Modelling low-trophic aquaculture in the North Sea: From parameter estimation to ecosystem dynamics

The North Sea represents a promising but complex system for expanding sustainable food production through low-trophic aquaculture, particularly using bivalves and seaweed. However, assessing production potential and ecological carrying capacity in such systems requires mechanistic approaches that account for strong environmental variability and ecosystem interactions. Here, we present the parametrisation, sensitivity analysis, and application of a one-dimensional pelagic ecosystem model for the Dutch North Sea called Aqua-DEB. The model describes three functional groups: phytoplankton, zooplankton, and decomposers, supplemented with blue mussel ( Mytilus edulis ), and sugar kelp ( Saccharina latissima ), within a Dynamic Energy Budget framework. Parameters were estimated using existing empirical datasets, and model behaviour was evaluated under realistic environmental forcing and aquaculture scenarios. The results indicate that seaweed strongly compete with phytoplankton, through higher uptake rates and significant shading effects. In contrast, mussels occupy a niche where they accelerate remineralization, thereby stimulating primary production and their own growth. Sensitivity analysis revealed that the introduction of mussel and seaweed substantially alters the controls on ecosystem dynamics. These findings highlight that low-trophic aquaculture cannot be evaluated in isolation but must be considered within the broader ecosystem context. While the present model is designed to resolve key ecological mechanisms, its parametrisation and process-based structure provide a robust foundation for predictive applications. Coupling Aqua-DEB to three-dimensional hydrodynamic models represents a critical next step towards evaluating aquaculture performance, carrying capacity, and spatial management under future environmental change.