Marine snow formation in the aftermath of the Deepwater Horizon oil spill in the Gulf of Mexico, May 5, 2010 to September 8, 2010

Large mucus rich marine snow floating at the sea surface in association with a visible oil layer from the Deepwater Horizon (DWH) spill was collected in May 2010 and characterized: Sizes, sinking velocities and solid hydrated density of component particles were determined in the laboratory and excess density and porosity of marine snow aggregates calculated. Furthermore exploratory marine snow formation experiments in the presence of oil were conducted using source water collected during three DwH oil spill response cruises between May 2010 and August 2010 in the vicinity of the spill and at a control station outside of the spill area. Experiments were conducted with marine snow free surface water, enriched or unenriched with natural Trichodesmium populations and with deep plume water. Marine snow formation was followed over time comparing treatments with or without oil different oils and different source waters. Experiments suggest that the marine snow appearing at the surface after the oil spill was formed through the interaction of three mechanisms: (1) Production of mucous webs through activities of bacterial oil-degraders associated with the floating oil layer. (2) Interactions of oil components with suspended matter and their coagulation, and (3) coagulation of phytoplankton with oil droplets incorporated into aggregates. Some of the formed marine snow sank, whereas some was positively buoyant.