title: Toxicity effects of an environmental realistic herbicide mixture on the seagrass Zostera noltei.
abstract: Worldwide seagrass declines have been observed due to multiple stressors. One of them is the mixture of pesticides used in intensive agriculture and boat antifouling paints in coastal areas. Effects of mixture toxicity are complex and poorly understood. However, consideration of mixture toxicity is more realistic and ecologically relevant for environmental risk assessment (ERA). The first aim of this study was to determine short-term effects of realistic herbicide mixture exposure on physiological endpoints of Zostera noltei. The second aim was to assess the environmental risks of this mixture, by comparing the results to previously published data. Z. noltei was exposed to a mixture of four herbicides: atrazine, diuron, irgarol and S-metolachlor, simulating the composition of typical cocktail of contaminants in the Arcachon bay (Atlantic coast, France). Three stress biomarkers were measured: enzymatic activity of glutathione reductase, effective quantum yield (EQY) and photosynthetic pigment composition after 6, 24 and 96 h. Short term exposure to realistic herbicide mixtures affected EQY, with almost 100% inhibition for the two highest concentrations, and photosynthetic pigments. Effect on pigment composition was detected after 6 h with a no observed effect concentration (NOEC) of 1 μg/L total mixture concentration. The lowest EQY effect concentration at 10% (EC10) (2 μg/L) and pigment composition NOEC with an assessment factor of 10 were above the maximal field concentrations along the French Atlantic coast, suggesting that there are no potential short term adverse effects of this particular mixture on Z. noltei. However, chronic effects on photosynthesis may lead to reduced energy reserves, which could thus lead to effects at whole plant and population level. Understanding the consequences of chemical mixtures could help to improve ERA and enhance management strategies to prevent further declines of seagrass meadows worldwide.
authors.affiliation: EcoLab, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France. Electronic address: noel.diepens@ensat.fr.
authors.forename: Noël J
authors.initials: NJ
authors.lastname: Diepens
authors.affiliation: EcoLab, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France.
authors.forename: Evelyne
authors.initials: E
authors.lastname: Buffan-Dubau
authors.affiliation: Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), UMR 5805 CNRS/Univ. Bordeaux 1, Laboratoire de Physico- et Toxico-Chimie de l'environnement (LPTC), 351, cours de la Libération, 33405 Talence, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Budzinski
authors.affiliation: EcoLab, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Kallerhoff
authors.affiliation: EcoLab, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France.
authors.forename: Georges
authors.initials: G
authors.lastname: Merlina
authors.affiliation: EcoLab, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France.
authors.forename: Jérome
authors.initials: J
authors.lastname: Silvestre
authors.affiliation: IFREMER Arcachon, Laboratoire Environnement Ressources, Quai du Cdt Silhouette, 33120 Arcachon, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Auby
authors.affiliation: Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), UMR 5805 CNRS/Univ. Bordeaux 1, Laboratoire de Physico- et Toxico-Chimie de l'environnement (LPTC), 351, cours de la Libération, 33405 Talence, France.
authors.lastname: Nathalie Tapie
authors.affiliation: EcoLab, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Elger
mesh_terms: D061006:Bays; D005602:France; D005980:Glutathione Reductase / Q000378:metabolism; D006540:Herbicides / Q000633:toxicity*; D007306:Insecticides / Q000633:toxicity; D010788:Photosynthesis / Q000187:drug effects*; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D035962:Zosteraceae / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism
chemical_list: D006540:Herbicides; D007306:Insecticides; D014874:Water Pollutants, Chemical; D005980:Glutathione Reductase
keywords: Effective quantum yield; Herbicides; Mixture toxicity; Pigments; Zostera noltei