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), oldsquaw (Clangula hyemalis), spectacled eider (Somateria fischeri), and Steller's eider (Polysticta stelleri) 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 1990August , 1991August , 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 pg/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.

Heavy-metal concentrations in three owl species from Korea

“…Essential elements such as iron, zinc, manganese, and copper in livers of owls in this study were greater than those of other Korean birds (Honda et al 1986;Lee et al 1987;Kim et al 2000;. However, these concentrations seemed to be within the normal range for birds (Custer and Hohman 1994;Puls 1994;Esselink et al 1995;Franson et al 1995;Henny et al 1995;Hothem et al 1998;Eisler 2000;Trust et al 2000;Stout et al 2002;Takekawa et al 2002;Custer et al 2003;) and are probably maintained by a normal homeostatic mechanism.…”

Morphological and Pathological Effects of Cadmium Ingestion on Pekin Ducks Exposed to Saline

“…Plankton sequester Cd from the water, and it passes through various food chains, eventually reaching significant concentrations in the tissues of invertebrate filter feeders, such as mussels. When these are eaten by seaducks, the ingested Cd is stored in the birds' organs, especially the liver and kidneys (Elliott & Scheuhammer, 1997;Henny et al, 1995;Elliott et al, 1992). In wood ducks (Aix sponsa; Mayack et al, 1981) and seabirds (Nicholson & Osborne, 1983), Cd-spiked diets produced renal tubular-cell necrosis with some calcification of epithelial cells that would presumably impair renal function.…”

Effect of Cadmium on Pekin Duck Total Body Water, Water Flux, Renal Filtration, and Salt Gland Function

“…Their u nusually high intake of w ater and N a + leaves seaducks particularly vulnerable to any impairment the ingested Cd might im pose on their ability to excrete water and N a + . The kidney Cd content (µg/g DW ) of Pekin ducks on the high-C d diet was roughly twice that of free-living seabirds (Elliott et al, 1992;Henny et al, 1995). The G FR of these Pekin ducks was significantly depressed, an effect that has been frequently associated w ith Cd (Jarup et al, 1995;Kim et al, 1988), possibly due to vasoconstriction induced by Cd (Balaram an et , 1989).…”