The Effects of Road Salt (NaCL), Predation, and Competition on the Growth and Development of Spotted Salamanders (Ambystoma maculatum) and Wood Frogs (Lithobates sylvaticus)

Road de-icing salts - primarily NaCl - are frequently used in the northern regions of the United States during the winter and early spring months. As a result, much of the road runoff into surrounding aquatic habitats contains road de-icing salts. Previous studies have found road salt contaminations in vernal pools that pond-breeding amphibians commonly use, including spotted salamanders (Ambystoma maculatum) and wood frogs (Lithobates sylvaticus). Because amphibians are the most threatened group of vertebrates and are important biotic elements of both terrestrial and aquatic ecosystems, it is crucial to determine the impact of road salt on amphibians. During the spring and summer of 2017, we conducted an outdoor mesocosm experiment in which we created eight experimental conditions with three main factors: presence/absence of NaCl (1000 mg/L Cl-), presence/absence of interspecific competition between the two amphibian species, and presence/absence of predatory dragonfly nymphs (Family Libellulidae). Our experiment revealed that salt delayed hatching and increased deformity in spotted salamander hatchlings. Additionally, salt significantly decreased salamander and frog survivorship, with the presence of wood frog tadpoles further exacerbating the decrease in salamander survivorship. The presence of salt also increased frog body size, while the presence of predators decreased frog body size. However, there was an interactive effect between salt and predators, with the presence of salt negating the effect of predator on body size. Salt also decreased the proportion of metamorphosed salamanders. Overall, our data suggest that the application of road de-icing salt has many far-reaching impacts on amphibians and their ecosystem