Temporal variability and habitat compartmentalization of methanotrophic microbes in Arctic permafrost ponds

Jakob Pernthaler
Gabriela Schaepman-Strub
Alizée Le Moigne

Aim: Study the biodiversity of aerobic and anaerobic methanotrophs in different pond types. Perform continuous temporal measurements of methane and water chemistry with newly developed instrumentation.     

Research: The same processes and microbial functional groups will be studied with comparable approaches at two URPP test sites (Kytalyk, Lake Zurich). This project is innovative as neither of the PIs previously focused on the mechanisms that affect methane biogeochemistry in freshwater systems; this topic has entirely emerged from our common investigation of thermokarst ponds during Phase II, and a related external project emerging from it, led by a collaborator at UniBasel, with us as Co-I’s (funded by Swiss Polar Institute). The thawing of the permafrost mobilizes an important stock of labile organic carbon and increases methane emissions from Arctic ponds. Will methanotrophs mitigate this development? The research will address interactions and feedbacks of a global change driver (predominantly climate change) and biodiversity.

The most prevalent water bodies of the northern tundra are small thermokarst ponds with a depth <2 m. Our research at the Siberian test site has identified at least 2 distinct categories of such ponds that differ in their genesis, in landscape-related aspects, and water chemistry. It is possible to distinguish between pond types through vegetation proxies using drones. These ponds tend to shrink or even dry up during growing seasons that are poor in precipitation, which, in turn, may affect their biogeochemical functioning. Thermokarst ponds are also hotspots of global change in the Arctic landscape, since the emissions of the potent greenhouse gas methane from such systems account for two-third of total emissions in regions above the latitude 50°N. A fraction of the newly produced methane in all aquatic environments is removed by the activity of aerobic and anaerobic methanotrophic microbes, thereby diminishing its flux to the atmosphere. We propose to deploy an automated measurement platform in thermokarst ponds to assess the temporal variability of physicochemical water properties and methane concentrations in response to different meteorological forcing. In addition, we will investigate the relationship between methane flux and the distribution of methanotrophs over different habitat compartments (water, sediment, biofilms).