| Petroleum pollution is a seriously global problem in the marine environment. Oilspill occurs frequently and the pollution scale is expanding due to the development ofmarine petroleum exploitation and transports, leading to serious damages to themarine ecosystem. As an important element of marine ecosystem, marineheterotrophic bacteria will respond to the petrol pollutants after the oil spill. In thispaper, Boxi crude petroleum was selected and the response characteristics of marineheterotrophic bacteria to this oil pollution was investigated by means of bothlaboratory study and simulated field trial in the levels of molecule, cell, populationand community. This study will provide experimental and decision-making basis forthe further understanding of effects of oil spills on marine ecosystem and remediationof marine oil pollution.The change characteristics of cultivable heterotrophic bacteria, bacteriaabundance, activity of dehydrogenase and Superoxide Dismutase (SOD) wereexamined in a period of96hours and a period of28days respectively underlaboratory conditions. It was found that the variation tendency of cultivableheterotrophic bacteria was similar with that of bacteria abundance, which all had nosignificant correlation with oil pollution concentration. In addition, the dehydrogenaseactivity of bacteria first increased and then decreased. The activities of0.05and0.15μg/mL groups had no significant correlations with the control group throughoutthe cultured period, whereas the activities of0.45and1.35μg/mL groups weresignificantly higher than other groups and kept rising until the14th day, when theyreduced to the same level as the other groups. The activity of SOD increased after24hours, a greater extent could be seen in the higher concentration groups (0.45and1.35μg/mL). However, all experimental groups had no marked impact on SODactivity after long-time cultivation.Under simulated natural conditions, the variation of bacterial communitystructure exposed to oil pollution during28days was analyzed and the dynamics of culturable heterotrophic bacteria, oil-degrading bacteria, bacteria abundance andbacteria biomass were also examined. The results showed that the change trends ofthe number of culturable heterotrophic bacteria, the bacteria abundance and thebacteria biomass were similar, that was, they decreased in first7days, then increasedfrom the14thday, and maintained at a relatively low level afterwards, which weredifferent from those under the laboratory condition. In addition, the oil-degradingbacteria count increased apparently with time. Furthermore, the analysis of bacterialcommunity structure before and after oil pollution was carried out by ARDRA(amplifed ribosomal DNA restriction analysis). As it turned out, bacteria of the naturalseawater sample fall into six main lineages: α-Proteobacteria, β-Proteobacteria,ε-Proteobacteria, Bacteroidetes, Actinobacteria and Flavobacteria. However, bacterialcommunity changed greatly after oil pollution of28days and the predominatingpopulation changed from ε-Proteobacteria to γ-Proteobacteria. The structure ofbacterial community became much more complicated and bacteria related topetroleum-degrading such as Cycloclasticus pugetii，Thalassospira sp.，Alcaligenessp.，Roseobacter sp. and Alteromonas sp. appeared. Meanwhile, a lot of unidentifiedbacteria were detected in petroleum pollution sample. The change of average bacteriavolume reflected bacterial community variation from the side. In conclusion,petroleum pollution will result in obvious change of bacteria community structure andthe bacteria diversity is apparently higher than that in natural seawater. |
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