Datensatz

Zusammenfassung

The microbial community inhabiting anaerobic sediments of Hydrate Ridge, an area characterized by extensive methane‐venting and gas hydrate occurrence on the Cascadia accretionary prism, is dominated by a complex consortium of archaea and bacteria which performs anaerobic methane oxidation (AMO). The process is indicated by the dominance of archaeal‐derived biomarkers such as crocetane, pentamethylicosane, and archaeol in anaerobic sediments and authigenic carbonates. The biomarkers are highly depleted in 1 3C relative to their methane carbon source, which results in carbon isotopic compositions as low as ‐128%o PDB. The essentially limitless reservoir of methane available to the archaea in this gas hydrate environment allows the kinetic carbon isotope effect (ϵCH4‐biomarker) associated with AMO to be fully developed (ϵmax = 72%o). No substrate depletion effects were detected. Varying isotope effects and concentrations of the biomarkers on and off Hydrate Ridge indicate that the abundance of these compounds is essentially dependent on the supply of methane from this special environmental setting.