Assessing the toxicity and teratogenicity of pond water in north-central Minnesota to amphibians.
BACKGROUND
Incidence of amphibian deformities have increased in recent years, especially in the northern region of the United States. While many factors have been proposed as being responsible for generating deformities (e.g., contaminants, ultraviolet radiation [UV], parasites), no single cause has been definitively established.


METHODS
To determine whether waterborne chemicals are responsible for amphibian deformities in ponds in north-central Minnesota, we deployed semipermeable membrane devices (SPMDs) in an impacted and a reference site to accumulate lipophilic contaminants. We then exposed native tadpoles (northern leopard frogs; Rana pipiens) to the SPMD extracts combined with two agricultural pesticides (atrazine, carbaryl) at two levels of UV radiation.


CONCLUSIONS
UV radiation alone caused a slight increase in hatching success and tadpole growth rate. Deformity rate among hatchlings was high following exposure to SPMD extracts from the reference site in the absence of UV, suggesting that chemicals present at this site are broken down by UV to less harmful forms, or become less bioavailable. Conversely, impacted site SPMD extracts caused hatchling deformities only in the presence of UV, suggesting that UV potentiates the teratogenicity of the compounds present there. Impacted site SPMD extracts significantly increased the number of bony triangles among metamorphs, a common deformity observed at this site. The incidence of skin webbings increased significantly with SPMD extracts from both sites as well as with our pesticide control containing atrazine and carbaryl alone.


CONCLUSIONS
Higher deformity rates among tadpoles reared in the presence of UV radiation and SPMD extracts from sites where deformities are common indicates a chemical compound (or compounds) in the water at this site may be causing the deformities.


CONCLUSIONS
It is important to examine the effects of chemical stressors in the presence of other natural stressors (e.g., UV radiation) to gain a better understanding of how multiple stressors work to impact amphibians and amphibian populations.
Bridges
Christine
C
USGS, BRD, Columbia Environmental Research Center, 4200 New Haven Rd., Columbia, MO 65201, USA. cbridges@usgs.gov
Little
Edward
E
Gardiner
David
D
Petty
James
J
Huckins
James
J
D000818:Animals; D000013:Congenital Abnormalities / Q000209:etiology* / Q000662:veterinary*; D004784:Environmental Monitoring; D015994:Incidence; D007814:Larva / Q000254:growth & development; D008910:Minnesota; D011894:Rana pipiens / Q000033:anatomy & histology* / Q000254:growth & development*; D014466:Ultraviolet Rays / Q000009:adverse effects; D014867:Water / Q000737:chemistry*; D014873:Water Pollutants / Q000633:toxicity*; D014881:Water Supply
D014873:Water Pollutants; D014867:Water