FN Archimer Export Format PT J TI Toxicity of binary mixtures of pesticides to the marine microalgae Tisochrysis lutea and Skeletonema marinoi: Substance interactions and physiological impacts BT AF Dupraz, Valentin Ménard, Dominique Akcha, Farida Budzinski, Hélène Stachowski-Haberkorn, Sabine AS 1:1,2;2:1;3:1;4:3,4;5:1; FF 1:PDG-RBE-BE-LEX;2:PDG-RBE-BE-LEX;3:PDG-RBE-BE-LEX;4:;5:PDG-RBE-BE-LEX; C1 Ifremer, Laboratoire d’Écotoxicologie, rue de l’île d’Yeu, BP 21105, F-44311 Nantes cedex 03, France Université de Nantes, UFR Sciences et Techniques, 2, rue de la Houssinière, BP 92208, 44322 Nantes Cedex 03, 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 C2 IFREMER, FRANCE UNIV NANTES, FRANCE UNIV BORDEAUX, FRANCE CNRS, FRANCE SI NANTES SE PDG-RBE-BE-LEX IN WOS Ifremer UPR copubli-france copubli-univ-france IF 4.344 TC 20 UR https://archimer.ifremer.fr/doc/00488/59928/63131.pdf LA English DT Article DE ;ROS;Photosynthesis;Lipids;Synergy;Isoproturon;Metazachlor AB This study screened binary mixtures of pesticides for potential synergistic interaction effects on growth of the marine microalgae Tisochrysis lutea and Skeletonema marinoi. It also examined the single and combined effects of three of the most toxic substances on microalgal physiology. Single substances were first tested on each microalgal species to determine their respective EC50 and concentration-response relationships. The toxicity of six and seven binary mixtures was then evaluated in microplate experiments on the growth of T. lutea and S. marinoi, respectively, using two mixture modelling approaches: isobolograms and the MIXTOX tool, based on Concentration Addition (CA) or Independent Action (IA) models. Significant cases of antagonism (for both species) and synergism (for S. marinoi) were observed for the mixtures of isoproturon and spiroxamine, and isoproturon and metazachlor, respectively. These two mixtures, together with that of isoproturon and diuron, for which additivity was observed, were further studied for their impacts on the physiology of each species. Exposures were thus made in culture flasks at three concentrations, or concentration combinations for mixtures, selected to cause 25%, 50% and 75% growth rate inhibition. The effects of the selected pesticides singly and in combination were evaluated at three perceived effect concentrations on esterase metabolic activity, relative lipid content, cytoplasmic membrane potential and reactive oxygen species (ROS) content by flow cytometry, and on photosynthetic quantum yield (ϕ’M) by PAM-fluorescence. Isoproturon and diuron singly and in mixtures induced 20–40% decreases in ϕ’M which was in turn responsible for a significant decrease in relative lipid content for both species. Spiroxamine and metazachlor were individually responsible for an increase in relative lipid content (up to nearly 300% for metazachlor on S. marinoi), as well as cell depolarization and increased ROS content. The mixture of isoproturon and metazachlor tested on S. marinoi caused a 28–34% decrease in ϕ’M that was significantly higher than levels induced by each of substances when tested alone. This strong decrease in ϕ’M could be due to a combined effect of these substances on the photosynthetic apparatus, which is likely the cause of the synergy found for this mixture. PY 2019 PD JUL SO Aquatic Toxicology SN 0166-445X PU Elsevier BV VL 211 UT 000468708500016 BP 148 EP 162 DI 10.1016/j.aquatox.2019.03.015 ID 59928 ER EF