Endolithic Microbial Habitats Hosted in Carbonate Nodules Currently Forming within Sediment at a High Methane Flux Site in the Sea of Japan
Katsunori Yanagawa,
Fumito Shiraishi,
Yusuke Tanigawa,
Toshinari Maeda,
Nurul Asyifah Mustapha,
Satoko Owari,
Hitoshi Tomaru,
Ryo Matsumoto,
Akihiro Kano
Affiliations
Katsunori Yanagawa
Department of Life and Environment Engineering, Faculty of Environmental Engineering, The University of Kitakyushu, Kitakyushu 808-0135, Japan
Fumito Shiraishi
Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
Yusuke Tanigawa
Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
Toshinari Maeda
Department of Biological Functions Engineering, Graduate School of Life Sciences and Systems Engineering, Kyushu Institute of Technology, Kitakyushu 808-0196, Japan
Nurul Asyifah Mustapha
Department of Biological Functions Engineering, Graduate School of Life Sciences and Systems Engineering, Kyushu Institute of Technology, Kitakyushu 808-0196, Japan
Satoko Owari
School of Marine Resources and Environment, Tokyo University of Marine Science and Technology, Minato-ku, Tokyo 108-8477, Japan
Hitoshi Tomaru
Department of Earth Sciences, Graduate School of Science, Chiba University, Chiba 263-8522, Japan
Ryo Matsumoto
Gas Hydrate Laboratory, Organization for the Strategic Coordination of Research and Intellectual Properties, Meiji University, Chiyoda-ku, Tokyo 101-8301, Japan
Akihiro Kano
Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
Concretionary carbonates in deep-sea methane seep fields are formed as a result of microbial methane degradation, called anaerobic oxidation of methane (AOM). Recently, active microorganisms, including anaerobic methanotrophic archaea, were discovered from methane seep-associated carbonate outcroppings on the seafloor. However sedimentary buried carbonate nodules are a hitherto unknown microbial habitat. In this study, we investigated the microbial community structures in two carbonate nodules collected from a high methane flux site in a gas hydrate field off the Oki islands in the Sea of Japan. The nodules were formed around sulfate-methane interfaces (SMI) corresponding to 0.7 and 2.2 m below the seafloor. Based on a geochemical analysis, light carbon isotopic values ranging from −54.91‱ to −37.32‱ were found from the nodules collected at the shallow SMI depth, which were attributed to the high contributions of AOM-induced carbonate precipitation. Signatures of methanotrophic archaeal populations within the sedimentary buried nodule were detected based on microbial community composition analyses and quantitative real-time PCR targeted 16S rRNA, and functional genes for AOM. These results suggest that the buried carbonate nodule currently develops AOM-related microbial communities, and grows depending on the continued AOM under high methane flux conditions.
