Sediment contamination and biological effects in a ... - Springer Link

Ecotoxicology, 4, 39-59 (1995)

Sediment contamination and biological effects in a Chesapeake Bay marina B E T H L. M c G E E I * ~ t , C H R I S T I A N E. S C H L E K A T I § , B O W A R D 1 and T E R R Y L. W A D E 2

D A N I E L M.

1Maryland Departmentof the Environment, 2500BroeningHighway, Baltimore, MD 21224, USA 2TexasA & M University, Geochemicaland EnvironmentalResearch Group, 833 GrahamRoad, College Station, TX 77845, USA

Received 15 November 1993; revised and accepted 11 February 1994

Complementary measures of sediment toxicity, sediment chemistry and benthic community structure were evaluated at stations within and on the outside perimeter of an enclosed marina on the Bohemia River, a northeastern tributary to Chesapeake Bay. Sediment concentrations of polynuclear aromatic hydrocarbons, copper and tributyltin (TBT) were elevated at stations inside the marina basin. A 28 day partial life-cycle test with the amphipod Hyalella azteca indicated no significant lethal effects associated with test sediments. However, amphipods exposed to sediments collected from three stations inside the marina basin were significantly larger than amphipods from control sediments, possibly as the result of hormesis. Sediment pore water from two out of the three stations eliciting enhanced amphipod growth caused a reduction in light emission by luminescent bacteria in the Microtox ® assay. Furthermore, sediments from these two stations contained the greatest measured concentrations of copper and TBT. Benthic infaunal communities that typically reflect environmental degradation were found exclusively at stations within the marina basin. The area of environmental impact appears to be localized to the enclosed basin, as the marina design limits flushing and, hence, contaminant export. Keywords: sediment contamination; marina; benthos; amphipod.

Introduction Intense boating activity has increased the demand for marinas in C h e s a p e a k e Bay and its tributaries. Marinas provide ease of access to, and enhanced recreational e n j o y m e n t of, the Bay, however; they are also a potential source of pollution. Marina-related activities, such as the combustion of fuel in boat engines, stormwater run-off f r o m i m p e r m e a b l e surfaces and boat maintenance can introduce a variety of chemical contaminants to the aquatic system (US E P A 1985, N C D E M 1990). M a n y of these compounds - heavy metals, polycyclic aromatic hydrocarbons and by-products of antifouling paints - adsorb onto particulate matter and accumulate in marina sediments *To whom correspondence should be addressed. :~Present address: University of Maryland, Wye Research and Education Center, PO Box 169, Queenstown, MD 21658, USA. §Present address: Science Application International Corporation, Narragansett, RI 02882, USA. 0963-9292 © 1995 Chapman & Hall

40

McGee, Schlekat, B o w a r d and Wade

(Vourdrias and Smith 1986, Marcus et al. 1988, Unger et al. 1988, Crecelius et al. 1990). Studies have linked sediment contamination to adverse effects on benthic biota (e.g. Swartz et al. 1982, Chapman et al. 1985, 1987, Giesy et al. 1988, Hoke et al. 1990, Ingersoll and Nelson 1990); however, these investigations focused on severely impacted areas such as heavily industrialized harbours and the primary response parameter was mortality. Sediment contamination originating from marina-related activity is low to moderate relative to highly urbanized areas (Vourdrias and Smith 1986, Marcus et al. 1988, Crecelius et al. 1990) and would be expected to result in subtle, rather than gross, biological effects (Dillon, 1993). This study explored this hypothesis through an intensive survey of a single, isolated marina in the Chesapeake Bay basin, including complementary measures of sediment toxicity, sediment chemistry and benthic community structure. This comprehensive, integrated approach to environmental impact assessment has been used successfully to identify adverse biological effects associated with sediment contamination in a variety of areas (e.g. Long and Chapman 1985, Chapman et al. 1987, 1991, Schlekat et al. in press). Specifically, the objectives of the study were to (1) conduct a physicochemical characterization of sediments within and on the outside perimeter of an enclosed marina and (2) determine if adverse biological effects (i.e. sediment toxicity and alterations of benthic community structure) were manifest at this site. Materials and methods Field sampling

Selection of an appropriate marina involved criteria designed to maximize the likelihood of marina-related contamination while excluding other potential sources: (1) a single exit-entrance channel to an enclosed marina, i.e. a two-segment design (NCDEM 1990), (2) more than 200 boats in the marina, (3) no major construction activities during the last 3 years and (4) no major sources of pollution from industrial, sewage treatment or storm water outfalls inside or near the marina. Based on these criteria, a marina located on the Bohemia River, Cecil County, MD was chosen (Fig. 1). This marina contained approximately 210 slips. Sampling stations were confined to regions of fine grain sediment because other studies of sediment contamination from marina-related activities reported higher concentrations of contaminants in mud than in sandy sediments (Marcus et al. 1988, Crecelius et al. 1990). Sediments were collected with a 0.02 m 2 Petite Ponar grab sampler on 3 September 1991. At each station, the top 2 cm of five to seven grabs was placed in a pre-cleaned stainless steel bowl and stirred until homogeneous in texture and colour. Aliquots for chemical and textural analyses and for use in the sediment toxicity test were placed into separate pre-cleaned glass containers and covered with Teflon®-lined lids. Sediments for Microtox ® pore water toxicity tests were placed in 500 ml centrifuge bottles. Sediments for toxicity tests and textural analyses were kept on ice and subsequently refrigerated (4°C) until analysis. Sediments for chemical analysis were kept on ice and frozen until analysis. The grab sampler, stainless steel bowl and mixing utensils were rinsed in ambient water prior to collection at each station. Bottom water quality parameters (dissolved oxygen, temperature, pH and salinity) and depth were measured at each

Sediment contamination and effects in a marina

41

/ 1

iAtTIMOI|

Approximate location of study site VIClNITT MJUI

WASHINGTON

;,b-

-.;'h

IO

I C A L Ir Of NILIrS 0 IO

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CHESAPEAKE BAY

Figure 1. Map indicating the approximate location of the marina on the Bohemia River, Cecil County, MD. The inset shows the position of Chesapeake Bay in North America.

McGee, Schlekat, Boward and Wade

42

station with a Hydrolab Surveyor II. Five grab samples were taken at each station for benthic macro-invertebrate community analysis. The contents of each grab, retained on a 500/~m sieve, were rinsed into a plastic bucket and preserved in 95% denatured ethanol. Sediment characterization Characterization of sediments included analysis of textural properties, as well as trace metals, organic compounds and butyltins (Table 1). Analyses were conducted within 6 months of collection using the same methodology as the National Oceanic and Atmospheric Administration's Status and Trends Program (Brooks et al. 1987, Wade et al. 1988). Polynuclear aromatic hydrocarbons were analysed by freeze-drying, grinding, extraction and gas chromatography-mass spectroscopy. Trace metals were analysed

Table 1. List of measured sediment parameters Bulk parameters Grain size Total organic carbon (TOC) % dry weight Acid volatile sulphide (AVS) Major elements Aluminium (AI) Manganese (Mn) Iron (Fe) Magnesium (Mg) Trace elements Arsenic (As) Boron (B) Barium (Ba) Berylium (Be) Cadmium (Cd) Chromium (Cr) Copper (Cu) Nickel (Ni) Lead (Pb) Mercury (Hg) Strontium (Sr) Vanadium (V) Simultaneously extractable metals (SEM) Arsenic Cadmium Copper Mercury Nickel Lead Zinc

Low molecular weight aromatic hydrocarbons Naphthalene 2-Methylnaphthalene 1-Methylnaphthalene Biphenyl 2,6-Dimethylnaphthalene Acenaphthylene Acenaphthene 2,3,4 Trimethylnaphthalene Fluorene Phenanthrene Anthracene 1-Methylphenanthrene High molecular weight aromatic hydrocarbons Fluoranthene Pyrene Benz(a)anthracene Chrysene Benzo(b)fluoranthene Benzo(k)fluoranthene Benzo(e)pyrene Benzo(a)pyrene Perylene Indenopyrene Dibenzanthracene Benzo(ghi)perylene Organo-metallic compounds Tributyltin (TBT) Dibutyltin (DBT) Monobutyltin (MBT)


43

by atomic absorption spectroscopy. Acid extractable metals were analysed by atomic absorption spectroscopy following leaching of samples with 1 N HCI. For the analysis of acid-volatile sulphide (AVS), the method of Cutter and Oatts (1987) was used. Concentrations of tributyltin (TBT) and its degradation products dibutyltin (DBT) and monobutyltin (MBT) were measured as described in Wade et al. (1990). Grain size analysis followed the sieve and pipette methods of Folk (1980); the total organic carbon (TOC) was determined with a Leco Total Carbon System (Model CR12). Details of chemical quality assurance/quality control (QA/QC) procedures are available (Velinsky et al. in press, Wade et al. in press) and include blanks, standards, intercalibrations and spiked samples. Sediment toxicity tests

A 28 day partial life-cycle test with the amphipod Hyalella azteca was initiated within 1 week of sediment collection (ASTM 1991a). End-points were survival and growth, as estimated by amphipod length. Specifics of the amphipod toxicity test including QA/QC procedures and culturing methods are described elsewhere (EAD 1990, Schlekat et al. in press). In brief, 20 laboratory cultured juvenile H. azteca per replicate were exposed for 28 days to test sediments under static-renewal conditions (i.e. one-third of the overlying water was replaced twice weekly). Amphipods were obtained by selecting those retained on a 250pm sieve after passing through a 1000/~m sieve. Test chambers were quart-sized glass jars containing water and sediment in a ratio of approximately 4:1 (v/v). Amphipods were fed a mixture of TetraMin ® and Tetra ® Conditioning Food three times per week. There were four replicates per treatment. Water quality parameters (dissolved oxygen, temperature, pH and specific conductivity) were monitored daily in one replicate per treatment on a rotating basis and in all chambers on the first and last day of the test. Test water was collected from Chattolanee Spring, Baltimore County, MD. Control sediment, defined as sediment known to be non-toxic to and within the geochemical requirements of the test organism (ASTM 1991a,b, McGee et al. 1993), was collected from the Corsica River on Maryland's eastern shore. The acceptability of this sediment to H. azteca has been demonstrated previously (McGee et al. 1993, Schlekat et al. in press). Control sediment was wet pressed through a 500/~m sieve into spring water to adjust the interstitial salinity (ASTM 1991b). Test sediments were not sieved to prevent disruption of chemical equilibria between sediments and associated pollutants. The Microtox® assay was conducted on dilutions of sediment pore water. Pore water was obtained by centrifuging samples in 500 ml containers for 75 min at 3400 r.p.m. Samples were held no longer than 2 days prior to centrifugation. The supernatant was tested using the Microtox® 100% test protocol (Microbics Corporation 1992) within 3 h of centrifugation. Luminescent bacteria, Photobacterium phosphoreum, were exposed for 15 min to the following dilutions of sediment pore water: 90, 45, 22 and 11%. Light emission of the bacteria was then measured with a photometer. The reduction in luminescence is proportional to the toxicity of the sample (Microbics Corporation 1992). Phenol and distilled water were used as positive and negative controls, respectively (Microbics Corporation 1992). Benthic community analysis

Benthic samples were stained with rose bengal to facilitate sorting. Taxonomic identifications were made using standard invertebrate keys (e.g. Smith 1964, Bousfield 1973,

44


Wiederholm 1983, Merritt and Cummins 1984, Brinkhurst 1986). Organisms were identified to species if possible, except for oligochaetes which were separated according to family. Damaged or immature organisms were identified to the lowest possible taxonomic level.

Data analyses Amphipod survival and growth were evaluated by one-way analysis of variance (ANOVA) on per cent survival and mean length per replicate, respectively. Significant differences between experimental treatments and the control were determined by pairwise contrasts using Fisher's least significant difference (Dowdy and Wearden 1983) with a = 0.05. Data analyses were performed using TOXSTAT and SAS statistical software packages (SAS Institute 1987, Gulley et al. 1989). Sediment pore water concentrations resulting in a 20% reduction of bioluminescence by P. phosphoreum (EC20), in 15 min exposures, were estimated using a linear regression package produced by the Microbics Corporation (1992). The following benthic community parameters were calculated for each station: taxa richness (i.e. number of species), total abundance, Shannon evenness (a measure of the uniformity of distribution of individuals among taxa) and the per cent contribution of each major taxonomic group to the total number of organisms per station. Cluster analysis was performed on the number of individuals per taxa per grab at each station. The clustering strategy incorporated the Bray-Curtis similarity coefficient and an unweighted mean linkage scheme (Nemec and Brinkhurst 1988, Nemec 1991).

Results

Field sampling Nine stations were sampled within and surrounding the marina (Fig. 2). Stations BR1 through to BR4 were located inside the marina (hereafter referred to as inner stations), BR5 was located in the narrow exit-entrance to the marina, adjacent to two fuel pumps and BR6 through to BR9 were located on the outside perimeter of the marina (hereafter referred to as outer stations), in the Bohemia River. The measured ambient water quality parameters and depth at the stations ranged as follows: depth 0.8-2.3 m, salinity 1.9-2.1 p.p.t., temperature 23.7-24.8°C, pH 7.3-8.3 and dissolved oxygen 5.9-6.4 p.p.m, at stations BR1-BR5 and 7.5-9.2 p.p.m, at stations BR6-BR9. Sediment characterization Sediment textural characteristics and concentrations of select chemical constituents at each station are summarized (Table 2). A complete list of all analyses can be found elsewhere (EAD 1993). The QA/QC for all analyses was acceptable, as measured by spike recovery and duplicate sample analysis. Grain size analysis classified all test sediments as either silts or a mixture of sand-silt-clay. The total organic carbon ranged from 1.24 to 2.68% dry weight. Sediment chemical concentrations were generally higher within the confines of the marina. Concentrations of copper and TBT exhibited the greatest magnitude of difference between the inner and outer stations (Table 2). Spatial distribution of both chemicals reflected a concentration gradient, with the greatest concentrations at stations


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-

0

-

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i

© BR4

-

DRIVEWAY/PARKING LOT

Figure 2. Location of marina sampling stations.

LIFT I

I-

REPAIR

FACILITY

42.8 42.9 53.9 40.8

50.9

46.2 65.9 48.4 53.6 45.8

BR5

BR6 BR7 BR8 BR9 Control

Dry weight (%)

BR1 BR2 BR3 BR4

Station

1.66 1.24 2.68 2.53 2.36

1.44

2.04 1.94 1.48 2.06

TOC (%)

25.38 28.21 19.38 12.55 5.17

36.84

11.33 16.60 42.01 7.09

Sand (%)

Conventional parameters

41.95 45.62 61.11 52.07 71.04

42.24

61.29 59.73 38.34 60.02

Silt (%)

32.67 26.17 19.06 35.38 23.79

20.92

27.38 23.67 19.65 32.89

Clay (%)

Entrance-exit Sand-silt-clay Outside Sand-silt-clay Sand-silt-clay Sandy silt Clayey silt Clayey silt

Inside Clayey silt Clayey silt Sand-silt-clay Clayey silt

Shepard's (1954) class

1.43 0.88 1.59 1.57 0.61

2.51

2.29 2.05 2.99 2.99

HPAH

0.56 0.36 0.99 0.88 0.44

0.55

1.68 0.89 1.04 0.93

LPAH

1.99 1.24 2.56 2.44 1.05

3.06

3.97 2.94 4.03 3.92

TPAH

Polynuclear aromatic hydrocarbons

15 12 6 9 0

75

222 240 126 122

TBT

6 6 2 7 0

16

56 35 26 15

DBT

Butyltins

6 1 0 2 0

6

9 7 6 2

MBT

Table 2. Selected sediment physical and chemical data. Trace metals and PAH concentrations are /~g g-1 dry sediment, butyltin concentrations are ng Sn g-1 dry sediment, acid volatile sulphide is expressed as ~mol S g-i dry sediment and total SEM is the sum of the molar quantities of the simultaneously extractable metals

t%

15 900 15600 11 400 19 000

10 700

13 400 10 700 20 700 19 000 20 700

BR5

BR6 BR7 BR8 BR9 Control

AI

BR1 BR2 BR3 BR4

Station

Trace metals

8.6 0.5 10.0 10.0 7.6

5.1

13.5 11.1 7.5 8.7

As

0.67 0.40 0.74 0.70 0.41

0.38

0.44 0.36 0.29 0.43

Cd

37.4 29.2 61.5 57.6 54.4

30.0

53.0 46.4 29.5 50.1

Cr

29.8 23.2 39.5 37.6 21.6

41.8

167 121 69.3 77.7

Cu Hg

Inside 35 100 0.21 32400 0.18 22 100 0.11 36 600 0.22 Entrance-exit 23 000 0.13 Outside 28 200 0.19 21 400 0.13 42 300 0.38 39 500 0.25 36 300 0.10

Fe

46.2 29.9 65.7 52.2 38.4

27.8

44.8 38.9 25.9 46.1

Pb

223 127 268 273 160

153

389 330 173 220

Zn

5.5 0.6 15.4 12.9 6.1

11.4

24.0 10.1 9.5 39.4

AVS

2.64 1.62 3.13 2.82 1.51

2.27

4.60 7.57 2.26 2.45

Total SEM

0.48 2.65 0.20 0.22 0.25

0.20

0.19 0.75 0.24 0.06

SEM:AVS

t~

48


BR1 and BR2. Copper ranged from 167pg g-1 dry weight in the marina to 23.2pg g-X dry weight outside. The concentration of TBT was 75-240 ng Sn g-1 dry weight in the marina basin and channel as compared to 6-15 ng Sn g-1 dry weight outside. Concentrations of the TBT degradation products, DBT and MBT, were less than concentrations of TBT, but followed a similar spatial trend. Butyltins were not detected in the control sediment from the Corsica River (Table 2). For each station, the ratio of the sum of molar quantities of the simultaneously extractable metals (SEM) to the molar quantity of acid volatile sulphide (AVS) was calculated. Only station BR7 had an SEM:AVS ratio >1 (Table 2); however, the AVS concentration at this station was 0.61/tmol g-X dry weight, an anomalously low value when compared to the remaining stations. The concentrations of 24 individual polynuclear aromatic hydrocarbons (PAHs) were measured. The PAHs were categorized into three groups: the low molecular weight PAHs (LPAHs), consisting of two- to three-ring aromatic hydrocarbons, the high molecular weight PAHs (HPAHs), consisting of four- to five-ring compounds and the total PAHs (TPAHs), the sum of the LPAHs and HPAHs (Table 2). Concentrations of TPAHs ranged from 1.05 to 3.97pg g-1 dry weight. Concentrations of PAHs, particularly HPAHs, are elevated in sediments inside and at the entrance to the marina relative to sediments outside (Table 2). The concentration of TPAHs was lowest in control sediment. Sediment toxicity test Means (ranges in parentheses) of overlying water quality parameters in amphipod toxicity test chambers were as follows: temperature 20.5°C (20.0-21.5), dissolved oxygen 8.2 p.p.m. (5.4-9.0), conductivity 561ktmhos (250-1700) and pH 8.03 (7.69-8.49). The high, upper limit conductivity value (1700/~mhos) reflects initial conditions in control sediment chambers. Conductivity in this treatment declined over the exposure period to values comparable to other test chambers. The mean survival of H. azteca exposed to control sediments, 88.7% (SD = 10.3, Table 3), was above the recommended minimum acceptable value of 80% (EAD 1990, ASTM 1991a). The mean survival of H. azteca in test sediments ranged from 80.0% (SD = 14.7) at BR2 to 95% (SD = 5.8) at BR5, with no significant differences in survival between control and test sediments (Table 3). The mean length of H. azteca was not reduced in any test sediments when compared to the control (Table 3). Instead, mean amphipod lengths in sediments from stations BR1 (4.12 mm, SD = 0.10), BR2 (4.12 mm, SD = 0.17) and BR5 (4.09 mm, SD = 0.17) were significantly greater than the control (3.70 mm, SD = 0.13). Pore water from stations BR1 and BR2 caused a reduction in light emission by the bacterium, P. phosphoreum, with EC20 values of 53.8 and 70.0%, respectively (Table 3). EC20 values for all other stations were >100%. Test results for positive and negative controls were within acceptable ranges. Benthic community analysis A total of 930 organisms, comprising 17 taxa, were identified from all stations. The number of observed taxa and the proportions of major taxonomic groups for each station are shown in Table 4 and Fig. 3, respectively. Fewer taxa were observed at the inner stations (BR1-BR4) relative to the outer stations (BR6-BR9) and the entrance-exit station (BR5). Tubificid oligochaete worms, a group some of whose members are

S e d i m e n t contamination and effects in a marina

49

Table 3. Results of sediment toxicity tests

Treatment

Amphipod survival (%)

Amphipod length (mm)

Control BR1

88.7 (10.3) 90.0 (14.1)

3.70 (0.13) 4.12" (0.10)

BR2

80.0 (14.7)

4.12" (0.17)

BR3 BR4 BR5 BR6 BR7 BR8 BR9

90.0 85.0 95.0 91.3 81.3 93.8 90.0

3.99 3.96 4.09* 3.88 3.82 3.88 3.94

(8.5) (14.7) (5.8) (6.3) (6.3) (6.3) (4.1)

(0.29) (0.19) (0.17) (0.16) (0.16) (0.22) (0.26)

EC2o (%) >100 53.8 (40.2, 72.1) 70.0 (61.8, 79.2) >100 >100 >100 >100 >100 >100 >100

Means (standard deviation in parentheses) are given for survival and length of H. azteca in the 28 day whole sediment test. Values that are significantlydifferent

from the control (p < 0.05) are indicated with an asterisk. Results of Microtox® bacterial luminescenceassay are reported as EC20 values (95% confidencelimits in parentheses) - the concentrationof pore water necessaryto reduce light output by 20% in 15 min exposures.

considered pollution tolerant, dominated the inner stations, accounting for more than 80% of the total organisms at each station. Chironomids (class Insecta) and polychaetes constituted the remainder of the organisms at the inner stations. Outer stations exhibited a more balanced benthic assemblage, comprised of chironomids, oligochaetes, polychaetes, bivalves and crustaceans (Figure 3). Taxa generally considered sensitive to pollution, such as amphipods (Hart and Fuller, 1974, US FWS 1988, US E P A 1990), were found exclusively at the outer stations. Three groups of stations were separated by cluster analysis (Fig. 4). The outer stations (BR6-BR9) were contained in group I, while group II contained the entrance-exit station (BR5) and group III contained the inner stations (BR1-BR4). The mean taxa richness and evenness of group I stations were greater than those of group III. These results indicate that benthic invertebrate assemblages outside the marina (group I) were structurally different than those inside the marina (group III). Discussion

This study was designed to evaluate the environmental impact of marina-related activity by integrating complementary measures of sediment chemistry, sediment toxicity and benthic community structure. That each of the three components contributed unique information to the assessment reflects the need for this 'burden of evidence approach' (Chapman et al. 1987, 1991). For example, results of benthic community analysis indicated structural differences between the resident infaunal assemblages found inside and outside the marina. Stations within the marina contained infaunal communities that

0

0

Mollusca Bivalvia Rangia cuneata

63 0

1 0 0

BR1

Nematoda

Oligochaeta Tubificidae (unid.) Lumbriculidae (unid.)

Annelida Polychaeta Hobsonia spp. Scolecolepides viridis Streblospio benedicti

Taxon

Inner

Station

0

1

72 1

1 0 0

BR2

0

0

149 0

15 0 0

BR3

0

0

159 0

3 0 0

BR4

1

0

35 0

4 1 0

BR5

9

0

28 0

0 0 1

BR6

Outer

1

3

40 0

0 5 0

BR7

2

0

19 0

0 0 0

BR8

1

0

13 0

0 0 1

BR9

Table 4. Invertebrate taxa, abundance, taxa richness and Shannon evenness for stations within and around the marina

g~

g~

t~

4 690 0.27

0 0 1 4 0 0

0 0

0 0

5 760 0.12

0 0 0 1 0 0

0 0

0 0

0 0 0 3 0 0

0 0

0 0

6 3 1840 1650 0.39 0.17

1 0 4 15 0 0

0 0

0 0

Note: those organisms not identifiable as separate taxa are not included. Values are pooled totals of five grabs per station.

Total taxa Number of organisms/m 2 Shannon evenness

Coelotanypus concinnus Coelotanypus scapularis Procladius spp. Chironomus spp. Cryptochironomus spp. Tanytarsus sp.

Insecta Chironomidae

Leptocheirus plumulosus Gammarus spp.

Amphipoda

Cyathura polita Edotea triloba

Arthropoda Crustacea Isopoda

11 870 0.74

2 14 16 9 2 1

0 0

2 0

17 1 0 30 0 0

14 2

2 0

11 10 1160 1150 0.68 0.73

52 11 3 7 1 0

2 0

1 1

6 770 0.7

40 2 0 2 0 0

12 0

0 0

7 410 0.74

40 0 0 1 0 0

11 0

0 0

%

l::t.


52

100 re,m,

......

,

iiiiiiiiiii 777777 ////// ////// ////// ////// ////// ////// ////// ////// ////// ////// //////

80 Z

O i

I-

60

0

D.

0

0 o~

40

////// 20

0

BR1

BR2

BR3

BR4

BR5

BR6

BR7

BR8

BR9

STATION

iAnnelida r-~Chironomidae []Mollusca I~]Crustacea Figure 3. Proportions of major benthic taxonomic groups. Values are calculated from the totals of five 0.02 m2 grabs per station. typically reflect environmental degradation. However, without complementary sediment toxicity and sediment chemistry data, it is difficult to differentiate between sediment contamination and other environmental variables (elg. water quality, biotic factors, sediment characteristics) as the cause of the altered benthic community. Sediment toxicity test data alone are similarly inadequate. Toxicity tests demonstrate quantifiable effects on laboratory organisms, but provide little interpretative evidence for potential ecological effects associated with the observed toxicity. By integrating the three measures, the degree of pollution-induced degradation may be evaluated with greater confidence. Sediment characterization Chemical concentrations measured in the marina basin sediments are comparable to values reported by Crecelius et al. (1990) for marinas in Puget Sound (Table 5). In that study, sediment concentrations of select trace metals, PAHs and butyltins were measured at stations within and outside of two marinas of differing capacity (450 and 900 slips). These data are included for comparative purposes (Table 5).

53

S e d i m e n t contamination and effects in a marina S I

0.2-

81

M

71

I 0.4-

J

L A R

31

0.6.

I T Y

0"8t

1

....... 1

1.0 BR7

I

BR9

BR8

OUTERSTATIONS I

GROUPI AVERAGETAXA RICHNESS AVERAGESHANNONEVENNESS

I

8.5 0.71

BR6

BR5

ENTRANCE/EXIT I I

I

GROUPII

I

11 0.74

BR4

1....

l_

BR3

BR2

1 BR1

INNERSTATIONS

I

GROUPIII

I

4.5 0.25

Figure 4. Dendogram derived from cluster analysis of the benthic taxa/abundance matrix. Linkages are numbered in order of decreasing similarity.

Copper and TBT are the contaminants with the greatest sediment concentration differences inside versus outside the marina. Sediment TBT concentrations are enhanced relative to mean sediment concentrations on the east, west and Gulf coasts of the USA (Wade et al. 1990) and fall within the range reported by Crecelius et al. (1990) for a larger marina (900 slips) in Puget Sound (Table 5). Sediment copper concentrations in the marina are also within the range of values reported by Crecelius et al. (1990) for both Puget Sound marinas and greater than those observed in a study of smaller marinas (35-70 boats) in South Carolina (Marcus et al. 1988). One obvious source of both TBT and copper is antifouling paint. In Maryland, legislation was enacted in 1988 to curtail TBT use on recreational watercraft. Legal application of TBT was restricted to aluminium hulled vessels, vessels greater than 25 m and spray can application to outboard motors and lower drive units (Hall et al. 1992). Because of the long residence time of TBT in sediments (Wade et al. 1990), it is not possible to differentiate between ongoing and historic activities as the source of TBT in marina sediments. Regardless of this, the high concentrations of TBT and copper at stations BR1 and BR2 (located adjacent to the marina boat repair facility; Fig. 2) suggest that boat maintenance activities such as scraping, sanding and painting have resulted in the introduction of TBT- and copperladen paint, paint chips and dust into the marina basin (Unger et al. 1988, Crecelius et al. 1990). Concentrations of PAHs, particularly HPAHs, are greater in sediments inside relative to outside the marina. Predominance of HPAHs over LPAHs in marina sediments is

l


54

Table 5. Mean values and ranges of concentrations of sediment contaminants (on a sediment dry weigh basis) and conventional parameters in and surrounding two marinas in Puget Sound (data taken fron Crecelius et al., 1990) Parameter

Inside 450 boat marina

Outside 450 boat marina

TOC (%)

1.07 0.32 - 3.15

1.54 0.25 - 2.12

3.80 3.34 - 5.58

2.86 0.66 - 5.40

22.50 7.40 - 72.03

67.10 5.83 - 91.01

92.82 81.60 - 96.27

63.07 50.09 - 86.46

60 26 - 130

29 13 - 34

86 60 - 137

29 17 - 68

Pb (ug g-l)

19.1 9.4 - 56

16.7 7.6 - 25

35.3 29 - 57

17.0 7 - 48

Zn ~ g g-l)

85.9 46 - 203

82.3 37 - 97

150.6 126 - 169

77.4 47 -113

% fines (1 - 6

284 92 - 872

14.1 2 - 43

also reported by Crecelius et al. (1990) (Table 5). H P A H s are commonly associated with pyrogenic sources such as fuel combustion in marine boat engines (Vourdrias and Smith 1986). The diffuse spatial distribution of the H P A H s in marina sediments supports this source. On the other hand, petroleum tends to be rich in L P A H s (Vourdrias and Smith 1986): Concentrations of L P A H s are greatest at station BR1, perhaps reflecting oil runoff from the parking lot or small fuel spills. Most probably, the T P A H s in sediments inside the marina result from a combination of both fuel combustion and run-off, while sites outside the marina are affected predominately by run-off. These P A H concentrations are within the range reported by Crecelius et al. (1990) for the small Puget Sound marina but are substantially less than concentrations reported by these investigators for the larger marina (Table 5). The Spatial distribution of chemical concentrations indicates there is minimal export of contaminants to sediments outside the marina basin. This is probably due to the twosegment design o f the marina which allows limited flushing of the basin ( N C D E M 1990). Marinas with an open-water design ( N C D E M 1990) exhibit a spatially m o r e diffuse chemical contamination pattern (Marcus et al. 1988), reflecting export and subsequent dilution of contaminants from the marina.

Sediment toxicity Results of the a m p h i p o d toxicity test indicated no significant lethal effects associated With test sediments. HoweVer, amphipods exposed to sediments collected inside the


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marina basin (stations BR1-BR5) were larger than those exposed to sediments from stations outside the marina (stations BR6-BR9) (Table 3). Significant effects on mean amphipod length were observed in sediments from stations BR1, BR2 and BR5 when compared to control sediments. The biological significance of these results is equivocal. One possible explanation is these test sediments contained some supplemental food source (e.g. particulate organic material) which promoted growth. However, if organic material contributed to amphipod growth then a correlation between total sediment organic carbon and amphipod length might be expected. This relationship was not apparent (Tables 2 and 3). Alternatively, the enhanced growth may be the result of hormesis, the stimulation of physiological processes upon exposure to low levels of toxicants (Laughlin et al. 1981, Stebbing 1981). The results of the Microtox® bacterial luminescence assay support this hypothesis. Light emission was reduced in bacteria exposed to sediment pore water from two out of the three stations eliciting enhanced amphipod growth, BR1 and BR2. Furthermore, sediment concentrations of TBT and copper were greatest at these two stations. Several researchers have observed enhanced growth of laboratory organisms upon exposure to field-collected contaminated sediments (Chapman et al. 1985, Scott and Redmond 1989, Ingersoll and Nelson 1990, Johns et al. 1991, McGee et al. 1993), although in many instances the response was not addressed or explained. It is likely that this phenomenon will be observed with increased frequency as more sediments with moderate to low concentrations of chemical contaminants are tested. If both inhibitory and stimulatory effects are regarded as perturbations (Burton 1991), then attention to the biological significance of hormesis is warranted. Benthic community

Results of cluster analysis indicate that the resident infaunal assemblages inside the marina (group III, BR1-BR4) are structurally different from those outside the marina (BR6-BR9, group I). The benthic community parameters of group III cluster stations are typical of an impacted benthic community, exhibiting low taxa richness and numerical dominance by oligochaetes, many of whose members are considered pollution tolerant. Increased concentrations of sediment-bound chemicals within the marina basin may explain the depauperate, benthic infaunal community, however, several factors other than sediment contamination could be responsible. For example, poor flushing of the marina basin could result in stagnation and accumulation of oxygen-demanding substances, ultimately causing water quality degradation. Water quality studies of marinas of similar design have reported lower dissolved oxygen levels inside marina basins (NCDEM 1990), comparable to what was observed in this study. Other factors that could contribute to the impoverished benthic community inside the marina include limited recruitment of benthic organisms caused by poor flushing of the marina basin and physical disturbance of bottom sediments by boat turbulence. Bioavailability

The high sediment concentrations of TBT and copper measured inside the marina prompted a literature investigation into the potential bioavailability of these compounds. TBT is extremely toxic in the water column (Hall et al. 1987), however, because of its sorption behaviour, significant amounts of TBT are sediment bound (Unger et al. 1988). Cardwell (1988) suggested that bioavailability of TBT in sediment could be predicted

56


by equilibrium partitioning between sediment organic carbon and pore water. In contrast, Unger et al. (1988) studied sorption behaviour of TBT on estuarine sediments and determined that organic carbon was not a good predictor of TBT sorption to sediments. Whatever the sorbate species, the sorption process is reversible, hence, TBT-contaminated sediments can serve as a source of dissolved TBT through partitioning to the interstitial and overlying waters (Unger et al. 1988, Hall et al. 1992). The significance of this sediment source of TBT was illustrated by Hall et al. (1992) who found no significant differences in TBT concentrations in the water column between years preceding and after the Maryland legislation that restricted use of the compound in Chesapeake Bay. They speculated that as aqueous concentrations of TBT were reduced, the equilibrium between the sediment and aqueous phase shifted and more TBT desorbed from the sediments. The bioavailability of copper and other divalent metals in sediment is thought to be governed by partitioning with the acid volatile sulphide (AVS) phase (DiToro et al. 1990). According to theory, when the molar quantity of AVS is greater than the molar quantity of the simultaneously extractable metals (SEM) i.e. SEM:AVS