[en] A system for the radiological protection of the environment, with special attention to the derivation of dose limits for flora and fauna, will require the use of modelling tools. This paper promotes one approach for modelling the consequences for the marine environment from radioactive contamination. The method is based on the modified approach for box modelling ('ARCTICMAR 2' model), which includes dispersion of radionuclides during time (non-instantaneous mixing in oceanic space). This approach was created in order to provide a better and more realistic/physical approach compared to traditional box modelling. The model can provide information concerning the dispersion of radionuclides in water, sediment and biota phases of the marine environment. The assessment of internal and external doses to the marine organisms is based on assumptions about uniform distributions of radionuclides in organisms as well as surrounding water and sediment boxes. The dose assessment uses dose conversion factors that account for the absorbed fraction for γ-emitting radionuclides. The potential of the present modelling approach is illustrated by calculations of doses for selected sets of scenarios and 'reference' organisms. (author)