Journal Article

Changes in microbial communities associated with gas hydrates in subseafloor sediments from the Nankai Trough

Amo, Miki, Katayama, Taiki, Takahashi, Hiroshi A., Yoshioka, Hideyoshi, Fujii, Tetsuya, Sakata, Susumu

2016

Overview

Little is known about the microbial distribution patterns in subseafloor sediments. This study examines microbial diversity and activities in sediments of the Nankai Trough, where biogenic gas hydrates are deposited. Illumina sequencing of 16S rRNA genes revealed that the prokaryotic community structure is correlated with hydrate occurrence and depth but not with the sedimentary facies. The bacterial phyla ‘Atribacteria’ lineage JS1 and Chloroflexi dominated in all samples, whereas lower taxonomic units of Chloroflexi accounted for community variation related to hydrate saturation. In archaeal communities, ‘Bathyarchaeota’ was significantly abundant in the hydrate-containing samples, whereas Marine Benthic Group-B dominated in the upper sediments without hydrates. mcrA gene sequences assigned to deeply branching groups and ANME-1 were detected only in hydrate-containing samples. A predominance of hydrogenotrophic methanogens, Methanomicrobiales and Methanobacteriales, over acetoclastic methanogens was found throughout the depth. Incubation tests on hydrate-containing samples with a stable isotope tracer showed anaerobic methane oxidation activities under both low- and seawater-like salinity conditions. These results indicate that the distribution patterns of microorganisms involved in carbon cycling changed with gas hydrate occurrence, possibly because of the previous hydrate dissociation followed by pore water salinity decrease in situ, as previously proposed by a geochemical study at the study site. In gas hydrate-bearing sediments from the Nankai Trough, the distribution patterns of microbial taxa involved in carbon cycling changed with hydrate occurrence, which might be linked to past geological events. Graphical Abstract Figure. In gas hydrate-bearing sediments from the Nankai Trough, the distribution patterns of microbial taxa involved in carbon cycling changed with hydrate occurrence, which might be linked to past geological events.

• Publisher: Oxford University Press
• Subject: Archaea - genetics / Bacteria - genetics / Carbon cycle / Chemical analysis / Chloroflexi / Community structure / dissociation / Ecology / Environmental aspects / Euryarchaeota - genetics / gas hydrate / Gas hydrates / gas production (biological) / genes / Geologic Sediments - microbiology / Hydrates / isotope labeling / Methane / Methanobacteriales / Methanobacteriales - genetics / methanogens / Methanomicrobiales / Methanomicrobiales - genetics / Microbial activity / Microbial colonies / microbial communities / Microbiology / Microorganisms / nucleotide sequences / oxidation / Pacific Ocean / Phylogeny / Pore water / ribosomal RNA / RNA, Ribosomal, 16S - genetics / Salinity / Seawater / Seawater - microbiology / Sediments / sequence analysis / Stable isotopes / Water analysis / Water Microbiology / water salinity