Use of FETAX to Examine Acute Survival of Xenopus laevis Larvae in Water from Natural and Constructed Ponds in the Upper Midwest.

.—Agricultural ponds are exposed to many contaminants that can negatively affect breeding amphibians. Despite therisks, such ponds are important amphibian breeding habitat if natural wetlands are scarce. We compared the survival ofXenopus laevis larvae reared in water from natural and constructed ponds. Agricultural (in the form of row-crop) and grazedponds had higher nutrient levels (total nitrogen and total phosphorus) than ungrazed or natural ponds in 2000, but weobserved no differences between agricultural ponds and natural ponds in 2001. All treatments had high survival rates (74-91%) in both years and we detected no significant differences in survival among treatments. These results support previousresearch on the same test ponds; thus we conclude that certain constructed agricultural ponds in the Driftless Area ecoregionof the Upper Midwest may be suitable for anuran larval survival. However, it is difficult to determine the biologicalsignificance of our findings, as indirect factors that could not be controlled for during this research, may influence the waterchemistry of ponds in this region.