Pockmark formation and methane emission in Lake Constance

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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?