Distribution and impact of neonicotinoid insecticides on wetland ecosystems of Prairie Canada

We are studying the environmental impact of agricultural practices and insecticide use in the Canadian Prairies. Neonicotinoids - are an economically important group of chemicals - but with chemical properties that potentially threaten Canada's freshwater resources through reduced aquatic insect production with consequences for birds and wildlife that are dependent on insects for food.

Shifts in agriculture toward large-scale production, mechanization and mono-cropping have seen exponential growth in chemical inputs designed for improved crop yields. Current agricultural practices are highly dependent on a newer class of insecticides - neonicotinoids. Valued for their versatility in application, most are used as seed treatments on major Prairie crops such as canola (oilseed rape). In Canada's Prairie Pothole Region (PPR), this is problematic as prime agricultural land is directly adjacent to ecologically valuable freshwater wetlands.

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We currently have a comprehensive set projects investigating potential impacts of neonicotinoids on Prairie wetland ecosystems:

1) Wetland and landscape features influencing fate and transport of neonicotinoids in Prairie Pothole wetlands

PhD student: Anson Main (completed)

Prairie wetlands are known to be susceptible to pesticidee transport - they typically occupy topographic depressions that naturally accumulate pesticides from seeding, spray-drift and surface run-off. Persistence and transport of neonicotinoids is also likely dependent on soil characteristic, plant cover and wetland size and permanency. Specific fate and transport of this insecticide is poorly understood and knowledge gaps presently exist around why certain wetlands are more susceptible to contamination. We have been undertaking a multi-year, large-scale wetland water quality survey of neonicotinoid contamination alongside wetland assessment methods. Our goal is to identify the wetland and landscape features that can be used to predict the distribution, persistence and transport of neonicotinoids in agricultural landscapes.

2) Role of neonicotinoid insecticides in affecting aquatic macroinvertebrate communities

PhD student Michael Cavallaro

Aquatic macroinvertebrates are widely accepted as sensitive biological indicators of water quality and environmental conditions. We are using combinations of lab and field studies to assess seasonal changes in macroinvertebrate abundance and community structure in response to neonicotinoid exposure. Responses in survival and emergence of individual macroinvertebrate species and communities appear to reflect the neonicotinoid compound (imidacloprid, clothianidin, thiamethoxam) and exposure duration. In situ wetland surveys and limnocorral experiments are adding environmental realism to our toxicity studies which are being backed up with controlled chronic lab studies using Chironomus dilutus. The primary goal of the project is to determine the role of neonicotinoid insecticides in affecting aquatic macroinvertebrate communities in Prairie wetlands which has implications for many birds and other wildlife that are dependent on this abundant food resource.

3) Evaluating the cumulative toxicity and mechanisms of action of neonicotinoid mixtures to aquatic invertebrates.

PhD student Erin Maloney

Our early water monitoring studies here in the Canadian prairies and those in other regions around the world have frequently detected mixtures of neonicotinoid insecticides in aquatic environments (Main et al. 2014 PlosOne; Morrissey et al. 2015 Env International). This is of concern, as current Canadian water quality guidelines only account for the toxic effects of individual neonicotinoids, and chemical mixtures often display a joint toxicity that can’t be predicted from studies with isolated compounds. Aquatic invertebrates native to the prairie region (such as Chironomus dilutus) are particularly susceptible to neonicotinoid toxicity, due to their physiological similarities to target pests. However, the toxic action of neonicotinoid mixtures has not been extensively studied for these organisms. Therefore, this project will focus on evaluating the actions of mixtures of neonicotinoids shown to be prevalent in the Canadian aquatic environment (clothianidin, thiamethoxam, and imidacloprid) by examining the toxicological effects of binary and tertiary mixtures under short and long term exposure conditions to Chironomus dilutus. We will use this information to fit robust statistical models to characterize the true toxicity risk of multiple neonicotinoid mixtures.