The ability of subsurface microbial populations to degrade organic contaminants is affected by nutrient availability. A study was performed to measure the change in microbial ecology of a weathered JP-4 jet fuel contaminated site (Eglin Air Force Base, Florida) over the course of a nitrate-based treatment in terms of heterotrophs, JP-4 degraders, oligotrophs, biosurfactant producers, bioemulsifier producers, and predators. Microbial numbers increased and species diversity decreased in the nitrate-amended site significantly more than in background areas. The surfactant producing potential of native microbial communities decreased significantly with nitrate addition. Bioemulsification capacity of these communities was slightly lowered with addition of nitrate. Aerobic predators decreased over the course of the experiment, while microaerophilic predators increased significantly. Due to fluctuations in measured JP-4, no conclusions could be drawn about the success of nitrate addition as a remedial enhancement technique at this site.