Atribacteria from the Subseafloor Sedimentary Biosphere Disperse to the Hydrosphere through Submarine Mud Volcanoes

Submarine mud volcanoes (SMVs) are formed by muddy sediments and breccias extruded to the seafloor from a source in the deep subseafloor and are characterized by the discharge of methane and other hydrocarbon gasses and deep-sourced fluids into the overlying seawater. Although SMVs act as a natural pipeline connecting the Earth’s surface and subsurface biospheres, the dispersal of deep-biosphere microorganisms and their ecological roles remain largely unknown. In this study, we investigated the microbial communities in sediment and overlying seawater at two SMVs located on the Ryukyu Trench off Tanegashima Island, southern Japan. The microbial communities in mud volcano sediments were generally distinct from those in the overlying seawaters and in the well-stratified Pacific margin sediments collected at the Peru Margin, the Juan de Fuca Ridge flank off Oregon, and offshore of Shimokita Peninsula, northeastern Japan. Nevertheless, in-depth analysis of different taxonomic groups at the sub-species level revealed that the taxon affiliated with Atribacteria, heterotrophic anaerobic bacteria that typically occur in organic-rich anoxic subseafloor sediments, were commonly found not only in SMV sediments but also in the overlying seawater. We designed a new oligonucleotide probe for detecting Atribacteria using the catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH). CARD-FISH, digital PCR and sequencing analysis of 16S rRNA genes consistently showed that Atribacteria are abundant in the methane plumes of the two SMVs (0.58 and 1.5 × 104 cells/mL, respectively) but not in surrounding waters, suggesting that microbial cells in subseafloor sediments are dispersed as “deep-biosphere seeds” into the ocean. These findings may have important implications for the microbial transmigration between the deep subseafloor biosphere and the hydrosphere

Dives of cruising-AUV "JINBEI" to methane hydrate area on Joetsu knoll and Umitaka Spur

Autonomous Underwater Vehicle "JINBEI", constructed in 2012, is a cruising type AUV with a weight of 2 ton and a length of 4.0m. The major purposes are observation of underwater CO2 distribution in deep sea and exploration of seabed mineral resources. It has four rear-thrusters, two mid-ship azimuthal thrusters, and a rear X-rudder. The AUV is equipped with three main sensors; a multi-beam echo sounder, a side scan sonar, and a hybrid CO2-pH sensor. During KY12-10 cruise in August 2012, we deployed "JINBEI" at a methane hydrate area in Joetsu knoll and Umitaka Spur, Japan Sea. The depth of the area is 850-950m. The vehicle cruised over the methane hydrate area at a speed of 2 knots. We obtained high-resolution side scan images of hydrate mounts as well as methane plumes. At same time, the CO2-pH sensor detected the methane plumes indirectly. Through the dives, we confirmed that the cruising AUV "JINBEI" is one of powerful tool for survey of scientific observations.Date of Conference: 23-27 September 2013http://www.godac.jamstec.go.jp/darwin/cruise/kaiyo/ky12-10/

Indian Monsoonal Variations During the Past 80 Kyr Recorded in NGHP-02 Hole 19B, Western Bay of Bengal: Implications From Chemical and Mineral Properties

金沢大学理工研究域地球社会基盤学系Detailed reconstruction of Indian summer monsoons is necessary to better understand the late Quaternary climate history of the Bay of Bengal and Indian peninsula. We established a chronostratigraphy for a sediment core from Hole 19B in the western Bay of Bengal, extending to approximately 80 kyr BP and examined major and trace element compositions and clay mineral components of the sediments. Higher δ 18 O values, lower TiO 2 contents, and weaker weathering in the sediment source area during marine isotope stages (MIS) 2 and 4 compared to MIS 1, 3, and 5 are explained by increased Indian summer monsoonal precipitation and river discharge around the western Bay of Bengal. Clay mineral and chemical components indicate a felsic sediment source, suggesting the Precambrian gneissic complex of the eastern Indian peninsula as the dominant sediment source at this site since 80 kyr. Trace element ratios (Cr/Th, Th/Sc, Th/Co, La/Cr, and Eu/Eu*) indicate increased sediment contributions from mafic rocks during MIS 2 and 4. We interpret these results as reflecting the changing influences of the eastern and western branches of the Indian summer monsoon and a greater decrease in rainfall in the eastern and northeastern parts of the Indian peninsula than in the western part during MIS 2 and 4. © 2018. American Geophysical Union. All Rights Reserved

R/V Natsushima Cruise Report NT12-13

調査海域: 日本海東縁 / Area: Japan Sea - western Joetsu Basin, Off Yamagata ; 期間: 2012年5月24日～2012年6月4日 / Operation Period: May 24, 2012～June 4, 2012http://www.godac.jamstec.go.jp/darwin/cruise/natsushima/nt12-13/

R/V Kaiyo Cruise Report KY12-10

調査海域: 相模湾, 日本海上越沖 / Area: Sagami Bay, Sea of Japan ; 期間: 2012年8月18日～2012年8月30日 / Operation Period: August 18, 2012～August 30, 2012http://www.godac.jamstec.go.jp/darwin/cruise/kaiyo/ky12-10/

R/V Natsushima Cruise Report NT12-28

調査海域: 伊平屋北海丘 / Area: Iheya North Knoll ; 期間: 2012年10月29日～2012年11月4日 / Operation Period: October 29, 2012～November 4, 2012http://www.godac.jamstec.go.jp/darwin/cruise/natsushima/nt12-28/

R/V Yokosuka Cruise Report YK13-14

調査海域: 沖縄トラフ伊平屋・伊是名海域 / Area: Iheya-Izena Zone, Okinawa Trough ; 期間: 2013年12月16日～2013年12月31日 / Operation Period: December 16, 2013～December 31, 2013http://www.godac.jamstec.go.jp/darwin/cruise/yokosuka/yk13-14/

(Table T1) Calcium carbonate mineralogy and stable isotopic composition of ODP Hole 182-1132C sediments

Petrographic observation and carbonate mineralogic and stable isotopic investigation were conducted on lower Oligocene to middle Miocene sediments recovered during Ocean Drilling Program Leg 182 from Site 1132, located at a water depth of 218.5 m immediately seaward of the shelf-slope break of the eastern Eyre Terrace in the western Great Australian Bight. The middle Miocene section consists of bioclastic packstone and grainstone with an interval of partially silicified nannofossil-foraminiferal chalk and is slightly to densely dolomitized. By contrast, the lower Oligocene to lower Miocene section is characterized by a predominance of planktonic and benthic foraminifers, high porosity, absence of chert, and weak dolomitization. The carbon and oxygen isotopic composition of calcites and dolomites between two sections, however, shows no significant difference