Macroinvertebrate communities and environmental dynamics in relation to land use activities along the Nyl River, South Africa.

Abstract

Rivers are dynamic freshwater ecosystems that play a crucial role in sustaining biodiversity, ecological processes, and human well–being. They function as natural pathways, transporting water, nutrients, and sediment across regions, shaping habitats and supporting diverse biological communities. In this study I have (i) assessed the broad use of developed biological tools of assessing river health in Southern African countries, (ii) assessed the spatio– temporal variation of metal pollution in water and sediments of a semi–arid river basin and, (iii) compared the taxonomic and functional characteristics of benthic macroinvertebrate communities in protected and non–protected areas. The findings of the study highlighted that the use of biological tools is increasing greatly across the country, although it shows some limitations in other countries where the indices/tool require modification. However, the method has shown effectiveness and reliability, as the indicator organisms are susceptible to a wide range of disturbances. Metal concentrations in water and sediments showed variations across sites and seasons, where metals in water were mostly high during dry season in the nonprotected areas, while metals in sediments were high during the dry and wet seasons in the protected areas. However, metals levels in the current study fell within the no effect levels and low effect levels, when compared with the Canadian sediment quality standards. Furthermore, all metals in water were below the baseline of the previous research, however, metals in sediments showed great variation with literature, as the results show decreased levels when compared to most studies and a sharp increase when compared to Ramogale (2008). Macroinvertebrate communities showed spatial and temporal variations, where results indicate that the non–protected area had a high diversity when compared to the protected area. However, the area was mostly dominated by the tolerant species which suggest that the area is not supporting a balanced diversity as results only indicate more tolerant species than sensitive species. The SASS and ASPT scores highlighted fair levels with few good levels for both sites and seasons. ANOSIM results also highlighted significant variation among macroinvertebrate community structure across sites and seasons. Overall, the results show a need for a continued monitoring of the system, in order to ensure its sustainability.