*This blog entry first appeared on Gareth's own blog, which you can find here
This blog is a one of two firsts: firstly, it is my first ever blog, and secondly, it concerns my first ever scientific paper! I figure why not combine the two, and I can tell you about this fascinating project whilst cutting my teeth on my first blog post. I am going to keep it nice and simple, an extended abstract as it were…it’s good practice for when I try to tell my mates down the pub about my work (glazed over eyes). NB: you will notice a few animations in the blog it’s a new trick I have taught myself and I wanted to show off! If you would like to view the full scientific journal paper then you can at this link: Agia Zoni II Oil-Spill, Greece
An embayment located on Salamina island, impacted by the Agia Zoni II oil-spill.
The Agia Zoni II oil-tanker sunk in September 2017, coincidentally a few weeks prior to when I would embark on my PhD journey, in the Saronic Gulf, Greece, impacting both the Athen’s and Salamina coastlines. We decided it would be a brilliant chance to leave a cold and wet UK and spend some time in the sun on the continent, drinking Mythos beer, eating outrageous amounts of hummus, and taking in the local culture…oh, and of course, we would collect some samples in our down time.
Sampling sites from the Agia Zoni II oil-spill (marked as an X where tanker sunk) in Greece (inlet; dark grey; red dot highlights spill-site) and affected Athens Riviera and Salamina coastline. Abbreviations for clean-up response applied at oil-contaminated sample sites (Athens 1-4 and Salamina 1-3) and non-oil impacted sites (control) are as follows: MN (manual removal of tar balls), HP (high-powered washing, to remove oil from hard surfaces), AB (use of absorbents to collect floating oil from the water surface), FL (flushing of sediment with medium pressure water), TR (trenching, used in conjunction with flushing to collect oil), and RM (removal of coastal sediment, either washed and replace or disposed in landfill).
Sampling sites from the Agia Zoni II oil-spill (marked as an X where tanker sunk) in Greece (inlet; dark grey; red dot highlights spill-site) and affected Athens Riviera and Salamina coastline. Abbreviations for clean-up response applied at oil-contaminated sample sites (Athens 1-4 and Salamina 1-3) and non-oil impacted sites (control) are as follows: MN (manual removal of tar balls), HP (high-powered washing, to remove oil from hard surfaces), AB (use of absorbents to collect floating oil from the water surface), FL (flushing of sediment with medium pressure water), TR (trenching, used in conjunction with flushing to collect oil), and RM (removal of coastal sediment, either washed and replace or disposed in landfill).
That’s exactly what we did, collecting sediment and water samples only five-days after the oil-spill occurred and then monthly thereafter. It’s hard to overstate how important “five-days after the spill” is…it just does not happen. Oil spills are a war zone of insurers, clean-up operators, charities, governments etc. all fighting for space and there for their own agendas. Scientists therefore are often left on the side of the road, partly due to this logistical nightmare but also the requirement for funds to be able to undertake any sampling. Fortunately, our friends at Archipelagos Institute of Marine Conservation (Samos, Greece) were there to help out and get those precious samples for us! Funding provided by the National Environmental Research Council (NE/R016569/1), thank you!
What did we want to know with our lovely sediment samples?
1. How effective were the clean-up operations? (i.e. how impacted were the sites?)
2. How did this large oil-spill affect the microbial communities?
How did we go about answering these questions?
1. Gas chromatography-mass spectrometry (i.e. tell us what chemicals (in this case hydrocarbons from oil) are in the sample and in what concentration).
2. Bacterial & archaeal 16S rRNA gene qPCR and amplicon library sequencing (i.e. what bugs are there and how many of them are there?)
“Tell me! What did you find out?!”
Concentrations (mean ± SE, n = 3) of hydrocarbons in control (Suffix “No Oil”) and contaminated (Suffix “Oil”) sediments along the Athens Riviera and Salamina coastline, sampled from September 2017 to April 2018.
1. Unsurprisingly, there was a lot of oil in the samples in September! Similar levels to those found after the Exxon Valdez oil-spill, but not as much as those after the Deep-Water Horizon oil-spill. Importantly though, from October on we were unable to detect any oil in the samples, indicating that the clean-up operations (see the map above) had been efficient.
Bacterial 16S rRNA gene abundance (mean ± SE, n = 6 (n = 3 for September as Athens only)) in unimpacted (“Control”) and oil-impacted (“Impacted”) sediments from both the Athens Riviera and Salamina coastlines, between September 2017 and April 2018.
2. Firstly it was observed that the absolute abundance of Bacteria (16S rRNA gene) was increased ~2.5-fold at the oil impacted sites in comparison to the control sites during the first few months (p>0.05). Whilst not conclusive, it would be safe to say that the oil is promoting this growth.
This growth is attributed to bacterial genera known to contain oil-degrading species (i.e. yum yum oil) increased in abundance from approximately 0.02% to >32% (collectively) of the total bacterial community. Think about that, it’s huge growth! After September though (remember we couldn’t detect anymore oil), they quickly declined in abundance. However, a legacy effect was observed within the bacterial community, whereby Alcanivorax and Cycloclasticus (two bugs that love oil for dinner) hung around in the sediments for several months after the oil spill.
Relative abundance (% of the bacterial community; mean ± SE, n = 3) of 16S rRNA gene OTUs assigned to putative obligate hydrocarbonoclastic bacteria (Top right = Marinobacter hydrocarbonoclasticus) in sediments from control (Suffix “No Oil”) and contaminated (Suffix “Oil”) sites along the Athens Riviera and Salamina coastline, from September 2017 to April 2018.
Clean-up operations underway at an impacted site.
There’s a load more results and discussion in the actual paper, it’s open access so please feel free to take a gander. Ultimately though, what does this information mean in the real world? Well, the results will help us, and other scientists, improve post-spill monitoring models, which can predict the capability of environments to naturally remove oil. It had provided some form of feedback on the clean-up operations which is useful to oil-spill response companies and operators, providing guidance on future remediation efforts. Lastly, it continues to build on our knowledge and data bank of oil-spill microbial ecology…because those little bugs are important!
Thanks for reading! I hope you enjoyed this whistle stop tour of the Agia Zoni II oil-spill. I would also like to once again thank Archipelagos Institute of Marine Conservation and NERC for their support. Lastly, but by no means least, thank you to all the co-authors and those who have supported this work along the way.
(Left to right: two volunteers with Archipelagos, Anastasia (co-founder of Archipelagos), Dr Tom Cameron (co-author), Dr Boyd McKew (the Boss), me (sober).
The Agia Zoni II shipwreck being removed the sea in November 2017
