Modelling population dynamics in mesocosms using an individual-based model coupled to a bioenergetics model

In risk assessment, developing population models is of great interest to extrapolate toxicity observed at the individual level to the population level. In this study, an individual-based model (IBM) coupled to a Dynamic Energy Budget (DEB) model was developed in order to predict three-spined stickleback population dynamics in semi-controlled stream experiments (in mesocosms). This model takes into account the natural variations of environmental conditions and prey dynamics. To develop it, several datasets obtained in mesocosms were used to both calibrate and evaluate the model predictions. These datasets integrate different environmental scenarios. Indeed, the most sensitive parameters of the DEB-IBM were identified by sensitivity analyses and were calibrated based on data from two independent mesocosm experiments. The predictive capacities of our model were successfully evaluated using three independent datasets. Finally, our model was applied to a theoretical case of toxicant effects to show an example of application of the model in risk assessment. While the most uncertain population processes (in particular, competition for food in mesocosms) in our three-spined stickleback DEB-IBM could be modelled more accurately, our model can already serve to assess the impacts of toxicants at the population level by improving the analyses of mesocosm experiments, in decreasing the uncertainty of the experimental results. Therefore, in a second step, it could be used to predict the consequences on viability of a population exposed to a contaminant under various environmental and exposure scenarios