Assessment of Functional Feeding Group Dynamics within the Community Structure of Macroinvertebrates in the Owena River, Southwestern Nigeria

This study assessed the community structure of macroinvertebrates in the Owena River, Southwestern Nigeria, to evaluate its ecological status. Sampling was conducted across six designated stations four times over 2024 and 2025, capturing data from both the wet and dry seasons. Water quality was evaluated using a Multi 3630 IDS digital meter to measure surface temperature, pH, total dissolved solids (TDS), dissolved oxygen (DO), and electrical conductivity (EC), while remaining physicochemical parameters were analyzed using standard laboratory techniques. Macroinvertebrates were collected via handpicking and long-handled D-frame nets, preserved in 70% ethanol, and classified into Functional Feeding Groups (FFGs) using taxonomic keys. Statistical analyses, including two-way ANOVA and paired T-tests, evaluated spatial and seasonal variations, while Spearman’s rank correlation determined relationships between macroinvertebrate abundance and environmental variables. A total of 1,197 macroinvertebrates spanning two phyla and four classes were identified, with Arthropoda displaying the highest diversity. FFG analysis revealed a dominance of predators and a scarcity of shredders. Significant negative correlations between macroinvertebrate abundance and specific physicochemical indicators pointed toward severe environmental stress. Elevated levels of biochemical oxygen demand (BOD), EC, TDS, and nitrates, alongside the notable rarity of pollution-sensitive species, collectively demonstrate that the Owena River is experiencing a substantial pollution load. Consequently, proactive management and conservation measures are urgently recommended to control anthropogenic inputs and prevent further deterioration of the river's water quality and aquatic biodiversity.