Lone Rykær Hansen, Peter Roslev, “Behavioral responses of juvenile Daphnia magna after exposure to glyphosate and glyphosate-copper complexes,” Aquatic Toxicology, 2016, 179: 36-43, DOI: 10.1016/j.aquatox.2016.08.010.

ABSTRACT:

Glyphosate (N-(phosphonomethyl)glycine) is the active ingredient in a range of popular broad-spectrum herbicide formulations. Glyphosate is a chelating agent that can form stable complexes with divalent metal ions including Cu(II). Little is known about the bioavailability and ecotoxicity of glyphosateCu(II) complexes to aquatic organisms. In this study, we used video tracking and behavior analysis to investigate sublethal effects of binary mixtures of glyphosate and Cu(II) to juvenile D. magna. Behavioral responses were quantified for individual D. magna after 24 h and 48 h exposure to glyphosate and glyhosate-Cu(II) mixtures. Sublethal concentrations resulted in decreases in swimming velocity, acceleration speed, and distance moved whereas inactive time of D. magna increased. Distance moved and inactive time were the most responsive parameters to glyphosate and glyphosate-Cu(II) exposure. On a molar basis, glyphosate-Cu(II) complexes appeared more toxic to D. magna than glyphosate alone. The 48 h EC50 for glyphosate and glyphosate-Cu(II) determined from swimming distance were 75.2 M and 8.4 M, respectively. In comparison, traditional visual observation of mobility resulted in 48 h EC50 values of 52.8 M and 25.5 M for glyphosate and glyphosate-Cu(II), respectively. The behavioral responses indicated that exposure of D. magna to mixtures of glyphosate and Cu(II) attenuated acute metal toxicity but increased apparent glyphosate toxicity due to complexation with Cu(II). The study suggests that glyphosate is a likely mediator of aquatic metal toxicity, and that video tracking provides an opportunity for quantitative studies of sublethal effects of pesticide complexes. FULL TEXT

María Sol Balbuena, Léa Tison, Marie-Luise Hahn, Uwe Greggers, Randolf Menzel, and Walter M. Farina, “Effects of sub-lethal doses of glyphosate on honeybee navigation,” Journal of Experimental Biology, 2015, 218: 2799-2805; doi: 10.1242/jeb.117291.

ABSTRACT:

Glyphosate (GLY) is a herbicide that is widely used in agriculture for weed control. Although reports about the impact of GLY in snails, crustaceans and amphibians exist, few studies have investigated its sublethal effects in non-target organisms such as the honeybee Apis mellifera, the main pollen vector in commercial crops. Here, we tested whether exposure to three sublethal concentrations of GLY (2.5, 5 and 10 mg l⁻¹: corresponding to 0.125, 0.250 and 0.500 μg per animal) affects the homeward flight path of honeybees in an open field. We performed an experiment in which forager honeybees were trained to an artificial feeder, and then captured, fed with sugar solution containing traces of GLY and released from a novel site either once or twice. Their homeward trajectories were tracked using harmonic radar technology. We found that honeybees that had been fed with solution containing 10 mg l⁻¹ GLY spent more time performing homeward flights than control bees or bees treated with lower concentrations. They also performed more indirect homing flights. Moreover, the proportion of direct homeward flights performed after a second release from the same site increased in control bees but not in treated bees. These results suggest that, in honeybees, exposure to levels of GLY commonly found in agricultural settings impairs the cognitive capacities needed to retrieve and integrate spatial information for a successful return to the hive. Therefore, honeybee navigation is affected by ingesting traces of the most widely used herbicide worldwide, with potential long-term negative consequences for colony foraging success.  FULL TEXT

Mailin Gaupp-Berghausen, Martin Hofer, Boris Rewald, and Johann G. Zaller, “Glyphosate-based herbicides reduce the activity and reproduction of earthworms and lead to increased soil nutrient concentrations,” Nature: Scientific Reports, 2015, 5: 12886, DOI: 10.1038/srep12886.

ABSTRACT:

Herbicide use is increasing worldwide both in agriculture and private gardens. However, our earthworms, is still very scarce. In a greenhouse experiment, we assessed the impact of the most strategies. We demonstrate, that the surface casting activity of vertically burrowing earthworms (Lumbricus terrestris) almost ceased three weeks after herbicide application, while the activity of soil dwelling earthworms (Aporrectodea caliginosa) was reduced by 56% within three months after herbicide application. Herbicide application led to increased soil concentrations of nitrate by 1592% and phosphate by 127%, pointing to potential risks for nutrient leaching into streams, lakes, or groundwater aquifers. These sizeable herbicide-induced impacts on agroecosystems are particularly worrisome because these herbicides have been globally used for decades.  FULL TEXT