The changing boreal carbon cycle at the land-water-sediment interfaces

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The demand for low-carbon power is rapidly increasing across Canada due to recent developments in technologies and environmental policies that aim at reducing human impacts on the global climate. Hydro-power is perceived as a clean source of power by many Canadians, but damming carries an environmental footprint in terms of greenhouse gases emission and mercury levels that cannot be ignored, which is a hurdle for future developments in the country and exports of hydro-electricity. Moreover, this footprint depends on the underlying baseline fluxes of C and Hg that would occur even in the absence of reservoirs, but this baseline is rapidly changing in response to natural and human driven perturbations such as global warming, extremes in precipitation patterns, changes in atmospheric deposition, as well as forest fires. Full understanding of the net environmental footprint of hydro-power hence relies on two main aspects: a) accurate estimations of the fluxes of carbon and mercury in hydro-electric reservoirs over time and b) quantification of the natural fluxes of carbon and mercury at the landscape before dams were constructed. The latter is not trivial because very few estimates exist in the water-rich Canadian boreal biome and because existing estimates ignore the disproportionately important but understudied small water bodies. With the long term goal of disentangling the net effects of reservoirs on the cycling of C and Hg from shifts in natural baselines, we aim, with this project, to 1) quantify the modern and historical variation in carbon and mercury fluxes in comparison to the effect of reservoirs, 2) improve understanding of the movement and transformation of carbon from land to water across under-studied small water bodies, and 3) better understand the association between the cycling of carbon and mercury in aquatic ecosystems found in different regions across the boreal biome. To do so we will conduct field work focusing on the sampling of water and sediments of small lakes, wetlands in three regions of boreal Québec where there are major hydro-electric activity. We will further leverage existing geographic and field data to model past and future changes in the fluxes of carbon and mercury. The knowledge generated by this research will provide industries and managers with the data needed to refine the net environmental impacts of hydro-power for a better assessment of its competitiveness compared to other sources of energy as well as to hydro-power produced in other countries.