Analysis of Agia Zoni II Reveals Bacterial Legacy Effects

On the 10th September 2017 the vessel Agia Zoni II sank in the Saronic Gulf, Greece; contaminating the coasts of Salamina and the Athens Riviera. Coastal sediment samples were taken immediately after, and monthly thereafter until April 2018. Analysis of microbial community composition, via Next Generation Sequencing, indicated that oil-contamination significantly (P<0.001) increased the abundance of known oil-degrading bacterial genera including Alcanivorax, Cycloclasticus, Marinobacter, Oleibacter, Oleiphilus, and Thalassolituus. Immediately after the spill, some of these genera formed over 60% of theentire bacterial community in oil-contaminated sites. The abundance of most hydrocarbon-degrading genera decreased during and after an extensive clean-up response. However, some genera, such as Alcanivorax, Cycloclasticus, and Marinobacter, persisted for several months after, albeit in highly reduced relative abundance. Analysis of hydrocarbon concentrations in September, via gas chromatography-mass spectrometry, revealed a mean total hydrocarbon concentration of 2,158 ± 800 µg g -1 dry sediment comprising approximately 91% alkanes and 9% PAHs. In contrast, analysis of latter months indicated an efficient clean-up operation, with limited hydrocarbon detection from October onwards, despite alegacy effect on the microbial community composition. Such data may assist in the design of efficient oil-spill monitoring and management strategies in the future.