Responses of macrobenthic invertebrates’ diversity to environmental factors in a tropical freshwater river in Edo State, Nigeria

Macroinvertebrates occupy an important trophic level in riverine ecosystems based on their composition and diversity. In this study, we explored the biodiversity pattern of macroinvertebrates in relation to environmental parameters in a bid to assess the water quality of the Uwagbe River, Nigeria. Sampling was carried out in three well marked stations from March 2018 to February 2020 following standard procedures. The physico-chemical parameters recorded were within the acceptable limit by World Health Organization and Federal Environmental Protection Agency of Nigeria standards except the pH and DO of Stations 2 and 3 and BOD of Station 3. The Principal Component Analysis showed pH and DO to be positively associated with Station 1. 13 orders of macroinvertebrates, comprising of 32 families, 45 taxa and 4,796 individuals were recorded. The most dominant order was Diptera (26.7%) while the least was Arachnida (0.1%). The most predominant taxon was Lumbricus sp. (7.9%), while the least was Aeschna sp. (4.3%). Diversity indices showed that Station 1 had the highest indices for Margalef index, Shannon-Wiener diversity index (H), Equitability index (E) and Simpsons’ dominance index while Station 3 had indices with the lowest values. Canonical Correspondence Analysis ordination showed that chloride, alkalinity, BOD, nitrate, phosphate and water depth were strongly correlated with families such as Lumbricidae, Chironomidae, Potamonautidae, Tabanidae and Palaemonidae in Station 3. DO and pH were strongly associated with Amphipodae, Hydrophilidae, Gerridae and Libellulidae families in Station 1. The study revealed the significance of the utility of macroinvertebrates community structure and its relationship with environmental factors in assessing the level of perturbation in riverine ecosystems. The results provide insight on how river managers can put in place appropriate conservation processes to forestall the incessant level of perturbation occurring in riverine ecosystems.