Metal and Metallothionein Concentrations in Scoter (Melanitta spp.) from the Pacific Northwest of Canada, 1989–1994

Abstract

Eighty-six surf (Melanitta perspicillata) and nine white winged (M. fusca) scoters were collected from 1989–1994 at 11 locations in British Columbia and the Yukon. Their kidney and liver tissues were analyzed for cadmium (Cd), copper (Cu), zinc (Zn), and metallothionein (MT) concentrations. Individual kidney Cd values ranged from 2.4 μg/g dry weight (DW) in birds from northern Vancouver Island to 390.2 μg/g (DW) in birds from the Queen Charlotte Islands, which is in the range of values potentially associated with kidney damage. Birds from the Queen Charlotte Islands also had high kidney Zn concentrations, which were significantly higher than values in birds from Naniamo and Westham Island on the south coast of BC. Cd values were significantly (p < 0.001) correlated with both Zn and MT concentrations in kidney tissue (r = 0.66 and 0.62, respectively). Male surf scoters had significantly higher kidney Cd and Zn levels than females, with mean Cd values of 47.3 and 19.7 μg/g DW (p < 0.002) for males and females, respectively. Mean Zn values were 120.8 and 108.0 μg/g DW (p < 0.05) for males and females, respectively. However, no sex differences were observed for either Cu or MT concentrations in kidney tissue. Individual MT values ranged from 2.7 to 416.8 μg/g wet weight (WW). Individual kidney Cu values ranged from 15.1 to 48.4 μg/g DW for both sexes. Kidney and liver Cd concentrations were significantly correlated (r = 0.90, p < 0.05) with kidney levels almost always higher than liver values. Although Cd accumulation by the Skidegate scoters was high, comparable tissue Cd values have been documented in other seabirds collected from the same general area, indicating elevated Cd concentrations in marine food chains around the Queen Charlotte Islands (Haida Gwaii) region of the Pacific coast.