Microbial communities and metabolic functions vary with spatial heterogeneity in cold-seep carbonates

Cold-seep carbonates, formed through interactions among methane, fluid chemistry, and microbial chemosynthesis, represent biodiversity hotspots in the deep sea. Spatial heterogeneity within these carbonates arises from variations in methane flux, yet the microbial contributions to this heterogeneity remain underexplored. Here we combined remotely operated vehicle-based in situ measurements, X-ray imaging, metagenomics, qPCR, and ¹³C-CH₄ stable-isotope labeling to investigate microbial communities across carbonate habitats in the South China Sea. We found that methane flux linked to carbonate structural properties, shapes microbial metabolic interactions, notably anaerobic methane oxidation coupled with aragonite and FeS precipitation. These processes may contribute to self-sealing carbonate features, potentially reducing methane permeability and influencing geochemical gradients and geomorphology. Our findings reveal that microbiomes and their feedbacks play a significant role in shaping habitat-scale spatial heterogeneity of cold-seep carbonates, improving our understanding of methane cycling and carbonate ecosystem dynamics.