The change of epilithic diatom assemblages on the river bed of the River Kakehashi-gawa in Ishikawa prefecture caused by the construction of Akaze Dam.

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Diatom assemblages were surveyed on the river bed for seven years (from October, 1974, just before Akaze Dam construction started to November, 1980, just after its completion) at five stations on the main stream of the River Kakehashi-gawa. The change of periphyton communities was investigated using epilithic diatom assemblages as bilogical indicators. The results of our research are as follows.<BR>During and after construction work, the ignition loss decreased (Figs. 2, 3) reflecting the reduction in standing crops of microorganisms after completion of construction. On the other hand, the ratio of ignition loss to ignition residence increased especially in the springtime. This fact clearly shows that the amount of silt settling on the river bed decreased after construction project.<BR>Ninety-five taxa belonging to twenty-seven genera were identified in this survey. The change of water quality in the downstream area of the River Kakehashi-gawa after the completion of Akaze Dam, caused the decrease of the standing crops of microorganisms, but did not affect the specific composition of the diatom assemblages to any significant degree. In autumn, however, the similarities became close between diatom assemblages in attached materials on the river bed of the downstream stations. This is presumably caused by increase of the water being discharged from the dam in order to control the flood.
日本陸水学会の論文