Deep-ocean foraging northern elephant seals bioaccumulate persistent organic pollutants
Faculty of Pharmaceutical, Biomedical and Veterinary Sciences. Pharmacy
The science of the total environment. - Amsterdam
, p. 144-155
University of Antwerp
As top predators in the northeast Pacific Ocean, northern elephant seals (Mirounga angustirostris) are vulnerable to bioaccumulation of persistent organic pollutants (POPs). Our study examined a suite of POPs in blubber (inner and outer) and blood (serum) of free-ranging northern elephant seals. For adult females (N=24), we satellite tracked and sampled the same seals before and after their approximately seven month long foraging trip. For males, we sampled different adults and sub-adults before (N=14) and after (N=15) the same foraging trip. For females, we calculated blubber burdens for all compounds. The highest POP concentrations in males and females were found for Sigma DDTs and Sigma PCBs. In blubber and serum, males had significantly greater concentrations than females for almost all compounds. For males and females, Sigma DDT and Sigma PBDEs were highly correlated in blubber and serum. While Sigma PCBs were highly correlated with Sigma DDTs and Sigma PBDEs in blubber and serum for males, Sigma PCBs showed weaker correlations with both compounds in females. As females gained mass while foraging, concentrations of nearly all POPs in inner and outer blubber significantly decreased; however, the absolute burden in blubber significantly increased, indicating ingestion of contaminants while foraging. Additionally, we identified three clusters of seal foraging behavior, based on geography, diving behavior, and stable carbon and nitrogen isotopes, which corresponded with differences in Sigma DDTs, Sigma PBDEs, MeO-BDE 47, as well as the ratio of Sigma DDTs to Sigma PCBs, indicating the potential for behavior to heighten or mitigate contaminant exposure. The greatest concentrations of Sigma DDTs and Sigma PBDEs were observed in the cluster that foraged closer to the coast and had blood samples more enriched in C-13. Bioaccumulation of POPs by elephant seals supports mesopelagic food webs as a sink for POPs and highlights elephant seals as a potential sentinel of contamination in deep ocean food webs.