Acute Toxicity of Atrazine to Green Algae, Heterotrophic Flagellate and Ciliates

The acute toxicity of herbicide atrazine to a species of green algae Scenedesmus obliquus, a species colorless heterotrophic flagellate Bodo saltans and two species of ciliates Tetrahymena priformis and Oxytricha saprobia was examined in laboratory tests. The results showed that the acute toxicity of atrazine to S. obliquus, B. saltans, T. priformis and C. pyrenoidosa was high. The median effective concentration (EC50) of atrazine to S. obliquus for 24, 48 and 72h were 40.6, 30.0 and 22.1μg/L. The EC50 of atrazine to B. saltans for 24, 48 and 72h were 14.5, 15.0 and 13.4 μg/L. The EC50 of atrazine to T. priformis for 24, 48 and 72h were 15.7, 14.7 and 13.0 μg/L. The EC50 of atrazine to O. saprobia for 24, 48 and 72h were 40.7, 38.6, 22.5 μg/L, respectively. Although atrazine is slightly to moderately toxic to mammals, it is highly toxic to the four tested aquatic unicellular organisms.