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The effects of the aquatic herbicide diquat on non-target aquatic biota – a mesocosm study


Native aquatic plant communities are essential components of healthy aquatic ecosystems and provide key habitat, refuge and food for aquatic species including fish. In contrast, invasive aquatic plant species are a significant threat to the health of aquatic ecosystems and can severely impair waterways. The effects of invasive plant species are compounded by nutrient enrichment, which can result in nuisance levels of native and invasive aquatic plants, as well as algae. As Canadian aquatic ecosystems face the combined stressors of invasive aquatic plants and nutrient enrichment, there is likely to be an increased demand for chemical control options to manage aquatic invasive plants. It is therefore important to better understand the effects of chronic, ecologically relevant concentrations of current-use aquatic herbicides on non-target organisms.

The objective of this research is to examine the impacts that the direct application of pesticides to control aquatic invasive plants has on non-target organisms. The research will focus on the active ingredient diquat, a currently registered pesticide in Canada used to control submerged plant species. This herbicide will be used according to label directions to represent an ecologically realistic application of the pesticide. A mesocosm (i.e. artificial pond) experimental approach will be used to examine the effects of diquat on aquatic organisms, including native and invasive plants, invertebrates and vertebrates that are representative of, and important to, Canadian aquatic ecosystems and which represent essential fish habitat and food sources.

This research will inform Fisheries and Oceans Canada of the potential management options for controlling aquatic invasive species and will assess potential risks that diquat poses to aquatic organisms that are important to fish species.

Program Name

National Contaminants Advisory Group (NCAG)


2015 - 2017



Principal Investigator(s)

Frances Pick
Professor, Department of Biology, University of Ottawa (Ontario)

Team Member(s)

Rebecca Dalton, Department of Biology, Carleton University (Ontario)

Stacey Robinson, Research Scientist, Céline Boutin, Research Scientist, National Wildlife Research Centre, Environment Canada

Adrienne Bartlett, Research Scientist, Canada Centre for Inland Waters, Environment Canada

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