The links between physical and biological processes in areas with very strong currents such as the Alderney Race (up to 12 knots of current), are very poorly understood. Currently it is very difficult to generate experimentally currents of similar intensity over sufficiently long periods to reproduce realistic conditions. Thus, the use of numerical modelling becomes essential to improve our understanding of the interactions between physical and biological processes and their consequences on the energy production of tidal turbines. In the Alderney Race fixed and encrusting fauna on hard granite substratum dominated hard substratum mainly barnacles and mussels, while a very diversified vagile macrofauna occupied the enclave sediments composed of coarse sands, gravels and pebbles (Foveau et al., 2017). Numerical modelling has been widely employed in recent years to model wake and dynamic stall effects near the turbine blades. Different methods have been used to take into fluid structure interaction (FSI) into account: addition of forces related to structure to the equations of fluid motion (BEM-CFD coupling, Vortex Method...). In addition, the strong swirling and unsteady nature of the flow around the blades requires an adaptive mesh to better simulate highly turbulent areas. The presence of fixed benthic organisms (number, size, form and implantation on the turbine pale) modifies turbulent activity (Rivier et al., 2018). Optimal turbulence modelling is therefore necessary, combined with a realistic representation of the target organizations. According to the 3D stationary results, 2D forced rotation dynamic simulations show a decrease of the turbine performances due to the dynamic stall generated by fouling species. Effects depend of the species height, density and their implantation position. The wake is also modified. Moreover, biofouling has not only an effect on the flow but also on the blades dynamics. Blades and added masses are indeed increased. To consider these effects, FSI approaches are envisaged: i) a full Large Eddy Simulation (LES) to validate calculation, ii) a LES/Vortex Method approach to have a low cost simulation allowing us to study a large number of configurations with a quite good precision. The main field of modelling is marine environment (Alderney Race), but application on large river such as Loire and Garonne should be explored in such fluvial environment with sessile freshwater species.