Atrazine and Nicosulfuron effects on phytoplanktonic communities of Lake of Geneva

Atrazine is a widely used herbicide in corn cultures. As Atrazine have cont aminated many aquatic ecosystems, other chemicals such as Nicosulfuron are proposed in replacement. Comparative studies of Atrazine and Nicosulforon e ffects on phytoplankton were performed on systems of increasing complexity: monocultures and out-door microcosms. Sensibilities of communities are different depending on experiments, specie s and toxicant. Algae in monoculture experiments seem to show a lower sensi bility than in microcosms. We conclude that experiments in monocultures are not enough to appreciate the effect of Nicosulfuron. The complexification of study system increases its sensitivity to the toxic Nicosulfuron.