Modelling BPA effects on three-spined stickleback population dynamics in mesocosms to improve the understanding of population effects.

Bisphenol A (BPA), a well-known endocrine-disrupting chemical, is ubiquitously present in the aquatic environment. Its impacts at the population level on three-spined sticklebacks (Gasterosteus aculeatus) have been studied in artificial streams with low-dose BPA concentrations. The causes explaining the observed effects remained unclear. Here, we used an individual-based model coupled to a Dynamic Energy Budget model to (i) assess the potential of modelling to predict impacts at the population level using individual level laboratory ecotoxicological endpoints and (ii) provide insight on the mechanisms of BPA toxicity in these mesocosms. To do that, both direct and indirect effects of BPA on three-spined sticklebacks were incorporated in the model. Indeed, direct BPA effects on fish have been identified based on literature data whereas indirect effects on sticklebacks have been taken into account using sampling data of their prey from the exposed artificial streams. Results of the modelling showed that direct BPA effects on fish (impacts on gonad formation, growth, male reproductive behavior, eggs and larvae survival) mainly explained the three-spined stickleback population structure in the mesocosms, but indirect effects were not negligible. Hence, this study showed the potential of modelling in risk assessment to predict the impacts on fish population viability from behavioral and physiological effects measured on organisms.