THE IMPACT OF ROUNDUP® ON DAPHNIA MAGNA

Glyphosate is the most commonly used herbicide in the world. Recent studies suggest that glyphosate-based herbicides (GBHs) have a higher toxicity towards animals than previously assumed by industry-funded studies. The EPA also lists glyphosate as being “practically nontoxic to fish, aquatic invertebrates....” Daphnia magna is an aquatic invertebrate and a well-established model organism for toxicological studies. GBHs list glyphosate as the active ingredient. They also contain “inert ingredients”, which include surfactants to improve adherence to plants. Retail forms of the herbicide were tested in order to assess the toxicity of the commercial product as used by consumers. Experiments were conducted to test the effects of “Roundup Ready-to-Use Weed and Grass Killer” (RU) on the heart rate and survival of adult D. magna. This product is intended for residential use without dilution. Three experiments monitoring the heart rates of adult D. magna were performed using 11 different concentrations of the “ready-to-use” product, ranging from 0.1% to 100%, with a 0% control. Heart rates were digitally recorded in slow motion for 10 seconds under a stereo microscope. The 7% to 100% concentrations reduced heart rates by about 50% after approximately 1 to 5 minutes of exposure before killing them in less than 10 minutes. The 3% and 5% concentrations killed the D. magna in less than 30 minutes. The 0.1%, 0.5%, and 1% concentrations remained within the normal heart rate range set by the control. To observe the effects of RU in a more natural environment, we performed two experiments using D. magna in 25mm x 150mm test tubes filled with spring water. Concentrations ranging from 0.1% to 10% with a 0% control were used. Death rates were monitored for up to 6 hours. The 0.1% and 0.5% concentrations did not cause death. The 2% concentration died after 106 minutes, the 3% concentration died after 36 minutes, the 4% concentration died after 24 minutes, the 5% concentration died after 10 minutes, and the 10% concentration died after 6 minutes. These data suggest that at very low concentrations of what is recommended for use, the GBH RU is toxic to D. magna. This contradicts the EPA’s recommendations for the safe use of GBHs. This also implies that surfactants may play a role in the toxicity of GBHs.