ABSTRACT
The abundance and seasonal changes of benthic macroinvertebrates and physicochemical condition of Osse River, Edo State, Nigeria, were studied from July to September 2021. Three sampling stations were selected along the course of the river. Macroinvertebrates were sampled using modified kick sampling techniques. The results from the river showed that water temperature ranged between (20-280C), air temperature (21-30), Depth (1.07-4.28m), Flow velocity (11.8-30.3m/s), Biochemical Oxygen Demand (2.46-4.0mg/L), Dissolved Oxygen (4.8- 7.14mg/L), pH (6.5-7.7), Conductivity (76-286μ/cm), Alkalinity (25-30mg/L), Turbidity (9.032- 19.005 NTU), Nitrate (3.676-8.027 mg/L) and Phosphate (0.033-0.063 mg/L). Water temperature and the pH level investigated were within permissible limit (FMEnv). Air temperature, flow rate, depth, BOD, and sulphate show spatial significant difference across stations, while transparency and DO show no significant seasonal variation. Macroinvertebrates were significantly more (P <0.05) in station 3 than in station 1 and 2. High abundance of macroinvertebrate were encountered during the dry season than in the rainy season. The abundance according to the Orders revealed that Ephemeroptera, were the most common groups encountered during the wet and dry seasons. Mollusca, Hemipterans and Oligochaeta were sparingly found in all stations. Macroinvertebrates abundance correlated with a physicochemical parameter. This study suggests that Macroinvertebrates distribution and abundance is influenced mostly by the seasonal variations.
