Seasonal Variation in the Physico-chemical and Microbial Characterization of Sediment and Water Samples from Selected Areas in Ondo Coastal Region, Nigeria

Water and sediment samples were collected along river Ilaje in the Ondo coastal area of Nigeria during the dry and wet season. Water analysis was carried out by using standard methods for the examination of water and waste water, water and sediment samples were digested and analyzed for heavy metals using atomic absorption spectrophotometer. Pour plate technique was employed for the enumeration of bacteria and fungi using nutrient agar and potato dextrose agar respectively, the cultured media was supplemented with 2% oil (petrol, diesel and kerosene) as the only source of carbon and energy. After incubation, biochemical test and morphological features were carried out to identify the microorganisms. The result shows that the physicochemical properties of water varies with the seasons total hardness (620-2,424 mg/l), calcium hardness (130-1,478 mg/l), Alkalinity (120-144 mg/l), phosphate (2.21-2.78 mg/l), nitrate (0.90-22.50 mg/l), sulphate (228-395 mg/l), chloride (1990-3532 mg/l), the concentration of metals in water samples varies with the season having the lowest in Cd (0.01 mg/l) and the highest in Cr (0.66 mg/l). The concentration of metals varies in season with a spatial distribution in the top and bottom sediment samples. Oil tolerating fungi and bacteria were detected from the sampling sites with variation in the dry and wet seasons, E. coli was only detected in the water samples during dry season only. The presence of pathogens and water properties exceeding the WHO standard renders the water unfit for drinking and domestic use.