Decreased sedimentation efficiency of petro- and non-petro-carbon caused by a dispersant for Macondo surrogate oil in a mesocosm simulating a coastal microbial community

Chen Xu, Saijin Zhang, Morgan Beaver, Andrew Wozniak, Wassim Obeid, Youmin Lin, Terry L. Wade, Kathleen A. Schwehr, Peng Lin, Luni Sun, Patrick G. Hatcher, Wei Chun Chin, Meng Hsuen Chiu, Anthony H. Knap, Kendra Dean, Antonietta Quigg, Peter H. Santschi

Research output: Contribution to journalArticle

Abstract

Large amounts of mucous-rich oil-containing marine snow formed in surface waters adjacent to the Deepwater Horizon spill. This marine oil snow (MOS) was implicated in oil delivery to the seafloor. Whether the use of chemical dispersants increased or decreased MOS sedimentation remains controversial. We conducted mesocosm experiments testing the effects of oil and oil plus a dispersant on MOS formation and sedimentation, in coastal seawater. The four treatments used were a surrogate Macondo oil water accommodated fraction (“WAF”), two concentrations of chemically-enhanced WAF (“CEWAF” and diluted CEWAF, “DCEWAF”) containing a dispersant and oil, and Controls (no additions). Based on radiocarbon and 13C NMR results, the presence of dispersants enhanced the amounts of petro-carbon being incorporated into the sinking oil-carrying aggregates (aka MOS). However, most of the chemically-dispersed oil preferentially partitioned into the colloidal and suspended particulate fractions rather than into the rapidly forming MOS. Thus the oil and non-petro-carbon sedimentation efficiency in treatments with a dispersant was much lower, compared to those in the Control and WAF treatments, during the four-day mesocosm experiment. Formation of MOS and its subsequent sinking sequestered the oil in two stages: first via terrestrial-derived detritus containing humic compounds, and subsequently via freshly produced material, such as exopolymeric substances produced by phytoplankton and bacteria.

Original languageEnglish (US)
JournalMarine Chemistry
DOIs
Publication statusAccepted/In press - Jan 1 2018
Externally publishedYes

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ASJC Scopus subject areas

  • Oceanography
  • Chemistry(all)
  • Environmental Chemistry
  • Water Science and Technology

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