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 associated with 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 for OCs, 76 pups (36 females and 40 males) were from western Alaska and the other 136 (63 females and 73 males) were from the Russian Far East. Concentrations of ∑PCBs in the whole blood of pups from western Alaska ranged from 0.21 to 13 ng/g wet weight with a mean of 2.1 ± 0.27 ng/g wet weight. In the Russian animals, ∑PCB concentrations in the whole blood of pups ranged from 0.33 to 36 ng/g wet weight with a mean of 4.3 ± 0.44 ng/g wet weight. ∑DDT 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, ∑DDT in the whole blood of pups ranged from undetectable to 26 ng/g wet weight with a mean of 3.3 ± 0.36 ng/g wet weight. Average OC concentrations were significantly higher in the blood of Russian animals compared to western Alaska (for PCBs and DDTs, p < 0.001) and in both areas females had higher concentrations than males. Male pups from western Alaska had significantly lower levels of ∑PCBs and ∑DDT when compared to male pups from Russia (for PCBs and DDTs p < 0.001). Female pups from western Alaska were significantly lower in ∑PCBs than Russian female pups (for PCBs p = 0.009) as were female pups for ∑DDT 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 chemicals may 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 that may be most at risk.