Can seal eating explain elevated levels of PCBs and organochlorine pesticides in walrus blubber from eastern Hudson Bay (Canada)? Original Research Article

Walrus (Odobenus rosmarus) blubber samples from Inukjuak and Akulivik (East Hudson Bay), Foxe Basin (Igloolik and Hall Beach) and Loks Land (East Baffin Island) were analysed for PCB congeners (ortho and non-ortho substituted) and other persistent organochlorines (DDT, toxaphene, chlordanes, dieldrin, mirex), as well as chlorinated dioxins/furans, to document spatial trends in contaminants in Canadian Arctic marine biota. Samples from 19 of 53 individuals had concentrations of ΣPCBs greater than 1000 ng g−1 (wet wt); the remaining individuals had much lower concentrations (50–600 ng g−1). Highest concentrations were found in samples from Inukjuak where average concentrations in blubber of females (N = 9) were 1450 ± 954 ng g−1 toxaphene, 2750 ± 1780 ng g−1 ΣCHLOR, 2160 ± 925 ng g−1 ΣDDT and 4790 ± 2380 ng g−1 ΣPCB. ΣPCB and ΣDDT concentrations greater than 1000 ng g−1 were unexpected based on previous studies of walrus from Greenland and Alaska. Local contamination was ruled out because levels of all organochlorines were elevated in each animal from Inukjuak, and elevated levels were also found in animals from Akulivik and Loks Land. Walrus from Inukjuak had δ13C and δ15N values in muscle intermediate between those of ringed seals (Phoca hispida) and those of walrus from Akulivik with low organochlorine levels. There was a weak but significant correlation between and δ15N and (log)ΣPCB. The Inukjuak walrus also had higher proportions of highly chlorinated PCB congeners, and higher DDE/ΣDDT ratios than walrus from Igloolik or Akulivik. The results suggest that the walrus with elevated organochlorines are feeding at a higher trophic level than those with low levels and are probably utilizing ringed seals for a portion of their diet.