The amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), infects the skin of amphibians and is a leading factor in recent global amphibian declines. Bd causes electrolyte imbalance by destroying the keratin in the skin and can eventually cause death via cardiac arrest. Growth and motility of Bd can be inhibited by elevated salt concentrations (NaCl), which has been suggested to be a mitigation technique. However, salts often infiltrate wetlands as road salts from de-icing applications in many parts of North America. There is little known about how various road salts impact Bd proliferation, and how they differ from common NaCl exposure. This study investigated how different road salts at various concentrations affect the growth and motility of Bd. We predict that Bd growth would be most inhibited by road salts that contain more de-icing chemicals such as calcium chloride (CaCl2) and that Bd growth will be the greatest in salts that are considered more “environmentally friendly,” such as Beet-infused road salt. Bd was cultured in NaCl, CaCl2, and Beet salt at concentrations of 2, 3, and 5 parts per thousand (ppt). We measured growth and viability of Bd via zoospore and zoosporangia identification and quantification.
Results/Conclusions
We found that the mean number of zoospores was higher in no-salt controls than in Beet salt, CaCl2, and NaCl treatments. The largest, negative effect on mean zoospore count occurred when Bd was exposed to NaCl at 5 ppt. Further, mean zoosporangia counts in what treatment? were lower than no-salt controls, but the interaction between salt type and salinity had a greater effect on mean zoospore count than mean zoosporangia counts. Our findings suggest several types of roads salts may have negative effects on Bd that could translate to lower infections in amphibians. Additionally, that negative effects of road salts are not equal across life stages; zoosporangia were more resistant to elevated salinity than zoospores. Future studies should explore how road salts directly affect amphibians and how infection dynamics change when both host and pathogen are in the presence of these salts.