ABSTRACT
The study of the macrobenthic fauna in the bottom as well as those clinging to macrophytes of Oke River, Edo state was carried out at three stations from January to May 2017. The physical and chemical parameters analysed were, Air and Water temperatures, Flow rate, Depth, Turbidity, pH, Dissolved oxygen, Biochemical oxygen demand, conductivity, Total Alkalinity, Nitrate, Phosphate, Calcium, Magnesium ion, Chloride content, Total dissolved solids, Total suspended solids and Salinity. These showed no significance difference (P>0.05) in their values except depth and flow rate which showed significant difference at confidence level of 99% (P<0.01). Station 3 had the highest values recorded for Water and Air temperature, Flow rate and depth while in station 2, the highest variation in terms of Calcium ion, Conductivity, Phosphate, Chloride, Biological Oxygen Demand as well as Hardness was recorded. Station 1 had the highest variation of depth, Total suspended solids and Turbidity. Twenty (20) species of macrobenthic invertebrates belonging to three major groups were sampled along the study stretch. A total of 377 individuals was recorded. Arthropoda (specifically Chironomidae) was the most dominant of the groups and it constituted 60%. Annelida constituted 37% while Mollusca made up 3% of the total individuals collected. The lowest taxa richness of individuals was in Station 2 (1.89) while the highest was in station 3 (2.26). Using Shannon Wieners index and Evenness index, station 1 had the highest value for general diversity (1.70) and Evenness (0.49). The low diversity of macrobenthic communities is suggestive of high anthropogenic activities which might have resulted in stress and ultimately, relegation of sensitive species.
