Japan Geoscience Union Meeting 2016

Presentation information


Symbol M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS33] Microbial ecology in earth and planetary sciences

Mon. May 23, 2016 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL6)

Convener:*Michinari Sunamura(University of Tokyo Dept. of Earth & Planetary Science), Ken Takai(Extremobiosphere Research Center, Japan Agency for Marine-Earth Science & Technology), Natsuko Hamamura(Kyushu University), Yuki Morono(Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology)

5:15 PM - 6:30 PM

[MIS33-P02] "Hot spot of methanogeneis" on the deep-seafloor after the mega-erathquake

*Eiji Tasumi1, Hidetaka Nomaki1, Katsunori Yanagawa2, Yuuta Konno, Sanae Sakai1, Miho Hirai1, Katsunori FUJIKURA1, Takuro Nunoura1, Ken Takai1 (1.Japan Agency for Marine-Earth Science and Technology, 2.Kyushu University)

Keywords:deep sea, methanogenesis, mega-earthquake

We investigated the deep-sea microbial ecosystem after the 2011 Off Tohoku Earthquake and tsunami. In the series of study, we found several "hot spot of methanogeneis" on the deep-seafloor after the mega-earthquake and demonstrated the methylotrophic methanegenesis in the deep-sea surface sentiment.
On the 2011 cruise, we found a lot of large microbial mats on the 5,000 m-depth deep-seafloor. The surface sediment cores (< 25 cm) were collected from microbial mats and analyzed their chemical and microbial profiles. On the top of the cores (a few centimeters), decomposing dead body of maline lives such as echinoderms that contains trimethylamine N-oxide, a precursor of trimetylamine (TMA), in the body were accumulated. In the surface layer (< 15 cm), high concentration of ammonium, TMA, and isotopically light methane was detected. In this layer, heterotrophic microbes such as Bacteroides, Firmicutes, and Spirochaeta were dominated. These results suggests that huge amount of organic matter had been recently supplied on the deep-seafloor. In addition, a large number of mcrA gene were also detected. Most of which were identified as those of Methanococcoides sp. that can grow on methyl compounds as the sole energy source. From the results of investigation in 2011, we hypothesized that high concentration of methane in the microbial mat sediments were generated by methylotrophic methanogen.
On the 2012 cruise, we conducted in-situ incubation to prove our hypothesis. In-situ incubation cores with 13C substrate, 13C-bicarbonate, 13C-acetate, 13C-monomethylamine (MMA) were set on the deep-seafloor where a large microbial mat had been found in 2011 and measured methanogenesis activity. During three days of incubation, significant activity was detected only in the incubation core supplied MMA.
We hope that our results provide important hints to understand the ecology and evolution of methanogenic/methanotrophic archaea in deep-sea environments.