南海南部次表层叶绿素a质量浓度最大值及其影响因子

摘要

文章分析了2013年南海南部4个季节航次的叶绿素a (Chl a)调查数据, 结果显示: 150m以浅水柱Chl a质量浓度均值分别为早春0.14mg.m-3、初夏0.12mg.m-3、初秋0.18mg.m-3、初冬0.16mg.m-3.早春和初夏偏低的原因与早春风速小, 初夏水温高, 不利于水体的垂直混合, 限制了深层海水中丰富的营养盐向上层水体补充有关.4个季节中海水次表层Chl a质量浓度最大值层(SCML)均出现在50m和75m, 这两个水层的Chl a质量浓度差异小, 季节变化不大, 平均值变化范围分别为0.24~0.26mg.m-3和0.22~0.26mg.m-3.受混合层深度和温跃层上界深度的共同影响, 50m水层Chl a质量浓度主要受制于深层富营养盐海水的向上补充, 75m水层Chl a质量浓度受水温的影响明显.%The four-season environment ecological comprehensive surveys were carried out at 34 stations in the southern South China Sea by the research vessel"NanFeng"from March to December in 2013. Results show that the average chlorophyll a (Chl a) concentration of shallow water at 150 m in early spring (0.14 mg.m-3) and early summer (0.12 mg.m-3) were lower than that in early autumn (0.18 mg.m-3) and early winter (0.16 mg.m-3). This was mainly due to the smallest spring wind speed in early spring and the highest water temperature in early summer, which were not conducive to vertical mixing, limiting deep nutrients being brought up. The subsurface Chl a maximum in the four seasons all appeared at both 50 m (0.24~0.26 mg.m-3) or 75 m (0.22~0.26 mg.m-3), and the difference of Chl a concentration at these two depths was small, with little season change. The 50 m and 75 m layers were located in the middle part and near the bottom of the euphotic seawater, and the light received by the two layers can meet the growth need of phytoplankton. With the combined impact of mixed layer depth and the upper bound of the thermocline, the Chl a concentration in the 50 m layer was mainly controlled by the supply of nutrients, and that in the 75 m layer, by ocean temperature, both being important factors affecting phytoplankton growth.