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Open AccessArticle

Endolithic Microbial Habitats Hosted in Carbonate Nodules Currently Forming within Sediment at a High Methane Flux Site in the Sea of Japan

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Department of Life and Environment Engineering, Faculty of Environmental Engineering, The University of Kitakyushu, Kitakyushu 808-0135, Japan
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Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
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Department of Biological Functions Engineering, Graduate School of Life Sciences and Systems Engineering, Kyushu Institute of Technology, Kitakyushu 808-0196, Japan
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School of Marine Resources and Environment, Tokyo University of Marine Science and Technology, Minato-ku, Tokyo 108-8477, Japan
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Department of Earth Sciences, Graduate School of Science, Chiba University, Chiba 263-8522, Japan
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Gas Hydrate Laboratory, Organization for the Strategic Coordination of Research and Intellectual Properties, Meiji University, Chiyoda-ku, Tokyo 101-8301, Japan
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Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
*
Author to whom correspondence should be addressed.
Geosciences 2019, 9(11), 463; https://doi.org/10.3390/geosciences9110463
Received: 3 October 2019 / Revised: 23 October 2019 / Accepted: 28 October 2019 / Published: 30 October 2019
(This article belongs to the Section Biogeosciences)
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. View Full-Text
Keywords: carbonate nodule; endolithic microbial community; methane carbonate nodule; endolithic microbial community; methane
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Yanagawa, K.; Shiraishi, F.; Tanigawa, Y.; Maeda, T.; Mustapha, N.A.; Owari, S.; Tomaru, H.; Matsumoto, R.; Kano, A. Endolithic Microbial Habitats Hosted in Carbonate Nodules Currently Forming within Sediment at a High Methane Flux Site in the Sea of Japan. Geosciences 2019, 9, 463.

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