Bioaccumulation and enantiomeric profiling of organochlorine pesticides and persistent organic pollutants in the killer whale (Orcinus orca) from British and Irish waters

Available online at www.sciencedirect.com

Marine Pollution Bulletin 54 (2007) 1724–1731 www.elsevier.com/locate/marpolbul

Note

Bioaccumulation and enantiomeric profiling of organochlorine pesticides and persistent organic pollutants in the killer whale (Orcinus orca) from British and Irish waters Brendan McHugh

b

a,*

, Robin J. Law b, Colin R. Allchin b, Emer Rogan c, Sinead Murphy M. Barry Foley e, Denise Glynn a, Evin McGovern a

c,d

,

a Marine Institute, Rinville, Oranmore, Galway, Ireland Centre for Environment, Fisheries and Aquaculture Science, Cefas Burnham Laboratory, Remembrance Avenue, Burnham on Crouch, Essex CM0 8HA, UK c Department of Zoology, University College Cork, Ireland d Sea Mammal Research Unit, Gatty Marine Laboratory, University of St Andrews, St Andrews, Fife KY16 8LB, UK e Dublin Institute of Technology, Kevin Street, Dublin 8, Ireland

Abstract Concentrations and enantiomeric profiles for a range of organochlorine compounds are reported in blubber samples from a number of individual killer whales (Orcinus orca) from British and Irish waters. Elevated contaminant levels and enriched isotopic ratios were determined in one individual whale sampled in the Scottish Western Isles compared to the others suggesting marine mammal based dietary influences. The potential application of isotopic ratios to model contaminant uptake, enantioselective enrichment and accumulation is demonstrated. Data are presented which provide information on enantioselective enrichment factors (EFs) for o,p 0 -DDT, a-HCH and toxaphene congeners CHB26 and CHB 50. This dataset further improves the current database on reported levels of a number of contaminants and provides additional background information on potential metabolic processes in killer whales from British and Irish waters.  2007 Elsevier Ltd. All rights reserved. Keywords: Killer whale; Persistent pollutant; Organochlorine; Isotope ratios

1. Introduction The killer whale (Orcinus orca) is a widely distributed, and intensely social marine mammal living in stable pods consisting of up to 50 individuals, in localised resident populations, or in highly migratory groups (Matkin and Leatherwood, 1986). In British and Irish waters, the killer whale has been observed along the Atlantic seaboard and in the northern North Sea (Evans, 1992), while sightings are rare in the English Channel and in the southern North Sea (Reid et al., 2003). Killer whales have been shown to prey on fish, squid, seals, sea otters, birds and small cetacean *

Corresponding author. Tel.: +353 0 91387200. E-mail address: [email protected] (B. McHugh).

0025-326X/$ - see front matter  2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2007.07.004

species and occasionally on blue, gray and sperm whales, seals and other cetacean species (Guinet, 1992; Jefferson et al., 1991; Hoyt, 1990; Pitman et al., 2001; Rice, 1968; Vos et al., 2006), and represent the top predator in many marine food webs. In the North Atlantic, herring, mackerel, salmon, cod and halibut have been shown to be among the main prey species of killer whales (Evans, 1980; Couperus, 1993; Ugarte and Simila, 1993). Regular predation of both harbour and grey seals around the Shetland Islands, off the Northeast coast of Scotland, has been reported (Fisher et al., 1999). Furthermore, porpoises and possibly other small cetaceans are also hunted in inshore waters (Fisher et al., 1999). Sighting records of wellmarked individuals off the Shetland Islands, suggest that individuals are returning to certain seal haul out sites,

B. McHugh et al. / Marine Pollution Bulletin 54 (2007) 1724–1731

and one pod reportedly killed as many as four seals during a single feeding episode (Fisher et al., 1999). Based on their lipophilic nature, environmental persistence and bioaccumulation potential, organochlorine pesticides (OCPs) represent a threat to marine organisms in general, but especially to those occupying the top of the marine food web, including marine mammals (Tanabe et al., 1994; Loganathan and Kannan, 1994; Calambokidis and Moore, 2004; O’Shea and Brownell, 1994; Jarman et al., 1996). The presence of such xenobiotic compounds has been linked to many health problems including dysfunctions in the reproductive and immune systems in marine mammals (Helle et al., 1976; Reijnders, 1986; Beland et al., 1992; de Swart et al., 1994). Marine mammals have low metabolic and/or excretory capabilities for these pollutants and so may exhibit adverse physiological and behavioural effects as a result of sustained exposure (Brooks, 1974; Hutzinger et al., 1974; Tanabe et al., 1988). While enantiomers of environmental contaminants may have identical physico-chemical properties, selective binding to structure-sensitive biological receptors may result in different degradation/accumulation rates in biota (Kallenborn and Hu¨hnerfuss, 2001; Fisk et al., 2001). Degradation and/or enrichment of individual enantiomers from the racemate has been shown to occur to varying degrees in abiotic and biological systems, however, few data are available related to enantiospecific degradation/enrichment of OCPs in marine mammals and especially in killer whales. The measurement of stable isotopes of nitrogen have previously been employed to assess relative trophic levels in aquatic biota, and as such have been shown to provide a quantitative, continuous variable for studying nutrient assimilation and the biomagnification of contaminants

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within complex food webs (De Niro and Epstein, 1978; Minigawa and Wada, 1984; Peterson and Fry, 1987; Rounick and Winterbourn, 1986; Fisk et al., 2001; Ruus et al., 2002; Hobson, 1999). Krahn et al. (2007) and Herman et al. (2005) report the application of stable isotope techniques in identifying a Pacific offshore killer whale ecotype and in further elucidating their dietary preferences, however few stable isotope based data are available for North Atlantic killer whales. Primary study objectives were to investigate the influence of stable isotope derived trophic status on the levels, bioaccumulation and enantioselective profile of selected OCPs and persistent organic pollutants in killer whales from British and Irish waters. 2. Materials and methodology Krahn et al. (2007) report blubber contaminant levels and stable isotope ratios in lipid free skin tissue of Pacific killer whales sampled by biopsy techniques. While it is preferable that biopsy-derived tissues are used for contaminants and stable isotopes analysis (Krahn et al. (2004, 2007), such sampling strategies are not readily achievable in killer whales from North Atlantic waters. Killer whales samples in this present study were obtained as a result of live stranding events or were collected from individuals washed ashore following death at sea. Post-mortem studies and the collection and preservation of tissue samples were conducted according to previously established protocols (Kuiken and Baker, 1993; Law et al., 2006). Sampling and biological details are reported in Table 1, and location information is illustrated in Fig. 1. The study sample comprised four females ranging in length from 525 to 610 cm (n = 3), two males ranging in length from 590 and 610 cm (n = 2) and one unsexed individual.

Table 1 Killer whale sampling and biological information Reference

Sex

Age (yrs)

Length (mm)

BT (mm)

Collection date

Location

Latitude

Longitude

Cause of death

British waters SW1995/54

F

24

525

28

26-04-95

5119.00 0

122.00 0

Starvation (Law et al., 1997)

SW1994/56a

F

NA

550

NA

15-04-94

5834.10 0

346.57 0

Tooth rot infection

SW1994/169a

M

NA

610

60

16-11-94

6016.15 0

111.73 0

Live stranding

SW1994/177b1

NA

NA

NA

NA

07-12-94

6041.31 0

055.17 0

No information

SW1997/135c

F

NA

610

30

16-08-97

5748.30 0

704.90 0

SW2001/234

M

NA

590

40

09-10-01

Pegwell Bay, Kent, England Sandside Bay, Reay, Scotland Catfirth Voe, Shetland, Scotland Uyeasound, Shetland, Scotland Harris, Western Isles, Scotland River Mersey, England

5326.02 0

300.97 0

Old age/worn teeth and tooth rot infection Starvation

Irish waters ENV-01

F

40–50

545

NA

08-07-01

5147.00

815.30 0

BT: Blubber thickness (mm). NA: not available.

Roches point, Cork, Ireland

Worn teeth causing Staphylococcus aureus septicaemia (Power and Murphy, 2002)

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B. McHugh et al. / Marine Pollution Bulletin 54 (2007) 1724–1731

Fig. 1. Geographic distribution of killer whale sampling locations.

2.1. OCP analysis OCPs were extracted from homogenised tissue samples utilising either Soxhlet apparatus or the method developed by Smedes (QUASH, 1998, 1999). Lipid extracts were cleaned up by alumina column chromatography followed by separation of PCBs from the chlorinated pesticides using silica gel column chromatography. OCP concentrations were determined by dual column Gas Chromatography with Electron Capture Detection (GC-ECD) using Varian 3800 or HP6890 instrumentation on fused silica capillary columns HT8, (J&W Scientific, Inc.) and CPSIL 8CB and CP-SIL 19CB, (Chrompack, Varian Inc.) and DB5 (J&W Scientific, Inc.) according to Glynn et al. (2003) and Allchin et al. (1989).

with two characteristic ions used for individual compound identification. GC-EI-MS was utilized for identification of enantiomerically separated o,p 0 -DDT, while negative chemical ionization (NCI) techniques were used for detection of all other OCPs. The enantiomeric composition was expressed on an enantiomer fraction (EF) basis as per Kallenborn and Hu¨hnerfuss (2001), and de Geus et al. (2000), calculated from peak areas of enantiomeric pairs by the following formula: EF ¼

ðÞA ðÞA þ ðþÞA

where A = peak area of the (+) and () enantiomers. EFs < 0.5 or >0.5 indicate selective depletion/enrichment of (+) and () enantiomers, respectively.

2.2. Enantiomeric separation 2.3. Stable isotope analysis Cleaned up sample extracts were analysed on a Varian 1200 Triple Quad by Gas Chromatrography Mass Spectrometry (GC-MS) utilizing a BGB-172 (20% tert-butyldimethylsilylated b-cyclodextrin dissolved in BGB-25) chiral column (BGB Analytik AG, Adiswil, Switzerland), dimensions (30 m · 0.25 mm id · 0.18 lm film thickness)

Tiezen et al. (1983) reports that the presence of lipid in biotic tissue samples can affect isotopic ratio determinations while Krahn et al. (2007) and Herman et al. (2005) both report analysis of stable isotopes on lipid free killer whale tissue. For the purposes of this study, lipid free tissue

B. McHugh et al. / Marine Pollution Bulletin 54 (2007) 1724–1731

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extracts were therefore prepared on all tissue samples according to the method of Smedes (QUASH, 1998, 1999) prior to stable isotope analysis. Lipid free tissues were freeze-dried and approximately 1 mg of sample was transferred to a 9 · 15 mm tin capsule before combustion in the presence of O2 and Cr2O3 at 1700 in a Carlo Erba NCS 2500 element analyser. Reduction of NOx to N2 was then performed in a Cu oven at 650 C. H2O was removed in a KMnO4chemical trap before separation of N2 and CO2 on a 3 m Poraplot Q GC column prior to on-line detection of d15N and d13C using a Micromass Optima Isotope Ratio Mass Spectrometer. Differences in stable isotope abundances are expressed by (d) notation as the deviation from standards in parts per thousand (&) by

Enantiomerically pure standards of a-HCH, (Dr. Ehrenstorfer, GmbH, Hamburg Germany) were analysed on a batch basis to ensure correct enantiomeric assignment. Enantiomerically pure standards for o,p 0 -DDT and two toxaphene congeners (CHB 26 and CHB50) are not currently commercially available, therefore a racemic mixture of each was employed for identification purposes. Enantiomers were then assigned nomenclature EN1 and EN2 (first and second eluting, respectively) for the purposes of this study.

dX ¼ ½ðRsample =RStandard Þ  1  1000

Nitrogen isotopic ratios (d15N) in individual killer whale blubber samples were determined to lie in the range 14.5–17.3& (see Table 2) suggesting that different (d15N derived) trophic status levels may exist in the killer whales sampled (De Niro and Epstein, 1978; Minigawa and Wada, 1984; Peterson and Fry, 1987). Highest d15N and lowest dC ratios were observed in the killer whale SW1997/135c from Harris, in the Western Isles, Scotland. Higher d15N ratios suggest that this individual may be of higher trophic status than the other individuals, while lower d13C results suggest that this individual may have derived its primary carbon intake from an offshore higher trophic status source than those of the other animals (Das et al., 2003). Salmon fish bones were found in the stomach of the Irish killer whale, however no dietary information is available for any of the other individuals. In such trophic level studies d15N and dC measurements are often ‘‘baseline’’ corrected using stable isotope ratio data from primary producers and/or prey organisms. In the absence of such prey data no baseline correction of (d15N and d13C) measurements were completed when estimating killer whale relative trophic status and contaminant uptake. Das et al. (2003) and Hobson et al. (2002) report that the general pattern of inshore, benthos-linked food webs tends to be more enriched in 13C compared to offshore, pelagic food webs. This hypothesis would support the findings of the current study, where killer whale SW1997/135c d13C data suggests that this whale may have derived a proportion of its prey from a marine-mammal and/or other high trophic level source.

where X relates to 13C or 15N and R is the corresponding ratio 13C/12C or 15N/14N. Rstandard for 13C and 15N relate to Pee Dee Belemnite standard and atmospheric N2, values, respectively. 2.4. Analytical quality control Although proficiency exercises related to analysis of OCPs in marine mammals are not currently available in Europe, both laboratories show continued successful participation in the Quality Assurance of Information for Marine Environmental Monitoring in Europe (QUASIMEME) laboratory proficiency scheme for the analysis of OCPs in other marine biological tissue. Full analytical quality control protocols involving the use of PCB112 as an internal standard for quantitation purposes and the analysis of blanks and within batch laboratory reference materials were utilised. LOQs generally ranged from 1 and 5 ng/g for all analytes. Certified Reference Materials (BCR349 cod liver oil) were run with each batch of samples with recovery criteria ranging from 70% to 120% of the certified values for individual analytes. Stable isotope analysis was completed in the Institute for Energy Technology (IFE) in Kjeller, Norway. Accuracy and precision of d15N and d13C analyses was evaluated against International Atomic Energy Agency (IAEA-N-1, IAEA-N-2) and US Geological Survey (USGS-24) standards in addition to an internal IFE trout standard material.

3. Results and discussion 3.1. Trophic status/stable isotope analysis

Table 2 Carbon and nitrogen isotopic ratios (&) and enantiomeric factors (EFs) for chiral OCPs in killer whale blubber samples Reference no.

dC

dN

a-HCH

o,p 0 -DDT

CHB26

CHB50

SW1994/56a SW1994/169a SW1994/177b4 SW1997/135c SW2001/234 ENV-01-DB

14.9 15.3 16.7 12.9 15 15

14.8 15 14.5 17.3 15.6 15.2

0.17 0.40 0.44 0.14 NA 0.49

0.49 0.49 0.52 0.41 0.52 0.55

0.52 0.51 0.49 0.52 0.49 0.52

0.47 0.45 0.51 0.54 0.49 0.50

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3.2. OCP levels in North Atlantic killer whales OCP levels were highest in lipid rich blubber tissues compared to muscle and kidney tissue. Wet weight OCP levels in the dorsal blubber of one individual (ENV-01) were found to be higher than those in mid blubber. Overall OCP levels were more elevated in one individual (SW1997/ 135c) than in the other whales analysed (see Table 2). Within the North East Atlantic, killer whales are known to feed predominately on fish species, however killer whales have been reported to feed on seals off the Shetland Islands (Fisher et al., 1999). Ylitalo et al. (2001) suggest that higher contaminant concentrations found in transient killer whales (as against residents) can be attributed to dietary differences in the two ecotypes, i.e. transient killer whales feed largely on marine mammals, with elevated POP levels, while resident animals are primarily piscivores. Stable isotope data from this study supports that hypothesis and suggests that this individual (SW1997/ 135c) may have been of a higher trophic status and had a greater marine mammal and higher trophic species influence in its feeding ecology than the other individuals. While it is still unclear to what extent killer whales in European waters feed on higher trophic level sources this current stable isotope dataset suggests that some killer whales may derive a proportion of their diet from such species.

3.3. HCH and HCB in North Atlantic killer whales Concentrations of a-HCH and c-HCH in individual blubber tissues ranged from <0.001 to 0.3 and from <0.001 to 0.18 mg/kg wet weight, respectively suggesting that killer whales, in common with a number of other marine species may have the capacity to regulate HCH levels within their metabolic system. Moisey et al. (2001) further suggested that the ability of an organism to degrade/eliminate a-HCH increases with trophic level. De Bruijn et al. (1989) and Isnard and Lambert (1988) further report that based on the log Kow value for a-HCH and associated isomers, HCH isomers would be expected to show relatively low levels of bioaccumulation. Krahn et al. (2007) report RHCH levels in the range 0.11–1.00 mg/kg lipid weight and 4.1–16 mg/kg lipid weight in resident and transient North Pacific killer whales, respectively. Herman et al. (2005) report RHCH in the range 0.2–1.0 mg/kg lipid weight in resident killer whales and from 6.3 to 15 mg/kg lipid weight in transient Pacific animals. Levels of RHCH in this current study range from
tially explaining the low levels of HCB observed in this study. 3.4. DDT and PCBs in killer whales This study found p,p 0 -DDE followed by (R)7 PCBs to be the predominant contaminants determined in all samples. In one female individual (SW1997/135c) from Scottish waters levels of p,p 0 -DDE reached 386 mg/kg wet weight, between 5 and 148 times higher on a wet weight basis than those determined in any of the other individuals. Additionally, elevated levels of polybrominated diphenylethers have been reported in this individual compared to others from UK waters (Law et al., 2005). The log Kow values for DDT, p,p 0 -DDE and PCB congeners in combination with their relatively low water solubility, can render these contaminant groups difficult to eliminate from within an organism, ultimately leading to bioaccumulation in lipid rich tissues such as blubber. Krahn et al. (2007) report RDDT levels ranging from 1.5 to 51 mg/kg lipid weight and 75 to 4600 mg/kg lipid weight in resident and transient North Pacific killer whales, respectively. Herman et al. (2005) report RHCH ranging from 10 to 35 mg/kg lipid weight in resident killer whales and from 200 to 340 mg/kg lipid weight in transient Pacific animals. RDDT levels in this current study ranged from 8.1 to 609 mg/kg lipid weight. A number of contaminant studies in marine mammals have determined the p,p 0 -DDE/RDDT ratio in order to assess the chronology of DDT inputs. Aguilar (1984) and Tanabe et al. (1997) state that a ratio > 0.6 is indicative of a stable system with no new DDT inputs. In the current study, p,p 0 -DDE/RDDT ratios determined in killer whales blubber samples ranged from 0.73 to 0.96, suggesting that killer whale DDT residues are derived from historic contamination. A degree of caution must be observed when interpreting such ratios however, as several studies in delphinid species (Aguilar, 1984; Borrell et al., 1995; McKenzie et al., 1997) have shown higher transfer rates of p,p 0 DDE from mother to calf during lactation than was observed for p,p 0 -DDT or RDDT, potentially altering the observed ratio. R40PCB levels reported by Krahn et al. (2007) lie in the range 1.9–28 mg/kg lipid weight and 59–720 mg/kg lipid weight in resident and transient North Pacific killer whales, respectively. Herman et al. (2005) additionally report R40PCBs in the range 8.2–25 mg/kg lipid weight in resident killer whales and from 100 to 180 mg/kg lipid weight in transient Pacific animals. For comparative purposes R7PCB levels in this current study ranged from 7.52 to 536 mg/kg lipid weight. 3.5. Trophic transfer and biomagnification of contaminants in killer whales Strong correlations were observed between log(X + 1) normalised OCP data and d15N derived trophic status for

B. McHugh et al. / Marine Pollution Bulletin 54 (2007) 1724–1731 3.00 Log (X+1) p.p'DDE

Log (X+1) Sum DDT

3.00 2.50 2.00 1.50 1.00 0.50 0.00 14.0

2.50 2.00 1.50 1.00 0.50

14.5

15.0

15.5

16.0

16.5

17.0

0.00 14.0

17.5

14.5

15.0

15.5

16.0

16.5

17.0

17.5

16.5

17.0

17.5

δ15 N Ratio 3.00 Log (X+1)Sum 7PCB

Log (X+1) HCB

δ15 N Ratio 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 14.0

1729

14.5

15.0

15.5

16.0

16.5

17.0

17.5

2.50 2.00 1.50 1.00 0.50 0.00 14.0

14.5

15.0

δ15 N Ratio

15.5 16.0 δ15 N Ratio

Fig. 2. Correlations between d15N derived trophic status and log (x + 1) normalised wet weight contaminant data. (a) RDDT (R = 0.88, p < 0.04), (b) p,p 0 DDE (R = 0.88, p < 0.04), (c) HCB (R = 0.80, p < 0.06) and (d) R7PCBs (R = 0.97, p < 0.008).

RDDT (R = 0.88, p < 0.04), p,p 0 -DDE (R = 0.88, p < 0.04) and p,p 0 -DDD (R = 0.83, p < 0.06). Positive correlations were also observed between log(X + 1) normalised PCB congeners CB52 (R = 0.98, p < 0.004), CB101 (R = 0.98, p < 0.003), CB118 (R = 0.98, p < 0.003), CB153 (R = 0.96, p < 0.009), CB105 (R = 0.98, p < 0.004), CB138 (R = 0.97, p < 0.007) and CB180 (R = 0.96, p < 0.008) and the RICES7CBs (R = 0.97, p < 0.008). Weaker correlations were observed for dieldrin (R = 0.85, p < 0.08) and HCB (R = 0.80, p < 0.06), while no correlation was observed between d15N derived trophic status and a- or c-HCH isomers (see Fig. 2). No correlations were observed between d15N derived trophic status and log(X + 1) normalised CB28, CB31 or CB156, each of which were only present in low concentrations. Mackay and Shiu (1992), reported log Kow values for

PCB congeners of between 5 and 8, with the log Kow value increasing with an increase in the degree of chlorination, supporting the findings of this current study where trophic transfer/bioaccumulation is less pronounced for lower chlorinated congeners with lower log Kow values. These results suggest that bioconcentration through the food chain of higher log Kow compounds is the primary exposure route for cetaceans and marine mammals for a number of organochlorine compounds. 3.6. Enantiomeric profiling Structurally sensitive biological receptors in animals can however differentiate between the subtle differences in molecular and enantiomeric configurations of chiral compounds, allowing enantioselective degradation or metabo-

Table 3 Concentrations of selected OCPs in killer whales (Orcinus orca) from British and Irish coastal waters (mg/kg) wet weight

Tissue %Lipida a-HCH c-HCH HCB p,p 0 -DDE p,p 0 -DDD p,p 0 -DDT Dieldrin CB153 R7PCBsb trans-Chlordane cis-Chlordane Aldrin Isodrin

SW1995/54

SW1994/56a

SW1994/169a

SW1994/177b4

SW1997/135c

SW2001/234

ENV-01-DB

ENV-01-MB

ENV-01-KD

ENV-01-MU

ENV-01-VB

B 49.0 0.07 0.05 0.74 18.0 2.90 3.60 2.40 2.90 9.54 NA NA NA NA

B 65.0 0.30 0.07 1.80 46.0 4.70 2.60 5.60 8.30 23.5 NA NA NA NA

B 71.0 <0.001 <0.001 0.27 18.0 0.81 0.62 0.82 3.70 11.6 NA NA NA NA

B 44.0 0.03 0.02 0.07 2.60 0.39 0.49 0.49 1.30 3.31 NA NA NA NA

B 68.0 0.20 0.18 5.80 386 16.0 6.4 50.0 141 365 NA NA NA NA

B 46.0 0.02 0.03 0.38 79.0 1.70 1.80 1.20 19.0 55.3 NA NA NA NA

DB 54.0 0.14 0.02 0.18 36.3 2.29 1.45 NA 19.2 47.0 0.05 0.05 <0.02 <0.02

MB 22.8 0.08 0.01 0.10 11.8 1.27 0.95 NA 13.8 34.1 0.02 0.13 <0.02 <0.02

K NA 0.01 <0.001 <0.03 0.04 0.09 0.04 NA 0.02 0.04 <0.02 <0.01 n.d. NA

M NA <0.001 0.001 <0.03 0.14 0.03 0.02 NA 0.07 0.16 0.08 <0.02 <0.02 <0.04

VB NA 0.13 0.02 <0.03 0.72 2.48 1.58 NA NA NA NA <0.02 <0.03 <0.03

NA = not available, n.d. = not detected, NA = not analysed, B = blubber, DB = dorsal blubber, MB = mid blubber, K = kidney, M = muscle, VB = ventral blubber. a

Hexane extractable lipid (%HEL) for British waters samples.

b

The sum of PCBs 28, 52, 101, 118, 138, 153 and 180.

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lism to take place (Ridal et al., 1997). Selective accumulation, degradation and/or metabolism of a particular enantiomer can provide further information on the fate, dynamics and toxicological relevance of the chemical, and such processes have been reported to occur at different rates between (and often within) species (Wiberg, 2001) and between different organisms at different trophic levels. Enantiomeric fractions for four compounds namely o,p 0 -DDT, a-HCH and toxaphene congeners CHB 26 and CHB50 were determined in each of the individual killer whales. a-HCH showed some enantioselective enrichment with EFs of 0.14–0.49 being determined. Buser and Muller (1992) reported that while each of the HCH isomers and enantiomers have identical physical and chemical properties and abiotic degradation rates, they may have different biotransformation rates. EFs of 0.41–0.55, 0.49–0.52 and 0.45–0.54 were observed for o,p 0 -DDT, CHB26 and CHB50, respectively (see Table 3), these values showed little deviation from that of the racemate. No clear correlations between enantioselective enrichment and (d13C) derived carbon intake or (d15N) derived trophic status was determined. 4. Conclusions Elevated contaminant levels, enriched nitrogen and depleted carbon isotopic ratios were determined in one individual whale from the Scottish Western Isles compared to the other killer whales suggesting marine mammal and/ or higher trophic level dietary influences in this animal. Enantioselective enrichment of a-HCH enantiomers and accumulation was demonstrated. This dataset further enhances the data record on the levels of a number of contaminant groupings and provides additional background information on potential metabolic processes of killer whales from British and Irish waters. Acknowledgements The authors wish to acknowledge the input from Eugene Power Agriculture Food and Rural Development, Model Farm Road, Cork, Ireland, from the Scottish Agriculture College, Inverness and the Institute of Zoology, London and Mr. Ingar Johansen, Energy Technology (IFE) Kjeller, Norway for completion of stable isotope analysis. References Aguilar, A., 1984. Relationship of DDE/RDDT in marine mammals to the chronology of DDT input into the ecosystem. Can. J. Fish Aqua. Sci. 41, 840–844. Allchin, C.R., Kelly, C.A., Portmann, J.E., 1989. Methods of analysis for chlorinated hydrocarbons in marine and other samples. Aquatic Environment protection: Analytical Method MAFF, Directorate of Fisheries Research, Lowestoft, (6), 25pp. Beland, P., De Guise, S., Plante, R., 1992. Toxicology and Pathology of St. Lawrence Marine Mammals, Project Report, World Wildlife Fund, Washington, DC.

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