EFFECTS OF POLYCHLORINATED DIBENZO-P-DIOXINS AND DIBENZOFURANS ON NESTING WOOD DUCKS (AIX-SPONSA) AT BAYOU-METO, ARKANSAS

Wood ducks (Aix sponsa) nesting along Bayou Meto downstream from a haz ardous waste site in central Arkansas were contaminated with polychlor inated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). Residues i n eggs, based on 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TCDD -EO), ranged up to 611 parts per trillion (ppt), and egg arithmetic me ans were 90-fold higher at the site nearest the point source compared with a reference site. We monitored productivity of wood ducks in arti ficial nest boxes at three sites on the bayou and at a reference site on a separate drainage during 1988-1990. Productivity was suppressed ( p<0.005) at the bayou sites compared with the reference site, and egg TCDD-EQs were inversely correlated (p<0.001) with productivity in corr esponding nests. The threshold range of toxicity, where reduced produc tivity was evident in wood ducks (based on TCDD-EQs), was > 20 to 50 p pt. Oxidative stress and teratogenic effects occurred in ducklings al the more contaminated nesting sites nearest the point source. These fi ndings suggest that wood ducks may he more sensitive to PCDD and PCDF contamination than some other aquatic birds and could serve as an indi cator species for monitoring biological impacts from these contaminant s.