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Ocean Science An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/os-2018-37
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
03 Apr 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Ocean Science (OS).
Hadal water biogeochemistry over the Izu-Ogasawara Trench observed with a full-depth CTD-CMS
Shinsuke Kawagucci1,2,3,*, Akiko Makabe3,*, Taketoshi Kodama4, Yohei Matsui2,3, Chisato Yoshikawa5, Etsuro Ono6,a, Masahide Wakita7, Takuro Nunoura3,8, Hiroshi Uchida6, and Taichi Yokokawa3,8 1Department of Subsurface Geobiological Analysis and Research (D-SUGAR), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2–15 Natsushima-cho, Yokosuka 237-0061, Japan
2Research and Development Center for Submarine Resources (SRRP), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2–15 Natsushima-cho, Yokosuka 237-0061, Japan
3Project Team for Development of New-Generation Research Protocol for submarine resources, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2–15 Natsushima-cho, Yokosuka 237-0061, Japan
4Japan Sea National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Niigata, Japan, 5939-22 Suido-cho, Niigata 951-8121, Japan
5Department of Biogeochemistry, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2–15 Natsushima-cho, Yokosuka 237-0061, Japan
6Research and Development Center for Global Change (RCGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2–15 Natsushima-cho, Yokosuka 237-0061, Japan
7Mutsu Institute for Oceanography, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 690 Kitasekine, Mutsu 035-0022, Japan
8Research and Development Center for Marine Biosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2–15 Natsushima-cho, Yokosuka 237-0061, Japan
apresent address: Japan Meteorological Agency, 1-3-4 Otemachi, Tokyo 100-8122, Japan
*These authors contributed equally to this work.
Abstract. Full-depth profiles of hydrographic and geochemical properties at the Izu-Ogasawara Trench were observed for the first time using a CTD-CMS (Conductivity Temperature Depth profiler with Carousel Multiple Sampling) system, supplemented by some comparative samplings at the northern Mariana Trench using the same methods. The CTD sensor, calibrated from measurements of seawater samples, demonstrated a well-mixed hydrographic structure below 7000 m within the Izu-Ogasawara Trench. Seawater samples collected from this well-mixed hadal layer exhibited constant concentrations of nitrate, phosphate, silicate, and nitrous oxide as well as constant nitrogen and oxygen isotopic compositions of nitrate and nitrous oxide. These results agree well with previous observations of the Izu-Ogasawara hadal waters and deep-sea water surrounding the Izu-Ogasawara Trench. In turn, methane concentrations and isotopic compositions indicated spatial heterogeneity within the well-mixed hadal water mass, strongly suggesting a local methane source within the trench, in addition to the background methane originating from the general deep-sea bottom water. Sedimentary compound releases, associated with sediment re-suspensions, are considered to be the most likely mechanism for generating this significant CH4 anomaly.
Citation: Kawagucci, S., Makabe, A., Kodama, T., Matsui, Y., Yoshikawa, C., Ono, E., Wakita, M., Nunoura, T., Uchida, H., and Yokokawa, T.: Hadal water biogeochemistry over the Izu-Ogasawara Trench observed with a full-depth CTD-CMS, Ocean Sci. Discuss., https://doi.org/10.5194/os-2018-37, in review, 2018.
Shinsuke Kawagucci et al.
Shinsuke Kawagucci et al.
Shinsuke Kawagucci et al.

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Short summary
In 2015, a full-depth-rated CTD-CMS system was equipped on the research vessel R/V Kaimei launched that year. The R/V Kaimei CTD-CMS system can illuminate the last frontier, hadal zone, oceanographic province deeper than 7000 m from the seasurface. A series of biogeochemical observations of hadal seawter at the Izu-Ogasawara and Mariana trenches revealed basically well-mixed water property and heterogeneous distribution of likely sediment-derived compound.
In 2015, a full-depth-rated CTD-CMS system was equipped on the research vessel R/V Kaimei...
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