Both concern over amphibian declines (Dunson et al., 1992; Blaustein, 1994) and the potential of amphibians as indicators (Phillips, 1990; Dunson et al., 1992; Boyer and Grue, 1995) of ecosystem health provided the impetus for this study. Utilizing amphibians as indicator species is comparable to the use of canaries in a coal mine when assessing the quality of an aquatic environment (Barinaga, 1990). Embryos, tadpoles, and adults are considered to be sensitive to environmental contaminants in part due to their unshelled eggs and permeable skins (Bridges et al., 2002; Blaustein et al., 2003; Kiesecker et al., 2004; Hogan et al., 2006). Amphibians offer a unique biphasic life cycle for studying water and land habitats as well as the interactions between the two environments. This study investigated the interaction between two human-mediated environmental changes on the development of a common North American anuran, (Rana sylvatica) the Wood Frog.
Anthropogenic changes have increased copper and sunlight in many amphibian habitats. Human disturbance often leads to a decrease in canopy cover, which thereby reduces shade for developing embryos and tadpoles of certain anuran species within the aquatic environments below (Werner and Glennemeier, 1999; Skelly et al., 2002). Water runoff from impermeable surfaces and agricultural and residential properties transport toxins
and excess nutrients into bodies of water, leading to algal blooms. In ponds, a common algaecide utilized to eliminate the ensuing blooms is copper sulfate.
This work investigated the effects of copper sulfate and increased solar radiation on the developmental rate and survival of Wood Frog tadpoles in high pH ponds. pH levels in Northeastern Ohio ponds are higher (7.0-8.5; Matson et al., unpublished data, 2006) than in many other areas of Wood Frog study and research is lacking in non-lab environments at these pH levels. A field study used cattle tanks for testing the influence of increased light, increased copper, and for interactions between these environmental perturbations. Copper was a significant source of variation in measures of tadpole developmental rate and marginally significant in tadpole survival. Shade was not a significant source of variation in survival, but did significantly slow development. In addition, copper and shade interacted in their effect on developmental rate as measured by an increase in body mass in ambient copper treatments. These results are beneficial in understanding whether the use of copper sulfate is a contributor to amphibian decline.