Assessment of mercury concentrations in fur, liver and brain tissue from necropsied southern sea otters (Enhydra lutris nereis)

Southern sea otters are a federally-listed threatened species. They are also valuable to the California coastal marine ecosystem as a keystone species and bioindicator of environmental pollution. Mercury (Hg) is a neurotoxic environmental pollutant and contamination of marine mammals is a growing concern. Hg loads have been quantified in the closely-related species of river otter and mink, however, little has been published on sea otter tissue Hg levels. In this work we analyzed hair, liver and brain tissues from 27 necropsied individuals from the Monterey Bay and Morro Bay regions for total Hg (THg), and found mean ± (1 sd) concentrations of 15.66 ± 9.80 μg/g, 12.58 ± 9.57 μg/g, and 1.72 ± 0.97 μg/g, respectively. The mean hair/brain and hair/liver concentration ratios were 8.9 ± 1.4 and 1.4 ± 0.7, respectively. These simple conversions between hair and internal tissues can be used to infer loads in live individuals through non-invasive fur sampling in order to better understand possible risks of neurological disease.