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Sediment Toxicity and Community Composition of Benthos and Colonized
Periphyton in the Everglades–Florida Bay Transitional Zone
MICHAEL A. LEWIS,* LARRY R. GOODMAN, JOHN M. MACAULEY AND JAMES C. MOOREUnited States Environmental Protection Agency, National Health and Environmental Effects Research
Laboratory, Gulf Ecology Division, 1 Sabine Island Drive, Gulf Breeze, FL 32561-5299, USA
Accepted 15 April 2003
Abstract. This survey provides information on sediment toxicity and structural characteristics of themacrobenthic and periphytic algal communities at 10 locations in northeast Florida Bay. Whole sedimentswere not acutely toxic to Mysidopsis bahia (marine invertebrate) and Hyalella azteca (freshwater inver-tebrate) relative to reference sediment. Survival was between 80% and 100%. Community structure of themacrobenthos and algal-periphyton varied spatially. A total of 116 benthic species were identified at the 10locations; mean density was greater in Shell Creek (10,017 organisms/m2) and least in Canal C-103(441 organisms/m2). Tubificids and the crustacean Halmyrapseudes bahamensis (Family: Apseudidae)dominated the benthos at 4 of 10 locations. One hundred and six species of periphytic algae representing 52genera were identified on substrates colonized for 21 days. Mean algal density was greater in FloridaBay (19,440 cells/cm2) and least in Long Sound (10 cells/cm2). Diatoms and blue green algae dominatedthe algal-periphyton. Major diatom genera were Navicula, Brachysira and Nitzschia. The more abundantand widely occurring blue–green taxa were species of Oscillatoria, Polycystis and Lyngbya. Ash free dryweight and chlorophyll a were significantly greater for periphyton colonized in Canal C-111 and FloridaBay and the least in Long Sound. Spatial variation and the availability of reference areas are importantissues that need consideration in future biomonitoring efforts conducted in this region to ensure relevancyof results.
Keywords: sediment toxicity; community composition; macrobenthos; algal-periphyton; Florida Bay;Everglades
Introduction
South Florida has experienced considerable envi-ronmental change during the past 50 years due toincreased urbanization and agricultural develop-ment (Cantillo et al., 1999). Florida Bay and theEverglades have received increasing regulatory,scientific and public scrutiny due to frequent sea-grass dieoffs, algal blooms, and shifts in biodi-
versity (Boesch et al., 1997; Finkl, 1994; Stoberet al., 1996; South Florida Ecosystem RestorationTask Force, 1997; Cantillo et al., 1999; USGS,1999). The focus of previous research in theseareas has centered on determining the effects ofnutrient enrichment, habitat alteration and hy-dropattern modification on indigenous flora andfauna (for example, Doren et al., 1997; Boyeret al., 1999; Orem et al., 1999). In contrast,information describing the fate and effects ofanthropogenic contaminants on indigenous biota
*To whom correspondence should be addressed:
E-mail: [email protected]
Ecotoxicology, 13, 231–244, 2004
� 2004 Kluwer Academic Publishers. Manufactured in The Netherlands.
is less available in the scientific literature (Atkesonet al., 1998).
The pesticide hazard in South Florida is con-sidered one of the highest in the US (Kucklicket al., 1996). The high annual rainfall coupled withthe extensive channelization in the south Floridawatershed leads to extensive and rapid runoff ofchemical contaminants from urbanized and agri-cultural areas to the Everglades and Florida Bay.As a consequence, pesticides such as endosulfan,chlorothalanil, chlorpyrifos and atrazine havebeen detected in surface water and sediment(Kucklick et al., l996) and some sediments foundtoxic to juvenile clams and benthic copepods(Kucklick et al., 1996; Chandler et al., 1998;Chung et al., 1999). Despite these findings, thedata base available in the scientific literatureconcerning this issue is limited. As a result, it isunknown if anthropogenic contaminants are animportant factor in the environmental declineoccurring in this region.
Due to the limited information, a multiyearstudy was conducted to provide baseline chemicaland biological information for several locationsin the Everglades–Florida Bay transitional zone.Some results have been reported (Goodmanet al., 1999, in press; Lewis et al., 2000). Thisreport describes the results for sediment toxicityand community composition of the macroben-thos and the algal-periphyton. The extent andmagnitude of contaminated sediments and theirbiological effects in coastal areas is an issue ofnational and regional concern and consideredimportant to understand (Engel and Evans, 1990;Cantillo and O’Conno, 1992; USEPA, 1994,1996a, 1997; Cantillo et al., 1997). The periphy-ton have been used as an indicator of environ-mental quality in a variety of habitats (Weitzek,1979) including several areas in the EvergladesNational Park (Browder et al., 1994; Vymazaland Richardson, 1995; McCormick et al., 1996,1997; Phillips and Badylak, 1996; McCormickand Stevenson, 1998) but not in contiguous areasextending into Florida Bay. Therefore, the resultsof this survey add to the current environmentaldata base for important media and biota whichwill be useful to judge the effectiveness of pro-posed restoration efforts in this geographic area(South Florida Ecosystem Restoration TaskForce, 1997).
Methods and materials
Study area and chemical quality
This study was conducted during September andOctober 1997 at 10 sampling sites located in CanalC-111, Canal C-103, Florida Bay, Shell Creek,Taylor River, Trout Creek and Long Sound(Table 1, Fig. 1). Concentrations of trace metalsand organochloride pesticides were determinedonce for surface water and sediment collected at ornear most study sites, and the results have beenreported (Goodman et al., 1999). These results arecompared in this report to those for toxicity and tonumerical sediment quality guidelines proposedfor Florida near-coastal areas (McDonald et al.,1996). The biological effects-based guidelines usedin the comparison were; the threshold effects level(TEL) and the probable effects level (PEL). Con-taminant concentrations greater than the TELguidelines and less than the PEL guidelines indi-cate adverse biological effects may occur but lesslikely than those exceeding PEL guideline values.
Nutrient concentrations were determined oncefor surface water at the periphyton colonizationsites following USEPA procedures (1983). Themethod detection limits (MDL) ranged from 0.01to 0.10 mg/l for total Kjeldhal nitrogen, ammonia-nitrogen, nitrate-nitrite, ortho-phosphorus and
Table 1. Locations of the 10 sampling sites and abbreviations
used in Fig. 1
Latitude Longitude
Florida Bay (FB) 25� 05.71¢ 80� 27.24¢Taylor River (TR)a 25� 10.34¢ 80� 37.69¢Shell Creek (SC)b 25� 12.42¢ 80� 29.22¢Long Sound A (LSA) 25� 14.15¢ 80� 27.40¢Long Sound B (LSB) 25� 12.76¢ 80� 29.17¢Trout Creek (TC)c 25� 12.96¢ 80� 32.00¢Canal C-111 A (C-111A)d 25� 24.52¢ 80� 31.45¢Canal C-111 B (C-111B)e 25� 24.14¢ 80� 33.50¢Canal C-111 C (C-111C)f 25� 17.24¢ 80� 26.50¢Canal C-103 (C-103)g 25� 31.006¢ 80� 30.72¢
aAt Madeira Bay.bAt Florida Bay.cAt St. Joe Bay.dAbove S-178.eSouth of S-177.fNorth of S-197.gAbove S-196.
232 Lewis et al.
total phosphorus. Temperature (�C), dissolvedoxygen (mg/l), pH and salinity (ppt) were deter-mined also at each study site at 0.5 m incrementaldepths using portable instrumentation.
Sediments and benthos
Sediment collectionReplicate sediment samples were collected fromeach of the 10 sites using a stainless steel grabsampler (volume ¼ 2.1 l). Sediments were collectedto an approximate maximum depth of 13 cm. Themacrobenthos was analyzed separately in tworeplicates collected from each site for communitycomposition. The remaining replicate samples werecombined and homogenized prior to determinationof chemical quality and acute toxicity.
Macrobenthic community compositionThe macrobenthos were removed from the sedi-ments (surface area ¼ 0.05 m2) using a 0.5 mmsieve and preserved in 70% isopropanol. All ben-thic organisms, except juveniles, damaged indi-
viduals, or other forms lacking necessarytaxonomic characters, were identified to the lowestpossible level. Most identifications were to orderand family using a stereoscopic microscope withup to 50· magnification. Genus and species wereidentified using a compound microscope withphase contrast capable of 1000· magnification.Taxonomic keys included, but were not limited to,those of Bousfield (1973), Heard (1982), Abele andKim (1986), Kensley and Schotte (1989), Eppler(1992) and Thomas (1993). Community com-position is reported based on broad taxonomiccategories; detailed species lists (benthos and algal-periphyton) are available from the correspondingauthor.
Mean and total taxa, density (numbers/m2) andindices of species diversity (H¢), and equitability(J¢) were calculated for the benthos at each sam-pling site (Shannon and Weaver, 1949; Pielou,1975). In addition, hierarchical cluster analysiswas conducted based on group-average linking ofBray–Curtis similarities (Bray and Curtis, 1957)using commercially available software (Clarke andWarwick, 1994).
Figure 1. Location of the 10 sampling sites and study area in south Florida. See Table 1 for specific site coordinates.
Sediment Toxicity in the Everglades–Florida Bay Transitional Zone 233
Whole sediment toxicity testsAcute and chronic toxicity tests were conductedwith sediments collected from the 10 sampling sitesand either the estuarine epibenthic mysid, Amer-icamysis bahia, or the freshwater amphipod, Hy-alella azteca. The choice of test species was basedon salinity at the 10 sediment collection sites. Thesediments were stored at 4 �C for less than 2 weeksbefore use. Standard methodologies were followed(ASTM, 1993; USEPA, 1996b); experimentalconditions appear in Table 2. A reference sedimentcollected from Perdido Bay (Escambia County),Florida, was included in the toxicity determina-tions. The non-toxic condition of this sediment hasbeen validated in numerous tests conducted pre-viously with the same test species at the USEPAGulf Ecology Division Laboratory (Gulf Breeze,Florida).
Periphyton
ColonizationPeriphyton were colonized at 10 sites on acrylicsubstrates contained in a periphytometer (60 cmlength, 18 cm height, and 20 cm width). Due toeither vandalism or wet weather events, results areavailable for seven sites. The substrates (surfacearea of one substrate ¼ 0.1 m2) were submergedapproximately 2.5–5.0 cm below the water surfacefor the 21 day colonization periods. The substrateswere rinsed with deionized water after colonizationto remove settled suspended solids. They were then
stored individually in plastic bags on ice fortransport to the laboratory where they were storedat 4 �C until analysis.
Community analysisPeriphyton were scraped from substrates within1 day after arrival at the laboratory and preservedin 10 ml of deionized water containing 3% buf-fered formalin and 0.1 ml Lugol’s iodine solution.The periphyton were stored in the dark untilanalysis using an inverted microscope and meth-ods of Utermohl (1931, 1956). After each pre-served sample was mixed, a known aliquot(following serial dilution if necessary) of 1–20 mlwas transferred into a standardized plankton sed-imentation chamber with a settling area of398 mm2. After 24 h of settling, the chamber wasplaced on a Zeiss Invertoscope ‘‘D’’ microscope(magnification to 1000·), and at least 300 cellswere enumerated for each sample when possible.For colonies and filaments consisting of a largenumber of cells, one-fourth or one-half of thecolony or filament was counted. The resultantnumber was multiplied to obtain the number ofcells for the entire colony or filament. Empty algalcells or diatom frustules were not included in thecounts. Identified cells were converted to thenumber of cells per square centimeter (cm2) foreach taxon as follows:
cells=cm2 ¼ CAcVtDNtAtSVaNs
� 100mm2=cm2
Table 2. Experimental conditions for whole sediment toxicity tests conducted with Americamysis bahia and Hyalella azteca
Americamysis bahia Hyalella azteca
Parameter Acute Chronic Acute
Temperature (�C) 20 25 20
Light intensity (fc) 50–100 50–100 50–100
Photoperiod 16L:8D 16L:8D 16L:8D
Test vessel volume (l) 1.9 1.9 1.0
Volume of sediment (ml) 200 200 200
Test water volume (ml) 800 800 750
Replicates 3 8 5
Organisms/rep 10 5 20
Salinity (ppt) 20 20 <1
Feeding Daily (Artemia) Twice daily (Artemia) None
Aeration Constant bubbling Constant bubbling Constant bubbling
Duration of test (d) 4 7 4
Endpoint Mortality Mortality, growth Mortality
234 Lewis et al.
where C ¼ number of cells counted; Ac ¼ area ofchamber bottom (398 mm2); Vt ¼ total volume ofsample (ml); D ¼ dilution ratio (i.e., for dilutionof 1:100, place 100 in numerator); Nt ¼ numberof transects counted; At ¼ area of one transect at1000· magnification (5.0 mm2); S ¼ area of oneplate, accounting for two sides scraped(23,750 mm2); Va ¼ volume of aliquot (ml);Ns ¼ number of plates composited.
All organisms were identified to species whenpossible, using standard taxonomic references suchas those by Utermohl (1931, 1956), Smith (1950),Drouet (1968, 1973, 1978), and Campbell (1973).Diatom identification was facilitated by makingburn mounts of portions of the samples to oxidizethe organic matter, including that containedwithin the diatoms (APHA et al., 1995). Perma-nent slides were made of the cleaned diatoms withHyrax mounting medium. Initial diatom identifi-cations were made from these slides using a mod-ified Olympus BHS compound microscopeequipped with Normarski Differential InterferenceContrast (DIC) optics. The same taxonomicmeasures of community structure calculated forthe macrobenthos were determined for periphytic-algae.
Biomass and chlorophyll aDry and ash-free dry weight biomass were deter-mined for periphyton colonized at each site usingstandard procedures (APHA et al., 1995) and re-sults were converted to g m)2. Spectrophotometricprocedures were used for the determination ofchlorophyll a corrected for the presence of phae-ophytin (APHA et al., 1995). Chlorophyll a wasextracted in acetone in the dark for 20 h at 4 �C.The extract was clarified by centrifugation at1000 g for 15 min and stored on ice to stabilizetemperature. The extracts were transferred to 1 cmcuvettes for spectrophotometric measurement andthe 90% acetone solvent served as the referenceblank. Chlorophyll a concentrations were con-verted to mg m)2.
Statistical analysis
The non-taxonomic and taxonomic structuralcharacteristics of the macrobenthos and peri-phytic-algae were compared among sites using aone way analysis of variance (ANOVA) and
commercially available software (SAS Institute,Inc., l989). A Tukey Studentized Range test wasused following the ANOVA to determine differ-ences among means. The level of statistical sig-nificance for all analyses was a ¼ 0.05.
Results
Physicochemical measurements and nutrientconcentrations
Physicochemical characteristics were spatiallyvariable as would be expected in this geomorphi-cally and hydrologically dynamic area. Surfacewater temperature ranged from 25.3 to 30.8 �C atthe 10 sampling sites. Dissolved oxygen was be-tween 1.0 mg/l (canal sites) and 7.2 mg/l (LongSound). The pH varied from 7.2 to 8.2 and surfacesalinity was between 0 psu (canal sites) and 28.7psu (Florida Bay site). Salinity at the remainingsites was between 1.3 and 6.4 ppt.
The total nutrient concentrations ranged from0.24 mg/l (C-111 A) to 0.58 mg/l (Long Sound A)(Table 3). Concentrations of total Kjeldahl nitro-gen (TKN) were below detection (<0.10 mg/l) inFlorida Bay but ranged elsewhere from 0.19 mg/l(Canal C-111 B) to 0.55 mg/l (Long Sound A).Ammonia–nitrogen concentrations ranged from<0.03 mg/l (Canal C-111) to 0.07 mg/l (LongSound B). Nitrite–nitrate concentrations were be-low detection (<0.05 mg/l) at all locations exceptin Canal C-111 B. Ortho-phosphorus was alsodetected infrequently and only at the Florida Bayand Canal C-111 A colonization sites where con-centrations were 0.14 and 0.02 mg/l, respectively.Total phosphorus concentrations were belowdetection (<0.01 mg/l) at four of seven sites.Concentrations at the Florida Bay, Long Sound Band Canal C-111 A sites were between 0.02 and0.20 mg/l.
Macrobenthos and sediment toxicity
Macrobenthic community compositionThe relative abundance of taxa representing PhylaAnnelida, Arthropoda and Mollusca at the 10sampling sites appears in Fig. 2. Arthropodscomprised most of the taxa at the Taylor River(total abundance ¼ 80%), Shell Creek (72%),
Sediment Toxicity in the Everglades–Florida Bay Transitional Zone 235
Figure 2. Relative abundance (%) of the macrobenthos (Phyla) and algal-periphyton (divisions) at the various study sites. Values are
for combined replicate sediment samples and multiple periphytometer substrates.
Table 3. Non-taxonomic structural characteristics of the periphyton and nutrient concentrations (mg/l) determined during September
1997
Periphyton Nutrients
Biomass Total
Kjeldahl
nitrogen
Ammonia-
nitrogen
Nitrite-
nitrate
Ortho-
phos-
phorus
Total
phos-
phorus
Total
nutrientsLocation DW AFDW Chlorophyll a
Florida Bay 24.6 B (8.2) 7.6 B (0.6) 1.7 A (0.5) <0.10 0.04 <0.05 0.14 0.20 0.39
Shell Creek 26.3 B (2.4) 4.2 CD (0.4) 0.2 B (0.02) 0.26 0.06 <0.05 <0.01 <0.01 0.32
Long Sound A 3.5 E (0.4) 0.57 F (0.5) 0.03 C (0.01) 0.55 0.03 <0.05 <0.01 <0.01 0.58
Long Sound B 12.7 BC (8.0) 3.1 DE (0.5) 0.3 B (0.02) 0.23 0.07 <0.05 <0.01 0.05 0.35
Trout Creek 9.6 D (1.3) 2.0 EF (0.3) 0.12 B (0.02) 0.33 0.05 <0.05 <0.01 <0.01 0.38
C-111 A 54.6 A (2.0) 14.5 A (0.6) 2.0 A (0.11) 0.20 <0.03 <0.05 0.02 0.02 0.24
C-111 B 13.0 CD (1.1) 5.1 C (0.4) 1.3 A (0.12) 0.19 <0.03 0.35 <0.01 <0.01 0.54
MDL – – – 0.10 0.03 0.05 0.01 0.01 –
Values for periphyton represent mean (±standard deviation) expressed as g/m2 (biomass) and mg/m2 (chlorophyll a). Different letters
represent significant difference among means (P < 0.05). MDL = method detection limit.
236 Lewis et al.
Trout Creek (74%), Canal C-111 C (60%), andLong Sound A (65%) sites. Annelids predominatedin the Florida Bay (84%) and Canal C-103 (83%).Molluscs were most numerous in Long Sound B(total abundance ¼ 44%) and comprised approxi-mately a third or more of the taxa in sedimentscollected from Long Sound A (35%), and Canal C-111 sites A (33%) and B (36%).
A total of 116 macrobenthic species represent-ing 98 genera were identified. The five moreabundant taxa collected from the sampling sitesappears in Table 4. The most common species wasthe crustacean, Halmrapseudes bahamensis (Tan-aidacea), which dominated at the Trout Creek,Shell Creek, Long Sound A and Taylor River sites(relative abundance range ¼ 47–65%). Tubificidswere more abundant (range ¼ 26–49%) in the ca-nals and Florida Bay. Dipterans, such as Tanypuspunctipennis and Tanytarsus spp., were dominantat Canal C-111 sites A and C. Polychaetes weremore abundant at the Florida Bay and LongSound B sites. Bivalves such as species of Tellina,Corbicula and Mytilus were more abundant inCanal C-111 and Long Sound.
The total number of species ranged from 6(Canal C-103) to 49 (Shell Creek) (Table 5). Themaximum difference in mean density (organisms/m2) among the sampling sites was almost 23-fold;density was greatest in Shell Creek (mean ¼10,017; ±1 standard deviation ¼ 8999) and theleast in Canal C-103 (441±89). Measures ofdiversity ranged from 1.1 to 2.5 (Shannon–Wienerdiversity index) and 0.45 to 0.82 (Pielou evennessindex). The lower Shannon–Wiener diversity indexvalues (H¢) were for benthos collected from TroutCreek (index value ¼ 1.1) and Canal C-103 (1.2)which contrast the greater values for benthos col-lected from Canal C-111 sites B (2.4) and C (2.5).Evenness index values (J) were lower for benthoscollected from Trout Creek, Taylor River andShell Creek (range ¼ 0.45–0.47). The Bray Curtissimilarity coefficients (S¢) ranged from 1 to 44based on macrobenthic species abundance at the10 collection sites.
Whole sediment toxicityThe sediments were not acutely or chronicallytoxic to either A. bahia or H. azteca relative toreference sediment (Table 6). Survival (4-d) of M.bahia was between 90–100% and 80–97% for H.
azteca. Survival in the reference sediment was 97%(A. bahia) and 90% (H. azteca). Survival of A.bahia after 7 days exposure to the whole sedimentswas between 93% and 100% relative to 97% in thereference sediment. Mean weight of mysids sur-viving the 7 days exposure to whole sediments(range ¼ 0.23–0.27 mg) was similar to that forreference sediment (0.26 mg) regardless of thesampling site (P>0.05).
Periphyton
Community compositionThere were spatial differences in relative abun-dance of periphytic-algae (Fig. 2, Table 7). Ingeneral terms, species of Chrysophyta and Cya-nophyta dominated at most sites. Diatoms weremore numerous in Florida Bay (100% of taxa),Shell Creek (96%), and in Canal C-111 B (79%).Species of Brachysira were one of the five moreabundant taxa at six of the seven colonizationsites. Brachysira aponina or B. vitrea, were themost abundant taxa at the Shell Creek, TroutCreek, Long Sound B and Canal C-111 B siteswhere they comprised 25–91% of the taxa, respec-tively. Navicula scopulorioides and N. wawrikaecombined, comprised 53% of the taxa at theFlorida Bay site. Four of the five most abundantperiphytic algae in Long Sound and Canal C-111A were blue–green species. Merismopedia glaucaand M. major, comprised 32% and 47% of the al-gal taxa in Long Sound and a Lyngbya speciesrepresented 49% of the taxa identified in Canal C-111 A. Oscillatoria spp. occurred at five of sevensites where their relative abundance ranged from4% to 22%. Green algal species were relativelyuncommon and were more abundant at the twoCanal C-111 sites where their total abundance was8% and 22%. Pithora spp. comprised 15% of thetaxa at the Canal C-111 A site.
One hundred and six species of periphytic algaerepresenting 52 genera were colonized at the sevensites. Diatoms were represented by 33 genera and76 species. Fifteen species and 11 genera of greenalgae were identified relative to 12 species and 8genera of blue–green algae. The total numberof species colonized at the seven sites ranged be-tween 16 (Long Sound B) and 37 (Florida Bay)(Table 8). Mean densities (cells/cm2) ranged from10 (±1 standard deviation ¼ 7) (Long Sound A) to
Sediment Toxicity in the Everglades–Florida Bay Transitional Zone 237
Table 4. The five more abundant benthic taxa identified at the 10 sites
Location Taxa Percent relative abundance
Florida Bay Tubificidae Oligochaeta 49
Capitellidae Polychaeta 14
Leitoscoloplos spp. Polychaeta 9
Acteocina canaliculata Gastropoda 7
Branchiura sowerbyi Oligochaeta 4
Trout Creek Halmyrapseudes bahamensis Tanaidacea 65
Hydrobiidae Gastropoda 23
Haplocytheridea sp. Ostracoda 3
Polypedium scalaenum Diptera 3
Cyathura polita Isopoda 2
Shell Creek Halmyrapseudes bahamensis Tanaidacea 63
Aricidea philbinae Polychaeta 7
Grandidierella bonnieroides Amphipoda 5
Syllis sp. Polychaeta 3
Aceteocina canaliculata Gastropoda 3
Long Sound A Halmyrapseudes bahamensis Tanaidacea 47
Hydrobiidae Gastropoda 15
Tellina sp. Bivalvia 12
Haplocytheridea sp. Ostracoda 13
Anomalocardia auberiana Bivalvia 5
Long Sound B Leitoscoloplos spp. Polychaeta 21
Aceteocina canaliculata Gastropoda 20
Tellina sp. Bivalvia 15
Halmyrapseudes bahamensis Tanaidacea 14
Hargeria rapax Tanaidacea 10
Taylor River Halmyrapseudes bahamensis Tanaidacea 56
Hydrobiidae Gastropoda 14
Hargeria rapax Tanaidacea 15
Grandidierella bonnieroides Amphipoda 3
Apseudidae Tanaidacea 3
C-111 A Tanypus punctipennis Diptera 31
Tubificidae Oligochaeta 23
Caenis spp. Ephemeroptera 14
Limnodrilus hoffmeisteri Oligochaeta 13
Tanytarsus spp. Diptera 5
C-111 B Tubificidae Oligochaeta 26
Branchiura sowerbyi Oligochaeta 15
Psidium sp. Bivalvia 14
Sphaeridae Bivalvia 11
Corbicula manilensis Bivalvia 7
C-111 C Tanytarsus spp. Diptera 31
Mytilus leucophaeta Bivalvia 23
Branchiura sowerbyi Oligochaeta 14
Haplocytheridea sp. Ostracoda 13
Corbicula manilensis Bivalvia 5
C-103 Tubificidae Oligochaeta 45
Limnadrilus hoffmeisteri Oligochaeta 38
Tanypus punctipennis Diptera 7
Hydrobiidae Gastropoda 5
Pyrogophorus platyrachii Gastropoda 2
Identification was to the lowest practical level.
238 Lewis et al.
19,440 (±46,305) (Florida Bay). The Shannon-Wiener diversity index values (H¢) were greater forperiphyton colonized in Florida Bay (index va-lue =3.2) and at both Long Sound sites (2.9 and3.0). The lowest value of 0.7 was for periphytoncolonized in Shell Creek where Brachysira aponinacomprised 91% of the taxa. Evenness index values(J) ranged from 0.16 (Shell Creek) to 0.73 (LongSound B). A cluster analysis dendogram based on
transformed species abundance data appears inFig. 3 showing the similarity (S¢) among the sevencolonization sites.
Biomass and chlorophyll aMean ash-free dry weight (AFDW) ranged be-tween 0.57 and 14.5 g dry mass/m2 for periphytoncolonized at the seven sites (Table 3). PeriphyticAFDW was significantly greater in Canal C-111 A
Table 5. Taxonomic structural parameters of the macrobenthos collected during September 1997
Location Density (#/m2) Total species
Shannon–Wiener
diversity (H¢)aPielou
evenness (J)b
Florida Bay 2405 (728) 21 1.9 0.63
Taylor River 5912 (7647) 7 1.6 0.47
Shell Creek 10,017 (8999) 49 1.8 0.46
Long Sound A 6993 (59) 19 1.7 0.58
Long Sound B 1103 (876) 19 2.2 0.76
Trout Creek 2352 (475) 12 1.1 0.45
C-111 A 1218 (693) 14 2.0 0.75
C-111 B 3665 (401) 23 2.4 0.76
C-111 C 1166 (74) 20 2.5 0.82
C-103 441 (89) 6 1.2 0.69
Values for density represent mean (±1 standard deviation) for two replicate samples collected at each site.aFrom Shannon and Weaver (1949), based on two combined replicates.bFrom Pielou (1975), based on two combined replicates.
Table 6. Results of the whole sediment toxicity tests
Mysidopsis bahia
Chronic (7 d)
Palaemonetes
pugiob (12 d)Location Acute (4 d) Survival Weighta Hyalella azteca (4 d)
Reference 97 97 0.26 (0.03) 90 86 (5)
Florida Bay 100 97 0.23 (0.02) – 13 (6)
Taylor River 90 97 0.27 (0.03) – 72c
Shell Creek 97 100 0.23 (0.04) – 44 (3)
Long Sound A 94 100 0.26 (0.02) – 71 (6)
Long Sound B 97 93 0.26 (0.03) – 70 (8)
C-111 A – – – 87 89
C-111 B – – – 80 72
C-111 C – – – 97 95
C-103 – – – 80 78
Hyalella azteca used as a test species only for freshwater sites (Canals C-111 and C-103). Values for survival in percent and weight in
mg. Test duration in parentheses.aValues represent mean (±1 standard deviation).bPore water exposure, values represent mean survival (±1 standard deviation) for two samples; data adapted from Lewis and Foss
(2000).cOne sample.
Sediment Toxicity in the Everglades–Florida Bay Transitional Zone 239
Table 7. The five more abundant algal-periphyton taxa identified at seven colonization sites
Location Taxa Percent relative abundance
Florida Bay Navicula wawrikae Chrysophyta 29
Navicula scopuloroides Chrysophyta 24
Brachysira sp. Chrysophyta 16
Amphora coffeaeformis Chrysophyta 5
Nitzschia longissima Chrysophyta 4
Trout Creek Brachysira aponia Chrysophyta 51
Oscillatoria spp. Cyanophyta 22
Merismopedia glauca Cyanophyta 9
Merismopedia tenuissima Cyanophyta 9
Nitzschia sp. Chrysophyta 1
Shell Creek Brachysira aponia Chrysophyta 91
Oscillatoria spp. Cyanophyta 4
Cylindrotheca closterium Chrysophyta 1
Amphora coffeaeformis Chrysophyta 1
Mastogloia crucicula Chrysophyta 1
Long Sound A Merismopedia glauca Cyanophyta 29
Brachysira vitrea Chrysophyta 19
Merismopedia major Cyanophyta 18
Johannebaptista pelliculum Cyanophyta 9
Merismopedia tenuissima Cyanophyta 6
Long Sound B Brachysira vitrea Chrysophyta 25
Merismopedia glauca Cyanophyta 17
Merismopedia major Cyanophyta 15
Polycystis aeruginosa Cyanophyta 12
Oscillatoria spp. Cyanophyta 11
Canal 111-A Lyngbya sp. Cyanophyta 49
Pithophora sp. Chlorophyta 15
Oscillatoria spp. Cyanophyta 10
Polycystis aeruginosa Cyanophyta 8
Aphanocapsa delicatissima Cyanophyta 3
Canal 111-B Brachysira vitrea Chrysophyta 67
Achnanthes minutissima Chrysophyta 5
Oscillatoria spp. Cyanophyta 5
Chroococcus dispersus Cyanophyta 4
Oedegonium sp. Chlorophyta 3
Table 8. Taxonomic structural parameters of the algal-periphyton colonized for 21 days during September 1997
Location Density (cells/cm2) Total species
Shannon–Wiener
diversityaPielou
evennessb
Florida Bay 19,440 (46,305) 37 3.2 0.62
Shell Creek 403 (699) 20 0.7 0.16
Long Sound A 10 (7) 21 3.0 0.68
Long Sound B 406 (595) 16 2.9 0.73
Trout Creek 234 (213) 20 2.1 0.50
C-111 A 3632 (3024) 24 2.7 0.58
C-111 B 3997 (4686) 27 2.2 0.46
Values for density represent mean (±1 standard deviation) for algae colonized on multiple substrates.aFrom Shannon and Weaver (1949), for combined taxa on multiple substrates.bFrom Pielou (1975), for combined taxa on multiple substrates.
240 Lewis et al.
(mean ¼ 14.5 ± 1 standard deviation ¼ 0.6 g/m2)and Florida Bay (mean ¼ 7.6 ± 0.6 g/m2)(P < 0.05). Mean AFDW was the least in LongSound A (0.57 ± 0.5 g/m2). Ash free dry weight,as a percent of dry weight, averaged 24.9 (1 stan-dard deviation ¼ ±8.3; range ¼ 16–39%) forperiphyton colonized at the seven sites.
Chlorophyll a, like AFDW, was statisticallygreater (P < 0.05) for periphyton colonized inCanal C-111 and Florida Bay (range of meanvalues =1.3–2.0 mg/m2) (Table 3). Mean chloro-phyll concentrations for periphyton colonized inthe Shell Creek, Long Sound B and Trout Creekareas were similar (P > 0.05) and greater thanthat (0.03 ± 0.01 mg/m2) at Long Sound A.
Discussion
Reported sediment toxicity results for this studyarea are limited primarily to those of Lewis et al.(2000) and Lewis and Foss (2000). Acute toxicitybased on bacterial luminescence and survival ofmysids was uncommon in these studies; however,several pore water samples were toxic to grassshrimp embryos (Palaemonetes pugio) (seeTable 6). Toxicity has been reported also forother test species and whole sediments collectedfrom other Florida Bay areas and Biscayne Bay(Long et al., 1996; Chung et al., 1999). The dif-ferences in reported toxicity results suggest thatsediment hazard evaluations conducted in thisregion, as they have been elsewhere (Traunspur-ger and Drew, 1996), are dependent upon thechoice of the test media and species and responseparameter.
The lack of acute and chronic toxicity observedin this study parallels the finding that only onenumerical effects-based guideline proposed forFlorida coastal sediments (McDonald et al., 1996)was exceeded. Trace metal concentrations wereless than probable effect level guidelines (PEL) butcopper was greater than threshold effect value(TEL) of 18.7 lg/g dry wt. in sediments collectedfrom Canal C-103 (measured concentration ¼27.0 lg copper/g) and Canal C-111 A (59.0 lgcopper/g) (Table 9). Despite elevated copper, sur-vival of H. azteca was 80% and 87%, respectively,relative to 90% in reference sediment.
Most chlorinated pesticides were below detec-tion in the sediments (data not shown) and onlydieldrin and p,p-DDD exceeded the TEL guidelinevalues of 0.72 and 1.22 ng/g dry wt. respectively.The dieldrin concentration in Canal C-103 sedi-ment was 2.1 ng/g and concentrations of p,p-DDDin sediments collected from Canals C-111 B and C-103 were 2.5 and 3.1 ng/g, respectively. Survival ofH. azteca exposed to these sediments was 80% inboth cases, relative to 90% for reference sediment.
Community composition of the benthos andperiphytic algae differed spatially. It was not anobjective of this survey to identify the cause forthis but it is likely due, alone or in combination to,habitat differences, naturally occurring chemicaland biological factors and, although less likely, thepresence of anthropogenic contaminants. As sta-ted earlier, only one sediment quality guideline wasexceeded. Likewise, there was no obvious waterborne contaminant that was thought to influencethe results for the periphyton. Non-nutrient con-taminant concentrations during the Septembercolonizations (Goodman et al., 1999) were belowFlorida water quality criteria to protect marine life(FDEP, 1993). There are no Florida or nationalnumerical water quality criteria for nutrients.However, concentrations of most nitrogen andphosphorus containing compounds in this study(Table 3) are relatively low when compared tothose for 690 stations in Florida estuaries reportedby Friedmann and Hand (1989). Concentrationsof TKN (total Kjeldahl nitrogen), nitrite-nitrateand ortho and total phosphorus in this study wereexceeded at approximately 80% of the estuarinestations. In contrast, ortho-phosphorus and totalphosphorus at the Florida Bay site were greaterthan those at 80% of the estuarine stations. The
Figure 3. Dendogram for the seven colonization sites using
group average clustering from Bray–Curtis similarities of the
algal-periphyton.
Sediment Toxicity in the Everglades–Florida Bay Transitional Zone 241
impact of these higher concentrations was notclear. AFDW and chlorophyll a were relativelyhigh at this site but less so than in Canal C-111where ortho and total phosphorus concentrationswere less.
Published information in the scientific literaturedescribing community composition of periphytonand benthos in the study area is limited. Data areavailable for a survey conducted during July 1995at locations near those used in this study. Eighty-five species of periphytic algae and 94 species ofmacrobenthos were identified (Lewis et al., 2000)compared to the 106 and 116 species reported here,respectively, for the same biota during September1997. The Shannon–Wiener diversity index valuesfor the macrobenthos were between 0.3 and 2.1(1995) and between 1.1 and 2.0 (1997). The indexvalues for periphytic algae ranged from 1.3 to 2.6(1995) and 0.7 to 3.2 (1997).
In summary, the results of this survey and oneconducted earlier at nearby locations, indicate thatcontaminants exceeded proposed quality criteriaonly for a few sediment samples. Whether theirpresence was a contributing factor to the few casesof toxicity and the differences in benthic commu-nity composition remains to be determined. Wholesediment toxicity appears to be less of an issue thanpore water toxicity in the study area. Therefore,future sediment hazard evaluations need to include
pore water as well utilize additional test species,and chronic toxicity tests to better define the extentand magnitude of contamination in this subtropi-cal area. In addition to toxicity assessments, thecharacterization of the biota in the Everglades–Florida Bay transitional area will not be simplistic.Spatial variation is considerable and the lack ofreported reference locations hinders the determi-nation of the geographical and environmental sig-nificance of results of these types of surveys.
Acknowledgements
The field collections of biota were conducted bythe following USEPA personnel: Robert Quarles,James Patrick and George Craven. The toxicitytests were conducted by Darrin Dantin and Ro-man Stanley. Taxonomic analyses were conductedby personnel of Barry A. Vittor Associates (Mo-bile, Alabama). Val Coseo (SEEP) prepared themanuscript and Stephen Embry (OAO Corp, GulfBreeze, FL) provide graphic support.
Disclaimer
The US Environmental Protection Agency throughits Office of Research and Development funded and
Table 9. Concentrations of trace metals in sediments collected from the study sites
Trace metals
Location As Cd Cr Cu Hg Ni Pb Zn
Taylor River <1.9 <0.16 4.3 <0.44 0.054 0.9 1.1 3.1
Shell Creek <1.9 0.18 15.0 1.3 0.023 3.8 1.4 3.4
Long Sound A 2.2 <0.16 8.1 1.1 0.030 1.8 <1.1 1.9
Long Sound B <1.9 0.17 11.0 1.2 0.027 2.8 1.6 2.8
Trout Creek 2.3 <0.16 20.0 0.65 0.025 4.2 1.1 3.4
C-111 A <1.9 0.16 36.0 59.0 0.068 8.2 9.3 89.0
C-111 B 3.5 0.21 13.0 2.9 0.018 3.6 <1.1 3.4
C-111 C 4.7 0.24 9.7 2.6 0.022 2.7 3.4 21.0
C-103 2.9 0.37 25.0 27.0 0.026 6.8 9.5 66.0
MDLa 1.9 0.16 0.31 0.44 0.0017 0.3 1.1 0.6
TELb 7.2 0.68 52.3 18.7 0.13 15.9 30.2 124.0
PELc 41.6 4.21 160.0 108.0 0.70 42.8 112.0 271.0
Values in lg/g dry weight except for mercury (ng/g dry wt.). Data from Goodman et al. (in press). No data available for Florida Bay
site due to weather event. Values in bold exceed the proposed sediment quality guideline for Florida near-coastal areas.aMDL – method detection limit.bTEL – threshold effects level (MacDonald et al., 1996).cPEL – probable effects level (MacDonald et al., 1996).
242 Lewis et al.
managed the research described here. It has beensubjected to the Agency’s peer and administrativereview and has been approved for publication as anEPA document. Mention of trade names or com-mercial products does not constitute endorsementor recommendation for use.
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