海水混合和层化对叶绿素a垂直分布的影响

根据长江口海区、近岸浅水区、黄海冷水团海区和水深超过200m的陆架区等四个区域的定点调查获得的数据，分析了温度、盐度与叶绿素a垂直分布的相互关系。结果表明，长江口海区，陆源径流与海水混合不充分，表层营养盐含量较高，表层叶绿素a含量高于中下水层。近岸浅水区的苏北近岸海水垂向没有温跃层和盐跃层，叶绿素a的垂向分布也均匀，东海西部沿岸出现逆温跃层和逆盐跃层，海水垂直混合不充分，叶绿素a含量(6．72mg／m^3)在10m深水域最高。黄海冷水团海区海水的垂直混合不充分，叶绿素a的垂直变化显著，高值区出现在温跃层下方(4．37mg／m^3)。水深超过200m的陆架区，温度的阶梯状结构、营养盐跃层、光照等因素共同导致整个水层叶绿素a含量普遍较低。同时，结合历史资料分析认为，海水的混合、温度和盐度的层化将影响营养盐的浓度和分布，从而影响海水中叶绿素a的垂直分布。

Impacts of sea water mixing and stratification on the vertical profile of chlorophyll a

Two comprehensive investigations were conducted in Yellow Sea and East China Sea in October, 2000 and May, 2001 for the National Key Project of Ecosystem Dynamics and Sustainable Development of Living Marine Resources in Yellow Sea and East China Sea. The survey areas consist of 4 subareas with different vertical profile of temperature and salinity, including the estuarine front of Changjiang River, the well mixed shallow coastal water, the Yellow Sea cold water mass with clear stratification, and the continental shelf with water depth more than 200 m. The paper analyzed the vertical distribution of temperature, salinity and chlorophyll a according to the CTD data and content of chlorophyll a obtained in May, 2001. The results showed that the sea water in the estuarine front of Changjiang River was not well mixed, resulting in higher contents of nutrients and higher content of chlorophyll in the surface layer. In Northern Jiangsu coastal area, the vertical profile of sea water did not showed thermocline and halocline, and vertical distribution of chlorophyll a was quite even. In western East China Sea coastal area appeared inversion thermocline and inversion halocline, so the vertical mixing was not sufficient in this area and stratification was clear. The highest value of chlorophyll a appeared at depth of 10m with a value of 6.72 mg/m3. In Yellow Sea Cold Water Masses area, thermocline occurred in water depth 10~25 m, where salinity had little change. So the stratification of temperature and salinity lead to deficient mixing. There were significant change of chlorophyll a on vertical profile, and high value zone was occurred under thermocline, which was 4.37 mg/m3. The continental shelf zone is which depth water more than 200 m, and station P1 is located southeastern continental shelf, which water depth is 1100 m. The ladder type change of temperature, more deeper isocline of nutrients and illumination, et al., result in a lower chlorophyll a content in the entire water column together. At the same time, integrated with historical data, suggest the mixing of sea water, stratification of temperature and salinity would affect the concentration and distribution of nutrients, accordingly affect distribution of chlorophyll a in the vertical profile of sea water.