7.4       Mercury trends in colonial waterbird eggs downstream of the oil sands region of Alberta, Canada

Bruce Pauli, Environment Canada




Colonial waterbird eggs have been used for decades to monitor levels and potential effects of environmental pollutants. In this study, colonial waterbird eggs were collected from two sites in northern Alberta and one site in southern Alberta over several years, with additional collection sites being added over the course of the study. Northern sites were located in receiving waters of the Athabasca River. Eggs collected from 1977, and from 2009-2013, were analysed for egg mercury (Hg) levels and for stable nitrogen isotope values (d15N) as an indicator of dietary change. In northern Alberta, results indicate a general increase across species (California Gulls, Ring-billed Gulls, Caspian Terns, Common Terns) in egg Hg concentrations compared to the earliest year of sampling for each species at each site. In southern Alberta, Hg concentrations in California Gull eggs declined through time, suggesting the pattern observed in northern Alberta is not consistent across the region. Bird dietary change was not responsible for any of these trends; neither were egg Hg trends related to recent forest fires. The data indicate the importance of local Hg sources in regulating regional Hg trends. Hg concentrations in gull and Common Tern eggs were generally below generic thresholds associated with toxic effects in birds, while in 2012, Hg levels in Caspian Tern eggs exceeded a lower toxicity threshold. Hg levels in eggs of multiple species nesting downstream of the oil sands region of northern Alberta warrant continued monitoring and research to further evaluate Hg trends and to conclusively identify sources.




Bruce Pauli‘s research on the effects of environmental pollution have the overarching goal of establishing techniques that can be used to evaluate and assess environmental change. His research focuses on aquatic ecosystems using amphibian species as sentinel organisms. This research has included efforts to standardize toxicity tests with native amphibian species, to examine determinants of disease in native amphibians, and attempts to further understand cumulative effects and the response of wild amphibian populations to multiple stressors. Bruce Pauli is currently a Research Manager and Chief, Ecosystem Health Research Section within the Ecotoxicology and Wildlife Health Division of Environment Canada.