Effects of habitat heterogeneity on macroinvertebrate community structure at upstream and downstream of dams

Abstract

 We investigated the effect of habitat heterogeneity within river reaches on macroinvertebrate commu-nity structure at upstream and downstream reaches of dams in Miyagi Prefecture, Japan. We compared environmental conditions and macroinvertebrate community structures among four habitat types, i.e., lotic habitat, bar-head lentic habitat, bar-tail lentic habitat and isolated pond, in six river sites. There were sig-nificant differences in water quality, physical parameters and biomass of fine and coarse particulate organic matters among the lotic habitat and lentic habitat types. Spatial variation of spatial factors (dam upstream / downstream, habitat area, and lentic habitat score) and environmental factors (flow velocity and electrical conductivity) between habitat types explained 34% of the variation of macroinvertebrate community struc-ture. Although the lentic habitats had a small space in the river sites, it contributed highly to increasing habitat heterogeneity (β-diversity) within the sites. They also highly contributed to an increase in the overall diversity (γ-diversity) of the upstream and downstream sites of the dams. Our findings suggest that resto-ration of gravel bars to increase habitat heterogeneity in river through the formation of lentic habitats is important for the conservation of riverine ecosystems.