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Mercury occurrence in water and biota across a spectrum of southeastern Alaskan streams
Sonia Nagorski1, sanagorski@uas.alaska.edu
John Hudson2, Eran Hood1
1University of Alaska Southeast; 2Independent Aquatic Ecologist

Southeastern Alaska is likely experiencing increased rates of deposition of atmospheric mercury (Hg), primarily due to growing emissions from upwind Asian sources. Very little information is available on the extent and magnitude of Hg occurrence in Alaskan watersheds. Here we present the first survey of Hg concentrations in a variety of regional streams.  We show that streams draining wetland-rich landscapes tend to have higher Hg concentrations in water and stream biota (mayfly larvae in the families Baetidae and Heptageniidae; and juvenile coho salmon (Oncorhynchus kisutch) ) than streams draining younger, glacially-influenced watersheds. Wetland-rich streams also carry the majority of the mercury load in their filtered phases, whereas Hg in glacially influenced streams is largely associated with particulates. Both methylmercury-- the more toxic and bioavailable form of the metal-- and dissolved organic carbon were significantly higher in the wetland-rich watersheds as well.  The distribution of Hg in the sprectrum of streams show that watersheds are variably sensitive to mercury inputs and that landscape characteristics may be controlling whether Hg is stored, released, and/or converted to toxic methylmercury.