THE EFFECT OF TWO COMMON HERBICIDES ON THE GROWTH AND DEVELOPMENT OF TWO ANURAN SPECIES (BOREORANA SYLVATICA AND DRYOPHYTES CHRYSOSCELIS)

Amphibian populations have been declining globally since the 1950s. Many species that have experienced declines are viewed as 'environmental indicators' that reveal habitat degradation. Declines can be attributed to several factors, including chemicals used in agriculture, such as Roundup and Atrazine. Agrochemicals contaminate water bodies through runoff or leaching and cause alterations to aquatic ecosystems. This study evaluated the effects of herbicide usage on two wild anuran populations using wood frogs (Boreorana sylvatica) and Cope’s gray tree frogs (Dryophytes chrysoscelis) as a model. We determined the effect of the herbicides at two concentrations, a high concentration that simulated a pulse dosage during a runoff event and low concentration that simulated a background level of exposure and identified synergistic effects resulting from the mixture of both herbicides at the high or low concentration. Effects of herbicide on larval growth and development were measured by recording variation in survival-to-, size-at-, and time-to-metamorphosis across treatment levels. Differences between treatments were assessed through the comparison of a null model (lacking treatment term) and an alternative model (including treatment term) using likelihood ratio tests. We determined that these agrochemicals induce negative effects on amphibian taxa, including metamorphic size and mortality. This research provides a better understanding of the environmental implications resulting from the effects of combined stressors on wild populations. Understanding how anthropogenic land use impacts amphibians is paramount in preventing amphibian population declines and environmental degradation.