Dynamic changes in the microbial community in the surface seawater of Jiaozhou Bay after crude oil spills: An in situ microcosm study

The changes in the composition and structure of microbial communities in Jiaozhou Bay are strongly affected by marine oil pollution, but the outcomes of the microbial responses and effects of dispersant application remain unclear. Herein, we performed an in situ microcosm study to investigate the response of the indigenous microbial community under crude oil alone and combined oil and dispersant treatment in the surface seawater of a semi-enclosed marine area of Jiaozhou Bay. The dynamics of the bacterial classification based on 16s rDNA sequencing were used to assess the changes with the crude oil concentration, dispersant use, and time. The crude oil resulted in a high abundance of the genera Pseudohongiella, Cycloclasticus, Marivita, and C1–B045 from the Gammaproteobacteria and Alphaproteobacteria classes, suggesting for hydrocarbon degradation. However, the dispersant treatment was more advantageous for Pacificibacter, Marivita, and Loktanella. Besides accelerating the rate of bacterial community succession, the dispersants had significantly stronger effects on the structure of the bacterial community and the degradation functions than the oil. A higher dose of oil exposure corresponded to fewer dominant species with a high relative abundance. Our study provides information for screening potential degradation bacteria and assessing the risks that oil spills pose to marine ecosystems. [Display omitted] •Crude oil induced dynamic changes of microbial community in Jiaozhou Bay waters.•Crude oil concentration affects the species of potential degrading bacteria.•Crude oil induced the abundance of Pseudohongiella, Cycloclasticus and C1–B045.•Dispersants have stronger selectivity for dominant species than crude oil. In situ microcosm studies revealed that continuous exposure to a low dose of crude oil contamination in the surface seawater in Jiaozhou Bay caused a remarkable increase in the bacterial abundance of the Pseudohongiella, Cycloclasticus, Marivita, and C1–B045 genera.