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Transfer and distribuion of diuron in biofilms and joint toxic effects

Abstract : Pesticides are ubiquitous in aquatic environments and impact aquatic organisms. In particular, freshwater biofilms which are at the basis of aquatic trophic foodwebs, are impacted by pollutants, especially herbicides, without being systematically accumulated. Biofilms are composed of microalgae and other microorganisms embedded in a polysaccharidic matrix (EPS). Nowadays, no method exists to characterize organic pesticide accumulation into such biological matrix. To overcome this lack, we developed a new approach dedicated to the determination of pesticide transfer and distribution into the matrix. This approach is based on the physical separation, and then analysis of the different matrix compartments: pore water, EPS and microorganisms. The aim of this study is to obtain a better understanding of mechanisms taking part into pesticide bioaccumulation on biofilms. In parallel, toxicokinetic are also coupled with toxicodynamic studies, in order to investigate the relationship between accumulation rate and joint effects of herbicides. In this study, we determined the accumulation and distribution of diuron, a photosynthesis inhibitor included in the priority substances in the EU Water Framework Directive into biofilms, over 21 days. imultaneously, we characterized biofilm biomass (dry weight, total organic carbon), protein and polysaccharide contents, coupled with the assessment of functional effects on enzymatic activities (β-Glucosidase and β-Glucosaminidase) and photosynthetic activity. After one month of colonization in Gazinet-Cestas pond (France) on glass slides, biofilms were exposed for 21 days in channels with three conditions: one control, and two contaminated with 5 and 50 µg.L-1 of diuron. For each sampling time, diuron-induced photosynthetic activity of the biofilms was assessed. Biofilms were further separated by centrifugation into colloidal EPS and microorganism pellet fractions. Protein and polysaccharide contents, enzymatic activities (β-Glucosidase and β-Glucosaminidase), and total organic carbon (TOC) were analysed, and diuron was quantified in both fractions. Pesticide quantification in the biofilm showed that diuron was quickly accumulated (i.e. after only 15 minutes of exposure) in both EPS and cells, highlighting early distribution in the whole biofilm, followed by cell internalization. Over time, dry weight and TOC significantly increased for control and 5 µg.L-1 condition, whereas biofilm did not grow in the 50 µg.L-1 condition. Protein and polysaccharide contents and of enzymatic activities were not significantly impacted during diuron exposure. However, photosynthesis was clearly inhibited from 15 minutes until 21 days in the biofilms exposed to 50 µg.L-1 of diuron, as an expectable result of its mode of action. All these results provide a basis to develop a pesticide bioaccumulation model. By linking toxicokinetic and toxicodynamic approaches, this study provides new information on diuron bioaccumulation mechanisms in biofilms.
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Conference papers
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https://hal.inrae.fr/hal-02606836
Contributor : Migration Irstea Publications <>
Submitted on : Saturday, May 16, 2020 - 1:09:10 PM
Last modification on : Monday, March 8, 2021 - 12:30:06 PM

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  • HAL Id : hal-02606836, version 1
  • IRSTEA : PUB00056094

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B. Chaumet, Soizic Morin, O. Hourtané, Joan Artigas, Sébastien Boutry, et al.. Transfer and distribuion of diuron in biofilms and joint toxic effects. Ecotoxicomic 2017 - First International Conference on Microbial Ecotoxicology, Nov 2017, Lyon, France. pp.43. ⟨hal-02606836⟩

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