MICROBIAL COMMUNITY DYNAMICS OF THE DEEPWATER HORIZON OIL SPILL Public Deposited

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  • March 19, 2019
Creator
  • Yang, Tingting
    • Affiliation: College of Arts and Sciences, Department of Marine Sciences
Abstract
  • The Deepwater horizon (DWH) oil spill released ~4.9 million (780,000 m3) barrels of crude oil into the Gulf of Mexico, causing the worst environmental disaster in U.S. history. Over 50% of the released oil could not be recovered. The task of biodegradation, to recycle the huge amount of hydrocarbon back to inorganic carbon and into microbial biomass, fell to the bacterial communities of the water column and the seafloor– which consequently changed in response to the oil fallout. These compositional and functional changes of the bacterial community in different stages of the spill provide the main focus of my study. My PhD project includes time series observation of the oil contaminated water column as well as the sediment of the Gulf of Mexico. The crude oil from the riser pipe at the seafloor (~1500 m depth) formed a deep sea hydrocarbon plume, as well as huge amount of surface oil slick. An uncultured Oceanospirillales group and the polycyclic aromatic hydrocarbon (PAH) degrader Cycloclasticus were extremely dominant during the spill within the plume and the oil slick during the spill, respectively. After the wellhead was capped, the plume could not be detected; however, Cycloclasticus was continuously found in post-spill water. The surface oil slicks formed mucus rich oily marine snow aggregates via the activities of EPS producers such as Halomonas. Inside the aggregates several hydrocarbon degraders (i.e. Cycloclasticus) and heterotrophic bacteria such as Roseobacter bloomed. These oil snow aggregates sank and eventually made their way to the seafloor, as sediments with oily surface layer has been recovered since September 2010. Bacterial dynamics within the oil contaminated sediment included the appearance of Roseobacter and Verrucomicrobiaceae in September 2010, increase of anaerobic sulfate-reducing bacteria and organic matter degrading Cytophaga in October 2010. The Planctomycetes increased from low clone library proportions in October 2010 towards higher representation in November 2010 and July 2011, one year after the oil spill. Notably, Cycloclasticus was detected in the oil contaminated sediment from September to November 2010, strongly supporting the hypothesis of precipitation of oily marine snow aggregates. Besides these molecular observations, novel species of oil-degrading bacteria and potential hydrocarbon and/or organic matter degraders were isolated or enriched from the water samples (plume and surface oil slick) as well as the seafloor sediments. This time series study reveals development of the oil-degrading community together with continuous movement of the release oil from the deep ocean and sea surface to the sediment, via precipitation of the oily snow particles, demonstrates the coincidence of the oil decomposition with its continuing microbial processing.
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  • In Copyright
Advisor
  • Joye, Samantha
  • Piehler, Michael
  • Teske, Andreas
  • MacGregor, Barbara
  • Martens, Christopher S.
  • Arnosti, Carol
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2014
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  • Chapel Hill, NC
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