Spatial and temporal trends of persistent organic pollutants and mercury in beluga whales ( Delphinapterus leucas ) from Alaska

Remote locations, such as the Arctic, are often sinks for persistent contaminants which can ultimately bioaccumulate in local wildlife. Assessing temporal contaminant trends in the Arctic is important in understanding whether restrictions on legacy persistent organic pollutants (POPs) have led to concentration declines. Beluga whale ( Delphinapterus leucas ) tissue samples were collected from two subpopulations (Cook Inlet, Alaska and the eastern Chukchi Sea) between 1989 and 2006. Several POPs (polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethane and related compounds (DDTs), chlordanes, hexachlorocyclohexanes (HCHs), chlorobenzenes, mirex, polybrominated diphenyl ethers (PBDEs) and semi-quantitatively hexabromocyclododecanes (HBCDs)) were measured in 70 blubber samples, and total mercury (Hg) was measured in 67 liver samples from a similar set of individuals. Legacy POPs (PCBs, chlordanes, DDTs, and HCHs) were the predominant organic compound classes in both subpopulations, with median concentrations of 2360 ng/g lipid for Σ 80 PCBs and 1890 ng/g lipid for Σ 6 DDTs. Backward stepwise multiple regressions showed that at least one of the four independent variables (subpopulation, sampling year, sex, and animal length) influenced the POP and Hg concentrations. ΣPCBs, ΣDDTs, Σchlordanes, Σchlorobenzenes, mirex, and Hg were significantly higher in belugas from the eastern Chukchi Sea than from the Cook Inlet ( p ≤ 0.0001). In contrast, Σ 8 PBDE and α-HBCD concentrations were significantly lower in belugas from the eastern Chukchi Sea than from the Cook Inlet ( p < 0.0001). Significant temporal increases in concentrations of Σ 8 PBDE and α-HBCD were observed for both subpopulations ( p ≤ 0.0003), and temporal declines were seen for ΣHCHs and Σchlorobenzenes in eastern Chukchi Sea belugas only ( p ≤ 0.0107). All other POP and Hg concentrations were stable, indicating either a lagging response of the Arctic to source reductions or the maintenance of concentrations by unregulated sources. Sex and length also significantly influenced some concentrations, and these findings are discussed.