Clone- and age-dependent toxicity of a glyphosate commercial formulation and its active ingredient in Daphnia magna

Abstract

Low levels of glyphosate based herbicide induced significant negative effects on the aquatic invertebrate Daphnia magna. Glyphosate herbicides such as brands of Roundup, are known to be toxic to daphnids. However, published findings on acute toxicity show significant discrepancies and variation across several orders of magnitude. To test the acute effects of both glyphosate and a commercial formulation of Roundup (hereafter Roundup), we conducted a series of exposure experiments with different clones and age-classes of D. magna. The results demonstrated EC50 (48) values in the low ppm-range for Roundup as well as for the active ingredient (a.i.) isopropylamine salt of glyphosate (glyphosate IPA) alone. Roundup showed slightly lower acute toxicity than glyphosate IPA alone, i.e. EC50 values of 3.7–10.6 mg a.i./l, as compared to 1.4–7.2 mg a.i./l for glyphosate IPA. However, in chronic toxicity tests spanning the whole life-cycle, Roundup was more toxic. D. magna was exposed to sublethal nominal concentrations of 0.05, 0.15, 0.45, 1.35 and 4.05 mg a.i./l for 55 days. Significant reduction of juvenile size was observed even in the lowest test concentrations of 0.05 mg a.i./l, for both glyphosate and Roundup. At 0.45 mg a.i./l, growth, fecundity and abortion rate was affected, but only in animals exposed to Roundup. At 1.35 and 4.05 mg a.i./l of both glyphosate and Roundup, significant negative effects were seen on most tested parameters, including mortality. D. magna was adversely affected by a near 100 % abortion rate of eggs and embryonic stages at 1.35 mg a.i./l of Roundup. The results indicate that aquatic invertebrate ecology can be adversely affected by relevant ambient concentrations of this major herbicide. We conclude that glyphosate and Roundup toxicity to aquatic invertebrates have been underestimated and that current European Commission and US EPA toxicity classification of these chemicals need to be revised.

Re-registration Challenges of Glyphosate in the European Union

“…As in the latter test Roundup systematically resulted in 25-100% higher effects than glyphosate at equivalent concentrations, the enhanced effect was attributed to POEA. Toxicity to the water flea (Daphnia magna) is of special importance, and not only formulated glyphosate-based herbicides (Cuhra et al, 2013;Ørsted and Roslev, 2015), but also glyphosate residues in GT soybean were shown to exert toxicity on this standard ecotoxicity indicator organism. Effects of glyphosate on somatic and ovarian growth, as well as of glyphosatebased formulations on ovarian growth and immune status of freshwater and estuarine crab species were reported (Hong et al, 2017;Avigliano et al, 2018;Canosa et al, 2018).…”

Are Ready for Market Genetically Modified, Conventional and Organic Soybeans Substantially Equivalent as Food and Feed?

“…Cuhra and co-workers tested chronic effects of glyphosate and Roundup and showed that environmental concentrations of 0.05-0.45 mg/l (active ingredient) cause negative effects on D. magna offspring size and reproduction (Cuhra et al 2013). Chemical residues of glyphosate and its primary metabolite, AMPA, are documented to be present in herbicide tolerant GM soy (Duke et al 2003;Bøhn et al 2014).…”

Soil and Environmental Health after Twenty Years of Intensive Use of Glyphosate

“…Effects of glyphosate are briefly summarized as the following: altered respiration in some eukaryotic organisms due to disruption of cytochrome function within the electron transport system; immobilization of nutrients essential for metabolic processes in microorganisms and plants; disruption of microbial diversity in plant rhizospheres; increase in potential root phytopathogens and suppression of beneficial antagonistic bacteria; inhibition of mycorrhizal spore germination leading to poor host plant infection and establishment of the symbiosis; reduced infection of legume roots by rhizobia leading to reduced nodulation required for symbiotic nitrogen fixation; disruption of earthworm activity; and reduction in growth and reproduction of numerous aquatic organisms including Daphnia spp. 10 as well as sediment-inhabiting organisms.…”