Contaminants and sea ducks in Alaska and the circumpolar region.

Abstract

We review nesting sea duck population declines in Alaska during recent decades and explore the possibility that contaminants may be implicated. Aerial surveys of the surf scoter (Melanitta perspicillata), white-winged scoter (M. fusca), black scoter (M. nigra), oldsqaw (Clangula hyemalis), spectacled eider (Somateria fischeri), and Steller's eider (Polysticta stellei) show long-term breeding population declines, especially the latter three species. The spectacled eider was recently classified threatened under the Endangered Species Act. In addition, three other diving ducks, which commonly winter in coastal areas, have declined from unknown causes. Large die-offs of all three species of scoters during molt, a period of high energy demand, were documented in August 1990, 1991, and 1992 at coastal reefs in southeastern Alaska. There was no evidence of infectious diseases in those scoters. The die-offs may or may not be associated with the long-term declines. Many scoters had elevated renal concentrations of cadmium (high of 375 micrograms/g dry weight [dw]). Effects of cadmium in sea ducks are not well understood. Selenium concentrations in livers of nesting white-winged scoters were high; however, the eggs they laid contained less selenium than expected based on relationships for freshwater bird species. Histological evaluation found a high prevalence of hepatocellular vacuolation (49%), a degenerative change frequently associated with sublethal toxic insult. Cadmium and selenium mean liver concentrations were generally higher in those birds with more severe vacuolation; however, relationships were not statistically significant. We do not know if sea duck population declines are related to metals or other contaminants.

Survival rates and blood metal concentrations in two species of free‐ranging North American sea ducks

“…White-tailed ptarmigan (Lagopus leucurus) in a Cd-polluted, low-Ca ecosystem showed evidence of renal tubular damage at kidney Cd levels greater than 100 g/g, and survival rates of ptarmigan from the Cd-polluted site were lower than those of birds from a nonpolluted site [28]. Cadmium levels in kidneys of sea ducks usually are less than 100 g/g wet weight, but levels as high as 70 g/g have been reported [5][6][7][8]29]. Evidence exists that Cd toxicity may occur at kidney concentrations less than 100 g/g wet weight.…”

“…If king eiders and whitewinged scoters are similar to common eiders in this regard, it is plausible that Hg could exacerbate the adverse effects of other environmental stressors. Total Hg levels in eiders, scoters, and other sea ducks are relatively low, however, especially compared to pelagic marine birds and fish-eating birds [5][6][7]43]. Moreover, marine birds, presumably including sea ducks, generally are well-adapted for coping with exposure to elevated Hg levels [44].…”

“…org). In particular, exposure of sea ducks to some trace metals often is high relative to that of other species of birds [5][6][7][8].…”

A Blood Survey of Elements, Viral Antibodies, and Hemoparasites in Wintering Harlequin Ducks (Histrionicus Histrionicus) and Barrow's Goldeneyes (Bucephala Islandica)

“…High blood selenium concentrations also have been described in otherwise healthy Alaskan waterfowl including Emperor Geese (Chen canagica), Long-tailed Ducks, Spectacled Eider, King Eider (Somateria spectabilis), and Common Eider (Franson et al, 1999Stout et al, 2002;Wayland et al, 2003;Franson et al, 2004;Wilson et al, 2004). Similarly, high tissue concentrations have been described in ducks from Canada (Henny et al, 1995;Wayland et al, 2001Wayland et al, , 2003Braune and Malone, 2006) and Russia (Stout et al, 2002). Samples have usually been collected from nesting birds when they are most easily caught.…”

“…Screening for elemental and organochlorine contaminants has been conducted in several Arctic waterfowl (Henny et al, 1995;Grand et al, 1998;Franson et al, 1999Franson et al, , 2002Franson et al, , 2004Braune et al, 2006) to determine causes for declining populations (Goudie et al, 1994). Lead appears to be a significant cause of mortality and influence on Spectacled Eider (Somateria fischerifisheri) populations (Grand et al 1998).…”