Aquatic Insect Diversity as Bioindicators of Water Quality in the Osun River Catchment, Osun State, South West Nigeria

Aquatic insects are sensitive to water quality degradation and are widely used in bioassessment programs globally as biological indicators of pollution. The Osun River, which supports both domestic water supply and spiritual tourism in Osun State, has experienced increasing pollution pressure from urban runoff and agricultural activities. This study uses aquatic insect community composition to assess water quality at six sampling stations along the Osun River catchment. Macroinvertebrates will be collected using Surber nets and kick-sampling methods at each station during wet and dry seasons. Insects will be identified to family level and assigned tolerance scores using the South African Scoring System adapted for West African taxa. Biotic indices will be calculated and correlated with physicochemical water quality parameters including pH, dissolved oxygen, turbidity, and nitrogen content. This study aims to provide a rapid biological assessment of river health that complements existing chemical monitoring conducted by the Osun State Environmental Protection Agency. Results will help identify pollution hotspots requiring regulatory intervention. The aquatic insect checklist generated will contribute to regional biodiversity databases. Keywords: aquatic insects, bioindicators, water quality, Osun River, bioassessment