Carbon transformation in lakes

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Lakes are inextricably linked to the land they drain. Organic carbon as well as other nutrients and minerals lost from the land are actively transformed once they reach lakes. For example, organic carbon dissolved (DOC) in streamwater can be decomposed within the lake, producing carbon dioxide that will eventually be lost to the atmosphere.  Yet, several aspects or carbon transformation in lakes remain poorly known. For example,  carbon dioxide is not homogeneously distributed over the surface of lakes, implying the at whole lake does not contribute equally to lake CO2 emission. We propose to study this heterogeneity using novel measurement techniques, to quantify its extent, the factors that determine its magnitude, its origin and whether it matters to our estimation of the rates at which CO2 escapes from the lakes'surface. In a second project, we propose to examine how aquatic weeds can alter the chemistry and biology of lakes by releasing a significant fraction of their photosynthesis as DOC. In lakes where weed cover continues to increase, such release of organic matter by plants can counterbalance and possibly overturn the amount of terrestrial organic carbon normally decomposed in the lake.   Lastly, we will explore an as yet unknown fraction of DOC in lakes, here called volatile DOC. This fraction is not measured by conventional methods and our focus will be to quantify its importance and ecological role in lakes.