This study investigates the interplay between hydrocarbon biodegradation and metal biocorrosion in the ballast tanks of US Navy vessels. Metagenomic and metabolite profiling of ballast water with varying residence times (1, ~20, and 31 weeks) revealed a rapid shift in microbial communities from aerobic *Gammaproteobacteria* dominating in younger ballast to anaerobic *Deltaproteobacteria* dominating in older ballast. This shift correlated with changes in hydrocarbon degradation genes and the presence of diagnostic metabolites. Elevated levels of Fe, Mn, Ni, and Cu in all ballast samples indicated corrosion, likely exacerbated by microbial activity. The findings suggest that marine microbial communities accelerate fuel and infrastructure deterioration in naval vessels.

Christopher R. Marks, Kathleen E. Duncan, Mark A. Nanny, Brian H. Harriman, Recep Avci, Athenia L. Oldham, Joseph M. Suflita