Toxicity of the herbicide atrazine, two of its degradation products and the herbicide metolachlor on photosynthetic microorganisms

The toxic effects of the herbicide Atrazine, its degradation products deethyl-atrazine and deisopropyl-atrazine, and the herbicide metolachlor were examined in unialgal cultures of Chlorella fusca var-fusca and Chlamydomonas moewssi. The order of toxicity for Chlorella fusca var-fusca was atrazine>metolachlor>deethyl-atrazine>deisopropyl-atrazine. EC50 of atrazine for Chlamydomonas moewssi. was 1384 mu g/l, while the other chemicals did not inhibit growth rate of the alga as much as 50 %, for the greatest concentration tested. Only atrazine and deisopropyl-atrazine, reduced their toxicity over time, to Chlorella fusca var-fusca.