中文摘要：

根据2005年2月28日—3月10日和5月30日—6月4日在长江口及其邻近水域进行的多学科综合外业调查,报道了冬季和春季浮游植物粒级生物量的空间分布和组成特征,并探讨了影响浮游植物粒级生物量的环境因子.结果表明：冬季长江口及其邻近水域表层叶绿素a平均浓度为1.28mg·m^-3,高值区集中在口门附近;小粒径浮游植物（〈20μm）对浮游植物生物量的贡献率为66.7%,但在冲淡水区大粒径浮游植物（〉20μm）占据优势.春季长江口及其邻近水域表层叶绿素a浓度大幅增加,口门内、外的平均值分别为0.67和6.03mg·m^-3,122.5°—123.0°E间水域因水华爆发出现显著的叶绿素a高值区;小粒径浮游植物对浮游植物生物量的贡献高达83.5%,其优势在水华区尤为明显.典型站位浮游植物粒级生物量的垂向分布显示,2种粒径浮游植物叶绿素a浓度的差异随水深增加而减小,至底层二者浓度相当.根据所获的环境因子资料,盐度和营养盐是影响长江口及其邻近水域浮游植物粒级生物量分布和组成的重要环境因子.

英文摘要：

Based on the multi-discipline investigation in 28th February-10th March and 30th May- 4th June, 2005, this paper studied the distribution of size-fractionated phytoplankton in the Yangtze River estuary and its adjacent waters, and the environmental factors that affected this distribution. The results showed that in winter, the average chlorophyll a concentration was 1.28 mg · m^-3, and the region with high concentration chlorophyll a was located near the river mouth. Small-sized phytoplankton （SSP, 〈20μm） contributed 66. 7% to the total phytoplankton biomass, but big-sized phytoplankton （ BSP, 〉 20μm） was dominant in the plume system. In spring, the average chlorophyll a concentration in inner river and outer estuary was 0. 67 and 6. 03 mg·m^-3, respectively, and the maximum of chlorophyll a concentration appeared in the waters between 122. 5°E and 123.0° E. The SSP dominated in the plume system, especially in the algal bloom frequently occurring area which located at south of survey area, contributed 83.5% to the total phytoplankton biomass. The vertical profile of size-fractionated chlorophyll a showed that with the increase of water depth, the SSP and BSP became equal in the offshores. Among the environmental factors in the Yangtze River estuary and its adjacent waters, salinity and nutrients were the main factors affecting the distribution and composition of size-fractioned phytoplankton biomass in winter and spring.