An isotopic investigation of mercury accumulation in terrestrial food webs adjacent to an Arctic seabird colony

摘要

At Cape Vera (Devon Island, Nunavut, Canada), a seabird colony of northern fulmars (Fulmarus glacialis) congregates and releases nutrients through the deposition of guano to the coastal terrestrial environment, thus creating nutrient-fertilized habitats important to insects, birds, and mammals. Here we determined whether mercury was similarly enriched in various terrestrial food web components in this High Arctic coastal ecosystem due to seabird inputs. Stable isotopes (δ~(15)N, δ~(13)C) were used to identify trophic linkages and possible routes of contaminant transfer in the food web. Values of δ~(15)N were significantly higher in lichens and certain plants collected closer to the bird colony, demonstrating a gradient of seabird influence, and were higher at Cape Vera than our reference site at Cape Herschel, on eastern Ellesmere Island, an area relatively unaffected by seabirds. In contrast, δ~(13)C showed little variation among terrestrial species, suggesting minimal influence by seabirds. Concentrations of total mercury (THg) in primary producers and phyto/zooplankton were not significantly correlated with distance from the seabird colony or δ~(15)N values, and were similar to other taxa from the High Arctic. Our results provide novel data on THg in several Arctic taxa where concentrations have not been reported previously. Moreover, the analyses indicate that δ~(15)N is significantly enriched in the adjacent environment by guano fertilization, but our study was unable to show an enrichment of THg and δ~(13)C in the terrestrial food web near the seabird colony.