February 17, 2016
The Deepwater Horizon oil spill was the largest in US history, unprecedented for the depth and volume of oil released, the amount of dispersants applied, and the unexpected sedimentation of oil-associated marine snow (MOS) to the seafloor. Marine snow formation, incorporation of oil, and the subsequent settling to the seafloor (termed MOSSFA in the paper: Marine Oil Snow Sedimentation and Flocculent Accumulation) was a significant pathway for the distribution and fate of the oil, accounting for as much as 14% of the total oil released. The paper suggests that long residence times of oil on the seafloor will result in prolonged exposure by benthic organisms and economically important fish. Major surface processes controlled the MOSSFA event, including an elevated and extended period of Mississippi River discharge, which enhanced phytoplankton production and suspended particle concentrations, zooplankton grazing, and enhanced microbial mucus formation. Oil-associated marine snow sedimentation also occurred during the Tsesis and Ixtoc-I oil spills in the Gulf of Mexico, which suggests that MOSSFA events may occur during future oil spills, particularly since 85% of global deep-water oil exploration sites are near river deltas.