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.
Highlights
The tonnage of glyphosate herbicide application has been constantly increasing since the introduction of this group of chemicals in 1971 (Dill et al 2010)
In the present experiments with D. magna we demonstrate that i) glyphosate and Roundup induce EC50 at concentrations typically below 10 mg/l in 48 h acute experiments, and ii) chronic exposure, to formulated Roundup, causes serious reproduction damage at levels close to (1.35 mg/l) or even below (0.45 mg/l) accepted threshold values for glyphosate in surface waters in the United States in general (0.7 mg/l) and in the state of California (1.0 mg/l)(California EPA 1997)
According to our experimental work and our literature reviews, we find that the previously published EC50 values of 780-930 mg/l for glyphosate (McAllister and Forbis 1978; Forbis and Boudreau 1981) are not representative
Summary
The tonnage of glyphosate herbicide application has been constantly increasing since the introduction of this group of chemicals in 1971 (Dill et al 2010). Glyphosate has been heralded as an ideal herbicide due to its target specificity and acclaimed low toxicity to non-target organisms (Cerdeira and Duke 2006; Duke and Powles 2008; Giesy et al 2000). Field studies on effects of prescription dosage application of aquatic glyphosate herbicide on non-target organisms in fresh-water systems have been carried out. Most of these have neither demonstrated shortterm nor long term adverse effects (Gardner and Grue 1996, Siemering et al 2008), Puertolas et al (2010) observed significant toxic effects on the aquatic invertebrate Daphnia magna from established methods for glyphosate control of giant reed in a Spanish River system
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
