The use of water quality, aquatic species composition and aquatic habitat conditions to access the river health condition of the Nzhelele River, Limpopo Province, South Africa.

Abstract

Health condition of a river is a necessity for the sustainability of aquatic ecosystems. River health status of the Nzhelele River was assessed through the use of water quality, macroinvertebrate taxa composition and aquatic habitat conditions. The study was conducted along the Nzhelele River in Limpopo Province of South Africa where the river transcends six tribal villages. The objectives were to assess water quality conditions in order to determine the magnitude of pollution impact, to correlate species diversity and water quality parameters, to measure the size of degraded areas with respect to species richness and to develop a model for managing river health condition of the Nzhelele River. Data were collected monthly between February and December 2016 (early autumn to mid-summer). Macroinvertebrates were sampled where water samples were collected to ensure that the relationship between water quality and macroinvertebrates was adequately correlated. Water quality parameters that were analysed were pH, stream temperature, river velocity, conductivity, Dissolved Oxygen, Total Dissolved Solids, nitrates, nitrites and chlorine. Assessment of habitat conditions was done through the assessment of habitat and riparian zone integrity. One-way ANOVA was used to determine if there were significant differences between the six sampling areas in terms of water quality and aquatic species composition. Principal Correspondence Analysis (PCA) was used to correlate water quality and macroinvertebrate data. The results indicated that water quality parameters significantly differed among the six sampling sites and that also explained the variations in diversity of macroinvertebrates that were sampled from the six sampling sites. Pollution tolerant organisms constituted a total of 46.7% and the remaining 53.3% represented pollution sensitive organisms. PCA results showed positive and negative correlations between macroinvertebrates and water quality parameters to indicate variations in the levels of pollution along the Nzhelele River. Habitat integrity results indicated that the Musekwa sampling site was the most degraded and had lower species diversity. The Ratio of Ephemeroptera, Plecoptera and Trichoptera (EPT) and Chironomidae Abundances should be reviewed to read as Ratio of EPT and Chironomidae-Thiaridae Abundances in order to strengthen the study of the relationship between pollution tolerant and pollution sensitive organisms.