Deicing Salts Influence Ranavirus Outbreaks in Wood Frog (Lithobates sylvaticus) Tadpoles

Ecosystems are increasingly being exposed to anthropogenic stressors that could make animals and thus populations more susceptible to disease. For example, the application of deicing salts to roads is increasing in the northeastern United States. Chronic stress that larval amphibians experience when living in vernal pools with high salinity may alter their susceptibility to ranavirus, a pathogen responsible for mass mortality events worldwide. This project quantifies the effects of road salts and ranavirus exposure on larval wood frog (Lithobates sylvaticus) growth and survival. Using outdoor mesocsoms, we raised wood frog tadpoles in salt treatments and then exposed them to the FV3 strain of ranavirus, with the hypothesis that individuals raised in salt treatments would have lower survival, and metamorph earlier at larger size when exposed to ranavirus than those from no salt treatments. We found that tadpoles raised in high and no salt treatments metamorphed earlier than those raised in low salt treatments (F2,111 = 21.63, P \u3c 0.0001). Tadpoles raised in high salt treatments had a greater mass than those raised in low and no salt treatments (F2, 111 = 9.628, P = 0.0001). Among the tadpoles exposed to ranavirus, survival to metamorphosis was lowest in low-salt tadpoles (95% CI: 0.02 – 0.11), while survival was highest in no-salt tadpoles (95% CI: 0.29 – 0.475). In summary, exposure to road salts altered the growth and survival of larval wood frogs in non-linear ways. Our results indicated that this anthropogenic stressor is altering the response of individual tadpoles, suggesting that the disease epidemiology within populations may be altered. Additional research on the severity and frequency of outbreaks in populations is warranted