Bioaccumulation and metabolism of benzo[a]pyrene in three species of polychaete worms

Polychaete worms which inhabit and ingest contaminated sediments may be exposed to a suite of sediment-sorbed xenobiotics, including polycyclic aromatic hydrocarbons (PAHs) such as benzo[a]pyrene (BaP). This study compared the accumulation and metabolism of sediment-sorbed BaP among various populations of polychaetes, including Leitoscoloplos fragilis, Nereis diversicolor, and Scolecolepides (= Marenzellaria) viridis. After exposure to trace amounts of BaP in sediment, N. diversicolor and S. viridis were found to metabolize BaP extensively, but metabolism of BaP appeared to be much slower in L. fragilis. Within each species, no consistent, significant differences in extent of BaP metabolism were observed between worms collected from contaminated versus reference sites. This result suggests that metabolism of BaP was not induced in worms from contaminated sites. To examine the extent to which metabolism of BaP is inducible in these species, worms were exposed in the lab to 3-methylcholanthrene (3MC), a potent inducer of PAH metabolism in other species. Only one species, S. viridis, showed a small increase in the percent of total tissue BaP that was biotransformed after treatment with 3MC. Whether or not worms were treated with 3MC, biota-sediment accumulation factors (lipid- and organic carbon-normalized tissue to sediment ratios) were highest for L. fragilis.