Lake biogeochemical dynamics: the conveyor belt between physics and biology

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The proposed research program focuses on coupled biogeochemical cycles in northern lakes. The context of this research is that water quality in lakes is impacted by multiple stressors, causing geochemical and ecological changes in lakes. Such stressors include climate change (impacting temperature, irradiance, wind and precipitation), and changing loads of elements. We lack the knowledge and quantitative tools to predict lake responses to these ongoing changes, which limits our capacity to act to either prevent or mitigate their deterioration. Our aim is to acquire, using data and models, a quantitative understanding of the complex interplay between coupled biogeochemical cycles and their responses to external and internal pressures affecting lakes. Students with backgrounds in chemistry, biology, bioinformatics and engineering will be provided with research opportunities and an international outlook. ******The overarching objective of the research program is to understand the response of coupled biogeochemical cycles in lakes to multiple pressures across spatial scales. It will focus on the cycles of chemical elements, namely carbon (dissolved and particulate C, CO2 and CH4), O, nutrients (P and N), metals (Fe, Mn and Al) and trace elements (e.g., As, Se, Mo). From a theoretical standpoint, we are interested in identifying the network of coupled processes in biogeochemical cycles that sustain water quality in contrasting lakes, and in quantifying how future lake functioning depends on their past history. Using models, we will disentangle changing external environmental pressures from accumulated internal pressures. The proposed research activities are distributed across three themes: (1) the sedimentary geochemistry of lakes affected by external and internal nutrient loads, (2) the response of lake oxygen dynamics, and in particular seasonal anoxia, to irradiance, ice phenology and organic matter loads along a latitudinal bioclimatic gradient reaching the Canadian arctic, and (3) the process-oriented modelling of physical and biogeochemical lake dynamics at the regional scale. **