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

在全球范围内，湖泊和河流只占景观的很小一部分。然而，我们的研究表明，它们向大气排放的温室气体（主要是二氧化碳）数量惊人，几乎与目前海洋每年吸收的温室气体一样多。同样，湖泊也会在沉积物中积累和储存有机碳。由于在淡水环境中观察到的高度保存，湖泊沉积物通常含有与整个流域土壤一样多的碳。从全球来看，这个碳汇比海洋的碳汇要大得多。在这项建议中，我们希望增进我们对下列因素的了解：1)碳排放到大气中的速率和2)碳在沉积物中积累的速率。更具体地说，我们建议在三个不同的时间尺度（年、多年代际和千年尺度）上建立多湖泊和多区域的湖泊碳积累模型。我们还建议研究影响气体交换的因素，这是一个决定二氧化碳和甲烷与大气交换速度的重要变量。此外，我们将进一步验证我们之前的发现，即相当一部分甲烷通过甲烷微泡的逃逸而逃逸到湖面，并测试其重要性是否可以更好地量化和预测。

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.