title: Theoretically exploring direct and indirect chemical effects across ecological and exposure scenarios using mechanistic fate and effects modelling.
abstract: Predicting ecosystem response to chemicals is a complex problem in ecotoxicology and a challenge for risk assessors. The variables potentially influencing chemical fate and exposure define the exposure scenario while the variables determining effects at the ecosystem level define the ecological scenario. In absence of any empirical data, the objective of this paper is to present simulations by a fugacity-based fate model and a differential equation-based ecosystem model to theoretically explore how direct and indirect effects on invertebrate shallow pond communities vary with changing ecological and exposure scenarios. These simulations suggest that direct and indirect effects are larger in mesotrophic systems than in oligotrophic systems. In both trophic states, interaction strength (quantified using grazing rates) was suggested a more important driver for the size and recovery from direct and indirect effects than immigration rate. In general, weak interactions led to smaller direct and indirect effects. For chemicals targeting mesozooplankton only, indirect effects were common in (simple) food-chains but rare in (complex) food-webs. For chemicals directly affecting microzooplankton, the dominant zooplankton group in the modelled community, indirect effects occurred both in food-chains and food-webs. We conclude that the choice of the ecological and exposure scenarios in ecotoxicological modelling efforts needs to be justified because of its influence on the prevalence and magnitude of the predicted effects. Overall, more work needs to be done to empirically test the theoretical expectations formulated here.
authors.affiliation: Namur University, Research Unit in Environmental and Evolutionary Ecology, Rue de Bruxelles 61, 5000 Namur, Belgium. Electronic address: frederik.delaender@unamur.be.
authors.forename: F
authors.initials: F
authors.lastname: De Laender
authors.affiliation: Department of Science and High Technology, University of Insubria, Via Valleggio 11, 22100 Como, Italy. Electronic address: melissa.morselli@uninsubria.it.
authors.forename: M
authors.initials: M
authors.lastname: Morselli
authors.affiliation: Alterra, Wageningen University and Research Centre, P.O. Box 47, 6700 AA Wageningen, The Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: Baveco
authors.affiliation: Alterra, Wageningen University and Research Centre, P.O. Box 47, 6700 AA Wageningen, The Netherlands; Department of Aquatic Ecology and Water Quality Management, Wageningen University, Wageningen University and Research Centre, P.O. Box 47, 6700 AA Wageningen, The Netherlands. Electronic address: paul.vandenbrink@wur.nl.
authors.forename: P J
authors.initials: PJ
authors.lastname: Van den Brink
authors.affiliation: Department of Science and High Technology, University of Insubria, Via Valleggio 11, 22100 Como, Italy. Electronic address: antonio.diguardo@uninsubria.it.
authors.forename: A
authors.initials: A
authors.lastname: Di Guardo
mesh_terms: D017753:Ecosystem; D004781:Environmental Exposure; D020387:Food Chain; D008962:Models, Theoretical; D018570:Risk Assessment
keywords: Ecological risk assessment; Ecological scenario dynamics; Ecosystem modelling; Fugacity modelling; Ordinary differential equation models