Impact of Lake Expansion on Mercury Concentrations in Lake Sediments, Mackenzie Bison Sanctuary, Northwest Territories, Canada

Spatial and temporal variations in total mercury, organic matter and lake surface area were assessed to determine if flooding in the Mackenzie Bison Sanctuary was influencing Hg inputs to lake sediments. Mercury concentrations in the sediment of lakes examined are below established guidelines. All lakes demonstrated increased Hg concentration and flux over the past century. Two expanding lakes exhibited maximum total Hg values in surface sediments which correlated with peaks in water surface area and changes in source of organic matter. Reference lakes demonstrated declining total Hg values in recent sediments and no correlation with organic matter or water surface area. This study presents land users and managers with a preliminary assessment of Hg concentrations within MBS lakes. Recommended future work should focus on methyl mercury concentrations and methylation rates in sediments, which often increase after landscapes are flooded, and can pose risks to wildlife species relying on the ecosystem.