Acute and chronic toxicities of zinc thiazole to Daphnia magna

Zinc thiazole is a high-efficiency thiadiazole organic zinc bactericide developed in China. Its main application is to control bacterial diseases of crops. The acute-chronic toxicity and conducted the offspring contamination and recovery tests of zinc thiazole to Daphnia magna by exposure tests at 48 h and 21 d were evaluated. The acute toxicity results indicated that zinc thiazole had high toxicity against D. magna. The 48 h-EC₅₀ value was 213.3 μg/L and the dose-effect relationship was y = 3.08x−7.10 (r = 0.93). 21 days after the exposure, each life index of D. magna changed significantly (P < 0.05) at the 4.26 μg/L group. After comparing with the vehicle, the total number of offspring per female and the number of brood per female of F₀ generation were decreased by 53.45% and 31.15%, respectively. The first reproduction time was also delayed by an average of 2.75 d. The number of cumulative molts were significantly reduced and shortened body length showed up. Among all the indexes, the no observed effect concentration(NOEC) of the total number of offspring per female, the number of brood per female and body length in F₀ generation was exposure to 2.13 μg/L zinc thiazole for 21 d. The total number of offspring per female and the number of brood per female of F₁ generation were significantly reduced, and the growth of D. magna was obviously inhibited, but there was no significant difference between the contamination and the control. F₁ recovery group had good resilience and had no significant difference in activity indexes versus the control. This study revealed that zinc thiazole can adversely impact on the reproduction and the development ability of D. magna, and showed certain risks to the aquatic ecology.