| Project/Area Number |
16K05618
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Geochemistry/Cosmochemistry
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| Research Institution | The University of Tokyo |
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Principal Investigator |
Tajika Eiichi 東京大学, 大学院理学系研究科(理学部), 教授 (70251410)
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| Research Collaborator |
OZAKI Kazumi
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Project Status |
Completed (Fiscal Year 2018)
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| Budget Amount *help |
¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2018: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2017: ¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000)
Fiscal Year 2016: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
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| Keywords | 海洋生物化学循環 / 微生物代謝過程 / 酸化還元環境 / モデリング / 原生代 / 微生物代謝 / 海洋環境 |
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| Outline of Final Research Achievements |
We investigated characteristic features of marine biogeochemistry and microbial ecosystem under the anoxic condition during the Proterozoic, by developing a coupled model of marine biogeochemical cycle, marine microbial ecosystem, and atmospheric photochemistry. We found that, under anoxic condition, Fe-based photosynthetic bacteria must have played an important role in producing a large methane flux to the atmosphere, which affected climate under the faint young Sun condition on early Earth. We also found that marine primary productivity and the O2 production during the Proterozoic under the weakly oxygenated condition are estimated to be only 10-20% and 25% of the present values, respectively. The smaller O2 production may be consistent with the very low levels of O2 in the Proterozoic atmosphere.
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| Academic Significance and Societal Importance of the Research Achievements |
地球環境は，本来的に，大気・海洋・生命圏・固体地球等が互いに関連し合って成立しているが，そうした地球のシステム論的な理解はこれまできわめて限定的である．本研究は，生命圏を含む地球システムのモデリングによって，暗い太陽のパラドックスとして知られる初期地球環境の古典的問題の定量的な説明に初めて成功したほか，原生代の海洋基礎生産が現在の10％程度しかなかったことが当時の低酸素環境の一因であったことを初めて明らかにすることができた．こうしたシステム論的アプローチは，今後ますます重要となるはずであり，そのような方法論の開拓に本研究の学術的意義がある．
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