International Ocean Discovery Program; Expedition 370 preliminary report; temperature limit of the deep biosphere off Muroto; 10 September-23 November 2016

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doi: 10.14379/iodp.pr.370.2017
Author(s): Heuer, Verena; Inagaki, Fumio; Morono, Yuki; Kubo, Yusuke; Maeda, Lena; Bowden, Stephen; Cramm, Margaret; Henkel, Susann; Hirose, Takehiro; Homola, Kira; Hoshino, Tatsuhiko; Ijiri, Akira; Imachi, Hiroyuki; Kamiya, Nana; Kaneko, Masanori; Lagostina, Lorenzo; Manners, Hayley; McClelland, Harry-Luke; Metcalfe, Kyle; Okutsu, Natsumi; Pan, Donald; Raudsepp, Maija Jocelyn; Sauvage, Justine; Schubotz, Florence; Spivack, Arthur; Tonai, Satoshi; Treude, Tina; Tsang, Man-Yin; Viehweger, Bernhard; Wang, David T.; Whitaker, Emily; Yamamoto, Yuzuru; Yang, Kiho; Kinoshita, Masataka
International Ocean Discovery Program, Expedition 370 Scientists, College Station, TX
Author Affiliation(s): Primary:
University of Bremen, MARUM-Center for Marine Environmental Sciences, Bremen, Germany
Other:
Japan Agency for Marine-Earth Science and Technology, Japan
University of Aberdeen, United Kingdom
University of Calgary, Canada
Alfred Wegener Institute, Germany
University of Rhode Island, United States
Nihon University, Japan
National Institute of Advanced Industrial Science and Technology, Japan
Eidgenössische Technische Hochschule Zürich, Switzerland
Plymouth University, United Kingdom
Washington University in Saint Louis, United States
California Institute of Technology, United States
University of Tokyo, Japan
University of Queensland, Australia
Kochi University, Japan
University of California at Los Angeles, United States
University of Toronto, Canada
Massachusetts Institute of Technology, United States
Texas A&M University, United States
Yonsei University, South Korea
Source: Preliminary Report - International Ocean Discovery Program, Vol.370, 29p. Publisher: International Ocean Discovery Program, College Station, TX, United States. ISSN: 2372-9562
Note: In English. 110 refs.
Summary: International Ocean Discovery Program (IODP) Expedition 370 aimed to explore the limits of life in the deep subseafloor biosphere at a location where temperature increases with depth at an intermediate rate and exceeds the known temperature maximum of microbial life (∼120°C) at the sediment/basement interface ∼1.2 km below the seafloor. Drilling Site C0023 is located in the vicinity of Ocean Drilling Program (ODP) Sites 808 and 1174 at the protothrust zone in the Nankai Trough off Cape Muroto at a water depth of 4776 m. ODP Leg 190 in 2000, revealed the presence of microbial cells at Site 1174 to a depth of 600 meters below seafloor (mbsf), which corresponds to an estimated temperature of ∼70°C, and reliably identified a single zone of higher cell concentrations just above the decollement at around 800 mbsf, where temperature presumably reached 90°C; no cell count data was reported for other sediment layers in the 70°-120°C range, because the limit of manual cell count for low-biomass samples was not high enough. With the establishment of Site C0023, we aimed to detect and investigate the presence or absence of life and biological processes at the biotic-abiotic transition with unprecedented analytical sensitivity and precision. Expedition 370 was the first expedition dedicated to subseafloor microbiology that achieved time-critical processing and analyses of deep biosphere samples by simultaneous shipboard and shorebased investigations. Our primary objectives during Expedition 370 were to study the relationship between the deep subseafloor biosphere and temperature. We aimed to comprehensively study the factors that control biomass, activity, and diversity of microbial communities in a subseafloor environment where temperatures increase from ∼2°C at the seafloor to ∼120°C at the sediment/basement interface and thus likely encompasses the biotic-abiotic transition zone. We also aimed to determine geochemical, geophysical, and hydrogeological characteristics in sediment and the underlying basaltic basement and elucidate if the supply of fluids containing thermogenic and/or geogenic nutrient and energy substrates may support subseafloor microbial communities in the Nankai accretionary complex. To address these primary scientific objectives and questions, we penetrated 1180 m and recovered 112 cores across the sediment/basalt interface. More than 13,000 samples were collected, and selected samples were transferred to the Kochi Core Center by helicopter for simultaneous microbiological sampling and analysis in laboratories with a super-clean environment. Following the coring operations, a temperature observatory with 13 thermistor sensors was installed in the borehole tp 863 mbsf.
Year of Publication: 2017
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 22 Environmental Geology; Asia; Basement; Biomass; Boreholes; Cores; Crust; Decollement; Deep biosphere; Ecology; Ecosystems; Expedition 370; Far East; Fluid flow; Geochemistry; Geomicrobiology; Geophysical methods; Geophysical profiles; Geophysical surveys; Heat flow; IODP Site C0023; International Ocean Discovery Program; Japan; Lithostratigraphy; Marine sediments; Microorganisms; Mineralization; Nankai Trough; North Pacific; Northwest Pacific; Oceanic crust; Pacific Ocean; Physical properties; Sedimentary rocks; Sediments; Seismic methods; Seismic profiles; Shikoku; Sub-seafloor environment; Surveys; Temperature; West Pacific
Coordinates: N322200 N322200 E1345800 E1345800
Record ID: 2017020558
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