Evaluating the influences of integrated culture on pelagic ecosystem by a numerical approach: A case study of Sungo Bay, China

Abstract

With increasing concern over the environment in mariculture, the integrated culture has received extensive attention in recent years. For management of aquaculture farms, a biophysical model was developed to quantify the potential influence of bivalves-seaweed integrated culture on pelagic ecosystem. We developed NEMURO.CULTURE model by coupling the cultivated species (kelp Laminaria japonica, oyster Crassostrea gigas, scallop Chlamys farreri) and phosphorus-related variables with NEMURO (North Pacific Ecosystem Model for Understanding Regional Oceanography). The entire culture area of Sungo Bay was divided into five boxes according to the culture layout (kelp monoculture areas (K-area), co-culture areas (K&O-area), scallop monoculture areas (S-area), oyster monoculture areas (O-area), fish culture areas (F-area), and no-culture areas (Boundary)). The application of the model to the integrated culture system in Sungo Bay has shown promising results as the simulations reasonably agreed with the observations. The model was then used for scenario simulations to analyse the impact of mariculture. The simulation results showed that: 1) the concentration of phytoplankton and nutrients was largely constrained by cultivated kelps during the late stage of kelp culture period, while the influence of cultivated bivalves was relatively small; 2) the influence of cultivated kelps and bivalves could be transported to neighbor areas and weakened in the K-area, while the influence of cultivated fishes was confined near F-area; 3) the integrated culture of shellfish and seaweed in Sungo Bay would reduce the risk of eutrophication in spring; 4) the addition of phosphorus-related variables enabled the model to depict more details and phosphorus could be the limiting factor for phytoplankton growth at some time in Sungo Bay. This modelling work provides a quantitative tool for helping planning and management of coastal aquaculture.