1995 Fiscal Year Final Research Report Summary
Environmental change and biogeochemical cycle in coral reef ecosystems
| Project/Area Number |
05404077
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
Environmental dynamic analysis
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| Research Institution | The University of Tokyo |
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Principal Investigator |
YONEKURA Nobuyuki The University of Tokyo, Graduate Schoolo of Science, Professor, 大学院・理学系研究所, 教授 (30011563)
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| Co-Investigator(Kenkyū-buntansha) |
ISHII Teruaki The University of Tokyo, Ocean Research Institute, Associate Professor, 海洋研究所, 助教授 (80111582)
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, Associate Professor, 大学院・理学系研究所, 助教授 (60192548)
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| Project Period (FY) |
1993 – 1995
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| Keywords | coral reefs / biogeochemical cycle / environmental change / Ishikaki Island / Ryukyu Islands |
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| Research Abstract |
Caral reefs are one of the dominant coastal landforms in tropical and subtropical seas and are known as an ecosysytem with high productivity and biological diversity surrounded by oligotrophic waters. The objects of this research are to understand the mechanism of high productivity and biological diversity of coral reef ecosystems and to know the response of coral reefs to environmental changes. For these purposes, we have investigated the processes and physical conditions of the formation of coral reef landforms and biogeochemical cycles in coral reef ecosysytems. We have investigated in coral reefs located at Kabira and Shiraho along the northern and eastern coasts, respectively, of Ishigaki Island, Ryukyu arc. The main results can be summarized in the following.
(1) Present coral reefs in Kabira represent a zonal distribution of landforms and biological communities from land to sea. The zonation of landforms is arranged as sandy beach, shallow moat, reef pavement, reef crest and reef front from land to sea. The zonation of biological communities is as follows : massive Porites in the moat, small patches of branching Montipora in the moat near reef crest, large patches of branching montipora on reef pavement and robust Acropora on reef edge. (2) The zonal distribution of biological communities in coral reefs is mainly controlled by both landforms of coral reefs and physical conditions such as the direction and velocity of water flows in the coral reefs. The northern wind is dominant in Ishigaki Island throughout the year, and the direction and velocity distribution of water flows in the coral reefs are mainly in fluenced by the dominant northern wind. (3) We have measured the rate of nitrogen fixation by blue-green algae to evaluate the importance of N fixation in coral reef ecosystems. The results suggested that the ability of N fixation by blue-green algae is high enough for contributing the uptake of new nitrogen in coral reef ecosystems.
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