Comparative effects of chemical dispersants and rhamnolipid biosurfactants on oil biodegradation and microbial community in coastal sediments

Marine coastal zones face pollution from both terrestrial and marine petroleum sources. Chemical and biological surfactants are employed to enhance oil dispersal and bioavailability in seawater, yet comparisons of their effects on microbial communities and oil degradation in sediments have not been well documented. Here, we conducted microcosm experiments mimicking oil spill scenarios with coastal sediment from the East China Sea, amended with either a dispersant (Jiefeite or Slickgone NS) or the biosurfactant rhamnolipid. The addition of Jiefeite, Slickgone, and rhamnolipid significantly enhanced oil biodegradation in sediments, with similar effects among them. The enhanced biodegradation activities observed were correlated with increased abundances of phnAc and alkB genes, as well as elevated abundances of predicted functional genes for the degradation of chloroalkane, chloroalkene, benzoates, toluene, and aromatic hydrocarbon. All oil microcosms showed significant growth in Sulfurovum and Woeseia. Oil microcosms treated with Jiefeite or Slickgone specifically enriched potential oil-degraders like Syntrophotalea, Marinobacter, and Sphingomonadaceae. In contrast, rhamnolipid-treated microcosms stimulated a more diverse community of oil-degrading bacteria, exhibiting increased abundances of Pseudomonas, Lachnospirales, Aestuariicella, Vibrio, and Marinobacterium. Our findings underscore the differential impacts of chemical dispersants and rhamnolipid on oil-degrading bacterial communities and their enhanced impacts on oil biodegradation, highlighting their potential in remediation of oil pollution in coastal sediments.