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Q.2-02: Impacts of neonicotinoid treated corn to aquatic invertebrates in floodplain wetlands

Presented by Kyle Kuechle - Email: kkuechle@ducks.org

Neonicotinoid insecticides (NI) are commonly used as seed-treatments on major agricultural row crops (e.g., corn). Indeed, neonicotinoid treated agricultural crops are often planted directly in floodplain wetlands managed for wildlife, specifically waterfowl. Numerous studies have documented impacts of neonicotinoids to aquatic invertebrates in laboratory and mesocosm settings; however, there is limited information on how direct application of neonicotinoids to wetlands impacts aquatic invertebrate in field settings. We investigated invertebrate community response to planting of neonicotinoid-treated seed in managed wetland ecosystems in Missouri. In 2016, we sampled water, sediment, and aquatic invertebrates from 22 paired wetlands during spring (pre-wetland drawdown) and fall (post-wetland flood-up) followed by a third sampling period (spring 2017). During summer, portions of study wetlands were planted with either neonicotinoid-treated corn or untreated corn (control). Water and sediment concentrations of the three most common neonicotinoids were used to calculate overall NI toxicity equivalents (NI-EQs). Mean total NI-EQs peaked in autumn and were an order of magnitude greater for sediment (0.60 g/kg) than water (0.02 g/L). Water quality parameters and pesticide concentrations were used to evaluate effects of neonicotinoid concentrations on aquatic macroinvertebrates using a series of generalized linear mixed effects models. Results indicate an overall decrease in aquatic insect abundance and richness with increasing NI-EQs in both wetland water and sediments. Post-treatment treated wetlands had lower insect richness and abundance compared to untreated wetlands, but invertebrate communities recovered in the following spring 2017. Our results have implications for aquatic invertebrates and wetland-dependant species (e.g., migrating waterfowl) as neonicotinoids, although below lethal concentrations for many common wetland insects, are impacting wetland ecosystems. Research results will be useful to wetland managers in making decisions regarding use of neonicotinoid seed-treatments, and potentially, provide broader considerations of the role agriculture may play in future wetland management and conservation plans.
Session: Poster Session 2 (Wednesday, August 28, 19:00 to 21:00)