The ecological assessment of the influence of anthropogenic activities on Palala River, Limpopo, South Africa

Abstract

Water quality integrity deterioration is a severe global issue due to urbanisation, population growth, pollution and other anthropogenic activities threatening freshwater integrity. Anthropogenic activities alter freshwater integrity which leads to negative impacts on general ecological functioning of rivers. The current study was conducted along the Palala River in the Waterberg district in Limpopo, South Africa. The study was designed to employ multivariate and multimeric methods to determine relationships between environmental variables and macroinvertebrate communities. Macroinvertebrates were used to assess spatial and temporal changes in water quality using SASS5 (South African Scoring System version 5). The ecological status of the Palala River was clearly revealed through measuring of nutrient concentrations and environmental variables that influence water quality, and the macroinvertebrate communities that are found within the river. The results indicated the water quality was significantly impacted by changes in chloride concentrations at the site which had the most human interactions. The multivariate analysis revealed that macroinvertebrate communities were impacted by changes in the concentrations of chlorides (Cl-), total dissolved solids (TDS), as well as electrical conductivity (EC). Additionally, simple linear regression indicated that the abovementioned environmental variables had an impact on Taxa richness, total abundance and taxa diversity. The river was revealed to be in a natural state as it drains through upstream (P1 and P2) and midstream sampling sites (P3 and P4). Interestingly, there was a massive improvement in water quality as the river drains within Lapalala Wilderness Reserve (sites P3 and P4). Unfortunately, there was a dramatic decrease in water quality as the river exited the reserve draining through downstream sites P5 and P6. The sampling site P5 was highly impacted by human settlements and domesticated livestock increasing nutrient concentrations in the river. The results revealed that an increase in chloride concentrations affected macroinvertebrate abundances at sampling site P5. Sampling site P5 was dominated by highly tolerant taxa at 75%, intermediate 25% and 0% sensitive taxa. The tolerant animals such as Chironomidae, Hydracarina and Ceratopogonidae were found in abundance at this site. The highest recorded SASS5 score was 165 at sampling site P4 and lowest was 80 at sampling site P5. The highest ASPT score was 8,5 at sampling site P3 and lowest was 3.8 at sampling site P6. The scores indicated that the river was severely impaired at sites P5 and P6.