TY - JOUR T1 - 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 JF - Marine Chemistry Y1 - 2018 A1 - Xu, Chen A1 - Zhang, Saijin A1 - Beaver, Morgan A1 - Wozniak, Andrew A1 - Obeid, Wassim A1 - Lin, Youmin A1 - Wade, Terry L. A1 - Schwehr, Kathleen A. A1 - Lin, Peng A1 - Sun, Luni A1 - Hatcher, Patrick G. A1 - Chin, Wei-Chun A1 - Chiu, Meng-Hsuen A1 - Knap, Anthony H. A1 - Dean, Kendra A1 - Quigg, Antonietta A1 - Santschi, Peter H. AB - 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. VL - 206 UR - https://linkinghub.elsevier.com/retrieve/pii/S0304420318301415 ER -