Metabolism of the polycyclic aromatic hydrocarbon fluoranthene by the polychaete Capitella capitata species I

Previous studies have shown that infaunal deposit feeders may enhance the l oss of organic contaminants from sediments. However, the extent to which th is occurs as a result of sediment microbial stimulation, porewater flushing , or biotransformation by infauna remains unclear. The purpose of this stud y was to determine whether the infaunal polychaete Capitella sp. I is able to metabolize the polycyclic aromatic hydrocarbon (PAH) fluoranthene and to provide an initial characterization of the metabolites produced. Our resul ts showed that Capitella sp. I is able to metabolize fluoranthene to more h ydrophilic products and that, after 24 h in clean sediment, fluoranthene co uld no longer be detected in worm tissues whereas a number of fluoranthene- derived metabolites were present. None of the metabolites released or retai ned by worms resembled known bacterial metabolites, suggesting that Capitel la, and not bacteria associated with its gut or body surface, were responsi ble for the biotransformation of fluoranthene in our system. On the basis o f ultraviolet maxima, peak shape, relative height, and order of elution, te ntative identities of two metabolites (i.e., 3- and 8-hydroxyfluoranthene) are proposed. The results demonstrate that, in addition to their effects on sediment geochemical properties, infaunal polychaetes such as Capitella ca n enhance the degradation of sediment-associated contaminants by directly m etabolizing them.