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 barium, cadmium, 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 which were contaminated through previous smelting operations. Extraction of elements from gizzard contents indicated that sentinel mallards experienced greater exposure to contaminants than their wild counterparts. Concentrations of the selected elements extracted from ingesta were lower than in seeds and sediments from the study site. Notable exceptions were barium and lead, which were not detected in seeds of some plant species, though they were present in the ingesta of one or more treatment groups. This technique may provide a more realistic means of estimating bioavailability and exposure than methods which measure total concentrations of elements in dietary components. The use of sentinel mallards may result in inflated estimates of risk to wild ducks using seasonally-available wetlands.