Nature-based solutions, as shellfish reefs, can support natural coastal defence and be a potential solution for climate resilient shorelines in the future. They are dependent on environmental conditions, and both influence benthic ecosystems. This thesis analysed the effects of a newly created mussel bed and hydrodynamic conditions on the biodiversity and functioning of macrobenthic communities for the two Coastbusters projects. In a first finished project, a mussel bed was formed during summer-autumn. In the second ongoing project, different hydrodynamic conditions were tested (sheltered versus exposed). Shifts in lifespan, feeding behaviour, and development mode were found. Functional diversity indices suggested a better utilization of the different niches, but lower trait differentiation compared to bare sediments, probably due to the higher abundance of oligochaetes in the mussel bed. Important differences in density, species richness, biomass and feeding, mobility, development, and bioturbation modes were found between the two hydrodynamic conditions in response to flow and food flux conditions. Moreover, functional diversity indices revealed a better resource-use efficiency in the sheltered area. Further studies with a long-lasting mussel bed are needed to draw strong conclusions on the influence of biogenic reefs under different hydrodynamic conditions on benthic ecosystems for the implementation of coastal protection.
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