| "Bed load would be a factor to decrease primary production of epilithic algae in gravel bed streams through the disturbance of stream bed， the processes of the decrease， however， have not been recognized well. In this research， we examined how bed load decreased primary production based on large scale experiments and a numerical model. An experimental stream with bed load supply consisting of sand indicated lower primary production， same level of standing crops of epilithic algae(chl-a) and higher areal cover ratio of sand， compared with a experimental stream without bed load supply. Algal standing crop had been expected to be lowered by ""abrasion effect""， this result， however， showed that the increase of areal cover ratio of sand was thought to be a dominant process(cover effect) because instable materials were not suitable for epilithic algae. A numerical model to predict algal standing crop， in which primary production， abrasion and cover effect were incorporated into， showed that cover effect increased as the accrual of bed load， but abrasion effect could be weakened if resources for algal growth are abundant." |
