2003 Fiscal Year Final Research Report Summary
Restoration of an ecosystem in the eutrophicated shallow estuary -dynamics of environments and benthic fauna at the experimental artificial tidal flat-
| Project/Area Number |
12480167
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
環境保全
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| Research Institution | Osaka City University |
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Principal Investigator |
YAMOCHI Susumu Osaka City University, Graduate school of engineering, Urban engineering, Professor, 大学院・工学研究科・都市系専攻, 教授 (30315973)
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| Co-Investigator(Kenkyū-buntansha) |
EGUCHI Mitsuru Kinki Univ., Faculty of agriculture, Fisheries, Professor, 農学部・水産学科, 教授 (40176764)
SHIGEMATU Takaaki Osaka City University, Graduate school of engineering, Urban engineering, Assoc.professor, 大学院・工学研究科・都市系専攻, 助教授 (80206086)
ODA Kazuki Osaka City University, Graduate school of engineering, Former professor, 大学院・工学研究科・都市系専攻, 前教授 (60047230)
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| Project Period (FY) |
2000 – 2003
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| Keywords | Artificial tidal flat / Budget of nitrogen / Optimum depth |
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| Research Abstract |
Benthic fauna and budgets of materials such as nitrogen, suspended solids and chlorophyll a were studied from June 2000 to September 2003 at the north pond of Nanko Bird Sanctuary and at an artificial tidal flat of Hannan Second District, Osaka Bay, Japan. Species and numbers od benthic organisms increased with time course at the artificial tidal flat of Hannan Second District, and its fauna became equivalent or rich compared to other artificial and/or natural tidal flats of the eutrphicated estuary of Japan. At the north pond of Nanko Bird Sanctuary, the output of suspended solids to coastal water exceeded its input to the pond, while chlorophyll a was intercepted within the pond through the tidal exchange. Dissolved inorganic nitrogen imported into the pond was temporally incorporated into the biomass and was then exported in the form of dissolved organic nitrogen. Particulate nitrogen was abundant as a resource of nitrogenous nutrients to coastal water in the summer of 2001. These phenomena are thought to be correlated with biological activities such as feeding, fixation and decomposition by benthic animals, seaweeds and microalgae. At the young artificial tidal flat, Hannan Second District, the net exchange of nitrogen significantly changed between 2000 and 2003. In September 2000 only five months after its construction, nitrogen was released from the artificial tidal flat to the adjacent waters at a rate of 5.39 kg N/day. In contrast, the artificial tidal flat functioned as a site of sink for nitrogen in relation to the growth of seaweeds in September of 2001 and 2002, but played as a source of nitrogen in accordance with seaweed decrese in October 2003. As a result, nitrogen uptake by the dominant species of seaweeds in Septembers 2001 and 2002 reached 4.8 and 3.3 kgN/day which accounted for 102 and 92% of the total nitrogen fixed at the artificial tidal flat within one day.
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