북부 동중국해에서 영양염 역학

Abstract

To understand nutrient dynamics within water column over the northern East China Sea(ESC) shelf, we conducted an extensive hydrographic survey in early June. Hydrographic characteristics, identified by T-S diagram and nutrient concentration, clearly showed the influence of various waters such as the Changjiang river discharge, Yellow Sea Cold Water (YSCW), Yellow Sea Modified Water (YSMW), the upwelled Kuroshio subsurface water (UKSSW). Nirate+nitrite and phosphate concentrations were depleted in the surface mixed layer while high nitrate+nitrite and phosphate concentrations were observed below the surface mixed layer. However, silicate concentrations were higher than 5 μM throughout the entire water column over the northern ESC shelf. Hydrographic conditions (temperature, salinity) suggest that high nutrient concentrations, observed below the nutrient depleted surface mixed layer, may be resulted from different processes over the northern ESC shelf. At the bottom layer of western region, high nutrient concentrations were closely related to the cold and turbid water, and occurred in relation to the UKSSW at the eastern region. N:P ratios were higher than 16 in the western region, but were about 16 in the eastern region. These results suggest that biological recycling at the bottom layer, riverine input, and nutrient intrusion by the UKSSW are major controlling factors for the nutrient dynamics in the northern ESC., clearly showed the influence of various waters such as the Changjiang river discharge, Yellow Sea Cold Water (YSCW), Yellow Sea Modified Water (YSMW), the upwelled Kuroshio subsurface water (UKSSW). Nirate+nitrite and phosphate concentrations were depleted in the surface mixed layer while high nitrate+nitrite and phosphate concentrations were observed below the surface mixed layer. However, silicate concentrations were higher than 5 μM throughout the entire water column over the northern ESC shelf. Hydrographic conditions (temperature, salinity) suggest that high nutrient concentrations, observed below the nutrient depleted surface mixed layer, may be resulted from different processes over the northern ESC shelf. At the bottom layer of western region, high nutrient concentrations were closely related to the cold and turbid water, and occurred in relation to the UKSSW at the eastern region. N:P ratios were higher than 16 in the western region, but were about 16 in the eastern region. These results suggest that biological recycling at the bottom layer, riverine input, and nutrient intrusion by the UKSSW are major controlling factors for the nutrient dynamics in the northern ESC.