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

加拿大北部通常被认为是一个原始的环境，但这个地区非常容易受到人为因素的影响，比如长期空气污染、气候变暖和工业发展。许多北方人，特别是土著北方人，依靠传统捕捞的鱼类来获取营养、社会和文化福祉。近年来，北方科学家、监管者和土著居民越来越关注压力源如何影响北方渔业的长期安全（例如，鱼是否可以安全食用？）和生产力（例如，是否有足够的鱼？）汞是与北方自给渔业安全有关的首要问题。汞是一种强效的神经毒素，来自自然和人为来源。随着鱼的成长和年龄的增长，它在鱼体内积累，并随着食物链的每一步而增加，因此食肉鱼（如湖鳟鱼，北梭鱼）的汞含量最高。工业化国家的污染减排计划已经稳定了大气中的汞含量，但是，与我们的预期相反，一些北部湖泊的汞含量继续上升。为了更好地预测未来北方鱼类体内的汞含量，我们需要了解影响汞含量的生态因素，如鱼类的生长速度和饮食，将如何对持续的压力源做出反应。影响鱼类体内汞积累的许多生态因素都受到气候引起的变化的影响，例如鱼类的生长速度、鱼类的饮食和海鱼进行海洋洄游的倾向。冰川和永久冻土的融化预计也会影响湖水的化学成分和污染物的浓度。在从冰川吸收大量融水的湖泊中，冰川沉积物的输入可能会影响顶级捕食鱼类的生长速度、饮食和汞含量，但我们对此的理解还不充分。在“发现”项目的头五年里，我将使用稳定同位素比率、脂肪酸和耳石的微化学分析来调查：1)为什么北部一些湖泊的鱼类汞含量在增加，而在其他湖泊则保持稳定；ii)冰川融化如何影响两种重要的北方鱼类湖鳟鱼和北极灰鲑的生长、饮食和汞含量；以及，iii)幼鱼生长率和湖泊温度如何影响北极湖鳟鱼部分溯河产卵（即海流）种群的生活史和生产力。这个创新和互补的研究项目包括在西北地区、育空地区和努纳武特偏远的北部湖泊进行优雅的、全生态系统的“自然实验”。研究将与土著和政府伙伴合作进行。研究结果将帮助科学家、监管机构、行业和社区了解、预测和管理人类引起的北方渔业安全和生产力的变化，通过回答有关北部湖泊鱼类汞含量变化的新问题，冰川融化将如何影响鱼类生态和鱼类汞含量，以及哪些环境和内部因素决定了部分海流湖鳟鱼是否开始向海洋迁移。与我实验室的其他研究一起，这些结果将有助于我的研究项目的基础长期目标，即通过在种群、群落和生态系统尺度上应用化学示踪剂，更好地了解湖泊化学、鱼类生活史和生态之间的相互作用，以及污染物的生物积累。

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.