EDBLOM, T.L.*; KARASOV, W.H.: Solar Ultraviolet-B Radiation Does Not Affect Hatching Success of Rana pipiens (Northern Leopard Frog) Eggs Under Natural Conditions Along a Contamination Gradient

We compared the hatching success of Rana pipiens (northern leopard frog) eggs at field sites located along a known contamination gradient in the Green Bay and Fox River ecosystem, Wisconsin, U.S.A. Our investigation was designed to determine whether there were differences in hatching success or incidence of deformities when eggs were covered with shields that transmitted different levels of UV-B. We also wanted to determine if UV-B might be acting synergistically with agents in the water to further reduce hatching success and increase incidence of deformities at the more contaminated field sites, as indexed by sediment polychlorinatd biphenyl (PCB) and heavy metal levels. One Green Bay pond and one Green Bay wetland site were relatively uncontaminated (both <0.025 mg/kg sediment PCB concentration). Another Green Bay wetland site and a Fox River site were relatively more contaminated (3.7 and 3.2 mg/kg sed. PCB conc., respectively). We found significant differences in both hatching success and incidence of deformities between sites in the field, but these differences were not attributable to UV-B. Furthermore, there was no relationship between hatching success and level of contamination. These results suggest that leopard frogs, at least at the egg (for hatching success) and early tadpole (for deformities) stages may not be sensitive to current levels of UV-B radiation even in somewhat polluted environments.