Science of the Total Environment 370 (2006) 70–79 www.elsevier.com/locate/scitotenv Congener-specific accumulation and patterns of chlorinated and brominated contaminants in adult male walruses from Svalbard, Norway: Indications for individual-specific prey selection ⁎ Hans Wolkers a, , Bert van Bavel b, Ingrid Ericson b, Eli Skoglund a, Kit M. Kovacs a, Christian Lydersen a a Norwegian Polar Institute, N-9296 Tromsø, Norway b MTM Research Center, Örebro University, 701 82 Örebro, Sweden Received 21 March 2006; received in revised form 30 May 2006; accepted 2 June 2006 Available online 17 August 2006 Abstract Blubber samples from 17 adult, male walruses were sampled in eastern Svalbard and analyzed for chlorinated and brominated contaminants. A wide range of contaminants were detected, including PCBs (mean 2000; 95% range 1165–4005 ng/g lipid), DDE (mean 100: 95% range 50–310) ng/g lipid), chlordanes (mean 2500; 95% range 1347–5009) ng/g lipid, toxaphenes (mean 80; 95% range 51–132 ng/g lipid) and polybrominated diphenyl ethers (PBDEs) (mean15 ng/g; 95% range 9–27 ng/g lipid). PCB and DDE levels were substantially lower than those of animals sampled 10 year earlier in this area, confirming a decreasing trend for these compounds in the Arctic. However, compared to other recently sampled marine mammals from Svalbard, walruses showed relatively high PCB and chlordane levels although they had lower levels of DDE, toxaphenes, and PBDEs, possibly due to species- and location-specific differences in exposure and metabolism. The range in contaminant levels found within the sample group was vast, despite the fact that the animals investigated were all adult males from the same location. The PCB pattern in highly contaminated animals was different from that in animals with low levels of contamination, with relatively more persistent PCBs in the highly contaminated group. This suggests that the more contaminated animals were feeding at higher trophic levels; possibly targeting seals in addition to mollusks as their prey. This suggestion was reinforced by the fatty acid profiles of the inner blubber layer of walruses with low versus high contaminant levels, which suggested different diets for the two groups. © 2006 Elsevier B.V. All rights reserved. Keywords: Walrus; Pollution; PCBs; Arctic; Svalbard; Pesticides; PBDEs; Diet 1. Introduction The walrus (Odobenus rosmarus) is an arctic pinniped species easily recognized by the formidable canines protruding from the upper jaw. Walruses live in ⁎ Corresponding author. Polar Environmental Centre, Hjalmar Johansengt.14, N-9296 Tromsø, Norway. Tel.: +47 77750521; fax: relatively shallow, coastal areas within the Arctic where +47 77750501. they dive to the bottom to forage on their benthic-living E-mail address: [email protected] (H. Wolkers). food. Adult males can weigh over 1.5 tons while the 0048-9697/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2006.06.005 H. Wolkers et al. / Science of the Total Environment 370 (2006) 70–79 71 females are smaller and rarely attain body masses above 98% of accumulated contaminants reside in blubber in 1ton(Fay, 1981). Walruses have a circumpolar seals (Stromberg et al., 1990), contaminant concentra- distribution and are found in the Pacific, Atlantic and tions in this tissue may give a record of total Arctic oceans. The Atlantic walrus (O. r. rosmarus) accumulation during an animal's lifespan as well as ranges from the eastern Canadian Arctic to Nova the potential exposure during lipid breakdown. Zemlya in Russia and consists of several geographically The arctic archipelago of Svalbard is known to be isolated populations; with the animals around Svalbard home to some of the most contaminated arctic animals, and Franz Josef Land comprising one such population with levels in various species exceeding those found in (Andersen et al., 1998). During the breeding season the same species in other arctic areas (Muir et al., 1992; walruses are often associated with the pack-ice, while at AMAP, 1998, 2004; Wolkers et al., 1998, 1999, 2000). other times of year, especially summer, they haul out in Indications for contaminant-induced biological effects large groups on land. They acquire sexual maturity have been found for a variety of arctic species (AMAP, between 6 and 10 years of age (Fay, 1981). Reproduc- 1998, 2004), including seals (Wolkers et al., 1998, tion is extremely slow with mature females giving birth 2000). Therefore, knowledge on contaminant accumula- to a single calf at 3-year intervals. These low tion in different species is essential to assess the risk for reproductive rates, combined with the tendency wal- contaminant-induced biological effects. However, very ruses have to aggregate in huge groups make them few studies exist on contaminant exposure and accumu- particularly vulnerable to over-exploitation and other lation in walrus, and data on this species from the human-related impacts. Walruses at Svalbard were Svalbard area are particularly scarce. The few studies extensively hunted for several centuries and were at that do exist involve a relatively limited set of the brink of extinction when they became protected in contaminants, often not presented as individual con- 1953. Since then the population has gradually increased; geners but as the sum of PCB, chlordanes, DDTs and the latest survey in 1993 suggested that the Svalbard- toaxaphenes (Wiig et al., 2000), making spatial and Franz Joseph Land population consist of 1450 walruses temporal comparisons difficult. Therefore, the current older than 2 years and an unknown number of calves study was carried out to assess the congener-specific (Gjertz and Wiig, 1994, 1995). Walruses are adapted to accumulation of a wide range of pollutants, including benthic feeding with various mollusks comprising their PCBs, chlorinated pesticides and polybrominated diphe- most important prey (Fay, 1982; Gjertz and Wiig, 1992). nyl ethers (PBDEs), in adult male walruses from However, some individual walrus are known to prey on Svalbard. In addition, differences in contaminant other pinnipeds, mainly ringed seals (Phoca hispida)as accumulation pattern and levels were related to possible well (Fay, 1960; Lowry and Fay, 1984). differences in diet based on fatty acid profiles of the inner It has been well documented that the arctic environ- blubber layer of these individuals (Skoglund, 2006). ment is exposed to a variety of pollutants (AMAP, 1998, 2004). Due to bioaccumulation through the food chain 2. Methods predatory animals are exposed to the highest degree. In mammals exposure to contaminants occurs mainly 2.1. Sample collection through their food and ingested compounds are either metabolized or accumulated in lipid-rich tissues, such as Blubber biopsies were collected from 17 adult male the blubber. Being predators, walruses are exposed to walruses from the eastern parts of the Svalbard relatively high contaminant concentrations (Muir et al., Archipelago during August 2002–04. The walruses 1992, 1995), particularly those individuals that prey on were immobilized with an intramuscular injection of seals (Muir et al., 1995). Since walruses are long-lived ethorphine hydrochloride which was reversed with marine predators and, like other pinniped species, go diprenorphine hydrochloride as described in Griffiths through seasonal lipid cycles, they might be particularly et al. (1993). Standard length (±5 cm) was measured in a sensitive to contaminants. During molting and breeding straight line from the tip of the snout to the end of the tail. walruses mobilize some of their lipid reserves to meet Then the length, and diameter at the base of the tusks, their energy demands, although their lipid cycles are not was measured (±1 cm). Walrus tusks grow in length and as dramatic as in some other seal species (Fay, 1982). girth throughout most the animal's life, reaching an Consequently, accumulated contaminants are released asymptotic value when the animals are 20–30 years of from these fat depots, enter circulation, and suddenly age (Fay, 1982). Tusk volume can therefore be used as a become bio-available. This may impose brief periods of crude indicator of age; volume was calculated assuming acute exposure to these animals. Because more than that the tusks were cone-shaped, and thus the formula 72 H. Wolkers et al. / Science of the Total Environment 370 (2006) 70–79 V=1/3πr2⁎ h (where r is tusk radius at the base and h is rate of 2 ml/min. The recovery standard, containing 13C- the length of the tusk) was used. labeled PCB 128 and 178, was then added and the Blubber biopsies were collected using a custom-made sample volume was reduced to 30 μl tetradecane, hollow stainless steel tube (diameter: 6 mm, length: producing an extract ready for GC/MS analysis. 150 mm) that was sharpened at one end and attached via Separate lipid determinations were performed by putting the other end to an electrical drill that enabled a rapid, some (∼1 g) of the homogenate in a small column and clean cut through the complete blubber layer. The quantitatively extracting the lipid with methylene biopsies were taken vertically at a mid dorsal point, chloride and hexane (1:1). The weight of the extracted approximately 60% of the way down the body from the lipids was determined gravimetrically. cranial end; they consisted of the skin and the entire Selected ion SIR HRGC/LRMS spectra were blubber layer down to the muscle (length 7–8 cm). Each recorded using an Agilent 6890 gas chromatograph biopsy was wrapped separately in aluminum foil and coupled to an Agilent 5973 mass spectrometer (HRGC/ kept frozen (ca. −20 °C) until analysis. LRMS) used in the selected ion recording mode (SIR). Chromatographic separation was achieved by split-less 2.2. Chemicals injection of 2 μl on a non-polar DB-5 column using helium as the carrier gas. The GC oven was programmed All chemicals used during the analyses were of as follows: 180 °C initial hold for 2 min increase at a rate pesticide grade and commercially available from Sigma of 15 °C/min to 205 °C; followed by an increase of (St.