22 巻 (2017) 4 号 p. 187-203
Natural biodegradation of heavy oil in the marine environment can be accelerated by the addition of nutrients or seeding of pre-selected microorganisms. In this study, a microcosm experiment was conducted to investigate the effects of inorganic nutrient supplementation (biostimulation) and bacterial consortium amendment (bioaugmentation) on the natural degradative processes of artificially contaminated sediment. Our results revealed that the addition of nutrients had greater effect on remediation than the addition of bacterial cells. Supplementation of inorganic nutrients promoted and sustained the growth of oil-degrading and heterotrophic bacteria throughout the experimental period. Highest reduction in the total petroleum hydrocarbons, and of their components, n-alkanes, polycylic aromatic hydrocarbons (PAHs) and alkyl PAHs, were obtained in the biostimulated microcosms. Changes in the bacterial community were monitored by the PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) method targeting the 16S rDNA gene. Results revealed different responses of the bacterial community to the addition of heavy oil and remediation agents. Shifts in the bacterial communities in the seawater were more dynamic than in the sediment. Results of this study showed that addition of remediation agents significantly enhanced the natural biodegradation of heavy oil in a sediment-seawater microcosm trial.