The application of road salts as deicing agents during winter can impact the quality of adjacent wetland habitats for many aquatic species. Amphibians are susceptible to road salt runoff in areas where they develop from embryos to larval and adult stages. Although current evidence suggests external inputs of salinity into these wetlands can be detrimental to amphibian development and survival, less is known about how the success or timing of amphibian life history processes change along a salinity gradient or with length of exposure time. We are conducting a meta-analysis to explore the impacts of salinity and salinity exposure time on amphibian development and survival. We hypothesize that as salinity and exposure time increases, survivability and development time of larvae will decrease and increase, respectively. To date, we have found 24 peer-reviewed sources that report data necessary to test our hypotheses. Here, we report preliminary results for the survivability of amphibian larvae.
Results/Conclusions
Using the metafor package in the program R, we calculated 40 raw mean effect sizes and sample variances from seven peer-reviewed sources that manipulated water salinity (0 – 16 g/L NaCl) and exposure time (48 – 1440 hours) and reported survivability for larvae of five amphibian species. Our multi-level meta-regression model suggests that salinity concentration, but not exposure time, negatively impacts the survivability of amphibian larvae. Estimated survivability in a non-saline environment was 96% (95% CI = 70 – 122%) and survivability decreased by 8% with each unit (g/L) increase of salinity. Our preliminary conclusion is that NaCl inputs from road salt runoff generally degrade roadside wetland areas as habitats for breeding amphibians by impacting the survival of early developmental life stages. We suspect, however, that the relationship of survival to salinity concentration exhibits a curvilinear Type I rather than a linear Type II survivorship pattern. As such, we are currently developing alternative models to explore this possibility. Current understanding of alternative deicing chemical impacts on aquatic organisms is relatively sparse compared to that of NaCl. We suggest more work be done to compare the relative risks of particular deicer chemicals on amphibians and other organisms to inform road management near aquatic ecosystems.