Microbial methane production rates in gas hydrate-bearing sediments from the eastern Nankai Trough, off central Japan

Author(s): Yoshioka, Hideyoshi; Sakata, Susumu; Cragg, Barry A.; Parkes, R. John; Fujii, Tetsuya
Author Affiliation(s): Primary:
National Institute of Advanced Industrial Science and Technology, Institute for Geo-Resources and Environment, Tsukuba, Japan
Other:
Cardiff University, United Kingdom
Japan Oil, Gas and Metals National Corporation, Japan
Volume Title: Geochemical Journal
Source: Geochemical Journal, 43(5), p.315-321. Publisher: Geochemical Society of Japan, Nagoya, Japan. ISSN: 0016-7002 CODEN: GEJOBE
Note: In English. 27 refs.; illus., incl. 3 tables, geol. sketch map
Summary: Gas hydrates and associated high methane concentrations are widely distributed along the boundary of the Nankai Trough off Japan. Radiotracer activity measurements were conducted to estimate current methane production rates in sediment cores at two sites in the eastern Nankai Trough off Tokai containing gas hydrates. Low rates of methanogenesis from CO2 reduction and acetate fermentation were detected within the gas hydrate-stability zone and below the Bottom Simulating Reflector (BSR), but not in sediments from shallow depths (<100 mbsf). The detected production rates of methane from acetate were much higher than those from carbon dioxide and hydrogen. Methanol or potentially some other methyl compounds could also be used for microbial methane production. Deep methane production rates from acetate in the gas hydrate-bearing sediments were higher than in pre-accretionary, hydrate-free, sediments at sites 1173, 1174 and 1177 of ODP Leg 190 from the floor of the western Nankai Trough off Shikoku Island. As previously suggested this might be due to upward fluid flow stimulating bacterial activities around and below the base of the gas hydrate zone. In contrast, methanogenesis from carbon dioxide and hydrogen was the main pathway for microbial methane production in the hydrate-free sediments at the ODP Nankai Trough sites.
Year of Publication: 2009
Research Program: ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Acetates; Alcohols; Aliphatic hydrocarbons; Alkalinity; Alkanes; Asia; Biogenic processes; Bottom-simulating reflectors; Carbon dioxide; Cores; Depth; Esters; Far East; Gas hydrates; Geophysical methods; Hydrocarbons; Hydrogen; Japan; Leg 190; Marine sediments; Methane; Methanol; Microorganisms; Nankai Trough; North Pacific; Northwest Pacific; ODP Site 1173; ODP Site 1174; ODP Site 1177; Ocean Drilling Program; Ocean floors; Organic compounds; Pacific Ocean; Porosity; Production; Radioactive tracers; Sediments; Seismic methods; Shikoku Basin; Total organic carbon; West Pacific
Coordinates: N321500 N321500 E1350200 E1350200
N322000 N322100 E1345800 E1345700
N313900 N314000 E1340100 E1340000
Record ID: 2010047741
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