T7 AM Metals in the Environment: Dietary Concerns in Aquatic Systems
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in 327-329
(GIL-1117-846708) Are ingested sediments a significant source of bioavailable Cu to Daphnia magna?.
Gillis, P1, Chow-Fraser, P1, Ranville, J2, Wood, C1, 1 Department of Biology, McMaster University, Hamilton, ON, Canada2 Colorado School of Mines, Golden, CO, USA
ABSTRACT- In aquatic environments with elevated levels of sediment-associated metals, organisms may be exposed to metals through both the dissolved and particulate phases. Daphnia magna were used to assess the bioavailability of sediment-associated metals using sediment collected from a mining-impacted stream (Clear Creek, CO). Whole-sediment exposures demonstrated that Cu released from the sediment into the overlying water, reached acutely toxic levels (Cu 35 
g/L). In order to distinguish metal toxicity originating from the particulate phase with that from the dissolved phase, it was necessary to remove, or at least significantly reduce the easily-mobilized metals. Repetitive rinsing (washing) of sediments resulted in a >60% reduction in dissolved Cu and significantly greater D. magna survival (96%) compared to exposures using unwashed sediments (42%). Whole-body tissue concentrations suggested that there was still bioavailable Cu associated with the washed sediment. However, closer examination revealed that unless D. magna were allowed to purge their gut in the presence of algae (8h), the presence of sediment in their gut led to an overestimation of accumulated Cu by 3-6 fold. Finally, an exposure with washed sediment and gut-cleared Daphnia revealed that the removal of suspended particles by filtration (>0.45m) did not significantly affect tissue Cu concentration, suggesting that the Cu that remained associated with the particles was not bioavailable. These data indicate that although there is substantial Cu associated with this sediment (2.5 mg/g), the labile portion is the main source of bioavailable metal, rather the Cu that remains associated with the particles. (Supported by CSME, USEPA)
Key words: sediment-associated metals, Copper, bioavailability, Daphnia magana