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

Yoshioka, Hideyoshi; Sakata, Susumu; Cragg, Barry A.; Parkes, Ronald John; Fujii, Tetsuya

doi:10.2343/geochemj.1.0028

Cited by 24 publications

(18 citation statements)

References 19 publications

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“…Methane production rates estimated from cores from the Nankai Trough imply that most of the methane in gas hydrates is not the result of current in situ microbial methanogenesis (Yoshioka et al . ). Therefore, migration of gas from lower sources is required to form gas hydrates in this region.…”

Section: Discussionmentioning

confidence: 97%

Foldback reflectors near methane hydrate bottom‐simulating reflectors: Indicators of gas distribution from 3D seismic images in the eastern Nankai Trough

et al. 2015

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Understanding of fluid behavior and gas distribution in the shallow subsurface are important considerations in gas hydrate formation and the global carbon cycle. Estimation of gas distribution based on reflection seismic surveys, however, is difficult because the boundary of a gas‐bearing zone is indistinct and not systematically defined. This study reports distinctive features related to gas‐hydrate distribution and possible fluid migration in high‐resolution 3D seismic‐reflection data from sediments of the eastern Nankai Trough. These features, here termed foldback reflectors (FBRs), descend in accordion shaped reflectors near the edges of bottom‐simulating reflectors (BSRs). FBRs generally correspond to lateral boundaries between two seismic facies, a ‘dimmed’ facies with relatively low amplitude and subdued high‐frequency components beneath the BSR and the contrasting facies around the BSR. The dimmed facies corresponds to areas of anomalously low velocity consistent with a small amount of free gas. FBR is mostly developed in well‐stratified formations in uplifted regions. Dip directions of the FBR appear to be restricted by orientation of the host formations. Edges of the FBR often correspond to high‐amplitude layers. Such occurrences of FBR suggest that regional uplift and layer‐parallel fluid migration are related to the formation of FBR as well as BSR.

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Section: Discussionmentioning

confidence: 97%

Foldback reflectors near methane hydrate bottom‐simulating reflectors: Indicators of gas distribution from 3D seismic images in the eastern Nankai Trough

et al. 2015

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“…It is of paramount importance that the sediment is not contaminated with oxygen during sediment handling, as molecular oxygen is toxic to most sulfate-reducing prokaryotes. [26][27][28]. The mini-cores in the syringes are injected with μL aliquots of tracer into the middle of each sediment plug and incubated for 1-60 days.…”

Section: Sulfate Reduction Rates Measured Withmentioning

confidence: 99%

14 Experimental assessment of community metabolism in the subsurface

Røy¹

2014

Microbial Life of the Deep Biosphere

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“…Inc., Brea, CA, USA) was injected into each syringe subcore with a glass microsyringe by using a special device that allowed steady injection of the tracer along the centre line of the subcore (Parkes et al, 1995). Yoshioka et al, 2009): We set the incubation temperature to 9°C for sediments from the surface to 170 mbsf and to 17°C for sediments from deeper than 170 mbsf so that incubation would be at a temperature close to the in situ temperature, which on the Cascadia Margin is 3-5°C in near-surface sediments and increases to 17-21°C at 300 mbsf (Riedel et al, 2006).…”

Section: Activity Measurementsmentioning

confidence: 99%

Activities and distribution of methanogenic and methane‐oxidizing microbes in marine sediments from the Cascadia Margin

et al. 2010

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We investigated methane production and oxidation and the depth distribution and phylogenetic affiliation of a functional gene for methanogenesis, methyl coenzyme M reductase subunit A (mcrA), at two sites of the Integrated Ocean Drilling Program Expedition 311. These sites, U1327 and U1329, are respectively inside and outside the area of gas hydrate distribution on the Cascadia Margin. Radiotracer experiments using (14)C-labelled substrates indicated high potential methane production rates in hydrate-bearing sediments [128-223 m below seafloor (mbsf)] at U1327 and in sediments between 70 and 140 mbsf at U1329. Tracer-free experiments indicated high cumulative methane production in sediments within and below the gas hydrate layer at U1327 and in sediments below 70 mbsf at U1329. Stable tracer experiments using (13)C-labelled methane showed high potential methane oxidation rates in near-surface sediments and in sediments deeper than 100 mbsf at both sites. Results of polymerase chain reaction amplification of mcrA in DNA were mostly consistent with methane production: relatively strong mcrA amplification was detected in the gas hydrate-bearing sediments at U1327, whereas at U1329, it was mainly detected in sediments from around the bottom-simulating reflector (126 mbsf). Phylogenetic analysis of mcrA separated it into four phylotype clusters: two clusters of methanogens, Methanosarcinales and Methanobacteriales, and two clusters of anaerobic methanotrophic archaea, ANME-I and ANME-II groups, supporting the activity measurement results. These results reveal that in situ methanogenesis in deep sediments probably contributes to gas hydrate formation and are inconsistent with the geochemical model that microbial methane currently being generated in shallow sediments migrates downward and contributes to the hydrate formation. At Site U1327, gas hydrates occurred in turbidite sediments, which were absent at Site U1329, suggesting that a geological setting suitable for a gas hydrate reservoir is more important for the accumulation of gas hydrate than microbiological properties.

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

Cited by 24 publications

References 19 publications

Foldback reflectors near methane hydrate bottom‐simulating reflectors: Indicators of gas distribution from 3D seismic images in the eastern Nankai Trough

Foldback reflectors near methane hydrate bottom‐simulating reflectors: Indicators of gas distribution from 3D seismic images in the eastern Nankai Trough

14 Experimental assessment of community metabolism in the subsurface

Activities and distribution of methanogenic and methane‐oxidizing microbes in marine sediments from the Cascadia Margin

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