Analysis of bacterial community composition in concretions formed on the USS Arizona, Pearl Harbor, HI

Invertebrate fouling communities called concretions form on archaeological metals submerged in marine environments. The concretions are inhabited by bacteria that play a role in formation and persistence of the concretion layer. We analyzed the bacterial community in concretion samples collected from the external hull of the USS Arizona in Pearl Harbor, HI. Variability in the size of the bacterial community was high and the concretions appear to harbor approximately 106 bacteria/g. Analysis of 16S rDNA clones indicated that the community consisted of bacteria related to three phyla: Firmicutes, Bacteroidetes, and Proteobacteria. The low bacterial diversity may indicate a late-succession stage community within the stable concretion. Alternatively, the low diversity could be the result of residual antifouling chemicals applied to the ship hull. It is likely that the bacterial community detected in these concretions plays an important role in the continuing corrosion of the USS Arizona.