Effects of sediment bioturbation by the estuarine amphipodCorophium volutatoron fluoranthene resuspension and transfer into the mussel(Mytilus edulis)

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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 μg/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 Koc(iw)), sediment–overlying water partitioning coefficients (log Koc(ow)), and normalized POC–water partitioning coefficients (log Kpoc). 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 sediment-bound contaminants to organisms in the aquatic food chain.

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