Aquatic Ecology and Contaminant Accumulation in Northern Lakes: Understanding and Predicting Change

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The Canadian north is often thought of as a pristine environment, but this region is extremely vulnerable to human-induced stressors such as long-range air pollution, climate warming, and industrial development. Many northerners, particularly Aboriginal northerners, rely on traditionally-harvested fish for nutritional, social, and cultural well-being. In recent years, northern scientists, regulators, and Aboriginals have become increasingly concerned with predicting how stressors will affect the long-term safety (e.g., are the fish safe to eat?), and productivity (e.g., will there be enough fish?) of northern fisheries. Mercury is at the forefront of issues relating to the safety of northern subsistence fisheries. Mercury is a potent neurotoxin that comes from both natural and human sources. It accumulates in fish as they grow larger and older and increases with each step in the food chain so that predator fish (e.g., Lake Trout, Northern Pike) have the highest mercury levels. Pollution abatement programs in industrialized countries have resulted in stabilizing mercury levels in the atmosphere, but, contrary to our expectations, mercury levels in some northern lakes continue to rise. To better predict future mercury levels in northern fishes, we need to understand how ecological factors that affect mercury levels, such as fish growth rate and diet, will respond to continuing stressors. Many ecological factors that affect accumulation of mercury in fish are subject to climate-induced change, such as fish growth rates, fish diet, and propensity of sea-run fish to make marine migrations. Melting of glaciers and permafrost is also expected to affect lake water chemistry and concentrations of contaminants. In lakes that receive significant meltwater from glaciers, inputs of glacial sediment could affect growth rates, diet, and mercury levels in top predator fishes, but our understanding of this is inadequate. In the first five years of my Discovery program, I will use analyses of stable isotope ratios, fatty acids, and microchemistry of otoliths to investigate: i) why fish mercury levels are increasing in some northern lakes but stable in other lakes; ii) how melting glaciers affects growth, diet, and mercury levels in two important northern fishes, Lake Trout and Arctic Grayling; and, iii) how juvenile growth rates and lake temperature may affect life history and productivity of partially anadromous (i.e., sea-run) populations of Lake Trout in the Arctic. This innovative and complementary research program includes elegant, whole-ecosystem ‘natural experiments’ at remote northern lakes in the Northwest Territories, Yukon Territory, and Nunavut. Research will be conducted in collaboration with Aboriginal and government partners. Results will help scientists, regulators, industry, and communities understand, predict, and manage human-induced changes in the safety and productivity of northern fisheries by answering novel questions about variability in fish mercury levels in northern lakes, how melting glaciers will affect fish ecology and fish mercury levels, and what environmental and internal factors determine whether partially sea-run Lake Trout begin migrations to the ocean or not. Together with other research in my lab, results will contribute to the foundational long-term objective of my research program, which is to better understand interactions among lake chemistry, fish life history and ecology, and contaminant bioaccumulation through application of chemical tracers at population, community, and ecosystem scales.