Coaccumulation of cadmium and zinc in tissues of sentinel mallards (Anas platyrhynchos) using a former dredge-disposal impoundment.

Six- to eight-month-old female farm-raised mallards (Anas platyrhynchos) were used to examine the accumulation of and association among cadmium (Cd), zinc (Zn), and copper (Cu) from an impoundment constructed to contain sediments dredged from a lake contaminated by a zinc smelter. Cd was not detectable in the livers t of farm-raised mallards (day 0), although sentinel mallards accumulated hepatic Cd in the first 7 days after release. By day 14, mean concentrations of Cd in kidneys (= 2.82 mg/kg wet weight) had increased 3.4-fold. The mean pancreatic Cd concentration increased 59% between days 7 and 14. Renal Zn increased nominally, whereas pancreatic Zn increased 63% in sentinel ducks after release. Hepatic Zn increased significantly in the first week of release. Renal and pancreatic Cu concentrations did not change significantly, whereas concentrations of Cu in livers of ducks increased 50% in the 7 days after release before decreasing by nearly the same degree. Concentrations of Cd and Zn were correlated in livers of sentinel mallards on days 7 and 14. Cd and Cu were not correlated in the tissues of any cohort. Cu and Zn were correlated in the livers of farm-raised mallards, in the pancreases of sentinel mallards at day 7, and in the kidneys of the ducks in all three treatments. The relationship between Cd and Zn in tissues of ducks in our study was complicated by simultaneous exposure to increased and heterogeneous concentrations of Cd and Zn, both of which can induce metallothionein and compete for this and other ligands.

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.

Effects of lead, iron, and bismuth alloy shot embedded in the breast muscles of game-farm mallards.

Effects of five lead (Pb), iron (Fe), or bismuth (Bi)/tin (Sn) alloy shot embedded in the breast muscles of game-farm mallards (Anas platyrhynchos) were studied from 28 March 1994 through 27 March 1995. We detected no differences in the mean survival times, mean hematocrits, or mean body weights among the three shot types. Connective tissue encapsulated Pb and Bi/Sn shot but only slight changes occurred in tissues surrounding the shot. Recovered Pb and Bi/Sn shot were essentially unchanged in appearance and weight. A thin zone of "oxide" surrounded Fe shot with a slight inflammatory response and a small amount of scarring adjacent to the embedded shot. Fe shot decreased slightly in weight while embedded. Bacterial infections were absent in all dosed ducks. Mean weights of kidneys, livers, and gonads did not vary by type of shot. Kidneys and livers of Bi-dosed ducks had higher concentrations of Bi than in Pb- and Fe-dosed ducks. Muscle and blood showed no differences in Bi concentrations among doses. We found no histological dose-related effects in kidneys, liver, and gonads from the embedded shot.