Methane-derived carbon flow through microbial communities in arctic lake sediments

Area of Science:

• Environmental Microbiology
• Biogeochemistry
• Arctic Ecology

Background:

• Aerobic methane (CH4) oxidation is crucial for mitigating CH4 release and channeling carbon into aquatic food webs.
• Arctic lakes contribute significantly to global CH4 emissions, yet CH4 assimilation within their food webs remains understudied.

Purpose of the Study:

• To quantitatively track carbon flow from methane (CH4) into sediment microorganisms in an Arctic lake.
• To identify key microbial groups involved in methane assimilation and secondary consumption of CH4-derived carbon.

Main Methods:

• Utilized stable isotope probing (SIP) techniques, specifically phospholipid fatty acid (PLFA-SIP) and DNA (DNA-SIP) analyses.
• Investigated carbon incorporation from CH4 into microorganisms within lake sediment near an active CH4 seepage.

Main Results:

• 15.8–32.8% of oxidized CH4-derived carbon was incorporated into microorganisms, representing up to 5.7% of estimated primary production in Alaskan Arctic lakes.
• Type I methanotrophs (e.g., Methylomonas, Methylobacter) were primary CH4 oxidizers.
• Actinomycetes were significant in secondary consumption of CH4-derived carbon, with microbial diversity incorporating CH4 increasing away from the seepage.

Conclusions:

• Methane carbon flows from methanotrophs into the wider microbial community in Arctic freshwater ecosystems.
• Type I methanotrophs, methylotrophs, and actinomycetes play vital roles in utilizing CH4-derived carbon in these environments.