Factors Influencing Mercury Exposure in Arctic-Breeding Shorebirds

Abstract Mercury (Hg) pollution remains a concern to Arctic ecosystems. The objective of this study was to identify factors influencing Hg concentrations in Arctic-breeding shorebirds and highlight regions and species at greatest risk of Hg exposure. We analyzed 2,478 blood and feather samples from 12 shorebird species breeding at nine sites across the North American Arctic during 2012 and 2013. Blood Hg concentrations, which reflect Hg exposure in the local area in individual shorebirds: 1) ranged from 0.01–3.52 µg/g, with an overall mean of 0.30 ± 0.27 µg/g; 2) were influenced by species and study site, but not sampling year, with birds sampled near Utqiaġvik, AK, having the highest concentrations; and 3) were influenced by foraging habitat at some sites. Feather Hg concentrations, which reflected Hg exposure from the wintering grounds, were generally higher than blood, ranging from 0.07–12.14 µg/g in individuals, with a mean of 1.14 ± 1.18 µg/g. Feather Hg concentrations were influenced by species and year. Most Arctic-breeding shorebirds had blood and feather Hg concentrations at levels where no adverse effects of exposure were likely, though some individuals sampled near Utqiaġvik had Hg levels that are certainly of concern. Overall, these data increase our understanding of how Hg is distributed in the various habitats of the Arctic, and what factors predispose Arctic-breeding shorebirds to Hg, and lay the foundation for future monitoring efforts.