ARTICLE pubs.acs.org/est
Bottlenose Dolphins as Indicators of Persistent Organic Pollutants in the Western North Atlantic Ocean and Northern Gulf of Mexico John Kucklick,*,† Lori Schwacke,‡ Randy Wells,§ Aleta Hohn,|| Aurore Guichard,† Jennifer Yordy,† Larry Hansen,|| Eric Zolman,‡ Rachel Wilson,^ Jenny Litz,# Doug Nowacek,z Teri Rowles,$ Rebecca Pugh,† Brian Balmer,§ Carrie Sinclair,& and Patricia Rosel@ †
)
National Institute of Standards and Technology, Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, South Carolina 29412, United States ‡ National Oceanic and Atmospheric Administration (NOAA) National Ocean Service, Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, South Carolina 29412, United States § Chicago Zoological Society, c/o Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, Florida 34326, United States NOAA National Marine Fisheries Service (NMFS), 101 Pivers Island Road, Beaufort, North Carolina 28516, United States ^ Department of Oceanography, Florida State University, 117 N. Woodward Avenue, Tallahassee, Florida 32036, United States # NOAA NMFS, 75 Virginia Beach Drive, Miami, Florida 33149, United States z Duke Marine Laboratory, Duke University, Duke Marine Lab Road, Beaufort, North Carolina 28516, United States $ Marine Mammal Health and Stranding Program, NOAA NMFS, 1315 East-West Highway, Silver Spring, Maryland 20910, United States & NOAA NMFS, 3209 Frederic Street, Pascagoula, Mississippi 39567, United States @ NOAA NMFS, 646 Cajundome Boulevard, Suite 234, Lafayette, Louisiana 70506, United States
bS Supporting Information ABSTRACT: Persistent organic pollutants (POPs) including legacy POPs (PCBs, chlordanes, mirex, DDTs, HCB, and dieldrin) and polybrominated diphenyl ether (PBDE) flame retardants were determined in 300 blubber biopsy samples from coastal and near shore/estuarine male bottlenose dolphins (Tursiops truncatus) sampled along the U.S. East and Gulf of Mexico coasts and Bermuda. Samples were from 14 locations including urban and rural estuaries and near a Superfund site (Brunswick, Georgia) contaminated with the PCB formulation Aroclor 1268. All classes of legacy POPs in estuarine stocks varied significantly (p < 0.05) among sampling locations. POP profiles in blubber varied by location with the most characteristic profile observed in bottlenose dolphins sampled near the Brunswick and Sapelo estuaries along the Georgia coast which differed significantly (p < 0.001) from other sites. Here and in Sapelo, PCB congeners from Aroclor 1268 dominated indicating widespread food web contamination by this PCB mixture. PCB 153, which is associated with nonAroclor 1268 PCB formulations, correlated significantly to human population indicating contamination from a general urban PCB source. Factors influencing regional differences of other POPs were less clear and warrant further study. This work puts into geographical context POP contamination in dolphins to help prioritize efforts examining health effects from POP exposure in bottlenose dolphins.
’ INTRODUCTION The U.S. coastline differs both regionally and locally in the amount and type of human development, land use, and land cover. Land-use differences among coastal areas are reflected in both contamination concentration and profile in U.S. estuaries and coastal waters.1 Likewise, land use and population densities influence contaminant concentrations in sessile aquatic organisms, such as bivalves, which have been monitored routinely for decades through programs such as the National Oceanic and Atmospheric Administration’s (NOAA) Mussel Watch r 2011 American Chemical Society
Program.2 Not surprisingly, the highest persistent organic pollutant (POP) concentrations in bivalves are associated with industrial areas or urbanization thus validating the utility of sessile organisms for monitoring contamination of estuarine areas.1 Received: December 16, 2010 Accepted: April 6, 2011 Revised: March 18, 2011 Published: April 28, 2011 4270
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Table 1. Sample Size, Collection Method, and Lipid Content (%, Mass Fraction) of Blubber Biopsies Collected from Male Bottlenose Dolphins at 14 U.S. Atlantic and Gulf of Mexico Locationsa sample type location
totals (n)
surgical
Bermuda
3
--
Cape May, NJ
3
3
Beaufort, NC Holden Beach, NC
2 3
2 3
Charleston, SC
20
Sapelo, GA
37
Brunswick, GA
lipid (%)
dart
dolphin stock type
population in adjacent countiesb
mean
SD
3
50.0
10.2
offshore
--
51.5
2.0
coastal
---
60.6 56.2
-3.2
estuarine coastal and estuarine
230,600 --
10
10
32.1
8.0
estuarine
558,100
--
37
22.0
9.8
estuarine
11,700
38
--
38
23.9
8.7
estuarine
127,400
Biscayne Bay, FL-North
15
--
15
26.4
9.8
estuarine
2,446,900
Biscayne Bay, FL-South
15
--
15
26.4
6.9
estuarine
--
Sarasota Bay, FL
46
46
--
36.7
16.5
estuarine
707,700
Tampa Bay, FL Apalachicola Bay, FL-East
5 20
---
5 20
15.7 30.4
7.7 7.4
estuarine coastal and estuarine
2,125,800 44,000
64,200 --
St. Joseph Bay, FL-West
38
5
33
32.3
11.9
coastal and estuarine
184,200
Mississippi Sound, MS
55
--
55
29.2
6.3
coastal and estuarine
658,500
a
Location details are given in Table S1. b Data are from the U.S. census Bureau (www.census.gov) and include population living in counties adjacent to dolphin sampling locations (see Supporting Information).
Monitoring programs in the marine environment frequently rely on higher trophic animals to establish geographic trends of environmental contamination.3 For example, studies undertaken in the arctic and North American Great Lakes regions have illustrated regional differences of current-use brominated flame retardants measured in herring gull eggs.4 Marine mammals in particular serve as useful environmental contamination indicators; many species are top-level predators and have a high potential to biomagnify pollutants. Additionally, some marine mammal species such as the bottlenose dolphin (Tursiops truncatus) have population subgroups demonstrating high site fidelity for coastal embayments and therefore have the potential to reflect POP contamination in that area. Few studies, however, have linked site characteristics to POP levels seen in marine mammals.5 The bottlenose dolphin is a particularly suitable species for examining regional trends of environmental contaminants in U.S. coastal areas. The species is broadly distributed, inhabiting estuarine and near shore waters along nearly the entire U.S. coast.6 Stocks that remain within a given coastal area or estuary year-round are recognized from North Carolina southward on the East Coast and along coastal areas of the Gulf of Mexico.6,7 Sampling of live bottlenose dolphins along the U.S. Atlantic coast was previously used to identify geographic variations in POP concentrations and patterns. Concentrations of polychlorinated biphenyls (PCBs) in adult male and juvenile bottlenose dolphins were significantly higher in Charleston, SC and Beaufort, NC relative to those in the Indian River Lagoon (IRL), FL.8 Polybrominated diphenyl ether (PBDE) concentrations were also significantly higher in dolphins sampled near Charleston, SC as compared to those sampled in the IRL.9 Litz et al.10 observed that similar POP variations in dolphins exist within a much smaller geographic area. Within Biscayne Bay, a coastal embayment adjacent to Miami, FL, resident bottlenose dolphins preferring the more urbanized, northern part of the bay had significantly higher ∑PCB concentrations than animals preferring the less urbanized, southern portion of the bay. Likewise, dolphins
living near a PCB-contaminated site in southern Georgia accumulate a PCB signature characteristic of that site.11 Cumulatively, these results suggest that bottlenose dolphins reflect the concentrations of contaminants within their environment, and proximity to urban or industrial sources increases their POP exposure. The current investigation greatly expands on previous efforts, integrating data from 14 independent studies with the goal of improving the understanding of factors influencing the concentrations and profiles of POPs in coastal bottlenose dolphins to help prioritize future work on POP health effects on marine mammals in near shore environments. Collection and sample processing protocols were standardized across studies, and all chemical analyses were conducted at the same laboratory, ensuring the comparability of results. The motivation for this effort stems from the observation that bottlenose dolphins routinely achieve POP concentrations in the tens or hundreds of parts per million and that POP concentrations of this magnitude may impact bottlenose dolphin health.
’ MATERIALS AND METHODS Sample Collection. A total of 300 blubber samples from male dolphins were collected from 2000 to 2007 from 14 locations along the U.S. East Coast (n = 8 locations), the Gulf of Mexico (n = 5 locations), and from Bermuda (Tables 1 and S1 in the Supporting Information (SI)). Sampling locations ranged from highly urbanized estuaries (e.g., Tampa Bay, FL and northern Biscayne Bay, FL) to more rural sites (e.g., Sapelo Island, GA and waters east of Apalachicola Bay, FL)(Figure 1). Animals sampled included those considered estuarine residents (estuarine stock), members of coastal stocks, or the Atlantic offshore ecotype (Table 1).6,7,10 Blubber samples were collected from live bottlenose dolphins by dart biopsy10 or by surgical biopsy during dolphin health assessment.12 Both techniques sample the full blubber thickness. Similar collection protocols utilizing solvent-rinsed instruments and Teflon storage containers were followed to ensure sampling 4271
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Figure 1. Geometric mean concentrations (mg/kg lipid) of Σchlordanes (ΣChlor), ΣDDTs, and ΣPCBs in bottlenose dolphin blubber.
comparability.13 Following collection, field samples were frozen in liquid nitrogen vapor shippers and then transferred to 80 C freezers for long-term storage until analysis.13 Sex was determined from skin using molecular methods.14 Dolphin length and age were not available for dart biopsied animals and it was assumed that sampling with respect to these two variables occurred randomly across the study. In addition, female dolphin samples were not included as POP concentrations vary greatly in females due to lactation loss and reproductive history was unknown for the majority of female dolphins sampled.15 Persistent Organic Pollutant Determination. POPs in blubber were determined using methods described elsewhere10,15 and included pressurized fluid extraction (PFE), size exclusion, and alumina solid phase extraction cleanup followed by gas chromatography mass spectrometry (GC/MS) using two different capillary columns (see SI) and two different ion sources. Samples were processed in lots of 3040 that included at least one blank and 13 aliquots of National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1945 Organics in Whale Blubber16 as a control sample. POPs determined in SRM 1945 averaged within 7.5% ( 3.5% of certified values. Statistical Analysis. Concentration data were lipid-normalized and log-transformed prior to statistical analysis to meet assumptions of normality and equal variance. A multivariate analysis of variance (MANOVA; JMP 7, SAS Institute, Cary, NC) was used to compare POP concentrations among locations; HCB, dieldrin, ΣPCB (sum PCB congeners in S2), ΣChlor (sum of cis- and trans-chlordane and nonachlor, oxychlordane, and heptachlor epoxide), ΣPBDE (sum of PBDE congeners 47, 99,
100, 153, and 154), and the ΣDDT (sum of 2,40 - and 4,40 -DDD, DDE, and DDT) were included as response variables and sampling location was the effects variable. ΣAroclor 1268 congeners is the sum of PCB congeners 201, 180 þ 193, 207, 194, 202, 187, 196, 199, 208, 209, and 206, which comprise, respectively, 0.6%, 0.9%, 1.8%, 2.7%, 3.0%, 3.0%, 7.1%, 9.1%, 9.9%, 11%, and 50% (mass fraction) of total PCBs in sediment adjacent to the Aroclor 1268 Superfund site.17 Individual one-way analysis of variances (ANOVAs) followed post hoc by Tukey’s Honestly Significant Difference (HSD) tests were then used to determine which locations were significantly different. Principal Components Analysis (PCA) using a correlation matrix was performed to investigate the variance of POP patterns among locations. Compounds with less than 75% detection were excluded from the PCA analysis, and values below the limit of detection were replaced with 1/2 of the limit of detection. Concentrations were converted to a percent of total basis and mean centered to remove concentration bias.
’ RESULTS AND DISCUSSION Comparison between Remote Dart and Surgical Blubber Biopsies. Blubber samples were obtained from 300 male
bottlenose dolphins from 14 locations (Figure 1). Samples were primarily collected using dart rather than surgical biopsies (231 versus 69, respectively) (Table 1). Samples from two locations, St. Joseph Bay and Charleston, were collected using both biopsy types prompting a comparison between the two collection techniques. Lipid content (%) was significantly lower in dart than in surgical biopsies from St. Joseph Bay dolphins 4272
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3 Bermuda
L95% and U95% are the lower and upper 95% confidence limits, respectively. a
81.9
86.1 17.4 38.8 70.1 13.7 30.9 12.2 2.19 5.16 3.37 0.82 1.66 0.41 0.06 0.15 1.45 0.26 0.62 0.51 0.12
78.9
55 Mississippi Sound
0.24
56.4
50.4 63.0
68.0 46.4
43.2 27.3
31.7 38.4
34.4 3.48
5.75 3.85
2.15 2.74
4.70 4.46
1.80 1.21
3.20 3.78
1.47 0.27
0.69 0.43
0.15 0.20
0.55 1.82
0.70 0.43
1.22 1.49
0.55 0.04
0.09 0.07
0.03 38 St. Joseph Bay
0.080
5 20 Tampa Bay East of Apalachicola Bay
0.034
203 45.1
94.7 54.1
58.9 24.3 109 33.1
71.6 49.7
53.5 32.0 15.1 17.0
26.9 36.5
28.4 23.3 32.3 3.82
29.9 17.7
8.54 1.97 16.6 2.74
23.0 2.29
2.48 0.91 0.83 0.53
1.59 1.91
1.43 0.69 2.09 0.26
2.05 1.24
0.45 0.12 0.97 0.17
1.59 2.81
5.28 0.88 1.40 0.46
1.37 1.96
2.72 0.63 0.05 0.04
0.10 0.07
0.01 0.02
33 Sarasota Bay
0.086
15
0.024 0.032
224
48.2 23.6 33.7 11.6 5.57 8.03 2.71 1.26 1.85 1.19 0.63 0.87 0.24 0.10 0.15 0.14 0.06 0.09 0.02 0.01
658
Biscayne Bay - South
0.016
110
307 450
157 23.0
36.1 18.9
11.1 15.9
26.1 6.32
9.32 4.33
3.90 4.97
6.35 3.24
4.57 2.85
1.72 2.36
3.61 0.57
0.81 0.34
0.30 0.41
0.52 0.23
4.30 1.94
0.11 0.16
2.89 0.075
0.05 0.03
0.04
15 Biscayne Bay - North
0.037
19 Brunswick
0.055
135
229 126
72.6 98.9
170 35.4
45.2 24.0
19.57 26.3
32.9 11.8
8.39 4.52
6.05 8.43
6.16 5.12
6.66 3.85
3.10 3.98
5.06 1.71
0.21 0.13
0.79 1.16
0.16 3.25
1.60 0.82
1.80 2.42
1.15 0.21
0.067 0.04
0.12
30 Sapelo
0.053
20 Charleston
0.16
310
115 127 16.3 25.7
62.8 139
43.3 57.1 57.0 38.0
115 22.5
7.68 7.39 20.9 16.8
51.0 21.3
7.11 9.86 0.87 1.77
3.83 9.03
2.48 4.18 3.47 7.41
13.3 3.23
0.61 1.80 1.46 3.65
6.56 5.96
2.76 2.33 0.24 0.32
0.82 2.22
0.82 0.87 1.09 0.39
0.53 0.10
0.13 0.07 0.38 0.17
0.23 0.25
0.09 0.18 0.02 0.04
0.06
2 3
0.038 0.084
3
Beaufort Holden Beach
0.12
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Cape May
L95% U95% L95% mean
L95%
U95%
mean
L95%
U95%
mean
L95%
U95%
mean
L95%
U95%
mean
L95%
U95%
mean
ΣDDT ΣChlor ΣPBDE dieldrin mirex HCB n location
Table 2. Geometric Mean Concentrations (mg/kg Lipid Mass) of Persistent Organic Pollutants in Bottlenose Dolphin Blubber from 14 Locationsa
mean
ΣPCB
U95%
Environmental Science & Technology
(Wilcoxon Rank Sum, p < 0.05); however, dart versus surgical biopsies from Charleston were not significantly different in lipid content. Concentrations of POP classes (Table 2), when expressed either on a lipid or wet mass basis, in dart and wedge biopsies from the two locations were not significantly different (Wilcoxon Rank Sums and t test, for St. Joseph Bay and Charleston, respectively). As a result, POP data from the two sample types were pooled for analysis. Ranges of Lipid and POP Concentrations. Lipid content (% mass fraction) ranged from 3.4% to 62% in male bottlenose dolphin blubber. Blubber lipid content varied significantly among sites (ANOVA, p < 0.0001), with higher content in animals sampled from Beaufort, Holden Beach, Cape May, and near Bermuda than most other locations (Figure S2). The variation in lipid content among locations may be due to numerous factors including ontogeny, nutritional status, and water temperature.13,18 POP concentrations in blubber were lipid-normalized for among-site comparisons, and concentrations presented are lipid-based. Samples were collected in both late fall/winter and summer at Sapelo, Brunswick, Sarasota Bay, and St. Joseph Bay while all other sites had nonwinter collections. Lipid-normalized POPs were significantly lower (t test, p < 0.05) in winter versus summer samples at Sapelo, Brunswick, and Sarasota Bay, therefore among-site comparisons excluded samples collected in the late fall/winter. Lipid-normalized POP concentrations in bottlenose dolphin blubber from the 14 locations are presented in Table 2 and in Figures 1 and S1. ΣPCB was the POP class present at highest concentrations, with ΣPCB (geometric mean values are reported throughout; error is given in Table 2 as upper and lower 95% confidence limits) concentrations ranging from 33.1 mg/kg in bottlenose dolphins from east of Apalachicola Bay up to 450 mg/kg in dolphins sampled from Brunswick (Figure 1; Table 2). The highest concentration observed was 2900 mg/kg in a dolphin sampled from Brunswick, a site heavily contaminated with the commercial PCB mixture Aroclor 1268.19 The mean ΣPCB concentration in the Brunswick dolphins was twice that observed in male transient killer whales from the Northeast Pacific Ocean that have elevated POP concentrations due to marine mammal consumption.20 ΣDDT was the compound class with the next highest concentration ranging from 8.03 mg/kg in Biscayne Bay-south up to 51.0 mg/kg in dolphins sampled near Cape May. In order of decreasing rank, concentrations of ΣDDT were followed by ΣChlor, ΣPBDE, mirex, dieldrin, and HCB (Table 2; Figures 1 and S1). Difference in POP Classes among Locations. Differences in POP concentrations among sites were assessed in fewer locations. Cape May, Beaufort, Holden Beach, and Bermuda were excluded due to small sample size (
