Diverse sediment microbiota shape methane emission temperature sensitivity in Arctic lakes

AbstractNorthern post-glacial lakes are significant, increasing sources of atmospheric carbon through ebullition (bubbling) of microbially-produced methane (CH4) from sediments. Ebullitive CH4 flux correlates strongly with temperature, reflecting that solar radiation drives emissions. However, here we show that the slope of the temperature-CH4 flux relationship differs spatially across two post-glacial lakes in Sweden. We compared these CH4 emission patterns with sediment microbial (metagenomic and amplicon), isotopic, and geochemical data. The temperature-associated increase in CH4 emissions was greater in lake middles—where methanogens were more abundant—than edges, and sediment communities were distinct between edges and middles. Microbial abundances, including those of CH4-cycling microorganisms and syntrophs, were predictive of porewater CH4 concentrations. Results suggest that deeper lake regions, which currently emit less CH4 than shallower edges, could add substantially to CH4 emissions in a warmer Arctic and that CH4 emission predictions may be improved by accounting for spatial variations in sediment microbiota.

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Diverse Arctic lake sediment microbiota shape methane emission temperature sensitivity

10.1101/2020.02.08.934661 ◽

2020 ◽

Author(s):

Joanne B. Emerson ◽

Ruth K. Varner ◽

Martin Wik ◽

Donovan H. Parks ◽

Rebecca B. Neumann ◽

...

Keyword(s):

Solar Radiation ◽

Microbial Communities ◽

Temperature Sensitivity ◽

Methane Emission ◽

Abiotic Factors ◽

Geochemical Data ◽

Northern Sweden ◽

Glacial Lakes ◽

Site Specific ◽

Primary Driver

AbstractNorthern post-glacial lakes are a significant and increasing source of atmospheric carbon (C), largely through ebullition (bubbling) of microbially-produced methane (CH4) from the sediments1. Ebullitive CH4 flux correlates strongly with temperature, suggesting that solar radiation is the primary driver of these CH4 emissions2. However, here we show that the slope of the temperature-CH4 flux relationship differs spatially, both within and among lakes.Hypothesizing that differences in microbiota could explain this heterogeneity, we compared site-specific CH4 emissions with underlying sediment microbial (metagenomic and amplicon), isotopic, and geochemical data across two post-glacial lakes in Northern Sweden. The temperature-associated increase in CH4 emissions was greater in lake middles—where methanogens were more abundant—than edges, and sediment microbial communities were distinct between lake edges and middles. Although CH4 emissions projections are typically driven by abiotic factors1, regression modeling revealed that microbial abundances, including those of CH4-cycling microorganisms and syntrophs that generate H2 for methanogenesis, can be useful predictors of porewater CH4 concentrations. Our results suggest that deeper lake regions, which currently emit less CH4 than shallower edges, could add substantially to overall CH4 emissions in a warmer Arctic with longer ice-free seasons and that future CH4 emission predictions from northern lakes may be improved by accounting for spatial variations in sediment microbiota.

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