Mercury trends in cormorant and great blue heron eggs from Pacific Canada: a question of local and global sources

• Main Authors: Brown, Tanya, Elliott, John E. (John Edward), Elliott, Kyle, Lee, Sandi
• Format: Text
• Language: English
• Published: Western CEDAR 2018
• Subjects: Mercury; Seabirds; Fresh Water Studies; Life Sciences; Marine Biology; Natural Resources and Conservation; Terrestrial and Aquatic Ecology; Arctic; Canada; Pacific
• Online Access: https://cedar.wwu.edu/ssec/2018ssec/allsessions/336; https://cedar.wwu.edu/cgi/viewcontent.cgi?article=2771&context=ssec

Mercury (Hg) levels and trends in the NE Pacific Ocean are due to the convergence between natural and anthropogenic sources, with the latter broadly related to a combination of local and long-range sources. Legacy and current local point sources include chlor-alkali plants, pulp and paper mills and other mixed sources. In addition, long-range atmospheric and oceanic pathways deliver mercury to the Pacific coast, primarily from points to the west, where it is taken up by algae and bacteria and transferred through the marine food web in its inorganic form, but also its organic form, methylmercury. We present data on Hg trends in pelagic cormorant ((Phalacrocorax pelagicus) and great blue heron (Ardea herodias) eggs in Pacific Canada over a 48 year period. Temporal trends are evaluated using both diet- and non-diet-adjusted data and compared to Hg trends observed in other seabird species in the region, as well as the Atlantic and Arctic Oceans. Mercury concentrations declined alongside δ34S over time in both species, but no trend for δ13C and δ15N was apparent. The present study provides explanations for these trends in the context of local and long-range sources in the region and dietary contributions.