Road Deicers: Which Are Best Tolerated by Amphibians?
Wildlife & Ecosystems
Research Idea Scope
Widespread contamination of freshwater habitats and groundwater sources from road salt deposition is well documented. The negative effects of road salt on freshwater habitats include changes in density gradients, increased chloride levels, salt-induced stratification, and nutrient overload. Of these effects, elevated chloride levels are considered a major stressor to freshwater organisms and may put aquatic communities at risk within the next century. Chloride levels peak in the spring, as snow and ice melt drains roadside runoff into nearby surface waters. Exposure to high chloride concentrations, if only briefly, is potentially very harmful to sensitive wildlife species.
Amphibians are sensitive to changes in salinity, which is thought to limit their global distribution. These species are particularly sensitive to chemical contaminants due to their highly permeable skin, aquatic larval stages, and use of wetlands for breeding. As such, amphibians are considered indicators of ecosystem health and are model organisms to investigate the effects of contamination from chemical deicers. Most species of amphibians breed in early spring, when chloride levels and deicing contaminants are most concentrated, making them particularly vulnerable. Surprisingly, the direct effects of chemical deicers on amphibian species have received relatively little attention. Several types of deicer (NaCl, MgCl2, CaCl2, KCl, CMA, etc.) are used in the transportation industry yet most research has focused on the most commonly used deicer, NaCl. Furthermore, deicers are commonly pre-wetted with additives whose effects on the environment are as yet unmeasured.
Our two objectives are to 1) quantitatively assess amphibian sensitivity to a suite of commonly used deicers and additives; and 2) measure the ecological effects of deicer use in the Upper Peninsula of Michigan. Our species include a much wider variety than previously examined: frogs (Bufo americanus, Hyla versicolor, Pseudacris crucifer, Rana sylvatica, R. clamitans, R. septentrionalis) and salamanders (Ambystoma maculatum, A. laterale, Notophthalmus viridescens). We will measure the salinities of 60 wetlands and vernal pools situated within and outside of the deicer travel zone, and survey amphibian communities at each site. These data will allow state DOTs to select the most environmentally benign deicers for use in sensitive wetland areas. The data will also be important in determining what effect deicers have in structuring amphibian communities at a landscape scale.
Urgency and Payoff
State DOTs will directly benefit from this research because it will provide quantitative data on the effects of a suite of commonly used deicers. As a group, amphibians have been experiencing drastic declines in population size, with some species approaching extinction. These declines have resulted in increased awareness and demands for amphibian protection by the general public, which may be met by selection and application of least-impact deicers. This research will fulfill a pressing need to determine the extent and causes of ecological damage to an array of amphibian species and their habitats associated with snow and ice removal.
Jacqualine Grant, Michigan Technological University, Telephone: (906) 487-1093