title: Variability in microbial community and venting chemistry in a sediment-hosted backarc hydrothermal system: Impacts of subseafloor phase-separation.
abstract: Phase-separation and -segregation (boiling/distillation of subseafloor hydrothermal fluids) represent the primary mechanisms causing intra-field variations in vent fluid compositions. To determine whether this geochemical process affects the formation of microbial communities, we examined the microbial communities at three different vent sites located within a few tens meters of one another. In addition to chimney structures, colonization devices capturing subseafloor communities entrained by the vent fluids were studied, using culture-dependent and -independent methods. Microbiological analyses demonstrated the occurrence of distinctive microbial communities in each of the hydrothermal niches. Within a chimney structure, there was a transition from a mixed community of mesophiles and thermophiles in the exterior parts to thermophiles in the interior. Beside the transition within a chimney structure, intra-field variations in microbial communities in vent fluids were apparent. Geochemical analysis demonstrated that different vent fluids have distinctive end-member compositions as a consequence of subseafloor phase-separation and -segregation, which were designated gas-depleted, normal and gas-enriched fluids. In comparison to gas-depleted and normal fluids, gas-enriched fluids harbored more abundant chemolithoautotrophs with gaseous component-dependent energy metabolism, such as hydrogenotrophic methanogenesis. Subseafloor phase-separation and -segregation may play a key role in supplying energy and carbon sources to vent-associated chemolithoautotrophs and subvent microbial communities.
authors.affiliation: Laboratory of Marine Microbiology, Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Japan. nakagawas@jamstec.go.jp
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nakagawa
authors.forename: Ken
authors.initials: K
authors.lastname: Takai
authors.forename: Fumio
authors.initials: F
authors.lastname: Inagaki
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Chiba
authors.forename: Jun-ichiro
authors.initials: J
authors.lastname: Ishibashi
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kataoka
authors.forename: Hisako
authors.initials: H
authors.lastname: Hirayama
authors.forename: Takuro
authors.initials: T
authors.lastname: Nunoura
authors.forename: Koki
authors.initials: K
authors.lastname: Horikoshi
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Sako
mesh_terms: D001105:Archaea / Q000145:classification* / Q000235:genetics; D001419:Bacteria / Q000145:classification* / Q000235:genetics; D015169:Colony Count, Microbial; D017753:Ecosystem; D019015:Geologic Sediments / Q000382:microbiology*; D010802:Phylogeny; D012623:Seawater / Q000737:chemistry / Q000382:microbiology*; D013440:Sulfides / Q000032:analysis
chemical_list: D013440:Sulfides