Acute exposure to Roundup has nonlinear effects on larval stream salamander behavior and recovery.

Glyphosate is a commonly used pesticide applied to agricultural fields, but runoff during rainfall introduces the chemical into surrounding waters. In stream systems, glyphosate has non-target effects and can negatively affect amphibian physiology, development, and behavior. These effects are previously documented from chronic exposure relative to the acute exposures more often experienced by organisms inhabiting streams. Previous studies indicate that glyphosate induces a dose-dependent effect on startle responses in stream salamanders, but it is unclear how long individuals need to recover from acute exposure. We described the behavioral recovery of stream salamander larvae, Eurycea wilderae, to short-term exposure of glyphosate. We observed that individuals recovered from glyphosate exposure between 2 and 4 h post-exposure. Length of exposure did not affect larval responses linearly, indicating a lack of accumulated effects and a non-monotonic response. Our data suggested that there was a maximum effect of glyphosate on stream salamander larvae that may be similar to exhaustion. We recommend researchers consider the frequency of testing when they explore this effect threshold. Because startle response is associated with swimming ability, impairment due to glyphosate could temporarily increase predation risk and contribute to downstream displacement of larvae inhabiting streams in agricultural and urban areas. [ABSTRACT FROM AUTHOR]