Bacterial Community Legacy Effects Following the Agia Zoni II Oil-Spill, Greece

Abstract

In September 2017 the Agia Zoni II sank in the Saronic Gulf, Greece, releasing approximately 500 tonnes of heavy fuel oil, contaminating the Salamina and Athens coastlines. Effects of the spill, and remediation efforts, on sediment microbial communities were quantified over the following 7 months. Five days post-spill, the concentration of measured hydrocarbons within surface sediments of contaminated beaches was 1,093-3,773 µg g −1 dry sediment (91% alkanes and 9% polycyclic aromatic hydrocarbons), but measured hydrocarbons decreased rapidly after extensive clean-up operations. Bacterial genera known to contain oil-degrading species increased in abundance, including Alcanivorax, Cycloclasticus, Oleibacter, Oleiphilus, and Thalassolituus, and the species Marinobacter hydrocarbonoclasticus from approximately 0.02 to >32% (collectively) of the total bacterial community. Abundance of genera with known hydrocarbon-degraders then decreased 1 month after clean-up. However, a legacy effect was observed within the bacterial community, whereby Alcanivorax and Cycloclasticus persisted for several months after the oil spill in formerly contaminated sites. This study is the first to evaluate the effect of the Agia Zoni II oil-spill on microbial communities in an oligotrophic sea, where in situ oil-spill studies are rare. The results aid the advancement of post-spill monitoring models, which can predict the capability of environments to naturally attenuate oil.

Evaluation of Polycyclic Aromatic Hydrocarbon Pollution From the HMS Royal Oak Shipwreck and Effects on Sediment Microbial Community Structure

“…Comparatively, a study within the Gulf of Mexico revealed that sediments around the shipwreck of the oil-tanker "Halo" (sunk May 1942) contained PAH concentrations ranging approximately 0-1,400 µg kg −1 of dry sediment respectively, resulting in an EIHE of 0.025 (see Figure 5 and Supplementary Table 3; Hamdan et al, 2018), twofold higher than the EIHE observed in surface sediments around HMS Royal Oak. Additionally, contaminated sediments sampled 5 days after the Agia Zoni II oil-spill, which contained average PAH concentrations of 210,000 µg kg −1 of dry sediment, resulted in an EIHE of 0.52, 42-fold higher than the EIHE observed in surface sediments of the present study (see Figure 5D and Supplementary Table 3; Thomas et al, 2020).…”

“…Analysis of OHCB genera revealed only a sporadic and very low abundance of FIGURE 5 | Ecological Index of Hydrocarbon Exposure (EIHE) (ratio up to 1) representing relative abundance of oil-degrading/associated Bacteria, (Lozada et al, 2014) measurements (±SE, n = 4), for sediments sampled around the shipwreck HMS Royal Oak (located in Scapa Flow, Scotland, United Kingdom, November 2019), over a 17.5 cm depth profile (A), a 950 m transect (where sediments further away act as controls) (B), and given the transect direction (C). Additionally, a comparison between the HMS Royal Oak EIHE and other studies investigating oil-polluted environments (D): "HMS Royal Oak" (present study, surface sediments), "Halo" (Hamdan et al, 2018), "Patagonian Coast" (Lozada et al, 2014), "Brazilian Mangrove" (Dos Santos et al, 2011), "Colne Estuary" (Coulon et al, 2012), "Ushuaia Bay (no nutrients)", "Pensacola Beach" (Kostka et al, 2011), "Agia Zoni II" (Thomas et al, 2020) and "Ushuaia Bay (added nutrients)" (Guibert et al, 2012).…”

“…Exposure to hydrocarbons can lead to adaptation within indigenous sediment bacterial communities and increases in hydrocarbon oxidising potential, priming the communities for any current or future oil-contamination (Leahy and Colwell, 1990). For example, increased abundance of known hydrocarbon-degrading bacteria (i.e., Alcanivorax and Cycloclasticus) has been observed in oil-contaminated coastal sediments, many months after hydrocarbons were undetectable (Thomas et al, 2020). Therefore, significantly higher abundance, and a broad diversity, of hydrocarbon-degrading bacteria in sediments close to the shipwreck compared to background levels (i.e., sediments sampled further away from the shipwreck), would indicate that any oil-contamination could be rapidly degraded.…”

“…Hydrocarbondegrading bacteria are particularly important responders to oilpollution as they remove a significant proportion of oil and act as bioindicators of hydrocarbon-pollution (Head et al, 2006;Lozada et al, 2014). Oil pollution will often significantly alter marine microbial community composition, whereby a species richness and diversity decreases as selection for oil-degrading bacteria occurs (McGenity et al, 2012;Thomas et al, 2020). After an oil spill, there is often an initial increase in the abundance of alkane-degrading microbes (e.g., Alcanivorax/Oleispira) followed by growth of PAH-degraders (e.g., Cycloclasticus) (Head et al, 2006;Ribicic et al, 2018).…”

Elucidate microbial characteristics in a full-scale treatment plant for offshore oil produced wastewater

“…γ-Protobaceria-affiliated Marinobacterium , Marinobacter , Pseudomonas , and Halomonas were dominant in ABRS and ABRW. Nearly all the sequences of the γ-protobaceria-affiliated OTUs showed the closest similarities to the sequences detected from oil-related environments ( S2 Fig ) and possess the ability to degrade hydrocarbons or polymers [ 33 , 34 ]. Another main group of hydrocarbon-degrading microbes were δ-protobaceria-affiliated Desulfotignum and Desulfoglaeba .…”