ISE 2016* Interannual flood impact on aquatic plant cover in a gravel-bed river (#40)
The growth of submerged aquatic plants is one of the important components of the river ecosystem. In some rivers in Japan, endemic species of underwater aquatic plants are disappearing because of regulation of water flow and due to changes in water quality. Some invasive species, on the contrary, have become prominent in a number of river reaches, and the overgrowth of invasive species caused serious problems in river environment, fishery activity and so on.
Egeria densa is native in South America but has widely settled in other parts of the world. A large number of Egeria densa communities have settled in the Gono River system. We focused on the river reach of the Jyouge River downstream of Haizuka dam. The flushing discharge fusing the Haizuka dam was implemented in early spring every year. An amount of the aquatic plants in the reach downstream of the dam was reduced and removed aquatic plant body was transported downstream.In this study, a spatial distribution of the Egeria densa communities has been surveyed. The seasonal changes in the spatial distribution including the washing-out due to flood disturbance are analyzed using images recorded by the time-lapse cameras. An amount of the Egeria densa transported during the flushing discharge implementation was measured in 2015.
