We found that bacteria closely related to Alcanivorax became a dominant bacterial population in petroleum-contaminated sea water when nitrogen and phosphorus nutrients were supplied in adequate quantity. The predominance of Alcanivorax bacteria was demonstrated under three experimental conditions: (i) in batch cultures of sea water containing heavy oil; (ii) in columns packed with oil-coated gravel undergoing a continuous sea water flow; and (iii) in a large-scale tidal flux reactor that mimics a beach undergoing tidal cycles with fresh sea water. These results suggest that bacteria related to Alcanivorax are major players in the bioremediation of oil-contaminated marine environments