Increasing temperature exacerbates acute toxicity effects of a glyphosate-based herbicide (Roundup) on the ostracod <i>Cypridopsis africana</i>

Predicted global temperature increase is expected to have unprecedented effects on freshwater ecosystems. While the individual impacts of temperature and chemical exposures on aquatic species physiology, life history and survival have received adequate attention, the interactive effects of temperature and chemical toxicity, particularly on the temporary pond ecosystems, have yet to be elucidated. Here, I conducted short-term toxicity tests to assess the impact of increased temperature on Roundup toxicity on an ostracod, Cypridopsis africana. Roundup is currently a widely used herbicide with glyphosate as its active ingredient. Test organisms were exposed to five nominal concentrations of Roundup (25, 50, 100, 200 and 400 mg/l active ingredient) and a control. These concentrations were crossed against two temperature conditions, 27°C and 31°C. After 48 h of exposure, Roundup lethal concentration 50 (LC50) at 27°C was 223±15.2 mg/l and decreased to 186.03±4.04 mg/l at 31°C. These findings show a decrease in LC50 by 16.5% following an increase of +4°C. This underscores the need for a tailored risk assessment paradigm that takes increasing temperature into consideration.