Isotopic and non-isotopic tracers for biogeochemical cycles of nutrients in pristine and impacted watersheds

营养物质驱动着水生淡水生态系统的食物网、生产力和作为人类饮用水来源的适宜性。营养物质的生物地球化学循环既包括主要营养物质(碳、氮、磷、氧)，也包括次要营养物质，特别是那些随氧气条件而变化的营养物质(铁、硫、痕量金属)。这些相互关联的周期是复杂的，可能很难将关键过程和对其速度的控制分开。预测人类活动(农业、采矿、林业)和气候变化(降水、温度和风暴)造成的养分循环变化需要这些知识。示踪器提供了其他方法无法获得的洞察力。在我们长期的、国际上成功的研究计划中，我们在使用自然产生的元素同位素和其他示踪剂方面获得了专业知识。我们的长期目标是开发和应用示踪剂，以深入了解北部、森林和受人类影响的流域的关键生物地球化学过程。*这项NSERC发现赠款计划建立在我们研究计划中的一些最新发现的基础上。选定了四个相互关联的项目，所有项目的共同主题都是战略性地利用示踪剂来解决加拿大社会关心的淡水问题。所有项目都以研究生研究为核心，涉及开发新的技术和方法，利用分析技术的进步和来自循环营养的生物体DNA的新信息。这些项目是：1.改变一种强有力的温室气体CH4的模式：对大气中CH4排放的影响、营养变化的影响、最近发现的新生物和食物网的同位素追踪；2.湖泊中铁和有机质的相互联系的循环：铁同位素和溶解有机物(DOM)形成有害藻华和碳在沉积物之间分配(碳固存)和作为温室气体排放到大气中的新技术；3.加拿大亚北极的高DOM环境：对北部社区饮用水供应的影响，包括消毒过程和消毒副产品的生产的有效性，以及加拿大对NASA碳排放计划的贡献；以及4.改变营养贫乏的加拿大高北极流域的营养循环。最后两个项目包括学生在亚北极(-67N)和北极高地(82N)的持续实地活动，是《北方研究增刊》申请的主题。通过我们与来自政府、土著社区和非营利组织的各种利益相关者的广泛的国内和国际合作，这些利益相关者需要以科学为基础的信息进行决策，我们的学生独特地准备好为加拿大社会贡献他们的专业知识。

Nutrients drive aquatic freshwater ecosystems in terms of their food webs, productivity and suitability as sources of drinking water for humans. Biogeochemical cycling of nutrients involves both major nutrients (carbon, nitrogen, phosphorus, oxygen) and minor nutrients, especially those that change form depending on oxygen conditions (iron, sulfur, trace metals). These interlinked cycles are complex and it can be difficult to tease apart critical processes and controls on their rates. Prediction of changes in nutrient cycling due to human activities (agriculture, mining, forestry) and climatic changes (precipitation, temperature and storms) requires this knowledge. Tracers provide insight that is not obtainable from other methods. In our longstanding, internationally successful research program, we have acquired specialized expertise in the use of naturally occurring isotopes of elements and other tracers. Our long term goal is to develop and apply tracers to provide insight into key biogeochemical processes in northern, forested and human impacted watersheds.*** This NSERC Discovery Grant proposal builds on a number of recent discoveries in our research program. Four interrelated projects have been selected, all with the common theme of strategic use of tracers for addressing freshwater issues of concern to Canadian society. All projects have graduate student research at their core and involve development of new techniques and approaches, capitalizing on advances in analytical technology and novel information available from DNA of organisms that cycle nutrients. These projects are: 1. Changing the paradigms for CH4, a potent greenhouse gas: implications for CH4 emissions to the atmosphere, effect of changing nutrients, recently discovered novel organisms and isotopic tracing of food webs; 2. Interlinked cycles of iron and organic matter in lakes: new techniques for iron isotopes and dissolved organic matter (DOM) for formation of harmful algal blooms and partitioning of carbon between sediments (carbon sequestration) and release to the atmosphere as a greenhouse gas; 3. High DOM environments in subarctic Canada: implications for drinking water supplies for northern communities including the efficacy of disinfection processes and production of disinfection by-products, and a Canadian contribution to the NASA program on carbon emissions; and 4. Changing nutrient cycles in nutrient poor High Arctic Canadian watersheds. The last two projects include sustained field activities by students in the subarctic (64-67N) and high Arctic (82N) and are the subject of a Northern Research Supplement application. Through our extensive national and international collaborations with a variety of stakeholders from government, indigenous communities and non-profits who require sciencebased information for decisions, our students are uniquely poised to contribute their expertise to Canadian society.