Mercury body burden in Steller sea lions (Eumetopias jubatus)

Mercury is a naturally occurring element that is known to have toxic effects.  Piscivorous mammals such as sea lions can bioaccumulate high mercury concentrations through the diet and can transfer mercury through the placenta to the developing fetus.  High mercury concentrations are known to have adverse effects on reproductive, neurological, and immunological functions. In this study, we examine total mercury (THg) concentrations in several body tissue compartments and calculate the body burden of THg in Steller sea lion (SSL; Eumetopias jubatus) pups.  SSL pups (n=2) were found dead on their natal rookery in the western Aleutians in June 2011.  Necropsy results could not determine a cause of death, however both pups were emaciated with no subcutaneous blubber. Although THg concentrations in these carcasses cannot be considered representative of the population, they provide a unique opportunity to study how THg is distributed among different tissues of the body in this endangered species based on both mass (mg of Hg) and concentration.   Total mercury concentrations were analyzed for all biological tissues from each pup using a Milestone Direct Mercury Analyzer.  Mercury tissue and body burdens were calculated using fresh weight of each biological tissue multiplied by the THg concentration for each specific tissue.  We conclude that while the two pups had very different concentrations of THg in their hair, the pattern of distribution of THg between tissue compartments was very similar.  In both pups, hair, liver, and pelt had the highest THg concentrations and pelt, muscle, and liver had the highest mercury burdens.