A new study published by a group of Brazilian researchers in the journal Phycologia shows that Monsanto’s most popular herbicide Roundup negatively affects life in freshwater ecosystems. More specifically, legal levels of Roundup, as well as those of its main ingredient glyphosphate, can alter and kill macroalgae (i.e. freshwater seaweed) by inhibiting photosynthesis.
The legal limits referenced in the study are those of Brazil, which are 0.28 mg l−1. Compare that to the US legal limit of 0.7 mg l−1. Macroalgae are extremely important in freshwater ecosystems as they function as primary producers, meaning they help form the bottom of the food chain on which other organisms depend. They also recycle nutrients and increase plankton populations, which are a main food source for many fish and other marine animals. Die-offs of macroalgae, regardless of the cause, reduce diversity and the populations of other animals in the ecosystem, which can put the entire ecosystem at risk of collapse if the die-off is sufficiently severe. The species of macroalgae used in the study, Nitella microcarpa, is found throughout the world, meaning that the implications of this study are global.
Even though this study focuses on the chemical’s legal limits, glyphosate, the main ingredient in Roundup herbicide, is frequently found in the natural environment well above the legally allowed levels, meaning that the damage to the environment is much greater than this study implies. In another study published in Analytical and Bioanalytical Chemistry, 41% of 140 groundwater samples in Spain were found to have levels of glyphosate above the legal limit. The study also showed that glyphosate does not break down rapidly in the environment, meaning it persists in ecosystems for long periods of time, causing an accumulation effect. Another study published in Environmental Toxicology and Chemistry found glyphosate in 60-100% of all air and rain samples tested due to its overuse.
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