Over the past five years, comprehensive annual surveys by U.S. Fish and Wildlife Service (USFWS) personnel have identified sites with a high prevalence of abnormal native amphibians. A number of these sites are located within National Wildlife Refuges (NWR) in the Northeast. In conjunction with the field surveys, prolonged (140-d) FETAX assays were performed with sediment and surface water samples from three potentially affected NWR sites: 1) Ferry Way Beaver Pond, Great Bay NWR, Newington, New Hampshire, 2) Brown Street Impoundment, Rachel Carson NWR, Wells, Maine and 3) Black Creek (Trails Site), Missisquoi NWR, Swanton, Vermont. Endpoints used to assess the effects of site sediment and surface water exposure on Xenopus development included survival, ability to complete metamorphosis, time to complete and size at metamorphosis, and frequency of malformations.

Exposure to Rachel Carson sediment and surface water had no significant (p > 0.05) detrimental effects on Xenopus (X. laevis) development, relative to control exposures. Exposure to Great Bay water and sediment caused a significant (p ≤ 0.05) reduction in Xenopus embryo survival, and significantly inhibited and delayed development and metamorphosis. Exposure to Missisquoi water, and sediment exposures with overlying Missisquoi water caused significant (p ≤ 0.05) embryo mortality and significantly inhibited metamorphosis in Xenopus embryos. There were no severe malformations observed in metamorphs from any of the NWR site exposures. Slight to moderate malformations were observed in embryos/tadpoles that died in the Great Bay and Missisquoi exposures.

Detectable concentrations of pesticides were measured in the Great Bay and Missisquoi sediment samples. The presence of pesticides, and low concentrations of essential ions in site water may have contributed to the adverse developmental effects observed in Xenopus in the Great Bay and Missisquoi exposures.