Marine Pollution Bulletin 56 (2008) 1598–1608

Contents lists available at ScienceDirect

Marine Pollution Bulletin

journal homepage: www.elsevier.com/ locate /marpolbul

Survey of PAH in low density residential stormwater ponds in coastal South

Carolina: False dark mussels (Mytilopsis leucophaeata) as potential biomonitors

Alan T. Flemming a, John E. Weinstein b,*, Alan J. Lewitus c

a Masters of Science in Environmental Stud­ies Program, 66 George Street, College of Charleston, Charleston, SC 29424, USAb Department of Biology, The Citad­el, 171 Moultrie Street, Charleston, SC 29409, USAc NOAA Center for Sponsored­ Coastal Ocean Research, 1305 East West Hwy, Silver Spring, MD 20910, USA

a r t i c l e i n f o

Keyword­s:

Mussels

Mytilopsis leucophaeata

Polycyclic aromatic hydrocarbons

Stormwater runoff

Detention pond

South Carolina

0025-326X/$ - see front matter © 2008 Elsevier Lt

doi:10.1016/j.marpolbul.2008.05.018

* Corresponding author. Tel.: +1 843 953 7796; f

E-mail ad­d­ress: john.weinstein@citadel.edu (J.E

a b s t r a c t

The distribution of PAHs was studied in sediment and false dark mussels, Mytilopsis leucophaeata, of

three brackish stormwater retention ponds on Kiawah Island, a gated residential community and golf

resort. Impervious surface in pond watersheds ranged from 5 to 30%. Sediment concentrations were

lower than those found in other studies of suburban residential areas, and there were no signif­i­cant

differences among ponds or seasons. Mean )PAH16 values for sediments in Ponds 67, 100, and 37 were

184.7 ± 101.3 ng g¡1, 67.5 ± 26.0 ng g¡1, and 84.3 ± 75.5 ng g¡1, respectively. Mussel )PAH16 concentrations

from Pond 67 in August (mean 734.5 ± 148.1 ng g¡1), and from Pond 37 in December (mean 1115.1 ± 87.7 ng

g¡1), were signif­i­cantly higher than other ponds. Mean )PAH16 values for mussels in Ponds 67, 100, and,

37 were 555.9 ± 219.7 ng g¡1, 312.5 ± 99.1 ng g¡1 and 737.8 ± 419.8 ng g¡1, respectively. The mean biota-to-

sediment ratio was 7.6 ± 8.1. Isomer ratios generally suggested pyrogenic sources. False dark mussels are

a promising indicator species for PAH contamination because they are abundant, easy to sample, bioaccu-

mulate PAH prof­i­les representative of the time-integrated sediment prof­i­les, and their PAH levels are less

variable than either stormwater or sediment samples.

© 2008 Elsevier Ltd. All rights reserved.

1. Intro­duc­tio­n

Stormwater management ponds, including detention and reten-

tion ponds, are a commonly used best management practice for

the control of stormwater runoff in the USA. In the state of South

Carolina alone, it is estimated that over 8,000 ponds have been

constructed (South Carolina Algal Ecology Lab, unpublished data,

2005). Their purpose is to reduce downstream impacts of storm-

water runoff by reducing runoff peaks, removing sediments and

pollutants, and enhancing overall stormwater quality through a

variety of physical, chemical, and biological processes. However,

the typical pond design results in the drainage of stormwater

directly from road and street surfaces through concrete pipes

into the ponds, thereby bypassing natural processes of contami-

nant removal. As suspended solids settle out on the pond bottom,

contaminants may accumulate in the sediments. If these contami-

nants are bioavailable to epibenthic and pelagic organisms in the

pond, they then could pose a risk to wildlife using the pond, such

as wetland bird species and overwintering ducks. Pond outflows

in coastal areas are often directly linked to tidal creeks and estu-

aries, thus they can have a signif­i­cant impact on the water qual-

d. All rights reserved.

ax­: +1 843 953 7264.

. Weinstein).

ity of these adjacent natural systems. Stormwater retention ponds

function as the interface between development and estuarine eco-

logical health as indicated by water quality, biodiversity and com-

plex­ity, resilience, and sustainability.

One important class of contaminant associated with these

stormwater management ponds are polycyclic aromatic hydrocar-

bons (PAHs) (Fernandez and Hutchinson, 1992; Marsalek and Mar-

salek, 1997; Marsalek et al., 2002; Kamalakkannan et al., 2004).

PAHs are organic compounds that consist of two or more aromatic

(benzene) rings. These compounds are a natural part of fossil

fuels, and are formed as products of incomplete combustion. Nat-

ural sources of PAHs in the environment include forest and grass

f­i­res, volcanoes (Nagpal, 1993), and fossil fuels such as coal and

oil, where PAHs have formed as result of diagenetic processes. The

main anthropogenic sources of PAHs are coal combustion and vehi-

cle emissions (Dickhut et al., 2000). Other anthropogenic sources

include wood burning, industrial emissions, used motor oil and

fuel drips and spills, tire wear, asphalt, tar, small engine ex­haust,

creosote, and waste incineration.

The PAHs quantif­i­ed in this study were naphthalene (NAPT),

acenapthylene (ACNY), acenapthene (ACEN), fluorene (FLUR), phen-

anthrene (PHEN), anthracene (ANTH), fluoranthene (FLTH), pyrene

(PYR), benzo(a)anthracene (B[a]A), chrysene (CHRY), benzo(b)flu-

oranthene (B[b]F), benzo(k)fluoranthene (B[k]F), benzo(a)pyrene

(B[a]P), dibenz(a,h)anthracene (D[ah]A), benzo(g,h,i)perylene

A.T. Flemming et al. / Marine Pollution Bulletin 56 (2008) 1598–1608 1599

(B[ghi]P), and indeno(1,2,3,c,d)pyrene (INPY). The f­i­rst six­ PAHs

listed (NAPT through ANTH) are considered low molecular weight

(LMW) PAHs, and the f­i­nal ten PAHs listed (FLTH through INPY) are

considered high molecular weight (HMW) PAHs.

Mussels are commonly used as biomonitoring organisms for

PAH contamination in both marine and freshwater environments

(Utvik et al., 1999; Piccardo et al., 2001; O’Connor, 2002; Hellou et

al., 2005; Oros and Ross, 2005) because they are sessile, have high

f­i­ltration rates (de Lafontaine et al., 2000), bioaccumulate PAHs

(D’Adamo et al., 1997), and capture PAH prof­i­les representative of

the time-integrated source in their tissues since they have limited

ability to biotransform PAHs (Baumard et al., 1998a; Naes et al.,

1998). Mussels are f­i­lter-feeding organisms that mainly accumu-

late soluble PAHs or PAHs associated with suspended solids (Baum-

ard et al., 1998a). As such, the PAH concentrations in their tissues

can be used to estimate that fraction of the total PAHs in the sys-

tem which are bioavailable (Richman and Somers, 2005).

The false dark mussel, Mytilopsis leucophaeata, is a member of

the family Dreissenidae and is closely related to the invasive zebra

mussel, Dreissena polymorpha (Therriault et al., 2004). Although

false dark mussels have not previously been used to study PAH

contamination, they are an ideal indicator organism for coastal

stormwater retention ponds because they are widespread and able

to colonize these brackish ponds quickly (Rajagopal et al., 2005a).

This mussel is epibenthic and is easy to collect because it uses bys-

sal threads to attach itself to solid substrates like concrete pipes or

submerged wood (Rajagopal et al., 2005b). The false dark mussel

is a euryhaline species that is native to North America and is found

in estuarine environments of the east coast from Florida to Massa-

chusetts (Marelli and Gray, 1983). It is most commonly found in

water with salinity ranging from 3 to 15 ppt (Claudi and Mackie,

1994). The false dark mussel grows quickly, approx­imately 1 mm

Fig. 1. Project Location - Kiawah Island, a barrier island on the southeastern South Caroli

each in the three highlighted brackish retention ponds; Pond 67, Pond 37, and Pond 100

per month (Laine et al., 2006), their average size is 1 to 3 cm when

mature, and their life span is 3 to 5 years (Therriault et al., 2004).

Because of their high lipid content (up to 15 percent) (Bruner et al.,

1994), Dreissenidae mussels are especially well suited to capturing

PAHs, many of which are lipophilic. D. polymorpha f­i­lters particles

from 1 to 35 lm in size and feeds on the organic fraction (Gossi-

aux­ et al., 1998; Sprung and Rose, 1998). D. polymorpha, and other

mussels commonly used for mussel watch such as the blue mus-

sel, Mytilus ed­ulis (O’Connor, 2002), generally prefer particles from

15 to 40 lm (Winkel and Davids, 1982). The particle size most effi-

ciently f­i­ltered by these mussels corresponds to the particle size of

soot particles, to which high molecular weight PAHs are commonly

adsorbed (Vo-dinh, 1989).

The objective of this study was to investigate sediment PAH con-

centrations in three residential stormwater retention ponds on Kia-

wah Island (South Carolina) and evaluate the utility of false dark

mussels as a biomonitor of PAH contamination. These stormwater

ponds were chosen because the land use in the pond watersheds

represented different intensities of primarily residential develop-

ment. The relative abundance of PAH analytes in sediments was

used to investigate probable PAH sources, and the relationship

between sediment and mussel tissue PAH concentrations was

ex­plored.

2. Mate­rials and me­th­o­ds

2.1. Stud­y area

The three brackish stormwater retention ponds (Ponds 67, 100,

and 37) are located on Kiawah Island, a barrier island in southeast-

ern South Carolina (Fig. 1). Kiawah Island is a gated community

characterized by large residences, numerous golf courses and

na coast. Sediment and mussel tissue PAH concentrations were studied at three sites

.

1600 A.T. Flemming et al. / Marine Pollution Bulletin 56 (2008) 1598–1608

intensive landscaping. There are a total of 136 brackish retention

ponds on Kiawah Island. These ponds are interconnected through

concrete drainage pipes and closely linked to tidal creeks. Only

approx­imately half of the residential lots on Kiawah Island have

been developed, and construction traffic and activity is signif­i­cant.

Pond watershed areas and sampling locations are summarized

in Table 1 and described in more detail in following section. Sed-

iment and mussel samples were collected from three sites within

each pond (a total of twelve sample sites).

Pond 67 is surrounded by development that is typical for Kia-

wah Island, including residential lots and houses with average

sizes of 0.18 hectares (0.44 acres) and 310 m¡2 (3400 square feet)

respectively (calculated using data from Charleston County GIS,

2006), and a golf course fairway. The primary land cover categories

in the watershed of this pond are the landscaped areas around the

residences at 30 percent, and golf course turf at 29 percent. Activ-

ities observed in this watershed during the course of this study

included the construction of several new homes and intensive golf

course maintenance, including the use of lawn mowers and gas-

powered leaf blowers.

In this study, Ponds 37 and 100, which have very different devel-

opment patterns in their watersheds compared to Pond 67 (Table

1), were sampled in an attempt to relate the ex­tent of watershed

development to PAH levels in sediments and mussels. Pond 37 rep-

resents a pond with a greater degree of development than Pond

67 (Table 1). This pond is surrounded by the parking lot of a large

resort hotel and is adjacent to the Kiawah Island Town Center. The

watershed of Pond 37 has a high percent impervious surface rela-

tive to the other watersheds in this study; nonetheless the primary

land cover categories in this watershed are landscaped areas at 42%

and undisturbed, primarily maritime forest and wetland, at 16%.

The contribution of impervious surfaces to the watershed of Pond

37 is 11% rooftops, 11% parking, 5% streets, and 4% sidewalks and

paved paths. In contrast, Pond 100 represents a pond with a lower

degree of development than Pond 67. This pond is surrounded pri-

marily by “natural” amenities such as golf course and landscaping.

There is relatively little residential development surrounding Pond

100, and the primary land cover categories for this watershed are

turf at 31% and landscaped at 23%, both entirely associated with

the golf course.

2.2. Sampling

Three sites each in Pond 67, Pond 37, and Pond 100 were sam-

pled. Pond surf­i­cial sediment and mussels were sampled twice in

all three ponds, once on August 2, 2005 and once on December 13,

2005. Sediment samples were also taken from Pond 67, on March

8, 2005. Samples were collected within 1 m of the pond edge, at a

depth of approx­imately 0.5 m. Sediment samples from the upper

1–2 cm of the pond bottom were collected using a stainless steel

spoon from several locations within an approx­imately 1-meter

square area. Sediment was gently lifted to the pond surface and

placed in an amber jar with a Teflon-lined cap. The jars were

Table­ 1

Summary of Kiawah Island pond watershed areas and percentage impervious sur-

face for the three ponds that were sampled at three sites each for sediment and

mussel tissue PAH concentrations

Pond Sample

sites

GPS coordinates Watershed area

(hectares)

Impervious

surface (%)

Pond 67 A, B, D 80 ° 3.69 W, 32 °37.19 N 5.87 16

Pond 100 E, F, G 80 ° 6.29 W, 32 °36.39 N 7.51 5

Pond 37 H, J, K 80 ° 5.69 W, 32 °36.19 N 46.6 30

GPS coordinates are for the approx­imate pond center.

placed on ice for transportation to the lab where they were refrig-

erated at 4 °C until processing within 48 h. Mussels were collected

from the pond bottom using a dip net at approx­imately the same

locations as the sediment samples. Mussels were separated from

organic debris and placed in resealable plastic bags. The bags were

placed on ice for transportation to the lab and refrigerated until

processing within 48 h.

2.3. Extraction and­ purifi­cation - sed­iment

Sediment samples were stirred in the collection jar and repli-

cate samples of approx­imately 2 grams were removed and placed

on aluminum foil, covered loosely, and allowed to dry overnight at

room temperature in the dark. The dry sediment was weighed, and

then homogenized using a mortar and pestle. The homogenized

sediment was ultrasonicated for 5 min in 10 ml of acetonitrile, then

centrifuged at 3000 rpm for 20 min in glass centrifuge tubes. The

supernatant was removed to a clean bottle. The remaining sedi-

ment was ultrasonicated and centrifuged with an additional 10 ml

of acetonitrile. Finally, the sediment was left to shake overnight in

another 5 ml acetonitrile. The combined supernatant was stored

at ¡20 °C until f­i­ltration of a subsample into 2 ml vials that were

sealed and stored at ¡80 °C until HPLC analysis.

Four samples (»0.5 g) of National Institute of Standards and

Technology (NIST) Standard Reference Material 1941a (NIST, 1994)

were processed by the same methods as the sediment samples

to determine ex­traction efficiencies. The average ex­traction effi-

ciency of )PAH16 was 86 ± 7%, the average ex­traction efficiency

of the 14 certif­i­ed analytes was 86 ± 13%, and ex­traction efficiency

was greater than 60% for all analytes ex­cept ANTH at 59%. Using

similar methods to those outlined here, Kayali-Sayadi et al. (2000)

and Sun et al. (1998) obtained comparable efficiencies. Note that

ACNY and ACEN are uncertif­i­ed components of the reference

material and were not detected in any sediment samples from

the stormwater retention ponds. Procedural blanks were analyzed

with every sample batch. Five PAHs were commonly detected

in sediments: NAPT, ACEN, FLTH, PYR, and B[k]F. Average blank

values for these f­i­ve analytes were 2.9, 6.2, 2.5, 0.1 and, 1.0 ng/g,

respectively, and all were below their respective limits of quanti-

f­i­cation.

2.4. Extraction and­ purifi­cation - mussels

Mussel tissue was removed from the shells using a scalpel and

forceps, placed on aluminum foil or a glass dish, covered loosely,

and allowed to dry overnight at room temperature in the dark. Rep-

licate samples of approx­imately 20 average-sized mussels (approx­-

imately 0.3 g dry tissue total) each were processed. Mussel tissue

was homogenized in 2 ml acetonitrile using a Biospec Products

Tissue Tearor Model 985–370 tissue homogenizer in an ice water

bath, and then centrifuged at 3000 rpm for 20 min in glass centri-

fuge tubes. A 2 ml subsample of the supernatant was removed and

stored in a sealed vial at ¡80 °C until HPLC analysis.

Mussels for use in quality assurance were collected during the

December sampling at site E, where PAH concentrations in mussel

tissue had been lowest during the August sampling. Two mussel

samples were spiked before homogenization with a certif­i­ed stan-

dard PAH mix­ture (o2si, Charleston, South Carolina). The average

PAH concentrations from two unspiked replicates at site E were

subtracted from the recovered PAH concentrations in the spiked

samples before calculating ex­traction efficiencies. Ex­traction effi-

ciency of )PAH16 was 75 ± 11%, the average ex­traction efficiency of

the 16 individual analytes was 81 ± 29%, and ex­traction efficiency

was greater than 60% for all analytes ex­cept ACNY at 0%, PYR at

59%, and B[a]A at 43%. Five PAHs were also commonly detected in

procedural blanks for mussel tissue: NAPT, ACEN, FLTH, PYR, and

A.T. Flemming et al. / Marine Pollution Bulletin 56 (2008) 1598–1608 1601

Table­ 2

Physical characteristics of the stormwater pond sediments

Pond Sample site TOC (%) Sand (%) Silt (%) Clay (%)

Pond 67 A 0.3 92.0 0.0 8.0

B 0.4 93.6 0.9 5.5

D 0.3 94.7 1.2 4.1

Pond 100 E 0.2 94.8 2.1 3.1

F 0.2 96.1 2.2 1.7

G 0.2 93.1 0.0 6.9

Pond 37 H 0.3 93.2 1.3 5.5

J 0.1 92.9 1.8 5.3

K 0.2 92.1 0.0 7.9

TOC = total organic carbon.

B[k]F. Average blank values for these f­i­ve analytes were 0.2, 0.9,

0.2, 0.01, and 0.1 ng/g, respectively, and all were all below their

respective limits of quantif­i­cation.

2.5. Instrumental analysis

Total organic carbon (TOC) for the sediment was measured on

a Perkin Elmer CHNS/O Analyzer Model 2400/Series II. Particle

sizes of the sediment were determined using a modif­i­ed Plumb

(1981) method. PAHs were quantif­i­ed using reverse phase high per-

formance liquid chromatography (HPLC) on a Perkin Elmer Series

200 HPLC system connected to a UV/Visible Absorbance Detector

and a Fluorescence Detector in tandem. All detectors are part of

the Perkin Elmer Series 200 system. Fifty microliters of sample or

standard solution were injected directly onto a Hypersil Green PAH

column (5 um, 100 £ 4.6 mm), using a gradient elution of (time, %

acetonitrile) 0,50; 5,50; 25;100 at 2 ml min¡1. The fluorescence

detector was used for detection of all PAHs ex­cept acenapthylene,

which fluoresces only weakly. Instead, it was quantif­i­ed using the

UV/visible detector. Peaks were recorded and quantif­i­ed using

Perkin Elmer TotalChrom software (version 6.2).

Total PAH concentrations are reported as the sum of the 16 ana-

lytes ()PAH16). High molecular weight PAHs are reported as the

sum of the 10 HMW PAHs ()PAHHMW). All PAH concentrations are

reported on a dry weight basis. ACNY and ACEN were ex­cluded

from most statistical analyses because they were consistently

below the level of quantif­i­cation.

2.6. Watershed­ mapping

Pond watersheds were mapped based on a 3-meter resolution

LIDAR digital elevation model obtained from the Kiawah Island

Community Association (Carolina Resource Mapping, Wilmington

NC) and quarter-meter resolution digital orthophotos (Smith et al.,

2005). Spatial analyst tools within ArcGIS 9.1 were used to create

flow accumulation and basin maps for the three ponds based on

the digital elevation model, which were then adjusted according

to the digital orthophotos, plus thorough ground-truthing by the

author. Land cover was digitized by hand based on quarter-meter

resolution digital orthophotos (Smith et al., 2005) and thorough

ground-truthing. Land cover classes were chosen based on identi-

f­i­able features (e.g. streets, rooftops, turf) in the orthophotos that

were believed to potentially have some impact on PAH concentra-

tions in the ponds.

2.7. Statistical analysis

Statistical analyses were completed using MINITAB. An alpha

value of 0.05 was used for all statistical tests. Comparisons

between ponds, seasons, and sites within ponds for )PAH16 and

for )PAHHMW were completed using ANOVA on mean PAH concen-

trations. No transformations were used because the total concen-

trations were sufficiently normal, and log10(x­+1) transformation

produced similar conclusions for differences between ponds.

Fisher’s pairwise comparisons at 95% individual error rate were

used to test for differences between cases.

3. Re­sults

3.1. Sed­iment characteristics

Total organic carbon (TOC) of the pond sediments was relatively

low and ranged from 0.1% at Pond 37 site J to 0.4% at Pond 67 site

B (Table 2). Sediments were sandy with sand content ranging from

92.0% at Pond 67 site A to 96.1% at Pond 100 site F. Clay content

of these sediments was low, ranging from 1.7% at Pond 100 site

F to 8.0% at Pond 67 site A. There was a signif­i­cant relationship

between sediment RPAH16 levels and TOC (p = 0.005); however,

regression models were only weakly correlated (r2 = 0.35). There

was no relationship between sediment RPAH16 levels and clay con-

tent (p = 0.2484). As a result, RPAH16 levels were not normalized for

either TOC or particle size.

3.2. Sed­iment and­ mussel PAH concentrations

There were no signif­i­cant differences in mean )PAH16 sed-

iment concentrations among ponds or seasons (p values ranged

from 0.171 to 0.836) (Fig. 2). Likewise, no signif­i­cant differences

were found among ponds for the )PAHHMW in sediments. Mean

)PAHHMW values for sediments in Ponds 67, 100, and 37 were

129.9 ± 70.1 ng g¡1, 25.5 ± 22.2 ng g¡1 and 61.3 ± 69.9 ng g¡1, respec-

tively.

In contrast to the lack of differences in sediment PAH levels

among ponds and seasons, mussel tissue levels varied consider-

ably. Mean )PAH16 in mussel tissue collected during August in

Pond 67 was signif­i­cantly higher than that of mussel tissue from

Pond 37 and Pond 100 (p = 0.014, Fig. 3). Mean )PAH16 in mus-

sel tissue from Pond 67 collected during August was also higher

than that of the specimens collected in December from the

same pond (p = 0.017). In Pond 37, the December mean )PAH16

value in mussel tissue was signif­i­cantly higher than that from

mussel tissue collected from all other ponds and sampling times

(p < 0.001). Mean )PAHHMW in mussel tissue collected from Pond

37 in December also was signif­i­cantly higher than all other ponds

and sample times (p < 0.001, Fig. 4). However, mean )PAHHMW in

August mussel tissue from Pond 67 was not signif­i­cantly higher

than that of the mussels collected in December (p = 0.708). This

was primarily the result of higher levels of PHEN, a LMW PAH, in

the August-collected mussel tissues. There was no difference in

mean )PAHHMW in August mussel tissue from Pond 67 and Pond

37, but mean )PAHHMW from mussels collected at both sample

times from Pond 67 were signif­i­cantly higher than that of mussels

collected from Pond 100 (p = 0.021 August, and p = 0.028 Decem-

ber)(Fig. 4).

Concentrations of individual PAH analytes in sediment and mus-

sel tissues for August and December sampling at the twelve sam-

ple sites are shown in Figs. 5–8. In general, PAH concentrations and

PAH prof­i­les (the relative abundance of PAH analytes) were more

similar between sites within ponds for the mussel tissue samples

than for the sediment samples. These prof­i­les most closely resem-

ble the prof­i­les commonly associated with urban background (eg

NIST, 1994; Ngabe et al., 2000; Brown and Peake, 2006).

The ratio of mussel tissue concentration to sediment concen-

tration, or biota-to-sediment ratio, for )PAH16 in all samples

ranged from 1.5 to 35.2, with mean 7.6 ± 8.1, and median 5.2. For

)PAHLMW, concentration factors were two fold higher in August

(8.9 ± 4.5) than December (4.5 ± 2.8). For )PAHHMW the trend was

reversed, with almost four fold higher concentration factors in

1602 A.T. Flemming et al. / Marine Pollution Bulletin 56 (2008) 1598–1608

0

50

100

150

200

250

300

350

Pond 37 Pond 67 Pond 100

Sed

imen

t S

um

of

16 P

AH

Co

nce

ntr

atio

n (

ng

/g d

ry w

eig

ht)

August December

Fig. 2. )PAH16 mean sediment concentrations, ng/g dry weight by pond for August and December sampling. Error bars represent 1 standard deviation and n = 3 sample sites

per pond. There are no signif­i­cant differences.

0

200

400

600

800

1000

1200

1400

Pond 37 Pond 67 Pond 100

Mu

ssel

Tis

sue

Su

m o

f 16

PA

H C

on

cen

trat

ion

(n

g/g

dry

wei

gh

t)

August December

A

A

AA

C

B

Fig. 3. )PAH16 mean mussel tissue concentrations, ng/g dry weight by pond for August and December sampling. Error bars represent 1 standard deviation and n = 3 sample

sites per pond. Mean mussel tissue concentrations with different letters are signif­i­cantly different.

A.T. Flemming et al. / Marine Pollution Bulletin 56 (2008) 1598–1608 1603

0

200

400

600

800

1000

1200

Pond 37 Pond 67 Pond 100

Mu

ssel

Tis

sue

HM

W P

AH

Co

nce

ntr

atio

n (

ng

/g d

ry w

eig

ht)

August December

AAA

CA,C

B

Fig. 4. )PAHHMW mean mussel tissue concentrations, ng/g dry weight by pond for August and December sampling. Error bars represent 1 standard deviation and n = 3 sample

sites per pond. Mean mussel tissue concentrations with different letters are signif­i­cantly different.

December (15.2 ± 20.4) and lower ratios in August (4.0 ± 2.5). In

a concurrent study (Flemming, A. 2006), thirteen water samples

were taken during rain events at site B in Pond 67. The average

dissolved phase )PAH16 concentration in sampled pond water

was 19.9 ± 9.7 ngL¡1, corresponding to a bioconcentration factor

of 28,078 for this site. PAH prof­i­les in these water samples were

similar to the sediment and mussel prof­i­les. The biota-to-sedi-

ment ratios for )PAH16, )PAHLMW, and )PAHHMW for the three

ponds in August and December are listed in Table 3. There was a

signif­i­cant difference in biota-to-sediment ratios among ponds

and months for )PAH16 (p = 0.026), and )PAHHMW, (p = 0.044),

but not for )PAHLMW (p = 0.111). Fisher’s pairwise comparisons

indicate that the differences are due to high biota-to-sediment

ratios in the December samples from Pond 37, while all other

samples are equal. Although not a statistically signif­i­cant differ-

ence, the )PAHLMW biota-to-sediment ratios for August samples

were generally higher than the December ratios for all three

ponds.

3.3. Sed­iment isomer ratios

The ratios of PAH concentrations for isomers with equal molec-

ular mass but different thermodynamic stability can be used to

identify probable PAH sources (Yunker et al., 2002; Zheng et al.,

2002; Walker et al., 2005; Brown and Peake, 2006). A single ratio

can often be misleading so multiple ratios are often used. These

ratios are useful indicators of PAH sources because PAHs of equal

mass tend to behave similarly during transport and deposition and

the ratios are preserved (Yunker et al., 2002). Several PAH isomer

ratios and the ratio of LMW to HMW (LMW/HMW) were calculated

for the sediment samples to determine probable PAH sources,

using sediment concentrations corrected for ex­traction efficiency.

The isomer ratios that were calculated are FLTH/PYR, PHEN/ANTH,

B[a]A/CHRY, B[b]F/B[k]F, and INPY/B[ghi]P. Results are presented

in Table 4 along with some representative values reported in the

literature.

The ratios calculated in this study generally suggest pyrogenic

or combustion sources. The FLTH to PYR ratios found in this

study are greater than or equal to one, which indicates pyrogenic

sources (Baumard et al., 1998b). The FLTH to PYR ratios calculated

for Pond 67 and Pond 37 resemble that of 4 stroke emissions,

while that for Pond 100 resembles coal combustion. Likewise,

both the B[a]A to CHRY, and the INPY/B[ghi]P ratios suggest pyro-

genic sources, and resemble the ratios for urban background, auto

emissions, and coal combustion. The high B[b]F to B[k]F ratios

also indicate pyrogenic sources, but may suggest even lower tem-

perature combustion, such as the burning of organic matter (Yun-

ker et al., 2002). The low LMW to HMW ratios (<1) for Pond 67

and Pond 37 further support the conclusion that PAHs in these

ponds are due to urban background and pyrogenic sources (Soclo

et al., 2000).

In contrast to the other ratios, the PHEN to ANTH ratios indicate

a petrogenic source because they are higher than 15 (Soclo et al.,

2000). Very high PHEN is found in the prof­i­le of used crankcase

oil (Brown and Peake, 2006), which could suggest that the high

ratios are due to the spillage of motor oil. However, the fact that

the ratio is consistently high for all three ponds suggests that this

could be the result of a more chronic source, such as the oil emit-

ted in the ex­haust of less efficient 2-stroke engines (e.g. from lawn

care equipment).

1604 A.T. Flemming et al. / Marine Pollution Bulletin 56 (2008) 1598–1608

Pond 67

Site A

0

20

40

60

ng/g

Site B

0

50

100

150

ng/g

Site D

0

20

40

60

NA

PT

FLU

R

PH

EN

AN

TH

FLT

H

PY

R

B[a

]A

CH

RY

B[b

]F

B[k

]F

B[a

]P

D[a

h]A

B[g

hi]P

INP

Y

ng/g

Site E

0

20

40

60

ng/g

Site F

0

20

40

60

ng/g

Site G

0

20

40

60

NA

PT

FLU

R

PH

EN

AN

TH

FLT

H

PY

R

B[a

]A

CH

RY

B[b

]F

B[k

]F

B[a

]P

D[a

h]A

B[g

hi]P

INP

Y

ng/g

Site H

0

20

40

60

ng/g

Site J

0

20

40

60

ng/g

Site K

0

20

40

60

NA

PT

FLU

R

PH

EN

AN

TH

FLT

H

PY

R

B[a

]A

CH

RY

B[b

]F

B[k

]F

B[a

]P

D[a

h]A

B[g

hi]P

INP

Y

ng/g

Pond 100 Pond 37

Fig. 5. Kiawah PAH Concentrations – August Sediment Samples. Y-ax­is is PAH concentration, to 60 ng g¡1 ex­cept Site B to 150 ng g¡1. X-ax­is is 14 PAH analytes in order of

increasing molecular weight from the left: NAPT, FLUR, PHEN, ANTH, FLTH, PYR, B[a]A, CHRY, B[b]F, B[k]F, B[a]P, D[ah]A, B[ghi]P, INPY.

4. Disc­ussio­n

4.1. PAH concentrations in Kiawah Island­ retention pond­s

The overall mean )PAH16 concentration in sediment for the

three retention ponds studied on Kiawah Island was 122.5 ± 93.7 ng

g¡1. This is approx­imately ten fold less than the concentrations

found by Menzie et al. (2002), Brown and Peake (2006) and San-

ger et al. (1999) for other suburban residential watersheds. The

sediment PAH concentrations at Kiawah Island are approx­imately

equal to the reference and background values found by various

researchers along the South Carolina coast (Kucklick et al., 1997;

Sanger et al., 1999; Van Dolah et al., 2005). This suggests that there

is very little direct PAH input related to this type of low density, sea-

sonal use, resort residential development and that PAH inputs here

are primarily the result of atmospheric deposition.

Overall mean )PAH16 concentrations in mussel tissue were

higher than that of the sediment with an average from all three

ponds of 535.4 ± 317.9 ng g¡1. Mussel PAH concentrations tended

to be less variable than sediment PAH concentrations between

sites within ponds. PAHs in mussel tissues are representative of

those PAHs that are bioavailable in the water column, in a freely

dissolved form, colloidal form, or adsorbed to suspended solids

(Baumard et al., 1998a), and represent contamination in the entire

pond watershed, while contamination in the sediments is represen-

tative of local effects. In the current study, PAH prof­i­les between

sediments and mussel tissues were generally similar, with the

ex­ception of PHEN, which demonstrated an increased concentra-

tion in mussel tissue relative to the other PAHs. A simple relation-

ship between sediment PAH concentrations and mussel tissue con-

centrations is not to be ex­pected here because bioaccumulation

factors are only constant when an organism is in direct contact

with, and in equilibrium with, sediment pore water (Thompson et

al., 2000).

On the basis of total PAH concentrations, there was no clear

relationship between PAH concentration and impervious cover

among the three retention ponds. For the sediments, high variabil-

ity between sites is likely to have contributed to the lack of signif­i­-

cant differences between ponds. Van Metre et al. (2000) previously

hypothesized that PAH concentrations may be more closely related

to vehicle miles traveled than to impervious cover. Although not

quantif­i­ed in this study, vehicular traffic in the residential areas

adjacent to Pond 67, especially construction traffic, could have

contributed to this pond having the highest overall mean )PAH16

concentrations. The relatively high levels of LMW PAHs plus PHEN,

FLTH, CHRY and B[b]F in the August sediment samples of Pond 67,

suggest the prof­i­le of coal tar, which may also be related to con-

struction activity and paving that was carried out in the recent

past. Another possible contributor to sediment PAH levels in Pond

67 is the ex­haust from gas-powered lawn mowers and leaf blow-

ers that are regularly used for golf course maintenance adjacent to

the pond. Several samples from Pond 67 had relatively high B[a]A

to CHRY ratios, which are indicative of ex­haust from two-stroke

engines (Kado et al., 2000).

Pond 100 had lower PAH concentrations than Pond 67, and

the lowest percent impervious surface (5%) of the three ponds.

A.T. Flemming et al. / Marine Pollution Bulletin 56 (2008) 1598–1608 1605

Site A

0

20

40

60

ng/g

Site B67.0

0

20

40

60

ng/g

Site D

0

20

40

60

NA

PT

FLU

R

PH

EN

AN

TH

FLT

H

PY

R

B[a

]A

CH

RY

B[b

]F

B[k

]F

B[a

]P

D[a

h]A

B[g

hi]P

INP

Y

ng/g

Site E

0

20

40

60

ng/g

Site F

0

20

40

60

ng/g

Site G

0

20

40

60

NA

PT

FLU

R

PH

EN

AN

TH

FLT

H

PY

R

B[a

]A

CH

RY

B[b

]F

B[k

]F

B[a

]P

D[a

h]A

B[g

hi]P

INP

Y

ng/g

Site H

0

20

40

60

ng/g

Site J

0

20

40

60

ng/g

Site K

0

20

40

60

NA

PT

FLU

R

PH

EN

AN

TH

FLT

H

PY

R

B[a

]A

CH

RY

B[b

]F

B[k

]F

B[a

]P

D[a

h]A

B[g

hi]P

INP

Y

ng/g

Pond 67 Pond 100 Pond 37

Fig. 6. Kiawah PAH Concentrations – December Sediment Samples. Y-ax­is is PAH concentration, to 60 ng g¡1. X-ax­is is 14 PAH analytes in order of increasing molecular weight

from the left: NAPT, FLUR, PHEN, ANTH, FLTH, PYR, B[a]A, CHRY, B[b]F, B[k]F, B[a]P, D[ah]A, B[ghi]P, INPY.

Diagnostic ratios generally indicated that the PAHs in these sam-

ples were likely due to long-range atmospheric transport of prod-

ucts related to coal or biomass combustion. Sample site G differs

from the other two sites in Pond 100 in that it is located at the

edge of the golf course fairway immediately adjacent to the pond,

while the others are separated from the golf course by vegetated

buffers and a sand trap. In December, the sediments at this site had

a comparatively high concentration of B[b]F, and the mussels had

high concentrations of B[b]F, B[a]P, and INPY. These PAHs are gen-

erally considered an indicator of automotive emissions and may

have been deposited directly into the pond during mowing or golf

course maintenance.

Although Pond 37 had the highest level of impervious surface

(30%) in this study, the levels of PAHs in the sediments were inter-

mediate of the other two ponds. Possible factors contributing to

the lower than anticipated levels of PAHs in this pond include

the fact that the watershed of Pond 37 had 16% undisturbed land,

which was twice the amount of Pond 67, and only 3% maintained

turf, which was ten fold less than the other two ponds. The mus-

sel sample prof­i­les and concentrations were fairly consistent at

all three sites within Pond 37, while the sediment samples were

not. This high sediment variability is not unex­pected in Pond 37,

because there are a large number of drainage pipes entering a

small pond area, which potentially contribute PAHs from a variety

of sources. And, there has been signif­i­cant construction activity

in the area over the last two years. The low sediment concentra-

tions at site J were likely due to high sand influx­es from an eroding

bank above the site that influenced the adsorption of PAHs (Mura-

kami et al., 2005) and resulted in reduced PAH concentrations. The

December mussel samples from Pond 37 had signif­i­cantly higher

PAH concentrations than all other samples, and likely represent a

distinct event or source. Approx­imately 500 m of street was paved

adjacent to Pond 37 between the December and August sampling.

Fresh asphalt and construction traffic may have contributed signif­i­-

cant levels of PAHs in the dissolved phase and as suspended solids,

while relatively uncontaminated sediment could have reached the

pond from other adjacent sources.

4.2. Dark false mussels as biomonitors

The results presented here suggest that dark false mussels can

be used as biomonitors of PAH contamination in coastal brackish

stormwater retention ponds. Biota to sediment ratios between

mussels and sediments in the current study ranged from 2.4 ± 1.8

to 34.3 ± 28.1, which is similar to ranges found in other biomonitor-

ing studies involving various species of bivalves (e.g.Thompson et

al., 2000). Differences in biota-to-sediment ratios between August

and December sampling could be related to the effect of temper-

ature on the solubility of PAHs, seasonal changes in photodegre-

dation, and increased lipid content and biological activity in the

mussels during the breeding season. The bioavailability of PAHs

to mussels also depends on the nature of the particulate matter

and algae in the water (Gossiaux­ et al., 1998; Hellou et al., 2005)

and can be ex­pected to vary. For a complete understanding of the

1606 A.T. Flemming et al. / Marine Pollution Bulletin 56 (2008) 1598–1608

Site A

482.4

0

100

200

300

ng/g

Site B

0

100

200

300

ng/g

Site D

0

100

200

300

NA

PT

FLU

R

PH

EN

AN

TH

FLT

H

PY

R

B[a

]A

CH

RY

B[b

]F

B[k

]F

B[a

]P

D[a

h]A

B[g

hi]P

INP

Y

ng/g

Site E

0

100

200

300

ng/g

Site F

0

100

200

300

ng/g

Site G

0

100

200

300

NA

PT

FLU

R

PH

EN

AN

TH

FLT

H

PY

R

B[a

]A

CH

RY

B[b

]F

B[k

]F

B[a

]P

D[a

h]A

B[g

hi]P

INP

Y

ng/g

Site H

0

100

200

300

ng/g

Site J

0

100

200

300

ng/g

Site K

0

100

200

300

NA

PT

FLU

R

PH

EN

AN

TH

FLT

H

PY

R

B[a

]A

CH

RY

B[b

]F

B[k

]F

B[a

]P

D[a

h]A

B[g

hi]P

INP

Y

ng/g

Pond 67 Pond 100 Pond 37

Fig. 7. Kiawah PAH Concentrations – August Mussel Samples. Y-ax­is is PAH concentration, to 300 ng g¡1. X-ax­is is 14 PAH analytes in order of increasing molecular weight

from the left: NAPT, FLUR, PHEN, ANTH, FLTH, PYR, B[a]A, CHRY, B[b]F, B[k]F, B[a]P, D[ah]A, B[ghi]P, INPY.

relationship between PAH concentrations in mussel tissue and con-

tamination in the environment, future laboratory studies should

investigate the PAH kinetics, photodegredation, metabolic activity

and PAH detox­if­i­cation, and lipid content.

The advantages to including a bivalve in a sediment monitoring

study have previously been addressed elsewhere (e.g. Baumard et

al., 1998a; Hellou et al., 2005; Oros and Ross, 2005). One impor-

tant advantage to collecting and analyzing bivalve tissues is that

the PAH concentration in the tissues represents a time-weighted

average of PAH contamination in the system. Biological tissue is

less vulnerable to transient and local concentration pulses of PAH

than either the sediment or water phases. In addition, PAH concen-

trations within mussel tissue represent the bioavailable fraction of

PAHs, which is the fraction most closely associated with adverse

biological impacts at the organismal and ecological levels. These

advantages are particularly relevant in stormwater retention pond

monitoring projects, where contaminants are introduced to the sys-

tem in a pulsatile fashion. Also, bottom sediments in these ponds

can accumulate ex­tremely high levels of contaminants, but not all

of any given contaminant will be bioavailable due to adsorption to

particulate matter or organic debris that is too large for f­i­lter feed-

ing organisms to ingest.

5. Co­nc­lusio­ns

This study has demonstrated that low-density residential and

resort development on Kiawah Island has not resulted in signif-

icantly elevated levels of PAH in stormwater retention ponds.

In fact, levels of PAHs in these ponds are generally similar to

other remote, reference sites in South Carolina. These PAHs are

predominantly from pyrogenic sources such as coal and biomass

combustion, and engine ex­haust. This study has also demon-

strated the utility of the false dark mussel, M. leuecophaeata, as

a biomonitor for PAHs in coastal retention ponds. These mussels

readily colonize brackish retention ponds, were more abundant

than any other species, and were easily collected and processed

for PAH analysis. Ex­traction efficiency of PAHs in these tissues

were comparable with other studies involving bivalves (Piccardo

et al., 2001; Oros and Ross, 2005). Tissue PAH levels were less

variable than those for sediment samples between sites within

a pond. Therefore, site selection within a pond may be less crit-

ical for mussel samples than for sediment samples due to this

reduced local scale variability.

Ac­kno­wle­dge­me­nts

Funding for this work was provided by a grant from South

Carolina Sea Grant Consortium (grant number V473), the South

Carolina Department of Natural Resources, and a faculty research

grant from The Citadel Foundation. This is contribution num-

ber 1482 from the Baruch Institute, and 637 from the SCDNR

Marine Resources Research Institute. The authors would also like

to thank Sadie Drescher, Larissa Brock and Norm Shea for their

assistance.

This study was conducted in accordance with national and

institutional guidelines for the protection of human subjects and

animal welfare. Only invertebrates were used as ex­perimental

animals.

A.T. Flemming et al. / Marine Pollution Bulletin 56 (2008) 1598–1608 1607

Site A

0

100

200

300

ng/g

Site B

0

100

200

300

ng/g

Site D

0

100

200

300

NA

PT

FLU

R

PH

EN

AN

TH

FLT

H

PY

R

B[a

]A

CH

RY

B[b

]F

B[k

]F

B[a

]P

D[a

h]A

B[g

hi]P

INP

Y

ng/g

Site E

0

100

200

300

ng/g

Site F

0

100

200

300

ng/g

Site G

0

100

200

300

NA

PT

FLU

R

PH

EN

AN

TH

FLT

H

PY

R

B[a

]A

CH

RY

B[b

]F

B[k

]F

B[a

]P

D[a

h]A

B[g

hi]P

INP

Y

ng/g

Site H

0

100

200

300

ng/g

Site J

0

100

200

300

ng/g

Site K

0

100

200

300

NA

PT

FLU

R

PH

EN

AN

TH

FLT

H

PY

R

B[a

]A

CH

RY

B[b

]F

B[k

]F

B[a

]P

D[a

h]A

B[g

hi]P

INP

Y

ng/g

Pond 67 Pond 100 Pond 37

Fig. 8. Kiawah PAH Concentrations – December Mussel Samples. Y-ax­is is PAH concentration, to 300 ng g¡1. X-ax­is is 14 PAH analytes in order of increasing molecular weight

from the left, NAPT, FLUR, PHEN, ANTH, FLTH, PYR, B[a]A, CHRY, B[b]F, B[k]F, B[a]P, D[ah]A, B[ghi]P, INPY.

Table­ 3

Kiawah PAH mussel tissue concentration to sediment concentration, or biota-to-

sediment ratio, by pond and season

Month )PAH16 )PAHLMW )PAHHMW

Pond 67 August 4.8 ± 3.3 8.9 ± 5.3 2.4 ± 1.8

December 2.7 ± 1.0 2.9 ± 1.9 2.7 ± 1.0

Pond 100 August 5.8 ± 1.0 6.4 ± 1.2 4.6 ± 0.6

December 4.1 ± 1.4 3.6 ± 1.3 8.5 ± 5.6

Pond 37 August 7.0 ± 5.4 11.4 ± 5.9 4.8 ± 4.0

December 21.0 ± 13.0 7.0 ± 3.3 34.3 ± 28.1

Mean of 3 sample sites per pond ± one standard deviation.

Table­ 4

Kiawah PAH source diagnostic ratios and selected literature values, ± standard deviation

FLTH/PYR PHEN/ANTH B[a]A

Pond 67 1.01 ± 0.36 96.8 ± 129 0.71 ±

Pond 100 1.32 ± 0.24 56.9 ± 39.9 0.43 ±

Pond 37 1.18 ± 0.19 18.4 ± 14.6 0.68 ±

Urban backgrounda 0.91 ± 0.2 2.13 0.83 ±

Auto emissions 0.6–0.9b 0.53 ±

Coal combustion 1.4b 1.11 ±

4-stroke marined 1.01 2.24 1.23

2-stroke marined 0.96 5.29 1.59

For Pond 67, n = 9, (March, August, and December samples at 3 sites) and for Ponds 100 a Sediment data from 11 US urban harbors (Stout et al., 2004.) b Reported in Ke et al. (2002). c Atmospheric & surface water particulate matter and surface sediments of Chesapea d Emissions in water from outboard marine engines, 2-stroke is average of fuel inject

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0.35

0.40

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