| Project/Area Number |
62540307
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
気象・海洋・陸水学
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| Research Institution | Tokai University |
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Principal Investigator |
MAZDA Yoshihiro Associate Prof., School of Marine Science and Technology, Tokai Univ., 海洋学部, 助教授 (80056100)
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| Co-Investigator(Kenkyū-buntansha) |
YOKOCHI Hiroyuki Lecturer, Institute of Oceanic Research & Development, Tokai Univ., 海洋研究所, 講師 (70119709)
SAWAMOTO Shozo Associate Prof., Institute of Oceanic Research & Development, Tokai Univ., 海洋研究所, 助教授 (90119678)
SATO Yoshio Lecturer, School of Marine Science and Technology, Tokai Univ., 海洋学部, 講師 (70056315)
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| Project Period (FY) |
1987 – 1988
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| Project Status |
Completed (Fiscal Year 1988)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1988: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1987: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | Mangrove swamp / Ecosystem / Sandy sill / Tidal circulation / Iriomote-jima / Benthic algae / Zooplankton / 嫌気状態 / sill(砂堆) / 浸透水 / クロロフィルの量 / マングローブ / 感潮河川 / シル地形 / 物質輸送 / 海水交換 / 化学物質の溶出 |
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| Research Abstract |
Hydrographical and physical effects the ecosystem of mangrove swamps were investigated at Bashita-minato and Ayanda-gawa, Iriomote-jima in summers of 1985 to 1988.
Many mangrove swamps have sills at their mouths. Open sea water passes over the sills into the bottom layer of the swamps at the flood tide, then upper layer water flows out at the following ebb tide ("Open type"). This water exchange is sometimes stopped owing to sand accumulation at the sills by waves and tide. In this case, the swamp water becomes stagnant and density strativication develops by strong solar radiation. The temperature at middle layer increases by the solar pond effect, and the extinction coefficient of irradiance of the water also increases ("Closed type").
These hydrographical and physical processes affect chemical properties and living organisms in the swamps, espedially in Bashita-minato, as follows; in case of the Open type: Abundance of phytoplankton varies fortnightly because of dilution with inflow of phytoplankton prro water from the open sea at the spring tide. Though heavy rain often turns the water into fresh, the water propety recovers within a few days by tidal exchange. Having euryhaline and eurythirmal characters, the benthic algae can survive such environmental flucuation. Zooplankters composed of invader, migrant and resident utilize the tidal water circualtion to maintain their populations. In case of the Closed type: Owing to a flow of seepage water through the sill, the water property of bottom layer varies with tide. However, in a day after the swamp is closed, the bottom water becomes anoxic, and nutrients, Fe(II) and H_2S are released from the mud. These lead to rapid decline of photosynthetic activity and consequential death of the algae. The invader and migrant zooplankters also die, while the resident may survive.
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