Effects of sediment bioturbation by the estuarine amphipod Corophium volutator on fluoranthene resuspension and transfer into the mussel (Mytilus edulis)

To better understand the effects of bioturbation on partitioning and availa bility of sediment-bound contaminants to infaunal amphipods and mussels, ex periments were carried out with fluoranthene-spiked sediment. Treatments in cluded different densities of the estuarine amphipod, Corophium volutator. Total suspended solids (TSS), particulate organic carbon/particulate organi c matter (POC/POM) in overlying water, fluoranthene concentrations in sedim ent, pore water, overlying water, amphipods, and mussels were measured. Bio turbation significantly increased TSS and POC/POM concentrations in overlyi ng water, and this effect became greater at higher animal density and longe r exposure time. Mean total aqueous fluoranthene concentrations increased f rom 2.40 to 4.1 and 5.45 mu g/L in the control, low-density, and high-densi ty treatments, respectively, after 10 d of exposure. The particle-bound fra ction of fluoranthene in the overlying water from the high-density treatmen t was two times higher than that from the low-density treatment. Bioturbati on did not affect the partitioning of fluoranthene over suspended solids an d water, nor did it affect the concentrations in sediment and pore water. T his was illustrated by the constancy of sediment-interstitial water partiti oning coefficients (log K-oc(iw)), sediment-overlying water partitioning co efficients (log K-oc(ow)), and normalized POC-water partitioning coefficien ts (log K-poc). Uptake of fluoranthene by filter-feeding mussels (Mytilus e dulis) increased linearly with the density of bioturbating amphipods and wi th exposure time. The difference in concentrations of fluoranthene in musse ls between the lowest and highest density of amphipods was more than a fact or of two. Our results showed that bioturbation significantly increases TSS concentration in the overlying water and consequently the total aqueous co ncentration of sediment-bound contaminants, which are subsequently accumula ted by filter-feeders. The increased accumulation in mussels, at a more or less constant concentration in the water, demonstrates the importance of bi oturbation as a flux phenomenon and its role in the transport of resuspende d sediment-bound contaminants to organisms in the aquatic food chain.