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Effects of fomesafen, alone and in combination with an adjuvant, on planktonic communities in freshwater outdoor pond mesocosms.

Abstract : Ecotoxicological effects of the diphenyl ether herbicide fomesafen, applied alone or in combination with the adjuvant Agral 90 (mixture of polyethoxylated derivatives of nonylphenol), were assessed on planktonic communities in 18-m3 outdoor mesocosms during a nine-month study. Four mesocosms were treated with fomesafen only (nominal concentration: 40 microg/L), four were treated with the mixture fomesafen-Agral 90 (nominal concentration: 40 microg/L and 90 microg/L, respectively), and four were kept as the controls. Five treatments were performed every three weeks from April 18, 2000. Mean (+/- standard error [SE]) values of fomesafen concentration in water of 62.5 (+/-5.3) and 19.4 (+/-7.6) microg/L were measured at the end of the treatment period in fomesafen- and mixture-treated mesocosms, respectively. Fomesafen, either alone or in mixture with Agral 90, had a significant positive effect on the abundance and biovolume of Cyanobacteria, Cryptophyceae, Dinophyceae, and Bacillariophyceae. Chlorophyceae were inhibited by the herbicide and laboratory toxicity tests confirmed that green algae were more sensitive toward fomesafen than other algal classes. A positive effect of treatments on phytoplankton taxonomic diversity also was observed, indicating that, like natural disturbances of intermediate strength, xenobiotics sometimes may enhance the diversity of algal communities. Fomesafen alone did not have any clear effect on zooplankton. Abundance of calanoid copepods was reduced significantly in the mixture-treated ponds, suggesting either a direct effect of the adjuvant and/or an enhancement of herbicide toxicity by Agral 90. The abundance of other zooplanktonic herbivorous groups increased due to a reduced competition for food for herbivorous species and a higher availability of preys for predators. No algal bloom was observed in the treated ponds, presumably because of grazing pressure and the low availability of nutrients.
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https://hal-bioemco.ccsd.cnrs.fr/bioemco-00177367
Contributor : Gérard Lacroix <>
Submitted on : Monday, October 8, 2007 - 5:07:33 AM
Last modification on : Sunday, May 31, 2020 - 6:59:44 PM

Identifiers

  • HAL Id : bioemco-00177367, version 1
  • PRODINRA : 318513
  • PUBMED : 16110989

Citation

Thierry Caquet, Laurence Deydier-Stephan, Gérard Lacroix, Bertrand Le Rouzic, Françoise Lescher-Moutoué. Effects of fomesafen, alone and in combination with an adjuvant, on planktonic communities in freshwater outdoor pond mesocosms.. Environmental Toxicology and Chemistry, Wiley, 2005, 24, pp.1116-1124. ⟨bioemco-00177367⟩

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