Human Impact on the Water Quality and Benthic Macro-Invertebrate Compositions in Ogunpa River, Nigeria

Human activities are important factors that affect the quality of water. The study was conducted to determine the impact of Human activities on the water quality and the Bio-diversity of the river system using benthic macro-invertebrates as indicators. Bottom samples were collected fortnightly from three sampling sites. The study showed that the majority of respondents were men and generated liquid wastes from washing of cars and motorcycles, oils from mechanic activities while the women generated solid wastes from household and domestic activities. The decomposition of such wastes had negative impact on the quality of water evident by high mean values of Biochemical Oxygen Demand (BOD) 20.79±6.82mg/l; Chemical Oxygen Demand (COD) 29.2±1.01mg/l and Nitrate 5.21±0.19mg/L and low Dissolved oxygen 6.10±0.66mg/l concentrations. Surface water temperature of 25.54ºC±0.14ºC, Phosphates 0.008±0.004mg/L and pH 7.85±0.21 were also recorded. The three sites showed significant differences (p<0.05) in concentration of Dissolved oxygen, Chemical Oxygen demand, Nitrate and Phosphate. The species diversity of macro-invertebrates was low and seven species namely; Lymnaea truncatula, L. grabla, Chironomus sp.Tubifex sp. Whirligig beetle larvae, Dragonfly larvae and leech were observed. The relative abundance of pollution tolerant species are L. truncatula (36.03%), L. grabla (15.35%) and Chironomus sp (14.70%). The study found that high values of BODCOD and high abundance of L. truncatula, a pollution tolerant macro-invertebrate indicates that the river is likely under pollution stress as a result of the negative impacts of human activities.