Studies Show How Pesticides Harm Organisms that Form the Foundation of Freshwater Ecosystems

September 15, 2021 | Toxic pesticide use, and glyphosate in particular, degrades the health of freshwater ecosystems by harming species that form the basis of aquatic food chains, according to research published by scientists at McGill University. In a series of studies, scientists investigated how freshwater bacteria and zooplankton are affected by varying levels of the weed killer glyphosate, the neonicotinoid insecticide imidacloprid, and nutrient levels. “Because plankton form the foundation of the food chain in freshwater ecosystems, it is very important to understand how plankton communities respond to widely used pesticides,” said Jesse Shapiro, PhD, an associate professor in McGill’s Department of Microbiology and Immunology. “Our research shows that the structure of these communities can be impaired under currently acceptable North American water quality guidelines.” Zooplankton were found to be much more sensitive to pesticide exposure than freshwater bacteria. However, glyphosate was found to be the most damaging exposure within both experiments. In the zooplankton study, low levels (.3 parts per million) of glyphosate resulted in persistent declines in rotifer populations, while both pesticides harm populations of copepod crustaceans (at 3 parts per billion with imidacloprid and 5.5 parts per million with glyphosate). At higher, yet still environmental relevant rates, scientists observe synergy between the two pesticides that result in significant declines in overall zooplankton biomass. [Barbosa da Costa, Naíla et al. Resistance, resilience, and functional redundancy of freshwater bacterioplankton facing agricultural stress. Molecular Ecology. July 2021; Hébert, Marie-Pier et al. Widespread agrochemicals differentially affect zooplankton biomass and community structure. Ecological Applications. July 2021.]