Role of prior exposure on anaerobic degradation of naphthalene and phenanthrene in marine harbor sediments

The anaerobic degradation of the polycyclic aromatic hydrocarbons(PAHs) nap hthalene and phenanthrene was investigated in several marine harbor sedimen ts. In sediments from Boston Harbor that were heavily contaminated with pet roleum, [C-14]-naphthalene and [C-14]-phenanthrene were oxidized to (CO2)-C -14 without a lag, suggesting that the microbial community was adapted for anaerobic PAH oxidation in situ. The addition of molybdate, a specific inhi bitor of sulfate-reducing microorganisms, inhibited PAH mineralization whic h suggested that sulfate reducers were involved in the anaerobic oxidation of the PAHs. PAHs were also anaerobically oxidized at another site in Bosto n Harbor that was less heavily contaminated, but at a slower rate than in t he most heavily contaminated sediments. Sediments not contaminated with pet roleum did not significantly oxidize the PAHs. A similar correspondence bet ween rates of anaerobic PAH oxidation and the degree of PAH contamination w as observed in sediments from Tampa Bay and San Diego Bay. When relatively pristine sediments from San Diego Bay that did not have a significant capac ity for anaerobic PAH oxidation were exposed to high concentrations of naph thalene, they developed a potential for naphthalene degradation that was co mparable to that in sediments that had a history of PAK contamination. The increase in potential for naphthalene degradation in the sediments exposed to naphthalene was associated with an increase in naphthalene-degrading mic roorganisms. These results suggest that many marine harbor sediments contai n microorganisms capable of anaerobically oxidizing PAHs under sulfate-redu cing conditions and that these microorganisms will respond with an increase in their activity when PAHs are introduced into the sediments. Thus, if PA H inputs into harbor sediments from petroleum can be reduced there may be a widespread potential for microorganisms to remove this PAH contamination f rom the sediments, despite anaerobic conditions. (C) 1999 Elsevier Science Ltd. All rights reserved.