HR: 15:05h
AN: OS52C-06 INVITED     [PDF]
TI: Geomicrobiology and Methanogenesis in Accretionary Complexes
AU: * Colwell, F S
EM: fxc@inel.gov
AF: Biotechnology Department, Idaho National Engineering and Environmental Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-2203 United States
AU: Delwiche, M
EM: mde1@inel.gov
AF: Biotechnology Department, Idaho National Engineering and Environmental Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-2203 United States
AU: Reed, D
EM: reeddw@inel.gov
AF: Biotechnology Department, Idaho National Engineering and Environmental Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-2203 United States
AU: Boyd, S
EM: boydss@inel.gov
AF: Biotechnology Department, Idaho National Engineering and Environmental Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-2203 United States
AU: Nunoura, T
EM: takuron@jamstec.go.jp
AF: Subground Animalcule Retrieval (SUGAR) Project, Japan Marine Science & Technology Center, Yokosuka, 237-0061 Japan
AU: Inagaki, F
EM: inagaki@jamstec.go.jp
AF: Subground Animalcule Retrieval (SUGAR) Project, Japan Marine Science & Technology Center, Yokosuka, 237-0061 Japan
AU: Takai, K
EM: kent@jamstec.go.jp
AF: Subground Animalcule Retrieval (SUGAR) Project, Japan Marine Science & Technology Center, Yokosuka, 237-0061 Japan
AB: As elsewhere in subsurface environments, microbes are known to colonize the sediments of accretionary margins. In fact, much of the methane present in hydrates along continental margins originates from microbial activity. However, models to predict hydrate distribution or the amount of methane in the sediments lack reliable values for in situ microbial methane production rates. Our studies of hydrate-bearing sediments focus first on the molecular identification of the microbes present and then on estimating realistic methanogenic rates to be used in these models. 16S rDNA extracted from deep marine sediments, then sequenced, and compared to known sequences indicates the presence of diverse bacterial and archaeal lineages. In one example, the Nankai Trough, {\it Archaea} (both Crenarchaeota and Euryarchaeota) and {\it Bacteria} (e.g., Proteobacteria, Actinobacteria, green non-sulfur) were detected at various depths above, within, and below the hydrate stability zone. Often methanogens cannot be detected using molecular approaches in accretionary sediments, but at least one methanogen ({\it Methanoculleus submarinus}) has been isolated from deep sediments that contain hydrates. Although culture-based enrichments for methanogens often yield evidence of methanogenic activity methanogenic rates derived from these studies are likely several orders of magnitude higher than the rates that are possible under in situ conditions. By combining data on methanogen numbers at various depths and realistic methanogenesis rates obtained from starved methanogens we hope to determine the productivity of methanogens on a volumetric basis for the sediments. These data will be used in models that predict hydrate distribution and formation rates in marine sediments.
DE: 0400 Biogeosciences
DE: 1050 Marine geochemistry (4835, 4850)
DE: 1615 Biogeochemical processes (4805)
DE: 4806 Carbon cycling
DE: 4840 Microbiology
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting