Influence of Suspended Aquaculture on Hydrodynamics and Nutrient Supply in the Coastal Yellow Sea

Abstract

AbstractEffects of aquaculture on hydrodynamics and associated nutrient supply in a typical aquaculture area of the coastal Yellow Sea are investigated with high‐resolution model experiments and in situ data. The results show a significant reduction in nutrient supply, which is associated with alternations of three hydrodynamic conditions: the onshore current across the outer‐boundary of aquaculture area, upwelling within the offshore (depth >10 m) aquaculture area, and water exchange in the near‐coastal (depth <10 m) aquaculture area. First, the onshore current in the bottom layer of the aquaculture boundary, which transports high‐concentration nutrients from the major nutrient source of offshore bottom water, is significantly weakened by suspended aquaculture. As a result, nutrient supply from offshore sources is reduced by 50%−60%. Second, the upwelling velocities in the offshore aquaculture area are reduced by 2–6 × 10−3 cm/s, which leads to an approximately 25% reduction in nutrient supply to the euphotic layer. Third, the water exchange in the near‐coastal aquaculture area remains approximately unchanged because the weakened onshore currents within the aquaculture layers (0–4 m) are compensated by the enhanced onshore currents in the lower layers. As a result, the nutrient supply in the near‐coastal aquaculture area does not significantly change, whereas the nutrient supply in the offshore aquaculture area has been reduced by approximately 60%.