BETA-CAROTENE AND RETINOIDS IN EGGS OF GREAT-BLUE HERONS (ARDEA-HERODIAS) IN RELATION TO ST-LAWRENCE-RIVER CONTAMINATION

The potential use of retinoids and beta-carotene as biomarkers in the eggs of the Great Blue Heron was investigated. In the spring of 1991, 65 eggs were collected from nine heronries (seven along the St Lawrenc e River and two reference sites). A method was specifically developed for the extraction and analysis of beta-carotene and the retinoids in heron egg yolks by reversed-phase HPLC. When results were expressed ei ther as the molar ratio of retinol: retinyl palmitate or as retinyl pa lmitate concentration, significant differences were found between colo nies; however, retinyl palmitate concentration was deemed the better b iomarker because it was not significantly influenced by embryonic stag e of development. Retinyl palmitate concentrations in freshwater colon ies were negatively related to PCB congeners Nos 105 and 118 as well a s their TCDD-EQ values (p < 0.02, r(2) = 0.78). Egg tetrachloro-mono-o rtho biphenyl concentrations were also negatively related to retinyl p almitate (p < 0.005, r(2) = 0.90). With the exception of the two mono- ortho co-planar congeners detected in the present study, the contamina tion levels found in heron eggs were well below those found for other bird species in the Great Lakes area and, so far, no detrimental effec ts have been reported in Great Blue Heron populations in Quebec. These results suggest that retinyl palmitate may be useful as a sensitive a nd non-invasive biomarker for monitoring organochlorine contaminant ef fects in the Great Blue Heron in freshwater sites.