Midwest Fish & Wildlife Conference 2018

AUTHORS. Kyle Kuechle, Missouri Cooperative Fish and Wildlife Research Unit, School of Natural Resources, University of Missouri; Elisabeth B. Webb, U.S. Geological Survey, Missouri Cooperative Fish and Wildlife Research Unit; Doreen Mengel, Missouri Department of Conservation, Resource Science Division; Anson Main, Missouri Cooperative Fish and Wildlife Research Unit, School of Natural Resources, University of Missouri

ABSTRACT. Neonicotinoids are the fastest-growing class of insecticides in the world, with seed-treatments widely applied across agricultural regions of North America. Neonicotinoid physico-chemical properties (e.g., high water solubility, low soil adsorption) enhance their potential environmental mobility and have resulted in detectable concentrations in North American surface waters. Neonicotinoids are under increasing scrutiny due to their documented direct and indirect effects on a range of non-target organisms such as aquatic invertebrates. Thus, in 2016, we sampled water, sediment and aquatic invertebrates from public wetlands under different management practices across Missouri during three sampling periods; pre-planting, immediately post-planting and post-autumn inundation. Sediment samples consistently contained neonicotinoid active ingredients (e.g., clothianidin, imidacloprid) across all sampling periods. Clothianidin detection frequency and concentrations ranged from 31% (post-planting, mean: 0.39 µg/kg; max: 7.85) to 55% (pre-planting, mean: 0.44 µg/Kg; max: 9.37). By comparison, imidacloprid detection frequency and concentrations ranged from 32% (autumn, mean: 0.74 µg/kg; max: 6.71 µg/kg) to 44% (post-planting, mean: 0.85 µg/Kg; max: 9.77). Neonicotinoid concentrations across all sampling periods were an order of magnitude higher in the sediment than associated water, indicating cross-seasonal persistence in wetland sediments. To evaluate neonicotinoid impacts on invertebrate diversity, morphology, and production; we used a series of linear mixed effects models which included water quality parameters, wetland depth, and pesticide concentrations. Preliminary results indicate an overall decrease in diversity as well as reduced abundance and size of benthic macroinvertebrates with increasing neonicotinoid concentrations in water and sediment. Finally, in 2017, we quantified emergent insect biomass and tree swallow nesting efforts across 14 wetlands to evaluate potential impacts of neonicotinoid concentrations to aquatic ecological subsidies and higher trophic levels. The outcomes of this full study will be useful in understanding landscape and seasonal drivers of neonicotinoid concentrations in wetlands and subsequent impacts to wetland food webs.