Background/Question/Methods   Population declines of amphibians are of great concern worldwide. Two significant factors impacting these declines are emerging infectious disease and anthropogenic contaminants. Bactrachochytrium dendrobatidis (Bd) is an emerging fungal pathogen known to cause rapid declines worldwide. The antimicrobial triclosan is commonly used in household soaps and can ultimately contaminate freshwater systems. While there is much literature documenting several causes for amphibian population declines, very few focus on the synergistic impacts of multiple stressors. In particular, the interaction of novel stressors with natural stressors, such as predation, is often overlooked. We conducted a 2 x 4 x 2 factorial design to examine the potential interactive impacts of Bd, triclosan (0, 10, 100, 1000 µg/L) and dragonfly predator cue on Woodhouse's Toad (Anaxyrus woodhousii) larvae. We measured the impacts of these stressors on survivorship, growth, and development of the tadpoles over a four week time span.

Results/Conclusions   There was a significant toxic effect of triclosan exposure on the tadpoles. All tadpoles in the 100 and 1000 µg/L concentrations died within 24 hours of exposure. Interestingly, there was a non-monotonic survival response at the lowest concentration (10 µg/L) where tadpoles survived better at low concentrations as compared to controls. This pattern was driven by a significant interaction between the factors Bd and triclosan. Tadpoles in non-Bd treatments exhibited only a marginal decrease in survival between control (84.1%) and low triclosan (10 µg/L; 77.3%) treatments. Tadpoles exposed to only Bd (no triclosan) had a markedly low survival rate (67.5%). Although, those exposed to both a low dosage of triclosan and Bd had a survival rate of 91.1%. A proposed mechanism for this increased survival is the potential toxicity of triclosan to Bd itself. No significant effects of predation were detected, as were no significant impacts to the sub-lethal measures of growth and development. Further investigation of the impacts of triclosan to both hosts and pathogens should provide a better understanding of the survival of species living in a multiple stressor environment.