Sclerosponge as archive of pCO2 in the past oceans

2019 Fiscal Year Annual Research Report

• Project/Area Number: 17K17669
• Research Institution: The University of Tokyo
• Principal Investigator: 田中 健太郎 東京大学, 大気海洋研究所, 特任研究員 (20792766)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 古環境 / 炭酸カルシウム / 海洋酸性化 / 硬骨海綿

Outline of Annual Research Achievements

本研究では過去の海洋のpHと二酸化炭素分圧(pCO2)の推定を目的とし，硬骨海綿骨格のホウ素同位体比およびホウ素濃度を測定した．また，人為起源の炭素が海洋に溶け込んだ痕跡を明らかにするため骨格の炭素同位体比の測定も行った．
今年度は現世試料（沖縄県で採取されたAstrosclera willeyanaと鹿児島県から採取されたAcanthochaetetes wellsi）の成長方向に沿ってホウ素同位体比，ホウ素濃度，炭素同位体比を測定した．ホウ素同位体比は炭酸塩骨格が形成された時期のpHを記録することが知られている．A. willeyanaとA. wellsiのホウ素同位体比を使って推定されたpHはそれぞれ7.8-8.0, 8.2-8.3の範囲で変動した．本研究で分析した沖縄県の化石試料と現世試料を比較すると，過去から現在にかけてpHが低下した海洋酸性化の傾向を捉えることができた．また炭素同位体比の測定結果から，現世試料の成長方向に沿って炭素同位体比が減少する傾向が認められ，化石燃料の消費で生産された人為起源のCO2が海洋に吸収された痕跡が明らかとなった．LA-ICP-MSを使って沖縄県で採取された化石試料と現世試料のホウ素濃度を定量した．平均値（±SD）はそれぞれ0.222±0.067 mmol/molと0.204±0.070 mmol/molで，大きな変化は認められなかった．海洋のアルカリ度などの条件が7,000年前から現在にかけて一定だったと仮定し，pHを用いて海洋のpCO2を計算した．その結果，約 100年-7,000年前のpCO2は258±12 マイクロatmで，現代のpCO2は564±150 マイクロatmだった．

Research Products

• [Journal Article] Evidence in the Japan Sea of microdolomite mineralization within gas hydrate microbiomes (2020)
  • Author(s): Glen T. Snyder, Ryo Matsumoto, Yohey Suzuki, Mariko Kouduka, Yoshihiro Kakizaki, Naizhong Zhang, Hitoshi Tomaru, Yuji Sano, Naoto Takahata, Kentaro Tanaka, Stephen A. Bowden, Takumi Imajo
  • Journal Title: Scientific Report Volume: 10 Pages: 1876
  • DOI: https://doi.org/10.1038/s41598-020-58723-y
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Geochemical constraints on the depositional environment of the 1.84 Ga Embury Lake Formation, Flin Flon Belt (2020)
  • Author(s): Kento Motomura, Shoichi Kiyokawa, Minoru Ikehara, Kentaro Tanaka, Yuji Sano
  • Journal Title: Island Arc Volume: 29 Pages: e12343
  • DOI: https://doi: 10.1111/iar.12343
  • Peer Reviewed
• [Journal Article] A review of transgenerational effects of ocean acidification on marine bivalves and their implications for sclerochronology (2020)
  • Author(s): Liqiang Zhao, Kotaro Shirai, Kentaro Tanaka, Stefania Milano, Tomihiko Higuchi, Naoko Murakami-Sugihara, Eric O. Walliser, Feng Yang, Yuewen Deng, Bernd R. Schone
  • Journal Title: Estuarine, Coastal and Shelf Science Volume: 235 Pages: 106620
  • DOI: https://doi.org/10.1016/j.ecss.2020.106620
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Trace elemental alterations of bivalve shells following transgenerational exposure to ocean acidification: Implications for geographical traceability and environmental reconstruction (2020)
  • Author(s): Liqiang Zhao, Stefania Milano, Kentaro Tanaka, Jian Liang, Yuewen Deng, Feng Yang, Eric O. Walliser, Bernd R. Schone
  • Journal Title: Science of Total Environments Volume: 705 Pages: 135501
  • DOI: https://doi.org/10.1016/j.scitotenv.2019.135501
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Structural-morphological and sedimentary features of forearc slope off Miyagi, NE Japan: implications for development of forearc basins and plumbing systems (2020)
  • Author(s): Jih-Hsin Chang, Jin-Oh Park, Tzu-Ting Chen, Asuka Yamaguchi, Tetsuro Tsuru, Yuji Sano, Ho-Han Hsu, Kotaro Shirai, Takanori Kagoshima, Kentaro Tanaka, Chiori Tamura
  • Journal Title: Geo-Marine Letters Volume: 40 Pages: 209-324
  • DOI: https://doi.org/10.1007/s00367-020-00636-w
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] New insight into light-enhanced calcification in mytilid mussels, Mytilus sp., infected with photosynthetic algae Coccomyxa sp.: δ13C value and metabolic carbon record in shells (2019)
  • Author(s): Liqiang Zhao, Michael Zuykov, Kentaro Tanaka, Kotaro Shirai, Julia Anderson, Chris McKindsey, Yuewen Deng, Graeme Spiers, Michael Schindler
  • Journal Title: Journal of Experimental Marine Biology and Ecology Volume: 520 Pages: 151211
  • DOI: https://doi.org/10.1016/j.jembe.2019.151211
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Determination of the geographical origin of marine mussels (Mytilus spp.) using 143Nd/144Nd ratios (2019)
  • Author(s): Liqiang Zhao, Kentaro Tanaka, Naoko Murakami-Sugihara, Hirofumi Tazoe, Tsuyoshi Iizuka, Kotaro Shirai
  • Journal Title: Marine Environmental Research Volume: 148 Pages: 12-18
  • DOI: https://doi.org/10.1016/j.marenvres.2019.05.002
  • Peer Reviewed / Int'l Joint Research
• [Presentation] Sea surface pH over the last 7 kyr reconstructed by boron isotope ratio of sclerosponges (2019)
  • Author(s): K. TANAKA, K. SHIRAI, A. KITAMURA, R. SHINJO
  • Organizer: Goldschmidt2019
  • Int'l Joint Research
• [Presentation] 硬骨海綿を使った過去の海水pHの推定 (2019)
  • Author(s): 田中健太郎，白井厚太朗，北村晃寿，上野大輔 ，矢島健，佐々木猛智，新城竜一
  • Organizer: 日本サンゴ礁学会第22回大会