title: Anaerobic methanotrophic community of a 5346-m-deep vesicomyid clam colony in the Japan Trench.
abstract: Vesicomyidae 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 Japan Trench 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 Desulfobulbaceae (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 Sulfurovum 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 Japan Trench. 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.
authors.affiliation: Helmholtz-Max Planck Research Group for Deep Sea Ecology and Technology, Max Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Felden
authors.forename: S E
authors.initials: SE
authors.lastname: Ruff
authors.forename: T
authors.initials: T
authors.lastname: Ertefai
authors.forename: F
authors.initials: F
authors.lastname: Inagaki
authors.forename: K-U
authors.initials: KU
authors.lastname: Hinrichs
authors.forename: F
authors.initials: F
authors.lastname: Wenzhöfer
mesh_terms: D000693:Anaerobiosis; D000818:Animals; D001105:Archaea / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification; D018407:Bacterial Physiological Phenomena; D058448:Biota; D049872:Bivalvia / Q000382:microbiology* / Q000502:physiology; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology; D060086:Hydrothermal Vents / Q000737:chemistry / Q000382:microbiology*; D050356:Lipid Metabolism; D008697:Methane / Q000378:metabolism; D008969:Molecular Sequence Data; D010140:Pacific Ocean; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013431:Sulfates / Q000378:metabolism
chemical_list: D012336:RNA, Ribosomal, 16S; D013431:Sulfates; D008697:Methane