| Abstract: |
Mercury concentration ([Hg]), δ15N, and δ13C were measured in eggs from common murres (Uria aalge), thick-billed murres (U. lomvia), glaucous gulls (Larus hyperboreus), and glaucous-winged gulls (L. glaucescens) collected throughout Alaska from 1999 to 2005. [Hg] was normalized to a common trophic level using egg δ15N values and published Hg trophic magnification factors. Murre eggs from the Gulf of Alaska, Cook Inlet, and Norton Sound had higher [Hg] than those from the Bering Sea and Bering Strait regions, independent of trophic level. The enrichment in egg [Hg] in Norton Sound is hypothesized to be from inputs from the Yukon River and other terrestrial Hg sources. Normalizing for trophic level generally eliminated or diminished differences in [Hg] among taxa, but temporal variability was unrelated to trophic level. These results indicate that normalizing murre egg [Hg] by trophic level improves the confidence in regional comparisons of Hg sources and biogeochemical cycling in Alaska. |
