Legacy contaminants in the eastern Beaufort Sea beluga whales (Delphinapterus leucas): are temporal trends reflecting regulations?

Once deposited onto Arctic ecosystems, persistent organic pollutants (POPs) biomagnify in foodwebs such that relatively high levels have been detected in predators like beluga whales (Delphinapterus leucas). Our study aimed at assessing temporal trends of legacy POPs in eastern Beaufort Sea beluga blubber collected during traditional harvests in the Mackenzie Estuary area, Northwest Territories. Concentrations of polychlorinated biphenyls (PCBs) and 14 pesticides were quantified in 185 blubber samples collected between 1989 and 2015. The majority of legacy POPs analyzed showed no significant changes during the study period (Sigma PCBs, Sigma chlordanes, Sigma dichlorodiphenyltrichloroethane, hexa-chlorobenzene, dieldrin, and mirex) and, therefore, did not reflect regulations put into place over the past decades. Although alpha- (82.6 +/- 12.6 and 15.9 +/- 1.9 ng/g in 1989 and 2015, respectively) and gamma-hexachlorocyclohexane (gamma-HCH) (126.6 +/- 23.9 and 13.9 +/- 0.9 ng/g, respectively) showed significant decrease between 1989 and 2015, beta-HCH showed a more complex trend with concentrations increasing between 1989 (71.2 +/- 13.4 ng/g) and 2004 g (276.8 +/- 13.5 ng/g) before decreasing until 2015 (174.7 +/- 8.3 ng/g). Differences in trends likely cu reflect physico-chemical properties affecting transport to the Arctic. With climate change and melting sea ice potentially affecting the transport and release of legacy POPs, continuous monitoring is necessary.