Climate Change Impacts on Mercury and Methylmercury Sources to Arctic Ecosystems

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The long-term objective of my research program is to better protect northern ecosystems from the impacts of environmental stressors, such as contaminants and climate change, in order to ensure the security of water and country food resources for Canadians living in the North. Mercury (Hg) contamination in Arctic ecosystems is a concern given that concentrations exceeding ecotoxicological thresholds have been reported in Arctic wildlife, and that aboriginal people rely on many of these same animals, such as fish and seals, as traditional food sources. The most toxic form of Hg and the only form capable of accumulating in living organisms is methylmercury (MeHg). Therefore, the conversion of mercury in its inorganic form to the organic MeHg form by a process called methylation is the key step that precedes the uptake of this toxin into aquatic food chains. To predict how exposure risk and concentrations of MeHg in biological systems in the North will respond to changes in climate and industrial Hg emissions, it is necessary to understand what the various sources of MeHg are, how Hg is methylated, and how processes that control the presence of Hg in the environment are affected by climate change. To address these knowledge gaps, my proposed research has three overarching objectives. The first objective is to measure unknown but potentially important sources of MeHg to Arctic freshwaters. These include the export of MeHg in snowmelt to downstream lakes, and Hg methylation in both snowpacks and lake waters. The second objective is to determine the relationship between MeHg production in lakes and climate-sensitive parameters, such as lake ice cover and primary production (i.e., algal photosynthesis). Therefore, in addition to Hg methylation in lakes, we will also measure lake metabolism (primary production and respiration), which will provide useful information on the energetic processes that support aquatic life, allowing us to understand how climate change may impact fish stocks, for example. Research pertaining to the first two objectives will be carried out at three locations in the High Arctic spanning a latitudinal gradient from 69°N to 82°N. The third objective is to examine the long-term relationship between Arctic atmospheric Hg concentrations and climate (e.g., temperature, precipitation, sea-ice extent and major climate modes) by measuring Hg in archived tree-ring samples from the Mackenzie Delta region that encompass the last 835 years. This research will provide valuable information on contaminants and ecosystem productivity that can be used by multiple stakeholders (e.g., government, aboriginal organizations, policy makers and public health officials) to manage northern aquatic resources.**