Freshwater Biology (1985) 15, 315-331 The organization of macroinvertebrate communities in the major tributaries of the LaTrobe River, Victoria, Australia R. MARCHANT, L. METZELING, A. GRAESSER and P. SUTER* Sut^ey Departtnent, Museum of Victoria, Abbotsford. Victoria, atid *Etigineering and Water Supply Department, Bolivar, South Australia SUMMARY. 1. Seventeen sites were each sampled six times over 2 years for macroinvertebrates. A range of physicochemical variables was also measured to determine which factors were related to the distribu- tion of species. 2. Numerical classification of the faunal data indicated that four groups of sites or communities were distinguishable: lowland sites; sandy upland sites; cobble upland sites from the northern catchment; cobble upland sites from the southern catchment. 3. Multiple discriminant analysis and multiple regression analysis demonstrated that particle size of the sediment, concentration of dissolved ions and altitude were the physicochemical features that were most strongly associated with changes in the faunal distribution. 4. Abundances of shredders and predators did not vary between the site groups while those of scrapers, gatherers and filterers did: scrapers were most abundant at cobble sites while gatherers and filterers were least abundant on sand and increased in abundance downstream. The distribution of the feeding groups showed some similarity with that predicted by the River Continuum Concept, but the fact that the shredders did not decrease in abundance downstream was a notable difference. 5. Abundance of the total fauna at a site was inversely related to the amount of benthic organic matter. This feature is contrary to the pattern usually reported from rivers in the northern hemisphere. Introduction tion of such commutiities has been the subject of much research in the temperate regions of The organization of macroinvertebrate com- the northern hemisphere as well as in temper- munities in undisturbed rivers and streams of ate New Zealand (e.g. Towns, 1979; Winter- temperate (southern) Australia is poorly bourn, 1978, 1982). Most previous work in known (Lake, 1982). In contrast, the organiza- temperate Australia has concerned the effects ^ . r^ T, ., 1. . K* f of various disturbances such as dam building. Correspondence: Dr R. Marchant. Museum of . . . , , , , , • ^ . , Victoria. 71 Victoria Crescent, Abbotsford .1067. orgamc and mdustrial pollution or heavy metal Victona. Australia, pollution on the fauna (Campbell. 1978; Blyth. 315