'n Studie van die gesondheid van die Olifantsrivier soos weerspieël deur die makro–invertebraatbiodiversiteit en geselekteerde abiotiese faktore

Abstract

This project entailed a complete study of the aquatic macroinvertebrate biodiversity and several abiotic factors at selected sites in the Olifants River and tributaries. The Olifants River Catchment area is subjected to a number of negative impacts from various activities and stretches of this river is under threat and considered as being critically transformed.

During this study, four surveys, over a period of two years, were conducted at seven preselected sites in the Olifants River and tributaries (Steenkoolspruit, Blyde River and Ga-Selati River). During each survey aquatic macroinvertebrates were collected in vegetation and sediment biotopes, while the pH, electrical conductivity and temperature were measured in-situ, using portable instruments. Water samples were also collected at the various sites while the coordinates and height above sea level were determined at each sampling site. In the laboratory, the macroinvertebrate samples were sorted, identified, classified and counted and biodiversity lists were compiled. The SASS5 and MiniSASS sensitivity guidelines were used to categorise all the macroinvertebrates collected during this study. A comprehensive chemical analysis was performed on all water samples. Relevant statistical analyses were done. A total number of 101 taxa were collected during this study of which seven families were categorised as highly sensitive, 41 as moderately sensitive and 53 as tolerant. From the results it was evident that the sites in the Olifants River and tributaries, evaluated during this study, varied from natural to critically transformed. Due to the complexity of this data, it was not possible to come to any meaningful conclusions regarding the general ecosystem health of the Olifants River.