Anthropogenic spatial and temporal changes in the aquatic macro invertebrate assemblages of the lower Mvoti River, KwaZulu-Natal, South Africa

Abstract

Industrial and urban impacts on the lower reaches of the Mvoti River were studied using changes in macroinvertebrate community structures as indicators of environmental change. Macroinvertebrates were sampled during high- and low-flows in 2005 in the lower Mvoti River and its tributaries. Uni- and multivariate analyses revealed significant spatial differences between sites on the Mvoti River and those on the tributaries, as well as between sites on the Mvoti above and below the confluences of these tributaries. No significant trends in temporal distributions were recorded. Spatial differentiation was attributed to the abundance of insensitive taxa such as chironimids and oligochaetes at impacted sites. Increased salts and chemical oxygen demand, with lower dissolved oxygen concentrations, were identified as the driving water quality parameters affecting macroinvertebrate community structures. Comparison of macroinvertebrate structures in the Mvoti River with those in the biogeographically similar Mhlathuze River indicated the absence of sensitive taxa such as Atyidae, Naucoridae, Gomphidae and Leptoceridae from the Mvoti.