Combining an individual-based model and an aquatic food web-ecosystem model to assess ecological risks: A case study with the endangered Topeka shiner
The Comprehensive Aquatic System Model (CASM) is a process-based integrated bioenergetics and habitat quality model that simulates population, community, and ecosystem-level effects of chemical stressors based on an aggregated population structure defined by an average-sized individual. An individual-based bioenergetics and population model (IBM) was developed for the endangered Topeka shiner (Notropis topeka) to incorporate detailed life-history and age-specific and size-specific attributes of population dynamics not represented in the CASM. The models were executed in tandem with daily IBM population growth dynamics transferred to CASM, which in turn computed the corresponding daily modifications to the food web. The CASM food web results were transferred back to the IBM in the form of adjusted Topeka shiner prey biomass values. This uniquely integrated model combination was implemented to simulate potential ecological risks for Topeka shiner in a generalized Iowa headwater pool, representative of known Midwestern habitat and range for this species. Ecological risks were computed using time-integrated differences between the population biomass values of 365-day baseline and exposure simulations. Risks were estimated for example daily pesticide exposures of varying magnitude, timing, and duration. Potential direct toxic effects to Topeka shiners were modelled within the IBM. The resulting modelled impacts on population biomass were used by the CASM to compute corresponding food web-ecosystem effects. The IBM provided the capability to examine the potential population-level risks based on detailed sensitivities of early life stages and adults to pesticide exposures. The CASM extended the IBM assessment capability by extrapolating potential direct effects on Topeka shiners to associated indirect changes in headwater pool community structure and ecosystem function. The presentation highlights the advantages afforded by the integrated IBM-CASM modeling approach to ecological risk assessment.
Steven Bartell (Cardno), Amelie Schmolke (Waterborne Environmental), Colleen Roy (Waterborne Environmental), Nicholas Ralston (University of North Dakota), Daniel Perkins (Waterborne Environmental), Nika Galic (Syngenta), Richard Brain (Syngenta). Combining an individual-based model and an aquatic food web-ecosystem model to assess ecological risks: A case study with the endangered Topeka shiner. Platform SETAC 2018. Sacramento, CA.
A US, field-scale, herbicide spray drift deposition and biological evaluation study: Methods and implications for risk assessment
Spray drift from pesticide applications is considered as a potential route of exposure in environmental risk assessment. Typically, spray drift deposition is modeled using terrestrial plant effects endpoint derived from worst-case, full rate direct spray studies, and combined in the risk assessment framework to represent extreme worst-case risk to non-target organisms. The objective of this work was to merge observed plant effects with spray drift exposure in a single study. A 40-acre field-scale, spray drift study was developed to simultaneously measure spray drift deposition, airborne interception, and potential biological effects of an herbicide under conservative drift conditions and a relatively low-drift nozzle. This study was conducted in four replications, each with a two-swath spray pattern (90 ft per swath) upwind of a deposition zone (perpendicular to wind direction), generally following the generic U.S. Environmental Protection Agency verification protocol, Testing Pesticide Application Spray Drift Reduction Technologies for Row and Field Crops. Within each replicate application, an array of three perpendicular sampling lines were used to measure drift deposition out to 400 ft, airborne interception out to 75 ft, and potential direct plant effects at set distances (5, 15, 25, 23, and 45 ft) from the edge of the downwind spray application . At each distance and sampling line, further replication of spray drift deposition, airborne interception, and biological effects were assessed in replicated fashion in a nested, replicated design. The timing of the herbicide application for each of the four replications targeted steady wind speeds between 8 to 12 mph. Wind direction was measured within a 30-degree angle of the downwind field orientation to ensure that spray drift would travel toward the collection area and across the furthest sampling points. Results from this study design refine effects determined in laboratory studies under worst-case exposure scenarios (i.e. direct over the top application) by addressing how terrestrial non-target plants actually experience exposure under natural conditions in the field, which can better inform risk assessment and risk management decisions.
Daniel Perkins (Waterborne Environmental), Greg Goodwin (Waterborne Environmental), Greg Kruger (University of Nebraska-Lincoln), Abby Lynn (All Aspects Consulting), Farah Abi-Akar (Waterborne Environmental), Richard Brain (Syngenta). A US, field-scale, herbicide spray drift deposition and biological evaluation study: Methods and implications for risk assessment. Platform SETAC 2018. Sacramento, CA.
Influence of particle size on prospectively modeled environmental concentrations of microplastics in the Sandusky River watershed
The presence of nano- and microplastics (MPs; particles < 5 mm) in the aquatic environment is a topic of increasing discussion and research. Although measurement and monitoring data are indispensable, there is a need to prospectively estimate concentrations to enable forward-looking assessments and to guide analysis of retrospective ecological analyses. For traditional chemicals, fate and exposure models have been proven to be very helpful and are widely used. However, to date few models exist that simulate the transport and fate of MPs in freshwater systems. This presentation presents simulations of the transport and fate of various-sized MPs emitted from wastewater treatment plants into freshwater riverine systems, and tracks concentrations moving downstream from headwater into Lake Erie. We linked the NanoDUFLOW model (a detailed MP aggregation-sedimentation model integrated in a hydrological and particle transport model) with iSTREEM® (developed to estimate chemical concentration distributions for all rivers receiving WWTP discharges in the US) for a range of particle sizes. This combines the mechanistic realism of NanoDUFLOW, accounting for formation and settling of heteroaggregates, with the US well-established iSTREEM implementation. Depth dependent in-stream first order removal rate constants simulated with NanoDUFLOW were combined with standard iSTREEM output which simulated the emission, transport and water column concentrations of different MP sizes. We modeled floating as well as non-buoyant MP, for sizes ranging from 100 nm to 1000 µm. We also modeled a combined mixture of particle sizes based on effluent measurements from Mason et al (2016). Simulations were spatially explicit with MP concentrations being modeled for the Sandusky River watershed in Ohio containing over 300 miles of river downstream of 20 WWTPs. Modelling results show the effects of population density, MP size and environmental conditions on riverine concentrations and export to Lake Erie. Buoyant as well as the smallest non-buoyant MP fractions can be transported over long distances, reaching receiving waters such as the Great Lakes. In contrast, larger non-buoyant MPs settle more locally in the vicinity of the WWTPs.
Christopher Holmes (Waterborne Environmental), Albert Koelmans (Wageningen University), Scott Dyer (Waterborne Environmental). Influence of particle size on prospectively modeled environmental concentrations of microplastics in the Sandusky River watershed. Poster SETAC 2018. Sacramento, CA.
Adequacy and uncertainty in models and scenarios developed to estimate pesticide wash-off and runoff in residential settings
A variety of pesticide products, including Insecticides, herbicides, and fungicides, are used by homeowners and licensed Pest Control Operatiors to eradicate or deter pests on lawns and ornamentals, vegetable gardens, homes, and other structures. Pesticide detections in urban streams have resulted in an increase in research over the past decade to understand the potential for pesticide washoff to occur from various pervious and impervious application sites. Regulatory agencies, chemical registrants, and other researchers have employed a variety of approaches to model pesticide runoff associated with residential uses. This presentation compares the underlying prinicipals in several models and scenarios that have been adopted or proposed for pesticide registration review and risk assessment by regulatory agencies in the U.S. and the E.U.; and evaluates their appropriateness for risk assessment for various categories of outdoor residential-use pesticide products. The models/scenarios include the Home and Garden scenario developed for the HardSPEC model by the Food and Environment Research Agency in the U.K., residential scenarios developed for PRZM5 by the U.S. Environmental Protection Agency, and adapting urban stormwater management models including the Stormwater Management Model (SWMM5) and the P8 Urban Catchment Model.
Marty Williams (Waterborne Environmental), Yuzhou Luo (CDPR), and Michael Winchell (Stone Environmental). Adequacy and uncertainty in models and scenarios developed to estimate pesticide wash-off and runoff in residential settings. Platform SETAC 2018. Sacramento, CA.
Setting a species-specific population model in the context of an aquatic food web model: A case example for the Topeka shiner
For species listed as threatened or endangered under the Endangered Species Act (ESA), higher-tier environmental risk assessments (ERAs) include assessing potential overlap of pesticide use patterns and the species’ geographical range. However, potential risks to populations also depend on temporal aspects of exposure and effects as well as interactions with ecosystem-mediated effects. We developed an individual-based population model (IBM) for the Topeka shiner (Notropis topeka), a fish species listed as endangered, and linked it with an aquatic food web model (comprehensive aquatic systems model, CASM). The CASM was parameterized and calibrated to represent the waterbody conditions and aquatic species community in a small headwater pool in Iowa, representative of a Topeka shiner’s key habitat within its geographical range. In the IBM, Topeka shiners feed on several groups in the aquatic food web according to published diet studies. Fish are simulated to grow according to a bioenergetics submodel that considers consumption, respiration and waste losses. We modelled the effects of alterations of the food web on the Topeka shiner populations by systematically reducing the available biomass of groups that the shiners consume. These alterations are generic simulations of the potential effects of pesticide exposures in agricultural landscapes around the shiner’s habitat. Potential pesticide effects on the food web depend on the compound, magnitude, timing and duration of exposure, and are simulated in the model by applying daily concentrations of a pesticide in the simulated waterbody which can be derived from field measurements or fate models. The linked models provide a platform for the assessment of potential direct and food-web mediated indirect effects of stressors such as pesticides on species populations.
Amelie Schmolke (Waterborne Environmental), Steven Bartell (Cardno), Colleen Roy (Waterborne Environmental), Nicholas Green (Waterborne Environmental), Daniel Perkins (Waterborne Environmental), Nika Galic (Syngenta), Richard Brain (Syngenta). Setting a species-specific population model in the context of an aquatic food web model: A case example for the Topeka shiner. Platform SETAC 2018. Sacramento, CA.
Taxa-focused approach to standardizing use of population models in ecological risk assessment
In spite of widespread acceptance of the utility of population modeling and advocacy of these approaches for more ecologically relevant perspective, they are not routinely incorporated in ecological risk assessments (ERA). A systematic framework for situation-specific model development is one of the major challenges to broadly adopting population models in ERA. As risk assessors confront the multitude of species and chemicals requiring evaluation, adaptable model templates and taxa-specific guidance on model parameterization would facilitate this process. We build on previous work that created a framework and decision guide for developing population models for ERA by focusing on anuran amphibians. Anurans have a unique life cycle with varying habitat requirements and physiological processes. These species belong to the amphibian class, which is facing global population declines, due in large part to anthropogenic stressors, including pesticide effects. A stage-based matrix model broadly represents the anuran life cycle. We synthesize information from databases and literature relevant to amphibian risks. At the individual, population, and ecological levels we identify traits that influence inherent sensitivity, population vulnerability, and environmental constraints. We also outline methods of modifying a basic population model to suit specific risk assessment needs with appropriate scale and parameterization to evaluate pesticide effects. A standardized population model approach for anuran ERA offers an example method of identifying potential risks and determining long-term impacts of chemical stressors to populations across taxonomic groups.
Jill Awkerman (USEPA), Sandy Raimondo (USEPA), Amelie Schmolke (Waterborne Environmental), Katherine Kapo (Waterborne Environmental), Nika Galic (Syngenta), and Valery Forbes (University of Minnesota). Taxa-focused approach to standardizing use of population models in ecological risk assessment. Platform SETAC 2018. Sacramento, CA.
Watershed modeling: Comparison of process-based model PRZM/SWAT with regression-based model SEAWAVE-QEX
Water quality monitoring data, specifically for pesticides, can represent best-available exposure profiles relevant to ecological risk assessment; however, there are challenges in synthesizing these data toward making conclusions about the nature of the potential range of risk. Some of these challenges include: data collection frequency, monitoring period duration, interpreting exposure profiles from one location to another, and monitoring system scale. To address these challenges, statistical approaches may be applied to characterize empirical trends. Additionally, process-based numerical modeling approaches can offer a different perspective on synthesis and interpretation of monitoring data. A comparison of a statistical and process-based numerical model was conducted to evaluate strengths and weaknesses of representing, synthesizing, and conclusions from monitoring data. This comparison was developed from pesticide measurements of six intensively-monitored HUC12 headwater watersheds in the Midwest. SEAWAVE-QEX is a regression model that incorporates a linear trend term, covariates accounting for seasonality, and a transformation of flow to represent a long-term pesticide trend at a specific monitoring location. PRZM/SWAT (Pesticide Root Zone Model/Soil Water Assessment Tool) is a spatially-distributed hydrologic and chemical transport numerical model that combines upland chemical and hydrologic processes from PRZM and stream flow and chemical transport processes from SWAT. The predictive quality and limitations of these two models (SEAWAVE-QEX and PRZM/SWAT) was assessed against observed, daily concentration measurements as well as hypothetical data collection frequency and timing (derived from sub-sampling the same data sets).
Wenlin Chen (Syngenta), Daniel Perkins (Waterborne Environmental), Andrew Jacobson (Waterborne Environmental), Colleen Roy (Waterborne Environmental), and Farah Abi-Akar (Waterborne Environmental). Watershed modeling: Comparison of process-based model PRZM/SWAT with regression-based model SEAWAVE-QEX. Platform SETAC 2018. Sacramento, CA.
Spatial and temporal variations of national cropping patterns for higher-tier pesticide exposure assessment
Pesticides are used on numerous agricultural crops across the United States to control pests and improve food yield and quality. This presentation focuses on the spatial and temporal aspects of a national scale assessment conducted by the Pyrethroid Working Group (PWG) to characterize the potential for pyrethroids to enter flowing surface waters based on a spatially explicit analysis of crop proximity to surface waters using multi-year data on diverse agricultural production patterns. Standard exposure calculations in the USEPA EFED regulatory risk assessment framework assume that 100% of the area around the water body (the Tier II pond) is cropped and treated, and therefore subject to drift and runoff entry. Over two million catchments within the National Hydrography Dataset (NHDPlus) were characterized using geospatial data to develop national or regional metrics related to potential surface water exposure related to crop proximity for more than 10 crop types. Crop locations were based on five years of data from USDA NASS Cropland Data Layer. Results highlight the variability of cropping density at the catchment scale across different geographies and scales, as well as situations in which density of potentially highly exposing crop (e.g., within 200m of surface water) may not match ‘entire catchment’ cropping density patterns. Variations in cropping density (as a proxy for potential exposure) across multiple years will be discussed in relation to how this variability may influence exposure estimates. When examining all catchments containing a specific crop, the 90th percentile crop density values (based on the 200m proximity zone) ranged from 1.3% (for vegetables in FL) to 44.4% (for tree nuts in CA). The resulting datasets provide a useful set of metrics across multiple crops which can be applied to pesticide exposure assessments that may need spatially-explicit refinements related to crop-water interactions. Because the crop proximity results are linked to the NHD+ framework, including these specific attributes into other NHD+-based analyses is extremely efficient.
Christopher Holmes, Joshua Amos (Waterborne Environmental), Paul Hendley (Phasera, Ltd.), Russell Jones (Bayer CropScience), Scott Jackson (Valent). Spatial and temporal variations of national cropping patterns for higher-tier pesticide exposure assessment. Poster SETAC 2018. Sacramento, CA.
A generalized life-history model for assessing indirect effects of pesticides on fish populations
Assessing population-level effects of stressors, such as pesticides, across species is challenging because effects are influenced not only by individual-level toxicity but also by species’ life history characteristics, ecology, and the duration, magnitude, and frequency of stressor exposure. Additionally, potential indirect population-level effects of stressor exposure (for example, effects resulting from changes in food availability) add further complexity to the assessment. To address these challenges, we developed a generalized population model for small fishes for assessing potential indirect effects of pesticide exposure on population dynamics. We applied the model to 17 species of darter (Percidae: Etheostomatinae) for which life history and diet data were readily available. The selected darter species (including two species listed under the Endangered Species Act) cover a range of life history strategies and diet compositions within the subfamily. We simulated several scenarios of pesticide exposure to assess how potential impacts of a pesticide on various prey species (invertebrates) included in the diets of selected darter species might affect darter population dynamics over extended time periods. We also investigated correlations between life history characteristics and population responses to the exposure scenarios. This analysis provides a framework for predicting food web mediated effects of pesticides on darter species for which little life history information is available. By combining life history variability in fish with estimates of potential indirect effects of pesticides on their prey, our model can provide a valuable tool for incorporating ecological complexity into the assessment process to quantify population-relevant risks to listed and non-target species of small fish.
Nicholas Green, Amelie Schmolke, Brian Kearns, Colleen Roy, Katherine Kapo, Matthew Kern (Waterborne Environmental), Alan Samel (FMC), Valery Forbes (University of Minnesota). A generalized life-history model for assessing indirect effects of pesticides on fish populations. Poster SETAC 2018. Sacramento, CA.
Model the effectiveness of vegetated filter strips in reducing contaminants in feedlot runoff
The National Pollutant Discharge Elimination System (NPDES) regulations require concentrated animal feeding operations (CAFO) with greater than 1000 head beef cattle to contain feedlot runoff in settling basins designed to hold runoff from a 25-year 24-hour rainfall. CAFO with less than 1000 head may discharge feedlot runoff to nearby waters under NDPES permits if there are certain best management practices (BMPs) in place like settling basins or vegetated filter strips. Runoff from feedlots may contain nutrients or veterinary pharmaceutical residues excreted in animal waste, which under some circumstances could be potentially harmful to aquatic organisms if released directly to nearby surface waters. The objective of this presentation is to model the effectiveness of vegetated filter strips (VFS) in reducing contaminants in feedlot runoff using the WINPRZM and VFSMOD models. Effectiveness of VFS in reducing nutrient concentrations in feedlot runoff will be presented as a case study. WINPRZM was enhanced to simulate runoff from an earthen or concrete uncovered beef feedlot. The model predicts the daily edge-of-field mass of nutrients and other constituents in runoff generated on a feedlot due to precipitation. The feedlot algorithm can model daily manure accumulation, various chemical administration patterns, and the periodic scraping of feedlots. The model uses the SCS curve number method to estimate runoff, a non-uniform mixing model to extract constituents from manure, and the manure erosion equation from the APEX model. The daily edge-of-field mass loadings estimated by WINPRZM are then input to the VFSMOD model which estimates the reduction of loadings based on the size of VFS and the resulting concentrations in runoff discharging from the VFS.
Ishadeep Khanijo, Marty Williams, Amy Ritter, Mark Cheplick (Waterborne Environmental), and Dawn Merritt (Zoetis). Model the effectiveness of vegetated filter strips in reducing contaminants in feedlot runoff. Platform SETAC 2018. Sacramento, CA.