Correspondence between mercury and stable isotopes in high Arctic marine and terrestrial avian species from northwest Greenland

Abstract

Birds are useful bioindicators of environmental contamination around the globe, but avian studies in the high Arctic have been primarily limited to a few abundant species. This study was designed to assess mercury (Hg) concentrations in both abundant and less-abundant marine and terrestrial avian species on breeding grounds in northwest Greenland using blood sampling. Twenty-four migratory avian species (n = 625) were sampled over a three-year period (2010–2012) along 750 km of coastline near Thule Air Base (77° N, 68° W). Whole blood samples were analyzed for total Hg along with δ13C and δ15N to estimate food web position. A significant positive correlation was observed between mean Hg concentrations and trophic position, with adult mean Hg concentrations ranging from 11.4 to 1164 ng g−1 wet weight. Eleven species examined in this study had blood Hg concentrations suggestive of a low risk for Hg toxicity. Some Peregrine Falcon (Falco peregrinus), Thick-billed Murre (Uria lomvia), and Black Guillemot (Cepphus grylle) individuals had concentrations of Hg suggestive of medium risk for Hg toxicity (Hg concentrations between 1000–3000 ng g−1 ww). Decreasing δ15N values in birds from the central study area suggest a nonuniform geographic pattern of increased freshwater influx and subsequent changes in prey availability, which correspond to lower avian Hg levels. This study provides strong evidence that marine and terrestrial feeding ecology of avian species in NW Greenland contributes to their mercury exposure; however, intraspecific variation in ecology and nesting locations in the region may influence those patterns.