REPRODUCTIVE AND PHYSIOLOGICAL-EFFECTS OF ENVIRONMENTAL CONTAMINANTS IN FISH-EATING BIRDS OF THE GREAT-LAKES - A REVIEW OF HISTORICAL TRENDS

During the 1950s and 1950s, reproductive failures and population decli nes were observed in fish-eating birds such as gulls, terns, cormorant s, herons, and eagles in the Great Lakes. DDE-induced eggshell thinnin g contributed to these declines, but other factors such as embryo toxi city also were implicated. With reduced releases of many pollutants, r eproduction recovered in some species. However, biomonitoring during t he 1980s and 1990s indicates continuing effects at highly contaminated sites. Improved analytical techniques and bioassays have allowed the assessment of the total dioxin-like toxicity of complex mixtures of or ganochlorines (TCDD-equivalents). Developmental defects such as embryo mortality, deformities, and edema have been associated with dioxin-li ke PCBs in several avian species. Improved biochemical techniques have allowed the measurement of biomarkers that detect physiological alter ations associated with contaminants. Specific biomarkers studied in Gr eat Lakes birds include cytochrome P-450 monooxygenases, highly carbox ylated porphyrins, thyroxine, vitamin A, and immune function. Reproduc tive and physiological alterations are associated with population-leve l effects in Caspian terns and bald eagles that feed on highly contami nated fish. Biomonitoring using biomarkers and population-level measur es in fish-eating birds will continue to be important for assessing th e effects of contaminants on the Great Lakes ecosystem.