Assessment of functional feeding groups of aquatic insect communities in the mohlapitsi river, south africa

The changes occurring in the catchment of the Mohlapitsi River in South Africa as a result of anthropogenic activities are affecting the integrity of the river and may subsequently alter the composition and functional structure of aquatic insect assemblages. The aim of this study was to assess aquatic insect composition and richness of the functional feeding groups at different sites along the river. The insect structural composition differed among sites and seasons. The number of taxa and the diversity of insects remained relatively high across the river, especially in the downstream. The highest abundance of aquatic insects was recorded at the downstream sites, S5 and S6. Taxa richness and abundance were higher during the dry season than during the wet season. Collector-gatherer was the dominant functional feeding group in abundance and the predator was the dominant group in taxa (family) richness. The spatial and temporal functional composition were related to the environmental variables in the river. These relationships suggest that the physicochemical variables have influence on the distribution, abundance, and diversity of functional groups. However, the low abundance and taxa richness in the midstream suggest that the activities along the river are gradually impacting the river. It is important to implement proper measures to reduce agricultural and domestic discharges into the river in order to maintain its integrity and conserve the aquatic biota.