vallisneria americana Springtape Sagittaria kurziana XX Chara Chara spp. 

Invertebrates 

Siltsnails Hydrobiidae (most freshwater taxa) XX River horn snails Elimia spp. XX Apple snail Pomacea paludosa Grass shrimp Palaemonetes paludosus Mayfly Stenacron spp. Mayfly Tricorythodes albilineatus Aquatic butterfly Paraponyx sp. Spiral-cased caddisfly (?) Helicopsyche spp. XX 

Fishes 

Longnose gar Lepisosteus osseus XX Florida gar Lepisosteus platyrhincus XX Golden shiner Notemigonus chrysoleucas Redeye chub (?) Notropis harperi XX Coastal shiner Notropis petersoni XX Sailfin shiner Pteronotropis hypselopterus XX Channel catfish Ictalurus punctatus XX Seminole killifish Fundulus seminolis XX White catfish Ameiurus catus XX 

23
Table 2-5. Continued. 

TAXON 

Spring run 

“Best Habitat” 

Bluefin killifish Lucania goodei Bluegill sunfish Lepomis macrochirus Redear sunfish Lepomis microlophus XX Spotted sunfish Lepomis punctatus XX 

Amphibians 

River Frog (?) Rana heckscheri XX 

Reptiles 

American alligator Alligator mississippiensis Florida snapping turtle Chelydra serpentina osceola XX Stinkpot Sternotherus odoratus Loggerhead musk turtle Sternotherus minor minor XX Florida red-bellied turtle Pseudemys nelsoni XX Brown water snake Nerodia taxispilota XX Rainbow snake Farancia erytrogramma erytrogramma XX 

Birds 

Great blue heron Ardea herodias Great egret Casmerodius albus Little blue heron Egretta caerulea Limpkin Aramus guarauna XX Wood duck Aix sponsa Swallow-tailed kite Elanoides forficatus Red-shouldered hawk Buteo lineatus Barred owl Strix varia Belted kingfisher Ceryle alcyon XX 

24
Table 2-5. Continued. 

TAXON 

Spring run 

“Best Habitat” 

Acadian flycatcher Empidonax virescens Prothonotary warbler Protonotaria citrea XX 

Mammals 

Southeastern myotis (?) Myotis austroriparius XX Red bat Lasiurus borealis XX Seminole bat Lasiurus seminolus Evening bat Nycticeius humeralis XX Florida manatee Trichechus manatus latirostris 

25
Table 2-6. Listed and endemic taxa largely dependent upon aquatic and wetland habitats that occur in 

system. U.S. = species officially listed under the Endangered Species Act; Florida = species listed by tFNAI = species listed by the Florida Natural Areas Inventory; FCREPA = species listed by the Florida Cand Endangered Plants and Animals. See bottom of table for definitions of status designations. 

TAXON Endemic U.S. Florida F

Plants 

Needle palm Rhapidophyllum hystrix T Cardinal flower Lobelia cardinalis T Hand fern Ophioglossum palmatum E Star anise Illicium parviflorum Y (?) E 

Invertebrates 

Wekiva springs hydrobe Aphaostracon monas Y Wekiva siltsnail Cincinnatia wekiwae Y Rock springs siltsnail Cincinnatia petrifons Y Sanlando siltsnail Cincinnatia ponderosa (extinct?) Y Seminole siltsnail Cincinnatia vanhyningi Y Rock springs horn snail Elimia vanhyningiana Y Orlando cave crayfish Procambarus acherontis Y S.E. spinyleg dragonfly Dromogomphus armatus Everglades sprite Nehalennia pallidula Y Microcaddisfly Orthotrichia instabilis Triaenode caddisfly Triaenodes furcella 

Fishes 

Bluenose shiner Pteronotropis welaka Y SSC 

Reptiles 

American alligator Alligator mississippiensis T SSC 

26
Table 2-6. Continued. 

TAXON Endemic U.S. Florida F

Birds 

Little blue heron Egretta caerulea SSC Snowy egret Egretta thula SSC Great egret Ardea alba Tricolored heron Egretta tricolor SSC Reddish egret Egretta rufescens SSC Limpkin Aramus guarauna SSC Yellow-crowned night heron Nyctanassa violacea Black-crowned night heron Nycticorax nycticorax White ibis Eudocimus alba SSC Glossy ibis Plegadis falcinellus Wood stork Mycteria americana E E Florida sandhill crane Grus canadensis pratensis Y T SSwallow-tailed kite Elanoides forficatus Peregrine falcon Falco peregrinus E S. E. American kestrel Falco sparverius paulus T Bald eagle Haliaeetus leucocephalus T T 

Mammals 

Florida black bear Ursus americanus floridanus Y T Florida manatee Trichechus manatus latirostris Y E E E=Endangered; T=Threatened; SSC=Species of Special Concern; R=Rare; S1=critically imperilled in Florida berarity or because of extreme vulnerability to extinction due to some natural or man-made factor; S2=imperilled in 

rarity or because of vulnerability to extinction due to some natural or man-made factor; S3=either very rare and found locally in a restricted range or vulnerable to extinction from other factors. 

27
River floodplain because these swamp forests were considered to be potential habitat 

for this endangered species (Jackson, 1996). In many cases, the water quality and 

habitat requirements of species of conservation interest are poorly understood in 

Florida, so the data do not exist to incorporate the needs of these taxa into this phase of 

PLRG development. 

Another relevant conservation issue is the documented global decline in amphibian 

diversity (Stuart et al. 2004; Sparling et al. 2000). In many regions of the world, 

amphibian species are disappearing or their range is dramatically declining. Related to 

this is an apparent increase in the incidence of deformities in amphibians (Sparling et al. 

2000). Mechanisms postulated for these include increasing levels of ultraviolet radiation 

due to degradation of the ozone layer, increased infestation of amphibian populations 

by parasites, toxicity from pesticides and other chemicals, and toxicity from nitrate due 

to fertilizer use (Marco et al. 1999; Rouse et al. 1999). 

2.5 Surrounding Land Use 

Current and past land use in the surface water drainage areas of the Wekiva River and 

Rock Springs Run were analyzed by WSI (2004). More intensive development (urban, 

suburban, and transportation) increased by about 350% between 1973 and 2000 (Table 

2-7), with much of the change occurring between 1973 and 1990. Nitrogen isotope 

analyses conducted by SJRWMD to evaluate sources contributing nitrates to Wekiwa 

Spring and Rock Springs indicated a combination of organic (wastewater, manure, etc.) 

and inorganic (fertilizer) sources, attributed largely to urban development in the spring 

recharge area (Toth and Fortich 2002). Although high nitrate concentrations were 

measured in the Floridan Aquifer beneath agricultural lands in the western part of the 

contributing area, Toth and Fortich believed that leachate from those agricultural lands 

was not influencing nitrate levels in Wekiwa Spring and Rock Springs. 

Table 2-7. Urban and developed land use in the surface drainage area of the Wekiva 

River and Rock Springs Run. Source: WSI 2004 (Appendix B). 

LAND USE (acres) 1973 1990 1995 2000 

Urban (including residential, 

commercial, & industrial) 4,390 15,010 16,090 17,492 

Transportation & Utilities 

(roads, powerlines, water 

supply, sewage, and 

generating facilities) 

42.5 483 526 612 

Total drainage area 59,280 59,280 59,280 59,280 

% urban and built up land 7.5% 26.1% 28.0% 30.5% 

28
3 DISTRICT STUDIES CONDUCTED FOR PLRG DEVELOPMENT 

Beginning in 2004, after passage of the Wekiva Parkway and Protection Act, SJRWMD 

contracted with private consultants to conduct investigations that would contribute to 

PLRG development for the Wekiva River and Rock Springs Run. District staff also 

reviewed scientific literature and analyzed water quality data. Information from these 

various lines of investigation was used to develop the pollutant concentration targets 

and related reductions recommended in this report. Following are brief descriptions of 

the objectives and methods of these concurrent efforts. Details can be found in the 

appendices. 

3.1 Ecosystem Metabolism in the Wekiva River, Rock Springs Run, and in 

Reference Spring-run Streams

Wetland Solutions Inc. (WSI) was contracted by SJRWMD in summer 2004 to compile 

and summarize existing data and information for the Wekiva River and Rock Springs 

Run and to develop a work plan for rapid PLRG development. WSI’s 2004 Work Plan 

Report is in Appendix B. 

The purpose of the work plan was to provide a scientifically based approach for 

verifying whether nutrients are elevated in the Wekiva River and Rock Springs Run, and 

to document nutrient impacts, if any, on ecosystem metabolism of these spring-run 

streams. Work plan methods included: 

1. Review and analysis of existing information on the Wekiva River and Rock 

Springs Run and similar reference spring-run streams to characterize a baseline 

for the streams’ designated uses 

2. Review of existing information and planning of focused studies to link specific 

nutrients to impaired conditions 

3. Implementation of those studies and analysis of resulting data 

4. Identification of nutrient reductions necessary to preserve or restore the Wekiva 

River and Rock Springs Run to an unimpaired condition. 

Two “reference” spring-run streams were recommended to help determine background 

conditions for the Wekiva River and Rock Springs Run. These were Juniper Creek and 

Alexander Springs Creek, both less impacted, low-nutrient spring-run streams in nearby 

Ocala National Forest. 

WSI was then contracted in fall 2004 to implement the Wekiva PLRG work plan. 

Impairment was evaluated by measuring ecosystem metabolism in upstream and 

downstream segments of the Wekiva River and Rock Springs Run and in comparable 

segments in Juniper Creek and Alexander Springs Creek, the two less impacted, 

reference spring-run streams in nearby Ocala National Forest. Tasks included: 

1. Reconnaissance of the four spring-run streams 

2. Water and nutrient mass-balance estimation for the four spring-run streams 

29
3. Detailed ecological evaluation under conditions of differing nutrient availability in 

segments in the Wekiva River, Rock Springs Run, Juniper Creek and Alexander 

Spring Creek 

4. Collection of ecosystem-level data (physical environment, water quality, plant 

communities, gross primary productivity, net primary productivity, ecological 

efficiency) 

5. Analysis and interpretation of data to evaluate impairment 

To identify pollutants of concern, ecosystem metabolism data from the Wekiva River 

and Rock Springs Run were compared to the reference streams to determine whether, 

and to what extent, nutrients affected ecosystem function. Water quality spatial trends 

were examined and compared to ecosystem data to look for onset of impairment. 

Nutrient concentrations and loads in the Wekiva River and Rock Springs Run were also 

compared to data from other Florida springs. 

 

Existing pollutant loadings were estimated for the four spring-run streams . This analysis 

also considered assimilation rates of nutrients and used the two reference streams to 

determine acceptable nutrient targets. Existing pollutant loads causing impairment were 

determined by calculation of water and nutrient mass balances. Overall nutrient mass 

balance loads and assimilation rates were estimated for the Wekiva River, Rock Springs 

Run, Alexander Springs Creek, and Juniper Creek. Diffuse runoff and nutrient loading 

rates for land use mapped in the year 2000 were used to estimate external 

contributions. Spring flows and nutrient concentrations were used to estimate 

groundwater loads. Upstream-downstream load changes were used to estimate 

assimilation rates in each stream reach. 

The relationship between pollutant loading rates and in-stream nutrient concentrations 

was determined using a simplified regression model relating nutrient mass loading rates 

to in-stream nutrient concentrations. This model includes estimated water and 

associated nutrient inputs from springs, non-point source runoff, tributaries, and from 

atmospheric inputs. Nutrient transformation rates were estimated from published 

reaction rates. Necessary pollutant load reduction was estimated as the difference 

between the existing pollutant load and the estimated load that will result in meeting the 

in-stream nutrient target, the concentration at which no impairment is likely to occur. 

Nutrient PLRGs were recommended for nitrate and total phosphorus, nutrient forms for 

which impairment is already occurring or for which impairment is considered to be likely 

in light of increasing trends in pollutant loading rates. Results of this work are presented 

in the pertinent sections of the PLRG Development chapter. Details on Wetland 

Solutions’ 2005 work can be found in Appendix C. 

3.2 Attached Algae in the Wekiva River and Rock Springs Run

GreenWater Labs Inc. was contracted to assess the distribution, composition and 

biomass of attached algae and to characterize habitats of attached algae in the Wekiva 

River and Rock Springs Run. A visual survey was conducted of attached algae in the 

Wekiva River and Rock Springs Run in 2004. Attached algae species composition, 

30
density and biomass were analyzed from 15 sites in Wekiwa Spring and the Wekiva 

River and 9 sites from Rock Springs and Rock Springs Run in winter 2004/05 and 

summer 2005. Algae were described and collected from various substrates (vegetation, 

rocks, and wood) at regular intervals along the streams. Algae growing on the sediment 

surface were not sampled. Field water quality parameters were measured concurrent 

with algal sampling, and water quality samples were collected for laboratory analysis. 

Results of this work are presented in the pertinent sections of the PLRG Development 

chapter. Details on this work can be found in GreenWater’s report in Appendix D. 

3.3 SJRWMD Review of Literature and Data 

SJRWMD staff conducted additional reviews of the scientific literature and analysis of 

available data to augment the contracted PLRG development work described above. 

Objectives and methods are summarized here. Results will be summarized in the 

upcoming PLRG Development chapter. Details for most of these efforts can be found in 

the appendices. Those not included in the Appendices can be obtained via the internet 

(URL links provided in the Literature Cited section) or are available from the scientific 

literature. 

3.3.1 Nitrate Toxicity to Aquatic Animals 

SJRWMD staff (Mattson et al. 2005) conducted a review of the scientific literature on 

nitrate toxicity to determine threshold levels of nitrate that have been demonstrated 

(experimentally or with field surveys) to cause adverse lethal or sub-lethal effects to 

aquatic animals. Toxicity values gleaned from the literature were in most cases derived 

from short-term acute laboratory assays. Uncertainty factors are a means of accounting 

for various sources of uncertainty, extrapolation from short-term laboratory results to 

long-term effects in the field, from one species to others, and from lethal thresholds to 

sublethal thresholds (Newman and Unger 2003). Uncertainty factors were applied to 

the literature-derived toxicity values to estimate protective threshold concentrations for 

nitrate. Details on this literature review and data analysis can be found in Appendix E. 

3.3.2 Coliform Bacteria Impairment 

SJRWMD staff (Lehmensiek 2005) analyzed water quality data collected by Orange 

County from 1997 through 2005 to determine if the Wekiva River and Rock Springs Run 

were impaired for total and fecal coliform bacteria levels according to numeric criteria in 

the Impaired Waters Rule (Chapter 62-303, FAC). Reductions in total coliform counts 

were calculated based on EPA’s percent-reduction method. Details on this coliform 

assessment can be found in Appendix F. 

3.3.3 Total Phosphorus Thresholds for Attached Algae Growth 

SJRWMD conducted additional analysis of the attached algae data collected by 

GreenWater Labs (2005) in the Wekiva River and Rock Springs Run to evaluate 

whether there was a relationship between phosphorus and the occurrence and 

31
proportion of algae generally considered to be “nuisance” taxa. These are primarily 

taxa in the Cyanobacteria and green algae (Chlorophyta). This additional analysis was 

prompted by the findings in the Upper St. Johns River basin (Keenan et al. 2003), which 

found that increased phosphorus accounted for increased biovolume of Cyanobacteria. 

The analysis is described in Appendix G 

3.3.4 Rainbow River Algal Bioassays 

The University of South Florida (Cowell and Dawes 2004) conducted laboratory assays 

for the Southwest Florida Water Management District (SWFWMD), examining nitrate 

levels and growth of the cyanobacterium, Lyngbya wollei, from the Rainbow River, a 

spring-run stream in western Marion County. 

 

3.3.5 Suwannee River Algae and Nutrients 

The Suwannee River Water Management District (Hornsby et al 2000) collected longterm (3 -10 years) quarterly data on periphyton in the Suwannee River and its major 

tributaries, concurrent with water chemistry sampling. These data were analyzed to 

evaluate relationships between algal abundance (as cell density and ash-free dry weight 

biomass) and nitrate. Relevant excerpts from their report are found in Appendix H. 

3.3.6 Nutrients in Less-Impacted Spring-Run Streams and in 130 Florida Springs 

Existing nitrate and total phosphorus data were retrieved from STORET for three Florida 

spring-run streams (Juniper Creek, Alexander Springs Creek, Wacissa River) 

considered to be less-impacted due to minimal urban and/or agricultural development in 

their springsheds, and for 130 Florida springs, including impacted springs. These data 

were analyzed and compared to the Wekiva River and Rock Springs Run. Results of 

these analyses are in Appendix I. 

3.3.7 Nutrients in Undeveloped Streams in the United States 

Clark et al. (2000) analyzed various forms of nitrogen and phosphorus and their yields 

from 85 sites representing relatively undeveloped watersheds in the continental U.S. 

Their data came from various U.S. Geological Survey water quality assessment 

programs conducted between 1990-1995. Binkley et al. (2004) extracted data from the 

published literature on nitrogen and phosphorus concentrations in 300 streams draining 

largely forested watersheds in the U.S. They examined regional and nationwide spatial 

trends in water quality using these data. 

3.3.8 Nitrate Targets for EPA’s TMDL 

The U.S. Environmental Protection Agency (USEPA 2005) issued a final Total 

Maximum Daily Load (TMDL) for nitrate in the Wekiwa Spring and Rock Springs Run in 

December 2005, as required by a Consent Decree. The TMDL was based on 

comparison with Juniper Spring, a less-impacted lower-nutrient spring-run stream in 

32
Ocala National Forest. A target concentration was selected based on the 90th percentile 

level of nitrate for Juniper Spring. The URL link to this report is listed in the Literature 

Cited section. 

 

3.3.9 Total Phosphorus and Epiphytic Algae in Ichetucknee Springs 

A contractor for Suwannee River Water Management District sampled epiphytic algae 

and water quality in headsprings contributing to the Ichetucknee River, a spring-run 

stream in Columbia County, Florida (PBS&J 2004). The relationship between nitrogen 

and phosphorus and algal biomass (as mg chlorophyll a per gram wet weight of host 

plant) was examined. Relevant excerpts from the final report from this effort are in 

Appendix J. 

3.3.10 Phosphorus in Florida Springs in the 1950’s 

The University of Florida (Odum 1953) collected phosphorus data from a variety of 

surface and ground waters in Florida (including springs) in the early 1950’s prior to more 

intensive agricultural and urban land use changes in many springsheds. These data 

were evaluated to determine potential historic or background conditions of phosphorus 

in springs. 

3.3.11 Nitrate Targets for FDEP’s Wastewater Treatment Criteria 

FDEP (2004) proposed a nitrate concentration target for development of enhanced 

central wastewater treatment standards and criteria for the Wekiva Study Area, as 

mandated by the Wekiva Parkway and Protection Act. This target was based on 

comparison with nitrate levels in less developed spring-run streams such as Juniper 

Creek, Alexander Springs Creek, and Silver Glen Run (C. Ferraro, FDEP Central 

District, personal communication; R. Drew, FDEP Tallahassee, personal 

communication). The URL link to this report is listed in the Literature Cited section.

33
4 PLRG DEVELOPMENT 

To briefly reiterate, the steps followed in this PLRG development process are: 

1. Identify the nature and extent of impairments, if any; 

2. Identify causative pollutants, if any; 

3. Determine acceptable concentrations of causative pollutants; 

4. Calculate necessary pollutant load reductions. 

The various investigations described in Chapter 3 each contributed to one or more of 

these steps. Key results of these investigations are briefly summarized in the following 

sections. Detailed reports for most of these efforts are in the Appendices. Prior to 

presentation of the findings, however, is a discussion of issues involved in identifying 

impairment and in defining nuisance algae. 

4.1 Determining Impairment 

Surface-water quality in Florida is managed by assigning “designated uses” (Chapter 

62-302.530, FAC). The Wekiva River and Rock Springs Run have a designated use of 

Class III, meaning they are managed for “recreation, propagation of a healthy, wellbalanced population of fish and wildlife”. A water body must meet a set of water quality 

standards specific to its designated use. If it does not meet those standards, it is 

considered impaired. Chapter 62-303, FAC (Identification of Impaired Surface Waters) 

establishes the criteria by which the State of Florida identifies impaired water bodies. 

An impaired water is defined in this rule as: 

“a water body or water body segment that does not meet its applicable water quality 

standards as set forth in Chapters 62-302 and 62-4, FAC, as determined by the 

methodology in Part III of this chapter, due in whole or in part to discharges of pollutants 

from point or nonpoint sources.” (Chapter 62-303.200[6], FAC) 

Water bodies are placed on FDEP’s Verified List of Impaired Waters if: 

• any of the water quality criteria listed in Chapter 62-302, FAC have exceedances 

surpassing a threshold (based on eligible data) with at least a 90% level of 

confidence that the actual exceedance frequency is >10%; 

• the water body fails a bioassessment, conducted using one of the departmentapproved methods (SCI, BioRecon, or LCI); 

• acute or chronic toxicity is determined; 

• a determination is made that there is a violation of the narrative nutrient criterion 

in the Class III water quality standards. For streams, this determination is made 

if: (1) algal mats are present in sufficient quantities to “pose a nuisance” or 

“hinder reproduction of a threatened or endangered species”, and/or (2) annual 

mean chlorophyll-a levels are >20 μg/L or have increased by more than 50% 

over “historical values” for “at least two consecutive years”. The rule also notes, 

however, that “Other information indicating an imbalance of flora or fauna due to 

34
nutrient enrichment, including, but not limited to, algal blooms, excessive 

macrophyte growth, decrease in the distribution (either in density or areal 

coverage) of seagrasses or other submerged aquatic vegetation, changes in 

algal species richness, and excessive diel oxygen swings, shall also be 

considered.” (Chapter 62-303.350[1], FAC); 

• the water body was subject to swimming area closures due to exceedance of 

primary contact bacteriological quality; 

• the water body is under a fish or shellfish consumption advisory; 

• the water body is used as a source of drinking water and exceedances of human 

health-based water quality criteria are demonstrated. 

Water bodies placed on this Verified List of Impaired Waters are then subject to the 

development of Total Maximum Daily Loads (TMDLs). 

4.1.1 FDEP Assessment of Impairment 

FDEP conducted a water quality assessment of the Wekiva River and its tributaries as 

part of its process to identify impaired water bodies in the Middle St. Johns River Basin 

(MSJRB). FDEP is required by the federal Clean Water Act to develop and implement 

TMDLs for these water bodies to reduce or eliminate impairment caused by pollution. 

The assessment of the MSJRB (FDEP 2003) considered water quality, biological and 

fish tissue data collected between 1991 and 2000. Water quality criteria analyzed were 

metals, chlorophyll-a, dissolved oxygen (DO), fecal and total coliforms, pH and 

unionized ammonia. Additional information from the FDEP Bioassessment program 

and fish tissue data/consumption advisories were also considered. See the FDEP 

website (link listed in Literature Cited) for a copy of the MSJRB Assessment Report. 

Based on their criteria and analysis, FDEP does not consider the Wekiva River and 

Rock Springs Run to be impaired for any constituent. 

4.1.2 SJRWMD Analysis of Impairment 

Impairment has to be scientifically demonstrated and causal pollutants identified before 

PLRGs can be developed. Consequently SJRWMD work focused on determining if the 

Wekiva River and Rock Springs Run are impaired according to criteria not considered 

by FDEP in their standard water-quality assessments described above. The broad 

range of issues that were considered in making a determination of impairment are listed 

in Table 4-1. 

Consideration of numeric water quality criteria is relatively straightforward – if numeric 

criteria are violated due to anthropogenic effects, then there is impairment. 

Consideration of ecological factors (e.g., ecosystem processes and biological 

communities) can be more difficult, particularly since the state standard for nutrients is 

narrative (Chapter 62-302.530 (48): “In no case shall nutrient concentrations of a body 

of water be altered as to cause an imbalance in natural populations of aquatic flora and 

fauna.” In some instances, such as impacts on populations of a listed species, there is 

a clear legal threshold that permits a finding of imbalance and impairment. In other 

35
Table 4-1. Issues that were considered in determining impairment of the Wekiva River 

and Rock Springs Run. 

Water Quality Comparison to Class III standards

Comparison to “typical values” for other springrun streams (or to reference spring-run systems)

Evaluate against OFW standard (i.e., degrading 

trends)

Toxicity to animals

Ecosystem Processes 

(production, respiration, etc.)

Imbalance considerations (what’s “natural” for a 

spring-run stream?)

Important limiting nutrients/nutrient thresholds 

for algal production

Stream metabolism

Comparison to other spring-run systems

Habitats/Communities/Populations Habitat alterations due to algal growth

Invertebrate and or fish community impacts

Aquatic macrophyte communities (aquatic plant 

management)

Impacts on listed species

Disruption by non-native species

Changes in taxa composition of algal community 

(increased proportion of “undesirable” taxa) 

Recreation/Aesthetics “Nuisance” algae (interference with recreational 

use; odors; visual impacts) 

Fishery impacts 

Human Health Coliform levels/Swim area closures 

Algal toxicity/allergic reactions 

Hydrology Potential changes in flows and levels 

(frequency, duration, magnitude) 

Interactions with established MFL for the Wekiva 

River 

36
cases (alterations in species composition of algal or benthic communities, impacts on 

sportfish habitat), a scientific judgment regarding what constitutes a balanced biota 

must be made. Florida law defines the natural background condition as “the condition 

of waters in the absence of man-induced alterations based on the best scientific 

information available to the Department. The establishment of natural background for 

an altered waterbody may be based upon a similar unaltered water body or on historical 

pre-alteration data.” (Chapter 62-302.200[15], FAC). Assuming that the natural 

background condition maintained a balanced biota, the determination of nutrient 

impairment can be based on comparisons to historical data predating impacts or to the 

biota of similar water bodies that are unimpacted (reference water bodies). 

Because data pre-dating anthropogenic effects are generally lacking for many aquatic 

ecosystems, a current approach towards assessing anthropogenic effects is to define a 

“reference” condition using minimally impacted, similar systems for a particular region 

(Hughes 1995; Bunn et al. 1999). The reference condition is generally interpreted to 

mean the condition of the system prior to human development of the landscape, and is 

assumed to represent optimal “biological integrity” or “ecosystem health” (Hughes 

1995). Karr (1991), citing some of his earlier work, defines biological integrity as: 

“the ability to support and maintain a balanced, integrated, adaptive community of 

organisms having a species composition, diversity, and functional organization 

comparable to that of natural habitat of the region. ” 

He defines ecological health as: 

(a biological system) “. . . can be considered healthy when its inherent potential is 

realized, its condition is stable, its capacity for self-repair when perturbed is preserved, 

and minimal external support for management is needed.” 

In a “reference” approach, deviation from the reference condition is inferred as 

impairment, including the above considerations regarding biological integrity and 

ecological health. 

For the Wekiva River system, water quality or ecological degradation that can be 

demonstrated to have occurred since 1979 (the baseline year for evaluating the nondegradation standard for OFWs) would constitute a violation of the no degradation 

standard in Chapter 62-302.700 [1], FAC and also may be considered impairment. 

Florida water quality standards also prohibit the presence of “Substances in 

concentrations which injure, are chronically toxic to, or produce adverse physiological or 

behavioral response in humans, plants, or animals” (Chapter 62-302.530 [62], FAC). 

Because nitrate can be toxic to aquatic organisms, our investigation included an 

assessment of the potential for nitrate toxicity and an analysis of concentrations that 

would result in minimal or no toxicity effects. 

37
4.2 Defining Nuisance Algae 

For purposes of this report, periphyton refers to the community of attached organisms, 

on submerged surfaces. This community includes microscopic algae (diatoms, green 

algae, blue-green bacteria and euglenophytes), as well as bacteria, protozoa, and 

microscopic animals embedded in a polysaccharide matrix (Lock et al. 1984). This 

community has been variously described as a “biofilm” or “benthic turf”. The periphyton 

can also include filamentous macrophytic algae or macroalgae. These species are 

macroscopic (easily visible), primarily filamentous green (Chlorophyta) and yellow-green 

(Xanthophyceae) algae and Cyanobacteria. They may form thick benthic or floating 

mats and may become nuisance species. In this report, growth of periphyton and 

growth/occurrence of filamentous “nuisance algae” are both considered. While some 

amount of periphyton growth is ecologically beneficial (due to increased food resources 

and additional habitat), excessive periphyton growth, especially of the filamentous 

macroalgae, can inhibit the growth of beneficial species of submersed aquatic 

vegetation (SAV), can have detrimental effects on faunal habitat, and/or can constitute 

an aesthetic nuisance. A determination of the level of periphyton that is harmful was 

beyond the scope of this work and is not available in the scientific literature. To reduce 

the potential for harmful levels of periphyton, we looked for inflection points between the 

growth potential of periphyton (at species and community levels) and levels of nitrate 

and total phosphorus. By limiting concentrations to levels below these points excessive 

growth of periphyton should be prevented. 

The perception of “nuisance” algae (primarily the filamentous macroalgae in the 

Cyanobacteria and Chlorophyta) and its possible link to elevated nitrate levels is of 

relevance in this PLRG analysis. Florida’s Impaired Waters Rule (Chapter 62-303.200, 

FAC) defines “nuisance species” as: 

“. . . species of flora or fauna whose noxious characteristics or presence in sufficient 

number, biomass, or areal extent may reasonably be expected to prevent, or 

unreasonably interfere with, a designated use of those waters.” 

The scientific literature generally defines “nuisance algae” in reference to interference 

with human uses; e.g., decreasing water flow, clogging water intakes, or interfering with 

recreational uses (Dodds and Welch 2000; Lembi 2003). Welch et al. (1988) 

considered a chlorophyll-a standing crop of >150 mg/m2

 (which equated to a cover of 

about 20% filamentous macroalgae) as a nuisance level in northern rocky streams. 

They interpreted nuisance to mean “aesthetically displeasing and interfere(s) with foot 

travel by fishermen.” Large mats of filamentous algae (Cyanobacteria and Chlorophyta) 

are also a aesthetic nuisance in that anaerobic decomposition of dead filaments within 

the mats produces a characteristic “sewage” or “septic” odor. 

To date, a determination of what constitutes a “nuisance level” of algae in Florida 

springs or spring-run streams has not been made. Based on the definition of nuisance 

species for a Class III water body, per the Impaired Waters Rule, algal growth that 

interferes with recreational uses or causes ecological changes which affect “health or 

38
balance” of fish or wildlife populations could be considered a nuisance, and thus an 

impairment of the water body. 

One algal group of major concern in Florida springs is the filamentous Cyanobacteria, 

primarily in the genus Lyngbya. With increased nutrient loading to a water body, it is 

frequently the Cyanobacteria that respond most prolifically (Komárek 2003; Brönmark 

and Hansson 1998), exhibiting large increases in abundance and excluding other algal 

taxa. Increase in Lyngbya biomass is a management issue in many Florida springs 

(Burns, unpublished paper; Stevenson et al. 2004). Lyngbya, and other Cyanobacteria, 

produce toxins that may be associated with skin reactions (dermatitis) and respiratory 

distress (Burns, unpublished paper; Komárek 2003). In some instances the allergic 

reaction may be severe enough to result in anaphylactic shock. The toxins may also 

have ecological impacts, but these have received much less attention than the human 

health effects. Large mats (= blooms) of filamentous Cyanobacteria may also adversely 

affect macroinvertebrate and fish habitat, water quality, and SAV. 

4.3 Results of PLRG Investigations 

4.3.1 Ecosystem Metabolism in the Wekiva River, Rock Springs Run, and in Reference 

Spring-run Streams 

Impairment. Data collected by WSI during 9 months in 2004-2005 demonstrated that 

nitrate and total phosphorus concentrations were elevated in the Wekiva River and 

Rock Springs Run compared to Juniper Creek and Alexander Spring Creek (WSI, 2005; 

Figure 4-1). Mass loading of total inorganic nitrogen (TIN) was higher in upstream 

segments of the Wekiva River and Rock Springs Run than in the Juniper and Alexander 

segments. Measures of ecosystem metabolism (gross primary productivity, net primary 

productivity, and ecological efficiency) were consistently lower in the Wekiva River and 

Rock Springs Run than in the two reference streams (Figure 4-2). High nutrient loading 

in the Wekiva River and Rock Springs Run appears to be causing disruption of 

ecosystem function in these aquatic ecosystems, evidenced by reductions in 

productivity and ecological efficiency (WSI 2005).

WSI (2005) noted other impacts to the Wekiva River and Rock Springs Run that could 

contribute to degradation and imbalances in flora and fauna. These impacts included 

high erosion rates in the contributing watershed, flow reduction due to increasing 

groundwater withdrawals, high-intensity aquatic plant management efforts, and 

recreation-related disturbance.

 

Nutrient Target Concentrations. Wetland Solutions (WSI 2005) recommended nutrient 

concentration targets for the Wekiva River and Rock Springs Run calculated to avoid 

degradation of aquatic ecological structure and function. These were based on 

evaluation of ecosystem metabolism data and water quality data for 130 Florida springs. 

Ecosystem metabolism data suggested an NOx target of 100 – 200 μg/L. About half of 

the 130 Florida springs had mean NOx concentrations greater than 500 μg/L and mean 

39
Nitrate

0

100

200

300

400

500

600

700

800

Wekiva River Rock Springs Run Alexander Spring

Creek

Juniper Creek

NO3/NO2-N (μg/L)

Total Phosphorus

0

20

40

60

80

100

120

140

160

Wekiva River Rock Springs Run Alexander Spring

Creek

Juniper Creek

TP (μg/L)

Figure 4-1. Mean nitrate and total phosphorus concentrations in intensive-study 

segments of the Wekiva River, Rock Springs Run, Alexander Spring Creek and Juniper 

Creek (from WSI 2005). 

40
Community GPP (gO2/m2

/day)

0

1

2

3

4

5

6

7

Wekiva River Rock Springs Run Alexander Spring

Creek

Juniper Creek

gO2/m2/day

Ecological Efficiency (%)

0

0.5

1

1.5

2

2.5

3

3.5

Wekiva River Rock Springs Run Alexander Spring

Creek

Juniper Creek

%

Figure 4-2. Mean gross primary productivity and ecological efficiency in the Wekiva 

River, Rock Springs Run, Alexander Spring Creek, and Juniper Creek (from WSI 2005). 

41
TP concentrations greater than 50 μg/L. Based on these lines of evidence, WSI 

calculated PLRGs for target concentrations of 100 μg/L NOx and 50 μg/L TP. 

PLRGs. Preliminary NOx and TP load reductions necessary to meet these 

concentration targets were calculated using simple linear models relating nutrient 

loading rates and in-stream nutrient concentrations for downstream points in each 

stream. These model relationships were weak and would need to be improved through 

additional data collection. Load reductions of 67% NOx would be required to meet the 

100 μg/L NOx target at a downstream point in the Wekiva River. A TP load reduction of 

76% would be required to meet the 50 μg/L TP target at a downstream point in the 

Wekiva River. 

See Appendix C for Wetland Solutions’ detailed methodology and data. 

4.3.2 Attached Algae in the Wekiva River and Rock Springs Run 

The highest biomass of attached algae was found at sites in and around the springs for 

both Wekiva River (WR) and Rock Springs Run (RSR). Diatoms were the dominant 

algal group in terms of biomass and diversity at the majority of sites (GreenWater Labs 

2005). Filamentous Cyanobacteria (particularly Lyngbya wollei and Phormidium) were 

most abundant in terms of biomass at sampling sites nearest the headsprings, although 

the thin cyanophyte filament Heteroleibleinia was important at some downstream sites. 

Cyanobacteria comprised a greater percentage of total biovolume in summer than in 

winter (GreenWater Labs 2005). Chlorophyta (particularly Spirogyra, Mougeotia and 

Cladophora glomerata) were most abundant in terms of biomass at the sites nearer the 

headsprings although accumulations of filamentous green algae (Cladophora glomerata

and Oedogonium) were observed in the wide, shallow section of the Wekiva River 

upstream of the SR46 bridge. The filamentous red alga Batrachospermum was found in 

both the WR and RSR, but was more abundant and at a higher percentage of sites in 

the WR. The filamentous xanthophyte Vaucheria was more abundant in WR and RSR 

than indicated by this study. The sampling method excluded benthic mats, of which 

some extensive ones composed of Vaucheria were present at times in both systems. 

Ash free dry weight (AFDW) and chlorophyll-a were both higher at sites nearer the 

headsprings on both spring-run streams. See Appendix D for details.

4.3.3 Nitrate Toxicity to Aquatic Animals 

Camargo and Ward (1995) estimated safe levels of nitrate for two species of caddisflies 

based on 96 h LC50s. Using multifactor probit analysis they extrapolated from the 

acute LC50 concentrations to estimate “safe concentrations” for chronic exposure for 

early instar larvae: 1,400 ug/L for the genus Hydropsyche and 2,400 ug/L for the genus 

Cheumatopysche. Both genera occur in the Wekiva River (Warren et al. 2000). 

Mosquitofish, which also occur in the Wekiva River (Warren et al. 2000), have exhibited 

adverse sublethal effects at nitrate levels of 4,000 μg/L and above (Edwards et al. 2004; 

Edwards 2005). Selected frog genera in Canada (Rana sp. and Pseudacris sp.) showed 

42
adverse sublethal effects at nitrate levels as low as 2,500 μg/L (Hecnar, 1995). 

Representatives of these frog genera are present in the Wekiva River and Rock Springs 

Run (Rana spp.) and its adjacent floodplain (Pseudacris spp). Many of the 

experimental studies were conducted over the larval lifetime of an animal (e.g., frogs 

from egg to adult). 

Figure 4-3 illustrates the reported toxicity thresholds for different aquatic animals 

relative to nitrate concentrations in the Wekiva River and Rock Springs Run. Maximum 

nitrate concentrations recorded through 2005 for the Wekiva River and Rock Springs 

Run were 1,500 and 1,800 μg/L, respectively. These concentrations may be toxic to at 

least one genus of caddisfly found in the Wekiva River and Rock Springs Run. An 

increase in maximum nitrate of 1000 μg/L (67%) for the Wekiva River and 700 μg/L 

(39%) in Rock Springs Run would meet or exceed toxicity thresholds for other 

caddisflies and for certain frogs. 

Derivation of a protective nitrate concentration requires consideration of the sources of 

uncertainty inherent in the limitations of the data derived from short-term, acute toxicity 

assays. The USEPA (1995a; 1995b), USFWS (2003), and USFWS et al. (2001) have 

employed up to four uncertainty factors to set protective exposure limits for toxic 

contaminants: 

1) an interspecies uncertainty factor (UFA); 

2) an exposure duration uncertainty factor (subchronic to chronic: UFS); 

3) an exposure endpoint uncertainty factor (UFL) – equivalent to a concentration 

between the “Lowest Observed Effect Level” (LOEL) and the “No Observed 

Effect Level” (NOEL), and; 

4) an intraspecific uncertainty factor (UFI). 

These factors were applied to the lowest nitrate toxicity thresholds derived from the 

literature review for caddisflies (1,400 μg/L) and amphibians (2,500 μg/L). Application 

of uncertainty factors yielded concentration thresholds of 140 and 125 μg/L, 

respectively. Detailed description of this procedure is in Appendix E. 

A statistical approach was developed to take the nitrate toxicity thresholds derived from 

application of uncertainty factors and use them to determine what a new mean nitrate 

level would be if the threshold were set at the upper end of the population of nitrate 

data. Nitrate data from the headspring regions of the Wekiva River and Rock Springs 

Run were used since these were the highest levels (Section 2.3) and thus potentially 

the most toxic. In order to use this statistical approach, the data must approximate a 

normal distribution or be transformed to conform to a normal distribution. The existing 

nitrate data from Wekiwa and Rock Springs met this requirement by deleting a very few 

outlier values from the dataset. From an ecologically conservative standpoint, the 

threshold criterion were set at the upper end of the population distribution, at the 90 %

probability level, in order to build in an explicit margin of safety. Using this as a starting 

point, the new mean nitrate concentration was calculated based on the probability of a 

43
Wekiva River 

0

500

Caddisfly Threshold 1 Caddisfly Threshold 2 Amphibian Threshold 1 Mosquitofish Threshold

Rock Springs Run 

Figure 4-3. Nitrate concentration in the Wekiva River and Rock Springs Run, showing 

selected toxicity thresholds for aquatic insects, amphibians, and mosquitofish. Source: 

SJRWMD data analysis and literature review (Mattson et al. 2005). 

0

500

1000

0

0

0

0

0

0

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004

NOx (μg/L)

150

200

250

300

350

400

Caddisfly Threshold 1 Caddisfly Threshold 2 Amphibian Threshold 1 Mosquitofish Threshold

1000

500

000

500

000

500

000

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004

NOx (μg/L)

4

3

3

2

2

1

44
randomly collected water sample having a nitrate concentration at or less than the 

specific threshold. To determine the target mean nitrate concentration: 

M + Z score*S = threshold concentration (Equation 1) 

M is the target mean nitrate concentration, S is the standard deviation of the target 

population distribution, and the Z score is the normal deviate associated with the 

probability assigned (these are obtained from standard tables in most statistics 

textbooks). This equation enables calculation of the percentage of samples in the new 

population which will have nitrate concentrations at or less than the established 

threshold target. 

Since S is unknown for the new population distribution, the coefficient of variation (CV) 

of the existing population (= the existing data) multiplied by the mean can substitute for 

S in the equation: 

 M + (Z score)(CV x M )= threshold target (Equation 2) 

CV is the Coefficient of Variation of the existing population distribution. This assumes 

that the population variance will vary in proportion to the mean with the coefficient of 

proportionality being the CV. As such, the CV will be the same for the existing and new 

distributions of data. To obtain the new target population mean, Equation 2 was solved 

for M: 

 M = threshold concentration/[Z score * CV* (1+Z)] (Equation 3) 

For consideration, the threshold selected was a nitrate level of 125 μg/L at a probability 

of 90% (i.e., 90% of the time, nitrate must be <125 μg/L). This was the threshold 

determined by applying uncertainty factors to the lowest amphibian threshold of 2,500 

μg/L NOx. Using the statistical methodology described above, the new population 

mean nitrate/nitrite nitrogen concentrations were 108 μg/L in the Wekiva River and 111 

μg/L in Rock Springs Run. These are the suggested nitrate targets in each spring run 

based on toxicity considerations. 

Results of SJRWMD’s nitrate toxicity literature review and the application of uncertainty 

factors are in Appendix E. 

4.3.4 Coliform Bacteria Impairment 

An analysis of recent data indicates that the Wekiva River and Rock Springs Run are 

impaired for total coliform bacteria according to criteria in Florida’s Impaired Waters 

Rule. The Class III standard of “no exceedance of 2,400 units/100ml at any time” was 

used to evaluate total coliform bacteria exceedances Since 1997, the upstream 

segment of the Wekiva River has exceeded the standard 40% of the time, the 

downstream segment 45% of the time, and Rock Springs Run 43% of the time. 

Additionally, the swim area in Kelly Park, at the headwaters of Rock Springs Run, was 

45
closed five times between 2000 and 2005 because of exceedance of primary contact 

bacteriological standards. The Wekiva River and Rock Springs Run are not impaired for 

fecal coliform bacteria. For details of SJRWMD’s coliform analysis, see Appendix F. 

4.3.5 Total Phosphorus Thresholds for Attached Algae Growth 

Although the study by GreenWater Labs (2005) sampled algae from a limited range of 

habitat types, these data can be used in an algae-based water quality assessment 

(Potapova and Charles 2005). Analysis of the attached algal data from the Wekiva 

River and Rock Springs Run indicated that % Cyanobacteria in the algal community (by 

biovolume) was positively correlated with total phosphorus (TP) and % Chlorophyta was 

not significantly correlated with TP. Graphical analysis of the data indicated that above 

TP concentrations of 90 μg/L, increased amounts of both Cyanobacteria and 

Chlorophyta were present in the algal community (Figure 4-4). The statistical procedure 

described in Section 4.3.3. on nitrate toxicity, was used to calculate a mean TP 

concentration for the Wekiva River and for Rock Springs Run by setting a threshold of 

maintaining TP levels <90 μg/L with a probability of 90%. This probability was selected 

to be ecologically protective. 

Mean TP resulting from this analysis was 59 μg/L for the Wekiva River and 61 μg/L for 

Rock Springs Run. Results of these analyses are summarized in Appendix G. 

4.3.6 Rainbow River Algal Bioassays 

Cowell and Dawes (2004) performed laboratory assays of nitrate concentration and 

growth of Lyngbya wollei from the Rainbow River and found a nitrate threshold of 300-

600 μg/L, above which growth of Lyngbya was significantly higher They recommended 

a reduction to <300 μg/L nitrate would be necessary to reduce growth of Lyngbya in the 

Rainbow River. A threshold nitrate target concentration of 250 μg/L was selected 

largely based on this scientific data and recommendation. 

4.3.7 Suwannee River Algae and Nutrients 

Long-term periphyton and water quality data collected on the Suwannee River (Hornsby 

et al. 2000) with glass-slide settling racks (periphytometers) indicate that periphyton 

biomass and abundance increase at threshold concentrations of 200 - 300 μg/L nitrate 

(Figure 4-5). This lends support to the threshold of 250 μg/L nitrate indicated in the 

Section above. An upper threshold of about 600 μg/L nitrate appears to be evident, 

above which nitrate is evidently not limiting to algal growth. Much of the length of the

Suwannee is heavily influenced by spring inflow, and the algal communities appear to 

be generally similar in composition to those in the Wekiva River and Rock Springs Run. 

Therefore, the Suwannee results are considered applicable to the Wekiva River and 

Rock Springs Run. See Appendix H for details of the Suwannee River work. 

46
0

10

20

30

40

50

60

70

80

60 75 90 105 120 135 150 165 180

Total P (ug/L)

% Composition by Biovolume

% BG algae % G algae Linear (% BG algae) Linear (% G algae)

Figure 4-4. Plot of percent Cyanobacteria (= ”BG algae”) and Chlorophyta (= ”G algae”) 

versus total phosphorus concentrations in the attached algal community in the Wekiva 

River and Rock Springs Run. Data from GreenWater Labs (2005) survey. 

47
Figure 4-5. Plots showing relationships between mean nitrate concentration and mean 

periphyton cell density and biomass from long term monitoring stations on the 

Suwannee River. Source: Hornsby et al. (2000) 

48
4.3.8 Nutrients in Less-Impacted Spring-Run Streams and in 130 Florida Springs 

Median nitrate concentrations in three less-impacted Florida spring-run streams 

(Alexander Springs Creek, Juniper Creek, Wacissa River) were all <100 μg/L. Median 

total phosphorus concentrations in these streams were all <50 μg/L (Appendix I). 

Median nitrate concentration in 130 Florida springs, including springs known to be 

impacted by elevated nitrate loading, was 480 μg/L and median total phosphorus was 

40 μg/L. Median nitrate/total phosphorus levels in Alexander Spring were 51/44 μg/L, in 

Juniper Spring 81/34 μg/L and in Fern Hammock Spring 90/31 μg/L. These correspond 

to the results reported above for less impacted spring runs (i.e., nitrate <100 μg/L and 

total phosphorus <50 μg/L). 

Data are summarized in Appendix I. 

4.3.9 Nutrients in Undeveloped Streams in the United States 

Median nitrate concentrations in streams draining undeveloped watersheds nationwide 

were 87 μg/L (Clark et al. 2000). Median total phosphorus levels in these streams 

nationwide were 22 μg/L. In forested watersheds in the southeastern U.S. (Binkley et 

al. 2004) mean nitrate levels were 180 μg/L and median levels were 50 μg/L. 

Nationwide, mean nitrate levels in these forested watersheds were 310 μg/L, with a 

nationwide median of 150 μg/L nitrate. Phosphate levels (whether this was PO4 or PO4-

P was not specified in the paper) in the southeastern U.S. from these forested 

watersheds showed a mean of 14 μg/L and a median of 7 μg/L (Binkley et al. 2004). 

4.3.10 Nitrate Targets for EPA’s TMDL 

The US Environmental Protection Agency defined a target concentration of 110 μg/L

NOx for Wekiwa Spring and Rock Springs based on the 90th percentile of nitrate 

concentration in Juniper Spring. Using this concentration target, USEPA proposed a 

91-95% reduction in nitrogen load to restore Wekiwa Spring and Rock Springs to 

natural background conditions. A TMDL for total phosphorus was not established by 

EPA. 

4.3.11 Total Phosphorus and Epiphytic Algae in Ichetucknee Springs 

No significant relationships were observed between biomass of epiphytic algae in 

springs of the Ichetucknee River and nitrate or total nitrogen (PBS&J 2004). Algal 

biomass was positively correlated with both total phosphorus and soluble reactive 

phosphorus (SRP), which were almost identical in these springs. Epiphytic algal 

biomass notably increased above a threshold of about 50-55 μg/L SRP or TP (PBS&J 

2004). Results and excerpts from this report are in Appendix J. 

49
4.3.12 Phosphorus in Florida Springs in the 1950’s 

Historic levels of phosphorus in Florida springs were identified by using data from Odum 

(1953). Springs within “phosphatic regions” (regions underlain with phosphorus-rich 

geologic strata) had a mean TP concentration of 61 μg/L (Odum 1953). Florida springs 

outside of phosphatic regions had a mean TP concentration of 45 μg/L. Odum’s map 

suggests the Wekiva River is outside of the phosphatic region, although the 

phosphorus-rich Hawthorn Formation is present in the Wekiva study area (Section 2.1). 

The concentrations from these earlier periods likely reflect conditions closer to the 

natural background condition. 

4.3.13 Nitrate Targets for FDEP’s Wastewater Treatment Criteria 

FDEP proposed a target nitrate level of 200 μg/L NOx for Wekiwa Spring (FDEP 2004). 

This was based on NOx levels exhibited by less-impacted reference springs such as 

Juniper and Alexander. 

4.4 Evidence of Impairment and Causative Pollutants 

4.4.1 Nutrients - Imbalance of Flora and Fauna 

Several lines of evidence indicate that the Wekiva River and Rock Springs Run are 

impaired due to an imbalance of flora and fauna caused by enrichment with nitrate and 

total phosphorus: 

• Gross and net primary productivity and ecological efficiency are lower than in 

less-impacted spring-run streams (Juniper Creek and Alexander Spring Creek). 

This indicates an “imbalance in natural populations of flora and fauna” as 

prohibited by Chapter 62-302.530[48b], FAC These effects are correlated with 

nutrient concentrations; 

• Laboratory and field studies indicate that present concentrations of nitrate and 

total phosphorus create the potential for high biomass and productivity of 

periphyton and potentially nuisance algal species, especially Cyanobacteria, 

again, constituting an imbalance of flora and fauna. 

4.4.2 Nitrate - Potential for chronic toxicity 

• Nitrate concentrations have been demonstrated to exceed nitrate toxicity 

thresholds for sensitive aquatic insects and frogs as prohibited by Chapter 62-

302.530[62], FAC 

50
4.4.3 Nutrients - Non-compliance with OFW designation 

• The high concentrations of nitrate and total phosphorus indicate anthropogenic 

enrichment that is not in compliance with part of the narrative nutrient standard 

(Chapter 62-302.530[48a], FAC); and is not permissible in OFWs (Chapter 62-

4.242[2], FAC); 

• One analysis indicated there has been an increase in nitrate concentrations in 

Rock Springs Run since the stream was designated an Outstanding Florida 

Water. This is prohibited by Chapter 62-4.242[2]. 

4.4.4 Total Coliform Impairment 

The Wekiva River and Rock Springs Run are impaired for total coliform bacteria based 

on the following evidence: 

• greater than 40% exceedance of the 2,400 counts/100 ml impairment criterion in 

the Impaired Waters Rule; 

• swim area closures in Kelly Park (Rock Springs Run); 

• increasing levels of coliform bacteria (i.e., a degrading trend in water quality) 

since OFW designation, a violation of the OFW Rule. 

4.5 Pollutant Target Concentrations 

4.5.1 Nutrients 

Potential nutrient concentration targets for PLRG development were discussed above 

(Section 4.3) and are summarized in Tables 4-2 (nitrate) and 4-3 (total phosphorus). 

These findings from multiple lines of investigation (Tables 4-2 and 4-3) were collectively 

considered to arrive at targets for nitrate and total phosphorus. 

4.5.2 Nitrate 

SJRWMD proposes mean target concentrations of 216 μg/L NOx for the Wekiva River 

and 221 μg/L NOx for Rock Springs Run. These mean nitrate targets will. 

• maintain nitrate levels <250 μg/L at a probability of 90% in order to limit 

excessive accumulation of periphyton biomass and limit growth of potential 

nuisance species of macroalgae such as Lyngbya; 

• restore ecological efficiency to that found in less-impacted spring-run streams; 

• maintain nitrate concentrations at levels that would be minimally toxic to aquatic 

fauna. The proposed mean concentrations are reduced by a factor of 11 to 12 

for the lowest observed amphibian toxicity threshold and by a factor of about 6 

51
Table 4-2. Potential nitrate-nitrite (NOx) concentration targets based on various lines of investigation. 

Reference Basis for Target N

Ecosystem metabolism in the Wekiva River and Rock Springs Run (WSI 2005) 

Comparison to metabolism in less-impacted spring-run streams (Juniper & Alexander) Comparison to other springs in SJRWMD 

Nitrate toxicity to aquatic animals (Mattson et al. 2005) 

90% probability of <1,400 μg/L (lowest toxicity threshold for caddisflies) 

Wekiwa Spring

Rock Spring New thresholds after application of uncertainty factors 90% probability of <125 μg/L (lowest threshold with uncertainty factor): 

Wekiwa Spring Rock Spring

Rainbow River algal bioassays (Cowell and Dawes 2004) 

Lyngbya wollei biomass 90% probability of < threshold of 250 μg/L: 

Wekiva River Rock Springs Run 

Suwannee River periphytic algae and nitrate levels (Hornsby et al. 2000) 

Algal biomass Algal cell density 

Nutrients in Florida springs (WSI and DEP databases) 

130 Florida springs, including impacted springs Juniper Spring, Fern Hammock Spring Alexander Spring 

Nutrients in less-impacted spring-run streams in Florida (STORET database) 

Juniper Creek Alexander Spring Creek Wacissa River 

Nutrients in undeveloped streams In the United States (Binkley et al., 2004; Clark et al. 2000) 

Forested stream basins in the southeastern U.S. Undeveloped watersheds in the U.S. 

EPA proposed TMDL for Wekiwa Spring and Rock Springs Run (USEPA 2005) 

Comparison to Juniper Spring 

FDEP wastewater treatment criteria in the Wekiva Study Area (FDEP 2004) 

Comparison to less-impacted Florida springs 

52
Table 4-3. Potential total phosphorus (TP) concentration targets based on various lines of investigatio

Reference Basis for Target TP 

Ecosystem metabolism in the Wekiva River and Rock Springs Run (WSI 2005) 

Comparison to metabolism in less-impacted spring-run streams (Juniper & Alexander) Comparison to springs in SJRWMD 

5

% Cyanobacteria and Chlorophyta in attached algae in Wekiva River and Rock Springs Run (analysis of data from GreenWater Labs 2005) 

90% probability of < 90 μg /L (threshold for increased levels of 

cyanobacteria and chlorophyta in attached algal community): 

Wekiva River Rock Springs Run 

Mapping and monitoring of submerged aquatic vegetation in the Ichetucknee River headsprings (PBS&J 2004) 

Epiphytic algal biomass 

Phosphorus in selected Florida springs in the 1950s (Odum 1953) 

Springs outside of phosphatic areas Springs within phosphatic areas 

Nutrients in Florida springs (WSI and DEP databases) 

130 Florida springs, including impacted springs Juniper Spring, Fern Hammock Spring Alexander Spring 

3

Nutrients in less-impacted spring-run streams in Florida (STORET database) 

Juniper Creek Alexander Spring Creek Wacissa River 

Nutrients in undeveloped streams in the United States (Clark et al. 2000) 

Undeveloped watersheds in the U.S. 

53
• for the estimated no effects threshold of caddisflies as reported in Mattson et al. 

(2005); 

• restore NOx concentrations to that characteristic of less-impacted springs and 

spring-run streams in Florida and in undeveloped watersheds in the southeastern 

U.S. and nationwide. 

These proposed targets fall within the upper mid-range of the range of possibilities 

considered in Table 4-2 (Figure 4-6). The Wekiva River and Rock Springs Run targets 

fall at the 29th percentile for the database of 130 Florida springs assembled by WSI 

(2005), thus both are in the lower third relative to springs in Florida. Scott et al. (2004) 

list a nitrate-nitrite measurement of 70 μg/L for Rock Spring in 1946, so the proposed 

targets are not as low as these springs may have historically been, but should be low 

enough to protect the ecological integrity of the spring-runs. Toth and Fortich (2002) 

suggest that levels in springs above 200 ug/L constitute a “problem threshold”, and the 

proposed targets are very close to this level. 

4.5.3 Total Phosphorus 

Orthophosphate is the analyte most frequently analyzed in groundwater and spring 

vents (Osburn et al. 2002; Scott et al. 2004). No research appears to have been done 

in Florida springs to separate the phosphate derived from natural leaching vs. that 

derived from surficial recharge. Orthophosphate is also rapidly taken up by plants and 

bacteria, while total phosphorus is less labile. Because of these reasons, SJRWMD 

made the decision to use total phosphorus (TP). Wastewater treatment and stormwater 

management are primarily focused on reductions in TP, so any improvements due to 

load reductions should be measureable by sampling TP in the spring-run streams. 

SJRWMD proposes mean target concentrations of 59 μg/L TP for the Wekiva River and 

61 μg/L TP for Rock Springs Run. These mean TP concentration targets will: 

• maintain TP concentrations below the threshold for increased growth of 

Cyanobacteria and green algae (90 μg/L) with a probability of 90%; 

• restore ecological efficiency to that found in less-impacted spring-run streams; 

• Limit accumulation of epiphytic algal biomass by keeping TP concentrations ~60 

μg/L; 

• restore TP concentration to that found in Florida springs in the 1950s; 

• restore TP concentration to that found in less-impacted springs and spring-run 

streams in Florida, and in undeveloped watersheds in the southeastern U.S. and 

nationwide. 

The proposed TP targets fall within the upper mid-range of the range of possibilities 

considered in Table 4-3 (Figure 4-7). The Wekiva River target falls at the 66th percentile 

for the database of 130 Florida springs assembled by WSI (2005) and Rock Springs 

Run falls at the 67th percentile, thus both exceed the median TP level relative to springs 

in Florida. They conform to the potential historic levels of TP found in Florida springs 

(45-61 μg/L) as reported in Odum (1953), which may be regarded as “natural 

background”. Reference springs in the Ocala National Forest, such as Alexander and 

54
0

100200300400500600

Alexander Spring Creek Alexander spring Wacissa River Juniper Creek Juniper spring US watersheds Fern Hammock spring

ecosystem metabolism - lower NITRATE TOXICITY - WEKIWA SPRING EPA TMDL NITRATE TOXICITY - ROCK SPRING SE US streams ecosystem metabolism - upper SJRWMD springs DEP wastewater criteria Suwannee River algae - lower ALGAL GROWTH - WEKIVA RIVER ALGAL GROWTH - ROCK SPRINGS RUN Suwannee River algae - upper Rainbow River algae - lower 130 Florid

Rainbow R

Potential NOx target concentration (ug/L) proposed target concentration means

Figure 4-6. Chart showing nitrate concentration targets that were considered and mean concentration for the Wekiva River and Rock Springs Run. 

55
Figure 4-7. Chart showing total phosphorus concentration targets that were considered and mean con

0

102030405060708090

US watersheds Juniper Creek Fern Hammock spring Juniper spring 130 Florida springs Alexander Spring Creek Wacissa River Alexander spring

1950s P in FL springs not in phosphatic areas ecosystem metabolism - lower SJRWMD springs epiphytic algae in Ichetucknee springs ATTACHED ALGAE IN THE WEKIVA RIVER ATTACHED ALGAE IN ROCK SPRINGS RUN 1950s P in FL springs in phosphatic 

ecosystem 

Potential TP target concentration (ug/L)

proposed target 

concentration means

proposed for the Wekiva River and Rock Springs Run.

56
Juniper also have TP values within or less than this range (40-60 μg/L). Odum (1953) 

reported TP values of 120-127 μg/L TP for Rock Spring in 1951. This approximates 

existing concentrations in the spring run (Figure 4-1), indicating either that this is the 

natural concentration or that anthropogenic TP loading affected the 1951 

measurements and has continued, either via groundwater and/or surfacewater inflow. 

Rock Spring continues to average around 80 μg/L TP and Wekiva Spring 200-600 μg/L 

(WSI 2004; Osburn et al. 2002), which lie above the apparent natural background levels 

of TP based on historic data (Odum 1953) and existing reference springs (Alexander 

and Juniper). It is likely that the TP levels seen in the Wekiva River and Rock Springs 

Run in part reflect both anthropogenic enrichment and phosphorus leached from 

geologic deposits in the region. 

4.5.4 Total Coliform Bacteria 

SJRWMD proposes a not-to-exceed target concentration of 2,400 counts/100 ml total 

coliform bacteria, which is the state water-quality standard for Class III waters. 

4.6 Pollutant Load Reduction Goals 

There are limited data available to calculate nutrient and coliform loading from various 

sources to the Wekiva River and Rock Springs Run and to relate in-stream 

concentrations to external loads. Therefore, only reductions in pollutant concentration 

could be calculated at this time. We assume that pollutant load reductions need to be 

proportional to pollutant concentration reductions. Throughout the remainder of this 

document, the percent load reduction is considered equal to the percent concentration 

reduction. 

4.6.1 Nutrients 

Nutrient load (concentration) reductions were calculated based on the formula: 

[(current mean – target mean) / current mean] x 100 (Equation 4) 

Spatial and temporal trends were considered in development of NOx and TP target 

concentrations. As appropriate, the required concentration reduction was calculated 

either for specific segments of each spring-run stream or for the entire stream. 

 

Nitrate 

Temporal Trends. Nitrate has significantly decreased in the Wekiva River since 1984 

(Figure 2-5). To address the temporal decrease in NOx, a “current condition” data set 

was created for each segment (see below) that consisted of the most recent and largest 

data set that showed no significant temporal trend. NOx load reductions were calculated 

based on the mean of the current condition data for each segment (Table 4-4). 

57
Spatial Trends. Nitrate concentrations significantly decrease from upstream to 

downstream in the Wekiva River and Rock Springs Run, probably due primarily to 

assimilation (Figures 2-7 and 2-8). To address the downstream decrease in NOx in 

calculating load reductions, both spring-run streams were divided into segments (Figure 

4-8; Table 4-4) with the headspring as the uppermost segment. The Wekiva River has 

two downstream segments separated by the confluence of the Little Wekiva River and 

corresponding to USEPA Water Body Identification (WBID) numbers. Rock Springs Run 

had one downstream segment consisting of the entire stream. Nitrate load reductions 

were calculated for each segment to account for the downstream decline in NOx (Table 

4-5). 

NOx PLRGs - Wekiva River. Based on the proposed mean target concentration of 216 

μg/L, nitrate load reductions required to restore the Wekiva River range from 36-82%, 

with the higher reductions needed in Wekiwa Spring and the Upper Wekiva River (Table 

4-5).

NOx PLRGs – Rock Springs Run. Based on the proposed mean target concentration of 

221 μg/L, nitrate load reductions required to restore Rock Springs Run range from 52-

85%, with the higher reductions needed in Rock Spring (Table 4-5). 

Total Phosphorus

Temporal Trends. Total phosphorus significantly decreased over the period of record in 

both the Wekiva River and Rock Springs Run (Figures 2-5 and 2-6). To address the 

temporal decrease in TP, a “current condition” data set was created for each spring-run 

stream that consisted of the most recent and largest data set the showed no significant 

temporal trend. Total phosphorus load reductions were calculated based mean of the 

current condition for each spring-run stream (Table 4-5). 

Spatial Trends. Total phosphorus showed no spatial trend in the Wekiva River or Rock 

Springs Run for the period of record (Figures 2-7 and 2-8). Consequently, total 

phosphorus load reductions were calculated for the entire length of each spring-run 

stream, with the exception of the headspring portion (Table 4-5). 

TP PLRGs - Wekiva River. Based on the proposed mean target concentration of 59 

μg/L, the total phosphorus load reduction required to restore the Wekiva River is 50% 

(Table 4-5).

TP PLRGs - Rock Springs Run. Based on the proposed mean target concentration of 

61 μg/L, the total phosphorus load reduction required to restore Rock Springs Run is 

29% (Table 4-5). 

The PLRGs for total phosphorus are applied to the upper and lower Wekiva River (as 

defined for nitrate) and the length of Rock Springs Run downstream from the 

headspring. The PLRGs will not be applied to the headsprings of either spring-run 

stream at this time due to the uncertainty of how much of the spring TP load is natural 

58
Figure 4-8. Map showing Wekiva River system segments and current conditions for 

nitrate (NOx) and total phosphorus (TP). 

59
Table 4-4. Segments in the Wekiva River and Rock Springs Run used for determination 

of nutrient load reductions. 

Segment 

Distance from 

Headspring (meters) 

USEPA Water Body 

Identification (WBID) 

Wekiwa Spring 0-1,267 2956C 

Upper Wekiva River 1,267-7,306 2956 

Lower Wekiva River 7,306-23,409 2956A 

Rock Spring 0-369 None 

Rock Springs Run 369-14,344 2967 

Table 4-5. Percent load reduction in nitrate, total phosphorus, and total coliform 

bacteria required to meet target mean concentrations proposed and applicable water 

quality standards in the Wekiva River and Rock Springs Run. 

Current 

Condition 

Mean 

Concentration 

Target Mean 

Concentration 

% Reduction 

Required to Meet 

Target 

(Concentration & Load)

Nitrate

Wekiwa Spring 1,202 μg/L 216 μg/L 82% 

Upper Wekiva River 704 μg/L 216 μg/L 69% 

Lower Wekiva River 335 μg/L 216 μg/L 36% 

Rock Spring 1,426 μg/L 221 μg/L 85% 

Rock Springs Run 458 μg/L 221 μg/L 52% 

Total Phosphorus 

Upper Wekiva River 119 μg/L 59 μg/L 50% 

Lower Wekiva River 119 μg/L 59 μg/L 50% 

Rock Springs Run 86 μg/L 61 μg/L 29% 

Total Coliform Class III standard 

Upper Wekiva River - - - 2,400 units/100 ml 49% 

Lower Wekiva River - - - 2,400 units/100 ml 30% 

Rock Springs Run - - - 2,400 units/100 ml 50% 

 

60
vs. anthropogenic. Further work will better separate these two components in the 

spring inflow. 

4.6.2 Total Coliform Bacteria 

Coliform concentration reductions were calculated by subtracting the target (2,400 

colonies/100 ml) from each data point that equaled or exceeded the target, determining 

the % reduction needed based on this difference and obtaining the median % reduction 

for all of the data in two segments in the Wekiva River (upper and lower) and in Rock 

Springs Run. Details are provided in Appendix F. 

Based on the proposed target concentration of 2,400 units/100ml, the total coliform 

bacteria load reduction required to restore the Upper Wekiva River is 49%, the Lower 

Wekiva River is 30%, and Rock Springs Run is 50% (Table 4-5). 

4.7 Discussion and Conclusions 

The Wekiva Parkway and Protection Act of 2004 directed SJRWMD to establish PLRGs 

for the Wekiva Study Area to assist FDEP in adopting Total Maximum Daily Loads 

(TMDLs) for impaired waters within the Wekiva Study Area. Consequently, SJRWMD 

and FDEP staff spent considerable time discussing and reviewing the various lines of 

evidence for PLRG development. The proposed Pollutant Load Reduction Goals 

represent the consensus of SJRWMD and FDEP. 

SJRWMD acknowledges that there is still considerable uncertainty in the proposed 

nutrient targets, given the limitations of the data and studies used to derive the targets. 

The approach taken was to err on the side of resource protection, deriving targets that 

should be highly protective of what are widely regarded to be two spring-run streams of 

regional and statewide significance. These nutrient targets are water-body specific; 

they are intended to apply to the Wekiva River and Rock Springs Run, and may not be 

applicable to other spring-run systems in the SJRWMD or other areas of the state. 

The pollutant concentration reductions proposed here by SJRWMD for nitrate, total 

phosphorus, and total coliform bacteria are based on the best data and information 

available within the time frame provided by the Wekiva Parkway and Protection Act. 

The proposed levels and load reductions should be highly protective but additional work 

is recommended to address remaining areas of uncertainty. The major areas of 

uncertainty are: 

1. The studies conducted by SJRWMD were necessarily short-term in order to meet 

the legislative deadline, and covered less than one year. This was an insufficient 

period of time to reflect the range of natural intra- and inter-annual variation in 

spring-run streams. This problem was compounded by the fact that, during these 

studies, hurricanes caused atypical conditions of high water flows, scouring of 

vegetation, transfer of sediments and atypical water quality conditions. 

61
2. There are no specific state standards, and no general scientific consensus, on 

criteria for identifying impairment of spring-run streams. Throughout the state 

there is attention being focused on nitrate, phosphorus and algal growth in 

springs and spring-runs, yet almost none of these systems are listed for these 

pollutants on the FDEP Verified List of Impaired Waters. Their characteristics 

are such that criteria in the Impaired Waters Rule for listing streams based on 

violations of the Narrative Nutrient Standard do not appear to apply to spring-run 

streams. Subsequent work will be used to refine the nutrient targets, which will 

most likely not be any lower than what is currently proposed in this report. 

3. The potential for nitrate toxicity needs further study. Fish eggs from some 

species have shown nitrate toxicity at very low concentrations. These studies 

used species not native to Florida and there were problems with fungal 

contamination, so these very low reported nitrate levels were not adopted as 

thresholds of toxicity. Further toxicological work is needed to confirm that the 

proposed nitrate target concentrations are protective of the aquatic life of the 

Wekivia River system. 

4. The relationships between periphytic algal growth and nutrient concentrations 

under varying conditions of current velocity and light are poorly known. These 

relationships need further study. Criteria for determining what levels of 

periphyton or macroalgae constitute a “nuisance” level need to be developed. 

5. The inhibitory effects of periphyton on SAV growth, and the effects of filamentous 

algal growth on macroinvertebrate and fish habitat is not understood 

quantitatively. Further work is needed to delineate the levels of algae associated 

with adverse impacts on SAV and aquatic fauna. 

To address some of the research needs described above, SJRWMD is performing 

additional work that could result in refinement of nutrient concentration targets and 

PLRGs for the Wekiva River and Rock Springs Run in the future. The work includes: 

• Wetland Solutions is repeating data collection on stream ecosystem metabolism 

in all four spring-run streams (Wekiva River, Rock Springs Run, Juniper Creek 

and Alexander Springs Creek) in the fall and winter of 2005/06 to obtain a full 

year of data collection; 

• Post, Buckley, Schue, and Jernigan (PBS&J), in conjunction with the University 

of North Carolina, are completing evaluation of in-stream surveys of algal 

communities and nutrients in the Wekiva River and Rock Springs Run, and are 

performing laboratory assays in mesocosms to determine limiting nutrients and 

the effects of nutrient reductions on algal growth; 

• Staff is reviewing additional scientific literature on nitrate toxicity effects on 

aquatic animals. 

62
Other research efforts are planned to further define impairment, pollutant impacts, and 

required reductions to restore and maintain the ecological integrity of these spring-run 

streams. SJRWMD is developing a five-year work plan for the Wekiva basin that will 

focus on improving understanding of spring-run stream ecosystems, impairment of 

spring-run streams, other pollutants of concern (including nutrient forms), and pollutant 

sources and loadings. These will contribute to future revisions of PLRGs proposed in 

this report. 

63
5 LITERATURE CITED 

Benke, A. C., T. C. Van Arsdall, Jr., and D. M. Gillespie. 1984. Invertebrate productivity 

in a subtropical blackwater river: the importance of habitat and life history. Ecol. 

Monographs 54(1): 25-63. 

Benke, A. C., R. L. Henry, III, D. M. Gillespie, and R. J. Hunter. 1985. Importance of 

snag habitat for animal production in southeastern streams. Fisheries 10(5): 8-13. 

Berndt, M. P., E. T. Oaksford, M. R. Darst, and R. L. Marella. 1996. Environmental 

Setting and Factors that Affect Water Quality in the Georgia-Florida Coastal Plain Study 

Unit. U. S. Geological Survey Water-Resources Investigations Report 95-4268. 46 pp. 

Binkley, D, G. G. Ice, J. Kaye, and C. A. Williams. 2004. Nitrogen and phosphorus 

concentrations in forest streams of the United States. J. American Water Resources 

Assoc. 40(5): 1277-1291. 

Brönmark, C and L.-A. Hansson. 1998. The Biology of Lakes and Ponds. Oxford 

University Press, New York, NY. 216 pp. 

Brown, M. T., J. M. Schaefer, K. H. Brandt, S. J. Doherty, et al. 1987. Buffer Zones for 

Water, Wetlands, and Wildlife. Report by the Center for Wetlands, University of Florida, 

Gainesville, FL. 163 pp, Appendix. 

Bunn, S. E., P. M. Davies, and T. D Mosisch. 1999. Ecosystem measures of river 

health and their response to riparian and catchment degradation. Freshwater Biology 

41: 333-345. 

Burns, J. M. Unpublished Report. Assessment of bloom-forming algae (Lyngbya) in 

Wekiwa Springs and the Wekiva River. Project proposal submitted to the St. Johns 

River Water Management District, Palatka, FL. 5 pp. 

Camargo, J. A. and J. V. Ward. 1995. Nitrate (NO3-N) toxicity to aquatic life: a 

proposal of safe concentrations for two species of Nearctic freshwater invertebrates. 

Chemosphere 31(5): 3211-3216. 

Canfield, D. E. and M. V. Hoyer. 1988. The Nutrient Assimilation Capacity of the Little 

Wekiva River. Final Report submitted to City of Altamonte Springs. Center for Aquatic 

Plants, University of Florida, Gainesville, FL. 288 pp. 

Clark, G. M., D. K. Mueller, and M. A. Mast. 2000. Nutrient concentrations and yields in 

undeveloped stream basins of the United States. J. American Water Resources Assoc. 

36(4): 849-860. 

Cowell, B. C. and C. J. Dawes. 2004. Growth and nitrate-nitrogen uptake by the 

cyanobacterium Lyngbya wollei. J. Aquatic Plant Management 42: 69-71. 

64
Dodds, W. K. and E. B. Welch. 2000. Establishing nutrient criteria in streams. J. North 

American Benthological Soc. 19(1): 186-196. 

Edwards, T. M. 2005. Environmental Influences on Mosquitofish Reproduction. Ph.D 

Dissertation. University of Florida, Gainesville, FL. 187 pp. 

Edwards, T. M., L. J. Guillette, Jr., K. McCoy, and T. Barbeau. 2004. Final Report. 

Effects of Nitrate/Nitrite on Two Sentinel Species Associated with Florida’s Springs. 

Technical Report to the Florida Department of Environmental Protection, Tallahassee, 

FL. 89 pp, appendix. 

FDEP. 2000. Ecological Assessment of the Wekiva River; Seminole, Lake and Orange 

Counties. Florida Department of Environmental Protection, Bureau of Laboratories, 

Division of Resource Assessment and Management, Tallahassee, FL. 8 pp. 

FDEP. 2003. Basin Status Report. Middle St. Johns. Report prepared by the Florida 

Department of Environmental Protection, Tallahassee, FL. 345 pp. Available at 

www.dep.state.fl.us/water/basin411/sj_middle/index.htm. 

FDEP. 2004. A Strategy for Water Quality Protection: Wastewater Treatment in the 

Wekiva Study Area. Report by the Florida Department of Environmental Protection, 

Orlando, FL. 77 pp. Available at www.dep.state.fl.us/water/docs/DEP_WekivaFacilities 

Report.pdf. 

FDNR. 1987. Wekiva River Aquatic Preserve Management Plan. Report by the 

Florida Department of Natural Resources, Bureau of Land and Aquatic Resource 

Management, Tallahassee, FL. 134 pp. 

Fernald, E. A. and E. D. Purdum. 1998. Water Resources Atlas of Florida. Institute of 

Science and Public Affairs, Florida State University, Tallahassee, FL. 312 pp. 

FNAI and FDNR. 1990. Guide to the Natural Communities of Florida. Report by the 

Florida Natural Areas Inventory and Florida Department of Natural Resources, 

Tallahassee, FL. 111 pp. 

Florida Springs Task Force. 2000. Forida’s Springs. Strategies for Protection and 

Restoration. Report by the Florida Springs Task Force. Florida Department of 

Environmental Protection, Tallahassee, FL. CD version. 

GreenWater Labs Inc. 2005. Final Report. Attached Algal Assessment for the Wekiva 

River and Rock Springs Run. Report submitted to the St. Johns River Water 

Management District, Palatka, FL. 45 pp. 

Griffith, G. E., J. M. Omernick, C. M. Rohm, and S. M. Pierson. 1994. Florida 

Regionalization Project. Report by the Environmental Research Laboratory, 

65
U. S. Environmental Protection Agency, Corvalis, OR. 83 pp. 

Hecnar, S. J. 1995. Acute and chronic toxicity of ammonium nitrate fertilizer to 

amphibians from southern Ontario. Environmental Toxicology and Chemistry 14(12): 

2131-2137. 

Hornsby, D., R. A. Mattson, and T. Mirti. 2000. Surfacewater Quality and Biological 

Monitoring. Annual Report. 1999. Suwannee River Water Management District 

Technical Report WR-00-04. iv, 148 pp. (.pdf file). 

Hughes, R. M. 1995. Defining acceptable biological status by comparing with 

reference conditions. Pp. 31-48 IN: W. S. Davis and T. P. Simon (eds.), Biological 

Assessment and Criteria. Tools for Water Resource Planning and Decision Making. 

Lewis Publishers, Boca Raton, FL. 

Hupalo, R. B., C. P. Neubauer, L. W. Keenan, D. A. Clapp, and E. F. Lowe. 1994. 

Establishment of Minimum Flows and Levels for the Wekiva River System. St. Johns 

River Water Management District Technical Publication SJ94-1. 86 pp. 

Jackson, J. A. 1996. Ivory-billed Woodpecker. Pp. 103-112 IN: J. A. Rodgers, Jr., H. 

W. Kale, III, and H. T. Smith (eds.), Rare and Endangered Biota of Florida. Volume V. 

Birds. University Press of Florida, Gainesville, FL. 

Karr, J. R. 1991. Biological integrity: a long-neglected aspect of water resource 

management. Ecological Applications 1(1): 66-84. 

Keenan, L. W., E. F. Lowe, and D. R. Dobberfuhl. 2003. Pollutant Load Reduction 

Goals for the Upper St. Johns River Basin. St. Johns River Water Management District, 

Palatka, FL. 33 pp. 

Komárek, J. 2003. Coccoid and colonial Cyanobacteria. Pp. 59-116 IN: J. D. Wehr 

and R. G. Sheath (eds.), Freshwater Algae of North America. Ecology and 

Classification. Academic Press, New York, NY. 

Lehmensiek, M. 2005. Verification of Impairment and Proposed Pollutant Load 

Reduction Goal (PLRG) for Total Coliform Bacteria in the Wekiva River and Rock 

Springs Run. SJRWMD Staff Report. November, 2005.16 pp. 

Lembi, C. A. 2003. Control of Nuisance Algae. Pp. 805-834 IN: J. D. Wehr and R. G. 

Sheath (eds.), Freshwater Algae of North America. Ecology and Classification. 

Academic Press, New York, NY. 

Light, H. M., M. R. Darst, L. J. Lewis, and D. A. Howell. 2002. Hydrology, Vegetation, 

and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, 

Florida, and Potential Impacts of Flow Reductions. U.S. Geological Survey Professional 

Paper 1656A. 124 pp. 

66
Lock, M. A., R. R. Wallace, J. W. Costerton, R. M. Ventullo, and S. E. Charlton. 1984. 

River epilithon: toward a structural-functional model. Oikos 42: 10-22. 

Marco, A., C. Quilchano, and A. R. Blaustein. 1999. Sensitivity to nitrate and nitrite in 

pond-breeding amphibians from the Pacific Northwest, USA. Environmental Toxicology 

and Chemistry 18(12): 2836-2839. 

Mattson, R. A., J. H. Epler, and M. K. Hein. 1995. Description of benthic communities 

in karst, spring-fed streams of north central Florida. J. Kansas Entomological Soc. 68 

(2) Supplement: 18-41. 

Mattson, R. A., E. F. Lowe, and C. L. Lippincott. 2005. Potential Nitrate Toxicity in 

Aquatic Animals in the Wekiva River and Rock Springs Run. SJRWMD Staff Report. 

September, 2005. 17 pp. 

Morris, A. 1995. Florida Place Names. Pineapple Press, Sarasota, FL. 291 pp. 

National Park Service. 1999. Wekiva River, Rock Springs Run, and Seminole Creek. 

Wild and Scenic River Study. Report produced by the Southeast Support Office, 

National Park Service, Atlanta, GA. 49 pp., 8 Appendices. 

Newman, M. C. and M. A. Unger. 2003. Fundamentals of Ecotoxicology. Second 

Edition. Lewis Publishers, New York, NY. 458 pp. 

Odum, H. T. 1953. Dissolved Phosphorus in Florida Waters. Florida Geological 

Survey Report of Investigations No. 9. Miscellaneous Studies. Pp. 1-40. 

Odum, H. T. 1957. Trophic structure and productivity of Silver Springs, Florida. 

Ecological Monographs 27: 55-112. 

Osburn, W., D. Toth, and D. Boniol. 2002. Springs of the St. Johns River Water 

Management District. SJRWMD Technical Report SJ2002-5. 

PBS&J. 2004. Mapping and Monitoring Submerged Aquatic Vegetation in Ichetucknee 

Springs – 2004. Final Report by Post, Buckley, Schue and Jernigan submitted to the 

Suwannee River Water Management District, Live Oak, FL. Pp. variously numbered, 6 

Appendices. 

Potapova, M. and D. F. Charles. 2005. Choice of substrate in algae-based water 

quality assessment. J. North American Benthological Soc. 24(2): 415-427. 

Rouse, J. D., C. A. Bishop, and J. Struger. 1999. Nitrogen pollution: an assessment of 

its threat to amphibian survival. Environmental Health Perspectives 107(10): 799-803. 

67
Schmidt, W. 1997. Geomorphology and physiography of Florida. Pp. 1-12 IN: A. F. 

Randazzo and D. S. Jones (eds.), The Geology of Florida. University Press of Florida, 

Gainesville, FL. 

Scott, T. M., G. H. Means, R. P. Meegan, R. C. Means, S. B. Upchurch, R. E. Copeland, 

et al. 2004. Springs of Florida. Florida Geological Survey Bulletin No. 66. 377 pp, 1 

CD. 

Simons, R. W. 1990. Terrestrial and Freshwater Habitats. Pp. 99-157 IN: An 

Ecological Characterization of the Florida Springs Coast: Pithlachascotee to 

Waccasassa Rivers. U. S. Fish and Wildlife Service Biological Report 90(21). 

SJRWMD. 2002. Middle St. Johns River Basin. Surface Water Improvement and 

Management Plan. Report by the St. Johns River Water Management District, Palatka, 

FL. iv, 87 pp. 

Sparling, D. W., G. Linder, and C. A. Bishop (eds.). 2000. Ecotoxicology of Amphibians 

and Reptiles. SETAC Press, Pensacola, FL. 877 pp. 

Stevenson, R. J. 1997. Resource thresholds and stream ecosystem sustainability. J. 

North American Benthological Soc. 16(2): 410-424. 

Stevenson, R. J., A. Pinowska, and Y-K Wang. 2004. Ecological Condition of Algae 

and Nutrients in Florida Springs. Final Report to the Florida Department of 

Environmental Protection, Tallahassee, FL. 101 pp. 

Stuart, S. N., J. S. Chanson, N. A. Cox, B. E. Young, A. S. L. Rodrigues, D. L. 

Fischman, and R. W. Waller. 2004. Status and trends of amphibian declines and 

extinction worldwide. Science 306(5702): 1783-1786. 

Toth, D. J. and C. Fortich. 2002. Nitrate Concentrations in the Wekiva Groundwater 

Basin, With Emphasis on Wekiva Springs. St. Johns River Water Management District 

Technical Publication SJ2002-2. 84 pp. 

USEPA, 1995a. Great lakes water quality initiative methodology for development of 

wildlife criteria. Federal Register 60 (56): 1541-15412. 

USEPA, 1995b. Great Lakes Water Quality Initiative Technical Support Document for 

Wildlife Criteria. Office of Science and Technology, Office of Water, USEPA, 

Washington, D.C. 

USEPA. 2005 . Total Maximum Daily Load (TMDL) for Nutrients in Wekiwa Spring 

(WBID 2956C), Rock Springs Run (WBID 2967), and Volusia Blue Spring (WBID 

28933), Middle St. Johns River Basin, Florida. Report by U.S. Environmental Protection 

Agency Region 4, Atlanta, GA. vi, 17 pp., 1 Appendix. Available at http://www.epa.gov/ 

Region4/water/tmdl/florida/index.htm#stjohns

68
USFWS, 2003. Evaluation of the Clean Water Act Section 304(a) human health criteria 

for methylmercury: protectiveness for threatened and endangered wildlife in California. 

U.S. Fish and Wildlife Service, Sacramento Fish and Wildlife Office, Environmental 

Contaminants Division, Sacramento, California. 96 pp. + appendix 

USFWS, USEPA, NJDEP, 2001. Derivation of New Jersey-specific wildlife values as 

surface water criteria for PCBs, DDT, and Mercury. Report produced by U.S. Fish and 

Wildlife Service, U.S. Environmental Protection Agency, and New Jersey Department of 

Environmental Protection. 36 pp. 

VanGenechten, D. T. 1999. Effects of Habitat and Season on Fish Communities of the 

Wekiva River System. M. S. Thesis. University of Florida, Gainesville, FL. 93 pp. 

Vince, S. W., S. R. Humphrey, and R. W. Simons. 1989. The Ecology of Hydric 

Hammocks: A Community Profile. U.S. Fish Wildl. Serv. Biol. Rep. 85(7.26). 81 pp. 

Walsh, S. J. and J. D. Williams. 2003. Inventory of Fishes and Mussels in Springs and 

Spring Effluents of North-Central Florida State Parks. Report to the Florida Park 

Service. U. S. Geological Survey, Center for Aquatic Resources, Gainesville, FL. iii, 

94 pp. 

Warren, G. L., D. A. Hohlt, C. E. Cichra, and D. VanGenechten. 2000. Fish and 

Aquatic Invertebrate Communities of the Wekiva and Little Wekiva Rivers: A Baseline 

Evaluation in the Context of Florida’s Minimum Flows and Levels Statutes. St. Johns 

River Water Management District Special Publication SJ2000-SP4. Pp. variously 

numbered. 

Weisman, B. R. 1993. An overview of the prehistory of the Wekiva River Basin. The 

Florida Anthropologist 46(1): 20-36. 

Welch, E. B., J. M. Jacoby, R. R. Horner, and M. R. Seeley. 1988. Nuisance biomass 

levels of periphytic algae in streams. Hydrobiologia 157: 161-168. 

Whitford, L. A. 1956. The communities of algae in the springs and spring streams of 

Florida. Ecology 37(3): 433-442. 

WRBCC. 2004. Wekiva River Basin Coordinating Committee. Final Report. Florida 

Department of Community Affairs, Tallahassee, FL. 54 pp. 

WSI Inc. 2004. Work Plan. Pollutant Load Reduction Goal (PLRG) Analysis for the 

Wekiva River and Rock Springs Run, Florida. Report prepared for the St. Johns River 

Water Management District, Palatka, FL. Pp. variously numbered. 

WSI Inc. 2005. Pollutant Load Reduction Goal (PLRG) Anaylsis for the Wekiva River 

and Rock Springs Run, Florida. Final Report. Report Prepared for the St. Johns River 

Water Management District, Palatka, FL. Pp. variously numbered. 

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6 APPENDICES 

70