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.
Abstract-To better understand the effects of bioturbation on partitioning and availability of sediment-bound contaminants to infaunal amphipods and mussels, experiments were carried out with fluoranthene-spiked sediment. Treatments included different densities of the estuarine amphipod, Corophium volutator. Total suspended solids (TSS), particulate organic carbon/particulate organic matter (POC/POM) in overlying water, fluoranthene concentrations in sediment, pore water, overlying water, amphipods, and mussels were measured. Bioturbation significantly increased TSS and POC/POM concentrations in overlying water, and this effect became greater at higher animal density and longer exposure time. Mean total aqueous fluoranthene concentrations increased from 2.40 to 4.1 and 5.45 g/L in the control, low-density, and high-density treatments, respectively, after 10 d of exposure. The particle-bound fraction of fluoranthene in the overlying water from the high-density treatment was two times higher than that from the low-density treatment. Bioturbation did not affect the partitioning of fluoranthene over suspended solids and water, nor did it affect the concentrations in sediment and pore water. This was illustrated by the constancy of sediment-interstitial water partitioning coefficients (log K oc(iw) ), sediment-overlying water partitioning coefficients (log K oc(ow) ), and normalized POC-water partitioning coefficients (log K poc ). Uptake of fluoranthene by filter-feeding mussels (Mytilus edulis) increased linearly with the density of bioturbating amphipods and with exposure time. The difference in concentrations of fluoranthene in mussels between the lowest and highest density of amphipods was more than a factor of two. Our results showed that bioturbation significantly increases TSS concentration in the overlying water and consequently the total aqueous concentration of sediment-bound contaminants, which are subsequently accumulated by filter-feeders. The increased accumulation in mussels, at a more or less constant concentration in the water, demonstrates the importance of bioturbation as a flux phenomenon and its role in the transport of resuspended sedimentbound contaminants to organisms in the aquatic food chain.
Four laboratories were compared to ascertain the reproducibility of test methods for five bioassays: the ten day whole sediment bioassay with the amphipod Corophium volutator, the fourteen day whole sediment bioassay with adult sea urchins Echinocardium cordatum, the Microtox solid phase bioassay with the bacterium Vibrio fischeri, the oyster larvae sediment elutriate bioassay using Crassostrea gigas and the sediment pore water bioassay with the rotifer Brachionus plicatilis. The bioassays were all conducted according to the standard operating procedures of the National Institute for Coastal and Marine Management/RIKZ and carried out with one control sediment and three moderately contaminated dredged materials from the Netherlands. Reference toxicant tests were also performed for every bioassay, to assess the condition of the test species. Reproducibility and inter-laboratory variability were evaluated by calculating coefficients of variation for the sediment bioassays and considering the ability of each laboratory to achieve the test acceptability criteria and to identify a number of confounding factors. The bioassays involving the amphipods and sea urchins had an acceptable inter-laboratory variability, with average coefficients of variation of 20% or less. The Microtox solid phase bioassay showed high reproducibility and the least variability among laboratories, with average coefficients of variation of 12%. In contrast, the results for percent net response in the oyster larvae bioassay were very variable and poorly reproducible: in three of the four sediments the coefficients of variation exceeded 100%. Two laboratories did not meet the test acceptability criterion for oyster embryo development in the control sediment. Survival in the rotifer bioassay also varied greatly among laboratories with average coefficients of variation of 48%. We conclude that the main sources of inter-laboratory variability were 1) individual differences in the skill and experience of laboratory technicians (for the amphipod, oyster larvae and rotifer bioassays); 2) the use of different batches of test organisms (sea urchin bioassay) and 3) the use of different dilution water (oyster larvae bioassay).
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.
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