SETAC Globe - Environmental Quality Through Science
  18 July 2013
Volume 14 Issue 7

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Modelling and Empirical Approaches for Improving the Ecological Realism of Ecotoxicology

Valery Forbes, University of Nebraska, Virginie Ducrot, INRA, Annemette Palmqvist, Roskilde University

It is often said that there is not enough ecology in ecotoxicology and that this lack can have unfortunate consequences for environmental risk assessment. In this session, held at the SETAC Europe meeting in Glasgow, we explored how ecological realities influence the fate and effects of chemicals in the environment and the consequences of such for ecological risk assessment. The session covered both modelling and empirical approaches, and we included a wide range of environmental compartments, taxa and legislative contexts in order to identify broad-ranging take-home messages for environmental managers and policy makers.

The first part of the session dealt with studies using Gammarus spp. and Lymnaea spp. as focal species and addressed the importance of indirect effects, physiological energetics, toxicokinetics/toxicodynamics and bioaccumulation for estimating risk. A combination of empirical and modelling approaches was used to mechanistically explain and predict differences in toxicity among individuals of the same species and among different species. Accounting for such differences can improve extrapolation and provide more accurate estimates of contaminant bioaccumulation and effects.

The second part of the session examined issues related to bioaccumulation in various fish species and examined how non-standard exposure scenarios and ecological variables can influence bioaccumulation patterns. The papers employed a variety of statistical, modelling, experimental and stable isotope methods to explain what were, at least in some cases, non-intuitive bioaccumulation patterns.

The third part of the session focused on studies of standard test species (Daphnia magna and Folsomia candida), in which the effects of additional environmental stressors such as predation, food availability and fluctuating temperatures were examined together with contaminants in model or empirical systems. Results showed how ignoring these additional ecological complexities can lead to unrealistic estimates of risk and provided examples of some useful tools for exploring the combined effects of contaminants and these other variables in a systematic manner.

The oral session ended with a poster spotlight with examples to clearly demonstrate how ignoring important ecological variables such as food availability, temperature stress and predation can both increase and decrease risk. The poster session continued along these themes and included a total of 26 contributions covering a wide range of taxonomic groups, models and empirical approaches to better understand and predict the influence of ecological complexities on contaminant exposure, bioaccumulation, toxicity and the linkage of effects across levels of biological organization.

An important take-home message from this session is that, given the impracticality of testing all possibly relevant combinations of ecological variables and chemicals empirically, mechanistic effect models have a key role to play as virtual laboratories to systematically explore when standard risk assessment scenarios are likely to under- or overestimate actual risk. At the same time, empirical studies are vital for parameterizing and testing models. As the examples in this session clearly demonstrated, ignoring ecological realities leads to estimates of risk that are both over and underprotective, and if we want to improve the scientific basis for risk management and policy decisions, these realities will need to be incorporated.

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