23 



occurs. The various forms of mercury, how- 

 ever, differ widely in their toxicities. Unless 

 otherwise specified, mercury concentrations 

 presented here represent concentrations of 

 total mercury. 



Exposure of Marine Birds to 

 Heavy Metals 



Animals acquire heavy metals from the 

 foods they eat, from the water that surrounds 

 them, and possibly from the air they breathe. 

 Quantities accumulated differ greatly among 

 organisms, depending upon exposure and 

 physiology (White and Stickel 1975). 



Mercury in tissues of living organisms is 

 often primarily in the more toxic methyl mer- 

 cury form (Westoo 1967; Fimreite 1974), and 

 methyl mercury is readily incorporated into 

 the bodies of aquatic organisms (Leland et al. 

 1975). Most of the mercury in fish is in the 

 form of methyl mercury (Koeman et al. 1975), 

 but the high mercury concentrations dis- 

 covered in the livers of six dead great cormor- 

 ants and in livers of three others that were col- 

 lected in the Netherlands were not primarily 

 methyl mercury (Koeman et al. 1973). Mer- 

 cury concentrations, primarily in forms other 

 than methyl mercury, increased with age in 

 some marine mammals and were correlated 

 with concentrations of selenium and bromine 

 (Koeman et al. 1975; Martin et al. 1976). Per- 

 haps, like some marine mammals, cormorants 

 may be able to detoxify methyl mercury by a 

 chemical mechanism in which selenium and 

 bromine are involved. However, mercury and 

 selenium concentrations in livers of common 

 murres and of a razorbill (Koeman et al. 1975) 

 and in liver and breast muscle of sooty terns 

 of known age were not correlated (P. G. 

 Connors et al., unpublished manuscript). Inor- 

 ganic and organic mercury from industrial 

 sources may be converted into methyl mer- 

 cury by some organisms, including birds 

 (Jensen and Jernelov 1969; Kiwimae et al. 

 1969). 



Mercury concentration increases with body 

 weight, or age, in fish (Bache et al. 1971; Fim- 

 reite et al. 1971), crayfish (Vermeer 1972), and 

 herons (Hoffman 1974). The concentration in- 

 creases at higher trophic levels in fish, other 

 aquatic organisms, fish-eating birds, or ducks 

 (de Goeij 1971; Fimreite et al. 1971; Fimreite 



1974; Hoffman 1974; Kleinert and DeGurse 

 1972; Vermeer et al. 1973; Baskett 1975). 



Mercury concentrations in various tissues 

 of the body are correlated with each other 

 (Fimreite 1971; Koeman et al. 1971; Vermeer 

 and Armstrong 1972a; Fimreite 1974; Heinz 

 1974, 1976a; Hoffman 1974). Eggs normally 

 contain between a fifth and a ninth of the mer- 

 cury concentration in the liver of the female 

 (Fimreite et al. 1970; M. T. Finley, personal 

 communication). Mercury in the liver of fe- 

 male California gulls (Larus californicus) aver- 

 aged 5.5 times that in their eggs (Vermeer 

 1971a). 



High mercury residues in aquatic 

 organisms and in the related avifauna are 

 often related to discharges from chlor-alkali 

 plants, pulp mills, or other industrial plants 

 that use mercury (Fimreite 1970; Fimreite et 

 al. 1971; Nelson et al. 1971; Vermeer 1971a). 

 Ospreys and great crested grebes (Podiceps 

 cristatus) now have about 3 times as much 

 mercury in some industrially contaminated 

 areas as in uncontaminated areas (Larsson 

 1970). 



In a survey of aquatic birds at 33 locations 

 in Alberta, Saskatchewan, and Manitoba, 

 mercury levels were generally higher in gulls 

 (Larus spp.) and fish-eating birds than in 

 ducks and geese (Vermeer 1971a). The highest 

 mercury levels were found in herring gulls, 

 possibly related to their scavenging and fish- 

 eating habits. 



Elevated mercury levels were found in 

 livers of common mergansers (Mergus mer- 

 ganser, up to 86 ppm), common loons 

 (90 ppm), and great blue herons (128 ppm) 

 from Ontario (Fimreite 1974). Lower concen- 

 trations were found in mallards (12.5 ppm) 

 and pintails (Anas acute; 6.2 ppm). Mercury 

 levels were higher in adults than in imma- 

 tures. A chlorine plant about 80 km upstream 

 from the collecting locality was believed to be 

 the source of mercury found in the birds. 



Mercury was present in spotted sandpiper 

 (Actitis macularia) eggs collected upstream 

 from Edmonton, Alberta, at lower concentra- 

 tions (0.09 ppm) than in those eggs collected 

 downstream (0.28 ppm), suggesting municipal 

 or industrial contamination originating at 

 Edmonton (Vermeer 197 Ib). 



During another survey in Canada, highest 

 concentrations of mercury in livers of fish-eat- 

 ing birds collected near sites of industrial con- 

 tamination were in red-necked grebes 



