Do aquatic macroinvertebrate communities respond to land-use effects in the Wilge River, Mpumalanga, South Africa?

Abstract

Aquatic macroinvertebrate community responses to the effects of various land uses were investigated in 2010–2013 in the Wilge River, a tributary of the Olifants River, South Africa. The catchment area is characterised by agricultural, mining and industrial activities, which potentially contribute to the river’s deteriorating water quality and poor in-stream habitat conditions. Agricultural activities comprise the predominant land use, causing major nutrient input into the Wilge River, resulting in eutrophic conditions. Thus it was expected that the functional feeding group (FFG) scraper/grazer populations would be the most abundant as they consume algae, but this was not the case. The primary FFGs present were predators and gathering collector populations, whilst shredders were the least abundant. The primary drivers responsible for separating the monitoring sites and their aquatic macroinvertebrate communities were differing in situ water quality, season and habitat availability. Therefore, land use was not a driving variable, probably owing to limited organic and inorganic water quality data.

Keywords: driving variables, functional feeding groups, seasonal variation, separation