Quantification of hydrodynamic changes induced by an offshore mussel aquaculture farm (SYMAPA)

The goal of this numerical study is the quantification of hydrodynamic changes (especially sea currents) induced by an offshore aquaculture farm similar to that of the industrial project “Westdiep Sea Farm”. To do that, a parameterization of the impact of longlines and droppers on hydrodynamics has been included in the 3D COHERENS hydrodynamic model and the impact of several configurations of the aquaculture farm on currents and bottom shear stress has been estimated in a simplified test case. The mussel aquaculture technique of longlines used in this project is known to disturb currents by, among other things, increasing the velocity of currents under the farm and significantly increasing the turbulence developing in the wake of the rigs. From an environmental point of view, an open question is whether or not these changes can modify the erosion/sedimentation pattern around the farm, leading, for example, to a risk of destabilization of the neighbouring sandbanks. As part of the SYMAPA (Synergy between Mariculture & Passive Fisheries) project, the goal is to link current variations in and around the farm to the amount of food available for mussels attached to droppers. At the seabed, a link between hydrodynamic processes and modification of the sedimentation scheme may be considered following this report. This preliminary study can help lead to the final goal of determining the scope of the impact that the aquaculture farm may have on the ecosystems in the farm and on the benthos. Three major effects will be studied for three different farm designs: the impact on surface currents, the sinking of currents under the farm and the impact on bottom shear stress.

Report

This report was written as a continuation of a report produced during an end-of-master internship at RBINS.