After accidental oil spills to seawater from production or transport facilities the oil will be spread on the water surface and in the water column, and a number of weathering processes will appear. Typical operational methods to remove the oil from the sea surface include physical limitation of the surface spreading with booms and collection of the oil by skimmers. An alternative method to remove surfaced oil is to use chemical dispersants. These chemicals create a more hydrophilic oil surface, resulting in the generation of small droplets by wave actions, which are spread into the water column. The generation of small droplet dispersions may increase the natural biodegradation of the oil in the seawater column. Recently, dispersant methods have also been used for sub-surface oil spills (blow-outs). The Norwegian Research Council and several oil companies have funded this research project in order to improve our knowledge and understanding about the effects of dispersant strategies on oil biodegradation and the microbial communities and processes involved. The data from this project will contribute to the optimization of dispersant strategies. The project will include experimental studies simulating both surface and subsurface oil discharges. The focus will be molecular microbiology analyses and bioinformatics, including phylogenetic characterization of microbial communities (characterization of 16S rRNA genes) and investigations of biochemical pathways associated with degradation of alkanes and aromatic oil compounds. Metagenomic and metatranscriptomic studies may be expected to be part of this work. Finally, generated experimental data should be incorporated into OSCAR model, a industry standard model for predicting the fate of the oil in the marine water column after an accidental oil spill.