Exposure of two species of deposit-feeding amphipods to sediment-associated [3H]benzo[a]pyrene: Uptake,metabolism and covalent binding to tissue macromolecules

Two species of deposit-feeding marine gammaridian amphipods, Rhepoxynius abronius and Eohaustorius washingtonianus, were exposed to sediment-associated ³H]benzoa]pyrene (BaP) at 12±1°C. Concentrations of BaP-derived radioactivity increased with time in both E. washingtonianus and R. abronius, and the levels of radioactivity were similar in both species after 7 days of exposure. A significantly (P<0.05) lower proportion (51%) of unconverted BaP was present in R. abronius than in E. washingtonianus (73%) at 1 day. The proportion of unconverted BaP decreased with time in R. abronius (30% at 7 days), but did not vary significantly with time in E. washingtonianus. Reverse-phase high-pressure liquid chromatography (HPLC) of organic solvent-soluble metabolites released from β-glucuronidase and arylsulfatase treated tissue extracts of amphipods showed the presence of metabolites such as 7,8-dihydroxy-7,8-dihydroBaP (BaP-7,8-diol), 9,10-dihydro-9,10-dihydroxyBaP (BaP-9,10-diol), 3-hydroxyBaP and 9-hydroxyBaP. The ratio of BaP-7,8-diol to BaP-9,10-diol obtained from normal-phase HPLC was 1.2 for R. abronius and 0.7 for E. washingtonianus. Moreover, the level of covalent binding of BaP intermediates to macromolecules was significantly (P≤0.01) higher at 7 days in R. abronius (7.00±0.98 pmol BaP equivalents/g-protein) than in E. washingtonianus (4.08±0.51 pmol/g-protein). Thus, using BaP as a representative of sediment-associated polynuclear aromatic hydrocarbons, it was shown that although both amphipod species accumulated similar concentrations of BaP-derived radioactivity, R. abronius converted a higher proportion of BaP into potentially toxic intermediates.