HR: 0800h
AN: V41B-1373    [Abstracts]
TI: Direct Measurement of Microbial Methane Oxidation at Hydrothermal Vent Ecosystems.
AU: * Utsumi, M
EM: utsumi@bsys.tsukuba.ac.jp
AF: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennoudai 1-1-1, Tsukuba, 305-8572 Japan
AU: Tsunogai, U
AF: Division of Earth and Planetary Sciences, Graduate School of Science, Hokkaido University, N10 W8, Kita-ku, Sapporo, 060-0810 Japan
AU: Ishibashi, J
AF: Planetary Sciences, Faculty of Science, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581 Japan
AB: Though methane concentration and isotope composition at hydrothermal vent areas have been extensively investigated, much remains to be learned about methane oxidation by vent microorganisms; microbial methane metabolism may be a quantitatively important component of organic carbon flow in vent ecosystems. We developed a new experiment system and measured microbial methane oxidation at the hydrothermal vent areas (Suiyo Seamount and south Mariana backarc spreading center) directly. The system was constructed by a combined Niskin sampler with Time-series water sampler attached to a manned submersible or a remotely operated vehicle (ROV). At the sea floor, the sea water inside the Niskin sampler was replaced by the hydrothermal fluid using a direct sampling system of hydrothermal vent fluid. Then the Niskin sampler was closed and the microbial methane oxidation experiment started on site. Hydrothermal fluid in the Niskin sampler was sampled at 30 min or 1 hour intervals by the Time-series sampler; microbial activities were stopped by addition of HgCl $_{2}$ solution to each cylinder of the Time-series sampler. On board, the time-series samples were transferred to glass serum bottles immediately; the samples were stored at $4\deg$C until methane analysis at the laboratory. Dissolved methane concentration was measured with an automatic system consisting of a purge and trap apparatus and a gas chromatograph with a flame ionization detector. The in situ methane oxidation rates were 0.039/h and 0.034/h, and methane consumption rates were 25 nM/h and 6.4 nM/h at Suiyo Seamount and south Mariana, respectively. These results suggest that microbial methane oxidation should be an important organic carbon sink in hydrothermal vent ecosystems.
DE: 4806 Carbon cycling
DE: 4815 Ecosystems, structure and dynamics
DE: 4894 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting