Abstract
The large quantity of river benthic community data, which were aggregated by the Ministry of the Environment (MOE) and the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) of Japan, were examined to evaluate river environments from the viewpoint of biodiversity. A set of biodiversity indicator taxa was proposed and validated using the MLIT data. Next, a biodiversity classification index was created by dividing the data into 4 classes according to the distribution of the number of indicator taxa collected in the MOE surveillance. This enabled the evaluation of the health of the sampling site using the MOE-water quality and biodiversity classes. It became apparent that the two evaluation indices were not completely dependent variables, although they had an effect on each other at some level. The relationships between certain conditions of the river environment and the two evaluation indices were also analyzed, which revealed that biodiversity cannot be evaluated using BOD values or riverbed morphology. Moreover, it was found that the sampling site condition tended to deteriorate as the BOD value increased and as the size of the riverbed material decreased. Consequently, basic and valuable information to conserve the river environment was obtained.
