DIOXIN-LIKE TOXIC POTENCY IN FORSTERS TERN EGGS FROM GREEN BAY, LAKE-MICHIGAN, NORTH-AMERICA

The endangered Forster's tem (Sterna forsteri) population on Green Bay , Wisconsin has exhibited symptoms of embryotoxicity, congenital defor mities, and poor hatching success. The putative causal agents are plan ar halogenated hydrocarbons (PHH). The objectives of this study were: 1) to evaluate the toxic potency of PHHs in extracts of Forster's tem eggs taken from Green Bay, Lake Michigan and a reference site, Lake Po ygan, WI; and 2) to compare the toxic potencies of the egg extracts wi th the reproductive data available from the same water bird colonies. The relative toxic potency of the egg extracts was assessed with the H 4IIE bioassay system to obtain 2,3,7,8-tetrachlorodibenzo-p-dioxin equ ivalents (TCDD-EQ). The average concentrations of TCDD-EQ in Forster's tem eggs were 214.5 pg/g and 23.4 pg/g from Green Bay and Lake Poygan , respectively. The bioassay results presented here concur with the bi ological effects and chemical analyses information from other studies on the same Forster's tem colonies.