Toxicity Response and Swimming Speed Regularity in Daphnia magna After Short-Term Exposure to Diuron

The agricultural production process contributes to the global issue of pesticide pollution. Based on the static toxicity test of diuron (DCMU) onDaphnia magna(D. magna) for EC50-48 h, a concentration range of 0.2 to 1 mg/L was set as sublethal concentrations, while lethal concentrations were set at 2 mg/L and 4 mg/L. This study analyzes the toxic response patterns of the swimming behavior indicators ofD. magnaexposed to different concentrations of DCMU. The results showed that the average speed (V) ofD. magnadecreased step by step with exposure time, regardless of exposure to sublethal concentration or lethal concentration. However, during the same short-term exposure period, the V ofD. magnaat lethal concentration was higher than that at sublethal concentration, which indicates that the swimming behavior ofD. magnaexposed to DCMU may be stimulated and accelerated. Compared to the control group, there is a statistically significant difference in the V ofD. magnaafter short-term exposure, especially showing an extremely significant difference after 5 min of exposure. Evidently, compared to the traditional 48 h static toxicity testing method, the swimming behavior indicators ofD. magnashow a more sensitive response to DCMU after 5 min of exposure, making it more suitable for rapid toxicity detection. By expanding the range of exposure concentrations, it was found that the V indicator ofD. magnaresponded significantly to a DCMU concentration of 0.05 mg/L after only 5 min of exposure, and a high degree of correlation was observed between the indicator and the exposure concentration. Through nonlinear fitting, the relationship between V and the dose–effect of DCMU toxicity presents an S-shaped curve, with R2> 0.9. Consequently, it becomes possible to study the dose–effect relationship between the changes in the swimming behavior indicators ofD. magnaand the stress concentration based on this theory. This further establishes a foundation for the development of comprehensive aquatic toxicity rapid detection technology based on the toxic response of swimming behavior indicators.