Microbial controls of mercury cycling

目前正在进行的重大环境变化，加上对北方自然资源开发的增加，对生态系统造成了重大压力，即改变了污染物的命运。为了确保对这些资源的合理管理，保护野生动物和人类健康，关键是要进一步提高我们预测毒物命运的能力，并在典型的加拿大景观和条件下制定补救策略。在有毒金属中，汞(Hg)是一种全球优先污染物，因为其最有毒的单甲基汞(MmHg)在食物网中被生物放大，即使在加拿大北极等偏远地区也是如此。汞作为一种对人类健康至关重要的化学物质，最近通过了《水银公约》，这是一项具有法律约束力的条约，2013年10月由包括加拿大在内的140多个国家签署，突显了汞作为一种化学物质的重要性。该条约要求政府机构有能力监测影响全球汞运输和自行车的过程。这项建议将填补联合国环境规划署最新汞评估报告中强调的与汞运输和自行车相关的重要知识空白。我的第一个目标是确定溶解有机物(DOM)如何影响汞和毫米汞的生物利用度，以评估汞沉积、甲基化和生物吸收之间的联系。我的第二个目标是描述适应寒冷的微生物的汞抗性策略的多样性，并开发新的基于微生物的生态系统服务，用于受污染场地的生物修复。我的第三个目标是开发新的古指标，通过评估遗传编码的细菌抗性机制如何随着汞向生态系统输送的最近变化而演变，来跟踪环境中的汞再动员。最后一个目标将有助于评估生态系统对汞沉积的反应所涉及的时间滞后，并预测汞排放减少后的恢复时间。

Major environmental changes now underway combined with increased exploitation of northern natural resources impose an important stress on ecosystems, namely by altering the fate of contaminants. To ensure sound management of these resources and protection of wildlife and human health, it is critical to further our ability to predict the fate of toxicants and to develop remediation strategies in typical Canadian landscapes and conditions. Among toxic metals, mercury (Hg) is a global priority contaminant due to the biomagnification of its most toxic form monomethylmercury (MMHg) in foodwebs, even in remote regions such as the Canadian Arctic. The importance of Hg as a chemical of major concern to human health was underscored by the recent adoption of the Minamata Convention on Mercury, a legally binding treaty signed in Oct 2013 by more than 140 countries including Canada. This treaty requires that government agencies be equipped to monitor processes affecting global Hg transport and cycling. This proposal will fill important gaps of knowledge related to Hg transport and cycling highlighted in the most recent UN Environmental Programme Hg assessment report. My first objective is to determine how dissolved organic matter (DOM) affects Hg and MMHg bioavailability to assess the link between Hg deposition, methylation and uptake by living organisms. My second objective is to characterize the diversity of Hg resistance strategies in cold-adapted microbes and develop new microbe-based ecosystem services for the bioremediation of contaminated sites. My third objective aims to develop new paleo-proxies that track Hg remobilization in the environment by evaluating how genetically encoded bacterial resistance mechanisms evolved in response to recent changes in Hg delivery to ecosystems. This last objective will contribute to evaluating the time lag involved in ecosystem responses to mercury deposition and predicting recovery time following the reduction in Hg emissions.