南海表层沉积物中放射虫多样性与丰度的分布与环境

Distributions of Radiolarian Diversity and Abundance in Surface Sediments of the South China Sea and Their Environmental Implications

采用定量分析方法,较系统地探讨了整个南海不同环境表层沉积物中放射虫的分布特征及其环境指示意义.结果显示:南海表层沉积物中放射虫的种类多样性和个体丰度随着水深而增加,表明南海较深水处的放射虫壳体溶解现象不明显;上升流活动和海底火山喷发有利于放射虫的大量繁殖,产生区域性的沉积富集;反之,较深水的陆坡区沉积物中出现放射虫种类与丰度异常减少,可能属浊流搬运再沉积的结果,物源来自陆架或上陆坡;种类组成以热带-亚热带特征为主,还包含了一定数量的冷水种或极区种,表明在特定海区的古环境分析中采用单一指标判断可能会造成误解.沉积物中放射虫的综合指标较好地反映了南海的生态与沉积环境特征.

The South China Sea （SCS） has relatively complete physiographical units and ecologic environments, where there are a lot of preservative radiolarian species and specimens in the sediments. Methods of quantitative statistics and clustering were used to analyze the radiolarian assemblages in surface sediments of the SCS, to understand their compositions and distributions. Results of clustering analyses show that the radiolarian assemblages in the SCS surface sediments may mainly he grouped as five types, including assemblages of shallow shelf, coral slope, central basin, southern rich nutrition and summer upwelling, corresponding to different special marine environments with certain radiolarian communities of dominant species. It is also indicated that the north, central and south of the SCS present as three areas of different ecologic conditions, such as the northern sea area affected mostly by terrigenous input, central sea area controlled mainly by the central basin waters, submarine volcanic and summer upwelling activities and the southern sea area falls obviously into a typical coral environ- ment, where there is a better ecologic and sedimental environment for radiolarian existing than that in the northern sea area. The radiolarian assemblages and distributions in the SCS surface sediments well reflect different marine ecologic conditions and sedimental environments, which may be used as reliable evidences for paleoceanographic explanation.