Effects of Environmental Contaminants at Great Bay National Wildlife Refuge on Anuran Development, Gonadal Histology, and Reproductive Steroidogenesis: A Comparison of In Situ and Laboratory Exposures

Previous monitoring at Great Bay National Wildlife Refuge (NWR), Newington, New Hampshire documented high prevalence of amphibian malformations at sites contaminated with potential endocrine active compounds. In the present study, a combination of in situ and laboratory experiments were used to determine whether contaminants present in the sites affect amphibian growth and reproductive development. Wood frog ( Rana sylvatica ) tadpoles were exposed in situ at four sites (Ferry Way, Beaver Pond, Lower Peverly, and Stubbs Pond) at Great Bay NWR and northern leopard frog ( Rana pipiens ) tadpoles were exposed in the lab to sediments collected from three sites (Beaver Pond, Ferry Way, Stubbs Pond) at Great Bay NWR as well as a positive (estradiol) and negative control. High mortality was observed at Stubbs Pond and extended larval period at Beaver Pond in the in situ exposure. Only three malformations were noted in the lab experiment, whereas there was a 63% prevalence of rounded femurs in Beaver Pond metamorphs in the in situ exposure. Only 2.4% (5 of 207) of R. sylvatica metamorphs exhibited abnormal reproductive development, whereas intersex metamorphs occurred in treatments and controls in the lab experiment at rates as high as 26%. Reproductive development was more advanced and estradiol to androgen ratios reduced in male metamorphs from Beaver Pond in both the in situ and lab exposures. DDT, PCBs, and PAHs were detected in sediments at Great Bay NWR at concentrations that exceed regulatory or guidance values, with concentrations of PAHs being highest at Lower Peverly Pond and DDT highest at Stubbs Pond. The effects on anuran development may be attributable to the primary contaminants—DDT and PCBs—acting on the thyroid and gonadal axes.