# St. Lucie River Estuary: Evidence of Impairment

July, 2002

G. Graves, M. Thompson, and D. Fike Southeast District Water Quality Section Florida Department of Environmental Protection Port Saint Lucie

## Table of Contents

E x e c u t i v e S u m m a r y 3

Introduction 4

Existing Docum e ntation of St. Lucie Im pairm e nt 5

S e d i m e n t 7

S e a g r a s s e s 9

O y s t e r s 1 0

Nutrient enrichm e nt/algal bloom s 11

F i s h 1 3

Benthic Macroinvertebrates 15

Benthic Com m unity Im pairm e nt Verification Study 17

Methods 17

R e s u l t s 2 0

D i s c u s s i o n 2 6

C o n c l u s i o n s 2 8

R e f e r e n c e s 2 9

2

### Executive Summary

Anthropogenic im pacts to the Saint Lucie Estuary (S LE) have im paired its function as an im portant estuarine ecosystem and resource. Stream channelization, wetland drainage and conversion, construction of drainage canal system s, urbaniza tion and agriculture activity have so com p letely

m odified the watershed that it can no longer function as a healthy ecosystem . Studies docum ent the loss of oyster and seagrass populations, fish abnor m a lities, increased sedim e ntation rates, high nutrient loadings, adverse f l uctuations in norm a l estuarine salinity regim e s, and im pacts to invertebrate populations. Under the Im paired W a te rs Rule adopted by Florida as the m e thodology for placing waters of the state on the EPA required 303(d) list, portions of the SLE m a y escape classification as “im p aired” unless a case can be pr esented which identif ies an im balance of f

l ora and fauna. Once a waterbody is listed as im paired, a process of developing basin-specific water quality criteria and source-loading allocations (Total Maxim u m Daily Loads-TMDL) can begin. This docum ent is intended to assure that the SLE is in cluded in the TMDL program by presenting previous studies which have shown im pairm e nt in the SLE and by providing new research which verifies an im balance in flora and fauna.

Over the last forty years sedim e nta tion in the SLE has increased to a rate two and a half tim es that of the pre-settlem e nt era. Thick m u ck deposits ha ve accum u lated throughout the estuary and have had detrim ental im pacts on benthic com m unities. These se dim e nts are also contam inated with pesticides and m e tals at levels that m a y be toxic to indigenous organism s. Research indicates that turbidity and algal bloom s have contributed to the near elim in ation of once abundant seagrasses from the SLE. Few oyster beds now exist in the SLE, and exis ting beds show high m o rtality. Studies have suggested that salinity fluctuations and sedim e nt sm othering caused by freshwater canal discharges are to blam e for the elim ination of once abundant oyster stocks. Freshwater discharges have also been correlated to outbreaks of fish abnorm a lities in the SLE. Construction of m a jor canal system s which discharge to the SLE have increased phos phorus inputs by 100 percent, and nitrogen inputs by 200 percent. This increased nutrient loading m a y be a factor in seagrass disappearance, occurrence of abnorm a l fish, a shift from m acrophyte-dom inated prim ary production to phytoplankton-dom inated production, occurrence of hypoxia/anoxia, occurrence of harm ful algal bloom s, and other detrim ental environm ental changes.

In an ef f o rt to verif y the im pairm e nt which pr evious studies have identified, twenty-one benthic invertebrate sam p les were taken along an upstream

- downstream gradient in the SLE and its receiving body, the Indian River Lagoon (IRL). These sam p les were analyzed using m u ltivariate statistical

m e thods and an Estuarine Index of Biotic Inte grity (IBI) was calculated for each sam p le. The analyses show a distinct difference between sites in the SLE and sites in th e IRL. The IBI scores showed that the m a jority of the SLE sites could be categorized as “degraded”, while no sites in the IRL were degraded. Historical water quality data an alyzed for this study showed that nutrient (total nitrogen and total phosphorus) levels were significantly higher in the SLE than in the IRL. These SLE nutrient concentrations were m u ch higher than the m ean for Florida estuaries, and significantly higher than EPA guidelines for nutrient concentrations in rivers and stream s (it is anticipated that concentration guidelines f o r estuaries will be lower than guidelines f o r rivers and stream s). W a ter quality data also showed the upper SLE had num erous violations of the water quality criteria for copper, and will likely m eet the definition of “im p aired” once data sufficiency requirem e nts have been satisfied. Based on the weight of evidence presented within this docum ent, the SLE should be included on the Florida list of verified im paired waters (303(d) list).

3

### Introduction

River-estuarine and coastal system s are am ong the m o st productive ecosystem s on earth (Livingston 2001). Most of Florida’s com m unities are highly de pendent on their natural resources, especially those related to natural water bodies, whether fres hwater or estuarine system s. However, the

rem a ining ecosystem s in south Florida no longer e xhibit the ecological functions, species richness, and spatial extent that defined the pre-draina ge system s (USACOE 1999). Many wetlands that once acted as natural f ilters and retention areas have b een im paired by over-drainage or lost altogether by conversion. Urban and agricultural developm ent utili zed an intricate and highly efficient system of drainage canals and ditches to rapidly discharge po llutant-laden runoff into the region’s waterbodies; these discharges affect norm a l salinity regim e s in downstream estuaries.

Nearly all of the natural waterbodies in south Fl orida have been m odified through channelization and dredging. Dredge spoil banks created next to canal s and channelized stream s such as the North Fork of the St. Lucie River, are easily eroded and becom e a source of turbidity. The banks also isolate oxbows and floodplain wetlands, thereby decreasing the storage and filtering capacities of the natural system

.
Excessive hum an-induced nutrient concentrations and loading in southern Florida waterbodies have led to a variety of negative im pacts to the ecosyst em . These im pacts include im balances in aquatic vegetation and anim al com m unities, algal bloom s, fish kills, depressed levels of dissolved oxygen (DO) and other signs of degraded ecosystem function and declining ecological productivity

. The Indian River Lagoon and its tributaries (e. g., the St. Lucie Estuary) “are a resource in peril, having been severely im pacted by hum an activities for over a hundred years” [United States Arm y Corps of Engineers (USACOE) a nd the South Florida W a ter Managem e nt District (SFW MD) 2001]. To address this situation, the W a ter Resources De velopm ent Act legislation was enacted in 1996 and 2000, the Com p rehensive Everglades Restoration Pl an (CERP) Design Agreem ent was executed in 2000, and Florida legislation in 2001 recognized that re storation of water quality was an integral and essential function of CERP.

The Florida Departm e nt of Environm ental Protecti on (FDEP) has been given the task of conducting Total Maxim u m Daily Load (TMDL) analyses in co m p liance with Section 303(d) of the Clean W a ter Act. States are required to identify waterbodies th at fail to m eet state surface water quality standards and place them on the 303(d) list. After the stat e has com p leted the United States Environm ental Protection Agency (USEPA) approved TMDL analysis , waterbodies can then be rem oved from the 303(d) list when a waterbody m eets water quality sta ndards, or when it is determ ined that other pollution control program s will result in attainm e nt of water quality standards (Florida Statute 62- 302.600). The purpose of the TMDL program is to id entify the causes and solutions to water quality im pairm e nt in water bodies and to establish an upper lim it or ceiling on the specific am ount of pollutant(s) which the water body can incorporate and still m eet standards.

To insure that the TMDL listing process was c onsistent and scientif ically based, the Florida Environm ental Regulatory Com m i ssion officia lly adopted Chapter 62-303 of the Florida Adm i nistrative Code (FAC) titled “Identification of Im paired Surface W a ters” in May 2002. The following text from the Im paired W a ters Rule (IW R) introduces its scope and intent:

“This chapter establishes a m e thodology to identif y surface waters of the state that will be included on the state’s planning list of waters that will be assessed pursuant to subsections 403.067(2) and (3), Florida Statutes (F.S.). It also establishes a m e thodology to identify

4

### im paired waters that will be included on the stat e’s verif i ed list of im paired waters, f o r which the Departm e nt will calculate Total Maxim u m Daily Loads (TMDLs), pursuant to subsection 403.067(4), F.S., and which will be subm itted to the United States Environm ental Protection Agency pursuant to paragraph 303(d)(1) of the Clean W a ter Act (CW A ).”

The FDEP W a tershed Assessm ent Group has divided the St. Lucie Estuary (SLE) and the Indian River Lagoon (IRL) into waterbody segm ents for eval uation under the IW R (Table 1). Portions of the SLE have been placed on the planning list fo r nutrients (303(d) listing) and dissolved oxygen (IW R listing), while other portions are currently not included on the list even though long-term

m onitoring of nutrient concentrations has docum ented elevated concentrations (FDEP 2001).

Table 1: W a terbody segm ents (W BID' s) included in the SLE and South IRL.

Planning Unit WB I D W a terbody Segment Name IW R Impairment Coastal 3193 Low er St. Lucie Estuary None 5003A South Indian River Lagoon None North St. Lucie 3194B North Fork St. Luc ie Estuary Dissolved Oxy gen, Nutrients South St. Lucie 3210 South Fork St. Lucie Estuary None



### A waterbody can be placed on the verified im paired lis t “for other inform ation” if an im balance in flora and fauna can be docum ented. The IW R cont ains specific provisions regarding placem ent of waterbodies on the verified list for im pairm e nt under these circum stances. Specifically the IW R states in subsection 62-303.450(2):

“If the water was listed on the planning list f o r nutrient enrichm e nt based on other inform ation indicating an im balance in flora or fauna, as provided in Rule 62-303.305(1), the Departm e nt shall verif y the im balance bef o re placing the water on the verif i ed list f o r im pairm e nt due to nutrients and shall provide documentation supporting the imbalance in flora or fauna .” (italics inserted)

This report was com posed to m eet the Departm e nt’s obligation to provide docum entation supporting an im balance in f l ora or f a una in the SLE. A wei ght of evidence approach will be used to establish that im pairm e nt, as evidenced by this im balance, doe s exist in the SLE. The evidence presented in this report is divided into two parts: (1) A sum m a ry of inform ation from previous st udies and reports which docum ented or related to SLE biological im balance, water quality im pairm e nt, and/or sedim e nt contam ination, and (2) New research which docum ents SLE biologi cal im pairm e nt pursuant to the requirem e nts and guidelines of the IW R.

Existing Documentation of St. Lucie Impairment

The SLE (Figure 1) is one of the largest estuar ine system s on the east coast of Florida and once provided vital habitat for substantial populations of fish and invertebrates that have biological and

econom ic im portance. The North Fork of the St. Lucie Estuary has been designated by the State of Florida as an aquatic preserve (Figure 1), whose m a nagem e nt objectives are to m a intain and im prove existing resources such as seagrasses, m a ngroves, aquatic plants, birds, and fish (FDEP 2002b). However, the potential of the SLE to function as a productive ecosystem has been adversely affected

5

### by m a ny anthropogenic watershed and shoreline activities (Haunert and Konyha 2001).

St. Luc i e Inle t



### Figure 1. The St. Lucie Estuary with Significant Features.

The Indian River Surface W a ter Im provem e nt a nd Managem e nt (SW I M) Plan was issued in

com p liance with the Florida Surface W a ter Im provem e nt and Managem e nt Act (Florida Statutes Chapter 373.451-373.4595) in 1989 and then revised a nd updated in 1993. The SLE was identified as a priority f o r water and sedim e nt quality im provem e nt within the IRL watershed. Major environm ental concerns within the SLE have b een identif ied as adverse salinity f l uctuations,

accum u lation of sedim e nts and toxins, poor water qua lity, and loss of seagrass and shellfish resources (St. Johns River W a ter Managem e nt District and South Florida W a ter Managem e nt District 1994). The SW IM Plan W a ter and Sedim e nt Quality Program identif ied f i ve m a in objectives that m u st be achieved f o r protection and enhancem ent of water quality within the IRL and SLE:

1. Managem e nt of freshwater inputs to m i nim i ze their negative im pacts on a natural salinity regim e

. 2. Assessm ent of sedim e nt loadings and deposition rates relative to m u ck and turbidity problem s, and reduction of suspended m a tter loadings to leve ls which will assure the overall health of the watershed. 3. Reduction of excessive point and nonpoint source loadings of nutrients to a level which will prom ote a m acrophyte-based (i.e., an ecosystem based on seagrasses rather than on plankton) system while slowing the rate of eutrophication. 4. Elim ination or significant reduction in releases of toxic substances from point and nonpoint

sources. 5. Reduction of anthropogenic loadings of fecal and total coliform s bacteria to shellfish harvesting

areas.

The SW IM Plan provided a good sum m a ry of the hist ory of problem s in the SLE but progress toward realizing the goals of the plan has been slow. Bringing the SLE into the TMDL developm ent process by listing it as im paired will provide a new m a ndate f o r im provem e nt of this vital estuarine resource. The f o llowing sections discuss water quality problem s that have contributed to the collapse of the form erly healthy SLE ecosystem

. 6

### Sediment

Several m a jor basin m odifications have increased sedim e nt deposition rates in the SLE. In 1892, the St. Lucie Inlet was opened and m a intained, transfor m i ng the form er norm a lly freshwater system to estuarine. The North St. Lucie River W a ter Manage m e nt District com p leted an extensive drainage system in the watershed of the North Fork of th e St. Lucie River basin in 1924. The St. Lucie canal (or C-44 canal), that connected the estuary to La ke Okeechobee, was also com p leted in 1924. The C23 and C-24 canals were com p leted in the early 1960s ; these canals routed additional agricultural and urban runoff into the SLE. Schrad er (1984) concluded that the average rate of sedim e ntation in the SLE has increased in the last 40 years, and that th e m a jor source of sedim e nt was terrigenous m a terial transported to the estuary as suspended load. Schropp et al. (1994) also concluded that the SLE sedim e ntation rate had increased in com p arison to pre-developm ent sedim e nt deposition rates. Due to the increase in the am ount of freshwater entering the St. Lucie Estuary, m u ck has been

accum u lating at a rate 2.5 tim es faster than historic or norm a l levels (USACOE and SFW M D 2001).

Areas where m u ck has accum u lated have becom e unf avorable environm ents for the survival of

norm a l estuarine com m unities, and these sedim e nts have caused water quality problem s due to resuspension (USACOE and SFW MD 2001). The fine or ganic m a terial which covers m u ch of the St. Lucie Estuary bottom is known locally as “St. Lucie ooze”. Resuspension of these sedim e nts releases nutrients to the water colum n, reduces light pe netration, and depletes oxygen content in overlying waters (Traxler 2002). Letters to the editors of local newspapers and recollections by long tim e area residents, describe the SLE as very productive with good water clarity and a sandy bottom throughout

m

u ch of its extent in the 1930’s and 1940’s. Som e suggested that catastrophic loads of sedim e nt carried from the C-44 canal (during water releases from Lake Okeechobee) into the estuary during storm events of that era coated the estuary with thick deposits and reduced its productivity (Stuart News 1992).

Muck sedim e nts have been presum ed to originat e f r om hum an activities and have been shown to have detrim ental im pacts on benthic biological co m m unities and the overlying water colum n (Taylor Engineering 1994; Schropp 1994). High levels of orga nic m a terials and elevated concentrations of copper have been docum ented in the central portion of the north fork of the estuary (organic m a terials represented as “ignition loss”; Haunert 1988; Table 2) . Exceptionally high levels of pesticides have been docum ented in the sedim e nts of the St. Luci e Estuary, and norm a l half-lives appear to be extended, presum ably due to the highly organi c and anoxic conditions caused by the ooze (FDEP 1995-2000 unpublished data 2002b).

Monitoring studies conducted by the FDEP Southeas t District W a ter Quality Section and SFW M D have found concentrations of som e heavy m e tals and pesticides in SLE sedim e nts to be above threshold effects levels (TELs) which are used as guidelines for evaluating sedim e nt quality (Haunert 1988; Thom pson et al. 2001; Table 3) . Studies have also suggested that the SLE sedim e nt m a y exhibit toxicity to decom poser com m unities, has a high organic content and is very resistant to

m i crobial degradation (Thom pson et al. 2001).

7

### Table 2: Heavy Metals in SLE Ooze. Survey of heavy m e tals in sedim e nts of the St. Lucie Estuary (Haunert 1988). Num b ers in blue exceed the TEL (threshold effects level), and in red exceed the ERL (effects range low) as per MacDonald et al. (1996).

Site Ag As Cd Cu Hg Ni Pb Zn I gnition Loss Mean Phi 1. 3 0

. 0 4 3 6 1. 2 2 2 9 4

. 3 2 1 6 2 2 3 5 59. 8 1 6

. 0 5 2. 2 0

. 2 3 28 0. 8 7 5 1

. 0 1 7 4 6 4 3 1 2

. 8 5 6. 1 5 6. 4 0

. 2 5 23 0. 5 8 0. 2 8 1 7 3 23. 6 7 3. 1 2 8. 3 0

. 0 5 33 0. 8 15 0. 4 1 7 3 9 4 2 1

. 9 4 4. 8 4 10. 3 0

. 2 4 27 0. 3 1 3 0. 5 2 7 40 5 4 1 4

. 8 7 6. 9 3 11. 1 0. 2 0 2 0

. 0 2 0

. 1 4 1 2 28. 9 6 1. 2 7 11. 2 0

. 0 9 46 1. 0 3 7 0

. 7 2 7 5 4 2 7 2 8

. 2 1 7. 5 5 11. 3 0

. 2 3 32 0. 7 15 0. 6 2 3 43 5 9 2 2

. 1 3 7. 3 0 12. 2 0

. 0 4 32 0. 7 2 3 0. 5 19 49 2 7 2 7

. 8 5 5. 0 1 12. 3 0

. 0 4 45 0. 9 2 2 0. 4 16 55 4 3 1 4

. 5 5 4. 7 6 13. 2 0

. 2 2 13 0. 4 6 0. 4 2 2 1 2 2 0 14. 1 6 2. 8 6 14. 2 0

. 2 4 32 0. 7 2 9 0. 5 3 8 35 6 5 4 8

. 9 4 6. 0 3 15. 3 0. 2 1 3 0

. 0 1 0

. 0 4 0 2 27. 5 8 1. 2 8 18. 4 0

. 2 4 23 0. 4 1 5 0. 2 1 3 2 4 3 8 15. 4 1 4. 2 3 19. 2 0. 94 30 0. 9 2 2 0. 5 3 4 31 6 6 2 2

. 9 7 5. 8 7 21. 1 0

. 2 2 30 0. 5 28 0. 3 2 1 39 6 2 3 0

. 6 6 5. 2 4 24. 1 0

. 2 4 24 0. 9 15 0. 2 2 6 2 5 5 8 33. 6 5 5. 6 1 26. 1 0

. 2 5 12 0. 3 1 3 0. 1 30 1 7 3 4 69. 2 7 2. 8 0 31. 2 0

. 2 4 28 0. 6 1 7 0. 2 2 3 42 6 1 2 1

. 2 7 6. 1 4 32. 1 0

. 0 4 30 0. 8 2 9 0. 4 2 9 40 6 3 2 3

. 5 3 4. 5 5 35. 2 0

. 2 0 27 0. 8 2 0 0. 6 3 7 41 7 1 4 1

. 1 6 7. 0 7 36. 2 0

. 0 5 45 1. 1 3 2 7. 8 2 3 5 9 5 5 6 3

. 5 4 8. 0 7 37. 2 0

. 0 4 45 0. 9 5 9 0

. 7 2 9 5 6 1 0 0 3 3

. 3 6 7. 7 5 40. 1 0

. 0 4 31 0. 8 3 6 0

. 4 14 31 3 4 2 0

. 9 3 5. 2 9 42. 1 0

. 0 5 25 0. 7 2 7 8. 5 9 2 2 1 5 47. 3 4 3. 7 4 44. 1 0

. 0 4 43 0. 8 6 0 0

. 4 1 9 4 2 6 9 3 4

. 0 2 6. 1 4 c24. 1 0

. 0 5 6 3 1

. 3 8 8 4

. 9 3 2 45 182 19. 0 7 7

. 2 2 c24. 3 0

. 0 5 46 0. 8 1 7 2 2

. 5 2 1 42 219 28. 6 3 7

. 2 1

s 4 9 0

. 2 4 28 0. 8 8 3 1

. 3 2 5 30 183 20. 9 4 6

. 8 9

s 5 0 0

. 2 4 27 0. 4 7 7 1

. 0 5 0 4 4 1 3 9 9. 6 1 4

. 2 2

s 8 0 0

. 3 0 31 0. 5 1 8 0. 0 19 2 2 4 6 2. 5 7 1. 4 2



### T able 3: SLE sedim e nt m onitoring data from Florida DEP Southeast District. Values exceeding threshold effects level (TEL) shown in blue . Values exceeding probable effects level (PEL) shown in red

.

Si t

e St o r e t Da t e Hg As Cd Cr Cu Pb M n Ni Z n DDE TE L 0. 13 7. 24 0. 68 52. 30 18. 70 30. 20 15. 90 124

. 0 0 2

. 0 7 PE L N E S

T 280 10037 9/ 14/ 00 0. 15 5. 90 2. 10 32. 10 71. 60 26. 60 244

. 0 0 7

. 3 0 110

. 0 0 4. 7 S E

S

T 280 10229 9/ 14/ 00 0. 20 5. 40 2. 20 25. 60 46. 40 25. 60 231

. 0 0 7

. 7 0 85. 00 9. 5 N E S

T 280 10037 7/ 25/ 00 0. 19 5. 30 0. 78 38. 30 70. 40 28. 00 238

. 0 0 8

. 6 0 110

. 0 0 7. 4 S E

S

T 280 10229 7/ 25/ 00 0. 24 4. 80 0. 83 36. 40 41. 10 25. 00 222

. 0 0 9

. 7 0 82. 00 12 N E S

T 280 10037 4/ 20/ 00 0. 16 6. 80 0. 60 32. 80 93. 10 27. 00 264

. 0 0 9

. 6 0 110

. 0 0 S E

S

T 280 10229 4/ 20/ 00 0. 20 5. 10 0. 49 27. 10 44. 10 26. 00 249

. 0 0 9

. 8 0 85. 00 8. 6 N E S

T 280 10037 11/ 23/ 99 0. 24 9. 40 0. 48 40. 00 68. 30 83. 10 197

. 0 0 12. 50 94. 00 6. 4 S E

S

T 280 10229 11/ 23/ 99 0. 17 13. 00 0. 33 28. 00 103

. 0 0 246

. 0 0 9

. 4 0 130

. 0 0 1 1 N E S

T 280 10037 8/ 25/ 99 0. 18 3. 71 0. 43 27. 50 38. 40 30. 50 223

. 0 0 7

. 1 2 106

. 0 0 7. 6 S E

S

T 280 10229 8/ 25/ 99 0. 26 2. 65 0. 44 23. 30 20. 70 26. 70 196

. 0 0 6

. 0 1 76. 10 10 N E S

T 280 10037 6/ 28/ 99 3. 00 0. 35 39. 30 23. 60 28. 50 234

. 0 0 9

. 0 8 63. 00 S E

S

T 280 10229 6/ 28/ 99 0. 25 2. 10 0. 45 37. 40 15. 20 28. 20 195

. 0 0 7

. 4 3 35. 80 7. 4 N E S

T 280 10037 9/ 30/ 98 5. 00 87. 80 4. 8 S E

S

T 280 10229 9/ 30/ 98 4. 00 34. 20 4. 9

M

ean 0. 20 5. 44 0. 79 32. 32 55. 71 38. 18 228

. 2 5 8

. 6 9 90. 58 7. 86 S

t de

v 0

. 0 4 2

. 8 5 0

. 6 5 5

. 8 9 31. 56 26. 02 22. 56 1. 72 25. 30 2. 44 Mi n 0. 15 2. 10 0. 33 23. 30 15. 20 25. 00 195

. 0 0 6

. 0 1 35. 80 4. 70 Ma

x 0. 26 13. 00 2. 20 40. 00 103

. 0 0 264

. 0 0 12. 50 130

. 0 0 9

. 5 0 0. 70 41. 60 4. 21 160

. 0 0 108

. 0 0 112

. 0 0 42. 80 271

. 0 0 374

125. 00

125

. 0 0



### 8

### It is of concern that these contam inated SLE sedim e nts could be transported to and result in degradation of the Indian River Lagoon (Haunert1988). McRae et al. (1998) analyzed EMAPEstuaries Carolinian Province Base Monitoring benthic data collected at 19 stations in Florida using

m

u ltivariate statistical m e thods (BIO-ENV procedure) . The study attributed dram atically different infaunal com m unity structure at a sam p le site located at the m outh of the SLE in the IRL to elevated

m e tals and organics concentrations in the sedim e nts.
Seagrasses

Subm erged aquatic vegetation (SAV) is probabl y the m o st productive habitat within the IRL (Gissendanner 1985; Dawes et al. 1995). SAV converts s unlight energy into food for fish, sea turtles,

m a natees, invertebrates, and other species. It provides habitat and nursery areas for m a ny aquatic organism s. Seagrasses provide oxygen, act as substrate for epiphytic algae which are used by higher trophic levels, and reduce turbidity by stabilizing se dim e nts and rem oving nutrients from the water colum n that m i ght otherwise cause harm fu l algal bloom s (W ood et al. 1969; Odum 1974; Gissendanner 1985).

Reductions in water transparency caused by dredgi ng, nutrient loading, storm w ater runoff, and other anthropogenic activities upset the natural process of water colum n filtration by seagrasses, and theref ore the stability and f unction of established and developing seagrass m eadows. Reduced light penetration also restricts growth and coverage of SAV, eventually leading to the loss of beneficial f unctions. W ith that loss com e s decreased botto m and shoreline stability, decrease m acroepif a unal and infaunal abundance, and increased turbidity (Kenworthy and Haunert 1991).

Relatively large and dense seagrass beds within the SLE were docum ented in the 1940s and 1950s, but have been sporadic since (URS Greiner W oodward-Clyde 1999). Current SAV resources in the SLE are restricted to narrow bands along the lower estuary downstream of the Sewells Point Bridge (Highway A1A, Stuart; Figure 2). Only the low-salinity tolerant seagrasses Najas and Ruppia were found in the upper estuary. A SAV survey conduc ted in the SLE by URS Greiner W oodward-Clyde (1999) revealed very little subm erged aquatic vege tation. The SAV found during the survey was so sparse that only point locations (not beds) coul d be m a pped. Low densities of SAV cover, m a inly shoal grass ( Halodule wrightii ), were found in the lower estuary. No SAV was docum ented in the

m i ddle estuary or the North Fork, and only sm a ll patches were found in the South Fork. The endangered Johnson’s seagrass ( Halophila johnsonii ) was found near the m outh of the lower estuary.

Figure 2: Range of subm erged aquatic vegetation in the SLE as of 1997. Taken from URS survey.

9

### High turbidities due to sedim e nt resuspension and f r eshwater inf l ow lim it light penetration and reduce the potential for sea grass colonization in the SLE (Schropp et al. 1994). Modeling indicates that som e species of SAV should be well establis hed in the shallow zones with sandy or m u cky sand substrates throughout m o st of the estuary (URS Greiner W oodward-Clyde 1999). However, the easily re-suspended sedim e nts of the St. Lucie Estu ary have covered habitats and caused turbidity, lim iting or preventing growth (USACOE and SFW MD 2001). Contrary to the State of Florida’s SW IM Plan goals for the SLE, the estuary has becom e a plankton-dom inated system with lim ited seagrass and m acroalgae (Cham b erlain and Ha yward 1996; USACOE and SFW MD 2001). Plankton dom inated com m unities are subject to decreased pho tic zones, algal bloom s, decreased dissolved oxygen, wide swings in dissolved oxygen concentra tions, and a shift in ecosystem structure and function. Studies in a Texas estuary have shown l ong-term declines in seagrass cover due to algae bloom s (Onuf 1996).

Oysters

Oysters are a valuable com m e rcial fishery in Flor ida (Com p and Seam an 1988). Their high filtration capacity facilitates rem oval of particulates a nd plankton from overlying waters (W oodward-Clyde 1998). Filtering activities of large m a sses of oyste rs can change the assem b lage of plankton

com m unities, reduce bacterioplankton and sea nettle s, and reduce turbidity of an entire estuary, benefiting seagrass due to enhanced light pene tration (Chesapeake Bay Program 1991). Larval, juvenile, and adult oysters are an im portant food source for m a ny estuarine predators (Stanley and Sellers 1986; W oodward-Clyde 1994; 1998).

Perhaps the m o st im portant role the oyster plays in es tuaries is as a builder of habitats. Oysters are known as a “keystone” species in W e stern Atla ntic ecosystem s (Stanley and Sellers 1986). According to W oodward-Clyde (1998), the “Am e rican oyster tends to provide the greatest volum e of hard substrate found in tem p erate and tropical estu aries of the western Atlantic. Under natural conditions, oyster reefs can be very large, and provi de extensive attachm e nt area for oyster spat and

num erous associated species such as m u ssels, t unicates, bryozoans, and barnacles." Num e rous species of m o lluscs, crustaceans, annelid worm s, and other organism s hide in and am ongst the elaborate hard structure of the typical natural oys ter reef (Stanley and Sellers 1986; W oodward-Clyde 1994; 1998).

In 1959, oyster populations were described as a bundant in the system (URS Greiner W oodwardClyde 1999). The SLE no longer supports perm anen t or extensive populations of oysters and seagrasses (Cham b erlain and Hayward 1996). Toge ther with docum ented declines in seagrass abundance over the last 30 years, oyster populations ha ve becom e virtually nonexistent (Janicki et al. 1996). In 1997, 27 oyster beds were m a pped, but less th an five percent of the oysters in 24 of the beds were alive (Figure 3). Percent cover of live oysters in the rem a ining three beds ranged from 5 - 40% (Becky Robbins, SFW MD, personal com m unication 2002).

Extended periods of salinity below 12 parts per thous and (ppt) can be fatal to oysters, or inhibit feeding, growth, and reproduction (Chesapeake Bay Program 1991; Stanley and Sellers 1986). Increased freshwater inputs from agricultural and ur ban drainage canal system s have probably been a

m a jor f actor in the decline of the oyster in the S LE. Storm events and freshwater releases from drainage canals can lower the salinity of the S LE to less than 5 ppt in 24 hours (Haunert and Startzm a n 1985). Releases from the C-44 canal can occur over an extended period of weeks to

m onths (Haunert and Startzm a n 1980; FDEP Sout heast District W a ter Quality Section personal observations). Even though oysters have devel oped efficient m echanism s for tolerating heavy

10

### sedim e nt loads and low salinities often found in estu aries, oysters can be overwhelm ed and buried by heavy sedim e ntation, dying from suffocation (Chesa peake Bay program 1991). Substrates with a high proportion of sand can cause oyster m o rtality due to abrasion and valve injury. Shifting sandy substrate also destroys young spat. The sedim e nt lo ad released into the SLE from the m a jor canal system s is largely sand.

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### Figure 3: Range of the eastern oyster, Crassostrea virginica, in the SLE as of 1997. Taken from URS survey (URS Greiner W oodward-Clyde 1999).
Nutrient enrichment/algal blooms

The addition of large nutrient loads (nitrogen and phos phorus) to estuarine waters fosters progressive organic enrichm e nt and eutrophication, prim arily due to accelerated phytoplankton production and biom ass accum u lation, followed by changes in the estuarine food web and periodic hypoxia and anoxia (Livingston 2001). Depletion of DO in bo ttom waters is typically caused by bacterial decom position of accum u lated phytoplankton and a quatic vegetation. Accelerated phytoplankton growth increases turbidity and light attenuation while decreasing production of subm erged aquatic vegetation. Increased nutrient loading has also b een associated with outbreaks of harm ful algal bloom s (HAB), suspected of killing f i sh, m a rine m a m m a ls and in som e instances possibly af f e cting hum an health (Burkholder and Glasgow 1997; Moe et al. 2001; Landsberg and Steidinger 1998).

Construction of the C-23, C-24, C-44, and other canal s has resulted in a 100% increase in phosphorus load and a 200% increase in nitrogen load (USA COE and SFW MD 2001). Nutrient enrichm e nt in the SLE has resulted in a shift from a seagra ss-dom inated to a phytoplankton-dom inated system (Cham b erlain and Hayward 1996). Increased nutrient loads have caused higher prim ary production, resulting in unhealthy DO levels in the estuary (Janic ki et al. 1996). Estim ates of nutrients and solids loading to the estuary based upon flow data and average concentrations (1980–1990) from the C-23, C-24, and C-44 canals indicated that m o re than 3600 m e tric tons of suspended solids, 910 m e tric tons of nitrogen and 91 m e tric tons of phosphorus ente r the estuary annually (Graves and Strom 1992). Because estim ates did not reflect peak flow pulses, when loadings were m u ch higher due to higher concentrations, actual transport to the estuary is believed m u ch higher. For exam ple, Haunert and Startzm a n (1980) calculated that 3.86-5.66 tons/day of suspended solids were delivered to the SLE during discharge events that they m onitored.

11 Populations of phytoplankton are often assessed by m easuring the am ount of chlorophyll a (chla) in water sam p les. The occurrence of large epis odic phytoplankton bloom s, often exceeding 50 m g /m 3

### chla, anoxic and hypoxic events, and nutrient concen trations well above the average for Florida estuaries, suggests that nutrient loading to the SLE is excessive (Doering 1996). However, Doering (1996) exam ined four years of water quality, freshwat er discharge, and tidal influence data from the SLE, and found that only 20-30 percent of the variability in chla could be explained by m u ltiple regression against secchi depth, NH4, DIP, N02+3, flow rate and salinity. This relative inability to correlate chlorophyll to any large degree with nutri ent concentration indicates that other factors (turbidity, light availability, grazing, stratificati on, flow dynam i cs, etc.) m a y dom inate the processes governing phytoplankton biom ass dynam i cs. Cham be rlain and Hayward (1996) reported a m e dian chla value of 9.2 m g /m 3 

### , which placed it at just over the 50 th 

### percentile f o r Florida estuaries (Friedem ann and Hand 1989). Highest chla values were associated with low to interm ediate flows, lower nutrient concentrations, and low color values . This inverse relationship between chla and discharge suggest that chla (as a surrogate for phytoplankton production) is m o re responsive to light lim itation (due to turbidity, sedim e nt resuspension, co lor, or other factors) than elevated nutrient concentrations associated with increased freshwat er inflows. This idea was supported by the chla

m odel proposed by Cham berlain and Hayward (1996), and the existence of a sim ilar condition in Charlotte harbor (Montgom ery et al. 1991; McPherson et al. 1990).

The chla production rate in the SLE was found to be less than the residence tim e of the estuarine water m a ss, indicating that the chla response to nut rient concentration m a y be m e diated by a wash out effect during higher flows (Cham b erlain and Haywar d 1996). This suggests that utilizing chla as an indicator f o r assessing nutrient status in the SLE m a y be inappropriate, and that the com p lexities involved result in a tendency to under-estim ate the actual estuarine nutrient enrichm e nt condition.

Scientif ic studies now link increased nutrient loadi ngs to estuarine bloom s of harm ful algae such as Pfiesteria and Karenia (e.g., Burkholder and Glasgow 1997). Bloom s of harm ful algae have in turn been linked to f i sh lesions, f i sh kills, m a rine m a m m a l deaths, and health concerns in hum ans (Burkholder and Glasgow 1997; Moe et al. 2001; La ndsberg and Steidinger 1998). Initial surveys conducted by Florida Marine Research Institute (FMRI) showed Pfiesteria and other harm ful algae were present within both the IRL and SLE at low densities (Landsberg 2001). Thus, nutrient enrichm e nt m a y increase the likelihood of bloom s of harm ful algae within the SLE and IRL.

A potential ram i fication of a high water volum e turnove r rate from the SLE is the im pact discharges of nutrient-laden storm w ater from the SLE have on nearshore reef ecosystem s. Recent studies have shown that nutrients from storm w ater m a y cause ecologically disruptive m acroalgal bloom s on coral reefs (Lapointe and Barile 2001).

Fish

There is a clear relationship between structural com p lexity of seagrass beds (particularly blade density) and fish abundance (e.g., Stoner 1983). Oy ster beds also provide habitat and support increased fish abundance in a sim ilar way (W oodwar d-Clyde 1998). The near elim ination of oyster beds and seagrasses from the SLE has had an e ffect on the abundance of fish and other aquatic organism s. An evaluation of the SLE by Haunert and Startzm a n (1985) revealed that the fish

com m unity exhibited low diversity and was dom inat ed by lower trophic level fish, especially bay anchovies. In contrast, the IRL supported diverse popul ations of estuarine benthic organism s and fish (Haunert and Startzm a n 1985).

In a com p arison between SLE and the Loxahatchee River Estuary, Browder (2002) reported that the highest overall prevalence of abnorm a l fish was in the SLE, based on the collection and exam ination of 3,906 fish of varying species. The report also suggested that the prevalence of fish abnorm a lities

12

### is higher in the upper and m i ddle SLE than in the Inlet area or the Jupiter Inlet area. The m o st

com m on type of abnorm a lity identified in the SLE wa s lesions, including fin erosion, spots or patches of inflam ed or blood-congested skin, and ulcers (Figure 4). Evaluations conducted in 1998 by the Florida Fish & W ildlife Conservation Com m i ssion (FFW CC) found that, alt hough both the St. Lucie and Caloosahatchee Estuaries experienced high leve ls of freshwater influx, the num ber of lesioned f i sh reported in the SLE was substantially higher than the num ber of lesioned fish reported in the Caloosahatchee. Increased public awareness of the condition on the east coast likely prom pted increased reporting of abnorm a l fish from the sout hwest Florida coast near Ft. Myers, but still only eleven reports of lesioned fish from that regi on were ever received ( FFW CC 2001) versus num erous and at tim es alm o st constant reports of lesioned fish in the SLE.

Figure 4: Striped m u llet, Mugil cephalus , from the SLE, exhibiting lesions.

An FFW CC Fisheries Independent Monitoring (FIM) m onitoring program was developed in the late 1980’s to provide projections of juvenile and adult m a rine and estuarine fish populations in selected estuaries in Florida (Apalachicola Bay, Cedar Ke y, Tam p a Bay, Florida Keys, Tequesta, the Indian River Lagoon, and the St. Johns River near Jacksonv ille). The St. Lucie Estuary was added to the FIM sam p ling program in April 1998. The FIM pr ogram (using non-selective gear and random ly selected sam p ling points within an estuary) now pr ovides a statistically valid, synoptic view of fish health in those estuaries.

Between April 1998 and Decem ber 2001, 941,459 m a rine and estuarine fish greater than 75m m in length were exam ined statewide for abnorm a lities by FIM staff using crite ria developed by FFW CC researchers (including categories such as bloody lesions , fin rot, skin erosion, ulcer, tum o r, skeletal deform ities, parasites, and other). Abnorm a lities were found in 1016 fish or 0.11% of those

exam ined (FFW W C unpublished data). Of the 74,080 fish exam ined at the Tequesta/SLE station 377 or 0.51% were abnorm a l. Selected abnorm a l specim e ns were transported within 24 hours to the fish health lab in St. Petersburg for confirm a tion a nd additional evaluations. In 1998 the num ber of lesioned fish collected from the other estuaries was dram atically lower than the num ber collected from the SLE. That year 75 percent of the abnorm a l fish collected statewide cam e from the Tequesta/SLE station (Table 4). The highest inci dence of lesions in the SLE was found in striped

m

u llet, Mugil cephalus.

Table 4: Results of an FFW CC/FMRI/FIM study of fish with abnorm a lities. The num ber of fish with abnorm a lities is shown along with total num ber of fish inspected (in parentheses). Monitoring Year Statew ide Tequesta/St. Lucie Estuary 1998 (April- Decem ber only) 396 (0.23%, n=170,690) 295 (0.95%, n=30,874)

13

### 1999 132 (0.05%, n=270,632) 42 (0.66%, n=6,368) 2000 295 (0.11%, n=261,285) 31 (0.16%, n=19,534) 2001 193 (0.08 %, n=238,852) 9 (0.05 %, n=17,304)

Fish with lesions have been reported from num er ous locations around the globe, in particular Asia, and in the last decade from the m i d-Atlantic s eaboard. A low-salinity tolerant pathogenic fungus, Aphanomyces invadans, has been associated with these lesi ons and with ulcerative m y cosis (UM). The Florida lesions are very sim ilar in appearance to fish with UM elsewhere and are typically found in low salinity environm ents. The m a jority of the skin lesions in Florida fish are bloody ulcers with raised irregular m a rgins and deeply penetrati ng fungal hyphae in the surrounding m u scle tissue. Recently, FW C researchers in collaboration with the University of North Carolina, identified Aphanomyces invadans from fish lesions in Florida us ing DNA technology. Increased observation and collection of f

i sh with lesions in the SLE is cl osely correlated to large freshwater influxes and the subsequent lowering of salinity in the m i ddle and upper estuary.

Harm ful algal bloom s have been linked to the occu rrence of abnorm a lities in fish. Because excessive nutrient loadings have been associated with incr easing the probability of harm f u l algal bloom s, there is evidence that nutrient inputs m a y be a factor influencing the incidence of fish abnorm a lities (Burkholder and Glasgow 1997).

There is som e evidence that sublethal exposure of fishes to copper m a y im pair reproductive success and suppress growth and feeding (Eisler 1997) whic h m a y in turn cause fish to becom e m o re susceptible to bacterial and funga l infections. Of the twelve estuarine water colum n sam p les collected from the SLE during 1999-2000, eight (67 %) exceeded the m a xim u m criteria for copper in Class III m a rine waters (62.302 FAC), which m a y lis t the estuary as verified im paired per 62.303 FAC for copper. The developing fish em bryo or la rva is generally considered the m o st sensitive stage in the lif e history, being particularly sensitiv e to all kinds of low-level environm ental changes (W esternhagen 1988). Kingsford and Gray (1996) argued that it should not be assum e d that pollutants sim p ly disperse from a point source, but have been shown to concentrate along fronts, such as haloclines or therm o clines. Fish larvae do not drift about, but accum u late along these fronts where zooplankton concentration is often an order of m a gnitude greater than in the surrounding water. Thus, fish larvae feeding on plankton can be exposed to pollutants for longer periods than expected from sim p le diffusion and transport m odels. Many pollutants, especially m e tals and pesticides, cause

m o rtality and chronic def o rm ity in larvae, and can cause m a jor deleterious ef f ects with less than 24 hours of exposure (Kingsford and Gray 1996). This has im portant im plications because it suggests larvae m a y develop deform ities with lim ited exposure to pollutants. Although larvae m a y not be killed im m e diately in plum es, they m a y suffer irreversible dam a ge (Kingsford and Gray 1996).

Scale disorientation (SD) which could not be expl ained by physical injury has been correlated with areas of increased sedim e nt contam ination. Areas of SD can appear spontaneously in norm a l juvenile and adult fish, and does not require prior scale loss (Corrales et al. 2000) . Significant difference between regions having different levels of sedim e nt contam ination suggest environm ental factors

m a y be im portant in developm ent of SD (Corrales et al. 2000). Sedim e nt contam inants have also been im plicated in severe viral outbreaks in m a ri ne m a m m a ls and liver lesions in bottom fish (W ilson et al. 2000; Stehr et al. 1998; Chang et al. 1998). Scale disorientation is com m on am ong St. Lucie Estuary fish (Browder 2001; 2002).

14

### Benthic Macroinvertebrates

Salinity and bottom substrate are im portant envir onm ental factors that affect fish and benthic

com m unities (Haunert and Startzm a n 1985). W h en wate r colum n stratification is strong and vertical

m i xing reduced, bottom water hypoxia m a y persist for m onths. As a result, opportunistic species

com m only dom inate benthic com m unities in im pacted waters (Kennish 1999).

In addition to im pacts from watershed m odificati ons, the shoreline and benthic com m unity has been negatively im pacted by hum an activities. Shorelines and inter-tidal areas of the estuary that were once populated by m a ngroves and other detritus exporting vegetation now support very little vegetation. In m a ny areas, seawalls and docks have replaced m a ngroves and seagrass (USACOE and SFW MD 2001). Unconsolidated sedim e nts have accum u lated in the estuary and are frequently resuspended by wave energy (Haunert 1988). This pr ocess has degraded habitat for bottom dwelling organism s, shaded out benthic vegetation, and ha s added to water quality problem s (Haunert and Konyha 2001).

Physical and chem ical characteristics of estuarine bottom sedim e nts affect the types of plants and anim als that can live there. S ubstrate instability selects f o r the relatively f e w species that can colonize the fine sedim e nts that dom inate the bottom of the SLE (Schropp et al. 1994).

Nutrient enrichm e nt of estuarine waters can enhance eutrophication, accelerating phytoplankton production and biom ass accum u lation, which m a y l ead to periodic hypoxia and anoxia (Livingston 2001). Depletion of DO in bottom waters is t ypically caused by bacterial decom position of

accum u lated phytoplankton and aquatic vegetation. Accelerated phytoplankton growth increases turbidity and light attenuation. These changes m a y drastically change the benthic com m unity structure.
Rudolph (1990) reported that the m acroinvertebrate com m unity at all stations in the North Fork of the St. Lucie River was com posed of tolerant organism s indicative of a physically stressed environm ent. The report was based upon the types of organism s pres ent, low diversity, and lo w Florida biotic index values. Schropp et al. (1994) reported that stress- tolerant opportunistic species dom inated the North Fork benthos. Graves and Strom (1995) also reported that the North Fork SLR benthic

m acroinvertebrate assem b lage was highly stressed, w ith a signif i cantly lower diversity as com p ared to the m o re natural, historic South Fork of the St . Lucie River. The differe nces were attributed to periodic exposure of m acroinvertebrates to a variet y of pesticides in the North Fork, som e at concentrations suf f i cient to cause docum ented f i sh kills. Statistical analysis of benthic

m acroinvertebrate data in the North Fork showed clear violations of state water quality standards based upon narrative biological criteria (Graves and Strom 1995).

15

### Benthic Community Impairment Verification Study

Methods

Seven sites were selected in the St. Lucie Estu ary and Indian River Lagoon from established water quality m onitoring locations described in the Com p rehensive South Florida W a ter Quality Monitoring Plan (Graves and Fike 2002; Figure 5). Boundaries were drawn m i dway between sites such that the study area was divided into seven subr egions. W ithin each of these subregions, three

sam p le sites were random ly chosen that m e t the following criteria:

1. W a ter at least 3 feet deep on low tide, 2. The site was not located in a dredged channel or basin. 3. The site was at least 200 feet from shore (Figure 5).

Figure 5: Benthic Macroinvertebrate Sam p ling Locations in the St. Lucie Estuary and the Indian River Lagoon. Core stations are circled in red; related sam p ling locations are given in yellow.

During the week of February 11, 2002, a grab sam p le of benthic substrate was taken using a petite ponar dredge (surface area = 0.024 m 2 

### ) from each of the 21 designated sam p ling sites. The portion of the sedim e nt retained on a Tyler series #30 (0.6-m m aperture) sieve was transferred into a sam p le bottle and preserved with a ten-percent buf f e red f o rm alin solution containing rose-bengal dye. Tem p erature, dissolved oxygen, conductivity, and pH m easurem ents were taken at top, m i d, and bottom depths at the tim e of sam p ling with a H ydrolab® m u lti-param e ter unit. Tim e of sam p ling, secchi depth, and the nature of the bottom substrate was also recorded.

In the laboratory, sam p les were passed through a Tyle r series # 30 sieve. Coarser m a terials were retained in a 2.0 aperture sieve a nd exam ined in a white enam el pan for organism s. Finer m a terial

was exam ined under a dissecting m i croscope until all m acroinvertebrates were rem oved. The specim e ns were preserved in 80 percent ethanol c ontaining glycerin. The organism s collected were

16

### identified using standard m a rine identification refe rences to the lowest practicable taxon. Exam ples of all identified species were retained as labeled voucher specim e ns, and all organism s were saved.

Species abundance data was entered into the FDEP centralized biological database system (SBIO). Monthly water quality m onitoring data (1991-2001) for stations used in this survey was obtained from the South Florida W a ter Managem e nt Distri ct DBHYDRO water quality database. Param e ters

m onitored by SFW MD at these stations included:

1. Chlorophyll 7. Color 2. Pheophytin 8. Depth 3. Dissolved oxygen 9. Salinity 4. pH 10. TSS 5. Nutrients (all form s of N and P) 11. Turbidity 6. Tem p erature
Mean water quality values were calculated and tabulated for each param e ter at each of the seven water quality m onitoring sites. These m ean values served as input to the statistical correlation program s used in this study. The results of water quality m onitoring for m e tals within the SLE were reviewed and sum m a rized within this docum ent.
Multivariate statistical analysis were perf orm e d using Prim er sof t ware developed by Plym outh Marine Laboratory specifically for use in evaluati ng m a rine biological data (Carr 1994; Clarke and W a rwick 1994). Prim er facilitates spatial analysis of relationships between environm ental and biological data. Prim er program s used in this evaluation included:

1. CLUSTER: Perform s hierarchical agglom erative clustering of data. 2. DIVERSE: Calculates a suite of biological indices. 3. SIMPER: Analyzes which species are m o st responsible for differences between sites by

exam ining the contribution of each species to the Bray-Curtis dissim ilarity between sam p le groups (Clarke 1993). 4. NMDS: A non-m e tric m u lti-dim e nsional sca ling (NMDS) program which produces an ordination of sites allowing analysis of sim ilarities and between-site dif f e rences in biological data (Kruskal and W i sh 1978). 5. BIOENV: A nonparam e tric statistical program that selects environm ental variables which best explain com m unity patterns by m a xim i zing a rank correlation between respective sim ilarity m a trices (Clarke and Ainsworth 1993).

The Prim er program DIVERSE was used to calcu late the f o llowing m e trics f o r each of the 21

sam p les (sites):

1. Species richness 2. Num b er of individuals 3. Margalef’s index (# species-1)/(log #individuals) 4. Shannon-W eaver index of diversity. 5. Evenness
The FDEP SBIO database system was used to obtain the com position of each biological sam p le according to functional feeding groups (shredders , filter-collectors, grazers, predators, deposit feeders). Species abundance data for each sam p le was analyzed using the NMDS programand a twodim e nsional plot of sim ilarity was developed. The SIMPER program identified which species had

17

### the greatest im pact in determ ining differences between sam p les in the NMDS ordination. The BIOENV program was used to exam ine correlati ons of sim ilarities in the distribution of

m acroinvertebrate data with water quality data . This program suggests which water quality param e ters had the highest probability of af f ecting the distribution of m acroinvertebrate data.

A Benthic Index of Biotic Integrity (IBI) was cal culated f o r each of the 21 sam p le sites using

m e thods developed by Van Dolah et al. (1999) specifi cally for estuarine waters of the southeastern USA. The following m e trics were calculated from the original species abundance data to obtain an IBI score at each site:

1. Mean abundance per 0.04 square m e ters 2. Mean taxa per 0.04 square m e ters 3. 100 – the percent of two dom inant taxa 4. The percent of sensitive taxa (i. e., Am pelis cidae, Haustoriidae, Tellinidae, Lucinidae, Hesionidae, Cirratulidae, Cyathura spp.).

Scoring criteria for these four m e trics were deve loped based on the distribution of values at nondegraded and degraded reference sites (Van Dolah et al. 1999). A score of 1 is given if the value falls within the lower 10 th 

### percentile of corresponding reference values. A score of 3 is given if the m e tric value obtained falls between the 10 th 

### and 50 th 

### percentile. A score of 5 is assigned if the value is greater than the 50 th 

### percentile value. Scores are assigned sepa rately to each m e tric for each of four habitat types using the 10 th 

### and 50 th 

### percentile threshold values (Table 5). An IBI score is calculated by assigning a score for each m e tric and averaging the individual scores. An IBI score less than three suggests the presence of a degraded (e. g., a com m unity for which som e level of stress is apparent) benthic assem b lage (Van Dolah et al. 1999).

Table 5: Scoring guidelines for m e trics in the IBI calcu lation (m odified from Van Dolah et al. 1999). Oligohaline-Mesohaline All Latitudes Polyhaline-Euryhaline Southern Metric

10 th 

### 50th 10th 50th Mean abundance per 0.04 m 2 

### 53.5 9 3

. 0 1 1 2

. 5 3 0 1

. 0

Mean num ber taxa per 0.04 m 2 

### 7

. 0 8

. 5 2 6

. 5 3 5

. 0

100- percent of two dom inant taxa 9

. 6 2 2 5

. 4 5 5 2

. 8 9 6 1

. 1 9

Percent pollution

sensitive taxa* 0

. 6 1 5

. 0 4 0

. 7 1 2

. 2 2

* A m p eliscid ae, Hu asto riid ae, Tellin id ae, Lu cin i d ae, Hesio n i d ae, Cirratu lid ae, C y at hura spp.


### The Minitab Statistical Software package (Minita b 1997) was used to perform all between sam p le

com p arisons and correlations not otherwise noted. Nonparam e tric m e thods were used exclusively in this study. An ∝ = 0.05 level of significance was used in all statistical tests.

18

### Results
A total of 145 unique m acroinvertebrate taxa were id entified in the twenty-one sam p les exam ined for this study (The raw m acroinvertebrate data is av ailable from the FDEP Southeast District W a ter Quality Section). The Prim er NMDS non-m e tric m u ltidim ensional scaling program used to evaluate this biological data, based on sim ilarities, showed two obvious groupings (Figur e 6). Eight iterations were used in the program and an acceptable stre ss level (0.12) was obtained. This stress level suggests that the two-dim e nsional representation of the data corresponds to a good ordination, and that the interpretation of the results will not be m i sleading (sim ilar sam p les are shown in close proxim ity and dissim ilar sites are a greater distance apart). The IRL sam p les and lower SLE sites were grouped together, while the m i ddle and upper estuary sam p les com p rised a separate grouping. W h ile the plots dem onstrate sim ilar assem b lage characteristics within these groups, they also dem onstrate the dissim ilarity between sam p les from the IRL group and sam p les from the upper estuary group (represented by the relative distance in Figure 6 between the upper estuary and the IRL

sam p ling sites).

-2 -1 0 1 2

- 1

- 0 .5 0 0 .5 1 1 .5 I R L 17C

I R L 17B S E 02A

S E 02C S E 02B

I R L25C SEO 1 B

S E 01C

I R L25A S E 01A

I R L25B SEO 3 B

HR1 A

HR1 B S E 03A

S E 08C S E 08B

HR1 C I R L17A

S E 03C S E 08A IR L and Low er SLE Stations

U pper SLE Stations



### Figure 6: NMDS two-dim e nsional ordination of species abundance data for the SLE/IRL showing grouping of sim ilar data.

The program SIMPER was used to evaluate which sp ecies were m o st responsible for the differences between sam p les. The bivalve Mulinia lateralis and the polychaete Mediomastus californiensis were the two species m o st responsible for differences between sam p les (Table 6)

. Hydrobiidae gastropods, the polychaetes Polydora aggregata, Glycinde solitaria , and Streblospio benedicti , and the bivalve Mytilopsis leucophaeata also influenced the differences in speci es distribution between sam p les. The upper SLE sam p les contained relatively higher densities of Mulinia lateralis , Hydrobiidae, and Mytilopsis leucophaeata. The Indian River sam p les contai ned relatively higher densities of the polychaetes Mediomastus californiensis and Polydora aggregata. The polychaetes Glycinde solitaria and Streblospio benedicti appeared to be m o re abundant in bot h the lower SLE and the Indian River sites.

19

### Table 6: Species m o st responsible for separation of sites by species abundance data.

Mulinia lateralis (29%) Mediomastus californiensis (17%) Hy drobiidae (9%) Polydora aggregata (5%) Mytilopsis leucophaeata (3.4%) Glycinde solitaria (2.9%) Streblospio benedicti

(2.8%) Acteocina canaliculata (2.8%) H R 1 A 4 8 0 1 9 0 4 0 0 2 H R 1 B 2 0 0 1 1 0 3 1 0 1 H R 1 C 1 0 0 4 0 4 0 0 0 S E 0 8 A 4 0 1 0 0 0 0 0 S E 0 8 B 1 2 4 0 1 8 0 0 0 1 0 S E 0 8 C 1 2 8 0 9 3 0 9 6 0 0 0 S E 0 3 A 1 6 0 3 2 2 8 8 0 0 1 S E 0 3 B 0 0 0 0 0 0 1 4 S E 0 3 C 5 0 0 0 0 0 0 0 S E 0 2 B 0 1 0 0 0 0 0 0 S E 0 2 C 0 1 1 0 0 0 6 1 2 0 S E O 2 A 0 1 0 0 0 0 0 0 S E 0 1 A 0 8 0 0 0 1 4 1 0 S E 0 1 B 0 7 0 1 0 0 3 7 3 0 S E 0 1 C 0 4 7 0 4 6 0 0 8 3 0 I R L 2 5 A 7 3 1 0 7 6 0 5 1 0 4 I R L 2 5 B 0 3 9 1 2 1 0 2 0 5 I R L 2 5 C 0 4 3 1 4 0 4 3 3 I R L 1 7 A 0 2 0 1 0 0 0 0 I R L 1 7 B 5 3 8 0 2 8 0 1 4 3 I R L 1 7 C 0 1 7 1 1 0 0 4 0 2


### In general, the Shannon-W eaver diversity index, species richness, and abundance were lower in

sam p les from the upper and m i ddle SLE (sam pling areas SE03 and SE02) and increased in sam p les from downstream estuary sites (Table 7). Th e Mann-W h itney test (u = 45, p = 0.018) showed a significantly greater m ean Shannon-W eaver diversity index value for pooled Indian River sam p le data when com p ared to pooled da ta from upper and m i d-SLE sam p les. The Mann-W h itney test also revealed significantly greater m ean species ric hness (u = 45, p = 0.0009) and evenness values (u = 58, p = 0.05) for the Indian River sam p les com p ared to sam p les from the SLE sites. Evenness, an inverse m easure of dom inance am ong species (m ore evenness equals less dom inance), was significantly greater for the IRL sites com p ared to the SLE sites.

Table 7: Metrics for describing benthic m acroinvertebrate sam p les from the SLE. Indices calculated from data pooled by sam p ling area.

Sampling

Area Distance from Ocean Inlet (miles) Species Richness Abundance Margalef’s Index Shannon Weaver diver s ity Evenness IRL17 1.7 - 5.8 66 387 10.9 3.24 0.773 IRL25 5.8 - 9.5 74 662 11.2 3.15 0.732

SE01 1.5 – 3.8 58 2150 7.43 1.89 0.464 SE02 3.8 – 6.6 30 95 6.37 2.97 0.872

SE03 6.6 – 9.5 19 262 3.23 1.72 0.584 SE08 9.5 – 11.5 14 506 2.09 1.38 0.521 HR1 10.1 – 13.2 15 154 2.78 1.65 0.608


### Classifying species into functional feeding groups is som e tim es used to help evaluate environm ental conditions. In this study, the filter/suspensi on-feeders functional feeding group m a de up a significantly (Mann-W h itney test, p=0.0157) higher proportion of the total species abundance in

sam p les from upper SLE sites, while the predator /carnivore feeding (Mann-W h itney test, p=0.03) and
20

### subsurface-gatherer/deposit feeder (Mann-W h itney, p=0.009) groups were significantly m o re prevalent at the Indian River sites (Table 8). No additional significant differences based on feeding groups were found.

Table 8: Functional feeding groups for each site.
Florida Index species % Brow/ graz % Filt/ susp % Epi gath/ dep % Paras % Plnt piercer % Pred % Sc av % Per i Scrap % Shred

(fw) % Subgath

/dep % Unknown H R 1 A 0

. 0 0

. 6 6 5

. 5 2 4

. 1 0

. 0 0. 0 4

. 6 0

. 6 2

. 3 0

. 0 0

. 0 2

. 3 H R 1 B 0

. 0 0

. 0 6 4

. 6 2 8

. 1 0

. 0 0. 0 4

. 9 0

. 0 2

. 4 0

. 0 0

. 0 0

. 0 H R 1 C 0

. 0 0

. 0 5 7

. 7 1 7

. 3 0

. 0 0. 0 1 7

. 3 0

. 0 0

. 0 0

. 0 0

. 0 7

. 7 S E 0 8 A 0

. 0 0

. 0 6 6

. 7 1 6

. 7 0

. 0 0. 0 1 6

. 7 0

. 0 0

. 0 0

. 0 0

. 0 0

. 0 S E 0 8 B 0

. 0 0

. 0 8 0

. 8 1 2

. 7 0

. 0 0. 0 3

. 3 0

. 0 2

. 6 0

. 7 0

. 0 0

. 0 S E 0 8 C 0

. 0 0

. 6 7 0

. 2 2 7

. 5 0

. 0 0. 0 0

. 6 0

. 6 0

. 3 0

. 3 0

. 0 0

. 0 S E 0 3 A 0

. 0 0

. 0 8 3

. 9 1 4

. 5 0

. 0 0. 0 0

. 8 0

. 0 0

. 4 0

. 0 0

. 0 0

. 4 S E 0 3 B 0

. 0 3

. 6 3

. 6 7

. 1 0

. 0 0

. 0 4 2

. 9 3

. 6 2 8

. 6 3

. 6 0

. 0 7

. 1 S E 0 3 C 0

. 0 0

. 0 8 3

. 3 0

. 0 0

. 0 0. 0 0

. 0 0

. 0 1 6

. 7 0

. 0 0

. 0 0

. 0 S E O 2 A 0

. 0 0

. 0 0

. 0 0

. 0 0

. 0 0

. 0 2 0

. 0 0

. 0 0

. 0 0

. 0 8 0

. 0 0

. 0 S E 0 2 B 0

. 0 2 9

. 0 1 3

. 2 7

. 9 0

. 0 0. 0 1 5

. 8 2 9

. 0 0

. 0 0

. 0 5

. 3 0

. 0 S E 0 2 C 0

. 0 1

. 4 2 4

. 7 1 0

. 6 0

. 0 0. 0 2 6

. 8 5

. 6 0

. 0 0

. 0 2 8

. 2 2

. 8 S E 0 1 A 0

. 0 0

. 7 3

. 7 1

. 0 0

. 0 0

. 0 1 0

. 7 0

. 7 0

. 0 0

. 0 8 3

. 3 0

. 0 S E 0 1 B 0

. 0 2 7

. 1 2 0

. 8 1 3

. 9 0

. 0 0. 0 4

. 3 2 8

. 1 1

. 0 0

. 0 2

. 6 2

. 3 S E 0 1 C 0

. 0 7

. 5 8

. 3 4

. 0 0

. 0 0

. 0 2

. 4 8

. 2 0

. 3 0

. 0 3

. 1 6 6

. 3 I R L 2 5 A 0

. 0 0

. 6 2 0

. 8 1 7

. 4 0

. 0 0. 0 2 7

. 2 1

. 2 3

. 1 0

. 0 2 7

. 7 2

. 1 I R L 2 5 B 0

. 0 0

. 5 1 7

. 7 7

. 6 0

. 0 0. 0 3 1

. 1 0

. 5 2

. 9 0

. 0 3 5

. 8 3

. 9 I R L 2 5 C 0

. 0 0

. 8 1 1

. 8 1 1

. 5 0

. 0 0. 0 1 4

. 2 1

. 2 3

. 4 0

. 0 5 1

. 7 5

. 5 I R L 1 7 A 0

. 0 2

. 8 3 0

. 6 2

. 8 0

. 0 0. 0 2 7

. 8 2

. 8 0

. 0 0

. 0 1 1

. 1 2 2

. 2 I R L 1 7 B 1

. 0 0

. 5 2 5

. 4 9

. 7 0

. 0 0. 0 2 6

. 6 1

. 8 4

. 3 0

. 0 2 1

. 9 1 0

. 0 I R L 1 7 C 1

. 0 0

. 0 3 1

. 6 5

. 9 0

. 0 0. 0 3 7

. 4 0

. 4 1

. 5 0

. 0 1 7

. 7 5

. 6



### 21

### The Benthic Index of Biotic Integrity (IBI; Van Dolah et al. 1999) calculated from this

m acroinvertebrate data showed a higher incidence of degraded sites located in the upper and m i ddle SLE (Table 9). Five of the nine (56%) SLE st ations located upstream of the Roosevelt (U. S. Highway 1) Bridge were classified as degrad ed (m ean score less than three) using the IBI

m e thodology. Three of the six SLE sites (50%) located in the m i ddle to lowe r estuary (from the SLE

m outh to the Roosevelt Bridge) were classified as degraded, and no sites (0%) in the Indian River Lagoon were classified as degraded.

Table 9: Estuarine Benthic Index of Biotic Integrity (IBI) scores for sites sam p led in this study.

Site Classification M ean A bund

* Score M ean Taxa* Score 100 – % 2 D o m Scor
e % Sen s itiv e** Score Total Sco r e*** M ean Scor

e HR1 A Mesohaline 145.29 5 10 5 23 3 0 1 14 3.5 H R 1 B M e s o h a l i n e 6 8

. 4 7 3 8 3 2 4

. 3 3 0 1 1 0 2

. 5 H R 1 C M e s o h a l i n e 4 3

. 4 2 1 9 5 4 6

. 1 5 0 1 1 2 3 SE08

A M e s o h a l i n e 1 0

. 0 2 1 3 1 1 6

. 5 3 0 1 6 1

. 5 SE08

B M e s o h a l i n e 2 5 7

. 1 8 5 6 1 7

. 8 1 0 1 8 2 SE08

C M e s o h a l i n e 5 7 7

. 8 2 5 1 2 5 3 5

. 3 5 0 1 1 6 4 SE03

A M e s o h a l i n e 4 0 4

. 1 4 5 1 1 5 2 5

. 6 5 0 1 1 6 4 SE03

B M e s o h a l i n e 2 3

. 3 8 1 8 3 5 0 5 0 1 1 0 2

. 5 SE03

C M e s o h a l i n e 1 0

. 0 2 1 2 1 0 1 0 1 4 1 SE02

A M e s o h a l i n e 8

. 3 5 1 4 1 4 0 5 0 1 8 2 SE02

B M e s o h a l i n e 3 1

. 7 3 1 6 1 5 7

. 9 5 0 1 8 2 SE02

C M e s o h a l i n e 1 1 8

. 5 7 5 2 2 5 6 7

. 5 5 1 1

. 2 6 5 2 0 5 SE01

A Poly haline - South 2 5 0

. 5 3 1 1 1 1 2

. 7 1 1

. 3 3 8 2 SE01

B Poly haline - S o u t h 5 0 6

. 0 1 5 2 1 1 3 3

. 7 1 4 2

. 6 5 1 2 3 SE01

C Poly haline - South 2833.9 9 5 3 6 5 2 2

. 2 1 1 2

. 4 5 1 6 4 IRL 17

A Poly haline - South 3 0

. 0 6 1 4 3 5 6 6

. 7 5 1 6

. 6 5 1 6 4 IRL 17

B Poly haline - S o u t h 3 8 9

. 1 1 5 3 2 3 71. 7 5 2

. 5 5 1 8 4

. 5 IRL 17

C Poly haline - S o u t h 2 2 7

. 1 2 3 3 4 3 66. 2 5 2

. 2 3 1 4 3

. 5 IRL 25

A Poly haline - S o u t h 5 5 2

. 7 7 5 1 2 1 6 2

. 8 5 0 1 1 2 3 IRL 25

B Poly haline - S o u t h 3 4 0

. 6 8 5 4 6 5 4 2

. 6 1 0

. 5 1 1 2 3 IRL 25

C Poly haline - S o u t h 2 1 2

. 0 9 3 3 1 3 58. 3 3 3

. 1 5 1 4 3

. 5 *Per 0.04m 2

* * S en sitiv e tax a : Am p e liscid ae, Hau s to riid ae, Tellin id ae, Lu cin i d ae, Hesio n i d ae, Cirratu lid ae, C y at hura spp

. ***Total score = m ean abundance score + m ean taxa score + (100 - % 2 dom inant species) score + % sensitive score.



### A sum m a ry of water quality data from the seven SFW MD m onitoring stations used in this study is given in Table 10. Stations HR1, SE08, SE03, and SE02 are classified as m e sohaline (salinity greater than 5 and less than 18 ppt) using m ean salinity va lues. Sites SE01, IRL17, and IRL25 are classified as polyhaline (salinity greater than 18 ppt and less than 30 ppt). Mean chlorophyll-a concentrations were higher f o r sites that were f u rther upstream in the estuary. Color was signif i cantly greater f o r the SLE sites com p ared to the IRL sites. Mean tota l suspended solids (TSS) values were higher for the IRL than for the SLE stations. Mean nutrient concen trations were higher for sites that were further upstream in the estuary. Review of water quality m onitoring data f o r m e tals in the SLE showed that the North Fork of the SLE (W BID 3194B) had 7 wa ter quality criteria violations out of 13 known

sam p les taken since 1996. The South Fork of th e SLE (W BID 3210) had 4 violations out of 15

sam p les collected since 1996.

22

### Table 10: Mean water quality values for SFW MD m onitoring stations used in this study.

SAL DEP CHLA COL DO TSS TUR NH4 NO2 NO3 TN OP TP

H R 1 9

. 5 3

. 2 1 3

. 1 6 9

. 9 6

. 6 8

. 6 4

. 3 0

. 0 6 0

. 0 1 0

. 0 8 1.2 2 0

. 1 7 0

. 2 1

SE 08 7.1 1.0 11.6 69.7 6.7 16. 5 1 1

. 0 0

. 0 6 0

. 0 1 0

. 1 1 1.2 2 0

. 1 3 0

. 1 9

SE 03 12. 4 6

. 2 1 1

. 4 6 4

. 2 6

. 1 14. 9 7

. 3 0

. 0 7 0

. 0 1 0

. 0 9 1.1 0 0

. 1 4 0

. 1 8

SE 02 16. 7 3

. 2 9

. 3 5 2

. 6 6

. 2 15. 9 6

. 1 0

. 0 6 0

. 0 1 0

. 0 7 0.9 9 0

. 1 1 0

. 1 5

SE 01 23. 7 5

. 0 8

. 0 4 1

. 1 6

. 2 19. 2 6

. 1 0

. 0 7 0

. 0 1 0

. 0 6 0.8 8 0

. 0 8 0

. 1 2

IRL17 30. 4 2

. 0 5

. 3 1 5

. 9 6

. 3 31. 1 6

. 1 0

. 0 1 0

. 0 0 0

. 0 1 0.7 4 0

. 0 3 0

. 0 6

IRL25 28. 5 1

. 2 7

. 2 1 3

. 9 7

. 2 27. 2 7

. 2 0

. 0 1 0

. 0 0 0

. 0 0 0.8 3 0

. 0 2 0

. 0 6 

### Substrate types were subjectively described during sam p ling events. Substrates in the upper and m i d SLE were m u ck while IRL sites were prim arily sandy (Table 11).

Table 11: Sedim e nt types at study sam p le sites. Sam p le Site Substrate Classification H R 1 A M u c k H R 1 B M u c k H R 1 C M u c k S E 0 8 A M u c k S E 0 8 B M u c k w / s h e l l h a s h SE08C M u ck w/ shel l h ash and det r i t u s S E 0 3 A M u c k w / s h e l l h a s h SE03B M u c k SE03C M u c k S E 0 2 A M u c k w / s h e l l h a s h SE02B M u c k SE02C M uddy S a n d S E 0 1 A C l ay / M u c k SE01B M uddy S a n d SE01C Sand w/ det r i t u s and shel l h ash IR L 1 7 A S a n d IR L17B M uddy S a n d IR L17C M uddy Sand w/ shel l h ash IR L 2 5 A M uddy S a n d IR L25B M u d IR L25C M uddy S a n d



### Results f r om the rank-correlation statistical pr ogram BIOENV indicated that the water quality param e ters with the m o st signif i cant correlations to m acroinvertebrate com m unity data distribution were color, TSS, and Total Phosphorous (TP). The differences in m ean water quality values for these param e ters correlated with differences in the pooled biological data (Figure 7).

23M D S of P oole d B i ologic a l D a t a

SE0 8 SE0 3 H R 1

SE0 2 SE0 1 IR L 1 7 IR L 2 5

M ean T SS Val u es at St u d y Sit e s

16 15 8

16 19 31 27

Mean Tot al Phophorus Va lues f o r Sam p le Sit e s

0.188 0.182 0.208

0.148 0.119 0.061 0.063

M ean Col o r V a l u es for S a m p l e S t ati ons

70 64 70

53 41 16 14



### Figure 7: Correlation of water quality data with biol ogical data showing sim ilarities in grouped stations for the three m o st highly correlated param e ters . Sites with sim ilar biological data are circled. Succeeding graphs show m ean water quality values for those sites. Sites that were sim ilar biologically were also sim ilar f o r these m ean water quality values.

24

### Discussion

In this study, nonparam e tric m u ltivariate statistical an alysis has shown that benthic m acroinvertebrate

com m unity sam p les taken from the Indian River La goon were distinctly different from the benthic

sam p les taken from the upper and m i ddle St. Lucie Estuary. Many natural and anthropogenic factors likely played a role in producing these differences between sites. Salinity regim e , substrate characteristics, flow regim e , tidal range, depth and vegetation are natural factors that m a y partially explain the differences in the com m unity structur e. W a ter quality, sedim e nt toxicity, dredging, and the alteration of f l ow and salinity regim e by hum an activities are also likely to inf l uence the differences between sites. The upper and m i ddle SLE serve as a settling basin for suspended m a tter transported downstream through the canals and stream s draining agricultural and urban areas in the watershed. Its close proxim ity to agricultural and urban pollutant sources, greater residence tim e, and lesser tidal inf l uence would seem to m a ke the SLE m o re susceptible to the inf l uences of suspended and dissolved pollutants such as nutrients than the IRL. The IRL in the area of the SLE receives no direct discharges from agricultural canals, has greater ocean flushing, and is far enough downstream of the upper SLE that m u ch the sedi m e nt-based pollutant load to the SLE has already been captured. Thus, pollutant im pacts to the IRL are likely to be not as severe as im pacts to the SLE.

Macroinvertebrate com m unities (as biological indicat ors of ecosystem health) m a y be useful as good integrators of total system stress (Kennish 1999). Multivariate analysis of the benthic

m acroinvertebrate sam p les collected in this study differentiated between sam p les collected from the SLE and those collected from IRL (Figure 6). Thes e dif f e rences are substantially attributable to im paired water quality and habitat. It has been shown that in general, species richness, abundance and the Shannon-W eaver Index of Diversity decreas e at pollution-im pacted sites (Barbour et al. 1996). Significantly lower species richness and Shannon- W eaver diversity index values were seen at the upper and m i d-SLE sites when com p ared to th e IRL. Species evenness (equitability) has been shown to decrease with increasing pollution im pact (USEPA 1990). The SLE sites had significantly lower evenness and diversity index values than the IRL sites.

The use of functional feeding groups has been discounted for use as biological indices in bioassessm ent due to highly variable responses (Bar bour et al. 1996; Rawer-Jost et al. 2000). For this reason inference regarding the relationships of f eeding groups am ong sites will not be attem p ted in this study.

Median total phosphorus values for the SLE were m o re than twice the statewide estuarine m e dian (Friedem ann and Hand 1989; FDEP 2001), while all form s of nitrogen were elevated above statewide estuarine m e dians. The IRL m e dians for nitr ogen and phosphorus were below statewide m e dians (FDEP 2001). Mean TP and TN values for the C 23, C24 and C44 canals which discharge into the SLE are m u ch greater than applicable USEPA nut rient guidelines for stream s (USEPA 2002; Table 12). These canals can be shown to be im paired for nutrients under the IW R using Chla as an indicator (FDEP 2002b). The prim ary inflows into the SLE are these nutrient-im paired waters (SFW MD 2001).

25

### Table 12: Mean nutrient and Chla concentrations in canals discharging to the SLE (FDEP unpublished data 2002b) Waterbody Chla TP TN C 2 4 4 8

. 2 9 0

. 2 7 1

. 3 5 C 2 3 5 4

. 2 9 0

. 3 6 1

. 4 6 C 4 4 2 1

. 0 0

. 3 1 1

. 3 2 USEPA Guidance 0

. 0 4 0

. 9 0 Florida IWR 20.00



### Prim er’s BIOENV program was used to objectively evaluate relationships between water quality and

m acroinvertebrate data. This m u ltivariate analysis im plicated TP concentration as a causal f a ctor linking observed differences in biologi cal data to water quality. Elevated levels of TP are associated with nutrient enrichm e nt, and the upper and m i ddle SLE sites had significantly higher concentrations of

TP than the IRL sites.

The waterbody segm ents which m a ke up the upper SLE were found to have a high proportion of copper criteria violations. The rate at which vi olations occur will m o st likely require the upper estuary to be listed as im paired due to copper c oncentrations under the IW R once the data sufficiency requirem e nts have been m e t. High concentrations of copper in the water colum n and sedim e nts m a y have an affect on the benthic and aquatic com m unity, and m a y be a factor reflected in low IBI scores and differences between the upper SLE and the IRL. The design of this study did not allow the correlation of copper data to biological data.

Fish and m a m m a l disease events have been correla ted with harm ful algal bloom s along the Atlantic Coast. Intense bloom s have now been associated with eutrophic conditions, and especially with high nitrogen concentrations. Though harm ful algal sp ecies are com m only present in low abundance in coastal estuaries, it has been hypothesized that nutrien t loadings m a y play a role in prom oting a shift in the phytoplankton com m unity, producing a harm ful al gal bloom . Mean concentrations of TP and TKN in the upper SLE are at or above concentrations which were correlated to fish and invertebrate effects due to HAB’s in the Neuse River (Burkholder and Glasgow 1997). The fish lesion event, which occurred in the SLE in 1998, was associated w ith large freshwater releases from drainage canals. The waters of the drainage canals discharg ing into the SLE are especially high in nutrients (Table 12). Though one-tim e sam p ling by FMRI found low concentrations of harm ful algal species in the SLE and IRL, current knowledge suggests a r eal potential for harm ful algal bloom s is present in the SLE due to high nutrient loadings.

Studies have found the presence of subm erged aquatic vegetation within the SLE has been drastically reduced over the past 50 years. Nutrient loadings prom ote algal bloom s that decrease water clarity and decrease the extent of the photic zone, lim iting light penetration, and thus the depth at which seagrasses can survive.

Substrates sam p led from the upper and m i ddle S LE sites were all m u ck-based, while the IRL substrates were prim arily sandy with som e m uddy co m ponent. The presence of thick ooze at all sites is itself an indicator of im pact. Historical accounts docum ent the SLE as naturally having a sandysedim e nt bottom (Schropp et al. 1994). Any role wh ich substrate type plays in differentiating the biological sam p les in this study also supports the idea that the differences are due to anthropogenic im pact.

26

### The Benthic Index of Biological Integrity (IBI) as presented by Van Dolah et al. (1999) was derived especially for estuarine system s of the southeastern United States. Benthic data from the St. Lucie Estuary was used in developm ent of this index. The IBI is a m u ltim etric index using the m e trics found to be m o st sensitive and consistent for identifying im pacted estuarine sites. This index was developed using a large m acroinvertebrate dataset co llected from southeastern United States estuarine stations, and the developm ent of the index was base d on a m u ltivariate analysis of site water quality, sedim e nt quality, and benthic biotic assem b lages. It used known degraded and non-degraded sites (with verification and an analysis of Type I and II error rates). Thus this index m a y serve as the single best biological tool available for assessing im pa irm e nt of sites within the SLE or IRL. The IBI analyses perform e d for this study showed a m a jority of the upper and m i ddle SLE sites should be classified as degraded, while no IRL sites are cla ssified as degraded. W h en this inform ation is

com b ined with the m u ltidim ensional scaling ordina tion results and water quality data, a case can be

m a de for the inference that differences in the s hown groupings m a y likely be due to pollution im pacts and habitat degradation. The IRL sam p les were grouped separately from the upper and m i ddle-SLE

sam p les, and water quality analyses suggest that th e IRL is a less im pacted system com p ared to the SLE. This is not to im ply that the IRL is pris tine; it has been shown to have suffered som e water quality im pairm e nt (Sigua et al. 2000). Results obt ained in this study show that half of the IRL

sam p les had IBI scores only slightly above “degraded” . Any inference in this paper that the IRL is not affected by im pairm e nt is not intended. Ho wever, it can be inf e rred that the SLE shows a significantly greater level of im pact than the Indian River Lagoon.

Conclusions

This assessm ent of the benthic biological com m unity in the SLE indicates that the m acroinvertebrate

com m unity is stressed and does not represent th e assem b lage that a healthy ecosystem should support. The new data presented he rein corroborates both the set of pre-existing data and the findings of other researchers who have studied of the St . Lucie Estuary. The loss of general ecosystem function, as evidenced by drastically dim i nished di stribution of seagrass and oysters, fish com m unity im balance and lesions, sedim e nt and water colu m n contam ination by heavy m e tals (especially copper) and pesticides, excessive algal bloom s, and failure to support a healthy and well-balanced benthic m acroinvertebrate com m unity, is proof that the St. Lucie Estuary f u lly satisf i es the legal criteria of an im paired waterbody as stipulated in 62-303.450(2) FAC. Using the weight of evidence argum ent presented in this docum ent, the St. Lucie Estuary (W BIDs 3210, 3194B, 3193) should be classified as im paired due to excessive nutrient i nputs which have resulted in an im balance in flora and fauna

, 

### a violation of water quality criteria pe r 62-302 FAC. Both phosphorus and nitrogen concentrations are high relative to other estuarine system s and relative to suggested guidelines. Copper concentrations in the wate r colum n of the estuary have exceeded applicable Class III m a rine water quality standard in 67% of sam p les collected and analyzed utilizing the MIBK copper protocol.

The SLE is a com p lex estuarine ecosystem adversely im pacted by a variety of hum an related factors. As a result, the im pairm e nt of this severely degrad ed system is readily apparent from an exam ination of any of a num ber of key ecological factors. A ccordingly, the SLE should be added to the list of waterbodies that are verified as im paired so that a TMDL plan can be form ulated and other critical restoration efforts can proceed unim p eded.

27

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