Southern sea otters (Enhydra lutris nereis) from the California coast continue to exhibit a slower population regrowth rate than the population in Alaska.
Infectious diseases have been identified as a frequent cause of death.
Infectious diseases caused by varied pathogens including bacteria, fungi, and parasites were suggestive of compromised immunological health of mature animals in this population. To test the hypothesis that elevated exposure to immunotoxic contaminants such as
polybrominated diphenyl ethers (
PBDEs) and
polychlorinated biphenyls (
PCBs) contribute to
disease susceptibility via immunosuppression, we determined concentrations of
PBDEs and
PCBs in livers of 80 adult female sea otters that died of
infectious diseases, noninfectious causes, or
emaciation. Concentrations of
PBDEs and
PCBs in sea otter livers varied widely (10-26,800 ng/g and 81-210,000 ng/g,
lipid weight, respectively). Concentrations of
PBDEs in sea otters were some of the highest values reported for marine mammals so far. Although PCB concentrations in sea otters have declined during 1992-2002, the mean concentration was at the threshold at which adverse health effects are elicited. Concentrations of
PBDEs and
PCBs were significantly correlated, suggesting co-exposure of these contaminants in sea otters. No significant association was found between the concentrations of
PBDEs and the health status of sea otters. Concentrations of
PCBs were significantly higher in otters in the
infectious disease category than in the noninfectious category, suggesting an association between elevated PCB concentrations and
infectious diseases in Southern sea otters.