Mercury concentrations in multiple tissues of Arctic Iceland Gulls (Larus glaucoides) wintering in Newfoundland

Abstract

Anthropogenic mercury (Hg) emissions are increasing and are potentially of concern for Arctic-nesting seabirds, particularly those that spend part of their year near dense human habitation. Iceland Gulls (Larus glaucoides B. Meyer, 1822) breed in the eastern Canadian Arctic and spend the majority of winter in towns and cities in eastern Newfoundland. We measured Hg in breast feathers, blood plasma, and red blood cells of Iceland Gulls wintering in and around St. John's, Newfoundland and Labrador, from 2011 to 2014. Mercury in blood plasma comprised <10% of the total blood Hg. We found no difference in red blood cell Hg between first-winter and adult birds, which likely reflects their similar feeding habits. Feather Hg in adults was significantly greater than that in first-winter birds because adults had accumulated a greater body Hg burden to excrete (up to a year, compared with a few months' accumulation in first-winter birds). Overall, concentrations were among the lowest found for Larus spp. and Arctic gulls, suggesting that Hg does not pose a risk to Iceland Gulls at the present.