中文摘要：

对南海南部25个表层沉积样进行了生物硅的测定分析，试图揭示南海南部表层沉积生物硅的分布及其对现代海洋环境的指示意义，以便为古海洋学研究提供进一步的科学依据。研究发现，表层沉积物中生物硅含量与其所处水深呈显著正相关关系，相关系数达到0．782。陆架浅水区表层沉积物中生物硅含量非常低，不能反映表层水体中硅质生物生产力情况，这可能与沉积类型和陆源物质输入影响有关。深水区表层沉积物中生物硅的含量分布表明，其不仅能反映出表层水体中硅质生物的古生产力水平，而且还能指示上升流的强弱，从而进一步证实了利用沉积物中生物硅含量来追踪上升流发育和变化的有效性与可信度。研究结果还显示，在研究区域中北部表层沉积生物硅中放射虫和海绵骨针较硅藻占有更大的比重，这可能是由于硅藻易被溶解并易被其他生物体摄食的缘故。在有上升流发育的海域，放射虫、硅藻和海绵骨针基本上均表现出较高的丰度，这与高的生物硅含量相一致。

英文摘要：

Biogenic silica content was determined in 25 surface sediment samples from the southern South China Sea to study its distribution and its modern oceanic environmental significance, which may provide further scientific evidence for paleoceanography explaination. This study showed that biogenic silica content in surface sediments and its water depth have evidently positive correlation, and the correlation coefficient was up to 0.782. Biogenic silica content was very low in continental shelf shallows and could not reflect the productivity of siliceous micropaleontology in surface waters, which may be affected by sedimentary types and terrigenous matter dilution. Distribution of biogenic silica content in surface sediments from deep water areas showed that it could not only reflect the paleoproductivity of siliceous micropaleontology in surface waters, but also indicate the strong or feeble upwelling. Thus, it was further confirmed that using biogenic silica content in sediments to trace upwelling and its change was effective and reliable. The analyzed result showed that radiolariia and poriferous specula have more contribution for biogenic opal, comparing with diatom in surface sediments from the northern studied area, probably owing to the diatom dissolved easily away and eaten by other organisms with little effort. In the upwelling areas, radiolarian, diatom and poriferous specula all approximately showed high abundance, which was consistent with high biogenic silica content.