Contamination and Biomarkers in the Great Blue Heron, an Indicator of the State of the St. Lawrence River
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In 1996–1997, nine breeding colonies of the great blue heron on the St. Lawrence River and its estuary (Québec, Canada) were investigated in the framework of a biomonitoring program. Fledglings from colonies in freshwater were more contaminated with mercury, PCBs and many organic contaminants than those from estuarine colonies. The level of contamination in the St. Lawrence River is generally below the levels of toxicological effects for the great blue heron. The molar ratio of retinol: retinyl palmitate in heron eggs was correlated with total PCBs (r=0.79) and Mirex (r=0.90). In plasma, all biochemical parameters were significantly different between freshwater and marine colonies. Plasma retinol concentrations at the Dickerson and Hérons colonies were significantly lower compared with those at Grande Ile (p<0.05) and Steamboat (p<0.001). Based on retinoid and β-carotene concentrations in eggs, low plasma retinol was not associated with possible dietary deficiency. Plasma retinol was negatively correlated with many PCB congeners, total PCBs (r=−0.78), p,p′-DDE, trans-nonachlor and α-HCH. Similarly, the hormone T3 was correlated with many PCB congeners, total PCBs (r=−0.69) and the same organochlorine chemicals. Plasma LDH concentrations were different among freshwater colonies, Grande Ile and Hérons colonies having LDH values significantly greater than those of Steamboat (respectively, p<0.05 and p<0.01). Globally, the health status of the St. Lawrence great blue heron population was judged to be acceptable, however, several biomarkers indicated positive responses to contaminants.