title: Microalgal sensitivity varies between a diuron-resistant strain and two wild strains when exposed to diuron and irgarol, alone and in mixtures.
abstract: A wild strain of Chaetoceros calcitrans and wild and diuron-resistant strains of Tetraselmis suecica, were exposed to the PSII inhibitor herbicides diuron and irgarol, individually and in mixtures. The effects of three concentrations of diuron and irgarol and four binary mixtures were evaluated on doubling time, relative reactive oxygen species and lipid content by flow cytometry, and on photosynthetic efficiency by pulse amplitude modulated fluorescence. In both wild strains, significant effects were observed for each molecule at the highest concentration tested: at irgarol 0.5 μg L(-1), C. calcitrans was shown to be more sensitive than T. suecica (+52% and +19% in doubling time, respectively), whereas at diuron 5 μg L(-1), T. suecica was more affected (+125% in doubling time) than C. calcitrans (+21%). Overall, irgarol had a higher toxicity at a lower concentration than diuron (no effect at diuron 0.5 μg L(-1)) for both wild strains. The strongest mixture (irgarol 0.5 μg L(-1) + diuron 5 μg L(-1)) increased doubling time by 356% for T. suecica, thus showing amplified effects when the two compounds were mixed. Sequencing of the diuron-resistant strain demonstrated a single mutation in the psbA gene coding sequence. Although resistance of this strain to diuron was confirmed with no effect at the highest diuron concentration, no resistance to irgarol was shown. In addition, the mutant strain exposed to the strongest mixture showed a 3.5-fold increase in doubling time compared with irgarol alone, thereby supporting the hypothesis of a biochemical interaction between these two compounds.
authors.affiliation: Ifremer, Laboratoire d'Écotoxicologie, rue de l'île d'Yeu, BP 21105, F-44311 Nantes Cedex 03, France.
authors.forename: Valentin
authors.initials: V
authors.lastname: Dupraz
authors.affiliation: Ifremer, Laboratoire d'Écotoxicologie, rue de l'île d'Yeu, BP 21105, F-44311 Nantes Cedex 03, France; Irstea, UR EABX, Centre de Bordeaux, 50 avenue de Verdun, F-33612 Cestas Cedex, France; Université de Bordeaux, UMR 5805, EPOC, Laboratoire de Physico Toxico Chimie de l'environnement, 351 Cours de la Libération, CS 10004, F-33405 Talence Cedex, France; CNRS, UMR 5805, EPOC, Laboratoire de Physico Toxico Chimie de l'environnement, 351 Cours de la Libération, CS 10004, F-33405 Talence Cedex, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Coquillé
authors.affiliation: Ifremer, Laboratoire d'Écotoxicologie, rue de l'île d'Yeu, BP 21105, F-44311 Nantes Cedex 03, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Ménard
authors.affiliation: Ifremer, Laboratoire d'Écotoxicologie, rue de l'île d'Yeu, BP 21105, F-44311 Nantes Cedex 03, France.
authors.forename: Rossana
authors.initials: R
authors.lastname: Sussarellu
authors.affiliation: Ifremer, Laboratoire d'Écotoxicologie, rue de l'île d'Yeu, BP 21105, F-44311 Nantes Cedex 03, France.
authors.forename: Larissa
authors.initials: L
authors.lastname: Haugarreau
authors.affiliation: Ifremer, Laboratoire d'Écotoxicologie, rue de l'île d'Yeu, BP 21105, F-44311 Nantes Cedex 03, France. Electronic address: Sabine.Stachowski.Haberkorn@ifremer.fr.
authors.forename: Sabine
authors.initials: S
authors.lastname: Stachowski-Haberkorn
mesh_terms: D017377:Diatoms / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D004237:Diuron / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004351:Drug Resistance / Q000187:drug effects* / Q000235:genetics; D006540:Herbicides / Q000494:pharmacology*; D058086:Microalgae / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D010788:Photosynthesis / Q000187:drug effects; D013045:Species Specificity; D014227:Triazines / Q000494:pharmacology*
chemical_list: D006540:Herbicides; D014227:Triazines; C103341:irgarol 1051; D004237:Diuron
keywords: Antifouling; Diuron; Diuron resistance; Herbicides; Irgarol; Microalgae