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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Microbiol. | doi: 10.3389/fmicb.2019.02387

Dispersant enhances hydrocarbon degradation and alters the structure of metabolically active microbial communities in shallow seawater from the northeastern Gulf of Mexico

  • 1School of Earth and Atmospheric Sciences, Georgia Institute of Technology, United States
  • 2Guangdong Institute of Eco-environmental Science & Technology, China
  • 3School of Biological Sciences, Georgia Institute of Technology, United States
  • 4School of Biology, Georgia Institute of Technology, United States
  • 5College of Marine Science, University of South Florida, United States
  • 6School of Earth and Atmospheric Sciences, College of Sciences, Georgia Institute of Technology, United States

Dispersant application is a primary emergency oil spill response strategy and yet the efficacy and unintended consequences of this approach in marine ecosystems remain controversial. To address these uncertainties, ex situ incubations were conducted to quantify the impact of dispersant on petroleum hydrocarbon (PHC) biodegradation rates and microbial community structure at as close as realistically possible to approximated in situ conditions (2 ppm v/v oil with or without dispersant, at a dispersant to oil ratio (DOR) of 1:15) in surface seawater. Biodegradation rates were not substantially affected by dispersant application at low mixing conditions, while under completely dispersed conditions, biodegradation was substantially enhanced, decreasing the overall half-life of total PHC compounds from 15.4 to 8.8 days. While microbial respiration and growth were not substantially altered by dispersant treatment, RNA analysis revealed that dispersant application resulted in pronounced changes to the composition of metabolically active microbial communities, and the abundance of nitrogen-fixing prokaryotes, as determined by qPCR of nitrogenase (nifH) genes, showed a large increase. While the Gammaproteobacteria were enriched in all treatments, the Betaproteobacteria and different families of Alphaproteobacteria predominated in the oil and dispersant treatment, respectively. Results show that mixing conditions regulate the efficacy of dispersant application in an oil slick, and the quantitative increase in the nitrogen-fixing microbial community indicates a selection pressure for nitrogen fixation in response to a readily biodegradable, nitrogen-poor substrate.

Keywords: hydrocarbon degradation, Deepwater Horizon, Dispersant, microbial community, Hydrocarbon analysis

Received: 24 Feb 2019; Accepted: 01 Oct 2019.

Copyright: © 2019 Sun, Lena, Mercando, Romero, Hollander and Kostka. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Joel E. Kostka, Georgia Institute of Technology, School of Biological Sciences, Atlanta, 30332, Georgia, United States, joel.kostka@biology.gatech.edu