南海北部浮游生态系统要素季节变化的模拟研究

Numerical Study on Seasonal Variations of the Vertical Structures of the Plankton Ecosystem in the Northern Area of South China Sea

本文基于南海SEATS站的观测资料,利用垂直一维海洋生态系统动力学模式（MEM-1D）模拟了南海北部生态要素垂直结构的季节变化。结果表明,南海北部表层Chla浓度具有明显的季节变化特征,夏季呈现低值（〈0.05 mg·m-3）,冬季呈现高值,12月为0.38 mg·m-3。春季,风速相对变小,垂直混合变弱,次表层Chla浓度极大值现象形成（80-100 m）,并可一直持续到10月末。冬季,海表温度降低,东北季风爆发,垂直混合增强,出现表层水华现象。浮游动物和细菌的垂直结构相似,冬季上层水体中浮游动物和细菌出现最大值,分别为13 mg·m-3和18 mg·m-3。3-10月细菌（12 mg·m-3）同浮游动物（14 mg·m-3）一样出现次表层最大值,其存在深度与浮游动物相似。

One-dimensional Modular Ecosystem Model（MEM-1D） was used to simulate the seasonal variations of the vertical structures of the plankton ecosystem in the northern area of South China Sea.Model results indicate that the concentration of chlorophyll-a at surface presents obviously seasonal variation with the minimum value in summer（0.05 mg·m-3） and the maximum value in winter（0.38 mg·m-3）.In spring,vertical mixing is weaker due to the weaker wind.It is hard for nutrients to reach the upper layer,so the sub-surface chlorophyll-a concentration maximum（SCM）（80~100 m） maintains until the end of October.In winter,the vertical mixing becomes stronger due to the decrease of the sea surface temperature and the strong northeast monsoon.As a result,nutrients can reach the upper layer,which induce the phytoplankton bloom.The vertical structures of the biomasses of zooplankton and bacteria are similar and the maximum values both appear in winter with 13 mg·m-3 and 18 mg·m-3 respectively.