A5033970580- Geology and Paleoclimatology Research
- Marine Biology and Ecology Research
- Isotope Analysis in Ecology
- Marine and coastal ecosystems
- Methane Hydrates and Related Phenomena
- Microbial Community Ecology and Physiology
- Marine and environmental studies
- earthquake and tectonic studies
- Paleontology and Stratigraphy of Fossils
- Marine and coastal plant biology
- Marine Bivalve and Aquaculture Studies
- Marine and fisheries research
- Geological and Geophysical Studies
- Hydrocarbon exploration and reservoir analysis
- Ocean Acidification Effects and Responses
- Geological formations and processes
- Photosynthetic Processes and Mechanisms
- Environmental DNA in Biodiversity Studies
- Geochemistry and Elemental Analysis
- Coral and Marine Ecosystems Studies
- Geological Studies and Exploration
- Protist diversity and phylogeny
- Radioactive contamination and transfer
- Polar Research and Ecology
- Evolution and Paleontology Studies
Tokyo University of Marine Science and Technology
2016-2024
Waseda University
2021-2022
International Union of Geological Sciences
2022
Tokyo University of Science
1977-2021
Japan Agency for Marine-Earth Science and Technology
2011-2020
Japanese Red Cross Kumamoto Hospital
2016
Red Cross Hospital
2016
Science Council of Japan
2014-2015
Shizuoka University
1997-2011
Kyoto University
2008
The nitrogen isotopic composition (δ 15 N) of amino acids is potentially useful as an alternative method for estimating the trophic levels organisms in food webs. However, because this “amino acid method” has been constructed from observations only a few case studies food‐consumer combinations previous studies, universality approach remains unclear. In study, we investigated δ N signatures 17 photoautotrophs and relationships during four controlled feeding experiments using green algae,...
Five distinct changes in the paleoenvironment of Japan Sea within last 85,000 years are revealed from sedimentary record a piston core recovered Oki Ridge. Changes both surface and deepwater conditions registered by lithology, calcium carbonate content, organic carbon oxygen isotope ratios, microfossil assemblages including calcareous nannoplankton, diatoms, radiolaria, foraminifera. Between 85 27 ka warm Tsushima Current did not flow into Sea, cold water prevailed. Environments at seafloor...
Surface seawaters are supersaturated with respect to calcite, but high concentrations of magnesium prevent spontaneous nucleation and growth crystals. Foraminifera the most widespread group calcifying organisms generally produce calcite a low Mg content, indicating that they actively remove Mg(2+) from vacuolized seawater before precipitation. However, one order foraminifera has evolved calcification pathway, by which it produces very suggesting these species do not alter Mg/Ca ratio...
MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout JournalEditorsTheme Sections 342:85-90 (2007) - doi:10.3354/meps342085 Metabolic control of nitrogen isotope composition amino acids in macroalgae and gastropods: implications for aquatic food web studies Yoshito Chikaraishi1,*, Yuichiro Kashiyama1,2, Nanako O. Ogawa1, Hiroshi Kitazato1, Naohiko Ohkouchi1 1Institute Research on Earth...
In situ video observations and sediment core samplings were performed at two hadal sites in the Japan Trench on July, 2011, four months after Tohoku–Oki earthquake. Video recordings documented dense nepheloid layers extending ~30–50 m above sea bed. At trench axis, benthic macrofauna was absent dead organisms along with turbid downslope current observed. The top 31 cm of axis revealed three recent depositions events characterized by elevated 137Cs levels alternating densities. 4.9 km seaward...
Abstract Ongoing ocean acidification is widely reported to reduce the ability of calcifying marine organisms produce their shells and skeletons. Whereas increased dissolution due a largely inorganic process, strong organismal control over biomineralization influences calcification hence complicates predicting response calcifyers. Here we show that driven by rapid transformation bicarbonate into carbonate inside cytoplasm, achieved active outward proton pumping. Moreover, this flux maintained...
Hadal trenches are considered to act as depo-centers for organic material at the trench axis and host unique elevated biomasses of living organisms compared adjacent abyssal plains. To explore diagenetic activity in hadal environments we quantified situ benthic O2 consumption rates sediment characteristics from two contrasting systems Pacific Ocean; Izu-Bonin Trench underlying mesotrophic waters Tonga oligotrophic waters. In oxygen site (9200 m; 746±103 µmol m−2 d−1; n=27) was 3-times higher...
Benthic foraminiferal populations through 1991–94 were investigated by taking cores and in situ observations from the submersible Shinkai 2000 Sagami Bay, Japan (1450 m water depth). At this location, a strong spring bloom causes seasonal deposition of phytodetrital material to sea floor. The population size benthic foraminifera is mainly controlled flux organic matter, which triggers rapid, opportunistic reproduction shallow infaunal taxa Bolivia pacifica Textularia kattegatensis . We...
MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout JournalEditorsTheme Sections 310:95-108 (2006) - doi:10.3354/meps310095 Different ingestion patterns of 13C-labeled bacteria and algae by deep-sea benthic foraminifera Hidetaka Nomaki1,2,*, Petra Heinz3, Takeshi Nakatsuka4, Motohiro Shimanaga2, Naohiko Ohkouchi1, Nanako O. Ogawa1, Kazuhiro Kogure2, Eiko Ikemoto2, Hiroshi Kitazato1...
We studied Mg/Ca in high‐Mg, shallow‐water benthic foraminifera culture and samples from natural environments, order to evaluate the expression of latitudinal seasonal temperature variability their tests. cultured Planoglabratella opercularis (d'Orbigny) Quinqueloculina yabei Asano under controlled (10°–25°C) salinity (30–38) conditions. Both species show a linear correlation between temperature, but they differ sensitivity. Salinity does not significantly influence Mg/Ca. In collected...
We measured organic carbon uptake rates by deep-sea benthic foraminifera and studied differences among species, living depth, seasons to investigate how these protists contribute consumption on the floor. In situ feeding experiments using 13C-labeled algae were carried out in central part of Sagami Bay from 24 29 November 2001 1 12 April 2002. Our results indicate that assimilation higher shallow infaunal species (Uvigerina akitaensis, Bulimina aculeata) lower intermediate (Textularia...
On the basis of in situ NO 3 −1 microprofiles and chamber incubations complemented by laboratory‐based assessments anammox denitrification we evaluate nitrogen turnover an ocean margin sediment at 1450‐m water depth. In profiles horizontally separated 12 mm reflected highly variable penetration depths, consumption rates, nitrification. average time pore‐water pool was ~0.2 d. Net release NH 4 + during mineralization (0.95 mmol m −2 d ) sustained a net efflux ammonia (53%), nitrification...
We present and compare small sediment‐water fluxes of O 2 determined with the eddy correlation technique, in situ chambers, from vertical sediment microprofiles at a 1450 m deep‐ocean site Sagami Bay, Japan. The average uptake for three approaches, respectively, was 1.62 ± 0.23 (SE, n = 7), 1.65 0.33 ( 2), 1.43 0.15 25) mmol −2 d −1 . very good agreement between flux chamber serves as new, important validation technique. It demonstrates that instrumentation available today is precise can...
Abstract A large portion of the surface‐ocean biomass is represented by microscopic unicellular plankton. These organisms are functionally and morphologically diverse, but it remains unclear how their diversity generated. Species marine microplankton widely distributed because passive transport lack barriers in ocean. How does speciation occur a system with seemingly unlimited dispersal potential? Recent studies using planktonic foraminifera as model showed that even among cryptic genetic...
Abstract Whale carcasses create remarkable habitats in the deep-sea by producing concentrated sources of organic matter for a food-deprived biota as well places evolutionary novelty and biodiversity. Although many faunal patterns on whale falls have already been described, biogeography these communities is still poorly known especially from basins other than NE Pacific Ocean. The present work describes community composition deepest natural carcass described to date found at 4204 m depth...
The planktonic foraminifera genus Globigerinoides provides a prime example of species-rich in which genetic and morphological divergence are uncorrelated. To shed light on the evolutionary processes that lead to present-day diversity Globigerinoides, we investigated genetic, ecological its constituent species. We assembled global collection single-cell barcode sequences show consists eight distinct types organized five extant morphospecies. Based evidence, reassign species Globoturborotalita...
An unfamiliar gastropod was collected from a deep-sea whale carcass at the base of São Paulo Ridge in Southwest Atlantic by manned research submersible Shinkai 6500, and is here described as new species abyssochrysoidean genus Rubyspira, R. brasiliensis sp. nov., following morphological molecular phylogenetic examinations. There are only two other known genus, which occur together Monterey Submarine Canyon off California. The present shown analysis to be closer one Californian than other. It...