In Québec, monitoring of pesticides (herbicides, fungicides and insecticides) in rivers and streams is mainly done through spot water sampling. However, heavy rain can wash pesticides into waterways, causing high levels of contamination that may go unnoticed if sampling is done a few days before or after the contaminants enter the environment. Biofilms—layers of microscopic organisms (bacteria, fungi, microalgae and microfauna) found on substrates in aquatic environments—accumulate metals and other contaminants. Could they be used to detect the presence of pesticide in Québec rivers?
This idea is being explored by Isabelle Lavoie, a professor at the Institut national de la recherche scientifique–Centre Eau Terre Environnement, who had previously designed a tool for estimating water quality in rivers and streams using diatoms, a group of microalgae that abound in biofilms. Together with her doctoral student Laura Malbezin, she studied the possibility of using the entire biofilm—not just diatoms—to develop a new tool for monitoring pesticide exposure.
Laboratory experiments showed how certain herbicides affect biofilm communities: reduced photosynthesis, changes in lipid content, etc. The team then took samples over several years from 14 agricultural rivers monitored by the Ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs (MELCCFP) in Montérégie, Centre-du-Québec and the southern Laurentians. The scientists wanted to see if the biofilms retained traces of a dozen of the pesticides most widely used and detected in the environment. They found that some pesticides were detected in the biofilms but not in the water, and vice versa.
This research shows the importance of taking measurements in environments other than the water itself; it also shows that the biofilm approach is useful and complementary to existing measures. These findings are a first step in the design of a future indicator, the development of which is being closely followed by the MELCCFP.
DOI: https://doi.org/10.69777/285440
References
- Lavoie, I., Campeau, S., Zugic-Drakulic, N., Winter, J.G. et Claude Fortin (2014). Using Diatoms to Monitor Stream Biological Integrity in Eastern Canada: An Overview of 10 Years of Index Development and Ongoing Challenges. Science of The Total Environment, vol. 475, p. 187‑200. https://doi.org/10.1016/j.scitotenv.2013.04.092
- Malbezin, L., Morin, S. et Lavoie, I. (2024). Effects of Atrazine and S-Metolachlor on Stream Periphyton Taxonomic and Fatty Acid Compositions. Ecotoxicology, 33(2), p. 190‑204. https://doi.org/10.1007/s10646-024-02738-y
- Malbezin, L., Mazzella, N., Boutry, S., Lavoie, I. et Morin, S. (2025). Interspecific Differences in the Response of Autotrophic Microorganisms to Atrazine and S-Metolachlor Exposure. Ecotoxicology and Environmental Safety, vol. 289. https://doi.org/10.1016/j.ecoenv.2024.117616