Microbial Reduction of Methane Emissions from High-Altitude Thermokarst Lakes

Area of Science:

• Environmental Science
• Microbiology
• Geochemistry

Background:

• Thermokarst lakes are significant methane (CH4) sources due to permafrost thaw.
• Climate change causes wet-dry cycles in lakes, impacting CH4 dynamics.
• Microbial community shifts under wet-dry conditions and their effect on CH4 emissions are poorly understood.

Purpose of the Study:

• To investigate how wet-dry alternations in seasonal thermokarst lakes affect microbial communities and CH4 emissions.
• To quantify the impact of microbial shifts on diffusive CH4 emissions.
• To identify key microbial pathways regulating CH4 production and oxidation.

Main Methods:

• Field observations of thermokarst lakes.
• Laboratory incubation experiments.
• Amplicon sequencing and functional gene analyses.

Main Results:

• Seasonal lakes with wet-dry cycles showed 41-70% lower CH4 emissions than perennial lakes.
• Wet-dry cycles decreased methanogens and syntrophs but increased anaerobic methanotrophic archaea (Candidatus Methanoperedens).
• Acetoclastic methanogenesis was the primary CH4 production pathway, with reduced emissions linked to microbial changes and enhanced anaerobic CH4 oxidation.

Conclusions:

• Wet-dry cycles significantly alter microbial communities in thermokarst lake sediments, reducing CH4 emissions.
• Shifts in microbial populations, particularly the increase of Candidatus Methanoperedens, play a key role in regulating CH4 flux.
• Understanding these microbial dynamics is vital for predicting permafrost carbon-climate feedback and developing CH4 mitigation strategies.