Characterization of the Hydrology, 

Water Chemistry, and Aquatic Communities 

of Selected Springs in the St. Johns River 

Water Management District, Florida, 2004

By G.G. Phelps, Stephen J. Walsh, Robert M. Gerwig, and William B. Tate

Prepared in cooperation with the

St. Johns River Water Management District

Open-File Report 2006-1107

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Dirk Kempthorne, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2006

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Suggested citation:

Phelps, G.G., and others, 2006, Characterization of the hydrology, water chemistry, and aquatic communities of 

selected springs in the St. Johns River Water Management District, Florida, 2004: U.S. Geological Survey Open-File 

Report 2006-1107, 51 p.
iii

Contents

Abstract ..........................................................................................................................................................1

Introduction.....................................................................................................................................................2

Purpose and Scope ..............................................................................................................................2

Previous Studies ...................................................................................................................................2

Acknowledgments................................................................................................................................4

Site-Numbering System.......................................................................................................................4

Environmental Setting .........................................................................................................................4

Methods...........................................................................................................................................................4

Hydrologic and Water-Chemistry Data ............................................................................................4

Aquatic Community Data ....................................................................................................................6

Characterization of Springs .........................................................................................................................8

Silver Springs.........................................................................................................................................8

Hydrology and Water Chemistry ...............................................................................................9

Aquatic Communities ................................................................................................................13

De Leon Spring....................................................................................................................................16

Hydrology and Water Chemistry .............................................................................................16

Aquatic Communities ................................................................................................................18

Gemini Springs ....................................................................................................................................23

Hydrology and Water Chemistry .............................................................................................24

Aquatic Communities ................................................................................................................25

Green Spring........................................................................................................................................26

Hydrology and Water Chemistry .............................................................................................27

Aquatic Communities ................................................................................................................29

Comparisons among Springs.....................................................................................................................30

Hydrology and Water Chemistry ......................................................................................................31

Aquatic Communities .........................................................................................................................31

Summary........................................................................................................................................................32

Selected References...................................................................................................................................34

Appendix A. Water-Chemistry Data, 2004...............................................................................................40

Appendix B. Compounds Commonly Detected in Wastewater...........................................................44

Appendix C. Pesticides Analyzed.............................................................................................................46

Appendix D. Macroinvertebrate Taxa Reported in this Study.............................................................48

Appendix E. Scientific Names, Authorities and Dates of Original Descriptions, and 

Common Names of Fishes Reported in this Study....................................................................50

Figures

 1. Map showing locations of Upper Floridan aquifer springs .............................................................3

 2. Graph showing monthly rainfall at DeLand and Sanford, Florida, 1940-2004 ...............................5

 3. Graph showing monthly rainfall at Ocala, Florida, 1940-2004..........................................................5

 4. Photograph showing Silver Springs group.........................................................................................8

 5. Graph showing discharge from the Silver Springs group, 1940-2004 ............................................9
iv

 6. Graph showing nitrate-nitrogen concentrations for Silver Springs, De Leon Spring, 

and Gemini Springs........................................................................................................................10

 7. Map showing location of De Leon Spring ........................................................................................16

 8. Photograph showing De Leon Spring pool.......................................................................................16

 9. Photograph showing De Leon Spring dam.......................................................................................16

10. Photograph showing view downstream from De Leon Spring to Spring Garden Lake ............17

11. Graph showing discharge from De Leon Spring, 1965-2004..........................................................17

12. Graph showing delta 18O of nitrate as a function of delta15N of nitrate for samples 

collected in 2004.............................................................................................................................18

13. Photograph showing periphyton sampler at De Leon Spring, August 11, 2004..........................22

14. Map showing locations of Gemini Springs and Green Spring ......................................................23

15. Map showing Gemini Springs.............................................................................................................23

16. Photograph showing view from Gemini Springs to the dam and Lake Monroe.........................23

17. Graph showing total combined discharge from Gemini Springs, 1995-2004 ..............................24

18. Photograph showing Gemini Springs south vent ............................................................................24

19. Photograph showing view toward old springhead at Gemini Springs ........................................26

20. Photograph showing view toward Gemini Springs south vent.....................................................26

21. Photograph showing periphyton sampler at Gemini Springs near the dam, 

August 11, 2004 ...............................................................................................................................26

22. Map showing Green Spring ................................................................................................................26

23. Photograph showing view from culvert to Green Spring pool......................................................27

24. Photograph showing view from steps at Green Spring toward culvert ......................................27

25. Graph showing Green Spring discharge, 2000-2004.......................................................................27

26. Photograph showing Green Spring (water is murky) .....................................................................28

27. Photograph showing Green Spring (water is clear) .......................................................................28

28. Photograph showing sulfur-reducing bacteria form light gray plumes around the 

edges of Green Spring pool..........................................................................................................28

29. Charts showing relative proportions of benthic invertebrates per order collected in 

De Leon Spring, Gemini Springs, and Green Spring, 2004.......................................................29

30. Diagram showing relative proportions of cations and anions in spring-water 

samples, 2004..................................................................................................................................30

31. Chart showing total number of all amphipods collected by season in De Leon Spring, 

Gemini Springs, and Green Spring, 2004 ....................................................................................31

32. Chart showing total number of Gammarus sp. and Hyallela azteca by season at 

De Leon Spring, 2004......................................................................................................................32

Tables

 1. Wastewater compounds, pesticides, and number of detections, 2004.......................................11

 2. Dissolved gas and sulfur hexafluoride data.....................................................................................12

 3. Fishes collected or observed in Silver Springs State Park, deposited in the 

Florida Museum of Natural History, and reported by Hubbs and Allen ................................14

 4. Mussels collected in Silver River State Park and the Ocklawaha River at the 

mouth of the Silver River, 2002 .....................................................................................................15

 5. Percent composition of total number of benthic macroinvertebrates collected in 

De Leon, Gemini, and Green Springs, 2004 ................................................................................19
v

 6. Richness and community measures for De Leon Spring ...............................................................19

 7. Fishes observed or collected in De Leon Springs State Park, and deposited in the 

Florida Museum of Natural History .............................................................................................21

 8. Richness and community measures for Gemini Springs ...............................................................25

 9. Richness and community measures for Green Spring.................................................................. 29

Conversion Factors

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

centimeter (cm) 0.3937 inch (in.)

Flow rate

foot per second (ft/s) 0.3048 meter per second (m/s)

cubic foot per second (ft3/s) 0.646 million gallons per day (Mgal/d)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3/s)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: 

°F=(1.8×°C)+32.

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

 °C=(°F-32)/1.8.

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29).

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).

Altitude, as used in this report, refers to distance above the vertical datum.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25°C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).
vi

Abbreviations

Ar argon

BOD biochemical oxygen demand

CH4 methane

CIAT 2-chloro-4-isopropylamino-6-amino-s-triazine

CO2 carbon dioxide

DEET N,N’-diethyl-methyl-toluamide

DO dissolved oxygen

EPT Ephemeroptera, Plecoptera, and Trichoptera taxa

ETO Ephemeroptera, Trichoptera, and Odonata taxa

FDEP Florida Department of Environmental Protection

FI Florida Index

FLMNH Florida Museum of Natural History

GIS geographic information system

H2S hydrogen sulfide

m meter

μm micrometer

μS/cm microsiemens per centimeter at 25 °C 

NWIS U.S. Geological Survey National Water Data Information System

NO3

- nitrate

NO2

- nitrite

N nitrogen

N2 nitrogen gas

O2 oxygen

P phosphorus

RSIL Reston Stable Isotope Laboratory

r richness

SJRWMD St. Johns River Water Management District

SCI Stream Condition Index

SAV submerged aquatic vegetation

SF6 sulfur hexafluoride

TOC total organic carbon

USEPA U.S. Environmental Protection Agency 

USGS U.S. Geological Survey
Abstract

The hydrology, water chemistry, and aquatic 

communities of Silver Springs, De Leon Spring, Gemini 

Springs, and Green Spring in the St. Johns River Water 

Management District, Florida, were studied in 2004 to 

provide a better understanding of each spring and to 

compile data of potential use in future water-management 

decisions. Ground water that discharges from these and 

other north-central Florida springs originates from the 

Upper Floridan aquifer of the Floridan aquifer system, a 

karstic limestone aquifer that extends throughout most 

of the State’s peninsula. This report summarizes data about 

flow, water chemistry, and aquatic communities, 

including benthic invertebrates, fishes, algae, and aquatic 

macrophytes collected by the U.S. Geological Survey, the 

St. Johns River Water Management District, and the 

Florida Department of Environmental Protection during 

2004, as well as some previously collected data.

Differences in water chemistry among these springs 

reflect local differences in water chemistry in the Upper 

Floridan aquifer. The three major springs sampled at the 

Silver Springs group (the Main Spring, Blue Grotto, and 

the Abyss) have similar proportions of cations and anions 

but vary in nitrate and dissolved oxygen concentrations. 

Water from Gemini Springs and Green Spring has higher 

proportions of sodium and chloride than the Silver Springs 

group. Water from De Leon Spring also has higher proportions of sodium and chloride than the Silver Springs group 

but lower proportions of calcium and bicarbonate. Nitrate 

concentrations have increased over the period of record at 

all of the springs except Green Spring. Compounds commonly found in wastewater were found in all the springs 

sampled. The most commonly detected compound was the 

insect repellant N,N’-diethyl-methyl-toluamide (DEET), 

which was found in all the springs sampled except 

De Leon Spring. The pesticide atrazine and its degradate 

2-chloro-4-isopropylamino-6-amino-s-triazine (CIAT) were 

detected in water from the Silver Springs group and in 

both boils at Gemini Springs. No pesticides were detected 

in water samples from De Leon Spring and Green Spring. 

Evidence of denitrification was indicated by the presence 

of excess nitrogen gas in water samples from most of the 

springs. 

Aquatic communities varied among the springs. Large 

floating mats of cyanobacteria (blue-green algae), identified 

as Lyngbya wollei, were observed in De Leon Spring 

during all sampling events in 2004. At Gemini Springs, the 

dominant periphyton was Rhizoclonium sp. Of the three 

springs sampled for benthic invertebrates, De Leon Spring 

had the highest overall species richness and most 

disturbance intolerant species (Florida Index = 4). Green 

Spring had the lowest species richness of the springs 

sampled. Based on qualitative comparisons, overall 

macroinvertebrate species richness seemed to be negatively 

related to magnesium, potassium, sodium, and specific 

conductance. Invertebrate abundance was greatest when 

dissolved oxygen and nitrate were high but phosphorus and 

potassium concentrations were low. Dipteran abundance 

seemed to be positively associated with specific conductance and total organic carbon but negatively associated 

with nitrate-N. Amphipods were the numerically dominant 

group collected in most (six of nine) collections. Shifts 

in amphipod abundance of the two species collected 

(Gammarus sp. and Hyalella azteca) varied by season 

among the three springs, but there were no trends evident in 

the variation. Fish populations were relatively species-rich 

at the Silver Springs group, De Leon Spring, and Gemini 

Springs, but not at Green Spring. Nonindigenous fish 

species were observed at all springs except Green Spring.

Characterization of the Hydrology, Water Chemistry, 

and Aquatic Communities of Selected Springs in the 

St. Johns River Water Management District, 

Florida, 2004

By G.G. Phelps, Stephen J. Walsh, Robert M. Gerwig, and William B. Tate
Introduction

Florida’s springs are important natural features, 

many of which are headwaters of spring runs or streams 

that support fragile ecosystems containing diverse biotas and endemic, rare, or unique species or assemblages. 

The springs also are important recreational, cultural, and 

economic assets to the State. All of the ground water that 

discharges from the largest springs and nearly all of the 

smaller springs comes from the Floridan aquifer system (a 

thick sequence of carbonate rocks of Eocene age); the water 

is recharged entirely within the State. In much of central 

and north-central Florida, the limestone of the Upper 

Floridan aquifer (the upper unit of the Floridan aquifer 

system) is at or near land surface, so recharge occurs 

rapidly. The landscape is characterized by gently rolling 

topography formed by a combination of karst depressions 

and hills capped with clastic sediments; sinkholes and 

springs are abundant. 

Demand for water for public supply, irrigation, and 

other uses continues to increase as Florida’s population 

grows. Ground water from the Floridan aquifer system 

traditionally has been the main source of water supply. 

Projections by water managers of the St. Johns River Water 

Management District (SJRWMD) and ground-water flow 

models developed by the SJRWMD and the U.S. Geological Survey (USGS) indicate that the increased pumping 

of ground water is likely to result in decreased discharge 

from many of Florida’s springs. Droughts place additional 

stress on ground-water resources. There have been recent 

periods of low flows associated with droughts; many 

Florida springs had record low discharge in 2000. The 

ecological effects of decreased discharge are largely 

unknown because the aquatic ecosystems of many of 

Florida’s springs have received little study. 

Florida’s springs vary substantially in such attributes 

as length of channel and size of adjacent wetlands, effects 

of backwater from other streams, water chemistry, land use 

in the springshed, and other factors. A standard or 

uniformly applied set of criteria to monitor water chemistry 

and biotic communities may not include all of the 

properties necessary to evaluate ecological integrity. For 

example, in some springs protection of adjacent wetlands 

may be an important priority, whereas in other springs the 

depth of water in the spring run may be an important factor 

for maintaining habitat for such prominent animals as fishes 

and manatees. A better understanding of the hydrologic and 

ecological conditions of Florida’s springs is needed in order 

to adequately assess the effects of land-use changes on 

ground-water resources and the biological communities that 

are dependent upon them. 

This study summarizes preliminary assessments 

of water chemistry and components of the aquatic 

communities of four springs in the St. Johns River 

drainage. Similar studies of other springs are in progress 

and results of these investigations are intended to provide 

baseline data for a subset of springs within the basin. The 

primary purpose of these studies is to present comparative 

data that can be used to evaluate interactions among flow, 

water chemistry, and ecological conditions.

Purpose and Scope

This report summarizes data collected during the first 

year of the study (2004) so that water managers can assess 

the sampling methodologies and plan future sampling of 

additional springs. The purpose of the report is to provide 

a baseline assessment of the aquatic ecosystems of the 

springs. Data were collected three times during the year 

by the USGS, the SJRWMD, and the Florida Department 

of Environmental Protection (FDEP) at the Silver Springs 

group (Marion County), De Leon Spring (Volusia County; 

formerly called Ponce de Leon Spring), Gemini Springs 

(Volusia County), and Green Spring (Volusia County) 

from October 1, 2003 to September 30, 2004. Data include 

discharge, water chemistry, and aquatic-community data 

for benthic invertebrates, fishes, algae, and aquatic macrophytes. Water-chemistry data were collected by the USGS 

to complement data collected by other agencies. The 

spring vents were sampled three times for physicochemical properties (specific conductance, dissolved oxygen 

(DO) concentration, temperature, and pH), and twice for 

concentrations of chlorophyll-a and –b, pesticides, and a 

suite of compounds commonly found in wastewater. The 

spring runs were sampled three times for the physicochemical properties and for concentrations of chlorophyll-a and 

–b, major anions and cations, and nutrients. Samples were 

collected for analysis of benthic invertebrate populations at 

De Leon Spring, Gemini Springs, and Green Spring on the 

same dates as the USGS water-chemistry sampling. Fish 

population, vegetation, and periphyton surveys were done 

once at each of the three springs during the study. Three 

springs of the Silver Springs group were sampled twice for 

the same constituents as the other spring vents; biological 

data were not collected because the aquatic ecosystem at 

this system was studied by other investigators (Wetland 

Solutions, Inc., 2004; Stevenson and others, 2004). The 

water-chemistry data collected by FDEP and SJRWMD that 

are described in this report include dissolved major anion 

and cation and nutrient concentrations for each spring vent. 

Previous Studies

Rosenau and others (1977) provided a detailed 

description of more than 200 of Florida’s springs. Scott 

and others (2002; 2004) revisited many of those springs, 

   Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
updated site descriptions, and collected water samples. 

Smaller springs such as Gemini Springs and Green Spring, 

however, were not included in either study by Scott and 

others (2002; 2004). 

Silver Springs, the largest non-tidal spring group in 

Florida, is a group consisting of at least 16 springs that 

form the headwaters of the Silver River in Marion County, 

FL (fig. 1). Annual mean discharge of the group for 1934-

2004 is about 780 cubic feet per second (ft3/s) (U.S. Geological Survey, 2005). Studies of the aquatic 

ecosystems of Silver Springs include Hubbs and Allen 

(1943) and Odum (1957). A recent study (Wetland 

Solutions, Inc., 2004) provided an updated evaluation 

of the Silver Springs ecosystem. Surveys of fish and 

mussel populations were summarized recently by Walsh 

and Williams (2003) and portions of their results are 

included in this report. Those surveys were augmented by 

additional information from literature sources and databases of the Florida Museum of Natural History (FLMNH), 

University of Florida, Gainesville, FL. The influence of 

Figure 1. Locations of Upper Floridan aquifer springs.

Introduction 
wastewater on water quality in three of the larger springs 

of the group (the Main Spring, the Abyss, and the Blue 

Grotto) was discussed by Phelps (2004), who also 

estimated ages of about 30 years or less for at least some 

portion of the water discharging from the Main Spring at 

Silver Springs. 

The other springs included in this study are smaller 

than the Silver Springs group and have been the subject 

of relatively little research. De Leon Spring (mean annual 

discharge about 30 ft3/s) is located at De Leon Springs State 

Park. A description of De Leon Spring by Rosenau and 

others (1977) was updated by Scott and others (2004). 

Green Spring and Gemini Springs were described by 

Rosenau and others (1977). Results of fish and mussel 

population surveys in the spring run of De Leon Spring 

(Walsh and Williams, 2003) were augmented by additional 

observations made during this study and updated in this 

report. 

Acknowledgments

Identification of algae specimens to species was made 

by Peter D’Aiuto (Green Water Laboratories, Palatka, FL). 

Douglas G. Strom (Water and Air Research, Inc., Gainesville, FL) provided selected taxonomic identifications of 

benthic invertebrates.

Site-Numbering System

The USGS National Water Data Information System 

(NWIS) uses a 15-digit num­ber (site identification 

number) based on latitude and longitude to identify wells 

and miscellaneous surface-water data-collection sites. The 

first six digits denote the degrees, minutes, and seconds of 

latitude; the next seven digits denote the degrees, minutes, 

and seconds of longitude; and the last two digits denote 

a sequential number for a site within a one-second grid. 

Well-site identification numbers generally end in “01” or 

“02.” Miscellaneous surface-water quality data-collection 

sites generally end in sequence number “00.” Sur­face-water 

sites that are part of the USGS data-collection network are 

identified by an 8-digit downstream order number. The 

8-digit site identification number for the main Sil­ver 

Springs data-collection site is 0229500 and for De Leon 

Spring is 02236110. 

Environmental Setting

Central Florida has an abundance of springs because 

the Florida peninsula is underlain by a thick sequence of 

limestone and dolomite, both of which are relatively easily 

dissolved by rainwater that seeps into the ground (Spechler 

and Schiffer, 1995). Carbon dioxide dissolved in recharging 

rainwater forms carbonic acid, a weak acid that dissolves 

the rocks, thus creating cavities and caverns. The result is a 

landform called karst, which is characterized by the 

presence of springs and sinkholes.

Springs can be classified on the basis of the amount of 

water that discharges from them. A first-magnitude spring 

discharges 100 ft3/s (65 million gallons per day (Mgal/d)) 

or more. A second magnitude spring discharges from 10 to 

100 ft3/s (6.5 to 65 Mgal/d), and a third magnitude spring 

from 1 to 10 ft3/s (0.65 to 6.5 Mgal/d). The amount of water 

discharging from a spring depends on many factors, 

including the size of caverns in the rocks, the water 

pressure in the aquifer, the size of the area contributing 

recharge to the spring (also called the springshed), and the 

amount of rainfall (Spechler and Schiffer, 1995). 

Climate in the study area is subtropical and is 

characterized by warm, humid, rainy sum­mers and 

temperate, dry winters. Average annual (30 years) daily 

temperature is about 71 degrees Fahrenheit (oF) (22o C) at 

DeLand and 73 oF at Sanford, FL (National Oceanic and 

Atmospheric Administration, 2004). Average annual 

rainfall (1971-2000) is about 57 inches (in.) at DeLand, 

51 in. at Sanford, and 50 in. at Ocala. Most of the rainfall 

occurs in June-September, with some months having as 

much as 20 in. of rainfall (figs. 2 and 3). About 

70-75 percent of the rainfall commonly returns to the 

atmosphere as evapotranspiration (Sumner, 1996; 

Knowles, 1996). 

Methods

The following sections describe the methods and 

techniques used to collect and analyze flow, water 

chemistry, and aquatic community data collected from the 

four springs. Unless noted otherwise, hydrologic, water 

chemistry, and aquatic community data all were collected 

on the same day for each sampling event.

Hydrologic and Water-Chemistry Data

Hydrologic data, including flow and stage data, are 

collected by the USGS and the SJRWMD. Continuous flow 

is calculated at Silver Springs by the USGS. Continuous 

flow data are not available for De Leon Spring, Gemini 

Springs, and Green Spring; however, monthly flow measurements are made by SJRWMD at De Leon Spring and 

Green Spring and quarterly flow measurements are made at 

Gemini Springs. Flow measurements also were made by the 

USGS at both vents of Gemini Springs on dates when water 

samples were collected.

Water-chemistry data were collected by the USGS, the 

SJRWMD, and the FDEP. Water samples were collected 

   Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
Figure 2. Monthly rainfall at DeLand and Sanford, Florida, 1940-2004.

Figure 3. Monthly rainfall at Ocala, Florida, 1940-2004.

Methods 
by the USGS from each spring by lowering an electric 

submersible stainless-steel pump (Fultz pump) with Teflon 

discharge tubing into the spring pool as close to the vent 

as possible. In the spring runs, the pump was placed at 

approximately half the depth of the run. Samples were 

collected when temperature, pH, and specific conductance 

had stabi­lized. Water samples for major ions and nutrients 

were collected according to U.S. Geological Survey (1997-

2003) protocols and analyzed at the USGS laboratories in 

Ocala, FL and Denver, CO. Water samples for anion and 

cation analysis were filtered by using 0.45 micrometer (μm) 

Gelman capsule filters. Cation samples were collected in 

acid-washed bottles and acidified with 70 percent nitric 

acid. Samples analyzed for nutrients were held in the 

field at 4o C before delivery to the laboratory. Because of 

changes in laboratory methodologies, nutrient samples 

collected after July 2004 were filtered. Generally, for 

ground water and spring water, concentrations of nutrients 

in filtered and unfiltered water samples are comparable. 

Appendix A contains cation, anion, and nutrient data 

collected during this study.

Nitrogen (N) occurs as anions in water as nitrite 

(NO2

-

) or nitrate (NO3

-

). Both species are mobile and NO3

-

is stable over a wide range of conditions (Hem, 1985). The 

NO2

-

 ion is unstable in aerated water and generally is 

present in negligible concentrations compared to NO3

-

. 

In this report, the combined concentration of nitrite-plusnitrate reported by the analytic laboratory is referred to as 

nitrate-N.

Samples for N isotope analysis were filtered and 

collected in 1-liter (L) plastic bottles, kept chilled at 

4o C and shipped to the USGS Stable Isotope Laboratory 

(RSIL) in Reston, VA, for analysis. Analytical techniques 

are described by Böhlke and Denver (1995) and Böhlke 

and Coplen (1995). Isotopic values are reported with the 

standard delta notation (δ) (Gonfiantini, 1981) as defined 

by the expression:

δ (per mil) = [(Rsample/Rstandard)-1] x 1,000, 

for δ15N, R= 15N/14N. Values of δ15N for nitrate-N 

concentrations greater than 0.5 milligrams per liter (mg/L) 

are normalized to values of +0.4 per mil for Inter­national 

Atomic Energy Agency standard IAEA-N1 and +180.0 

per mil for USGS-32 (Böhlke and Coplen, 1995), with 

analytical uncertainties of about ±0.25 per mil.

Water samples analyzed for organic compounds 

commonly found in wastewater (app. B) and pesticides 

(app. C) were filtered through a 0.7-μm nominal pore size 

glass-fiber fil­ter and collected in baked 1-L amber glass 

bottles, chilled at 4 oC and shipped to the USGS laboratory 

in Denver, CO. For quality-assurance purposes, replicate 

samples and field blank samples were collected during 

each sampling trip. Because caffeine and insecticides were 

included in the chemical analysis, field personnel 

neither consumed caffeine nor used personal insecticides on 

sampling days. Samples for organic wastewater compounds 

were analyzed by using gas chromatography and mass 

spectrometry, as described by Zaugg and others (2002). 

Pesticides were analyzed by using solid-phase extraction 

and capillary-column gas chromatography/mass 

spectrometry with selected-ion monitoring (Zaugg and 

others, 1995). Acetophenone, phenol, and tetrachloroethylene were detected in one or more of the field blanks, 

so detections of those compounds less than 10 times the 

concentration determined in the blanks were not reported 

in this report. Water samples for dissolved gas analysis 

were collected in septum glass vials and samples for sulfur 

hexafluoride (SF6) analysis were collected in glass bottles 

and shipped to USGS Chlorofluorocarbon Laboratory in 

Reston, VA, for analysis. 

Land-use data for 2000 for the areas contributing 

recharge to each spring (springshed) were compiled 

from geographic information system (GIS) coverages 

provided by the SJRWMD (St. Johns River Water 

Management District, 2002). Approximate springshed areas 

were calculated by adding backwards particle tracking 

to a calibrated model of ground-water flow developed by 

Sepúlveda (2002), using a maximum travel time of 

500 years. 

Aquatic Community Data

Aquatic macroinvertebrate samples were collected 

with a D-frame dip net (500 μm mesh, 0.3 meter (m) width) 

and a petite ponar dredge. Dip net sampling was based on 

a multihabitat approach outlined in the U.S. Environmental 

Protection Agency (USEPA) rapid bioassessment manual 

(Barbour and others, 1999). Collections using a petite 

ponar dredge followed methods used as standard operating 

procedures by the Florida Department of Environmental 

Protection (2004a). Sampling was conducted to coincide 

with dates of water-chemistry sampling at Green Spring, 

Gemini Springs, and De Leon Spring and to represent 

seasonal conditions during winter (February), spring (May), 

and summer (August) 2004. All samples were taken downstream of main spring vents in each system, generally at a 

distance where low DO was not expected to limit diversity, 

and in spring pools or runs where benthic habitats provided 

suitable habitats for macroinvertebrates.

A dip net sample consisted of 20 sweeps taken from 

leaf packs, snags, aquatic macrophytes (submersed and 

emergent), roots or undercut banks, sediment (muck or 

sand) and rock habitats in proportion to the approximate 

percent coverage of each habitat type estimated visually. 

Each sweep consisted of a 0.5-m sweep, jab, or the 

substrate was disturbed by kicking or agitating with hands 

 Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
and allowing invertebrates and organic matter to flow 

into the net held stationary 0.5 m downstream. Material 

was rinsed in a 500 μm sieve after two or three individual 

sweeps for removal of large debris, vegetation, detritus, and 

sediment. The combined material from all 20 sweeps was 

preserved in a solution of 10 percent formalin, containing a 

small amount of Rose Bengal dye for ease of processing in 

the laboratory. 

Three separate samples were collected at each site 

with a Wildco® petite ponar dredge. Samples were taken 

in areas with suitable substrate to ensure complete closure 

of the device, and to prevent loss of course material and 

invertebrates from the dredge. Each sample was rinsed in a 

500 μm sieve and transferred into a 0.5 or 1 gallon jar and 

preserved with a 10 percent formalin solution containing 

Rose Bengal dye.

All preserved samples were transferred to the USGS 

laboratory in Gainesville, FL for taxonomic identification and enumeration. Each sample (i.e., combined dip net 

sweeps or individual ponar dredge collection) was treated 

on an individual basis depending on the number of 

organisms present. Samples that contained large numbers 

of organisms were subsampled for a target of approximately 100±10 percent individuals. Subsampling 

procedures followed commonly applied techniques

 (Rosenberg and Resh, 1993) as outlined in the USEPA 

rapid bioassessment protocols, FDEP standard operating 

procedures, and methods developed for Florida benthic 

assessments (Barbour and others, 1999; Florida Department of Environmental Protection, 2004b; Fore, 2004). The 

entire sample was spread evenly across a gridded pan 

(30 centimeters (cm) x 36 cm) with 30 grids (6 cm x 6 cm). 

Grids were selected four at a time with the use of a 

random numbers table. If the four grids chosen still contained far greater than 100 (+10 percent) organisms, a 

second subsample was made using the same method. This 

was repeated until a target of approximately 100-110 

individuals was obtained. All organisms picked for 

identification and enumeration were placed in vials with 

75 percent ethanol. The remainder of the sample material 

was rinsed, transferred to a jar, and stored in 75 percent 

ethanol. 

All organisms were identified to the lowest 

practical taxonomic level with the use of an Olympus 

SZH10 dissecting microscope and enumerated with the use 

of a hand counter (for a discussion of the merits of 

identifications to different taxonomic scales, see Bailey and 

others, 2001). Primary aids used in invertebrate identifications included Thompson (1984), Berner and Pescador 

(1988), Daigle (1991, 1992), Pescador and Rasmussen 

(1995), Epler (1996), Merritt and Cummins (1996), Smith 

(2001), and Thorp and Covich (2001). No effort was made 

to identify chironomids or oligochaetes to species. A list of 

taxonomic names and authorities (for genera and species) 

is provided in appendix D. Higher taxonomic groups are 

listed in approximate phylogenetic order (app. D). Voucher 

specimens are archived at the USGS laboratory in 

Gainesville, FL.

Macroinvertebrate community richness and 

relative abundance metrics of taxa were calculated for 

Green Spring, Gemini Springs, and De Leon Spring. 

Seasonal taxonomic lists were tabulated for each spring 

and included organisms collected in combined ponar and 

sweep samples. Three community richness (r) 

measures were determined from the lists: richness, 

i.e., total number of taxa at the lowest level of identification; EPTr (number of Ephemeroptera, Plecoptera, and 

Trichoptera taxa); and ETOr (number of Ephemeroptera, 

Trichoptera, and Odonata taxa). All three richness 

measures were simple counts of distinct taxa. Scores for 

the Florida Index (FI) (Ross and Jones, 1979) were 

assigned to Class I and II taxa and the FI calculated for 

each spring using the formula:

FI = (2 x number Class I taxa) + number of Class II taxa.

The FI is a composition metric that was developed for 

Florida based on taxa sensitive to environmental perturbation, especially insects and crustaceans (Beck, 1954); 

it represents the weighted sum of least tolerant taxa (i.e., 

most sensitive, assigned a score of 2) and tolerant taxa (less 

sensitive, scored 1). Because relatively few organisms from 

either FI class were collected in seasonal samples during 

this study, calculations were made by using pooled 

taxonomic data for all seasons for each spring.

For dip net samples, abundance estimates of taxa for 

each sample were extrapolated from the number of 

organisms in each taxon from subsamples; for example, by 

multiplying the count data by a factor of 7.5 for each 

subsample (i.e., in cases where one subsample was sufficient to obtain the target of 100-110 individuals). The 

following indices were determined to be important in 

Florida waters based on Resh and Jackson (1993), Graves 

and others (1998), and Barbour and others (1999): total 

number of organisms (=total abundance); most commonly 

occurring (dominant) taxon based on number of individuals; total individuals of EPT and EPO taxa; and 

percent (of total organism number) of dipterans and 

odonates. The values generated from these estimates were 

used to determine relative abundances for select orders, 

combinations of taxa, and dominant groups. Because 

amphipods were numerous in most samples, the 

calculations were repeated excluding amphipods. 

Passive diffusion periphytometers were placed in De 

Leon Spring and Gemini Springs for 2 weeks during the 

summer of 2004. These devices consisted of vials containing solutions enriched in N, phosphorus (P), both N and 

P, and deionized water as a control. Glass microfiber filters 

Methods 
were placed on the open ends of each vial so that 

differential colonization of periphyton species relative to a 

particular nutrient could be determined. 

Recent surveys of fish and mussel populations in the 

Silver Springs system and De Leon Spring as reported by 

Walsh and Williams (2003) are summarized in this report. 

Those surveys were augmented by additional information 

from literature sources, databases of the FLMNH, and 

observations made during this study. Sampling of fishes 

was done by using boat electro-shocking, seines, dip nets, 

and underwater observation by divers using mask and 

snorkel. Mussel sampling was accomplished by dip netting, 

grubbing, and snorkeling; details of sampling methodology 

was provided by Walsh and Williams (2003). Scientific and 

common names of fishes reported in this study (app. E) 

follow Nelson and others (2004).

Fish surveys at Green Spring and Gemini Springs 

were limited by conditions at the respective springs. The 

vent at Green Spring is too deep to effectively sample with 

conventional gears. Modified crayfish traps (Johnson and 

Barichivich, 2004) were deployed on August 17, 2004, at 

both springs. On the same date, three snorkelers visually 

surveyed Gemini Springs, including the impounded pool, 

and recorded species presence and general abundance.

Characterization 

of Springs

The springs selected 

for study are representative of the many springs 

in central Florida. The 

Silver Springs group, 

one of the largest spring 

groups in Florida, is wellknown as a recreational 

destination for tourists 

and residents alike. De 

Leon Spring is reputed 

to have been discovered 

by Ponce de Leon as the 

possible “Fountain of 

Youth” and is a popular 

recreation area. Even 

smaller springs, such 

as the twin springs of 

Gemini Springs and 

Green Spring, also attract 

human visitors. The areas 

surrounding all four 

springs studied were at 

one time privately owned but 

are now (2006) in public ownership by the State or by local 

government. The data collected during this study include a 

broad range of chemical and biological information. Each 

spring is discussed individually; to facilitate comparisons, 

all the data are included in the appendixes. 

Silver Springs

The Silver Springs group is recognized as an 

hydrologically important feature in north-central Florida 

since its discovery by the first human residents of the area. 

Early indigenous people regarded Silver Springs as the 

home of their “water gods” because of the abundance of 

food and freshwater found at the spring (Wetland Solutions, 

Inc., 2004). 

The Silver Springs group consists of at least 16 springs 

(fig. 4). Flows from the springs combine to form the Silver 

River. For consistency in terminology, “Silver Springs 

group” is used to designate the combination of all springs 

contributing to flow at the USGS gaging station. “Main 

Spring” is used to designate the primary headspring and 

often is referred to as Silver Spring or Mammoth Spring. 

The Main Spring has at least two caverns that produce 

water with differing chemical quality (A. Biddlecomb, 

Jones, Edmonds, Associates, written commun., 1997). 

Figure 4. Silver Springs group.

 Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
This conclusion is based on data from hourly measurements 

of temperature, DO, pH and specific conductance from 

each of the vents in May 1997. The “left vent” had an 

average temperature of about 22.7 oC, specific conductance 

of about 445 microsiemens per centimeter (μS/cm), and 

DO of 1.18 mg/L, whereas the “right vent” had an average 

temperature of about 23.3 oC, average specific conductance 

of about 487 μS/cm, and DO of about 3.34 mg/L (Wetland 

Solutions, 2004, fig. 2-5). Variations in water chemistry 

from the Main Spring also were reported by Phelps (2004) 

who observed differences in nitrate concentration and δ15N 

values during different sampling events. 

A bathymetric map of the Silver River was prepared 

by Phlips and Allen (2004), based on fathometer surveys 

completed during February-March 2004. Maximum depth 

was about 30 feet (ft) at the Main Spring. Depth was about 

21 ft at the Jacob’s well spring. Much of the Silver River is 

about 9 ft deep or less.

Analysis of land-use data for the Silver Springs 

springshed in 2000 (St. Johns River Water Management 

District, 2002) indicates that the springshed consisted 

of about 28 percent forest, 25 percent agriculture, 

22 percent urban, 18 percent water or wetlands, 6 percent 

rangeland, and 1 percent other uses. Urban land use in the 

springshed has increased by about 12 percent since 1973. 

Hydrology and Water Chemistry

The Silver Springs group is the largest non-tidal 

spring group in Florida, with a combined average 

discharge of about 780 ft3/s for the period of record, 

1932-2004 (fig. 5) (U.S. Geological Survey, 2005). Flow 

measurements are made at a site about 1.5 mile (mi) 

downstream from the Main Spring (fig. 4). Continuous 

flow is calculated based on a relation between the water 

stage at the gaging site and the head in the Upper Floridan 

aquifer at a nearby well and takes into account backwater from the Ocklawaha River. A drought in 2000-2002 

resulted in the lowest flow measurement on record for 

the Silver Springs group, 350 ft3/s in June 2001 (U.S. 

Geological Survey, 2002). 

Water-chemistry data have been collected by the 

USGS at Silver Springs since 1956. Concentrations of 

nitrate-N in water from the Main Spring have increased 

from about 0.1 mg/L in 1956 to about 1.2 mg/L (fig. 6). 

The concentration of calcium also has an increasing trend 

(ranging from 48 to 78 mg/L, all values since 1996 have 

been greater than 70 mg/L). Sulfate concentration, 

however, does not show an increasing trend (Phelps, 

2004). Nitrogen isotope-data indicated that the sources of 

N generally are mixed organic and inorganic and also that 

the isotope signature of the water from the Main Spring 

Figure 5. Discharge from the Silver Springs group, 1940-2004.

Characterization of Springs 
can vary, sometimes strongly indicating inorganic 

(fertilizer) sources but other times indicating mixed sources 

with a strong influence of organic N (Phelps, 2004). The 

Main Spring, the Abyss, and the Blue Grotto were sampled 

for organic constituents commonly found in wastewater 

in January 2001 (Phelps, 2004). N,N’-diethyl-methyltoluamide (DEET) was detected in the Main Spring and the 

Blue Grotto. Para-nonylphenol, a detergent metabolite, was 

detected in water from the Main Spring and isophorone, a 

solvent, in water from the Abyss. None of these compounds 

was detected in field blanks. These data indicate that 

human activities have influenced the water chemistry of the 

springs. 

Water samples were collected during this study from 

the Main Spring, the Blue Grotto, the Abyss, and at a site 

in the Silver River near the USGS gaging station at times 

to coincide with data collection by FDEP (app. A). Water 

chemistry differed slightly among the three springs, mostly 

with respect to concentrations of DO and nitrate-N. Concentrations of DO in water from the Main Spring ranged 

from 1.7-2.7 mg/L but was higher in water from the Abyss 

(3.4-4.4 mg/L) and the Blue Grotto (3.6-4.5 mg/L). Concentrations of nitrate-N were about 0.96-1.2 mg/L in water 

from the Main Spring, about 1.2-1.5 mg/L in water from 

the Abyss, and about 1.4 mg/L in water from the Blue 

Grotto. Differences in DO and nitrate-N concentrations 

among springs of the Silver Springs group probably result 

from differences in source areas for recharge and the 

relative contributions of N originating from different 

sources. Total P concentrations were about the same in 

water from the three springs. Sulfate was lower in water 

from the Main Spring (median value about 38 mg/L) compared to the Abyss (about 69 mg/L) and the Blue Grotto 

(64 mg/L), probably because water discharging from these 

springs moves along different flow paths in the aquifer. 

Water in the Silver River differed from the spring-water 

samples mainly with respect to concentrations of DO, 

which ranged from 5.0-5.7 mg/L. Concentration of nitrateN in the river samples ranges from 0.96-1.2 mg/L. Neither 

chlorophyll-a nor –b was detected in any of the samples 

from the Silver Springs group or the Silver River. 

Water samples collected from the three springs in 

April and July 2004 were analyzed for organic compounds 

commonly found in wastewater (app. B) and for pesticides 

(app. C). Four wastewater compounds and two pesticides 

were detected in the Main Spring (table 1); the insect 

repellent DEET was detected in the Main Spring during 

both sampling events. Six wastewater compounds and one 

pesticide were detected in water samples from the Abyss, 

including DEET during one sampling. At the Blue Grotto, 

15 wastewater compounds and one pesticide were detected, 

although none of the compounds were detected during both 

sampling events. Diethoxy-octylphenol, a known endocrine 

disruptor, was detected once in each of the three springs. 

Figure 6. Nitrate-nitrogen concentrations for Silver Springs, De Leon Spring, and Gemini Springs.

10 Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
Table 1. Wastewater compounds, pesticides, and number of detections, 2004.

[P, pesticide. All other compounds are wastewater compounds. Endocrine disrupting potential: S, suspected; K, known]

Compound names

Endocrine 

disrupting 

potential

Silver Springs Group

De Leon Green Gemini 

North

Gemini 

South Main Blue Grotto Abyss

1,4-Dichlorobenzene S 1

1-Methylnaphthalene 1 1

2,6-Dimethylnaphthalene 1

2-Chloro-4-isopropylamino6-amino-s-triazine (CIAT) (P)1 1 1 2 2

2-Methylnaphthalene 1 1 1

3-Methyl-1(H)-indole (skatol) 1

Atrazine (P) 1 2 2

Benzophenone S 1 1 1 1

Bisphenol A K 1 1 1 1

Caffeine 1

Camphor 1

d-Limonene 1

Indole 1 1

Isopropylbenzene (cumene) 1

Methyl salicylate 1 1 1

N,N’-diethyl-methyl-toluamide (DEET) 2 1 1 2 2 1

Naphthalene 1 1 1

Octylphenol, diethoxy- K 1 1 1 1

para-Cresol S 1 1 1 1

para-Nonylphenol (total) K 1 1

Phenanthrene 1

Triphenyl phosphate 1

The presence of these constituents indicates that wastewater is affecting the water discharged from all three 

springs sampled at the Silver Springs group. The pesticide 

degradate 2-chloro-4-isopropylamino-6-amino-s-triazine 

(CIAT) was detected at all three springs during both 

sampling events and its parent compound atrazine was 

detected in the Main Spring in April 2004.

Water samples collected during this study from the 

Main Spring, the Abyss, and the Blue Grotto also were 

analyzed for dissolved gases and SF6 (table 2). There was 

no evidence of excess nitrogen gas (N2) dissolved in the 

water samples from the Main Spring and the Abyss, 

indicating that denitrification had not occurred. A small 

amount of excess N2 gas was detected in the sample from 

the Blue Grotto, possibly indicating the occurrence of 

some denitrification. The SF6 results from this study were 

not consistent with previous results (Phelps, 2004). For 

example, the sample collected from the Main Spring in 

2002 indicated a recharge year of 1986-87 (Phelps, 2004), 

whereas the sample collected in July 2004 indicated a 

recharge year of 1994. The discrepancies may have resulted 

because sampling in 2004 was disrupted by boat traffic, 

possibly allowing the water to be contaminated with 

atmospheric SF6 during the sampling process. The inconsistencies also could result from the varying concentrations 

of SF6 in wastewater that has entered the aquifer and 

subsequently discharged at the springs. 

Water from the springs generally is a mixture of 

varying proportions of younger water from shallow flow 

paths and older water from deeper flow paths. Tritiumhelium dating of water from the Silver Springs group generally indicated older ages than SF6

 (Phelps, 2004). 

The young fraction of water from the Main Spring was 

about 27 years old (compared to about 15 years based on 

SF6) and from the Blue Grotto about 18 years (compared 

to 6 years). For the Abyss, the tritium-helium and SF6 ages 

were the same, about 10 years, possibly indicating that flow 

to the Abyss is relatively rapid and shallow. 

Characterization of Springs 11
Table 2. Dissolved gas and sulfur hexafluoride (SF6) data.

[mg/L, milligrams per liter; pptv, parts per trillion volume; STP, standard temperature and pressure; c, cannot date sample because concentration is greater than 2004 atmospheric value; s, sample lost. Dissolved gas samples were collected and analyzed in duplicate]

Spring name

Date 

collected

Field 

temperature oC 

N2, 

mg/L

Ar, 

mg/L

O2, 

mg/L

CO2, 

mg/L

CH4, 

mg/L

Excess N2, 

mg/L

Recharge 

elev. 

ft.

Estimated 

recharge 

temperature

o

C

Excess 

air cm3

at STP

Uncorrected 

SF6

(pptv)

SF6 corrected for 

excess air 

(pptv)

Piston flow 

model 

recharge year

Silver Springs Group

Main 7/14/2004 23.1 16.20 0.55 1.18 14.90 0.00 55 23.3 2.1 4.6 3.3 1994.0

7/14/2004 23.1 16.07 .55 1.34 14.59 .00 55 23.3 2.0

Blue Grotto 7/14/2004 23.7 15.43 .53 2.76 11.12 .00 0.8 55 22.1 .2 6.8 6.6 c

7/14/2004 23.7 15.15 .53 2.67 11.28 .00 .8 55 21.8 -.1

Abyss 7/14/2004 23.7 15.52 .54 2.87 11.86 .00 55 23.4 1.5 6.9 5.6 2003.5

7/14/2004 23.7 15.13 .54 2.70 12.14 .00 55 23.3 1.1

De Leon 5/12/2004 23 19.38 .59 .07 6.79 .00 1.5 50 22.6 3.7 3.0 1.8 1987.0Spring 5/12/2004 23 18.95 .58 .05 9.25 .00 1.5 50 22.4 3.2

8/23/2004 23.5 18.46 .57 .04 6.81 .00 1.5 50 23.0 2.8 2.7 1.8 1987.08/23/2004 23.5 18.13 .57 .04 6.86 .00 1.5 50 22.7 2.4

Gemini 5/11/2004 23 17.16 .57 .05 11.33 .00 .5 50 22.4 2.4 52.2 36.8 cSpring 5/11/2004 23 16.86 .56 .06 10.92 .00 .5 50 22.8 2.2North 8/18/2004 24.25 16.84 .56 .05 12.02 .00 .8 50 22.0 1.6 91.7 71.3 c

8/18/2004 24.25 s s s s s s s s s s s s

Gemini 5/12/2004 23 17.32 .57 .05 11.14 .00 .8 50 22.2 2.2 59.4 42.1 cSpring 5/12/2004 23 17.60 .57 .04 10.99 .00 .8 50 22.0 2.4South 8/18/2004 24.2 17.02 .57 .05 12.24 .00 .8 50 21.6 1.8 97.6 76.1 c

8/18/2004 24.2 16.61 .56 .05 12.25 .00 .8 50 21.7 1.3

Green 5/11/2004 23 17.45 .57 .00 10.57 .23 .5 60 22.4 2.7 2.5 1.7 1986.5Spring 5/11/2004 23 17.57 .58 .00 10.63 .23 .5 60 22.0 2.7

8/18/2004 26 17.75 .57 .19 11.01 .27 1.0 60 22.9 2.6 2.0 1.3 1984.08/18/2004 26 17.95 .57 .18 11.06 .27 1.0 60 22.8 2.8

12 Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
Aquatic Communities

Fishes in the Silver River were sampled in October 

2001 (Walsh and Williams, 2003). A total of 29 species 

representing 22 genera and 15 families was collected from 

sites near the source of the Silver River downstream to its 

confluence with the Ocklawaha River (table 3). Previous 

collections of fishes in the Silver River by various investigators included 22 species of 15 genera and 11 families 

deposited in the FLMNH. The most complete historical 

survey of the fishes in any of Florida’s first magnitude 

springs recorded a total of 35 species of 25 genera and 

18 families in this system (Hubbs and Allen, 1943). Based 

on these combined sources, at least 45 fish species have 

been documented from the Silver River, although some 

of Hubbs and Allen’s (1943) records were invalidated or 

represent species that have undergone subsequent taxonomic changes. USGS personnel (Walsh and Williams, 

2003) did not collect 16 species that were represented by 

material in the FLMNH collection or reported by Hubbs 

and Allen (1943), probably because of limitations of the 

gear used (boat electrofishing) and the likely presence of 

these species in backwater and shallow, well-vegetated 

habitats where collection efforts were not targeted. Species 

collected in 2001 (Walsh and Williams, 2003) that were 

not present in the museum material or recorded by Hubbs 

and Allen (1943) included pugnose minnow (Opsopoeodus 

emiliae), brown bullhead (Ameiurus nebulosus), vermiculated sailfin catfish (Pterygoplichthys disjunctivus), and 

swamp darter (Etheostoma fusiforme). Hubbs and Allen 

(1943) also reported the possible occurrence of white mullet (Mugil curema), smallmouth bass (Micropterus dolomieu), and a species of Enneacanthus. The white mullet 

observation was provisional and the authors suggested the 

possibility of a misidentification. Smallmouth bass were 

introduced into Lake Weir, which is connected to the 

Ocklawaha River by a canal, and records of this species 

in the Silver River were based on visual reports; however, 

there is no evidence that this species is established in the 

drainage. Specimens of Enneacanthus were reported to 

have been collected, but Hubbs and Allen (1943) did not 

examine them and were unable to render identification; 

two species are likely to be present in backwater areas, the 

banded sunfish (E. obesus) and the bluespotted sunfish 

(E. gloriosus). The most diverse families in the Silver River 

are centrarchids (8 species), ictalurids (6 species), fundulids 

(5 species), and cyprinids (4 species).

Specimens from the Silver River in the FLMNH 

collection were dominated by rainwater killifish (Lucania 

parva), redeye chub (Notropis harperi), bluefin killifish 

(L. goodei), and sailfin molly (Poecilia latipinna), accounting for a combined total of nearly three-fourths of all 

museum specimens; however, the proportions of specimens 

of different taxa deposited as museum specimens may not 

reflect overall relative abundances of species over time. 

Four species taken in the 2001 survey (Walsh and 

Williams, 2003) accounted for a combined 45 percent 

of the sample composition: redeye chub, mosquitofish 

(Gambusia holbrooki), sailfin molly, and spotted sunfish 

(Lepomis punctatus). Families represented by the greatest numbers of specimens were centrarchids (32.1 percent 

combined percent composition of all fish), poeciliids 

(22.8 percent), cyprinids (16.1 percent), and fundulids 

(13 percent). The greatest fish biomass consisted of gar 

(Lepisosteus spp.), lake chubsuckers (Erimyzon sucetta), 

and centrarchids. The most abundant species noted in visual 

surveys by Phlips and Allen (2004) during two counting 

events in March and April 2004 was the bluegill (Lepomis 

macrochirus).

Silver Springs has at least one nonindigenous 

species, the vermiculated sailfin catfish. This South 

American species was introduced into west-central Florida 

and has spread rapidly in recent years to colonize the 

upper St. Johns River drainage, including several other 

large-magnitude springs and their spring runs. This 

represents the first known occurrence in an Ocklawaha 

River tributary.

Mussels were surveyed in August 2002 in four areas: 

from about 0.5 mi downstream of the Main Spring pool 

to 1.5 mi downstream in the Silver River; at another site 

downstream from the extent of this segment; in the springinfluenced section of the river near its mouth; and at one 

site in the Ocklawaha River near the confluence with the 

Silver River (Walsh and Williams, 2003). Mussels were 

located at all sites in the Silver River but were low in 

abundance. Conversely, mussels were more common at the 

single site in the Ocklawaha River, and species composition at that site differed from those collections made in the 

spring-influenced sites. Five species of native unionids 

were collected in the Silver River (table 4), with samples 

dominated (89 percent of total number of specimens) by a 

species of Elliptio that warrants further taxonomic study. 

All other native mussels from spring habitats were 

represented by fewer than five specimens, and two of these 

(variable spike, Elliptio icterina and iridescent lilliput, 

Toxolasma paulus) were represented by single specimens. 

These two species plus one other (Florida pondhorn, 

Uniomerus carolinianus) were found in the Silver River 

but were not present in the collection made in the 

Ocklawaha River. In contrast, the sample from the 

Ocklawaha River had three species not present in the Silver 

River: barrel floater (Anodonta couperiana), Florida shiny 

spike (E. buckleyi), and paper pondshell (Utterbackia 

imbecillis). Variation in species composition between these 

sites is attributed to habitat conditions and probable differences in ecological requirements of the individual species. 

The site in the Ocklawaha River was characterized by 

warmer, more tannic, turbid water and a substrate of mud 

Characterization of Springs 13
Table 3. Fishes collected or observed in Silver Springs State Park (Walsh and Williams, 2003), deposited in the Florida 

Museum of Natural History (FLMNH), and reported (x) by Hubbs and Allen (1943).

 Family Species

 USGS FLMNH ichthyological 

collection Hubbs & 

Allen 

(1943) Number of 

specimens

Percent 

composition

Number of 

specimens

Percent of 

material

Lepisosteidae Lepisosteus osseus 11 1.2 -- -- X

Lepisosteus platyrhincus 23 2.4 -- -- X

Amiidae Amia calva 3 .3 -- -- X

Anguillidae Anguilla rostrata 5 .5 1 .1 X

Clupeidae Dorosoma cepedianum 10 1.1 -- -- X

Dorosoma petenese -- -- -- -- X

Cyprinidae Notemigonus crysoleucas 1 .1 -- -- X

Notropis harperi 126 13.3 200 22.4 --

Notropis petersoni 20 2.1 44 4.9 --

Opsopoeodus emiliae 6 .6 -- -- --

Catostomidae Erimyzon sucetta 19 2.0 -- -- X

Ictaluridae Ameiurus catus -- -- 2 .2 X

Ameiurus natalis -- -- 1 .1 X

Ameiurus nebulosus 1 .1 -- -- ---

Ictalurus punctatus -- -- -- -- X

Noturus gyrinus 5 .5 3 .3 --

Noturus leptacanthus -- -- 6 .7 --

Loricariidae* Pterygoplichthys disjunctivus 7 .7 -- -- --

Esocidae Esox americanus -- -- -- -- X

Esox niger 2 .2 -- -- X

Aphredoderidae Aphredoderus sayanus -- -- -- -- X

Mugilidae Mugil cephalus -- -- -- -- X

Atherinopsidae Labidesthes sicculus 27 2.8 2 .2 X

Belonidae Strongylura marina -- -- 2 .2 X

Fundulidae Fundulus chrysotus -- -- -- -- X

Fundulus lineolatus -- -- -- -- X

Jordanella floridae -- -- -- -- X

Lucania goodei 55 5.8 106 11.9 X

Lucania parva 68 7.2 258 29.0 X

Poeciliidae Gambusia holbrooki 109 11.5 40 4.5 X

Heterandria formosa 12 1.3 18 2.0 X

Poecilia latipinna 95 10.0 99 11.1 X

Centrarchidae Lepomis auritus 30 3.2 11 1.2 X

Lepomis gulosus 10 1.1 4 .4 X

Lepomis macrochirus 57 6.0 -- -- X

Lepomis marginatus -- -- 1 .1 --

Lepomis microlophus 36 3.8 -- -- X

Lepomis punctatus 96 10.1 71 8.0 X

Micropterus salmoides 75 7.9 7 .8 X

Pomoxis nigromaculatus -- -- -- -- X

Percidae Etheostoma fusiforme 1 .1 -- -- --

Percina nigrofasciata 30 3.2 9 1.0 X

Elassomatidae Elassoma evergladei -- -- -- -- X

Elassoma okefenokee 8 .8 1 .1 --

Achiridae Trinectes maculatus -- -- 5 .6 X

Total number of species 29 22 35

Total number of specimens 948 891

*

nonindigenous species

14 Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
and organic detritus, in comparison with the clear, cool 

water of the Silver River and substrate dominated by 

hard-packed sand with abundant growth of submerged 

aquatic plants and filamentous algae. The nonindigenous 

Asian clam (Corbicula fluminea) was relatively common in 

both systems.

The Silver Springs group was one of 28 Florida 

springs studied in 2003 by Stevenson and others (2004) 

to document and increase understanding of the ecological condition and relations between algae and nutrients. 

They reported that macroalgal cover at Silver Springs was 

about 70 percent in fall 2003, of which about 70 percent 

was Lyngbya majuscule. Lyngbya species are N-fixing, 

blue-green algae (cyanobacteria), some of which produce 

saxitoxins that can cause symptoms ranging from skin 

irritation to nausea in humans. Stevenson and others (2004) 

reported that the taxonomic status of Lyngbya majuscula

is not clear. It may be a nonindigenous species in a phase 

of range expansion, possibly a marine species that can 

adapt to fresh water. Lyngbya majuscule is not affected by 

low N levels (Lundgren and others, 2003) and grows well 

in low-light conditions (Rossi and others, 1997). Lyngbya 

majuscula was associated with high-nutrient and high-discharge springs; however, overall nutrient concentrations in 

the 28 springs studied were not directly related to cover by 

Lyngbya majuscula (Stevenson and others, 2004). Control 

of nutrients could indirectly constrain Lyngbya because 

Lyngbya has no direct method of attaching to surfaces 

except by becoming entangled with rough surfaces or other 

objects attached to the bottom. Lyngbya generally was 

found attached to Vaucheria and aquatic plants, the proliferation of which could be constrained by nutrient reduction. 

Cowell and Botts (1994) suggested that Lyngbya colonizes 

areas after a disturbance such as removal of nuisance 

vegetation or after hurricanes. Thus, disturbance of aquatic 

vegetation by human activities in spring habitats may promote invasion by macroalgae during subsequent periods of 

low human activity (Stevenson and others, 2004). 

A survey of the aquatic communities in the Silver 

River was made in December 2003-January 2004 (Phlips 

and Allen, 2004). These investigators observed submerged 

aquatic vegetation (SAV), algal, and vertebrate communities and compared the results to descriptions by Odum 

(1957). The dominant SAV, both as observed by Odum 

(1957) and Phlips and Allen (2004), was strap-leaf 

sagittaria (Sagittaria kurtziana). Algae blooms covered the 

SAV (Wetland Solutions, Inc., 2004). The dominant 

epiphytic algae based on biomass were the green alga 

Ulothrx, the diatom Aulocosira (=Melosira), and a variety 

of other diatoms. The dominant benthic algal species was 

Lyngbya sp., which covered 100 percent of the substrate in 

some parts of the study area. The predominance of Lyngbya in the benthic algal assemblage of the Silver River is 

an important change from the observations by Odum in 

1957, when Lyngbya was not observed (Phlips and Allen, 

2004). Whitford (1954; 1956) also described the algal 

assemblage in the Silver 

River and noted that the 

dominant species was the 

diatom Cocconeis placentula—similar to Odum’s 

(1957) observation. Odum 

(1957) also reported 

small mats of Spirogyra 

sp., Oedogonium sp. and 

Rhizoclonium sp. in Silver 

Springs. According to 

Whitford (1954; 1956), 

the most important factor 

for distribution of algal 

communities was water 

velocity rather than 

temperature or light 

levels. Martin (1966) 

described dense filamentous growths of Spirogyra in the Main Spring 

and epiphytic Lyngbya

attached to exposed 

surfaces in the Main 

Spring. 

Table 4. Mussels collected in Silver River State Park and the Ocklawaha River at the mouth of 

the Silver River, 2002.

[Data from Walsh and Williams, 2003]

Species Common 

 name

Number 

for each 

subsample

Percent 

for each 

subsample

Silver River

Corbicula fluminea Asian clam 31 8.8

Elliptio icterina variable spike 1 .3

Elliptio sp. unidentified spike 315 89.0

Toxolasma paulus iridescent lilliput 1 .3

Uniomerus carolinianus Florida pondhorn 2 .6

Villosa amygdala Florida rainbow 4 1.1

 Total number of specimens 354

Ocklawaha River

Anodonta couperiana barrel floater 1 1.1

Corbicula fluminea Asian clam 14 15.4

Elliptio buckleyi Florida shiny spike 36 39.6

Elliptio sp. unidentified spike 1 1.1

Utterbackia imbecillis paper pondshell 9 9.9

Villosa amygdala Florida rainbow 30 33.0

 Total number of specimens 91

Characterization of Springs 15
De Leon Spring

De Leon Spring, located 

near the town of De Leon 

Springs in Volusia County, is 

a 603-acre State park popular 

as a site for swimming, scuba 

diving, and other recreational 

activities. Downstream from 

the spring is a boat ramp with 

public access to the Lake 

Woodruff National Wildlife 

Refuge (fig. 7). In 2000, land 

use in the springshed was 

about 7 percent urban, 

16 percent agricultural, 

5 percent rangeland, 

38 percent forest, 33 percent 

water or wetlands and 

1 percent other types. 

Hydrology and Water 

Chemistry 

The spring pool is an 

almost circular, conical 

depression measuring 189 ft 

north to south and 168 ft east 

to west (fig. 8). The pool 

depth measures 28 ft over the spring vent (Scott and 

others, 2004). The pool is surrounded by a low concrete 

wall bordered by a concrete walk. A dam was constructed 

at the west side of the pool to maintain the water level in 

the spring pool (figs. 9 and 10). Two weir outlets in the 

Figure 7. Location of De Leon Spring.

Figure 8. De Leon Spring pool. Figure 9. De Leon Spring dam.

16  Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs

De LEON

SPRING

AREA

Source: U.S. Geological Survey Topographic map; 1:24,000

0

0

.5 1 MILE

.5 1 KILOMETER
dam can be used to regulate the water level in the pool, and 

a flume at the southwest side of the pool diverts some flow 

to a large water wheel that formerly was used to operate a 

sugar mill. A boil usually is visible over the spring vent. 

Spring flow originates from a single cavern with a chimney 

vent in the north-central part of the pool (Rosenau and 

others, 1977). 

The mean discharge of De Leon Spring, based on 

244 measurements from 1929 to 2000, was 27.2 ft3/s (U.S. 

Geological Survey, 2001) (fig. 11). Discharge measurements less than 20 ft3

/s were recorded during droughts 

in the early 1990s and in 2000; the minimum discharge 

recorded by the USGS was 12.7 ft3/s on May 25, 2000 

(U.S. Geological Survey, 2001). A discharge of 61.6 ft3/s 

was measured by the SJRWMD on August 25, 2004 (St. 

Johns River Water Management District, 2005). Almost 

22 in. of rain fell at DeLand, FL, in August 2004 partly as 

a result of hurricanes (National Oceanic and Atmospheric 

Administration, 2004). Discharge from De Leon Spring is 

difficult to measure because of the dam. Mats of algae and 

aquatic vegetation can partially block the culverts that carry 

flow through the dam, causing the water level in the spring 

pool to rise. Flows that are measured immediately after the 

vegetation is cleared reflect ponded water in the spring pool 

in addition to actual spring flow. Also, the shape of the 

spring vent does not allow good access for 

divers to make underwater measurements. 

 Water samples were collected from 

the spring vent by both the USGS and 

the SJRWMD and by the USGS from a 

site about 100 ft downstream from the 

dam. Concentration of DO in the spring 

water generally was low (0.8 to 1.5 mg/L) 

whereas the concentration was higher (1.5 

to 6.7 mg/L) at the downstream site owing 

to turbulence and reaeration from the atmosphere. Specific conductance was similar 

at the vent and the downstream site: about 

800 to 1,100 μS/cm. Chloride and sulfate 

concentrations also were similar at the two 

sites, ranging from about 140 to 240 mg/L 

for chloride and for sulfate from 28 to 

38 mg/L. Nitrate-N concentration was only 

slightly higher at the spring vent (0.64 to 

0.83 mg/L) compared to the downstream 

site (0.52 to 0.67 mg/L). Total P concentration was slightly higher in the spring run: 

0.05 to 0.08 mg/L, compared to 0.05 in the 

spring. Total organic carbon (TOC) concentration ranged from 1.1 to 1.3 mg/L at the 

vent and from 1.1 to 3.9 downstream. 

Concentration of biochemical oxygen 

demand (BOD) ranged from 0.3 to 1.2 

mg/L at both sites. On two sampling days, 

Figure 10. View downstream from De Leon Spring to Spring 

Garden Lake.

Figure 11. Discharge from De Leon Spring, 1965-2004.

Characterization of Springs 17
chlorophyll-a was not detected in the vent but 

was 5.7 mg/L in May 2004; at the downstream site, 

chlorophyll-a was undetected in March 2004 but as high 

as 21 mg/L in February, on a day it was not detected at 

the spring vent. Chlorophyll-b was detected once at this 

spring during the study, in August 2004 at the downstream 

site. Chlorophyll-a is found in all plants, green algae, and 

cyanobacteria that photosynthesize whereas chlorophyll-b 

occurs only in plants and green algae (University of 

California Berkeley, 2005) so the relative amounts of the 

two types of chlorophyll may be helpful in understanding 

the periphyton community in a water body. 

 Historic nitrate-N data indicate an 

apparent increasing trend in concentration in the 

water from De Leon Spring (fig. 6) from about 

1985 to 2004, although the concentrations fluctuated during this period. There are insufficient 

paired nitrate-N and discharge data to determine 

the relation (if any) between the two, but the low 

concentration in November 2004, when flow was 

high, could indicate that nitrate-N concentration is inversely related to discharge at De Leon 

Spring. Total P apparently has not increased since 

data collection began in 1972.

Excess dissolved N2 concentrations of about 

1.5 mg/L during both USGS sampling events 

indicate that denitrification was taking place in 

the Upper Floridan aquifer in the vicinity of De 

Leon Spring (table 2). Four conditions must be 

met for denitrification to occur (Korom, 1992): 

presence in the water of NO3

-

; presence of denitrifying bacteria; an electron donor (such as organic 

carbon); and anaerobic conditions (low DO). 

Nitrogen and oxygen isotope data for the 

dissolved NO3

-

 indicate that N isotopes likely 

were being fractionated by denitrification 

(fig. 12). The SF6 data indicate a recharge year of 

about 1987 for some fraction of the spring water, 

assuming that flow through the Upper Floridan 

aquifer to the spring can be approximated by 

piston flow. 

 Sampling for organic compounds 

commonly found in wastewater resulted in 

detections of four compounds (table 1) including 

para-Cresol (a wood preservative) at a level of 

1.7 micrograms per liter (μg/L). Pesticides 

were not detected in water samples from 

De Leon Spring during either sampling. Waterchemistry data from De Leon Spring generally 

indicate the springshed has been affected by 

human activities. 

Aquatic Communities

An estimated total of 42,335 macroinvertebrates was 

collected from ponar and sweep samples at De Leon Spring 

during three sampling events in 2004 (table 5). From those 

samples, 45 distinct taxa were identified. Taxon richness 

was highest in the sample collected in summer (August) 

and lowest in spring (May) but always greater than 10 total 

taxa (table 6). Ponar samples accounted for 18 taxa not 

collected in sweeps. Richness of EPT taxa varied from 0 

(spring) to 3 (summer). Richness of ETO taxa ranged from 

1 (spring) to 7 (summer); however, the relative abundance 

of odonates collected was highest in winter (table 6). 

Figure 12. Delta 18O of nitrate as a function of delta 15N of nitrate for 

samples collected in 2004.

18  Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
Table 5. Percent composition of total number of benthic macroinvertebrates (combined ponar and dip net sweep samples 

for all seasons) collected in De Leon, Gemini, and Green Springs, 2004. 

[--, not differentiated or not observed]

Major

taxon Family Species Percent composition

De Leon Gemini Green

Porifera -- -- 0.018 -- --

Tricladida -- -- .035 2.052 --

Nematoda -- -- .135 .327 0.068

Oligochaeta -- -- 3.780 20.310 48.950

Hirudinea Erpobdellidae -- .005 -- --

Hirudinea Glossiphoniidae -- 1.337 .270 --

Gastropoda Ampullaridae Pomacea paludosa .133 -- --

Gastropoda Ancylidae -- .005 .016 --

Gastropoda Hydrobiidae -- 4.790 11.888 .685

Gastropoda Physidae Physella sp. .019 .297 .452

Gastropoda Planorbidae Micromenetus floridensis .009 -- --

Gastropoda Planorbidae Planorbella scalaris .067 .097 --

Gastropoda Planorbidae Planorbella trivolvis intertextum .133 -- --

Gastropoda Pleuroceridae Elimia floridensis 2.733 -- --

Gastropoda Thiaridae Melanoides tuberculata .142 -- --

Gastropoda Viviparidae Viviparus georgianus 1.214 -- --

Pelecypoda Corbiculidae Corbicula fluminea .133 -- --

Pelecypoda Unionidae Uniomerus carolinianus .133 -- --

Hydracarina -- -- .019 -- --

Arachnida Pisauridae Dolomedes sp.1 -- .014 --

Ephemeroptera -- -- .029 -- --

Ephemeroptera Baetidae Callibaetis floridanus .002 -- --

Ephemeroptera Caenidae Caenis diminuta .273 .014 --

Odonata Coenagrionidae Enallagma sp. .266 -- --

Odonata Coenagrionidae Nehalennia sp. .268 -- --

Odonata Coenagrionidae Telebasis byersi -- .014 --

Odonata Corduliidae Epitheca princeps regina .133 -- --

Odonata Libellulidae -- .002 -- --

Odonata Libellulidae Erythemis plebeja .133 -- --

Hemiptera Belostomatidae -- -- .208 --

Hemiptera Belostomatidae Belostoma sp. -- -- .120

Hemiptera Belostomatidae Lethocerus sp. -- -- .904

Hemiptera Gerridae -- -- .104 --

Hemiptera Mesoveliidae Mesovelia sp. .002 -- --

Hemiptera Naucoridae Pelocoris sp. .135 .028 .060

Homoptera -- -- .133 -- --

Trichoptera Hydroptilidae Neotrichia sp. -- .014 --

Trichoptera Hydroptilidae Orthotrichia sp. .002 -- --

Coleoptera Chrysomelidae -- .266 -- .060

Coleoptera Dryopidae Pelonomus obscurus -- .014 --

Coleoptera Haliplidae Peltodytes sp. -- .327 --

Coleoptera Hydrophilidae Helocombus sp. .018 -- --

Diptera Ceratopogonidae -- .133 -- 5.987

Diptera Chironomidae -- 3.553 19.541 19.202

Diptera Ephydridae -- -- -- .452

Diptera Ptychopteridae -- -- -- .452

Characterization of Springs 19
Table 5. Percent composition of total number of benthic macroinvertebrates (combined ponar and 

dip net sweep samples for all seasons) collected in De Leon, Gemini, and Green Springs, 2004—

Continued. 

[--, not differentiated or not observed]

Major 

taxon Family Species Percent composition

De Leon Gemini Green

Diptera Stratiomyidae -- .035 -- .422

Diptera Tabanidae -- .002 -- --

Cladocera1 -- -- .019 -- --

Ostracoda1 -- -- .085 8.964 1.428

Isopoda Asellidae2 -- .002 .006 --

Isopoda Asellidae Lirceus lineatus .266 -- --

Isopoda Sphaeromatidae Cassidinidea ovalis .135 -- --

Amphipoda -- -- -- 1.980 --

Amphipoda Gammaridae Gammarus sp. 18.496 18.152 --

Amphipoda Hyalellidae Hyalella azteca 60.502 15.087 20.309

Decapoda Cambaridae Procambarus sp. .135 .236 .452

Decapoda Palaemonidae Palaemonetes 

paludosus .135 .042 --

Total number 42,335 53,968 12,451

1

Not regarded as a component of the benthic macroinvertebrate fauna by the Florida Department of 

Environmental Protection.

2

Possibly a terrestrial form.

Table 6. Richness and community measures for De Leon Spring.

 [--, not calculated. EPT, Ephemeroptera, Plecoptera, and Trichoptera taxa; ETO, Ephemeroptera, Trichoptera, and Odonata taxa. 

Richness measures (taxon richness, EPTr, ETOr, and Florida Index) were tabulated from taxonomic lists from combined petite ponar 

dredge and dip net sweep samples. All other measures (# individuals; percentages) were calculated using total abundance estimates 

derived from dip net sweep collections only]

Winter Spring Summer Combined

Taxon Richness (total # taxa) 15 11 18 45

Total Abundance 8,944 7,425 22,275 38,644

EPTr (# taxa) 1 0 3 4

EPT (# individuals) 56 0 56 112

Odonata (# taxa) 2 1 4 5

ETOr (# taxa) 3 1 7 9

ETO (# individuals) 225 56 169 350

Florida Index -- -- -- 4

Dominant Taxon Amphipoda Amphipoda Amphipoda Amphipoda

Percent Dominant Taxon 77.4 75 81.3 79

Percent Diptera 4.4 10.6 .8 3.5

Percent Odonata 1.9 .8 .5 .9

Amphipoda excluded

Total Abundance 2,025 1,856 4,163 8,044

Dominant Taxon Gastropoda Diptera Gastropoda Gastropoda

Percent Dominant Taxon 52.8 42.5 48.6 45

Percent Diptera 19.5 42.5 4.1 16.8

Percent Odonata 8.3 3 2.7 4.1

20 Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
None of five odonate taxa 

(including an unidentified 

species of Libellulidae) 

collected at De Leon 

Spring was collected at 

Gemini Springs or Green 

Spring. Based on all 

samples combined, De 

Leon Spring had an FI 

value of 4. Given this FI 

score, De Leon Spring 

would receive a 

“moderate” score when 

calculating the Stream 

Condition Index (SCI) 

for a peninsular Florida 

stream (Barbour and 

others, 1996). Amphipods dominated sweep 

samples from all three 

sampling events, with 

relative abundances 

by season of 75 to 

82 percent. Dipteran 

abundance was 

relatively low during 

summer, highest in 

spring, and intermediate 

in winter. When amphipods were omitted from 

calculations of relative 

abundance, gastropods 

dominated in winter and 

summer and dipterans 

dominated in spring. 

Seasonal differences in 

relative abundances of 

different macroinvertebrate groups and overall 

densities did not show 

any obvious trends. It 

is possible that greater 

relative abundances of 

certain insect groups (i.e., 

dipterans and odonates) 

during winter and spring months and lower abundance during summer may have been the result of emergences from 

aquatic stages to winged adults. 

Shelton (2005) reported two notable hydrobiid snails 

from De Leon Spring: Tryonia aequicostata, a species 

endemic to the St. Johns River, and an unidentified species 

of Aphaostracon. The samples collected during this study 

contained gastropods, in order of descending abundance, 

of hyrobiids (presumably the species identified by Shelton), 

Table 7. Fishes observed or collected in De Leon Springs State Park (Walsh and Williams, 2003), and 

deposited in the Florida Museum of Natural History (FLMNH).

[--, not observed]

Family Species

USGS FLMNH ichthyological 

collection

Number of 

specimens

Percent 

composition

Number of 

specimens

Percent of 

material

Dasyatidae Dasyatis sabina 3 0.4 -- --

Lepisosteidae Lepisosteus osseus 1 .1 -- --

Amiidae Amia calva 1 .1 -- --

Anguillidae Anguilla rostrata 3 .4 -- --

Clupeidae Dorosoma cepedianum 2 .3 -- --

Cyprinidae Notemigonus crysoleucas 17 2.5 2 3.2

Catostomidae Erimyzon sucetta 29 4.3 -- --

Ictaluridae Ameiurus natalis 1 .1 -- --

Noturus leptacanthus -- -- 1 1.6

Esocidae Esox niger 1 .1 -- --

Mugilidae Mugil cephalus 15 2.2 -- --

Belonidae Strongylura marina 2 .3 -- --

Fundulidae Fundulus chrysotus 3 .4 -- --

Fundulus rubrifrons -- -- 3 4.8

Fundulus seminolis 12 1.8 8 12.7

Lucania goodei 49 7.3 20 31.7

Lucania parva 42 6.3 1 1.6

Poeciliidae Gambusia holbrooki 69 10.3 -- --

Heterandria formosa 22 3.3 -- --

Poecilia latipinna 15 2.2 -- --

Centrarchidae Enneacanthus gloriosus 1 .1 4 6.3

Lepomis auritus 11 1.6 5 7.9

Lepomis gulosus 9 1.3 4 6.3

Lepomis macrochirus 196 29.3 5 7.9

Lepomis microlophus 69 10.3 7 11.1

Lepomis punctatus 9 1.3 -- --

Micropterus salmoides 76 11.4 1 1.6

Pomoxis nigromaculatus 5 .7 1 1.6

Percidae Etheostoma fusiforme 5 .7 -- --

Cichlidae Oreochromis aureus* 1 .1 -- --

Achiridae Trinectes maculatus -- -- 1 1.6

Total number of species 28 14

Total number of specimens 669 63 *

nonindigenous species

the pleurocerid Elimia floridensis, and the viviparid 

Viviparus georgianus. Collectively, gastropods comprised 

9.2 percent of all invertebrates collected from De Leon 

Spring. 

Descriptions of the fish populations at De Leon Spring 

are based on the FLMNH collection and on data collected 

in 2002 by the USGS (Walsh and Williams, 2003). The 

FLMNH collection included 14 species representing 

9 genera and 5 families from De Leon Spring (table 7). 

Characterization of Springs 21
The 2002 survey resulted in 28 species comprising 

23 genera and 16 families collected or observed from the 

headspring area (Walsh and Williams, 2003). Species 

represented in the FLMNH collection that were not found 

in the 2002 survey were speckled madtom (Noturus 

leptacanthus), redface topminnow (Fundulus rubrifrons), 

and hogchoker (Trinectes maculatus). In contrast, 

17 species were found in the 2002 survey that were not 

represented by museum material; thus, a total of 

31 species of fishes has been recorded from De Leon 

Spring. This includes four species of marine derivation 

(Atlantic stingray, Dasyatis sabina; striped mullet, Mugil 

cephalus; Atlantic needlefish, Strongylura marina; 

hogchoker, Trinectes maculatus), although populations of 

the Atlantic stingray within parts of the St. Johns River 

drainage may reside year-round in fresh water. 

One nonindigenous species, the blue tilapia 

(Oreochromis aureus), was found in the 2002 survey of 

De Leon Spring (Walsh and Williams, 2003). During this 

study, several individuals of an introduced armored catfish, 

the brown hoplo (Hoplosternum littorale), were observed 

in the spring run below the dam on February 11, 2004; this 

species was not reported from this location by Walsh and 

Williams (2003). Hoplosternum littorale has rapidly colonized parts of the St. Johns River and other drainages in 

Florida. It is usually associated with marshes, lakes, canals, 

and wetlands with an abundance of macrophytes (including 

the invasive Hydrilla verticillata) that are used to construct 

bubble nests (Nico and others, 1996; Nico and Muench, 

2004). In this study, USGS personnel observed individuals 

of Hoplosternum littorale hiding in benthic vegetation, 

rapidly ascending to the surface to “pipe” (gulp air), and 

then quickly returning to the substrate. In addition to the 

above, Davis and Herring (2005) observed nonindigenous 

“suckermouth catfish” in the spring run; these were likely 

the vermiculated sailfin catfish noted to be widely distributed elsewhere in the drainage (see discussion of Silver 

Springs group and Gemini Spring).

Fish species at De Leon Spring represented by the 

most specimens in the FLMNH collection were the bluefin 

killifish (Lucania goodei), Seminole killifish (Fundulus 

seminolis), and redear sunfish (Lepomis microlophus), 

together representing 56 percent of museum specimens. 

Other species of centrarchids accounted for an additional 

32 percent of the museum material. Walsh and Williams’ 

(2003) samples were dominated by bluegill (Lepomis 

macrochirus), largemouth bass (Micropterus salmoides), redear sunfish, and eastern mosquitofish (Gambusia 

holbrooki), each totaling more than 10 percent of the total 

number of specimens and, combined, representing 

61 percent of all specimens. Other relatively common 

species collected included bluefin killifish, rainwater killifish (L. parva), and lake chubsucker (Erimyzon sucetta).

 Mussels were collected in August 2002 from the main 

spring pool area (near the west shore downstream from 

the sugar mill) by snorkeling and by using seines and dip 

nets (Walsh and Williams, 2003). The substrate was muck 

bottom with thick mats of filamentous algae, which made 

sampling difficult and provided few suitable areas for live 

mussels. Dead valves of five native species were found: 

barrel floater (Anodonta couperiana, N=2); Florida shiny 

spike (Elliptio buckleyi, N=1); flat spike (E. jayensis, N=1); 

paper pondshell (Utterbackia imbecillis, N=13); and downy 

rainbow (Villosa amygdala, N=2). A few shells of the 

nonindigenous Asian clam (Corbicula fluminea) were 

collected. The number of dead specimens indicates that 

native mussels formerly existed or may persist in low 

numbers within the spring run. Water-chemistry conditions, 

habitat perturbation, or limiting abiotic and/or biotic factors 

may account for the apparent lack of mussel populations 

within the spring run.

Large floating mats of filamentous algae, identified as 

Lyngbya wollei, were observed in the spring during all 

sampling events. Stevenson and others (2004) identified 

another Lyngbya species, Lyngbya majuscule, in other 

springs in central Florida, although the distinction between 

L. wollei and L. masjuscule has not been clearly defined 

in the literature (Shannon and others, 1992; Speziale and 

Dyck, 1992). Recent molecular work (Joyner, 2004) 

indicates that L. wollei is not related to L. masjuscule. 

Two passive periphyton sampling devices were placed 

in De Leon Spring, one on the dam spillway and the other 

about 50 ft downstream from the dam, from July 28-

August 11, 2004. Both samplers were recovered but large 

mats of floating Lyngbya were attached to the samplers so 

that smaller periphyton had little opportunity to grow in the 

filters (fig. 13). No determinations of periphyton density 

as related to the N or P content of the solution in the vials 

could be made. 

Figure 13. Periphyton sampler at De Leon Spring, August 11, 2004.

22 Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
Gemini Springs

Gemini Springs consist of two small vents near the 

north shore of Lake Monroe and is operated as a park by 

Volusia County (figs. 14 and 15). A previous owner built 

a dam to create an impoundment for swimming (fig. 16); 

water from the springs and pool discharges at a shallow 

weir into the lake. A third feature at the far west end of the 

impoundment may be an old spring head and a seep 

is located north of the primary vents. Park personnel 

reported that another spring is located in the center of the 

impoundment. 

Figure 14. Locations of Gemini Springs and Green Spring.

Figure 15. Gemini Springs. Figure 16. View from Gemini Springs to the dam and 

Lake Monroe.

Characterization of Springs 23

Source: U.S. Geological Survey Topographic map; 1:24,000

0

0

.5 1 MILE

.5 1 KILOMETER

GEMINI

SPRINGS

AREA

GREEN

SPRING

LAKE MONROE
Hydrology and Water 

Chemistry

Flow measurements are 

made quarterly by SJRWMD at 

the downstream end of the dam. 

Total flow at the dam ranged from 

about 7.5 ft3/s during the drought 

of 2001 to about 13 ft3/s during 

the summer of 1996, which was 

during a wet period (fig. 17). 

During this study, individual 

measurements were made at each 

boil and at the dam to determine if 

additional springs were discharging into the impoundment. On 

February 10, 2004, measured flow 

from the north boil was 6.74 ft3/s 

and from the south boil, 3.52 ft3/s. 

Flow at the dam was 10.2 ft3/s. On 

August 19, 2004, flow from the 

north vent was 6.74 ft3/s and from 

the south boil (fig. 18), 3.05 ft3/s. 

Flow at the dam was 10.1 ft3/s. The 

fact that flow at the dam is about equal 

to the total flow from both boils indicates that it is unlikely that other springs are contributing 

flow to the impoundment. Flow measurements at the 

dam were 11.6 ft3/s on August 24, 2004, and 11.8 ft3/s on 

December 1, 2004. 

Water-chemistry data have been collected at the dam 

at Gemini Springs by SJRWMD since 1995. Nitrate-N 

concentrations increased from about 0.65 mg/L in 1995 

to 1.1 mg/L in 2004 (fig. 6). During this study, samples 

were collected by the USGS from both spring vents and 

at the dam. Water chemistry at both vents and at the dam 

was similar, except that DO was higher at the dam 

(app. A). Concentration of DO of water from the spring 

vents was less than 1.0 mg/L and ranged from 2.2 to 

4.8 mg/L at the dam. Specific conductance ranged from 

about 2,400 to 2,700 μS/cm at all sites. Major constituents showed little spatial or seasonal variability: calcium 

concentration was about 100 mg/L, magnesium concentration about 40 mg/L, potassium concentration about 

8 mg/L, and sodium concentration about 340 mg/L. 

Chloride concentration ranged from about 600 to about 

690 mg/L and sulfate concentration from 110 to 

129 mg/L. Concentration of nitrate-N ranged from 

0.88 to 1.13 mg/L and total P from 0.07 to 0.14 mg/L. 

The maximum value of total P concentration was measured in July 2004 at the dam. Concentrations of TOC 

ranged from 0.8 to 4.34 mg/L; the highest value was in 

water from the north vent on August 18, 2004. BOD concentrations ranged from 0.2 to 0.5 mg/L. Chlorophyll-a

Figure 17. Total combined discharge from Gemini Springs, 1995-2004.

Figure 18. Gemini Springs south vent.

24 Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
was detected in the samples collected at the dam in May 

and August 2004, but not in the February sample. Chlorophyll-b was not detected in any of the samples. 

 Both vents at Gemini Springs were sampled in May 

and August 2004 for pesticides and compounds commonly 

found in wastewater. Atrazine and its degradate CIAT were 

detected in water from both vents during both USGS 

sampling events. DEET was detected at the north vent 

during both sampling events (table 1) and at the south vent 

once. Four other compounds were detected at the north vent 

and two others at the south vent.

Water samples from both vents at Gemini Springs 

contained SF6 concentration much higher than atmospheric 

levels, indicating the influence of excess SF6, probably 

from wastewater sources (table 2). Thus, the water samples 

cannot be dated by the SF6 method. Dissolved gas results 

show small concentrations of excess N2 (table 2), indicating 

that denitrification probably was taking place in the Upper 

Floridan aquifer near the springs. 

Aquatic Communities

An estimated total of 

53,968 macroinvertebrates 

was collected from ponar and 

sweep samples at Gemini 

Springs during 2004; from 

these samples, 24 distinct 

taxa were identified 

(table 5; unidentified 

amphipods were presumed 

to be either Gammarus sp. 

or Hyalella azteca). Species 

richness was highest in the 

summer sample and lowest in 

winter (table 8). No EPT or 

ETO taxa were collected 

during winter or spring; 

richness values for EPTr and 

ETOr were 2 and 3, respectively, during summer. One 

trichopteran species (Neotrichia sp.) and one odonate 

species (Telebasis byersi) 

collected at Gemini Springs 

were not collected at De Leon 

Spring or Green Springs 

(app. D). Based on all 

samples combined, Gemini 

Springs had an FI =2. 

Barbour and others (1996) 

indicate that a peninsular 

stream with an FI < 4 receives 

the lowest score when calculating the stream condition 

index. Amphipods dominated sweep samples during winter 

(71 percent) and summer (61 percent), and dipterans were 

the most abundant organisms collected during spring 

(table 8). Relative abundance of dipterans was very low 

during winter (0 percent) and summer (0.3 percent), but 

dipterans dominated the macroinvertebrate samples 

during spring (28 percent). When amphipods were 

excluded, oligochaetes and gastropods were dominant in 

winter and summer samples, respectively. Gemini Springs 

had the highest total species richness, EPTr, and ETOr 

values in summer. The May sample had the greatest overall 

abundance of invertebrates; excluding amphipods, this 

sample was dominated by large numbers of dipterans 

(Chironomidae), oligochaetes, and hydrobiid snails.

Crayfish traps were inefficient at capturing fishes in 

Gemini Springs, possibly because of clear water and 

aversion by fishes to enter the traps. A moderate number 

of Seminole killifish (Fundulus seminolis) and bluefin 

killifish (Lucania goodei) were captured in traps. 

Table 8. Richness and community measures for Gemini Springs. 

[--, not calculated. Richness measures (taxon richness, EPTr, ETOr, and Florida index) were tabulated from 

taxonomic lists from combined petite ponar dredge and dip net sweep samples. All other measures (# individuals; 

percentages) were calculated using total abundance estimates derived from dip net sweep collections only]

Winter Spring Summer Combined

Taxon Richness (total # taxa) 8 14 20 25

Total Abundance 9,394 37,912 5,130 52,436

EPTr (# taxa) 0 0 2 2

EPT (# individuals) 0 0 16 56

Odonata (# taxa) 0 0 1 1

ETOr (# taxa) 0 0 3 3

ETO (# individuals) 0 0 24 67

Florida Index -- -- -- 2

Dominant Taxon Amphipoda Diptera Amphipoda Amphipoda

Percent Dominant Taxon 70.7 27.7 61.0 35

Percent Diptera 0 27.7 0.3 20

Percent Odonata 0 0 0.16 0.01

Amphipoda excluded

Total Abundance 2,756 29,250 2,003 34,009

Dominant Taxon Oligochaeta Diptera Gastropoda Diptera

Percent Dominant Taxon 40.8 36 90.3 30

Percent Diptera 0 36 0.7 31

Percent Odonata 0 0 0.4 0.1

Characterization of Springs 25
In addition to these two species, the following fishes 

were observed by snorkelers on August 17, 2004: eastern mosquitofish (Gambusia holbrooki), largemouth bass 

(Micropterus salmoides), bluegill (Lepomis macrochirus), 

redear sunfish (L. microlophus), redbreast sunfish (L. 

auritus), gizzard shad (Dorosoma cepedianum), blue tilapia 

(Oreochromis aureus), common carp (Cyprinus carpio), 

and vermiculated sailfin catfish (Pterygoplichthys disjunctivus). The last three species are nonindigenous. Common 

carp are not known to be established in the St. Johns River, 

hence their presence at Gemini Springs is of concern. The 

SJWRMD and Florida Fish and Wildlife Conservation 

Commission were notified of the observation. Presence of 

the vermiculated sailfin catfish in other springs of the St. 

Johns is known and this species was observed in large 

numbers at Gemini Springs during this study. Armored 

catfishes are of particular concern because of their potential 

to alter existing habitats (through nest borrowing) and 

possible interactions with native species.

Perhaps because of low flow velocities and relatively 

high nitrate-N and P concentrations, the water at Gemini 

Springs contains large amounts of aquatic vegetation 

(which is mechanically harvested twice a year by park 

personnel) and algae (figs. 19 and 20). At Gemini Springs, 

the dominant periphyton was Rhizoclonium sp., a green 

alga with no known toxin-producing capabilities. Periphyton samplers also were placed at Gemini Springs from 

July 28-August 11, 2004. One sampler was placed just 

downstream of the confluence of the spring runs from the 

north and south boils and the other was placed near the dam 

(fig. 21). Both samplers were covered by floating mats of 

filamentous algae, which prevented meaningful analysis of 

any preference of the periphyton for either N or P solutions. 

Green Spring

Green Spring is a third-magnitude spring located along 

the north shore of Lake Monroe, near the town of DeBary, 

FL (figs. 14 and 22); the spring is owned by Volusia 

County. The spring pool is about 90 ft in diameter and has 

Figure 19. View toward old springhead at Gemini Springs.

Figure 20. View toward Gemini Springs south vent.

Figure 21. Periphyton sampler at Gemini Springs near the 

dam, August 11, 2004. Figure 22. Green Spring.

26  Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
a reported depth of 125 ft (Rosenau and others, 1977). A 

concrete retaining wall and steps were built along the north 

edge of the spring run when the spring was privately owned 

(fig. 23). A concrete culvert was built about 100 ft downstream from the spring pool, modifying the natural spring 

run (fig. 24). 

Hydrology and Water Chemistry

Discharge measurements have been made by 

SJRWMD since 2000. Flow ranges from about 0.2 to 

2.9 ft3/sec (fig. 25). During the study, flow ranged from 

a minimum of 0.67 ft3/s on June 16, 2004, to a maximum 

of 2.58 ft3/s on September 30, 2004. 

Figure 23. View from culvert to 

Green Spring pool.

Figure 24. View from steps at Green Spring toward culvert.

Figure 25. Green Spring discharge, 

2000-2004.

Characterization of Springs 27
Green Spring presumably derives its name from water 

that usually appears murky green, although on rare occasions, the water is clear but still appears dark green 

(figs. 26 and 27). The water usually has a hydrogen sulfide 

(H2S) odor. Concentration of DO in water from the spring 

vent was very low—about 0.1 mg/L. At the culvert downstream from the vent, DO concentrations ranged from 0.4 

to 0.6 mg/L. Specific conductance from the vent water 

ranged from 2,430 to 2,700 μS/cm and at the culvert from 

2,620 to 2,670 μS/cm. The sample collected on 

August 18, 2004, may be anomalous, based on the low 

major ion concentrations compared with other samples, so 

the values from that sample are not considered to be the 

actual minimum values. Calcium concentrations ranged 

from 84-88 mg/L in water from the vent and from 

88-91 mg/L at the culvert. Magnesium concentrations 

ranged from 39-45 mg/L at the vent and from 42-46 mg/L 

at the culvert. Concentrations of potassium and sodium 

were about the same at both the vent and at the culvert: 

potassium concentrations ranged from 11-12 mg/L at the 

vent to 11-13 mg/L at the culvert; sodium concentrations 

ranged from 345-400 mg/L at the vent to 350-430 mg/L at 

the culvert. Chloride concentration generally was slightly 

lower at the culvert, ranging from 620-764 mg/L at the vent 

to 690-740 mg/L at the culvert. Sulfate concentration was 

about the same at the vent and the culvert: 100-110 mg/L at 

the vent and 104-110 at the culvert. The spring water was 

not analyzed for sulfide but the odor of hydrogen sulfide 

(H2S ) and the presence of sulfur-reducing bacteria in the 

spring pool (fig. 28) and spring run indicate high H2S 

concentration in the water, which probably accounts for the 

murky appearance of the water. 

At Green Spring, nitrate-N concentrations usually are 

too low to be detected; the highest reported concentration 

was 0.03 mg/L from a sample collected by SJRWMD at the 

vent; no nitrate-N could be detected in any of the samples 

collected at the culvert. Total P values ranged from 0.07 

to 0.15 at the vent and from 0.07 to 0.09 at the culvert. 

Concentrations of TOC ranged from 2.1 to 2.5 mg/L at the 

vent and from 2.2 to 2.7 mg/L at the culvert. The concentration of BOD was 0.7 mg/L at the vent and ranged from 

0.8 to 1.2 at the culvert. Neither chlorophyll-a nor –b was 

detected in water from the vent. At the culvert, chlorophyll-b was not detected during the study; chlorophyll-a 

was not detected in the winter sample, but the concentration 

was 1.6 mg/L in May 2004 and 0.5 mg/L in August 2004. 

Dissolved gas results indicated excess dissolved N2 in a 

concentration of about 0.5 mg/L in the May 2004 sample 

(table 2), and 1.0 mg/L in August 2004, indicating denitrification likely was occurring in the aquifer. 

No pesticides were detected at Green Spring during 

the study. Nine compounds commonly found in wastewater 

were detected in water from Green Spring, including DEET 

during both sampling events (table 1). Data for SF6 from 

Figure 26. Green Spring (water is murky).

Figure 27. Green Spring (water is clear).

Figure 28. Sulfur-reducing bacteria form light gray plumes 

around the edges of Green Spring pool.

28  Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
Green Spring indicated a recharge year of about 1984-1986 

for some fraction of the water discharging from the spring. 

Aquatic Communities

An estimated total of 12,451 macroinvertebrates was 

collected at Green Spring from ponar and sweep samples 

during 2004; of these, 16 distinct taxa were identified 

(table 5). Green Spring was not taxonomically rich and 

macroinvertebrate abundance was generally low. Species 

richness was highest in the spring (10 taxa) and lowest in 

winter (5 taxa) (table 9). No ephemeropterans or 

odonates were collected during any sampling at Green 

Spring. Based on all samples combined, Green Spring had 

an FI=0. Overall, oligochaetes were the first-, second-, or 

third-most abundant taxon in spring, summer, and winter, 

respectively. When amphipods were omitted from tabulations, oligochaetes represented their highest percentage 

composition in summer and lowest in spring. Relative 

abundance of dipterans was highest during winter 

(52 percent) and spring (32 percent) and declined during 

summer (9 percent). Dipteran abundance consisted mainly 

of chironomids (72 percent of all dipterans) and ceratopogonids (22 percent). Amphipods composed 27 percent 

of all invertebrates taken by sweep samples at Green 

Spring. Combined, oligochaetes, dipterans, and amphipods 

made up 95 percent of all specimens collected (fig. 29). 

Shelton (2005) reported a species of hydrobiid snail 

(Aphaostracon sp.) from Green Spring and speculated that 

this could be an endemic and undescribed species.

Species richness and the total number of macroinvertebrates collected in Green Spring were lowest of the 

three springs sampled and EPTr, ETOr, and the FI were 

consistently zero in all seasons. The apparent low richness 

and relative abundance of aquatic invertebrates may have 

been attributable, in part, to sampling restricted to the short 

spring run, because of the steep-sided nature and inaccessibility of the main pool. Substrate in the spring run consisted 

mainly of flocculent detritus without aquatic macrophytes. 

Submerged aquatic vegetation, woody debris, and 

filamentous algae were noted in deep areas near the edges 

of the cavern, and likely provide additional habitat for 

benthic invertebrates. Water chemistry, however, especially 

the low concentrations of DO and high concentrations of 

Table 9. Richness and community measures for Green Spring. 

[--, not calculated. Richness measures (taxon richness, EPTr, ETOr, and Florida index) were 

tabulated from taxonomic lists from combined petite ponar dredge and dip net sweep samples. All 

other measures (# individuals; percentages) were calculated using total abundance estimates derived 

from dip net sweep collections only]

Winter Spring Summer Combined

Taxon Richness 

(total # taxa) 5 10 9 16

Total Abundance 1,928 5,906 1,628 9,461

EPTr (# taxa) 0 0 0 0

EPT (# individuals) 0 0 0 0

Odonata (# taxa) 0 0 0 0

ETOr (# taxa) 0 0 0 0

ETO (# individuals) 0 0 0 0

Florida Index -- -- -- 0

Dominant Taxon Diptera Oligochaeta Amphipoda Oligochaeta

Percent Dominant Taxon 51.8 34.9 57.6 35.8

Percent Diptera 51.8 32.1 8.8 32.2

Percent Odonata 0 0 0 0

Amphipoda excluded

Total Abundance 1,807 4,387 690 6,941

Dominant Taxon Diptera Oligochaeta Oligochaeta Oligochaeta

Percent Dominant Taxon 55.2 47.4 72.9 48.8

Percent Diptera 55.2 43.6 20.7 32.2

Percent Odonata 0 0 0 0

Figure 29. Relative proportions of benthic 

invertebrates per order collected in 

De Leon Spring, Gemini Springs, and Green 

Spring, 2004.

Characterization of Springs 29
H2

S, also may be a major factor for the relatively 

depauperate invertebrate community. Further study is 

needed to determine relations between all aspects of the 

macroinvertebrate assemblage (richness, taxonomic composition, and relative abundance) and environmental 

variables at Green Spring.

Green Spring does not seem to have a substantial fish 

fauna, with the exception of a dense population of 

mosquitofish and other poeciliids. The only fishes visually 

observed and captured by minnow traps and petite ponar 

dredge at Green Spring were eastern mosquitofish 

(Gambusia holbrooki) and sailfin molly (Poecilia 

latipinna). It is possible that other poeciliids were present 

(e.g., Heterandria formosa) in the spring run and the 

margins of the spring vent and that centrarchids, cyprinids, 

or ictalurids were present in deeper parts of the spring. 

The isolated nature of this spring accounts, in part, for the 

apparent absence of other fishes. Moreover, hypoxic 

conditions may be a limiting factor. Additional sampling 

efforts would require use of other gear types, such as 

hook-and-line or visual surveys.

No macroalgae were observed in Green Spring. The 

occurrence of chlorophyll-a in May and August 2004, 

however, indicates some growth of periphyton in summer.

Green Spring had limited communities of macroinvertebrates and fishes. This is likely related to the unique 

water chemistry characterized by the relatively high 

specific conductance, low DO, and the presence of H2S. 

Comparisons among Springs

The springs sampled during this study are 

representative of the wide range of characteristics 

exhibited by springs in central Florida. This diversity 

reinforces the conclusion that study of individual springs 

is desirable to provide water managers with adequate data 

to support their decisions.

Figure 30. Relative proportions of cations and anions in spring-water samples, 2004.

30 Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
Hydrology and Water Chemistry

The springs studied range from the first-magnitude 

Silver Springs group, with an average discharge of about 

780 ft3/s to Green Spring, a third magnitude spring, with 

an average discharge of about 2 ft3/s. Silver Springs has the 

least disturbed natural flow system, whereas the spring runs 

at De Leon Spring, Gemini Springs, and Green Spring have 

been modified by water-control structures. 

Differences in water chemistry among the springs 

sampled reflect local differences in water chemistry in the 

Upper Floridan aquifer. Total dissolved solids concentrations ranged from about 270 mg/L at the Silver Springs 

group and 450 mg/L at De Leon Spring to about 1,500 

to 1,550 mg/L at Gemini Springs and Green Spring. The 

three springs sampled in the Silver Springs group (the Main 

Spring, Blue Grotto, and Abyss) have similar proportions 

of cations and anions (fig. 30). The water from Gemini 

Springs and Green Spring has higher proportions of sodium 

and chloride. The water from De Leon Spring has higher 

proportions of sodium and chloride than water from Silver 

Springs, but lower proportions of calcium and bicarbonate 

than Silver Springs. 

All of the springs studied are affected by human 

activities, based on the presence of organic compounds 

found in wastewater in all the spring-water samples, as 

well as qualitative observations of algae and periphyton. 

The most commonly detected compound was DEET, which 

was found in all the springs sampled except De Leon 

Spring. The pesticide atrazine and its degradate CIAT were 

detected in water from Silver Springs and in both vents 

at Gemini Springs. No pesticides were detected in water 

samples from De Leon Spring and Green Spring. Levels of 

wastewater compounds and pesticides were low and likely 

not high enough to cause direct harm to organisms (U.S. 

Environmental Protection Agency, 2004), but little information exists about possible effects of mixtures of various 

chemicals.

Aquatic Communities

Available habitats for macroinvertebrates varied 

greatly from site to site. Green Spring run contained nearly 

all leaf pack and snag material with a thin band of water 

pennywort (Hydrocotyle sp.) and an abundance of detritus. 

Gemini Springs contained areas of bare sand, muck, extensive beds of algae, and submersed and emergent vegetation 

along the margins of the run. De Leon Spring run contained 

an abundance of submersed and emergent vegetation and an 

artificial waterfall at the outflow of the spring pool that was 

covered with algae. 

The macroinvertebrate data indicated some differences 

among De Leon Spring, Gemini Springs, and Green Spring. 

None of the five odonate taxa collected at De Leon Spring 

were collected at either Gemini Springs or Green Spring 

(table 5). One species each of an odonate (Telebasis byersi) 

and a trichopteran (Neotrichia sp.) was collected from 

Gemini Springs, but not from the other springs. No 

plecopteran taxa were collected during this study. Of the 

three springs sampled, De Leon Spring had the highest 

overall species richness, EPTr, and ETOr, and had the most 

disturbance-intolerant assemblage (FI = 4) (table 6). 

Gemini Springs had high relative abundances of 

oligochaetes, chironomids, amphipods, hydrobiids, and 

ostracods (fig. 29). The impounded pool and presence of 

zooplankton, phytoplankton, and attached algae at Gemini 

Springs are somewhat indicative of eutrophic conditions in 

comparison to most relatively oligotrophic spring runs in 

close proximity to source vents. It is also notable that 

during visits to Gemini Springs in 2004, the impounded 

pool was closed to swimming and a sign was posted 

warning of high coliform bacteria levels in the water. 

Green Spring had the lowest species richness, no EPT or 

ETO taxa, and a community dominated by three organisms 

(collectively comprising 88 percent of all animals 

collected): oligochaetes, amphipods, and chironomids. 

The unusual water chemistry of Green Spring and the 

spring morphology (deep vent and shallow, short run 

modified by an impoundment) are hypothesized to be 

limiting factors in terms of richness and abundance of the 

benthic fauna.

Amphipods are commonly associated with karst 

habitats of Florida and may often occur in great 

abundance (Woodruff, 1993; Mattson and others, 1995; 

Walsh, 2001). In De Leon Spring and Gemini Springs, 

amphipods made up the largest percentage of any invertebrate group collected (fig. 31) and were consistently 

dominant in all months of the study except for a shift in 

dipteran abundance at Gemini Springs in spring (May) 

Figure 31. Total number of all amphipods collected by season in 

De Leon Spring, Gemini Springs, and Green Spring, 2004.

Comparisons among Springs  31
(tables 6 and 8). At De Leon Spring, both amphipod 

species peaked in abundance in summer (August), but the 

lowest abundance of Gammarus sp. occurred in winter 

(February) whereas Hyalella azteca was least abundant in 

spring (fig. 32). Only one amphipod species (H. azteca) 

was identified in samples from Green Spring.

Sample sizes of invertebrates collected in this study 

were too limited to allow for detailed quantitative or 

statistical analysis of trends or correlations with waterquality properties; however, some qualitative observations 

suggested possible associations between biological 

metrics and water chemistry. Species richness appeared to 

be negatively related to magnesium, potassium, sodium, 

and specific conductance. More invertebrates were 

collected when DO and nitrate-N were high but 

phosphorus and potassium concentrations were low. The 

relative abundance of dipterans was positively associated 

with specific conductance and TOC but negatively 

associated with nitrate-N. 

Invertebrate assemblages observed in springs of the 

St. Johns River were consistent with communities that have 

been studied in other north-central springs and spring-fed 

streams or rivers. Beck (1965) characterized benthic 

communities of calcareous streams in Florida as consisting 

primarily of mollusks, chironomids, ephemeropterans 

(e.g., baetids and heptageniids), trichopterans (e.g., Cheumatopsyche), and crustaceans (e.g., Palaemonetes paludosus and Hyalella azteca). Woodruff (1993) found that 

benthic sediments of Manatee Spring (lower Suwannee 

River drainage) had a community dominated by oligochaetes, amphipods, leeches, and isopods. The study by 

Mattson and others (1995) provided the most detailed 

tabulation of aquatic invertebrate communities in Florida 

karst habitats. Mattson and others (1995) noted that 

species richness and/or relative abundance generally 

increased in association with hard, alkaline spring water. 

Moreover, substrata of limestone outcrops, wood, and 

submerged macrophytes provide important habitat for 

benthic invertebrates in these systems. In the present study, 

sampling of rock and wood habitats was not feasible; thus, 

it is likely that species richness of the aquatic communities at De Leon, Gemini, and Green Springs is greater than 

reported herein.

Fish assemblages in Silver Springs and De Leon 

Spring had the greatest species richness of the springs 

surveyed. Centrarchids and poeciliids generally were in 

greatest abundance during surveys by USGS personnel 

(Walsh and Williams 2003) (tables 3, 7). Silver Springs 

had centrarchids and poeciliids in greatest abundance 

(32.1 percent and 22.8 percent composition, respectively), 

followed by cyprinids (16.1 percent) and fundulids 

(13.0 percent) (table 3). Centrarchids (56 percent) dominated in De Leon Spring and were followed by poeciliids 

and fundulids in numerical abundance (15.8 percent) 

(table 7). Fish collections at Gemini Springs and Green 

Spring were limited to the use of crayfish traps, minnow 

traps, and visual surveys. Taxonomic composition of the 

fishes in Gemini Springs was similar to the fauna of De 

Leon Spring. The fish assemblage at Green Spring was 

dominated by poeciliids (possibly the only family 

represented), presumably because of the water chemistry 

(low DO and presence of H2S), small size, and isolation 

from Lake Monroe. The presence of nonindigenous fishes 

in three of the four springs surveyed is of particular 

concern. Three nonindigenous fish species were observed 

in Gemini Springs, two in De Leon Spring (and a third 

reported by Davis and Herring, 2005), and one in Silver 

Springs. 

Summary

The hydrology, water chemistry, and aquatic 

communities of Silver Springs, De Leon Spring, Gemini 

Springs, and Green Spring in the St. Johns River Water 

Management District, Florida, were studied in 2004 to 

provide a better understanding of each spring and to 

provide baseline data that may be useful in watermanagement decisions. Ground water that discharges 

from the springs studied flows from the Upper Floridan 

aquifer of the Floridan aquifer system; the water is 

recharged entirely within the State. This report summarizes 

data about flow, water-chemistry, and aquatic communities 

(benthic invertebrates, fishes, algae, and selected aquatic 

macrophytes) collected by the U.S. Geological Survey, the 

St. Johns River Water Management District, and the Florida 

Department of Environmental Protection during 2004, as 

well as previously collected data. 

32 Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs

Figure 32. Total number of Gammarus sp. and Hyallela azteca by 

season at De Leon Spring, 2004.
The physical size and flow of the springs varies 

greatly. Silver Springs consists of a group of at least 

16 springs located along about 0.5 mile of the Silver River. 

Maximum depth of the springs in the group is about 

33 feet. The average combined discharge from the 

Silver Springs group is about 780 cubic feet per second. 

De Leon Spring is a single conical pool about 170 feet 

across and about 28 feet deep. Average discharge from 

De Leon Spring is about 27 cubic feet per second. Gemini 

Springs consists of two small vents; flow from the springs 

is impounded and discharge totals about 10 cubic feet per 

second. Green Spring is a single pool about 90 feet in 

diameter with a reported depth of about 125 feet and 

discharge of about 2 cubic feet per second.

Differences in water chemistry among the springs 

sampled reflect differences in local water chemistry in the 

Upper Floridan aquifer as well as differences in anthropogenic inputs (agricultural or wastewater effects). The 

three springs sampled at the Silver Springs group (the Main 

Spring, Blue Grotto, and the Abyss) have similar proportions of cations and anions. The water from Gemini Springs 

and Green Spring has higher proportions of sodium and 

chloride. Water from De Leon Spring has higher proportions of sodium and chloride than at the Silver Springs 

group but lower proportions of calcium and bicarbonate. 

Nitrate nitrogen concentrations have increased with time at 

Silver Springs, De Leon Spring, and Gemini Springs, 

but apparently not at Green Spring. Evidence of denitrification in the Upper Floridan aquifer was indicated by the 

presence of excess nitrogen gas in water samples from 

most of the springs. Organic compounds found in wastewater were detected in all the springs sampled, indicating 

the effects of human activities in the springsheds. The most 

commonly detected compound was N,N’-diethylmethyl-toluamide (DEET), which was found in all the 

springs sampled except De Leon. The pesticide atrazine and 

its degradate 2-chloro-4-isopropylamino-6-amino-s-triazine 

(CIAT) were detected in water from Silver Springs and in 

both boils at Gemini Springs. No pesticides were detected 

in water samples from De Leon Spring and Green Spring. 

Macroinvertebrate communities were sampled at 

De Leon Spring, Gemini Springs and Green Spring. 

Amphipods were the dominant group in most benthic 

invertebrate collections. A total of 57 taxa was identified 

from all springs combined. De Leon Spring had the greatest 

species richness (45 taxa), followed by Gemini Springs (24) 

and Green Spring (16). Five odonate taxa were collected 

only from De Leon Spring, and samples from Gemini 

Springs had a single species each of an odonate and a 

trichopteran that were not collected at the other springs. 

Total abundance of invertebrates was greatest at Gemini 

Springs primarily because of the large numbers of 

oligochaetes, dipterans, and hydrobiids. 

Fish assemblages in the Silver River and De Leon 

Spring were similar; both were dominated by centrarchids, 

poeciliids, and fundulids. Gemini Springs could not be 

sampled adequately, but the fish population is moderately 

species-rich and seems to be similar in composition to 

the large springs. The fish assemblage in Green Spring is 

heavily dominated by poeciliids, possibly because of the 

spring’s unique water chemistry, small size, and/or isolation 

from Lake Monroe. The presence of nonindigenous fishes 

in Silver Springs, De Leon Spring, and Gemini Springs 

is of concern and is indicative of the rapid colonization 

of certain invasive species throughout the St. Johns River 

drainage.

Assemblages of aquatic plants and algae varied among 

the springs, perhaps influenced by physical characteristics 

of the springs and water chemistry. The dominant 

submerged aquatic vegetation in the Silver River is 

strap-leaf sagittaria (Sagittaria kurtziana). Algae blooms 

generally cover the vegetation. The dominant epiphytic 

algae, based on biomass, were the green alga Ulothrx, 

the diatom Aulocosira (Melosira), and a variety of other 

diatoms. The dominant benthic algal species was Lyngbya 

sp. In De Leon Spring, large floating mats of filamentous 

algae, identified as Lyngbya wollei, were observed 

during all sampling events in 2004. Two passive periphyton 

sampling devices placed in De Leon Spring from 

July 28-August 11, 2004, had large mats of floating 

Lyngbya attached to the samplers so that smaller periphyton 

had little opportunity to grow in the filters. Gemini Springs 

contains large quantities of aquatic vegetation, perhaps 

because of low flow velocities and relatively high nitrogen 

and phosphorus concentrations in the water. The dominant periphyton at Gemini Springs was Rhizoclonium sp., 

a green alga with no known toxin-producing capabilities. 

Periphyton samplers also were placed at Gemini Springs 

from July 28-August 11, 2004. Both samplers were covered 

by floating mats of filamentous algae. No macroalgae were 

observed in Green Spring, although occurrence of chlorophyll-a in some water samples may indicate the growth of 

periphyton in summer. The water at Green Spring usually is 

murky green in appearance, although on rare occasions, the 

water is clear but appears dark green.

The short duration of this study, the low number of 

samples, and variability of the invertebrate data preclude 

drawing anything but general comparisons within and 

among the springs. Long-term monitoring would elucidate 

trends and allow statistical comparisons of biological, 

environmental, and physical data within and among 

springs. Additional monitoring and research of Florida’s 

springs is essential to the long-term preservation of these 

natural treasures. 

Summary  33
Selected References

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34 Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
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biomonitoring and benthic macroinvertebrates: New 

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36  Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
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Selected References  37
38  Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
Appendixes A-E

Appendixes

Appendixes  39
40 Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs Appendix A. Water-chemistry data, 2004. [<, less than; *, sample lost. Yellow shading indicates data obtained from the St. Johns River Water Management District; blue shading indicates data obtained from the Florida Department of Environmental Protection; pink shading indicates filtered samples] Site name Site ID Date Color Turbidity Dissolved oxygen pH Specific conductance, laboratory Specific conductance, field Temperature Calcium Magnesium Potassium Sodium Acid neutralizing capacity De Leon Spring2236110 2004/02/11 5 0.12 0.8 7.52 810 886 22.5 51 14 4.2 94 119 2236110 2004/03/18 1.5 7.4 884 23 2236110 2004/05/12 <5 .62 .8 7.4 758 801 22.7 50 13 4.4 78 130 2236110 2004/08/23 8 1.2 6.8 1,030 1,127 23.5 59 19 5.6 128 124 De Leon run 290804081214800 2004/02/11 5 .22 6.7 7.7 1,140 1,060 21.3 55 18 5.8 130 122 290804081214800 2004/03/18 5.5 7.5 900 22.9 290804081214800 2004/05/12 7 .67 6 7.6 865 869 23.1 50 14 4.6 94 124 290804081214800 2004/07/28 1.5 7.2 832 23.1 290804081214800 2004/08/23 3.6 7 949 969 23.8 52 17 5.7 121 114 Green Spring 285145081145500 2004/02/10 <5 .13 .1 7.4 2,700 2,900 22.5 88 45 12 400 410 285145081145500 2004/03/18 .1 7.3 2,920 22.6 285145081145500 2004/05/11 5 .62 .1 7.2 2,430 2,640 22.6 84 39 11 345 179 285145081145500 2004/08/18 8 .4 7 1,725 2,760 23.2 34 10 1.6 5.4 109 Green run 285146081145100 2004/02/10 5 .16 .4 7.4 2,900 2,920 22.5 91 46 13 430 156 285146081145100 2004/05/11 5 .43 .6 7.3 2,620 2,630 22.8 89 40 12 360 159 285146081145100 2004/08/18 12 .6 7.2 2,670 2,720 23.2 88 42 11 350 158 Gemini Spring North 285146081184100 2004/02/10 <5 .19 .8 7.2 2,510 2,620 22.9 102 41 8.6 360 139 285146081184100 2004/05/11 <5 .6 7.2 2,510 22.9 285146081184100 2004/08/18 1 7 2,590 2,710 24.2 106 41 8.2 333 144 Gemini Spring South 285147081184000 2004/02/10 <5 .2 .9 7.1 2,640 2,650 22.9 105 41 8.7 370 140 285147081184000 2004/03/18 .6 7.2 2,690 22.9 285147081184000 2004/05/12 <5 * .6 7.2 * 2,541 22.9 * * * * * 285147081184000 2004/08/18 5 .8 7 2,620 2,740 24.1 103 41 8.5 327 145 Gemini Dam 285144081183900 2004/02/10 <5 .38 3.2 7.4 2,430 2,650 22.9 104 41 8.6 360 139 285144081183900 2004/02/16 2,166 2,500 22.6 103 41 8.4 351 135 285144081183900 2004/03/18 4.8 7.3 2,710 23.7

285144081183900 2004/05/11 6 .57 3.8 7.3 2,480 2,540 23.4 103 38 8 330 140285144081183900 2004/05/13 7.4 2,370 2,445 24 100 38 8 324 148285144081183900 2004/07/28 2.2 7 2,620 22.9285144081183900 2004/08/18 10 <2 3 7.1 2,670 2,730 26.6 107 41 8.4 340 143
Appendix A. Water-chemistry data, 2004—Continued.

[<, less than; *, sample lost. Yellow shading indicates data obtained from the St. Johns River Water Management District; blue shading indicates data obtained from the Florida Department of Environmental Protection; pink shading indicates filtered samples]

Site name Site ID Date Color Turbidity Dissolved oxygen pH Specific conductance, laboratory Specific conductance, field Temperature Calcium Magnesium Potassium Sodium Acid neutralizing capacity 

Silver Springs Group Main 2239500 2003/09/08 <5 2.6 7.1 446 483 23.4 185

2239500 2003/10/21 <5 2.2 7.2 464 456 23.1 187DEP 2003/10/23 5 .1 1.7 7.32 430 425 23.3 78 9.5 0.52 5.3 1822239500 2004/02/19 5 2.7 6.8 457 475 23.2 1892239500 2004/04/14 2.5 7.2 470 23.22239500 2004/04/14 5 2.5 7.2 416 470 23.2 1892239500 2004/07/14 <5 .12 1.9 7 382 23.12239500 2004/08/02

 Blue Grotto DEP 2003/10/23 5 .05 3.6 7.36 449 465 23.7 76 12 1.59 5.4 151

291255082030000 2004/04/14 4.5 7.3 473 23.5291255082030000 2004/07/14 <5 .13 3.9 7.1 390 23.7

 Abyss DEP 2003/10/23 5 .15 3.4 7.31 497 509 23.6 88 13 0.63 5.7 172

291253082030600 2004/04/14 4.4 7.2 491 23.5291253082030600 2004/07/14 <5 .16 3.9 7.1 404 23.7

 Silver River 291256082022800 2004/01/15 <5 .1 5.4 7.4 454 465 23.4 74 10 0.6 6.2 172

291256082022800 2004/04/14 5 .17 5.7 7.2 449 451 23.4 68 9.4 0.8 6.4 170291256082022800 2004/07/14 <5 .16 5 6.9 450 373 23.8 68 9.3 0.6 6.3 168

Appendixes 41
42 Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs Appendix A. Water-chemistry data, 2004—Continued. [<, less than; *, sample lost. Yellow shading indicates data obtained from the St. Johns River Water Management District; blue shading indicates data obtained from the Florida Department of Environmental Protection; pink shading indicates filtered samples] Site name Chloride Fluoride Silica Sulfate Residue on evapora- tion Nitrite plus nitrate Orthophosphate Phosphorus Organic carbon Biochemi- cal oxygen demand Chlorophyll-a Chlorophyllb Iron Strontium De Leon Spring 165 33 466 0.83 0.06 0.05 1.3 0.3 <0.1 <0.1 <.1 <.1 140 28 415 .74 .05 .05 1.1 1 5.7 <.1 217 37 603 .64 .05 .05 De Leon run 240 <0.1 6.5 38 627 .62 .04 .06 2.5 1.2 21 <.1 17 460 <.1 <.1 170 <.1 6.6 30 476 .63 .04 .05 1.1 .6 8.3 <.1 10 370 .67 .048 .07 227 <.17 7.2 38 546 .52 .055 .073 3.9 7.8 .6 48 408 Green Spring 764 110 1,570 .106 .08 2.5 .7 <.1 <.1 <.1 <.1 620 100 1,450 .06 .07 2.1 .7 <.1 <.1 431 62 1,060 .03 .115 .15 2.5 Green run 740 <.1 7.8 110 1,690 <.02 .06 .07 2.5 1.2 <.1 <.1 27 1,740 670 <.1 7.8 100 1,490 <.02 .11 .07 2.2 .8 1.6 <.1 14 1,550 690 <.17 8.1 104 1,420 .01 .075 .09 2.7 .5 <.1 26 1,560 Gemini Spring North 650 .1 9.5 120 1,540 1.1 .06 .07 1.1 .2 <.1 <.1 98 1,660 .06 .8 .3 <.1 <.1 670 9.9 128 1,510 1.04 .058 .078 4.34 85 1,660 Gemini Spring South 650 .1 9.6 120 1,610 1.1 .06 .07 1.3 .2 <.1 <.1 76 1,710 <.1 <.1

* * * * * * .06 * .9 .4 <.1 <.1 * *

692 9.9 129 1,530 1.02 .061 .07 1.67 62 1,680

Gemini Dam 670 .1 9.4 120 1,560 1 .05 .07 1.1 .2 <.1 <.1 85 1,700

641 118 1,470 .124 .07

1.13 .07 <.1 <.1

640 .1 9 110 1,420 1 .06 .06 1 .5 2.2 <.1 63 1,610586 118 1,450 1.15 .07 .07

1.07 .057 .14

686 <.17 9.6 128 1,480 .88 .065 .09 3.04 .5 <.1 71 1,700
Appendix A. Water-chemistry data, 2004—Continued.

[<, less than; *, sample lost. Yellow shading indicates data obtained from the St. Johns River Water Management District; blue shading indicates data obtained from the Florida Department of Environmental Protection; pink shading indicates filtered samples]

Site name Chloride Fluoride Silica Sulfate 

Residue 

on evaporation

Nitrite 

plus 

nitrate 

Orthophosphate Phosphorus Organic carbon Biochemi- cal oxygen demand Chlorophyll-a Chlorophyll-b Iron Strontium 

Silver Springs Group Main 11 47 318 1.2 .04 .04

11 42 276 1.1 .04 .04

9.8 .2 27 251 .96 .04 1 15 441

10 38 278 1.2 .03 .0510 37 270 1.1 .03 .04

1.1 .04 .04 .5 <.1

.04

 Blue Grotto 11 .16 64 273 1.4 .04 1 .16 669

1.4 .03 .03 .4 .2

 Abyss 11 .19 69 299 1.2 .05 1 823

1.5 .04 .03 .4 .3

 Silver River 11 .2 10 49 278 1.2 .04 .04 .3 <.1 <.1 <.1 3 630

11 .2 9.8 48 275 1.2 .03 .03 .3 .4 <.1 3.1 57010 .2 10 46 271 .96 .03 .02 .5 .1 <.1 <.1 2 590

Appendixes 43
Appendix B. Compounds commonly detected in wastewater.

[%, percent; >, greater than. Endocrine disrupting potential: K, known, S, suspected. CAS, Chemical Abstract Service; F, fungicide; H, herbicide; 

I, insecticide; GUP, general use pesticide; FR, flame retardant] 

Compound names

Endocrine 

disrupting 

potential

CAS 

number Common use, application, or occurrence

1,4-Dichlorobenzene S 106-46-7 moth repellent, fumigant, deodorant

1-Methylnaphthalene 90-12-0 nearly equal concentrations (2-5%) in gasoline/diesel/

crude

2,6-Dimethylnaphthalene 58-14-2 indicator of diesel, kerosene (not much in gasoline)

2-Methylnaphthalene 91-57-6 nearly equal concentrations (2-5%) in gasoline/diesel/

crude

3-beta-Coprostanol 360-68-9 usually a carnivore fecal indicator

3-Methyl-1(H)-indole (skatol) 83-34-1 fragrance: odor in feces and coal tar

3-tert-Butyl-4-hydroxy anisole (BHA) K 25013-16-5 antioxidant, preservative

4-Cumylphenol K 599-64-4 nonionic detergent metabolite

4-n-Octylphenol K 1806-26-4 nonionic detergent metabolite

4-tert-Octylphenol K 140-66-9 nonionic detergent metabolite

5-Methyl-1H-benzotriazole 136-85-6 antioxidant in antifreeze, deicers

Acetophenone 98-86-2 fragrance: soap, detergent, tobacco; flavor: beverages

Acetyl hexamethyl tetrahydronaphthalene 

(AHTN) 21145-77-7 fragrance: musk; widespread usage; persistent in ground water

Anthracene 120-12-7 wood preservative, in tar/diesel/crude (not gasoline)

Anthraquinone 84-65-1 manufacture of dye/textiles, seed treatment, bird repellent

Benzo(a)pyrene K 50-32-8 regulated polychlorinated aromatic hydrocarbon, used in 

cancer research

Benzophenone S 119-61-9 fixative for perfumes and soaps

beta-Sitosterol 83-46-5 generally a plant sterol

beta-Stigmastanol 19466-47-8 generally a plant sterol

Bisphenol A K 80-05-7 FR, manufacture of polycarbonate resins, antioxidant, 

Bromacil 314-40-9 H, GUP, >80% non-crop grass/brush control

Bromoform 75-25-2 by-product of wastewater ozonation, military uses/explosives

Caffeine 58-08-2 medical: diuretic, highly mobile/biodegradable

Camphor 76-22-2 flavor, odorant, in ointments

Carbaryl K 63-25-2 I, crop and garden uses, low environmental persistence

Carbazole 86-74-8 I, manufacture of dyes, explosives, and lubricants

Chlorpyrifos K 2921-88-2 domestic pest/termite control, highly restricted (2000)

Cholesterol 57-88-5 often a fecal indicator, also a plant sterol

Cotinine 486-56-6 primary nicotine metabolite

Diazinon K 333-41-5 I, > 40% non-agricultural uses, ants, flies, etc.

Dichlorvos S 62-73-7 I, pet collars, fly spray; breakdown of naled & trichlofon

d-Limonene 5989-27-5 F, antimicrobial, antiviral, fragrance in aerosols

Fluoranthene 206-44-0 common in coal tar/asphalt (not gasoline/diesel)

Hexahydrohexamethyl Cyclopentabenzopyran 

(HHCB) 1222-05-5 fragrance: musk; widespread usage; persistent in ground water

Indole 120-72-9 pesticide inert, fragrance: coffee

Isoborneol 124-76-5 fragrance: perfumery, disinfectants

Isophorone 78-59-1 solvent for lacquers, plastics, oils, silicon, resins

Isopropylbenzene (cumene) 98-82-8 manufacture of phenol/acetone, component of fuels/paint 

thinner

Isoquinoline 119-65-3 flavors and fragrances

44 Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
Appendix B. Compounds commonly detected in wastewater—Continued.

[%, percent; >, greater than. Endocrine disrupting potential: K, known, S, suspected. CAS, Chemical Abstract Service; F, fungicide; H, herbicide; 

I, insecticide; GUP, general use pesticide; FR, flame retardant] 

Compound names

Endocrine 

disrupting 

potential

CAS 

number Common use, application, or occurrence

Menthol 89-78-1 cigarettes, cough drops, liniment, mouthwash

Metalaxyl 57837-19-1 H, F, GUP, soil pathogens, mildew, blight, golf turf

Methyl salicylate 119-36-8 liniment, food, beverage, UV-adsorbing lotions

Metolachlor 51218-45-2 H, GUP, indicator of agricultural drainage

N,N’-diethyl-methyl-toluamide (DEET) 134-62-3 I, urban uses, mosquito control

Naphthalene 91-20-3 fumigant, moth repellent, about 10% of gasoline

Nonylphenol, diethoxy- (total) K 26027-38-3 nonionic detergent metabolite

Octylphenol, diethoxy- K 26636-32-8 nonionic detergent metabolite

Octylphenol, monoethoxy- K 26636-32-8 nonionic detergent metabolite

para-Cresol S 106-44-5 wood preservative

para-Nonylphenol (total) K 84852-15-3 nonionic detergent metabolite

Pentachlorophenol S 87-86-5 H, F, wood preservative, termite control

Phenanthrene 85-01-8 manufacture of explosives, in tar/diesel/crude (not gasoline)

Phenol 108-95-2 disinfectant, manufacture of several products, leachate

Prometon 1610-18-0 H, only non-crop areas, applied prior to blacktop

Pyrene 129-00-0 common in coal tar/asphalt (not gasoline/diesel)

Tetrachloroethylene 127-18-4 solvent, degreaser; veterinary: anthelminic

tri(2-Chloroethyl) phosphate S 115-96-8 FR, plasticizer

tri(Dichlorisopropyl) phosphate S 13674-87-8 FR

Tributylphosphate 126-73-8 FR, antifoaming agent

Triclosan S 3380-34-5 disinfectant, antimicrobial (concern: induced resistance)

Triethyl citrate (ethyl citrate) 77-93-0 cosmetics, pharmaceuticals, widely used

Triphenyl phosphate 115-86-6 FR, plasticizer, resins, waxes, finishes, roofing paper

tris(2-Butoxyethyl) phosphate 78-51-3 FR

Appendixes 45
Appendix C. Pesticides analyzed. 

[CAS, Chemical Abstract Service; μg/L, microgram per liter]

Analyte CAS 

number

Reporting 

limit Units

2,4-D 94-75-7 0.0218 μg/L

2,4-D methyl ester 1928-38-7 .0086 μg/L

2,4-DB 94-82-6 .016 μg/L

3(4-Chlorophenyl)-1- methyl 5352-88-5 .0242 μg/L

3-Ketocarbofuran 16709-30-1 1.5 μg/L

Acifluorfen 50594-66-6 .0066 μg/L

Aldicarb 116-06-3 .04 μg/L

Aldicarb sulfone 1646-88-4 .02 μg/L

Aldicarb sulfoxide 1646-87-3 .0082 μg/L

Chloramben, methyl ester 7286-84-2 .018 μg/L

Atrazine 1912-24-9 .009 μg/L

2-Hydroxyatrazine 2163-68-0 .008 μg/L

Deethylatrazine 6190-65-4 .0282 μg/L

Deethyldeisopropyla­trazine 3397-62-4 .01 μg/L

Deisopropylatrazine 1007-28-9 .044 μg/L

Bendiocarb 22781-23-3 .0252 μg/L

Benomyl 17804-35-2 .0038 μg/L

Bensulfuron-methyl 83055-99-6 .0158 μg/L

Bentazon 25057-89-0 .011 μg/L

Bromacil 314-40-9 .033 μg/L

Bromoxynil 1689-84-5 .017 μg/L

Caffeine 58-08-2 .0096 μg/L

Carbaryl 63-25-2 .0284 μg/L

Carbofuran 1563-66-2 .0056 μg/L

3-Hydroxycarbofuran 16655-82-6 .0058 μg/L

Chlorimuron-ethyl 90982-32-4 .0096 μg/L

Chlorothalonil 1897-45-6 .035 μg/L

Clopyralid 1702-17-6 .0138 μg/L

Cycloate 1134-23-2 .013 μg/L

Dacthal monoacid 887-54-7 .0116 μg/L

Dicamba 1918-00-9 .0128 μg/L

Dichlorprop 120-36-5 .0138 μg/L

Dinoseb 88-85-7 .012 μg/L

Diphenamid 957-51-7 .0264 μg/L

46  Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
Appendix C. Pesticides analyzed—Continued.

[CAS, Chemical Abstract Service; μg/L, microgram per liter]

Analyte CAS 

number

Reporting 

limit Units

Diuron 330-54-1 .015 μg/L

Fenuron 101-42-8 .0316 μg/L

Flumetsulam 98967-40-9 .011 μg/L

Fluometuron 2164-17-2 .031 μg/L

Imazaquin 81335-37-7 .016 μg/L

Imazethapyr 81335-77-5 .017 μg/L

Imidacloprid 138261-41-3 .0068 μg/L

Linuron 330-55-2 .0144 μg/L

MCPA 94-74-6 .0162 μg/L

MCPB 94-81-5 .015 μg/L

Metalaxyl 57837-19-1 .02 μg/L

Methiocarb 2032-65-7 .008 μg/L

Methomyl 16752-77-5 .0044 μg/L

Metsulfuron methyl 74223-64-6 .025 μg/L

Neburon 555-37-3 .012 μg/L

Nicosulfuron 111991-09-4 .013 μg/L

Norflurazon 27314-13-2 .016 μg/L

Oryzalin 19044-88-3 .0176 μg/L

Oxamyl 23135-22-0 .0122 μg/L

Picloram 1918-02-1 .0198 μg/L

Propham 122-42-9 .0096 μg/L

Propiconazole 60207-90-1 .021 μg/L

Propoxur 114-26-1 .008 μg/L

Siduron 1982-49-6 .0168 μg/L

Sulfometuron-methyl 74222-97-2 .0088 μg/L

Tebuthiuron 34014-18-1 .0062 μg/L

Terbacil 5902-51-2 .0098 μg/L

Tribenuron-methyl 101200-48-0 .0088 μg/L

Triclopyr 55335-06-3 .0224 μg/L

Appendixes 47
Appendix D. Macroinvertebrate taxa reported in this study. 

[--, not differentiated. Major taxa (phyla through orders) are in approximate ascending phylogenetic sequence, 

with families, genera, and species in each listed alphabetically. Authorities and dates are for lowest level of 

identification (i.e., genus or species). Authorities listed for genera and species were obtained from the Integrated 

Taxonomic Information System, 2006]

Major 

taxon Family Species

Porifera -- --

Nematoda -- --

Oligochaeta -- --

Hirudinea Erpobdellidae --

Hirudinea Glossiphoniidae --

Gastropoda Ampullariidae Pomacea paludosa (Say, 1829)

Gastropoda Ancylidae --

Gastropoda Hydrobiidae --

Gastropoda Physidae Physella sp. Haldeman, 1842

Gastropoda Planorbidae Micromenetus floridensis Baker, 1945

Gastropoda Planorbidae Planorbella scalaris (Jay, 1839)

Gastropoda Planorbidae Planorbella trivolvis intertextum (Sowerby, 1878)

Gastropoda Pleuroceridae Elimia floridensis (Reeve, 1860)

Gastropoda Thiaridae Melanoides tuberculata (Müller, 1774)

Gastropoda Viviparidae Viviparus georgianus (Lea, 1834)

Pelecypoda Corbiculidae Corbicula fluminea Müller, 1774

Pelecypoda Unionidae Anodonta couperiana Lea, 1840

Pelecypoda Unionidae Elliptio sp. Rafinesque, 1819

Pelecypoda Unionidae Elliptio buckleyi (Lea, 1843)

Pelecypoda Unionidae Elliptio icterina (Conrad, 1834)

Pelecypoda Unionidae Toxolasma paulus (Lea, 1840)

Pelecypoda Unionidae Uniomerus carolinianus (Bosc, 1801)

Pelecypoda Unionidae Utterbackia imbecillis (Say, 1829)

Pelecypoda Unionidae Villosa amygdala (Lea, 1843)

Hydracarina -- --

Arachnida Pisauridae Dolomedes sp. Latreille, 1804

Ephemeroptera -- --

Ephemeroptera Baetidae Callibaetis floridanus Banks, 1900

Ephemeroptera Caenidae Caenis diminuta Walker, 1853

Odonata Coenagrionidae Enallagma sp. Charpentier, 1840

Odonata Coenagrionidae Nehalennia sp. Selys, 1850

Odonata Coenagrionidae Telebasis byersi Westfall, 1957

Odonata Corduliidae Epitheca princeps regina (Hagen in Selys, 1871)

Odonata Libellulidae --

Odonata Libellulidae Erythemis plebeja (Burmeister, 1839)

Hemiptera Belostomatidae --

Hemiptera Belostomatidae Belostoma sp. Latreille, 1807

Hemiptera Belostomatidae Lethocerus sp. Mayr, 1853

Hemiptera Gerridae --

Hemiptera Mesoveliidae Mesovelia sp. Mulsant and Rey, 1852

Hemiptera Naucoridae Pelocoris sp. Stal, 1876

Homoptera -- --

Trichoptera Hydroptilidae Neotrichia sp. Morton, 1905

Trichoptera Hydroptilidae Orthotrichia sp. Eaton, 1873

Coleoptera Chrysomelidae --

48  Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
Appendix D. Macroinvertebrate taxa reported in this study—Continued.

[--, not differentiated. Major taxa (phyla through orders) are in approximate ascending phylogenetic sequence, 

with families, genera, and species in each listed alphabetically. Authorities and dates are for lowest level of 

identification (i.e., genus or species). Authorities listed for genera and species were obtained from the Integrated 

Taxonomic Information System, 2006]

Major 

taxon Family Species

Coleoptera Dryopidae Pelonomus obscurus Leconte, 1852

Coleoptera Haliplidae Peltodytes sp. Regimbart, 1878

Coleoptera Hydrophilidae Helocombus sp. Horn, 1890

Diptera Ceratopogonidae --

Diptera Chironomidae --

Diptera Ephydridae --

Diptera Ptychopteridae --

Diptera Stratiomyidae --

Diptera Tabanidae --

Cladocera -- --

Ostracoda -- --

Isopoda Asellidae --

Isopoda Asellidae Lirceus lineatus (Say, 1818)

Isopoda Sphaeromatidae Cassidinidea ovalis (Say, 1818)

Amphipoda -- --

Amphipoda Gammaridae Gammarus sp. Fabricius, 1775

Amphipoda Hyalellidae Hyalella azteca Saussure, 1858

Decapoda Cambaridae Procambarus sp. Ortmann, 1905

Decapoda Palaemonidae Palaemonetes paludosus (Gibbes, 1850)

Appendixes 49
Appendix E. Scientific names, authorities and dates of original descriptions, and common names of fishes 

reported in this study. 

[Families are organized in approximate phylogenetic order; genera and species within families are listed alphabetically. 

Species designated by an asterisk are nonindigenous. Names follow Nelson and others (2004)]

Family Scientific name Common name

Dasyatidae Dasyatis sabina (Lesueur, 1824) Atlantic stingray

Lepisosteidae Lepisosteus osseus (Linnaeus, 1758) longnose gar

Lepisosteidae Lepisosteus platyrhincus DeKay, 1842 Florida gar

Amiidae Amia calva Linnaeus, 1766 bowfin

Anguillidae Anguilla rostrata (Lesueur, 1817) American eel

Clupeidae Dorosoma cepedianum (Lesueur, 1818) gizzard shad

Clupeidae Dorosoma petenese (Günther, 1867) threadfin shad

Cyprinidae Cyprinus carpio Linnaeus, 1758* common carp

Cyprinidae Notemigonus crysoleucas (Mitchill, 1814) golden shiner

Cyprinidae Notropis harperi Fowler, 1941 redeye chub

Cyprinidae Notropis petersoni Fowler, 1942 coastal shiner

Cyprinidae Opsopoeodus emiliae Hay, 1881 pugnose minnow

Catostomidae Erimyzon sucetta (Lacepède, 1803) lake chubsucker

Ictaluridae Ameiurus catus (Linnaeus, 1758) white catfish

Ictaluridae Ameiurus natalis (Lesueur, 1819) yellow bullhead

Ictaluridae Ameiurus nebulosus (Lesueur, 1819) brown bullhead

Ictaluridae Ictalurus punctatus (Rafinesque, 1818) channel catfish

Ictaluridae Noturus gyrinus (Mitchill, 1817) tadpole madtom

Ictaluridae Noturus leptacanthus Jordan, 1877 speckled madtom

Callichthyidae Hoplosternum littorale (Hancock, 1828)* brown hoplo

Loricariidae Pterygoplichthys disjunctivus (Weber, 1991)* vermiculated sailfin catfish

Esocidae Esox americanus Gmelin, 1789 redfin pickerel

Esocidae Esox niger Lesueur, 1818 chain pickerel

Aphredoderidae Aphredoderus sayanus (Gilliams, 1824) pirate perch

Mugilidae Mugil cephalus Linnaeus, 1758 striped mullet

Atherinopsidae Labidesthes sicculus (Cope, 1865) brook silverside

Belonidae Strongylura marina (Walbaum, 1792) Atlantic needlefish

Fundulidae Fundulus chrysotus (Günther, 1866) golden topminnow

Fundulidae Fundulus lineolatus (Agassiz, 1854) lined topminnow

Fundulidae Fundulus rubrifrons (Jordan, 1880) redface topminnow

Fundulidae Fundulus seminolis Girard, 1859 Seminole killifish

Fundulidae Lucania goodei Jordan, 1880 bluefisn killifish

Fundulidae Lucania parva (Baird & Girard, 1855) rainwater killifish

Poeciliidae Gambusia holbrooki Girard, 1859 eastern mosquitofish

Poeciliidae Heterandria formosa Agassiz, 1855 least killifish

Poeciliidae Poecilia latipinna (Lesueur, 1821) sailfin molly

Cyprinodontidae Jordanella floridae Goode & Bean, 1879 flagfish

Centrarchidae Enneacanthus gloriosus (Holbrook, 1855) bluespotted sunfish

Centrarchidae Lepomis auritus (Linnaeus, 1758) redbreast sunfish

Centrarchidae Lepomis gulosus (Cuvier, 1829) warmouth

Centrarchidae Lepomis macrochirus Rafinesque, 1819 bluegill

Centrarchidae Lepomis marginatus (Holbrook, 1855) dollar sunfish

Centrarchidae Lepomis microlophus (Günther, 1859) redear sunfish

Centrarchidae Lepomis punctatus (Valenciennes, 1831) spotted sunfish

Centrarchidae Micropterus salmoides (Lacepède, 1802) largemouth bass

Centrarchidae Pomoxis nigromaculatus (Lesueur, 1829) black crappie

50 Characterization of the Hydrology, Water Chemistry, and Aquatic Communities of Selected Springs
Appendix E. Scientific names, authorities and dates of original descriptions, and common names of fishes 

reported in this study—Continued.

[Families are organized in approximate phylogenetic order; genera and species within families are listed alphabetically. 

Species designated by an asterisk are nonindigenous. Names follow Nelson and others (2004)]

Family Scientific name Common name

Percidae Etheostoma fusiforme (Girard, 1854) swamp darter

Percidae Percina nigrofasciata (Agassiz, 1854) blackbanded darter

Elassomatidae Elassoma evergladei Jordan, 1884 Everglades pygmy sunfish

Elassomatidae Elassoma okefenokee Böhlke, 1956 Okefenokee pygmy sunfish

Cichlidae Oreochromis aureus (Steindachner, 1864)* blue tilapia

Achiridae Trinectes maculatus (Block & Schneider, 1801) hogchocker

Appendixes  51