HR: 14:15h
AN: V43F-03 INVITED     [Abstracts]
TI: Lessons from Suiyo Seamount studies, for understanding extreme (ancient?) microbial ecosystems in the deep-sea hydrothermal fields
AU: * Maruyama, A
EM: maruyama-aki@aist.go.jp
AF: AIST-IBRF, Higashi, Tsukuba, 305-8566 Japan
AU: Higashi, Y
EM: y-higashi@aist.go.jp
AF: AIST-IBRF, Higashi, Tsukuba, 305-8566 Japan
AU: Sunamura, M
EM: sunamura@eps.s.u-tokyo.ac.jp
AF: U. of Tokyo, Hongo, Bunkyo, Tokyo, 113-0033 Japan
AU: Urabe, T
EM: urabe@eps.s.u-tokyo.ac.jp
AF: U. of Tokyo, Hongo, Bunkyo, Tokyo, 113-0033 Japan
AB: Deep-sea hydrothermal ecosystems are driven with various geo-thermally modified, mainly reduced, compounds delivered from extremely hot subsurface environments. To date, several unique microbes including thermophilic archaeons have been isolated from/around vent chimneys. However, there is little information about microbes in over-vent and sub-vent fields. Here, we report several new findings on microbial diversity and ecology of the Suiyo Seamount that locates on the Izu-Bonin Arc in the northwest Pacific Ocean, as a result of the Japanese Archaean Park project, with special concern to the sub-vent biosphere. At first, we succeeded to reveal a very unique microbial ecosystem in hydrothermal plume reserved within the outer rim of the seamount crater, that is, it consisted of almost all metabolically active microbes belonged to only two Bacteria phylotypes, probably of sulfur oxidizers. In the center of the caldera seafloor (ca. 1,388-m deep) consisted mainly of whitish sands and pumices, we found many small chimneys (ca. 5-10 cm) and bivalve colonies distributed looking like gray to black patches. These geo/ecological features of the seafloor were supposed to be from a complex mixing of hydrothermal venting and strong water current near the seafloor. Through quantitative FISH analysis for various environmental samples, one of the two representative groups in the plume was assessed to be from some of the bivalve colonies. Using the Benthic Multi-coring System (BMS), total 10 points were drilled and 6 boreholes were maintained with stainless or titanium casing pipes. In the following submersible surveys, newly developed catheter- and column-type in situ growth chambers were deployed in and on the boreholes, respectively, for collecting indigenous sub-vent microbes. Finally, we succeeded to detect several new phylotypes of microbes in these chamber samples, e.g., within epsilon-Proteobacteria, a photosynthetic group of alpha-Proteobacteria, and hyperthermophile-related Euryarchaea. By the FISH analysis, however, some specific members of Bacteria that differed from those in the chamber samples were occasionally abundant in hot vent fluids. In clone library analysis of column-type chamber samples, we also found very unique vertical profiles in the community of Archaea, i.e., rich in uncultivable Marine Group I & II members in the upper and middle columns situated at a warm vent site, while heterotrophic thermophiles in the middle and bottom. In a bottom column sample from a hot vent site, hyperthermophilic anaerobes were detected. From these results, we will propose a vertical profile model for the sub-vent Archaea community. From geophysical, geochemical and geological surveys, this sub-vent ecosystem is supposed to be restricted in a shallow subsurface region. Whether these unique ecosystems are general in hydrothermal fields over the sea or specific only to this submarine volcano will be discussed.
DE: 8135 Hydrothermal systems (8424)
DE: 4815 Ecosystems, structure and dynamics
DE: 4840 Microbiology
DE: 1724 Ocean sciences
DE: 0400 Biogeosciences
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting