Mercury concentrations of a resident freshwater forage fish at Adak Island, Aleutian Archipelago, Alaska

The Aleutian Archipelago is an isolated arc of over 300 volcanic islands stretching 1,600km across the interface of the Bering Sea and North Pacific Ocean. Although remote, some Aleutian Islands were heavily impacted by military activities from World War II until recently and were exposed to anthropogenic contaminants, including mercury (Hg). Mercury is also delivered to these islands via global atmospheric transport, prevailing ocean currents, and biotransport by migratory species. Mercury contamination of freshwater ecosystems is poorly understood in this region. Total Hg (THg) concentrations were measured in threespine stickleback fish (Gasterosteus aculeatus) collected from eight lakes at Adak Island, an island in the center of the archipelago with a long military history. Mean THg concentrations for fish whole-body homogenates for all lakes ranged from 0.314 to 0.560mg/kg dry weight. Stickleback collected from seabird-associated lakes had significantly higher concentrations of THg compared to non-seabird lakes, including all military lakes. The δ¹³C stable isotope ratios of stickleback collected from seabird lakes suggest an input of marine-derived nutrients and/or marine-derived Hg.