Using a Dynamic Energy Budget (DEB) Model to Analyze the Sublethal and Lethal Effects of Insecticides at Different Temperatures

Temperature is an important factor for biological processes, i.e., by affecting growth, feeding, and reproduction, especially for aquatic ectothermic species. Furthermore, temperature changes the behaviour of chemicals, such as their fate and bioavailability in the environment. The importance of gaining a better understanding of how temperature affects chemical toxicity is emphasized by the observation that many previous studies have found that the acute lethal toxicity of chemicals increases with temperature. Although a better understanding of the impacts of temperature on lethal and sublethal endpoints is important, few studies have been conducted, and the underlying mechanisms of temperature effects are largely unknown. Temperature can affect the toxicity of chemical substances by effects on the kinetics: temperature affects the uptake of chemicals, and therefore (apparent) toxicity could be changed. Also, the intrinsic sensitivity of organisms can be influenced by altering certain gene expressions or enzyme activities. To understand these processes and allow to separate the drivers, toxicokinetictoxicodynamic (TKTD) models like the Dynamic Energy Budgets (DEB) models are needed for lethal and especially sub-lethal endpoints. In this study, we have applied DEB models to data on the lethal and sublethal effects of imidacloprid and flupyradifurone on Gammarus pulex at different temperatures. Our results showed that for both insecticides, the dominant rate constant and threshold value tend to decrease with increasing temperature for both lethal and sublethal effects, while the effect strength and background mortality tend to increase with increasing temperature. The results showed that temperature influences both the kinetic of chemicals and the intrinsic sensitivity of organisms. In addition, a 180-day experiment is currently being performed to capture the effect of temperature on mortality and growth. The preliminary results suggest that the DEB model fits well and that damage from imidacloprid is diluted by growth. SETAC Europe 33rd Annual Meeting 187 Overall, the current results indicate that the relationship between each parameter and temperature might vary with species and chemicals; therefore, more studies need to be conducted to get a general and clearer picture. Also, this present study deepens the understanding of the mechanism of temperature on pesticide toxicity, which can be used for future risk assessment when the temperature is integrated.