Climate-induced natural disasters such as floods and storms are expected to become more frequent and intense in the coming years. From 2017 till 2020, a pilot project was set up where mussel reefs were established as a nature-based solution to mitigate coastal erosion off the Belgian Coast. These subtidal mussel reefs were created by applying a longline mussel aquaculture technique consisting of filamentous and non-filamentous dropper lines of different materials. In this study, several biological aspects of the Nature-based Solution (NbS) set-up were examined: the suitability of the set-up as a whole, the suitability of the seven dropper line types, distribution of biofouling organism on the dropper lines and the spatio-temporal evolution of the mussel reef and its impact on the underlying benthic communities. Only during the summer months, a mussel reef could be established under the dropper line structure. Filamentous and non-filamentous dropper lines harbored different mussel densities and sizes, leading to a possible different effect on the underlying mussel reef. The biofouling community on the dropper lines was also defined in this study with amphipod species such as Jassa sp. and Monocorophium sp. as the dominant species. The impact of the NbS set-up on the macrofaunal communities remained low for the study period. First indications of a shift towards a less diverse and oligochaete dominated community was observed, although longer time series and an optimized sampling protocol will be needed. This pilot study showed the application of using a mussel longline technique in order to establish a subtidal mussel reef in a soft-sediment environment.
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