The spatio-temporal evolution of a newly created mussel bed and its effects on benthic communities

Nanou Goedefroo

Creating a subtidal mussel bed in a soft-sediment environment for coastal protection is a great challenge. Besides having an effect on underlying macrobenthic communities, its own development is subjected to external pressures. This thesis tried to analyze and explain the spatio-temporal evolution of the created mussel bed and its effect on benthic communities for the Coastbusters project. Mussel beds showed great temporal variability and were only present during the late summer months and the beginning of fall. Wave action and predation were identified as possible factors causing a temporal and spatial variability within mussel beds, limiting their development. Dropper lines hung in the water column positively affected the development of the mussel bed by increasing the local mussel recruitment. A limited impact on the macrobenthos was observed. Only alpha-diversity measures were found to be significantly different between the reef and control sites. A lower diversity and a slightly higher abundance of oligochaetes in the reef site might be a first indication of a possible shift towards an oligochaete dominated community. Long-term observations and changes in the sampling design are needed to draw hard conclusions on the spatio-temporal variability of the mussel bed and its effects on the underlying macrobenthic communities.

Key words: coastal protection, biogenic reefs, Mytilus edulis, ecosystem engineer, soft- sediment, benthic impact