Carbon gas dynamics in aquatic ecosystems: integrating physical processes and biogeochemical cycling

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The central goal of my research is to establish a solid quantitative framework to assess the role of inland waters in landscape C budgets, from local to global. Recent research by our group and elsewhere has identified CH4 as a significant player. Owing to the much more complex nature of the biogeochemical cycling of methane relative to CO2, estimates of its current contribution to total GHG emissions are still loosely constrained. However, with its high warming potential and temperature sensitivity, its future role is potentially much more important but even less foreseeable. I contend that part the difficulty in assessing and predicting its contribution is the lack of a physical-biogeochemical framework in which to integrate the main fluxes, namely production pathways, transport mechanisms, degree of oxidation and ultimately evasion to the atmosphere. The proposed research program is articulated around several sub-projects focussing on methane dynamics with an emphasis on the role played by physical constraints impinging on the rates of biogeochemical processes. The study will first be conducted on a model lake (L. Croche) and then be extended to a cross section of representative lakes covering gradients of ecosystem size, shape and nutrient status. We will also conduct detailed investigations to further our understanding of a key component of emission, gas exchange (k600), with an emphasis on the ecological role it plays. Together, these components of the research program will provide the necessary framework to better understand CH4 dynamics in lakes that will ultimately lead to the better predictions of CH4 emission from aquatic ecosystems. **