[ACG55-P02] Effects of the inflow of hot spring drainage into rivers in Beppu City, Oita Prefecture on benthos in the estuary area.
Keywords:hot spring drainage, benthos, estuary area
The survey was conducted in the non-tidal and tidal areas of major two rivers in Beppu City, Oita Prefecture. One is the Hirata River where hot spring drainage flows in. The other is the Hiyakawa River where hot spring drainage does not flow in among major rivers in. Ten areas of a 1-meter square at each point were randomly set and living things within those areas were collected using hand nets. After that, the samples were fixed with alcohol and brought back to the laboratory to identify the species of the benthos (crustaceans and shellfish).
Shrimps are often found in the Hirata River, especially a lot of Palaemon serrifer in the tidal area. On the other hand, Crabby was very common in the Hiyakawa River, especially in the non-tidal area. For shellfish, there is a big difference in Clithon retropictus and that was very common in the Hiyakawa River, especially in the non-tidal area. We found that Semisulcospira libertina libertina is common in the Hiyakawa River and Melanoides tuberculate Muller is common in the Hirata River.
Focusing on the results of shellfish observations, Melanoides tuberculate Muller lived in more places in the Hirata River, where hot spring drainage flows than in the Hiyakawa River. Melanoides tuberculate Muller is a hot drainage liking species known to be common in rivers with high water temperatures. From this habitat condition, we suggest that the effects of the drainage of the hot spring water may be exerted on benthos as well as on exogenous fish such as tilapia, which was previously studied.