Abstract
In this study, time-series samples were taken from a gravel beach to ascertain whether a periodic oil input induced by tidal action at the early stage of an oil spill can be a trigger to stimulate the development of hydrocarbon-degrading bacteria under natural in situ attenuation. High-throughput sequencing shows that the microbial community in beach sediments is characterized by the enrichment of hydrocarbon-degrading bacteria, including Alcanivorax, Dietzia, and Marinobacter. Accompanying the periodic floating-oil input, dynamic successions of microbial communities and corresponding fluctuations in functional genes (alkB and RDH) are clearly indicated in a time sequence, which keeps pace with the ongoing biodegradation of the spilled oil. The microbial succession that accompanies tidal action could benefit from the enhanced exchange of oxygen and nutrients; however, regular inputs of floating oil can be a trigger to stimulate an in situ “seed bank” of hydrocarbon-degrading bacteria. This leads to the continued blooming of hydrocarbon-degrading consortia in beach ecosystems. The results provide new insights into the beach microbial community structure and function in response to oil spills.
Highlights
The marine coastal environment is highly susceptible to oil spills induced by the expansion of offshore oil and gas exploration and transportation
Thereafter, the gravel beach is periodically affected by tidal action with fresh inputs of spilled oil, the residue oils, depending on the time sequence, exhibited full depletion of n-alkanes, a decreasing trend for isoprenoids, and no discernible changes in saturated biomarker distributions
The pattern of oil weathering due to photooxidation, in which aromatic hydrocarbons are more susceptible than aliphatic hydrocarbons, was generally consistent across different conditions[22,23], it is difficult to differentiate this from biodegradation with conventional gas chromatography-mass spectrometry (GC-MS) techniques, due to transformation to polar species[24]
Summary
The marine coastal environment is highly susceptible to oil spills induced by the expansion of offshore oil and gas exploration and transportation. The oil biodegradation rate strongly depends on environmental factors that may stimulate the development of in situ hydrocarbon-degrading consortia This phenomenon was recently hypothesized as an “autoinoculation effect” by Valentine et al.[17] in the investigation of Deepwater Horizon oil spill in the Gulf of Mexico. An oil polluted beach can be a natural laboratory to test the “autoinoculation effect” hypothesis due to the pulsed oil input and nutrient and oxygen exchange induced by periodic tidal action. If the “autoinoculation effect” hypothesis is correct, the response of the microbial community in a polluted beach over time can be monitored and captured Such a study can further probe how it interacts with or benefits from periodic oil input induced by tidal action during the early stage of an oil spill, especially for the microbial dynamic pattern and its drivers
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