Kentaro Tanaka

The University of Tokyo

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Kotaro Shirai

The University of Tokyo

Yuji Sano

The University of Tokyo

Naoto Takahata

The University of Tokyo

Shigeru Ohde

University of the Ryukyus

Takanori Kagoshima

The University of Tokyo

Naoko Murakami‐Sugihara

The University of Tokyo

Liqiang Zhao

Guangdong Ocean University

Ryuichi Shinjo

Research Institute for Humanity and Nature

Dung Quang Le

Laboratoire d'Informatique de l'École Polytechnique

Bernd R. Schöne

Johannes Gutenberg University Mainz

Cooperative Institutions

The University of Tokyo

Sphere Institute

University of the Ryukyus

Universiti Malaysia Terengganu

Graduate School USA

Tokyo University of Science

Planetary Science Institute

National Taiwan University

Japan Agency for Marine-Earth Science and Technology

University of the Ryukyus University Hospital

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Fluoride in non-symbiotic coral associated with seawater carbonate

Marine Chemistry (2012)

Kentaro Tanaka Tomonori Ono Yoshimi Fujioka Shigeru Ohde

10.1016/j.marchem.2012.12.004

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Citations (11)

GEOLOGY AND GEOCHEMISTRY OF SILICEOUS ROCKS IN THE EOARCHEAN NUVVUAGITTUQ SUPRACRUSTAL BELT: ESTIMATION OF THEIR ORIGIN AND EVIDENCE FOR LIFE

Abstracts with programs - Geological Society of America (2022)

Yuki Ishihara Kentaro Tanaka Shiono Miki S. Yoshida Yusuke Sawaki

10.1130/abs/2022am-378912

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Citations (0)

Fluoride in coral aragonite related to seawater carbonate

GEOCHEMICAL JOURNAL (2010)

Kentaro Tanaka Shigeru Ohde

In order to elucidate the controlling factors for fluoride incorporation into coral aragonite (CaCO3), we determined the ratio of fluorine to calcium (F/Ca) in coral skeletons collected from Pohnpei (Micronesia), Khang Khao (Thailand), Cebu (The Philippines), Tosa Bay (Kochi, Japan), Sakai Port (Wakayama, Japan), Tateyama (Chiba, Japan), Sesoko, Rukan-sho and Mizugama (Okinawa, Japan) using the ion-chromatograph method. The F/Ca (mmol/mol) ratio was highest in Tateyama with an average ratio of 6.04, whereas coral collected from Sakai Port, Tosa Bay, Okinawa, Cebu, Pohnpei and Khang Khao exhibited F/Ca ratios of 5.57, 5.02, 4.49, 4.24, 4.00 and 3.75, respectively. The factor controlling F/Ca ratio is discussed based on the proposed coprecipitation process of F in coral aragonite as the ion-exchange reaction: CaCO3(s) + 2F-(aq) = CaF2(s) + CO32-(aq). The equilibrium constant for the above equation can be expressed as: KF´ = [CaF2][CO32-]/[CaCO3][F-]2. In this paper, analyzed F/Ca ratio in coral shows a proportional change to calculated seawater [F-]2/[CO32-]. This finding suggests that F/Ca in coral skeletons is possibly controlled by carbonate ion concentration in seawater.

10.2343/geochemj.1.0079

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Citations (9)

Pb/Ca in Thailand Coral Determined by LA-ICP-MS: Anthropogenic Pb Input of River Run-off into a Coral Reef from Urbanised Areas

Water Air & Soil Pollution (2009)

Kentaro Tanaka Shigeru Ohde Aya Sakaguchi Cameron W. McLeod A. G. Cox

10.1007/s11270-009-0293-4

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Citations (5)

An integrated chemostratigraphic (δ13C-δ18O-87Sr/86Sr-δ15N) study of the Doushantuo Formation in western Hubei Province, South China

Precambrian Research (2018)

Zhongwu Lan Yuji Sano Takuya Yahagi Kentaro Tanaka Kotaro Shirai

Biogeochemical Cycle

δ18O

10.1016/j.precamres.2018.10.018

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Citations (24)

Oxygen Isotope Composition in Porites Coral from the Northern Gulf of Thailand: an Implication for Its Skeletal Growth

Mohammad Sazzad Hossain Shigeru Ohde Kentaro Tanaka Sittipun Sirirattanachi Anond Snidvongs

Porites

10.11457/swsj1965.62.112

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Citations (2)

Late Holocene coral reef environment recorded in Tridacnidae shells from archaeological sites in Okinawa‐jima, subtropical southwestern Japan

Island Arc (2014)

Ryuji Asami Mika Konishi Kentaro Tanaka Ryu Uemura M. Furukawa

Abstract Seasonally resolved records of carbon and oxygen isotopic composition (δ 18 O ) in fossil shells of giant clams ( T ridacnidae) recovered from the K ogachibaru S hell M ound (26°26′ N , 127°49′ E ) and the S econd A ragusuku‐ S hichabaru R uin (26°18′ N , 127°46′ E ) in O kinawa‐jima, southwestern J apan, were investigated to reconstruct subtropical coral reef environments of the past. The samples, mainly composed of aragonite shells with limited amounts of diagenetically‐altered calcite cements, were selected for geochemical analyses. The radiocarbon dating of the samples for stable isotope analyses yields about 4000 yr cal. BP for the K ogachibaru S hell M ound and about 1900–1700 yr cal. BP for the S econd A ragusuku‐ S hichabaru R uin, respectively, that correspond to the early and middle S hell M ound periods in O kinawa‐jima. These show good agreement with the respective ages inferred from excavation. The shell δ 18 O values roughly show seasonal variations, coincident with the occurrence of annual growth bands. Applying corrections for the effect of diagenetic alteration, the averages of annual, summer, and winter δ 18 O values of fossil shells were significantly lower (by 0.1–0.7‰) than those of aragonite theoretically precipitated in present‐day coral reef water of O kinawa‐jima. These results demonstrate that annual mean seawater temperature and salinity at the sites where the T ridacnida spp. lived were about 1–3°C higher and/or about 1–2 lower than at present. This variation cannot be fully explained by global climate change, sea level change, and topographic growth of coral reef. Therefore, it is likely that the giant clams lived in extremely small and/or closed coral‐reef lagoons with less water circulation where seawater is highly susceptible to insolation‐induced temperature increase and input of fresh water; the effect could be enhanced by the fisheries lifestyle that stonewalling would be constructed at shallow waters through the use of tidal variation during the early and middle S hell M ound period in O kinawa‐jima.

Before Present

10.1111/iar.12076

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Citations (9)

Response of Acropora digitifera to ocean acidification: constraints from δ11B, Sr, Mg, and Ba compositions of aragonitic skeletons cultured under variable seawater pH

Coral Reefs (2015)

Kentaro Tanaka Michael Holcomb Asami TAKAHASHI Haruko Kurihara Ryuji Asami

Ocean Acidification

Artificial seawater

Stylophora pistillata

Saturation (graph theory)

10.1007/s00338-015-1319-6

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Citations (34)

Feeding habitats of juvenile reef fishes in a tropical mangrove–seagrass continuum along a Malaysian shallow-water coastal lagoon

Bulletin of Marine Science (2019)

Dung Quang Le Siau Yin Fui Kentaro Tanaka Suhaimi Suratman Yuji Sano

We conducted stable isotope (δ 13 C and δ 15 N) and gut content analyses to understand habitat use of juvenile reef fishes ( Lethrinus lentjan , Lutjanus russellii , and Epinephelus coioides ), particularly the influence of spatial habitat structure along seagrass–mangrove continua. Sampling was conducted in Setiu Lagoon, located in the southern waters of the South China Sea (Malaysia). Gut content analysis indicated that the focal fishes preyed mainly on benthic invertebrates and other smaller fishes; these were used as potential prey items for isotopic tracers to track fish habitat use. Stable isotope analyses highlighted that the juvenile reef fishes were highly associated with seagrass beds as feeding grounds; however, site-specific analyses suggest differences in fish feeding habitats. The juvenile fishes, particularly large juveniles, preyed in both mangrove and seagrass areas from the central lagoon, whereas all juveniles showed preferential foraging within seagrass meadows in the nearby lagoon mouth. Furthermore, the mean stable isotope values of muscle tissue differed among fish size classes, indicating their ontogenetic habitat/diet shifts, especially for L. lentjan and E. coioides . This study provides important information to support current efforts in protecting and preserving mangroves and seagrasses as crucial nursery habitats for juvenile reef fishes from the anthropogenic activities influencing Setiu Lagoon.

Juvenile fish

Epinephelus

10.5343/bms.2018.0093

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Citations (6)

Raman analysis of octocoral carbonate ion structural disorder along a natural depth gradient, Kona coast, Hawai‘i

American Mineralogist (2022)

Kyle Conner Shiv K. Sharma Ryohei Uchiyama Kentaro Tanaka Naoko Murakami‐Sugihara

Abstract Both environmental and physiological factors cause carbonate ion structural disorder in biogenic Mg-calcites. A major component of this disorder is driven by the incorporation of Mg through environmental forcing and growth rate kinetics although non-Mg factors (e.g., other cation/anion impurities, organic molecules) also contribute. Understanding the drivers of Mg content in biogenic calcite and its effects on disorder has implications for octocoral Mg paleo-proxies and the stability and diagenetic alteration of their calcitic skeletons. However, prior studies of biogenic Mg-calcites have often been complicated by sampling inconsistencies over space and time and potential intra-sample Mg variability. This study aims to analyze the relative contributing factors of octocoral Mg-calcite structural disorder along gradients of both depth and growth rate. Calcitic octocorals (Coralliidae and Keratoisididae, N = 28) were collected from 221–823 m depths across a natural gradient in biogeochemical parameters (pH: 7.4–7.9, T: 5–16 °C) off the Kona coast of Hawai‘i Island and were analyzed using Raman spectroscopy. Samples were collected during the same month, controlling for potential seasonal variability. Raman spectral parameters from the ν1 peak quantified total carbonate ion structural disorder (full-width at half maximum height [FWHM] of ν1) and Mg content (ν1 position, Raman shift). The total structural disorder was then partitioned into Mg-driven and non-Mg driven components (residual ν1 FWHM). The total structural disorder and Mg content decreased significantly with increasing depth, correlating with temperature and carbonate system parameters. The Mg-temperature relationships from this study were also consistent with prior studies. Non-Mg structural disorder did not correlate to any environmental parameters. When measured across an intra-sample gradient of ontogenetic growth rate, total structural disorder, Mg content, and non-Mg structural disorder increased with growth rate for all but one taxon, demonstrating the kinetic effect of growth rate as well as potential taxon-specific physiological effects. These results provide insight into how environmental and growth rate kinetic effects independently affect different components of carbonate ion structural disorder (Mg content and non-Mg factors). These findings also suggest that Raman spectroscopy may be helpful in quantifying solubility within biogenic calcites.

Carbonate Ion

10.2138/am-2022-8406

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Citations (2)