Fire retardants are composed of fertilizer salts and commonly used for fighting wildfires. Retardant chemicals washed via runoff into aquatic systems may be concentrated inside the aquatic habitat, thus exposing aquatic species to high levels of ammonium, phosphate and iron. These chemicals directly affect individual species, which can also cascade to the rest of the aquatic community. Here, the Fire Salamander, Salamandra infraimmaculata, was chosen as a model amphibian species to test the effects of fire retardant on its survival and development. It is an endangered species in Israel and represents the genus’ southern-most limit. They larviposit live larvae in various aquatic habitats in northern Israel, and thus can potentially be affected by anthropogenic effluents such as fire retardants. Currently, no studies have evaluated how fire retardants may affect S. infraimmaculata, which is the top predator in aquatic habitats of northern Israel. First, we used outdoor mesocosms to test the effects of FR CROS 134 (FR) on S. infraimmaculata larval development and followed the concurrent changes in the aquatic community, including bacteria, algae and invertebrates. Second, we assessed the effects of FR on the predatory efficiency of S. infraimmaculata larvae in a controlled environment to isolate direct consumption effects.
Results/Conclusions
We show a significant negative dose-dependent response to the presence of FR on the survivorship and time to metamorphosis of salamander larvae in the mesocosm experiment. Moreover, increasing FR concentrations were found to inhibit the predation rate of salamander larvae on mosquito larvae in labratory settings. However, FR had no significant deleterious effect on the survival or development of mosquito larvae themselves. No significant effect of FR was found for invertebrate species richness. In contrast, FR addition significantly decreased the invertebrate community diversity with composition change and shifts in evenness and dominance (e.g., cladoceran species abundance increased, whereas calanoid copepod species declined). Finally, cyanobacteria and eukaryotic algal abundance increased, while heterotrophic bacterial abundance decreased with FR addition. Our study show that FR affects the aquatic community in a species-specific response. The question of whether in decreasing or increasing effect may be related to the sensitivity of different species to the direct effects of FR or to the extent of indirect effects on the food web dynamics. The effects of fire retardants on biodiversity found here and the growing use of fire retardants worldwide call for additional evidence-based assessment of their impact, especially in the highly valued aquatic ecosystems.