2011 Volume 9 Issue 4 Pages 381-389
The objective of this study was to assess the biological safety and river health in an actual river and to clarify their relationship. In this study, "biological safety" meant safety level of contaminants in river water to aquatic creatures, which was evaluated by performing various bioassays. "River health" meant conditions of water quality and biodiversity from a viewpoint of benthic macroinvertebrate assemblages, which was desired by humans. At nine sites on the Sakawa River system (Japan), biological safety was evaluated as a toxicity score and bio-safety rank (BSR) using an algae growth inhibition test, a daphnia immobilization test, and a larval medaka assay. According to the result, the biological safety was found to be completely different among the sampling sites and the test species. River health was evaluated according to the Ministry of the Environment (MOE) of Japan water quality and biodiversity (taxa number) at the nine sites. According to the result, the number of taxa were found to be completely different among the sites. The results of the bioassays and macroinvertebrate collections were compared and indicated that the number of taxa and BSR described similar behavior when going downstream, although no clear correlation was found between BSR and MOE-water quality class. Therefore, biodiversity tended to deteriorate as the intensity of toxicity became more severe.