Pockmark formation and methane emission in Lake Constance

在前一个项目中，首次详细研究了淡水环境（德国南部康斯坦茨湖）中的麻点。第一批的结果显示，阿尔卑斯河莱茵河入口附近的湖底有相当大的面积布满了密密麻麻的麻点。这些直径可达16米的麻点大多位于沿着山脊。甲烷释放主要是大量的气体沸腾，这大大增加了水柱中的甲烷浓度。甲烷排放在时间和空间上变化很大。对气体的同位素分析显示出一种轻微而明显的生物成因特征。基于第一个资助期的良好结果，下一个资助期将研究以下新课题：（1）博登湖麻点的形成是否仅与有机质的高投入有关，麻点的形成与哪些时间尺度有关？(2)甲烷通量和沸腾如何随时间（如季节性周期）和空间变化？(3)甲烷氧化细菌在减少甲烷通量中扮演什么角色，它们是否适应这种特定的环境？(4)在底栖和远洋食物链中能否追踪甲烷产生的轻质碳？

In the preceding project, pockmarks in a freshwater environment (Lake Constance, Southern Germany) were studied in detail for the first time. The results of the first granting period revealed that a considerable area of the lake bottom near the entrance of the Alpine River Rhine is densely covered with pockmarks. These pockmarks with a diameter of up to 16 m are mostly located along ridges. Methane release was dominated by massive gas ebullition, which increased the methane concentrations in the water column substantially. Methane releases were highly variable in time and space. Isotopic analysis of the gas revealed a light and clearly biogenic signature. Based on the promising results of the first granting period, the following new topics will be investigated within the next granting period: (1) is the formation of pockmarks in Lake Constance only related to high input of organic matter and which time scales are relevant for pockmarks? (2) How does the methane flux and ebullition vary over time (e.g. seasonal cycle) and space? (3) Which role play methane-oxidizing bacteria in reducing the methane flux, and are they adapted to this specific environment? (4) Can the light methane-derived carbon be followed up in the benthic and pelagic food chains?