Relationships between Land Use Changes and Benthic Macroinvertebrates’ Community Structure in an East African Riverine Environment

Abstract

Anthropogenic land use activities affects the health status of river ecosystems in supporting aquatic biodiversity. Undisturbed wetlands ensure water bodies are ecologically healthy for community livelihoods. Recent years have witnessed degradation of aquatic ecosystems and this has devastating effects on the environment and community livelihoods. One of such wetlands is river Isiukhu of western Kenya. This study analysed water physico-chemical parameters and benthic macroinvertebrates’ assemblages of River Isiukhu between August to November, 2022. Four sampling stations were selected along the longitudinal river gradient based on anthropogenic impact and dominance of land use activities. Sampling stations were classified as ‘very high’, ‘high’, ‘moderate’ and ‘low’ and rated 4,3,2 and 1 respectively, depending on the anthropogenic impact. Macroinvertebrates were sampled using D-frame net and classified using appropriate keys. Anthropogenic activities and habitat characteristics were noted and recorded. Water quality parameters were determined in situ. Macroinvertebrates’ population indices were calculated to determine community structure. Sorenson’s Coefficient quantified similarities of species in different stations. Pearson correlation and ANOVA tested the study hypothesis. About 1,391 invertebrates were collected belonging to 12 orders, 32 families and 30 genera. Orders Ephemeroptera, Hemiptera, Diptera and Coleoptera recorded highest percentage taxonomical composition. Upper pristine stations (F and G) supported more species richness and diversity than lower stations (L and T). Macroinvertebrates’ communities in terms of diversity, abundance, richness, evenness, and functional feeding groups responded differently to impacts of anthropogenic activities, due to their varied adaptation traits. Water quality varied significantly between sampling stations (ρ <0.05). Close relationship existed between land use activities and species diversity (r=0.8; ρ < 0.05); richness (r=0.8779; ρ < 0.05); evenness (r=0.1067; ρ < 0.05); and abundance (r=0.962; ρ < 0.05). The study recommends the need to conserve riparian vegetation as a way of mitigating and adapting to the impact climate change on stream ecosystem.