Carbon dioxide and methane annual emissions from two boreal reservoirs and nearby lakes in Quebec, Canada

Abstract. The results of dissolved GHG (CO₂ and CH₄) measurement campaigns carried out in Quebec (Canada) during the open-water periods and under-ice in a newly created reservoir (Eastmain 1), a 25 year old reservoir (Robert-Bourassa) and in three reference lakes are presented. While CO₂ partial pressures varied with season with a net increase under the ice cover, CH₄ partial pressures did not. We were able to extrapolate the highest CO₂ partial pressures reached in the different studied systems just before ice break-up with high spring emission period. We then estimated the springtime CO₂ fluxes and compared them to annual CO₂ fluxes and GHG fluxes. Thus we clearly demonstrated that in our systems CH₄ fluxes was of minor importance in the GHG emissions, CO₂ fluxes representing around 90% of the annual fluxes. We also pointed out the importance of springtime emissions in the annual budget.