南黄海秋季叶绿素a的分布特征与浮游植物的固碳强度

Distributions of chlorophyll-a and carbon fixed strength of phytoplankton in autumn of the southern Huanghai Sea waters

依据2005年10月中下旬对南黄海的调查结果，系统阐述了2005年秋季南黄海叶绿素a的分布特征，并估算了南黄海和东中国近海初级生产力水平及浮游植物固碳强度，分析了控制其变化的生物地球化学机制．结果表明，南黄海表层叶绿素a含量的变化范围为0．11～2．38mg／m^3，平均浓度为0．66mg／m^3，明显高于50m层的含量．南黄海表层和次表层叶绿素a分布趋势基本一致，均显现出西北高、东南低的趋势，在近岸海域出现显著的高值带，这主要是由于受到陆源输入和沿岸流带来的高营养盐的影响；中部海域的低值区则主要受控于来自东海低营养盐海流的“冲淡”作用．在垂直分布上，叶绿素a最高值基本出现在次表层，与以往发现的该海域次表层溶解氧最大值一致，这显然与南黄海浮游植物及区域水团特性有关．2005年秋季南黄海初级生产力（C）变化在95～1634mg／（m^2·d），平均为586mg／（m^2·d），其分布趋势显示了海洋初级生产力与海水磷浓度以及水团、海流的关系．应用初级生产力估算的浮游植物固碳强度的结果表明，我国东部近海浮游植物年总固碳量约为222Mt，约占全球近海浮游植物的年固碳量的2．0％，为我国东部近海通过海-气界面总表观碳汇强度每年l369万t的16．2倍，在不同的海域，浮游植物固碳量是其通过海-气界面总表观碳汇强度的倍数不同（渤海为3．0倍，黄海为6．7倍，东海为81．6倍）．

Chlorophyll-a （Chl a） concentration, primary productivity and carbon fixed strength in the southorn Huanghai Sea （SYS） were examined for their distribution features and biogeochemical mechanisms based on the investigations along four transects in October and November 2005. The Chl a concentration in surface waters ranged from 0. 11 to 2.38 mg/m^3 with a mean of 0. 66 mg/m3, which was much higher than that in the 50 m layer. Owing to a good seawater exchange induced by strong hydrodynamic process in the SYS, the Chl a distributions in the surface and 20m layer were generally similar with high values observed in nutrient-laden inshore waters. However, in the middle of the southern Huanghai Sea where was occupied by the currents from the East China Sea characterized hy low nutrients contents, the Chl a concentrations were correspondingly low. As for the vertical distributions of Chl a in the southern Huanghai Sea, the deep Chl a maximum profile was the predominant pattern. It followed the previous result of the deep dissolved oxygen maximum profile, which was significantly correlated with phytoplankton and regional water mass. The estimates of primary productivity in autumn of the southern Huanghai Sea ranged from 95 to 1 634 mg/（m^2 · d） with an average of 586 mg/（m^2 · d）. Study showed that the pattern of primary productivity was well correlated with phosphate concentration in seawater and chemical hydrography. Furthermore, according to the present study results together with previous investigations, the annual value of carbon fixed production of phytoplankton in the entire marginal seas of eastern China was estimated to be 222 Mt, which accounted for 2 % of the annual value of carbon fixed production of phytoplankton in global marginal sea areas. Besides, it was as 16.2 times as the annual value of apparent carbon sink strength （13. 69 Mt） in the entire marginal seas of eastern China. The above mentioned multiple was different in different sea areas （3. 0 in the Bohai Sea, 6. 7 in the Huanghai Sea and 81.6 in the East China Sea）.