Sea Otters, Mercury, and Monitoring Climate Change

An increase in mobility of heavy metals, like mercury (Hg), has the potential to be one of the climate change related impacts on Arctic and sub-Arctic ecosystems. Sea level rise and flooding events in high latitude coastal ecosystems could increase the bioavailability of contaminants such as mercury. Mercury concentrations have been used as an indicator of past exposure to heavy metals in ancient Pacific cod and here we report on concentrations in archeologically recovered sea otter bones (Enhydra lutris). Methods utilizing stable isotope ratios can be used to reconstruct ancient food webs and help identify prey which may have bioaccumulated high concentrations of mercury. Modern sea otters have δ13C, δ15N, and mercury values corresponding largely to a benthic diet. Conversely, if higher δ15N and mercury levels were found in ancient sea otter bones located in a coastal ecosystem, these increases may be associated with rising sea level following the last glacial maximum. These data place present day and projected climate change related perturbations, like sea level rise, in a historical context.