Use of a simulated gizzard to measure bioavailability of metals and other elements to waterfowl

We used a simulated gizzard environment to examine the bioavailability of b arium, cadmium, nobreak copper, lead and zinc to wild and sentinel mallards (Anas platyrhynchos) using a seasonally-flooded wetland. This impoundment was originally constructed as a containment area for dredged sediments whic h were contaminated through previous smelting operations. Extraction of ele ments from gizzard contents indicated that sentinel mallards experienced gr eater exposure to contaminants than their wild counterparts. Concentrations of the selected elements extracted from ingesta were lower than in seeds a nd sediments from the study site. Notable exceptions were barium and lead, which were not detected in seeds of some plant species, though they were pr esent in the ingesta of one or more treatment groups. This technique may pr ovide a more realistic means of estimating bioavailability and exposure tha n methods which measure total concentrations of elements in dietary compone nts. The use of sentinel mallards may result in inflated estimates of risk to wild ducks using seasonally-available wetlands.