title: Chemical dispersants can suppress the activity of natural oil-degrading microorganisms.
abstract: During the Deepwater Horizon oil well blowout in the Gulf of Mexico, the application of 7 million liters of chemical dispersants aimed to stimulate microbial crude oil degradation by increasing the bioavailability of oil compounds. However, the effects of dispersants on oil biodegradation rates are debated. In laboratory experiments, we simulated environmental conditions comparable to the hydrocarbon-rich, 1,100 m deep plume that formed during the Deepwater Horizon discharge. The presence of dispersant significantly altered the microbial community composition through selection for potential dispersant-degrading Colwellia, which also bloomed in situ in Gulf deep waters during the discharge. In contrast, oil addition to deepwater samples in the absence of dispersant stimulated growth of natural hydrocarbon-degrading Marinobacter. In these deepwater microcosm experiments, dispersants did not enhance heterotrophic microbial activity or hydrocarbon oxidation rates. An experiment with surface seawater from an anthropogenically derived oil slick corroborated the deepwater microcosm results as inhibition of hydrocarbon turnover was observed in the presence of dispersants, suggesting that the microcosm findings are broadly applicable across marine habitats. Extrapolating this comprehensive dataset to real world scenarios questions whether dispersants stimulate microbial oil degradation in deep ocean waters and instead highlights that dispersants can exert a negative effect on microbial hydrocarbon degradation rates.
authors.affiliation: Department of Marine Sciences, University of Georgia, Athens, GA 30602;
authors.forename: Sara
authors.initials: S
authors.lastname: Kleindienst
authors.affiliation: Department of Marine Sciences, University of Georgia, Athens, GA 30602;
authors.forename: Michael
authors.initials: M
authors.lastname: Seidel
authors.affiliation: Department of Marine Sciences, University of North Carolina, Chapel Hill, NC 27599;
authors.forename: Kai
authors.initials: K
authors.lastname: Ziervogel
authors.affiliation: Josephine Bay Paul Center, Marine Biological Laboratory, Woods Hole, MA 02543;
authors.forename: Sharon
authors.initials: S
authors.lastname: Grim
authors.affiliation: Department of Marine Sciences, University of Georgia, Athens, GA 30602;
authors.forename: Kathy
authors.initials: K
authors.lastname: Loftis
authors.affiliation: Department of Marine Sciences, University of Georgia, Athens, GA 30602;
authors.forename: Sarah
authors.initials: S
authors.lastname: Harrison
authors.affiliation: Department of Marine Sciences, University of Georgia, Athens, GA 30602;
authors.forename: Sairah Y
authors.initials: SY
authors.lastname: Malkin
authors.affiliation: Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR 97331;
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Perkins
authors.affiliation: Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR 97331;
authors.forename: Jennifer
authors.initials: J
authors.lastname: Field
authors.affiliation: Josephine Bay Paul Center, Marine Biological Laboratory, Woods Hole, MA 02543;
authors.forename: Mitchell L
authors.initials: ML
authors.lastname: Sogin
authors.affiliation: Research Group for Marine Geochemistry, Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University, 26129 Oldenburg, Germany; Max Planck Institute for Marine Microbiology (MPI), 28359 Bremen, Germany;
authors.forename: Thorsten
authors.initials: T
authors.lastname: Dittmar
authors.affiliation: Marine Science Institute, University of California, Santa Barbara, CA 93106.
authors.forename: Uta
authors.initials: U
authors.lastname: Passow
authors.affiliation: Department of Marine Sciences, University of Georgia, Athens, GA 30602;
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Medeiros
authors.affiliation: Department of Marine Sciences, University of Georgia, Athens, GA 30602; mjoye@uga.edu.
authors.forename: Samantha B
authors.initials: SB
authors.lastname: Joye
mesh_terms: D001673:Biodegradation, Environmental; D060851:Gulf of America; D053520:Marinobacter / Q000254:growth & development*; D010578:Petroleum / Q000378:metabolism*; D059392:Petroleum Pollution; D012623:Seawater / Q000382:microbiology*; D014871:Water Microbiology
chemical_list: D010578:Petroleum
keywords: chemical dispersants; hydrocarbon cycling; microbial dynamics; oceanography; oil spills