南海表层沉积物浮游有孔虫的氧碳同位素及其海洋学意义

从太阳号(SONNE95)1994航次的南海表层沉积物中分离出了有孔虫,并分析了它们的氧碳同位素组成.浮游有孔虫氧同位素组成的空间变化,主要和海洋物理因素有关.在蒸发作用较强的东沙、中沙和南沙海域,表层种G.ruber氧同位素偏重,而在淡水来水方向,即南海北部、西部和西南部,其氧同位素偏轻;次表层种P.obliquiloculata的氧同位素等值线图,指示氧同位素较重的黑潮水经由巴士-巴林塘海峡进入南海,并与氧同位素偏轻的南海冲淡水混合.浮游有孔虫的碳同位素空间变化趋势主要受海洋生物因素影响.在饵料来源丰富的珠江口外水域,以及光照充沛的南沙海域,G.ruber的碳同位素偏轻.在黑潮水所经之处,P.obliquiloculata的碳同位素偏重.浮游有孔虫氧碳同位素等值线在东沙和中沙海域变化梯度较大,与黑潮入侵引起的海水环流有关.

Oxygen and Carbon isotope composition of planktonic foraminifera in surface sediments from South China Sea and its oceanography significance

Foraminifera were separated from surface sediments sampled from South China Sea by SONNE95-1994 cruise and analyzed for carbon and oxygen isotope composition. Variation of planktonic foraminifera oxygen isotope in space depends predominantly on marine physics factors. In Dongsha, Zhongsha and Nansha areas where evaporation is strong, O-isotope of the surface species, G. ruber is heavier, but it is lighter in the north, west and southwest of the Sea, where fresh water comes in. In the O-isotope contour diagram of the sub-surface species, P. obliquiloculata, it is illustrated that Kuroshiro water with heavier O-isotope enters into South China Sea through Bashi and Luzon Straits, then mixes with diluted seawater there. C-isotope variation of planktonic foraminifera is affected mainly by marine bio-factors. In the off shore of Zhujiang Estuary where food supply is abundant, and in Nansha area where irradiance is strong, C-isotope of G. ruber is lighter. Along the route of Kuroshiro invasion, C-isotope of P. obliquiloculata is heavier. O and C isotope variation gradient of planktonic foraminifera is rather sharp in Dongsha and Zhongsha areas, which can be related to seawater circulation caused by Kuroshiro invasion.