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

营养物在其食物网、生产力和作为人类饮用水源的适宜性方面驱动着水生淡水生态系统。营养物的生物地球化学循环涉及主要营养物（碳、氮、磷、氧）和次要营养物，特别是那些根据氧条件改变形式的营养物（铁、硫、微量金属）。这些相互关联的周期是复杂的，很难将关键流程和对其速率的控制分开。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方面的知识。示踪剂提供了其他方法无法获得的洞察力。在我们长期的国际成功的研究计划中，我们获得了使用元素和其他示踪剂的天然同位素的专业知识。我们的长期目标是开发和应用示踪剂，以深入了解北方、森林和人类影响流域的关键地球化学过程。* 这个NSERC发现补助金提案建立在我们研究计划中的一些最新发现之上。已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使用示踪剂，以解决加拿大社会关注的淡水问题。所有项目都以研究生研究为核心，涉及新技术和新方法的开发，利用分析技术的进步和从循环营养物质的生物体DNA中获得的新信息。这些项目是：1.改变模式的甲烷，一个强大的温室气体：甲烷排放到大气中的影响，不断变化的营养物质的影响，最近发现的新生物和同位素示踪的食物网; 2。铁和有机物在湖泊中的相互联系的循环：铁同位素和溶解有机物（DOM）的新技术，用于形成有害藻华和沉积物之间的碳分配（碳封存）和作为温室气体释放到大气中; 3.高DOM环境在亚北极加拿大：饮用水供应的影响，包括消毒过程的功效和消毒副产品的生产，北方社区，加拿大的贡献，美国宇航局计划的碳排放量;和4。加拿大高北极地区营养贫乏流域的营养循环变化。最后两个项目包括学生在亚北极（北纬64- 67度）和高北极（北纬82度）的持续实地活动，是北方研究补充申请的主题。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家和国际合作，他们需要基于科学的信息进行决策，我们的学生独特地准备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.