Use of passive samplers extracts for toxicity assessment of environmental realistic mixture of pesticides on natural biofilms communities

S. Kim Tiam; Stéphane Pesce; A. Feurtet Mazel; Nicolas Mazzella; Soizic Morin; P. Gonzalez

Abstract : The objective of this study was to evaluate the potential use of passive samplers extracts in order to highlight effects of representative pesticide mixtures on natural biofilm communities. Chronic and acute impacts of pesticides in mixture were evaluated using POCIS (Polar Organic Chemical Integrative Sampler) extracts on natural biofilm communities. Biofilms were exposed to POCIS extracts (PE+) or placed in clean water (PE-) in order to maintain or to model a removal of a toxic pressure in relation with a realistic pesticide mixture directly isolated from the field. After 13 days of exposure, a significant decrease of DW, AFDM and diatoms density on downstream biofilms exposed to PE compared to non exposed biofilms was observed; moreover mean chla amount was lower for biofilms exposed to PE compared to non exposed biofilms. Acute toxicity tests at day 13 revealed a significant higher tolerance for PE+ compared to PE- biofilms. Moreover a decrease of tolerance of downstream biofilms from day 0 to day 13 was observed for both treatments; with 51±13 and 43±2% of inhibition at day 13 compared to 25±3% of inhibition at day 0 in the highest concentration (d0). This global decrease of tolerance to PE with time could be explained by differences between channel and field conditions (light intensity, PE composition different from real river exposure due to POCIS selectivity, pesticides concentrations lower in channels than in river,…) Nevertheless, tolerance of downstream biofilms at day 13 still be much more higher than tolerance of biofilms originated from upstream site (significant inhibition of Fv/Fm for d0, d1, d2 and d3 for upstream biofilms). Our results underline impacts of pesticides in mixture on both growth (DW, AFDM and diatoms density) and community tolerance of a natural biofilm. In the one hand, removing the toxic pressure stimulates global biofilm growth but in the other hand it leads to a decrease of biofilms tolerance. A global decrease of tolerance over time for both treatments was observed; nevertheless without reaching the tolerance levels of upstream biofilms. This study highlights the potential use of passive sampler extracts combined with acute toxicity tests in order to evaluate effects of more realistic pesticide mixtures on natural biofilms communities, and then the future and likely applications of such approaches for ecological risk assessment.

Use of passive samplers extracts for toxicity assessment of environmental realistic mixture of pesticides on natural biofilms communities

Utilisation d'extraits d'échantillonneurs passifs pour l'évaluation d'un mélange réaliste de pesticides sur du biofilm naturel

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en fr Use of passive samplers extracts for toxicity assessment of environmental realistic mixture of pesticides on natural biofilms communities Utilisation d'extraits d'échantillonneurs passifs pour l'évaluation d'un mélange réaliste de pesticides sur du biofilm naturel