Hadal water biogeochemistry over the Izu–Ogasawara Trench observed with a full-depth CTD-CMS
S. Kawagucci,
S. Kawagucci,
S. Kawagucci,
S. Kawagucci,
A. Makabe,
A. Makabe,
A. Makabe,
T. Kodama,
Y. Matsui,
Y. Matsui,
C. Yoshikawa,
C. Yoshikawa,
E. Ono,
E. Ono,
M. Wakita,
T. Nunoura,
T. Nunoura,
H. Uchida,
T. Yokokawa,
T. Yokokawa
Affiliations
S. Kawagucci
Department 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
S. Kawagucci
Research and Development Center for Submarine Resources (SRRP), Japan
Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15
Natsushima-cho, Yokosuka 237-0061, Japan
S. Kawagucci
Project 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
S. Kawagucci
These authors contributed equally to this work.
A. Makabe
Research and Development Center for Submarine Resources (SRRP), Japan
Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15
Natsushima-cho, Yokosuka 237-0061, Japan
A. Makabe
Project 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
A. Makabe
These authors contributed equally to this work.
T. Kodama
Japan Sea National Fisheries Research Institute, Japan Fisheries
Research and Education Agency, Niigata, 5939-22 Suido-cho, Niigata
951-8121, Japan
Y. Matsui
Research and Development Center for Submarine Resources (SRRP), Japan
Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15
Natsushima-cho, Yokosuka 237-0061, Japan
Y. Matsui
Project 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
C. Yoshikawa
Research and Development Center for Submarine Resources (SRRP), Japan
Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15
Natsushima-cho, Yokosuka 237-0061, Japan
C. Yoshikawa
Department of Biogeochemistry, Japan Agency for Marine-Earth Science
and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka 237-0061, Japan
E. Ono
Research and Development Center for Global Change (RCGC), Japan Agency
for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho,
Yokosuka 237-0061, Japan
E. Ono
Present address: Japan Meteorological Agency, 1-3-4 Otemachi, Tokyo 100-8122, Japan
M. Wakita
Mutsu Institute for Oceanography, Japan Agency for Marine-Earth
Science and Technology (JAMSTEC), 690 Kitasekine, Mutsu 035-0022, Japan
T. Nunoura
Project 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
T. Nunoura
Research and Development Center for Marine Biosciences, Japan Agency
for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho,
Yokosuka 237-0061, Japan
H. Uchida
Research and Development Center for Global Change (RCGC), Japan Agency
for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho,
Yokosuka 237-0061, Japan
T. Yokokawa
Project 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
T. Yokokawa
Research and Development Center for Marine Biosciences, Japan Agency
for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho,
Yokosuka 237-0061, Japan
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. Additionally, comparative samplings were done at the northern Mariana Trench using the same methods. A well-mixed hydrographic structure below 7000 m was observed 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.
