Biogeochemical investigation of sediments at the Hakon Mosby Mud Volcano (Barents Sea)

An internally stored nitrate reservoir with average concentrations of 110 mmol L-1 enables the Beggiatoa to oxidize sulfide anaerobically. The pH profile indicates sequential sulfide oxidation with elemental sulfur as intermediate. Gray thiotrophic mats associated with perturbed sediments showed a high heterogeneity in sulfate turnover and high sulfide fluxes, balanced by the opposing oxygen and nitrate fluxes so that biological oxidation dominates over geochemical sulfide removal processes.

The three habitats indicate substantial small-scale variability in carbon fixation pathways either through direct biological use of methane or through indirect carbon fixation of methane-derived carbon dioxide by chemolithotrophic sulfide oxidation.