Dissolution of sedimentary polycyclic aromatic hydrocarbons into the lugworm's (Arenicola marina) digestive fluids

We studied the mechanism(s) by which a deposit feeder can solubilize PAH from contaminated sediments as well as the implications of these mechanisms for factors controlling PAH bioavailability. Arenicola marina digestive fluids solubilize 4.6 mu g mL-' phenanthrene and 2.0 mu g mL(-1) benzo[a]pyrene-concentrations greater than the PAH's seawater solubilities-when incubated with pure PAH solids. This enhanced solubilization is largely due to surfactant micelles in the digestive fluid. In experiments with contaminated sediments that repeat the incubation or vary the solid-fluid ratio, these and other PAHs saturate at much lower concentrations (often between 0.01 and 0.1 mu g mL(-1)). Less solubilization is likely due to sorption of digestive surfactants by sedimentary organic matter and competition from other sedimentary hydrophobic solutes, such as aliphatic hydrocarbons, for remaining micellar space. Nevertheless, gut fluid concentrations of high molecular weight PAHs are greater than those predicted from equilibrium partitioning theory, indicating the importance of the digestive pathway for hydrophobic organic contaminant exposure and bioaccumulation.