2024/07/16 更新

写真a

イノウエ マユリ
井上 麻夕里
INOUE Mayuri
所属
環境生命自然科学学域 教授
職名
教授
外部リンク

学位

  • 博士(理学) ( 2005年3月   東北大学 )

学歴

  • 東北大学   大学院理学研究科  

    2002年4月 - 2005年3月

  • 岡山大学    

    2000年4月 - 2002年3月

  • 岡山大学   教育学部  

    1996年4月 - 2000年3月

所属学協会

  • 日本第四紀学会

  • 日本海洋学会

  • 日本地球環境史学会

  • 日本サンゴ礁学会

  • 日本地球化学会

 

論文

  • Assessment of chemical compositions in coral skeletons (Acropora digitifera and Porites australiensis) as temperature proxies

    Shoko Sakata, Mayuri Inoue, Yasuaki Tanaka, Takashi Nakamura, Kazuhiko Sakai, Minoru Ikehara, Atsushi Suzuki

    Frontiers in Marine Science   11   2024年2月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Frontiers Media SA  

    Although biogenic carbonates, such as foraminifera and coccolithophorids, are valuable tools for reconstructing past environments, scleractinian corals also offer environmental data from tropical to subtropical regions with a higher time resolution. For example, oxygen isotopes (δ18O) and strontium-calcium (Sr/Ca) ratios have been utilized to reconstruct sea surface temperatures and salinity, primarily through the use of massive-type Porites sp. from the Pacific, as well as corals like Diploria and Montastrea from the Atlantic. While a few types of corals other than Porites have been utilized in paleoclimate studies, comprehensive evaluations of their geochemical tracers as temperature proxies have not been thoroughly conducted. Therefore, in this study, we focused on branching-type Acropora, which are found worldwide and are often present in fossil corals. We conducted a comparison of the chemical compositions (δ18O, δ13C, Sr/Ca, U/Ca, Mg/Ca, and Ba/Ca) of Acropora digitifera and Porites australiensis through temperature-controlled culture experiments. The validity of using the chemical components of A. digitifera as temperature proxies was then evaluated. Three colonies of A. digitifera and P. australiensis were collected for culture experiments on Sesoko Island, Okinawa, Japan. We reared coral samples in seawater with five different temperature settings (18, 21, 24, 27, 30°). The calcification rate and photosynthesis efficiency (Fv/Fm) of each nubbin were measured during the experimental period. After the culture experiment for 77 days, chemical components in skeletal parts grown during the experiment were then measured. Consequently, the mean growth rates and Fv/Fm throughout the experiment were higher for A. digitifera (0.22%/d and 0.63 for growth rate and Fv/Fm) compared to those for P. australiensis (0.11%/d and 0.38 for growth rate and Fv/Fm). This suggests that the higher efficiency of photosynthesis in A. digitifera would promote greater calcification compared to P. australiensis. Regarding the potential use as temperature proxies, A. digitifera exhibited a strong negative correlation, on average, between δ18O and the water temperature (r = 0.95, p< 0.001). The temperature dependency was found to be comparable to that reported in Porites corals (-0.11 and -0.17 ‰/°C for P. australiensis and A. digitifera, respectively). Thus, the δ18O of A. digitifera appeared to be a useful temperature proxy, although it was also slightly influenced by skeletal growth rate at the same temperature. A strong negative correlation was also observed between the mean Sr/Ca ratio and temperature in A. digitifera (r = 0.61, p< 0.001) as well as P. australiensis (r = 0.56, p< 0.001), without a clear influence from the skeletal growth rate. Therefore, the skeletal Sr/Ca ratio in corals may have been primarily influenced by water temperature, although large deviations in Sr/Ca were observed in A. digitifera, even at the same temperature settings. This deviation can be reduced by subsampling an apical part of a polyp including the axis of skeletal growth. The U/Ca ratio of A. digitifera appeared to be affected by internal pH variation within the corals, especially at 30°C. Similar to U/Ca ratios, metabolic and kinetic effects on corals were observed in δ13C of A. digitifera at 18 and 30°C. In addition, considering the variation pattern of both U/Ca and δ13C of A. digitifera at 30°C, it has been suggested that respirations may overwhelm photosynthesis for coral samples at 30°C. Therefore, the U/Ca and δ13C of A. digitifera could potentially be used as proxies of biomineralization processes, whereas the δ18O and Sr/Ca displayed a high possibility of acting as temperature proxies.

    DOI: 10.3389/fmars.2024.1329924

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  • Natural and Anthropogenic Climate Variability Signals in a 237-Year-Long Coral Record From the Philippines 査読

    M. Inoue, A. Fukushima, M. Chihara, A. Genda, M. Ikehara, T. Okai, H. Kawahata, F. P. Siringan, A. Suzuki

    Paleoceanography and Paleoclimatology   38 ( 11 )   2023年11月

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    担当区分:筆頭著者, 責任著者   掲載種別:研究論文(学術雑誌)  

    Both proxy and model studies conducted to understand anthropogenic warming have revealed historical variations in sea-surface temperature (SST) since the industrial revolution. However, because of discrepancies between observations and models in the late nineteenth century, the timing and degree of anthropogenic warming remain unclear. In this study, we reconstructed a 237-year-long record of SST and salinity using a coral core collected from Bicol, southern Luzon, Philippines, which is located at the northern edge of the western Pacific warm pool. The SST record showed volcanic cooling after several volcanic eruptions, including the 1815 Tambora eruption, but the pattern of change differed. Decadal SST variations at Bicol are connected to Pacific Decadal Variability (PDV). Therefore, it is suggested that the PDV conditions at the time of the eruption may have influenced marine conditions, such as the degree and duration of cooling and/or salinity, after the eruptions. Although there were discrepancies in SST variations among the modeled, observed, and proxy SST data from the late nineteenth to early twentieth centuries, SST data from the late twentieth century showed globally coherent anthropogenic warming, especially after 1976. In particular, summer SST in the northwestern Pacific has become more sensitive to anthropogenic forcing since 1976.

    DOI: 10.1029/2022PA004540

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  • Sea Surface Temperature and Salinity in Lombok Strait Reconstructed From Coral Sr/Ca and δ18O, 1962–2012 査読

    Ai Genda, Minoru Ikehara, Atsushi Suzuki, Ali Arman, Mayuri Inoue

    Frontiers in Climate   4   2022年7月

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    担当区分:最終著者   掲載種別:研究論文(学術雑誌)   出版者・発行元:Frontiers Media SA  

    Coral geochemical tracers have been used in studies of the paleoclimatology and paleoceanography of the tropics and subtropics. We measured Sr/Ca and oxygen isotope ratios (δ18O) in a coral sample collected from the southern part of Lombok Strait, a significant outlet of the Indonesian Throughflow (ITF) to the Indian Ocean, to reconstruct the historical record of sea surface temperature (SST) and seawater δ18O. Seawater δ18O can be used to approximate sea surface salinity (SSS) because it reflects the balance of evaporation and precipitation. The resulting time series reconstructed SST and SSS, covering the period 1962–2012, shows no clear trend of global warming, although the record includes a large cooling event (~4°C) during 1996–1997. Although neither SST nor SSS shows a systematic relationship with El Niño–Southern Oscillation and Indian Ocean Dipole (IOD), weak but significant correlations are found partly. In addition, the coral data show signals of major IOD and El Niño events in 1994 and 1997, respectively, although climatic trends recorded in the coral are not consistent with those found along the Java-Sumatra coast. To evaluate other influences on the ITF in Lombok Strait, we compared our coral record with coral records from sites in the Java Sea, the southern part of Makassar Strait, and Ombai Strait. During the northwest monsoon (December–January–February), variations in SST and SSS at Lombok Strait site are similar to those at the Java Sea and southern Makassar sites for the period 1962–1995, which suggests that low-salinity water from the Java Sea is carried at least to the southern part of Makassar Strait where it suppresses the ITF upstream from Lombok Strait. However, the SST and SSS records differ at the three sites during the southeast monsoon (June–July–August), indicating that surface conditions in Lombok Strait vary separately from those in the Java Sea. In the longer term, although global warming has been widely identified in the Indonesian Seas, the coral record shows no clear warming trend in the southern part of Lombok Strait, where fluctuations in the ITF may be modulating the distribution of heat in the surface waters of the western Pacific and eastern Indian Ocean.

    DOI: 10.3389/fclim.2022.918273

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  • Unique behavior of marine conditions in the Java Sea reconstructed from a 70 yr coral δ<sup>18</sup>O and Sr/Ca record from the Seribu Islands, Indonesia 査読

    Ai Genda, Minoru Ikehara, Atsushi Suzuki, Wahyoe S. Hantoro, Mayuri Inoue

    GEOCHEMICAL JOURNAL   56 ( 3 )   e1 - e7   2022年

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    担当区分:最終著者   掲載種別:研究論文(学術雑誌)   出版者・発行元:Geochemical Society of Japan  

    DOI: 10.2343/geochemj.gj22007

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  • Whole-Genome Sequencing Highlights Conservative Genomic Strategies of a Stress-Tolerant, Long-Lived Scleractinian Coral, Porites australiensis Vaughan, 1918 査読 国際誌

    Chuya Shinzato, Takeshi Takeuchi, Yuki Yoshioka, Ipputa Tada, Miyuki Kanda, Cédric Broussard, Akira Iguchi, Makoto Kusakabe, Frédéric Marin, Noriyuki Satoh, Mayuri Inoue

    Genome Biology and Evolution   13 ( 12 )   2021年12月

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    担当区分:最終著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Oxford University Press (OUP)  

    <title>Abstract</title>
    Massive corals of the genus Porites, common, keystone reef builders in the Indo-Pacific Ocean, are distinguished by their relative stress tolerance and longevity. In order to identify genetic bases of these attributes, we sequenced the complete genome of a massive coral, Porites australiensis. We developed a genome assembly and gene models of comparable quality to those of other coral genomes. Proteome analysis identified 60 Porites skeletal matrix protein genes, all of which show significant similarities to genes from other corals and even to those from a sea anemone, which has no skeleton. Nonetheless, 30% of its skeletal matrix proteins were unique to Porites and were not present in the skeletons of other corals. Comparative genomic analyses showed that genes widely conserved among other organisms are selectively expanded in Porites. Specifically, comparisons of transcriptomic responses of P. australiensis and Acropora digitifera, a stress-sensitive coral, reveal significant differences in regard to genes that respond to increased water temperature, and some of the genes expanded exclusively in Porites may account for the different thermal tolerances of these corals. Taken together, widely shared genes may have given rise to unique biological characteristics of Porites, massive skeletons and stress tolerance.

    DOI: 10.1093/gbe/evab270

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    その他リンク: https://academic.oup.com/gbe/article-pdf/13/12/evab270/41839460/evab270.pdf

  • Coral Record of Younger Dryas Chronozone Warmth on the Great Barrier Reef 査読

    Logan D. Brenner, Braddock K. Linsley, Jody M. Webster, Donald Potts, Thomas Felis, Michael K. Gagan, Mayuri Inoue, Helen McGregor, Atsushi Suzuki, Alexander Tudhope, Tezer Esat, Alex Thomas, William Thompson, Stewart Fallon, Marc Humblet, Manish Tiwari, Yusuke Yokoyama

    PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY   35 ( 12 )   2020年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    The Great Barrier Reef (GBR) is an internationally recognized and widely studied ecosystem, yet little is known about its sea surface temperature (SST) evolution since the Last Glacial Maximum (LGM) (similar to 20 kyr BP). Here, we present the first paleo-application of Isopora coral-derived SST calibrations to a suite of 25 previously published fossil Isopora from the central GBR spanning similar to 25-11 kyr BP. The resultant multicoral Sr/Ca- and delta O-18-derived SST anomaly (SSTA) histories are placed within the context of published relative sea level, reef sequence, and coralgal reef assemblage evolution. Our new calculations indicate SSTs were cooler on average by similar to 5-5.5 degrees C at Noggin Pass (similar to 17 degrees S) and similar to 7-8 degrees C at Hydrographer's Passage (similar to 20 degrees S) (Sr/Ca-derived) during the LGM, in line with previous estimates (Felis et al., 2014, ). We focus on contextualizing the Younger Dryas Chronozone (YDC, similar to 12.9-11.7 kyr BP), whose Southern Hemisphere expression, in particular in Australia, is elusive and poorly constrained. Our record does not indicate cooling during the YDC with near-modern temperatures reached during this interval on the GBR, supporting an asymmetric hemispheric presentation of this climate event. Building on a previous study (Felis et al., 2014, ), these fossil Isopora SSTA data from the GBR provide new insights into the deglacial reef response, with near-modern warming during the YDC, since the LGM.

    DOI: 10.1029/2020PA003962

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  • Dataset of characteristic remanent magnetization and magnetic properties of early Pliocene sediments from IODP Site U1467 (Maldives platform)

    Luca Lanci, Elena Zanella, Luigi Jovane, Simone Galeotti, Montserrat Alonso-Garcia, Carlos A. Alvarez-Zarikian, Nagender Nath Bejugam, Christian Betzler, Or M. Bialik, Clara L. Blattler, Gregor P. Eberli, Junhua Adam Guo, Sebastien Haffen, Senay Horozal, Mayuri Inoue, Dick Kroon, Juan Carlos Laya, Anna Ling Hui Mee, Thomas Luedmann, Masatoshi Nakakuni, Kaoru Niino, Loren M. Petruny, Santi D. Pratiwi, John J. G. Reijmer, Jesus Reolid, Angela L. Slagle, Craig R. Sloss, Xiang Su, Peter K. Swart, James D. Wright, Zhengquan Yao, Jeremy R. Young

    DATA IN BRIEF   27   2019年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER  

    This data article describes data of magnetic stratigraphy and anisotropy of isothermal remanent magnetization (AIRM) from "Magnetic properties of early Pliocene sediments from IODP Site U1467 (Maldives platform) reveal changes in the monsoon system" [1]. Acquisition of isothermal magnetization on pilot samples and anisotropy of isothermal remanent magnetization are reported as raw data; magnetostratigraphic data are reported as characteristic magnetization (ChRM). (C) 2019 The Authors. Published by Elsevier Inc.

    DOI: 10.1016/j.dib.2019.104666

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  • Magnetic properties of early Pliocene sediments from IODP Site U1467 (Maldives platform) reveal changes in the monsoon system 査読

    Luca Lanci, Elena Zanella, Luigi Jovane, Simone Galeotti, Montserrat Alonso-Garcia, Carlos A. Alvarez-Zarikian, Nagender Nath Bejugam, Christian Betzler, Or M. Bialik, Clara L. Blattler, Gregor P. Eberlik, Junhua Adam Guo, Sebastien Haffen, Senay Horozal, Mayuri Inoue, Dick Kroon, Juan Carlos Laya, Anna Ling Hui Mee, Thomas Luedmann, Masatoshi Nakakunir, Kaoru Niino, Loren M. Petruny, Santi D. Pratiwi, John J. G. Reijmer, Jesus Reolid, Angela L. Slagle, Craig R. Sloss, Xiang Su, Peter K. Swart, James D. Wright, Zhengquan Yao, Jeremy R. Young

    PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY   533   2019年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER  

    We report a study of the magnetic stratigraphy and the anisotropy of isothermal remanent magnetization of Pliocene sediments from International Ocean Discovery Program (IODP) Site U1467 drilled in the Maldives platform (Indian Ocean) during Exp. 359. Magnetic stratigraphy gives a precise record of geomagnetic reversals of the early Pliocene from approximately 5.3 Ma to 3.1 Ma providing a detailed age model in an interval where the biostratigraphic record is scarce. We use the anisotropy of isothermal remanent magnetization (AIRM) to investigate the statistical orientation of fine magnetic particles and provide data on the strength and direction of bottom currents during the early Pliocene. The strength of bottom currents recorded by the AIRM, shows a prominent increase at the top of Chron C3n.1n (about 4.2 Ma), and the current direction (NE - SW) is consistent with that of modern instrumental measurements. Since bottom currents in the Maldives are driven by the monsoon, we speculate that the 4.2 Ma increase of bottom currents could mark the onset of the present-day setting, probably related to the coeval uplift phase of the Himalayan plateau.

    DOI: 10.1016/j.palaeo.2019.109283

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  • Cyclic anoxia and organic rich carbonate sediments within a drowned carbonate platform linked to Antarctic ice volume changes: Late Oligocene-early Miocene Maldives 査読

    Peter K. Swart, Clara L. Blattler, Masatoshi Nakakuni, Greta J. Mackenzie, Christian Betzler, Gregor P. Eberli, Jesus Reolid, Montserrat Alonso-Garcia, Angela L. Slagle, James D. Wright, Dick Kroon, John J. G. Reijmer, Anna L. Hui Mee, Jeremy R. Young, Carlos A. Alvarez-Zarikian, Orr M. Bialik, Junhua Adam Guo, Sebastian Haffen, Senay Horozal, Mayuri Inoue, Luigi Jovane, Luca Lanci, Juan Carlos Laya, Thomas Luedmann, B. Nagender Nath, Kaoru Niino, Loren M. Petruny, Santi Dwi Pratiwi, Xiang Su, Craig R. Sloss, Zhengquan Yao

    EARTH AND PLANETARY SCIENCE LETTERS   521   1 - 13   2019年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER  

    This paper reports on the newly discovered occurrence of thick sequences (similar to 100 m) of Late Oligocene and Early Miocene (similar to 24.9 to similar to 20 Ma) interbedded organic-rich sediments (sapropels) and pelagic (organic poor) carbonates at Sites 01466 and U1468 drilled in the Maldives archipelago during the International Ocean Discovery Program (IODP) Expedition 359. This occurrence is unusual in that this sequence is located > 1000 m above the surrounding ocean floor within an inter-atoll basin and not linked to any known global oceanic events. Total organic content reaches as high as 35% in the darker layers, while the interbedded carbonates have concentrations of less than 0.1%. Trace elements characteristic of anoxic waters, such as Mo, V, Cr, U, and Pb, correlate positively with concentrations of organic carbon. Nitrogen isotopic data show no evidence that the intervals of high total organic carbon are related to enhanced productivity driven by upwelling. Instead, high organic carbon is associated with intervals of anoxia. We propose that sea-level fluctuations linked to changes in Antarctic ice volume restricted exchange with the open ocean causing bottom waters of the inter-atoll basin to become anoxic periodically. The architecture of the platform at the end of the Oligocene, combined with the global sea-level highstand, set the stage for orbitally-driven sea-level changes producing cyclic deposition of sapropels. The proposed mechanism may serve as an analogue for other occurrences of organic carbon rich sediments within carbonate platform settings. (C) 2019 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.epsl.2019.05.019

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  • A two million year record of low-latitude aridity linked to continental weathering from the Maldives (vol 5, pg 86, 2018) 査読

    Tereza Kunkelova, Simon J. A. Jung, Erica S. de Leau, Nick Odling, Alex L. Thomas, Christian Betzler, Gregor P. Eberli, Carlos A. Alvarez-Zarikian, Montserrat Alonso-Garcia, Or M. Bialik, Clara L. Blattler, Junhua Adam Guo, Sebastien Haffen, Senay Horozal, Anna Ling Hui Mee, Mayuri Inoue, Luigi Jovane, Luca Lanci, Juan Carlos Laya, Thomas Luedmann, Nagender N. Bejugam, Masatoshi Nakakuni, Kaoru Niino, Loren M. Petruny, Santi D. Pratiwi, John J. G. Reijmer, Jesus Reolid, Angela L. Slagle, Craig R. Sloss, Xiang Su, Peter K. Swart, James D. Wright, Zhengquan Yao, Jeremy R. Young, Sebastian Lindhorst, Stephanie Stainbank, Andres Rueggeberg, Silvia Spezzaferri, Igor Carrasqueira, Siyao Yu, Dick Kroon

    PROGRESS IN EARTH AND PLANETARY SCIENCE   6   2019年2月

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    記述言語:英語   出版者・発行元:SPRINGEROPEN  

    In the original version of this article (Kunkelova et al. 2018), published on 18 December 2018, there was 1 error in the author name of Dr. Yu.

    DOI: 10.1186/s40645-019-0259-0

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  • Perspective on the response of marine calcifiers to global warming and ocean acidification-Behavior of corals and foraminifera in a high CO2 world "hot house" 査読

    Hodaka Kawahata, Kazuhiko Fujita, Akira Iguchi, Mayuri Inoue, Shinya Iwasaki, Azumi Kuroyanagi, Ayumi Maeda, Takuya Manaka, Kazuyoshi Moriya, Haruka Takagi, Takashi Toyofuku, Toshihiro Yoshimura, Atsushi Suzuki

    PROGRESS IN EARTH AND PLANETARY SCIENCE   6   2019年1月

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    記述言語:英語   出版者・発行元:SPRINGEROPEN  

    The CO2 concentration of air has increased over the last two centuries and recently surpassed 400ppm. Carbon cycle models project CO2 concentrations of 720 to 1000ppm for the IPCC intermediate scenario (RCP 6.0), resulting in an increase in global mean temperature of similar to 2.6 degrees C and a decrease in seawater pH of similar to 0.3. Together, global warming and ocean acidification are often referred to as the evil twins of climate change, potentially inducing severe threats in the near future. In this paper, our discussion is focused on the response of two major calcifiers, foraminifera and corals, which contribute much to the global carbonate burial rate. Photosymbiosis is regarded as an adaptive ecology for living in warm and oligotrophic oceans, especially for reef-building corals and larger reef-dwelling benthic foraminifera. As a consequence of global warming, bleaching may be a global threat to algal symbiont-bearing marine calcifying organisms under conditions of high temperature and light intensity. If CO2 is dissolved in seawater, the partial pressure of CO2 in seawater (pCO(2)) and dissolved inorganic carbon (DIC) increases while pH and the saturation state of carbonate minerals decreases without any change in total alkalinity. Generally, marine calcifying organisms show decreases in calcification rates in response to acidified seawater. However, the response often differs depending on situations, species, and life-cycle stage. Some benthic foraminifera showed a positive response to low pH conditions. The Acropora digitifera coral calcification of adult branches was not reduced markedly at higher pCO(2) conditions, although calcification tended to decrease versus pCO(2) in both aposymbiotic and symbiotic polyps. New analytical technologies help identify important constraints on calcification processes. Based upon Ca isotopes, the transport path of Ca2+ and the degree of its activity would predominantly control the carbonate precipitation rate. Visualization of the extracellular pH distribution shows that proton pumping produces the high internal pH and large internal-external pH gap in association with foraminiferal calcification. From the perspective of a long-term change in the Earth's surface environment, foraminifera seem to be more adaptive and robust than corals in coping with ocean warming and acidification but it is necessary to further understand the mechanisms underlying variations in sensitivity to heat stress and acidified seawater for future prediction. Since CO2 is more soluble in lower temperature seawater, ocean acidification is more critical in the polar and high-latitude regions. Additionally, older deep-water has enhanced acidity owing to the addition of CO2 from the degradation of organic matter via a synergistic effect with high pressure. With current ocean acidification, pH and the saturation state of carbonate minerals are decreasing without any change in total alkalinity. However, in the Earth's history, it is well known that alkalinity has fluctuated significantly. Therefore, it is necessary to quantitatively reconstruct alkalinity, which is another key factor determining the saturation state of carbonate minerals.The rapid release of anthropogenic CO2 (in the present day and at the Paleocene/Eocene boundary) induces severe ocean acidification, whereas in the Cretaceous, slow environmental change, even at high levels of pCO(2), could raise alkalinity, thereby neutralizing ocean acidification.

    DOI: 10.1186/s40645-018-0239-9

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  • Corrigendum to “Carbonate delta drift: A new sediment drift type” [Mar. Geol. 401 (2018) 98–111] (Marine Geology (2018) 401 (98–111), (S0025322717302761) (10.1016/j.margeo.2018.04.011))

    Thomas Lüdmann, Christian Betzler, Gregor P. Eberli, Jesús Reolid, John J.G. Reijmer, Craig R. Sloss, Or M. Bialik, Carlos A. Alvarez-Zarikian, Montserrat Alonso-García, Clara L. Blättler, Junhua Adam Guo, Sébastien Haffen, Senay Horozal, Mayuri Inoue, Luigi Jovane, Dick Kroon, Luca Lanci, Juan Carlos Laya, Anna Ling Hui Mee, Masatoshi Nakakuni, B. Nagender Nath, Kaoru Niino, Loren M. Petruny, Santi D. Pratiwi, Angela L. Slagle, Xiang Su, Peter K. Swart, James D. Wright, Zhengquan Yao, Jeremy R. Young

    Marine Geology   406   214 - 215   2018年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier B.V.  

    The authors regret the mistake in the drawing of the delta drift architecture in figure 11. The authors would like to apologise for any inconvenience caused. [Figure presented]

    DOI: 10.1016/j.margeo.2018.10.005

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  • A two million year record of low-latitude aridity linked to continental weathering from the Maldives

    Tereza Kunkelova, Simon J. A. Jung, Erica S. de Leau, Nick Odling, Alex L. Thomas, Christian Betzler, Gregor P. Eberli, Carlos A. Alvarez-Zarikian, Montserrat Alonso-Garcia, Or M. Bialik, Clara L. Blattler, Junhua Adam Guo, Sebastien Haffen, Senay Horozal, Anna Ling Hui Mee, Mayuri Inoue, Luigi Jovane, Luca Lanci, Juan Carlos Laya, Thomas Luedmann, Nagender N. Bejugam, Masatoshi Nakakuni, Kaoru Niino, Loren M. Petruny, Santi D. Pratiwi, John J. G. Reijmer, Jesus Reolid, Angela L. Slagle, Craig R. Sloss, Xiang Su, Peter K. Swart, James D. Wright, Zhengquan Yao, Jeremy R. Young, Sebastian Lindhorst, Stephanie Stainbank, Andres Rueggeberg, Silvia Spezzaferri, Igor Carrasqueira, Siyao Hu, Dick Kroon

    PROGRESS IN EARTH AND PLANETARY SCIENCE   5   2018年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGER  

    Indian-Asian monsoon has oscillated between warm/wet interglacial periods and cool/dry glacial periods with periodicities closely linked to variations in Earth's orbital parameters. However, processes that control wet versus dry, i.e. aridity cyclical periods on the orbital time-scale in the low latitudes of the Indian-Asian continent remain poorly understood because records over millions of years are scarce. The sedimentary record from International Ocean Discovery Program (IODP) Expedition 359 provides a well-preserved, high-resolution, continuous archive of lithogenic input from the Maldives reflecting on low-latitude aridity cycles. Variability within the lithogenic component of sedimentary deposits of the Maldives results from changes in monsoon-controlled sedimentary sources. Here, we present X-ray fluorescence (XRF) core-scanning results from IODP Site U1467 for the past two million years, allowing full investigation of orbital periodicities. We specifically use the Fe/K as a terrestrial climate proxy reflecting on wet versus dry conditions in the source areas of the Indian-Asian landmass, or from further afield. The Fe/K record shows orbitally forced cycles reflecting on changes in the relative importance of aeolian (stronger winter monsoon) during glacial periods versus fluvial supply (stronger summer monsoon) during interglacial periods. For our chronology, we tuned the Fe/Kcycles to precessional insolation changes, linking Fe/K maxima/minima to insolation minima/maxima with zero phase lag. Wavelet and spectral analyses of the Fe/K record show increased dominance of the 100kyr cycles after the Mid Pleistocene Transition (MPT) at 1.25Ma in tandem with the global ice volume benthic O-18 data (LR04 record). In contrast to the LR04 record, the Fe/K profile resolves 100-kyr-like cycles around the 130kyr frequency band in the interval from 1.25 to 2 million years. These 100-kyr-like cycles likely form by bundling of two or three obliquity cycles, indicating that low-latitude Indian-Asian climate variability reflects on increased tilt sensitivity to regional eccentricity insolation changes (pacing tilt cycles) prior to the MPT. The implication of appearance of the 100kyr cycles in the LR04 and the Fe/K records since the MPT suggests strengthening of a climate link between the low and high latitudes during this period of climate transition.

    DOI: 10.1186/s40645-018-0238-x

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  • A simple role of coral-algal symbiosis in coral calcification based on multiple geochemical tracers

    Mayuri Inoue, Takashi Nakamura, Yasuaki Tanaka, Atsushi Suzuki, Yusuke Yokoyama, Hodaka Kawahata, Kazuhiko Sakai, Nikolaus Gussone

    GEOCHIMICA ET COSMOCHIMICA ACTA   235   76 - 88   2018年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Light-enhanced calcification of reef-building corals, which eventually create vast coral reefs, is well known and based on coral-algal symbiosis. Several controversial hypotheses have been proposed as possible mechanisms for connecting symbiont photosynthesis and coral calcification, including pH rise in the internal pool, role of organic matrix secretion, and enzyme activities. Here, based on the skeletal chemical and isotopic compositions of symbiotic and asymbiotic primary polyps of Acropora digitifera corals, we show a simple pH increase in the calcification medium as the predominant contribution of symbionts to calcification of host corals. We used the symbiotic and asymbiotic primary polyps reared for 10 days at four temperatures (27, 29, 31, and 33 degrees C), five salinities (34, 32, 30, 28, and 26), and four pCO(2) levels (<300, 400, 800, and 1000)(atm). As a result of analyzing multiple geochemical tracers (U/Ca, Mg/Ca, Sr/Ca, delta O-18, delta C-13, and 8 44 Ca), a clear and systematic decrease in skeletal U/Ca ratio (used as a proxy for calcification fluid pH) was observed, indicating a higher pH of the fluid in symbiotic compared to asymbiotic polyps. In contrast, Mg/Ca ratios (used as a tentative proxy for organic matrix secretion) and 8 44 Ca (used as an indicator of Ca2+ pathway to the fluid) did not differ between symbiotic and asymbiotic polyps. This suggests that organic matrix secretion related to coral calcification is controlled mainly by the coral host itself, and a transmembrane transport of Ca2+ does not vary according to symbiosis relationship. Skeletal delta O-18 values of both symbiotic and asymbiotic polyps showed offsets between them with identical temperature dependence. Based on a newly proposed model, behavior of delta O-18 in the present study seems to reflect the rate of CO2 hydration in the calcifying fluid. Since CO2 hydration is promoted by enzyme carbonic anhydrase, the offset of delta O-18 values between symbiotic and asymbiotic polyps is attributed to the differences of enzyme activity, although the enzyme is functional even in the asymbiotic polyp. Symbiotic delta C-13 values in the temperature and salinity experiments were higher compared to those in the asymbiotic polyps due to photosynthesis, although photosynthetic delta C-13 signals in the pCO(2) experiment were masked by the dominant delta C-13 gradient in dissolved inorganic carbon in seawater caused by C-13-depletd CO2 gas addition in the higher pCO(2) treatments. Sr/Ca ratios showed a negligible relationship according to variation of temperature, salinity, and pCO(2), although it might be attributed to relatively large deviations of replicates of Sr/Ca ratios in the present study. Overall, only the U/Ca ratio showed a significant difference between symbiotic and asymbiotic polyps throughout all experiments, indicating that the critical effect on coral calcification caused by symbiotic algae is the increase of pH of the calcifying fluid by photosynthesis. (C) 2018 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.gca.2018.05.016

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  • Carbonate delta drift: A new sediment drift type

    Thomas Luedmann, Christian Betzler, Gregor P. Eberli, Jesus Reolid, John J. G. Reijmer, Craig R. Sloss, Or M. Bialik, Carlos A. Alvarez-Zarikian, Montserrat Alonso-Garcia, Clara L. Blaettler, Junhua Adam Guo, Sebastien Haffen, Senay Horozal, Mayuri Inoue, Luigi Jovane, Dick Kroon, Luca Lanci, Juan Carlos Laya, Anna Ling Hui Mee, Masatoshi Nakakuni, B. Nagender Nath, Kaoru Niino, Loren M. Petruny, Santi D. Pratiwi, Angela L. Slagle, Xiang Su, Peter K. Swart, James D. Wright, Zhengquan Yao, Jeremy R. Young

    MARINE GEOLOGY   401   98 - 111   2018年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    Based on high-resolution reflection seismic and core data from IODP Expedition 359 we present a new channel related drift type attached to a carbonate platform slope, which we termed delta drift. Like a river delta, it is comprised of several stacked lobes and connected to a point source. The delta drifts were deposited at the exit of two gateways that connect the Inner Sea of the Maldives carbonate platform with the open ocean. The channels served as conduits focusing and accelerating the water flow; Entrained material was deposited at their mouth where the flows relaxed. The lobe-shaped calcareous sediment drifts must have formed under persistent water through flow. Sediment supply was relatively high and continuous, resulting in an average sedimentation rate of 17 cm ka(-1). The two delta drifts occupy 342 and 384 km(2), respectively; with a depositional relief of approximately 500 m. They have a sigmoidal clinoform reflection pattern with a particular convex upward bending of the foresets. In the Maldives the drift onset marks the transition from a sea-level controlled to a progressively current dominated depositional regime. This major event occurred in the Serravallian about 13 Ma ago, leading to the partial drowning of the carbonate platform and the creation of shallow seaways. The initial bank-enclosed topography resembles an "empty bucket" geometry which is rapidly filled by the drift sediments that aggrade and prograde into the basin. Thereby the depositional environment of the delta drifts changes from deep water (> 500) to shallow-water conditions at their topsets, indicated by the overall coarsening upward trend in grain size and the presence of shallow water large benthic foraminifers at their top.

    DOI: 10.1016/j.margeo.2018.04.011

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  • Refinement of Miocene sea level and monsoon events from the sedimentary archive of the Maldives (Indian Ocean)

    C. Betzler, G. P. Eberli, T. Luedmann, J. Reolid, D. Kroon, J. J. G. Reijmer, P. K. Swart, J. Wright, J. R. Young, C. Alvarez-Zarikian, M. Alonso-Garcia, O. M. Bialik, C. L. Blattler, J. A. Guo, S. Haffen, S. Horozal, M. Inoue, L. Jovane, L. Lanci, J. C. Laya, A. L. Hui Mee, M. Nakakuni, B. N. Nath, K. Niino, L. M. Petruny, S. D. Pratiwi, A. L. Slagle, C. R. Sloss, X. Su, Z. Yao

    PROGRESS IN EARTH AND PLANETARY SCIENCE   5   2018年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGEROPEN  

    International Ocean Discovery Program (IODP) Expedition 359 cored sediments from eight borehole locations in the carbonate platform of the Maldives in the Indian Ocean. The expedition set out to unravel the timing of Neogene climate changes, in particular the evolution of the South Asian monsoon and fluctuations of the sea level. The timing of these changes are assessed by dating resultant sedimentary alterations that mark stratigraphic turning points in the Neogene Maldives platform system. The first four turning points during the early and middle Miocene are related to sea-level changes. These are reliably recorded in the stratigraphy of the carbonate sequences in which sequence boundaries provide the ages of the sea-level lowstand. Phases of aggradational platform growth give precise age brackets of long-term sea-level high stands during the early Miocene and the early to middle Miocene Climate Optimum that is dated here between 17 to 15.1 Ma. The subsequent middle Miocene cooling coincident with the eastern Antarctic ice sheet expansion resulted in a long-term lowering of sea level that is reflected by a progradational platform growth. The change in platform architecture from aggradation to progradation marks this turning point at 15.1 Ma.& para;& para;An abrupt change in sedimentation pattern is recognized across the entire archipelago at a sequence boundary dated as 12.9-13 Ma. At this turning point, the platform sedimentation switched to a current-controlled mode when the monsoon-wind-driven circulation started in the Indian Ocean. The similar age of the onset of drift deposition from monsoon-wind-driven circulation across the entire archipelago indicates an abrupt onset of monsoon winds in the Indian Ocean. Ten unconformities dissect the drift sequences, attesting changes in current strength or direction that are likely caused by the combined product of changes in the monsoon-wind intensity and sea level fluctuations in the last 13 Ma. A major shift in the drift packages is dated with 3.8 Ma that coincides with the end of stepwise platform drowning and a reduction of the oxygen minimum zone in the Inner Sea.& para;& para;The strata of the Maldives platform provides a detailed record of the extrinsic controlling factors on carbonate platform growth through time. This potential of carbonate platforms for dating the Neogene climate and current changes has been exploited in other platforms drilled by the Ocean Drilling Program. For example, Great Bahama Bank, the Queensland Plateau, and the platforms on the Marion Plateau show similar histories with sediment architectures driven by sea level in their early history (early to middle Miocene) replaced by current-driven drowning or partial drowning during their later history (Late Miocene). In all three platform systems, the influence of currents on sedimentations is reported between 11 and 13 Ma.

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  • 多元素・同位体分析に基づく造礁サンゴの骨格成長における褐虫藻の役割 査読

    井上 麻夕里, 中村 崇, 田中 泰章, 鈴木 淳, 横山 祐典, 川幡 穂高, 酒井 一彦, Nikolaus Gussone

    日本地球化学会年会要旨集   65   2018年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人日本地球化学会  

    <p>本研究ではサンゴの骨格成長における褐虫藻の役割を明らかにするために、褐虫藻有りと無しのポリプ試料を作成し、温度、塩分、pCO2を調整した水槽で飼育した。飼育実験の後、ポリプ骨格について6種類の化学成分を分析した。その結果、海水のpH指標とされているU/Ca比についてのみ、褐虫藻有りと無しの間に有意な差が見られた。これは、褐虫藻有りのサンゴ体内のpHが上昇していることを示しており、これにより褐虫藻と共生関係にあるサンゴは骨格成長が早いことが分かった。</p>

    DOI: 10.14862/geochemproc.65.0_23

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  • Effects of intensification of the Indian Summer Monsoon on northern Andaman Sea sediments during the past 700 years

    Yuki Ota, Hodaka Kawahata, Masafumi Murayama, Mayuri Inoue, Yusuke Yokoyama, Yosuke Miyairi, Thura Aung, H. M. Zakir Hossain, Atsushi Suzuki, Akihisa Kitamura, Kyaw Thu Moe

    JOURNAL OF QUATERNARY SCIENCE   32 ( 4 )   528 - 539   2017年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY  

    Recent studies have revealed an intensification of the Indian Summer Monsoon (ISM) over the past 700 years, but its influence on the sediments in the northern Andaman Sea is unclear. To examine this influence, we used radiocarbon-dated sediment core StMY6, acquired 100km offshore in the northern Andaman Sea from the Ayeyarwady River mouth, and obtained a 700-year-long record of the grain-size distribution and geochemistry of the sedimentary sequence. The ISM influences precipitation surrounding the Ayeyarwady River, and thus the river water and sediment discharges to the northern Andaman Sea near the river mouth in the Ayeyarwady River and the weathering intensity in the river catchment. Based on the system, we propose that higher sedimentation rates and larger modal grain size (the most abundant size in the grain-size distribution of sediments) and lower carbonate concentrations after about AD 1600 can be attributed to higher ISM intensity. Profiles of total organic carbon (TOC) content and carbon/nitrogen (C/N) ratios, however, did not show any trends after about AD 1600, which suggests that the ISM has had little influence on these proxies at this site.

    DOI: 10.1002/jqs.2947

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  • An aposymbiotic primary coral polyp counteracts acidification by active pH regulation

    Yoshikazu Ohno, Akira Iguchi, Chuya Shinzato, Mayuri Inoue, Atsushi Suzuki, Kazuhiko Sakai, Takashi Nakamura

    SCIENTIFIC REPORTS   7   2017年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:NATURE PUBLISHING GROUP  

    Corals build their skeletons using extracellular calcifying fluid located in the tissue-skeleton interface. However, the mechanism by which corals control the transport of calcium and other ions from seawater and the mechanism of constant alkalization of calcifying fluid are largely unknown. To address these questions, we performed direct pH imaging at calcification sites (subcalicoblastic medium, SCM) to visualize active pH upregulation in live aposymbiotic primary coral polyps treated with HCl-acidified seawater. Active alkalization was observed in all individuals using vital staining method while the movement of HPTS and Alexa Fluor to SCM suggests that certain ions such as H+ could diffuse via a paracellular pathway to SCM. Among them, we discovered acid-induced oscillations in the pH of SCM (pH(SCM)), observed in 24% of polyps examined. In addition, we discovered acid-induced pH up-regulation waves in 21% of polyps examined, which propagated among SCMs after exposure to acidified seawater. Our results showed that corals can regulate pHSCM more dynamically than was previously believed. These observations will have important implications for determining how corals regulate pHSCM during calcification. We propose that corals can sense ambient seawater pH via their innate pH-sensitive systems and regulate pHSCM using several unknown pH-regulating ion transporters that coordinate with multicellular signaling occurring in coral tissue.

    DOI: 10.1038/srep40324

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  • Calcification process dynamics in coral primary polyps as observed using a calcein incubation method 査読 国際誌

    Ohno, Yoshikazu, Iguchi, Akira, Shinzato, Chuya, Gushi, Mikako, Inoue, Mayuri, Suzuki, Atsushi, Sakai, Kazuhiko, Nakamura, Takashi

    Biochemistry and biophysics reports   9   289 - 294   2017年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier  

    Calcification processes are largely unknown in scleractinian corals. In this study, live confocal imaging was used to elucidate the spatiotemporal dynamics of the calcification process in aposymbiotic primary polyps of the coral species Acropora digitifera. The fluorophore calcein was used as a calcium deposition marker and a visible indicator of extracellular fluid distribution at the tissue-skeleton interface (subcalicoblastic medium, SCM) in primary polyp tissues. Under continuous incubation in calcein-containing seawater, initial crystallization and skeletal growth were visualized among the calicoblastic cells in live primary polyp tissues. Additionally, the distribution of calcein-stained SCM and contraction movements of the pockets of SCM were captured at intervals of a few minutes. Our experimental system provided several new insights into coral calcification, particularly as a first step in monitoring the relationship between cellular dynamics and calcification in vivo. Our study suggests that coral calcification initiates at intercellular spaces, a finding that may contribute to the general understanding of coral calcification processes.

    DOI: 10.1016/j.bbrep.2017.01.006

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    その他リンク: http://orcid.org/0000-0002-8894-1977

  • The role of symbiotic algae in the formation of the coral polyp skeleton: 3-D morphological study based on X-ray microcomputed tomography

    Shinya Iwasaki, Mayuri Inoue, Atsushi Suzuki, Osamu Sasaki, Harumasa Kano, Akira Iguchi, Kazuhiko Sakai, Hodaka Kawahata

    GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS   17 ( 9 )   3629 - 3637   2016年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Symbiotic algae of primary polyps play an important role in calcification of coral skeletons. However, the function of the symbiotic algae, including the way they influence the physical features of their host skeleton under various conditions, is not well understood. We used X-ray microcomputed tomography to observe skeletal shape characteristics in symbiotic and aposymbiotic primary polyps of Acropora digitifera that were cultured at various temperature and pCO(2) levels (temperature 27, 29, 33 degrees C; pCO(2) 400, 800, 1000 mu atm). Symbiotic polyps had a basal plate with a well-developed folding margin supporting the branched skeleton, whereas aposymbiotic ones did not. The features of the folding margin suggest that it might be the initial growth stage of the epitheca. In addition, three-dimensional (3-D) morphological measurements made by X-ray microcomputed tomography show that the branched skeletons of symbiotic primary polyps were taller than those of aposymbiotic ones, suggesting that zooxanthellae in coral primary polyps play a critical role in the height growth of skeletal branches. Furthermore, results of the temperature- and pCO(2)-controlled experiments suggest that global warming might greatly affect the activity of zooxanthellae, whereas ocean acidification might reduce calcification by damaging the coral host itself. Our findings provide new knowledge about the role of zooxanthellae in coral calcification.

    DOI: 10.1002/2016GC006536

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  • The abrupt onset of the modern South Asian Monsoon winds

    Christian Betzler, Gregor P. Eberli, Dick Kroon, James D. Wright, Peter K. Swart, Bejugam Nagender Nath, Carlos A. Alvarez-Zarikian, Montserrat Alonso-Garcia, Or M. Bialik, Clara L. Blattler, Junhua Adam Guo, Sebastien Haffen, Senay Horozal, Mayuri Inoue, Luigi Jovane, Luca Lanci, Juan Carlos Laya, Anna Ling Hui Mee, Thomas Luedmann, Masatoshi Nakakuni, Kaoru Niino, Loren M. Petruny, Santi D. Pratiwi, John J. G. Reijmer, Jesus Reolid, Angela L. Slagle, Craig R. Sloss, Xiang Su, Zhengquan Yao, Jeremy R. Young

    SCIENTIFIC REPORTS   6   2016年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:NATURE PUBLISHING GROUP  

    The South Asian Monson (SAM) is one of the most intense climatic elements yet its initiation and variations are not well established. Dating the deposits of SAM wind-driven currents in IODP cores from the Maldives yields an age of 12.9 Ma indicating an abrupt SAM onset, over a short period of 300 kyrs. This coincided with the Indian Ocean Oxygen Minimum Zone expansion as revealed by geochemical tracers and the onset of upwelling reflected by the sediment's content of particulate organic matter. A weaker 'proto-monsoon' existed between 12.9 and 25 Ma, as mirrored by the sedimentary signature of dust influx. Abrupt SAM initiation favors a strong influence of climate in addition to the tectonic control, and we propose that the post Miocene Climate Optimum cooling, together with increased continentalization and establishment of the bipolar ocean circulation, i.e. the beginning of the modern world, shifted the monsoon over a threshold towards the modern system.

    DOI: 10.1038/srep29838

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  • Intensification of the meridional temperature gradient in the Great Barrier Reef following the Last Glacial Maximum (vol 5, 4102, 2014) 査読

    Thomas Felis, Helen V. McGregor, Braddock K. Linsley, Alexander W. Tudhope, Michael K. Gagan, Atsushi Suzuki, Mayuri Inoue, Alexander L. Thomas, Tezer M. Esat, William G. Thompson, Manish Tiwari, Donald C. Potts, Manfred Mudelsee, Yusuke Yokoyama, Jody M. Webster

    NATURE COMMUNICATIONS   7   2016年6月

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    記述言語:英語   出版者・発行元:NATURE PUBLISHING GROUP  

    DOI: 10.1038/ncomms12006

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  • Controlling factors of Ca isotope fractionation in scleractinian corals evaluated by temperature, pH and light controlled culture experiments

    Mayuri Inoue, Nikolaus Gussone, Yasuko Koga, Akihiro Iwase, Atsushi Suzuki, Kazuhiko Sakai, Hodaka Kawahata

    GEOCHIMICA ET COSMOCHIMICA ACTA   167   80 - 92   2015年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    In this study, the Ca-44/Ca-40 ratios of Porites australiensis grown under three different culture experiments composed of temperature, pH and light controlled culture experiments are measured. The temperature dependent isotope fractionation of 0.02 parts per thousand/degrees C deduced from this study is similar to inorganic aragonite, but the degree of isotope fractionation is about +0.4 parts per thousand offset in corals. These observations agree with earlier results on different coral species, suggesting Ca isotope fractionation during Ca transmembrane transport in corals. While in cultured corals a significant temperature dependence of delta Ca-44 is observed, the relationships between calcium isotope fractionation and pH as well as light intensity are negligible. Therefore variation of delta Ca-44 in Porites corals is mainly controlled by temperature. A combination of delta Ca-44 and Sr/Ca of corals in temperature controlled experiments cannot be explained by Rayleigh type fractionation directly from a fluid, which is seawater-like in terms of delta Ca-44 and Sr/Ca. Through coral-specific biomineralization processes, overall mean delta Ca-44 of scleractinian corals including previous studies are different from biogenic aragonites secreted by sclerosponges and pteropods, but are comparable with those of bivalves as well as calcitic coccolithophores and foraminifers. These findings are important for better understanding biomineralization in corals and in order to constrain the Ca isotopic composition of oceanic Ca sinks in response to climate changes and associated with shifts of calcite and aragonite seas. (C) 2015 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.gca.2015.06.009

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  • Nutrient availability affects the response of juvenile corals and the endosymbionts to ocean acidification

    Yasuaki Tanaka, Akira Iguchi, Kozue Nishida, Mayuri Inoue, Takashi Nakamura, Atsushi Suzuki, Kazuhiko Sakai

    LIMNOLOGY AND OCEANOGRAPHY   59 ( 5 )   1468 - 1476   2014年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY  

    The interactive effects of nutrient availability and ocean acidification on coral calcification were investigated using post-settlement juvenile corals of Acropora digitifera cultured in nutrient-sufficient or nutrient-depleted seawater for 4 d and then exposed to seawater with different partial pressure of carbon dioxide (P-CO2) conditions (38.8 or 92.5 Pa) for 10 d. After the nutrient pretreatment, corals in the high nutrient condition (HN corals) had a significantly higher abundance of endosymbiotic algae than did those in the low nutrient condition (LN corals). The high abundance of endosymbionts in HN corals was reduced as a result of subsequent seawater acidification, and the chlorophyll a per algal cell increased. The photosynthetic oxygen production rate by endosymbionts was enhanced by the acidified seawater regardless of the nutrient treatment, indicating that the reduction in endosymbiont density in HN corals due to acidification was compensated for by the increase in chlorophyll a per cell. Though the photosynthetic rate increased in the acidified conditions for both LN and HN corals, the calcification rate significantly decreased for LN corals but not for HN corals. The acquisition of nutrients from seawater, rather than the increase in alkalinity caused by photosynthesis, might effectively alleviate the negative response of coral calcification to seawater acidification, suggesting that the response of corals and their endosymbionts to ocean acidification can be influenced by nutrient conditions.

    DOI: 10.4319/lo.2014.59.5.1468

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  • Loss of zooxanthellae in a coral under high seawater temperature and nutrient enrichment

    Yasuald Tanaka, Mayuri Inoue, Takashi Nakamura, Atsushi Suzuki, Kazuhiko Sakai

    JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY   457   220 - 225   2014年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    To investigate the effect of nutrient concentrations on coral-algal symbiosis under thermal stress, the abundance and release of zooxanthellae in the coral Acropora tenuis were quantified under laboratory conditions. The coral fragments were first cultured in either low-nutrient (LN) or high-nutrient (HN) seawater condition at 27 degrees C for 25 days and the seawater temperature was then elevated and kept at 31 degrees C for 1 week for both nutrient conditions. Nutrient enrichment at 27 degrees C increased the densities of symbiotic algae and chlorophyll a and the algal release rates (AR) from the host coral to the ambient seawater. The percentage of algal release rate to the standing stock (AR%) was approximately 0.015%h(-1) for both nutrient conditions at 27 degrees C. After the seawater temperature was elevated to 31 degrees C, the densities of zooxanthellae in the corals decreased by 21-61%, and AR and AR% increased. The corals in HN lost more zooxanthellae per unit surface area than those in LN, but the lost percentages were not significantly different between LN and HN. AR% was also not significantly different between LN and HN at 31 degrees C. These results indicated that the percentage rate of symbiotic algal loss was not affected by the nutrient condition, implying that nutrient incorporation itself would not accelerate coral bleaching susceptibility. (C) 2014 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jembe.2014.04.019

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  • Skeletal oxygen and carbon isotope compositions of Acropora coral primary polyps experimentally cultured at different temperatures

    Kozue Nishida, Kei Ishikawa, Akira Iguchi, Yasuaki Tanaka, Mizuho Sato, Toyoho Ishimura, Mayuri Inoue, Takashi Nakamura, Kazuhiko Sakai, Atsushi Suzuki

    GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS   15 ( 7 )   2840 - 2849   2014年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    We investigated temperature and growth-rate dependency of skeletal oxygen and carbon isotopes in primary polyps of Acropora digitifera (Scleractinia: Acroporidae) by culturing them at 20, 23, 27, or 31 degrees C. Calcification was most rapid at 27 and 31 degrees C. We obtained a delta O-18-temperature relationship (-0.18 parts per thousand degrees C-1) consistent with reported ranges for Porites, indicating that juvenile Acropora polyps can be used for temperature reconstruction. A growth-rate dependency of skeletal isotopes was detected in the experimental polyps cultured at lower water temperatures, when the skeletal growth rate of these polyps was also low. The estimated upper calcification flux limit for a kinetic isotope effect to be observed in the delta O-18-growth rate relationship (similar to 0.4-0.7 g CaCO3 cm(-2) yr(-1)) was similar to the calcification flux in Porites corresponding to a linear extension rate of 5 mm yr(-1), the maximum rate at which the kinetic isotope effect is evident. This result suggests that the calcification flux can be used as a measure of growth rate-related isotope fractionation, that is, the kinetic isotope effect, in corals of different genera and at different growth stages.

    DOI: 10.1002/2014GC005322

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  • Evaluation of Mn and Fe in coral skeletons (Porites spp.) as proxies for sediment loading and reconstruction of 50 yrs of land use on Ishigaki Island, Japan

    Mayuri Inoue, Daisaku Ishikawa, Tsuzumi Miyaji, Atsuko Yamazaki, Atsushi Suzuki, Hiroya Yamano, Hodaka Kawahata, Tsuyoshi Watanabe

    CORAL REEFS   33 ( 2 )   363 - 373   2014年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGER  

    Manganese (Mn) and iron (Fe) concentrations were measured in coral skeletons (Porites spp.) collected from the Todoroki River on Ishigaki Island, Japan, to reconstruct the history of land use in the river catchment area. We prepared (1) five bulk samples to investigate the present spatial distribution and (2) micro-samples from two long cores to study the temporal variability of sediment loading from the Todoroki River. The existing state of the elements Mn and Fe in bulk coral skeleton samples was examined by a chemical cleaning experiment. The results of the experiment suggested that Fe was not incorporated into the crystal lattice of the coral skeleton but that Mn was incorporated, as previously reported. The bulk sample data, with and without chemical cleaning, indicated that the spatial distribution of both elements in corals collected along a sampling line from the river mouth toward the reef crest was complex and most likely reflected salinity changes and the amount of suspended particulate matter. The temporal variation of Mn and Fe, in particular the variation of baseline/background levels, mainly reflected the history of land development on Ishigaki Island. In addition, Mn showed clear seasonal variability that appeared to be controlled by a combination of temperature, primary productivity, and precipitation. The results of the present study suggest that Mn may be a useful proxy for river discharge or biological activity depending on local marine conditions, if the specific behavior of Mn at the coral growth site is known.

    DOI: 10.1007/s00338-014-1128-3

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  • Intensification of the meridional temperature gradient in the Great Barrier Reef following the Last Glacial Maximum

    Thomas Felis, Helen V. McGregor, Braddock K. Linsley, Alexander W. Tudhope, Michael K. Gagan, Atsushi Suzuki, Mayuri Inoue, Alexander L. Thomas, Tezer M. Esat, William G. Thompson, Manish Tiwari, Donald C. Potts, Manfred Mudelsee, Yusuke Yokoyama, Jody M. Webster

    NATURE COMMUNICATIONS   5   2014年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:NATURE PUBLISHING GROUP  

    Tropical south-western Pacific temperatures are of vital importance to the Great Barrier Reef (GBR), but the role of sea surface temperatures (SSTs) in the growth of the GBR since the Last Glacial Maximum remains largely unknown. Here we present records of Sr/Ca and delta O-18 for Last Glacial Maximum and deglacial corals that show a considerably steeper meridional SST gradient than the present day in the central GBR. We find a 1-2 degrees C larger temperature decrease between 17 degrees and 20 degrees S about 20,000 to 13,000 years ago. The result is best explained by the northward expansion of cooler subtropical waters due to a weakening of the South Pacific gyre and East Australian Current. Our findings indicate that the GBR experienced substantial meridional temperature change during the last deglaciation, and serve to explain anomalous deglacial drying of northeastern Australia. Overall, the GBR developed through significant SST change and may be more resilient than previously thought.

    DOI: 10.1038/ncomms5102

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  • A Snapshot of a Coral "Holobiont": A Transcriptome Assembly of the Scleractinian Coral, Porites, Captures a Wide Variety of Genes from Both the Host and Symbiotic Zooxanthellae

    Chuya Shinzato, Mayuri Inoue, Makoto Kusakabe

    PLOS ONE   9 ( 1 )   2014年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PUBLIC LIBRARY SCIENCE  

    Massive scleractinian corals of the genus Porites are important reef builders in the Indo-Pacific, and they are more resistant to thermal stress than other stony corals, such as the genus Acropora. Because coral health and survival largely depend on the interaction between a coral host and its symbionts, it is important to understand the molecular interactions of an entire "coral holobiont". We simultaneously sequenced transcriptomes of Porites australiensis and its symbionts using the Illumina Hiseq2000 platform. We obtained 14.3 Gbp of sequencing data and assembled it into 74,997 contigs (average: 1,263 bp, N50 size: 2,037 bp). We successfully distinguished contigs originating from the host (Porites) and the symbiont (Symbiodinium) by aligning nucleotide sequences with the decoded Acropora digitifera and Symbiodinium minutum genomes. In contrast to previous coral transcriptome studies, at least 35% of the sequences were found to have originated from the symbionts, indicating that it is possible to analyze both host and symbiont transcriptomes simultaneously. Conserved protein domain and KEGG analyses showed that the dataset contains broad gene repertoires of both Porites and Symbiodinium. Effective utilization of sequence reads revealed that the polymorphism rate in P. australiensis is 1.0% and identified the major symbiotic Symbiodinium as Type C15. Analyses of amino acid biosynthetic pathways suggested that this Porites holobiont is probably able to synthesize most of the common amino acids and that Symbiodinium is potentially able to provide essential amino acids to its host. We believe this to be the first molecular evidence of complementarity in amino acid metabolism between coral hosts and their symbionts. We successfully assembled genes originating from both the host coral and the symbiotic Symbiodinium to create a snapshot of the coral holobiont transcriptome. This dataset will facilitate a deeper understanding of molecular mechanisms of coral symbioses and stress responses.

    DOI: 10.1371/journal.pone.0085182

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  • Interlaboratory study for coral Sr/Ca and other element/Ca ratio measurements

    Ed C. Hathorne, Alex Gagnon, Thomas Felis, Jess Adkins, Ryuji Asami, Wim Boer, Nicolas Caillon, David Case, Kim M. Cobb, Eric Douville, Peter deMenocal, Anton Eisenhauer, Dieter Garbe-Schoenberg, Walter Geibert, Steven Goldstein, Konrad Hughen, Mayuri Inoue, Hodaka Kawahata, Martin Koelling, Florence L. Cornec, Braddock K. Linsley, Helen V. McGregor, Paolo Montagna, Intan S. Nurhati, Terrence M. Quinn, Jacek Raddatz, Helene Rebaubier, Laura F. Robinson, Aleksey Sadekov, Rob Sherrell, Dan Sinclair, Alexander W. Tudhope, Gangjian Wei, Henri Wong, Henry C. Wu, Chen-Feng You

    GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS   14 ( 9 )   3730 - 3750   2013年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twenty-one laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7 degrees C. However, most of the data fall within a narrower range and the Porites coral reference material JCp-1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5 degrees C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is <0.5 degrees C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1.

    DOI: 10.1002/ggge.20230

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  • Microscopic observation of symbiotic and aposymbiotic juvenile corals in nutrient-enriched seawater

    Yasuaki Tanaka, Akira Iguchi, Mayuri Inoue, Chiharu Mori, Kazuhiko Sakai, Atsushi Suzuki, Hodaka Kawahata, Takashi Nakamura

    MARINE POLLUTION BULLETIN   68 ( 1-2 )   93 - 98   2013年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Symbiotic and aposymbiotic juvenile corals, which were grown in the laboratory from the gametes of the scleractinian coral Acropora digitifera and had settled down onto plastic culture plates, were observed with a microscope under different nutrient conditions. The symbiotic corals successfully removed the surrounding benthic microalgae (BMA), whereas the aposymbiotic corals were in close physical contact with BMA. The areal growth rate of the symbiotic corals was significantly higher than that of the aposymbiotic corals. The addition of nutrients to the culture seawater increased the chlorophyll a content in the symbiotic coral polyps and enhanced the growth of some of the symbiotic corals, however the average growth rate was not significantly affected, most likely because of the competition with BMA. The comparison between the symbiotic and aposymbiotic juvenile corals showed that the establishment of a symbiotic association could be imperative for post-settlement juvenile corals to survive in high-nutrient seawater. (C) 2012 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.marpolbul.2012.12.017

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  • Growth-rate influences on coral climate proxies tested by a multiple colony culture experiment

    Erika Hayashi, Atsushi Suzuki, Takashi Nakamura, Akihiro Iwase, Toyoho Ishimura, Akira Iguchi, Kazuhiko Sakai, Takashi Okai, Mayuri Inoue, Daisuke Araoka, Shohei Murayama, Hodaka Kawahata

    EARTH AND PLANETARY SCIENCE LETTERS   362   198 - 206   2013年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    As application of coral-based climate reconstruction has become more frequent at tropical sites, increased attention is being paid to the potential ambiguities of coral thermometers that are intrinsic to the biomineralisation process, including the so-called vital effect, the growth-rate-related kinetic effect, and the [CO32- I effect. Here we studied how the growth rate influenced the skeletal oxygen and carbon isotope ratios (delta O-18 and delta C-13) and the Sr/Ca ratio in a common-garden experiment involving the long-term culture of Porites australiensis clone colonies. Comparison of the seasonal minimum delta O-18 values during summer showed a negligible influence of the large intercolony variation in growth rate (2-10 mm yr(-1)) on delta O-18 variation, but delta O-18 was relatively sensitive to temporary intracolony growth-rate changes related to colony health. In contrast, the Sr/Ca ratio was robust against both inter- and intracolony growth-rate variation. We found a positive shift in delta C-13 in slower growing corals, which we attributed to the kinetic behaviour of the calcification reaction. The seasonal fluctuation in delta C-13 corresponded not to changes in light intensity nor to delta C-13 of dissolved inorganic carbon in seawater, but to photosynthetic efficiency as measured by pulse-amplitude photometry. These findings support the inference that coral skeletal Sr/Ca and delta O-18 in a long-lived colony can function as a palaeoclimate archive by recording signals of clonal growth. We also propose practical guidelines for the proper interpretation of coral records. (C) 2012 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.epsl.2012.11.046

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  • Calcification responses of symbiotic and aposymbiotic corals to near-future levels of ocean acidification 査読

    Ohki S, Irie T, Inoue M, Shinmen K, Kawahata H, Nakamura T, Kato A, Nojiri Y, Suzuki A, Sakai K, van Woesik R

    BIOGEOSCIENCES   10 ( 11 )   6807 - 6814   2013年

  • Estimate of calcification responses to thermal and freshening stresses based on culture experiments with symbiotic and aposymbiotic primary polyps of a coral, Acropora digitifera

    Mayuri Inoue, Kotaro Shinmen, Hodaka Kawahata, Takashi Nakamura, Yasuaki Tanaka, Aki Kato, Chuya Shinzato, Akira Iguchi, Hironobu Kan, Atsushi Suzuki, Kazuhiko Sakai

    GLOBAL AND PLANETARY CHANGE   92-93   1 - 7   2012年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER  

    Although coral calcification is directly related to coral health, few studies have examined the responses of coral calcification to environmental stresses, with the exception of ocean acidification. In this study, we experimentally exposed aposymbiotic (lacking symbionts) and symbiotic primary polyps of the scleractinian coral Acropora digitifera to several seawater temperatures (27, 29, 31, and 33 degrees C) and salinities (26, 28. 30, 32, and 34) to investigate the effects of thermal and freshening stresses on coral calcification from the standpoint of coral-algal symbiosis. Calcification rates were higher for symbiotic versus aposymbiotic polyps in both sets of experiments, except for those reared at 31 degrees C and 33 degrees C. Calcification responses of symbiotic polyps were a non-linear function of temperature, and the threshold temperature affecting skeletal growth and bleaching was between 29 degrees C and 31 degrees C. Calcification rates of aposymbiotic polyps were also a non-linear function of temperature, with a maximum polyp weight at 31 degrees C, suggesting that thermal stress also did some damage to the coral host itself. In contrast, skeletal growth of both aposymbiotic and symbiotic polyps decreased linearly with increased salinity. Observations of the microstructure of polyp samples revealed a clearly cyclic feature of skeletal surfaces that was likely related to organo-mineral deposition of calcium carbonate even under lowered-salinity conditions. However, neither type of polyp reared at 33 degrees C evidenced this characteristic, suggesting that thermal stress had compromised the normal calcification process, which involves secretion of an organic matrix by the coral host. Our results suggest that the effects of future global warming will include a reduction in coral calcification itself and the collapse of coral-algal symbiosis, at least at the primary polyp stage. The present experiments showed that thermal stress would affect the host's physiological functionality, whereas freshening stress, which is simply the dilution of ambient seawater, would affect the mineralization process associated with coral calcification. (C) 2012 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.gloplacha.2012.05.001

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  • Effects of acidified seawater on coral calcification and symbiotic algae on the massive coral Porites australiensis

    Akira Iguchi, Saori Ozaki, Takashi Nakamura, Mayuri Inoue, Yasuaki Tanaka, Atsushi Suzuki, Hodaka Kawahata, Kazuhiko Sakai

    MARINE ENVIRONMENTAL RESEARCH   73   32 - 36   2012年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCI LTD  

    We investigated the effect of acidified seawater on calcification and symbiotic algae (zooxanthellae density, chlorophyll content per single algal cell, fluorescence yield (Fv/Fm)) on a massive coral, Porites australiensis, a common species in the Ryukyu Archipelago of Japan. We found that acidified seawater significantly decreased the calcification and fluorescence yield, but did not affect zooxanthellae density and chlorophyll content per single algal cell. This indicates low levels of photoacclimation to acidified seawater in this species, and this is contrary to the findings of previous studies of Acropora species. A significant correlation between calcification and fluorescence yield was observed, indicating the presence of a strong relationship between calcification and algal photosynthesis. Our results indicate that endosymbiont photosynthetic dysfunction may enhance the decrease of coral calcification in future acidified ocean conditions. Calcification and fluorescence yield among colonies clearly differed, showing that the response to acidified seawater is highly variable among colonies in natural coral populations. (C) 2011 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.marenvres.2011.10.008

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  • Mg isotope fractionation in biogenic carbonates of deep-sea coral, benthic foraminifera, and hermatypic coral

    Toshihiro Yoshimura, Masaharu Tanimizu, Mayuri Inoue, Atsushi Suzuki, Nozomu Iwasaki, Hodaka Kawahata

    ANALYTICAL AND BIOANALYTICAL CHEMISTRY   401 ( 9 )   2755 - 2769   2011年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGER HEIDELBERG  

    High-precision Mg isotope measurements by multiple collector inductively coupled plasma mass spectrometry were applied for determinations of magnesium isotopic fractionation of biogenic calcium carbonates from seawater with a rapid Mg purification technique. The mean delta Mg-26 values of scleractinian corals, giant clam, benthic foraminifera, and calcite deep-sea corals were -0.87aEuro degrees, -2.57aEuro degrees, -2.34aEuro degrees, and -2.43aEuro degrees, suggesting preferential precipitation of light Mg isotopes to produce carbonate skeleton in biomineralization. Mg isotope fractionation in deep-sea coral, which has high Mg calcite skeleton, showed a clear temperature (T) dependence from 2.5 A degrees C to 19.5 A degrees C: 1,000 x ln(alpha) = -2.63 (+/- 0.076) + 0.0138 (+/- 0.0051) x T(R (2) = 0.82, p < 0.01). The delta Mg-26 values of large benthic foraminifera, which are also composed of a high-Mg calcite skeleton, can be plotted on the same regression line as that for deep-sea coral. Since the precipitation rates of deep-sea coral and benthic foraminifera are several orders of magnitude different, the results suggest that kinetic isotope fractionation may not be a major controlling factor for high-Mg calcite. The Mg isotope fractionation factors and the slope of temperature dependence from deep-sea corals and benthic foraminifera are similar to that for an inorganically precipitated calcite speleothem. Taking into account element partitioning and the calcification rate of biogenic CaCO3, the similarity among inorganic minerals, deep-sea corals, and benthic foraminiferas may indicate a strong mineralogical control on Mg isotope fractionation for high-Mg calcite. On the other hand, delta Mg-26 in hermatypic corals composed of aragonite has been comparable with previous data on biogenic aragonite of coral, sclerosponges, and scaphopad, regardless of species differences of samples.

    DOI: 10.1007/s00216-011-5264-0

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  • Effects of seawater pH on growth and skeletal U/Ca ratios of Acropora digitifera coral polyps

    Mayuri Inoue, Ryota Suwa, Atsushi Suzuki, Kazuhiko Sakai, Hodaka Kawahata

    GEOPHYSICAL RESEARCH LETTERS   38   2011年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    The impact of ocean acidification caused by the increasing atmospheric CO2 has been studied in marine calcifiers, including hermatypic corals. However, the effect of elevated pCO(2) on the early developmental life-cycle stage of corals has been little studied. In this study, we reared polyps of Acropora digitifera in seawater at pH(T) 6.55, 7.31, 7.64, 7.77, and 8.03, controlled by CO2 bubbling. We measured the dry weights of polyp skeletons after the 40-d experiment to investigate the relationship between the seawater aragonite saturation state and polyp growth. In addition, we measured skeletal U/Ca ratio to estimate their pH dependence. Skeletal weights of coral polyps increased with the aragonite saturation state and reached an apparent saturation plateau above pH 7.77. U/Ca ratios had a strong inverse relationship with pH and a negligible relationship with skeletal growth rate (polyp weight), suggesting that skeletal U/Ca could be useful for reconstructing paleo-pH. Citation: Inoue, M., R. Suwa, A. Suzuki, K. Sakai, and H. Kawahata (2011), Effects of seawater pH on growth and skeletal U/Ca ratios of Acropora digitifera coral polyps, Geophys. Res. Lett., 38, L12809, doi:10.1029/2011GL047786.

    DOI: 10.1029/2011GL047786

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  • Abrupt shift toward cooler condition in the earliest 20th century detected in a 165 year coral record from Ishigaki Island, southwestern Japan

    Mari Mishima, Atsushi Suzuki, Masayuki Nagao, Toyoho Ishimura, Mayuri Inoue, Hodaka Kawahata

    GEOPHYSICAL RESEARCH LETTERS   37   2010年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    We analyzed a 165 year delta(18)O coral record from Ishigaki Island, southwestern Japan, and compared our results with observed sea surface temperatures, as well as with the East Asian winter monsoon and El Nino Southern Oscillation. Coral skeletal delta(18)O fluctuations were consistent with other available SST information since the 1890s. The coral delta(18)O data indicated abrupt shift toward cooler condition during 1900-1905, consistent with the extremely cold winter air temperatures observed in Japan in 1902. The cold event was also supported by coral Sr/Ca data. Development of the Siberian High may have intensified the EAWM at this time, in association with active heat convection in the tropics and weak westerlies. This cooling may also have been related to surface ocean freshening in the Ogasawara Islands in the early 20th century. Thus, several phenomena were uniquely coupled during the first few years of the 20th century in the northwestern subtropical Pacific. Citation: Mishima, M., A. Suzuki, M. Nagao, T. Ishimura, M. Inoue, and H. Kawahata (2010), Abrupt shift toward cooler condition in the earliest 20th century detected in a 165 year coral record from Ishigaki Island, southwestern Japan, Geophys. Res. Lett., 37, L15609, doi: 10.1029/2010GL043451.

    DOI: 10.1029/2010GL043451

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  • Enhanced riverine carbon flux from carbonate catchment to the ocean: A comparative hydrogeochemical study on Ishigaki and Iriomote islands, southwestern Japan

    Hiroyuki Ushie, Hodaka Kawahata, Atsushi Suzuki, Shohei Murayama, Mayuri Inoue

    JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES   115   2010年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Riverine carbon transportation is an important carbon flux connecting reservoirs of the atmosphere, continents, and oceans. The flux is strongly related to the important roles of rivers such as regulation of climate change and buffering of ocean acidification. Here, to evaluate the linkage of such functions of rivers and geological characteristics of the watersheds, we present the results of a comparative hydrogeochemical study conducted on small subtropical watersheds of aluminosilicate-dominated Iriomote Island and carbonate-based Ishigaki Island, southwestern Japan. Rivers on Ishigaki Island exhibited much higher alkalinity than rivers on Iriomote Island, which was even higher than the mean value of major rivers in the world, such as the Saint Lawrence and the Mississippi. This high alkalinity was the result of carbonate dissolution enhanced by soil-originated CO2. As a result of this high inorganic carbon input, the ratio of inorganic carbon and nutrients of the river water was higher than that of marine organic matter such as the Redfield ratio, making the coastal seas a potential source of CO2 for the atmosphere.

    DOI: 10.1029/2009JG001039

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  • Historic 1771 Meiwa tsunami confirmed by high-resolution U/Th dating of massive Porites coral boulders at Ishigaki Island in the Ryukyus, Japan

    Daisuke Araoka, Mayuri Inoue, Atsushi Suzuki, Yusuke Yokoyama, R. Lawrence Edwards, Hai Cheng, Hiroyuki Matsuzaki, Hironobu Kan, Naotatsu Shikazono, Hodaka Kawahata

    GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS   11   2010年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    The chronicles of the Ryukyu Kingdom describe at least four coastal inundation events at Ishigaki Island during the seventeenth through nineteenth centuries: the 1771 Meiwa earthquake tsunami, which killed 12,000 people; another earthquake tsunami (1687); and two events with unrecorded causes (1625 and 1714). We used a high-resolution U/Th method to date well-preserved surface parts of massive Porites spp. coral head boulders that had been cast ashore and found that the ages of two boulders correspond to the 1771 event. One large Porites boulder (diameter > 4 m) was dated to 1625, suggesting that that event was also a large inundation event. Calibrated C-14 ages, based on a newly estimated local value for the radiocarbon marine reservoir effect, clustered around 1625 and 1771, suggesting that these events were larger than the others. Our study demonstrated that Porites boulders have enormous potential value for studies of paleoinundation events such as tsunamis and extreme storms.

    DOI: 10.1029/2009GC002893

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  • Trace element variations in fossil corals from Tahiti collected by IODP Expedition 310: Reconstruction of marine environments during the last deglaciation (15 to 9 ka)

    Mayuri Inoue, Yusuke Yokoyama, Mariko Harada, Atsushi Suzuki, Hodaka Kawahata, Hiroyuki Matsuzaki, Yasufumi Iryu

    MARINE GEOLOGY   271 ( 3-4 )   303 - 306   2010年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    Climate responses and changes in marine environments during the last deglaciation have been controversial and few paleoceanographic data are available from the tropical South Pacific, though this region is crucial in the investigations of ocean-atmosphere interactions. Integrated Ocean Drilling Program Expedition 310 was conducted to establish the time course of the postglacial sea-level rise at Tahiti in the South Pacific. A principal objective of this expedition was to examine the variation of marine environments during the last deglaciation. As fossil Porites coral is ideal for assessing past marine environments, we selected only Porites specimens from the many coral specimens retrieved, examined them by XRD, and dated them by the C-14 method. In all, we obtained 17 pristine Porites specimens composed of only aragonite with ages from 15 to 9 ka. Then, we measured Mg/Ca, Ba/Ca, and U/Ca ratios and Cd contents as proxies for upwelling and sea surface temperature. Higher Ba/Ca ratios and Cd content together with lower reconstructed SSTs using U/Ca ratios in the coral specimens between 12.6 and 9.8 cal ka compared to around 15 cal ka suggest that upwelling and/or entrainment of subsurface water into mixed layer was enhanced around Tahiti during this period. This finding is consistent with previous reports and supports the idea that the South Pacific was characterized by La Nina-like conditions at least from 12.6 to 9.8 cal ka. (C) 2010 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.margeo.2010.02.016

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  • Reconstruction of the East China Sea palaeoenvironment at 16 ka by comparison of fossil and modern Faviidae corals from the Ryukyus, southwestern Japan

    Mari Mishima, Hodaka Kawahata, Atsushi Suzuki, Mayuri Inoue, Takashi Okai, Akio Omura

    JOURNAL OF QUATERNARY SCIENCE   24 ( 8 )   928 - 936   2009年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY  

    We conducted paired measurements of the Sr/Ca ratio and oxygen and carbon stable isotopes of a fossil Faviidae coral specimen (MYK90), age 16 ka, collected from near Miyako Island, the Ryukyus, southwestern Japan. Our study aimed to reconstruct the palaeoenvironment in the East China Sea at 16 ka by comparing the fossil sample with modern Faviidae corals. Our data with annual or longer time resolution may be very suitable for palaeoceanographic reconstruction, although no general calibration method for Faviidae corals has been reported. Our calibration showed that the annual mean sea surface temperature was approximately 5 degrees C lower and sea surface salinity (SSS) at the study site was locally higher at 16 ka than at present. Even though the mouths of the Yellow and Changjiang rivers were east of their present locations because sea level was much lower, our results suggest that the influence of the terrestrial water discharge may not have extended to Miyako Island. Weak summer monsoon activity during the last glacial, which decreased summer precipitation over the Asian continent, and an enhanced winter monsoon, which may have led to more evaporation, likely contributed to the inferred high SSS at the study site. Copyright (C) 2009 John Wiley & Sons, Ltd.

    DOI: 10.1002/jqs.1268

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  • Anthropogenic lead inputs to the western Pacific during the 20th century

    Mayuri Inoue, Masaharu Tanimizu

    SCIENCE OF THE TOTAL ENVIRONMENT   406 ( 1-2 )   123 - 130   2008年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    Unlike in the North Atlantic, no continuous record of anthropogenic lead (Pb) has been available in the western Pacific. We reconstructed historical changes in anthropogenic Pb on the basis of Pb isotope ratios recorded in annually-banded coral retrieved from Ogasawara Island, Japan. Whereas the predominant natural source of Pb to the surface of the western Pacific apparently is Chinese loess, anthropogenic Pb has affected the western Pacific at least since the late 19th century. From the late 19th to the early 20th century, Australian Pb used in Japan was an important source of anthropogenic Pb. During 1920-1940, Pb emitted from parts of the world other than Japan contributed somewhat to the western Pacific, and the amount of Pb imported from Australia declined. Alkyl Pb used in Japan became the main source from 1950 until the mid-1970s, when leaded gasoline began to be regulated in Japan. Since the mid-1980s, aerosols from China have been the predominant source of Pb in the western Pacific. During the 1990s, around 60% of Pb in the surface of the western Pacific was from Chinese aerosols. We also investigated the present spatial distribution and likely sources of Pb in the western Pacific by using coral samples. Enrichment in (208)Pb, which is a characteristic of Pb from China, was found in all coral samples except that from Pohnpei, Micronesia, suggesting that at present anthropogenic Pb is transported to the western Pacific mainly from China via westerly winds. (C) 2008 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.scitotenv.2008.07.032

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  • Empirical assessment of coral Sr/Ca and Mg/Ca ratios as climate proxies using colonies grown at different temperatures

    Mayuri Inoue, Atsushi Suzuki, Masato Nohara, Kohei Hibino, Hodaka Kawahata

    GEOPHYSICAL RESEARCH LETTERS   34 ( 12 )   2007年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Coral strontium/calcium (Sr/Ca) and magnesium/ calcium (Mg/Ca) ratios might be useful for reconstructing past sea surface temperature (SST) in tropical oceans where instrumental data are limited. However, the link between coral skeletal trace elements and SST is disputed, and biological factors such as skeletal growth rate may also affect trace elements in a coral. We studied the relationships between growth rate and SST and Sr/Ca and Mg/Ca ratios using corals (Porites spp.) cultured in thermostated tanks. Sr/Ca was controlled primarily by SST, while Mg/Ca mainly reflected the growth rate with negligible contribution from species on both the variations. These relationships are consistent with modeled results of cation partitioning during aragonite crystal formation.

    DOI: 10.1029/2007GL029628

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  • Distribution and temporal changes of lead in the surface seawater in the western Pacific and adjacent seas derived from coral skeletons

    Mayuri Inoue, Akiko Hata, Atsushi Suzuki, Masato Nohara, Naotatsu Shikazono, Wyss W. -S. Yim, Wahyoe S. Hantoro, Sun Donghuai, Hodaka Kawahata

    ENVIRONMENTAL POLLUTION   144 ( 3 )   1045 - 1052   2006年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCI LTD  

    We determined Pb contents together with Pb isotopic compositions in coral skeletons (Porites spp.) collected from the western Pacific and adjacent seas to examine distribution of Pb in sea surfaces. Temporal records of Pb were also investigated using coral skeletons from Hainan and Ogasawara Island, located in China and Japan, respectively. The spatial distribution of Pb showed a clear dilution pattern of Pb from Asian continent to the open ocean. Also the similar trend was found in the Java Sea from Jakarta to the offshore. In addition to the spatial distribution, Pb contents in Ogasawara coral have gradually increased during last 108 years. It may be attributed to Pb emission mainly from industrial activities in Asian countries. Hainan coral, which provided 10 years record of Pb, showed a remarkable decline around 1997 probably due to the partial introduction of unleaded gasoline in China. (c) 2006 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.envpol.2005.11.048

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  • Stable isotope and chemical composition of pearls: Biomineralization in cultured pearl oysters in Ago Bay, Japan

    Hodaka Kawahata, Mayuri Inoue, Masato Nohara, Atsushi Suzuki

    JOURNAL OF OCEANOGRAPHY   62 ( 4 )   405 - 412   2006年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGER  

    The delta O-18, delta C-13 and trace element composition of pearls collected from Ago Bay, Japan, were investigated in order to evaluate biomineralization in the cultured pearl oyster (Pinctada fucata martensii). The oxygen isotopic data suggest that the pearls were produced around 23-24 degrees C, mainly in June to early July, which is consistent with their occurrence in the field. Therefore the pearls were produced under or close to isotopic equilibrium conditions, although they showed high calcification rates (higher than 0.2-1.0 g cm(-2) yr(-1)) under which, for example, coral skeletons (calcification rate similar to 0.28 g cm(-2) yr(-1)) often show non-equilibrium isotope partitioning. The delta C-13 values were similar to-2.9 parts per thousand lower than those calculated for offshore waters under equilibrium conditions. This may be due to low-delta C-13 bottom waters resulting from the degradation of organic matter (OM) or to a contribution of low-delta C-13 food. In the latter case, a simple mass balance calculation gives a respiration component of 14%. Twelve trace elements of bulk pearl samples were classified into four groups on the basis of their enrichment/depletion patterns relative to seawater and inter-element relationships: group 1, Co, Cr, Ph; group 2, Ba, Cs, U; group 3, Cu, Sn, V, and group 4, Mn, Rb, Mo. Comparison with coral skeletons suggests that Ba and Mn (groups 2 and 4) were definitely much enriched in proteinaceous OM relative to aragonite crystals in pearls and that V (group 3) in pearls showed only slight enrichment in the organic-rich layer. By contrast, the other elements showed small differences between both layers (enrichment factor of < 3), suggesting that these elements occur largely in aragonite crystals.

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  • Coral skeletal tin and copper concentrations at Pohnpei, Micronesia: possible index for marine pollution by toxic anti-biofouling paints

    M Inoue, A Suzuki, M Nohara, H Kan, A Edward, H Kawahata

    ENVIRONMENTAL POLLUTION   129 ( 3 )   399 - 407   2004年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCI LTD  

    We present 40 year-long, skeletal chronologies of tin (Sri) and copper (Cu) from an annully-banded coral (Porites sp.) collected from Pohnpei Island. Micronesia (western equatorial Pacific). Both the elements are present in antifouling marine paints and are released inadvertently into ambient seawater. Especially, Sri has often been used in the form of tributyltin (TBT). Based on a stepwise pretreatment examination. Sri and Cu both inside and Outside the aragonite lattice of the coral skeleton show a potential for providing marine pollution indicators. High values of extra-skeletal Cu/Ca and Sn/Ca atomic ratios were found between late 1960s and late 1980s during a period of active use of TBT-based antifouling paints worldwide. However, a significant decrease in both the ratios in the beginning, of 1990s can be attributed to regulation Of the use of TBT oil cargo ships by Countries Such as the USA, Japan and Australia. (C) 2004 Elsevier Ltd. All rights reserved.

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  • Endocrine disrupter nonylphenol and bisphenol A contamination in Okinawa and Ishigaki Islands, Japan - within coral reefs and adjacent river mouths

    H Kawahata, H Ohta, M Inoue, A Suzuki

    CHEMOSPHERE   55 ( 11 )   1519 - 1527   2004年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Certain chemicals possess the potential to modulate endocrine systems, and thereby interfere with reproduction and developmental processes in the wild. We analyzed endocrine disrupters nonylphenol (NP) and bisphenol A (BPA) levels at various sites in Okinawa and Ishigaki Islands, Japan. River-water samples showed undetectable to low concentrations of NP and BPA at most of the sites investigated. However, an appreciable amount of BPA was detected in sediments at one coral reef site. In addition, significant numbers of river sediment samples showed appreciable amounts of NP and BPA. Most of the sampling sites for this study are located within a distance of I km from the coral reefs, which are under influence of river-waters to a variable extent. Therefore, influence of endocrine disrupters may have already begun on adjacent coral reefs. Both endocrine disrupters were positively correlated with human population densities, but not with the contents of red soil generated by farm land reformation. Therefore, it is concluded that NP and BPA pollution is a consequence of human waste discharge, both domestic and industrial, and not by agricultural activities. (c) 2004 Elsevier Ltd. All rights reserved.

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  • Concentrations of trace elements in carbonate reference materials coral JCp-1 and giant clam JCt-1 by inductively coupled plasma-mass spectrometry

    M Inoue, M Nohara, T Okai, A Suzuki, H Kawahata

    GEOSTANDARDS AND GEOANALYTICAL RESEARCH   28 ( 3 )   411 - 416   2004年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:GEOSTANDARDS  

    Trace elements in the Geological Survey of Japan carbonate reference materials Coral JCp-1 and Giant Clam JCt-1 were determined by inductively coupled plasma-mass spectrometry after digestion with 2% v/v HNO3. A standard addition method was adopted in this determination in order to neutralise the Ca matrix effect. in addition, Sc, Y, In and Bi were used as internal standards to control the matrix effect and correct instrumental drift. Of the eighteen elements measured in JCp-1, precisions for fourteen elements, including Cu, Cd and Ba, were better than 10% RSD and concentrations ranged from 0.002 mu g g(-1) (Cs) to 8.02 mu g g(-1) (Ba). The concentrations of measured trace elements in JCt-1, except for Cu, were lower than those in JCp-1. Precisions for all elements with concentrations higher than 0.04 mu g g(-1) in JCt-1 were also better than 10% RSD and concentrations were found to be between 0.001 mu g g(-1) (Cs) and 4.84 mu g g(-1) (Ba). The concentrations of more than fifteen trace elements in the aragonite reference materials are reported here for the first time. Both reference materials are suitable for use in geochernical studies of environmental reconstruction based upon biogenic carbonate materials.

    DOI: 10.1111/j.1751-908X.2004.tb00759.x

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  • 海洋におけるカルシウムの地球科学と安定同位体指標

    吉村寿紘, 井上麻夕里

    海の研究   25 ( 3 )   81‐99 - 99   2016年

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    記述言語:日本語   出版者・発行元:日本海洋学会  

    DOI: 10.5928/kaiyou.25.3_81

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  • 環境指標としてのサンゴ骨格中の微量元素とその変動メカニズムの解明に向けて

    井上 麻夕里, Mayuri Inoue, Atmosphere and Ocean Research Institute The University of Tokyo

    海の研究   21 ( 5 )   159 - 175   2012年9月

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    記述言語:日本語   出版者・発行元:日本海洋学会  

    <p>近年,人為起源の大気中二酸化炭素濃度の増加に伴う地球温暖化や海洋酸性化の問題が懸念されているが,近い将来地球環境がどのように変化するのか,その近未来予測を定量的に行うためには,過去から現在に至る環境変動とそのプロセスを詳細に知る必要がある。炭酸塩生物殻はそのツールとして古気候・古海洋学の分野で威力を発揮しているが,有孔虫や円石藻などと同様に造礁サンゴも広く用いられており,熱帯から亜熱帯域の海洋環境を月単位の高時間分解能で復元できるという特徴を持っている。本報ではサンゴ骨格中の微量元素に注目し,化石サンゴを用いた鮮新世から歴史時代までの環境復元,現生サンゴを用いた月単位での近過去の環境復元,そして週から日単位の微小スケールでの微量元素変動,と時空間スケールに沿ってこれまでの研究をまとめつつ,問題点を整理していきたい。さらにサンゴの石灰化メカニズムの視点も踏まえながら,今後の研究の展望についても述べたい。</p>

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  • 造礁サンゴ類の石灰化機構と地球環境変動に対する応答

    鈴木 淳, 井上 麻夕里, Atsushi Suzuki, Mayuri Inoue, Atmosphere and Ocean Research Institute The University of Tokyo

    海の研究   21 ( 5 )   177 - 188   2012年9月

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    記述言語:日本語   出版者・発行元:日本海洋学会  

    <p>造礁サンゴの石灰化について,特に溶存無機炭素の役割に着目し,これまでに提唱されている石灰化メカニズムをレビューした。サンゴの石灰化は造骨細胞と骨格に挟まれた間隙の,いわゆる石灰化母液で進行する。石灰化の進行には,この石灰化母液にカルシウムイオンと溶存無機炭素(特に炭酸水素イオン)が適切に供給される必要があり,石灰化の阻害因子となる水素イオンが適切に除去されなければならない。造骨細胞に存在する炭酸脱水酵素は溶存無機炭素の供給に寄与していると考えられる。サンゴの石灰化機構の解明は,いまだ道半ばであり,今後の一層の研究の進展が待たれる。サンゴの石灰化メカニズムの解明は,その海洋酸性化影響を評価する上でも重要である。</p>

    DOI: 10.5928/kaiyou.21.5_177

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  • 「地球環境変動と造礁サンゴ」(再掲)

    井上 麻夕里, M. Inoue

    海の研究   21 ( 5 )   145 - 146   2012年9月

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    記述言語:日本語   出版者・発行元:日本海洋学会  

    DOI: 10.5928/kaiyou.21.5_145

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  • 海洋酸性化がサンゴ礁域の石灰化生物に及ぼす影響

    諏訪 僚太, 中村 崇, 井口 亮, 中村 雅子, 守田 昌哉, 加藤 亜記, 藤田 和彦, 井上 麻夕里, 酒井 一彦, 鈴木 淳, 小池 勲夫, 白山 義久, 野尻 幸宏, Ryota Suwa, Takashi Nakamura, Akira Iguchi, Masako Nakamura, Masaya Morita, Aki Kato, Kazuhiko Fujita, Mayuri Inoue, Kazuhiko Sakai, Atsushi Suzuki, Isao Koike, Yoshihisa Sirayama, Yukihiro Nojiri, Seto Marine Biological Laboratory Field Science Education and Research Center Kyoto University, Amakusa Marine Laboratory Kyusyu University, Sesoko Station Tropical Biosphere Research Center University of the Ryukyus, Sesoko Station Tropical Biosphere Research Center University of the Ryukyus, Sesoko Station Tropical Biosphere Research Center University of the Ryukyus, Graduate School of Engineering and Science University of the Ryukyus, Graduate School of Engineering and Science University of the Ryukyus, Ocean Research Institute The University of Tokyo, Sesoko Station Tropical Biosphere Research Center University of the Ryukyus, Geological Survey of Japan National Institute of Advanced Industrial Science and Technology(AIST), Seto Marine Biological Laboratory Field Science Education and Research Center Kyoto University, Center for Global Environmental Research National Institute for Environmental Studies

    海の研究   19 ( 1 )   21 - 40   2010年1月

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    記述言語:日本語   出版者・発行元:日本海洋学会  

    産業革命以降の二酸化炭素(CO_2)排出量の増加は,地球規模での様々な気候変動を引き起こし,夏季の異常高海水温は,サンゴ白化現象を引き起こすことでサンゴ礁生態系に悪影響を及ぼしたことが知られている。加えて,増加した大気中CO_2が海水に溶け込み,酸として働くことで生じる海洋酸性化もまた,サンゴ礁生態系にとって大きな脅威であることが認識されつつある。本総説では,海洋酸性化が起こる仕組みと共に,海洋酸性化がサンゴ礁域の石灰化生物に与える影響についてのこれまでの知見を概説する。特に,サンゴ礁の主要な石灰化生物である造礁サンゴや紅藻サンゴモ,有孔虫に関しては,その石灰化機構を解説すると共に,海洋酸性化が及ぼす影響について調べた様々な研究例を取り上げる。また,これまでの研究から見えてきた海洋酸性化の生物への影響評価実験を行う上で注意すべき事項,そして今後必要となる研究の方向性についても述べたい。The increase of the atmospheric carbon dioxide (CO_2) concentration after the industrial revolution caused global climate change. During the last several decades, coral reef ecosystems have been devastated by the mass-scale coral bleaching events caused by abnormally high seawater temperature in summer. In addition, increased atmospheric CO_2dissolves in the ocean, acts as an acid and finally decreases the pH level of seawater. This phenomenon, known as ocean acidification, is now being considered as a future threat to the calcifying organisms in coral reef ecosystems. In this review, we summarize basic backgrounds of ocean acidification as well as its potential impacts on coral reef calcifiers. Together with the distinctive mechanisms of calcification among specific groups, we review the impacts of ocean acidification on major reef-builders such as scleractinian corals, calcareous red algae and reef-dwelling foraminifera. Finally, we point out some recently-recognized problems in acidified seawater experiments as well as the future direction of this research field.

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  • 飼育実験に基づくサンゴ骨格中の微量元素変動 (総特集 バイオミネラリゼーションと石灰化--遺伝子から地球環境まで) -- (造礁サンゴ)

    井上 麻夕里, 鈴木 淳, 野原 昌人

    号外地球   ( 59 )   12 - 17   2008年

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    記述言語:日本語   出版者・発行元:海洋出版  

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  • 水槽飼育実験による造礁サンゴ骨格の環境指標研究 (特集:生物鉱化作用と地球環境)

    鈴木 淳, 井上 麻夕里, 川幡 穂高

    地質ニュース   ( 632 )   23 - 28   2007年4月

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    記述言語:日本語   出版者・発行元:実業公報社  

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  • 温度指標としてのサンゴ骨格中のSr/Ca比変動に関する再考察

    井上 麻夕里

    地球化学   40 ( 3 )   209 - 219   2006年

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    記述言語:日本語   出版者・発行元:一般社団法人日本地球化学会  

    Components in biogenic carbonates have been recognized to be attractive tools for reconstructing past oceanographic and climatic changes. Although chemical components in coral aragonite are precipitated away from equilibrium, fluctuations of Sr/Ca ratio in coral skeletons have been empirically considered to be controlled by temperature. Thus, Sr/Ca ratio in coral skeletons has been applied for paleoclimate reconstruction. Recently, coupled measurements of coral skeletal δ<sup>18</sup>O, indicator of both SST and seawater δ<sup>18</sup>O, and Sr/Ca ratio are used to reconstruct seawater salinity as well as SST. On the other hand, it has been reported that Sr/Ca is also affected by growth rate of coral skeleton besides SST. However, the impact of skeletal growth rate on Sr/Ca ratio is a matter of debate and controversial results have been reported at the present. In this review, recent progress of studies on the topics and a mechanism of growth rate-related Sr/Ca variation based on a physiological model are summarized.

    DOI: 10.14934/chikyukagaku.40.209

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  • 危険化学物質による環境汚染(その3)ミクロネシア連邦ポンペイ島における船底塗料による海洋汚染の歴史的変遷--サンゴ骨格中の銅とスズを指標として

    鈴木 淳, 井上 麻夕里, 野原 昌人

    地質ニュース   ( 604 )   8 - 14   2004年12月

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  • 危険化学物質による環境汚染(その2)琉球列島サンゴ礁および隣接地域の外因性内分泌攪乱物質(環境ホルモン)ノニルフェノールとビスフェノールAの汚染

    川幡 穂高, 井上 麻夕里, 北田 幸男

    地質ニュース   ( 603 )   20 - 24   2004年11月

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  • 産総研地球化学標準物質JCp-1(サンゴ),JCt-1(シャコガイ)の共同分析結果

    岡井 貴司, 鈴木 淳, 寺島 滋, 井上 麻夕里, 野原 昌人, 川幡 穂高, 今井 登

    地球化学   38 ( 4 )   281 - 286   2004年

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    記述言語:日本語   出版者・発行元:一般社団法人日本地球化学会  

    The chemical composition of coral skeleton and clamshell is closely linked to the composition of surface sea water in which skeletal or shell calcium carbonate is precipitated. For this reason, several chemical components in coral and clam have been determined to be indicatrs of sea surface environmental conditions. However, there is no reference material having the same chemical composition as coral or clam. Therefore, GSJ/AIST has issued the reference materials JCp-1 (Coral <i>Porites</i> sp.) and JCt-1 (Giant Clam <i>Tridacna</i>), for the determination and evaluation of elements in coral, clam and other biogenic carbonates. In this study, collaborative analysis for the certification of reference materials JCp-1 and JCt-1 was carried out in ten laboratories. The analytical data were compiled for 9 components (CaO, Ba, Fe, K, Mg, Mn, Na, P and Sr). The ICP-AES and AAS were mainly used, and the analytical results agreed relatively well. In the statistical analysis, the reference values were mainly decided using the robust method. ISO typically recommends that data should be submitted from no fewer than 15 laboratories for deciding the certified values; the reference values given in this paper could be considered as preliminary certified values.

    DOI: 10.14934/chikyukagaku.38.281

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  • 琉球列島の石垣島周辺のサンゴ礁における底質と海水濁度の関係

    鳥取 海峰, 鈴木 淳, 長尾 正之, 森本 直子, 井上 麻夕里, 岩瀬 晃啓, 渋野 拓郎, 藤岡 義三, 大葉 英雄, 菅 浩伸

    日本サンゴ礁学会誌   2004 ( 6 )   1 - 19   2004年

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    出版者・発行元:日本サンゴ礁学会  

    石垣島東海岸3地域と石西礁湖内のシモビシにおいて、堆積物とその礁内海水の濁度への影響を調査した。堆積物中の細粒物質の定量には、大見謝 (1987) の底質中懸濁物質含量簡易測定法 (SPSS測定法) を用いた。宮良川などが流入する宮良湾のサンゴ礁の礁池の一部と水路部分、轟川河口から北側の海岸部にSPSS値の高い海域が見出された。一方、河川の影響が少ない安良崎、白保、シモビシでは全体的にSPSS値が低かった。サンゴ礁海水の濁度には、大局的にSPSS値との有意な相関関係が認められ、礁内での海水の濁度の成因が堆積物中の細粒物質の再懸濁であることが示唆された。SPSS測定法の定量精度は、簡易携帯型の濁度計を用いることで精度が向上した。この方法は、簡易環境調査のみならず、環境の悪化したサンゴ礁で重要なサンゴと藻類の競争現象に影響していると考えられる水中光環境の研究にも応用しうる可能性を有している。

    DOI: 10.3755/jcrs.2004.1

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  • サンゴ骨格を用いた古海洋環境の復元 (特集 環境を記録する生物(1))

    井上 麻夕里

    地質ニュース   ( 575 )   26 - 33   2002年7月

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    記述言語:日本語   出版者・発行元:実業公報社  

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  • 海洋汚染指標としてのサンゴ骨格中の重金属元素

    井上 麻夕里, 鈴木 淳, 菅 浩伸

    日本海水学会誌   56 ( 2 )   113 - 117   2002年

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    記述言語:日本語   出版者・発行元:The Society of Sea Water Science, Japan  

    DOI: 10.11457/swsj1965.56.113

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  • サンゴ骨格中の微量元素 –海洋汚染の指標としての可能性–

    井上 麻夕里, 菅 浩伸, 鈴木 淳

    地球化学   36 ( 2 )   65 - 79   2002年

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    記述言語:日本語   出版者・発行元:一般社団法人日本地球化学会  

    Coral reefs are increasingly threatened by human activities (e.g., sewage discharge and industrial effluents). Composition of coral skeleton is expected to quantitatively record the change in marine environments in which skeletal calcium carbonate is precipitated. Recently, trace elements, particularly heavy metals, in the skeleton of massive and annually banded corals have been successfully used as a proxy of marine pollution at regional and local scale. Critical problems, however, exist due to lack of a well-established method for analyzing trace elements in coral skeleton. Large range in reported values for heavy metal concentrations in coral skeleton could be attributed to differences in pretreatment procedures of skeletal materials rather than the real extent of marine pollution. In this review, we summarize recent progress of studies on the topics and key factors for the further application of coral proxies in order to reconstruct the history of marine pollution.

    DOI: 10.14934/chikyukagaku.36.65

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共同研究・競争的資金等の研究

  • 沿岸浅海域の地理学研究:浅海底地形学の構築および海底景観の可視化と啓発

    研究課題/領域番号:21H04379  2021年04月 - 2025年03月

    日本学術振興会  科学研究費助成事業  基盤研究(A)

    菅 浩伸, 後藤 和久, 藤田 和彦, 横山 祐典, 渡部 真史, 後藤 秀昭, 島津 弘, 清野 聡子, 長谷川 均, 堀 信行, 今里 悟之, 小野 林太郎, 高橋 そよ, 伊藤 幸司, 鈴木 淳, 井上 麻夕里, 藤田 喜久, 平林 頌子, 木村 淳, 中西 裕見子, 片桐 千亜紀, 山舩 晃太郎

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    配分額:42250000円 ( 直接経費:32500000円 、 間接経費:9750000円 )

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  • 日本周辺の堆積物・サンゴ試料を用いた高時間解像度の気候復元と社会への影響評価研究

    研究課題/領域番号:20H01981  2020年04月 - 2025年03月

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    川幡 穂高, 井上 麻夕里, 鈴木 淳, 吉田 明弘, 大石 龍太

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    配分額:17160000円 ( 直接経費:13200000円 、 間接経費:3960000円 )

    近年,完新世の気候変動は,人間の移動と発達に大きな影響を与えたと考えられている.日本では,中石器時代の文明は約16,000年前(縄文時代)に始まった.そして,3000年前頃,水稲栽培の技術を持った人々が中国本土から日本列島に移住し弥生時代となった.本研究では,水稲栽培の発祥の地である中国の浙江沿岸の沿岸から復元された古水温と比較するため,博多湾の堆積物より今回新たに古温度変化を復元した.アルケノンから復元した水温は18.7℃から21.8℃まで変動し,数百年から数千年のスケールで変動した.過去7,000年間の温度は数百年から数千年の規模で変動し,両者で類似していた.この中で約300年前と約4,200年前の寒冷イベントは,小氷期と4.2 kaイベントに対応していた.この「4200年前イベント」は, 2018年7月に国際年代層序表に関する国際層序委員会により完新世の中期/後期境界として正式に認定された.興味深いことに,場所によって乾燥,洪水,寒冷など特徴が異なっているものの,気候の異常が報告された地域はほぼ温帯域に位置していた.筆者たちは,私達の研究地域の寒冷化はアジアモンスーンや偏西風などの変調が原因と考えている.さらに,浙江海岸では,約4,200年前の寒冷イベントに伴い,沿岸湧昇が強化されたために寒冷化が増幅されたと示唆された.現代日本人の半分程度の遺伝子をもたらした祖先である弥生・渡来人は,4200年前は中国に暮らしていた.水稲栽培が始まった長江下流域では,文明が途絶えるほどの厳しい寒冷化を経験した.現代日本人の遺伝子の中に,当時中国に生活していた日本人の祖先の遺伝子を特定できる.この遺伝子のグループについて,過去の人口変動を現代人の遺伝子の解析から推定できる.このデータに基づくと,水稲栽培を生業としていた人びとの人口が大きく減少したことが示唆される.

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  • 人間活動が支配する新しい地球環境時代の開始とその評価に向けて

    研究課題/領域番号:20K12135  2020年04月 - 2024年03月

    日本学術振興会  科学研究費助成事業  基盤研究(C)

    井上 麻夕里

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    配分額:4290000円 ( 直接経費:3300000円 、 間接経費:990000円 )

    本研究では東南アジア海域から採取されたサンゴ骨格試料を用いて、全球同時的な地球温暖化が開始した時期、および地球温暖化を含む全球規模の人間活動の局所的な海域への影響評価を目的としている。昨年度、バリ島のサンゴ年輪についてSr/Ca比および酸素同位体比を測定したところ、年輪カウントによる年数と化学分析による年数が一致していない箇所があり、サンゴの年輪形成機構について精査する必要があることが分かった。よって、本年度はインドネシア・ジャワ海のサンゴ試料について、微小試料採取を行い、細かくSr/Ca比およびMg/Ca比測定を実施し、骨格の密度バンド(年輪)がどのような環境で形成されているのか、ということについて調査を開始した。今のところ、Sr/Ca比の変動と密度パターンが毎年一致しておらず、必ずしも海水温が骨格密度を規定している要因だとは限らないことが推察されている。今後、異なる場所のサンゴ試料でも検証していく予定である。
    また、すでに分析済みのフィリピンのサンゴ試料のSr/Ca比および酸素同位体比について228年間分のデータを見直し、再構築を行った上で、先行研究との比較なども実施し、論文を投稿した。新たな考察の結果、1800年代はクラカタウやタンボラのような大規模噴火に伴う寒冷化が何度か認められていたこと、1975年以降から全球規模でより画一的な温暖化が加速していることが分かってきた。同様に、バリ島のSr/Ca 比と酸素同位体比の結果についても、こちらは特にインドネシア通過流とその気候に及ぼす影響の観点からデータをまとめ、論文を投稿した。バリ島では全球規模の近年の温暖化に反して、寒冷化傾向が認められており、インドネシア多島海での海洋環境の複雑性、また気候の調節機能があることが示唆されている。

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  • 海洋酸性化が沿岸生物の世代交代、群集・個体群構造に及ぼす長期影響評価

    研究課題/領域番号:19H04288  2019年04月 - 2023年03月

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    高見 秀輝, 林 正裕, 井上 麻夕里, 村岡 大祐, 小埜 恒夫, 酒井 一彦, 井口 亮

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    配分額:17290000円 ( 直接経費:13300000円 、 間接経費:3990000円 )

    二酸化炭素濃度を1000ppmおよび2000ppmに調整した海水と約400ppmの原海水(対照区)で4年間飼育したキタムラサキウニを親として用い、対照区の親から得られた子世代を1000ppmと2000ppmで飼育する実験区(非順化区)と、1000ppmと2000ppmで飼育した親から得られた子世代をそれぞれ親と同じ濃度で飼育する実験区(順化区)を設定した。各実験区の子世代について、受精後8日目の八腕期浮遊幼生の段階で腕長を比較した結果、2000ppmの非順化区のみ対照区と比較して平均値が低下した。以上から、幼生期における酸性化環境への順化・適応については2000ppmで影響が出る可能性が考えられた。親ウニの棘の微量元素の経年分析の結果から、幼生期は成熟個体よりも棘のMg/Ca比が高くなる傾向にあることが示唆された。造礁サンゴの三種の長期飼育実験に向けて、異なる二酸化炭素濃度条件で短期飼育実験を実施した。その結果、これらサンゴ種の長期飼育条件が明らかとなり、海水酸性化にエダコモンサンゴが最も脆弱であることが判明した。遺伝子解析について、サンゴのトランスクリプトームデータから、サンゴと褐虫藻に加えて、他の内在生物の遺伝子データの分離を行い、各生物での発現量マトリックスの作成を進めた。褐虫藻組成に関しては、ストレス暴露処理間では明瞭な差異は見られなかった。キタムラサキウニに関しては、ストレス暴露処理サンプルのRNA抽出を行い、RNA-seqによるショートリードデータの取得に成功した。魚類に関しては、トランスクリプトーム解析に向けたサンプル処理の準備を進めた。
    二酸化炭素濃度の精度管理については、船舶観測用pCO2計を用いて飼育水のpCO2レベルを直接測定し、飼育実験装置のpCO2制御装置に生じたずれの検出とずれ補正式の作成を行いより精度の高い濃度管理が可能となった。

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  • ドミニカ共和国沿岸の重金属汚染の時空間的推移と流入実態の調査と負荷源対策の検証

    研究課題/領域番号:16H05631  2016年04月 - 2019年03月

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    作野 裕司, 中井 智司, 鈴木 淳, 長尾 正之, 陸田 秀実, 西嶋 渉, 井上 麻夕里

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    配分額:16120000円 ( 直接経費:12400000円 、 間接経費:3720000円 )

    ドミニカ共和国沿岸域への重金属の流出実態を把握するため,河口部におけるサンゴ試料の化学分析と衛星リモートセンシングや数値モデルによる流出パターンの解析が行われた.この研究により,首都サントドミンゴ周辺は生活及び産業廃棄物処理施設が不十分であることから,ハイナ川に代表される大河川から洪水に伴って重金属類が海域にもたらされる可能性が示唆された.特にバッテリー工場による鉛汚染を塊状サンゴにより検出できることが明らかとなった.さらに,ハリケーン等の洪水イベントによって他の汚染源からの深刻な負荷もあることも見出された.

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  • インドネシア通過流の表層環境が気候システムおよびサンゴ礁環境に及ぼす影響評価

    研究課題/領域番号:15H05329  2015年04月 - 2019年03月

    日本学術振興会  科学研究費助成事業  若手研究(A)

    井上 麻夕里

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    配分額:24700000円 ( 直接経費:19000000円 、 間接経費:5700000円 )

    ジャワ海に位置するインドネシア・セリブ島より採取されたサンゴ骨格試料についてストロンチウム・カルシウム比やウラン・カルシウム比、酸素・炭素同位体比を測定することで、過去約70年間の海洋環境を復元した。その結果、この海域ではこの70年間で海水温が約0.7度上昇していることが分かった。また、1970年代以降は化石燃料放出の影響を受けて海水のpHが低下していることも推察された。

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  • 海洋酸性化の沿岸生物と生態系への影響評価実験

    研究課題/領域番号:26220102  2014年05月 - 2019年03月

    日本学術振興会  科学研究費助成事業  基盤研究(S)

    野尻 幸宏, 林 正裕, 井上 麻夕里, 酒井 一彦, 高見 秀輝, 井口 亮, 鈴木 淳, 石田 明生, 中野 智之

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    配分額:194870000円 ( 直接経費:149900000円 、 間接経費:44970000円 )

    沿岸海洋生物の海洋酸性化影響を将来シナリオが予測するCO2濃度範囲を含めて実験した。わが国沿岸のサンゴ、二枚貝、ウニなどの種の影響評価実験と、特に昇温影響を受けるサンゴについて温暖化との複合影響評価を行った。アワビ幼生のCO2濃度日周変動を含む実験では閾値を越す度合の積算が影響する、沖縄のサンゴ種では酸性化と温暖化の両方が石灰化に影響するなどの知見を得た。生態系影響評価としてCO2濃度調整水槽への加入実験を行い、加入生物の炭酸殻のMg/Ca比に酸性化の影響が現れる結果を得た。魚類の再生産実験では魚種による酸性化への応答の違いが見られ、世代交代の早い魚種の継代飼育実験から順化の評価を行った。

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  • 造礁サンゴ骨格による気候変動解析の新展開

    研究課題/領域番号:24244090  2012年04月 - 2015年03月

    日本学術振興会  科学研究費助成事業  基盤研究(A)

    鈴木 淳, 酒井 一彦, 中村 崇, 岡井 貴司, 加藤 亜記, 張 勁, 中島 礼, 磯野 良介, 吉川 貴志, 井口 亮, 井上 麻夕里, 村山 昌平, 林 正裕, 堀田 公明

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    配分額:48620000円 ( 直接経費:37400000円 、 間接経費:11220000円 )

    造礁サンゴ骨格に記録された気候変動情報は、精度や時間分解能の点で他の間接指標と比較しても良好な性能を持つ。本課題では、サンゴ骨格の「間接指標(酸素同位体比・Sr/Ca比)の成長速度依存特性」、「炭素同位体比の制御因子」、「種内変異(群体間差異)が抑制/拡大されるメカニズム」について、琉球大学瀬底研究施設の屋外水槽で長期飼育されたハマサンゴ試料を対象に検討した。炭素同位体比>酸素同位体比>Sr/Ca比の順でサンゴの健康状態(そして骨格成長速度)に影響される。Sr/Ca比は頑強で、優れた水温の間接指標である。これらの結果は、サンゴ骨格による気候変動研究の確度の高さを支持するものである。

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  • ドミニカ共和国における近過去から現在のバッテリー工場起源沿岸域鉛汚染の調査・解明

    研究課題/領域番号:24404006  2012年04月 - 2015年03月

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    中井 智司, 陸田 秀実, 作野 裕司, 奥田 哲士, 鈴木 淳, 長尾 正之, 井上 麻夕里

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    配分額:17420000円 ( 直接経費:13400000円 、 間接経費:4020000円 )

    バッテリー工場由来の鉛による河川及び沿岸域の汚染状況を把握するため、ドミニカ共和国のハイナ川河口付近において底質や塊状サンゴを採取し、鉛含有量を分析した。そして、懸濁物質を指標として、衛星データを使ってハイナ川からの周辺海域への拡散状態の推定を行った。分光反射率とSSの関係を元に、解像度のよい衛星データからハイナ川河口部のSS分布を定量化するモデルを導いた。また、これらのモデルから実際のALOS AVNIR-2データを使ってSS等のマッピングを行った。ハイナ川河口部からカリブ海に流出する物質の拡散を三次元的に求めるため、海洋環境シミュレーションを行った。

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  • 地球表層システムにおける海洋酸性化と生物大量絶滅

    研究課題/領域番号:22224009  2010年04月 - 2015年03月

    日本学術振興会  科学研究費助成事業  基盤研究(S)

    川幡 穂高, 鈴木 淳, 山岡 香子, 井上 麻夕里, 西弘 嗣, 山岡 香子

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    配分額:142610000円 ( 直接経費:109700000円 、 間接経費:32910000円 )

    陸域の化学風化は,海洋酸性化にとっては「中和」として機能します.大陸の緩衝作用を確かめる目的でバングラデシュ,ミャンマー,タイの大河を調査しました.その結果,ヒマラヤ山脈源流の河川では大気中の二酸化炭素を吸収する効果は小さいことがわかりました.5,500万年前の暁新世/始新世(P/E)境界は「海洋酸性化」の地球的規模での実験と言えます.深海底では石灰殻の底棲有孔虫が絶滅し,生き残った有孔虫も膠着質の殻をもつものに変化してしまいました.現代はP/E境界の約30倍のスピードで二酸化炭素が放出されています.大陸風化は追いつけないので,将来深刻な海洋酸性化とそれに伴う絶滅が起こると予想されます.

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  • 精密飼育実験に基づく間接指標の開発と低中緯度域の気候変動システムの解明

    研究課題/領域番号:22244064  2010年

    日本学術振興会  科学研究費助成事業  基盤研究(A)

    川幡 穂高, 鈴木 淳, 井上 麻夕里

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    配分額:23920000円 ( 直接経費:18400000円 、 間接経費:5520000円 )

    研究の目的は,(1)サンゴ礁に生息する大型底棲有孔虫(Amphistegina lobifera,Marginopora kudakajimensis)を対象に精密飼育実験を行い,水温・塩分・pHに関して新しい環境間接指標を開発し,IODP(統合国際深海掘削計画)のグレートバリアリーフとタヒチから得られた試料に適用し,低緯度域のエルニーニョ・南方振動を明らかにする.(2)サンゴの飼育実験より,pH指標に関して,サンゴ骨格のU/Ca比などの新しい指標を開発するとともに,それを用いてpH時系列のデータを復元し,石灰化への影響,海洋環境や気候変動からの影響を明らかにする.(3)また,翼足類について,精密飼育実験を行い,水温・塩分・pHに関して新しい環境間接指標を開発するとともに,実海域での分布などを把握し,将来の海洋酸性化による影響を評価することである.
    サンゴについては,試料を採取し,精密飼育実験のセットアップを行い,飼育を継続できた.現在,その試料について,1)酸素・炭素の安定同位体比,2)ホウ素同位体,3)微量無機元素などを分析中である.また,翼足類についても,プランクトンネットにても,現生の試料を採取した.そして,海水中の二酸化炭素濃度をコントロールした海水中で飼育中である.

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  • 最終氷期最盛期の化石サンゴを用いた熱帯海域の海水温・塩分の季節変動復元

    研究課題/領域番号:21740387  2009年 - 2011年

    日本学術振興会  科学研究費助成事業  若手研究(B)

    井上 麻夕里

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    配分額:4420000円 ( 直接経費:3400000円 、 間接経費:1020000円 )

    最終氷期最盛期(LGM)における熱帯海域の海水温、塩分の季節変動の復元は、今後の気候変動を予測する上で重要なデータとなり得る。本研究では約22, 000年前の南太平洋のバヌアツから採取された化石サンゴ(Porites sp.)を用いてLGMの季節変動を明らかにした。その結果、LGMでは海水温に約5℃の季節性があったことが示唆され、現在(~ 3℃)に比べ海水温の季節変動が大きかったこと、特にそれが冬の海水温低下に起因していたことが示された。また、年平均の海水温は現在に比べ4. 5-5℃低かったことが推察された。

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  • 造礁サンゴの骨格形成と環境情報を記録するメカニズムに関する研究

    研究課題/領域番号:21340166  2009年 - 2011年

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    鈴木 淳, 井上 麻夕里, 酒井 一彦, 加藤 亜記, 岡井 貴司, 川幡 穂高, 村山 昌平

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    配分額:14820000円 ( 直接経費:11400000円 、 間接経費:3420000円 )

    サンゴの炭酸塩骨格の化学組成は、古気候を推定する間接指標として広く用いられている。しかし、その記録プロセスには生物が介在するため、これまで十分に考慮されてこなかった環境-生物間相互作用に起因する「推定の不安定性」が存在する。本研究では、長期飼育サンゴについて、酸素同位体比およびSr/Ca比の気候指標としての安定性を検証した。また、琉球列島石垣島のサンゴ記録から復元された20世紀初期の海洋変動について考察した。

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  • ストレスとサンゴ礁の歴史的変化

    研究課題/領域番号:20121004  2008年 - 2012年

    日本学術振興会  科学研究費助成事業  新学術領域研究(研究領域提案型)

    山野 博哉, 長谷川 均, 渡邊 剛, 井上 麻夕里, 鈴木 淳, 小熊 宏之, 白井 厚太朗

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    配分額:131950000円 ( 直接経費:101500000円 、 間接経費:30450000円 )

    石垣島の陸域と海域を対象として、過去から現在にかけて土地利用図、空中写真、衛星データの画像解析と土砂流出モデルによる流入負荷の推定を行った。これらにより、土砂流出の増大によってサンゴの被度が低下していることを明らかにした。また、海域においては、化石と現在の塊状のサンゴからコアを採取し、骨格中に含まれる蛍光、同位体比、微量金属、密度に関する分析を行い、環境変化がサンゴ骨格に記録されるとともに骨格形成に影響を与えていることを示した。

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  • サンゴの閉鎖系飼育システムの開発とその骨格を用いた環境指標の高精度化

    研究課題/領域番号:19840020  2007年 - 2008年

    日本学術振興会  科学研究費助成事業  若手研究(スタートアップ)

    井上 麻夕里

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    配分額:3105000円 ( 直接経費:2700000円 、 間接経費:405000円 )

    サンゴ骨格中のストロンチウム/カルシウム(Sr/Ca)比やマグネシウム/カルシウム(Mg/Ca)比は、海水温指標としてこれまで世界的に広く測定されているが、近年これら微量元素が海水温のみではなくサンゴ骨格の成長速度にも依存している可能性が指摘されている。そこで本研究では、温度と光量のみを厳密に制御したサンゴの飼育実験を行い、Sr/Ca比はこれまでの報告と同様海水温に、一方Mg/Ca比は温度ではなく成長速度により強く依存して変動していることを明らかにした。

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  • サンゴ骨格を用いた熱帯域における微量化学物質による海洋汚染の精密復元に関する研究

    研究課題/領域番号:04J03245  2004年 - 2005年

    日本学術振興会  科学研究費助成事業  特別研究員奨励費

    井上 麻夕里

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    配分額:1800000円 ( 直接経費:1800000円 )

    人為起源の鉛は,有鉛ガソリンの使用,石炭燃焼や鉛・銅などの鉱山の採掘など主に工業化に附随して放出されることが知られているが,近年アジアにおいて工業起源の鉛の放出量が増加していることが指摘されている.前年度の研究から、西太平洋においては大陸起源の鉛が外洋表層まで広がっていることが明らかにされている。そこで今年度はサンゴ骨格を用いて,アジアから排出される汚染物質の影響を強く受ける西太平洋表層における鉛の時系列変動を明らかにした.試料は海南島,小笠原,ジャカルタ湾から採取されたサンゴ骨格(Porites sp.)を用い,過去それぞれ約10年間,100年間,70年間の鉛濃度変動を復元した.サンゴ骨格中の鉛濃度の測定はICP-MSを用いて行い,サンゴ標準試料であるJCp-1の15回の繰り返し測定による誤差は2.3%だった.
    サンゴ年輪に沿った鉛の測定結果からは,小笠原,ジャカルタ湾ともに過去それぞれ100年,70年において鉛濃度が上昇傾向にあった.このことから,アジア大陸から西太平洋,インドネシア各都市からジャワ海へと放出されている人為起源の鉛が,過去70年以上にわたって増加し続けていることが明らかとなった.特に小笠原のコアからは、1950年以降に鉛濃度の急激な上昇が見られ、これは日本を始めとするアジア各国における工業化のためと考えられる。また海南島のサンゴ骨格からは,1997年に急激な鉛濃度の減少が見られた.中国沿岸部では1997年から無鉛ガソリンの導入が行われ始めたので,この無鉛ガソリンの導入に対応して,サンゴ骨格中の鉛濃度が減少したことが示唆された.

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