Climate Effects on Contaminant Exposure of Arctic Marine and Freshwater Biota

Contaminant concentrations in arctic freshwater and marine biota have been monitored fairly consistently since the late 1980s. The prevailing paradigm attributes observed changes to global emissions, usage patterns and to processes such as long-range atmospheric transport, food web structures, and length. There is no doubt that the global banning and restricted usage of pesticides and industrial chemicals and stricter emissions regulations for mercury during the late 20th century have resulted in reduced exposure. However, since the mid-1990s, the levels of these contaminants in many species of arctic marine and fresh water biota and sediments have not declined and in some cases have even increased. These increases, which oppose the decreasing trends in the atmosphere, rule out atmospheric contaminant levels as a dominant driver and other mechanisms must be considered. Several examples of climate driven changes to contaminant loadings and exposure in Canadian Arctic biota are discussed. First, we present temporal trend results for mercury and selected PCBs in Mackenzie River burbot collected between 1985 and 2008 and examine the relationship between the trends of mercury in these fish and those in a dated sediment core collected from a nearby lake whose limnology is profoundly affected by climate warming and which feeds directly into a tributary along the Mackenzie River where these fish are thought to feed. Secondly, we examine a unique time series of ringed seal samples collected from a single location in the western Canadian Arctic between 1973 and 2007 to test for changes in total mercury in muscle tissue associated with year and length of ice-free season. Results offer insight into how marine mammals may respond to directional changes in the arctic ice-free season.