Porewater concentrations, pH, single cell number, anaerobic oxidation of methane (AOM) rate, sulfate reduction (SR) rate of samples during METEOR cruise M76/3b at the REGAB cold seep site from the West African margin in 2008

The giant pockmark REGAB (West African margin, 3160 m water depth) is an active methane-emitting cold seep ecosystem, where the energy derived from microbially mediated oxidation of methane supports high biomass and diversity of chemosynthetic communities. Bare sediments interspersed with heterogeneous chemosynthetic assemblages of mytilid mussels, vesicomyid clams and siboglinid tubeworms form a complex seep ecosystem. To better understand if benthic bacterial communities reflect the patchy distribution of chemosynthetic fauna, all major chemosynthetic habitats at REGAB were investigated using an interdisciplinary approach combining porewater geochemistry, in situ quantification of fluxes and consumption of methane, as well bacterial community fingerprinting. This study revealed that sediments populated by different fauna assemblages show distinct biogeochemical activities and are associated with distinct sediment bacterial communities. The methane consumption and methane effluxes ranged over one to two orders of magnitude across habitats, and reached highest values at the mussel habitat, which hosted a different bacterial community compared to the other habitats. Clam assemblages had a profound impact on the sediment geochemistry, but less so on the bacterial community structure. Moreover, all clam assemblages at REGAB were restricted to sediments characterized by complete methane consumption in the seafloor, and intermediate biogeochemical activity. Overall, variations in the sediment geochemistry were reflected in the distribution of both fauna and microbial communities; and were mostly determined by methane flux.

Gridded bathymetry from multibeam echosounder EM120 data of the cruise M72/3a and M72/3b (2007)

Bathymetry based on data recorded during M72-3 between 17.03.2007 and 23.04.2007 in the Black Sea. This cruise concentrated on interdisciplinary work on gas hydrates with a main focus on the gas hydrate transition zone in and below 750 m water depth. Gas hydrate environments have been studied in various geological settings, mainly of the eastern Black Sea. Origins, distributions and dynamics of methane and gas hydrates in sediments and also methane fluxes from the sediment to the water column have been the focus. Main working areas were the Sorokin Trough, an area south of the Kerch Strait and the Andrusov Ridge in Ukrainian waters and the Gudauta Ridge and Gurian Trough in Georgian waters.