Effects of pyridaphenthion on growth of five freshwater species of phytoplankton. A laboratory study

The acute toxicity of the insecticide and acaricide pyridaphenthion to five species of freshwater phytoplankton, Seenedesmus acutus, Scenedesmus subsp icatus, Chlorella vulgaris, Chlorella saccharophila and Pseudanabaena galea ta was determined. Insecticide concentrations eliciting a 50% growth reduct ion over 96 h (EC50) ranged from 2.2 to 30.9 mg/l. The two species of Chlor ella and the cyanobacteria P. galeata were more tolerant than the two speci es of Scenedesmus. Concentrations of pyridaphenthion detected in some natur al waters were less than the toxic threshold for these species. (C) 2001 El sevier Science Ltd. All rights reserved.