Reviewing Pesticide Impacts on Frogs to Suggest Management Applications in the Gambles Mill Eco-Corridor

For years, frog populations have been declining due to a variety of anthropogenic sources, including pesticide use. Pesticides work by inhibiting bodily functions in their target pest species, though they frequently have unintentional impacts on other life forms in an ecosystem. Some researchers have evaluated these effects, but their studies mainly focus on finding an LC50 - a concentration that will kill 50% of their test species sample. However, these LC50 levels are often higher than what would be found in nature, and pesticides have been shown to still impact species at lower concentrations. Thus, this study attempted to summarize literature that included these lower concentrations to identify the level at which three target pesticides began to disrupt frog function. The target chemicals were atrazine, carbaryl, and glyphosate, all of which are commonly used pesticides or pesticide bases. This study was done specifically in the context of management for the Gambles Mill Eco-Corridor (referred to as the Eco-Corridor) in Richmond, Virginia, the site of a recent creek restoration project with a focus on storm water management and ecosystem health. To make results more applicable to the study area, four frog species with known or potential ranges in the Eco-Corridor were selected: The Gray Treefrog (Hyla versicolor), the Spring Peeper (Pseudacris crucifer), the American Bullfrog (Lithobates catesbeiana), and the Eastern Spadefoot (Scaphiopus holbrookii). The goal of this study was to determine if the selected frog species and pesticides could be connected to provide motivation for the use of frogs as indicator species and contribute insight into water testing requirements for the Eco-Corridor. The results suggested that atrazine is impactful at 0.0025ppm, glyphosate is impactful at 0.018ppm and carbaryl is impactful at 0.07ppm for one or more of the target frog species. These lowest concentrations of concern can be used to set detection thresholds when conducting water quality testing in the Eco-Corridor. This study also discussed potential sources of pesticides for the Eco-Corridor and suggested water quality testing locations. However, the results showed a lack of consistency in literature availability for the target species. Thus, P. crucifer was recommended as an indicator species, largely due to capture availability. Paper prepared for the Environmental Studies Senior Seminar/Geography Capstone