南海中部沉积物捕集器中浮游有孔虫的稳定同位素分析

PRELIMINARY REPORT ON THE STABLE ISOTOPIC CHANGEOF PLANKTONIC FORAMINIFERS FROM THE SEDIMENT TRAPSIN THE CENTRAL SOUTH CHINA SEA

通过对南海中部沉积物捕集器中浮游有孔虫的氧、碳稳定同位素分析,探讨了它们与海洋学参数之间的关系。分析结果显示,G.ruber的δ18O值和δ13C值都比G.sacculifer的轻;两者的δ18O差值(Δδ18O)平均为0.520‰,δ13C差值(Δδ13C)平均为0.544‰,证明G.ruber的生活水深(约30m)比G.sacculifer的(约50m)浅。G.ruber与G.sacculifer之间的Δδ18O呈现夏季大、冬季小的特点,可能与海水的垂向温度梯度在夏季较大有关。G.ruber幼体的δ13C比成年个体的轻,幼体的δ18O比成年个体的重,揭示了该种在繁殖期前,随着个体发育,生活的水层深度逐渐变浅。

The relationship between stable carbon and oxygen isotopes and oceanography was approached based on isotopic analysis of planktonic foraminifers collected from sediment traps mooring in the central South China Sea. G.ruber is more depleted in both δ18O and δ13C than G.sacculifer; the average Δδ18O is 0520‰ and Δδ13C is 0544‰. It is the reflection of the temperature variation with water depth that G. ruber is lighter in δ18O than G. sacculifer, which indicates the different depth habitats, with G. ruber living at water depths around 30 m and G. sacculifer living at depths around 50 m. The Δδ18O between G. ruber and G. sacculifer changes with season, it is big in summer and small in winter, revealing its relationship to the vertical temperature gradient in water column. The steep thermal gradient in summer between the habitats where G. ruber and G. sacculifer live, resulted in the steep δ18O gradient between the species. The stable isotopic value changes as G. ruber increases in size. The big test depleted in δ18O and rich in δ13C suggests that the species moves upwards during growth before reproduction stage.