| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2005: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2004: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2003: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
Water quality and bottom sediment survey were carried out on Abashiri Lake, Aso sea, Uranouchi Bay, Notoro Lake and Nakaumi Lake and Shinji Lake in order to do this study problem. Features of the brackish environment are to be the environment where the top and bottom mixing is difficult to happen by the halocline. Therefore, the advection of water mass of bottom is mainly horizontally generated of the fresh water of the inflow side from the seaward. The bottom water mixes with the surface water, and it is discharged by the flow of the surface water. Inflow direction of surface water and bottom layer water is reverse-directional. Therefore, the weak mixing happens in the boundary of two flow. In addition, in the end of the water mass, the upwelling is generated by the river direction pushing in the tide, and the mixing becomes frequent. Therefore, the high production is maintained with the surface water by the mixture of bottom water of rich nutrient in Nakaumi Lake and Abashiri Lake, e
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tc.. Driving force of this bottom layer water circulation is water current from the river, mixed action by the wind, tide actions and so on. It continuously changes to the sediment of which only the reduced layer is seen from the sediment with thick oxidized layer in order to almost continuously shift to the end which shows absence of oxygen from entrance side which shows the environment where the bottom water is oxidative for such bottom water circulation for surface sediments. When it is considered at organic composition of the surface sediments, in entrance side which piles up in the environment where the organic substance is easy to be decomposed, the TOC contents is low. On the other hand, in end side which piles up in the environment where the organic substance is difficult to be decomposed, the TOC contents is high. In addition, the difference will be extremely possible for the TOC contents in entrance and end side of bottom water mass, since there is some the enhanced production layer near the halocline. Less
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