PARENT SESSION

PH11 Bioaccumulation and Biotransformation of POPs
Exhibit Hall
8:00 AM - Thursday, 13 November 2003

(PH107) Tissue residue levels in Great Egrets fed fish environmentally exposed to organochlorine pesticides.

Grosso, J¹, Gross, T², Sepulveda, M¹, Ruessler, D², Conrow, R³, Coveney, M³, Mace, L³, Lowe, E³, Richter, S³, Marzolf, E³, ¹ Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA² USGS-BRD Center for Aquatic Research Studies, Gainesville, FL, USA³ St. Johns River Water Management District, Palata, FL, USA

ABSTRACT- During 1998-1999, a significant mortality of several piscivorous bird species occurred on the former agricultural property on the north shore of Lake Apopka (North Shore Restoration Area, NSRA). Although this mortality has been linked to organochlorine pesticide (OCP) toxicosis, risk assessments so far have not been able to support this. The objective of this study was to determine tissue residues and bioaccumulation of OCPs in great egrets (Ardea albus) fed diets consisting of tilapia raised for 2 - 4 m in fish ponds (1/4 acre) built within the NSRA. Ten egrets were collected from the wild in early May 2002, and raised for 4.5 m of age prior to the start of the feeding trial. Birds were fed a mean of 105 ± 58 g of fish/day (8 % body weight) of a diet consisting of approximately 40% OCP-contaminated tilapia and 60% no OCP fish (silversides and capelin). The contaminated tilapia was harvested from the ponds, finely ground, and administered to the birds in the form of sausages. Mean toxaphene, p,p′-DDE, and dieldrin in several sausage composites were 9.4, 2.7, and 0.7 ppm wet wt., respectively. It was estimated that birds were fed at overall rates of 256, 74, and 19 g/kg body weight/day for toxaphene, p,p′-DDE, and dieldrin, respectively. Five birds were euthanized at 9 weeks and 5 at 11 weeks. Liver, brain, and abdominal fat were analyzed for OCPs. Mean concentrations (mg/kg) in liver, brain, and abdominal fat were as follows: sum of DDTs: 0.3, 0.1, 1.5; dieldrin: 0.1, 0.4, 3.3; and toxaphene: 1.3, 0.3, 60, respectively. Two great egrets found dead in 1999 at the NSRA had an average brain toxaphene value of 15 mg/kg, a value almost ten times higher to the one attained in this study. Overall these results suggest that egrets would need to be fed a much higher OCP-diet in order to attain the tissue residue concentrations observed during the die-off at the NSRA.

Key words: body, egrets, burdens, pesticides