Environmental Risk Assessment of pesticides is generally based on the comparison of environmental exposure concentrations (EECs) with regulatory concentrations that are considered to be protective of aquatic organisms. However, it is uncertain whether laboratory derived EECs thresholds for single indicator organisms are sufficiently protective for the receiving aquatic systems where complex food webs are present. Vegetative filter strips (VFS) have been proposed for the protection of threatened and endangered biological organisms from pesticide in runoff (National Marine Fisheries Service Biological Opinion-BiOp issued November 18, 2008), but there is debate regarding their efficiency and filter size requirements. VFS modeling with VFSMOD has also been proposed as a mitigation practice in high-tier pesticide risk assessment modeling frameworks. Recent improvements in mechanistic aquatic effects models like AQUATOX allow modeling the potential ecological effects of chemical pollutants on different food-web compartments of the aquatic ecosystem. In this research, we link EPA’s long-term pesticide risk assessment modeling framework with AQUATOX to evaluate the efficacy of VFS as mitigation measurement to reduce long-term pesticide risk to salmonids. EPA’s agro-ecological scenario for Oregon-wheat with variable VFS lengths (0 to 9 m) was selected at the margin of a representative river segment to simulate daily 30-yr runoff, sediment and pesticide loads at the river edge. The field loads were used as daily inputs to AQUATOX parameterized as a river segment matching ecological characteristics of a representative salmonid river in Oregon based on a previous case study. With this strategy, we estimate dynamic effects of pesticide loads on the ecosystem and salmonid biomass and the potential mitigating effects of VFSs. Preliminary results indicate that VFS could be a useful measure to prevent pesticide-derived long-term deleterious effects on salmonid communities. Relevant metrics describing dynamic ecological effects and ecological effects thresholds are explored.

Evaluating VFS efficacy to mitigate pesticide risk to aquatic threatened species using coupled exposure-effect models: The case of salmonids

254th National Meeting (2017)

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