Biological transport and mammal to mammal transfer of organochlorines in Arctic fauna

https://doi.org/10.1016/S0141-1136(99)00079-3Get rights and content

Abstract

Ringed seal (Phoca hispida) is assumed to be the most important and common prey of polar bears (Ursus maritimus). However, during a scientific survey in the ice area of the northern Barents Sea east of Svalbard in June 1995, an unexpectedly high number of polar bears were observed feeding on harp seal (Phoca groenlandica) carcasses. Samples of both harp and ringed seals were obtained and organochlorine (OC) occurrence and pattern in these two potential polar bear prey species were determined. Significantly higher OC concentrations were found in harp seals, as compared to the ringed seals. All animals in the northern harp seal group were lean specimens in late moult. The industrial chemicals, polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB), and the OC pesticides bis-2,2,(chlorophenyl)-1,1,1-trichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), and chlordanes (CHLORs) were analysed in blubber. The concentrations of ΣPCB (sum of concentrations of 16 PCB congeners) and ΣDDT (sum of concentrations of p,p′-DDT and p,p′-DDE) in the northern harp seal group ranged from 2093 to 20,382 and 1460 to 10,381 ng g−1 lipid weight, with mean concentrations of 11,133 and 6847 ng g−1 lipid weight, respectively. The mean concentrations of the CHLORs, oxychlordane and trans-nonachlor, were 1311 and 3743 ng g−1 lipid weight, respectively, while the mean concentrations of HCB and HCH isomers (α-, β- and γ-HCH) were all <500 ng g−1 lipid weight. No significant difference was found in the mean total blubber mass between the two seal species when collected in June. This indicates that polar bears preying on harp seals instead of ringed seals at this time of the year could accumulate significantly higher PCB concentrations. We suggest that polar bears feeding along the ice-edge east of Svalbard in May and June preferentially prey on harp seals instead of ringed seals, and that this may partly explain the variation in PCB concentrations among polar bears from the Norwegian Arctic. An hypothesis is that the harp seal may function as a transport vector of OCs into the high Arctic environment.

Introduction

The presence of persistent organochlorines (OCs) in biota from pristine areas like the Arctic, is exclusively ascribed to long-range transport Barrie et al., 1992, Bidleman et al., 1982, Pacyna & Oehme, 1988. An essential part of this transport is thought to be of aerial origin, but transport by ocean currents and biological transport is also likely to occur Barrie et al., 1992, Wania & Makay, 1993. The lipophilic nature and persistence of OCs contribute to their high bioaccumulating potential and their biomagnification in biota Gabrielsen et al., 1995, Hargrave et al., 1992, Letcher et al., 1998, Muir et al., 1988, Skaare, 1995, Tanabe et al., 1988. The highest OC concentrations are found in top predator species of marine food webs Bernhoft et al., 1997, Kleivane et al., 1997, Kleivane et al., 1995, Muir et al., 1992, Norstrom et al., 1988, Skaare et al., 1990. Furthermore, the metabolism of these components differs between and within species Boon et al., 1991, Luckas et al., 1990, Tanabe et al., 1988, Tatsukawa, 1992. Thus, the OCs are filtered through the food web resulting in a different OC pattern in, for example, fish, seal and in top predators like the polar bear (Ursus maritimus). Furthermore, different feeding strategies between species and between individuals of a species may influence their OC burden (Tanabe, Tanaka & Tatsukawa, 1984). In environmental monitoring programs, biological data such as age, sex, reproductive status, feeding behaviour, nutritional status and health status, as well as information on the location and date of capture are important and essential when interpreting analytical OC results.

The levels of certain OC pollutants demonstrate a high degree of biomagnification, especially of polychlorinated biphenyls (PCBs) in the Arctic ecosystem Bernhoft et al., 1997, Norheim et al., 1992, Norstrom et al., 1990, Skaare, 1995. The OC burden in marine mammals is exclusively of dietary origin, and variations in prey availability may have an impact on the feeding habits, and possibly also on the migratory behaviour of top predators like the polar bears. The relatively high intraspecies variation in PCB concentrations found in the polar bear population at Svalbard, and the higher PCB concentrations in this population as compared to polar bears from the Canadian Arctic Bernhoft et al., 1997, Norstrom et al., 1990, are not well understood. Relatively little information is available on the feeding habits of polar bears inhabiting the Svalbard area, while polar bears from the Canadian Arctic feed preferentially on ringed seal and bearded seal, and to a lesser extent on other seal species (Stirling & Archibald, 1977). To determine whether these differences in PCB concentrations may be partly due to differences in feeding strategies, we would like to focus on the possiblility of high harp seal predation by polar bears inhabiting the area along the ice-edge east of Svalbard during the moulting season for this seal species. The present study was also designed to investigate whether the harp seal may function as a transport vector for OCs to the high Arctic environment.

Section snippets

Sampling

In April 1993, sternum blubber samples of harp seals were obtained during sealing activities in the moulting areas outside the White Sea (southern ice area), while in June 1995 sternum blubber samples of moulting harp seals and ringed seals were obtained during research surveys in the ice area east of Svalbard, denoted the northern ice area (Fig. 1). Morphometric data were obtained and ventral blubber samples (sternum) were stored at −20°C. The blubber thickness was measured at the sternum and

Results

The concentrations of ΣPCB (16 PCB congeners; PCB Nos. 66, 101, 99, 118, 153, 105, 138, 187, 128, 156, 157, 180, 170, 194, 206 and 209), ΣDDT (p,p′-DDT, p,p′-DDE), ΣCHLOR (oxychlordane, trans-nonachlor), ΣHCH (γ-, α-, β-HCH), and HCB detected in blubber of harp and ringed seals are listed in Table 2, Table 3. These xenobiotics were detected in all individuals of the two species. The concentrations of OCs in a group of 20 polar bears (adult males) from the same area reported by Bernhoft et al.

Discussion

The present concentrations of OCs in the northern harp seal group were substantially higher than previously reported in this species Kleivane et al., 1997, Oehme et al., 1995, while the OC concentrations in the ringed seal group are in the upper range of corresponding data published from the Norwegian and Russian Arctic Nakata et al., 1998, Severinsen et al., 1995, Wolkers et al., 1998. Approximately six, four and three times higher concentrations, respectively, of ΣCHLOR, ΣPCB and ΣDDT were

Conclusions

As a top predator in the marine Arctic food chain the polar bear is an important key species indicator for persistent and bioaccumulating contaminants. When the polar bear enters a period of hyperphagia in May and June, resting and moulting harp seals holding out on ice-floes in the northern Barents Sea may represent an easier prey to catch than ringed seals. In the moulting period during fasting the total blubber mass of harp seals decreases dramatically, resulting in an elevated OC burden in

Acknowledgments

The authors wish to thank the scientists and the crew during the ICBAR 1995 survey. We would like to thank Ketil Hylland for critical reading of this manuscript, and Vidar Berg and Elisabeth Lie for performing the OC analysis.

References (44)

  • M. Oehme et al.

    Determination of levels of polychlorinated dibenzo-p-dioxins, dibenzofurans, biphenyls and pesticides in harp seals from the Greenland Sea

    The Science of the Total Environment

    (1995)
  • J.M. Pacyna et al.

    Long-range transport of some organic compounds to the Norwegian Arctic

    Atmospheric Environment

    (1988)
  • J.U. Skaare et al.

    Levels of polychlorinated biphenyls, organochlorine pesticides, mercury, cadmium, copper, selenium, arcenic, and zinc in the harbour seal, Phoca vitulina, in Norwegian Waters

    Environmental Pollution

    (1990)
  • J. Wolkers et al.

    Congener specific PCB and polychlorinated camphene (toxaphene) levels in Svalbard ringed seals (Phoca hispida) in relation to sex, age, condition, and cytochrome P450 enzyme activity

    Science of the Total Environment

    (1998)
  • J. Wolkers et al.

    Cytochrom P450-mediated enzym activities and polychlorinated biphenyl accumulation in harp seal (Phoca groenlandica)

    Marine Environmental Research

    (1999)
  • Anon. (1995). Report on the results of the ICES/IOC/OSPARCOM intercomparison programme on the analyses of...
  • Anon. (1996). Ecological processes in the marginal ice-zone of the northern Barents Sea (Cruise Report No. 93-Tromsø...
  • K. Ballschmiter et al.

    Analysis of polychlorinated biphenyls (PCB) by glass capillary gas chromatography

    Fresenius Journal of Analytical Chemistry

    (1980)
  • A. Bernhoft et al.

    Organochlorines in polar bears (Ursus maritimus) at Svalbard

    Environmental Pollution

    (1997)
  • T.F. Bidleman et al.

    Atmospheric transport of organochlorines in the North Atlantic gyre

    Journal of Marine Research

    (1982)
  • J.P. Boon et al.

    The toxicokinetics of PCBs in marine mammals with special reference to possible interactions of individual congeners with the cytochrome P450-dependent monooxygenase system—an overview

    Applied Science Project of The Nedrelands Institute for Sea Research

    (1991)
  • W.D. Bowen et al.

    Validation of age estimation in harp seal, Phoca groenlandica, using dentinal annuli

    Canadian Journal of Fisheries and Aquatic Sciences

    (1983)
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