Mercury concentrations in deer mouse (Peromyscus maniculatus) tissues from Isle Royale National Park

We used deer mice (Peromyscus maniculatus) to investigate variation in mercury exposure across the terrestrial ecosystem of Isle Royale National Park (Michigan, USA). Although previous work suggested that mercury (Hg) levels may be higher inside the Sargent Lake watershed of Isle Royale than outside the watershed, Hg concentrations in livers were higher outside the Sargent Lake watershed (100.13 ng Hg/g dry tissue) than inside the watershed (35.50 ng Hg/g dry tissue; P = 0.06). Mercury levels in kidneys did not differ significantly (P = 0.57) between samples collected outside (443.23 ng Hg/g dry tissue) and inside (360.62 ng Hg/g dry tissue) the Sargent Lake watershed. Mean Hg concentrations in the livers of mice at some sites in Isle Royale are not significantly lower (P = 0.62) than Hg concentrations considered by some government agencies to be unhealthy for human consumption. Although Hg concentrations in mouse tissues were not remarkably high (compared to heavily polluted sites), concern is warranted because: (1) Isle Royale National park is a protected area in a remote location; (2) any exposure in deer mice represents a path for biomagnification in the terrestrial food web; and (3) the source of this mercury remains unidentified.