Bioaccumulation of sediment-associated fluoranthene in benthic copepods: uptake, elimination and biotransformation

Abstract

Most polycyclic aromatic hydrocarbons (PAHs) entering aquatic systems reside in sediments and in the storage lipids of the benthic biota. Massive amounts of PAHs reach estuarine systems and threaten their ecosystems. Copepods abound in the estuarine benthos, where they are an important component of food webs. The accumulation of sediment-associated [ 14C]fluoranthene was examined in adult females of two species of sediment-dwelling copepods, Schizopera knabeni and Coullana sp., collected from a Louisiana salt marsh. Accumulation was measured throughout a short- (24 h) and a long-term (10-day) exposure to concentrations in the sediment ranging from 0 to 1652 nmol (g dry wt.) −1. Fluoranthene apparent steady state body residue was reached very rapidly (<12 h) at all concentrations for both species. Lipid and organic-carbon-normalized bioaccumulation factors (BSAFs) calculated at day 1 were 0.57–0.80 for S. knabeni and 0.35–0.71 for Coullana sp. Fluoranthene body burden in female Coullana sp. changed dramatically during their reproductive cycle. A significant fraction of the fluoranthene residue was stored in the lipid-rich maturing eggs which were extruded into paired egg sacs. For S. knabeni, fluoranthene depuration occurred at similar rates in sediment and water (half life approximately 4.8 h), while it was faster in sediment than in water for Coullana sp. (half lives=4.2 and 7.4 h). Fluoranthene was biotransformed to polar compounds in both species. Metabolites accounted for approximately 12% of the 14C activity in the tissues following a 96-h sediment exposure in both species. Given that fluoranthene was taken up from spiked sediment very efficiently and reached steady-state levels in the tissues very rapidly, PAH-contaminated sediments may pose a risk for benthic copepods and their predators.