title: Microbial community in a sediment-hosted CO2 lake of the southern Okinawa Trough hydrothermal system.
abstract: Increasing levels of CO2 in the atmosphere are expected to cause climatic change with negative effects on the earth's ecosystems and human society. Consequently, a variety of CO2 disposal options are discussed, including injection into the deep ocean. Because the dissolution of CO2 in seawater will decrease ambient pH considerably, negative consequences for deep-water ecosystems have been predicted. Hence, ecosystems associated with natural CO2 reservoirs in the deep sea, and the dynamics of gaseous, liquid, and solid CO2 in such environments, are of great interest to science and society. We report here a biogeochemical and microbiological characterization of a microbial community inhabiting deep-sea sediments overlying a natural CO2 lake at the Yonaguni Knoll IV hydrothermal field, southern Okinawa Trough. We found high abundances (>10(9) cm(-3)) of microbial cells in sediment pavements above the CO2 lake, decreasing to strikingly low cell numbers (10(7) cm(-3)) at the liquid CO2/CO2-hydrate interface. The key groups in these sediments were as follows: (i) the anaerobic methanotrophic archaea ANME-2c and the Eel-2 group of Deltaproteobacteria and (ii) sulfur-metabolizing chemolithotrophs within the Gamma- and Epsilonproteobacteria. The detection of functional genes related to one-carbon assimilation and the presence of highly 13C-depleted archaeal and bacterial lipid biomarkers suggest that microorganisms assimilating CO2 and/or CH4 dominate the liquid CO2 and CO2-hydrate-bearing sediments. Clearly, the Yonaguni Knoll is an exceptional natural laboratory for the study of consequences of CO2 disposal as well as of natural CO2 reservoirs as potential microbial habitats on early Earth and other celestial bodies.
authors.affiliation: Subground Animalcule Retrieval (SUGAR) Program, Extremobiosphere Research Center, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka 237-0061, Japan. inagaki@jamstec.go.jp
authors.forename: Fumio
authors.initials: F
authors.lastname: Inagaki
authors.forename: Marcel M M
authors.initials: MM
authors.lastname: Kuypers
authors.forename: Urumu
authors.initials: U
authors.lastname: Tsunogai
authors.forename: Jun-Ichiro
authors.initials: J
authors.lastname: Ishibashi
authors.forename: Ko-Ichi
authors.initials: K
authors.lastname: Nakamura
authors.forename: Tina
authors.initials: T
authors.lastname: Treude
authors.forename: Satoru
authors.initials: S
authors.lastname: Ohkubo
authors.forename: Miwako
authors.initials: M
authors.lastname: Nakaseama
authors.forename: Kaul
authors.initials: K
authors.lastname: Gena
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Chiba
authors.forename: Hisako
authors.initials: H
authors.lastname: Hirayama
authors.forename: Takuro
authors.initials: T
authors.lastname: Nunoura
authors.forename: Ken
authors.initials: K
authors.lastname: Takai
authors.forename: Bo B
authors.initials: BB
authors.lastname: Jørgensen
authors.forename: Koki
authors.initials: K
authors.lastname: Horikoshi
authors.forename: Antje
authors.initials: A
authors.lastname: Boetius
mesh_terms: D001105:Archaea / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D015415:Biomarkers / Q000737:chemistry / Q000378:metabolism; D002245:Carbon Dioxide / Q000737:chemistry* / Q000378:metabolism; D017753:Ecosystem; D004777:Environment; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology; D006801:Humans; D008055:Lipids / Q000737:chemistry; D008969:Molecular Sequence Data; D010140:Pacific Ocean; D010802:Phylogeny; D012623:Seawater / Q000737:chemistry*; D014871:Water Microbiology
chemical_list: D015415:Biomarkers; D008055:Lipids; D002245:Carbon Dioxide