Quantitative studies on marine biodegradation of oil I. Nutrient limitation at 14 °C

A method for measuring oxygen uptake due to oil biodegradation for a long period, in a semi-closed system, with continuous nutrient replenish­ment is described. The rate and extent of degradation of Kuwait crude residues in the absence of high nutrient concentrations at 14 °C was measured, and related to the supply and uptake of inorganic nutrients. The rate controlling factor was the rate of replenishment of nitrogen as nitrate or ammonia. Approximately 26% (based on oxygen uptake) or 44% (based on oil recovery) of the oil was degraded, the difference pro­bably being due to the production of soluble organic compounds. Some properties of the recovered oil were measured. The residues after partial degradation were of sufficient density to sink in seawater. It appears that at 14 °C, approximately 4 μmol available nitrogen is required per milli­gram of oil oxidized (based on oxygen consumption). The capacity of sea water to degrade oil in the natural environment is tentatively discussed.