A dynamic model for prediction of bioaccumulation in aquatic macrofauna is described. The model, entitled SHRIMP (Simulation of Heavy-metal Rate of Intake for Macrofaunal sPecies), consists of five coupled submodels, which simulate individual growth, population dynamics, metal transport in the abiotic part of the system, metal bioaccumulation at the organism level, and upscaling of individual contamination to the population scale. The sublethal effects of metal toxicity on individual and population levels are shown to act through the reduction of individual growth rates. The model was tested for cadmium and mercury using epibenthic crustacea from an estuarine system. Individual and population patterns of bioaccumulation were analyzed by comparing the simulated results of five different scenarios of dissolved metal concentrations. Model results suggest that the subtle effect of growth reduction due to metal toxicity is sufficient to cause a decrease on population numbers simply by affecting the growth of the mature females and males.