Are embryonic and larval green frogs (Rana clamitans) insensitive to road deicing salt?

Abstract

Deicing agents have been used to control ice build-up on roads in winter for at least five decades in North America and Europe. This legacy of contamination of streams and wetlands threatens the availability of fresh water in these regions. The issue is of interest because amphibian skin and membranes of amphibian eggs are highly permeable, rendering amphibians particularly sensitive to chemical contaminants. In addition, saline solutions can travel nearly 200 m from roads and into wetlands, thereby contaminating amphibian habitats. The objective of this study was examine the effects of road salt on an amphibian that breeds in permanent wetlands, the Green Frog (Rana clamitans), for comparison with prior research on vernal pool-breeding species. Survival in all five ecologically-relevant treatment levels was > 93% in embryos and > 87% in larvae. However, when accounting for malformations, survival at the highest treatment level (3000 μS conductivity) dropped to 80% and 82%, respectively. Larval growth was unaffected by road salt, but 15% of larvae were malformed at the highest conductivity level. Rana clamitans appears to be relatively tolerant to road salt at low and moderate concentrations and less sensitive than other North American amphibians. At conductivity levels observed in the field, it is unlikely that road salt currently impacts populations of R. clamitans.