Ann. Limnol. - Int. J. Lim.
Volume 55, 2019
|Number of page(s)||9|
|Published online||28 February 2019|
Effects of herbicide mixtures on freshwater microalgae with the potential effect of a safener★
EcoLab, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France
2 Laboratoire de Biologie Moléculaire Eucaryote (LBME), UMR 5099 CNRS/Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex 9, France
* Corresponding author: email@example.com
Accepted: 15 January 2019
Freshwater microalgae are primary producers and cosmopolitan species subjected to the effects of herbicides. In this work, the in vitro algal growth inhibitory effects of 11 agrochemicals (9 herbicides, 1 metabolite, and 1 safener) were quantified. Chemical compounds were applied singly and in specific mixtures. Three species were used in axenic condition: the green alga Desmodesmus subspicatus (Chodat), the diatoms Nitzschia palea (Kützing) W. Smith and Navicula pelliculosa (Kützing) Hilse. When exposed to single compounds, N. palea and N. pelliculosa were only sensitive to atrazine/desethylatrazine and the safener benoxacor (BE), respectively. D. subspicatus was equally sensitive to four herbicides including atrazine and its metabolite and significantly more sensitive to iodosulfuron-methyl-sodium (IODO). The mixture of these five compounds induced a significantly higher growth inhibition of about 1.5-fold than IODO alone, which could be attributed to the four other herbicides. The mixture of all compounds was twofold less toxic than IODO on D. subspicatus. A halogen atom is present in IODO as in the herbicides to which the safener BE − known to induce glutathione-S-transferases − is associated in agrochemical preparations. We then showed that IODO was less toxic when combined with non-toxic concentrations of BE. These results indicated that the toxicity of the most active herbicide studied was decreased by a non-herbicide compound present in agrochemical formulations of other herbicides. These results suggest the importance to take into account the chemistry and the mechanisms of action for each compound in a risk assessment approach of a complex mixture.
Key words: agrochemical mixtures / benoxacor / diatom / green alga / growth inhibition assay / microbial ecotoxicology
© EDP Sciences, 2019
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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