EcotoxicoMic Webinar: Valentin DUPRAZ (IFREMER-University of Nantes, France)

4th EcotoxicoMic Webinar

Friday, October 12, 2018  (9:10 am, Paris Time Zone)

Webinar Registration: click here

Valentin DUPRAZ

(IFREMER-University of Nantes, France)


How to interpret the toxicity of complex environmetal mixtures? a method combining analytical chemistry and mixture modelling approaches

Valentin Dupraz1,2, Dominique Ménard1, Nathalie Tapie3,4, Farida Akcha1, Hélène Budzinski3,4, Sabine Stachowski-Haberkorn1
Ifremer, Laboratoire d’Écotoxicologie, rue de l’île d’Yeu, BP 21105, 44311 Nantes cedex 03, France; Université de Nantes, 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; 4 CNRS, UMR 5805, EPOC, Laboratoire de Physico Toxico Chimie de l’environnement, 351 Cours de la Libération, CS 10004, F-33405 Talence Cedex, France

Keywords: microalgae; passive samplers; synergy; mixtures; vineyards

Pesticides used in viticulture end up in aquatic systems downstream of vineyard plots.  Concentrations of single substances are often below the maximum residue level imposed by the WFD but few is known about their potential toxicity in mixtures.

According to their chemical properties, pesticides accumulate over time in POCIS passive samplers deployed in contaminated environments and the toxicity of the whole mixture from POCIS can be tested after extraction. As phytoplankton plays a key role in the aquatic food web, this study aimed to assess the toxicity of pesticides as well as POCIS extracts towards the growth of two marine microalgae, Tisochrysis lutea (haptophyte) and Skeletonema marinoi (diatom). POCIS were placed in three stations along a contamination gradient in small watercourses close to the vineyards plots over four one-month periods.

The toxicity tests consisted in 96-h exposures of microalgae to ii) single and binary combinations of pesticides expected in the extracts and ii) POCIS extracts, in sterile 48-well microplates incubated under controlled conditions. Each species was exposed to six concentrations of the single or mixed (at three different mixture ratios) substances and five dilutions of the POCIS extracts. The toxicity was assessed by calculating the growth rate inhibition using chlorophyll fluorescence. To assess the interactive effect of pesticide mixtures, a mixture modelling approach was used. Chemical analyses were performed to monitor exposure concentrations of the tested pesticides in the microplate test system and to quantify the expected substances in diluted POCIS extracts.

Nine pesticides tested singly induced a significant toxicity. The binary combination of isoproturon and metazchlor was found to be significantly synergistic for the diatom S. marinoi. POCIS extracts induced a varying toxicity depending on the period and/or station. The toxicity of the extracts was partially explained by compiling results from both single and mixed substances toxicity assays and chemical analyses of the diluted POCIS extracts.

The testing of complex mixtures from the environment provides additional information regarding the contamination of aquatic ecosystems and enlights the necessity of focusing on mixture effects, along with single compound toxicity.

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