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The Science Bulletin of the Faculty of Agriculture. University of the Ryukyus >
No.44 (1997/12) >

 
Title :マングローブ群落の潮の干満に伴う泡やコロイド状浮遊物および表層堆積物の特徴
Title alternative :Characterization of the foam and the colloidal floating materials transported by the ebb and flow of the tide and the surface sediments in the mangrove forest
Authors :渡嘉敷, 義浩
金城, 民明
佐藤, 一紘
志茂, 守孝
Authors alternative :Tokashiki, Yoshihiro
Kinjyo, Tamiaki
Sato, Kazuhiro
Shimo, Moritaka
Issue Date :1-Dec-1997
Abstract :潮の干満の影響を受ける入り江や河口付近のマングローブ群落は, 水産資源の涵養, 環境保全や国土保全, 生物生産等に大きな機能的役割を果すと考えられる。しかし, 上げ潮や下げ潮時にマングローブ群落内を流入・流出・移動し, 表層堆積物の形成に関わるコロイド状浮遊物の特性や動態等については不明なことが多い。ここでは, 石垣島の吹通川流域のマングローブ群落を選定し, 潮の干満前後や昼夜間における表層堆積物およびコロイド状浮遊物の特徴を調べた。潮の干満に伴う水中浮遊物は, 河口付近ほど海浜由来, 中流や上流付近ほど陸地由来の粒子類の多い傾向を示した。また, それらの浮遊物は流水路より群落内部ほど粒径が細かく, 腐植含量も高い特徴を示した。潮の干満前後の表層堆積物は, 表面に薄い粘土皮膜が形成され, 河川の縁より群落内部ほど粒径が粗く, CaCO_3含量, あられ石や方解石の含量も多い特徴を示した。それらの腐植含量は群落の縁で最も高く, 夜間より昼間に高い特徴を示した。表層堆積物周辺の浮遊物は, 腐植含量が群落内部で最も高く, 群落の縁, 河川の縁の順に少ない傾向の他, 昼間より夜間に若干高い傾向を示した。上げ潮時の表層堆積物表面の泡と下げ潮時の水面浮遊物では, 腐植含量が後者で著しく高く, いずれも夜間より昼間に高い特徴を示した。これらのことから, 昼間や群落内部では表層堆積物中や周辺の生物活動が活発で, それらに由来する有機物(腐植)の増加が示唆された。そして, 群落の縁付近に多い有機物(腐植)は, 水中や群落中の浮遊物が潮の干満に伴って流入・流出・移動・堆積する過程に大きな影響を及ぼすことが示唆された。
It is known that mangrove swamp and forest play an important role in the conservation of national land, the preservation of environment and ecosystem in coastal area. There was few information on a characteristic of the colloidal floating materials regarding to a formation of the surface sediment in mangrove forest. The purposes of this investigation were to characterize of the foam on flood tide, the colloidal floating materials on ebb tide and the surface sediment in each of the day- and night-time in mangrove forest around Fukito river at Ishigaki island. As for the floating materials transported by the ebb and flow of the tide, there was a tendency that origin of the sediment in nearby the river mouth differed with the sediment in nearby the mid- and upper-stream of the river. The floating materials were finer in particle size and higher in humus content in the mangrove forest than in the river, respectively. The results showed that the surface sediment at before and after the ebb and flow of the tide were characterized with a formation of clay film on the sediment, the particle size was coarser and the contents of inorganic carbon, aragonite and calcite minerals were higher in the inside of the mangrove forest in comparison with the edge of the river. The humus content of the surface sediments was highest at the edge of the mangrove forest nearby the river and higher in the day- than night-time. The floating materials nearby the surface sediments were highest in the inside of the mangrove forest decreasing in order of the edge of the river from the edge of the mangrove forest and slightly higher in the night- than day- time. As for the foam on flood tide and the colloidal floating materials on ebb tide, humus content of the latter was remarkable higher than the former, and both humus content were higher in the day- than night-time. According to the results, it was suggested that living of the organisms nearby the surface sediment were active in the day-time and in the inside of the mangrove forest, and organic matter was increased by the activities of the organisms. It was also suggested that a lot of organic matter at the edge of the mangrove forest have a great influences on the transportation and sedimentation processes of the colloidal floating materials transported by the ebb and flow of the tide in the mangrove forest.
Type Local :紀要論文
ISSN :0370-4246
Publisher :琉球大学農学部
URI :http://hdl.handle.net/20.500.12000/3716
Citation :琉球大学農学部学術報告 = The Science Bulletin of the Faculty of Agriculture. University of the Ryukyus no.44 p.281 -290
Appears in Collections:No.44 (1997/12)

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