Microbial Carbon Degradation Processes in Thermokarst Lake Sediments from Bykovsky Peninsula, Northern Siberia
Abstract
Permafrost is increasingly affected by rising temperatures. The associated thawing processes are responsible for the development of thermokarst lakes which cover ~20% of the permafrost region of the Northern Hemisphere today. Thermokarst lakes are considered large sources of CH4 contributing to the permafrost carbon feedback and thus, potentially, to climate change. Once thermokarst development is initiated, the organic carbon becomes available for microbial degradation and conversion to CH4 and CO2.
Our study provides a first approach to quantify microbial process rates involved in the anaerobic oxidation of methane (AOM), which potentially mitigates CH4 emissions from thermokarst lake sediments. We retrieved sediment cores of up to 6.1 m length from three lakes situated on the Bykovsky Peninsula, Northeast Siberia, of which each lake represents a different stage of thermokarst development. We produced a large biogeochemical data set to characterize the sediment and its pore water constituents. Using radiotracers, we quantified rates of AOM and sulfate reduction (SR) that are often synthrophically coupled to each other. The sediment of all three lakes is characterized by anoxia and high organic carbon content. Organic matter quality showed no correlation to the biogeochemical data, possibly caused by the complex evolution of the thermokarst systems on Bykovsky Peninsula. However, we suggest that there is an active community mediating AOM throughout the sediment column of all three lakes as we were able to detect potential AOM in all samples. Due to the fact that microbial SR could also be detected throughout the cores, we consider sulfate reducers to be the most probable syntrophic partners for the methane oxidizers. Our study shows that AOM is much more widely distributed in thermokarst lake sediments than previously thought and could play a role as a natural methane filter.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B23M2578K
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0702 Permafrost;
- CRYOSPHERE;
- 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE