Environmental Drivers of Pesticide Toxicity: Temperature and pH Shift Azoxystrobin’s Effects on Zebrafish (Danio rerio) Early Development

Azoxystrobin, a widely used strobilurin fungicide, poses a potential risk to aquatic ecosystems due to its frequent detection in surface waters. Although its toxicity to non-target organisms has been extensively studied under standardized conditions, few investigations have considered how environmental factors can modulate the adverse effects of this chemical. In this study, we examined the toxicity of azoxystrobin to zebrafish (Danio rerio) embryos under different pH (5, 7, 9) and temperature (21 °C, 26 °C, 31 °C) conditions. Embryos were exposed to azoxystrobin concentrations ranging from 0 to 1000 μg/L, and endpoints such as survival, hatching rate, heart rate, malformations, developmental delay, and Hsp70 expression were assessed over 96 h post-fertilization. Our results demonstrate that azoxystrobin induces significant malformations (including edema, eye, tail, and spinal defects) and developmental delays at 1000 μg/L across all environmental conditions. Furthermore, both pH and temperature were found to modulate azoxystrobin toxicity: elevated temperature and alkaline pH partly alleviated mortality at high concentrations. The hsp70 expression patterns revealed complex interactions between the effects of the chemical and environmental factors. These findings highlight the importance of incorporating environmental variables into ecotoxicological risk assessments of pesticides to better reflect realistic exposure scenarios and potential ecological impacts.