Particle counts in different size fractions taken during mesocosms GOMOO, GOM open ocean, and GOMCOAST, GOM coastal waters

Aggregation is a phenomenon that has been observed following oil spills. The size and number of aggregates can change with specific microbial communities, or the presence of chemical dispersants such as Corexit. In order to assess the impact of oil exposure on the formation of small aggregates (<100um), two mesocosm experiments were conducted during July 2016; GOMOO (Gulf of Mexico Open Ocean) and GOMCOAST (Gulf of Mexico Coastal waters). Oil and dispersant exposure were facilitated using the water accommodated fraction (WAF) of oil, a chemically enhanced WAF (CEWAF, mixture of oil and Corexit) and a dilute CEWAF (DCEWAF). 15mL aliquots were taken every 24h from each mesocosm for immediate analysis on a Z2 dual-threshold Coulter counter (Beckman Coulter). The Coulter counter was outfitted with a 100µm aperture, and particles were counted in three ranges; 10-20µm, 20-50µm and >50µm. The data presented will be particle counts (particles/mL) over time within each size fraction. Estimated oil equivalents are reported in GRIIDC datasets R4.x263.000:0038 and R4.x263.000:0039.