【摘要】 <正> 众所周知,生物生长取决于所栖息的环境,作为海洋主要的微体植物之一的硅藻,当然也遵循这一规律,受制于海洋地理环境如物理、化学、生物等因素。仅就盐度而言,可以分出广盐种、狭盐种;而就生活方式而言,就有底栖种和浮游种之分。大洋每克悬浮物(干样)中硅藻个体的数量从6.25百万个到4亿多个,每克沉积物(干样)中的含量从0到大于1亿个个体(Lisitzin,1971),说明海洋地理环境的差异不仅造成了硅藻种类性质的不更多还原

【Abstract】 The size changes of the marine diatom Coscinodiscus nodulifer A. Schmidt from the column sediments are records of the climatic fluctuation in geological history. The curves based on （?）60μ ratio of the valve diameter of Coscinodiscus nodulifer A. Schmidt from the column sediments may be directly related with oxygen isotope curves with which we can determine dates of Late Quaternary sediments and reconstruct paleogeographic environment more easily, especially in the absence of oxygen isotope data. Maximum ratio located at 30cm downcore of V₁ core and 100 cm down-core of V（?） core represents the boundary of Holocene and Pleistocene. There are a subtropical diatom complex below the boundary and a tropical-subtropical diatom complex over it. The former reflects that warm climate and lowering sea level resulted in the exposure of most of the continental shelf and the latter indicates that the climate and paleogeography of that time were similar to those today.更多还原