南海南部活体浮游有孔虫分布特征及其影响因素初探

通过对2002年5月采自南海南部海区11个站位20个垂直分层浮游拖网样品的浮游有孔虫组成和分布特征的初步分析,发现该区表层水体中浮游有孔虫分布广泛,共鉴定属种20种,以热带暖水种占绝对优势,广适应性冷水种有零星出现。深水种Globorotalia menardii在南海南部50 m水层中广泛出现,但壳体相对较小,壳壁较薄。该区0—50m水层活体浮游有孔虫丰度范围为(6 138—64 174)枚.1 000 m-3海水,大致呈西高东低的分布趋势,在西南部浅水区和西北部上升流区丰度最高,与表层水体的营养水平密切相关。将水样浮游有孔虫分布数据与该海区23个站位表层沉积样数据进行对比分析,发现遗壳浮游有孔虫与活体的分布关系密切,虽然在种属丰度以及分布范围等方面有明显差异,但两者具有相似的优势种组合。主要差异在于水体中浮游有孔虫优势种相对丰度差异较大,易溶种Hastigerina pelagica含量较高,而遗壳中浮游有孔虫各种属分布趋向于均匀化。此外,陆源物质的释稀作用对沉积物中的有孔虫丰度分布有明显的控制作用。

A preliminary study of living planktonic foraminifera distribution and its affecting factors in southern South China Sea

Living planktonic foraminifera was quantitatively analyzed for 20 stratified plankton tow samples collected from 11 sites in the southern South China Sea(SCS) in May,2002.The assemblage and distributing pattern of planktonic foraminifera were preliminarily analyzed based on these data.The result showed that living planktonic foraminifera distributed wildly in the surface water of the studied area,and totally 20 species were identified,of which most were tropic warm water species,cold water species only distributed sporadically.Globorotalia menardii,originally considered as a deep water species,appeared abundantly in the upper 50m water layer of the southern SCS,with generally thin and small shells.The abundance of living planktonic foraminifera in the upper 50 m water layer ranged from 6 138 to 64 174 individuals per 1 000 m~3 sea-water and showed a decreasing trend from west to east.High abundance values occurred in the southwest shallow-water area and the northwest upwelling area,suggesting that the abundance of living planktonic foraminifera may have a close relationship with nutrition level of the surface water.By comparing the planktonic foraminifera in the water samples with that in the surface sediment samples at 23 sites in the southern SCS,it could be found that they had a close relationship with each other.Although there were obvious differences in the distribution pattern and relative abundance of species,they showed very similar assemblages of dominant species.The main differences between them were that the relative abundance of dominant species in the water samples fluctuated violently with sampling sites,while it showed small variations in the surface sediment samples;and Hastigerina pelagica,a species apt to be dissolved,was abundant in the water samples but disappeared in the sediment samples.Besides,the dilution of terrigenous matter may have an obvious influence on the abundance distribution of planktonic foraminifera in the surface sediments.