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Aims The aim of this study was to investigate the dynamic changes in the bacterial structure and potential interactions of an acclimatized marine microbial community during a light crude oil degradation experiment. Methods and Results The bacterial community effectively removed 76·49% of total petroleum hydrocarbons after 30 days, as evidenced by GC‐FID and GC‐MS analyses. Short‐chain alkanes and specific aromatic compounds were completely degraded within the first 6 days. High‐throughput sequencing of 16S rRNA gene indicated that the starting bacterial community was mainly composed by Marinobacter and more than 30 non‐dominant genera. Bacterial succession was dependent on the hydrocarbon uptake with Alcanivorax becoming dominant during the highest degradation period. Sparse correlations for compositional data algorithm revealed one operational taxonomic unit (OTU) of Muricauda and an assembly of six OTUs of Alcanivorax dieselolei and Alcanivorax hongdengensis as critical keystone components for the consortium network maintenance and stability. Conclusions This work exhibits a stabilized marine bacterial consortium with the capability to efficiently degrade light crude oil in 6 days, under laboratory conditions. Successional and interaction patterns were observed in response to hydrocarbon consumption, highlighting potential interactions between Alcanivorax and keystone non‐dominant OTUs over time. Significance and Impact of the Study Our results contribute to the understanding of interactions and potential roles of specific members of hydrocarbonoclastic marine bacterial communities, which will be useful for further bioaugmentation studies concerning the associations between indigenous and introduced micro‐organisms.

Crude oil spills have caused substantial impacts to aquatic ecosystems. Chemical dispersants are used to palliate the impact of oil spillages, but their use is polemic due to their additional potential toxic effect when mixed with oil-derived components. In this work, we used a 16S-based metagenomic approach to analyze the changes of the gut microbiota of adult zebrafish (Danio rerio) exposed to the water accommodated fraction (WAF) of a light crude oil (35 • API gravity), and the chemically enhanced WAF (CEWAF), prepared with Nokomis 3-F4 ® dispersant. After 96 h of exposure, WAF induced an increase in the alpha and beta diversity, altering the relative abundance of Vibrio, Flavobacterium, and Novosphingobium. In contrast, CEWAF only caused an increase in the beta diversity, and an enrichment of the genus Pseudomona. Both treatments diminished the abundances of Aeromonas, Cetobacterium, Coxiella, Dinghuibacter, and Paucibacter. Moreover, the co-occurrence network among genera was more complex in WAF than in CEWAF, indicating a greater bacterial interaction in response to WAF. Our results indicate that short-term exposure to WAF and CEWAF can induce a dysbiosis in the gut microbiota of D. rerio, but these changes are specific in each treatment.