On the Relation between the Benthic Fauna and Water Quality in the Iseri River, Kumamoto City

Benthic fauna have frequently been used to assess the impact of domestic and industrial waste discharge on receiving water. The primary object of this study was to give an accurate assessment of the water quality on the basis of Benthic fauna in the Iseri River, Kumamoto City. The drainage basin of this river is occupied by farmland at its upper stream and an urban area at its lower one.Water samples were collected monthly at six stations along the river, month by month from November of 1975 to October of 1977, and some chemical properties (DO%, MPN, COD, BOD, NH3-N, Cl-, Na+, Ca2+, SO42-, 4.3Bx, T-Re) were analysed. Benthic faunae were sampled quarterly from 1976 to 1977, with two samples collected at each station by a server net.Chemical properties of water samples at the lower stream were clearly different from those at the upper one, reflecting the influence of the wastewater effluents. Also, species composition of benthic animals showed a similar trend.A statistically significant correlation was observed between some chemical parameters and biological indices, such as species diversity and pollution index.