Biological methane production and accumulation under sulfate-rich conditions at Cape Lookout Bight, NC

Frontiers in Microbiology

Microbiology

Raegan Paul¹  Paul D. Duesing¹  Jennifer A. Baily¹  Gage R. Coon¹  Karen G. Lloyd² 

[1] Department of Microbiology, The University of Tennessee, Knoxville, TN, United States;null;

关键词: marine sediments;    methanogenesis;    sulfate reduction;    AOM;    hydrogen;    thermodynamics;   

DOI  :  10.3389/fmicb.2023.1268361

 received in 2023-07-27, accepted in 2023-09-14,  发布年份 2023

来源: Frontiers

【 摘 要 】

IntroductionAnaerobic oxidation of methane (AOM) is hypothesized to occur through reverse hydrogenotrophic methanogenesis in marine sediments because sulfate reducers pull hydrogen concentrations so low that reverse hydrogenotrophic methanogenesis is exergonic. If true, hydrogenotrophic methanogenesis can theoretically co-occur with sulfate reduction if the organic matter is so labile that fermenters produce more hydrogen than sulfate reducers can consume, causing hydrogen concentrations to rise. Finding accumulation of biologically-produced methane in sulfate-containing organic-rich sediments would therefore support the theory that AOM occurs through reverse hydrogenotrophic methanogenesis since it would signal the absence of net AOM in the presence of sulfate.Methods16S rRNA gene libraries were compared to geochemistry and incubations in high depth-resolution sediment cores collected from organic-rich Cape Lookout Bight, North Carolina.ResultsWe found that methane began to accumulate while sulfate is still abundant (6–8 mM). Methane-cycling archaea ANME-1, Methanosarciniales, and Methanomicrobiales also increased at these depths. Incubations showed that methane production in the upper 16 cm in sulfate-rich sediments was biotic since it could be inhibited by 2-bromoethanosulfonoic acid (BES).DiscussionWe conclude that methanogens mediate biological methane production in these organic-rich sediments at sulfate concentrations that inhibit methanogenesis in sediments with less labile organic matter, and that methane accumulation and growth of methanogens can occur under these conditions as well. Our data supports the theory that H2 concentrations, rather than the co-occurrence of sulfate and methane, control whether methanogenesis or AOM via reverse hydrogenotrophic methanogenesis occurs. We hypothesize that the high amount of labile organic matter at this site prevents AOM, allowing methane accumulation when sulfate is low but still present in mM concentrations.

【 授权许可】

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Copyright © 2023 Coon, Duesing, Paul, Baily and Lloyd.