Abstract
The limitation of nutrient concentrations on degradation of n-hexadecane by marine Bacillus sp. was investigated by use of a semi-batch incubation system. This bacterium is a candidate organism for seeding, i.e. artificial enhancement of biodegradation of spilled oils. The degradation rate did not change greatly from 244 μmol-total inorganic N (TIN)/l and 6.5 μmol-PO4-P/l down to 4 μmol-TIN/l and 0.4 μmol-PO4-P/l, respectively. But at 2 μmol-TIN/l and 0.3 μmol-PO4-P/l, it decreased rapidly to as low as one-tenth of that with higher N and P concentrations. Both degradation rate and cell growth were approximated by the same Michaelis-Menten form equations. The concentration where the rate was reduced to half was 3 μmol-TIN/l. The nitrogen uptake rate was proportional to nitrogen concentration.
Retardation of biodegradation at the sea surface due to poor nutrient transport from underlying water was evaluated using a simple model and was shown to be small. Accordingly, the application of fertilizer is generally unnecessary in eutrophic coastal seas when this bacterium is used as seed organism.
