Lipids and lipophilic pollutants in three species of migratory shorebirds and their food in shepody bay (Bay of Fundy, New Brunswick)

Abstract

AbstractTo study food web transfers of lipids in the intertidal zone, three specimens of each of the semipalmated sandpiper (Calidris pusilla [L.]), the semipalmated plover (Charadrius semipalmatus Bonaparte) and the short‐billed dowitcher (Limnodromus griseus [Gmelin]) were examined after capture during the summer of 1989. They were feeding intensively, prior to migration, on the amphipod,Corophium volutator, on the mudflats of Dorchester Cape, New Brunswick, Canada. The ragworm,Nereis diversicolor, and samples of sea foam were also collected from the mudflats at the same location in 1989 and 1990. Total body lipids of semipalmated sandpipers and short‐billed dowitchers were about 20% of the wet weights, while those of the semipalmated plovers ranged from 35 to 40%. Adipose tissue fatty acids showed a trend from marine fatty acids (20∶5n−3, 22∶6n−3) at 10% ofC. pusilla acids through 5% inC. semipalmatus to 1% inL. griseus. These proportions confirm differences in feeding habits proposed from analyses of gut contents. Short‐billed dowitcher adipose fat included the lowest values of polychlorinated biphenyls (0.078 to 0.266 ppm). The other two species of shore‐birds showed levels as high as 1.64 ppm. Concentrations of 1,1‐bis(4‐chlorophenyl)‐2,2,2‐trichloroethane and 2,2‐bis(4‐chlorophenyl)‐1,1‐dichloroethylene were also variable, but with three exceptions were ≤0.1 ppm of adipose fat. Sea foam collected in the tidal channels and at the edge of the water during the rising tides was found to include diverse lipophilic materials, capable of transfer to higher trophic levels. Triacylglycerols, phospholipids, sterols, hydrocarbons and pigments were typically present at a concentration of 65×103 μg/L. The long‐chain isoprenoid squalene, of endogenous origin and apparently derived from featherwax, was the only hydrocarbon present in the depot fats of the three species of birds analyzed. This indicates that the birds basically inhabited a pristine environment free of hydrocarbon pollutants. The hydrocarbon present in the sea foam consisted of a series of normal alkanes, from C20 to C39, with no odd/even chain‐length preference (carbon preference index=1.008). These hydrocarbons probably originated in detritus from decaying vascular plants but could possibly reflect a very low level of petroleum contamination. The lack of local pollution appears to favor continued success of the migratory pattern of these birds.