Re-evaluating Ecotoxicology with Thermal Fluctuations

Abstract

Since the industrial revolution, humans have introduced a substantial amount of greenhouse gases and other pollutants to the natural environment. These stressors are especially challenging to ectotherms living in variable thermal environments. Ectotherms in the wild coping with one environmental stressor, like diel thermal fluctuations, may have a diminished ability to cope with additional ones. Therefore, regulatory agencies seeking to determine acceptable concentrations of potentially harmful substances may need to alter the way in which ecotoxicological studies (which are typically done under constant temperatures) are performed. By challenging model species with multiple stressors at once, scientists may be able to generate ecotoxicological data that better reflect organisms’ energetic trade-offs. This study seeks to determine if exposure to the stress of thermal fluctuations alters an organism’s susceptibility to a chemical pollutant. We exposed Pimephales promelas embryos reared under three temperature regimes (constant 25°C, daily fluctuations between 22 and 28°C, and 19° to 31°C fluctuations) to varying concentrations of vanadium pentoxide (V2O5), a largely unregulated industrial chemical. We quantified the interrelationship between stressors and rates of growth, survival, and incidence of scoliosis (curvature of the spine) across all experimental treatments using generalized linear modelling. During acute exposure, fluctuating temperatures and vanadium pentoxide worked individually and interactively to reduce survival, while only fluctuating temperatures altered growth outcomes. Further experimentation will be needed to ascertain the full scope of vanadium pentoxide’s effects.