Organochlorine concentrations in ice seals harvested in Alaska in the 2000s and 2010s

Ringed, bearded, spotted, and ribbon seals are important subsistence resources to coastal Alaska Native communities and sentinels of Pacific Arctic ecosystem health. We sampled blubber and liver from subsistence harvested seals and analyzed them for organochlorines (OCs), including hexachlorobenzene (HCB), chlordanes (CHLs), hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), and polychlorinated biphenyls (PCBs). Organochlorine concentrations were higher in blubber tissue than liver tissue for all species, and higher in the blubber of ringed, spotted, and ribbon seals than in bearded seals. In most cases, blubber thickness and lipid content were not related to OC concentrations. Concentrations of several OCs increased with seal age, but often only for males. We found declines of some OCs between an earlier (2003-2007) and later (2011-2016) period for ringed and bearded seals, whereas most OCs declined in spotted seals between the same two periods. While dieldrin was detected in nearly all ringed, spotted, and ribbon seal samples, it was rarely detected in bearded seal samples and when detected it was at much lower concentrations. Although OCs are generally declining throughout the Pacific Arctic, their presence in sea ice and biota, biomagnification through the food web, and their accumulation in seal blubber, an important dietary resource for Alaska Native communities and polar bears, warrants continued contaminant monitoring of ice seals.