The growth of aquatic mosses attached to cobbles as a bed material in riffles was confirmed in a river in Japan. Covering bed material with aquatic mosses reduces the biomass of attached algae that is a source of energy for commercial fish. We sought to understand how aquatic mosses maintain coverage on the river bed in riffles from the viewpoint of response to flood disturbance. Resistance to disturbances due to water flow and sediment impingement on mosses was investigated with a laboratory

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... periment. We observed that intermediate impact seems to remove silt in the biofilm but that the majority of mosses maintain coverage. Based on visual inspection of moss cover following the experiment, we found that remaining moss consists of short fresh stems. In general, mosses seem well adapted to the high-speed flow environment typical in riffles.