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

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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 (64-67°N) and high Arctic (82°N) 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 science-based information for decisions, our students are uniquely poised to contribute their expertise to Canadian society.