Lethal and Sublethal Effects of Embryonic and Larval Exposure of Hyla versicolor to Stormwater Pond Sediments

Abstract

Stormwater ponds are common features of modern stormwater management practices. Stormwater ponds often retain standing water for extended periods of time, develop vegetative characteristics similar to natural wetlands, and attract wildlife. However, because stormwater ponds are designed to capture pollutants, wildlife that utilize ponds might be exposed to pollutants and suffer toxicological effects. To investigate the toxicity of stormwater pond sediments to Hyla versicolor, an anuran commonly found using retention ponds for breeding, we exposed embryos and larvae to sediments in laboratory microcosms. Exposure to pond sediments reduced survival of embryos by approximately 50% but did not affect larval survival. Larvae exposed to stormwater pond sediment developed significantly faster (x = 39 days compared to 42 days; p = 0.005) and were significantly larger at metamorphosis (x = 0.49 g compared to 0.36 g; p < 0.001) than controls that were exposed to clean sand. Substantial amounts (712-2215 mg/l) of chloride leached from pond sediments into the water column of treatment microcosms; subsequently, survival of embryos was negatively correlated (r (2) = 0.50; p < 0.001) with water conductivity during development. Our results, along with the limited number of other toxicological studies of stormwater ponds, suggest that road salt contributes to the degradation of stormwater pond habitat quality for amphibian reproduction and that future research should focus on understanding interactions among road salts and other pollutants and stressors characteristic of urban environments.

Road Salt Stress Induces Novel Food Web Structure and Interactions

“…Our study joins a small but growing literature base that highlights changes in time to and size at metamorphosis among tadpoles exposed to road salts. Brand et al (2010) observed the same trends in faster time to and larger size at metamorphosis among gray treefrogs developing in stormwater pond sediments with elevated Cl − levels. Chinathamby et al (2006) reported an increase in mass at metamorphosis among brown treefrogs (Litoria ewingii) exposed to low and moderate concentrations of sea salts.…”

“…Much like zooplankton and algae, chloride salt effects on anurans are likely to be species-specific and dependent upon life history as well as environmental factors such as water chemistry and temperature (Brand et al 2010). Our study joins a small but growing literature base that highlights changes in time to and size at metamorphosis among tadpoles exposed to road salts.…”

“…It may seem that chloride salts are beneficial to gray treefrogs by contributing to larger size at and shorter time to metamorphosis. However, since both size of larvae and duration of the larval period ultimately affect survival and fitness of anurans (Berven and Gill 1983;Smith 1987), potential impacts on embryonic (Brand et al 2010) and adult life stages need to be evaluated further. We chose to expose developing larvae to elevated chloride upon reaching Gosner stage 25 (Gosner 1960), the point in larval development where tadpoles begin to serve as consumers in the pond food web, which was the focus of this study.…”

“…Many studies report reduced survival (Dougherty and Smith 2006;Sanzo and Hecnar 2006;Karraker 2007;Snodgrass et al 2008 and others) and developmental rates (Bishop et al 2000;Chinathamby et al 2006;Sanzo and Hecnar 2006;Brand et al 2010) of amphibians exposed to elevated salts. Any ecosystem disturbance that poses a threat to amphibian development and survival, such as salt stress, is likely to have ecological consequences for other trophic levels given the important role of tadpoles as grazers in pond food webs (Dickman 1968;Seale 1980).…”

Road Salts as Environmental Constraints in Urban Pond Food Webs

“…This study was designed to be sublethal to gray treefrog ( Hyla versicolor ) larvae; therefore, the higher chloride concentration used reflected the uppermost limit for successful embryonic and larval survival as determined by Brand et al [31]. The stormwater ponds used to collect inoculum were representative of those in Red Run Watershed that can support successful amphibian development and survival [23].…”