Influence of selected abiotic factors on aquatic macroinvertebrate assemblages in the Olifants River catchment, Mpumalanga, South Africa

Abstract

Biodiversity is frequently seen as an indicator of ecological health. Therefore a survey of the macroinvertebrates of the Olifants River, one of the most polluted rivers in South Africa, was conducted in 2010–2011. Four surveys were conducted at a total of seven sampling sites in four ecoregions, Highveld-Upper, Highveld-Lower, Lowveld-Lower and Eastern Escarpment mountain range, using sweepnets to sample vegetation and substratum. Conductivity, pH and temperature were measured in situ. Macroinvertebrates were identified to family level and counted. Ninety-four taxa were collected, of which 12 were each represented by more than 1% of the total number specimens collected. The influence of abiotic factors on biodiversity was assessed through canonical correspondence analysis, species richness, Shannon–Wiener index and Pielou's evenness index. Ecoregion and associated temperatures played dominant roles in the distribution of families. Although the level of organic enrichment at some sites could benefit families tolerant to, or with a preference for, such conditions, this proved insufficient to exclude the less-tolerant families from those sites.