Addo-Bediako: Assessment of functional feeding groups of aquatic insect communities in the Mohlapitsi River, South Africa - 4283 - APPLIED ECOLOGY AND ENVIRONMENTAL RESEARCH 20(5):4283-4294. http://www.aloki.hu ● ISSN 1589 1623 (Print) ● ISSN 1785 0037 (Online) DOI: http://dx.doi.org/10.15666/aeer/2005_42834294 © 2022, ALÖKI Kft., Budapest, Hungary ASSESSMENT OF FUNCTIONAL FEEDING GROUPS OF AQUATIC INSECT COMMUNITIES IN THE MOHLAPITSI RIVER, SOUTH AFRICA ADDO-BEDIAKO, A. Department of Biodiversity, University of Limpopo, Private Bag X1106, Sovenga 0727, South Africa (e-mail: abe.addo-bediako@ul.ac.za; phone: +27-15-268-3145; ORCID: 0000-0002-5055-8315) (Received 25 th Mar 2022; accepted 11 th Jul 2022) Abstract. 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. Keywords: bioindicators, functional structure, land use changes, macroinvertebrates, water quality Introduction Many freshwater ecosystems are being polluted due to discharges from mining, industrial, agricultural, and domestic activities (Li et al., 2018; Chen et al., 2019). Furthermore, land use changes have caused destruction of riparian vegetation and loss of habitats, which have affected both the integrity of freshwater bodies and the aquatic biota. The community structure of many aquatic organisms, specifically aquatic insects, represents a high degree of spatial variation along rivers and therefore serves as good indicators of water quality (Keke et al., 2017; Sor et al., 2017; Addo-Bediako, 2021). The spatial variation in their composition may be influenced by physicochemical variables (Al-Shami et al., 2013; Cortes et al., 2013; Kumar and Khan, 2013) and trophic factors (Nicola et al., 2010; Cai et al., 2012). Many metrics such as abundance, taxa richness and diversity of macroinvertebrates have been used in monitoring freshwater ecosystems. Recently, a functional approach based on macroinvertebrate functional feeding groups (FFG) is being used as indicator of ecosystem attributes and to assess the ecological health of rivers/streams (Merritt et al. 2005; Fierro et al., 2017). Functional feeding group is an important tool for establishing trophic relationships and community dynamics (Vannote et al., 1980; Cummins et al., 2005; Fu et al., 2016). The classification of FFG considers the morphological and behavioural characteristics used in food acquisition (Ramirez and Gutiérrez-Fonseca, 2014). Macroinvertebrates can be classified into five groups based on consumption of diverse food resources and feeding