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Last Updated :2024/07/25

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Master

Affiliation (Master)

  • Faculty of Environmental Earth Science　Earth System Science　Biogeosystem Science

Affiliation (Master)

  • Faculty of Environmental Earth Science　Earth System Science　Biogeosystem Science

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Profile and Settings

Affiliation

  • Hokkaido University, Graduate School of Environ. Sci. Division of Earth System Science, Assistant professor

Degree

  • Ph.D.（2014/03 Kyushu University）
  • M.Sc.（2011/03 Kyushu University）
  • B.Sc.（2009/03 Kyushu University）

Profile and Settings

  • Name (Japanese)

    IWASAKI

  • Name (Kana)

    SHINYA

  • Name

    202301010999647794

Affiliation

  • Hokkaido University, Graduate School of Environ. Sci. Division of Earth System Science, Assistant professor

Achievement

Research Experience

  • 2020/07 - 2023/03 MARUM, the University of Bremen
  • 2017/04 - 2020/03 Japan Agency for Marine-Earth Science and Technology
  • 2016/04 - 2017/03 National Institute of Advanced Industrial Science and Technology Geological Survey of Japan
  • 2014/04 - 2016/03 The University of Tokyo Atmosphere and Ocean Research Institute

Education

  • 2011/04 - 2014/03  Kyushu University  Graduate School of Sciences  Department of Earth and Planetary Sciences
  • 2009/04 - 2011/03  Kyushu University  Graduate School of Sciences  Department of Earth and Planetary Sciences
  • 2005/04 - 2009/03  Kyushu University  School of Sciences  Department of Earth and Planetary Sciences

Published Papers

  • Shinya Iwasaki, Katsunori Kimoto, Michal Kucera
    2022/12/16
  • Shinya Iwasaki, Lester Lembke-Jene, Kana Nagashima, Helge W. Arz, Naomi Harada, Katsunori Kimoto, Frank Lamy
    Nature Communications 2022/11/11
  • Stergios D. Zarkogiannis, Shinya Iwasaki, James William Buchanan Rae, Matthew W. Schmidt, P. Graham Mortyn, George Kontakiotis, Jennifer E. Hertzberg, Rosalind E. M. Rickaby
    FRONTIERS IN MARINE SCIENCE 9 2022/06 
    The mass of well-preserved calcite in planktonic foraminifera shells provides an indication of the calcification potential of the surface ocean. Here we report the shell weight of 8 different abundant planktonic foraminifera species from a set of core-top sediments along the Mid-Atlantic Ridge. The analyses showed that near the equator, foraminifera shells of equivalent size weigh on average 1/3 less than those from the middle latitudes. The carbonate preservation state of the samples was assessed by high resolution X-ray microcomputed tomographic analyses of Globigerinoides ruber and Globorotalia truncatulinoides specimens. The specimen preservation was deemed good and does not overall explain the observed shell mass variations. However, G. ruber shell weights might be to some extent compromised by residual fine debris internal contamination. Deep dwelling species possess heavier tests than their surface-dwelling counterparts, suggesting that the weight of the foraminifera shells changes as a function of the depth habitat. Ambient seawater carbonate chemistry of declining carbonate ion concentration with depth cannot account for this interspecies difference. The results suggest a depth regulating function for plankton calcification, which is not dictated by water column acidity.
  • Hiroto Kajita, Yuki Ota, Toshihiro Yoshimura, Daisuke Araoka, Takuya Manaka, Ouyang Ziyu, Shinya Iwasaki, Takuya Yanase, Akihiko Inamura, Etsuo Uchida, Hongbo Zheng, Qing Yang, Ke Wang, Atsushi Suzuki, Hodaka Kawahata
    Aquatic Geochemistry 26 (2) 137 - 159 1380-6165 2020/04/23 [Refereed][Not invited]
  • S. Iwasaki, K. Kimoto, Y. Okazaki, M. Ikehara
    Geochemistry, Geophysics, Geosystems 20 (12) 6051 - 6065 2019/12
  • S. Iwasaki, K. Kimoto, O. Sasaki, H. Kano, H. Uchida
    Scientific Reports 2019/07/05
  • 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 2197-4284 2019/01 
    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.
  • Shinya Iwasaki, Katsunori Kimoto, Azumi Kuroyanagi, Hodaka Kawahata
    MARINE MICROPALEONTOLOGY 130 1 - 14 0377-8398 2017/01 
    Observations of the horizontal and vertical distributions of modern planktic foraminifera facilitate formation of ecological and geochemical inferences derived from the study of foraminiferal shells. In this study, we used plankton tows to collect planktic foraminifera at nine sites distributed longitudinally throughout the subarctic Pacific. A total of nine planktic foraminiferal species were identified. The horizontal distributions of the foraminiferal assemblages could be assigned to four regions. Characteristics of the foraminiferal assemblages and the horizontal distributions of their shell sizes appeared to be influenced by the sea-surface structure within each water mass. The vertical distributions of Globigerina bulloides and Globigerina quinqueloba were associated with the depth of the pycnocline; those of Neogloboquadrina pachyderma and Neogloboquadrina incompta were different and appeared to reflect a significant difference of optimum habitat temperatures. Based on the vertical distribution of shell sizes, we found evidence of vertical migrations during shell growth of G. bulloides and N. incompta. This information about the distribution of modern planktic foraminifera will facilitate reconstruction of past oceanographic conditions based on geochemical proxies in the subarctic Pacific. (C) 2016 Elsevier B.V. All rights reserved.
  • Shinya Iwasaki, Mayuri Inoue, Atsushi Suzuki, Osamu Sasaki, Harumasa Kano, Akira Iguchi, Kazuhiko Sakai, Hodaka Kawahata
    GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS 17 (9) 3629 - 3637 2016/09 
    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.
  • Shinya Iwasaki, Kozo Takahashi, Yoshiyuki Kanematsu, Hirofumi Asahi, Jonaotaro Onodera, A. C. Ravelo
    DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 125 145 - 154 0967-0645 2016/03 
    Site U1341 in the southern Bering Sea was drilled and cored down to 600 meters below sea-floor (mbsf) during Integrated Ocean Drilling Program (IODP) Expedition 323, covering a nearly complete record of the last 4.3 million years (Myrs). Analyses of the biogenic opal content of sediments at the site provide detailed and useful information on past biological productivity and paleoceanographic changes that occurred in the region including shifts in the oceanographic condition during the intensification of the Northern Hemisphere Glaciation (NHG) and the Mid-Pleistocene Transition (MPT). An overall decreasing trend in the %biogenic opal record, combined with evidence from microfossil assemblages, indicates a gradual shift in environmental conditions during the last 4.3 Myrs, from warm and nutrient-rich conditions to cool conditions with sea-ice. On the other hand, biogenic opal mass accumulation rates (MAR) were high during 2.6-2.1 Ma after the intensification of the NHG, unlike in the western North Pacific. High biological productivity during this specific interval is consistent with the results of previous studies in the other Marginal Seas, possibly suggesting that iron leakage from the Bering Continental Shelf occurred. After the MPT, the data suggest that there was sea-ice expansion and discharge of lithogenic matter during glacial periods, and high productivity during interglacial periods. (C) 2015 Elsevier Ltd. All rights reserved.
  • Shinya Iwasaki, Katsunori Kimoto, Osamu Sasaki, Harumasa Kano, Makio C. Honda, Yusuke Okazaki
    PALEOCEANOGRAPHY 30 (4) 317 - 331 0883-8305 2015/04 
    We performed a 9 day dissolution experiment with tests of the planktic foraminifer Globigerina bulloides at pH 6.70.1 in water undersaturated with respect to calcite. The initial stage of the dissolution process, which is not recognizable from the surface structure of the tests, was quantitatively evaluated by X-ray microcomputed tomography (XMCT). XMCT revealed three distinct test structures: early-developed calcite formed during the juvenile stage of G. bulloides, an inner calcite layer, and an outer calcite layer. The test ultrastructure was observed by scanning electron microscopy, and CT number evaluated the density distribution in the test. The early-developed calcite and inner calcite layer had low CT numbers (500-1300; low density, porous) and were sensitive to dissolution, whereas the outer calcite layer had high CT numbers (<1300; high density) and resisted dissolution. Both the modes and the frequencies of the CT numbers decreased with progress of dissolution. Changes in the CT number histogram with progress of dissolution were quantified in terms of the percentage of calcite volume accounted for by low-density calcite (%Low-CT-number calcite). A clear linear relationship (R-2=0.87) between %Low-CT-number calcite and %Test weight loss was found. This relationship indicates that the amount of test dissolution can be estimated from the distribution of CT numbers. We propose that XMCT measurements will be useful for quantitatively estimating the amount of carbonate loss from foraminiferal tests by dissolution.
  • Shinya Iwasaki, Kozo Takahashi, Yusuke Ogawa, Seiichiro Uehara, Christoph Vogt
    JOURNAL OF OCEANOGRAPHY 70 (3) 241 - 249 0916-8370 2014/06 
    Accurate knowledge of the extent of biogenic opal preservation in marine sediment cores is important for paleoceanographic reconstructions. The alkaline leaching method is widely employed for %biogenic opal analysis due to its ease and speed. In this study, a revised method for measuring %biogenic opal in sediment from arctic coring expedition samples was suggested. The studied middle Eocene sediments from the central Arctic Ocean presented a problem in insufficiently leaching biogenic opal with a Na2CO3 solution. Based on XRD analysis, it was suggested that such an alkaline resistance results from slight diagenesis of biogenic opal. In order to solve this problem, an alkaline leaching method utilizing a 2 M NaOH solution was suggested for the accurate measurement of %biogenic opal in the Eocene sediments from the central Arctic. Furthermore, dissolution rates from lithogenic matter by NaOH solution were measured in order to correct the %biogenic opal values.
  • Shinya Iwasaki, Kozo Takahashi, Takuya Maesawa, Tatsuhiko Sakamoto, Saburo Sakai, Koichi Iijima
    DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 61-64 50 - 62 0967-0645 2012/02 
    Analyses of geochemical constituents (organic carbon, nitrogen, calcium carbonate, and biogenic opal) on Core YK07-12 PC3B (Core PC3B) provided detailed and useful information in biological productivity and paleoceanographic changes, which occurred in the central Okhotsk Sea during the last 500 kyrs. An age model for Core PC3B was established based on changes in benthic foraminiferal delta O-18. The trend in organic carbon (OC) content represented the temporal change that can be correlated with the delta O-18 curve in Core PC3B: high during the interglacial periods: MIS 1, 5, 9, 11, and 13. The trend in CaCO3 content represented is similar to the trend seen in the OC content. The high correlation between OC and CaCO3 contents indicates an increase in coccolithophorid productivity during the early deglaciations. The comparison between the changes in CaCO3 and biogenic opal indicates that the dominant phytoplankton group was coccolithophorids during the early deglaciations, which was subsequently replaced by diatoms during the late deglaciations. It appears that such a temporal phytoplankton succession was caused by an increase in dissolved silicon supply to the euphotic layer, possibly associated with a change in surface hydrography that subsequently caused an upward expansion of the intermediate layer. Such ecological changes probably played an important role in the uptake of atmospheric CO2. (C) 2011 Elsevier Ltd. All rights reserved.

Research Projects

  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2018/04 -2022/03 
    Author : 鈴木 淳, 千徳 明日香, 新垣 誠司, 林 正裕, 天野 敦子, 垣田 浩孝, 井口 亮, 石村 豊穂, 岩崎 晋弥, 大野 良和
     
    研究計画3年目に相当する期間については、サンゴ骨格成長量についての3次元計測の実現に向けた検討を継続した。X線CTスキャン画像によるハマサンゴ年輪の三次元構造の把握を目的とした。同一成長輪を追跡・対比して、1年分の成長量を群体全体で積分すれば、1年間の成長量が計測できる。さらに、密度情報を付加することができれば、群体全体での石灰化量（例えば1群体あたりのgCaCO3 y-1）を求めることができる。これにより、現在進行中の海洋酸性化トレンドに対応したサンゴの石灰化量の変化を検討することが本研究課題の目的の一つである。琉球大学熱帯生物圏研究センター瀬底研究施設（沖縄県本部町）及び海洋生物環境研究所実証試験場（新潟県柏崎市）にて、高精度二酸化炭素濃度調整海水生成装置（いわゆるAICAL装置）を用いた海洋酸性化実験を実施してきた。これら過年度の各種環境制御飼育実験によって得られた各種のサンゴ群体について、X線CT分析データの蓄積を進めた。群体表面が部分的に斃死したと判定される部分については、サンゴ白化現象により、ポリプが斃死し骨格成長が停止した可能性があるため、注意して観察を実施した。また、琉球列島及びフィリピン（ルソン島南東端部）、インドネシア（ジャワ島北西部セリブ諸島）から採取された100年間以上の長尺試料について、酸素同位体比及びSr/Ca比の分析を進め、今後サンゴ骨格成長量についての3次元計測の対象となる試料の拡充を図った。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2018/04 -2021/03 
    Author : Nagashima Kana
     
    To examine the westerlies changes before and after the onset of global warming and to assess background variability, we reconstructed past westerlies changes of both hemispheres during the last ca. eight hundred years using marine sediment cores obtained from the upper continental slope of southern Chile and lake sediment cores derived from Lake Suigetsu and Onuma, Japan. The deposition flux of Asian dust in Lake Suigetsu sediments suggests a relatively stable westerly jet path after the onset of global warming. In contrast, detrital material fluxes and provenance of marine sediments derived from the continental slope of southern Chile suggest a poleward shift of the southern westerlies since the late 1800s, especially during the late 1900s.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Early-Career Scientists
    Date (from‐to) : 2018/04 -2020/03 
    Author : 岩崎 晋弥
     
    本研究はマイクロフォーカスX線CTスキャナによる浮遊性有孔虫の殻溶解測定を用いて、南大洋における最終氷期以降の深層水炭酸イオン濃度変動を定量的に復元し、大気二酸化炭素濃度の急激な上昇に重要な役割を果たしたと考えられている南大洋（太平洋セクター）における海洋炭素循環メカニズムの解明を目的としている。そのために令和元年度は、前年度に引き続き、南大洋チリ沖における深層水炭酸イオン濃度変動の復元に取り組んだ。具体的な研究内容としては、チリ沿岸域で採取された3本のピストンコア試料（MR16-09_leg.2航海で採取）を利用し、所属研究機関が所有するマイクロフォーカスX線CTスキャナによる浮遊性有孔虫の殻溶解指標の測定を通して、最終氷期極大期以降の深層水炭酸イオン濃度変動を定量的に復元した。その結果、水深2787 mのピストンコアにおいて最終氷期極大期（19,000年前）から最終退氷期（16,000年前）にかけて、炭酸イオン濃度が著しく低下するイベントを発見した。この変動は、大気中への二酸化炭素の放出域である南大洋において、従来の理解よりも複雑な海洋炭素循メカニズムが存在していたことを示唆している。この研究成果を令和元年11月に産業技術総合研究所（茨城県つくば市）で開催された2019年度地球環境史学会において発表した他、その内容をまとめた筆頭論文を近く国際誌に投稿する予定である。また2019年度はマイクロフォーカスX線CTスキャナによる有孔虫殻密度測定の古海洋研究指標としての重要性を示す研究成果として筆頭論文を2本、国際誌（Scientific ReportsおよびGeophysics Geochemistry Geosystems）に掲載するなど、本研究の成果公表に重点をおいて研究活動を行なった。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for JSPS Fellows
    Date (from‐to) : 2017/04 -2020/03 
    Author : 岩崎 晋弥
     
    本研究は、過去に大気中の二酸化炭素濃度が上昇し、海洋表層の酸性化が進行した「最終退氷期」に着目し、酸性化が浮遊性有孔虫の骨格形成にどのような影響を与えたのかを復元することを目的としている。本研究の目的を達成するためには堆積物中の有孔虫化石から酸性化影響を読み解く指標が必要であるが、従来の研究で利用されてきた殻重量指標は有孔虫の死後、溶解によって指標が歪められるため、海洋酸性化影響の定量的な評価が不可能であった。そこで本研究はマイクロフォーカスX線CTスキャナ（以下MXCT）を利用した有孔虫殻密度測定を新たに導入し、浮遊性有孔虫が殻形成時に受ける影響と、死後の溶解による影響を切り分けて評価する手法の実用化に取り組んでいる。令和元年度は、MR14-06航海で北太平洋亜寒帯域において採取したプランクトンネット試料中の現生浮遊性有孔虫および北太平洋西部で採取した海底表層堆積物中の浮遊性有孔虫化石の殻密度測定をMXCTを用いて実施し、そのデータ解析を行った。またMR16-09航海において南大洋チリ沖で採取したピストンコア試料についてMXCTによる有孔虫殻密度測定を実施し、最終氷期極大期以降の浮遊性有孔虫の殻密度変動を世界で初めて定量的に復元した。上記の研究成果を公表するために筆頭論文を2本国際誌に掲載したほか、国内の学会において成果発表を行った。さらに、今後の研究の発展を見据えて、南大洋で実施された国際深海科学掘削計画（IODP Exp.383航海）に参加し、より古い年代まで遡ることが可能な堆積物コア試料の採取を行った。
  • 日本学術振興会：科学研究費助成事業 特別研究員奨励費
    Date (from‐to) : 2013/04 -2015/03 
    Author : 岩崎 晋弥
     
    本研究は最終氷期に大気二酸化炭素濃度低下分の炭素が海洋深層に貯蔵されていたことを証明するため、有孔虫殻の溶解量を利用して深層水炭酸イオン濃度を定量的に復元することを目標としている。従来の研究で利用されてきた有孔虫殻の溶解指標である殻重量や殻破片率には溶解量を定量的に測定できないという問題があり、深層水炭酸イオン濃度の定量的復元は不可能であった。そこで本研究は東北大学総合学術博物館に設置されたマイクロフォーカスX線CTスキャナ（以下MXCT）による殻密度測定を有孔虫殻の定量的な溶解指標として提案した。MXCTによる有孔虫殻密度測定を溶解指標として利用した研究はJohnstone et al, 2010, Marine Micropaleontology, 77.を除いて前例がない。また、有孔虫の殻密度や殻内部構造が溶解にともなってどのように変化するのかという基本的な理解が不足していた。そこで本研究はまず「MXCTによる有孔虫殻内部構造の観察と殻密度分布の解明」および「炭酸塩に不飽和な環境における有孔虫殻の溶解プロセスの解明」という二つの課題に取り組んだ。その結果、かつてない程詳細な浮遊性有孔虫殻の溶解プロセスが明らかになり、さらにMXCTを用いた測定により殻溶解量の定量化が可能であることを示した。この成果は論文にまとめられ、国際誌Plaeoceanographyに掲載される予定である。また本研究の最終的な目標である深層水炭酸イオン濃度復元のため、海底堆積物中に保存された浮遊性有孔虫殻について新手法を用いた溶解量測定を実施した。その結果、堆積物中の有孔虫殻溶解量と深層水炭酸イオン濃度との間には優位な相関関係はみられなかった。そのため今後の研究の展開においては「堆積物中における浮遊性有孔虫殻溶解メカニズムの解明」が課題になると考えられる。

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