A Hybrid Individual‐Based and Food Web–Ecosystem Modeling Approach for Assessing Ecological Risks to the Topeka Shiner (Notropis topeka): A Case Study with Atrazine

Abstract

A hybrid model was used to characterize potential ecological risks posed by atrazine to the endangered Topeka shiner. The model linked a Topeka shiner individual‐based bioenergetics population model (TS‐IBM) to a comprehensive aquatic system model (CASMTS) to simulate Topeka shiner population and food web dynamics for an Iowa (USA) headwater pool. Risks were estimated for monitored concentrations in Iowa, Missouri, and Nebraska (USA), and for monitored concentrations multiplied by 2, 4, and 5. Constant daily atrazine concentrations of 10, 50, 100, and 250 µg/L were assessed. Exposure–response functions were developed from published atrazine toxicity data (median effect concentrations [EC50s] and no‐observed‐effect concentrations). Two toxicity scenarios were developed: the first included sensitive and insensitive species of algae, and the second reduced algal EC50 values to increase atrazine sensitivity. Direct and indirect effects of atrazine on Topeka shiner prey were modeled; direct effects on Topeka shiner were not assessed. Risks were characterized as differences between population biomass values of 365‐d baseline and exposure simulations. The results indicated no discernable food web effects for monitored atrazine concentrations or constant exposures of 10 µg/L on Topeka shiner populations for either toxicity scenario. Magnified monitored concentrations and higher constant concentrations produced greater modeled indirect effects on Topeka shiners. The hybrid model transparently combines species‐specific and surrogate species data to estimate food web responses to environmental stressors. The model is readily updated by new data and is adaptable to other species and ecosystems. Environ Toxicol Chem 2019;38:2243–2258. © 2019 SETAC.

Assessment of risks to listed species from the use of atrazine in the USA: a perspective

“…Listed species are not available for direct field collection or laboratory studies, thus consideration of the potential effects of pesticides relies on the development and application of innovative ecological modeling approaches. One such modeling approach was used to examine the potential effects of atrazine exposure on the ecological production dynamics of species of aquatic plants, invertebrates, and fish in a generalized Iowa headwater pool and the consequences for Topeka shiner (Notropis topeka) populations (Bartell et al 2019). The Topeka shiner is a small, endangered minnow that inhabits the upper Great Plains of the USA and its speciesrange overlaps areas of atrazine use (Figure 23).…”

The Comprehensive Aquatic Systems Model (CASM): Advancing Computational Capability for Ecosystem Simulation

“…The basic structure and function of the CASM are derived from decades of modeling the production dynamics of aquatic ecosystems (DeAngelis et al 1989; Bartell et al 1999Bartell et al , 2013Bartell et al , 2018Bartell et al , 2019Nair et al 2015). Using bioenergetics-based equations to describe time-varying values of the biomass of aquatic organisms and populations dates at least to the 1970s (Kitchell et al 1974(Kitchell et al , 1977Park et al 1974).…”

“…The CASM has also been used to forecast the food‐web and ecosystem outcomes of coastal marine habitat restoration (Bartell et al 2010a) and water quality management in a large freshwater impoundment (Bartell et al 2010b). Recent applications have integrated the CASM with an individual‐based model to assess the potential ecological risks posed by pesticides to endangered species, particularly the Topeka shiner ( Notropis topeka ; Bartell et al 2019; Schmolke et al 2019).…”

“…Food web–ecosystem models provide the ecological context needed to address complex direct and indirect effects of environmental stressors (including pesticides) on food web components (Pastorok et al 2001; Galic et al 2010). Importantly, food web–ecosystem models such as the CASM can be integrated with other modeling approaches; for example, individual‐based models (Bartell et al 2019; Schmolke et al 2019) to produce new approaches to ecological risk assessment. The present short communication also highlights the attributes of a user‐friendly version of the model that will be publicly available.…”

Applying a Hybrid Modeling Approach to Evaluate Potential Pesticide Effects and Mitigation Effectiveness for an Endangered Fish in Simulated Oxbow Habitats

“…Hybrid modeling approaches combine models that represent different levels of organization (Jager and DeAngelis 2018). Combining species‐specific population models with an ecosystem‐level model sets the population dynamics in the context of species interactions, and thus can address indirect effects mediated by the food web (Strauss et al 2017; Bartell et al 2019; Schmolke et al 2019).…”