Microbial Sulfate Reduction Potential in Coal-Bearing Sediments Down to ~2.5 km below the Seafloor off Shimokita Peninsula, Japan.

摘要: Sulfate reduction is the predominant anaerobic microbial process of organic matter mineralization in marine sediments, with recent studies revealing that sulfate not only occurs sulfate-rich but even extends to deeper, methanogenic sediments at very low background concentrations sulfate. Using samples retrieved off Shimokita Peninsula, Japan, during Integrated Ocean Drilling Program (IODP) Expedition 337, we measured potential rates by slurry incubations 35S-labeled deep between 1276.75 and 2456.75 meters below seafloor. Potential were generally extremely (mostly 0.1 pmol cm-3 d-1) showed elevated values (up 1.8 a coal-bearing interval (Unit III). A increase hydrogenase activity horizons coincided this local rates. This paired enzymatic response suggests hydrogen potentially important electron donor for coalbed biosphere. By contrast, no stimulation was observed treatments where methane added as an donor. In coalbeds, small amounts might be provided cryptic sulfur cycle. The isotopically heavy pyrites (34S = +43‰) found horizon consistent its formation via has been continuously utilizing small, increasingly 34S-enriched reservoir over geologic time scales. Although our results do represent in-situ activity, reducers have persisted dormant, spore-like state, findings show organisms capable survived more than 20 Ma. highlights ability sulfate-reducers persist geological timespans sulfate-depleted environments. Our study moreover represents deepest evidence date.