Abstracts

Presented by Elisabeth B. Webb - Email: webbli@missouri.edu

Widespread use of neonicotinoid insecticides in North America has led to frequent detection of neonicotinoids in surface waters. Despite frequent surface water detections, little is known about neonicotinoid concentrations in floodplain wetlands. Thus, we sampled water and sediments for neonicotinoids during a one year period at 40 intensively managed floodplain wetlands throughout Missouri. Water and sediment samples analyzed for six common neonicotinoids consistently (63% of samples) contained neonicotinoids (e.g. imidacloprid, clothianidin) in all sampling periods and mean sediment and aqueous neonicotinoid concentrations were 1.19 g kg-1 (range: 0 to 17.99 g kg-1) and 0.03 g L-1 (0 to 0.97 g L-1), respectively. We used Boosted Regression Tree analysis to explain sediment neonicotinoid concentrations and ultimately identified six variables that accounted for 31.6% of concentration variability with water temperature (31.8%), % wetland planted to agriculture (23.5%), and water depth (18.3%) having the greatest variable importance scores. Therefore, efforts to mitigate sediment neonicotinoid contamination could include reducing agriculture within a wetland (<25% planted) to limit contamination. Also, prolonging periods of overlying water >25cm deep when water temperatures reach/exceed 18C could promote conditions favorable for neonicotinoid degradation. Results of this study can be useful in determining potential routes and levels of neonicotinoid exposure experienced by non-target benthic aquatic invertebrates which represent an important food resource for migrating waterfowl. Additionally, BRT results identify key mitigating factors to limit neonicotinoid contamination of wetland sediments through the reduction of seed treated agriculture within and surrounding the wetland. Further water management practices can facilitate the degradation of neonicotinoids once in sediments, as we detected concentrations in wetlands with no record of seed treatment use.