title: Microbial community stratification controlled by the subseafloor fluid flow and geothermal gradient at the Iheya North hydrothermal field in the Mid-Okinawa Trough (Integrated Ocean Drilling Program Expedition 331).
abstract: The impacts of lithologic structure and geothermal gradient on subseafloor microbial communities were investigated at a marginal site of the Iheya North hydrothermal field in the Mid-Okinawa Trough. Subsurface marine sediments composed of hemipelagic muds and volcaniclastic deposits were recovered through a depth of 151 m below the seafloor at site C0017 during Integrated Ocean Drilling Program Expedition 331. Microbial communities inferred from 16S rRNA gene clone sequencing in low-temperature hemipelagic sediments were mainly composed of members of the Chloroflexi and deep-sea archaeal group. In contrast, 16S rRNA gene sequences of marine group I Thaumarchaeota dominated the microbial phylotype communities in the coarse-grained pumiceous gravels interbedded between the hemipelagic sediments. Based on the physical properties of sediments such as temperature and permeability, the porewater chemistry, and the microbial phylotype compositions, the shift in the physical properties of the sediments is suggested to induce a potential subseafloor recharging flow of oxygenated seawater in the permeable zone, leading to the generation of variable chemical environments and microbial communities in the subseafloor habitats. In addition, the deepest section of sediments under high-temperature conditions (∼90°C) harbored the sequences of an uncultivated archaeal lineage of hot water crenarchaeotic group IV that may be associated with the high-temperature hydrothermal fluid flow. These results indicate that the subseafloor microbial community compositions and functions at the marginal site of the hydrothermal field are highly affected by the complex fluid flow structure, such as recharging seawater and underlying hydrothermal fluids, coupled with the lithologic transition of sediments.
authors: Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan Department of Earth and Planetary Science, University of Tokyo, Tokyo, Japan kyanagawa@jamstec.go.jp.
authors: Katsunori
authors: K
authors: Yanagawa
authors: Geomicrobiology, Federal Institute for Geosciences and Natural Resources, Hannover, Germany.
authors: Anja
authors: A
authors: Breuker
authors: Geomicrobiology, Federal Institute for Geosciences and Natural Resources, Hannover, Germany.
authors: Axel
authors: A
authors: Schippers
authors: Laboratory of Ocean-Earth Life Evolution Research, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan.
authors: Manabu
authors: M
authors: Nishizawa
authors: Geomicrobiology Group, Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, Kochi, Japan.
authors: Akira
authors: A
authors: Ijiri
authors: Marine Functional Biology Group, Research and Development Center for Marine Biosciences, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan.
authors: Miho
authors: M
authors: Hirai
authors: Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan.
authors: Yoshihiro
authors: Y
authors: Takaki
authors: Department of Earth and Planetary Science, University of Tokyo, Tokyo, Japan.
authors: Michinari
authors: M
authors: Sunamura
authors: Department of Earth and Planetary Science, University of Tokyo, Tokyo, Japan.
authors: Tetsuro
authors: T
authors: Urabe
authors: Marine Functional Biology Group, Research and Development Center for Marine Biosciences, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan.
authors: Takuro
authors: T
authors: Nunoura
authors: Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan.
authors: Ken
authors: K
authors: Takai
mesh_terms: D001105:Archaea / Q000235:genetics / Q000302:isolation & purification*; D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification*; D001483:Base Sequence; D016000:Cluster Analysis; D017931:DNA Primers / Q000235:genetics; D019641:DNA, Archaeal / Q000737:chemistry / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D017753:Ecosystem; D005101:Expeditions; D005843:Geography; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology*; D060086:Hydrothermal Vents; D009792:Oceans and Seas; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012623:Seawater / Q000737:chemistry / Q000382:microbiology*; D017422:Sequence Analysis, DNA
chemical_list: D017931:DNA Primers; D019641:DNA, Archaeal; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S