Impact of agricultural land-use on functional feeding groups of Afrotropical Ephemeroptera, Plecoptera and Trichoptera in the Kat River, Eastern Cape, South Africa

Abstract

Despite Africa experiencing a substantial rise in inadequately managed agricultural practices, studies examining the effects of these activities on the functional organisation of macroinvertebrates in tropical streams are underdeveloped. The responses of Ephemeroptera, Plecoptera and Trichoptera (EPTs) functional feeding groups (FFGs) to agricultural pollution were investigated in the Kat River, Eastern Cape, South Africa, to identify potential FFG indicators. Physicochemical parameters and macroinvertebrates were sampled from eight sites delineated into four land-use impact categories (highly impacted, HIC; impacted category, IC; moderately impacted, MIC; and least impacted, LIC) based on the percentage of agricultural land cover. The Permutational multivariate analyses of variance (PERMANOVA) results revealed land use (F = 4.2, 3.62; p < 0.05) and season (F = 2.89, p < 0.03) influenced FFGs in the river, with shredder abundances decreasing with increasing agricultural stress. Conversely, collectors, predators and scrapers were tolerant of agricultural disturbance. Nutrient variables (NO₃-N, NO₂-N and NH₄-N), canopy and depth were the critical variables that affected FFG structure in the river. Our findings provided more understanding and insights into the functional structure of EPT in relation to agricultural pollution and can contribute to developing trait-based biomonitoring tools in Africa.