中文摘要：

报道了2005年春季南海北部23个大面站网采浮游植物的调查结果，对浮游植物的群落结构进行了初步研究。共鉴定浮游植物3门73种，硅藻种类最多（50种），其次为甲藻（22种）和金藻（1种）；浮游植物细胞丰度平均为3．07×10^4cells／m^3，以硅藻为主（相对丰度平均93．8％），其次为甲藻（相对丰度平均6．16％）和金藻（相对丰度平均6．16％）；陆坡海域的细胞丰度高于海盆，与历史同期资料相比分布趋势相似但细胞丰度总体较低。南北群落结构差异较大，虽然整个调查海域北部浮游植物丰度较高，但浮游植物群落的多样性高值区却出现在海盆东部和南部，整个调查区浮游植物的生物多样性是较低的。

英文摘要：

The investigation on net phytoplankton in the northern of South China Sea in spring of 2005 was carried out with samples taken from 23 grid stations and the results were reported in this paper. A preliminary study of the phytoplankton community structure was studied. A total of 71 species in 3 phyta of net phytoplankton were identified, in which diatoms （50 species） were most dominant and followed by dinoflagellates （22 species） and gold alga （1 species）. The average cell abundance of phytoplankton was 3.07 104 cells/m^3, with diatoms dominated （93.8%）, followed by dinoflagellates （6. 16%）, and golden algae （6. 16M）; Cell abundance of shelf slope waters was above the basin. Comparison with historical data distribution trends is similar to the same period, but the abundance of the cell was generally low. Community structure of north and south is quite different. Although in the entire investigation a higher abundance of phytoplankton in the northern area, the diversity of phytoplankton communities in high-value areas have emerged in the eastern and southern basin. Biological diversity of phytoplankton in the entire survey area was lower.