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Farm ponds as critical habitats for native amphibians

CHAPTER 3
Effects of Agricultural Land Use on the Survival of Anuran Larvae in Constructed and Natural Ponds in the Upper Midwest

Joshua M. Kapfer
University of Wisconsin-La Crosse,
Department of Biology and River Studies Center
1725 State Street
La Crosse, Wisconsin 54601

Abstract
Global declines in amphibian populations are, in part, because of loss of habitat. Consequently, artificially constructed habitats, such as farm ponds, may be important for maintaining regional amphibian populations. The objective of this study was to assess the potential toxicity of water from agricultural ponds on anuran eggs and larvae. Mesocosms were placed in six constructed ponds adjacent to row crops (primarily corn and soybeans) and in four natural ponds. Mesocosms were stocked with embryos of the northern leopard frog (Rana pipiens) that were allowed to develop through metamorphosis. Differences in mortality of leopard frogs between constructed ponds adjacent to row crops and natural ponds were assessed. Concurrently, the Frog Embryo Teratogenesis Assay Xenopus was used to assess effects of pond water from agricultural, grazed, non-grazed, and natural ponds (2000), and agricultural and natural ponds (2001) on development and survival of the African clawed frog (Xenopus laevis). Additionally, concentrations of total nitrogen, total phosphorus, ammonia, and selected pesticides (e.g., atrazine and alachlor) were measured in ponds and compared to survival of X. laevis. There were no significant differences in survival of X. laevis larvae among agricultural, grazed, non-grazed, and natural ponds during 2000. In addition, no significant difference in the survival of X. laevis larvae between agricultural and natural ponds was detected during 2001. Finally, no significant difference in the survival of R. pipiens held in mesocosms from agricultural and natural ponds was detected during 2001. While concentrations of pesticides and nutrients detected were generally higher in agricultural ponds than other ponds, neither nutrients nor pesticides had a biologically significant effect on larval survival. Results suggested that, from a standpoint of water quality, farm ponds within the Driftless Area Ecoregion of Minnesota make suitable habitats for larval anurans.

Keywords: amphibian, agriculture, farm pond, FETAX, mesocosm, Rana pipiens, Xenopus laevis