title: Individual and joint toxicity of the herbicide S-metolachlor and a metabolite, deethylatrazine on aquatic crustaceans: Difference between ecological groups.
abstract: We studied the individual and joint acute toxicity of S-metolachlor (SMOC) and deethylatrazine (DEA - a metabolite of atrazine) on different non-target freshwater crustaceans. We used animals from different ecological groups: two amphipods from surface running water (Gammarus pulex and Gammarus cf. orinos), an isopod from surface stagnant water (Asellus aquaticus) and an amphipod living in groundwater (Niphargus rhenorhodanensis). Organisms were exposed to different levels of SMOC and DEA, alone or in binary mixture. Temperature effect on SMOC toxicity was assessed by exposing G. pulex and N. rhenorhodanensis to SMOC at 11 °C and 15 °C. Studying mortality as the biological endpoint, N. rhenorhodanensis was more resistant than surface water species towards SMOC and DEA. Among surface water species, G. pulex was the most sensitive while Gammarus cf. orinos and A. aquaticus showed similar responses to both compounds. Temperature increase did not change SMOC toxicity but modify the shape and steepness of the dose-response curve. We used a Model Deviation Ratio (MDR) approach to evaluate the predictability of Concentration Addition (CA) and Independent Action (IA) models to mixture toxicity. Results indicated either an additive or an antagonistic or a synergistic interaction depending on the concentrations combination and the test species. Our finding conclusively show the suitability of CA and IA in predicting mixture toxicities but results should be interpreted with caution according to ecological group of exposed species in risk assessment procedures.
authors.affiliation: Université de Lyon, UMR5023 Ecologie des Hydrosystèmes Naturels et Anthropisés, Université Lyon 1, ENTPE, CNRS, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne, France. Electronic address: chafik.maazouzi@univ-lyon1.fr.
authors.forename: C
authors.initials: C
authors.lastname: Maazouzi
authors.affiliation: Bureau de Recherches Géologiques et Minières, 3 Avenue Claude Guillemin, BP 6009, 45060 Orléans Cedex 2, France.
authors.forename: C
authors.initials: C
authors.lastname: Coureau
authors.affiliation: Université de Lyon, UMR5023 Ecologie des Hydrosystèmes Naturels et Anthropisés, Université Lyon 1, ENTPE, CNRS, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne, France.
authors.forename: C
authors.initials: C
authors.lastname: Piscart
authors.affiliation: Bureau de Recherches Géologiques et Minières, 3 rue Marie Curie, B.P. 49, 31527 Ramonville-Saint-Agne, France.
authors.forename: M
authors.initials: M
authors.lastname: Saplairoles
authors.affiliation: Bureau de Recherches Géologiques et Minières, 3 Avenue Claude Guillemin, BP 6009, 45060 Orléans Cedex 2, France.
authors.forename: N
authors.initials: N
authors.lastname: Baran
authors.affiliation: Université de Lyon, UMR5023 Ecologie des Hydrosystèmes Naturels et Anthropisés, Université Lyon 1, ENTPE, CNRS, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne, France.
authors.forename: P
authors.initials: P
authors.lastname: Marmonier
mesh_terms: D000081:Acetamides / Q000378:metabolism / Q000633:toxicity*; D033304:Amphipoda / Q000187:drug effects / Q000254:growth & development; D000818:Animals; D001280:Atrazine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000633:toxicity; D003445:Crustacea / Q000187:drug effects* / Q000254:growth & development; D004463:Ecology; D005618:Fresh Water / Q000737:chemistry; D060587:Groundwater / Q000737:chemistry; D006540:Herbicides / Q000378:metabolism / Q000633:toxicity*; D033321:Isopoda / Q000187:drug effects / Q000254:growth & development; D007928:Lethal Dose 50; D008962:Models, Theoretical; D018570:Risk Assessment; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000633:toxicity*
chemical_list: D000081:Acetamides; D006540:Herbicides; D014874:Water Pollutants, Chemical; C446541:deethylatrazine; D001280:Atrazine; C051786:metolachlor
keywords: Aquatic toxicity; Groundwater; Herbicides mixture; Metabolites; Surface water