"It is proposed to model the bioaccumulation of the toxic trace metals zinc (Zn) (essential), cadmium (Cd) and silver (Ag) (both non-essential) by an infaunal benthic invertebrate, the lugworm Arenicola marina, a keynote species in European estuaries, from solution and diet (sediment) using biodynamic modelling. The predictions of a model constructed from biodynamic accumulation parameters (uptake and efflux rates, assimilation efficiencies) measured in the laboratory will be validated against field data (from biological and physical (water and sediment) samples) from reference and metal-contaminated estuaries, particularly in southwest England. The subcellular compartmentalisation of accumulated trace metals in the lugworms will be fractionated into detoxified and non-detoxified components to model the metabolically available metal fraction, thereby predicting the potentially toxic fraction of accumulated metal, and hence toxicity. Toxicity tests will then be used to seek correlations between modelled concentrations of the potentially toxic component of accumulated metal and the environmental exposure conditions causing ecotoxicological effects in the field. The conclusions of the project will contribute to the advancement of our ability to develop a scientifically consistent basis for making a transition from the predictive modelling of bioaccumulation to the prediction of environmental thresholds of ecotoxicological effects. The results have the great potential to contribute to the implementation of environmental quality standards – for example, those for sediments in the Water Framework Directive."