Bioavailability of lab-contaminated and native polycyclic aromatic hydrocarbons to the amphipod Corophium volutator relates to chemical desorption.

In the present study, the relationship between bioavailability of polycyclic aromatic hydrocarbons (PAHs) to benthic amphipods and the PAH desorption kinetics was examined. To that end, field-contaminated sediment was treated in three different ways. One subsample had no addition of PAHs and contained native PAHs only. To a second subsample, six PAHs (phenanthrene, fluoranthene, anthracene, pyrene, benzo[b]fluoranthene, and benzo[k]fluoranthene) were added in the laboratory. Two of the PAHs were added at higher concentrations to a third subsample, serving as a control for concentration-dependent uptake. Marine amphipods (Corophium volutator) were exposed to the three subsamples for a maximum of 25 d and were subsequently analyzed. Desorption kinetics were determined for both the lab-contaminated and the native PAHs. The biota-to-sediment accumulation factor (BSAF) values of the individual native and lab-contaminated PAHs correlated well with the rapidly desorbing fraction (R2 = 0.76). The BSAFs were 1.4 to 3.3 higher for the lab-contaminated PAHs compared with the native PAHs, while the difference between the rapidly desorbing fractions was a factor of 1.1 to 1.8. The BSAFs of the lab-contaminated PAHs in the second and third subsample were equal, indicating concentration-independent accumulation. The results suggest that lab-contaminated PAHs are more available to amphipods than native PAHs and that differences in bioavailability of lab-contaminated and native PAHs to marine amphipods are related to differences in desorption behavior.

Ecotoxicity Assessment of Contaminated Dredged Material with the Marine Amphipod Corophium volutator

The incorporation of toxicological data from bioassays can improve the present system of sediment quality criteria in the Netherlands. The use of acute lethality toxicity tests alone does not however provide sufficient discrimination and sensitivity for predicting ecological effects of slightly and moderately contaminated dredged material. Sublethal endpoints are needed for the assessment of environmental hazards of such dredged material. In this study, two approaches were used to identify toxicity of marine sediments collected from 16 locations classified as "slightly and moderately contaminated" on the basis of chemical data: (1) a comparison of growth vs. mortality as different endpoints in the marine amphipod Corophium volutator (Pallas); (2) an investigation on the use of sediment dilutions to characterize the degree of toxicity. The influence of sediment storage time on toxicity was also evaluated. In four out of 16 locations, mortality over 10 days of exposure ranged 80-100%; in two out of 16 locations mortality ranged 40-60%. In the other 10 locations, mortality was below 15%. Results on growth showed that in all locations final dry weight values were significantly lower (a factor of 1.5 to 3) than in controls. Results of dilution experiments showed that if sediments were diluted with a reference sediment of similar physicochemical characteristics, total concentrations of metals, mineral oil, and PAHs decreased as expected and so did the effects on C. volutator. In the 100% contaminated sediments growth was reduced by 32-60% compared to controls. The dilution rate necessary to reduce toxicity to the EC10 value for growth of C. volutator was considered an appropriate endpoint for the evaluation. When sediments were stored for a period of 3-5 months at 4 degreesC and retested, effects on mortality and growth decreased, although some effects on growth were still measured after 5 months of storage. The experiments illustrate the usefulness of ecotoxicity assessment to evaluate contaminted dredged material.