人工基盤上における河川付着藻類相の付着状況に関する現地実験

抄録

In the upper Chikugo River, the so-called "Ohyama River," decrease of the flow rate due to intake to hydroelectric power stations by dams has made the riverine environment worse. Thus, it is necessary to decide an appropriate flow condition as a maintenance discharge to improve it. In this study, we attempted to confirm availability of artificial substrata instead of natural stones for sampling of attached algae in order to reduce arbitrariness with natural stones. In May-June 2009, we carried out weekly sampling of attached algae on both natural and artificial stones which we installed at three sampling sites. As a result of the present research, we clarified the followings: 1) Less biomass of algae (chlorophyll-a) can attach on artificial stones than on natural stones, because shear stress can readily obstruct the growth due to their flat shapes; 2) judging from amount of sediment trapped into attached algae and identifying species of algae, their adherence patterns and species on natural stones and artificial ones are not significantly different; 3) attached algae which contain biofilm and bacterium tend to show larger δ¹³C; and 4) artificial stones can assimilate into natural stones by installing for more than 2 weeks.