Effects of atrazine and nicosulfuron on periphytic diatom communities in freshwater outdoor lentic mesocosms

Abstract

One of the agro-environmental characteristics of Brittany is the extensive use of pesticides, which leads to high concentrations of atrazine in continental water systems. Periphytic algae play a basic part in aquatic ecosystems and some of them, diatoms, are highly sensitive to environmental changes. Analyses of diatoms can thus indicate the impact of a herbicide on aquatic systems. We compared the effects of two herbicides (atrazine and nicosulfuron) on an aquatic ecosystem in 1998. This study was conducted in 15 identical ponds, each containing a holder for installing artificial substrates. The periphytic diatoms were analysed for cell density, biomass, species diversity and morphology. The general specific diversity was poor, and the diatom community was essentially dominated by Achnanthidium minutissimum. The first results showed a strong similarity between the different categories of mesocosms. Chlorophyll a concentration only seems to be affected by high herbicide concentrations. Effets de deux herbicides (atrazine et nicosulfuron) sur les diatomées du periphyton : approche expérimentale en méso-cosmes aquatiques lentiquesMots-clés : Ecotoxicologie, herbicides, mésocosmes aquatiques, periphyton.Le contexte agro-environnemental de Bretagne est caractérisé par l'utilisation importante de pesticides et par des concentrations parfois élevées en atrazine dans les écosystèmes aquatiques. Les algues du periphyton jouent un rôle fondamental sur le plan fonctionnel de ces écosystèmes et certaines, les diatomées, ont la particularité de présenter une forte sensibilité aux changements environnementaux. L'analyse de ce compartiment diatomique est justifiée dans le cadre d'une étude d'impacts d'herbicides en milieu aquatique. Une expérimentation visant à comparer les effets de deux herbicides (atrazine et nicosulfuron), sur un écosystème aquatique a été effectuée en 1998. Cette étude a été réalisée dans 15 mésocosmes-réplicats. Chaque mésocosme comporte un dispositif permettant la mise en place de substrats artificiels destinés à l'échantillonnage périodique du periphyton. Les diatomées du periphyton ont été analysées selon quatre critères : densité cellulaire, diversité, biomasse et morphologie. D'une manière générale on a observé une faible diversité spécifique et un peuplement largement dominé par Achnanthidium minutissimum. Les premiers résultats ont montré une forte similitude entre les différentes catégories de mésocosmes. Seule la teneur en chlorophylle a semble être affectée par les fortes teneurs en herbicides.

Glyphosate-Based Herbicide Toxicophenomics in Marine Diatoms: Impacts on Primary Production and Physiological Fitness

“…However, exposure to the highest concentration led to an increase in all pigments, particularly in chlorophyll content, in opposition to what has been described for higher plants [72] and is likely a compensatory mechanism by which the diatoms counteract the lower efficiency of the affected reaction centers. In other works [73][74][75][76][77], an increase in chlorophyll a concentration was observed in algae communities exposed to low concentrations of atrazine (10 to 32 µg L −1 ) but not at higher concentrations. Thus, this rise in chlorophyll content associated with the increase in fucoxanthin content may provide cells with the ability to counteract the decrease in the number of RC/CS, and therefore an increase in the efficiency of each RC available to trap photons occurs.…”

Application of diatom biotic indices in the Guadalquivir River Basin, a Mediterranean basin. Which one is the most appropriated?

“…Nevertheless, since rivers there are highly regulated through human intervention, the artificial floods coming from the reservoirs in such instances should also be taken into account. (b) A. minutissimum has been identified in the literature as being both pesticide and metal tolerant (Sabater 2000;Seguin et al 2001).…”

Flow cytometric analysis to evaluate physiological alterations in herbicide-exposed Chlamydomonas moewusii cells

“…Such physicochemical properties also render them susceptible to off-site transfer into the aquatic environment, so that high herbicide concentrations could reach aquatic systems and become toxic for phototrophic microorganisms, such as microalgae, even without being the original target species for which the herbicide was designed (Deneer 2000;Warren et al 2003). Therefore, pollution with herbicides must be considered as a potential risk for aquatic ecosystems, altering phototrophic species assemblages (Kish 2006;Seguin et al 2001), as well as for the quality of drinking water (Katsumata et al 2006), since some herbicides in use are known to be mutagenic, carcinogenic or teratogenic (Nguyen-Ngoc et al 2009). …”