New evidences of Roundup® (glyphosate formulation) impact on the periphyton community and the water quality of freshwater ecosystems

Abstract

Argentina is the second largest world producer of soybeans (after the USA) and along with the increase in planted surface and production in the country, glyphosate consumption has grown in the same way. We investigated the effects of Roundup (glyphosate formulation) on the periphyton colonization. The experiment was carried out over 42 days in ten outdoor mesocosms of different typology: "clear" waters with aquatic macrophytes and/or metaphyton and "turbid" waters with great occurrence of phytoplankton or suspended inorganic matter. The herbicide was added at 8 mg L(-1) of the active ingredient (glyphosate) in five mesocosms while five were left as controls (without Roundup addition). The estimate of the dissipation rate (k) of glyphosate showed a half-life value of 4.2 days. Total phosphorus significantly increased in treated mesocosms due to Roundup degradation what favored eutrophication process. Roundup produced a clear delay in periphytic colonization in treated mesocosms and values of the periphytic mass variables (dry weight, ash-free dry weight and chlorophyll a) were always higher in control mesocosms. Despite the mortality of algae, mainly diatoms, cyanobacteria was favored in treated mesocosms. It was observed that glyphosate produced a long term shift in the typology of mesocosms, "clear" turning to "turbid", which is consistent with the regional trend in shallow lakes in the Pampa plain of Argentina. Based on our findings it is clear that agricultural practices that involve the use of herbicides such as Roundup affect non-target organisms and the water quality, modifying the structure and functionality of freshwater ecosystems.

Re-registration Challenges of Glyphosate in the European Union

“…A recent concern is that glyphosate (along with other herbicide active ingredients dicamba and 2,4-D), as well as common surfactants (Tween80, carboxymethyl cellulose) at or below recommended application concentrations can change the susceptibility of bacteria to a diverse range of antibiotics (ampicillin, chloramphenicol, ciprofloxacin, kanamycin, tetracycline) upon concurrent exposure, and thus, glyphosate may serve as one of the drivers for antibiotic resistance (Kurenbach et al, 2017;Van Bruggen et al, 2018). As indicated, through water pollution its formulations can disturb aquatic ecosystems (Vera et al, 2010;Perez et al, 2011) including fish (Jofré et al, 2013). Removal or degradation of glyphosate residues from raw drinking water by bank filtration may not be efficient, but oxidants used in water treatment (e.g., Cl 2 or O 3 ) were shown to be effective in degrading their concentration below the EU drinking water threshold level of 0.1 µg/l (Jönsson et al, 2013).…”

Herbicide Contamination of Freshwater Ecosystems: Impact on Microbial Communities

“…These methods can also be used to identify the temporary, progressive or persistent effects of contaminants on communities (Rand et al, 2000;Belanger et al, 2002), by measuring their resilience, and also to distinguish between the direct and indirect ecological effects of disturbances caused by contaminants (Belanger et al, 2000;Culp et al, 2000;Hense et al, 2003). Just to provide recent examples of the variety of systems used, 3L liter Pyrex Erlenmeyer flasks have been used to study the response of microbial communities following exposure to glyphosate (Pesce et al, 2009a), indoor experimental channels have been used to study the combined effect of physical factors and exposure to diuron on benthic microbial communities (Villeneuve, 2008), and artificial outdoor mesocosms (surface area 25 m 2 ) have been used by Vera et al (2010) to evaluate the impact of Roundup on periphyton communities.…”

“…For example, Dorigo et al (2007) found that there were changes in the composition of microbial communities in a small river displaying an upstream-downstream pollution gradient, and that species located in the polluted downstream area were more tolerant towards herbicides than those located in the upstreamunpolluted area. Recently, Vera et al (2010) have shown that diatoms were more susceptible than cyanobacteria to glyphosate in periphyton communities, and consequently that over the long term a shift occurred in the composition of these communities. In the same way, Lürling & Roessink (2006) showed, by an experimental approach, that Scenedesmus (green algae) out competed Microcystis (Cyanobacteria) in the absence of metribuzin, a photosynthesis-inhibiting herbicide, whereas the reverse was true in the presence of this herbicide.…”

“…However, Austin et al (1991) suggested that the degradation of glyphosate could increase the concentration of soluble phosphorus, and consequently increase the biomasses of the communities. Subsequently, Vera et al (2010) showed that the periphytic colonization of substrata was delayed in Roundup-contaminated large mesocosms, and that this phenomenon could be attributed to a direct effect of the contaminant. In addition they showed that in periphyton communities Roundup produced a long-term shift in the typology and functioning of contaminated mesocosms, which was consistent with data available from natural lakes in the Argentine Pampas.…”

Effects of Herbicide Glyphosate and Glyphosate-Based Formulations on Aquatic Ecosystems

“…Comparable results were obtained by Pesce et al (2009), reporting changes in riverine algal communities exposed to about 10 μg/L of glyphosate alone, in a microcosms experiment. In addition, mesocosms studies showed remarkable results with a single pulse application of Roundup ® at concentrations of 6 and 8 mg a.i./L (Pérez et al, 2007;Vera et al, 2010). Even if these two contributions assessed herbicide effects in worst case scenarios, glyphosate concentration at the end of the experiments (11 and 14 days respectively), were around 2 mg a.i./L and effects were still clearly observed.…”