Oil is a source of pollution in sea-water. Oil pollution is due to ship accidents, loading and discharging of oil at the harbour, oil refineries and off-shore oil production. Degree of impurity of after due to organic matter is measured in terms of BOD (Biochemical Oxygen Demand). It is the demand for O2 to decompose organic wastes in liter of water.
water is less polluted
consumption of organic matter in the water is higher by the microbes