A) Schematic diagram of the experimental design. For both mechanically dispersed (MD) and chemically dispersed (CD) oil, 3 concentrations – low (L), medium (M) and high (H) – were used (n = 4 for all). Dispersions were made using two dispersant generators where oil-in-water-dispersions were generated from either oil premixed with dispersant, or from oil alone. Dilution of the dispersions was computer controlled using solenoid vales to collect defined ratios of dispersions and clean seawater from the two feed tubes running along the exposure chambers. A total of 4 control chambers were used. B) Cumulative size distribution based on volume of oil droplets recorded at the outlet of the high exposure vessels with mechanically and chemically dispersed oil. Data in each group are average of 4 parallel vessels. Algae with mean size of 4.7 μm have been subtracted.