GEOMORPHIC HETEROGENEITY IN COBBLE-BED ENVIRONMENT AND ITS EFFECT ON BENTHIC MACROINVERTEBRATE ASSEMBLAGE WITH PARTICULAR REFERENCE TO WATARSHED GEOLOGY

Abstract

Geology is one of the crucial components for defining riverbed materials and textures, which might effects on their aquatic communities. In this study, the Kushida River basin, central Japan, composed of different geologic units such as plutonic, metamorphic, and sedimentary terrains, was selected to clarify the relationships between riverbed textures and benthic micro invertebrates.

Field surveys were conducted at riffle units in each of the three stations (the main stem and its two tributaries with the watershed geological differences) and also control experiments in the main stem station with the ex-closures replacing their beds with the cleaned sediment in other two stations. Some of the statistical analyses could indicated that there were strong relationships among the watershed geologies, the physical characteristics of cobble-bed textures and the features of species and life type compositions of benthic micro invertebrates.