PS 27-131 - Long-term, landscape-level assessment of aquatic pesticide exposure identifies amphibian ontological traits affecting vulnerability

Abstract: Amphibians worldwide are threatened by habitat loss, some of which is driven by a changing climate, as well as exposure to pesticides, amongst other causes. The timing and duration of the larval development phase varies between species, thereby influencing the relative impacts of stochastic hydroregime conditions as well as potential aquatic pesticide exposure. We describe the stages of breeding through metamorphosis for eight amphibian species, based on optimal hydroregime conditions and use a model of pesticide fate and exposure representative of central Florida citrus groves to simulate hydrodynamics based on observed weather data. Using the Pesticide in Water Calculator we estimated daily wetland depth and pyraclostrobin exposure, based on recommended application protocols. Timing and duration of larval development was influential in determining years of suitable hydroregime for breeding, and timing of pesticide application influenced peak concentrations of pyraclostrobin during the larval stage. Although frequency of pesticide exposure influenced differences in larval survival between species, density dependent constraints of wetland hydroregime also affected larval survival across species and seasons. Further defining categorical amphibian life history types and habitat requirements could provide a screening-level assessment approach at the appropriate temporal resolution to adequately incorporate environmental stochasticity. Subsequent refinement of these screening-level assessments to include spatially explicit landscape data along with terrestrial exposure estimates would offer additional insights into species vulnerability throughout the life cycle.