10th U6+ Consortium of African Universities International Conference

Freshwater ecosystems in tropical Africa face escalating anthropogenic pressures, underscoring the urgent need for robust and cost-effective biomonitoring frameworks. This study evaluated stream health across three freshwater streams; Famak, Tokunbo, and Kofawe tributaries of Oluwa River in Igbokoda, southwest Nigeria, using aquatic insect assemblages associated with leaf-litter and leaf-pack substrates as biological indicators of water quality. Leaf-litter and leaf-pack samplers were deployed at 2 stations across each stream, and insects were identified to genus level. Physicochemical parameters; pH, dissolved oxygen, temperature, electrical conductivity, turbidity, sulphate (SO₄²⁻), phosphate (PO₄³⁻), and nitrate (NO₃⁻) were measured concurrently. Community structure was quantified using the Shannon-Wiener (H’), Simpson’s (D), Evenness (J’), and Margalef’s Richness indices, while spatial variation was assessed using one-way ANOVA and Pearson’s correlation. Six insect orders were recorded: Diptera, Odonata, Hemiptera, Coleoptera, Ephemeroptera, and Trichoptera. Chironomidae (Chironomus) dominated across stations; indicative of organic enrichment, while Ephemeroptera and Trichoptera (pollution-sensitive) were scarce. Diversity indices varied across biotopes: leaf-litter yielded H’ = 0.57–2.13, D = 0.20–0.86, J’ = 0.20–0.84, Margalef = 1.64–2.65; leaf-pack yielded H’ = 1.57–2.17, D = 0.70–0.88, J’ = 0.69–0.97, Margalef = 1.70–2.46. ANOVA revealed significant spatial differences in electrical conductivity, temperature, and dissolved oxygen (p < 0.05). Correlation analysis revealed slight associations between insect community structure, and physicochemical parameter. Sensitive taxa characterizing less disturbed stations and tolerant Chironomus prevailing in degraded reaches. The results from this study affirm the diagnostic utility of leaf-pack and leaf-litter as tools for tropical freshwater bioassessment, it also provides critical baseline data for biodiversity conservation and sustainable water resource management.