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Herbicide effects on freshwater benthic diatoms: Induction of nucleus alterations and silica cell wall abnormalities

Debenest, Timothée and Silvestre, Jérôme and Coste, Michel and Delmas, François and Pinelli, Eric Herbicide effects on freshwater benthic diatoms: Induction of nucleus alterations and silica cell wall abnormalities. (2008) Aquatic Toxicology, vol. 8 (n°1). pp.88-94.

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Official URL: http://dx.doi.org/10.1016/j.aquatox.2008.03.011

Abstract

Benthic diatoms are well known bio-indicators of river pollution by nutrients (nitrogen and phosphorus). Biological indexes, based on diatom sensitivity for non-toxic pollution, have been developed to assess the water quality.Nevertheless, they are not reliable tools to detect pollution by pesticides. Many authors have suggested that toxic agents, like pesticides, induce abnormalities of the diatom cell wall (frustule). High abnormal frustule abundances have been reported in natural diatom communities sampled in streams contaminated by pesticides. However, no direct link was found between the abundances of abnormal frustules in these communities and the pesticide concentrations in stream water. In the present study, a freshwater benthic diatomcommunity, isolated fromnatural biofilm and cultured under controlled conditions, was treated with a known genotoxic herbicide, maleic hydrazide (MH). Cells were exposed to three concentrations of MH (5×10−6, 10−6, 10−7 M) for 6 h followed by a 24 h-recovery time. After MH treatments, nucleus alterations were observed: abnormal nucleus location, micronucleus, multinuclear cell or disruption of the nuclear membrane. A dose-dependent increase of nuclear alterations was observed. The difference between the control (9.65 nuclear alterations per 1000 cells observed (9.65‰), S.D. = 4.23) and the highest concentrations (29.40‰, S.D. = 8.49 for 10−6Mand 35.96‰, S.D. = 3.71 for 5×10−6 M)was statistically significant (Tukey test, P < 0.05). Diatoms also exhibited frustules with deformed morphology and abnormal ornamentation. Significantly increased abundances of abnormal frustules were observed for the highest concentrations (10−6 and 5×10−6 M; Tukey test, P < 0.05). These two parameters tended to increase together (Pearson correlation = 0.702, P < 0.05). The results suggest that the induction of abnormal frustules could be associated with the genotoxic effects of MH. The alterations observed could be related to the effects of MH on the synthesis of the proteins involved in frustule formation or in the regulation of the cytoskeleton of the diatom cells.

Item Type:Article
Additional Information:Thanks to Elsevier editor. The definitive version is available at http://www.sciencedirect.com. The original PDF of the article can be found at Aquatic Toxicology website : http://www.elsevier.com/wps/find/journaldescription.cws_home/505509/description#description
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution: Université de Toulouse > Institut National Polytechnique de Toulouse - INPT
French research institutions > Institut national de recherche en sciences et technologies pour l’environnement et l’agriculture - CEMAGREF
Université de Toulouse > Université Paul Sabatier-Toulouse III - UPS
French research institutions > Centre National de la Recherche Scientifique - CNRS
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Deposited By: Florence Amor

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