Apports de la modélisation des effets des toxiques sur l’individu et la population en écotoxicologie aquatique

Abstract

SUMMARYTraditional analysis of toxicity tests provides toxicity parameters that are estimated with purely statistical methods. Consequently, thèse parameters do not hâve any intrinsic biological meaning and thèse methods provide no information about the mode of action of the tested chemicals. It is also difficult for thèse methods to change scale from the individual level to the population level, or to account for temporal and spatial heterogeneity. Modelling is an important tool in ecotoxicology and recently it appears to hâve gained more interest. Developments in modelling are currently expanding in two directions, modelling effects at the individual level and applying toxicity data obtained at the individual level to responses at the population level. The objective of the current study was to présent thèse two complementary modelling approaches together with the opportunities they offer.Modelling at the individual level provides parameters that are biologically relevant. Modelling also facilitâtes the formulation and the testing of hypothèses concerning toxicity processes (physiological mode of action and kinetics). Confounding factors such as time, varying exposure concentrations, or feeding can also be incorporated into models. In this paper, two kinds of models were examined: biochemistry-based models (Hill models) and energybased models (Dynamic Energy Budget models). In the Hill approach, effects are modelled as the interaction between chemicals and receptors in the organisms, which leads to a relationship between concentration and effects close to the logistic équation often used in toxicity test analysis. In the energybased approach, models are built on the dynamic energy budget theory, in which energy derived from food is used for maintenance, growth and reproduction. The effect of compounds is then described as a change in one of the parameters describing thèse physiological functions. Kinetics are taken into Rev. Sci. Eau, 17(4), 2004 P. Flammarion et A. Péry