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 PARENT SESSION
2I - High-tiered Studies
Hall 7
8:30 AM - 12:30 PM, Monday, 28 April 2003
Chair: Streloke, M.1, 1
Co-chair: Schutz, R.2, 2
(MO7/5) Community-level effects of the mixture between a diphenyl-ether herbicide (fomesafen) and a polyethoxylated nonylphenol-based adjuvant (Agral® 90) in outdoor freshwater pond mesocosms.
Caquet, Th.1, Lagadic, L.1, Cravedi, J.P.2, Le Rouzic, B.3, Lacroix, G.4, Azam, D.5, Heydorff, M.1, Roucaute, M.1, Deydier-Stephan , L.3, 1 INRA EQHC, Rennes, France2 INRA Xenobiotiques, Toulouse, France3 UMR 6553 Ecobio, Rennes, France4 UMR 7625, Paris, France5 INRA U3E, Rennes, France
ABSTRACT- The fate and ecotoxicological effects of a diphenyl ether herbicide, fomesafen, applied alone or in combination with Agral 90® (mixture of polyethoxylated derivatives of nonylphenol) were assessed in 18 m3 outdoor mesocoms during a 9 months study. Nominal concentrations of both compounds were 40  g/L and 90 g/L respectively. Four mesocosms were contaminated with fomesafen only, four were treated with the mixture fomesafen-Agral 90® and four were kept as untreated controls. Five treatments were performed every three weeks from April 18, 2000. At the end of the contamination period, herbicide concentrations at water mid-depth were 60.33 ± 2.68 g/L and 30.33 ± 14.91 g/L in fomesafen- and mixture-treated mesocosms, respectively. PRC analysis showed that fomesafen, either alone or in mixture with Agral 90®, had a significant positive effect on phytoplankton taxonomic diversity through a decrease of the dominance of Chlorophyceae. Cyanobacteria, Cryptophyceae and Dinophyceae abundance increased in all treated mesocosms. Phytoplankton size index was not affected by the treatments. Positive effects on emerging insects were demonstrated for the mixture only and were presumably due to a change in food availability in the treated mesocosms. No significant effects of both type of treatements were detected on benthic macroinvertebrates. These results demonstrate that adjuvants may greatly modify the fate and effects of pesticide. It is therefore necessary to include these products in the ecotoxicological risk assessment of plant protection products.
Key words: aquatic mesocosms, herbicide-adjuvant mixture, community level effects
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