Organochlorine contaminants in endangered Steller sea lion pups (Eumetopias jubatus) from western Alaska and the Russian Far East

Investigations into the cause of the Steller sea lion population decline have focused on numerous factors, including exposure to toxic contaminants such as organochlorines (OCs). OCs, such as polychlorinated biphenyls (PCBs), 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane, or dichlorodiphenyltrichloroethane (DDT), have been associatedwith various biological effects in marine mammals. We measured these compounds in whole blood of free-ranging Steller sea lion pups in order to determine the extent and magnitude of contamination across their geographical range. Of 212 pups analyzed forOCs, 76 pups (36 females and 40males)were from western Alaska and the other 136 (63 females and 73 males) were from the Russian Far East. Concentrations of ΣPCBs in the whole blood of pups fromwestern Alaska ranged from0.21 to 13 ng/g wet weight with a mean of 2.1±0.27 ng/g wet weight. In the Russian animals, ΣPCB concentrations in thewhole blood of pups ranged from0.33 to 36 ng/gwet weight with amean of 4.3±0.44 ng/g wet weight. ΣDDT concentrations in the whole blood of pups from western Alaska ranged from 0.18 to 11 ng/g wet weight with a mean of 1.6±0.23 ng/g wet weight. In Russia,ΣDDT in thewhole blood ofpups ranged fromundetectable to 26 ng/gwetweightwitha mean of 3.3±0.36 ng/g wetweight. Average OC concentrationswere significantly higher in the blood of Russian animals compared to western Alaska (for PCBs and DDTs, pb0.001) and in both areas females had higher concentrations thanmales.Male pups fromwestern Alaska had significantly lower levels of ΣPCBs and ΣDDT when compared to male pups from Russia (for PCBs and DDTs pb0.001). Female pups fromwestern Alaska were significantly lower in ΣPCBs than Russian female pups (for PCBs p=0.009) as were female pups for ΣDDT levels between areas (for DDTs p=0.026). OC contaminants data indicate that Steller sea lion pups have measurable concentrations of these synthetic chemicals. While any physiological effect and the specific role these chemicalsmay have in either the decline or the failure of the endangered Steller sea lion population to recover needs to be further investigated, this study indicates specific areas and animals thatmay be most at risk.