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Anaerobic methanotrophic community of a 5346‐m‐deep vesicomyid clam colony in the J apan T rench
Author(s) -
Felden J.,
Ruff S. E.,
Ertefai T.,
Inagaki F.,
Hinrichs K.U.,
Wenzhöfer F.
Publication year - 2014
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1111/gbi.12078
Subject(s) - cold seep , chemosynthesis , anaerobic oxidation of methane , petroleum seep , biogeochemical cycle , microbial population biology , sulfate , oceanography , biogeochemistry , sediment , benthic zone , microbial mat , bioturbation , ecology , environmental chemistry , methane , environmental science , geology , biology , chemistry , hydrothermal vent , hydrothermal circulation , bacteria , paleontology , cyanobacteria , organic chemistry
V esicomyidae clams harbor sulfide‐oxidizing endosymbionts and are typical members of cold seep communities where active venting of fluids and gases takes place. We investigated the central biogeochemical processes that supported a vesicomyid clam colony as part of a locally restricted seep community in the J apan T rench at 5346 m water depth, one of the deepest seep settings studied to date. An integrated approach of biogeochemical and molecular ecological techniques was used combining in situ and ex situ measurements. In sediment of the clam colony, low sulfate reduction rates (maximum 128 nmol mL −1 day −1 ) were coupled to the anaerobic oxidation of methane. They were observed over a depth range of 15 cm, caused by active transport of sulfate due to bioturbation of the vesicomyid clams. A distinct separation between the seep and the surrounding seafloor was shown by steep horizontal geochemical gradients and pronounced microbial community shifts. The sediment below the clam colony was dominated by anaerobic methanotrophic archaea ( ANME ‐2c) and sulfate‐reducing D esulfobulbaceae ( SEEP ‐ SRB ‐3, SEEP ‐ SRB ‐4). Aerobic methanotrophic bacteria were not detected in the sediment, and the oxidation of sulfide seemed to be carried out chemolithoautotrophically by S ulfurovum species. Thus, major redox processes were mediated by distinct subgroups of seep‐related microorganisms that might have been selected by this specific abyssal seep environment. Fluid flow and microbial activity were low but sufficient to support the clam community over decades and to build up high biomasses. Hence, the clams and their microbial communities adapted successfully to a low‐energy regime and may represent widespread chemosynthetic communities in the J apan T rench. In this regard, they contributed to the restricted deep‐sea trench biodiversity as well as to the organic carbon availability, also for non‐seep organisms, in such oligotrophic benthic environment of the dark deep ocean.