Regional, Temporal, and Species Patterns of Mercury in Alaskan Seabird Eggs: Mercury Sources and Cycling or Food Web Effects?
Russell D. Day, David G. Roseneau, Stacy S. Schuur, Keith A. Hobson, O.F.X Donard, Rebecca S. Pugh, Amanda J. Moors, Paul R. Becker
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.