Author(s): Yuji Toda; Tetsuro Tsujimoto; Noriomi Fujimori
Linked Author(s): Yuji Toda
Keywords: Periphyton; Sand river; Primary production; River discharge
Abstract: Periphyton is known to be one of major primary producer for river ecosystem, and it develops the bio-film type communities on solid surface submerged into water. While the growth of periphyton usually observed on the stone surface in gravel river, the large growth of periphyton is sometimes seen even in sand river with relatively small river discharge. In the present study, field observations and numerical simulations were performed to know the growth of periphyton in sand river. In the field observation, the growth of periphyton on fixed sand bed was measured weekly. The results of the field observations show that the large growth of periphyton occurs in sand river until the bed material sands have not moved. It was also found that the growth of periphyton is not affected by the gain size of bed material sands as long as the sands have not moved. An integrated numerical simulation model is presented to describe the growth of periphyton at observed river reach, and the series of numerical simulations were performed to know the effect of river discharge on growth of periphyton in the sand river. The results of the numerical simulations show that the net primary production of periphyton decrease with the river discharge, and that approximately becomes 0 at the observed reach for the case that the increased river discharge is about 30 m3/s. These results suggest that the reduction of river discharge at ordinary water stage strongly affects the primary productivity of periphyton even in sand river, and excess intake of river water may induce the increase of primary production of periphyton in sand river.
Year: 2005