Hydrology, Water Quality, and Aquatic 

Communities of Selected Springs in the 

St. Johns River Water Management 

District, Florida

By Stephen J. Walsh, Leel Knowles, Jr., Brian G. Katz, and Douglas G. Strom

Prepared in cooperation with the 

St. Johns River Water Management District

Scientific Investigations Report 2009-5046

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2009

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Detailed Geographic Information System (GIS) data for the St. Johns River Water Management District are available on the District’s spatial data website (http://sjr.state.fl.us/gisdevelopment/docs/themes.html). Due to the way 

certain land-use codes were combined in this study, and differences in coding between years of available data, some 

differences exist between codes used for land-use and land-cover categories. For example, some of the percentages 

provided on figure 4 reflect a different overall pattern than would be evident from a broad landscape-scale area of 

coverage. Readers of this report and land-use and land-coverage data users are encouraged to utilize the original GIS 

sources for any indepth applications requiring detailed spatial data.

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Walsh, S.J., Knowles, Leel Jr., Katz, B.G., and Strom, D.G., 2009, Hydrology, Water Quality, and Aquatic 

Communities of Selected Springs in the St. Johns River Water Management District, Florida: U.S. Geological 

Survey Scientific Investigations Report 2009-5046, 116 p.
iii

Contents

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

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

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

Environmental Setting..........................................................................................................................3

Acknowledgments................................................................................................................................3

Methods of Investigation..............................................................................................................................3

Delineation of Springsheds.................................................................................................................5

Land Use Data Compilation.................................................................................................................6

Hydrologic Data Compilation ..............................................................................................................6

Collection and Analysis of Spring Water..........................................................................................8

Age Dating of Spring Water................................................................................................................8

Aquatic Community Data Collection and Analysis..........................................................................9

Hydrology, Water Quality, and Aquatic Communities of Selected Springs........................................11

Alexander Spring ................................................................................................................................17

Land Use...................................................................................................................................17

Discharge .................................................................................................................................17

Water Chemistry and Age......................................................................................................19

Aquatic Communities..............................................................................................................21

Apopka Spring.....................................................................................................................................26

Land Use...................................................................................................................................26

Discharge .................................................................................................................................26

Water Chemistry and Age......................................................................................................26

Aquatic Communities..............................................................................................................28

Bugg Spring .........................................................................................................................................32

Land Use...................................................................................................................................32

Discharge .................................................................................................................................32

Water Chemistry and Age......................................................................................................32

Aquatic Communities..............................................................................................................34

De Leon Spring....................................................................................................................................40

Land Use...................................................................................................................................40

Discharge .................................................................................................................................40

Water Chemistry and Age......................................................................................................40

Aquatic Communities..............................................................................................................42

Fern Hammock Springs......................................................................................................................46

Land Use...................................................................................................................................46

Discharge .................................................................................................................................46

Water Chemistry and Age......................................................................................................47

Gemini Springs ....................................................................................................................................48

Land Use...................................................................................................................................48

Discharge .................................................................................................................................49

Water Chemistry and Age......................................................................................................49

Aquatic Communities..............................................................................................................50
iv

Green Spring........................................................................................................................................53

Land Use...................................................................................................................................53

Discharge .................................................................................................................................53

Water Chemistry and Age......................................................................................................54

Aquatic Communities..............................................................................................................55

Juniper Springs...................................................................................................................................57

Land Use...................................................................................................................................57

Discharge .................................................................................................................................57

Water Chemistry and Age......................................................................................................57

Rock Springs........................................................................................................................................59

Land Use...................................................................................................................................59

Discharge .................................................................................................................................60

Water Chemistry and Age......................................................................................................60

Aquatic Communities..............................................................................................................60

Silver Springs Group...........................................................................................................................65

Land Use...................................................................................................................................65

Discharge .................................................................................................................................65

Water Chemistry and Age......................................................................................................66

Aquatic Communities..............................................................................................................66

Silver Glen Springs .............................................................................................................................68

Land Use...................................................................................................................................68

Discharge .................................................................................................................................68

Water Chemistry and Age......................................................................................................69

Aquatic Communities..............................................................................................................71

Wekiwa Springs ..................................................................................................................................74

Land Use...................................................................................................................................74

Discharge .................................................................................................................................75

Water Chemistry and Age......................................................................................................75

Aquatic Communities..............................................................................................................77

Land-Use Changes among Springsheds.........................................................................................77

Trends in Spring Discharge and Rainfall.........................................................................................77

Comparison of Aquatic Communities ..............................................................................................80

Benthic Macroinvertebrates.................................................................................................80

Fishes ........................................................................................................................................86

Concluding Discussion................................................................................................................................89

References Cited..........................................................................................................................................92

Appendix 1: Macroinvertebrate taxa collected by dip net and petite ponar dredge from

selected springs in the St. Johns River drainage, 2004-07......................................................98

Appendix 2: Fishes species recorded from selected springs sampled in the St. Johns River

drainage, 2004-07..........................................................................................................................104

Appendix 3: Physicochemical data for springs on dates that benthic macroinvertebrate

samples were collected in 2004-07 ...........................................................................................105

Appendix 4: Concentrations of organic wastewater compounds detected in water 

samples from selected springs in the St. Johns River drainage..........................................111

Appendix 5: Concentrations of pesticides analyzed in water samples from selected 

springs in the St. Johns River drainage, 2004-07 ....................................................................114
v

Figures

1. Map showing location of springs within the study area in central Florida ........................4

2. Map showing Thiessen rainfall polygons and springsheds for selected springs 

of the St. Johns River drainage ..................................................................................................7

3. Graph showing input of sulfur hexafluoride to the atmosphere in the northern 

hemisphere and tritium concentrations in rainfall from Ocala, Florida during 

1950-2006........................................................................................................................................8

4. Pie charts showing relative proportions of springshed land-use categories for the 

years 1973 and 2004....................................................................................................................12

5. Photograph showing aerial view of Alexander Spring ........................................................17

6. Photograph showing Alexander Spring run immediately downstream of 

spring pool ...................................................................................................................................17

7. Graph showing average annual discharge for Alexander Spring and rainfall for the 

springshed ...................................................................................................................................18

8. Graph showing periodic discharge data for Alexander Spring, 1931-2007 ......................18

9. Trilinear plot showing the major-ion composition of spring waters and water types

of selected springs in the St. Johns River drainage.............................................................19

10. Graph showing nitrate-N concentrations in water from Alexander, Silver Glen, 

Fern Hammock, and Juniper springs located in Ocala National Forest............................20

11. Graph showing phosphorus concentrations in water from Alexander, Silver Glen, 

Fern Hammock and Juniper Springs located in Ocala National Forest ............................20

12. Photograph showing aggregation of adults of the nonindigenous vermiculated 

sailfin catfish (Pterygoplichthys disjunctivus) above the Alexander Spring vent, 

February 2007 ..............................................................................................................................23

13. Photograph showing diver taking discharge measurements at Apopka 

Spring vent...................................................................................................................................26

14-17. Graphs showing:

14. Average annual discharge for Apopka Spring and rainfall for the Apopka 

springshed ..........................................................................................................................27

15. Periodic discharge data for Apopka Spring,1971-2007 ...............................................27

16. Nitrate-N concentrations in water from Apopka, De Leon, Gemini, and Green 

Springs.................................................................................................................................28

17. Phosphorus concentrations in water from De Leon, Gemini, Green, and Apopka 

Springs.................................................................................................................................29

18. Photograph showing surface view of Bugg Spring pool .....................................................32

19. Photograph showing Bugg Spring run downstream of spring pool...................................32

20-23. Graphs showing 

20. Average annual discharge for Bugg Spring and rainfall for the 

Bugg springshed................................................................................................................33

21. Periodic discharge data for Bugg Spring, 1943-2007...................................................33

22. Nitrate-N concentrations in water from Bugg, Rock, and 

Wekiwa Springs.................................................................................................................34

23. Phosphorus concentrations in water from Bugg, Rock, and 

Wekiwa Springs.................................................................................................................35
vi

24. Photograph showing aerial view of Bugg Spring and run showing differences in 

land use and riparian vegetation between upper and lower sections of the run............39

25-27. Graphs showing:

25. Average annual discharge for De Leon Spring and rainfall for 

De Leon springshed...........................................................................................................41

26. Periodic discharge data for De Leon Spring, 1929-2007 .............................................41

27. Measured concentrations of sulfur hexafluoride and the ratio of measured 

tritium to the initial tritium in water samples from selected springs, and 

output curves from various lumped parameter models for various scenarios 

of ground-water flow to springs......................................................................................42

28. Photograph showing main pool of Fern Hammock Springs ................................................46

29. Photograph showing large sand boil at Fern Hammock Springs that was sampled 

for this study ................................................................................................................................46

30-37. Graphs showing:

30. Average annual discharge for Fern Hammock Springs and rainfall 

for the Fern Hammock springshed..................................................................................47

31. Periodic and continuous discharge data for Fern Hammock Springs, 

1935-2007.............................................................................................................................48

32. Average annual discharge for Gemini Springs and rainfall for the Gemini 

springshed ..........................................................................................................................49

33. Periodic discharge data for Gemini Springs, 1966-2007..............................................50

34. Average annual discharge for Green Spring and rainfall for the 

Green springshed ..............................................................................................................53

35. Periodic discharge data for Green Spring, 1932-2007.................................................54

36. Average annual discharge for Juniper Springs and rainfall for the Juniper 

springshed ..........................................................................................................................58

37. Periodic and continuous discharge data for Juniper Springs, 

1931-2007.............................................................................................................................58

38. Photograph showing Rock Springs cavern............................................................................59

39. Photograph showing Rock Springs run at central swimming area in Kelly Park ............59

40-43. Graphs showing:

40. Average annual discharge for Rock Springs and rainfall for the 

Rock springshed ................................................................................................................61

41. Periodic and continuous discharge data for Rock Springs, 1931-2007 ....................61

42. Average annual discharge for Silver Springs and rainfall for the 

Silver springshed ...............................................................................................................65

43. Continuous discharge data for Silver Springs, 1932-2007 ..........................................67

44. Photograph showing main vent of Silver Glen Springs........................................................68

45. Photograph showing Silver Glen Springs and upper section of run..................................68

46. Graph showing average annual discharge for Silver Glen Springs and rainfall 

for the Silver Glen springshed ..................................................................................................69

47. Graph showing periodic and continuous discharge data for Silver Glen Springs, 

1931-2007......................................................................................................................................70

48-50. Photographs showing

48. Upstream view of Wekiwa Springs pool from 

footbridge spanning upper section of spring run.........................................................74

49. Close-up view of Wekiwa Springs main vent ...............................................................74

50. Wekiwa Springs run near confluence with Rock 

Springs Run.........................................................................................................................74
vii

51-58. Graphs showing:

51. Average annual discharge for Wekiwa Springs and rainfall for 

the Wekiwa springshed....................................................................................................75

52. Periodic and continuous discharge data for Wekiwa Springs, 

1932-2007.............................................................................................................................76

53. Number of macroinvertebrate taxa collected by dip net and petite ponar 

dredge from selected springs of the St. Johns River drainage, 2004-07..................81

54. Lognormal ranked species abundance curves for macroinvertebrate 

taxa collected by petite ponar dredge and dip net from springs

in the St. Johns River drainage, 2004-07........................................................................82

55. Species accumulation curves for macroinvertebrates collected 

by petite ponar dredge and dip net from springs of the St. Johns River 

drainage, 2004-07...............................................................................................................83

56. Pielou’s evenness and loge Shannon-Wiener diversity index for

macroinvertebrate samples from selected springs of the St. Johns 

River drainage, 2004-07.....................................................................................................84

57. Stream Condition Index values for dip net samples of macroinvertebrates 

collected from selected springs of the St. Johns River drainage, 2004-07..............85

58. Percent very tolerant macroinvertebrate taxa collected by dip net from 

selected springs of the St. Johns River drainage, 2004-07.........................................85

59. Agglomerative hierarchical cluster of selected springs in the St. Johns River

drainage based on square-root transformed Bray-Curtis similarity values of 

macroinvertebrates collected by dip net, 2004-07 ................................................................87

60. Graph showing nonmetric multidimensional scaling ordination based on 

Bray-Curtis similarity values derived from square-root transformed means of 

macroinvertebrate samples collected by dip net from selected springs in the 

St. Johns River drainage, 2004-07............................................................................................87

61. Principal components analysis scatter plot of environmental variables for

selected springs of the St. Johns River drainage .................................................................88

62. Pie chart showing relative abundance of fish families in springs of the 

St. Johns River drainage surveyed in 2004-07 .......................................................................88

Tables

1. Springs in the study area.............................................................................................................5

2. Rainfall stations in the study area..............................................................................................6

3. Median values for physical and chemical characteristics, and saturation indices

with respect to calcite, dolomite, gypsum, and carbon dioxide partial pressure for

selected springs in the St. Johns River Water Management District ...............................13

4. Diversity indices for macroinvertebrates by pooled petite ponar dredge samples

from selected springs of the St. Johns River drainage, 2004-07.........................................15

5. Diversity indices for macroinvertebrates collected by dip net from selected 

springs of the St. Johns River drainage, 2004-07 ..................................................................16

6. Statistically significant (p less than 0.05) trends of nitrite plus nitrate as N,

orthophosphate as PO4

, and phosphorus with time..............................................................21
viii

7. Number of specimens and percent density per square meter of

macroinvertebrates collected by pooled petite ponar dredge samples 

from Alexander Spring, February-October 2007....................................................................22

8. Number of specimens and percent composition of macroinvertebrates

collected by dip net from Alexander Spring, February-October 2007................................24

9. Fishes collected or observed in Alexander Spring and Silver Glen Springs 

in 2007 ...........................................................................................................................................25

10. Number of specimens and percent density per square meter of 

macroinvertebrates collected by pooled petite ponar dredge samples 

from Apopka Spring, December 2005-September 2006........................................................30

11. Fishes collected by boat electroshocker in vicinity of Apopka, Bugg, Rock, and

Wekiwa springs in 2006 .............................................................................................................31

12. Number of specimens and percent density per square meter of 

macroinvertebrates collected by pooled petite ponar dredge samples from 

Bugg Spring, December 2005-September 2006 .....................................................................36

13. Number of specimens and percent composition of macroinvertebrates

collected by dip net from Bugg Spring, December 2005-September 2006........................37

14. Number of specimens and percent density per square meter of 

macroinvertebrates collected by pooled petite ponar dredge samples from 

De Leon Spring, February-August 2004...................................................................................43

15. Number of specimens and percent composition of macroinvertebrates

collected by dip net from De Leon Spring, February-August 2004 .....................................45

16. Number of specimens and percent density per square meter of 

macroinvertebrates collected by pooled petite ponar dredge samples from 

Gemini Springs, February-August 2004...................................................................................51

17. Number of specimens and percent composition of macroinvertebrates

collected by dip net from Gemini Springs, February-August 2004 .....................................52

18. Number of specimens and percent density per square meter of

macroinvertebrates collected by pooled petite ponar dredge samples from 

Green Spring, February-August 2004 ......................................................................................55

19. Number of specimens and percent composition of macroinvertebrates

collected by dip net from Green Spring, February-August 2004.........................................56

20. Number of specimens and percent density per square meter of

macroinvertebrates collected by pooled petite ponar dredge samples from 

 Rock Springs, December 2005-September 2006....................................................................62

21. Number of specimens and percent composition of macroinvertebrates

collected by dip net from Rock Springs, December 2005-September 2006 ......................64

22. Number of specimens and percent density per square meter of

macroinvertebrates collected by pooled petite ponar dredge samples from 

Silver Glen Springs, January-October 2007 ...........................................................................72

23. Number of specimens and percent composition of macroinvertebrates

collected by dip net from Silver Glen Springs, January-October 2007..............................73

24. Number of specimens and percent density per square meter of

macroinvertebrates collected by pooled petite ponar dredge samples from 

Wekiwa Springs, December 2005-September 2006..............................................................78

25. Number of specimens (n) and percent composition of macroinvertebrates

collected by dip net from Wekiwa Springs, December 2005-September 2006 ................79

26. Results of trend testing of annually averaged spring discharge and 

springshed rainfall......................................................................................................................80
ix

Conversion factors

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square inch (in2) 6.452 square centimeter (cm2

)

square foot (ft2

) 0.0929 square meter (m2

) 

square mile (mi2

) 259.0 hectare (ha)

square mile (mi2

) 2.590 square kilometer (km2

) 

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3

/s)

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

Acronyms and Abbreviations

BMM binary mixing model

CFC chlorofluorocarbon

EFM exponential flow model

EPM exponential and piston flow model

FDEP Florida Department of Environmental Protection

FSI Florida Springs Initiative

FI Florida Index

FSTF Florida Springs Task Force

GWML global meteoric water line

ln natural logarithm

LPIL lowest practicable identification level 

MDS multidimensional scaling

MFLs minimum flows and levels

MWL meteoric water line

NOAA National Oceanic and Atmospheric Administration

NTU nephelometric turbidity units

PCA principal components analysis

PFM piston flow model

pmc percent modern carbon

ppm parts per million

ppt parts per thousand

pptv parts per trillion by volume

SCI stream condition index

SJRWMD St. Johns River Water Management District

TU tritium units

TL total length

USGS U.S. Geological Survey

μg microgram

μm micrometer
x
Hydrology, Water Quality, and Aquatic Communities 

of Selected Springs in the St. Johns River Water 

Management District, Florida

By Stephen J. Walsh1, Leel Knowles, Jr.2, Brian G. Katz3, and Douglas G. Strom4

Abstract

Hydrologic, physicochemical, and aquatic community 

data were collected and compiled by the U.S. Geological 

Survey (USGS) for selected springs within the St. Johns River 

Water Management District (SJRWMD) from January 2004 to 

October 2007. Nine springs were included in this study: Alexander, Apopka, Bugg, De Leon, Gemini, Green, Rock, Silver 

Glen, and Wekiwa. In addition, hydrologic and water-quality 

data are provided for Fern Hammock, Juniper, and Silver 

Springs from a supplemental study. Particle tracking analysis 

was used to delineate the 100-year springshed for each of the 

targeted springs. Land-use data were compiled for the surface 

area contributing recharge to each springshed and are reported 

in general categories (urban, agriculture, forested, open-water/

wetlands, and non-forested) to evaluate change for a 31-year 

period from 1973 and 2004 data sets. Retrospective hydrologic 

and physicochemical data for each spring were summarized 

from records of the USGS, SJRWMD, Florida Department of 

Environmental Protection, and a private landowner. Waterquality data collected by the USGS during the period of study 

consisted of quarterly physicochemical, chlorophyll-a, and 

pheophytin-a measurements taken simultaneously with the 

collection of benthic macroinvertebrate samples. Aquatic 

community data are summarized for collections of benthic 

macroinvertebrates made quarterly at Apopka, Bugg, Rock, 

and Wekiwa Springs in 2006, at Alexander and Silver Glen 

Springs in 2007, and for fish collections made once at each 

of these sites. In addition, benthic macroinvertebrate data 

collected from Gemini, Green, and De Leon Springs in 2004 

are reanalyzed following re-identification of organisms to a 

finer taxonomic scale.

Predominant land use varied among all of the target 

springsheds, and notable changes occurred within several 

springsheds during the period of record. Alexander, Apopka, 

De Leon, Gemini, Green, and Wekiwa springsheds became 

increasingly urbanized, with a concomitant loss of forested 

and/or agricultural lands occurring in most springsheds. 

Forested cover increased and open surface waters and 

wetlands decreased in the Bugg and Rock springsheds. 

Land use in the Silver Glen springshed remained relatively 

unchanged. Land-use data were unavailable for Fern 

Hammock and Juniper Springs, but ground-based observations 

indicated relatively little change. Both springsheds consist of 

mostly forested land cover, with lesser amounts of the other 

land-use categories.

No significant trends were observed in rainfall records 

within each springshed. However, analysis of spring discharge 

records revealed a decreasing trend for De Leon, Fern 

Hammock, Rock, Silver, and Wekiwa Springs. Decreasing 

discharges may be associated, in part, with land-use changes 

that reduce springshed recharge and increased ground-water 

pumping. Nevertheless, climate cannot be dismissed as a major, 

if not primary, factor acting in conjunction with other variables 

that have contributed to the apparent decreasing trends in spring 

discharge. 

Nitrate concentrations showed a significant increasing 

trend with time in water samples from Apopka, Fern Hammock, 

Gemini Springs run, and Juniper Springs. Conversely, nitrate 

concentrations showed a significant decreasing trend with time 

for Alexander Spring, Bugg Spring run, Rock Springs, and 

Wekiwa Springs. Phosphorus concentrations generally were low 

and relatively constant over time for most springs. However, 

water from Juniper Springs showed a significant increase in 

phosphorus with time, whereas significant decreases in phosphorus occurred with time at Apopka, De Leon, Rock, Silver 

Glen, and Wekiwa Springs.

Benthic macroinvertebrate communities among the 

targeted springs ranged from relatively low diversity assemblages, such as at Green Spring, to assemblages with high taxonomic richness, diversity, and dominance, such as at Rock and 

De Leon Springs. Mean values of the Shannon-Wiener diversity 

index among samples pooled by spring were lowest for Apopka 

Spring and greatest for Rock, Bugg, and Silver Glen Springs. 

1

 U.S. Geological Survey, 7920 N.W. 71st Street, Gainesville, Fla. 32653,

swalsh@usgs.gov

2

 U.S. Geological Survey, 12703 Research Parkway, Orlando, Fla. 32826,

lknowles@usgs.gov

3

 U.S. Geological Survey, 2639 N. Monroe St. Ste. A200, Tallahassee,

FL 32303, bkatz@usgs.gov

4 Water and Air Research, Inc., 6821 S.W Archer Road, Gainesville, 

Fla. 32608, dstrom@waterandair.com
2 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

The Stream Condition Index (SCI), a multimetric measure 

of ecosystem health based on the benthic macroinvertebrate 

community profile, was very low for all springs and all seasonal 

sampling events. SCI values ranged from 6 to 34; mean SCI for 

pooled samples per spring was lowest for De Leon and Gemini 

Springs and highest for Rock and Wekiwa Springs. Low SCI 

scores were probably the result of a combination of factors, 

including lack of natural association of taxa used in calculation 

of the SCI with spring habitats (for example, ephemeropteran, 

trichopteran, and sensitive species) and water-quality constituents (for example, low dissolved oxygen, high conductivity). 

Springs with extensive land-use changes exhibited the greatest 

visible signs of nutrient enrichment, as evidenced by abundant 

algal growth, and in some cases, these springs had proportionally high numbers of taxa considered to be very tolerant. Mean 

percentage of very tolerant taxa was lowest for Alexander 

Spring (less than 4 percent), modest (10-20 percent) for Gemini, 

De Leon, Rock, Silver Glen, and Wekiwa Springs, and highest 

(greater than 40 percent) for Bugg and Green Springs. In 

general, most springs had high dominance of relatively few 

species; dominant taxa differed among seasonal samples for 

some springs but most often consisted of gastropods (especially 

hydrobiids, for example, Amnicola dalli, Aphaostracon sp.), 

amphipods (Hyalella and Gammarus spp.), and oligochaetes.

Richness of fish communities was lowest for Green 

Spring (only two species observed) and greatest for Alexander 

Spring run (29 species of 31 historically recorded) and Silver 

Glen Springs (24 species). A combined total of 45 fish species 

representing 35 genera and 23 families were collected or 

observed from all springs in this study. Samples were dominated by centrarchids (23.7 percent), cyprinids (22.0 percent), 

fundulids (14.5 percent), atherinopsids (13.9 percent), and 

poeciliids (12.4 percent).

Introduction

The springs and spring runs of Florida are renowned for 

their intrinsic beauty, value as ground-water resources, and 

their cultural, recreational, and ecological importance (Rosenau 

and others, 1977; Scott and others, 2002; 2004). Threats to 

springs, including declining flow rates and increased nutrient 

and contaminant concentrations, have escalated over time as 

the human population of Florida expands and land-use patterns 

change (Miller 1997; Upchurch and Randazzo 1997). Ground 

water that discharges from most Florida springs originates from 

the Floridan aquifer system, which is the main source of water 

supply in the central part of the State and elsewhere. 

Projections by water managers of the St. Johns River 

Water Management District (SJRWMD) and ground-water 

flow models developed by the SJRWMD and U.S. Geological 

Survey (USGS) indicate that increased pumping of ground 

water likely will result in decreased discharge from many 

Florida springs (Knowles and others, 2002; Sepúlveda 2002); 

in some cases, the decreases have been documented previously. Nitrate concentrations have increased in many springs in 

central Florida over time (Spechler and Halford 2001; Florida 

Department of Environmental Protection, 2007; Stevenson and 

others, 2007; Brown and others, 2008), and Florida groundwater resources are especially vulnerable to pesticides and 

other organic compounds (Katz 1992; Upchurch and Randazzo 

1997). The ecological effects of decreased discharge and the 

presence of nutrients and contaminants in Florida springs are of 

increasing concern to natural resource managers. Consequently, 

in recent years much effort has focused on studying Florida 

spring ecosystems to improve knowledge about their structure 

and function. In 2001, the Florida Springs Initiative (FSI) 

was established by the Florida Department of Environmental 

Protection (FDEP) in response to recommendations made by the 

Florida Springs Task Force (FSTF) and growing public awareness of the declining condition of Florida springs. This initiative 

was a pivotal point in the history of research, monitoring, and 

management of Florida springs, resulting in an unprecedented 

level of involvement in vital assessments of springs throughout 

the State by multiple agencies, nongovernmental organizations, 

and the public and private sectors. Priority recommendations of 

the FSI call for collaborative actions by stakeholders to delineate springshed and recharge areas, identify relations between 

nutrients and ecological conditions, understand how water quantity and quality affect ecosystem structure and function, and 

apply a multi-pronged approach to managing, protecting, and 

restoring Florida springs (Florida Department of Environmental 

Protection, 2007). 

The USGS, in cooperation with the SJRWMD, conducted 

a 4-year study to investigate the status and conditions of 

aquatic resources of selected springs identified as high priority 

for baseline ecological assessment. The USGS provides 

relevant scientific data to aid in understanding the condition of 

natural resources and the factors that affect them. This study 

is applicable to the major science strategies within the mission 

of the USGS (U.S. Geological Survey, 2007); in particular, the 

study includes elements of assessing the structure, patterns, 

and function of ecosystems, and evaluating and quantifying 

the status of freshwater resources.

Purpose and Scope

The purpose of this report is to describe selected springs in 

the SJRWMD, delineate their basins, summarize historic land 

use within each, and provide assessments of the hydrology, 

water chemistry, and benthic macroinvertebrate and fish 

communities. Data collected by the USGS during 2004-07 are 

provided in addition to compiled retrospective information on 

discharge and water chemistry obtained from multiple sources 

for variable periods of record. Nine springs were included in 

this study: Alexander, Apopka, Bugg, De Leon, Gemini, Green, 

Rock, Silver Glen, and Wekiwa Springs. In addition, comparative hydrologic and water-quality information is included for 

three additional springs (Fern Hammock, Juniper, and Silver 

Springs) as the result of an ancillary study to compile data for 

the FDEP. The present study was designed to provide baseline 

data and augment existing information of potential use in establishing or assessing Minimum Flows and Levels (MFLs) and 
Methods of Investigation 3

assisting in the evaluation of water-resource value assessments 

for these springsheds. The project was initiated in 2004 with 

trimester collections of physicochemical and biological data 

for De Leon, Gemini, Green, and Silver Springs, as summarized by Phelps and others (2006). In 2006, data on physicochemical parameters, benthic macroinvertebrates, fishes, and 

chlorophyll-a and pheophytin-a concentrations were collected 

quarterly for Apopka, Bugg, Rock, and Wekiwa Springs, and 

were summarized in an interim report by Walsh and Kroening 

(2007). In 2007, similar data were collected quarterly at 

Alexander and Silver Glen Springs.

Environmental Setting

Springs are abundant in Florida because the peninsula 

is underlain by limestone and dolomite, both of which are 

dissolved relatively easily by rain water that seeps into 

the ground (Spechler and Schiffer, 1995). Carbon dioxide 

dissolved in aquifer-recharging rain water forms carbonic acid, 

a weak acid that slowly dissolves subsurface rock, creating 

cavities and caverns. The process results in a landform known 

as karst, which is characterized by the presence of springs and 

sinkholes (Lane 1986; Scott and others, 2004). The springs 

examined in this study are representative of many springs in 

central Florida, and are popular recreational destinations for 

residents and tourists (fig. 1, table 1). The study springs are 

located in the St. Johns River surface-water basin of northcentral Florida within Orange, Lake, Marion, and Volusia 

Counties. Water from these springs discharges from the 

extensive Floridan aquifer system, one of the largest and most 

productive aquifers of the world (Miller 1990).

Following Meinzer (1927), Rosenau and others (1977) and 

Scott and others (2002; 2004), springs are classified, among 

other factors, by their average rate of discharge of water: a first 

magnitude spring is defined as having a discharge rate of greater 

than 100 ft3

/s (65 Mgal/d), a second magnitude spring has an 

average discharge rate of 10 to 100 ft3

/s (6.5 to 65 Mgal/d), and 

a third magnitude spring has an average discharge rate of 1 to 

10 ft3

/s (0.65 to 6.5 Mgal/d). The rate of discharge from a spring 

depends on many factors, including the size of caverns in the 

rocks, water pressure in the aquifer, size of the area contributing 

recharge to the spring (the springshed), and amount of preceding 

rainfall (Spechler and Schiffer, 1995). Of the springs examined 

in this study, 3 were first magnitude (Alexander, Silver, Silver 

Glen), 7 were second magnitude (Apopka, Bugg, De Leon, Fern 

Hammock, Juniper, Rock, Wekiwa), and 2 were third magnitude 

(Gemini, Green). Spring discharge responds mostly to rainfall 

occurring within a springshed; however, local pumping can 

reduce spring flow by intercepting water that would otherwise 

flow to a spring. The short-term effects of pumping on spring 

flow are greatest during intensive consumptive periods of water 

use, such as for agricultural irrigation and freeze protection.

The climate in the study area is subtropical and characterized by warm, humid, rainy summers and temperate dry 

winters. The 30-year average for annual daily temperature is 

about 22°C (71°F) at DeLand and 23°C (73°F) at Sanford, 

Florida (National Oceanic and Atmospheric Administration, 

1930-2007). Within the study area, average annual rainfall 

(1930-2007) is about 49 in. at Leesburg, Eustis and Lisbon; 

50 in. at Orlando; 51 in. at Bushnell, Clermont, Mt. Plymouth, 

Plymouth, and Zellwood; 52 in. at Sanford and Crescent City; 

and 56 in. at DeLand. Typically, more than 50 percent of the 

annual rainfall occurs from June through September. About 70 

to 75 percent of the rainfall commonly returns to the atmosphere as evapotranspiration (Sumner, 1996; Knowles, 1996).

Acknowledgments

Support for this project was provided by a joint funding 

agreement between the SJRWMD and the USGS. We are 

grateful to SJRWMD employees, G.B. (Sonny) Hall, Chris 

Ware, Robert Epting, and Bill Osburn for logistical support 

and constructive advice. Dr. Joseph and Margaret Branham 

provided access to Bugg Spring and generously contributed 

historical information about the spring as well as physicochemical data. Joseph A. Rotarius assisted with transporting 

equipment and personnel at Rock Springs, provided access to 

private properties and launch sites in the downstream section of 

the spring run, and assisted with electrofishing. Alice M. Bard 

issued permits to collect macroinvertebrates and fishes within 

Wekiwa Springs State Park. Laura Line provided expertise 

with taxonomic identification of macroinvertebrates. Elizabeth 

Miller provided macroinvertebrate records from the FDEP 

statewide database. Selected photographs in the SJRWMD 

archives were supplied by Beth Hickenlooper. We also thank 

the following individuals for their assistance in the field: Buck 

Albert, Cole Albert, W. Jamie Barichivich, O. Towns Burgess, 

Elissa N. Buttermore, Robert M. Gerwig, Dane H. Huge, 

Howard L. Jelks, Leo G. Nico, J. Travis Smith (deceased), 

Jennifer Staiger, and William B. Tate. Sherry L. Bostick 

assisted with specimen sorting and data entry. Technical review 

comments were received from Marian P. Berndt, Lari A. 

Knochenmus, Lori J. Lewis, and Chris Ware. Coinvestigators in early phases of this study were G.G. (Trudy) Phelps 

and Sharon E. Kroening and the project could not have been 

completed without their invaluable contributions in the field 

and assistance with data analysis and interpretation.

Methods of Investigation

This section contains information about (1) the procedures used to delineate springsheds and (2) how flow, water 

chemistry and age, and aquatic community data were collected 

or compiled for the springs examined in this study. Summaries 

of spring discharge were compiled from data sets maintained 

by the SJRWMD and the USGS, including measurements 

obtained at the time of this study as detailed in individual 

spring accounts. Water-chemistry data, including nutrient 

and contaminant constituents, were compiled from data 
4 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

EXPLANATION

POLK

MARION

OSCEOLA

VOLUSIA

LAKE

ORANGE

PASCO

PUTNAM

SUMTER

FLAGLER

SEMINOLE

0

0

10 20 MILES

10 20 KILOMETERS

Silver

Springs

Silver

Glen

Springs

Alexander

Spring

De Leon

Spring

Gemini

Springs Green

Spring

Rock

Springs

Wekiwa

Springs

Apopka

Spring

Bugg

Spring

Juniper

Springs

Fern

Hammock

Springs

29°00 ́

29°30 ́

28°45 ́

28°30 ́

28°15 ́

29°15 ́

82°15 ́ 82°00 ́ 81°45 ́ 81°30 ́ 81°15 ́ 81°00 ́

Base from U.S. Geological Survey digital data,

Universal Transverse Mercator projection, zone 17

OCALA

NATIONAL

FOREST

SPRING LOCATION AND NAME

Juniper

Creek

Lake

George

Lake

Weir

St. Johns

Lake

Harris

Lake Monroe

Lake

Apopka

Ocklawaha River

Alexander Creek

River

Juniper

Prairie

Wilderness

Silver River

Lake

Denham

Gourd

Neck

Helena

Canal

Figure 1. Location of springs within the study area in central Florida.
Methods of Investigation 5

Table 1. Springs in the study area. 

[Coordinates for springs are from Scott and others (2004). Beginning of record indicates starting year of discharge measurements collected by agency listed 

under source of data. SJRWMD, St. Johns River Water Management District; USGS, U.S. Geological Survey; dd mm ss.ss, degrees, minutes, seconds]

Site name Latitude 

(dd mm ss.ss)

Longitude 

(dd mm ss.ss) Source of data Beginning of record

Location and 

access information

Alexander 29° 04 ́ 52.68 ̋ 81° 34 ́ 33.18 ̋ USGS, SJRWMD, 

FDEP

1931 About 6 mi south of Astor Park and about 17 mi northwest of 

De Land. The spring and spring run are within the Alexander Spring Recreation Area in Ocala National Forest.

Apopka 

(Gourdneck)

28° 33 ́ 59.77 ̋ 81° 40 ́ 50.41 ̋ USGS, SJRWMD, 

FDEP

1971 At the southwestern shoreline of Lake Apopka in an area 

referred to as the Gourd Neck, a narrow cove of the lake. 

The spring is accessible only by boat.

Bugg 28° 45 ́ 07.15 ̋ 81° 54 ́ 05.46 ̋ USGS, SJRWMD, 

FDEP

1943 About 0.4 mi northwest of Okahumpka and 3.5 mi southsouthwest of Leesburg. The spring is on private property 

and is not accessible to the public; it is leased to the U.S. 

Navy, which maintains a research laboratory used for 

underwater calibration of sonar systems. 

De Leon 30° 43 ́ 16.33 ̋ 85° 55 ́ 50.47 ̋ USGS, SJRWMD, 

FDEP

1932 In De Leon Springs State Park, northwest of the municipality 

of De Leon Springs and about 7 mi northwest of the City 

of De Land.

Fern Hammock 29° 11 ́ 00.86 ̋ 81° 42 ́ 29.50 ̋ USGS, SJRWMD, 

FDEP

1935 In the Juniper Springs Recreational Area in Ocala National 

Forest.

Gemini 28° 51 ́ 45.98 ̋ 81° 18 ́ 41.06 ̋ USGS, SJRWMD, 

FDEP

1966 In Gemini Springs County Park.

Green 28° 51 ́ 46.04 ̋ 81° 14 ́ 50.92 ̋ USGS, SJRWMD, 

FDEP

1932 Spring is along the north shore of Lake Monroe near the town 

of De Bary.

Juniper 29° 11 ́ 01.34 ̋ 81° 42 ́ 44.68 ̋ USGS, SJRWMD, 

FDEP

1935 In the Juniper Springs Recreational Area in Ocala National 

Forest about 10 mi west of Astor Park.

Rock 28° 45 ́ 23.20 ̋ 81° 30 ́ 06.25 ̋ USGS, SJRWMD, 

FDEP

1931 In Dr. Howard A. Kelly Park, approximately 6 mi north of the 

City of Apopka. The spring and spring run are within the 

boundaries of the Wekiva River Aquatic Preserve.

Silver 29° 12 ́ 58.34 ̋ 82° 03 ́ 09.47 ̋ USGS 1932 East of Ocala in Marion County.

Silver Glen 29° 14 ́ 45.04 ̋ 81° 38 ́ 36.50 ̋ USGS, SJRWMD, 

FDEP

1931 About 11 mi south of the city of Salt Springs and 30 mi 

northeast of Ocala in eastern Marion County. The spring 

head and part of the run are in the Silver Glen Springs 

Recreational Area of the Ocala National Forest.

Wekiwa 28° 42 ́ 42.79 ̋ 81° 27' 37.52 ̋ USGS, SJRWMD, 

FDEP

1932 About 4 mi northeast of the City of Apopka. The spring pool 

and run are located within Wekiwa Springs State Park.

sets downloaded from databases maintained by the USGS, 

SJRWMD, and FDEP. Age-dating data, including tritium (3

H) 

concentration, gases (helium, 3

He, 4He), sulfur hexafluoride 

(SF6

), and nutrient isotopes (δ1) were compiled from a database maintained by the USGS. 

Delineation of Springsheds

The procedure used to delineate 100-year springsheds 

or areas contributing recharge to springs involved particletracking analyses (Pollock, 1994) using the output from a 

ground-water flow model (Knowles and others, 2002). The 

particle-tracking analyses for each spring was performed 

using the MODPATH program (Pollock, 1994) and required 

steps including (1) assigning effective porosity values to the 

hydrogeologic units, (2) using forward and backward particle 

tracking, (3) determining the number of particles to use and 

assigning starting locations for each particle, (4) determining 

how particles interact with weak sinks such as specified-flux, 

specified-head, or head-dependent flux internal boundaries that 

do not discharge all of the ground water entering the model cell, 

and (5) selecting ground-water flow model grid cells having 

travel times of less than 100 years. The term “springshed” used 

in this report is defined as the contributing area of ground-water 

flow to the spring head with a travel time of less than 100 years.

Given the uncertainties in effective porosity, uniform 

values were assigned to each layer in the model (Knowles 

and others, 2002). A value of 0.4 each was assigned to the 

surficial aquifer system and intermediate confining unit 

model layers. A value of 0.2 each was assigned to the Upper 

Floridan aquifer and the middle semiconfining unit model 

layers. The value of effective porosity affects only particle 

travel time, but has no effect on particle paths calculated by 

MODPATH (Shoemaker and others, 2004). This procedure 

for delineating springsheds accounts for the slight difference 

in the Silver Springs springshed presented in this report and 

the springshed presented in Shoemaker and others (2004).

Forward particle tracking was used to delineate areas 

contributing recharge, because the complex discontinuous 
6 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

areas were more clearly defined by using forward (rather 

than backward) tracking. Forward tracking was performed 

by first identifying extensive areas surrounding each spring 

cell where particles would initially be placed to encompass 

all potential areas. Using the maximum number of particles, 

these particles initially were placed at the water-table surface 

in active surficial aquifer system cells. The areas contributing 

recharge for each spring were then delineated by noting the 

location of model cells with forward particles that entered 

the spring cell. Backward tracking was used to compute the 

percent of total spring discharge as a function of particle 

travel time. Particles were allowed to pass through weak 

sinks during forward and backward tracking, because many 

pumping wells simulated as weak sinks were located within 

the areas contributing recharge to each spring. Stopping 

particles at these pumping wells would have reduced the areas 

contributing recharge to unrealistic zone limits. In addition, 

particles were allowed to pass through weak sinks because 

discharge from many weak sinks was negligible compared to 

the total inflow to the model cell.

Land Use Data Compilation

To determine approximate 30-year land-use changes for 

each springshed, land-use data from 1973 and 2004 for areas 

contributing recharge to each spring (100-year springshed) 

were compiled from geographic information system (GIS) 

data sets provided by the SJRWMD and the Southwest Florida 

Water Management District (SWFWMD). At the time of this 

study, the 1973 land-use data set was the earliest available 

that covered the entire study area. Land-use changes for each 

springshed were determined in ArcMap by overlaying and 

comparing land-use and springshed data sets. Land-use types 

are consolidated from land-use codes contained in the data 

sets and are presented for simplicity herein as the following 

general land-use types: urban/mining/recreation/transportation, 

agriculture/pastureland/rangeland, non-forested (barren) land, 

forestland, and open-water surfaces/wetlands.

Hydrologic Data Compilation

The period of record used herein for the analysis of spring 

discharge and associated rainfall begins in 1930, although a few 

measurements were collected at some springs prior to 1930. 

Hydrologic data, including flow and stage data, were collected 

by the USGS and SJRWMD. Continuous flow was calculated 

for Rock and Wekiwa Springs by the SJRWMD, and measured 

at Silver Glen Springs by the USGS. Noncontinuous flow 

measurements were made weekly at Bugg Spring by a qualified 

observer for the SJRWMD since 1990, monthly at Alexander 

by the USGS and SJRWMD since 1982, quarterly at Apopka 

by a contractor for the SJRWMD since 1997, and intermittently at Juniper and Fern Hammock Springs by the USGS and 

SJRWMD since 1908 and 1935, respectively. Annual discharge 

values for each spring were computed by averaging all of the 

measurements made during each year for that spring.

Kendall’s tau (τ) test (Helsel and Hirsch, 1992) was used 

to determine if variations in spring discharge and rainfall were 

statistically significant trends rather than random occurrences. 

The Kendall test is a nonparametric procedure that measures the 

strength of a monotonic relation, whether linear or nonlinear, 

between x and y. Distribution of discharge and rainfall data was 

assumed to be monotonic for the period of record in this study. 

Rainfall for each springshed was determined areally in 

ArcMap using the Thiessen method for a set of 10 polygons 

with each polygon representing a single rain-gage station 

(Fetter 1980) (table 2, fig. 2). Weighted rainfall values, which 

were computed for the percentage of total springshed area in 

each Thiessen polygon, were summed to determine the total 

rainfall for each springshed.

Table 2. Rainfall stations in the study area. 

[Station locations are shown in figure 2. Coordinates are from agency station records. Beginning of record is 1930 for 

all stations. All rainfall data collected by National Oceanic and Atmospheric Administration (NOAA), except where 

indicated; dd mm ss.ss, degrees, minutes, seconds]

Site

number Site name Latitude (dd mm ss.ss)

Longitude 

(dd mm ss.ss)

1 Orlando 28° 26 ́ 02 ̋ 81° 19 ́ 30 ̋

2 Clermont 28° 27 ́ 00 ̋ 81° 43 ́ 00 ̋

3 Bushnell 28° 39 ́ 43 ̋ 82° 04 ́ 58 ̋

4 Mt. Plymouth/Plymouth/Zellwood1 28° 47 ́ 56 ̋ 81° 32 ́ 06 ̋

5 Sanford 28° 49 ́ 00 ̋ 81° 17 ́ 00 ̋

6 Leesburg/Eustis 28° 49 ́ 00 ̋ 81° 49 ́ 00 ̋

7 Lisbon 28° 52 ́ 00 ̋ 81° 47 ́ 00 ̋

8 De Land 29° 01 ́ 00 ̋ 81° 19 ́ 00 ̋

9 Ocala 29° 05 ́ 00 ̋ 82° 05 ́ 00 ̋

10 Crescent City 29° 25 ́ 42 ̋ 81° 31 ́ 00 ̋

1

Data collected by NOAA and private observer.
Methods of Investigation 7

0

0

10 20 MILES

10 20 KILOMETERS

2

hv hv

hv

hv hv

hv

hv

hv

hv

hv

1 2

3

6

7

4 5

8

9

10

EXPLANATION

SPRING LOCATION AND NAME

RAINFALL STATION AND NUMBER

SPRINGSHED DELINEATED

BY GROUND-WATER FLOW

MODEL (KNOWLES AND

OTHERS, 2002)

RAINFALL POLYGON BOUNDARY

POLK

MARION

OSCEOLA

VOLUSIA

LAKE

ORANGE

PASCO

PUTNAM

SUMTER

FLAGLER

SEMINOLE

Silver

Springs

Silver Glen

Springs

Alexander

Spring

De Leon

Spring

Gemini

Springs

Green

Spring

Rock

Springs Wekiwa

Springs

Apopka

Spring

Bugg

Spring

29°00 ́

29°30 ́

28°45 ́

28°30 ́

28°15 ́

29°15 ́

82°15 ́ 82°00 ́ 81°45 ́ 81°30 ́ 81°15 ́ 81°00 ́

Thiessen Polygon

Base from U.S. Geological Survey digital data,

Universal Transverse Mercator projection, zone 17

Lake

George

Lake

Weir

St. Johns

Lake

Harris

Lake Monroe

Lake

Apopka

Ocklawaha River

River

Silver

River

Lake

Denham

Gourd

Neck

Helena

Canal

station information is provided in table 2. 

Figure 2. Thiessen rainfall polygons and springsheds for selected springs of the St. Johns River drainage. Rainfall 
8 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

600

500

400

300

200

100

0

1,000

100

10

1

SULFUR HEXAFLUORIDE CONCENTRATION,

IN PARTS PER TRILLION BY VOLUME

LOG TRITIUM CONCENTRATION,

IN TRITIUM UNITS

Tritium, rainfall,

Ocala, Florida

Sulfur Hexafluoride x100

Tritium,

decay

corrected

to 2005

1945 1965 1985 2005

Figure 3. Input of sulfur hexafluoride to the atmosphere in the northern hemisphere and tritium concentrations in rainfall from Ocala, Florida during 1950-2006 

(modified from Katz and others, 2007).

Collection and Analysis of Spring Water

Water samples were collected by the USGS, SJRWMD, 

and FDEP using an electric submersible stainless-steel pump 

with Teflon discharge tubing by immersion into the spring 

pool as close to the vent as possible (Phelps and others, 2006). 

In the spring runs, the pump was placed at approximately onehalf the depth of water in the run (Phelps and others, 2006). 

Water samples were collected after field constituents (pH, 

specific conductance, temperature, and dissolved oxygen) had 

stabilized, and were collected according to U.S. Geological 

Survey (1997-2006) protocols as described in Phelps and 

others (2006). The USGS National Water Quality Laboratory in Lakewood, Colorado, analyzed water samples for 

major ions, nutrients, pesticides, and organic wastewater 

compounds. Samples for nitrogen and oxygen isotopes of 

nitrate were analyzed at the USGS Stable Isotope Laboratory 

in Reston, Virginia. Isotopic values are reported using the 

standard delta (δ) notation (Gonfiantini, 1981). Chlorophyll-a

and pheophytin-a were measured following the methods of 

Arar and Collins (1997).

Kendall’s tau (τ) test (Helsel and Hirsch, 1992) was 

used to determine if variations in nitrate-N and phosphorus 

concentrations in spring waters showed significant trends over 

the time period of sampling. A probability level of 5 percent 

(p < 0.05) was used as the criterion for significance, which 

indicated that the probability of a correlation trend between 

nitrate-N or phosphorus concentration and time occurring by 

chance was less than 5 percent.

The saturation index of minerals that are present in the 

aquifer matrix (calcite, dolomite, and gypsum) is used to 

determine if spring water is in thermodynamic equilibrium 

with a given mineral. When spring water is undersaturated 

with respect to a mineral (saturation index < 0), the mineral 

has the thermodynamic potential to dissolve. When water is 

saturated with respect to a mineral (saturation index = 0 ± 0.1), 

the mineral is in equilibrium with the aqueous phase. When 

the saturation index is greater than zero, the mineral has the 

thermodynamic potential to precipitate from the water phase.

Age Dating of Spring Water

To better understand the age of water discharging 

from springs, water samples were analyzed for the transient 

environmental tracers sulfur hexafluoride (SF6

), tritium (3H), 

and its radioactive decay product helium-3 (3

He). Anthropogenic activities, such as industrial processes and atmospheric 

testing of thermonuclear devices, have released SF6

, and 3H 

into the atmosphere in low but measurable concentrations 

(fig. 3). Precipitation that incorporates SF6

, and 3H from the 

atmosphere infiltrates into the ground and carries a particular 

chemical or isotopic signature related to atmospheric conditions at the time of recharge to the Upper Floridan aquifer. The 

dating methods assume that gas exchange between the unsaturated zone and air is rapid, but that shallow ground water 

remains closed to gas exchange after recharge (Schlosser and 

others, 1989; Plummer and Busenberg, 2000; Busenberg and 

Plummer, 2000). Sampling and analytical procedures for SF6

sampling are described by Busenberg and Plummer (2000).
Methods of Investigation 9

Water samples for the determination of 3H, 3He, 4He, 

and neon were collected in pinched-off copper tubes (10-mm 

[0.39 in.] diameter, 80-cm [3.15 in.] length, approximately 

40-mL volume) while applying back pressure to prevent 

formation of gas bubbles. These samples were analyzed at the 

Noble Gas Laboratory of Lamont-Doherty Earth Observatory 

by using quantitative gas extraction followed by mass spectrometry techniques (Schlosser and others, 1989; Ludin and 

others, 1998).

Lumped parameter models have been used to estimate the 

age distribution of spring waters and spring-water mixtures in 

previous studies in the St. Johns Water Management District 

(Toth and Katz, 2006) and elsewhere in Florida (Katz and 

others, 1999; Katz, 2004). In this study, lumped parameter 

models were used to estimate the age distribution of spring 

water from the Upper Floridan aquifer. These models treat 

the aquifer system as a homogeneous compartment in which 

tracer input concentrations are converted to tracer output 

concentrations according to the system response function used 

(Zuber, 1986). By fitting measured tracer concentrations to 

modeled output curves, the response function accounts for the 

distribution of ages at a sampled site (Zuber and others, 2001). 

No detailed information is needed regarding the flow system, 

such as boundary conditions, porosity, and hydraulic conductivity—all of which are necessary for numerical models based 

on Darcy’s law. Lumped parameter models assume a steadystate flow system and assume that the selected tracers behave 

like water molecules. Although this assumption typically is 

valid for 3

H, which is part of the water molecule, the gas tracer 

SF6

 may or may not be transported in the same exact manner 

as the water.

Ground-water flow system characteristics are represented 

by two end-member lumped-parameter models: piston flow 

and exponential flow. The piston-flow model (PFM) assumes 

that after a tracer is isolated from the atmosphere at the time 

of ground-water recharge, it becomes incorporated in a parcel 

of water that moves from the recharge area with the mean 

velocity of ground water. All flow lines are assumed to have 

similar velocities, and hydrodynamic dispersion and molecular 

diffusion of the tracer are assumed to be negligible. 

The exponential flow model (EFM) represents an aquifer 

system in which the mean residence time of ground water is 

exponentially distributed. Ground-water flow is composed 

of recharge from all past years. Ground-water contributions 

to well discharge, however, decrease exponentially from the 

most recent recharge to that which has occurred in the distant 

past. Although the exponential model may provide a reasonable approximation of homogeneous unconsolidated aquifers, 

it may not be as useful in karst systems where ground water 

moves slowly through small openings in the carbonate matrix, 

fractures or fissures, and much more rapidly through large 

conduits or caverns.

Other lumped parameter models that account for mixing 

include the combined exponential and piston flow model 

(EPM). The EPM has one additional fitted parameter, which is 

the ratio of the PFM to the EMM. 

In addition to the above models, simple binary mixing 

models (BMM) are used to evaluate mixing scenarios that 

involve relatively young water (recharged within the past 

5 years) with older water (decades), presumably from deeper 

parts of the Upper Floridan aquifer. In principle, both end 

members of a binary mixture can be of any age, but the calculation is greatly simplified if it is assumed that one or both end 

members is either “young” (assumed to represent recharge 

that occurred after 1995) or “old” (recharged before 1950 with 

undetectable SF6

 concentrations). Ground-water ages were 

determined using combinations of tracers including SF6

 and 3

H, and SF6 and 3H /3H(0). The 3H(0) tracer represents the 

initial tritium concentration at the time of recharge and is the 

sum of the measured concentrations of 3

H and 3He. The ratio 

of 3

H /3H(0) is a surrogate for the relative age of water, in that 

values near 0.0 represent old waters, and conversely, values 

near 1.0 represent young waters. The computer program 

TRACERMODEL1 (Böhlke, 2006) was used in this study to 

calculate theoretical curves for the different lumped parameter 

models using atmospheric input data for the various tracers.

Aquatic Community Data Collection and 

Analysis

Aquatic macroinvertebrates were collected with a 

D-frame dip net (500-μm mesh, 0.3-m width) and WildcoTM 

petite ponar dredge. Dip net sampling was based on a multihabitat approach (Barbour and others, 1999) to determine 

richness and diversity metrics and to calculate the Stream 

Condition Index (SCI; Barbour and others, 1996b; Fore and 

others, 2007). Collections made with the petite ponar dredge 

were done to estimate abundance as density of organisms per 

square meter. Dip net collections and those made with the 

petite ponar dredge followed standard operating procedures 

used by the Florida Department of Environmental Protection (2004). Sampling was done within wadeable reaches 

downstream of main spring vents or on the periphery of spring 

pools in those systems with a spring run (Alexander, Bugg, 

De Leon, Gemini, Green, Rock, Silver Glen, and Wekiwa). 

Sampling in Apopka Spring was limited to deploying a petite 

ponar dredge from a boat in close proximity to the surface 

boil. Microhabitats selected for sampling were based on areas 

inferred to provide suitable conditions of substrate and cover 

to support macroinvertebrate communities (for example, 

Barbour and others, 1999).

Each dip net sample consisted of 20 sweeps or scrapes 

taken from leaf packs, aquatic macrophytes (submersed 

and emergent), root mats, undercut banks, unconsolidated 

sediment (muck or sand), rock, and woody snag microhabitats in proportion to the approximate percent coverage of 

each habitat type estimated visually. Each sweep or scrape 

consisted of collecting epifauna from a 0.5-m (1.64 ft) section 

of substrate or cover by scraping or jabbing the dip net, or 

manually agitating or brushing in a manner to allow benthic 
10 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

macroinvertebrates and organic matter to flow into the net 

held stationary downstream or into a bucket that was then 

strained through the net. Material was rinsed through a series 

of sieves to remove coarse debris, vegetation, detritus and 

sediment. Three replicate samples were taken with the petite 

ponar dredge at each site and on individual sampling dates. 

Rinsed dip net samples and the entire contents of each ponar 

grab were preserved in a 10-percent solution of formalin 

containing Rose Bengal dye.

Freshly preserved samples were transferred to the 

USGS laboratory in Gainesville, Florida, soaked and rinsed 

in water for 24 to 48 hours following a fixation period of at 

least 2 days, and placed in a solution of 70-percent ethanol. 

Samples were then transferred to Water and Air Research, 

Inc., in Gainesville, where macroinvertebrates were sorted, 

identified, and enumerated. Subsampling procedures were 

applied to randomly select a minimum target number of 

100 to 110 organisms per collection (Florida Department 

of Environmental Protection, 2004). Taxonomic identifications were made to the lowest practicable identification 

level (LPIL). A voucher collection of representative taxa is 

maintained at the USGS facility in Gainesville. A list of all 

macroinvertebrates collected in this study and taxonomic 

authorities are provided in appendix 1. Taxonomic authorities 

were obtained from the Integrated Taxonomic Information 

System (http://www.itis.gov/, accessed October 1, 2008), 

Epler (2001), Bright (2007), and Wetzel and others (2008).

For individual dip net samples, raw data were “upward 

collapsed” using FDEP standard operating procedures. 

Specifically, closely related organisms in a sample that were 

identified to different supraspecific categories were allocated 

among presumed congeneric or species-level taxa. For 

example, Chironomidae LPIL and/or Dicrotendipes sp. would 

be combined with Dicrotendipes modestus. Data from ponar 

samples were pooled for each set of replicates taken at an 

individual spring on the same date.

Standard community metrics for benthic macroinvertebrates were calculated using “Warstat” (proprietary software 

of Water and Air Research Inc.), PRIMER® (Version 6.1.6; 

Clarke and Warwick, 2001; Clarke and Gorley, 2006), and 

PC-ORD® (Version 5.0; McCune and Grace, 2002; McCune 

and Mefford, 2006). Kwak and Peterson (2007) recommend 

providing explicit equations used in reporting community 

indices of species diversity, equitability, and dominance, 

because there are numerous alternative forms and occasional 

inconsistent use of terminology. The Shannon-Wiener 

diversity index, H' (Shannon, 1948), was calculated as:

H p p i e i

i

s

' log = − =

∑1 (1)

where H' (index of diversity) is the information content of the 

sample (nits/individual), s is the number of species, and pi

 is 

the proportion of the total sample belonging to the ith species. 

Calculation of H' is with a logarithmic base of e, 2, or 10; 

conversion factors are provided by Krebs (1999), Zar (1999), 

and others. The logarithmic base 2 for calculation of H' is 

specified in Florida Statutes Chapter 62-30 of the Florida 

Biological Integrity Rule. Therefore, calculated values using 

each of the logarithmic bases are included in table summaries.

The Shannon-Wiener diversity index may also be 

expressed as units of numbers of species (MacArthur, 1965; 

Krebs, 1999):

N eH

1 = '

(2)

where N1 is the number of equally common species that 

would produce the same diversity as H' and e is the natural 

log base; N1

 has been suggested to be among the best heterogeneity measures that are sensitive to abundances of rare 

species in a community (Peet, 1974).

Evenness or equitability (Pielou, 1966) was calculated 

as:

J H

H

H

S ' ''

'

log max

= =

(3)

where J' is evenness and H'

max is the maximum possible value 

of the Shannon-Wiener index, a value that would be achieved 

if all species were equally abundant (= log S, where S is the 

number of species) (Clarke and Warwick, 2001).

Simpson’s index of diversity was calculated as:

1 1 2 − = − D p ∑ i ( ) (4)

where (1-D) is the Simpson’s index of diversity (that is, 

complement of the original index, D; Simpson, 1949) and pi

is the proportion of individuals of species i in the community 

(that is, 1-D = probability of selecting two organisms at 

random that are different taxa). Simpson’s index of diversity 

emphasizes more abundant species in a sample and ranges 

from 0 (low diversity) to near 1 (that is, 1[1-1/s] where s is 

the number of species in the sample). 

The Stream Condition Index (SCI) is a multimetric index 

used to evaluate the relative condition of the water quality of 

a water body based on characteristics of the benthic invertebrate community (Barbour and others, 1996a and 1996b; Fore 

and others, 2007). The index is a summation of macroinvertebrate metrics that are responsive to environmental disturbance. The SCI has been modified (recalibrated) since first 

established and currently includes the following core metrics: 

(1) taxonomic richness; (2) numbers of Ephemeroptera, 

Trichoptera, Tanytarsini, clinger taxa, long-lived taxa, sensitive taxa; and, (3) percentages of filter feeders, dominant taxa, 

and very tolerant taxa (Fore and others, 2007). The index is 

calibrated for three ecoregions of Florida and is normalized to 

a scale of 0 to 100 by multiplying by 0.9. Threshold values of 

SCI scores are interpreted to define biocriteria for classification of aquatic life use categories as: “exceptional” = 71 to 

100; “healthy” = 35 to 70; and “impaired” = 0 to 34. Details 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 11

on the calculation of the SCI are provided in FDEP Standard 

Operating Procedure LT7200, Stream Condition Index 

Determination (http://www.dep.state.fl.us/labs/qa/sops.htm, 

accessed October 1, 2008). At the time of this study, subsampling to calculate the SCI was based on a target number of 

100 to 110 individual organisms selected by a randomization 

process; the SCI procedures were subsequently modified to 

include subsampling of a larger number of organisms (140-

160) based on average scores from two subsamples per site 

or date.

Scores for the Florida Index (FI; Ross and Jones, 1979) 

were assigned to Class I and II taxa and calculated for each 

spring using the formula:

FI = 2 × number of Class I taxa + number of Class II taxa (5)

The FI is a composite 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 the least tolerant taxa (that is, most sensitive, which are assigned a score of 2) and more tolerant taxa 

(less sensitive, assigned a score of 1).

Multivariate ordinations of benthic macroinvertebrate 

data for dip net collections were used to examine assemblages 

among springs and to associate observed relationships with 

environmental data using PRIMER® version 6.1.6 (Clarke 

and Warwick, 2001; Clarke and Gorley, 2006). Agglomerative 

hierarchical clustering using Bray-Curtis similarities of means 

for each spring and nonmetric multidimensional scaling 

(MDS) were used to identify groups. Physicochemical data 

were analyzed with principal components analysis (PCA) 

and the resulting vectors then compared with the assemblage 

ordination using the BioEnv procedure of PRIMER®.

Fishes were collected using an electroshocking boat 

equipped with a Smith-RootTM GPP 9.0 controller. Frequency 

and voltage settings on the controller were adjusted in the 

range of 60 to 120 Hz and 100 to 680 volts to produce about 2 

to 14 amps. Two netters at the front of the boat retrieved fish 

with dip nets and placed them in a live well. Large fish were 

identified, measured (total length, TL, in millimeters), and 

released near the site of capture. Small fish (less than about 

75 mm [2.95 in.]) were fixed in a 10-percent formalin solution 

and returned to the laboratory for identification and enumeration. Accessibility to head spring areas by boat or using 

other gears to catch fish was precluded in some instances; 

consequently, most fish collections were made in spring runs, 

occasionally a considerable distance downstream from the 

main spring vent(s). Snorkeling and seining was also used 

in some cases to observe and/or catch fish in habitats inaccessible by boat. Voucher specimens of representative fishes 

were deposited in the ichthyology collection of the Florida 

Museum of Natural History, University of Florida, Gainesville (http://www.flmnh.ufl.edu/fish/collection/collection.htm, 

accessed October 1, 2008). Scientific and common names of 

fishes collected during this study are listed in appendix 2 and 

follow the nomenclature of Nelson and others (2004).

Hydrology, Water Quality, and Aquatic 

Communities of Selected Springs 

Individual spring descriptions provided herein are based on 

those presented by Rosenau and others (1977), Scott and others 

(2002; 2004), Phelps and others (2006), and personal observations made at the time of this study. No biological sampling was 

conducted at Fern Hammock, Juniper, or Silver Springs during 

this study; hydrologic and land-use data for these springs are 

summarized from the results of an ancillary investigation for the 

FDEP (Munch and others, 2006) conducted simultaneously with 

the present study.

Spring accounts describe boil and spring pool characteristics, related surface-water attributes, vegetation abundance in 

the spring pool and spring run, and surrounding land features.

Springshed land-use characterization and percentage of 

each category for the years covered are summarized in individual spring accounts, and land-use changes from 1973 to 

2004 for the springsheds included in this study are presented 

in figure 4. Wastewater treatment and disposal systems are 

characterized for each springshed in terms of current use and 

changes that have occurred between 1973 and 2004.

Discharge data for individual springs are presented in 

each spring account as annual means. Discharge ranges are 

presented as minimum and maximum annual means and 

instantaneous values.

Physicochemical data collected simultaneously with 

macroinvertebrates for springs sampled during 2004-07 are 

summarized in appendix 3. Data that were collected at the 

spring vent or boil and in stream sections downstream in the 

spring runs where benthic macroinvertebrates were sampled 

include the following: water temperature, specific conductance, dissolved oxygen, pH, turbidity, and chlorophyll-a and 

pheophytin-b. Summaries of these data are presented in each 

of the spring accounts. Median values of physicochemical data 

reported in individual springs and table 3 were derived from 

the entire period of record for each spring as compiled from 

the sources listed in the “Methods of Investigation” section.

Detailed summaries of benthic macroinvertebrate samples 

are provided in each spring account, and a comparison among 

all springs in the “Comparison of Aquatic Communities” 

section. Benthic macroinvertebrate data are presented as 

richness (total taxa), percent composition, and dominance for 

subsamples of collections made with both petite ponar dredge 

and dip net. Density estimates, reported herein as the number of 

organisms per square meter, are provided for benthic macroinvertebrates collected by petite ponar dredge. Diversity indices, 

represented by the Shannon-Wiener index (to natural log base, 

2, and 10), Pielou’s evenness, and Simpson’s index of diversity, 

are presented in individual spring accounts and tables 4 and 5. 

In addition, the Florida Index is provided for samples collected 

by petite ponar dredge, and the SCI and percent very tolerant 

taxa are reported for collections made with dip net.

Total numbers of fishes collected or estimated to 

have been observed at each spring are summarized in each 

account and in tabular format, where appropriate, listed by 

family, species, and percent composition of each sample. 
12 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

SPRINGSHED LAND-USE

CATEGORY PERCENTAGES

AGRICULTURE

BARREN

FOREST

URBAN

OPEN-WATER

1973 2004

Alexander Spring

Apopka Spring

Bugg Spring

De Leon Spring

Gemini Springs

Green Spring

Rock Springs

Silver Glen Springs

Wekiwa Springs

LAND-USE CATEGORY

EXPLANATION

Figure 4. Relative proportions of springshed land-use categories for the years 

1973 and 2004. 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 13

Table 3. Median values for physical and chemical characteristics, and saturation indices with respect to calcite, dolomite, gypsum, and carbon dioxide partial pressure for selected springs in the St. Johns River Water Management District. [In shaded cells, period of water-quality data are shown below each spring name and number of observations are shown in parentheses. All concentration units are milligrams per liter unless otherwise noted. Temp, water temperature in degrees Celsius; SC, specific conductance in microsiemens per centimeter; DO, dissolved oxygen; DS, dissolved solids; HCO , bicarbonate; NO -NO -N, nitrite plus nitrate as 3 2 3

nitrogen; o-PO , orthophosphate, as P; Ca, calcium; Mg, magnesium; Na, sodium; K, potassium; Cl, chloride; SO , sulfate; F, fluoride; SiO , silica; log pCO (g), log partial pressure of carbon dioxide in 4 4 2 2

atmospheres; SI, saturation index with respect to calcite, dolomite, and gypsum calculated using median chemistry (unitless)]

Spring Temp SC DO pH DS HCO3

NO -2

NO -3

N

o-PO4 Ca Mg Na K Cl SO4 F SiO2

log 

pCO2

(g)

Calcite

 SI

Dolomite 

SI

Gypsum

 SI

Alexander 23.5 1,100 2.12 7.80 596 82 0.04 0.05 46 20.3 137 4.0 252 66 0.12 8.8 -2.92 -0.16 -0.34 -2.00

1960-2007 (113) (97) (16) (92) (77) (76) (70) (34) (79) (80) (80) (80) (82) (79) (49) (7)

Apopka 24.2 249 3.76 8.09 146 74 4.41 0.09 29 8.0 5.5 1.5 12 9.9 0.08 4.9 -3.23 0.01 -0.19 -2.83

1972-2007 (99) (101) (34) (92) (89) (89) (84) (84) (101) (100) (100) (93) (91) (89) (10) (26)

Bugg 23.6 293 1.43 7.60 167 125 0.58 0.07 48 3.0 5.9 0.93 11 6.1 0.10 8.6 -2.52 -0.05 -0.97 -2.84

1972-2006 (18) (17) (11) (17) (12) (10) (9) (191) (12) (12) (12) (12) (12) (11) (9) (5)

Bugg Run 23.6 290 3.58 7.56 172 125 0.50 0.08 50 3.2 7.7 1.1 13 8.8 9.2 -2.48 -0.08 -1.01 -2.68

1991-2007 (43) (43) (24) (43) (25) (38) (39) (221) (25) (24) (24) (22) (35) (35) (14)

De Leon 23.0 640 1.48 7.60 416 120 0.90 0.16 50 12.8 79 4.4 115 27 0.10 6.6 -2.55 -0.12 -0.50 -2.28

1932-2007 (220) (201) (89) (77) (79) (63) (5) (80) (81) (81) (79) (180) (81) (61) (15)De Leon Run 23.1 900 5.52 7.46 546 0.63 0.16 52 16.7 121 5.7 227 38 0.10 6.6 -2.42 -0.27 -0.71 -2.17

2004-2007 (5) (5) (5) (5) (3) (4) (2) (3) (3) (3) (3) (3) (3) (3) (3)

Fern 21.9 118 6.20 8.17 68 45 0.08 0.02 13 4.7 2.7 0.30 4.5 6.9 0.07 9.6 -3.53 -0.46 -1.06 -3.25 Hammock

1972-2007 (92) (89) (12) (81) (66) (67) (65) (17) (70) (70) (47) (18) (67) (69) (46) (2)

Gemini N 23.1 2,508 1.01 7.25 1,523 1.07 0.18 104 41.0 346 8.4 660 124 0.14 9.7 -2.12 -0.19 -0.45 -1.56 Boil

2004-2006 (7) (7) (7) (7) (2) (2) (2) ) (2) (2) (2) (2) (2) (2) (2)
14 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District Table 3. Median values for physical and chemical characteristics, and saturation indices with respect to calcite, dolomite, gypsum, and carbon dioxide partial pressure for selected springs in the St. Johns River Water Management District.—Continued [In shaded cells, period of water-quality data are shown below each spring name and number of observations are shown in parentheses. All concentration units are milligrams per liter unless otherwise noted. Temp, water temperature in degrees Celsius; SC, specific conductance in microsiemens per centimeter; DO, dissolved oxygen; DS, dissolved solids; HCO , bicarbonate; NO -NO -N, nitrite plus nitrate as 

3 2 3

nitrogen; o-PO , orthophosphate, as P; Ca, calcium; Mg, magnesium; Na, sodium; K, potassium; Cl, chloride; SO , sulfate; F, fluoride; SiO , silica; log pCO (g), log partial pressure of carbon dioxide in 4 4 2 2

atmospheres; SI, saturation index with respect to calcite, dolomite, and gypsum calculated using median chemistry (unitless)]

Spring Temp SC DO pH DS HCO3

NO -2

NO -

3

N

o-PO4 Ca Mg Na K Cl SO4 F SiO2

log 

pCO2

(g)

Calcite

 SI

Dolomite 

SI

Gypsum

 SI

Gemini S 23.3 2,579 0.86 7.23 1,572 1.06 0.19 104 40.9 349 8.6 671 124 0.14 9.7 -2.10 -0.21 -0.49 -1.57 Boil

2004-2006 (7) (7) (7) (7) (2) (2) (2) (2) (2) (2) (2) (2) (2) (2) (2)

Gemini Run 22.9 2,412 3.20 7.35 1,420 136 0.91 0.08 101 39.0 334 8.3 633 120 0.12 9.2 -2.28 -0.15 -0.39 -1.58

1972-2007 (50) (49) (7) (47) (45) (42) (47) (20) (48) (48) (48) (48) (48) (50) (33) (6)

Green 22.7 2,480 0.41 7.36 1,500 158 0.03 0.07 87 40.6 357 11 682 102 0.09 7.4 -2.22 -0.14 -0.29 -1.71

1960-2007 (43) (43) (9) (43) (33) (34) (18) (17) (35) (35) (35) (35) (35) (35) (16) (2)

Green Run 22.8 2,716 0.60 7.30 1,490 0.02 0.07 89 41.9 360 12 690 104 0.10 7.8 -2.16 -0.19 -0.39 -1.70

2004 (3) (3) (3) (3) (3) (3) (3) (3) (3) (3) (3) (3) (3) (3) (3)

Juniper 22.0 117 6.60 8.43 66 45 0.08 0.02 13 4.4 2.7 0.30 4.4 6.0 0.07 8.8 -3.80 -0.21 -0.58 -3.31

1908-2007 (110) (110) (11) (102) (84) (91) (77) (33) (95) (92) (94) (27) (91) (92) (53) (8)

Rock 23.8 251 1.38 7.65 144 93 1.45 0.08 30 9.1 5.1 1.3 8.6 18 0.15 9.4 -2.69 -0.32 -0.83 -2.56

1931-2007 (203) (140) (16) (122) (107) (107) (87) (37) (112) (113) (112) (111) (114) (114) (80) (23)

Silver Glen 23.2 1,951 3.68 7.84 1,070 68 0.04 0.02 71 34.5 250 8.7 453 179 0.12 8.8 -3.06 -0.10 -0.18 -1.51

1972-2007 (94) (89) (16) (85) (62) (65) (60) (12) (68) (37) (67) (68) (67) (66) (50) (4)

Wekiwa 23.7 314 0.40 7.42 179 120 1.30 0.12 39 11.0 9.0 1.5 14 19 0.16 9.3 -2.36 -0.35 -0.91 -2.46

1956-2007 (200) (150) (20) (127) (108) (110) (93) (45) (115) (116) (115) (114) (117) (117) (81) (22)
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 15

Table 4. Diversity indices for macroinvertebrates by pooled petite ponar dredge samples from selected springs of the St. Johns River 

drainage, 2004-07.

[N , power function of base of the natural log to H'] 1

Spring Date

Number of 

taxa

(S)

Number of 

individuals

(n)

Shannon W

H’ (log )

e

iener diversity Index (H’)

H’ (log )2 H’ (log ) 10

N1

Pielou’s 

evenness

(J’)

Simpson’s 

index of 

diversity

(1-D)

Florida 

Index

Alexander

Apopka

Bugg

De Leon

Gemini

Green

Rock

Silver Glen

Wekiwa

2/1/2007

5/10/2007

8/7/2007

10/10/2007

12/30/2005

3/28/2006

7/13/2006

9/21/2006

12/30/2005

3/17/2006

7/12/2006

9/21/2006

2/11/2004

5/11/2004

8/18/2004

2/10/2004

5/11/2004

8/17/2004

2/10/2004

5/11/2004

8/17/2004

12/6/2005

3/27/2006

6/21/2006

9/27/2006

1/31/2007

5/10/2007

8/7/2007

10/10/2007

12/7/2005

3/27/2006

6/22/2006

9/27/2006

22

16

5

21

10

7

13

10

12

17

14

15

7

23

46

17

11

11

3

13

17

13

20

37

39

22

24

21

19

17

17

12

23

16,206

31,955

1,207

11,077

13,806

8,706

10,775

13,619

2,959

3,280

10,443

9,773

530

4,062

12,622

2,470

4,598

1,752

115

4,396

20,630

2,497

8,838

5,339

8,095

22,875

26,122

12,646

21,152

23,706

13,451

6,438

35,802

2.020

0.996

1.393

1.490

0.463

0.391

1.482

1.349

2.090

2.606

1.539

2.260

1.169

1.622

1.595

1.563

1.569

1.820

0.897

1.533

0.938

1.880

1.962

3.152

3.034

2.089

1.995

1.897

2.003

1.613

2.121

1.927

1.416

2.915

1.437

2.010

2.150

0.667

0.564

2.138

1.946

3.016

3.759

2.221

3.260

1.687

2.340

2.301

2.255

2.263

2.626

1.294

2.211

1.354

2.712

2.830

4.548

4.377

3.014

2.879

2.736

2.889

2.327

3.060

2.779

2.043

0.878

0.433

0.605

0.647

0.201

0.170

0.644

0.586

0.908

1.132

0.669

0.981

0.508

0.704

0.693

0.679

0.681

0.790

0.390

0.666

0.408

0.816

0.852

1.369

1.318

0.907

0.867

0.824

0.870

0.701

0.921

0.837

0.615

7.538

2.707

4.027

4.437

1.588

1.479

4.402

3.854

8.085

13.545

4.660

9.583

3.219

5.063

4.928

4.773

4.802

6.172

2.452

4.632

2.556

6.554

7.114

23.383

20.780

8.077

7.352

6.666

7.411

5.018

8.339

6.869

4.121

0.654

0.359

0.866

0.490

0.201

0.201

0.578

0.586

0.841

0.920

0.583

0.834

0.601

0.517

0.417

0.552

0.654

0.759

0.816

0.598

0.331

0.733

0.655

0.873

0.828

0.676

0.628

0.623

0.680

0.569

0.749

0.775

0.452

0.797

0.407

0.708

0.621

0.169

0.142

0.604

0.587

0.845

0.914

0.624

0.860

0.561

0.703

0.651

0.595

0.740

0.800

0.534

0.640

0.466

0.803

0.786

0.939

0.922

0.816

0.704

0.669

0.798

0.729

0.776

0.798

0.509

4

0

0

2

2

1

1

2

0

0

0

0

2

1

7

2

1

1

0

0

0

4

2

11

10

6

4

5

2

2

1

0

1
16 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Table 5. Diversity indices for macroinvertebrates 

[N , power function of base of the natural log to H′] 1

collected by dip net from selected springs of the St. Johns River drainage, 2004-07. 

Spring Date

Number of 

taxa

(S)

Shannon Wiener diversity index (H’)

N1

Pielou’s 

evenness

(J’)

Simpson’s 

index of 

diversity

(1-D)

Stream 

condition 

index

(SCI)

Percent very 

tolerant taxa

H’ (log ) (%VTT) e H’ (log )2 H’ (log ) 10

Alexander

Bugg

De Leon

Gemini

Green

Rock

Silver Glen

Wekiwa

2/1/2007

5/10/2007

8/7/2007

10/10/2007

12/30/2005

3/17/2006

7/12/2006

9/21/2006

2/11/2004

5/11/2004

8/18/2004

2/10/2004

5/11/2004

8/17/2004

2/10/2004

5/11/2004

8/17/2004

12/6/2005

3/27/2006

6/21/2006

9/27/2006

1/31/2007

5/10/2007

8/7/2007

10/10/2007

12/7/2005

3/27/2006

6/22/2006

9/27/2006

10

8

10

17

11

26

22

22

12

14

11

7

14

6

9

18

10

15

14

25

16

14

19

15

16

15

13

11

12

1.127

0.433

1.366

2.114

1.809

2.834

1.768

2.444

1.131

1.647

1.289

1.052

2.234

0.850

1.664

2.250

1.077

1.700

1.712

2.777

1.350

2.008

2.383

1.815

2.078

1.711

1.820

1.318

1.422

1.626

0.625

1.970

3.051

2.609

4.088

2.550

3.526

1.631

2.376

1.860

1.517

3.224

1.226

2.401

3.246

1.554

2.453

2.470

4.007

1.948

2.897

3.438

2.618

2.998

2.468

2.626

1.901

2.052

0.490

0.188

0.593

0.918

0.785

1.231

0.768

1.061

0.491

0.715

0.560

0.457

0.970

0.369

0.723

0.977

0.468

0.738

0.744

1.206

0.587

0.872

1.035

0.788

0.902

0.743

0.791

0.572

0.618

3.086

1.542

3.920

8.281

6.104

17.013

5.859

11.519

3.099

5.191

3.629

2.863

9.337

2.339

5.280

9.488

2.936

5.474

5.540

16.071

3.857

7.448

10.837

6.141

7.988

5.534

6.172

3.736

4.145

0.490

0.208

0.593

0.746

0.754

0.870

0.572

0.791

0.455

0.624

0.538

0.541

0.847

0.474

0.758

0.778

0.468

0.628

0.649

0.863

0.487

0.761

0.809

0.670

0.749

0.632

0.710

0.550

0.572

0.499

0.157

0.625

0.833

0.759

0.926

0.630

0.863

0.440

0.690

0.591

0.490

0.872

0.516

0.783

0.852

0.526

0.721

0.708

0.919

0.515

0.818

0.884

0.760

0.837

0.665

0.792

0.555

0.624

13

12

8

22

7

34

13

23

10

10

9

9

13

8

6

15

6

19

13

33

12

16

16

14

25

10

32

15

22

1.8

0.9

7.2

5.4

77.8

38.1

19.3

36.3

3.6

14.5

6.3

5.5

39.1

2.7

53.6

43.7

26.3

4.6

16.3

22.9

11.8

2.7

23.6

6.4

5.4

19.1

9.9

4.5

2.7
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 17

Alexander Spring

Alexander Spring (figs. 1 and 5, table 1) is a first magnitude spring (mean and median discharge 104 and 102 ft3

/s, 

respectively) (Rosenau and others, 1977; Scott and others, 

2004). The spring and spring run are within the Ocala National 

Forest and are maintained by the U.S. Forest Service as a 

multiple-use recreation area open to the public. The spring pool 

measures about 300 ft from north to south and about 258 ft 

from east to west. Maximum depth is about 25 to 28 ft to a 

conical depression containing multiple clustered vents within 

a mix of sand and limestone outcrop, boulders, and a rock 

ledge that extends north to south along the downstream edge of 

the main vent. A large boil is visible at the surface. The south 

shoreline of the spring pool consists of a concrete retaining 

wall and two sets of stairs adjacent to a sandy beach and picnic 

area. Aquatic vegetation surrounds the main spring vent and 

is present throughout most of the run in the upstream reaches 

where there is open tree canopy; the pool bottom near the beach 

is mostly open sand. Mats of algae accumulate during the winter 

and spring months in the pool and run areas when recreational 

activity in the spring is at a minimum; later during the spring 

and summer months when swimming activity is high, much 

of the algae that has accumulated during the previous season 

becomes dislodged and drifts down the run. The pool discharges 

to Alexander Spring run (fig. 6), which flows westward from 

the spring vent for a few hundred yards and then flows eastward 

about 8 mi to the St. Johns River. Riparian areas surrounding 

Alexander Spring and Alexander Spring run are mixed hardwood, pine, and palm forest and wetlands. The areal extent of 

the Alexander springshed is 58.5 mi2

.

Land Use

Land use in the Alexander springshed changed markedly 

from 1973 to 2004 as a result of the conversion of agricultural 

lands to urban use, which approximately doubled in area over 

the 31-year period; by 2004 more than half of the Alexander 

springshed was urbanized (fig. 4). Land use in the springshed 

in 1973 consisted of agriculture (38.4 percent), urban/mining/

transportation/recreation (27.4 percent), open-water/wetlands 

(25.1 percent), and forestland (9.1 percent). Land use of the 

springshed in 2004 consisted of urban/mining/transportation/

recreation (58.2 percent), open-water/wetlands (25.3 percent), 

agriculture (7.5 percent), and forestland (9.0 percent). As 

of 2007, no wastewater treatment facilities were active in 

the Alexander springshed and septic systems were the only 

method of wastewater treatment and disposal.

Discharge

Discharge from Alexander Spring has been measured 

intermittently by the USGS since 1931, with more frequent 

measurements made since 1982 (fig. 7). During this study, the 

SJRWMD and the USGS measured the discharge of Alexander 

Springs at least monthly. Discharge was measured in the 

uppermost part of the run about 150 ft downstream of the vent. 

Discharge of Alexander Spring averaged 104 ft3

/s annually 

and varied with rainfall that averaged 52.10 in/yr within the 

springshed. Average annual discharge ranged from 79 ft3

/s in 

1977 to 136 ft3

/s in 1956. Measured (instantaneous) discharge 

from Alexander Spring ranged from 55.9 ft3

/s in May 1986 to 

202 ft3

/s in January 1984 (fig. 8).

Figure 5. Aerial view of Alexander Spring. Photograph 

courtesy of the St. Johns River Water Management District, 

used with permission.

Figure 6. Alexander Spring run immediately downstream of 

spring pool. The spring run contains extensive floating and 

submerged algae. Photograph by S.J. Walsh, May, 9, 2007.
18 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

ALEXANDER SPRING

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

YEAR

ANNUAL DISCHARGE, IN

CUBIC FEET PER SECOND

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

ANNUAL RAINFALL, IN INCHES

AVERAGE ANNUAL RAINFALL

= 52.10 INCHES

ANNUAL DISCHARGE =

104 CUBIC FEET PER SECOND

AVERAGE

SPRING DISCHARGE

ANNUAL RAINFALL

EXPLANATION

Figure 7. Average annual discharge for Alexander Spring and rainfall for the springshed.

Figure 8. Periodic discharge data for Alexander Spring, 1931-2007. Data collected by the St. Johns River 

Water Management District (SJRWMD) and U.S. Geological Survey. SJRWMD data used with permission.

ALEXANDER SPRING

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

210

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

YEAR

DISCHARGE, IN CUBIC FEET PER SECOND

AVERAGE INSTANTANEOUS DISCHARGE

=104 CUBIC FEET PER SECOND

EXPLANATION

INSTANTANEOUS DISCHARGE

AVERAGE INSTANTANEOUS

DISCHARGE
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 19

20

40

60

80

20

40

60

80

20

40

60

80

20

40

60

80

EXPLANATION

GREEN SPRING

APOPKA SPRING

BUGG SPRING

BUGG RUNSPRING

DE LEON SPRING

DE LEON RUNSPRING

GEMINI NORTH BOIL SPRINGS

GEMINI SOUTH BOIL SPRINGS

GREEN RUNSPRING

ALEXANDER SPRING

FERN HAMMOCK SPRINGS

JUNIPER SPRINGS

SILVER GLEN SPRINGS

ROCK SPRINGS

WEKIWA SPRINGS

GEMINI RUN SPRINGS

Ca-HCO ,

Ca, Mg-HCO

water type

3

3

mixed

water type

Na-Cl

water

type

MAGNESIUM

CALCIUM

CATIONS

CHLORIDE

ANIONS

SULFATE + CHLORIDE

CALCIUM + MAGNESIUM

SULFATE

SODIUM + POTASSIUM

CARBONATE + BICARBONATE

PERCENT

80

60

40

20

20

40

60

80

PERCENT

PERCENT

Figure 9. Trilinear plot showing the major-ion composition of spring waters and water types of 

selected springs in the St. Johns River drainage. 

Water Chemistry and Age

The water quality of Alexander Spring has been sampled 

periodically by the USGS since 1931 and sampled by the 

SJRWMD since 1983. At the time of this study, the SJRWMD 

and the USGS jointly sampled Alexander Spring at least four 

times per year.

Alexander Spring has a Na-Cl water type (fig. 9), and the 

spring water is slightly undersaturated with respect to calcite 

and dolomite (table 3). The Na-Cl water type for Alexander 

Spring likely originates from vertical upconing of water from 

the Lower Floridan aquifer (Knowles and others, 2002). 

Median values of pH, dissolved oxygen, and dissolved solids 

were 7.8, 2.1 mg/L, and 596 mg/L, respectively, for the period 

of record (1960-2007).

Nitrate-N concentrations have remained below 0.1 mg/L 

over the past 30 years (fig. 10), and from 1960 to 2007, 

nitrate-N concentrations showed a significant decreasing trend 

(p < 0.01) (table 6). Total phosphorus (P) concentrations 

remained relatively constant over time as indicated by samples 

collected sporadically during the past 35 years (fig. 11). The 

P concentration in Alexander Spring was 0.04 mg/L in April 

1972 and September 1977, and 0.06 mg/L in January 1985. 

From November 2003 to October 2007, P concentrations 

remained relatively constant at 0.04 to 0.05 mg/L, which 

were slightly higher than P concentrations measured in 

other springs in the Ocala National Forest (Silver Glen, 

Fern Hammock, and Juniper Springs) (fig. 11). In 2007, 

the USGS sampled Alexander Spring for chlorophyll-a and 

pheophytin-a to determine the richness of suspended photosynthetic organisms in the run approximately 100 ft downstream of the spring vent. Chlorophyll-a values ranged from 

less than 0.1 to 0.88 μL (May and February, respectively), 

and pheophytin values ranged from 0.15 to 1.5 μL (October 

and February, respectively) (app. 3).

Data for the stable isotopes of water (delta 18O and 2

H) plot along the Global Meteoric Water Line (GMWL) 

or local Meteoric Water Line (MWL) that is parallel to the 

GMWL (Toth, 1999), indicating that recharge to the spring 

does not undergo evaporation. The 3

H concentration of 

2.7 TU (Toth, 1999) indicates that recharge occurred during 

the past 30 years. The delta 34S composition was 21.0 per 
20 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

YEAR

1970 1980 1990 2000 2010

NITRATE-N CONCENTRATION, IN MILLIGRAMS PER LITER

0

0.1

0.2

0.3

0.4

0.5

-0.1

Alexander Spring

Silver Glen Springs

Fern Hammock Springs

Juniper Springs

EXPLANATION

Figure 10. Nitrate-N concentrations in water from Alexander, Silver Glen, Fern Hammock, and 

Juniper springs located in Ocala National Forest. 

1970 1980 1990 2000 2010

0.01

0.1

1

10

YEAR

PHOSPHORUS (AS P) CONCENTRATION,

IN MILLIGRAMS PER LITER

Alexander Spring

Silver Glen Springs

Fern Hammock Springs

Juniper Springs

EXPLANATION

Figure 11. Phosphorus concentrations in water from Alexander, Silver Glen, Fern Hammock and Juniper 

Springs located in Ocala National Forest. 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 21

Table 6. Statistically significant (p less than 0.05) trends of nitrite plus nitrate as N, orthophosphate as PO4, and phosphorus with time. 

[NS, not statistically significant; Kendall tau; Kendall tau correlation coefficient; p, probability value of exceeding null hypothesis; <, less than value. Significant increasing trends are highlighted in dark gray; significant decreasing trends are highlighted in light gray]

Spring

Nitrite plus nitrate as N Orthophosphate as PO4

-

unfiltered Orthophosphate as PO4

-filtered Phosphorus (P)-unfiltered

N Kendall 

tau p value N Kendall tau p value N Kendall tau p value N Kendall tau p value

Alexander 70 -0.23 0.005 28 0.07 NS 0 NS 34 -0.13 NS

Apopka 84 0.21 0.005 5 -0.40 NS 1 NS 84 -0.16 0.036

Bugg 9 0.00 NS 1 1.00 NS 1 NS 191 -0.003 NS

Bugg Run 39 -0.32 0.004 13 0.33 NS 0 NS 221 0.03 NS

De Leon 63 0.02 NS 15 -0.79 <0.001 5 -0.32 NS 17 -0.23 NS

De Leon Run 4 0.00 NS 2 0.00 NS 2 NS 4 0.67 NS

Fern Hammock 65 0.21 0.016 10 -0.18 NS 0 NS 17 -0.20 NS

Gemini N Boil 2 NS 2 NS 1 NS 2 NS

Gemini S Boil 2 NS 2 NS 1 NS 2 NS

Gemini Run 47 0.63 <0.001 11 -0.33 NS 3 0.33 NS 20 -0.09 NS

Green 18 0.11 NS 11 -0.35 NS 0 NS 17 -0.24 NS

Green Run 3 -0.82 NS 2 NS 1 NS 3 0.81 NS

Juniper 77 0.17 0.033 20 0.35 0.030 1 NS 33 -0.03 NS

Rock 87 -0.17 0.021 1 NS 3 -0.33 NS 37 -0.54 <0.001

Silver Glen 60 -0.03 NS 12 -0.53 0.016 12 20 0.02 NS

Wekiwa 93 -0.34 <0.001 3 -0.82 NS 4 0.72 NS 45 -0.25 0.022

mil (Toth, 1999), which is similar to that for modern sulfate 

evaporite minerals likely present in the aquifer matrix. Based 

on concentrations of 3

H, 3He, and chlorofluorocarbons (CFCs) 

measured in water samples from Alexander Springs in 2001, 

spring water represents a mixture containing approximately 

30 percent of water from the Lower Floridan aquifer and 

about 70 percent of water from the Upper Floridan aquifer 

with a mean residence time of about 15 years (Toth and Katz, 

2006). Previous water samples were collected in July 1995 to 

assess the age of water discharging from Alexander Springs 

by measuring the concentration of 3

H, delta 13C, and 14C. The 3

H concentration of 2.7 TU for Alexander Spring indicated 

that the younger fraction of the water likely was less than 

42 years old, whereas the 3

H/3He age indicated an age of 

25 years for the young-water fraction. Alexander Spring had 

a delta 13C value of -9.50 per mil and a 14C concentration of 

28 percent modern carbon (pmc), which likely indicates mixing 

of Upper and Lower Floridan aquifer water. The adjusted 14C 

age is recent (Toth and Katz, 2006).

Aquatic Communities

A total of 47 macroinvertebrate taxa were collected 

by petite ponar dredge from Alexander Spring across four 

sampling dates (table 7). By season, the number of taxa 

collected from Alexander Spring with this gear ranged 

from 5 in August 2007 to 22 in February 2007. Combined, 

samples were dominated by gastropods (70.2 percent, most 

of which were hydrobiids) and oligochaetes (22.1 percent). 

Density of all organisms ranged from approximately 

1.2 × 103 per m2 (12.9 × 103 per ft3) in August 2007 to 

32.0 × 103

 per m2 (34.4 × 103 per ft3) in May 2007. The few 

taxa and low number of total organisms collected in May were 

likely the result of inefficient grabs for one or more of the three 

replicate petite ponar samples. For petite ponar samples pooled 

across all dates, the log2

 Shannon-Wiener index ranged from 

1.44 to 2.92, Simpson’s index of diversity ranged from 0.41 

to 0.80, Pielou’s evenness ranged from 0.36 to 0.87, and the 

Florida Index ranged from 0 to 4 with a mean of 1.5 (table 4).
22 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Table 7. Number of specimens (n) and percent density (%) per square meter of macroinvertebrates collected by pooled petite ponar 

dredge samples (n = 3 per date) from Alexander Spring, February-October 2007.

[LPIL, lowest practicable identification level]

Clade Taxon

Feb. 1, 2007 May 10, 2007 Aug. 7, 2007 Oct. 10, 2007

n % n % n % n %

Turbellaria

Gastropoda

Hirudinea

Oligochaeta

Arachnida

Diptera

Ephemeroptera

Odonata

Trichoptera

Total

Number of Taxa

Tricladida (LPIL)

Amnicola dalli

Aphaostracon sp.

cf. Aphaostracon sp.

cf. Tarebia sp.

Elimia floridensis

Hydrobiidae (LPIL)

Hydrobiidae sp. C Line

Melanoides turricula

Planorbella scalaris

Spilochlamys gravis

cf. Helobdella fusca

Erpobdellidae (LPIL)

Gloiobdella elongata

Glossiphoniidae (LPIL)

Hirudinea (LPIL)

Mooreobdella microstoma

Dero digitata complex

Dero pectinata

Dero sp.

Limnodrilus hoffmeisteri

Naididae (LPIL)

Pristina leidyi

Pristina sp.

Slavina appendiculata

tubificoid Naididae immature sp. A (LPIL)

Neumania sp.

Amphipoda (LPIL)

Gammarida (LPIL)

Gammarus cf. tigrinus LeCroy

Gammarus sp.

Hyalella azteca complex Lecroy

Ablabesmyia mallochi

Chironominae (LPIL)

Chironomus sp.

Cladopelma sp.

Dicrotendipes sp. (immature)

Polypedilum halterale group Epler

Polypedilum scalaenum group Epler

Polypedilum sp.

Tanypus carinatus

Tanypus sp.

Tanytarsus sp. L Epler

Caenis diminuta

Caenis sp.

Epitheca princeps regina

Leptoceridae (LPIL)

115

3,218

1,207

345

115

115

5,575

57

115

115

3,103

115

287

115

115

230

690

172

115

115

115

57

16,206

22

0.7

19.9

7.4

2.1

0.7

0.7

34.4

0.4

0.7

0.7

19.1

0.7

1.8

0.7

0.7

1.4

4.3

1.1

0.7

0.7

0.7

0.4

1,034

460

3,908

24,253

345

115

115

345

115

345

115

345

115

115

115

115

31,955

16

3.2

1.4

12.2

75.9

1.1

0.4

0.4

1.1

0.4

1.1

0.4

1.1

0.4

0.4

0.4

0.4

115

345

115

517

115

1,207

5

9.5

28.6

9.5

42.8

9.5

158

1,451

29

14

29

14

14

1,609

115

14

6,451

14

72

72

187

345

115

115

115

29

115

11,077

21

1.4

13.1

0.3

0.1

0.3

0.1

0.1

14.5

1.0

0.1

58.2

0.1

0.6

0.6

1.7

3.1

1.0

1.0

1.0

0.3

1.0
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 23

A total of 27 macroinvertebrate taxa were identified 

in subsamples collected by dip net from Alexander Spring 

(table 8). The number of taxa ranged from 8 in May 2007 

to 17 in October 2007. Similar to the petite ponar samples, 

combined dip net subsamples were numerically dominated by 

hydrobiid snails (74.8 percent), although tubificoid (Naididae) 

worms constituted a smaller overall proportion (2.3 percent) in 

these samples than in pooled petite ponar samples. Amphipods 

constituted 11.4 percent of the total number of organisms 

subsampled across all dates. For dip net samples among 

dates, the log2

 Shannon-Wiener index ranged from 0.63 to 

3.05, Simpson’s index of diversity ranged from 0.16 to 0.83, 

Pielou’s evenness ranged from 0.21 to 0.75, the SCI ranged 

from 8 to 22 with a mean of 14, and percent very tolerant 

taxa ranged from 0.9 to 7.2 with a mean of 3.8 (table 5). 

The dominant taxon in both ponar and dip net samples, 

Spilochlamys gravis, is a hydrobiid snail that is limited in 

distribution to the upper St. Johns River drainage (Thompson, 

2004) and also previously recorded from Alexander, Rock, 

and Wekiwa Springs (Shelton, 2005); in this study, specimens 

from Alexander Spring were identified to this species, whereas 

many hydrobiids from Rock and Wekiwa Springs were not 

identified beyond the family level. 

Efforts were made to use a boat electroshocker to collect 

fishes from Alexander Spring run in the vicinity of the State 

Road 445 bridge (about 1.3 mi downstream from the head 

spring) on May 10 and 24, 2007. However, low water levels, 

abundant macrophyte and algae growth, and high water 

conductivity precluded effective sampling with either boat or 

backpack electroshocking equipment. Therefore, on August 

28, 2007, a crew of eight people used a variety of qualitative 

gears (seines, cast nets, dip nets, mask and snorkel) to collect 

and observe fishes near the highway bridge and within several 

hundred yards upstream along the spring run. A total of 

1,674 fish specimens were collected or recorded by visual 

observation, representing 29 species of 23 genera and 

14 families (table 9). The sample was dominated by cyprinids 

(35.4 percent, especially Notropis petersoni), atherinopsids 

(29.8 percent, especially Menidia beryllina), fundulids 

(17.0 percent, especially Lucania goodei), and poeciliids 

(9.7 percent, especially Poecilia latipinna). An examination 

of the holdings of the ichthyology collection in the Florida 

Museum of Natural History revealed that only two species 

historically recorded from this site were not collected nor 

observed on the sampling date during this study: Notropis

chalybeus and Pteronotropis welaka. Although no nonindigenous fishes were taken or observed along the spring run during 

dates of general sampling, numerous adult Pterygoplichthys

disjunctivus were observed resting on the substrate in close 

proximity to the Alexander Spring vent during the spring and 

early summer months of 2007 (fig. 12). These fish retreated 

to crevices in the rock when swimmers approached them, and 

when not disturbed were observed “piping” for air by 

(1) slowly swimming toward the surface of the boil, 

(2) rapidly ascending within the last few feet of the surface, 

(3) gulping a bubble of air, and (4) slowly swimming back 

to the substrate. 

Figure 12. Aggregation of adults of the nonindigenous vermiculated sailfin 

catfish (Pterygoplichthys disjunctivus) above the Alexander Spring vent, 

February 2007. Photograph courtesy of Brian MacGregor, used with permission. 
24 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Table 8. Number of specimens (n) and percent composition (%) of macroinvertebrates collected by dip net from Alexander Spring, 

February-October 2007.

[Values represent material as subsampled to obtain the target number of organisms required for calculation of the Stream Condition Index. LPIL, lowest 

practicable identification level]

Clade Taxon

Feb. 1, 2007 May 10, 2007 Aug. 7, 2007 Oct. 10, 2007

n % n % n % n %

Gastropoda

Hirudinea

Oligochaeta

Amphipoda

Isopoda

Decapoda

Diptera

Ephemeroptera

Hemiptera

Total

Number of Taxa

Amnicola dalli

Aphaostracon sp.

cf. Aphaostracon sp.

cf. Tarebia sp.

Haitia cubensis

Hydrobiidae sp. C Line

Melanoides turricula

Planorbella scalaris

Pomacea paludosa

Spilochlamys gravis

Gloiobdella elongata

tubificoid Naididae immature sp. A (LPIL)

Gammarus cf. tigrinus LeCroy

Gammarus sp.

Hyalella azteca complex LeCroy

Cassidinidea ovalis

Palaemonetes paludosus

Procambarus sp. (immature)

Chironomus sp.

Cladopelma sp.

Dicrotendipes sp. A Epler

Polypedilum halterale group Epler

Polypedilum nubifer

Pseudochironomus sp.

Caenis sp.

Callibaetis floridanus

Trepobates subnitidus

17

4

1

1

76

3

4

1

2

1

110

10

15.5

3.6

0.9

0.9

69.1

2.7

3.6

0.9

1.8

0.9

101

1

1

1

3

1

1

1

110

8

91.8

0.9

0.9

0.9

2.7

0.9

0.9

0.9

62

26

6

5

2

2

2

3

1

1

110

10

56.4

23.6

5.5

4.5

1.8

1.8

1.8

2.7

0.9

0.9

11

6

36

1

1

7

16

18

1

2

4

1

2

1

1

1

1

110

17

10.0

5.5

32.7

0.9

0.9

6.4

14.5

16.4

0.9

1.8

3.6

0.9

1.8

0.9

0.9

0.9

0.9
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 25

Table 9. Fishes collected or observed in Alexander Spring and Silver Glen Springs in 2007. 

[n, total number of specimens; %, percent composition; >, greater than value. Relative abundances are considered qualitative based on visual estimates for 

several species]

Family Species Alexander Spring Silver Glen Springs

n % n %

Lepisosteidae

Amiidae

Anguillidae

Cyprinidae

Catostomidae

Ictaluridae

Callichthyidae

Loricariidae

Aphredoderidae

Mugilidae

Atherinopsidae

Belonidae

Fundulidae

Poeciliidae

Moronidae

Centrarchidae

Percidae

Lutjanidae

Elassomatidae

Cichlidae

Gobiidae

Total

Number of Taxa

Lepisosteus osseus

Lepisosteus platyrinchus

Amia calva

Anguilla rostrata

Notemigonus crysoleucas

Notropis harperi

Notropis petersoni

Opsopoeodus emiliae

Pteronotropis metallicus

Erimyzon sucetta

Ameiurus nebulosus

Noturus gyrinus

Hoplosternum littorale 1

Pterygoplichthys disjunctivus 1

Aphredoderus sayanus

Mugil cephalus

Labidesthes sicculus

Menidia beryllina

Strongylura marina

Fundulus seminolis

Lucania goodei

Lucania parva

Gambusia holbrooki

Heterandria formosa

Poecilia latipinna

Morone saxatilis

Lepomis auritus

Lepomis gulosus

Lepomis macrochirus

Lepomis marginatus

Lepomis microlophus

Lepomis punctatus

Micropterus salmoides

Percina nigrofasciata

Lutjanus griseus

Elassoma okefenokee

Oreochromis aureus 1

Gobiosoma bosc

1

2

2

15

526

18

34

17

1

4

3

30

23

476

5

44

195

46

25

10

127

25

3

2

5

9

12

12

2

1,674

29

0.06

0.12

0.12

0.90

31.42

1.08

2.03

1.02

0.06

0.24

0.18

1.79

1.37

28.43

0.30

2.63

11.65

2.75

1.49

0.60

7.59

1.49

0.18

0.12

0.30

0.54

0.72

0.72

0.12

7

1

>100

75

21

2

1

±36

1

4

12

>224

>52

1

>200

5

1

10

28

6

±20

1

2

1

811

24

0.86

0.12

12.33

9.25

2.59

0.25

0.12

4.44

0.12

0.49

1.48

27.62

6.41

0.12

24.66

0.62

0.12

1.23

3.45

0.74

2.47

0.12

0.25

0.12

1 Nonindigenous species.
26 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Apopka Spring

Apopka Spring (figs. 1 and 13, table 1) is a second 

magnitude spring (mean and median discharge 28.1 and 

26.8 ft3

/s, respectively) (Rosenau and others, 1977; Scott and 

others, 2004). The spring discharges at the bottom of Lake 

Apopka from a deep bowl-shaped depression into a circular 

spring pool approximately 180 ft in diameter. The vent 

opening is about 45 ft below the water surface of the lake. The 

spring emerges from an underground cave system; the vent 

opening narrows vertically downward into the limestone for 

16 ft, and then slopes northward at about 45 degrees to a depth 

of 90 ft as determined by cave divers. The spring discharge 

pool is clear when springflow is high and clouded by lake 

water when flow is low. When the lake is quiescent, a gentle 

boil may be visible at the pool surface. Emergent vegetation 

and an organic muck bottom surround the pool perimeter in 

the cove area, which is buffered by marsh and lowland swamp 

forests along the western shoreline. Hurricanes that affected 

the area in 2004 deposited debris and a thick floating mass 

of vegetation, blanketing the western shoreline, so that the 

distance between the spring vent and the new shoreline was 

reduced to about 10 to 15 ft during this study. The areal extent 

of the Apopka springshed is 17.7 mi2

.

Land Use

Land use in the Apopka springshed remains predominantly agricultural; however, increased urban land use 

from 1973 to 2004 resulted in the decline of other land-use 

types (fig. 4). Open-water/wetlands had decreased by more 

than 5 percent during the 31-year period and were nearly 

nonexistent by 2004. Land use in the springshed in 1973 

consisted of agriculture (92.7 percent), open-water/wetlands 

Figure 13. Diver taking discharge measurements at Apopka 

Spring vent. Photograph is courtesy of Jill Heinreth, Karst Environmental Services, Inc., and the SJRWMD, used with permission. 

(5.4 percent), forestland (1.9 percent), and urban/mining/

transportation/recreation (less than 0.1 percent). Land use in 

the springshed in 2004 consisted of agriculture (80.6 percent), 

urban/mining/transportation/recreation (19.3 percent), and 

open-water/wetlands (0.1 percent). By 2004, municipal and 

centralized sewer systems, currently the primary means of 

wastewater treatment and disposal, had replaced most of the 

septic systems in the Apopka springshed. By 2005, treated 

(reclaimed) wastewater was being applied to 5.7 mi2

 of land 

surface in the southern half of the Apopka springshed.

Discharge

Apopka Spring is a submerged spring, and accurate 

discharge measurements must be made at the vent opening 

by scuba divers. The USGS measured the spring discharge 

seven times from 1971 to 1992. Since 1997, a contractor for 

the SJRWMD has measured discharge at least four times per 

year. Spring discharge is controlled mostly by the regulated 

water level in Lake Apopka, with discharge diminished by 

higher lake levels. Annual discharge for Apopka Spring and 

rainfall in the springshed averaged 28.1 ft3

/s and 51.22 in., 

respectively (fig. 14). Average annual discharge for Apopka 

Spring ranged from 23.9 ft3

/s in 2001 to 66.8 ft3/s in 1989. 

Measured (instantaneous) discharge from Apopka Spring averaged 27.2 ft3

/s, and ranged from 21.0 ft3/s in September 2001 

to 70.4 ft3

/s in November 1988 (fig. 15). The highest discharge 

measurements for Apopka Spring made in 1988-89 likely 

are erroneous and may have resulted from an undocumented 

decrease in the size of the vent opening. Occasionally, tree 

debris and anchors partially block the Apopka Spring vent, 

which results in a higher flow velocity until the spring vent is 

cleared. Diving at Apopka Spring is dangerous and visibility is 

restricted to the immediate area just above the vent; therefore, 

any vent obstructions could have easily been unobserved at 

the time when abnormally high measurements were made. 

Using artificially high flow velocities with the original crosssectional opening area of the vent would elevate the value of 

mean discharge calculations. Therefore, average discharges 

shown for Apopka Spring reported here do not include those 

measurements made in 1988-89.

Water Chemistry and Age

Water-quality samples were collected from Apopka 

Spring once in 1972, periodically from 1986 to 1990, 

and quarterly from 1995 to the present by the SJRWMD 

and/or USGS. Apopka Spring has a Ca-Mg-HCO3

 water type 

(fig. 9), low dissolved solids (137 mg/L), and is at equilibrium 

(saturated) with respect to calcite and slightly undersaturated 

with respect to dolomite (table 3). Median values of pH, 

dissolved oxygen, and dissolved solids were 8.1, 3.8 mg/L, 

and 146 mg/L, respectively. The 3

H concentration of 2.3 TU 

(Toth, 2003) indicates recent recharge. Apopka spring water 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 27

APOPKA SPRING

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

70

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

ANNUAL DISCHARGE, IN

CUBIC FEET PER SECOND

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

ANNUAL RAINFALL, IN INCHES

SPRING DISCHARGE

YEAR

ANNUAL DISCHARGE =

28.1 CUBIC FEET PER SECOND

AVERAGE

AVERAGE ANNUAL RAINFALL

= 51.22 INCHES

ANNUAL RAINFALL

EXPLANATION

Figure 14. Average annual discharge for Apopka Spring and rainfall for the Apopka springshed. 

INSTANTANEOUS DISCHARGE

AVERAGE INSTANTANEOUS DISCHARGE

APOPKA SPRING EXPLANATION

20

30

40

50

60

70

80

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

YEAR

DISCHARGE, IN CUBIC FEET PER SECOND

AVERAGE INSTANTANEOUS

DISCHARGE = 27.2 CUBIC FEET PER SECOND

Figure 15. Periodic discharge data for Apopka Spring,1971-2007. Data collected by the St. Johns River 

Water Management District (SJRWMD) and U.S. Geological Survey. SJRWMD data used with permission. 
28 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

YEAR

1970 1980 1990 2000 2010

NITRATE-N CONCENTRATION, IN MILLIGRAMS PER LITER

0

1

2

3

4

5

6

De Leon Spring

De Leon Spring Run

Gemini Springs North Boil

Gemini Springs South Boil

Gemini Springs Run

Green Spring

Green Spring Run

Apopka Spring

EXPLANATION

Figure 16. Nitrate-N concentrations in water from Apopka, De Leon, Gemini, and Green Springs. 

has a slightly enriched delta 18O and 2H composition that 

plots along an evaporation trend line for lakes (Toth, 2003), 

indicating that recharge has undergone some evaporation.

Nitrate-N concentrations in Apopka Spring were the 

highest of all springs in this study (median 4.4 mg/L during 

1986-2007), and nitrate-N concentrations showed large 

fluctuations over time, from 0.42 to 5.4 mg/L (fig. 16, table 3). 

From May 1986 to November 1989, nitrate-N concentrations 

ranged from 2.5 to 5.4 mg/L. Since May 1990, nitrate-N 

concentrations ranged from 0.4 to 5.4 mg/L. Nitrate-N 

concentrations showed a significant (p < 0.01) increase 

from 1972 to 2007 (table 6). Phosphorus (total P) concentrations in Apopka Spring also fluctuated widely over the past 

20 years; the earliest sample had a P concentration of 

0.033 mg/L in October 1986. Although most water samples 

from Apopka Spring had P concentrations that fluctuated 

from 0.02 to 0.06 mg/L, several spikes in P concentration as 

high as 0.6 mg/L have occurred sporadically over the past 

20 years (fig. 17); however, phosphorus concentrations 

showed a significant (p < 0.04) decreasing trend from 1972 to 

2007 (table 6). Elevated nitrate-N concentrations and several 

spikes in phosphorus concentrations in Apopka Spring likely 

are related to the springshed having more than 50 percent 

agricultural land use. In 2005-06 the USGS sampled Apopka 

Spring on two occasions for chlorophyll-a and pheophytin-a

to determine the richness of suspended photosynthetic 

organisms in the boil approximately 45 ft above the spring 

vent; chlorophyll-a values ranged from 13.9 to 18.4 μg/L and 

pheophytin-a values ranged from to 3.2 to 5.8 μg/L (app. 3).

The age of water discharging from Apopka Spring was 

determined by measuring the concentration of 3

H, 3He, 4He, 

and neon in the spring discharge in August 1999. Apopka 

Spring had a 3

H concentration of 2.9 TU, which indicates that 

the younger fraction of the water likely is less than 46 years 

old, whereas the 3

H /3He age indicated an age of 25 years for 

the younger fraction.

Aquatic Communities

Due to the location of Apopka Spring at the bottom 

of Lake Apopka, sampling of the benthos could only be 

accomplished using a petite ponar dredge. On each of four 

sampling occasions, four replicate grabs were made. The 

dredge often had to be deployed numerous times to obtain a 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 29

1970 1980 1990 2000 2010

0.01

0.1

1

10

YEAR

PHOSPHORUS (AS P) CONCENTRATION,

IN MILLIGRAMS PER LITER

De Leon Spring

De Leon Spring Run

Gemini Springs North Boil

Gemini Springs South Boil

Gemini Springs Run

Green Spring

Green Spring Run

Apopka Spring

EXPLANATION

Figure 17. Phosphorus concentrations in water from De Leon, Gemini, Green, and Apopka Springs. 

suitable collection, because large snags and other debris often 

prevented the jaws of the dredge from closing completely. 

An effort was made to drop the dredge over the vent (that is, 

lower it within the water column over the boil). The substrate 

mostly consisted of coarse decayed wood and organic matter.

A total of 29 macroinvertebrate taxa were collected 

from Apopka Spring, with the number of taxa from each 

sampling event ranging from 7 in March 2006 to 13 in July 

2006 (table 10). The overall density of organisms ranged from 

8.7 × 103

 per m2 (93.7 × 103 per ft2) in March 2006 to 13.8 × 

103

 per m2 (148.6 × 103 per ft2) in December 2005. Samples 

were dominated by amphipods (76.0 percent; Hyallela azteca

complex) and isopods (7.2 percent; Caecidotea racovitzai

australis and/or Caecidotea sp.). Across all sampling dates, 

the log2

 Shannon-Wiener index ranged from 0.56 to 2.14, 

Simpson’s index of diversity ranged from 0.14 to 0.60, 

Pielou’s evenness ranged from 0.20 to 0.59, and the Florida 

index ranged from 1 to 2 with a mean of 1.5 (table 4).

A boat-mounted electroshocker was used on May 25, 

2006, to sample fishes along the shoreline of Lake Apopka 

around Apopka Spring and in the Gourd Neck cove of the 

lake. A total of 554 specimens were collected representing 22 

species of 16 genera and 11 families (table 11). Specimens 

were dominated by centrarchids (82.5 percent, especially 

Lepomis macrochirus, Micropterus salmoides, and L. auritus), 

poeciliids (6.5 percent, especially Gambusia holbrooki), and 

the atherinopsid Labidesthes sicculus (4.9 percent). These 

common species are typical of both lotic waters and margins 

of vegetated lakes. During most sampling events, a large 

aggregation of L. sicculus was observed schooling at the 

surface in the clear water of the spring boil. A few large adults 

of the nonindigenous Oreochromis aureus were collected; one 

or more of these were mouthbrooding females that disgorged 

a large number of young-of-the-year fry into a cooler used 

as a holding well (these individuals are not included in the 

summary total). Three passes with the electroshocking boat 

were made along most of the shoreline of Gourd Neck, and 

qualitative field observations suggested that fish appeared to 

be most abundant (and many of the largest adults present) in 

closest proximity to the spring outflow. Catch per-unit-effort 

was lowest along the shallow northern margin of Gourd Neck 

(25 fish/min for all species) and greatest in the two passes 

along the western and southern shoreline nearest the spring 

(40-45 fish/min).
30 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Table 10. Number of specimens (n) and percent density (%) per square meter of macroinvertebrates collected by pooled petite ponar 

dredge samples (n = 4 per date) from Apopka Spring, December 2005-September 2006.

[LPIL, lowest practicable identification level]

Clade Taxon

Dec. 30, 2005 Mar. 28, 2006 July 13, 2006 Sept. 21, 2006

n % n % n % n %

Porifera

Turbellaria

Gastropoda

Bivalvia

Hirudinea

Oligochaeta

Amphipoda

Isopoda

Diptera

Odonata

Total

Number of Taxa

Spongilla sp.

Tricladida (LPIL)

Turbellaria (LPIL)

Amnicola dalli

cf. Floridobia sp.

cf. Notogillia wetherbyi

Hydrobiidae (LPIL)

Melanoides tuberculata

Planorbella scalaris

Bivalvia (LPIL)

cf. Musculium sp.

Pisidiidae (LPIL)

Desserobdella phalera

Helobdella stagnalis

Helobdella triserialis

Myzobdella lugubris

Dero trifida

Eclipidrilus palustris

Pristina leidyi

Psammoryctides convolutus

tubificoid Naididae immature sp. A (LPIL)

Hyalella azteca complex Lecroy

Caecidotea racovitzai australis

Caecidotea sp.

Chironomus sp.

Glyptotendipes meridionalis group

Glyptotendipes paripes

Goeldichironomus amazonicus

Perithemis tenera seminole

345

57

115

57

12,572

14

72

402

115

57

13,806

10

2.5

0.4

0.8

0.4

91.1

0.1

0.5

2.9

0.8

0.4

86

86

86

216

8,060

86

86

8,706

7

1.0

1.0

1.0

2.5

92.6

1.0

1.0

1,379

431

172

86

259

86

86

86

517

259

172

6,552

690

10,775

13

12.8

4.0

1.6

0.8

2.4

0.8

0.8

0.8

4.8

2.4

1.6

60.8

6.4

1,034

431

86

86

776

86

8,448

948

1,552

172

13,619

10

7.6

3.2

0.6

0.6

5.7

0.6

62.0

7.0

11.4

1.3
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 31

Table 11. Fishes collected by boat electroshocker in vicinity of Apopka, Bugg, Rock, and Wekiwa springs in 2006. 

[n, total number of specimens; %, percent composition per sample]

Family Species

Apopka Spring Bugg Spring Rock Springs Wekiwa Springs

n % n % n % n %

Lepisosteidae Lepisosteus osseus 1 0.18

Lepisosteus platyrinchus 7 1.26 2 0.56 5 5.49 5 1.57

Amiidae Amia calva 2 0.36 9 2.53 7 7.69 13 4.09

Anguillidae Anguilla rostrata 2 2.20

Clupeidae Dorosoma petenense 1 0.18

Cyprinidae Notemigonus crysoleucas 3 0.54 8 8.79 49 15.41

Notropis maculatus 1 0.18

Notropis petersoni 6 1.89

Catostomidae Erimyzon sucetta 3 0.84 13 14.29 32 10.06

Ictaluridae Ameiurus catus 1 0.18 1 1.10

Ameiurus natalis 2 0.63

Ameiurus nebulosus 4 0.72 2 2.20

Callichthyidae Hoplosternum littorale 1 1 1.10

Loricariidae Pterygoplichthys disjunctivus 1 2 2.20 16 5.03

Esocidae Esox americanus 6 1.69

Atherinopsidae Labidesthes sicculus 27 4.87 1 1.10

Fundulidae Fundulus seminolis 3 0.54 7 1.97 3 3.30

Lucania goodei 3 0.54 2 0.56 5 1.57

Lucania parva 2 0.63

Poeciliidae Gambusia holbrooki 35 6.32 2156 43.82 1 1.10 1 0.31

Heterandria formosa 1 0.18 5 1.40

Poecilia latipinna 56 15.73

Centrarchidae Lepomis auritus 34 6.14 4 1.12 16 17.58 45 14.15

Lepomis gulosus 13 2.35 4 1.12 15 4.72

Lepomis macrochirus 336 60.65 9 2.53 39 12.26

Lepomis marginatus 2 0.36

Lepomis microlophus 17 3.07 26 7.30 23 7.23

Lepomis punctatus 52 14.61 18 19.78 36 11.32

Micropterus salmoides 46 8.30 13 3.65 11 12.09 27 8.49

Pomoxis nigromaculatus 9 1.62

Percidae Etheostoma fusiforme 1 0.18

Percina nigrofasciata 2 0.63

Cichlidae Oreochromis aureus1 3

7 1.26 2 0.56

Total 554 356 91 318

Number of Taxa 22 16 15 17

1

 Nonindigenous species.

2

 Disproportionately large number of specimens collected as schooling adults at the surface.

3

 An additional 288 small fry collected when disgorged from buccal cavities of adult mouthbrooding females, not included.
32 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Bugg Spring

Bugg Spring (figs. 1 and 18, table 1) is a second magnitude 

spring (mean and median discharge 11.2 and 10.3 ft3

/s, respectively) (Rosenau and others, 1977; Scott and others, 2004). 

Bugg Spring discharges into a spring run (fig. 19) that flows 

about 1.5 mi north and east into Helena canal, which connects 

Lake Denham and Lake Harris. The spring has a deep circular 

pool about 400 ft in diameter. Water discharges from a cave 

at the bottom of the spring pool at a depth of approximately 

170 ft below the water surface. The limestone walls of the 

spring pool are almost vertical and extend to the vent on all 

sides except the western shoreline. No boil is evident on the 

pool surface due to the substantial depth of the spring vent and 

large pool diameter. Except for algae, there is little aquatic 

vegetation in the spring pool; algae and macrophytes (mostly 

emergent and floating) are present in the spring run. Low-lying 

areas around the spring are densely forested, with sand hills 

present along the southern shoreline. The areal extent of Bugg 

springshed is 10.1 mi2

.

Land Use

Land use in the Bugg springshed changed little from 1973 

to 2004, with some transition of open-water/wetlands to forestland as a result of land-surface drying and enhanced drainage 

(fig. 4). Land use in the springshed in 1973 consisted of forestland (66.4 percent), open-water/wetlands (33.6 percent), and 

urban/mining/transportation/recreation (less than 0.1 percent). 

Land use in the springshed in 2004 consisted of forestland 

(89.1 percent), open-water/wetlands (10.9 percent), and urban/

mining/transportation/recreation (less than 0.1 percent). By 

2004, a municipal sewer system was the primary mean of 

wastewater treatment and disposal, having replaced many of the 

relatively few septic systems in the northern part of the Bugg 

springshed prior to that time. Reclaimed wastewater, mostly 

imported from outside the springshed, was being applied as 

spray irrigation to 0.77 mi2

 of the land surface in the northern 

part of the Bugg springshed within 1 mi of the spring head.

Discharge

Discharge from Bugg Spring was measured intermittently 

by the USGS from 1943 to 1985. Since 1990, discharge has 

been measured at least monthly by the landowner. Discharge 

for Bugg Spring averaged 11.2 ft3

/s annually and varied 

greatly with rainfall, which averaged 50.22 in/yr in the springshed (fig. 20). Average annual discharge for Bugg Spring 

ranged from 8.1 ft3

/s in 2000 to 18.6 ft3/s in 1960. Spring 

discharge is affected in winter months by nearby pumping of 

the Floridan aquifer system, particularly for freeze protection 

of local agricultural and horticultural crops (J. Branham, oral 

commun., 2005). Measured (instantaneous) discharge from 

Bugg Spring averaged 11.0 ft3

/s, and ranged from a pumpingaffected minimum of 3.70 ft3

/s in December 2000 to 19.8 ft3/s 

in July 1991 (fig. 21).

Water Chemistry and Age

Bugg Spring has been sampled intermittently by the 

USGS since 1967. The SJRWMD sampled the spring three 

times in 1991 and at least two to four times per year since 

Figure 18. Surface view of Bugg Spring pool. Large structure 

is U.S. Navy sonar testing facility. Photograph by S.J. Walsh, 

September 21, 2006. 

Figure 19. Bugg Spring run downstream of spring pool. 

Photograph by S.J. Walsh, May 25, 2006. 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 33

YEAR

ANNUAL DISCHARGE =

11.2 CUBIC FEET PER SECOND

AVERAGE

AVERAGE ANNUAL RAINFALL

= 50.22 INCHES

BUGG SPRING

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

ANNUAL DISCHARGE, IN

CUBIC FEET PER SECOND

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

ANNUAL RAINFALL, IN INCHES

SPRING DISCHARGE

ANNUAL RAINFALL

EXPLANATION

Figure 20. Average annual discharge for Bugg Spring and rainfall for the Bugg springshed. 

BUGG SPRING

0

10

20

30

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

SPRING DISCHARGE, IN CUBIC FEET PER SECOND

AVERAGE INSTANTANEOUS DISCHARGE

=11.0 CUBIC FEET PER SECOND

INSTANTANEOUS DISCHARGE

AVERAGE INSTANTANEOUS DISCHARGE

EXPLANATION

YEAR

Figure 21. Periodic discharge data for Bugg Spring, 1943-2007. Data collected by the St. Johns River 

Water Management District (SJRWMD) and U.S. Geological Survey. SJRWMD data used with permission. 
34 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

YEAR

NITRATE-N CONCENTRATION,

IN MILLIGRAMS PER LITER

1950 1960 1970 1980 1990 2000 2010

0

0.5

1.0

1.5

2.0

2.5

-0.5

BUGG SPRING

BUGG SPRING RUN

ROCK SPRINGS

WEKIWA SPRINGS

EXPLANATION

Figure 22. Nitrate-N concentrations in water from Bugg, Rock, and Wekiwa Springs. 

1997. At the time of this study, the SJRWMD and USGS 

jointly sampled Bugg Spring at least four times per year.

Bugg Spring has a Ca-HCO3

 water type (fig. 9) and is 

at equilibrium (saturated) with respect to calcite and slightly 

undersaturated with respect to dolomite (table 3). Median 

values of pH, dissolved oxygen, and dissolved solids were 

7.6, 1.4 mg/L, and 167 mg/L, respectively. A 3

H concentration 

of greater than 2.3 TU was reported by Toth (2003). Delta 

18O and 2

H values were slightly enriched and plot along an 

evaporation trend line for lakes (Toth 2003), indicating that 

Bugg Spring receives recharge from surface water. Nutrient 

concentrations, such as nitrate-N, total P, and orthophosphate, 

have remained slightly higher than background conditions for 

the period of record (Maddox and others, 1992). Nitrate-N 

concentrations in Bugg Spring have remained relatively 

constant over time (fig. 22). In May 1985, the nitrate-N 

concentration was 0.58 mg/L, and nitrate-N concentrations 

ranged from 0.46 mg/L in August 1999 to 0.63 mg/L in March 

2005 (fig. 22). Median concentrations of nitrate-N and total 

P for the period from 1972 to 2006 were 0.58 and 0.07 mg/L, 

respectively. Phosphorus (total P) concentrations in Bugg 

Spring generally have fluctuated between 0.04 to 0.09 mg/L 

(fig. 23), with a median value of 0.07 mg/L; however, there 

were large spikes in P concentrations above 0.2 mg/L in June 

2002 and March 2004. In 2006, the USGS sampled Bugg 

Spring for chlorophyll-a and pheophytin-a to determine the 

richness of suspended photosynthetic organisms in the run 

where discharge measurements are made, approximately 

200 ft downstream of the spring vent.

The age of water discharging from Bugg Spring was 

determined by measuring the concentration of 14C and 13C 

in the spring discharge in April 2001. Bugg Spring had a 14C 

concentration of 42 pmc and a delta 13C value of -9.95 per mil. 

Based on the 14C results, and the use of the Fontes and Garnier 

(1979) model, the estimated age of water from Bugg Spring is 

less than 50 years.

Aquatic Communities

Because of the pool depth at Bugg Spring, the collection 

of macroinvertebrates was limited to a reach extending about 

150 m (492 ft) downstream of the U.S. Navy fence, which 

spans the head of the run. Substrate along the spring run 

consisted of sand, soft organic detritus, muck, mats of filamentous algae, encrusting periphyton, and an abundance of dead 

gastropod shells.

A total of 39 macroinvertebrate taxa were collected by 

petite ponar dredge from Bugg Spring across four sampling 

dates (table 12). It is possible that five taxa, Dero sp., 

Goeldichironomus sp., immature Dicrotendipes sp., immature 

Melanoides sp., and Spirosperma sp., represented congeneric 

taxa identified to species; therefore, richness may have been 

lower than the 39 recorded. The number of taxa collected 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 35

1970 1980 1990 2000 2010

0.01

0.1

1

10

YEAR

BUGG SPRING

BUGG SPRING RUN

ROCK SPRINGS

WEKIWA SPRINGS

EXPLANATION

PHOSPHORUS (AS P) CONCENTRATION,

IN MILLIGRAMS PER LITER

Figure 23. Phosphorus concentrations in water from Bugg, Rock, and Wekiwa Springs. 

with this gear ranged from 12 in December 2005 to 17 in 

March 2006. Pooled samples were dominated by oligochaetes 

(41.7 percent of all organisms collected, consisting of 10 or 

fewer taxa, including immature forms and those not identifiable 

to species), amphipods (27.4 percent; Hyalella azteca complex), 

and gastropods (15.8 percent; 6 or fewer taxa, primarily 

Melanoides tuberculata and immature Melanoides). 

Density of all organisms ranged from approximately 

2.9 × 103

 per m2 (31.9 × 103 per ft2) in December 2005 to 

10.4 × 103

 per m2 (112.4 × 103 per ft2) in July 2006. For petite 

ponar samples pooled across all dates, the log2

 Shannon-Wiener 

index ranged from 2.21 to 3.76, Simpson’s index of diversity 

ranged from 0.62 to 0.91, Pielou’s evenness ranged from 0.58 

to 0.92, and the Florida index was consistently zero (table 4).

A total of 58 macroinvertebrate taxa were identified in subsamples collected by dip net from Bugg Spring 

(table 13); the fewest (11) were collected in the December 

2005 sample and the most (26) in the March 2006 sample. 

The target number of organisms (110) was not obtained 

during sorting of the December 2005 (n = 45), March 2006 

(n = 97), or July 2006 (n = 108) collections; the especially 

low number for the December 2005 sample likely accounts 

for the minimum number of taxa collected on that date and 

may have been the result of ineffective sampling. Subsamples 

from all dates combined were numerically dominated by 

amphipods (28.9 percent; all Hyallela azteca complex), oligochaetes (18.3 percent), and gastropods (15.3 percent). The 

nonindigenous snails Melanoides tuberculata and M. turricula

dominated the December 2005 dip net sample (57.8 percent) 

and constituted a substantial proportion (15.4 percent) of the 

September 2006 sample. For dip net samples pooled across 

all dates, the log2

 Shannon-Wiener index ranged from 2.55 to 

4.09, Simpson’s index of diversity ranged from 0.63 to 0.93, 

Pielou’s evenness ranged from 0.57 to 0.87, the SCI ranged 

from 7 to 34 with a mean of 19.25, and percent very tolerant 

taxa ranged from 19.3 to 77.8 (table 5).

An attempt to collect or observe fishes in the Bugg Spring 

pool was impractical due to the spring depth and prohibited 

motorized boat access near the U.S. Navy sonar calibration 

facility. However, the spring run was accessed on June 7, 

2006, with an electroshocker boat launched at Lake Harris. 

Two electroshocking passes (with a total of 30 minutes power 

output) were made from the U.S. Navy fence just downstream 

of the spring pool to near the mouth of the spring run. Margins 

of the spring run were shallow and contained large amounts 

of thick brush, overhanging branches, floating logs, and 

submerged or partially exposed large woody debris, making 

electrofishing difficult and somewhat inefficient. It is likely 

that the number of fallen trees and amount of woody debris in 

the spring run was increased by hurricanes in 2004.

A total of 356 fish specimens were collected, representing 16 species of 12 genera and 8 families (table 11). 

Specimens were dominated by poeciliids (61 percent, mostly 
36 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Table 12. Number of specimens (n) and percent density (%) per square meter of macroinvertebrates collected by pooled petite ponar 

dredge samples (n = 3 per date) from Bugg Spring, December 2005-September 2006.

[LPIL, lowest practicable identification level]

Clade Taxon

Dec. 30, 2005 Mar. 17, 2006 July 12, 2006 Sept. 21, 2006

n % n % n % n %

Porifera

Turbellaria

Gastropoda

Bivalvia

Hirudinea

Oligochaeta

Arachnida

Amphipoda

Decapoda

Diptera

Ephemeroptera

Total

Number of Taxa

Porifera (LPIL)

Ephydatia sp.

Tricladida (LPIL)

Amnicola dalli

Ancylidae (LPIL)

Hebetancylus excentricus

Melanoides sp. (immature)

Melanoides tuberculata

Viviparus georgianus

Bivalvia (LPIL)

Pisidiidae (LPIL)

Sphaerium striatinum

Erpobdella punctata

Helobdella stagnalis

Helobdella triserialis

Mooreobdella tetragon

Dero digitata

Dero sp.

Dero trifida

Ilyodrilus templetoni

Limnodrilus hoffmeisteri

Naididae (LPIL)

Spirosperma ferox

Spirosperma sp.

tubificoid Naididae immature sp. A (LPIL)

tubificoid Naididae immature sp. B (LPIL)

Piona sp.

Hyalella azteca complex Lecroy

Cambaridae (LPIL)

Chironomus sp.

Dicrotendipes modestus

Dicrotendipes sp. (immature)

Einfeldia natchitocheae

Goeldichironomus carus

Goeldichironomus sp.

Palpomyia/Sphaeromias group Brigham

Tanytarsus sp. G Epler

Zavreliella marmorata

Caenis diminuta

115

29

316

115

172

172

402

718

690

144

29

57

2,959

12

3.9

1.0

10.7

3.9

5.8

5.8

13.6

24.3

23.3

4.9

1.0

1.9

144

230

144

29

29

431

101

532

230

158

144

259

230

259

101

230

29

3,280

17

4.4

7.0

4.4

0.9

0.9

13.1

3.1

16.2

7.0

4.8

4.4

7.9

7.0

7.9

3.1

7.0

0.9

115

345

575

129

86

402

546

1,494

172

6,149

86

86

86

172

10,443

14

1.1

3.3

5.5

1.2

0.8

3.8

5.2

14.3

1.6

58.9

0.8

0.8

0.8

1.6

230

115

115

805

1,724

345

115

805

690

690

230

230

2,644

920

115

9,773

15

2.4

1.2

1.2

8.2

17.6

3.5

1.2

8.2

7.1

7.1

2.4

2.4

27.1

9.4

1.2
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 37

Table 13. Number of specimens (n) and percent composition (%) of macroinvertebrates collected by dip net from Bugg Spring, 

December 2005-September 2006. 

[Values represent material as subsampled to obtain the target number of organisms required for calculation of the Stream Condition Index. LPIL, lowest 

practicable identification level]

Clade Taxon

Dec. 30, 2005 Mar. 17, 2006 July 12, 2006 Sept. 21, 2006

n % n % n % n %

Gastropoda

Bivalvia

Hirudinea

Oligochaeta

Arachnida

Amphipoda

Decapoda

Hebetancylus excentricus

Laevapex sp.

Melanoides sp. (immature)

Melanoides tuberculata

Melanoides turricula

Planorbella scalaris

Viviparus georgianus

Bivalvia (LPIL)

Corbicula fluminea

Sphaerium striatinum

Utterbackia imbecilis

Erpobdellidae (LPIL)

Glossiphoniidae (LPIL)

Helobdella stagnalis

Mooreobdella tetragon

Aulodrilus pigueti

Bratislavia unidentata

Dero flabelliger

Dero pectinata

Ilyodrilus templetoni

Limnodrilus hoffmeisteri

Nais communis complex

Nais elinguis

Pristina leidyi

Spirosperma ferox

Acariformes (LPIL)

Limnesia sp.

Hyalella azteca complex LeCroy

Palaemonetes sp.

Procambarus sp. (immature)

1

21

5

3

3

1

1

5

3

2.2

46.7

11.1

6.7

6.7

2.2

2.2

11.1

6.7

2

1

3

3

2

1

8

4

2.1

1.0

3.1

3.1

2.1

1.0

8.2

4.1

1

1

4

3

3

1

8

1

1

1

65

1

0.9

0.9

3.7

2.8

2.8

0.9

7.4

0.9

0.9

0.9

60.2

0.9

2

15

2

1

6

1

1

5

3

5

10

1

5

1

35

2

1.8

13.6

1.8

0.9

5.5

0.9

0.9

4.5

2.7

4.5

9.1

0.9

4.5

0.9

31.8

1.8
38 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Table 13. Number of specimens (n) and percent composition (%) of macroinvertebrates collected by dip net from Bugg Spring, 

December 2005-September 2006.—Continued

[Values represent material as subsampled to obtain the target number of organisms required for calculation of the Stream Condition Index. LPIL, lowest 

practicable identification level]

Clade Taxon

Dec. 30, 2005 Mar. 17, 2006 July 12, 2006 Sept. 21, 2006

n % n % n % n %

Diptera

Ephemeroptera

Hemiptera

Odonata

Total

Number of Taxa

Beardius truncates

Bezzia/Palpomyia complex Brigham

Chironomus sp.

Cladotanytarsus sp. A Epler

Clinotanypus sp.

Cryptochironomus sp.

Dicrotendipes modestus

Dicrotendipes sp. (immature)

Einfeldia natchitocheae

Glyptotendipes sp.

Larsia decolorata

Monopelopia boliekae

Palpomyia/Sphaeromias group Brigham

Parachironomus supparilis

Polypedilum illinoense group Epler

Polypedilum tritum

Pseudochironomus sp.

Tanypus carinatus

Tanypus sp.

Tanytarsus sp.

Tanytarsus sp. G Epler

Tanytarsus sp. L Epler

Zavreliella marmorata

Caenis diminuta

Caenis sp.

Callibaetis floridanus

Mesovelia sp. (immature)

Coenagrionidae (LPIL)

1

1

1

45

11

2.2

2.2

100

5

1

1

1

9

7

1

1

1

1

1

6

20

2

2

7

4

3

1

97

26

5.2

1.0

1.0

1.0

9.3

7.2

1.0

1.0

1.0

1.0

1.0

6.2

20.6

2.1

2.1

7.2

4.1

3.1

100

1

3

3

1

1

5

1

1

1

1

108

22

0.9

2.8

2.8

0.9

0.9

4.6

0.9

0.9

0.9

0.9

100

7

2

1

2

2

1

110

22

6.4

1.8

0.9

1.8

1.8

0.9

100

1 Failed to obtain target number of subsampled organisms (100-110) during sorting process. 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 39

0

0

0.5 MILE

0.5 KILOMETER

81°54′30′′ 81 54 00° ′ ′′ 81 53 30° ′ ′′ 81 53 00° ′ ′′

28 45 30° ′ ′′

28 45 00° ′ ′′

Bugg Spring

Okahumpka

A

B

C

Figure 24. Aerial view of Bugg Spring and run showing differences in land use and riparian vegetation 

between upper and lower sections of the run. Circles A and B represent endpoints of upstream electrofishing 

pass, and circles B and C represent endpoints of downstream electrofishing pass in this study. 

Gambusia holbrooki) and centrarchids (30.3 percent, mostly 

Lepomis punctatus). Two specimens of the nonindigenous 

Oreochromis aureus were collected in the spring run, and 

the landowner of the spring-head property indicated that 

adults were common in the spring pool. The fish community 

in the spring run was relatively depauperate and overall 

abundance was low. Qualitative field observations indicated 

that total fish abundance was greatest in the upstream portion 

of the spring run and diminished in the lower section. 

Excluding G. holbrooki (all of which were collected in the 

first upstream pass), catch per-unit-effort for all other species 

was 9.0 fish/min in the upstream section (a distance of about 

580 m [0.36 mi], shown in figure 24) and was 4.5 fish/min in 

the downstream section (a distance of about 790 m [0.49 mi]).

The observed difference in relative abundance between 

the upstream and downstream sections of the spring run may 

be related to gear efficiency, habitat variation, or a combination 

of both. The upstream section was characterized by a heavy 

tree canopy, more in-stream woody debris, undercut banks 

with root mats and other structurally complex microhabitats 

(but devoid of aquatic macrophytes), and greater spring-water 

influence as evidenced by water clarity. The lower section 

of the spring run had a relatively open canopy, very shallow 

depth, extensive submergent, emergent, and floating marsh 

vegetation on the shoreline with a less defined bank, as well 

as lower water clarity. The substrate throughout the run was 

flocculent muck and detritus, in the upstream section overlain 

by leaf packs, branches, and dead gastropod shells. Large mats 

of floating algae were observed in several areas of the spring 

run. Differences in riparian vegetation and land use between 

the upstream and downstream sections of the sinuous spring 

run are evident in an aerial photograph of the site (fig. 24).
40 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

De Leon Spring

De Leon Spring (fig. 1) is a second magnitude spring 

(mean and median discharge 27.9 and 26.4 ft3

/s, respectively) 

(Rosenau and others, 1977; Scott and others, 2004; Phelps and 

others, 2006). Although this spring is listed as “Ponce de Leon 

Springs” in the USGS Geographic Names Information System 

(http://geonames.usgs.gov), that name is not in general usage 

to avoid confusion with Ponce de Leon Springs in Holmes 

County, Florida. Discharge is from a cavern and chimney 

opening in the central part of a semicircular pool, forming 

a boil above the vent. The spring pool of De Leon Spring is 

impounded by a large concrete weir along the west wall, where 

discharge measurements were made; spring outflow then flows 

over a 3-ft drop and into a wide natural spring run that flows 

toward the west and discharges at about 0.25 mi into Lake 

Woodruff. The bottom of the spring pool is sand with exposed 

rock near the vent. Aquatic macrophytes are absent in the pool, 

although patches of algae are present seasonally. A concrete 

walkway with numerous ladders and access points encircles the 

spring pool. The spring is a popular recreational attraction and 

is used extensively for swimming and boating. Direct effects of 

human disturbance to the pool bottom necessitated collecting 

macroinvertebrate samples from the dam overflow area and in 

the broad section of the run immediately downstream of the 

dam, which was heavily vegetated with submergent, emergent, 

and floating macrophytes encrusted by abundant periphyton. 

The substrate where macroinvertebrates were collected varied 

extensively from rock and artificial hard surfaces, sand, and 

areas of extensive organic muck and detritus. The areal extent 

of the De Leon springshed is 10.8 mi2

.

Land Use

Land use in the De Leon springshed changed from 1973 

to 2004, mainly as a transition from forestland to agriculture, 

but the springshed remains mostly rural in character (fig. 4). 

Land use in the springshed in 1973 consisted of forestland 

(59.0 percent), open-water/wetlands (33.4 percent), agriculture 

(6.5 percent), and urban/mining/transportation/recreation 

(1.1 percent). Land use in the springshed in 2004 consisted 

of open-water surface/wetlands (32.9 percent), forestland 

(28.5 percent), agriculture (26.8 percent), urban/mining/transportation/recreation (9.5 percent), and non-forested/barren 

land (2.3 percent). As of 2004, a municipal sewer system had 

replaced septic systems in a 1.0-mi2

 area along the southern 

edge of the De Leon springshed, and no reclaimed wastewater 

was applied to the land surface within the springshed. Septic 

systems remain the primary means of wastewater treatment 

and disposal in the De Leon springshed.

Discharge

Discharge from De Leon Spring was measured by the 

USGS from 1929 to 2002. The SJRWMD measured discharge 

bimonthly from 1983 to 2005, and monthly since 2005. 

Discharge for De Leon Spring averaged 27.9 ft3

/s annually, and 

varied greatly with rainfall that averaged 56.02 in/yr within 

the springshed (fig. 25). Average annual discharge for De Leon 

Spring ranged from 19.2 ft3

/s in 2000 to 43.1 ft3/s in 2006. 

Measured (instantaneous) discharge for De Leon Spring averaged 32.5 ft3

/s, and ranged from 12.2 ft3/s in November 1997 to 

61.6 ft3

/s in August 2004 following Hurricane Charley (fig. 26).

Water Chemistry and Age

De Leon Spring has been sampled periodically by the 

USGS since 1932, with the highest sampling frequency 

occurring from 1956 to 1990. The SJRWMD sampled De Leon 

Spring from 1984 to 2005, and currently samples the spring four 

times per year. 

De Leon Spring has a mixed water type (fig. 9), and is 

slightly undersaturated with respect to calcite and dolomite. 

Median values of pH, dissolved oxygen, and dissolved solids 

were 7.6, 1.5 mg/L, and 416 mg/L, respectively (table 3). 

The delta 18O and 2

H composition plotted along the GMWL, 

or local MWL parallel to the GMWL, and the 3

H concentration was 2.1 TU (Toth, 1999). The delta 34S concentration 

was 13.9 per mil, which typically corresponds to low sulfate 

concentrations and indicates variable sources of sulfate, 

including rainfall, mixtures of shallow and deep ground water, 

and geochemical reactions along ground-water flow paths 

(Toth, 1999).

Nitrate-N concentrations increased from 1984 to 2005 

(0.7-1.4 mg/L), but decreased below 1.0 mg/L from May 2006 

to August 2007 (fig. 16). The median nitrate-N concentration 

from 1984 to 2007 was 0.9 mg/L. Excess dissolved nitrogen 

concentrations of about 1.5 mg/L were found during previous 

sampling events during May 2004 and August 2004 (Phelps 

and others, 2006). Water samples collected in 2005 (January 28, 

May 17, June 30, and September 1) also had excess dissolved 

nitrogen concentrations of about 1 mg/L. It is likely that denitrification was occurring in the Upper Floridan aquifer in the 

vicinity of De Leon Spring. Additional evidence for denitrification was indicated by the fractionation of nitrogen and oxygen 

isotopes of nitrate, which had elevated values relative to other 

spring-water samples (Phelps and others, 2006). Phosphorus 

(total P) concentrations in De Leon Spring generally have 

been uniform (0.03-0.06 mg/L) with a median concentration 

of 0.05 mg/L (fig. 17), although orthophosphate concentrations 

showed a significant (p < 0.001) decreasing trend over time 

(1968-2007) (table 6).

Water samples collected from De Leon Spring in May and 

August 2004 were analyzed for 64 organic chemicals commonly 

associated with wastewater sources and 52 pesticides. The 

following organic wastewater compounds were detected (in 

microgram per liter concentrations) in the May 2004 samples: 

phenol (E0.4), indole (E0.4), and p-cresol (2) (app. 4). Here, 

“E” denotes estimated concentrations reported by the laboratory 

that are quantifiable between the method detection limit and the 

method reporting level. No pesticides were detected in water 

samples from De Leon Spring (app. 5).
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 41

DE LEON SPRING

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

ANNUAL DISCHARGE, IN

CUBIC FEET PER SECOND

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

ANNUAL RAINFALL, IN INCHES

YEAR

AVERAGE ANNUAL RAINFALL

= 56.02 INCHES

ANNUAL DISCHARGE =

27.9 CUBIC FEET PER SECOND

AVERAGE

SPRING DISCHARGE

ANNUAL RAINFALL

EXPLANATION

Figure 25. Average annual discharge for De Leon Spring and rainfall for De Leon springshed. 

INSTANTANEOUS DISCHARGE

YEAR

AVERAGE INSTANTANEOUS

DISCHARGE = 32.5 CUBIC FEET PER SECOND

EXPLANATION

AVERAGE INSTANTANEOUS DISCHARGE

DE LEON SPRING

0

10

20

30

40

50

60

70

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

DISCHARGE, IN CUBIC FEET PER SECOND

Figure 26. Periodic discharge data for De Leon Spring, 1929-2007. Data collected by the St. Johns River 

Water Management District (SJRWMD) and U.S. Geological Survey. SJRWMD data used with permission. 
42 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

PISTON FLOW MODEL (PFM)

EXPONENTIAL MIXING MODEL

(EMM)

BINARY MIXING MODEL (BMM)

EXPONENTIAL AND PISTON FLOW

MODEL (EPM)

GREEN SPRING (2005)

DE LEON SPRING (2005)

GEMINI NORTH BOIL (2005)

GEMINI SOUTH BOIL (2005)

FERN HAMMOCK (2006-07)

EXPLANATION

0

1

2

3

4

5

6

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

SULFUR HEXAFLUORIDE CONCENTRATION,

IN PARTS PER TRILLION BY VOLUME

TRITIUM/(TRITIUM PLUS HELIUM-3), IN TRITIUM UNITS

Figure 27. Measured concentrations of sulfur hexafluoride (SF6, y-axis) and the ratio of measured tritium (3H) 

to the initial tritium (measured concentrations of tritium plus helium-3 (3

He) radioactive decay product of tritium) 

in water samples from selected springs, and output curves from various lumped parameter models for various 

scenarios of ground-water flow to springs. 

Based on concentrations of 3H, 3He (daughter product of 

tritium decay), SF6 and chlorofluorocarbons (CFCs) measured 

in water samples from De Leon Spring in 2001, the age of 

spring water represents an exponential mixture containing 

approximately 30 percent old water (greater than 60 years) and 

about 70 percent younger water having a mean residence time 

of 14 years (Toth and Katz, 2006). The SF6, 3H, and 3He data 

from recent water samples from De Leon Spring collected in 

2005 were plotted, along with the output curves showing age 

distributions for various lumped-parameter models (fig. 27). 

The modeled output curves are based on various assumptions of

ground-water flow in the spring contributing area and atmospheric concentrations of SF6

, 3H, and 3He over time (fig. 3). 

The tracer data indicated a similar exponential mixture of old 

and young waters from the Floridan aquifer system (fig. 27). 

The age of water discharging from De Leon Spring also was 

determined by measuring the concentration of 3H, delta 13C, 

and 14C in the spring discharge in May 1995 and 3H and 3He in 

July 1995. De Leon Spring had a 3

H concentration of 2.1 TU, 

which indicates that the younger fraction of water likely is less 

than 42 years old. The 3H /3He age of the water was 28.6 years. 

De Leon Spring had a delta 13C value of -7.96 per mil and a 14C concentration of 35 pmc, which is indicative of mixing of 

Upper and Lower Floridan aquifer water. The adjusted 14C age 

is recent.

Aquatic Communities

General descriptions of the aquatic macroinvertebrate and 

fish assemblages of De Leon Spring were presented by Phelps 

and others (2006). Previously, macroinvertebrate samples were 

sorted, identified, and enumerated, but the oligochaetes and 

most dipterans (families Chironomidae and Ceratopogonidae) 

were not identified beyond family or higher level taxonomic 

categories. These specimens were subsequently identified to 

species or lowest practicable identification level. The macroinvertebrate data were, therefore, reanalyzed and are reported here 

in greater detail.

A total of 61 macroinvertebrate taxa were collected by 

petite ponar dredge from De Leon Spring across three sampling 

dates (table 14). The number of taxa collected with this gear 

ranged from 7 in February 2004 to 46 in August 2004. The 

total number of organisms collected in February was much 

lower than the numbers collected on the other dates. Pooled 

samples across all dates were dominated by amphipods 

(78.9 percent, Hyalella azteca complex and Gammarus cf. 

tigrinus), gastropods (8.3 percent, most of which were hydrobiids), and dipterans (5.4 percent). Density of all organisms 

ranged from 530 per m2

 (5.7 × 103 per ft2) in February 2004 

to 12.6 × 103

 per m2 (135.9 × 103 per ft2) in August 2004. The 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 43

Table 14. Number of specimens (n) and percent density (%) per square meter of macroinvertebrates collected by pooled petite ponar 

dredge samples (n = 3 per date) from De Leon Spring, February-August 2004.

[LPIL, lowest practicable identification level]

Clade Taxon

Feb. 11, 2004 May 11, 2004 Aug. 18, 2004

n % n % n %

Porifera

Turbellaria

Gastropoda

Hirudinea

Oligochaeta

Arachnida

Amphipoda

Isopoda

Decapoda

Coleoptera

Porifera (LPIL)

Tricladida (LPIL)

Ancylidae (LPIL)

Elimia floridensis

Haitia sp.

Hydrobiidae (LPIL)

Melanoides tuberculata

Micromenetus floridensis

Planorbella scalaris

Viviparus georgianus

cf. Actinobdella inequiannulata

Glossiphoniidae (LPIL)

Helobdella sp.

Helobdella stagnalis

Helobdella triserialis

Mooreobdella tetragon

Aulodrilus pigueti

cf. Lumbriculus sp.

Dero digitata complex

Dero nivea

Dero pectinata

Dero sp.

Eclipidrilus sp.

Enchytraeidae (LPIL)

Limnodrilus hoffmeisteri

Spirosperma ferox

Spirosperma sp.

tubificoid Naididae immature sp. A (LPIL)

Acariformes (LPIL)

Gammarus cf. tigrinus LeCroy

Hyalella azteca complex Lecroy

Caecidotea sp.

Cassidinidea ovalis

Palaemonetes paludosus

Procambarus sp.

Helocombus sp.

14

29

14

330

115

14

2.6

5.5

2.6

62.3

21.7

2.6

29

43

29

14

14

14

14

172

14

14

14

57

1,480

1,580

14

14

0.7

1.1

0.7

0.3

0.3

0.3

0.3

4.2

0.3

0.3

0.3

1.4

36.4

38.9

0.3

0.3

14

29

72

115

776

302

14

43

86

14

43

14

14

29

29

29

29

14

14

86

101

115

3,621

6,451

14

14

0.1

0.2

0.6

0.9

6.1

2.4

0.1

0.3

0.7

0.1

0.3

0.1

0.1

0.2

0.2

0.2

0.2

0.1

0.1

0.7

0.8

0.9

28.7

51.1

0.1

0.1
44 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Table 14. Number of specimens (n) and percent density (%) per square meter of macroinvertebrates collected by pooled petite ponar 

dredge samples (n = 3 per date) from De Leon Spring, February-August 2004.—Continued

[LPIL, lowest practicable identification level]

Clade Taxon

Feb. 11, 2004 May 11, 2004 Aug. 18, 2004

n % n % n %

Diptera

Ephemeroptera

Hemiptera

Odonata

Trichoptera

Total

Number of Taxa

Bezzia/Palpomyia complex Brigham

Chironomidae (LPIL)

Chironomus sp.

Cladotanytarsus sp.

Cryptochironomus sp.

Dicrotendipes modestus

Labrundinia neopilosella

Larsia decolorata

Monopelopia boliekae

Odontomyia/Hedriodiscus group Merritt 

and Cummins

Paratanytarsus sp.

Pseudochironomus sp.

Tabanidae (LPIL)

Tanypodinae (LPIL)

Tanytarsini (LPIL)

Tanytarsus sp. F Epler

Tanytarsus sp. G Epler

Caenis diminuta

Callibaetis floridanus

Ephemeroptera (LPIL)

Mesovelia sp.

Pelocoris sp.

Argia sp.

Libellulidae (LPIL)

Orthotrichia sp.

14

530

7

2.6

14

29

417

29

14

14

29

4,062

23

0.3

0.7

10.3

0.7

0.3

0.3

0.7

14

14

14

14

14

230

14

14

14

14

14

29

43

14

14

14

14

14

14

14

12,622

46

0.1

0.1

0.1

0.1

0.1

1.8

0.1

0.1

0.1

0.1

0.1

0.2

0.3

0.1

0.1

0.1

0.1

0.1

0.1

0.1
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 45

Table 15. Number of specimens (n) and percent composition (%) of macroinvertebrates collected by dip net from De Leon Spring, 

February-August 2004. 

[Values represent material as subsampled to obtain the target number of organisms required for calculation of the Stream Condition Index]

Clade Taxon

Feb. 11, 2004 May 11, 2004 Aug. 18, 2004

n % n % n %

Gastropoda

Bivalvia

Hirudinea

Oligochaeta

Amphipoda

Decapoda

Coleoptera

Diptera

Odonata

Total

Number of Taxa

Elimia floridensis

Hydrobiidae (LPIL)

Pomacea paludosa

Viviparus georgianus

Corbicula fluminea

Gloiobdella elongata

Helobdella stagnalis

Allonais inaequalis

Bratislavia unidentata

Limnodrilus hoffmeisteri

Spirosperma ferox

tubificoid Naididae immature sp. A (LPIL)

Gammarus cf. tigrinus LeCroy

Hyalella azteca complex LeCroy

Procambarus sp. (immature)

Chrysomelidae (LPIL)

Chironomus sp.

Cricotopus politus

Dicrotendipes modestus

Pseudochironomus sp.

Tanytarsus sp.

Argia sp.

Enallagma sp.

Erythemis plebeja

5

4

1

2

1

1

5

82

2

4

2

1

110

12

4.5

3.6

0.9

1.8

0.9

0.9

4.5

74.5

1.8

3.6

1.8

0.9

6

3

1

1

3

2

24

56

2

3

6

1

1

1

110

14

5.5

2.7

0.9

0.9

2.7

1.8

21.8

50.9

1.8

2.7

5.5

0.9

0.9

0.9

3

7

1

1

1

4

24

66

1

1

1

110

11

2.7

6.4

0.9

0.9

0.9

3.6

21.8

60.0

0.9

0.9

0.9

ratio of Hyalella to Gammarus was 1:0.3, 1:1.1, and 1:1.8 in 

February, March, and August, respectively. For petite ponar 

samples pooled across all dates, the log2

 Shannon-Wiener 

index ranged from 1.69 to 2.34, Simpson’s index of diversity 

ranged from 0.56 to 0.70, Pielou’s evenness ranged from 0.42 

to 0.60, and the Florida Index ranged from 1 to 7 with a mean 

of 3.3 (table 4).

A total of 24 macroinvertebrate taxa were identified 

in subsamples collected by dip net from De Leon Spring; 

over three sampling dates, the number of taxa collected 

ranged from 11 in August 2004 to 14 in May 2004 (table 15). 

Although far fewer taxa were collected with this gear than by 

petite ponar dredge, subsamples from all dates combined were 

numerically dominated by amphipods (77.9 percent), followed 

by gastropods (10.0 percent), and dipterans (5.5 percent). The 

taxonomic composition of the most abundant taxa, therefore, 

was similar to the composition of samples collected by petite 

ponar dredge. For dip net samples pooled across all dates, the 

log2

 Shannon-Wiener index ranged from 1.63 to 2.38, Simpson’s index of diversity ranged from 0.44 to 0.69, Pielou’s 

evenness ranged from 0.45 to 0.62, SCI ranged from 9 to 10 

with a mean of 10, and percent very tolerant taxa ranged from 

3.6 to 14.5, with a mean of 8.1 (table 5). 
46 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Fern Hammock Springs

Fern Hammock Springs (figs. 1, 28, and 29, table 1), 

also known as “The Aquarium,” is a second-magnitude spring 

(mean and median discharge 13.0 and 12.7 ft3

/s, respectively) 

located in the Ocala National Forest (Rosenau and others, 

1977; Scott and others, 2004). The irregularly shaped main 

pool measures about 160 ft by 75 ft, with a depth ranging from 

2 to 6 ft. The bottom of the pool contains over 25 sand boils, 

and is mostly fine, white sand with patches of aquatic macrophytes, and muck. A wooden footbridge spans the spring pool 

near its center, with the largest sand boil in the pool situated 

directly under the footbridge (fig. 29). The clear, bluish spring 

water has exceptionally low mineralization (mean and median 

specific conductance: 125 and 118 μS/cm, respectively) among 

Floridan aquifer system springs, which typically have a specific 

conductance of greater than about 300 μS/cm. Discharge from 

Fern Hammock Springs flows about 600 ft through a gently 

meandering run to Juniper Creek. The head of Fern Hammock 

Springs is located downgradient of a low-volume wastewater 

treatment facility (used for the recreation area) that may 

potentially affect the water quality in the spring. Swimming is 

prohibited in Fern Hammock Springs because of ecological, 

human-health, and safety considerations. The areal extent of 

the Fern Hammock springshed has not been determined.

Land Use

Land-use data for the Fern Hammock springshed were 

not available at the time of this study. Based on personal 

observations of the Fern Hammock springshed, land use 

from 1973 to 2004 was estimated to be relatively unchanged, 

and consisted mostly of forestland, some open-water 

Figure 28. Main pool of Fern Hammock Springs. Photograph 

by L. Knowles, Jr., March 29, 2007. 

Figure 29. Large sand boil at Fern Hammock Springs that 

was sampled for this study. Photograph by L. Knowles, Jr., 

March 29, 2007. 

surface/wetlands, and lesser areas of non-forested/barren land 

with small tracts for urban/mining/transportation/recreation 

mostly near the spring head. A few existing septic systems are 

the only means of wastewater treatment and disposal in the 

Fern Hammock springshed.

Discharge

Discharge at Fern Hammock Springs was measured by 

the USGS from 1935 to 1984, and by the SJRWMD from 

1985 to the present. At the time of this study, the USGS and 

SJRWMD jointly measured discharge of Fern Hammock 

Springs at least once per month. Discharge for Fern Hammock 

Springs averaged 13.0 ft3

/s annually, and varied with rainfall 

that averaged 49.33 in/yr within the springshed (fig. 30). 

Average annual discharge for Fern Hammock Springs ranged 

from 9.3 ft3/s in 2000 to 19.9 ft3/s in 1936. Measured (instantaneous) discharge for Fern Hammock Springs averaged 

12.7 ft3

/s and ranged from 9.3 ft3/s in May 2000 to 19.9 ft3/s in 

September 1936 (fig. 31). 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 47

FERN HAMMOCK SPRINGS

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

ANNUAL DISCHARGE, IN

CUBIC FEET PER SECOND

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

ANNUAL RAINFALL, IN INCHES

EXPLANATION

ANNUAL DISCHARGE =

13.0 CUBIC FEET PER SECOND

AVERAGE

AVERAGE ANNUAL RAINFALL

= 49.33 INCHES

YEAR

SPRING DISCHARGE

ANNUAL RAINFALL

Figure 30. Average annual discharge for Fern Hammock Springs and rainfall for the Fern Hammock springshed. 

Water Chemistry and Age

Fern Hammock Springs was sampled once per year by 

the USGS in 1972 and 1980, with periodic field measurements made from 1980 to the present. The SJRWMD has 

sampled the spring quarterly from 1985 to 2005, and at the 

time of this study, sampled the spring four times per year.

Fern Hammock Springs has a Ca-Mg-HCO3

 water type 

(fig. 9) and is undersaturated with respect to calcite and 

dolomite (table 3). Median values of pH, dissolved oxygen, 

and dissolved solids were 8.2, 6.2 mg/L, and 68 mg/L, 

respectively. The 3

H concentration was reported as greater 

than 2.3 TU by Toth (2003). Delta 18O and 2

H values plot 

along the GMWL (Toth, 2003), indicating that isotopic 

fractionation of rain water during recharge was not occurring.

Nitrate-N concentrations from 1990 to 2006 generally 

were uniform and less than 0.2 mg/L, although some recent 

spikes in concentration of up to 0.4 mg/L have been observed 

(fig. 10). Nitrate-N concentrations showed a significant 

(p < 0.02) increasing trend with time from 1972 to 2007 

(table 6). Phosphorus (total P) concentrations generally were 

uniform, averaging approximately 0.02 mg/L during 2004-07 

(fig. 11). Concentrations of dissolved nitrogen and argon in 

water samples from Fern Hammock Springs were consistent 

with atmospheric equilibration during ground-water recharge 

with the addition of minor amounts of excess air. Values of 

delta 15N (5.93 per mil) and delta 18O (1.84 per mil) of nitrate 

in water samples collected in October 2006 did not indicate 

any isotopic fractionation. This result indicates that active 

denitrification likely was not occurring in the Upper Floridan 

aquifer in the vicinity of Fern Hammock Springs. Water 

samples collected from Fern Hammock Springs on October 

19, 2006, were analyzed for antibiotics, and all compounds 

were below method reporting levels. Water samples collected 

from Fern Hammock Springs in October 2006 and March 

2007 were analyzed for 64 organic chemicals commonly 

associated with wastewater sources, plus 52 pesticides. 

Tritethyl citrate (E0.1 μg/L) was the only compound detected 

and quantified in the October 2006 samples (app. 4). No 

pesticides were detected in samples from Fern Hammock 

Springs (app. 5).

Concentrations of 3

H, 3He, and SF6 measured in water 

samples from Fern Hammock Spring in 2006-07 can 

be described by a piston model curve, and the apparent 

springwater age ranged from 20 to 23 years (fig. 27). Fern 

Hammock Springs had a delta 13C value of -8.4 per mil and 

a 14C concentration of 26 pmc. Based on an adjusted initial 

value of 14C using the Fontes and Garnier (1979) model, 

the age of the older fraction of water was approximately 

2,000 years.
48 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

YEAR

AVERAGE INSTANTANEOUS

DISCHARGE = 12.7 CUBIC FEET PER SECOND

EXPLANATION

INSTANTANEOUS DISCHARGE

AVERAGE INSTANTANEOUS DISCHARGE

FERN HAMMOCK SPRINGS

0

10

20

30

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

DISCHARGE, IN CUBIC FEET PER SECOND

Figure 31. Periodic and continuous discharge data for Fern Hammock Springs, 1935-2007. Data collected by 

the St. Johns River Water Management District (SJRWMD) and U.S. Geological Survey. SJRWMD data used 

with permission. 

Gemini Springs

Gemini Springs (fig. 1, table 1) is a third-magnitude 

system (mean and median discharge 9.9 and 9.8 ft3

/s, respectively) (Rosenau and others, 1977; Scott and others, 2004; 

Phelps and others, 2006). The springs consist of two primary 

vents (north and south) plus an additional vent and seepage 

from an adjacent hillside. Flows from the springs converge to 

form a run that is impounded by a low-head dam. Flow from 

the south boil emanates from a small cavern under a rock 

ledge about 3 ft below the water surface and forms a circular 

pool (pool 1). Discharge from the north vent emanates from 

a horizontal cavern opening in limestone rock and forms a 

circular pool (pool 2) about 15 ft in diameter. The cavern 

opening is about 6 ft high and 8 ft wide, with the cavern 

appearing to extend laterally underground to the north or 

northeast. Discharge from the north boil flows about 150 ft 

to the east-southeast and converges with the flow from the 

south boil at the west end of the reservoir. The reservoir is 

impounded on its east end by an earthen dam with a concrete 

weir outlet. Flow is through the weir and then to the eastnortheast for about 150 ft through a marsh area to Lake 

Monroe. Collections of macroinvertebrates were made in 

sections of the run flowing from the north vent and adjacent 

to, and just downstream of, the south vent (Phelps and others, 

2006). Substrate consisted primarily of sand, cobble, and 

submergent macrophytes, overlain with periphyton and filamentous algae in some areas. The areal extent of the Gemini 

springshed is 3.59 mi2

.

Land Use

Land use in the Gemini springshed changed considerably 

from 1973 to 2004. During this period, the areal extent of 

urbanized areas increased four-fold, open-water/wetland areas 

doubled in size, and forestland decreased 95 percent (fig. 4). 

Land use in the springshed in 1973 consisted of forestland 

(59.7 percent), open-water/wetlands (26.4 percent), urban/

mining/transportation/recreation (9.4 percent), non-forested/

barren land (2.4 percent), and agriculture (2.1 percent). 

Land use in the springshed in 2004 consisted of open-water/

wetlands (54.7 percent), urban/mining/transportation/recreation (40.9 percent), forestland (3.0 percent), non-forested/

barren land (0.8 percent), and agriculture (0.6 percent). As of 

2004, two municipal sewer systems were the primary means of 

wastewater treatment and disposal in the Gemini springshed, 

replacing preexisting septic systems. Reclaimed wastewater 

is applied to 1.2 mi2

, or about a third of the land surface in the 

Gemini springshed.
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 49

GEMINI SPRINGS

-50

-40

-30

-20

-10

0

10

20

30

40

50

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

ANNUAL DISCHARGE, IN

CUBIC FEET PER SECOND

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

ANNUAL RAINFALL, IN INCHES

YEAR

SPRING DISCHARGE

ANNUAL RAINFALL

EXPLANATION

ANNUAL DISCHARGE =

9.9 CUBIC FEET PER SECOND

AVERAGE

AVERAGE ANNUAL RAINFALL

= 51.92 INCHES

Figure 32. Average annual discharge for Gemini Springs and rainfall for the Gemini springshed. 

Discharge

Discharge at Gemini Springs was measured by the USGS 

from 1966 to 1999, and has been measured by the SJRWMD 

since 1996; at the time of this study, measurements were made 

by the SJRWMD at least four times per year. Spring discharge is 

controlled mostly by the water level in the reservoir. Occasionally the stage is high enough in Lake Monroe or the St. Johns 

River to elevate the water level in the reservoir and results in 

a reduction in spring discharge. Discharge for Gemini Springs 

averaged 9.9 ft3

/s annually and varied with rainfall, which 

averaged 51.92 in/yr in the springshed (fig. 32). Average annual 

discharge for Gemini Springs ranged from 7.6 ft3/s in 2002 

to 12.0 ft3/s in 1967. Measured (instantaneous) discharge for 

Gemini Springs averaged 10.1 ft3/s and ranged from 6.2 ft3/s in 

June 1995 to 15.3 ft3

/s in November 2005 (fig. 33).

Water Chemistry and Age

Gemini Springs has been sampled periodically by the 

USGS since 1972 and by the SJRWMD since 1986. At the 

time of this study, the SJRWMD sampled the spring four times 

per year. In 2006, the USGS sampled Gemini Springs for 

human antibiotics and hormones.

The north and south boils of Gemini Springs have a 

Na-Cl water type (fig. 9) and are undersaturated with respect to 

calcite and dolomite (table 3). Median values of pH, dissolved 

oxygen, and dissolved solids in water from the north boil were 

7.3, 1.0 mg/L, and 1,520 mg/L, respectively. Median values of 

pH, dissolved oxygen, and dissolved solids in water from the 

south boil were 7.2, 0.9 mg/L, and 1,570 mg/L, respectively. 

Values of 18O and 2

H plotted along the GMWL or local MWL, 

parallel to the GMWL (Toth, 1999). The 3

H concentration was 

3.3 TU (Toth, 1999). Only two water samples were collected 

from the north and south boils of Gemini Springs during 2004, 

and nitrate-N concentrations were about 1.0 mg/L. Concentrations of dissolved nitrogen and argon in water samples from 

Gemini Springs (both north and south boils) were consistent 

with atmospheric equilibration during ground-water recharge 

with the addition of minor amounts of excess air. Based 

on nitrogen and argon data in water samples collected in 

January, May, June, and August 2005, the calculated recharge 

temperature was 22 to 23o

C (assuming a recharge elevation of 

50 ft and 100-percent humidity at the water table). One water 

sample collected from the south boil at Gemini Springs in 

May 2004 (Phelps and others, 2006) had a slightly elevated 

dissolved nitrogen concentration (0.5 mg/L), indicating that 

some denitrification may have been occurring in the Upper 

Floridan aquifer in the vicinity of the south boil at Gemini 

Springs. Nitrite plus nitrate concentration within Gemini 

Springs run showed a significant increasing trend over time 

(table 6). Phosphorus (total P) concentrations were approximately 0.07 mg/L, based on two water samples collected in 

2004 from the north and south boils.

Water samples collected from the north and south 

boils in May and August 2004 were analyzed for 64 organic 

chemicals commonly associated with wastewater sources, 

plus 52 pesticides. The following organic wastewater 

compounds were detected in water samples from the north 

boil: phenol (0.7 μg/L), benzophenone (E0.1 μg/L), DEET 
50 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

YEAR

AVERAGE INSTANTANEOUS

DISCHARGE = 10.1 CUBIC FEET PER SECOND

AVERAGE INSTANTANEOUS DISCHARGE

EXPLANATION

INSTANTANEOUS DISCHARGE

GEMINI SPRINGS

0

10

20

30

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

DISCHARGE, IN CUBIC FEET PER SECOND

Figure 33. Periodic discharge data for Gemini Springs, 1966-2007. Data collected by the St. Johns River Water 

Management District (SJRWMD) and U.S. Geological Survey. SJRWMD data used with permission. 

(E0.1 μg/L), and triphenyl phosphate (E0.1 μg/L) (app. 4). 

The following compounds were detected in water samples 

from the south boil: benzophenone (E0.1 μg/L), DEET 

(E0.1 μg/L), and triphenyl phosphate (E0.1 μg/L) (app. 4). 

The following pesticides were detected in water samples 

from the north boil: atrazine (0.015-0.017 μg/L), and an 

atrazine degradate (2-chloro-4-isopropylamino-6-amino-striazine, CIAT) (E0.011-E0.012 μg/L) (app. 5). Both atrazine 

(0.013-0.019 μg/L) and CIAT (E0.010-E0.013 μg/L) also were

detected in water samples from the south boil (app. 5).

The age of water from the north and south boils at 

Gemini Springs appeared to be young (less than 5 years) 

as indicated by SF6

 and 3H concentrations that are similar 

to recent atmospheric concentrations. However, the high 

concentrations of SF6

 (10-12 pptv) in some of the 2005 

samples greatly exceeded atmospheric levels and likely 

indicated contamination from non-atmospheric SF6

 sources, 

which render SF6 concentrations unusable for age dating. 

Water samples also were collected for 3

H, 13C, and 14C in the 

spring discharge in May 1996, and for 3

H/3He in August 1999.

Gemini Springs had a 3

H concentration of 3.3 TU, which indicates that the younger fraction of water was less than 43 years 

old. The 3

H/3He results indicate that the younger fraction of 

water from Gemini Springs was 19 years old. Gemini Springs 

had a delta 13C value of –10.4 ppm and a 14C concentration of 

41 pmc, which indicates mixing of Upper and Lower Floridan 

aquifer water.

Gemini Springs run has a Na-Cl water type (fig. 9). 

Median values of pH, dissolved oxygen, and dissolved 

solids were 7.4, 3.2 mg/L, and 1,420 mg/L, respectively (table 3). Nitrate concentrations from 1995 to 

2007 showed large fluctuations (0.05-2.2 mg/L, median 

0.91 mg/L) (fig. 16). Phosphorus concentrations ranged 

from 0.06 to 0.18 mg/L during 1999-2007, with a median 

concentration of 0.08 mg/L (fig. 17).

Aquatic Communities

General descriptions of aquatic macroinvertebrate and 

fish assemblages of Gemini Springs are presented in Phelps 

and others (2006). Prior to that report, macroinvertebrates 

were enumerated but oligochaetes and most dipterans (Chironomidae) were not identified beyond family or higher level 

taxonomic categories. These specimens were subsequently 

identified to species or lowest practicable identification level. 

The macroinvertebrate data were, therefore, reanalyzed and 

are reported here in greater detail.
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 51

Table 16. Number of specimens (n) and percent density (%) per square meter of macroinvertebrates collected by pooled petite ponar 

dredge samples (n = 3 per date) from Gemini Springs, February-August 2004.

[LPIL, lowest practicable identification level]

Clade Taxon

Feb. 10, 2004 May 11, 2004 Aug. 17, 2004

n % n % n %

Turbellaria

Gastropoda

Hirudinea

Oligochaeta

Amphipoda

Isopoda

Diptera

Total

Number of Taxa

Tricladida (LPIL)

Turbellaria (LPIL)

Ancylidae (LPIL)

Haitia sp.

Hydrobiidae (LPIL)

Gloiobdella elongata

Helobdella fusca

Helobdella sp.

Helobdella stagnalis

Helobdella triserialis

Myzobdella lugubris

Dero digitata complex

Dero sp.

Dero trifida

Eclipidrilus palustris

Eclipidrilus sp.

Limnodrilus hoffmeisteri

tubificoid Naididae immature sp. A (LPIL)

Gammarus cf. tigrinus LeCroy

Hyalella azteca complex Lecroy

Caecidotea sp.

Chironomus decorus group Epler

Chironomus sp.

158

14

43

14

43

14

29

43

29

29

14

216

144

1,537

43

43

57

2,470

17

6.4

0.6

1.7

0.6

1.7

0.6

1.2

1.7

1.2

1.2

0.6

8.7

5.8

62.2

1.7

1.7

2.3

144

14

101

14

101

14

14

848

1,595

1,451

302

4,598

11

3.1

0.3

2.2

0.3

2.2

0.3

0.3

18.4

34.7

31.6

6.6

72

489

14

14

86

474

259

259

14

14

57

1,752

11

4.1

27.9

0.8

0.8

4.9

27.1

14.8

14.8

0.8

0.8

3.3

A total of 23 macroinvertebrate taxa were collected 

by petite ponar dredge from Gemini Springs across three 

sampling dates (table 16). The number of taxa collected with 

this gear ranged from 11 in May and August 2004 to 17 in 

February 2004. The total numbers of organisms collected 

in February and August were considerably lower than the 

number collected in May. Pooled samples across all dates were 

dominated by oligochaetes (41.7 percent; mostly tubificoid 

Naididae immature sp. A and Limnodrilus hoffmeisteri), 

amphipods (40.4 percent, Gammarus cf. tigrinus complex and 

Hyalella azteca complex), gastropods (7.5 percent, mostly 

hydrobiids), and turbellarians (4.4 percent). Density of all 

organisms ranged from 1.8 × 103

 per m2 (18.9 × 103 per ft2) in 

August 2004 to 4.6 × 103

 per m2 (49.5 × 103 per ft2) in May 

2004. For petite ponar samples pooled across all dates, the log2

Shannon-Wiener index ranged from 2.26 to 2.63, Simpson’s 

index of diversity ranged from 0.59 to 0.80, Pielou’s evenness 

ranged from 0.55 to 0.76, and the Florida Index ranged from 1 

to 2 with a mean of 1.3 (table 4).
52 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Table 17. Number of specimens (n) and percent composition (%) of macroinvertebrates collected by dip net from Gemini Springs, 

February-August 2004. 

[Values represent material as subsampled to obtain the target number of organisms required for calculation of the Stream Condition Index. LPIL, lowest 

practicable identification level]

Clade Taxon

Feb. 10, 2004 May 11, 2004 Aug. 17, 2004

n % n % n %

Turbellaria

Gastropoda

Hirudinea

Oligochaeta

Amphipoda

Decapoda

Diptera

Total

Number of Taxa

Tricladida (LPIL)

Haitia sp.

Hydrobiidae (LPIL)

Planorbella scalaris

Helobdella sp.

Dero digitata complex

Eclipidrilus palustris

Eclipidrilus sp.

Limnodrilus hoffmeisteri

Gammarus cf. tigrinus LeCroy

Gammarus mucronatus complex LeCroy

Hyalella azteca complex LeCroy

Procambarus sp. (immature)

Ceratopogonidae (LPIL)

Chironomus sp. A Line

Culicoides group Brigham

Goeldichironomus holoprasinus

Larsia decolorata

Tanytarsus sp. V Epler

10

12

1

6

77

3

1

110

7

9.1

10.9

0.9

5.5

70.0

2.7

0.9

1

1

16

10

3

19

6

27

8

5

3

7

1

3

110

14

0.9

0.9

14.5

9.1

2.7

17.3

5.5

24.5

7.3

4.5

2.7

6.4

0.9

2.7

1

41

1

1

65

1

110

6

0.9

37.3

0.9

0.9

59.1

0.9

A total of 19 macroinvertebrate taxa were identified 

in subsamples collected by dip net from Gemini Springs 

(table 17); the number of taxa ranged from 6 in August 2004 

to 14 in May 2004. The overall composition of organisms in 

samples collected by dip nets was similar to the composition 

of samples collected by petite ponar dredge. Specifically, the 

dip net samples were dominated by amphipods (54.2 percent) 

and gastropods (21.8 percent), but dipterans constituted a 

slightly greater proportion (8.2 percent). For dip net samples 

collected across all dates, the log2

 Shannon-Wiener index 

ranged from 1.23 to 3.22, Simpson’s index of diversity ranged 

from 0.52 to 0.87, Pielou’s evenness ranged from 0.47 to 0.85, 

the SCI ranged from 8 to 13 with a mean of 10, and percent 

very tolerant taxa ranged from 2.7 to 39.1 (table 5).

The fish community of Gemini Springs was summarized by Phelps and others (2006), who recorded a total of 

11 species by visual survey of the impounded spring pool. 

Crayfish traps were relatively inefficient at capturing fish, but 

a moderate number of Fundulus seminolis and Lucania goodei

were collected with this gear. In the qualitative visual surveys, 

other native species observed, all in relatively low abundance, 

included Gambusia holbrooki, Micropterus salmoides, 

Lepomis macrochirus, L. microlophus, and Dorosoma cepedianum. Three nonindigenous fish species were observed: 

Cyprinus carpio, Oreochromis aureus, and Pterygoplichthys

disjunctivus. Of the nonindigenous species, C. carpio is 

unknown to be established in the St. Johns River drainage.
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 53

Green Spring

Green Spring (fig. 1) is a third-magnitude spring (mean 

and median discharge both 1.1 ft3

/s) (Rosenau and others, 

1977; Scott and others, 2004; Phelps and others, 2006). Green 

Spring discharges from a 125-ft deep, conical limestone vent 

into a nearly circular pool about 90 ft in diameter. Water in 

the pool generally is milky green with poor visibility of less 

than 0.5 ft; however, the water occasionally becomes clear 

with visibility of 10 ft or more, as observed during a visit on 

June 14, 2006. An eastward extension of the pool is bordered 

on the north and east by a concrete retaining wall where a 

shallow run from 3 to 6 ft wide begins. The run flows toward 

the southeast for about 200 ft and discharges into a small 

creek that flows south for about 0.25 mi and discharges into 

Lake Monroe. Sampling of the macroinvertebrate fauna was 

conducted at three sites within the spring run. The substrate 

consisted of detritus and leaf packs with submergent and emergent macrophytes covered by cyanobacteria. The areal extent 

of the Green springshed is 1.79 mi2

.

Land Use

Urbanization of the Green springshed from 1973 to 2004 

replaced much of the forestland urban and open-water/wetland 

areas (fig. 4). Forestland only remains around the immediate 

vicinity of Green Spring. Land use in the springshed in 

1973 consisted of urban/mining/transportation/recreation 

(58.1 percent), open-water/wetlands (24.0 percent), forestland 

(17.7 percent), non-forested/barren land (0.2 percent), and 

agriculture (less than 0.1 percent). Springshed land use in 

2004 consisted of urban/mining/transportation/recreation 

(68.4 percent), open-water/wetlands (29.9 percent), forestland 

(1.7 percent), non-forested/barren land (less than 0.1 percent), 

and agriculture (less than 0.1 percent). As of 2005, two 

municipal sewer systems, currently the primary means of 

wastewater treatment and disposal, had replaced septic 

systems in the Green springshed. Reclaimed wastewater is 

applied to 0.39 mi2

 of the land surface in the springshed.

Discharge

Discharge at Green Spring has been measured periodically by the USGS since 1932. The SJRWMD has been 

measuring discharge since 1995, and at the time of this study, 

measured discharge at least monthly. Discharge for Green 

Spring averaged 1.1 ft3

/s annually and varied with rainfall that 

averaged 51.92 in/yr within the springshed (fig. 34). Average 

annual discharge for Green Spring ranged from 0.0 ft3

/s (no 

flow) in 1981 and 2001 to 3.6 ft3

/s in 2006. Measured 

(instantaneous) discharge for Green Spring averaged 1.4 ft3

/s 

and ranged from 0.0 ft3

/s in April 1981, June-July 2000, and 

January-July 2001 to 3.6 ft3

/s in February 2006 (fig. 35). 

GREEN SPRING

-30

-20

-10

0

10

20

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

ANNUAL DISCHARGE, IN

CUBIC FEET PER SECOND

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

ANNUAL RAINFALL, IN INCHES

SPRING DISCHARGE

ANNUAL RAINFALL

EXPLANATION

YEAR

ANNUAL DISCHARGE =

1.1 CUBIC FEET PER SECOND

AVERAGE

AVERAGE ANNUAL RAINFALL

= 51.92 INCHES

Figure 34. Average annual discharge for Green Spring and rainfall for the Green springshed. 
54 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

GREEN SPRING

0

2

4

6

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

5

3

1

INSTANTANEOUS DISCHARGE

YEAR

AVERAGE INSTANTANEOUS

DISCHARGE = 1.4 CUBIC FEET PER SECOND

EXPLANATION

AVERAGE INSTANTANEOUS DISCHARGE

DISCHARGE, IN CUBIC FEET PER SECOND

Figure 35. Periodic discharge data for Green Spring, 1932-2007. Data collected by the St. Johns River Water 

Management District (SJRWMD) and U.S. Geological Survey. SJRWMD data used with permission. 

Water Chemistry and Age

Green Spring was first sampled by the USGS in 1972, 

and was sampled frequently by the SJRWMD from 1995 to 

2005, including at least four times per year during this study. 

In 2006, the USGS sampled Green Spring for human antibiotics and hormones.

Green Spring has a Na-Cl water type (fig. 9) and is 

slightly undersaturated with respect to calcite and dolomite 

(table 3). Median values of pH, dissolved oxygen, and 

dissolved solids in water were 7.4, 0.4 mg/L, and 1,500 mg/L, 

respectively. Spring water had a 3

H concentration greater than 

2.3 TU and a slightly enriched 18O and 2

H composition that 

plots along an evaporation trend line for lakes (Toth, 2003). 

Water samples collected from Green Spring since May 1996 

generally had nitrate-N concentrations less than 0.06 mg/L, 

with the exception of a January 2001 sample that had a nitrateN concentration of 0.16 mg/L (fig. 16). 

Concentrations of dissolved nitrogen and argon in water 

samples from Green Spring (January, May, June 2005) were 

consistent with atmospheric equilibration during groundwater recharge with the addition of minor amounts of excess 

air. However, dissolved gas analyses of water samples 

collected in May and August 2004 (Phelps and others, 2006) 

and August 2005 indicated a slight excess of dissolved 

nitrogen (0.5-1.0 mg/L), which indicates that denitrification 

likely was occurring in the Upper Floridan aquifer in the 

vicinity of Green Spring during those time periods. Based 

on nitrogen and argon data in water samples collected in 

2004-05 (Phelps and others, 2006), the calculated recharge 

temperature was 22 to 23o

C (assuming a recharge elevation of 

60 ft and 100-percent humidity at the water table). Dissolved 

phosphorus (total P) concentrations in water samples 

collected from January 2001 to August 2007 ranged from 

0.06 to 0.15 mg/L (fig. 17).

Water samples collected from Green Spring in May 

and August 2004 were analyzed for 64 organic chemicals 

commonly associated with wastewater sources, plus 52 

pesticides. The following compounds were detected in water 

samples from Green Spring: phenol (E0.2 μg/L, E0.3 μg/L), 

benzophenone (E0.1 μg/L), and DEET (E0.2 μg/L) (app. 4). 

No pesticides were detected in water samples from Green 

Spring (app. 5).

Water from Green Spring was estimated to be about 

20 years in age, based on concentrations of SF6

, 3H, and 3He. 

Concentrations of SF6 in the two samples collected in January 

and May 2005 varied considerably (2.5-4.7 pptv); the higher 

concentration may indicate some contamination occurred 

during sampling.
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 55

Table 18. Number of specimens (n) and percent density (%) per square meter of macroinvertebrates collected by pooled petite ponar 

dredge samples (n = 3 per date) from Green Spring, February-August 2004.

[LPIL, lowest practicable identification level]

Clade Taxon

Feb. 10, 2004 May 11, 2004 Aug. 17, 2004

n % n % n %

Gastropoda

Oligochaeta

Amphipoda

Diptera

Total

Number of Taxa

Hydrobiidae (LPIL)

Dero digitata

Dero digitata complex

Dero furcata

Dero sp.

Dero trifida

Dero vaga

Eclipidrilus palustris

Haemonais waldvogeli

Limnodrilus hoffmeisteri

tubificoid Naididae immature sp. A (LPIL)

Hyalella azteca complex Lecroy

Bezzia/Palpomyia complex Brigham

Ceratopogonidae (LPIL)

Chironomini (LPIL)

Chironomus decorus group Epler

Chironomus sp.

Chironomus sp. A Line

Culicoides group Brigham

Goeldichironomus holoprasinus

Goeldichironomus sp.

Larsia sp.

29

72

14

115

3

25.2

62.6

12.2

230

29

115

704

2,500

115

14

14

14

129

115

72

273

72

4,396

14

5.2

0.7

2.6

16.0

56.9

2.6

0.3

0.3

0.3

2.9

2.6

1.6

6.2

1.6

201

144

115

14

14

57

14

14

29

4,626

14,325

14

805

43

43

101

57

14

20,630

18

1.0

0.7

0.6

0.1

0.1

0.3

0.1

0.1

0.1

22.4

69.4

0.1

3.9

0.2

0.2

0.5

0.3

0.1

Aquatic Communities

General descriptions of the aquatic macroinvertebrate and 

fish assemblages of Green Spring were presented in Phelps 

and others (2006). Prior to that report, macroinvertebrates 

were enumerated, but oligochaetes and dipterans (Chironomidae and Ceratopogonidae) were not identified beyond 

family or higher level taxonomic categories. These specimens 

were subsequently identified to species or lowest practicable 

identification level. The macroinvertebrate data were, therefore, reanalyzed and are reported here in greater detail.

A total of 22 macroinvertebrate taxa were collected by 

petite ponar dredge from Green Spring across three sampling 

dates (table 18). The number of taxa collected with this gear 

ranged from 3 in February 2004 to 18 in August 2004. The 

number of taxa and density of organisms in pooled samples 

varied considerably among the collection dates. This result 

may indicate variation in sampling efficiency of the petite 

ponar grabs, patchiness of the benthic fauna, and/or seasonal 

variation; the very low number of organisms collected in 

February 2004 was likely the result of ineffective grabs. 

Pooled samples across all dates were dominated by oligochaetes (91.6 percent; consisting of no fewer than seven and 

possibly as many as nine taxa), with dipterans constituting 

7.1 percent of the remaining organisms; the only other taxon 

collected with this gear consisted of one amphipod (Hyalella

azteca complex) and unidentified hydrobiid snails. Density 

of all organisms ranged from 115 per m2

 (1,238 per ft2) in 

February 2004 to 20.6 × 103

 per m2 (222.1 × 103 per ft2) in 

May 2004. For petite ponar samples pooled across all dates, 

the log2

 Shannon-Wiener index ranged from 1.29 to 2.21, 

Simpson’s index of diversity ranged from 0.47 to 0.64, and 

Pielou’s evenness ranged from 0.33 to 0.82; the Florida index 

was zero on all dates (table 4).
56 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Table 19. Number of specimens (n) and percent composition (%) of macroinvertebrates collected by dip net from Green Spring, 

February-August 2004.

[Values represent material as subsampled to obtain target number of organisms required for calculation of the Stream Condition Index. LPIL, lowest practicable 

identification level]

Clade Taxon Feb. 10, 2004 May 11, 2004 Aug. 17, 2004

n % n % n %

Gastropoda

Oligochaeta

Amphipoda

Decapoda

Coleoptera

Diptera

Hemiptera

Total

Number of Taxa

Haitia sp.

Hydrobiidae (LPIL)

Dero digitata complex

Dero trifida

Eclipidrilus palustris

Limnodrilus hoffmeisteri

Hyalella azteca complex LeCroy

Procambarus sp. (immature)

Chrysomelidae (LPIL)

Bezzia/Palpomyia complex Brigham

Ceratopogonidae (LPIL)

Chironomus decorus group Epler

Chironomus sp. A Line

Culicoides group Brigham

Einfeldia sp. A Epler

Ephydridae (LPIL)

Goeldichironomus holoprasinus

Goeldichironomus sp.

Larsia decolorata

Polypedilum tritum

Ptychoptera sp.

Stratiomys sp.

Tanytarsus sp. V Epler

Belostoma sp.

Lethocerus sp.

1

1

35

7

29

1

20

14

2

110

9

0.9

0.9

31.8

6.4

26.4

0.9

18.2

12.7

1.8

1

1

4

5

19

26

1

1

7

2

7

1

1

7

1

1

2

2

1

89

18

1.1

1.1

4.5

5.6

21.3

29.2

1.1

1.1

7.9

2.2

7.9

1.1

1.1

7.9

1.1

1.1

2.2

2.2

1

1

1

27

71

1

1

4

2

1

110

10

0.9

0.9

0.9

24.5

64.5

0.9

0.9

3.6

1.8

0.9

1

Failed to obtain target number of subsampled organisms (100-110) during sorting process.

A total of 25 macroinvertebrate taxa were identified in 

subsamples of dip net collections from Green Spring, ranging 

from 9 in February 2004 to 18 in May 2004 (table 19). Subsampling of the May dip net collection failed to obtain the target 

number (110) of organisms, even though the May collection had 

the greatest taxonomic richness by season. The lower number 

of taxa collected by dip net in February corresponded to a lower 

number also collected in the petite ponar samples, thus suggesting 

a possible seasonal difference in the assemblage composition. Dip 

net collections differed notably from petite ponar dredge samples 

in percent composition of subsampled organisms. Dip net 

subsamples combined for all dates were more evenly represented 

by amphipods (33.7 percent; Hyalella azteca complex), dipterans 

(33.3 percent; no fewer than 13 total taxa, greatest richness in 

May with 10 taxa), and oligochaetes (30.4 percent). For dip net 

samples across all dates, the log2

 Shannon-Wiener index ranged 

from 1.55 to 3.25, Simpson’s index of diversity ranged from 

0.53 to 0.85, Pielou’s evenness ranged from 0.47 to 0.78, the SCI 

ranged from 6 to 15 with a mean of 9, and percent very tolerant 

taxa ranged from 26.3 to 53.6 (table 5).

Phelps and others (2006) reported that Green Spring has 

relatively low fish diversity and abundance; the only species 

observed were the poeciliids Gambusia holbrooki and Poecilia

latipinna, which were present in moderate abundance near the 

shoreline of the spring pool. Crayfish traps submerged near the 

edges of the spring pool captured few fish. Although Phelps 

and others (2006) speculated that other species could be present 

(such as other poeciliids, centrarchids, cyprinids, or ictalurids), 

the spring depth, nearly vertical walls of the spring pool, and low 

water clarity prevented any other practical means of effective 

sampling. No fish were observed or collected in the spring run. 

The isolated nature of the spring and unusual water chemistry 

(very low dissolved O2

 and high H2S concentrations) are likely 

limiting factors responsible for the depauperate fish fauna.
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 57

Juniper Springs

Juniper Springs (fig. 1), located in the Ocala National 

Forest, is a second-magnitude spring (mean and median 

discharge 10.8 and 10.9 ft3

/s, respectively) and forms an ovalshaped pool that measures about 120 by 90 ft (Rosenau and 

others, 1977; Scott and others, 2004). Multiple vents are present 

on the pool bottom; the substrate is sand, limestone bedrock 

is exposed near the vents, and scattered patches of aquatic 

macrophytes are present. The clear, bluish water has a lower 

dissolved solids concentration than most other Florida springs. 

The largest vent, which was sampled for this study, is located on 

the east side of the pool next to a limestone retaining wall that 

surrounds most of the pool. A historical millhouse and spillway 

are located on the east side of the pool. The pool drains into the 

spring run, Juniper Creek, which meanders to the east-northeast 

through the Juniper Prairie Wilderness area of Ocala National 

Forest for about 10 mi, where it discharges into Lake George 

on the St. Johns River. Fern Hammock Springs is located about 

0.25 mi downstream from Juniper Springs.

Near its headwaters, Juniper Creek historically had 

numerous additional small boils. Most of the sand boils 

located in the run downstream of the pool disappeared during 

this study as a result of pumping sand that had filled in the 

main spring vents over a 20-year period. In early 2006, spring 

boils had begun to undercut the banks, threatening to undermine the millhouse and create a safety risk. Therefore, in late 

2006 the U.S. Forest Service had the sand pumped from the 

spring vents, which had become boils themselves, in the pool 

area to reduce the pressure head on the spring system. After 

nearly 20 ft of sand was pumped from each of two vents in 

the pool area, hydrostatic pressure on the system was reduced 

enough to eliminate many of the boils in the spring run immediately downstream of the pool. The areal extent of the Juniper 

springshed has not been determined.

Land Use

Land-use data for the Juniper springshed were estimated 

based on observations made during this study. Because the 

spring is located deep within the Ocala National Forest, land 

use in the springshed during 1973-2004 was considered to be 

unchanged, and consisted mostly of forestland, some openwater/wetlands, and lesser areas of non-forested/barren land with 

small tracts for urban/mining/transportation/recreation mainly 

near the spring head. A few existing septic systems are the only 

means of wastewater treatment and disposal in the springshed.

Discharge

Discharge at Juniper Springs has been measured by the 

USGS and the SJRWMD since 1908 and 1983, respectively. 

At the time of this study, the USGS and SJRWMD jointly 

measured the discharge of Juniper Springs at least monthly. 

Discharge for Juniper Springs averaged 10.5 ft3

/s annually 

and varied with rainfall that averaged 49.33 in/yr within the 

springshed (fig. 36). Average annual discharge for Juniper 

Springs ranged from 6.0 ft3

/s in 1931 to 14.1 ft3/s in 1946. 

Measured (instantaneous) discharge from Juniper Springs 

averaged 10.7 ft3

/s, and ranged from 5.6 ft3/s in May 1991 

to 16.3 ft3

/s in July 1936 (fig. 37). Upper Floridan aquifer 

pumping for water supply at the Juniper Springs Recreation 

Area has an unknown effect on spring discharge. 

Water Chemistry and Age

Juniper Springs has a Ca-Mg-HCO3 water type (fig. 9) and 

is slightly undersaturated with respect to calcite and dolomite 

(table 3). Median values of pH, dissolved oxygen, and dissolved 

solids in spring water were 8.4, 6.6 mg/L, and 66 mg/L, respectively. Values of 18O and 2

H plot along the GMWL or local MWL 

parallel to the GMWL (Toth, 1999). The delta 34S concentration 

was 17.0 ppm, similar to that for modern sulfate evaporite 

minerals, and the 3

H concentration was 4.2 TU (Toth, 1999).

Nitrate-N concentrations from 1990 to 2006 generally were 

uniform and less than 0.2 mg/L, but recent spikes in concentration of up to 0.5 mg/L have occurred (fig. 10). Nitrate-N 

concentrations showed a significant (p < 0.04) increasing trend 

with time for samples collected during 1984-2007 (table 6). 

Concentrations of dissolved nitrogen and argon in water 

samples from Juniper Springs were consistent with atmospheric 

equilibration during ground-water recharge with the addition of 

minor amounts of excess air. Based on nitrogen and argon data 

in water samples collected in October 2006 and March 2007, 

the calculated recharge temperature was 20 to 21o

C (assuming 

a recharge elevation of 80 ft and 100 percent humidity at the 

water table). Values of delta 15N (5.35 per mil) and delta 18O 

(1.34 per mil) of nitrate in water samples collected in October 

2006 did not indicate any isotopic fractionation; therefore, active 

denitrification likely was not occurring in the Upper Floridan 

aquifer in the vicinity of Juniper Springs. Phosphorus (total P) 

concentrations in water samples collected during 2004-07 were 

uniformly low, averaging approximately 0.02 mg/L (fig. 11).

Water samples collected from Juniper Springs in October 

2006 and March 2007 were analyzed for 64 organic chemicals commonly associated with wastewater sources, plus 52 

pesticides. Triethyl citrate (E0.1 μg/L) was the only compound 

detected and quantified in the October 2006 water sample 

(app. 4). No pesticides were detected in water samples from 

Juniper Springs (app. 5). Water samples collected from Juniper 

Springs on October 19, 2006, were analyzed for antibiotics 

and all compounds were below method reporting levels.

Based on concentrations of CFCs in water samples 

collected from Juniper Springs in 2001, the age of spring 

water likely indicates a mixture of water recharged during 

1980-90 with 60 to 80 percent of old (greater than 60 years) 

tracer-free water (Toth and Katz 2006). Water samples also 

were collected in April 1996 and analyzed for 3

H, delta 13C, 

and 14C. Juniper Springs had a 3

H concentration of 4.2 TU, 

which indicated that the age of water was less than 43 years. 

Juniper Springs had a delta 13C of –9.5 per mil and a 14C 

concentration of 31 pmc. The adjusted 14C age is recent, and 

recharge likely occurred after about 1960.
58 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

YEAR

ANNUAL DISCHARGE =

10.5 CUBIC FEET PER SECOND

AVERAGE

AVERAGE ANNUAL RAINFALL

= 49.33 INCHES

JUNIPER SPRINGS

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

ANNUAL DISCHARGE, IN

CUBIC FEET PER SECOND

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

ANNUAL RAINFALL, IN INCHES

SPRING DISCHARGE

ANNUAL RAINFALL

EXPLANATION

Figure 36. Average annual discharge for Juniper Springs and rainfall for the Juniper springshed. 

INSTANTANEOUS DISCHARGE

EXPLANATION

AVERAGE INSTANTANEOUS DISCHARGE

JUNIPER SPRINGS

0

5

10

15

20

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

DISCHARGE, IN CUBIC FEET PER SECOND

YEAR

AVERAGE INSTANTANEOUS

DISCHARGE = 10.7 CUBIC FEET PER SECOND

Figure 37. Periodic and continuous discharge data for Juniper Springs, 1931-2007. Data collected by the 

St. Johns River Water Management District (SJRWMD) and U.S. Geological Survey. SJRWMD data used 

with permission. 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 59

Rock Springs

Rock Springs (figs. 1, 38, 39, table 1) is a second magnitude spring (mean and median annual discharge 59.3 and 

58.5 ft3

/s, respectively) (Rosenau and others, 1977; Scott and 

others, 2004). The spring is a popular recreational site, and the 

spring run is used extensively by swimmers, snorkelers, and 

tubers. Spring water discharges from two partly submerged 

caves at the base of a 20-ft limestone and sand bluff (fig. 38). 

Clear, bluish water discharges from the caves with considerable 

velocity and has substantially eroded the limestone along the 

initial part of the spring run. In contrast to most large springs in 

peninsular Florida, Rock Springs has no well-defined large pool 

at the spring head. About 10 ft downstream from the cavern 

opening, additional water is discharged through a submerged 

opening in the channel bottom. Rock ledges protrude from the 

banks of the run for about 100 ft downstream of the cavern 

opening. A boardwalk spans the spring run about 120 ft downstream from the cavern. About 1,000 ft downstream from the 

spring cavern, part of the spring flow is diverted from the spring 

run into a large swimming area mostly surrounded by concrete 

retaining walls (fig. 39). Overflow from the swimming area 

rejoins the run after passing through a concrete weir. The areal 

extent of the Rock springshed is 16.8 mi2

.

Macroinvertebrate samples were taken from several 

distinctly different sites in Rock Springs run to characterize, 

to the maximum extent possible, the fauna influenced by the 

spring outflow. The uppermost site was sampled between 

30 and 150 ft downstream of the cavern opening, where the 

substrate consisted of bare and periphyton-encrusted rock, 

mixed gravel, sand, crushed fossil shells, organic detritus 

and leaf pack, and rooted macrophytes (Valisneria). Along 

the middle reach, samples were collected near the swimming 

and picnic area on the east shoreline, and in the channelized 

sections just upstream of the swimming pool, in locations 

with minimal human disturbance. The substrate in these areas 

consisted of coarse sand, cobble, bare rock, snags, filamentous 

algae, and submergent, emergent, and floating macrophytes. 

The third sampling site was near the downstream boundary 

of the park, along a reach between 10 and 75 ft upstream of 

the boardwalk that spans the spring run. Substrate along this 

reach consisted of sand, submergent and floating macrophytes, 

snags, and detritus, with minimal algae cover due to moderate 

flow velocities caused by narrow channel morphology. 

Land Use

Land use in the Rock springshed from 1973 to 2004 

shifted primarily from open-water/wetlands to non-forested/

barren and urban lands, probably as a result of enhanced 

drainage and consequent drying of the land surface (fig. 4). 

Land use in the springshed in 1973 consisted of open-water/

wetlands (60.5 percent), urban/mining/transportation/

recreation (26.9 percent), and non-forested/barren land 

(12.6 percent). Land use in the springshed in 2004 consisted of 

non-forested/barren land (49.6 percent), urban/mining/transportation/recreation (30.6 percent), and open-water/wetlands 

(19.8 percent). As of 2005, municipal and centralized sewer 

systems, which are currently the primary means of wastewater 

treatment and disposal, replaced slightly more than 50 percent 

of the septic systems, primarily in the southern half of the 

springshed. Reclaimed wastewater, which is applied to 3.2 mi2

of the land surface, and discharge from the remaining septic 

units both augment ground-water recharge in the springshed.

Figure 38. Rock Springs cavern. Photograph by S.J. Walsh, 

September 27, 2006. 

Figure 39. Rock Springs run at central swimming area in Kelly 

Park. Photograph by S.J. Walsh, June 20, 2006. 
60 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Discharge

Discharge from Rock Springs has been measured by 

the USGS and SJRWMD since 1931 and 1983, respectively. 

At the time of this study, the SJRWMD and USGS jointly 

measured the discharge of Rock Springs at least bimonthly. 

Discharge for Rock Springs averaged 59.3 ft3

/s annually and 

varied greatly with rainfall that averaged 51.18 in/yr within 

the springshed (fig. 40). Average annual discharge for Rock 

Spring ranged from 45.9 ft3

/s in 2001 to 80.7 ft3/s in 1960. 

The lowest periods of discharge corresponded to periods of 

well-below average rainfall in the springshed. During periods 

of extremely low spring discharge, particularly in late spring 

and early summer, the Rock Springs swimming area is closed 

because of high bacteria counts. Reduced flushing action in 

the swimming area of the run, caused by low spring discharge, 

encourages the proliferation of animal fecal bacteria in the 

run that can present a public health risk to those who come in 

contact with contaminated water. Continued urbanization in 

the springshed of Rock Springs likely will slowly continue to 

reduce spring flow while adversely affecting the water quality 

of the spring. Measured (instantaneous) discharge from Rock 

Springs averaged 59.2 ft3

/s and ranged from 34.1 ft3/s in July 

1998 to 83.2 ft3

/s in October 1960 (fig. 41).

Water Chemistry and Age

Rock Springs has been sampled periodically by the 

USGS since 1956, with most samples collected during 

discharge measurements made until 1983; the SJRWMD has 

sampled Rock Springs since 1987. At the time of this study, 

the SJRWMD and the USGS jointly sampled Rock Springs at 

least four times per year.

Rock Springs has a Ca-Mg-HCO3

 water type (fig. 9) that 

is undersaturated with respect to calcite and dolomite (table 3). 

Median values of pH, dissolved oxygen, and dissolved solids 

were 7.7, 1.4 mg/L, and 144 mg/L, respectively. Values of 18O 

and 2

H plot along the GMWL or local MWL parallel to the 

GMWL (Toth, 1999). The 3

H concentration was 3.1 TU (Toth, 

1999), and the concentration of delta 34S was 9.4 per mil, 

which typically corresponds to low sulfate concentrations 

and indicates variable sources of sulfate, including rainfall 

and geochemical reactions along ground-water flow paths 

(Toth, 1999).

Nitrate-N concentrations in Rock Springs showed large 

fluctuations (0.17 to 1.8 mg/L) during 1984-2007, but especially during 2006-07 (fig. 22). The median nitrate-N concentration was 1.4 mg/L during 1984-2007. Nitrate concentrations 

showed a significant (p = 0.02) decreasing trend with time for 

samples collected during 1956-2007 (table 6). Phosphorus 

(total P) concentrations in Rock Springs were generally 

uniform (0.06-0.09 mg/L) during 2001-07 (fig. 23), but 

showed a significant (p < 0.001) decreasing trend with time 

for samples collected during 1999-2007 (table 6).

Based on concentrations of CFCs, 3

H, and 3He in water 

samples collected from Rock Springs in 2001, the age of 

spring water likely indicates a mixture of about 80 percent 

water recharged in 1980 with about 20 percent old (greater 

than 60 years) tracer-free water (Toth and Katz, 2006). Water 

samples also were collected in July 1995 and analyzed in 1995 

for 3

H, delta 13C, and 14C. The water samples had a 3H concentration of 3.1 TU, which indicated that the young fraction of 

water was less than 42 years old. Rock Springs had a delta 13C 

value of -9.08 per mil and a 14C value of 41 pmc. The adjusted 14C age of Rock Springs is less than 50 years (recharge 

occurred after about 1960).

Aquatic Communities

A total of 70 macroinvertebrate taxa were collected by 

petite ponar dredge from Rock Springs across four sampling 

dates (table 20). The number of taxa collected with this gear 

ranged from 13 in December 2005 to 39 in September 2006. 

Numerically dominant taxa in pooled samples across all 

dates were amphipods (32.5 percent; Gammarus cf. tigrinus, 

Gammarus sp., and Hyalella azteca complex), dipterans 

(26.7 percent; no fewer than 22 taxa), gastropods (19.9 percent; 

no fewer than 10 taxa), and oligochaetes (13.6 percent, no 

fewer than 14 taxa). Density of all organisms ranged from 

2.5 × 103

 per m2 (26.9 × 103 per ft2) in December 2005 to 

8.8 × 103

 per m2 (95.1 × 103 per ft2) in March 2006. For petite 

ponar samples across all dates, the log2 Shannon-Wiener index 

ranged from 2.71 to 4.55, Simpson’s index of diversity ranged 

from 0.79 to 0.94, Pielou’s evenness ranged from 0.65 to 

0.87, and the Florida Index ranged from 2 to 11 with a mean 

of 5.7 (table 4).

A total of 45 macroinvertebrate taxa were identified in 

subsamples of dip net collections from Rock Springs; the 

fewest was 14 in March 2006 and the greatest was 37 in June 

2006 (table 21). The percent composition of subsampled 

organisms combined for all collection dates was dominated by 

gastropods (52.6 percent, mostly the hydrobiid Amnicola dalli), 

amphipods (17.8 percent), and dipterans (17.8 percent). For dip 

net samples pooled across all dates, the log2 Shannon-Wiener 

index ranged from 2.45 to 4.01, Simpson’s index of diversity 

ranged from 0.71 to 0.92, Pielou’s evenness ranged from 0.49 

to 0.86, the SCI ranged from 12 to 33 with a mean of 19, and 

percent very tolerant taxa ranged from 4.6 to 22.9 (table 5). 

Rock Springs run in Kelly Park could not be electrofished 

due to a lack of boat access and heavy recreational use by 

park visitors. Therefore, an electroshocking boat was used on 

August 25, 2006, to sample a reach of the spring run downstream from Kelly Park (at approximately 28°46'17.04′′N, 

81°30'11.52′′W). The spring run in this section is moderately 

wide (20-100 ft), deep (3-6 ft), and heavily forested on both 

shorelines, but with a relatively open canopy. The water 

was moderately tannic and the substrate consisted of soft 

muck, detritus, fallen trees, and branches; areas of the spring 

run had patches of submergent and emergent macrophytes. 

Three passes were made with the electroshocking boat for a 

combined total of 30 min power output.
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 61

SPRING DISCHARGE

ANNUAL RAINFALL

ROCK SPRINGS EXPLANATION

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

90

100

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

ANNUAL DISCHARGE, IN

CUBIC FEET PER SECOND

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

ANNUAL RAINFALL, IN INCHES

YEAR

ANNUAL DISCHARGE =

59.3 CUBIC FEET PER SECOND

AVERAGE

AVERAGE ANNUAL RAINFALL

= 51.18 INCHES

Figure 40. Average annual discharge for Rock Springs and rainfall for the Rock springshed. 

ROCK SPRINGS

30

40

50

60

70

80

90

100

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

INSTANTANEOUS DISCHARGE

EXPLANATION

AVERAGE INSTANTANEOUS DISCHARGE

YEAR

AVERAGE INSTANTANEOUS

DISCHARGE = 59.2 CUBIC FEET PER SECOND

DISCHARGE, IN CUBIC FEET PER SECOND

Figure 41. Periodic and continuous discharge data for Rock Springs, 1931-2007. Data collected by the St. 

Johns River Water Management District (SJRWMD) and U.S. Geological Survey. SJRWMD data used 

with permission. 
62 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Table 20. Number of specimens (n) and percent density (%) per square meter of macroinvertebrates collected by pooled petite ponar 

dredge samples (n = 3 per date) from Rock Springs, December 2005-September 2006.

[LPIL, lowest practicable identification level]

Clade Taxon

Dec. 6, 2005 Mar. 27, 2006 June 21, 2006 Sept. 27, 2006

n % n % n % n %

Hydrozoa

Turbellaria

Gastropoda

Hirudinea

Oligochaeta

Amphipoda

Isopoda

Decapoda

Diptera

Hydra sp.

Tricladida (LPIL)

Turbellaria (LPIL)

Amnicola dalli

Ancylidae (LPIL)

Campeloma floridense

cf. Floridobia sp.

cf. Tarebia sp.

Elimia floridensis

Hydrobiidae (LPIL)

Laevapex peninsulae

Melanoides sp. (immature)

Melanoides tuberculata

Melanoides turricula

Pomacea paludosa

Helobdella stagnalis

Allonais inaequalis

Dero digitata

Dero furcata

Dero sp.

Eclipidrilus palustris

Eclipidrilus sp.

Haber speciosus

Ilyodrilus templetoni

Limnodrilus hoffmeisteri

Lumbriculus sp.

Lumbriculus variegatus

Naididae (LPIL)

Nais communis complex

Nais sp.

Slavina appendiculata

tubificoid Naididae immature sp. A (LPIL)

tubificoid Naididae immature sp. B (LPIL)

Varichaetadrilus angustipenis

Gammarus cf. tigrinus LeCroy

Gammarus sp.

Hyalella azteca complex Lecroy

Caecidotea sp.

Procambarus sp. (immature)

Ablabesmyia rhamphe group Epler

Bezzia/Palpomyia complex Brigham

cf. Cricotopus sp.

747

14

172

14

273

690

14

187

14

14

29.9

0.6

6.9

0.6

10.9

27.6

0.6

7.5

0.6

0.6

920

115

14

14

29

14

115

29

2,730

2,773

115

10.4

1.3

0.2

0.2

0.3

0.2

1.3

0.3

30.9

31.4

1.3

57

115

129

43

790

57

172

158

43

43

43

129

43

43

489

129

86

460

302

57

57

43

43

1.1

2.2

2.4

0.8

14.8

1.1

3.2

3.0

0.8

0.8

0.8

2.4

0.8

0.8

9.2

2.4

1.6

8.6

5.7

1.1

1.1

0.8

0.8

57

1,494

57

575

57

460

115

57

57

115

57

115

57

115

57

57

57

57

230

57

402

517

460

57

57

0.7

18.5

0.7

7.1

0.7

5.7

1.4

0.7

0.7

1.4

0.7

1.4

0.7

1.4

0.7

0.7

0.7

0.7

2.8

0.7

5.0

6.4

5.7

0.7

0.7
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 63

Table 20. Number of specimens (n) and percent density (%) per square meter of macroinvertebrates collected by pooled petite ponar 

dredge samples (n = 3 per date) from Rock Springs, December 2005-September 2006.—Continued

[LPIL, lowest practicable identification level]

Clade Taxon

Dec. 6, 2005 Mar. 27, 2006 June 21, 2006 Sept. 27, 2006

n % n % n % n %

Ephemeroptera

Odonata

Trichoptera

Total

Number of Taxa

Chironomidae (LPIL)

Chironomus sp.

Cricotopus bicinctus

Cricotopus politus

Cryptochironomus sp.

Dicrotendipes neomodestus

Dicrotendipes sp. (immature)

Larsia decolorata

Orthocladiinae (LPIL)

Paralauterborniella nigrohalteralis

Pentaneura inconspicua

Polypedilum flavum

Polypedilum scalaenum group Epler

Pseudochironomus sp.

Stempellinella sp.

Stenochironomus sp.

Tanytarsus sp.

Tanytarsus sp. C Epler

Tanytarsus sp. G Epler

Tanytarsus sp. L Epler

Tanytarsus sp. V Epler

Tribelos sp.

Caenis diminuta

Tricorythodes albilineatus

Macromia sp.

Cernotina sp.

Cheumatopsyche sp.

Nectopsyche pavida

14

172

172

2,497

13

0.6

6.9

6.9

101

690

115

230

230

230

115

230

29

8,838

20

1.1

7.8

1.3

2.6

2.6

2.6

1.3

2.6

0.3

57

345

302

43

86

129

43

86

388

43

57

129

86

14

5,339

37

1.1

6.5

5.7

0.8

1.6

2.4

0.8

1.6

7.3

0.8

1.1

2.4

1.6

0.3

172

115

57

57

115

115

1,092

115

115

460

57

115

57

57

8,095

39

2.1

1.4

0.7

0.7

1.4

1.4

13.5

1.4

1.4

5.7

0.7

1.4

0.7

0.7

A total of 91 fish specimens were collected representing 

15 species of 14 genera and 12 families (table 11). The 

community appeared to be relatively depauperate and abundance was low; catch per-unit-effort for each of the passes 

ranged from 2.1 to 4.6 fish/min and averaged 3.1 fish/min. 

The sample was dominated by centrarchids (49.4 percent, 

similar equitability for Lepomis auritus, L. punctatus, and 

Micropterus salmoides) and the catostomid Erimyzon sucetta

(14.3 percent). Notemigonus crysoleucas, Lepisosteus

platyrinchus, and Amia calva each constituted over 5 percent 

of the sample. Thus, six species accounted for 78 percent 

of the specimens collected. Two species of nonindigenous 

armored catfishes (Hoplosternum littorale and 

Pterygoplichthys disjunctivus) were collected; both species 

have colonized widely throughout the St. Johns drainage in 

recent years. Large adults of P. disjunctivus were observed in 

the swimming area of Kelly Park, and a park attendant indicated that this species was first observed in low numbers about 

5 years earlier (circa 2000), and was seen by the hundreds in 

2005-06. A midden of dead partial carcasses of this species 

was found in the park and was presumed to have been the 

result of predation by one or more otters (Lutra canadensis).
64 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Table 21. Number of specimens (n) and percent composition (%) of macroinvertebrates collected by dip net from Rock Springs, 

December 2005-September 2006. 

[Values represent material as subsampled to obtain the target number of organisms required for calculation of the Stream Condition Index. LPIL, lowest 

practicable identification level]

Clade Taxon Dec. 6, 2005 Mar. 27, 2006 June 21, 2006 Sept. 27, 2006

n % n % n % n %

Gastropoda

Hirudinea

Oligochaeta

Arachnida

Amphipoda

Isopoda

Decapoda

Diptera

Ephemeroptera

Hemiptera

Odonata

Trichoptera

Total

Number of Taxa

Amnicola dalli

cf. Tarebia sp.

Melanoides tuberculata

Melanoides turricula

Pyrgophorus platyrachis

Rissoidea (LPIL)

Helobdella stagnalis

Allonais inaequalis

Bratislavia unidentata

Dero digitata complex

Limnodrilus hoffmeisteri

Nais communis complex

Pristina leidyi

tubificoid Naididae immature sp. A (LPIL)

Hydrodroma sp.

Lebertia sp.

Limnesia sp.

Gammarus cf. tigrinus LeCroy

Hyalella azteca complex LeCroy

Cassidinidea ovalis

Palaemonetes paludosus

Chironomus sp.

Cricotopus bicinctus

Cricotopus politus

Cryptochironomus sp.

Dicrotendipes modestus

Dicrotendipes neomodestus

Paralauterborniella nigrohalteralis

Pentaneura inconspicua

Polypedilum flavum

Polypedilum scalaenum group Epler

Polypedilum tritum

Pseudochironomus sp.

Stempellinella fimbriata

Tanytarsus sp.

Tanytarsus sp. C Epler

Tanytarsus sp. L Epler

Thienemanniella sp.

Tipulidae (LPIL)

Tricorythodes albilineatus

Merragata sp.

Mesovelia mulsanti

Argia sp.

Enallagma sp.

Hydropsychidae (LPIL)

52

2

2

21

16

6

2

1

1

1

1

2

1

1

1

110

15

47.3

1.8

1.8

19.1

14.5

5.5

1.8

0.9

0.9

0.9

0.9

1.8

0.9

0.9

0.9

56

2

14

1

1

1

12

7

1

1

6

6

1

1

110

14

50.9

1.8

12.7

0.9

0.9

0.9

10.9

6.4

0.9

0.9

5.5

5.5

0.9

0.9

24

3

1

3

6

1

1

8

7

11

1

3

7

2

1

3

1

7

4

7

1

1

1

2

4

110

25

21.8

2.7

0.9

2.7

5.5

0.9

0.9

7.3

6.4

10.0

0.9

2.7

6.4

1.8

0.9

2.7

0.9

6.4

3.6

6.4

0.9

0.9

0.9

1.8

3.6

76

1

2

2

1

1

1

1

1

3

1

9

1

2

2

6

110

16

69.1

0.9

1.8

1.8

0.9

0.9

0.9

0.9

0.9

2.7

0.9

8.2

0.9

1.8

1.8

5.5
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 65

Silver Springs Group

The Silver Springs group (fig. 1, table 1) has the largest 

discharge (mean and median annual discharge 767 and 771 ft3

/s, 

respectively) of all inland first-magnitude springs in Florida. 

The Silver Springs group forms the headwaters of the Silver 

River (Marion County), which flows into the Ocklawaha River 

(Rosenau and others, 1977; Scott and others, 2004). Silver 

Springs has been a major tourist attraction for over 100 years 

(Munch and others, 2006). The upper 3,937 ft (1,200 m) of 

the river includes numerous named major spring vents and the 

majority of the smaller vents, the combined total of which may 

exceed 150 in number. The headspring consists of two vents, 

Mammoth East and West, which combined, contribute about half 

of the total flow of the springs group (Munch and others, 2006). 

A springshed area of 33,720 acres (52.7 mi2

) was delineated by 

Munch and others (2006) on the basis of the 2-year capture zone. 

Limited physicochemical samples were collected during 

the initial year (2004) of this study because of the amount 

of previous and ongoing research by other investigators. In 

a collaborative effort between the SJRWMD, University of 

Florida, and Wetland Solutions, Inc., Munch and others (2006) 

assessed the Silver Springs ecosystem in the context of a 

retrospective comparison with the benchmark studies of Odum 

(1957) and Knight (1980; 1983). The benchmark studies represent the most in-depth analyses of a first-magnitude spring in 

evaluating the complex linkages between land use, hydrology, 

water quality, and ecosystem function. Recent conditions 

and changes that have occurred over several decades are 

documented in the comprehensive assessment by Munch and 

others (2006).

Land Use

Munch and others (2006) provided detailed analyses 

of land use within the Silver Springs springshed, including 

identification of threats, high-risk areas, and a spatial land-use 

model to associate nitrogen loading rates with land cover. 

Between 1949 and 1989, the springshed (2-year capture zone) 

shifted from a predominantly natural to more urbanized land 

use. In 1949, natural land cover (including forest and vegetative areas, wetlands, and open water) accounted for 74 percent 

of the surface area for the 2-year capture zone, whereas urban 

areas covered only 3.3 percent. By 1989, natural land cover 

had diminished to 45 percent, and the urban areas increased 

to 29 percent. From 1989 to 2005, the trend in urbanization 

continued, with natural and urban lands constituting a total 

of 36 percent and 37 percent of springshed area, respectively. 

The percentages of land covered by agriculture and pasture 

remained fairly constant over the entire 1949-2005 period, 

with declines of about 1.5 percent for each land-use category.

Discharge

Discharge from Silver Springs has been measured by 

the USGS since 1932. Continuous, daily discharge record is 

computed from the relationship among artesian pressure at 

a local well (CE-76), spring-pool elevation, and discharge 

measured at a site 0.7 mi downstream from the head of the 

springs on the Silver River. Discharge for Silver Springs 

averaged 767 ft3

/s annually and varied greatly with rainfall 

that averaged 50.86 in/yr within the springshed (fig. 42). 

Average annual discharge for Silver Springs ranged from 

SILVER SPRINGS

10

100

1,000

10,000

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

ANNUAL DISCHARGE, IN

CUBIC FEET PER SECOND

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

ANNUAL RAINFALL, IN INCHES

YEAR

ANNUAL DISCHARGE =

767 CUBIC FEET PER SECOND

AVERAGE

AVERAGE ANNUAL RAINFALL

= 50.86 INCHES

SPRING DISCHARGE

ANNUAL RAINFALL

EXPLANATION

Figure 42. Average annual discharge for Silver Springs and rainfall for the Silver springshed. 
66 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

445 ft3/s in 2001 to 1,108 ft3/s in 1960. Measured (instantaneous) discharge from Silver Springs averaged 768 ft3

/s and 

ranged from 350 ft3

/s in June 2001 to 1,290 ft3/s in October 

1960 (fig. 43).

Water Chemistry and Age

Descriptions of the water chemistry and synoptic waterquality data for the Silver Springs group were summarized 

by Phelps (1994), Scott and others (2002; 2004), Phelps 

and others (2006), and Munch and others (2006). The Silver 

Springs group has a Ca-HCO3

 water type. Average values of 

pH, dissolved oxygen, and specific conductance at the Main 

Spring Boil reported by Munch and others (2006) were 7.3, 

2.2 mg/L, and 452 μS/cm, respectively. Average dissolved 

oxygen concentrations in surface water varied between 

sampling stations and ranged from 1.3 mg/L at Christmas 

Tree Spring to 4.1 mg/L at a station 0.74 mi (1,200 m) 

downstream from the Main Spring Boil. The following 

constituents were found to decline from the farthest upstream 

to farthest downstream stations, as summarized by Munch 

and others (2006): average total alkalinity (184 to 169 mg/L 

as CaCO3

), total Kjeldahl nitrogen (0.05 to 0.04 mg/L), total 

ammonia nitrogen (0.015 to 0.013 mg/L), total nitrogen 

(1.19 to 1.17 mg/L), calcium (77 to 72 mg/L), turbidity 

(0.16 to 0.10 NTU), total fluoride (0.19 to 0.17 mg/L), and 

total potassium (0.62 to 0.57 mg/L). Constituent concentrations that increased, on average, between the upstream and 

downstream stations included sulfate (44 to 54 mg/L), sodium 

(5.9 to 6.4 mg/L), total dissolved solids (277 to 281 mg/L), 

nitrate plus nitrite nitrogen (1.10 to 1.14 mg/L), total 

phosphorus (0.046 to 0.060 mg/L), total coliforms (7.1 to 

131 col/100 mL), and fecal coliforms (1.7 to 77 col/100 mL). 

No differences were observed between these stations in 

average concentrations of total suspended solids and orthophosphorus, or in average color.

The average concentration of nitrate nitrogen values in 

Silver Springs waters has increased over 200 percent during 

the last 50 years (Munch and others, 2006). Odum (1957) 

reported an average nitrate nitrogen concentration in the Main 

Spring Boil of 0.46 mg/L in 1953. Data collected during 

1978-79 and 2003-05 indicated average values of about 

0.67 mg/L and 1.14 mg/L, respectively (Munch and others, 

2006). No similar increase in any other form of nitrogen or 

phosphorus was observed over the 50-year period examined 

by Munch and others (2006).

In a study of nitrate concentrations and land-use patterns, 

Phelps (2004) estimated water issuing from Silver Springs to 

be less than 30 years old. Toth (2003) examined water quality 

and measured isotopes, and concluded that the age of the 

spring water was less than 100 years. Thus, the geology of the 

springshed recharge zone suggests that ground water within 

the uppermost part of the Floridan aquifer system provides a 

large percentage of total Silver Springs discharge (Munch and 

others, 2006).

Aquatic Communities

The aquatic communities of Silver Springs were not examined in this study. Collectively, the fauna and flora of the Silver 

River is the best studied of any spring or spring-fed river in Florida 

and was summarized in detail by Munch and others (2006).

The FDEP sampled benthic macroinvertebrates biannually 

at Silver Springs each year from 2002 to 2007, except in 2005 

when only one sample was collected. These samples were 

collected using standardized FDEP protocols with D-frame 

dip net for calculation of the SCI. During this time period, 

recalibration of the SCI procedures yielded different numbers of 

targeted organisms and replicate samples, depending on the year 

of collection. For combined samples, total number of benthic 

macroinvertebrate taxa ranged from 18 to 31 with a mean of 

22.4. The SCI ranged from 19 to 46 (mean = 27.2), percent 

dominant taxon ranged from 24.3 to 73.1 (mean = 45.9 percent), 

percent very tolerant taxa ranged from 0 to 32.4 (mean = 11.3), 

and the Florida Index ranged from 5 to 14 (mean = 8). Most 

samples were dominated by the amphipod Hyalella azteca; 

however, samples in October 2002 and November 2004 were 

dominated by the chironomid Tanytarsus sp. C Epler, and 

samples in June 2006 and October 2007 were co-dominated, 

respectively, by the chironomid Rheotanytarsus sp. (exiguus

group) and the hydrobiid Spilochlamys gravis.

Several fish surveys of the Silver River have used 

qualitative and quantitative methods (Hubbs and Allen, 1943; 

Odum, 1957; Knight, 1980; Walsh and Williams, 2003; Munch 

and others, 2006). Although approximately 41 species have been 

recorded among these surveys, the number of species collected 

during each study is imprecise due to questionable identifications and nomenclature reported by previous authors. Some 

taxa reported in early studies, but not verified in more recent 

surveys, suggest misidentifications (for example, Hybopsis sp., 

Mugil curema); other taxa, however, may represent species 

that were historically present and likely still present but not 

recently detected due to small body size, low abundance, habitat 

preference, or other factors (for example, Leptolucania ommata, 

Jordanella floridae, Enneacanthus sp., Elassoma evergladei). 

There is evidence of a recent shift in the community structure of 

fish populations in the Silver River due to the greater biomass 

of carnivorous species in comparison to omnivores, with 

three historically dominant species (Mugil cephalus, Ictalurus

punctatus, and Dorosoma cepedianum) having been reduced 

in abundance by approximately 92 percent over a 50-year 

time span (Munch and others, 2006). Two nonindigenous fish 

species, Pterygoplichthys disjunctivus and Oreochromis aureus, 

were recently recorded (Walsh and Williams, 2003; Munch and 

others, 2006); however, the effects of their presence on native 

communities, if any, are unknown. A few individuals of an 

unidentified species of pacu (probably Colossoma macropomum

or Piaractus brachypomus) were observed in upper reaches 

of the Silver River in 2008 (R.L. Knight, Wetlands Solutions, 

Inc., oral commun., 2008). Pterygoplichthys disjunctivus and 

O. aureus are well established in the St. Johns River, but there 

is no evidence that any species of pacu is. Additional studies of 

the Silver River fish fauna are warranted to better document and 

quantify the diversity and relative abundances of populations, 

and to evaluate the potential effects of changes to the springshed.
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 67

SILVER SPRINGS

100

1,000

10,000

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

YEAR

SPRING DISCHARGE, IN CUBIC FEET PER SECOND AVERAGE INSTANTANEOUS DISCHARGE = 768 CUBIC FEET PER SECOND

AVERAGE INSTANTANEOUS DISCHARGEINSTANTANEOUS DISCHARGE

EXPLANATION

Continuous discharge data for Silver Springs, 1932-2007. Data collected by the St. Johns River Water Management 

. SJRWMD data used with permission. 

 Figure 43.

District (SJRWMD) and U.S. Geological Survey
68 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Silver Glen Springs

Silver Glen Springs (figs. 1, 44, 45, table 1) is a first 

magnitude spring (mean and median discharge 104 and 102 ft3

/s, 

respectively) (Rosenau and others, 1977; Scott and others, 

2004). The spring head and a portion of the run are located in 

a multi-use recreation area in the Ocala National Forest. Two 

vents contribute discharge that coalesces to form a large pool 

measuring about 200 ft across from north to south and about 

175 ft east to west. Boils are evident at the surface above both of 

the main spring vents. The primary vent (fig. 44) is northeast of 

the secondary vent and lies in a conical depression of exposed 

limestone at a depth of about 18 ft. The secondary vent is in a 

vertical, limestone cave opening at a depth of about 40 ft with 

a pool diameter of about 12 to 15 ft; this vent is sometimes 

referred to as the “Natural Well” (Scott and others, 2004). The 

secondary vent is roped off near where its short run joins the 

main spring pool, and is inaccessible to recreational users. Water 

that issues from the secondary vent is more mineralized than 

that of the primary vent. Additional flow is supplied from sand 

boils in the bottom of the spring run downstream from the head 

of the spring vents. Most of the large pool area is shallow and 

has a sand substrate with limestone outcrops and patches of 

submergent vegetation. The north and west edge of the spring 

pool consists of an extensive limestone ledge. The “Natural 

Well” spring run and sections of the main spring pool, especially 

on the southwest side, are densely vegetated with submergent 

rooted macrophytes. The spring pool receives heavy use by 

swimmers and snorkelers, and the run downstream of the spring 

pool is often crowded with boats and people during peak periods 

of recreational use. A cable extends across the entire spring 

run downstream of the spring pool to prevent boat traffic from 

entering the vent areas. The spring run (fig. 45) is about 200 ft 

wide and flows easterly about 0.75 mi into the west side of Lake 

George. Large schools of fish congregate in the spring pool, 

especially near the vents. Thick mats of algae cover the substrate 

and rooted macrophytes in extensive areas of the spring pool 

and spring run, and partly cover the water surface when mats 

float to the top of the water column as a result of off-gassing. 

Algae are more prevalent in the spring and early summer prior to 

heavy recreational activity that dislodges and redistributes them 

downstream along the spring run.

Land Use

Land use in the Silver Glen springshed remained relatively unchanged from 1973 to 2004, and consisted primarily 

of forested land. Slight changes were attributed to a decrease 

in open-water/wetlands, a decrease in non-forested/barren 

land, and a small increase in lands used for agriculture (fig. 4). 

Land use in the springshed in 1973 consisted of forestland 

(95.2 percent), non-forested/barren land (4.4 percent), openwater/wetlands (0.4 percent), and urban/mining/transportation/

recreation (less than 0.1 percent). Land use in the springshed 

in 2004 consisted of forestland (93.8 percent), agriculture 

(3.3 percent), non-forested/barren land (2.8 percent), openwater/wetlands (less than 0.1 percent), and urban/mining/

transportation/recreation (less than 0.1 percent). As of 2007, 

no wastewater services were active in the Silver Glen springshed, and septic systems were the only method of wastewater 

treatment and disposal.

Discharge

Discharge from Silver Glen Springs has been measured by 

the USGS since 1931 and by the SJRWMD since 1983. At the 

time of this study, the SJRWMD and the USGS measured the 

discharge from Silver Glen Springs at least monthly. Continuous 

discharge record was computed using the relation between 

artesian pressure at a nearby well, spring-pool elevation, and 

Figure 44. Main vent of Silver Glen Springs. Photograph by 

S.J. Walsh, January 31, 2007. 

Figure 45. Silver Glen Springs and upper section of run. 

Photograph courtesy of the St. Johns River Water Management District, used with permission. 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 69

SILVER GLEN SPRINGS

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

ANNUAL DISCHARGE, IN

CUBIC FEET PER SECOND

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

ANNUAL RAINFALL, IN INCHES

YEAR

ANNUAL DISCHARGE =

104 CUBIC FEET PER SECOND

AVERAGE

AVERAGE ANNUAL RAINFALL

= 51.06 INCHES

SPRING DISCHARGE

ANNUAL RAINFALL

EXPLANATION

Figure 46. Average annual discharge for Silver Glen Springs and rainfall for the Silver Glen springshed. 

discharge measured approximately 50 ft downstream of both 

vents. Discharge for Silver Glen Springs averaged 104 ft3

/s 

annually, and varied greatly with rainfall that averaged 

51.06 in/yr within the springshed (fig. 46). Average annual 

discharge for Silver Glen Springs ranged from 61.5 ft3

/s in 1986 

to 135 ft3

/s in 1982. Flow in the spring run is tidally affected and 

controlled by stage in the St. Johns River (Lake George), which 

occasionally is high enough to cause backwater in the run, 

elevate pool stage, and consequently, suppress spring discharge. 

Measured (instantaneous) discharge from Silver Glen Springs 

averaged 103 ft3

/s, and ranged from 57.0 ft3/s in June 2007 to 

259 ft3

/s in September 2004 (fig. 47).

Water Chemistry and Age

Silver Glen Springs has been sampled by the USGS since 

1972, with field measurements made periodically through 

1999. The SJRWMD has sampled Silver Glen Springs since 

1984. At the time of this study, the SJRWMD and the USGS 

jointly sampled the main vent of Silver Glen Springs at least 

four times per year.

Silver Glen Springs has a Na-Cl water type (fig. 9) and is 

at equilibrium (saturated) with respect to calcite and slightly 

undersaturated with respect to dolomite (table 3). Median 

values of pH, dissolved oxygen, and dissolved solids in water 

were 7.8, 3.7 mg/L, and 1,070 mg/L, respectively. Delta 18O 

and 2

H plot along the GMWL or local MWL parallel to the 

GMWL (Toth, 1999). Delta 34S was 20.2 ppm, similar to that 

for modern sulfate evaporite minerals (Toth, 1999).

Nitrate-N concentrations generally were uniform and 

less than 0.2 mg/L from 1990 to 2006, although recent spikes 

in concentration of up to 0.5 mg/L have occurred (fig. 10). 

Phosphorus (total P) concentrations were generally uniform, 

averaging approximately 0.02 mg/L during 2004-07 (fig. 11); 

however, orthophosphate concentrations showed a significant 

(p < 0.02) decreasing trend with time for samples collected 

from 1972 to 2007 (table 6). Median concentrations of nitrateN and total P were 0.04 and 0.02 mg/L, respectively, for 

the 1972-2007 period. Concentrations of dissolved nitrogen 

and argon in water samples from Silver Glen Springs were 

consistent with atmospheric equilibration during ground-water 

recharge with the addition of minor amounts of excess air. 

Based on nitrogen and argon data in water samples collected 

in October 2006 and March 2007, the calculated recharge 

temperature was 22 to 23o

C (assuming a recharge elevation of 

75 ft and 100-percent humidity at the water table). Values of 

delta 15N (5.63 per mil) and delta 18O (-0.68 per mil) of nitrate 

in water samples collected in October 2006 did not indicate 

any isotopic fractionation; therefore, active denitrification 

likely was not occurring in the Upper Floridan aquifer in the 

vicinity of Silver Glen Springs. 

Water samples collected from Silver Glen Springs on 

October 19, 2006, were analyzed for antibiotics, and all 

compounds were below method reporting levels. Water samples 

collected from Silver Glen Springs in October 2006 and 

March 2007 were analyzed for 64 organic chemicals commonly 

associated with wastewater sources, plus 52 pesticides. 

Phenol (E0.17 μg/L) was the only compound detected in the 
70 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

INSTANTANEOUS DISCHARGE

EXPLANATION

AVERAGE INSTANTANEOUS DISCHARGE

SILVER GLEN SPRINGS

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

210

220

230

240

250

260

270

280

290

300

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

DISCHARGE, IN CUBIC FEET PER SECOND

YEAR

AVERAGE INSTANTANEOUS

DISCHARGE = 103 CUBIC FEET PER SECOND

Figure 47. Periodic and continuous discharge data for Silver Glen Springs, 1931-2007. Data collected by 

the St. Johns River Water Management District (SJRWMD) and U.S. Geological Survey. SJRWMD data used 

with permission. 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 71

March 2007 water sample (app. 4). No pesticides were detected 

in water samples from Silver Glen Springs (app. 5). In 2006-07, 

the USGS sampled the main vent at Silver Glen Springs 

for chlorophyll-a, pheophytin-a, wastewater compounds, 

pesticides, antibiotics, and dissolved gases. Chlorophyll-a

and pheophytin-a concentrations in 2007 ranged from 0.1 to 

0.66 μg/L and 0.1 to 1.77 μg/L, respectively. No wastewater 

compounds, pesticides, or antibiotics were detected in water 

samples from Silver Glen Springs. Dissolved gas concentrations 

(nitrogen and argon) were consistent with atmospheric 

equilibration, and no excess nitrogen gas was measured. 

Based on concentrations of CFCs in water samples 

collected from Silver Glen Springs in 2001, the age of 

spring water likely indicates a mixture of about 20 percent 

of water recharged in about 1980 and about 80 percent 

older tracer-free water (greater than 60 years) (Toth and 

Katz 2006). The 3

H/3He age indicated an age of 26 years 

for the young fraction. Silver Glen Springs had a delta 13C 

value of –7.70 per mil and a 14C concentration of 20 pmc, 

which results from the mixing of Upper and Lower Floridan 

aquifer water. The adjusted 14C age is less than 50 years, with 

recharge occurring after about 1960.

Aquatic Communities

A total of 47 macroinvertebrate taxa were collected by 

petite ponar dredge from Silver Glen Springs across four 

sampling dates (table 22). The number of taxa collected with 

this gear ranged from 19 in October 2007 to 24 in May 2007. 

Numerically dominant taxa for samples pooled across all 

dates were mostly amphipods (57.1 percent; no fewer than 

four taxa) and gastropods (18.2 percent; no fewer than six 

taxa), with oligochaetes and dipterans comprising most of the 

remaining taxa (12.4 percent and 4.4 percent, respectively). 

The density for all organisms ranged from 12.6 × 103

 per m2 

(136.1 × 103 per ft2) in August 2007 to 26.1 × 103 per m2

(281.2 × 103

 per ft2) in May 2007. For petite ponar samples 

for all dates, the log2

 Shannon-Wiener index ranged from 

2.74 to 3.01, Simpson’s index of diversity ranged from 0.67 

to 0.82, Pielou’s evenness ranged from 0.62 to 0.68, and 

the Florida Index ranged from 2 to 6 with a mean of 4.25 

(table 4).

A total of 36 macroinvertebrate taxa were identified in 

subsamples of dip net collections from Silver Glen Springs 

(table 23). The number of taxa ranged from 14 in January 2007 

to 19 in March 2007. The percent composition of subsampled 

organisms combined for all collection dates was dominated 

by amphipods (45.7 percent) and gastropods (31.8 percent, 

mostly cf. Aphaostracon sp. and cf. Tarebia sp.), with 

lesser numbers of oligochaetes (7.3 percent) and dipterans 

(6.4 percent). For dip net samples pooled across all dates, 

the log2

 Shannon-Wiener index ranged from 2.62 to 3.44, 

Simpson’s index of diversity ranged from 0.76 to 0.88, the 

SCI ranged from 14 to 25 with a mean of 18, and percent very 

tolerant taxa ranged from 2.7 to 23.6 (table 5).

The benthic macroinvertebrate fauna of Silver Glen 

Springs includes several taxa that are most commonly 

associated with estuarine or nearshore waters: the amphipods 

Gammarus mucronatus complex, G. cf. tigrinus, 

Grandidierella bonnieroides, and unidentified species of 

the family Aoridae; the isopods Cassidinidea ovalis and 

Uromunna reynoldsi; and the decapod Palaemonetes vulgaris. 

The occurrence of these taxa at Silver Glen Springs is 

probably due to the high water conductivity, relict connate 

saltwater reserves in the vicinity of the spring, and connection of Lake George with the Atlantic Ocean by way of the 

St. Johns River. Specimens provisionally assigned to the 

G. mucronatus complex may be a disjunct population of an 

undescribed form known from the northern Gulf of Mexico, 

or a newly discovered species. 

Fishes were sampled by electroshocking boat in the Silver 

Glen Spring run downstream of the spring pool on May 15, 

2007. Collecting with this gear was relatively inefficient due to 

the depth of the spring run and high water conductivity; thus, 

assessment of the fish community was augmented by using 

mask and snorkel in the spring pool to visually observe species 

presence and relative abundances on May 15 and August 7, 

2007. At least 811 specimens were collected or observed, 

representing 24 species of 19 genera and 16 families (table 9). 

Numerical estimates were made for species visually recorded 

but not collected (for example, Morone saxatilis, Lutjanus

griseus, Mugil cephalus, Lucania parva, and Notropis spp.). 

The fish assemblage was dominated by fundulids 

(29.6 percent, especially L. parva), the moronid M. saxatilis

(24.7 percent), and cyprinids (21.6 percent, Notropis harperi

and N. petersoni). Relative abundances are considered 

qualitative, however, given the large area of unsurveyed habitat 

and the presumably large margin of error in visual count 

estimates. Three nonindigenous species, Hoplosternum

littorale, Pterygoplichthys disjunctivus, and Oreochromis aureus, 

were observed or collected, but they appeared to be in lower 

abundance here than in other springs where they were recorded 

during this study. 

A notable characteristic of the Silver Glen Springs 

ichthyofauna was the presence of diadromous and/or 

euryhaline species of marine derivation: M. saxatilis, 

L. griseus, M. cephalus, Anguilla rostrata, Menidia beryllina, 

and Gobiosoma bosc. These species likely inhabit this system 

due to the high carbonate and other ionic content of the spring 

water. The large numbers of M. saxatilis fluctuated seasonally; in early spring, numerous large adults were observed 

rheophilically oriented in and around the main spring vent, 

but many apparently dispersed from the spring pool during 

summer months when recreational use peaked. Most if not all 

individuals of this species were presumed to have originated 

as hatchery-reared, stocked fish. Small schools of M. cephalus

were observed and videotaped grazing on abundant mats of 

algae in the spring pool.
72 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Table 22. Number of specimens (n) and percent density (%) per square meter of macroinvertebrates collected by pooled petite ponar 

dredge samples (n = 3 per date) from Silver Glen Springs, January-October 2007.

[LPIL, lowest practicable identification level]

Clade Taxon

Jan. 31, 2007 May 10, 2007 Aug. 7, 2007 Oct. 10, 2007

n % n % n % n %

Turbellaria

Gastropoda

Hirudinea

Oligochaeta

Amphipoda

Isopoda

Decapoda

Diptera

Total

Number of Taxa

Tricladida (LPIL)

Turbellaria (LPIL)

cf. Pyrgophorus platyrachis

cf. Tarebia sp.

Elimia floridensis

Hydrobiidae (LPIL)

Hydrobiidae sp. C Line

Laevapex sp.

Melanoides sp. (immature)

Melanoides turricula

Gloiobdella elongata

Chaetogaster diaphanus

Dero digitata complex

Dero lodeni

Dero sp.

Eclipidrilus palustris

Ilyodrilus templetoni

Limnodrilus hoffmeisteri

Pristina breviseta

Pristina leidyi

Pristina sp.

tubificoid Naididae immature sp. A (LPIL)

tubificoid Naididae immature sp. B (LPIL)

Amphipoda (LPIL)

Aoridae (LPIL)

Gammarus cf. tigrinus LeCroy

Gammarus mucronatus complex LeCroy

Gammarus sp.

Grandidierella bonnieroides

Hyalella azteca complex Lecroy

Caecidotea racovitzai australis

Caecidotea sp.

Cassidinidea ovalis

Cyathura polita

Uromunna reynoldsi

Cambaridae (LPIL)

cf. Cricotopus sp.

Chironomus sp.

Cricotopus politus

Cryptochironomus sp.

Dicrotendipes sp. (immature)

Goeldichironomus carus

Polypedilum tritum/illinoense group Epler

Pseudochironomus sp.

Tanypodinae (LPIL)

Tanytarsus sp.

Tanytarsus sp. C Epler

115

115

230

230

115

115

345

575

345

5,517

5,747

920

5,402

230

1,264

230

230

115

690

115

115

115

22,875

22

0.5

0.5

1.0

1.0

0.5

0.5

1.5

2.5

1.5

24.1

25.1

4.0

23.6

1.0

5.5

1.0

1.0

0.5

3.0

0.5

0.5

0.5

115

115

690

1,149

115

805

230

805

374

575

115

805

1,149

1,379

13,793

345

115

115

1,494

115

1,264

115

230

115

26,122

24

0.4

0.4

2.6

4.4

0.4

3.1

0.9

3.1

1.4

2.2

0.4

3.1

4.4

5.3

52.8

1.3

0.4

0.4

5.7

0.4

4.8

0.4

0.9

0.4

460

115

460

115

115

115

115

115

345

460

460

230

115

115

460

575

7,126

230

690

115

115

12,646

21

3.6

0.9

3.6

0.9

0.9

0.9

0.9

0.9

2.7

3.6

3.6

1.8

0.9

0.9

3.6

4.5

56.3

1.8

5.5

0.9

0.9

345

5,862

6,437

345

230

115

920

3,448

230

345

115

575

805

690

115

115

115

115

230

21,152

19

1.6

27.7

30.4

1.6

1.1

0.5

4.3

16.3

1.1

1.6

0.5

2.7

3.8

3.3

0.5

0.5

0.0

0.5

0.5

1.1
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 73

Table 23. Number of specimens (n) and percent composition (%) of macroinvertebrates collected by dip net from Silver Glen Springs, 

January-October 2007 

[Values represent material as subsampled to obtain target number of organisms required for calculation of the Stream Condition Index. LPIL, lowest practicable 

identification level]

Clade Taxon

31 Jan 2007 10 May 2007 7 Aug 2007 10 Oct 2007

n % n % n % n %

Turbellaria

Gastropoda

Oligochaeta

Arachnida

Amphipoda

Isopoda

Decapoda

Diptera

Ephemeroptera

Hemiptera

Total

Number of Taxa

Tricladida (LPIL)

cf. Aphaostracon sp.

cf. Floridobia sp.

cf. Spilochlamys sp.

cf. Tarebia sp.

Melanoides sp. (immature)

Melanoides tuberculata

Planorbella scalaris

Dero digitata complex

Limnodrilus hoffmeisteri

Lumbriculus sp.

Pristina leidyi

tubifoid Naididae immature sp. A (LPIL)

Arrenurus sp.

Aoridae (LPIL)

Gammarus cf. tigrinus LeCroy

Gammarus mucronatus complex LeCroy

Hyalella azteca complex LeCroy

Caecidotea racovitzai australis

Caecidotea sp.

Cassidinidea ovalis

Palaemonetes paludosus

Palaemonetes vulgaris

Procambarus sp. (immature)

Bezzia/Palpomyia complex Brigham

Chironomus sp.

Cladotanytarsus cf. daviesi Epler

Cricotopus politus

Cryptochironomus sp.

Dicrotendipes sp. A Epler

Polypedilum illinoense group Epler

Pseudochironomus sp.

Tanytarsus limneticus

Caenis sp.

Callibaetis sp.

Heteroptera (LPIL)

2

4

26

1

1

4

4

8

35

16

2

3

1

3

110

14

1.8

3.6

23.6

0.9

0.9

3.6

3.6

7.3

31.8

14.5

1.8

2.7

0.9

2.7

3

3

24

1

1

13

2

2

9

3

15

19

1

1

6

1

4

1

1

110

19

2.7

2.7

21.8

0.9

0.9

11.8

1.8

1.8

8.2

2.7

13.6

17.3

0.9

0.9

5.5

0.9

3.6

0.9

0.9

39

1

36

7

1

1

2

1

3

9

2

3

2

1

2

110

15

35.5

0.9

32.7

6.4

0.9

0.9

1.8

0.9

2.7

8.2

1.8

2.7

1.8

0.9

1.8

1

2

3

22

27

25

1

2

13

4

3

2

2

1

1

1

110

16

0.9

1.8

2.7

20.0

24.5

22.7

0.9

1.8

11.8

3.6

2.7

1.8

1.8

0.9

0.9

0.9
74 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Wekiwa Springs

Wekiwa Springs (figs. 1, 48, 49, table 1) is a second 

magnitude spring (mean and median discharge 68.0 and 

66.5 ft3

/s, respectively) (Rosenau and others, 1977; Scott 

and others, 2004). Wekiwa Springs is listed in the USGS 

Geographic Names Information System (http://geonames.usgs.

gov/domestic/index.html) as “Wekiva Springs.” Although the 

name used herein follows Scott and others (2004), the plural 

form (“springs”) is used because there are two main vents. The 

spring pool is located in a semitropical forest at the base of a 

northeastern-sloping, grassy hillside. The spring pool is used 

for swimming and snorkeling, and the area surrounding the 

spring pool and upper reach of the spring run is developed as a 

recreation area with concession facilities and boardwalks. Two 

areas of discharge in Wekiwa Springs produce surface boils in 

the southeastern half of the pool near its edge. The strongest 

boil (fig. 49) is over a large, irregularly shaped vent about 

35 ft long by 5 ft wide in the limestone bottom and about 15 ft 

below the surface. The other boil is above a rock ledge along 

the extreme southeastern edge of the pool. The pool substrate 

is mostly sand, except for the limestone rock bottom in the 

southeastern part of the pool. The spring pool is kidneyshaped, about 200 ft long and 100 ft wide, and elongated 

toward the southeast. A sidewalk surrounds the pool and a 

wooden footbridge crosses the run immediately downstream 

of the pool. A limerock retaining wall encloses the pool and 

extends a short distance down the run. At its widest point, the 

upper section of the Wekiwa Springs run expands into a large 

slow-flowing pool about 320 ft across and 490 ft long; the run 

then narrows to about 20-40 ft wide and flows approximately 

2,900 ft (0.55 mi) to its confluence with Rock Springs run 

Figure 48. Upstream view of Wekiwa Springs pool from 

footbridge spanning upper section of spring run. Photograph by 

S.J. Walsh, August 21, 2002. 

Figure 49. Close-up view of Wekiwa Springs main vent. 

Photograph courtesy of the St. Johns River Water Management 

District, used with permission. 

(fig. 50). The combined discharge from Rock and Wekiwa 

Springs forms the headwaters of the Wekiva River, a National 

Wild and Scenic River that is designated as an Outstanding 

Florida Water by the FDEP. The areal extent of the Wekiwa 

springshed is 31.6 mi2

.

Land Use

The Wekiwa springshed shifted from predominantly agricultural toward urbanized land use from 1973 to 2004 (fig. 4). 

Drying and enhanced drainage of the land surface probably 

Figure 50. Wekiwa Springs run near confluence with Rock 

Springs Run. Photograph by S.J. Walsh, July 17, 2006. 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 75

WEKIWA SPRINGS

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

90

100

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

ANNUAL DISCHARGE, IN

CUBIC FEET PER SECOND

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

ANNUAL RAINFALL, IN INCHES

YEAR

ANNUAL DISCHARGE =

68.0 CUBIC FEET PER SECOND

AVERAGE

AVERAGE ANNUAL RAINFALL

= 51.19 INCHES

SPRING DISCHARGE

ANNUAL RAINFALL

EXPLANATION

Figure 51. Average annual discharge for Wekiwa Springs and rainfall for the Wekiwa springshed. 

contributed to a substantial decrease in open-water/wetlands and 

a slight increase in non-forested/barren lands. These changes, 

combined with a reduction in agriculture, yielded available 

land for development. Land use in the springshed in 1973 

consisted of open-water/wetlands (61.7 percent), agriculture 

(23.0 percent), forestland (8.3 percent), urban/mining/transportation/recreation (5.3 percent), and non-forested/barren land 

(1.7 percent). Land use in the springshed in 2004 consisted of 

open-water/wetlands (50.8 percent), urban/mining/transportation/recreation (28.4 percent), agriculture (8.8 percent), forestland (7.6 percent), and non-forested/barren land (4.4 percent). 

As of 2005, municipal and centralized sewer systems were the 

primary means of wastewater treatment and disposal, and had 

replaced most of the septic systems in the Wekiwa springshed. 

Reclaimed wastewater (applied to 2.8 mi2

 of the springshed) 

and discharge from the remaining septic units augment groundwater recharge in the Wekiwa springshed.

Discharge

Discharge from Wekiwa Springs has been measured by 

the USGS since 1932. The SJRWMD has measured discharge 

since 1983. At the time of this study, the SJRWMD and the 

USGS jointly measured the discharge of Wekiwa Springs 

at least bimonthly. Discharge for Wekiwa Springs averaged 

68.0 ft3

/s annually, and varied with rainfall that averaged 

51.19 in/yr within the springshed (fig. 51). Average annual 

discharge for Wekiwa Springs ranged from 55.1 ft3

/s in 2007 

to 88.9 ft3

/s in 1960. Spring discharge is occasionally affected 

by localized pumping of the Upper Floridan aquifer within the 

Wekiwa springshed. Measured (instantaneous) discharge from 

Wekiwa Springs averaged 63.5 ft3

/s, and ranged from 38.6 ft3/s 

in July 1998 to 91.7 ft3

/s in October 1960 (fig. 52).

Water Chemistry and Age

Wekiwa Springs has been sampled by the USGS and 

SJRWMD since 1956 and 1984, respectively. At the time 

of this study, the SJRWMD and the USGS jointly sampled 

Wekiwa Springs at least four times per year. In 2006-07, 

the USGS sampled Wekiwa Springs for chlorophyll-a, 

pheophytin-a, wastewater compounds, pesticides, antibiotics, 

and dissolved gases.

Wekiwa Springs has a Ca-Mg-HCO3

 water type (fig. 9) 

and is undersaturated with respect to calcite and dolomite 

(table 3). Median values of pH, dissolved oxygen, and 

dissolved solids of water were 7.4, 0.4 mg/L, and 180 mg/L, 

respectively. Delta 18O and 2

H of water from Wekiwa Springs 

plots along the GMWL or local MWL parallel to the GMWL 

(Toth, 1999), indicating no evaporation during recharge. The 

3

H concentration was 3.0 TU (Toth, 1999), indicating that 

recharge has occurred during the past 20 years. Delta 34S 

equaled 5.7 ppm, typically corresponding to low sulfate 

concentrations and indicating variable sources of sulfate 

including rainfall and geochemical reactions along groundwater flow paths (Toth, 1999). 

The median nitrate concentration from 1977 to 2007 was 

1.3 mg/L. Nitrate-N concentrations showed a significant (less 
76 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

WEKIWA SPRINGS

30

40

50

60

70

80

90

100

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

DISCHARGE, IN CUBIC FEET PER SECOND

INSTANTANEOUS DISCHARGE

YEAR

AVERAGE INSTANTANEOUS

DISCHARGE = 63.5 CUBIC FEET PER SECOND

EXPLANATION

AVERAGE INSTANTANEOUS DISCHARGE

Figure 52. Periodic and continuous discharge data for Wekiwa Springs, 1932-2007. Data collected by the St. 

Johns River Water Management District (SJRWMD) and U.S. Geological Survey. SJRWMD data used with 

permission. 

than 0.001) decreasing trend with time for samples collected 

during 1970-2007 (table 6). Excess dissolved nitrogen concentrations of about 3 mg/L were found in water samples collected 

in October 2006 and March 2007, indicating that denitrification 

was occurring in the Upper Floridan aquifer in the vicinity of 

Wekiwa Springs. Elevated values of delta 15N and delta 18O of 

nitrate (14.7 and 12.9 per mil, respectively) were indicative of 

isotopic fractionation due to denitrification. In addition, low 

dissolved methane concentrations (0.006 mg/L) were indicative of reducing conditions in the Upper Floridan aquifer in the 

vicinity of Wekiwa Springs. Dissolved oxygen concentrations 

generally were less than 0.5 mg/L, which is indicative of anoxic 

conditions. Phosphorus concentrations in Wekiwa Springs 

generally were uniform around 0.1 mg/L from 1970 to 2007, 

although spikes in concentration have occurred (up to 2 mg/L) 

(fig. 23). The phosphorus (total P) median concentration was 

0.12 mg/L from 1972 to 2007. Phosphorus concentrations 

showed a significant (p = 0.02) decreasing trend with time for 

samples collected from 1970 to 2007 (table 6).

Water samples collected from Wekiwa Springs in October 

2006 and March 2007 were analyzed for 64 organic chemicals commonly associated with wastewater sources, plus 52 

pesticides. Of the organic wastewater compounds analyzed, 

triethyl citrate (E0.1 μg/L) was detected in the October 

2006 water sample, and phenol (E0.1 μg/L) was detected in 

the March 2007 water sample (app. 4). Pesticides detected 

in water samples from Wekiwa Springs included atrazine 

(E0.007, E0.008 μg/L), an atrazine degradate (2-chloro-4-

isopropylamino-6-amino-s-triazine) (E0.008 μg/L), fipronil 

(E0.005-E0.007 μg/L), and simazine (E0.004-E0.005 μg/L) 

(app. 5).

Based on concentrations of 3

H and 3He in water samples 

collected from Wekiwa Springs in 2001, the age of spring 

water indicates a mixture dominated by relatively young 

water (less than 9 years old) (Toth and Katz 2006). More 

recent samples collected in October 2006 and March 2007 

had concentrations of 3

H and 3He that indicated an apparent 

age of 16 to 20 years. Concentrations of SF6

 were considerably higher than atmospheric concentrations, indicating that 

ground water discharging from Wekiwa Spring has been 

affected by non-atmospheric sources of SF6

 and thus, cannot 

be dated using this technique. Water samples collected in 

April 1995 were analyzed for 3

H, 13C, and 14C. Wekiwa 

Springs had a 3

H concentration of 3.0 TU, which indicated 

that the young fraction of water was less than 42 years old. 

Wekiwa Springs had a delta 13C value of –10.1 per mil and 

a 14C of 50 pmc. The adjusted 14C age of Wekiwa Springs is 

recent, with recharge likely occurring after about 1960.
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 77

Aquatic Communities

A total of 41 macroinvertebrate taxa were collected 

by petite ponar dredge from Wekiwa Springs across four 

sampling dates (table 24). The number of taxa collected with 

this gear ranged from 12 in June 2006 to 23 in September 

2006. Numerically dominant taxa in pooled samples across 

all dates were gastropods (51.2 percent, mostly Amnicola

dalli and unidentified hydrobiids, but at least four species 

total), chironomids (22.2 percent, at least nine species), and 

oligochaetes (14.1 percent, at least seven species). Density of 

all organisms ranged from 6.4 × 103

 per m2 (69.3 × 103 per ft2) 

in June 2006 to 35.8 × 103

 per m2 (385.4 × 103 per ft2) in 

September 2006. For petite ponar samples pooled across all 

dates, the log2

 Shannon-Wiener index ranged from 2.04 to 

3.06, Simpson’s index of diversity ranged from 0.51 to 0.80, 

Pielou’s evenness ranged from 0.45 to 0.77, and the Florida 

Index ranged from 0 to 2 with a mean of 1 (table 4).

A total of 31 macroinvertebrate taxa were identified 

in subsamples of dip net collections from Wekiwa Springs 

(table 25). The number of taxa ranged from 11 in June 2006 to 

15 in December 2005. The percent composition of subsampled 

organisms combined for all collection dates was dominated 

by gastropods (56.9 percent, mostly Amnicola dalli and 

Aphaostracon monas), with most of the remaining specimens 

comprising chironomids (15.9 percent), ephemeropterans 

(11.0 percent, all Caenis diminuta), amphipods (6.9 percent, 

all Hyalella azteca complex), and oligochaetes (5.4 percent). 

The Wekiwa Springs endemic hydrobiid Floridobia wekiwae

constituted 2.4 percent of the subsampled specimens collected 

by dip net. For dip net samples pooled across all dates, the 

log2

 Shannon-Wiener index ranged from 1.90 to 2.63, Simpson’s index of diversity ranged from 0.55 to 0.79, Pielou’s 

evenness ranged from 0.55 to 0.71, the SCI ranged from 10 to 

32 with a mean of 20, and percent very tolerant taxa ranged 

from 2.7 to 19.1 (table 5). 

Fishes were sampled by electroshocking boat in the 

Wekiwa Springs run downstream of the spring pool on 

July 27, 2006. Three passes were made with the boat in the 

broadest portion of the spring run upstream of its sinuous 

course through a narrow, closed canopy section. Power was 

applied for 30 min during the sampling effort. A total of 

318 specimens were collected or observed, representing 17 

species of 12 genera and 10 families (table 11). The sample 

was dominated by centrarchids (58.2 percent, six species), 

cyprinids (17.3 percent, mostly Notemigonus crysoleucas), 

and the catostomid Erimyzon sucetta (10.1 percent). The 

nonindigenous Pterygoplichthys disjunctivus was estimated to 

constitute approximately 5 percent of the sample (not all individuals were netted); this species is common in the spring pool 

and park personnel routinely remove adults from the swimming area (R. Owen, Florida Park Service, oral commun., 

2006). Composition of the sample was considered to be 

under-representative of the entire fish community based on the 

limited effort and gear used. A previous survey of fishes in the 

Wekiwa Springs run (including a longer reach that extended 

downstream of the confluence with Rock Springs run) resulted 

in the collection or observation of 24 species, although based 

on fewer (n = 275) total specimens (Walsh and Williams, 

2003). Species collected by Walsh and Williams (2003) but 

not in this study were Lepisosteus osseus, Notropis maculatus, 

Opsopoeodus emiliae, Pteronotropis metallicus, Labidesthes

sicculus, Fundulus seminolis, Heterandria formosa, and 

Poecilia latipinna. Except for L. osseus, all of these species 

are small-bodied fishes and cannot be sampled reliably using 

boat electroshocking gear. In this study, two specimens of 

Ameiurus natalis were collected, a species not recorded by 

Walsh and Williams (2003).

Land-Use Changes among Springsheds

Springsheds examined in this study range in area from 

about 1.8 mi2

 (Green Spring) to 52.7 m2 (Silver Springs), 

and land use within each varied considerably for the 1973 to 

2004 period. The Bugg and Silver Glen springsheds remained 

primarily rural in character, consisting mostly of forest and 

wetlands (fig. 4). Urban land tracts have increased substantially 

within the Alexander, Apopka, Gemini, Green, and Wekiwa 

springsheds. Although urban lands in the Apopka springshed 

increased by about 20 percent, most of the springhsed has 

remained agricultural. In contrast, the Alexander and Wekiwa 

springsheds lost agricultural lands, whereas land-use changes 

in the De Leon springshed resulted in the conversion of nearly 

35 percent of forest land to tracts of agricultural and, to a lesser 

extent, urban lands. The Rock springshed had a slight increase in 

urban area and a large loss of open-water/wetlands accompanied 

by increased barren lands. The Gemini springshed had a marked 

change from predominantly forest to urban land and open water.

Trends in Spring Discharge and Rainfall

Temporal trends in annually averaged measurements 

of spring discharge and springshed rainfall were evaluated 

with Kendall’s tau (τ) (Helsel and Hirsch, 1992) for the 12 

springs included in this study using weighted rainfall from 

10 rainfall sites (table 26). Five of the springs (De Leon, Fern 

Hammock, Rock, Silver, and Wekiwa Springs) exhibited 

statistically significant decreases in discharge, whereas none 

of the weighted rainfall data for the springsheds exhibited any 

statistically significant trends. These tests assume a monotonic 

distribution of data across the period of coverage. Springs 

exhibiting putative decreases in discharge may be those most 

affected by human activities such as increased ground-water 

withdrawals and land-use alterations that decrease recharge 

to the springs. Nevertheless, climate cannot be dismissed as a 

major, if not primary, factor acting in conjunction with other 

variables that have contributed to the apparent decreasing 

trends in spring discharge.
78 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Table 24. Number of specimens (n) and percent density (%) per square meter of macroinvertebrates collected by pooled petite ponar 

dredge samples (n = 3 per date) from Wekiwa Springs, December 2005-September 2006.

[LPIL, lowest practicable identification level]

Clade Taxon

Dec. 7, 2005 Mar. 27, 2006 Jun. 22, 2006 Sept. 27, 2006

n % n % n % n %

Turbellaria

Gastropoda

Hirudinea

Oligochaeta

Amphipoda

Isopoda

Decapoda

Diptera

Ephemeroptera

Total

Number of Taxa

Tricladida (LPIL)

Turbellaria (LPIL)

Amnicola dalli

Aphaostracon monas

cf. Floridobia sp.

Floridobia wekiwae

Hydrobiidae (LPIL)

Melanoides turricula

Desserobdella phalera

Helobdella stagnalis

Helobdella triserialis

Dero botrytis

Dero digitata

Dero digitata complex

Dero pectinata

Dero sp.

Limnodrilus hoffmeisteri

Naidinae (LPIL)

Nais communis complex

Nais elinguis

Nais variabilis

tubificoid Naididae immature sp. A (LPIL)

Hyalella azteca complex Lecroy

Caecidotea racovitzai australis

Caecidotea sp.

Procambarus sp. (immature)

Chironomidae (LPIL)

Chironomini (LPIL)

Chironomus sp.

Cladopelma sp.

Dicrotendipes modestus

Dicrotendipes sp. (immature)

Polypedilum halterale group Epler

Polypedilum scalaenum group Epler

Rheotanytarsus sp.

Tanytarsus sp.

Tanytarsus sp. C Epler

Tanytarsus sp. T Epler

Tribelos jucundum

Caenis diminuta

Caenis sp.

43

6,207

43

2,644

43

57

517

273

2,974

345

43

72

57

244

9,871

43

230

23,706

17

0.2

26.2

0.2

11.2

0.2

0.2

2.2

1.2

12.5

1.5

0.2

0.3

0.2

1.0

41.6

0.2

1.0

690

5,977

230

1,149

575

460

690

230

460

460

115

230

115

575

115

460

920

13,451

17

5.1

44.4

1.7

8.5

4.3

3.4

5.1

1.7

3.4

3.4

0.9

1.7

0.9

4.3

0.9

3.4

6.8

345

1,724

115

115

345

115

805

115

345

2,069

230

115

6,438

12

5.4

26.8

1.8

1.8

5.4

1.8

12.5

1.8

5.4

32.1

3.6

1.8

1,379

24,885

115

115

1,034

345

172

115

57

115

402

230

805

57

115

57

1,379

1,149

115

172

1,494

690

805

35,802

23

3.9

69.5

0.3

0.3

2.9

1.0

0.5

0.3

0.2

0.3

1.1

0.6

2.2

0.2

0.3

0.2

3.9

3.2

0.3

0.5

4.2

1.9

2.2
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 79

Table 25. Number of specimens (n) and percent composition (%) of macroinvertebrates collected by dip net from Wekiwa Springs, 

December 2005-September 2006.

[Values represent material as subsampled to obtain the target number of organisms required for calculation of the Stream Condition Index. LPIL, lowest 

practicable identification level]

Clade Taxon

Dec. 7, 2005 Mar. 27, 2006 June 22, 2006 Sept. 27, 2006

n % n % n % n %

Turbellaria

Gastropoda

Hirudinea

Oligochaeta

Amphipoda

Isopoda

Diptera

Ephemeroptera

Odonata

Total

Number of Taxa

Tricladida (LPIL)

Turbellaria (LPIL)

Amnicola dalli

Aphaostracon monas

Floridobia wekiwae

Melanoides sp. (immature)

Melanoides turricula

Planorbella scalaris

Helobdella stagnalis

Dero digitata complex

Limnodrilus hoffmeisteri

Nais communis complex

Nais elinguis

Nais variabilis

Pristina sp.

tubificoid Naididae immature sp. A (LPIL)

Hyalella azteca complex LeCroy

Caecidotea racovitzai australis

Caecidotea sp.

Chironomus sp.

Cladopelma sp.

Cladotanytarsus cf. daviesi Epler

Dicrotendipes sp. (immature)

Polypedilum halterale group Epler

Pseudosmittia sp.

Stenochironomus sp.

Tanytarsus sp. C Epler

Tanytarsus sp. T Epler

Tribelos sp.

Caenis diminuta

Enallagma sp.

62

2

2

1

2

5

2

11

5

4

2

1

2

1

8

110

15

56.4

1.8

1.8

0.9

1.8

4.5

1.8

10.0

4.5

3.6

1.8

0.9

1.8

0.9

7.3

30

2

3

1

1

6

1

2

4

1

27

30

2

110

13

27.3

1.8

2.7

0.9

0.9

5.5

0.9

1.8

3.6

0.9

24.5

27.3

1.8

2

72

1

4

4

9

1

1

1

4

11

110

11

1.8

65.5

0.9

3.6

3.6

8.2

0.9

0.9

0.9

3.6

10.0

3

64

11

1

1

3

4

1

1

1

19

1

110

12

2.7

58.2

10.0

0.9

0.9

2.7

3.6

0.9

0.9

0.9

17.3

0.9
80 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Table 26. Results of trend testing of annually averaged spring discharge and springshed rainfall.

[NOAA, National Oceanic and Atmospheric Administration; ft3/s, cubic foot per second]

Spring 

name

Period of

record 

analyzed

Spring discharge

NOAA 

station(s)

Rainfall

Slope 

median 

(ft3

/s/yr)

Kendall 

tau p value Significant trend

Slope 

median 

(in/yr)

Kendall 

tau p value

Significant 

trend

Alexander

Apopka

Bugg

De Leon

Fern Hammock

Gemini

Green

Juniper

Rock

Silver

Silver Glen

Wekiwa

1931-2007

1971-2007

1943-2007

1930-2007

1935-2007

1966-2007

1932-2007

1908-2007

1931-2007

1932-2007

1931-2007

1932-2007

-0.1943

-0.2673

-0.0303

-0.2000

-0.0500

0.0650

0.0065

0.0000

-0.1538

-2.7762

-0.1835

-0.2087

-0.1508

-0.4103

-0.1367

-0.3404

-0.2336

0.1619

0.0917

0.0016

-0.2572

-0.2905

-0.1402

-0.3639

0.2003

0.0586

0.3501

0.0008

0.0500

0.4285

0.6522

1.0000

0.0057

0.0002

0.2580

0.0002

No

No

No

Decreasing

Decreasing

No

No

No

Decreasing

Decreasing

No

Decreasing

DeLand/Lisbon/Plymouth

Clermont

Leesburg/Bushnell

DeLand

Crescent City/Lisbon

Sanford

Sanford

Crescent City/Lisbon

Plymouth/Leesburg/Clermont

Ocala/Lisbon/Leesburg

Crescent City/Ocala/Lisbon

Plymouth/Clermont

0.0190

-0.0128

-0.0541

0.0568

-0.0169

0.0040

0.0040

-0.0169

0.0119

-0.0412

-0.0378

0.0191

0.0436

-0.0193

-0.0942

0.0783

-0.0296

0.0073

0.0073

-0.0296

0.0190

-0.0696

-0.0729

0.0287

0.5749

0.8057

0.2237

0.3127

0.7042

0.9278

0.9278

0.7042

0.8091

0.3695

0.3469

0.7151

No

No

No

No

No

No

No

No

No

No

No

No

Comparison of Aquatic Communities

Numerous benthic invertebrates and fishes were collected 

from springs in this study. Their characteristics and differences 

in assemblages among springs are discussed in the subsequent 

sections.

Benthic Macroinvertebrates

A total of 249 benthic macroinvertebrate taxa were 

collected from springs in this study; of these, 60 taxa were represented solely in dip net samples, 84 solely in ponar grab samples, 

and the remaining 105 represented in both (app. 1). The number 

of taxa collected using combined gears was variable among dates 

for each spring (fig. 53A). Cumulative numbers of taxa were 

lowest for Apopka Spring (29), Gemini Springs (32), and Green 

Spring (33); intermediate for Wekiwa Springs (48), Alexander 

Spring (57), and Silver Glen Springs (65); and greatest for De 

Leon Spring (71), Bugg Spring, (76), and Rock Springs (89) 

(fig. 53B). Rank-order plots for both dip net and ponar 

samples indicated log-normal distributions, with relatively few 

species dominant in abundance (fig. 54). Many additional taxa 

would likely have been obtained with greater sampling effort, 

as evidenced by species-accumulation curves (fig. 55). 

Numerous richness estimators are commonly applied 

to community data; figure 55 includes nonparametric 

approaches dependent on simple functions of the number 

of taxa observed in only one or two samples (Jacknife1), 

number of taxa with only one or two individuals in the entire 

pool of samples (Chao1), set of proportions of samples that 

contain each species (Bootstrap), and a parametric model 

(Michaelis-Menton) (Colwell and Coddington, 1994; Clarke 

and Gorley, 2006; Colwell, 2006). For dip net subsamples, 

eight taxa represented 58.7 percent of all specimens 

recorded: Hyalella azteca complex (19.6 percent), Amnicola

dalli (12.2 percent), Gammarus cf. tigrinus (6.8 percent), 

cf. Aphaostracon sp. (5.6 percent), Limnodrilus hoffmeisteri

(5.1 percent), Gammarus mucronatus complex (5.0 percent), 

Hydrobiidae sp. (3.6 percent), and cf. Tarebia sp. (3.3 percent). 

For ponar samples, eight taxa as mean abundance across 

samples for each spring represented 62.2 percent of specimens recorded: Hydrobiidae sp. (21.4 percent), Hyalella

azteca complex (12.0 percent), Amnicola dalli (11.2 percent), 

immature tubificoid Naididae sp. (7.0 percent), cf. Tarebia sp. 

(4.2 percent), Gammarus cf. tigrinus (3.2 percent), and 

Spilochlamys gravis (3.2 percent). 

Differences in assemblages among springs were attributable to both natural dissimilarity in community structure and 

to variation in ecological conditions among sites. Diversity 

indices for benthic macroinvertebrates collected by petite 

ponar dredge and dip net are summarized in tables 4 and 5. 

Pielou’s evenness index and mean Shannon-Wiener (ln) 

diversity index for each spring are shown in figure 56. For 

combined gears, greatest diversity was represented in samples 

from Rock, Bugg, and Silver Glen Springs, with Bugg Spring 

also exhibiting greatest evenness. Apopka Spring had the 

lowest diversity and evenness. The SCI values and percent 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 81

0 20 40 60 80 100

Wekiwa Springs

Silver Glen Springs

Rock Springs

Green Spring

Gemini Springs

De Leon Spring

Bugg Spring

Apopka Spring

Alexander Spring

SPRING AND COLLECTION DATE

A

CUMULATIVE NUMBER OF TAXA

B

SPRING

TOTAL NUMBER OF TAXA

0 10 20 30 40 50 60 70

Alexander Feb 2007

Alexander May 2007

Alexander Aug 2007

Alexander Oct 2007

Apopka Dec 2005

Apopka Mar 2006

Apopka Jul 2006

Apopka Sep 2006

Bugg Dec 2005

Bugg Mar 2006

Bugg Jul 2006

Bugg Sep 2006

De Leon Feb 2004

De Leon May 2004

De Leon Aug 2004

Gemini Feb 2004

Gemini May 2004

Gemini Aug 2004

Green Feb 2004

Green May 2004

Green Aug 2004

Rock Dec 2005

Rock Mar 2006

Rock Jun 2006

Rock Sep 2006

Silver Glen Jan 2007

Silver Glen May 2007

Silver Glen Aug 2007

Silver Glen Oct 2007

Wekiwa Dec 2005

Wekiwa Mar 2006

Wekiwa Jun 2006

Wekiwa Sep 2006

Figure 53. Number of macroinvertebrate taxa collected by dip net and petite ponar dredge from selected 

springs of the St. Johns River drainage, 2004-07. Taxa are shown by (A) date (month and year) and (B) cumulative 

number per spring. 
82 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

TAXA IN RANK ORDER

0 10 20 30 40

NUMBER OF INDIVIDUALS

1

10

100

1,000

TAXA IN RANK ORDER

0 20 40 60 80 100

NUMBER OF INDIVIDUALS

10

100

1,000

10,000

A

B

Figure 54. Lognormal ranked species abundance curves for macroinvertebrate taxa collected 

by (A) petite ponar dredge and (B) dip net from springs in the St. Johns River drainage, 2004-07. 

Number of individuals for ponar samples are from means pooled by spring. Dip-net data are based 

on raw numbers. 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 83

0 10 20 30 40

0

50

100

150

200

250

300

SPECIES COUNT

A

SPECIES COUNT

NUMBER OF SAMPLES

B

0

0 5 10 15 20 25 30

50

100

150

200

250

NUMBER OF SAMPLES

Sobs

Chao1

Jacknife1

Bootstrap

MM

RICHNESS ESTIMATOR

EXPLANATION

Sobs

Chao1

Jacknife1

Bootstrap

MM

RICHNESS ESTIMATOR

EXPLANATION

Figure 55. Species accumulation curves for macroinvertebrates 

collected by (A) petite ponar dredge and (B) dip net from springs of the St. 

Johns River drainage, 2004-07. Richness estimators are as follows: Sobs, 

observed number of taxa in sample; Chao1, Jacknife 1, and Bootstrap are 

nonparametric models; MM (Michaelis-Menten) is a parametric model 

(see text). 
84 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

0.2

0.4

0.6

0.8

1.0

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Alexander

Apopka

Bugg

Gemini

Green

De Leon

Rock

Silver Glen

Wekiwa

PIELOU’S EVENNESS LOGe SHANNON-WIENER DIVERSITY INDEX

A

B

EXPLANATION

1SE

MEAN

1SE

DIP NET

SAMPLES

PETITE PONAR

SAMPLES

1SE

MEAN

1SE

Figure 56. (A) Pielou’s evenness (J‘ ) and (B) loge Shannon-Wiener diversity index (H‘ ) for 

macroinvertebrate samples from selected springs of the St. Johns River drainage, 2004-07. 

SE is standard error. 
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 85

Alexander Feb 2007

Alexander May 2007

Alexander Aug 2007

Alexander Oct 2007

Bugg Dec 2005

Bugg Mar 2006

Bugg Jul 2006

Bugg Sep 2006

De Leon Feb 2004

De Leon May 2004

De Leon Aug 2004

Gemini Feb 2004

Gemini May 2004

Gemini Aug 2004

Green Feb 2004

Green May 2004

Green Aug 2004

Rock Dec 2005

Rock Mar 2006

Rock Jun 2006

Rock Sep 2006

Silver Glen Jan 2007

Silver Glen May 2007

Silver Glen Aug 2007

Silver Glen Oct 2007

Wekiwa Dec 2005

Wekiwa Mar 2005

Wekiwa Jun 2006

Wekiwa Sep 2006

STREAM CONDITION INDEX

0

10

20

30

40

Healthy

Impaired

SPRING NAME AND DATE

Figure 57. Stream Condition Index (SCI) values for dip net samples of 

macroinvertebrates collected from selected springs of the St. Johns River 

drainage, 2004-07. Horizontal dashed line indicates SCI value separating 

categories classified as “impaired” (0-34) and “healthy” (35-70) as 

recognized by the Florida Department of Environmental Protection (Fore 

and others, 2007). PERCENT VERY TOLERANT TAXA

0

10

20

30

40

50

60

Alexander Spring

Bugg Spring

De Leon Spring

Gemini Springs

Green Spring

Rock Springs

Silver Glen Springs

Wekiwa Springs

SPRING

Figure 58. Percent very tolerant macroinvertebrate taxa collected by dip 

net from selected springs of the St. Johns River drainage, 2004-07. Solid 

bars represent means +1 SE (vertical line) for 3-4 samples per spring. 

SE is standard error. 
86 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

very tolerant taxa per spring and date are summarized in 

table 5, and figures 57 and 58. The SCI scores for all dip 

net samples ranged from 6 to 34, and thus, fell within the 

“impaired” category as recognized by the FDEP (Fore and 

others, 2007). Mean percent very tolerant taxa values ranged 

from less than 4 percent for Alexander Spring to greater than 

40 percent for Bugg and Green Springs (fig. 58).

Multivariate Analysis of Spring Communities and 

Environmental Parameters—Mean dip net data across sampling 

dates for each spring were analyzed for relationships between 

benthic macroinvertebrate assemblages and environmental 

parameters. An agglomerative hierarchical cluster analysis 

of Bray-Curtis similarities derived from square-root transformed means (fig. 59) and a nonmetric multidimensional 

scaling (MDS) plot of the same data matrix (fig. 60) indicated 

two major groupings of springs, each with two sub-clusters 

consisting of paired springs: [(Alexander + Silver Glen) + (Rock 

+ Wekiwa)] and [(Bugg + De Leon) + (Green + Gemini)].

Median values of environmental data for each spring 

(table 3) were examined using draftsman plots in PRIMER®

to identify correlated variables. Specific conductance, Ca, 

Mg, Na, K, Cl, total dissolved solids, and gypsum saturation 

index were highly correlated (r greater than 0.95); therefore, 

all of these variables except specific conductance were 

omitted from the data matrix prior to principal components 

analysis (PCA).

A PCA plot of the normalized data matrix of environmental variables indicated similar groupings of paired springs 

corresponding to the assemblage cluster plot, but with different 

separation of sub-clusters along the horizontal axis (principal 

component 1; PC1), the vertical axis (principal component 2; 

PC2), or both (fig. 61). Cumulative percent variation on the first 

three principal components was 46.6 percent, 75.0 percent, and 

91.4 percent, respectively. Loadings on the first two principal 

components were relatively low. Factors with greatest positive loadings on PC1 were specific conductance (0.367), SiO2

(0.363), dolomite saturation index (0.350), o-PO4

 (0.336), and 

log pCO2

 (0.330); greatest negative loadings on PC1 were 

temperature (-0.368), HCO3

 (-0.281), and NO2-NO3-N (-0.266). 

Factors with greatest positive loadings on PC2 were calcite saturation index (0.491) and NO2

-NO3-N (0.350); greatest negative 

loadings on PC2 were pH (-0.486), mean discharge (-0.431), 

and dissolved oxygen (-0.214). The BioEnv (“Best”) procedure 

of PRIMER® was used to perform 99 random permutations of 

sample combinations, linking the environmental data with the 

assemblage matrix. The resulting ranked Spearman correlation 

(ρ) value was significant (p ≤ 0.01), indicating concordance in 

multivariate patterns observed between the data sets. Greatest 

agreement (r > 0.80) between the MDS assemblage ordination and the PCA of environmental variables was attributed to 

combinations of SO4

 + SiO2 + mean discharge (0.813), followed 

by specific conductance + SO4

 + mean discharge (0.804).

Fishes

A total of 45 species of fishes representing 35 genera 

and 23 families were collected from target springs in this 

study (app. 2). Greatest species richness was within the 

Centrarchidae, Cyprinidae, Ictaluridae, Fundulidae, and 

Poeciliidae. Greatest relative abundance, accounting for 

over 85 percent of more than 3,800 specimens collected 

or observed, was limited to five families: Centrarchidae 

(23.7 percent), Cyprinidae (21.9 percent), Fundulidae 

(14.5 percent), Atherinopsidae (13.8 percent), and Poeciliidae (12.4 percent) (fig. 62). Eight species accounted for 

68.9 percent of fish specimens collected or observed among all 

springs: Notropis petersoni (16.0 percent), Menidia beryllina

(12.5 percent), Lepomis macrochirus (10.4 percent), Lucania 

parva (7.2 percent), Gambusia holbrooki (7.1 percent), 

Lucania goodei (5.7 percent), Morone saxatilis (5.3 percent), 

and Poecilia latipinna (4.8 percent). However, relative abundances (as percent composition of samples) of N. petersoni, 

M. beryllina, L. parva, L. goodei, and M. saxatilis were 

skewed due to intensive sampling at Alexander Spring and 

visual observations at Silver Glen Springs.
Hydrology, Water Quality, and Aquatic Communities of Selected Springs 87

Gemini Springs

Green Spring

De Leon Spring

Bugg Spring

Wekiwa Springs

Rock Springs

Silver Glen Springs

Alexander Spring

20 40 60 80 100

PERCENT SIMILARITY

Figure 59. Agglomerative hierarchical cluster of selected springs in the St. Johns River 

drainage based on square-root transformed Bray-Curtis similarity values of macroinvertebrates 

collected by dip net, 2004-07. 

Transform: Square root

Resemblance: S17 Bray Curtis similarity

Percent Similarity

30

Alexander

Bugg

De Leon

Gemini

Green

Rock

Silver Glen

Wekiwa

2D Stress: 0.06

Figure 60. Nonmetric multidimensional scaling ordination based on Bray-Curtis 

similarity values derived from square-root transformed means of macroinvertebrate 

samples collected by dip net from selected springs in the St. Johns River drainage, 

2004-07. Ellipses indicate springs clustered at 30 percent similarity; stress values less 

than 0.1 are considered a measure of good fit (Clarke and Warwick, 2001; Clarke and 

Gorley, 2006). 
88 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District PRINCIPAL COMPONET 2

PRINCIPAL COMPONENT 1

Calcite SI

NO -NO -N 2 3

pH

Mean discharge

Dissolved O2

Temperature

HCO3

NO -NO -N 2 3

Specific Conductance

SiO

Dolomite SI

o-PO

log pCO

2

4

2

-4 -2 0 2 4

-4

-2

0

2

4

Alexander

Bugg De Leon

Gemini

Green

Rock

Silver Glen

Wekiwa

Figure 61. Principal components 

analysis (PCA) scatter plot of environmental variables for selected springs of 

the St. Johns River drainage. Variables 

shown on the PC axes are those that 

loaded most heavily (described in text). 

Figure 62. Relative abundance (as 

percent composition of collective 

samples) of fish families in springs of 

the St. Johns River drainage surveyed 

in 2004-07. 

23.7

13.7

21.9

14.5

12.4

13.8

CENTRARCHIDAE

CYPRINIDAE

FUNDULIDAE

ATHERINOPSIDAE

POECILIIDAE

18 OTHER FAMILIES

EXPLANATION

FISH FAMILIES
Concluding Discussion 89

Concluding Discussion

The SJRWMD identified the following nine springs for 

this study based on priorities for establishing or evaluating 

minimum flows and levels (MFLs): Alexander, Apopka, Bugg, 

De Leon, Gemini, Green, Rock, Silver Glen, and Wekiwa 

Springs. Three additional springs (Fern Hammock, Juniper, 

and Silver Springs) were included, based on ancillary data 

collection for water chemistry and discharge parameters as 

part of a separate study for the FDEP or other investigations 

in progress. This report augments existing information and 

compiles additional baseline data to assist the SJRWMD in 

developing guidelines for a long-term strategy for evaluating, 

monitoring, and protecting these springs.

Springs of the St. Johns River drainage examined herein 

exhibit a wide range of physical, chemical, and biological 

characteristics that are representative of springs in north-central 

Florida. Much of the variation observed from data collected 

and compiled for these springs is reflected in (1) diverse natural 

characteristics, ranging from large, first-magnitude springs with 

substantial discharge and springshed area (such as Silver and 

Silver Glen Springs) to those with smaller recharge areas (such 

as Gemini and Green Springs), (2) land-use within each springshed, (3) differences in water chemistry, and (4) composition 

of the biological communities. Current land use within the 

springsheds examined varies from being predominately forested 

(Bugg, Silver Glen, and Wekiwa), agricultural (Apopka), to 

mixed (all others). Notable land-use changes over the 30-year 

period of record were documented for all springsheds except 

Fern Hammock, Juniper, and Silver Glen, which remain mostly 

forested. Urban lands increased substantially within the Alexander, Gemini, and Wekiwa springsheds, and to a lesser extent, 

in the Apopka, De Leon, Green, and Rock springsheds. The 

increase in urban lands was accompanied by a considerable loss 

of forested lands in the De Leon, Gemini, and Green springsheds, whereas forested lands remained relatively unchanged in 

the Alexander, Silver Glen, and Wekiwa springsheds. Although 

the Apopka springshed lost virtually all forested lands during 

the last 35 years, this land-use category composed a small 

percentage of total land use in 1973 within that springshed. 

Among the springsheds combined, most land-use changes over 

time correspond to increased loss of forested, open/wetland, 

and agricultural lands accompanied by increased conversion 

to urban lands within large corridors of the St. Johns River 

drainage. However, some exceptions to this general trend were 

noted; specifically, the Gemini and Green springsheds gained 

open/wetland lands, and agricultural lands increased in the De 

Leon and Silver Glen springsheds, although by a relatively 

small percentage for the latter.

Land-use changes and accompanying increases in water 

withdrawals are presumed to be important factors affecting 

the diminished discharge for some of these springs. Past and 

future trends of increased consumptive use can be expected 

to contribute to changes in ground-water quantity and quality 

within portions of the basin, and these changes are likely to be 

accompanied by ecological effects.

Four primary water types (Ca-HCO3

, Ca-Mg-HCO3, 

mixed, and Na-Cl) were identified in the springs included 

in this study based on the composition of major ions. Most 

springs were of the Ca-Mg-HCO3

 water type (Apopka, Fern 

Hammock, Juniper, Rock, and Wekiwa Springs). Bugg and 

Silver Springs had a Ca-HCO3

 water type, De Leon Spring and 

De Leon run had a mixed water type, and four springs (Alexander, Gemini, Green, and Silver Glen Springs) had a Na-Cl 

water type. Early classifications of Florida springs based on 

water chemistry included those of Whitford (1956) and Slack 

and Rosenau (1979). To provide finer resolution, Woodruff 

(1993) used an average linkage cluster analysis to compare 

170 Florida springs based on ionic composition and recognized four major water types: low ionic, calcium bicarbonate, 

mixed, and salt. The study further recognized three types 

within the Ca-HCO3

 category: low (Ca ≤ 20 mg/L; HCO3 ≤ 

75 mg/L), medium (Ca ≤ 45 mg/L; HCO3

 ≤ 150 mg/L), and 

high (Ca ≤ 75 mg/L; HCO3

 ≤ 255 mg/L). According to the 

Woodruff (1993) classification scheme, springs examined in 

this study belong to the following categories: low Ca-HCO3

(Apopka, Fern Hammock, and Juniper Springs); medium 

Ca-HCO3

 (Bugg, Rock, and Wekiwa Springs); high Ca-HCO3

(Silver Springs); mixed (Alexander and De Leon Springs), 

and salt (Green, Gemini, and Silver Glen Springs). The 

terminology used herein utilizes a trilinear plot that explicitly 

separates springs based on combinations of all major ions. 

Nevertheless, it is useful to recognize springs in general 

terms that are meaningful relative to major characteristics; for 

example, calcium-bicarbonate or salt, insofar as distinguishing 

larger groupings based on other factors such as their biotic 

assemblages. The classification scheme of Woodruff (1993) 

was associated with karstic geology and geography; salt 

and mixed springs emerge nearer coastal regions, whereas 

calcium-bicarbonate springs are more typical of river downcutting areas (such as the Suwannee River), although all three 

partially overlap in distribution.

Increased nutrient input to Florida springs is the single 

greatest threat to the ecology of these systems. In particular, 

nitrate-N loading has been identified for many springs 

(Brown and others, 2008), where it promotes eutrophication 

(Stevenson and others, 2007) and can have direct toxic as 

well as sublethal effects on aquatic organisms (Guillette and 

Edwards, 2005; Edwards and Guillette, 2007; Mattson and 

others, 2007; Jacoby and others, 2008). Waters with nitrate 

levels above about 0.2 mg/L are considered to be enriched 

by human activities (Toth, 1999; Cohen and others, 2007). 

Based on a review of the literature, Mattson and others 

(2007) reported nitrate toxicity threshold minima of 0.23, 

1.1, and 5 mg/L NO3

-N for invertebrates, fishes, and amphibians, respectively. Mattson and others (2007) suggested that 

nitrate levels found in Rock Springs Run may contribute to 

chironomid larval mortality and may be chronically toxic 

to caddisflies and the amphipod Hyalella sp. Because these 

macroinvertebrates are important food sources as both larvae 

and adults for a variety of animals, there are implications of 

broad adverse effects on spring system food webs in general. 
90 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

As noted by these authors, food-web related effects may result 

from interactions between grazers and primary producers, 

especially periphytic and filamentous algae. Therefore, nitrate 

enrichment may have bottom-up effects (greater nutrient levels 

promoting algal growth), top-down effects (reduced grazer 

abundance or activity allowing for greater algal growth and 

biomass), or a combination of both.

Nitrate concentrations varied spatially among springs 

examined in this study, and temporally within several springs. 

For the springs examined in this study, only Apopka Spring 

had a median nitrate level above 2 mg/L; however, several of 

the springs exhibited nitrate levels elevated over presumed 

historical levels, and in some cases showed spikes in nitrate 

concentration. Lowest median nitrate levels were observed for 

Alexander, Fern Hammock, Green, Juniper, and Silver Glen 

Springs, all below 0.1 mg/L. The low levels for these springs 

are likely due to their location within the Ocala National 

Forest (except for Green Spring). Gemini, Rock, and Wekiwa 

Springs had median levels above 1.0 mg/L. Bugg and De Leon 

Springs had median levels between 0.5 and 1.0 mg/L. Nitrate 

concentrations showed a statistically significant (p < 0.05) 

increasing trend with time in water samples from Apopka, 

Fern Hammock, Gemini run, and Juniper Springs. Conversely, 

several other springs showed a statistically significant 

(p < 0.05) decreasing trend with time (Alexander, Bugg 

run, Rock and Wekiwa Springs). Phosphorus concentrations 

generally were low and relatively constant over time for most 

springs. However, water from Juniper Springs showed a statistically significant increase in phosphorus with time, whereas 

other spring waters showed statistically significant decreasing 

phosphorus trends with time (Apopka, De Leon, Rock, Silver 

Glen, and Wekiwa Springs). In many cases, these trends are 

based on limited sampling data, and continued sampling for 

phosphorus compounds would be desirable for establishing 

trends over time. 

Spring-water ages and residence times of water 

discharging from springs were estimated using measured 

concentrations of various transient tracers in water samples. 

These tracers have been released into the atmosphere during 

the past 50 years as CFCs, SF6

, 3H, and 3He (the decay product 

of tritium). Concentrations of the various tracers in spring 

waters are consistent with various mixtures of young and old 

waters. For example, waters from Juniper and Silver Glen 

Springs are a mixture of 60 to 80 percent old (tracer-free) 

water (greater than 60 years), with 20 to 40 percent young 

water (recharged after 1980). In contrast, water from Alexander, De Leon, and Wekiwa Springs contains mixtures that 

are dominated by young waters, and waters discharging from 

these springs have residence times that are 20 years or less. 

Springs of the St. Johns River drainage harbor unique 

assemblages of benthic macroinvertebrates. In this study, 

considerable variation in richness, diversity, and abundance 

was documented among springs as well as between independent samples from each spring. Based on combined gear types 

used to collect benthic macroinvertebrates, a total of approximately 249 taxa were identified among all springs surveyed: 

60 taxa were limited to dip net samples, 84 to petite ponar 

samples, and 105 were common to both. Cumulative number 

of taxa pooled among samples per spring ranged from 29 to 89 

in Apopka and Rock Springs, respectively. Greatest taxonomic 

richness and diversity was found in Alexander, Bugg, De 

Leon, Rock, Silver Glen, and Wekiwa Springs, whereas lowest 

was in Apopka, Gemini, and Green Springs. Bugg, Rock, and 

Silver Glen Springs exhibited the greatest diversity and evenness for dip net and ponar samples combined. For most of the 

springs, relatively few taxa dominated dip net and petite ponar 

samples as either percent composition or abundance (density 

as organisms per square meter). Eight taxa represented 

58.7 percent of all subsampled individuals for combined dip 

net samples across all springs. Eight taxa, as mean abundance 

across samples for each spring, represented 62.2 percent of 

specimens recorded from petite ponar samples. Collectively, 

the benthic macroinvertebrate fauna was dominated by gastropods, amphipods, oligochaetes, and dipterans.

The gastropod fauna of the St. Johns River drainage, 

especially species of the family Hydrobiidae, is notable due 

to endemism of many taxa, some of which are confined to 

a single spring (Walsh, 2001; Thompson, 2004; Shelton, 

2005). Hydrobiid snails are diminutive and require special 

preservation methods and expertise in identification; therefore, 

many of the specimens collected in the present study were 

provisionally identified only to genus or family. Spilochlamys

gravis is restricted in distribution to the mid- to upper St. 

Johns River; we collected this species, or specimens identified 

as cf. Spilochlamys sp., from Alexander Spring, where this 

taxon dominated both dip net and petite ponar samples, and 

Silver Glen Springs. Shelton (2005) also reported S. gravis

from Rock and Wekiwa Springs; it is possible that this species 

was represented among the numerous unidentified hydrobiids 

collected from these springs during this study. Floridobia

alexander is endemic to Alexander Spring; no specimens 

explicitly identified as this taxon were collected, although a 

large number of hydrobiids from petite ponar samples were 

not identified below family level. Floridobia petrifons is 

endemic to Rock Springs, and in the current study, specimens 

of cf. Floridobia sp. were collected from Rock Springs in 

petite ponar samples from September 2006. Aphaostracon

pycnum is endemic to Alexander and Silver Glen Springs, 

and specimens identified as cf. Aphaostracon sp. were 

recorded from both of these springs. Floridobia wekiwae and 

Aphaostracon monas are endemic to Wekiwa Springs; in this 

study, both species were collected in low numbers in dip net 

samples, and were absent in petite ponar samples on three of 

the four sampling dates, but were collected using this gear in 

September 2006. Shelton (2005) did not report any rare or 

endemic snails from Apopka Spring, although specimens of 

cf. Floridobia sp. were collected in this study in July 2006. 

None of the other rare taxa reported by Shelton (2005) were 

documented from the same springs in this study.

The Silver Glen Springs benthic macroinvertebrate 

fauna exhibits unique characteristics in comparison to other 

springs examined in this study. Several species were collected 
Concluding Discussion 91

that are typically associated with estuarine or nearshore 

habitats: the amphipods Gammarus mucronatus complex, 

G. cf. tigrinus, Grandidierella bonnieroides, and unidentified 

species of the family Aoridae; the isopods Cassidinidea ovalis

and Uromunna reynoldsi; and the decapod Palaemonetes

vulgaris. The water chemistry of Silver Glen Springs accounts 

for the presence of these taxa, particularly the high specific 

conductance and ionic content, with high values of Na, Ca, 

Cl, and SO4

. Although Alexander Spring exhibits similar 

water chemistry as Silver Glen Springs, only two of the taxa 

previously mentioned (G. cf. tigrinus and C. ovalis) were 

collected from both springs. Nevertheless, the grouping of 

these two springs in the multivariate ordinations of community 

assemblage and water chemistry indicates that their biotas are 

strongly influenced by the latter, especially the high degree 

of mineralization within the aquifer (Katz, 1992) and connate 

relict saltwater reserves within this part of the basin.

The importance of water chemistry in structuring 

the benthic macroinvertebrate communities of the springs 

examined in this study was further evidenced by results of 

the ordination analyses. Alexander and Silver Glen Springs 

were separated from the other springs on principal components that loaded most negatively for pH, dissolved O2

, and 

discharge. Gemini and Green Springs clustered together and 

loaded positively for several parameters, including nitrate and 

specific conductance. Gemini and Green Springs may also 

show faunistic similarities due to their geographic location, 

isolation, and low-flow characteristics. Rock and Wekiwa 

Springs clustered together and were separated from the other 

springs on the basis of negative principal component loadings 

for temperature and median concentrations of bicarbonate and 

nitrate. Bugg and De Leon Springs clustered together and were 

generally intermediate among other springs for loadings on the 

physical and chemical parameters. Further study is needed to 

elucidate the assemblage patterns and to identify the full suite 

of environmental parameters that characterize or influence the 

faunal composition of these springs.

The characterization of Florida springs as chemostatic 

systems (Odum, 1957) has been challenged over time with 

accumulation of long-term data sets and evidence of fluxes in 

water chemistry. Although changes involving such parameters 

as dissolved oxygen or total dissolved solids may not be unexpected based on diel variation or under different flow regimes 

(Munch and others, 2006), changes in ion concentrations 

or their ratios over time may be more subtle, yet potentially 

could affect ecological conditions. In addition to nitrate-N 

concentrations, which have demonstrable ecological effects 

(Brown and others, 2008), changes in other ion constituents 

are of interest in monitoring springs and their biological 

communities relative to establishing or assessing MFLs. 

Considering the importance of water chemistry in structuring 

benthic macroinvertebrate assemblages (and other fauna and 

flora), potential long-term changes in discharge that can alter 

historical conditions, such as increased salinity, have potential 

consequences for aquatic communities.

The SCI values for all samples in this study fell within 

the “impaired” category as recognized by the FDEP (Fore and 

others, 2007). Beginning in 2000, the FDEP has conducted 

regular water-quality monitoring at 18 major springs in 

north-central Florida, including 5 of the springs sampled in 

this study (Florida Department of Environmental Protection, 

2007). As part of the FDEP monitoring program, benthic 

macroinvertebrate communities are assessed at most of the 

sites using the SCI protocol. Results of FDEP springs monitoring are summarized as “EcoSummaries,” and made available online (http://www. dep.state.fl.us/, accessed October 1, 

2008). Similar to the results of this study, FDEP scored many 

of the same springs as “impaired” based on SCI evaluations. 

It is possible that low SCI values for many of these springs 

may be attributable to individual metrics within the SCI 

scoring procedure that are strongly affected by community 

characteristics. For example, hydrobiid snails can exert strong 

dominance, yet they are not considered to represent impaired 

conditions. In the case of springs considered to be good reference sites in this study, Alexander and Silver Glen, SCI scores 

indicating impairment could be due, in part, not only to the 

abundance of hydrobiids, but also to the high specific conductance and low dissolved oxygen, both factors that would 

reduce the number of sensitive organisms (Florida Department 

of Environmental Protection, 2007). Samples from all springs 

in this study contained very few sensitive taxa (as listed by 

the FDEP; http://www.dep.state.fl.us/labs/cgi-bin/sbio/keys.

asp#keys, accessed October 1, 2008).

Taxonomic richness of fish assemblages observed at each 

of the springs varied from 2 species in Green Spring to 29 

species in Alexander Spring. For most of the springs it is likely 

that taxonomic richness was underestimated due to limited 

sampling efforts and habitat inaccessibility. A combined total 

of 45 fish species, representing 35 genera of 23 families, was 

collected from all springs. Fish communities of the springs 

in this study were dominated by centrarchids (23.7 percent), 

cyprinids (22.0 percent), fundulids (14.5 percent), atherinopsids (13.9 percent), and poeciliids (12.4 percent). The 

communities studied were characteristic of springs throughout 

north-central Florida and shared species composition and 

relative abundances similar to those of many others surveyed 

by Walsh and Williams (2003). Green Spring showed very low 

richness and abundance, likely due to its isolation and unusual 

water chemistry, most notably its high hydrogen sulfide 

content. Gemini Springs also had relatively low richness and 

abundance, probably due in part to its isolation from the mainstem St. Johns River by an artificial weir. The large magnitude 

springs generally had the greatest taxonomic richness as well 

as overall biomass of fishes. Silver Glen Springs was most 

notable among these; large numbers of striped bass (Morone

saxatilis) were observed in the spring pool, as were schools of 

striped mullet (Mugil cephalus). As with the benthic macroinvertebrate fauna, Silver Glen Springs also supports a characteristic fish assemblage. Three species were observed that 

are most commonly associated with salt water but are known 

to penetrate into inland Florida waters, especially springs: 
92 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Atlantic needlefish (Strongylura marina), gray snapper 

(Lutjanus griseus), and naked goby (Gobiosoma bosc). The 

inland silverside (Menidia beryllina) was collected from 

Alexander Spring but not from Silver Glen Springs, although 

it is likely to occur in the latter and was probably undetected 

due to sampling limitations. Although striped bass populations 

in the St. Johns River are augmented by artificial stocking, this 

species is native and presumably utilized many springs historically as thermal refugia; the striped bass is considered to be 

potadromous or diadromous in that it migrates seasonally within 

river systems and estuaries. Fish surveys conducted during this 

study confirmed that two nonindigenous species, the vermiculated sailfin catfish (Pterygoplichthys disjunctivus) and brown 

hoplo (Hoplosternum littorale), continue to increase their range 

and population size throughout the St. Johns River drainage. 

Blue tilapia (Oreochromis aureus) is also widely established 

throughout the watershed. Other reported nonindigenous species 

require further survey and monitoring.

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96 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District
Appendixes 1-5
98 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Appendix 1. Macroinvertebrate taxa collected by dip net (D) and petite ponar dredge (P) from selected springs in the St. Johns River 

drainage, 2004-07.

[Authorities are listed for lowest practicable identification level (LPIL) indicated. Taxa are listed in approximate phylogenetic order by suprafamilial categories 

and alphabetically by genus and species]

Phylum Class Order Family Taxon Authority D P

Porifera

Porifera

Porifera

Cnidaria

Platyhelminthes

Platyhelminthes

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

Mollusca

--

Demospongiae

Demospongiae

Hydrozoa

Turbellaria

Turbellaria

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Gastropoda

Bivalvia

Bivalvia

Bivalvia

Bivalvia

Bivalvia

--

Haplosclerida

Haplosclerida

Anthoathecatae

Tricladida

--

Neotaenioglossa

Basommatophora

Neotaenioglossa

Neotaenioglossa

Architaenioglossa

Neotaenioglossa

Neotaenioglossa

Neotaenioglossa

Neotaenioglossa

Neotaenioglossa

Neotaenioglossa

Neotaenioglossa

Neotaenioglossa

Neotaenioglossa

Basommatophora

Basommatophora

Basommatophora

Neotaenioglossa

Neotaenioglossa

Basommatophora

Basommatophora

Neotaenioglossa

Neotaenioglossa

Neotaenioglossa

Basommatophora

Basommatophora

Basommatophora

Architaenioglossa

Neotaenioglossa

Neotaenioglossa

Neotaenioglossa

Architaenioglossa

--

Veneroida

Veneroida

Veneroida

Veneroida

--

Spongillidae

Spongillidae

Hydridae

--

--

Hydrobiidae

Ancylidae

Hydrobiidae

Hydrobiidae

Viviparidae

Hydrobiidae

Hydrobiidae

Hydrobiidae

Hydrobiidae

Hydrobiidae

Hydrobiidae

Thiaridae

Pleuroceridae

Hydrobiidae

Physidae

Physidae

Ancylidae

Hydrobiidae

Hydrobiidae

Ancylidae

Ancylidae

Thiaridae

Thiaridae

Thiaridae

Planorbidae

Planorbidae

Planorbidae

Ampullariidae

Hydrobiidae

Hydrobiidae

Hydrobiidae

Viviparidae

--

Pisidiidae

Corbiculidae

Pisidiidae

Pisidiidae

Porifera (LPIL)

Ephydatia sp.

Spongilla sp.

Hydra sp.

Tricladida (LPIL)

Turbellaria (LPIL)

Amnicola dalli

Ancylidae (LPIL)

Aphaostracon monas

Aphaostracon sp.

Campeloma floridense

cf. Amnicola dalli

cf. Aphaostracon sp.

cf. Floridobia sp.

cf. Notogillia wetherbyi

cf. Pyrgophorus platyrachis

cf. Spilochlamys sp.

cf. Tarebia sp.

Elimia floridensis

Floridobia wekiwae

Haitia cubensis

Haitia sp.

Hebetancylus excentricus

Hydrobiidae (LPIL)

Hydrobiidae sp. C Line

Laevapex peninsulae

Laevapex sp.

Melanoides sp. (immature)

Melanoides tuberculata

Melanoides turricula

Micromenetus floridensis

Planorbella scalaris

Planorbella trivolvis intertexta

Pomacea paludosa

Pyrgophorus platyrachis

Rissoidea (LPIL)

Spilochlamys gravis

Viviparus georgianus

Bivalvia (LPIL)

cf. Musculium sp.

Corbicula fluminea

Pisidiidae (LPIL)

Sphaerium striatinum

Grant 1836

Lamouroux 1816

Lamarck 1816

Linnaeus 1758

--

--

(Pilsbry and Beecher 1892)

--

(Pilsbry 1899)

Thompson 1968

Call 1886

(Pilsbry and Beecher 1892)

Thompson 1968

Thompson and Hershler 2002

(Dall 1885)

Thompson 1968

Thompson 1968

H. Adams and A. Adams 1854

(Reeve 1860)

(Thompson 1968)

(Pfeiffer 1839)

Taylor 2003

(Morelet 1851)

Simpson 1865

Simpson 1865

(Pilsbry 1903)

Walker 1903

Olivier 1804

(Müller 1774)

(Lea 1862)

(Baker 1945)

(Jay 1839)

(Sowerby 1878)

(Say 1829)

Thompson 1968

--

Thompson 1968

(Lea 1834)

Linnaeus 1758

Link 1807

Müller 1774

Gray 1857

(Lamarck 1818)

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x
Appendixes 99

Appendix 1. Macroinvertebrate taxa collected by dip net (D) and petite ponar dredge (P) from selected springs in the St. Johns River 

drainage, 2004-07.—Continued

[Authorities are listed for lowest practicable identification level (LPIL) indicated. Taxa are listed in approximate phylogenetic order by suprafamilial categories 

and alphabetically by genus and species]

Phylum Class Order Family Taxon Authority D P

Mollusca

Mollusca

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Bivalvia

Bivalvia

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Unionoida

Unionoida

Rhynchobdellida

Rhynchobdellida

Rhynchobdellida

Arhynchobdellida

Arhynchobdellida

Rhynchobdellida

Rhynchobdellida

Rhynchobdellida

Rhynchobdellida

Rhynchobdellida

Rhynchobdellida

--

Arhynchobdellida

Arhynchobdellida

Rhynchobdellida

Haplotaxida

Haplotaxida

Haplotaxida

Lumbriculida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Lumbriculida

Lumbriculida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Lumbriculida

Lumbriculida

Haplotaxida

Unionidae

Unionidae

Glossiphoniidae

Glossiphoniidae

Glossiphoniidae

Erpobdellidae

Erpobdellidae

Glossiphoniidae

Glossiphoniidae

Glossiphoniidae

Glossiphoniidae

Glossiphoniidae

Glossiphoniidae

--

Erpobdellidae

Erpobdellidae

Piscicolidae

Naididae

Naididae

Naididae

Lumbriculidae

Naididae

Naididae

Naididae

Naididae

Naididae

Naididae

Naididae

Naididae

Naididae

Naididae

Naididae

Naididae

Lumbriculidae

Lumbriculidae

Enchytraeidae

Naididae

Naididae

Naididae

Naididae

Lumbriculidae

Lumbriculidae

Naididae

Uniomerus caroliniana

Utterbackia imbecilis

cf. Actinobdella inequiannulata

cf. Helobdella fusca

Desserobdella phalera

Erpobdella punctata

Erpobdellidae (LPIL)

Gloiobdella elongata

Glossiphoniidae (LPIL)

Helobdella fusca

Helobdella sp.

Helobdella stagnalis

Helobdella triserialis

Hirudinea (LPIL)

Mooreobdella microstoma

Mooreobdella tetragon

Myzobdella lugubris

Allonais inaequalis

Aulodrilus pigueti

Bratislavia unidentata

cf. Lumbriculus sp.

Chaetogaster diaphanus

Dero botrytis

Dero digitata

Dero digitata complex

Dero flabelliger

Dero furcata

Dero lodeni

Dero nivea

Dero pectinata

Dero sp.

Dero trifida

Dero vaga

Eclipidrilus palustris

Eclipidrilus sp.

Enchytraeidae (LPIL)

Haber speciosus

Haemonais waldvogeli

Ilyodrilus templetoni

Limnodrilus hoffmeisteri

Lumbriculus sp.

Lumbriculus variegatus

Naididae (LPIL)

(Bosc 1801)

(Say 1829)

Moore 1901

(Castle 1900)

(Graf 1899)

(Leidy 1870)

Blanchard 1894

(Castle 1900)

Vaillant 1890

(Castle 1900)

Blanchard 1896

Linnaeus 1758

(Blanchard 1849)

Lamarck 1818

(Moore 1901)

Sawyer and Shelley 1976

Leidy 1851

(Stephenson 1911)

Kowalewski 1914

(Harman 1973)

Grube 1844

(Gruithuisen 1828)

Marcus 1943

(Müller 1773)

(Müller 1773)

(Stephenson 1931)

(Müller 1773)

Brinkhurst 1986

Aiyer 1930

Aiyer 1930

Okem 1815

Loden 1979

(Leidy 1880)

(Smith 1900)

Eisen 1881

--

(Hrabe 1931)

Bretscher 1900

(Southern 1909)

Claparède 1862

Grube 1844

(Müller 1774)

--

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x
100 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Appendix 1. Macroinvertebrate taxa collected by dip net (D) and petite ponar dredge (P) from selected springs in the St. Johns River 

drainage, 2004-07.—Continued

[Authorities are listed for lowest practicable identification level (LPIL) indicated. Taxa are listed in approximate phylogenetic order by suprafamilial categories 

and alphabetically by genus and species]

Phylum Class Order Family Taxon Authority D P

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Annelida

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Clitellata

Arachnida

Arachnida

Arachnida

Arachnida

Arachnida

Arachnida

Arachnida

Malacostraca

Malacostraca

Malacostraca

Malacostraca

Malacostraca

Malacostraca

Malacostraca

Malacostraca

Malacostraca

Malacostraca

Malacostraca

Malacostraca

Malacostraca

Malacostraca

Malacostraca

Malacostraca

Malacostraca

Malacostraca

Malacostraca

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Haplotaxida

Acariformes

Trombidiformes

Trombidiformes

Trombidiformes

Trombidiformes

Trombidiformes

Trombidiformes

Amphipoda

Amphipoda

Amphipoda

Amphipoda

Amphipoda

Amphipoda

Amphipoda

Amphipoda

Amphipoda

Isopoda

Isopoda

Isopoda

Isopoda

Isopoda

Isopoda

Decapoda

Decapoda

Decapoda

Decapoda

Naididae

Naididae

Naididae

Naididae

Naididae

Naididae

Naididae

Naididae

Naididae

Naididae

Naididae

Naididae

Naididae

Naididae

--

Arrenuridae

Hydrodromidae

Lebertiidae

Limnesiidae

Unionicolidae

Pionidae

--

Aoridae

--

Gammaridae

Gammaridae

Gammaridae

Gammaridae

Aoridae

Hyalellidae

Asellidae

Asellidae

Sphaeromatidae

Anthuridae

Asellidae

Munnidae

Cambaridae

Palaemonidae

Palaemonidae

Palaemonidae

Nais communis complex

Nais elinguis

Nais sp.

Nais variabilis

Pristina breviseta

Pristina leidyi

Pristina sp.

Psammoryctides convolutus

Slavina appendiculata

Spirosperma ferox

Spirosperma sp.

tubificoid Naididae immature sp. A 

(LPIL)

tubificoid Naididae immature sp. B 

(LPIL)

Varichaetadrilus angustipenis

Acariformes (LPIL)

Arrenurus sp.

Hydrodroma sp.

Lebertia sp.

Limnesia sp.

Neumania sp.

Piona sp.

Amphipoda (LPIL)

Aoridae (LPIL)

Gammarida (LPIL)

Gammaridae (LPIL)

Gammarus cf. tigrinus LeCroy

Gammarus mucronatus complex 

LeCroy

Gammarus sp.

Grandidierella bonnieroides

Hyalella azteca complex Lecroy

Caecidotea racovitzai australis

Caecidotea sp.

Cassidinidea ovalis

Cyathura polita

Lirceus lineatus

Uromunna reynoldsi

Cambaridae (LPIL)

Palaemonetes paludosus

Palaemonetes sp.

Palaemonetes vulgaris

Piquet 1906

Müller 1773

Müller 1773

Piquet 1906

Bourne 1891

Smith 1896

Ehrenberg 1828

Loden 1978

(D’udekem 1855)

Eisen 1879

Eisen 1879

--

--

(Brinkhurst & Cook 1966)

--

Duges 1835

Koch 1837

Neumann 1880

Koch 1835

Trouessart 1888

Koch 1842

Latreille 1816

Walker 1908

Latreille 1802

Latreille 1802

Sexton 1939

(Say 1818)

Fabricius 1775

Coutière 1904

Saussure 1858

(Williams 1970)

Packard 1871

(Say 1818)

(Stimpson 1855)

(Say 1818)

(Frankenberg and Menzies 

1966)

Hobbs 1942

(Gibbes 1850)

Heller 1869

(Say 1818)

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x
Appendixes 101

Appendix 1. Macroinvertebrate taxa collected by dip net (D) and petite ponar dredge (P) from selected springs in the St. Johns River 

drainage, 2004-07.—Continued

[Authorities are listed for lowest practicable identification level (LPIL) indicated. Taxa are listed in approximate phylogenetic order by suprafamilial categories 

and alphabetically by genus and species]

Phylum Class Order Family Taxon Authority D P

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Malacostraca

Malacostraca

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Decapoda

Decapoda

Coleoptera

Coleoptera

Coleoptera

Coleoptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Cambaridae

Cambaridae

Chrysomelidae

Hydrophilidae

Dryopidae

Haliplidae

Chironomidae

Chironomidae

Chironomidae

Ceratopogonidae

Ceratopogonidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Ceratopogonidae

Ceratopogonidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Ephydridae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Procambarus sp.

Procambarus sp. (immature)

Chrysomelidae (LPIL)

Helocombus sp.

Pelonomus obscurus

Peltodytes sp.

Ablabesmyia mallochi

Ablabesmyia rhamphe group 

Epler

Beardius truncatus

Bezzia/Palpomyia complex 

Brigham

Ceratopogonidae (LPIL)

cf. Cricotopus sp.

Chironomidae (LPIL)

Chironominae (LPIL)

Chironomini (LPIL)

Chironomus decorus group Epler

Chironomus sp.

Chironomus sp. A Line

Cladopelma sp.

Cladotanytarsus cf. daviesi Epler

Cladotanytarsus sp.

Cladotanytarsus sp. A Epler

Clinotanypus sp.

Cricotopus bicinctus

Cricotopus politus

Cryptochironomus sp.

Culicoides group Brigham

Dasyhelea sp.

Dicrotendipes modestus

Dicrotendipes neomodestus

Dicrotendipes sp. A Epler

Dicrotendipes sp. (immature)

Einfeldia natchitocheae

Einfeldia sp. A Epler

Ephydridae (LPIL)

Glyptotendipes meridionalis

group

Glyptotendipes paripes

Glyptotendipes sp.

Goeldichironomus amazonicus

Goeldichironomus carus

Goeldichironomus holoprasinus

Ortmann 1905

Ortmann 1905

Latreille 1802

Horn 1890

LeConte 1852

Regimbart 1878

(Walley 1925)

Sublette 1964

Reiss and Sublette 1985

Kieffer 1899 (Bezzia); Meigen 

1818 (Palpomyia)

--

Wulp 1874

--

--

--

Johannsen 1905

Meigen 1803

Meigen 1803

Kieffer 1921

Bilyj 1989

Kieffer 1921

Kieffer 1921

Kieffer 1913

(Meigen 1818)

(Coquillett 1902)

Kieffer 1918

Latreille 1809

Kieffer 1911

(Say 1823)

(Malloch 1915)

Kieffer 1913

Kieffer 1913

(Sublette 1964)

Kieffer 1924

--

Dendy and Sublette 1959

(Edwards 1929)

Kieffer 1913

(Fittkau 1965)

(Townes 1945)

(Goeldi 1905)

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x
102 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Appendix 1. Macroinvertebrate taxa collected by dip net (D) and petite ponar dredge (P) from selected springs in the St. Johns River 

drainage, 2004-07.—Continued

[Authorities are listed for lowest practicable identification level (LPIL) indicated. Taxa are listed in approximate phylogenetic order by suprafamilial categories 

and alphabetically by genus and species]

Phylum Class Order Family Taxon Authority D P

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Stratiomyidae

Chironomidae

Ceratopogonidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Ptychopteridae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Stratiomyidae

Tabanidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Goeldichironomus sp.

Labrundinia neopilosella

Larsia decolorata

Larsia sp.

Monopelopia boliekae

Odontomyia/Hedriodiscus group 

Merritt and Cummins

Orthocladiinae (LPIL)

Palpomyia/Sphaeromias group 

Brigham

Parachironomus supparilis

Paralauterborniella 

nigrohalteralis

Paratanytarsus sp.

Pentaneura inconspicua

Polypedilum flavum

Polypedilum halterale group 

Epler

Polypedilum illinoense group 

Epler

Polypedilum scalaenum group 

Epler

Polypedilum nubifer

Polypedilum sp.

Polypedilum tritum

Polypedilum tritum/illinoense

group Epler

Pseudochironomus sp.

Pseudosmittia sp.

Ptychoptera sp.

Rheotanytarsus sp.

Stempellinella sp.

Stempellinella fimbriata

Stenochironomus sp.

Stratiomys sp.

Tabanidae (LPIL)

Tanypodinae (LPIL)

Tanypus carinatus

Tanypus sp.

Tanytarsini (LPIL)

Tanytarsus limneticus

Tanytarsus sp.

Tanytarsus sp. C Epler

Tanytarsus sp. F Epler

Fittkau 1965

Beck and Beck 1966

(Malloch 1915)

Wiedemann 1824

Beck and Beck 1966

Meigen 1803; Enderlein 1914

Lenz 1921

Meigen 1818 (Palpomyia); 

Curtis 1829 (Sphaeromias)

Edwards 1931

(Malloch 1915)

Thienemann and Bause 1913

(Malloch 1915)

(Johannsen 1905)

(Coquillett 1901)

(Malloch 1915)

(Schrank 1803)

Kieffer 1913

Kieffer 1913

(Walker 1856)

(Walker 1856) for tritum; 

(Malloch 1915 for 

illinoense)

Malloch 1915

Goetghebuer 1932

Meigen 1803

Bause and Thienemann 1913

Brundin 1947

Ekrem 2007

Kieffer 1919

Geoffroy 1762

--

--

Sublette 1964

Meigen 1803

--

Sublette 1964

Wulp 1874

Wulp 1874

Wulp 1874

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x
Appendixes 103

Appendix 1. Macroinvertebrate taxa collected by dip net (D) and petite ponar dredge (P) from selected springs in the St. Johns River 

drainage, 2004-07.—Continued

[Authorities are listed for lowest practicable identification level (LPIL) indicated. Taxa are listed in approximate phylogenetic order by suprafamilial categories 

and alphabetically by genus and species]

Phylum Class Order Family Taxon Authority D P

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Arthropoda

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Insecta

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Diptera

Ephemeroptera

Ephemeroptera

Ephemeroptera

Ephemeroptera

Ephemeroptera

Ephemeroptera

Hemiptera

Hemiptera

Hemiptera

Hemiptera

Hemiptera

Hemiptera

Hemiptera

Hemiptera

Hemiptera

Hemiptera

Heteroptera

Odonata

Odonata

Odonata

Odonata

Odonata

Odonata

Odonata

Odonata

Odonata

Trichoptera

Trichoptera

Trichoptera

Trichoptera

Trichoptera

Trichoptera

Trichoptera

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Chironomidae

Tipulidae

Chironomidae

Chironomidae

Chironomidae

Caenidae

Caenidae

Baetidae

Baetidae

--

Leptohyphidae

Belostomatidae

Belostomatidae

--

Belostomatidae

Hebridae

Mesoveliidae

Mesoveliidae

Mesoveliidae

Naucoridae

Gerridae

Gerridae

Coenagrionidae

Coenagrionidae

Coenagrionidae

Corduliidae

Libellulidae

Libellulidae

Corduliidae

Libellulidae

Coenagrionidae

Polycentropodidae

Hydropsychidae

Hydropsychidae

Leptoceridae

Leptoceridae

Hydroptilidae

Hydroptilidae

Tanytarsus sp. G Epler

Tanytarsus sp. L Epler

Tanytarsus sp. T Epler

Tanytarsus sp. V Epler

Thienemanniella sp.

Tipulidae (LPIL)

Tribelos jucundum

Tribelos sp.

Zavreliella marmorata

Caenis diminuta

Caenis sp.

Callibaetis floridanus

Callibaetis sp.

Ephemeroptera (LPIL)

Tricorythodes albilineatus

Belostoma sp.

Belostomatidae (LPIL)

Heteroptera (LPIL)

Lethocerus sp.

Merragata sp.

Mesovelia mulsanti

Mesovelia sp.

Mesovelia sp. (immature)

Pelocoris sp.

Trepobates subnitidus

Gerridae (LPIL)

Argia sp.

Coenagrionidae (LPIL)

Enallagma sp.

Epitheca princeps regina

Erythemis plebeja

Libellulidae (LPIL)

Macromia sp.

Perithemis tenera seminole

Telebasis byersi

Cernotina sp.

Cheumatopsyche sp.

Hydropsychidae (LPIL)

Leptoceridae (LPIL)

Nectopsyche pavida

Neotrichia sp.

Orthotrichia sp.

Wulp 1874

Wulp 1874

Wulp 1874

Wulp 1874

Kieffer 1911

--

(Walker 1848)

Townes 1945

Kieffer 1920

Walker 1853

Stephens 1835

Banks 1900

Eaton 1881

--

Berner 1946

Latreille 1807

Leach 1815

Latreille 1810

Mayr 1853

White 1877

White 1879

Mulsant and Rey 1852

Mulsant and Rey 1852

Stål 1876

Esaki 1926

Leach 1815

Rambur 1842

--

Charpentier 1840

(Hagens in Selys 1871)

(Burmeister 1839)

--

Rambur 1842

(Say 1839)

Westfall 1957

Ross 1938

Wallengren 1891

Curtis 1835

Leach in Brewster 1815

(Hagen 1861)

Ross 1956

Eaton 1873

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x
104 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Appendix 2. Fish species recorded from selected springs sampled in the St. Johns River drainage, 2004-07. 

[Scientific and common names follow Nelson and others (2004)]

Family Scientific name Common name Family Scientific name Common name

Lepisosteidae

Amiidae

Anguillidae

Clupeidae

Cyprinidae

Catostomidae

Ictaluridae

Callichthyidae

Loricariidae

Esocidae

Aphredoderidae

Mugilidae

Atherinopsidae

Lepisosteus platyrhincus

Lepisosteus osseus

Amia calva

Anguilla rostrata

Dorosoma petenense

Notropis petersoni

Notropis harperi

Notemigonus crysoleucas

Pteronotropis metallicus

Opsopoeodus emiliae

Notropis maculatus

Erimyzon sucetta

Ameiurus nebulosus

Noturus gyrinus

Ameiurus catus

Ameiurus natalis

Hoplosternum littorale

Pterygoplichthys disjunctivus

Esox americanus

Aphredoderus sayanus

Mugil cephalus

Menidia beryllina

Labidesthes sicculus

Florida gar

longnose gar

bowfin

American eel

threadfin shad

coastal shiner

redeye chub

golden shiner

sailfin shiner

pugnose minnow

taillight shiner

lake chubsucker

brown bullhead

tadpole madtom

white catfish

yellow bullhead

brown hoplo

vermiculated sailfin catfish

redfin pickerel

pirate perch

striped mullet

inland silverside

brook silverside

Belonidae

Fundulidae

Poeciliidae

Moronidae

Centrarchidae

Percidae

Lutjanidae

Elassomatidae

Cichlidae

Gobiidae

Strongylura marina

Lucania parva

Lucania goodei

Fundulus seminolis

Gambusia holbrooki

Poecilia latipinna

Heterandria formosa

Morone saxatilis

Lepomis macrochirus

Lepomis punctatus

Lepomis auritus

Micropterus salmoides

Lepomis microlophus

Lepomis gulosus

Pomoxis nigromaculatus

Lepomis marginatus

Percina nigrofasciata

Etheostoma fusiforme

Lutjanus griseus

Elassoma okefenokee

Oreochromis aureus

Gobiosoma bosc

Atlantic needlefish

rainwater killifish

bluefin killifish

Seminole killifish

eastern mosquitofish

sailfin molly

least killifish

striped bass

bluegill

spotted sunfish

redbreast sunfish

largemouth bass

redear sunfish

warmouth

black crappie

dollar sunfish

blackbanded darter

swamp darter

gray snapper

Okefenokee pygmy sunfish

blue tilapia

naked goby
Appendixes 105

Appendix 3. Physicochemical data for springs on dates that benthic macroinvertebrate samples were collected in 2004-07. 

[DO, dissolved oxygen; DS, downstream; NTU, nephelometric turbidity units; LB, left bank; RB, right bank; --, not available]

Spring Location Date Time Depth 

(feet)

Temper

ature 

(degrees 

C)

Specific 

conductance 

(μS/cm)

DO

(mg/L) pH Turbidity (NTU)

Chlorophyll-a, 

phytoplankton 

(μg/L)

Pheophytin-a, 

phytoplankton 

(μg/L)

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Alexander

Apopka

Apopka

Apopka

Apopka

Apopka

Apopka

Apopka

Apopka

Apopka

Apopka

Apopka

Apopka

Apopka

Apopka

100 ft DS of boil; 25 ft from LB

100 ft DS of boil; 60 ft from LB

100 ft DS of boil; 100 ft from LB

100 ft DS of boil; 125 ft from LB

100 ft DS of boil; 150 ft from LB

100 ft DS of boil; 25 ft from LB

100 ft DS of boil; 60 ft from LB

100 ft DS of boil; 100 ft from LB

100 ft DS of boil; 125 ft from LB

100 ft DS of boil; 150 ft from LB

100 ft DS of boil; 10 ft from LB

100 ft DS of boil; 40 ft from LB

100 ft DS of boil; 70 ft from LB

100 ft DS of boil; 100 ft from LB

100 ft DS of boil; 125 ft from LB

100 ft DS of boil; 10 ft from LB

100 ft DS of boil; 40 ft from LB

100 ft DS of boil; 70 ft from LB

100 ft DS of boil; 100 ft from LB

100 ft DS of boil; 125 ft from LB

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Boil

2/2/2007

2/2/2007

2/2/2007

2/2/2007

2/2/2007

2/2/2007

5/10/2007

5/10/2007

5/10/2007

5/10/2007

5/10/2007

5/10/2007

8/7/2007

8/7/2007

8/7/2007

8/7/2007

8/7/2007

8/7/2007

10/10/2007

10/10/2007

10/10/2007

10/10/2007

10/10/2007

10/10/2007

12/30/2005

12/30/2005

3/28/2006

3/28/2006

3/28/2006

3/28/2006

3/28/2006

3/28/2006

7/13/2006

7/13/2006

7/13/2006

7/13/2006

7/13/2006

7/13/2006

1100

1103

1109

1113

1117

1150

1000

1001

1004

1008

1012

1015

900

903

907

910

914

930

1000

1042

1045

1047

1049

1052

1530

1530

1200

1237

1239

--

--

--

1013

1017

1019

1020

1022

1027

2

2

2

2

2

2

2.2

2.5

2.5

1

1

2

2

2

2

1

2

3

3

2

28

4.9

1.1

18

15

10

22

20

15

10

5

1

23.5

23.4

23.4

23.4

23.5

23.5

23.4

23.5

23.4

23.4

23.4

23.4

23.5

23.3

23.2

23.2

23.2

23.2

23.3

23.4

23.3

23.2

23.2

23.4

18.6

--

22.4

22.4

22.4

22

22.1

22.1

23.9

24.2

24.4

24.4

24.7

24

1,117

1,101

1,095

1,125

1,138

1,117

1,097

1,121

1,058

1,085

1,098

1,097

1,167

1,148

1,120

1,110

1,116

1,118

1,167

1,210

1,195

1,142

1,174

1,185

297

--

286

285

286

288

288

287

266

267

271

271

283

263

2

2

1.9

1.4

2.4

2.03

1.73

1.9

1.5

1.4

1.7

2.1

--

--

--

--

--

--

1.49

1.8

1.8

1.4

1.6

2.3

6.8

--

4.88

4.8

4.9

5

5

5

2.7

3.2

3.4

3.4

4.3

4

7.8

7.9

7.9

7.8

7.9

7.9

7.9

7.9

7.9

7.9

7.9

7.9

7.6

7.6

7.7

7.8

7.8

7.7

7.8

7.7

7.7

7.8

7.8

7.9

8

--

8.3

8.4

8.3

8.5

8.5

8.4

7.9

8

8

8

8.2

8.1

0

0

0

0

0

0

0

0.2

0

0

0

0

--

--

--

--

--

--

0.2

0.3

0.2

0.3

0.2

0.2

--

--

--

--

--

--

--

--

0

0

0

0.1

1.2

0

0.88

<0.1

0.78

0.15

18.39

13.91

1.5

0.19

0.32

0.15

5.76

3.23
106 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Appendix 3. Physicochemical data for springs on dates that benthic macroinvertebrate samples were collected in 2004-07.—Continued

[DO, dissolved oxygen; DS, downstream; NTU, nephelometric turbidity units; LB, left bank; RB, right bank; --, not available]

Spring Location Date Time Depth 

(feet)

Temper

ature 

(degrees 

C)

Specific 

conductance 

(μS/cm)

DO

(mg/L) pH Turbidity (NTU)

Chlorophyll-a, 

phytoplankton 

(μg/L)

Pheophytin-a, 

phytoplankton 

(μg/L)

Apopka

Apopka

Apopka

Apopka

Apopka

Apopka

Apopka

Apopka

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

Bugg

De Leon

De Leon

De Leon

De Leon

De Leon

De Leon

Boil

Boil

Boil

Boil

Boil

Boil

Head of run

Head of run

300 ft DS

150 ft DS

Head of run

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Boil

300 ft DS

450 ft DS

600 ft DS

Vent, inside 5 ft

Run, 100 ft DS of dam

Vent, inside 5 ft

Run, 100 ft DS of dam

7/13/2006

9/21/2006

9/21/2006

9/21/2006

9/21/2006

9/21/2006

9/21/2006

9/21/2006

12/30/2005

12/30/2005

3/17/2006

3/17/2006

7/12/2006

7/12/2006

7/12/2006

7/12/2006

7/12/2006

7/12/2006

7/12/2006

7/12/2006

7/12/2006

7/12/2006

9/21/2006

9/21/2006

9/21/2006

9/21/2006

9/21/2006

9/21/2006

9/21/2006

9/21/2006

9/21/2006

9/21/2006

2/11/2004

2/11/2004

2/11/2004

3/18/2004

3/18/2004

3/18/2004

1030

1430

1440

1444

1446

1448

1450

1451

1210

1210

1250

1250

930

945

1000

1000

1040

1041

1043

1044

1046

1048

926

931

933

935

937

938

1000

1000

1015

1020

1035

1035

1133

1145

1145

1210

22

20

15

10

5

1

1.6

1

1

1

1

25

20

15

10

5

1

24

20

15

10

5

1

1

1

1

33

2

33

2

24

24.4

24.4

24.2

24.2

24.2

24.4

24.4

22

--

23.9

23.9

24.3

24.1

24

24.1

23.2

23.2

23.2

23.2

23.6

24.1

23.4

23.4

23.4

23.4

23.5

23.6

23.8

23.8

24.1

24

22.5

22.5

21.3

23

23

22.9

263

265

265

261

262

261

262

261

283

--

312

312

307

307

308

307

311

311

311

311

310

308

315

315

314

314

314

314

312

312

312

313

886

886

1,060

884

884

900

4.04

2.5

2.5

2.3

2.3

2.2

2.5

2.8

2.6

--

5.3

5.33

7.4

7.7

7

7.38

0.6

0.7

0.8

1.1

4.8

7.8

1.4

1.3

2

2.2

2.4

2.7

3.6

3.56

3.7

3.5

0.8

0.8

6.7

1.5

1.5

5.5

7.9

8

8

8

8

8

8

8.3

7.6

--

7.4

7.4

7.8

8

7.9

7.9

7.3

7.3

7.3

7.4

7.7

8.1

7.4

7.4

7.5

7.5

7.5

7.6

7.6

7.6

7.6

7.7

7.5

7.5

7.7

7.4

7.4

7.5

0

0.2

0.2

0

0

0

0

0

0

--

--

--

3.4

2

0.4

2

0

0

0

0

0

0.4

0

0

0

0

0

0

0.2

0.2

0.2

0.3

0.1

0.1

0.2

--

--

--

5.91

0.63

0.66

2.19

41.2

24.8

<0.1

<0.1

1.27

0.17

0.42

1.43

24.9

13.4

<0.1

<0.1
Appendixes 107

Appendix 3. Physicochemical data for springs on dates that benthic macroinvertebrate samples were collected in 2004-07.—Continued

[DO, dissolved oxygen; DS, downstream; NTU, nephelometric turbidity units; LB, left bank; RB, right bank; --, not available]

Spring Location Date Time Depth 

(feet)

Temper

ature 

(degrees 

C)

Specific 

conductance 

(μS/cm)

DO

(mg/L) pH Turbidity (NTU)

Chlorophyll-a, 

phytoplankton 

(μg/L)

Pheophytin-a, 

phytoplankton 

(μg/L)

De Leon

De Leon

De Leon

De Leon

De Leon

De Leon

De Leon

Gemini

Gemini

Gemini

Gemini

Gemini

Gemini

Gemini

Gemini

Gemini

Gemini

Gemini

Gemini

Gemini

Gemini

Gemini

Gemini

Gemini

Gemini

Gemini

Gemini

Gemini

Green

Green

Green

Green

Green

Green

Green

Green

Green

Green

Vent, inside 5 ft

Run, 100 ft DS of dam

Run, 100 ft DS of dam

Vent, inside 5 ft

Run, 100 ft DS of dam

Vent, South Boil

Vent, North Boil

Dam, run

Dam, run

Vent, South Boil

Dam, run

Vent, North Boil

Dam, run

Vent, South Boil

Dam, run

Dam, run

Dam, run

Vent, North Boil

Vent, South Boil

Vent, North Boil

Vent, North Boil

Vent, North Boil

Vent, South Boil

Vent, South Boil

Vent, South Boil

Vent, South Boil

Run

Vent

Vent

Vent

Run

Vent

5/12/2004

5/12/2004

5/12/2004

7/28/2004

8/23/2004

8/23/2004

8/23/2004

2/10/2004

2/10/2004

2/10/2004

2/16/2004

3/18/2004

3/18/2004

5/11/2004

5/11/2004

5/12/2004

5/13/2004

7/28/2004

8/18/2004

8/18/2004

8/18/2004

2/10/2004

5/11/2004

8/18/2004

2/10/2004

3/18/2004

5/12/2004

8/18/2004

2/10/2004

2/10/2004

2/10/2004

3/18/2004

3/18/2004

5/11/2004

5/11/2004

5/11/2004

8/18/2004

8/18/2004

1100

1100

1300

1430

1040

1200

1200

1312

1341

1430

--

1450

1525

1435

1710

1600

--

1330

1400

1500

1600

1341

1435

1500

1312

1450

1600

1600

1341

1600

1600

1420

1420

1035

1035

1435

1100

1100

33

2

2

33

2

5

4

2

2

4

2

5

2

4

2

2

2

5

5

2

20

20

20

2

20

22.7

22.7

23.1

23.1

23.5

23.8

23.5

22.9

22.9

22.9

22.6

22.9

23.7

22.9

23.4

22.9

24

22.9

26.6

24.2

24.1

22.9

22.9

24.2

22.9

22.9

22.9

24.1

22.5

22.5

22.5

22.6

22.6

22.6

22.6

22.8

23.2

23.2

801

801

869

832

1,127

969

1,127

2,650

2,620

2,650

2,500

2,690

2,710

2,510

2,540

2,541

2,445

2,620

2,730

2,710

2,740

2,620

2,510

2,710

2,650

2,690

2,541

2,740

2,920

2,900

2,900

2,920

2,920

2,640

2,640

2,630

2,760

2,760

0.8

0.8

6

1.5

1.2

3.6

1.2

0.9

0.8

3.2

--

0.6

4.8

0.6

3.8

0.6

--

2.2

3

1

0.8

0.8

0.6

1

0.9

0.6

0.6

0.8

0.4

0.1

0.1

0.1

0.1

0.1

0.1

0.6

0.4

0.4

7.4

7.4

7.6

7.2

6.8

7

6.8

7.1

7.2

7.4

--

7.2

7.3

7.2

7.3

7.2

7.4

7

7.1

7

7

7.2

7.2

7.2

7.1

7.2

7.2

7

7.4

7.4

7.4

7.3

7.3

7.2

7.2

7.3

7

7

0.6

0.6

0.7

--

--

--

--

0.2

0.2

0.4

--

--

--

--

0.6

--

--

--

<2

--

--

0.2

--

--

0.2

--

--

--

0.2

0.1

0.1

--

--

0.6

0.6

0.4

--

--

5.7

--

<0.1

<0.1

--

<0.1

<0.1

<0.1

--

<0.1

<0.1

<0.1

--

<0.1

--

<0.1

<0.1

--

<0.1

<0.1

<0.1

--

<0.1

<0.1

<0.1

--
108 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Appendix 3. Physicochemical data for springs on dates that benthic macroinvertebrate samples were collected in 2004-07.—Continued

[DO, dissolved oxygen; DS, downstream; NTU, nephelometric turbidity units; LB, left bank; RB, right bank; --, not available]

Spring Location Date Time Depth 

(feet)

Temper

ature 

(degrees 

C)

Specific 

conductance 

(μS/cm)

DO

(mg/L) pH Turbidity (NTU)

Chlorophyll-a, 

phytoplankton 

(μg/L)

Pheophytin-a, 

phytoplankton 

(μg/L)

Green

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Rock

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Run

Boil

Swimming area

Lower section (end tube run)

Boil; 5 ft from RB

Boil; 10 ft from RB

Boil; 15 ft from RB

Boil; 20 ft from RB

Midreach; 3 ft from RB

Midreach; 6 ft from RB

Midreach; 10 ft from RB

Lower section; 5 ft from RB

Lower section; 10 ft from RB

Lower section; 15 ft from RB

Lower section; 20 ft from RB

Lower section; 25 ft from RB

Lower section; 30 ft from RB

Boil

Swimming area; RB footbridge

Swimming area; LB footbridge

Lower section (end tube run)

Boil

Swimming area; RB footbridge

Swimming area; LB footbridge

Swimming area; steps

Lower section (end tube run)

100 ft DS of both vents; 5 ft from LB

100 ft DS of both vents; 25 ft from LB

100 ft DS of both vents; 50 ft from LB

100 ft DS of both vents; 75 ft from LB

100 ft DS of both vents; 100 ft from LB

8/18/2004

12/6/2005

12/6/2005

12/6/2005

12/6/2005

3/17/2006

3/17/2006

3/17/2006

3/17/2006

3/17/2006

3/17/2006

3/17/2006

3/17/2006

3/17/2006

3/17/2006

3/17/2006

3/17/2006

3/17/2006

3/27/2006

6/21/2006

6/21/2006

6/21/2006

6/21/2006

6/28/2006

9/27/2006

9/27/2006

9/27/2006

9/27/2006

9/27/2006

9/27/2006

10/19/2006

10/30/2006

1/31/2007

1/31/2007

1/31/2007

1/31/2007

1/31/2007

1/31/2007

1500

1310

1500

1615

1615

1147

1149

1150

1152

1242

1244

1247

1335

1337

1339

1341

1342

1344

1318

1117

1238

1242

1347

1015

940

1100

1105

1130

1140

1210

1600

1145

1100

1103

1107

1110

1114

1135

2

0.6

0.4

0.4

1.6

1.7

1.6

1.5

2

2.1

1

1.5

1.5

1.7

1.7

1.3

0.4

0.4

0.5

0.5

0.3

1.5

1

1

1

1

1

2

2.5

3

3.5

23.2

23.7

23.6

23.4

--

23.6

23.7

23.7

23.7

23.8

23.8

23.8

24

24.1

24.1

24.1

24.1

24.1

23.8

23.7

23.9

23.9

24.3

23.7

23.8

23.9

23.9

24.1

24.1

24.2

23.3

23.5

23.2

23.2

23.2

23.2

23.2

23.2

2,720

236

237

237

--

258

258

258

258

257

257

258

250

257

258

258

258

258

257

265

265

265

265

259

262

262

262

262

262

262

1,917

1,921

2,022

2,016

1,894

1,870

1,843

1,894

0.6

1.1

2.1

2.8

--

1.1

1

1

1

2.1

2.2

3

4.1

4.1

3.7

3.6

3.7

3.7

2.23

0.9

2

2.1

3

1.74

1.3

2.4

2.3

2.9

2.89

3.5

3.5

3.55

4.1

3.6

3.7

3.6

3.5

3.65

7.2

7.6

7.7

7.7

--

7.5

7.6

7.6

7.6

7.8

7.8

7.8

8

8

8

8

8

8

7.8

7.5

7.9

8

7.9

7.6

7.6

7. 8

7.8

7.9

7.9

8

7.8

7.8

8

7.9

7.9

7.8

7.8

7.9

--

0

0

0

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

6.5

16.5

6.7

30.3

--

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0.19

0.57

0.23

0.4

--

--

0.1

0.17

0.71

0.42

0.66

--

--

<0.1
Appendixes 109

Appendix 3. Physicochemical data for springs on dates that benthic macroinvertebrate samples were collected in 2004-07.—Continued

[DO, dissolved oxygen; DS, downstream; NTU, nephelometric turbidity units; LB, left bank; RB, right bank; --, not available]

Spring Location Date Time Depth 

(feet)

Temper

ature 

(degrees 

C)

Specific 

conductance 

(μS/cm)

DO

(mg/L) pH Turbidity (NTU)

Chlorophyll-a, 

phytoplankton 

(μg/L)

Pheophytin-a, 

phytoplankton 

(μg/L)

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

Silver Glen

100 ft DS of both vents; 5 ft from LB

100 ft DS of both vents; 25 ft from LB

100 ft DS of both vents; 50 ft from LB

100 ft DS of both vents; 75 ft from LB

100 ft DS of both vents; 100 ft from LB

100 ft DS of both vents; 5 ft from LB

100 ft DS of both vents; 25 ft from LB

100 ft DS of both vents; 50 ft from LB

100 ft DS of both vents; 75 ft from LB

100 ft DS of both vents; 100 ft from LB

100 ft DS of both vents; 10 ft from LB

100 ft DS of both vents; 25 ft from LB

100 ft DS of both vents; 75 ft from LB

100 ft DS of both vents; 100 ft from LB

100 ft DS of both vents; 125 ft from LB

3/15/2007

5/10/2007

5/10/2007

5/10/2007

5/10/2007

5/10/2007

5/10/2007

8/7/2007

8/7/2007

8/7/2007

8/7/2007

8/7/2007

8/7/2007

10/10/2007

10/10/2007

10/10/2007

10/10/2007

10/10/2007

10/10/2007

1530

1320

1324

1328

1330

1332

1336

1200

1204

1208

1212

1216

1230

1220

1221

1223

1225

1227

1300

1

2

2.5

3

3.5

1

2

2.5

3

3.5

2

2

3

3

4

23.8

23.3

23.2

23.2

23.2

23.2

23.2

23

23

23.1

23.1

23

23

23.1

23

23.1

23.1

23.2

23.1

1,951

1,887

1,909

1,936

1,936

1,997

2,001

1,894

1,903

1,898

1,928

2,054

1,928

1,953

1,961

1,974

1,984

2,083

1,929

2.8

2.8

2.7

2.7

2.81

2.8

2.8

--

--

--

--

--

--

3.3

3.2

3.3

3.6

4.1

3.31

7.6

7.8

7.8

7.8

7.8

7.9

7.9

7.2

7.5

7.6

7.7

7.7

7.6

7.8

7.8

7.8

7.8

8

7.8

0

0

0

0

0

0

0.1

--

--

--

--

--

--

0.2

0.1

0.1

0.1

0.1

0.1

--

0.66

0.21

0.37

--

1.09

1.77

0.17

Abyss

Abyss

Abyss

Blue Grotto

Blue Grotto

Blue Grotto

Silver (Mammoth)

Silver (Mammoth)

Silver (Mammoth)

Silver (Mammoth)

Silver (Mammoth)

Silver (Mammoth)

Silver (Mammoth)

Silver River

Silver River

Silver River

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Boil

Run, 0.25 miles DS of Mammoth

Run, 0.25 miles DS of Mammoth

Run, 0.25 miles DS of Mammoth

Silver Springs Group

10/23/2003 -- 40

4/14/2004 1030 40

7/14/2004 925 40

10/23/2003 -- 30

4/14/2004 1120 30

7/14/2004 1000 30

9/8/2003 945 20

10/21/2003 1100 20

10/23/2003 -- 20

2/19/2004 1145 20

4/14/2004 810 20

8/2/2004 1230 20

7/14/2004 840 20

1/15/2004 1420 10

4/14/2004 1200 10

7/14/2004 1045 10

23.6

23.5

23.7

23.7

23.5

23.7

23.4

23.1

23.3

23.2

23.2

--

23.1

23.4

23.4

23.8

509

491

404

465

473

390

483

456

425

475

470

--

382

465

451

373

3.4

4.4

3.9

3.6

4.5

3.9

2.6

2.2

1.7

2.7

2.5

--

1.9

5.4

5.7

5

7.3

7.2

7.1

7.4

7.3

7.1

7.1

7.2

7.3

6.8

7.2

--

7

7.4

7.2

6.9

0.2

--

0.2

0.1

--

0.1

--

--

0.1

--

--

--

0.1

0.1

0.2

0.2

Wekiwa

Wekiwa

Foot bridge 12/7/2005

12/7/2005

1100

1100

0.4 23.7

--

317

--

0.7

--

7.3

--

0

-- <0.1 <0.1
110 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District

Appendix 3. Physicochemical data for springs on dates that benthic macroinvertebrate samples were collected in 2004-07.—Continued

[DO, dissolved oxygen;; DS, downstream; NTU, nephelometric turbidity units; LB, left bank; RB, right bank; --, not available]

Spring Location Date Time Depth 

(feet)

Temper

ature 

(degrees 

C)

Specific 

conductance 

(μS/cm)

DO

(mg/L) pH Turbidity (NTU)

Chlorophyll-a, 

phytoplankton 

(μg/L)

Pheophytin-a, 

phytoplankton 

(μg/L)

Wekiwa

Wekiwa

Wekiwa

Wekiwa

Wekiwa

Wekiwa

Wekiwa

Wekiwa

Wekiwa

Wekiwa

Wekiwa

Wekiwa

Wekiwa

Wekiwa

Wekiwa

Wekiwa

Foot bridge; 5 ft from RB

Foot bridge; 10 ft from RB

Foot bridge; 15 ft from RB

Foot bridge; 20 ft from RB

Foot bridge; 25 ft from RB

Foot bridge; RB

Foot bridge; middle

Foot bridge; LB

Foot bridge; 40 ft from LB

Foot bridge; center

Foot bridge; 60 ft from LB

3/27/2006

3/27/2006

3/27/2006

3/27/2006

3/27/2006

3/27/2006

6/22/2006

6/22/2006

6/22/2006

6/28/2006

9/27/2006

9/27/2006

9/27/2006

9/27/2006

10/18/2006

3/22/2007

1540

1541

1542

1543

1544

1605

1021

1023

1029

840

1310

1312

1315

1345

1300

1100

0.3

0.8

0.8

0.9

0.8

0.2

0.2

0.2

0.5

1

1

23.8

23.8

23.7

23.7

23.7

23.8

23.9

23.8

23.8

23.7

23.9

23.9

23.9

23.9

24.5

23.7

342

344

344

344

339

344

355

354

355

342

344

344

344

344

344

347

0.8

0.6

0.6

0.5

0.6

0.61

0.7

0.7

0.5

0.82

1.2

1.2

1.1

1.14

--

0.4

7.3

7.3

7.3

7.3

7.3

7.3

6.7

7

7.2

7.2

7.3

7.3

7.3

7.3

7.3

7.3

--

--

--

--

--

--

12.6

5.7

5.9

--

0

0

0

0

0

0.1

<0.31

<0.1

0.15

--

--

<0.31

<0.1

0.13

--

--
Appendixes 11

1

Appendix 4. Concentrations of organic wastewater compounds detected in water samples from selected springs in the St. Johns River drainage.[Concentrations are in micrograms per liter; E, estimated value reported by laboratory that is between the method reporting level and the method detection level; M, presence verified but not quantified]

Organic 

compound

Spring

De Leon Fern Hammock Gemini-N Boil Gemini-S Boil Green Juniper Silver Glen Wekiwa

DateSample start time

Medium code

1,4-Dichlorobenzene

 1-Methylnaphthalene

2,6-Dimethylnaphthalene

2-Methylnaphthalene

3-beta-Coprostanol

3-Methyl-1H-indole

3-tert-Butyl-4-

hydroxyanisole

4-Cumylphenol

4-Nonylphenol

4-Octylphenol

4-tert-Octylphenol

5-Methyl-1Hbenzotriazole

9,10-Anthraquinone

Acetophenone

Acetyl hexamethyl 

tetrahydro naphthalene

Anthracene

Benzo[a]pyrene

Benzophenone

beta-Sitosterol

beta-Stigmastanol

BisABisphenol A-d3, 

surrogate, % recovery

Bromacil

Caffeine

5/12/04 8/23/04

1100 1040

6 6

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<2 <2

M <1

<5 <5

<1 <1

<5 <5

<1 <1

<1 <1

<2 <2

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<2 <2

<2 <2

<1 <1

104 54.7

<0.5 <0.5

<0.5 <0.5

10/19/06 10/30/06 3/15/07

1330 930 930

6 6 6

<0.1 <0.1

<0.1 <0.1

<0.2 <0.2

<0.1 <0.1

<2 <2

<0.08 <0.08

<0.6 <0.6

<0.14 <0.14

<2 <2

<0.16 <0.16

<0.10 <0.10

<2 <2

<0.2 <0.2

<0.1 <0.1

<0.5 <0.5

<0.1 <0.1

<0.1 <0.1

<0.2 <0.2

<2 <2

<2 <2

5.8 55.6

<0.4 <0.4

<0.2 <0.2

5/11/04 8/18/04

1435 1500

6 6

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

M <0.5

<2 <2

<1 <1

<5 <5

<1 <1

<5 <5

<1 <1

<1 <1

<2 <2

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

E0.1 <0.5

<2 <2

<2 <2

<1 <1

66.7 37

<0.5 <0.5

<0.5 <0.5

5/12/04 8/18/04

1600 1600

6 6

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<2 <2

<1 <1

<5 <5

<1 <1

<5 <5

<1 <1

<1 <1

<2 <2

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

E0.1 <0.5

<2 <2

<2 <2

<1 <1

82.6 70.6

<0.5 <0.5

<0.5 <0.5

5/11/04 8/18/04

1035 1100

9 9

<0.5 <0.5

M <0.5

<0.5 <0.5

M <0.5

<2 <2

<1 <1

<5 <5

<1 <1

M <5

<1 <1

<1 <1

<2 <2

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

E0.1 <0.5

<2 <2

<2 <2

M <1

133 58.9

<0.5 <0.5

<0.5 <0.5

10/19/06 3/15/07

1045 1300

6 6

<0.1 <0.1

<0.1 <0.1

<0.2 <0.2

<0.1 <0.1

<2 <2

<0.08 <0.08

<0.6 <0.6

<0.14 <0.14

<2 <2

<0.16 <0.16

<0.10 <0.10

<2 <2

<0.2 <0.2

<0.1 <0.1

<0.5 <0.5

<0.1 <0.1

<0.1 <0.1

<0.2 <0.2

<2 <2

<2 <2

9.6 61.7

<0.4 <0.4

<0.2 <0.2

10/19/06 10/30/06 3/15/07

1600 1145 1530

6 6 6

<0.1 <0.1

<0.1 <0.1

<0.2 <0.2

<0.1 <0.1

<2 <2

<0.08 <0.08

<0.6 <0.6

<0.14 <0.14

<2 <2

<0.16 <0.16

<0.10 <0.10

<2 <2

<0.2 <0.2

<0.1 <0.1

<0.5 <0.5

<0.1 <0.1

<0.1 <0.1

<0.2 <0.2

<2 <2

<2 <2

26 50

<0.4 <0.4

<0.2 <0.2

10/18/06 3/22/07

1300 1100

6 6

<0.1 <0.1

<0.1 <0.1

<0.2 <0.2

<0.1 <0.1

<2 <2

<0.08 <0.08

<0.6 <0.6

<0.14 <0.14

<2 <2

<0.16 <0.16

<0.10 <0.10

<2 <2

<0.2 <0.2

<0.1 <0.1

<0.5 <0.5

<0.1 <0.1

<0.1 <0.1

<0.2 <0.2

<2 <2

<2 <2

7.3 71.9

<0.4 <0.4

<0.2 <0.2
112 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District Appendix 4. Concentrations of organic wastewater compounds detected in water samples from selected springs in the St. Johns River drainage.—Continued [Concentrations are in micrograms per liter; E, estimated value reported by laboratory that is between the method reporting level and the method detection level; M, presence verified but not quantified] Organic compound Spring De Leon Fern Hammock Gemini-N Boil Gemini-S Boil Green Juniper Silver Glen Wekiwa Caffeine-13C, surrogate, % recovery Camphor Carbaryl Carbazole Chlorpyrifos Cholesterol Cotinine Decafluorobiphenyl, surrogate, % recovery DEET Diazinon Diethoxynonylphenol Diethoxyoctylphenol D-Limonene Fluoranthene Fluoranthene-d10, surrogate, filtered, % recovery Hexahydrohexamethyl cyclopentabenzo- pyran Indole Isoborneol Isophorone Isopropylbenzene Isoquinoline Menthol Metalaxyl Methyl salicylate Metolachlor 109 90.7 <0.5 <0.5 <0.041 <0.041 <0.5 <0.5 <0.005 <0.005 <2 <2 <1.00 <1.00 73.9 37.2 <0.5 <0.5 <0.005 <0.005 <5 <5 <1 <1 <0.5 <0.5 <0.5 <0.5 109 97.5 <0.5 <0.5 E0.4 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.013 <0.013 80.5 80.6

M

M

<1 <0.060 <0.060

<0.1 <0.1

<0.2 <0.005 <0.005

<1 <1

<0.400 <0.400

50.5 66.4

<0.2 <0.2<0.2 <0.005 <0.005

<5 <5

<1 <1

<0.1 <0.1

<0.1 <0.1

80.2 76.8

<0.5 <0.5

<0.1 <0.1

<0.1 <0.1

<0.1 <0.1

<0.1 <0.1

<0.4 <0.4

<0.2 <0.2

<0.2 <0.2

<0.2 <0.2

<0.2 <0.010 <0.010

121 73.9

<0.5 <0.5

<0.041 <0.041

<0.5 <0.5

<0.005 <0.005

<2 <2

<1.00 <1.00

83.3 55.7

E0.1 E0.1

<0.005 <0.005

<5 <5

<1 <1

<0.5 <0.5

<0.5 <0.5

125 83.7

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

M <0.5

<0.013 <0.013

135 82.5

<0.5 <0.5

<0.041 <0.041

<0.5 <0.5

<0.005 <0.005

<2 <2

<1.00 <1.00

78.3 41

E0.1 <0.5

<0.005 <0.005

<5 <5

<1 <1

<0.5 <0.5

<0.5 <0.5

135 95.1

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.013 <0.013

129 81.9

<0.5 <0.5

<0.041 <0.041

<0.5 <0.5

<0.005 <0.005

<2 <2

<1.00 <1.00

75 48

E0.2 E0.1

<0.005 <0.005

<5 <5

<1 <1

<0.5 <0.5

<0.5 <0.5

125 89.2

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

M <0.5

<0.013 <0.013

80.7 85

<0.1 <0.1

<0.060 <0.060

<0.1 <0.1

<0.005 <0.005

<1 <1

<0.400 <0.400

49.4 62.3

<0.2 M

<0.005 <0.005

<5 <5

<1 <1

<0.1 <0.1

<0.1 <0.1

81.1 82.6

<0.5 <0.5

<0.1 <0.1

<0.1 <0.1

<0.1 <0.1

<0.1 <0.1

<0.4 <0.4

<0.2 <0.2

<0.2 <0.2

<0.2 <0.2

<0.010 <0.010

82.2 81

<0.1 <0.1

<1 <0.060 <0.060

<0.1 <0.1

<0.2 <0.005 <0.005

<1 <1

<0.400 <0.400

47.6 61.2

<0.2 <0.2

<0.2 <0.005 <0.005

<5 <5

<1 <1

<0.1 <0.1

<0.1 <0.1

79.2 80.1

<0.5 <0.5

<0.1 <0.1

<0.1 <0.1

<0.1 <0.1

<0.1 <0.1

<0.4 <0.4

<0.2 <0.2

<0.2 <0.2

<0.2 <0.2

<0.2 <0.010 <0.010

79.3 94.1

<0.1 <0.1

<0.060 <0.060

<0.1 <0.1

<0.005 <0.005

<1 <1

<0.400 <0.400

43.3 78.1

<0.2 <0.2

<0.005 <0.005

<5 <5

<1 <1

<0.1 <0.1

<0.1 <0.1

77.4 102

<0.5 <0.5

<0.1 <0.1

<0.1 <0.1

<0.1 <0.1

<0.1 <0.2

<0.4 <0.4

<0.2 <0.2

<0.2 <0.2

<0.2 <0.2

<0.010 <0.010
Appendixes 11

3

Appendix 4. Concentrations of organic wastewater compounds detected in water samples from selected springs in the St. Johns River drainage.—Continued[Concentrations are in micrograms per liter; E, estimated value reported by laboratory that is between the method reporting level and the method detection level; M, presence verified but not quantified]

Organic 

compound

Spring

De Leon Fern Hammock Gemini-N Boil Gemini-S Boil Green Juniper Silver Glen Wekiwa

Monoethoxyoctylphenol

Naphthalene

p-Cresol

PentachlorophenolPhenanthrene

PhenolPrometon

Pyrene

Sample volume, 

wastewater method, water, filtered, milliliters

Tetrachloroethene

Tribromomethane

Tributyl phosphate

Triclosan

Triethyl citrateTriphenyl phosphate

Tris(2-butoxyethyl) 

phosphate

Tris(2-chloroethyl) 

phosphate

Tris(dichloroisopropyl) 

phosphate

<1 M

<0.5 <0.5

2 <1

<2 <2<0.5 <0.5

E0.4 <0.5

<0.01 <0.01

<0.5 <0.5

877 893

M <0.5

<0.5 <0.5

<0.5 <0.5

<1 <1

<0.5 <0.5<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<1 <1

<0.1 <0.1

<0.18 <0.18

<0.1 <0.1

<0.4 <0.4<0.4 <0.01 <0.01

<0.1 <0.1

926 907

<0.2 <0.2

<0.1 <0.1

<0.2 <0.2

<0.2 <0.2

E0.1 <0.4

<0.2 <0.2

<0.5 <0.5

<0.2 <0.2

<0.2 <0.2

<1 <1

M <0.5

<1 <1

<2 <2<0.5 <0.5

<0.5 0.7<0.01 <0.01

<0.5 <0.5

832 889

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<1 <1

<0.5 <0.5

E0.1 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<1 <1

<0.5 <0.5

<1 <1

<2 <2<0.5 <0.5

<0.5 <0.5<0.01 <0.01

<0.5 <0.5

866 858

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<1 <1

<0.5 <0.5

E0.1 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<1 <1

M <0.5

M <1

<2 <2<0.5 <0.5

E0.3 E0.2

<0.01 <0.01

<0.5 <0.5

834 886

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<1 <1

<0.5 <0.5<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<0.5 <0.5

<1 <1

<0.1 <0.1

<0.18 <0.18

<0.1 <0.1

<0.4 <0.4<0.01 <0.01

<0.1 <0.1

924 908

<0.2 <0.2

<0.1 <0.1

<0.2 <0.2

<0.2 <0.2

E0.1 <0.4

<0.2 <0.2

<0.5 <0.5

<0.2 <0.2

<0.2 <0.2

<1 <1

<0.1 <0.1

<0.18 <0.18

<0.1 <0.1

<0.4 E0.2

<0.4 <0.01 <0.01

<0.1 <0.1

938 900

<0.2 <0.2

<0.1 <0.1

<0.2 <0.2

<0.2 <0.2<0.4 <0.4

<0.2 <0.2

<0.5 <0.5

<0.2 <0.2

<0.2 <0.2

<1 <1

<0.1 <0.1

<0.18 <0.18

<0.1 <0.1<0.4 E0.1

<0.01 <0.01

<0.1 <0.1

942 861

<0.2 <0.2

<0.1 <0.1

<0.2 <0.2

<0.2 <0.2

E0.1 <0.4

<0.2 <0.2

<0.5 <0.5

<0.2 <0.2

<0.2 <0.2
114 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District Appendix 5. Concentrations of pesticides analyzed in water samples from selected springs in the St. Johns River drainage, 2004-07. [Concentrations are in micrograms per liter; E, estimated concentration reported by laboratory that is quantifiable below the method reporting level] Pesticide Spring De Leon Fern Hammock Gemini-N Boil Gemini-S Boil Green Juniper Silver Glen Wekiwa Sample date Sample time Medium code Sample type code alpha-HCH Acetochlor Alachlor 2,6-Diethylaniline Atrazine Azinphos-methyl Benfluralin Butylate Carbaryl Carbofuran Chlorpyrifos cis-Permethrin Cyanazine DCPA 2-Chloro-4- isopropylamino-6- amino-s-triazine Diazinon Dieldrin Disulfoton EPTC Ethalfluralin Ethoprop Desulfinylfipronil amide 5/12/04 8/23/04 1100 1040 6 6 9 9 <0.005 <0.005 <0.006 <0.006 <0.005 <0.005 <0.006 <0.006 <0.007 <0.007 <0.050 <0.050 <0.010 <0.010 <0.004 <0.004 <0.041 <0.041 <0.020 <0.020 <0.005 <0.005 <0.006 <0.006 <0.018 <0.018 <0.003 <0.003 <0.006 <0.006 <0.005 <0.005 <0.009 <0.009 <0.02 <0.02 <0.004 <0.004 <0.009 <0.009 <0.005 <0.005 <0.029 <0.029 10/19/06 10/30/06 3/15/07 1330 930 930 6 6 6 9 9 9 <0.006 <0.006 <0.005 <0.005 <0.006 <0.006 <0.007 <0.007 <0.080 <0.080 <0.010 <0.010 <1 <0.060 <0.060 <0.2 <0.005 <0.005 <0.010 <0.010 <0.003 <0.003 <0.014 <0.014 <0.2 <0.005 <0.005 <0.009 <0.009 <0.029 <0.029 5/11/04 8/18/04 1435 1500 6 6 9 9 <0.005 <0.005 <0.006 <0.006 <0.005 <0.005 <0.006 <0.006 0.015 0.017 <0.050 <0.050 <0.010 <0.010 <0.004 <0.004 <0.041 <0.041 <0.020 <0.020 <0.005 <0.005 <0.006 <0.006 <0.018 <0.018 <0.003 <0.003 E0.011 E0.012 <0.005 <0.005 <0.009 <0.009 <0.02 <0.02 <0.004 <0.004 <0.009 <0.009 <0.005 <0.005 <0.029 <0.029 5/12/04 8/18/04 1600 1600 6 6 9 9 <0.005 <0.005 <0.006 <0.006 <0.005 <0.005 <0.006 <0.006 0.013 0.019 <0.050 <0.050 <0.010 <0.010 <0.004 <0.004 <0.041 <0.041 <0.020 <0.020 <0.005 <0.005 <0.006 <0.006 <0.018 <0.018 <0.003 <0.003 E0.010 E0.013 <0.005 <0.005 <0.009 <0.009 <0.02 <0.02 <0.004 <0.004 <0.009 <0.009 <0.005 <0.005 <0.029 <0.029 5/11/04 8/18/04 1035 1100 9 9 9 9 <0.005 <0.005 <0.006 <0.006 <0.005 <0.005 <0.006 <0.006 <0.007 <0.007 <0.050 <0.050 <0.010 <0.010 <0.004 <0.004 <0.041 <0.041 <0.020 <0.020 <0.005 <0.005 <0.006 <0.006 <0.018 <0.018 <0.003 <0.003 <0.006 <0.006 <0.005 <0.005 <0.009 <0.009 <0.02 <0.02 <0.004 <0.004 <0.009 <0.009 <0.005 <0.005 <0.029 <0.029 10/19/06 3/15/07 1045 1300 6 6 9 9 <0.006 <0.006 <0.005 <0.005 <0.006 <0.006 <0.007 <0.007 <0.080 <0.080 <0.010 <0.010 <0.060 <0.060 <0.005 <0.005 <0.010 <0.010 <0.003 <0.003 <0.014 <0.014 <0.005 <0.005 <0.009 <0.009 <0.029 <0.029 10/19/06 10/30/06 3/15/07 1600 1145 1530 6 6 6 9 9 9 <0.006 <0.006 <0.005 <0.005 <0.006 <0.006 <0.007 <0.007 <0.080 <0.080 <0.010 <0.010 <1 <0.060 <0.060 <0.2 <0.005 <0.005 <0.010 <0.010 <0.003 <0.003 <0.014 <0.014 <0.2 <0.005 <0.005 <0.009 <0.009 <0.029 <0.029 10/18/06 3/22/07 1300 1100 6 6 9 9 <0.006 <0.006 <0.005 <0.005 <0.006 <0.006 0.008 E0.007 <0.080 <0.080 <0.010 <0.010 <0.060 <0.060 <0.005 <0.005 <0.010 <0.010 <0.003 <0.003 E0.008 E0.008 <0.005 <0.005 <0.009 <0.009 <0.029 <0.029
Appendixes 11

5

Appendix 5. Concentrations of pesticides analyzed in water samples from selected springs in the St. Johns River drainage, 2004-07.—Continued[Concentrations are in micrograms per liter; E, estimated concentration reported by laboratory that is quantifiable below the method reporting level]

Pesticide

Spring

De Leon Fern Hammock Gemini-N Boil Gemini-S Boil Green Juniper Silver Glen Wekiwa

Fipronil sulfide

Fipronil sulfone

Desulfinylfipronil

FipronilFonofos

Lindane

Linuron

Malathion

Methylparathion

Metolachlor

Metribuzin

Molinate

Napropamide

p,p’-DDE

Parathion

Pebulate

Pendimethalin

Phorate

Prometon

Propyzamide

Propachlor

Propanil

Propargite

Simazine

Tebuthiuron

Terbacil

Terbufos

Thiobencarb

Triallate

<0.013 <0.013

<0.024 <0.024

<0.012 <0.012

<0.016 <0.016<0.003 <0.003

<0.004 <0.004

<0.035 <0.035

<0.027 <0.027

<0.015 <0.015

<0.013 <0.013

<0.006 <0.006

<0.003 <0.003

<0.007 <0.007

<0.003 <0.003

<0.010 <0.010

<0.004 <0.004

<0.022 <0.022

<0.011 <0.011

<0.01 <0.01

<0.004 <0.004

<0.025 <0.025

<0.011 <0.011

<0.02 <0.02

<0.007 <0.005

<0.02 <0.02

<0.034 <0.034

<0.02 <0.02

<0.010 <0.010

<0.002 <0.002

<0.013 <0.013

<0.024 <0.024

<0.012 <0.012

<0.016 <0.016<0.006 <0.006

<0.016 <0.016

<0.008 <0.008

<0.2 <0.010 <0.010

<0.012 <0.012

<0.020 <0.020

<0.020 <0.020

<0.4 <0.01 <0.01

<0.004 <0.004

<0.006 <0.006

<0.02 <0.02

<0.01 <0.01

<0.013 <0.013

<0.024 <0.024

<0.012 <0.012

<0.016 <0.016<0.003 <0.003

<0.004 <0.004

<0.035 <0.035

<0.027 <0.027

<0.015 <0.015

<0.013 <0.013

<0.006 <0.006

<0.003 <0.003

<0.007 <0.007

<0.003 <0.003

<0.010 <0.010

<0.004 <0.004

<0.022 <0.022

<0.011 <0.011

<0.01 <0.01

<0.004 <0.004

<0.025 <0.025

<0.011 <0.011

<0.02 <0.02

<0.005 <0.005

<0.02 <0.02

<0.034 <0.034

<0.02 <0.02

<0.010 <0.010

<0.002 <0.002

<0.013 <0.013

<0.024 <0.024

<0.012 <0.012

<0.016 <0.016

<0.003 <0.003

<0.004 <0.004

<0.035 <0.035

<0.027 <0.027

<0.015 <0.015

<0.013 <0.013

<0.006 <0.006

<0.003 <0.003

<0.007 <0.007

<0.003 <0.003

<0.010 <0.010

<0.004 <0.004

<0.022 <0.022

<0.011 <0.011

<0.01 <0.01

<0.004 <0.004

<0.025 <0.025

<0.011 <0.011

<0.02 <0.02

<0.005 <0.005

<0.02 <0.02

<0.034 <0.034

<0.02 <0.02

<0.010 <0.010

<0.002 <0.002

<0.013 <0.013

<0.024 <0.024

<0.012 <0.012

<0.016 <0.016

<0.003 <0.003

<0.004 <0.004

<0.035 <0.035

<0.027 <0.027

<0.015 <0.015

<0.013 <0.013

<0.006 <0.006

<0.003 <0.003

<0.007 <0.007

<0.003 <0.003

<0.010 <0.010

<0.004 <0.004

<0.022 <0.022

<0.011 <0.011

<0.01 <0.01

<0.004 <0.004

<0.025 <0.025

<0.011 <0.011

<0.02 <0.02

<0.005 <0.005

<0.02 <0.02

<0.034 <0.034

<0.02 <0.02

<0.010 <0.010

<0.002 <0.002

<0.013 <0.013

<0.024 <0.024

<0.012 <0.012

<0.016 <0.016

<0.006 <0.006

<0.016 <0.016

<0.008 <0.008

<0.010 <0.010

<0.012 <0.012

<0.020 <0.020

<0.020 <0.020

<0.01 <0.01

<0.004 <0.004

<0.006 <0.006

<0.02 <0.02

<0.01 <0.01

<0.013 <0.013

<0.024 <0.024

<0.012 <0.012

<0.016 <0.016

<0.006 <0.006

<0.016 <0.016

<0.008 <0.008

<0.2 <0.010 <0.010

<0.012 <0.012

<0.020 <0.020

<0.020 <0.020

<0.4 <0.01 <0.01

<0.004 <0.004

<0.006 <0.006

<0.02 <0.02

<0.01 <0.01

<0.013 <0.013

<0.024 <0.024

<0.012 <0.012

E0.007 E0.005

<0.006 <0.006

<0.016 <0.016

<0.008 <0.008

<0.010 <0.010

<0.012 <0.012

<0.020 <0.020

<0.020 <0.020

<0.01 <0.01

<0.004 <0.004

E0.005 E0.004

<0.02 <0.02

<0.01 <0.01
116 Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District Appendix 5. Concentrations of pesticides analyzed in water samples from selected springs in the St. Johns River drainage, 2004-07.—Continued [Concentrations are in micrograms per liter; E, estimated concentration reported by laboratory that is quantifiable below the method reporting level] Pesticide Spring De Leon Fern Hammock Gemini-N Boil Gemini-S Boil Green Juniper Silver Glen Wekiwa Trifluralin Sample volume, Schedule 2001, milliliters Diazinon-d10, surrogate, water, filtered (0.7-micron glass fiber filter), percent recovery alpha-HCH-d6, surrogate, percent recovery <0.009 <0.009 879 888 120 107 94.4 97.1 <0.009 <0.009 <0.009 <0.009 903 876 103 96.9 100 90.1 <0.009 <0.009 880 860 113 108 95.6 97.6 <0.009 <0.009 902 814 103 102 101 91.9 <0.009 <0.009 <0.009 <0.009 <0.009 <0.009