研究分析了南海南部海域不同粒径浮游动物春季和夏季的生物量和氮稳定同位素特征。结果表明, 海域大部分站位春季浮游动物生物量高于夏季(p<0.05), 而夏季在西南陆架区生物量出现极高值(受西南陆架上升流影响), 拉高了夏季的均值。根据粒径将浮游动物分成3组, 分别是大于500μm组(大型)、380~500μm组(中型)和180~380μm组(小型)。大型浮游动物生物量在夏季的比例更高, 而中型和小型浮游动物在春季的比例更高。春季浮游动物氮稳定同位素δ¹⁵N值高于夏季, 大部分站位大型浮游动物的δ¹⁵N值高于中型, 而小型浮游动物的δ¹⁵N值最低。广义加性模型(GAM)分析显示, 小型浮游动物δ¹⁵N值受环境和生物因子的共同影响非常明显。

Stable isotope analysis has emerged as one of the primary means to analyze the structure of food webs. Size fractionated zooplankton biomass and stable isotopes in the southern South China Sea during spring and summer 2013 were investigated. The results showed that zooplankton biomass in spring was higher than those in summer at most sites (p<0.05), while the maximal value was found in the southwestern continental shelf (influenced by coastal upwelling) with increased mean value of zooplankton biomass during summer. Zooplankton was divided into three groups according to size. Macro- zooplankton contributed more to the total zooplankton biomass during summer, while meso- and micro-zooplankton contributed more during spring. Mean δ¹⁵N value in spring was higher than that in summer, and the δ¹⁵N value of macro-zooplankton was higher than those of meso- and micro-zooplankton at most sites. Zooplankton biomass was negatively related to mixed layer depth and seawater temperature at 75-m depth, and positively related to salinity at 75 m, indicating that zooplankton biomass was influenced by vertical mixing. The result of GAM (generalized additive model) indicated that the δ¹⁵N value of micro-zooplankton was affected by combined impacts by environmental and biological factors.