Downloaded By: [ABM Utvikling STM / SSH packages] At: 12:58 14 July 2008 Journal of Toxicology and Environmental Health, Part A, 71: 1009–1018, 2008 Copyright © Taylor & Francis Group, LLC ISSN: 1528-7394 print / 1087-2620 online DOI: 10.1080/15287390801907558 1009 UTEH Biomarker Responses and Decreasing Contaminant Levels in Ringed Seals (Pusa hispida) from Svalbard, Norway Decreasing Contaminant Levels in Ringed Seal Hans Wolkers 1 , Bjørn A. Krafft 1 , Bert van Bavel 2 , Lisa B. Helgason 1 , Christian Lydersen 1 , and Kit M. Kovacs 1 1 Norwegian Polar Institute, Tromsø, Norway, and 2 MTM Research Center, Örebro University, Örebro, Sweden Blubber was analyzed for a wide range of contaminants from five subadult and eight adult male ringed seals sampled in 2004, namely, for polychlorinated biphenyls (PCBs), hexachloroben- zene (HCB), toxaphenes, chlordanes, dichlorodiphenyldichloroet- hylene (DDE), and polybrominated diphenylethers (PBDEs). Contaminant levels were compared to previously sampled ani- mals from the same area, as well as data from literature for other arctic wildlife species from a wide variety of locations. Ringed seals sampled in 2004 showed 50–90% lower levels of legacy con- taminants such as PCBs and chlorinated pesticides compared to animals sampled in 1996 of similar age (14 subadults and 7 adult males), indicating that the decline of chlorinated contaminants observed during the 1990s in a variety of arctic wildlife species is continuing into the 21st century. The results also indicated that PBDE declined in ringed seals; levels in 2004 were about 70–80% lower than in animals sampled in 1998. This is one of the first observations of reduced exposure to these compounds and might be a first indication that restrictions of production and use of these contaminants have resulted in lower exposures in the Arctic. The PCB pattern shifted toward the less chlorinated (i.e., less per- sistent) PCBs, especially in adult ringed seals, possibly as a result of reduced overall contaminant exposures and a consequently lower cytochrome P-450 (CYP) induction, which results in a slower metabolism of less persistent PCBs. The overall effect would be relative increases in the lower chlorinated PCBs and a relative decreases in the higher chlorinated PCB. Possibly due to low exposure and consequent low induction levels, ethoxyresoru- fin O-deethylation (EROD) activity proved to be a poor biomarker for contaminant exposure in ringed seals in the present study. The close negative correlation (r 2 =70.9%)between EROD activity and percent blubber indicates that CYP might respond to increased bioavailability of the contaminant mixtures when they are mobi- lized from blubber during periods of reduced food intake. The Arctic is chronically exposed to a wide variety of con- taminants, most of which originate from lower latitudes (Pacyna & Oehme, 1988; AMAP, 1998). Monitoring levels and effects of these pollutants in arctic biota is a political priority of the circumpolar arctic nations, including Norway. Polychlo- rinated biphenyls (PCBs), chlorinated pesticides like DDT, chlordane and toxaphene, and polybrominated diphenyl ethers (PBDEs) are of special concern because of their persistence and bioaccumulative properties (AMAP, 1998, 2004). These com- pounds are listed by the Stockholm Convention and are included in the global monitoring program (GMP) that will evaluate the effectiveness of the convention (www.chem.unep.ch). The Arctic is dominated by the marine environment, and due to the lipophilic nature of these chemicals, they easily enter the food chain through absorption by lipid-rich arctic plankton. Because many of these compounds are persistent they accumulate through the food chain, reaching their highest levels in arctic top or apex predators like seals, whales, and polar bears (Ursus maritimus). In seals, more than 95% of the total amount of accumulated contaminants resides in their blubber layer (Stromberg et al., 1990). Besides thermo-insulation properties, blubber lipids also serve as an energy storage; blubber is mobi- lized during the breeding and molting periods as well as other times when the animals experience reduced food intake. Dur- ing lipid mobilization accumulated contaminants are released into circulation and reach more sensitive tissues (Lydersen et al., 2002; Jørgensen et al., 2002). Consequently, both tissue con- taminant levels and the response of biomarkers are affected by the degree of lipid mobilization (Lydersen et al., 2002; Jørgensen et al., 2002). These life-cycle-dependent fluctuations in con- taminant levels and bioavailability pose a considerable chal- lenge to studies dealing with monitoring of contaminant levels and associated contaminant-induced biological effects. The ringed seal (Pusa hispida) is an abundant, circumpolar arctic species that occupies a central place in the arctic food web. Ringed seals feed mostly on pelagic fish and crustaceans. They in turn are preyed on predominantly by polar bears (Ursus maritimus) and constitute an important resource for indigenous people. Due to their high trophic position, this seal species is exposed to relatively high levels of halogenated Received 26 September 2007; accepted 6 December 2007. Address correspondence to Hans Wolkers, Norwegian Polar Institute, 9296 Tromsø, Norway. E-mail: Hans.Wolkers@npolar.no