Carbon transformation in lakes

湖泊与它们排干的土地有着千丝万缕的联系。有机碳以及从陆地上流失的其他养分和矿物质一旦到达湖泊，就会被积极转化。例如，溶解在溪水中的有机碳(DOC)可以在湖泊中分解，产生二氧化碳，最终将损失到大气中。然而，湖泊中的几个方面或碳转化仍然知之甚少。例如，二氧化碳在湖泊表面的分布并不均匀，这意味着整个湖泊对湖泊二氧化碳排放的贡献并不相等。我们建议使用新的测量技术来研究这种非均质性，以量化其程度，决定其大小的因素，其来源，以及它是否对我们估计二氧化碳从湖泊表面逃逸的速度重要。在第二个项目中，我们建议研究水生杂草如何通过释放光合作用的很大一部分DOC来改变湖泊的化学和生物。在杂草覆盖不断增加的湖泊中，植物释放的这种有机物可以抵消甚至可能颠覆通常在湖泊中分解的陆地有机碳的数量。最后，我们将探索湖泊中一种未知的DOC部分，这里称为挥发性DOC。这一比例不是用传统方法测量的，我们的重点将是量化它在湖泊中的重要性和生态作用。

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.