| Project/Area Number |
18510014
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Environmental dynamic analysis
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| Research Institution | Osaka City University |
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Principal Investigator |
YAMOCHI Susumu Osaka City University, Graduate School of Engineering, Professor (30315973)
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| Project Period (FY) |
2006 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥2,210,000 (Direct Cost: ¥2,000,000、Indirect Cost: ¥210,000)
Fiscal Year 2007: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2006: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | Artificial salt marsh / Green Tide / Artificial tidal flat / Nitrogen budget / Salinity Increase / Urban Area / Biomass / 人工塩性湿地 / ジュズモ / アオサ |
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| Research Abstract |
Field studies were carried out at the north and south ponds of Osaka Nanko Bird Sanctuary to clarify the distribution and transition of Chlorophycean seaweeds. Indoor experiments were also conducted to examine the tolerance to exposure to the air and low salinity. A green alga Ulva pertusa was abundant at the north pond, while Chaetomorpha sp. was densely populated at the south pond of Osaka Nanko Bird Sanctuary. Coexistences of Ulva pertusa and Chaetomorpha sp. were not observed except for small areas of the two ponds. These phenomena could partly be explained by the difference of exposure time to the air between the two ponds, along with a high tolerance to dry conditions in Ulva pertusa compared to Chaetomorpha sp.
At Osaka-Nanko Sakishima Canal, bottom waters exceeded surface ones in the concentration of dissolved oxygen in late spring. This phenomenon results from the active photosynthesis of a green alga, Chaetomorpha sp. on the bottom sediment. A marked decline in nutrient concentration was observed below 3m in depth near a sluice gate of the canal. The facts obtained here suggest that decreased water level of the canal, deepened mouth of the sluice gate, together with enhancement of water exchange are effective for the improvement of water quality and depression of algal blooms at the canal.
Nitrogen budgets and standing crops of the benthic organism at tidal flats and .salt marshes in and near Osaka Bay were compared. As the result, the net exchange of nitrogen markedly changed from a source to a sink within 2 or 3 years of construction due to the massive reproduction of benthic organisms at the young artificial tidal flat. The semi-natural tidal flat yielded a large quantity of bivalves and its nitrogen budget was well balanced compared to the artificial ones.
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