| Project/Area Number |
08408004
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
自然地理学
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| Research Institution | The University of Tokyo |
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Principal Investigator |
YONEKURA Nobuyuki The University of Tokyo, Graduate School of Science, Department of Geography, Professor, 大学院・理学系研究科, 教授 (30011563)
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| Co-Investigator(Kenkyū-buntansha) |
KOIKE Isao The University of Tokyo, Ocean Research Institute, Professor, 海洋研究所, 教授 (30107453)
KAYANNE Hajime The University of Tokyo, Graduate School of Science, Department of Geography, As, 大学院・理学系研究科, 助教授 (60192548)
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| Project Period (FY) |
1996 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥14,400,000 (Direct Cost: ¥14,400,000)
Fiscal Year 1998: ¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 1997: ¥5,000,000 (Direct Cost: ¥5,000,000)
Fiscal Year 1996: ¥6,700,000 (Direct Cost: ¥6,700,000)
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| Keywords | coral reefs / biogeochemical cycle / Kabira Reef / Ishigaki Island / Ryukyu Islands / Holocene / sea-level change / foraminifera / 界面変化 |
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| Research Abstract |
Investigations on the landform formation and biogeochemical cycle have been conducted mainly on coral reefs of Ishigaki Island and Kikai Island, Ryukyu Islands. Main results are summarized in the following.
(1)Landform structure, distribution of corals and related Caroline algae, movements of seawater on coral reefs have been investigated in Kabira Reefs, Ishigaki Island. Boring operation has been conducted on coral reefs in Kabira Reefs and collected samples have been sedimentologically analyzed and dated by carbon-14 age measurements.
(2)Sediment distribution and distribution of corals on Kabira Reefs are well controlled by the seawater movements on the reefs, in particular by strong movements associated with typhoons.
(3)Reef crest of Kabira Reef have been formed along with Holocene sea-level rise and caught up to the sea-level around 4000 years ago. Reef crest was emerged slightly around 2000 years ago and the production of benthic foraminifera on the reef crest increased since then. Shallow moat behind the reef crest has been buried by coral fragments and bioclusts. The portion of foraminifera fossils in the sediments of moat increased since the emergence of the reef crest.
(4)Bathymetric measurements have been conducted along the offshore of Kikai Island to investigate the submarine landforms of island shelf and the age of submarine landforms was estimated on the basis of global curves of post-glacial sea-level rise
(5)Annual bands of coral colonies of Holocene ages collected from Kikai Island were analyzed by dO18 measurements and the temperature of seawater around 6000 years ago was estimated at lower than the present.
(6)To evaluate net C02 flux on coral reefs, continuous monitoring system for pCO2, total alkalinity and total inorganic carbon in the reef water have been developed. Partial pressure of seawater C02 shows a definite pattern of diumal changes from 100 to 700 ppm and the values are high during the daytime and low at night.
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