Bacterial diversity and biogeochemistry of different chemosynthetic habitats of the REGAB cold seep (West African margin, 3160 m water depth)

[摘要] The giant pockmark REGAB (West African margin, 3160 m water depth) is anactive methane-emitting cold seep ecosystem, where the energy derived frommicrobially mediated oxidation of methane supports high biomass anddiversity of chemosynthetic communities. Bare sediments interspersed withheterogeneous chemosynthetic assemblages of mytilid mussels, vesicomyidclams and siboglinid tubeworms form a complex seep ecosystem. To betterunderstand if benthic bacterial communities reflect the patchy distributionof chemosynthetic fauna, all major chemosynthetic habitats at REGAB wereinvestigated using an interdisciplinary approach combining pore watergeochemistry, in situ quantification of fluxes and consumption of methane, as wellas bacterial community fingerprinting. This study revealed that sedimentspopulated by different fauna assemblages show distinct biogeochemicalactivities and are associated with distinct sediment bacterial communities.The methane consumption rates and methane effluxes ranged over one to twoorders of magnitude across habitats, and reached highest values at themussel habitat, which hosted a different bacterial community compared to theother habitats. Clam assemblages had a profound impact on the sedimentgeochemistry, but less so on the bacterial community structure. Moreover,all clam assemblages at REGAB were restricted to sediments characterized bycomplete methane consumption in the seafloor, and intermediatebiogeochemical activity. Overall, variations in the sediment geochemistrywere reflected in the distribution of both fauna and microbial communities;and were mostly determined by methane flux.

[学科分类] 地球化学与岩石