Modeling the effects of thiamethoxam on Midwestern farm ponds and emergent wetlands

Potential toxic effects of thiamethoxam on nontarget organisms and the community structure of a generic Midwestern farm pond and emergent wetland were assessed using 2 versions of the comprehensive aquatic system model: CASM_GFP , a generic farm pond model, and CASM_GWL , a generic wetland model. The CASM_GFP and CASM_GWL are integrated bioenergetics-based and habitat quality models that describe the daily biomass values of selected producer and consumer populations representative of generalized Midwestern farm ponds and emergent wetlands. The CASM_GFP demonstrated the ability to reproduce values of population biomass reported for Midwestern (and other) pond ecosystems; the CASM_GWL provided a similar modeling capability for Midwestern emergent wetlands. Lethal and sublethal effects of thiamethoxam were modeled as extrapolations of laboratory toxicity assays using the CASM_GFP and the CASM_GWL . Time series of daily environmental concentrations of thiamethoxam constructed for 6 regional pesticide applications across the United States failed to produce any calculated impacts on modeled population biomass or changes in community structure of modeled trophic guilds in the CASM_GFP or the CASM_GWL . However, evaluation of systematically increased daily concentrations demonstrated the ability of both models to simulate direct and indirect toxic effects of this pesticide. The present model study suggests that process-based food web/ecosystem models can be used to characterize the potential ecological effects of thiamethoxam on generalized farm pond and emergent wetland ecosystems. Environ Toxicol Chem 2018;37:738-754. © 2017 SETAC.