Whole ecosystem carbon dynamics in lakes: accumulation, processing and degassing at different temporal and spatial scales

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At the global scale, lakes and rivers occupy a very small fraction of the landscape. Yet, our research has shown that they emit surprisingly large quantities of greenhouse gases (mostly carbon dioxide) to the atmosphere, nearly as much as the oceans currently absorb annually. Similarly, lakes also accumulate and store organic carbon in their sediments. Because of the high preservation observed in freshwater environments, lake sediments often contain as much carbon as the soils of their entire watersheds. Globally, this carbon sink is much larger than that of the oceans. In this proposal, we wish to increase our understanding of the factors determining 1) the rate at which carbon is emitted to the atmosphere and 2) the rates at which it accumulates in sediments. More specifically, we propose to develop multi-lake and multi-regional models predicting carbon accumulation in lakes at three different time scales (annual, multi-decadal, and millennial scales). We also propose to examine the factors influencing gas exchange, an important variable that determines how fast carbon dioxide and methane can be exchanged with the atmosphere. In addition, we will further test our earlier discovery that a significant part of methane escapes lake surface through evasion of methane microbubbles and test whether their importance can be better quantified and predicted.