Mercury, selenium, cadmium and organochlorines in eggs of three Hawaiian seabird species

Eggs of three representative species of seabirds (wedge-tailed shearwater Puffinus pacificus; red-footed booby Sula sula; and sooty tern Sterna fuscata) were collected in 1980 to determined differences in heavy metal, Se, and organochlorine residues among species nesting in the Hawaiian Archipelago and among the four nesting sites sampled (Oahu, French Frigate Shoals, Laysan, and Midway). Hg and Se were present in all eggs analysed, but Cd was not detected. Hg was usually highest in booby eggs, and there was a southeast-to-northeast trend toward higher concetrations in this species; booby eggs from Midway contained the highest mean concentration of Hg (0·36 μg g⁻¹, wet weight). Se consistently occurred at lowest concentrations in booby eggs. When Se and Hg concentrations were expressed as nanomoles per gram, Se constituted 94–96% of the combined total at each location for shearwater and tern eggs. In booby eggs, the proportion as Se declined significantly (α = 0·05) from Oahu (93·4%) westward to Midway (85·9%). Although DDT occurred in most of the shearwater eggs from each site, it was not found in booby or tern eggs. DDE occured in all eggs, but mean concentrations did not exceed 0·6 μg g⁻¹. DDE concentrations were higher in eggs from the two south-eastern nesting sites and were consistently highest in shearwater eggs. PCBs were found in most of the shearwater and booby eggs, but were not detected in tern eggs. Other organochlorines usually occurred more frequently in eggs of shearwaters than in other species. The only exception were α-HCH and HCB, which occurred more frequently in booby eggs. Kepone, heptachlor epoxide, chlordane compounds, and toxaphene were not detected. Differences in residue concentrations seem to reflect differences in diets and seasonal movements of the birds, and perhaps other factors such as atmospheric and oceanic transport of chemicals and physiological differences among the species.