Macroinvertebrate assemblages in channelized and unchannelized sections of the Bunyip River, Victoria

The macroinvertebrate fauna of channelized and unchannelized sections of the Bunyip River in southern Victoria was investigated. There were no significant differences in the physicochemical characteristics of the water between the two sections. The three sites in the channelized section were deeper and narrower than the three sites in the unchannelized section. Two of the sites in the channelized section had significantly lower mean particle size and the most stable substratum. The amount of detritus and amount of algae did not differ significantly between sites. There were no significant and consistent differences in species richness, density and standing crop of macroinvertebrates between sites. A difference in the faunal composition of the sites was clearly evident in autumn only, but differences in diversity (H') and evenness (J') between sites were not consistent. The most important factor affecting density, standing crop and species richness on the basis of principal component analysis was substratum stability, which, if decreased by channelization, is likely to reduce the abundance and species richness of resident macroinvertebrate assemblages.