Climate Change Impacts on Mercury and Methylmercury Sources to Arctic Ecosystems

我的研究计划的长期目标是更好地保护北方生态系统免受环境压力因素的影响，如污染物和气候变化，以确保生活在北方的加拿大人的水和国家粮食资源的安全。北极生态系统中的汞污染是一个令人担忧的问题，因为据报道，北极野生动物的汞浓度超过了生态毒理学阈值，而土著居民依赖许多相同的动物，如鱼和海豹，作为传统的食物来源。汞的毒性最大的形式和唯一能够在生物体中积累的形式是甲基汞（MeHg）。因此，通过甲基化过程将无机形式的汞转化为有机形式的甲基汞是将这种毒素吸收到水生食物链之前的关键步骤。为了预测北方生物系统中甲基汞的暴露风险和浓度如何响应气候和工业汞排放的变化，有必要了解甲基汞的各种来源是什么，汞是如何甲基化的，以及控制环境中汞存在的过程如何受到气候变化的影响。为了解决这些知识差距，我提出的研究有三个总体目标。第一个目标是测量未知但可能重要的北极淡水甲基汞来源。这包括融雪中汞向下游湖泊的输出，以及积雪和湖水中汞的甲基化。第二个目标是确定湖泊中甲基汞生产与气候敏感参数（如湖泊冰盖和初级生产（即藻类光合作用））之间的关系。因此，除了湖泊中的汞甲基化外，我们还将测量湖泊代谢（初级生产和呼吸），这将提供有关支持水生生物的能量过程的有用信息，使我们能够了解气候变化如何影响鱼类种群等。与前两个目标有关的研究将在高北极地区横跨北纬69°至北纬82°的三个地点进行。第三个目标是检验北极大气汞浓度与气候（如温度、降水、海冰范围和主要气候模式）之间的长期关系，方法是测量过去835年麦肯齐三角洲地区存档的树木年轮样本中的汞含量。这项研究将提供有关污染物和生态系统生产力的宝贵信息，可供多个利益攸关方（如政府、土著组织、决策者和公共卫生官员）用于管理北方水生资源。

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.