Assessing the bio-mitigation effect of integrated multi-trophic aquaculture on marine environment by a numerical approach

•A three-dimensional (3D) ocean model coupled with ecosystem and individual-based submodels was developed.•The bio-mitigation effect of integrated multi-trophic aquaculture (IMTA) was assessed.•We modeled interactions among physical, biochemical, and ecological environments in IMTA.•Phytoplankton reduced by seaweed and bottom dissolved oxygen (DO) improved after releasing sea cucumbers.

With increasing concern over the aquatic environment in marine culture, the integrated multi-trophic aquaculture (IMTA) has received extensive attention in recent years. A three-dimensional numerical ocean model is developed to explore the negative impacts of aquaculture wastes and assess the bio-mitigation effect of IMTA systems on marine environments. Numerical results showed that the concentration of surface phytoplankton could be controlled by planting seaweed (a maximum reduction of 30%), and the percentage change in the improvement of bottom dissolved oxygen concentration increased to 35% at maximum due to the ingestion of organic wastes by sea cucumbers. Numerical simulations indicate that seaweeds need to be harvested in a timely manner for maximal absorption of nutrients, and the initial stocking density of sea cucumbers > 3.9 individuals m− 2 is preferred to further eliminate the organic wastes sinking down to the sea bottom.