A DEB-based ecosystem model to assess the potential and ecosystem effects of low-trophic mariculture

The increasing reliance on the marine environment for food provisioning will likely further increase pressures on coastal marine ecosystems. In the Dutch part of the North Sea, low-trophic mariculture in the form of seaweed and shellfish production is stimulated and should occur alongside restoration of the marine ecosystem. A timely issue is therefore the extent to which large-scale mariculture practises will limit primary and secondary productivity and threaten nature restoration goals. Here we extend a minimum ecosystem model based on DEB theory to include seaweed ( i.e. the sugar kelp Saccharina latissima ) and shellfish ( i.e. blue musssels Mytilus edulis ). In addition, we include phosphorus dynamics for all ecosystem components and improve the co-limitation of nutrient uptake and assimilation. The resulting model is based on a strong theoretical foundation and can be used to study potential impacts of large-scale mariculture on marine ecosystems. As an illustration, we show that growing seaweed can potentially have a large effect on primary and secondary productivity, both through nutrient depletion and by limiting light availability. In addition, seaweed can limit the potential for shellfish growth if light self-limitation is moderate. With these developments, we make an essential step towards integration of DEB-based ecosystem models into 3D hydrodynamical models.