ANME-2a perform methane oxidation in brackish coastal sediments via multiple pathways.

ANME-2a archaea in brackish coastal sediments perform anaerobic methane oxidation across multiple pathways, with highest potential activity rates in sediments below the SMTZ.

• Why it matters: Coastal methane removal depends on AOM, but how ANME-2a can use different electron acceptors in brackish settings—and where activity is strongest—was unclear.
• What they did: Geochemical profiles localized AOM to the shallow metal oxide-rich sulfate-methane transition zone, while ANME-2a were the only methanotrophs detected and metatranscriptomics showed peak ANME-2a gene expression there. Sediment incubations measured AOM with sulfate, metal oxides, and graphene oxide, revealing the highest potential rates below the SMTZ.
• The result: The pathway diversity and continued presence of methanotrophs below the SMTZ likely support resilience of the microbial methane filter when electron acceptor limitation is alleviated.

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