To assess the potential ecological impact of seaweed farming on the North Sea we propose to study the impact of seaweed losses on the surroundings by characterisation of the (1) genetic intermingling with natural assemblages and (2) spread of potentially harmful microorganisms in one PhD project. The biological environmental assessment of seaweed farming will be combined with available 3D hydrodynamic and sedimentation models to predict routes and duration of pelagic existence that detached seedlings, fronds and reproductive cells of seaweed and their associated microbiota could travel. The integration of biological and geographical data may subsequently be used for policy decisions on ecological risk management of seaweed aquaculture in the North Sea, but will also contribute to feasibility of developing a seaweed sector in the North Sea as it will help to identify what are the ecological boundary conditions.