# 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 32177Executive 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 t he SJRWMD developed

PLRG recommendations. PLRGs are the reduct ions in pollutant loadings needed to meet water quality standards or goals. The development of a PLRG is a four-step process: 1) determine the nat ure and degree of impairment, 2) identify the causative pollutant(s), 3) determine the acceptable co ncentration 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 mu ltiple lines of evidence for the PLRG:

relevant information in the scientific literatur e; 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 Flori da. Two reference streams were used to aid the assessment of impairment: Alexan der Spring Creek Run and Juniper Creek (Figure 2). This work indicates potentia l impairment of the Wekiva River and Rock Springs Run in terms of ecosystem proces ses, overgrowth of periphytic algae, dominance of the periphyton by Cyanobacte ria (blue-green algae), and toxic effects on

larvae of nitrate-sensitive aquatic organisms. Two causat ive pollutants create these potential effects: nitrate and total phosphorus (TP).

Two water quality standards apply to these effects: nutrient s 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 pr esence 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 t hese standards, there are several lines of evidence that

the concentrations of nitrate and TP in t he Wekiva River and Rock Springs Run are too high:

1) They are higher than in the referenc e 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 metabo lism are altered in the Wekiva River and Rock Springs Run, as compared to the reference streams and these changes are correlated with higher concent rations of nitrate and TP; 4) In laboratory studies the growth of f ilamentous Cyanobacteria is accelerated by
nitrate; 5) In field studies of other springs, the abundance and growth of epiphytes was
correlated with TP;

iFigure 1 (Executive Summary). The Weki va River basin, spring recharge area, and 2004 Wekiva Study Area. Source: SJRWMD data.

iiFigure 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).

iii6) In the Wekiva River and Rock Springs Run , the relative abundance of Cyanobacteria and Chlorophyta (al gae which are generally considered “nuisance” taxa) was higher in sites with higher TP; 7) Data from studies reported in the scientific literature indi cate that nitrate is toxic to larvae of sensitive aquatic insects and am phibians at concentrations that have occurred in the Wekiva River and Rock Sp rings Run . Nitrate concentrations in the Wekiva River and Rock Springs Run have commonly exceeded estimated

no-effects levels for these nitrat e-sensitive aquat ic organisms.

These observations lead to a variety of pot ential target concentrations for nutrients (Tables 1 and 2; Figures 3 and 4).

To reduce the potential for violation of water quality st andards, the SJRWMD

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

and 59 μ g/L total phosphorus in the Wekiva River and 221 μ g/L nitrate and 61 μ g/L total phosphorus in Rock Springs Run. These conc entrations 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 co liform 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 c oncentration for total coliform bacteria.

In order to calculate PLRG s 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). R eductions in total coliform counts were calculated based on EPA’s percent-r eduction method (Lehmensiek, 2005).

Spatial and temporal trends were considered in the calculation of PLRGs. Where there was a decreasing temporal trend, the cmc onl y reflected the recent period when there was no significant trend (i.e. data extending ba ck from the present to that time when a non-significant trend became statistically si gnificant). Spatial trends were also examined (from headspring to confluenc e with the next downstream system), and where appropriate, concentration reductions we re applied to specific segments of each spring-run stream or to the entire stream.

ivTable 1 (Executive Summary). Potentialnitrate-nitrite (NOx) concentration targets based on various lines of investigation.ReferenceBasis for TargetNOx (μg/L)StatisticEcosystem metabolism in the WekivaRiver and Rock Springs Run (WSI2005)Comparison to metabolism in less-impacted spring-run streams (Juniper &Alexander)Comparison to other springs in SJRWMD100 - 200200ThresholdMedianNitrate toxicity to aquatic animals(Mattson et al. 2005)90% probability of<1,400μg/L (lowest toxicity threshold for caddisflies)Wekiwa SpringRock SpringNew thresholds after application of uncertainty factors90% probability of <125μg/L (lowest threshold with uncertainty factor):Wekiwa SpringRock Spring1,2001,240125 - 140108111MeanMeanThresholdMeanMeanRainbow River algal bioassays(Cowell and Dawes 2004)Lyngbya wolleibiomass90% probability of<threshold of 250μg/L:Wekiva RiverRock Springs Run300 – 600216221ThresholdMeanMeanSuwannee River periphytic algae andnitrate levels (Hornsby et al. 2000)Algal biomassAlgal cell density200 - 300300ThresholdThresholdNutrients in Florida springs (WSI andDEP databases)130 Florida springs, including impacted springsJuniper Spring, Fern Hammock SpringAlexander Spring48081, 9051MedianMedianMedianNutrients in less-impacted spring-runstreams in Florida (STORETdatabase)Juniper CreekAlexander Spring CreekWacissa River805060MedianMedianMedianNutrients in undeveloped streams Inthe United States (Binkley et al.,2004; Clark et al. 2000)Forested stream basins in the southeastern U.S.Undeveloped watersheds in the U.S.18087MeanMedianEPA proposed TMDL for WekiwaSpring and Rock Springs Run(USEPA 2005)Comparison to Juniper Spring110ThresholdFDEP wastewater treatment criteria inthe Wekiva Study Area (FDEP 2004)Comparison to less-impacted Florida springs200ThresholdvTable 2 (Executive Summary). Potential total phosphorus (TP) concentrationtargets based on various lines ofinvestigation.ReferenceBasis for TargetTP (μg/L)StatisticEcosystem metabolism in the Wekiva Riverand Rock Springs Run (WSI 2005)Comparison to metabolism in less-impacted spring-run streams(Juniper & Alexander)Comparison to springs in SJRWMD50-8050ThresholdMedian% Cyanobacteria and Chlorophyta in attachedalgae in Wekiva River and Rock Springs Run(analysis of data from GreenWater Labs 2005)90% probability of<90μg /L (threshold for increased levels ofcyanobacteria and chlorophyta in attached algal community):Wekiva RiverRock Springs Run5961MeanMeanMapping and monitoring of submerged aquaticvegetation in the Ichetucknee Riverheadsprings (PBS&J 2004)Epiphytic algal biomass55ThresholdPhosphorus in selected Florida springs in the1950s (Odum 1953)Springs outside of phosphatic areasSprings within phosphatic areas4561MeanMeanNutrients in Florida springs (WSI and DEPdatabases)130 Florida springs, including impacted springsJuniper Spring, Fern Hammock SpringAlexander Spring4034, 3144MedianMedianMedianNutrients in less-impacted spring-run streamsin Florida (STORET database)Juniper CreekAlexander Spring CreekWacissa River234444MedianMedianMedianNutrients in undeveloped streams in the UnitedStates (Clark et al. 2000)Undeveloped watersheds in the U.S.22Medianvi0100200300400500600

Ale x an der S pri ng Cre ek

A l exander s p r i n g Wacissa R iver Juniper Creek Junip er spring US w at ersheds

Fe r n Hammock spring ecosystem metabolism - lower NITRATE TOXICITY - WEKIWA S P RING E P A T MDL

N I T RA T E T O X I C ITY - RO CK S PRI N G SE US streams

e c os ystem meta b olism - upper

S JRW MD s pri ngs

DEP w ast ewat e r criteria

Suwann ee Ri v e r alga e - lo wer

A LG AL GROWTH - WEKIV A RI V ER

ALG A L GROWT H - ROCK S PRINGS R UN

S u wannee River al gae - u pper

R ain bow Ri ver al gae - l ower

13 0 Florid a springs

R ai nbow River al gae - uppe r

Potential NOx target concentration (ug/L)proposed target concentrationmeansFigure 3 (Executive Summary). Potentialand proposed nitrate targets based on Table 1.vii0102030405060708090 US watersheds Juniper Creek Fern Ham mo ck sp rin g Ju n ip e r sp r i n g 13 0 F l o rid a s pr i ngs Alexander Spri n g Cre e k Wacis sa R ive r Al exa n de r sp r i n g 1950s P in FL springs not in phosphatic areas

eco sys tem metab o li sm - lower SJ R W MD spri n gs

e p ip h yt i c al g a e in Ic h e t u ckne e sp rin g s

AT TACHED AL G AE IN THE WEKIVA RI VER ATTACHED ALGAE IN ROCK SPRING S RUN

1 9 50 s P in FL springs in phosphatic areas

eco syst e m me t a bo l ism - up p er

Potential TP target concentration (ug/L)proposed targetconcentration meansFigure 4 (Executive Summary). Potential andproposed total phosphorus targets based on Table 2.viiiTable 3 (Executive Summary). Recommended perc ent 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 in formation 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 We kiva River and Rock Springs Run were conducted when there were significant im pacts from the unusua lly strong hurricane

season of 2004. Sediment s 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 func tion of spring-fed streams is still developing. These ecosyst ems have not been extensively studied, and

much additional research is needed before th ey are as well understood as are lakes and wetlands. The potential for nitrate toxi city 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 safe ty margins were employed to ensure that the PLRGs will be protective. Additional resear ch may allow these safety margins to be reduced, resulting in higher concentration ta rgets than those currently proposed. This will reduce the pollutant load reductions r equired to meet these higher targets.

ixTABLE 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 Epiphyti c Algae in Ichetucknee Springs ............... 33

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

x3.3.11 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 Epiphyti c 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).

xiAPPENDIX C. Pollutant Load Reduction Goal (PLRG) Analysis for the Wekiva River and Rock Springs Run, Florida. Final R eport from Wetland So lutions Inc. (2005).

APPENDIX D. Attached Algae Survey on th e 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 t he 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 Ni trate Levels in the Suwannee River. Excerpted from: Hornsby, D. , R. A. Mattson, and T. Mi rti. 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 an d in 130 Florida Springs.

APPENDIX J. Epiphytes on Submerged A quatic Vegetation in Headsprings of the Ichetucknee River, Fl orida. Excerpted from: PBS&J. 2004. Mapping and Monitoring Submerged Aquatic Vegetation in Ichetucknee Springs – 2004. Report

submitted to the Suwannee River Water Man agement District, Live Oak, FL. Pp. variously numbered; 6 Appendices.

xiiLIST OF FIGURES

Figure 1-1. The Wekiva River system, sho wing 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 su rface of the Floridan Aquifer in the Wekiva Study area. .. 9

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

Figure 2-4. Mean daily flows in the Weki va River prior to and during the studies conducted for the PLRG effort, showing m edian 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 to tal 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 phosphor us concentration in intensive-study segments of the Wekiva River, Rock Spring s 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 Spri ng 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 inse cts, amphibians, and mosquitofish. ....... 44

xiiiFigure 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 biom ass from long term monitoring stations on the

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

Figure 4-6. Chart showing nitrate concentra tion 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

xivLIST OF TABLES

Table 2-1. Hydrogeologi c framework for the Wekiva region.. .................................. 8

Table 2-2. Summary of stream-flow char acteristics for the Wekiva River and Rock Springs Run. ................................................................................................10

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

Run. Values are means of available data fo r 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 abu ndance in, spring-run

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

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

habitats that occur in the We kiva River system. ................................................. 26

Table 2-7. Urban and developed land use in the surface dr ainage area of the Wekiva River and Rock Springs Run. ......................................................................... 28

Table 4-1. Issues that we re considered in determining im pairment of the Wekiva River and Rock Springs Run. ................................................................................. 36

Table 4-2. Potential nitrate- nitrite (NOx) concentration target s 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 c oncentrations proposed and applicable water quality standards in the Wekiva River and Rock Springs Run. ............................... 60

xvLIST 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

m 2 - square meters

mi 2 - 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 (NO 3 /NO 2 ) – 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

xvi1 INTRODUCTION

The Wekiva River, its main tributaries (R ocks Springs Run, Little Wekiva River, and Blackwater Creek) and their 30 contributi ng groundwater springs (Figure 1-1) are resources of regional and statewide signifi cance (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 Spri ngs Run, are classified by the Florida Natural Areas Inventory as sp ring-run streams and are considered imperiled

in Florida.

1.1 Wekiva River Protection Area

Efforts to protect the Weki va River basin began in 1988 when Governor Bob Martinez appointed the Wekiva River Task Force to reco mmend strategies to protect the Wekiva River basin (EOG #88-26). As a result of this group’s work, t he Florida Legislature passed the Wekiva River Protection Act (Chapter 369, Part II, Flori da Statutes [FS]). The purpose of this Act was to protect t he 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 (MF L) for the river and development of a scientifically defensible buffer adjacent to th e river and its tributar ies (Chapter 373.415, FS). The Wekiva River Protection Act of1988 also required development of basinspecific criteria for surface water management permits issued in the basin. Basinspecific criteria addressed drawdown of surf ace water, erosion control, riparian habitat protection zones, and local government authorizat ion 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 Coor dinating Committee (WRBCC) to expand on the Task Force re commendations and develop implementation strategies (EOG #2003-112).

As a result of the recommendat ions of the WRBCC, the Fl orida Legislature passed the Wekiva Parkway and Protection Act in 2004 (C hapter 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:

1Figure 1-1. The Wekiva River system sho wing major tributaries and 30 contributing springs.

2“By December 1, 2005, t he St. Johns River Water Managem ent 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 Dece mber 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 requirem ents of the Wekiva Pa rkway and Protection Act.

1.3 Other Protective Designations

1.3.1 Surface Water Improv ement and Management Program

The Wekiva River basin is part of SJ RWMD’s Surface Water Improvement and Management (SWIM) Program for the Middle St. Johns River Ba sin. The primary goal of the SWIM program is protecti on and restoration of aquatic re sources 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 compon ents of the ecosystem while restoring, where feasible, such conditions to the degraded portions of the system;

• To preserve, or where necessary re store, the quantity and quality of water necessary to support thriving biologica l communities, containing appropriate diversities of native spec ies within the riverine and la custrine systems of the St.
Johns River Middle Basin;

• To pursue the development and implem entation 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 Outsta nding Florida Water (OFW; Chapter 62- 302.700, Florida Administrative Code [FAC]). This designation is conferred on water

bodies within state and federal conserva tion areas and that have exceptional recreational or ecological sign ificance (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

3Run, 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 biologi cal, aesthetic, and scientific value (Chapter 258.36, FS). They are established and managed “for the purpose of being pr eserved in an essentially natural or existing condition so that their aesthetic, biological and scientific values may endure for the enjoyment of future generat ions” (Chapter 18-20.001 [2], FAC).

1.3.4 National Wild and Scenic River

Most recently, the Wekiva River and portion s 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 designati on 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 fo r PLRGs is found in state

law.

• Chapter 373.016 (FS) indicate s 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.” (C hapter 62-40.310 [2][a], FAC).

PLRGs are part of the Surface Water Im provement and Managemen t (SWIM) planning process. They may also be developed as pa rt 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, PLRG s 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.

4Collect and analyze data to determine if the stream’s designat ed-use is impaired because of a violation of water-quality st andards and/or because of an imbalance of

flora and fauna.

2. Identify the causativ e pollutants, if any.

Assess the degree to which pollutant(s) such as nut rients are the cause of impairment. Impairments may stem from factors other than pollutants, such as altered hydrology, physical damage to biot a, 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 ar e safely below the levels associated with impairment.

4. Calculate necessary pollutant load reductions.

Relate acceptable pollutant targets to po llutant concentrations, and where feasible calculate pollutant load reductions needed to meet the target concentration.

52 WEKIVA RIVER SYSTEM DESCRIPTION

The Wekiva River Study Area (“WSA”; Fi gure 2-1) was delineated by the WRBCC (2004) and encompasses 473 square miles. The word We kiva (alternate spelling Wekiwa – which is applied to the spring it self) derives from the Seminole/Creek for “spring” or “spring of wa ter” (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 th e river and its headspring, called Wekiwa Spring. Over the past century the river floodpl ain has served as a source of timber, and its springs as a respite for their “healing wa ters”, with various resorts and spas nearby. The Wekiva River and Rock Springs Run an d their headsprings currently provide a variety of recreational opport unities including canoeing, s wimming, 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 t he confluence of the Wekiva River and Blackwater Creek (WSI 2004) . Five marine terraces in the region were formed by sediment deposition and rework ing during periods of higher sea level (Schmidt 1997). Wekiwa Spring and Rock Spri ngs 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, l and elevations are generally < 25 feet above MSL with poorly draining wetland and flatwoods soils.

The region also lies within the Southern C oastal Plain ecoregion (Berndt et al. 1996) and encompasses two stream-type subecoregi ons (Griffith et al. 1994); the Eastern Florida Flatwoods and Central Florida Ridge s and Uplands. The Eastern Flatwoods subregion is characterized by variable soils, ranging from moderately draining sandy soils of the flatwoods to poorly draining cl ay or muck soils of wetlands. The Central Ridges subregion is characterized by deep, m oderate- 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 t op of the limestone unit beari ng the Floridan Aquifer (‘Floridan’) lies 50 to 100 feet beneath land su rface (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.

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

Area. Source: SJRWMD data.

7Table 2-1. Hydrogeologic fram ework 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 O ligocene Suwannee Limestone

Eocene Ocala Limestone

Avon Park Formation

Oldsmar Formation

The Floridan Aquifer is the main water source for springs that di scharge to the Wekiva River and its tributaries (Toth and Fortich 2002; Osburn et al. 2002). Figure 2-2 shows the potentiometric surface of t he Floridan Aquifer in the We kiva region in 2002. Water flow is perpendicular to the c ontours of the potentiometric su rface. The principal areas of rainfall recharge to the Floridan are in the western and southern por tions of the region (Osburn et al. 2002), with rechar ge of up to 12” of rainfall ann ually. 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 We kiva region is generally hard and high in dissolved calcium bicarbonate, reflecting the li mestone matrix of the aquifer. Toth and Fortich (2002) identified areas of the Floridan aquifer in t he 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 “nat ural background” for ni trate 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 Pur dum, 1998). WSI (2004) found no apparent long-term temporal trend in rainfall based on data from seven stations in or near the

Wekiva River.

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

Source: SJRWMD data.

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

River basin are derived from surface dr ainage from the watershed and groundwater inflow from the Floridan Aqui fer. Location of springs and st ream flow-gaging stations in the basin are shown in Figure 2-3. A summ ary of stream-flow characteristics for the Wekiva River and Rock Springs Run are shown in Table 2-2.

Spring inflow appears to account fo r a majority of base flow in the Wekiva River. Thirty springs have been identified in the Wekiva Riv er basin (Figure 2-3). Mean flows in these springs range from 67.1 cfs (Wekiwa Spri ng) 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 Spri ng), spring flow represents at

least 67% of the base flow of the Wekiva Riv er. This figure is probably low because it does not include groundwater inflow from ot her 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 stream s, water quality in the springs exerts a major influence on wa ter 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 fore sts, and transfer of

sediment.

Table 2-2. Summary of stream-flow char acteristics 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 – Descript ion, Status, and Trends

2.3.1 Water Quality Description

The Wekiva River and Rock Springs Run ar e 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 adjac ent drainage area. During the course of these studies,

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

11Wekiva River at SR 4602004006008001000120014001600 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 6/30/2005 7/14/2005 7/28/2005 8/11/2005 8/25/2005

Flow (cfs)Mean Daily FlowPOR MedianMedian Sep04 to Aug05Charley Frances JeanneFigure 2-4. Mean daily flows in the Wekiva River prior to and during the studies conductedfor the PLRG effort, showingmedian flows for the period of record (1935-2005), for the study period (Sept.2004 to Aug. 2005), and dates of passageof hurricanes.12Table 2-3. Summary of water quality dat a 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 ( ų mhos/cm) 624 244
pH (units) 7.42 7.31
Alkalinity (mg/L as CaCO 3 ) 94.9 86.6
Color (pcu) 61.5 203
Turbidity (NTU) 3.34 1.60

Dissolved O 2 (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

NO 3 /NO 2 -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 ( ų g/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 colo r was high due to contribution of tannins from the floodplain forests. Nit rate 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 exhibi ts 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 St ream Bioassessment Program (FDEP 2000).

Results indicated nitrate enrichment in both streams because ni trate concentrations

exceeded those found in 95% of other Florida streams. Amm onia, total Kjeldahl nitrogen and total phosphorus levels approximat ed the statewide stream median.

Habitat Assessment scores at all sites in both streams fell within the optimum range for peninsular streams. Macroinv ertebrate Stream Condition I ndex scores were all in the good or excellent range based on reference leve ls for peninsular streams (FDEP 2000). Average Algal Growth Potential (AGP) score s exceeded the “problem threshold”,

13indicating that nutrient levels were high enough to potentially support high levels of algal growth in both streams.

SJRWMD Water Quality Analysis . In 2004, SJRWMD staf f analyzed water quality

status and trends for the Wekiva River and Ro ck Springs Run using data from stations located in the spring-run streams. Water qua lity 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 al so degraded since OFW designation.

Table 2-4. Results of SJRW MD 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

14SJRWMD 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 Ru n since 1974 (Figures 2-5 and 2-6), with decreases in both wet and dry seasons. Nitra te 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 fr om the headsprings is being a ssimilated in the spring-run streams, with lesser amounts exported downstr eam to the St. Johns River. There was no downstream trend in total phosphorus in ei ther stream (Figures 2-7 and 2-8), although Rock Springs Run showed an incr easing downstream trend in total phosphorus during the wet season.

2.3.3 Water Quality Issues

Nitrate concentrations are elevated in m any 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 spec ulation that elevated nitrate levels cause excessive algae growth, with possible detrim ental 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 rulema king 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 nece ssary 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 t he 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 t he Florida Natural Areas Inventory (FNAI) classification system (FNAI and FDNR 1990) . Figure 2-9 shows natural community types based on the Florida Land Use, Co ver and Forms Classification System (FLUCFCS). Natural community types include:

150 200 400 600 800 1000 1200 1400 1600 1800

1983 1985 1987

1 9 8 9 1991 1993 1995 1997 1999 2001 2003 2005NOx (μg/L) 2000

0 100 200 300 400 500 600

1972 197 4

1 97

6 197 8 198 0 1982 198 4

1 98

6 198 8 199 0 1992 199 4

1 99

6 199 8 200 0 2002 200 4
2 00

6

Figure 2-5. Temporal trends in nitrate and to tal phosphorus in the Wekiva River for the period of record. Line indicates stat istically significant decreasing trend.Total P(μg/L)

160 200 400 600 800 1000 1200 1400 1600 1800 2000

1983 1985 1987

1 989

1 991 199 3 1995 1997 1999 2001 2003
2 005NOx (μg/L)

0 100 200 300 400 500 600

197

2 1974 197 6 197 8 198 0 198 2 1984 198 6 198 8

1 99

0 199 2 1994 199 6 199 8
2 0 00 200 2 200 4 200 6Total P (μg/L)

Figure 2-6. Temporal trends in nitrate and total phosphorus in Rock Springs Run for the period of record. Line indicates statis tically significant decreasing trend.

170 200 400 600 800 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 statis tically significant decreasing trend.

180 200 400 600 800 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 stat istically significant decreasing trendTotal P (μ

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

20Upland 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 regul ar 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 domi nated 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 t he 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. Wa rren, 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 southeaste rn coastal plain streams have documented the importance of wood snag hab itat 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 We kiva 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.

21Bare sediment (mud or sand) is a third ma jor aquatic habitat type in the streams, and supports a diverse assemblage of macroinv ertebrates. Warren et al. (2000) found highest total invertebrate taxa richness in this habitat in the Wekiva River (166 taxa). Invertebrate densities (#/m 2 ) were also high in this habi tat. A number of fish taxa (catfish, sucker, and minnows) generally pref er 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 fi sh 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, herpet ofauna (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, mo llusks, 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 t he invertebrate diversity and abundance in most habitats. Mayflies (Ephemeroptera) , caddisflies (Trichoptera), aquatic beetles (Coleoptera) and amphipods were the other abundant groups in t he river. Eight taxa of hydrobiid snails (a group most frequent ly associated with springs and spring-run streams, with many endemics) we re 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 comm unity 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 (her petofauna, birds and mammals) on the Wekiva River or Rock Spri ngs 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 spec ies and other rare and endemi c species (Table 2-6). Additionally, searches for ivory-billed woodpeckers from 1987-1992 included the Wekiva

22Table 2-5. Taxa primarily associatedwith, or that reach high abundance in, spring-run streams. Adapted from Simons(1990) and Mattson et al. (1995). All taxa listed here are known to occur in theWekiva River basin except (?), which arelikely to occur in the basin.Spring-run Stream“Best Habitat”Spring-run Stream“Good Habitat”PlantsEelgrassVallisneria americanaXXSpringtapeSagittaria kurzianaXXCharaCharaspp.XXInvertebratesSiltsnailsHydrobiidae (most freshwater taxa)XXRiver horn snailsElimiaspp.XXApple snailPomacea paludosaXXGrass shrimpPalaemonetes paludosusXXMayflyStenacronspp.XXMayflyTricorythodes albilineatusXXAquatic butterflyParaponyxsp.XXSpiral-cased caddisfly (?)Helicopsychespp.XXFishesLongnose garLepisosteus osseusXXFlorida garLepisosteus platyrhincusXXGolden shinerNotemigonus chrysoleucasXXRedeye chub (?)Notropis harperiXXCoastal shinerNotropis petersoniXXSailfin shinerPteronotropis hypselopterusXXChannel catfishIctalurus punctatusXXSeminole killifishFundulus seminolisXXWhite catfishAmeiurus catusXX23Table 2-5. Continued.TAXONSpring run“Best Habitat”Spring run“Good Habitat”Bluefin killifishLucania goodeiXXBluegill sunfishLepomis macrochirusXXRedear sunfishLepomis microlophusXXSpotted sunfishLepomis punctatusXXAmphibiansRiver Frog (?)Rana heckscheriXXReptilesAmerican alligatorAlligator mississippiensisXXFlorida snapping turtleChelydra serpentina osceolaXXStinkpotSternotherus odoratusXXLoggerhead musk turtleSternotherus minor minorXXFlorida red-bellied turtlePseudemys nelsoniXXBrown water snakeNerodia taxispilotaXXRainbow snakeFarancia erytrogramma erytrogrammaXXBirdsGreat blue heronArdea herodiasXXGreat egretCasmerodius albusXXLittle blue heronEgretta caeruleaXXLimpkinAramus guaraunaXXWood duckAix sponsaXXSwallow-tailed kiteElanoides forficatusXXRed-shouldered hawkButeo lineatusXXBarred owlStrix variaXXBelted kingfisherCeryle alcyonXX24Table 2-5. Continued.TAXONSpring run“Best Habitat”Spring run“Good Habitat”Acadian flycatcherEmpidonax virescensXXProthonotary warblerProtonotaria citreaXXMammalsSoutheastern myotis (?)Myotis austroripariusXXRed batLasiurus borealisXXSeminole batLasiurus seminolusXXEvening batNycticeius humeralisXXFlorida manateeTrichechus manatus latirostrisXX25Table 2-6. Listed and endemic taxa largely dependent upon aquatic and wetland habitats that occur in the Wekiva Riversystem. U.S. = species officially listedunder the Endangered Species Act; Florida = species listed by the State of Florida;FNAI = species listed by the Florida Natural Areas Inventory; FCREPA = species listed by the Florida Committee on Rareand Endangered Plants and Animals. See bottom oftable for definitions of status designations.TAXONEndemicU.S.FloridaFNAIFCREPAPlantsNeedle palmRhapidophyllum hystrixTCardinal flowerLobelia cardinalisTHand fernOphioglossum palmatumES2Star aniseIllicium parviflorumY (?)ES2InvertebratesWekiva springs hydrobeAphaostracon monasYS1TWekiva siltsnailCincinnatia wekiwaeYS1Rock springs siltsnailCincinnatia petrifonsYSanlando siltsnailCincinnatia ponderosa(extinct?)YS1Seminole siltsnailCincinnatia vanhyningiYS1Rock springs horn snailElimia vanhyningianaYOrlando cave crayfishProcambarus acherontisYS1TS.E. spinyleg dragonflyDromogomphus armatusS3REverglades spriteNehalennia pallidulaYSSCMicrocaddisflyOrthotrichia instabilisTTriaenode caddisflyTriaenodes furcellaTFishesBluenose shinerPteronotropis welakaYSSCSSCReptilesAmerican alligatorAlligator mississippiensisTSSC26Table 2-6. Continued.TAXONEndemicU.S.FloridaFNAIFCREPABirdsLittle blue heronEgretta caeruleaSSCSSCSnowy egretEgretta thulaSSCS3SSCGreat egretArdea albaSSCTricolored heronEgretta tricolorSSCSSCReddish egretEgretta rufescensSSCS2RLimpkinAramus guaraunaSSCS3SSCYellow-crowned night heronNyctanassa violaceaS3SSCBlack-crowned night heronNycticorax nycticoraxS3SSCWhite ibisEudocimus albaSSCSSCGlossy ibisPlegadis falcinellusS3SSCWood storkMycteria americanaEES2EFlorida sandhill craneGrus canadensis pratensisYTS2/S3TSwallow-tailed kiteElanoides forficatusS2TPeregrine falconFalco peregrinusES2ES. E. American kestrelFalco sparverius paulusTS3TBald eagleHaliaeetus leucocephalusTTS3TMammalsFlorida black bearUrsus americanus floridanusYTS2TFlorida manateeTrichechus manatus latirostrisYEES2EE=Endangered; T=Threatened; SSC=Species of Special Concern; R=Rare; S1=critically imperilled in Florida because of extremerarity or because of extreme vulnerability to extinction due to some natural or man-made factor; S2=imperilled in Florida because ofrarity or because of vulnerability to extinction due to some natural or man-made factor; S3=either very rare and local in Florida orfound locally in a restricted range or vulnerable to extinction from other factors.27River floodplain because these swamp forest s 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 incorporat e 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 regi ons 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 amphibia ns (Sparling et al. 2000). Mechanisms postulated for these include in creasing 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 wate r drainage areas of the Wekiva River and Rock Springs Run were analyzed by WSI (20 04). More intensive development (urban, suburban, and transportation) increased by about 350% between 1973 and 2000 (Table 2-7), with much of the change occurri ng between 1973 and 1990. Nitrogen isotope analyses conducted by SJRWMD to evaluate s ources contributing ni trates to Wekiwa Spring and Rock Springs indicated a combinati on of organic (wastewater, manure, etc.) and inorganic (fertilizer) source s, attributed largely to urban development in the spring recharge area (Toth and Fortich 2002). Alt hough high nitrate concentrations were measured in the Floridan Aquifer beneath agricult ural lands in the western part of the contributing area, Toth and Fortich believed t hat 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 dr ainage 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%

283 DISTRICT STUDIES CONDUCT ED FOR PLRG DEVELOPMENT

Beginning in 2004, after passage of the We kiva Parkway and Protection Act, SJRWMD contracted with private consult ants to conduct investigations that would contribute to PLRG development for the Wekiva River and Rock Springs Run. District staff also

reviewed scientific literatur e 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 concurr ent efforts. Details can be found in the appendices.

3.1 Ecosystem Metabolism in the Weki va 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 fo r the Wekiva River and Rock Springs Run and to develop a work plan for rapid PL RG development. WSI’s 2004 Work Plan Report is in Appendix B.

The purpose of the work plan was to pr ovide 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 in formation on the Wekiva River and Rock Springs Run and similar reference spring-r un streams to characterize a baseline for the streams’ designated uses 2. Review of existing information and plannin g 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 im plement the Wekiva PLRG work plan. Impairment was evaluated by measuri ng 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-bal ance estimation for the four spring-run streams

293. Detailed ecological evaluat ion under conditions of diffe ring nutrient availability in segments in the Wekiva River, Rock Spri ngs Run, Juniper Creek and Alexander Spring Creek 4. Collection of ecosystem-level data ( physical environment, water quality, plant communities, gross primary productivity, net primary producti vity, ecological efficiency) 5. Analysis and interpretation of data to evaluate impairment

To identify pollutants of c oncern, ecosystem metabolism data from the Wekiva River and Rock Springs Run were compared to the re ference streams to determine whether, and to what extent, nutrients affected ecosyst em function. Water quality spatial trends were examined and compared to ecosystem data to look for onset of impairment.

Nutrient concentrations and loads in the Weki va 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 nutri ents and used the two reference streams to determine acceptable nutrient tar gets. Existing pollutant loads causing impairment were determined by calculation of water and nut rient mass balances. Overall nutrient mass

balance loads and assimilation rates were esti mated for the Wekiva River, Rock Springs Run, Alexander Springs Creek, and Juniper Cr eek. 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. Th is model includes estimated water and associated nutrient inputs from springs, non-poi nt source runoff, tributaries, and from atmospheric inputs. Nutrient transforma tion rates were estimated from published reaction rates. Necessary pollutant load reduction was estimated as the difference between the existing pollutant load and the esti mated 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 nitr ate 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. Result s 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 as sess 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,

30density and biomass were analyzed from 15 si tes 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 t he streams. Algae grow ing on the sediment surface were not sampled. Field water quality parameters were measured concurrent with algal sampling, and water quality sample s 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 lit erature 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 chapt er. 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 sect ion) 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 le vels of nitrate t hat have been demonstrated (experimentally or with field surveys) to caus e 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. Un certainty factors are a means of accounting for various sources of uncertainty, extrapolat ion from short-term la boratory results to long-term effects in the field, from one specie s to others, and from lethal thresholds to sublethal thresholds (Newman and Unger 20 03). Uncertainty factors were applied to the literature-derived toxicity values to esti mate protective threshold concentrations for

nitrate. Details on this lit erature 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 bacteri a levels according to numeric criteria in the Impaired Waters Rule (Chapter 62-303, FA C). Reductions in total coliform counts were calculated based on EPA’s percent-reduc tion 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 Riv er and Rock Springs Run to evaluate whether there was a relationship bet ween phosphorus and the occurrence and

31proportion of algae generally considered to be “nuisance” taxa. These are primarily taxa in the Cyanobacteria and green algae (Chl orophyta). 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 (Cowe ll and Dawes 2004) conduc ted laboratory assays for the Southwest Florida Water Managemen t 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 Distri ct (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 densit y 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, Al exander Springs Creek, Wacissa River) considered to be less-impacted due to mini mal 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 undevel oped watersheds in the continental U.S.

Their data came from various U.S. G eological Survey water quality assessment programs conducted between 1990-1995. Binkley et al. (2004) extracted data from the published literature on nitrogen an d phosphorus concentrations in 300 streams draining largely forested watersheds in the U.S. T hey 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 A gency (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 Cons ent Decree. The TMDL was based on comparison with Juniper Spring, a less-impac ted lower-nutrient spring-run stream in

32Ocala National Forest. A target conc entration was selected based on the 90 th percentile level of nitrate for Juniper Spring. The URL lin k to this report is listed in the Literature

Cited section.

3.3.9 Total Phosphorus and Epiphyti c Algae in Ichetucknee Springs

A contractor for Suwannee River Water Ma nagement 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 chlo rophyll 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) co llected phosphorus data fr om 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 histor ic or background conditions of phosphorus in springs.

3.3.11 Nitrate Targets for FDEP’s Wastewater Treatment Criteria

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

central wastewater treatment standards and criteria for the Wekiva Study Area, as mandated by the Wekiva Parkway and Prot ection Act. This target was based on comparison with nitrate levels in less dev eloped spring-run streams such as Juniper Creek, Alexander Springs Creek, and Silv er 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.

334 PLRG DEVELOPMENT

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

1. Identify the nature and ext ent of impairments, if any; 2. Identify causative pollutants, if any; 3. Determine acceptable concentrati ons of causative pollutants; 4. Calculate necessary pollutant load reductions.

The various investigations described in Chap ter 3 each contributed to one or more of these steps. Key results of these investigat ions are briefly summarized in the following sections. Detailed reports for most of these efforts are in the Appendices. Prior to presentation of the findings, how ever, is a discussion of issues involved in identifying impairment and in defin ing 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 Ro ck Springs Run have a designated use of Class III, meaning they are managed for “rec reation, propagation of a healthy, wellbalanced population of fish and wildlife”. A wa ter body must meet a set of water quality standards specific to its designated use. If it does not meet t hose standards, it is considered impaired. Chapter 62-303, FAC (Identification of Impaired Surface Waters) establishes the criteria by wh ich the State of Florida iden tifies 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 Veri fied 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 bioassessmen t, 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 viol ation 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 suffi cient quantities to “pose a nuisance” or “hinder reproduction of a threatened or endangered species”, and/or (2) annual mean chlorophyll-a levels are >20 μ g/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 indicati ng an imbalance of flora or fauna due to

34nutrient enrichment, including, but not limited to, algal blooms, excessive macrophyte growth, decrease in the dist ribution (either in density or areal coverage) of seagrasses or other s ubmerged aquatic vegetation, changes in algal species richness, and excessive diel oxygen swings, shall also be considered.” (Chapt er 62-303.350[1], FAC);

• the water body was subject to swi mming area closures due to exceedance of primary contact bacteri ological 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 cr iteria are demonstrated.

Water bodies placed on this Verified List of Impaired Waters are then subject to the development of Total Maxi mum 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 MSJR B (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 informati on from the FDEP Bioassessment program and fish tissue data/consumpt ion advisories were also considered. See the FDEP website (link listed in Literature Cited) fo r a copy of the MSJR B Assessment Report. Based on their criteria and analysis, FDEP d oes 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 demonstr ated and causal pollut ants 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 ma king 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 diffi cult, 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 imbalanc e 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 findi ng of imbalance and impai rment. In other

35Table 4-1. Issues that we re considered in determining im pairment of the Wekiva River and Rock Springs Run.

Water Quality Comparison to Class III standardsComparison 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 nutrient s/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 (interfe rence 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, durati on, magnitude)

Interactions with established MFL for the Wekiva

River

36cases (alterations in species composition of algal or benthic co mmunities, impacts on sportfish habitat), a scientific judgment r egarding what constitutes a balanced biota

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

of waters in the absence of man-induced alterations based on the best scientific information available to the Department. T he 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). A ssuming that the natural background condition maintained a balanced biota, the determination of nutrient impairment can be based on comparisons to hist orical data predating impacts or to the

biota of similar water bodies that ar e unimpacted (reference water bodies).

Because data pre-dating anthropogenic effects are generally lacking for many aquatic ecosystems, a current approach towards asse ssing anthropogenic effects is to define a “reference” condition using minimally impact ed, similar systems for a particular region (Hughes 1995; Bunn et al. 1999). The refer ence condition is generally interpreted to mean the condition of the syst em 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 earlie r work, defines biological integrity as:

“the ability to support and maintain a balanc ed, 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 wh en its inherent potential is realized, its condition is stable, its capacit y for self-repair when perturbed is preserved, and minimal external suppor t for management is needed.”

In a “reference” approach, deviation from the reference condition is inferred as impairment, including the above consideratio ns regarding biological integrity and ecological health.

For the Wekiva River system, water qualit y or ecological degradation that can be demonstrated to have occurred since 1979 (t he baseline year for evaluating the nondegradation standard for OFWs) would consti tute 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 to xic to, or produce adve rse physiological or behavioral response in humans, plants, or an imals” (Chapter 62-302.530 [62], FAC). Because nitrate can be toxic to aquatic organisms, our inve stigation included an assessment of the potential for nitrate toxi city and an analysis of concentrations that would result in minimal or no toxicity effects.

374.2 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 polysacchar ide matrix (Lock et al. 1984). This community has been variously described as a “bio film” or “benthic turf ”. The periphyton can also include filamentous macrophytic algae or macroalgae. These species are macroscopic (easily visible), primarily f ilamentous green (Chlorophyta) and yellow-green (Xanthophyceae) algae and Cyanobac teria. They may form th ick 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), excessi ve periphyton growth, espec ially 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 t he level of periphyton that is harmful was beyond the scope of this work and is not available in the scientific liter ature. To reduce the potential for harmful levels of periphyton, we looked for inflection points between the growth potential of periphyton (at species an d 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 (prima rily the filamentous macroalgae in the Cyanobacteria and Chlorophyta) and its possible li nk to elevated nitrate levels is of relevance in this PLRG analysis. Flori da’s Impaired Waters Rule (Chapter 62-303.200,

FAC ) defines “nuisance species” as:

“. . . species of flora or fauna whose noxious characterist ics or presence in sufficient
number, biomass, or areal extent ma y reasonably be expected to prevent, or unreasonably interfere with, a designated use of thos e 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/m 2 (which equated to a cover of about 20% filamentous macroalgae) as a nuis ance level in northern rocky streams. They interpreted nuisance to mean “aesthetic ally displeasing and in terfere(s) with foot travel by fishermen.” Lar ge mats of filamentous algae (Cyanobacteria and Chlorophyta)

are also a aesthetic nuisance in that anaerobic decomposition of dead filaments within the mats produces a characteri stic “sewage” or “septic” odor.

To date, a determination of w hat 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 Im paired Waters Rule, algal growth that

interferes with recreational uses or causes ecological changes which affect “health or

38balance” of fish or wildlife populations coul d be considered a nuisance, and thus an impairment of the water body.

One algal group of major concer n in Florida springs is t he 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; St evenson et al. 2004). Lyngbya , and other Cyanobacteria, produce toxins that may be associated with ski n reactions (dermatitis) and respiratory distress (Burns, unpublished paper; Komárek 2003) . In some instances the allergic reaction may be severe enough to result in anaphy lactic shock. The toxins may also have ecological impacts, but these have re ceived 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 PL RG 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 m onths 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 inorgan ic nitrogen (TIN) was higher in upstream segments of the Wekiva River and Rock Springs Run than in the J uniper and Alexander segments. Measures of eco system metabolism (gross primar y productivity, net primary productivity, and ecological efficiency) were c onsistently lower in the Wekiva River and Rock Springs Run than in the two reference st reams (Figure 4-2). High nutrient loading in the Wekiva River and Rock Springs R un appears to be causing disruption of ecosystem function in these aquatic eco systems, evidenced by reductions in productivity and ecological efficiency (WSI 2005).

WSI (2005) noted other impacts to the Weki va 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 wa tershed, flow reduction due to increasing groundwater withdrawals, hi gh-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 struct ure and function. These were based on evaluation of ecosystem metabolism data and water quality data for 130 Florida springs. Ecosystem metabolism data sugges ted an NOx target of 100 – 200 μ g/L . About half of the 130 Florida springs had mean NOx concentrations greater than 500 μ g/L and mean

39Nitrate

0 100 200 300 400 500 600 700 800

Wekiva River Rock Springs Run Alexander Spring

Creek Juniper CreekNO3/NO2-N (μg/L)

Total Phosphorus

0 20 40 60 80 100 120 140 160

Wekiva River Rock Springs Run Alexander Spring

Creek Juniper CreekTP (μg/L)

Figure 4-1. Mean nitrate and total phosphor us concentrations in intensive-study segments of the Wekiva River, Rock Spring s Run, Alexander Spring Creek and Juniper Creek (from WSI 2005).

40Community GPP (gO 2 /m 2 /day)

0 1 2 3 4 5 6 7

Wekiva River Rock Springs Run Alexander Spring

Creek Juniper CreekgO2/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).

41TP concentrations greater than 50 μ g/L . Based on these lines of evidence, WSI

calculated PLRGs for tar get concentrations of 100 μ g/L NOx and 50 μ g/L TP.

PLRGs

. Preliminary NOx and TP load reducti ons necessary to meet these concentration targets were calculated using simple linear models relating nutrient loading rates and in-stream nutrient concent rations 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 μ g/L NOx target at a downstream point in t he Wekiva River. A TP load reduction of 76% would be required to meet the 50 μ g/L TP target at a downstream point in the

Wekiva River.

See Appendix C for Wetland Soluti ons’ 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 R un (RSR). Diatoms were the dominant algal group in terms of biomass and diversity at the majority of si tes (GreenWater Labs 2005). Filamentous Cyanobacteria (particularly Lyngbya wollei and Phormidium ) were most abundant in terms of biomass at samplin g 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 bi omass 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 sampli ng 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 pr obit analysis they extrapolated from the

acute LC50 concentrations to estimate “saf e concentrations” for ch ronic 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 We kiva 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 μ g/L and above (Edwards et al. 2004; Edwards 2005). Selected frog genera in Canada ( Rana sp. and Pseudacris sp.) showed

42adverse sublethal effects at nitrate levels as low as 2,500 μ g/L (Hecnar, 1995). Representatives of these frog genera are pres ent in the Wekiva River and Rock Springs Run ( Rana spp.) and its adjacent floodplain ( Pseudacris spp). Many of the experimental studies were c onducted over the larval lifet ime of an animal (e.g., frogs from egg to adult).

Figure 4-3 illustrates the reported toxicity thre sholds for different aquatic animals

relative to nitrate concentrations in the We kiva River and Rock Springs Run. Maximum nitrate concentrations recorded through 200 5 for the Wekiva River and Rock Springs
Run were 1,500 and 1,800 μ g/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 μ g/L (67%) for the Wekiva River and 700 μ g/L (39%) in Rock Springs Run would meet or exceed toxicity thresholds for other caddisflies and for certain frogs.

Derivation of a protective nitrate concentrati on requires consideration of the sources of uncertainty inherent in the limit ations 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 uncertai nty factors to set protecti ve exposure limits for toxic

contaminants:

1) an interspecies uncertainty factor (UF A ); 2) an exposure duration uncertainty factor (subchronic to chronic: UF S ); 3) an exposure endpoint uncertainty factor (UF L ) – equivalent to a concentration

between the “Lowest Observed Effect Level” (LOEL) and the “No Observed Effect Level” (NOEL), and; 4) an intraspecific uncertainty factor (UF I ).

These factors were applied to the lowest ni trate toxicity thresholds derived from the literature review for caddisflies (1,400 μ g/L) and amphibians (2,500 μ g/L). Application of uncertainty factors yielded co ncentration thresholds of 140 and 125 μ g/L, respectively. Detailed description of this procedure is in Appendix E.

A statistical approach was developed to take t he nitrate toxicity thresholds derived from application of uncertainty fact ors and use them to determine what a new mean nitrate

level would be if the threshold were set at the upper end of the po pulation of nitrate

data. Nitrate data from t he headspring regions of the We kiva River and Rock Springs Run were used since these were the highest le vels (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 confo rm 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 distri bution, at the 90 % probability level, in order to build in an explicit margin of safety. Us ing this as a starting point, the new mean nitrate concentration wa s calculated based on the probability of a

43Wekiva 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 inse cts, amphibians, and mosq uitofish. Source: SJRWMD data analysis and literatur e review (Mattson et al. 2005). 0 500 100 0 0 0 0 0 0 0

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004NOx (μg/L)

150 200 250 300 350 400 Caddisfly Threshold 1 Caddisfly Threshold 2 Amphibian Threshold 1 Mosquitofish Threshold 1 000 500 000 500 000 500 000

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004NOx (μg/L) 4

3

3

2

2

1

44randomly collected water sample having a ni trate concentration at or less than the specific threshold. To determine the target mean nitrate concentration:

M + Z score*S = threshold concentrati on (Equation 1)

M is the target mean nitrate concentration, S is the standard devia tion 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 concentra tions at or less than the established threshold target.

Since S is unknown for the new population distribution, the c oefficient of variation (CV) of the existing population (= t he 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 ex isting population distribution. This assumes that the population variance wi ll vary in proportion to the me an 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 μ g/L at a probability of 90% (i.e., 90% of the time, nitrate must be < 125 μ g/L). This was the threshold determined by applying uncertainty factors to the lowest amphibian threshold of 2,500

μ g/L NOx. Using the stat istical methodology described above, the new population mean nitrate/nitrite nitrogen concentrations were 108 μ g/L in the Wekiva River and 111

μ g/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 literat ure 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 exceedanc e 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

45closed five times between 2000 and 2005 bec ause 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 GreenW ater Labs (2005) sampled al gae 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 t he attached algal data from the Wekiva River and Rock Springs Run indicated that % Cyanobacteria in the algal community (by biovolume) was positively correlated with to tal phosphorus (TP) and % Chlorophyta was not significantly correlated with TP. Graphica l analysis of the data indicated that above

TP concentrations of 90 μ g/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 to xicity, was used to calculate a mean TP

concentration for the Wekiva River and for Ro ck Springs Run by setting a threshold of maintaining TP levels < 90 μ g/L with a probability of 90%. This probability was selected to be ecologically protective.

Mean TP resulting from this analysis was 59 μ g/L for the Wekiva River and 61 μ g/L for Rock Springs Run. Results of these analyses are summariz ed in Appendix G.

4.3.6 Rainbow River Algal Bioassays

Cowell and Dawes (2004) perfo rmed laboratory assays of nitrate concentration and growth of Lyngbya wollei from the Rainbow River and found a nitrate threshold of 300-

600 μ g/L , above which growth of Lyngbya was significantly higher They recommended

a reduction to <300 μ g/L nitrate would be necessary to reduce growth of Lyngbya in the Rainbow River. A threshold nitrate target concentration of 250 μ g/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 co llected on the Suwannee River (Hornsby et al. 2000) with glass-slide settling racks (periphytometers) indicate that periphyton

biomass and abundance increase at th reshold concentrations of 200 - 300 μ g/L nitrate (Figure 4-5). This lends s upport to the threshold of 250 μ g/L nitrate indicated in the Section above. An upper threshold of about 600 μ g/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 infl ow, and the algal communities appear to be generally similar in composition to those in the Wekiva River and Rock Springs Run. Therefore, the Suwannee re sults are considered applicable to the Wekiva River and Rock Springs Run. See Appendix H for details of the Suwannee River work.

460 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.

47Figure 4-5. Plots showing relationships between mean nitrate concentration and mean periphyton cell density and bi omass from long term monitoring stations on the Suwannee River. Source: Hornsby et al. (2000)

484.3.8 Nutrients in Less-Impacted Spring-R un 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 μ g/L . Median total phosphorus concentrations in these streams were all <50 μ g/L (Appendix I).

Median nitrate concentration in 130 Florida springs, including springs known to be impacted by elevated nitr ate loading, was 480 μ g/L and median total phosphorus was

40 μ g/L. Median nitrate/total phosphorus leve ls in Alexander Spring were 51/44 μ g/L, in Juniper Spring 81/34 μ g/L and in Fern Hammock Spring 90/31 μ g/L. These correspond to the results reported above for less im pacted spring runs (i.e., nitrate <100 μ g/L and total phosphorus <50 μ g/L)

.

Data are summarized in Appendix I.

4.3.9 Nutrients in Undeveloped St reams in the United States

Median nitrate concentrations in streams draining undeveloped watersheds nationwide

were 87 μ g/L (Clark et al. 2000). Median total phosphorus levels in these streams

nationwide were 22 μ g/L . In forested watersheds in the southeastern U.S. (Binkley et al. 2004) mean nitrate levels were 180 μ g/L and median levels were 50 μ g/L

. Nationwide, mean nitrate levels in these forested watersheds were 310 μ g/L , with a

nationwide median of 150 μ g/L nitrate. Phosphate leve ls (whether this was PO 4 or PO 4 - P was not specified in the paper) in the southeastern U.S. from these forested

watersheds showed a mean of 14 μ g/L and a median of 7 μ g/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 μ g/L NOx for Wekiwa Spring and Rock Springs based on the 90 th percentile of nitrate concentration in Juniper Spring. Using th is concentration target, USEPA proposed a 91-95% reduction in nitrogen load to rest ore 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 Epiphyti c Algae in Ichetucknee Springs

No significant relationships were obser ved 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 bot h total phosphorus and soluble reactive phosphorus (SRP), which were almost identic al in these springs. Epiphytic algal biomass notably increased abov e a threshold of about 50-55 μ g/L SRP or TP (PBS&J 2004). Results and excerpts from this report are in Appendix J.

494.3.12 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 μ g/L (Odum 1953). Florida springs outside of phosphatic regions had a mean TP concentration of 45 μ g/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 perio ds 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 μ g/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 - Imbal ance 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 producti vity 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 fo r high biomass and productivity of periphyton and potentially nuis ance algal species, especially Cyanobacteria, again, constituting an imbal ance of flora and fauna.

4.4.2 Nitrate - Potential for chronic toxicity

• Nitrate concentrations have been demons trated to exceed nitrate toxicity thresholds for sensitive aquatic insects and frogs as prohibit ed by Chapter 62- 302.530[62], FAC

504.4.3 Nutrients - Non-comp liance with OFW designation

• The high concentrations of nitrate and total phosphorus indicate anthropogenic enrichment that is not in compliance wit h part of the narrati ve 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 in crease in nitrate concentrations in Rock Springs Run since the stream wa s designated an Outstanding Florida Water. This is prohibit ed 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 viol ation 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 invest igation (Tables 4-2 and 4-3) were collectively

considered to arrive at tar gets for nitrate and total phosphorus.

4.5.2 Nitrate

SJRWMD proposes mean target concentrations of 216 μ g/L NOx for the Wekiva River

and 221 μ g/L NOx for Rock Springs Run. Thes e mean nitrate targets will.

• maintain nitrate levels < 250 μ g/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 f ound in less-impacted sp ring-run streams;

• maintain nitrate concentrations at levels that would be minimally toxic to aquatic fauna. The proposed mean concentrations ar e reduced by a factor of 11 to 12 for the lowest observed amphibian toxicity threshold and by a factor of about 6

51Table 4-2. Potential nitrate-nitrite (NOx) concentration targets basedon various lines of investigation.ReferenceBasis for TargetNOx (μg/L)StatisticEcosystem metabolism in the WekivaRiver and Rock Springs Run (WSI2005)Comparison to metabolism in less-impacted spring-run streams (Juniper &Alexander)Comparison to other springs in SJRWMD100 - 200200ThresholdMedianNitrate toxicity to aquatic animals(Mattson et al. 2005)90% probability of <1,400μg/L (lowest toxicity threshold for caddisflies)Wekiwa SpringRock SpringNew thresholds after application of uncertainty factors90% probability of <125μg/L (lowest threshold with uncertainty factor):Wekiwa SpringRock Spring1,2001,240125 - 140108111MeanMeanThresholdMeanMeanRainbow River algal bioassays(Cowell and Dawes 2004)Lyngbya wolleibiomass90% probability of <threshold of 250μg/L:Wekiva RiverRock Springs Run300 – 600216221ThresholdMeanMeanSuwannee River periphytic algae andnitrate levels (Hornsby et al. 2000)Algal biomassAlgal cell density200 - 300300ThresholdThresholdNutrients in Florida springs (WSI andDEP databases)130 Florida springs, including impacted springsJuniper Spring, Fern Hammock SpringAlexander Spring48081, 9051MedianMedianMedianNutrients in less-impacted spring-runstreams in Florida (STORETdatabase)Juniper CreekAlexander Spring CreekWacissa River805060MedianMedianMedianNutrients in undeveloped streams Inthe United States (Binkley et al.,2004; Clark et al. 2000)Forested stream basins in the southeastern U.S.Undeveloped watersheds in the U.S.18087MeanMedianEPA proposed TMDL for WekiwaSpring and Rock Springs Run(USEPA 2005)Comparison to Juniper Spring110ThresholdFDEP wastewater treatment criteria inthe Wekiva Study Area (FDEP 2004)Comparison to less-impacted Florida springs200Threshold52Table 4-3. Potential total phosphorus (TP) concentration targets based on various lines of investigation.ReferenceBasis for TargetTP (μg/L)StatisticEcosystem metabolism in the Wekiva Riverand Rock Springs Run (WSI 2005)Comparison to metabolism in less-impacted spring-run streams(Juniper & Alexander)Comparison to springs in SJRWMD50-8050ThresholdMedian% Cyanobacteria and Chlorophyta in attachedalgae in Wekiva River and Rock Springs Run(analysis of data from GreenWater Labs 2005)90% probability of <90μg /L (threshold for increased levels ofcyanobacteria and chlorophyta in attached algal community):Wekiva RiverRock Springs Run5961MeanMeanMapping and monitoring of submerged aquaticvegetation in the Ichetucknee Riverheadsprings (PBS&J 2004)Epiphytic algal biomass55ThresholdPhosphorus in selected Florida springs in the1950s (Odum 1953)Springs outside of phosphatic areasSprings within phosphatic areas4561MeanMeanNutrients in Florida springs (WSI and DEPdatabases)130 Florida springs, including impacted springsJuniper Spring, Fern Hammock SpringAlexander Spring4034, 3144MedianMedianMedianNutrients in less-impacted spring-run streamsin Florida (STORET database)Juniper CreekAlexander Spring CreekWacissa River234444MedianMedianMedianNutrients in undeveloped streams in the UnitedStates (Clark et al. 2000)Undeveloped watersheds in the U.S.22Median53• for the estimated no effects threshold of caddisflies as reported in Mattson et al. (2005);

• restore NOx concentrations to that char acteristic 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 (Fi gure 4-6). The Wekiva River and Rock Springs Run targets

fall at the 29 th 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-nitrit e measurement of 70 μ g/L for Rock Spring in 1946, so the proposed targets are not as low as these springs ma y have historically been, but should be low enough to protect the ecological integrity of the spring-r uns. 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 rese arch appears to have been done in Florida springs to separate the phosphate derived from natural leaching vs. that

derived from surficial rechar ge. Orthophosphate is also r apidly 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 treatm ent and stormwater management are primarily focused on reductions in TP, so any improvements due to load reductions should be measureable by sa mpling TP in the spring-run streams. SJRWMD proposes mean target concentrations of 59 μ g/L TP for the Wekiva River and

61 μ g/L TP for Rock Springs Run. These mean TP concentration targets will:

• maintain TP concentrations below t he threshold for increased growth of Cyanobacteria and green algae (90 μ g/L) with a probability of 90%;

• restore ecological efficiency to that f ound in less-impacted spring-run streams;

• Limit accumulation of epiphytic algal biom ass by keeping TP concentrations ~60

μ g/L;

• restore TP concentration to that f ound 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 uppe r mid-range of the range of possibilities considered in Table 4-3 (Figure 4-7). The Wekiva River tar get falls at the 66 th percentile for the database of 130 Florida springs assembled by WSI (2005) and Rock Springs

Run falls at the 67 th 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 μ g/L) as reported in Odum (1953), which may be regarded as “natural background”. Reference springs in the Ocal a National Forest, such as Alexander and

540100200300400500600

A lex an der S prin g Cre ek

A l exan d er s p ring W ac iss a R iv er J unipe r Cre e k Juni p er sp r ing

U S w ater sh eds

Fer n Hammoc k spr i ng

eco sy ste m me ta boli sm - lo wer NITRATE TOXICITY - WE K IWA SPRING E PA T MD L

N I TRA T E T O XICITY - ROCK SPRING SE U S str ea ms

ecos y stem met a bolis m - u p per

S J RW M D sp rin gs

DE P wastewater cr i teria

S uwa nn ee River a lgae - low er

AL G AL G RO W TH - W E KIV A RIV E R

A LG A L G R OW T H - R O CK S PR IN GS R U N Suwanne e Riv e r alg a e - u p per Rainbow Ri v er a lg ae - l ower

1 3 0 Fl o rida s pring s

R ai nbow Riv e r alg a e - u p per

Potential NOx target concentration (ug/L)proposed targetconcentration meansFigure 4-6. Chart showing nitrate concentration targets that were considered and mean concentration targets proposedfor the Wekiva River and Rock Springs Run.55Figure 4-7. Chart showing total phosphorus concentration targets that were considered and mean concentration targets0102030405060708090

U S watersheds Juniper Creek Fern Hammock spri n g J uni p er sp ri ng

1 30 Fl ori da s prin gs

A l ex an der Spri ng C ree k Wac is s a R i ve r Al exa nd er s pri ng

195 0 s P in FL sp ri ngs not i n phosphati c area s ecosy s tem meta b oli s m - low e r S JRWMD s prin g s

ep i phy ti c al gae i n Ic he tuc k nee s prin gs

ATTAC H ED A L G A E IN THE W E KIVA R IVER

ATTAC HE D A L G AE IN RO C K SP RIN G S RU N

1 95 0s P i n FL s p rings in ph osp ha tic areas

e c os y ste m me t abol i sm - upper

Potential TP target concentration (ug/L)proposed targetconcentration meansproposed for the Wekiva River and Rock Springs Run.56Juniper also have TP values within or less than this range (40-60 μ g/L). Odum (1953) reported TP values of 120-127 μ g/L TP for Rock Spring in 1951. This approximates existing concentrations in the spring run (Figur e 4-1), indicating either that this is the

natural concentration or that anthr opogenic TP loading affected the 1951
measurements and has continued, either via groundwater and/or surfacewater inflow. Rock Spring continues to average around 80 μ g/L TP and Wekiva Spring 200-600 μ g/L (WSI 2004; Osburn et al. 2002), which lie a bove 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 enr ichment and phosphorus leached from geologic deposits in the region.

4.5.4 Total Coliform Bacteria

SJRWMD proposes a not-to-exc eed 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 av ailable to calculate nutrient and coliform loading from various sources to the Wekiva River and Rock Sp rings Run and to relate in-stream concentrations to external loads. Therefore, only reductions in pol lutant concentration

could be calculated at this time. We assume that pollutant load reductions need to be proportional to pollutant concentration reduc tions. Throughout the remainder of this document, the percent load reduction is cons idered 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 consider ed in development of NOx and TP target concentrations. As appropriate, the require d concentration reduction was calculated either for specific segments of each spri ng-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 c onsisted 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 da ta for each segment (Table 4-4).

57Spatial Trends. Nitrate concentrations significant ly 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 str eams 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 c onfluence of the Little Wekiva River and corresponding to USEPA Water Body Identific ation (WBID) numbers. Rock Springs Run had one downstream segment consisting of t he 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 tar get concentration of 216

μ g/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 μ g/L , nitrate load reductions required to re store 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 condi tion” data set was created for each spring-run

stream that consisted of t he most recent and largest data set the showed no significant temporal trend. Total phosphorus load reduct ions were calculated based mean of the current condition for each spri ng-run stream (Table 4-5).

Spatial Trends. Total phosphorus showed no spatial tr end 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 ex ception of the headspring por tion (Table 4-5).

TP PLRGs - Wekiva River. Based on the proposed mean target concentration of 59

μ g/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 μ g/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 Ro ck 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

58Figure 4-8. Map showing Wekiva River system segments and current conditions for nitrate (NOx) and total phosphorus (TP).

59Table 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 c oncentrations 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 μ g/L 216 μ g/L 82% Upper Wekiva River 704 μ g/L 216 μ g/L 69%

Lower Wekiva River 335 μ g/L 216 μ g/L 36%

Rock Spring 1,426 μ g/L 221 μ g/L 85% Rock Springs Run 458 μ g/L 221 μ g/L 52%

Total Phosphorus Upper Wekiva River 119 μ g/L 59 μ g/L 50%

Lower Wekiva River 119 μ g/L 59 μ g/L 50%

Rock Springs Run 86 μ g/L 61 μ g/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%

60vs. anthropogenic. Further wo rk will better separate these two components in the spring inflow.

4.6.2 Total Coliform Bacteria

Coliform concentration reductions were calc ulated 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 diffe rence and obtaining the median % reduction for all of the data in two segments in t he Wekiva River (upper and lower) and in Rock Springs Run. Details are provided in Appendix F.

Based on the proposed target conc entration 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 FD EP in adopting Total Maximum Daily Loads (TMDLs) for impaired waters within the We kiva Study Area. Consequently, SJRWMD and FDEP staff spent considerable time di scussing 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 Riv er 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 propo sed here by SJRWMD for nitrate, total phosphorus, and total coliform bacteria ar e 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 nec essarily 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 nat ural intra- and inter-annual variation in spring-run streams. This problem was compounded by the fact that, during these studies, hurricanes caused atypical conditi ons of high water flows, scouring of vegetation, transfer of sediments and atypical water quality conditions.

612. There are no specific state standar ds, and no general scientific consensus, on criteria for identifying im pairment of spring-run str eams. Throughou t 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 Im paired 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 pr oblems with fungal contamination, so these very low repor ted nitrate levels were not adopted as thresholds of toxicity. Further toxicolo gical work is needed to confirm that the proposed nitrate target concentrations are pr otective of the aquatic life of the Wekivia River system.

4. The relationships between periphytic al gal growth and nutrient concentrations under varying conditions of current veloci ty and light are poorly known. These relationships need further study. Criter ia 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 macroinvertebrat e and fish habitat is not understood quantitatively. Further work is needed to del ineate 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 re sult 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 colle ction 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 eval uation of in-stream surveys of algal

communities and nutrients in the Wekiva River and Rock Springs Run, and are performing laboratory assays in mesocosm s to determine limiting nutrients and

the effects of nutrient r eductions on algal growth;

• Staff is reviewing additional scientific lit erature on nitrate toxicity effects on aquatic animals.

62Other research efforts are planned to further define impai rment, pollutant impacts, and required reductions to restore and maintain t he 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 ecosystem s, impairment of spring-run streams, other pollutants of conc ern (including nutrient forms), and pollutant sources and loadings. These will contribute to future revisions of PLRGs proposed in this report.

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696 APPENDICES

70