中文摘要：

根据2004年5、8、11月和2005年2月在长江口4个航次的海洋综合调查,通过物种多样性、累积优势度曲线等群落水平指标和相似性检验分析（ANOSIM）,对长江口北港和北支浮游动物群落及其主要优势种的差异,以及主要生态因子对浮游动物群落的影响进行了分析.结果表明：北港主要由潮汐影响的淡水和低盐水组成,北支由中、高盐水组成.春季,北港浮游动物丰度和多样性均低于北支,主要优势种为中华华哲水蚤;北支浮游动物优势种数较多,主要优势种为真刺唇角水蚤.夏季,北港和北支的多样性较接近,但种类组成差别较大,北港以中华华哲水蚤为主;北支由火腿许水蚤、虫肢歪水蚤和太平洋纺锤水蚤等构成河口和近岸群落.秋季,北港的丰度和多样性均低于北支,且两个水域的浮游动物群落差异明显,北港以中华华哲水蚤为主,北支则由小拟哲水蚤、针刺拟哲水蚤、真刺唇角水蚤和中华哲水蚤等组成.冬季,两个水域种数和多样性均较低,群落差别在四季中最小,均以中华华哲水蚤占绝对优势.温度和盐度及其相互作用是决定长江口浮游动物群落特征的最主要因素.其中温度是研究水域浮游动物群落季节变化的主要因素,而由径流和外海水之间的消长引起的盐度变化是北港和北支浮游动物群落区域变化的决定因素.

英文摘要：

According to the four cruises investigations in the Yangtze River Estuary from May, August and November 2004 and February 2005, and by using species diversity indices, K-dominance curves, and similarity analysis （ ANOSIM）, the features of mesozooplantkon communities and their dominant species in the North Channel （NC） and North Branch （NB） were analyzed, with the effects of ecological factors, especially water salinity and temperature, on the dominant species and communities in these two waters discussed. The results indicated that the NC was composed of tidal water and oligo-haline water, while the NB was featured by meso-haline or poly-haline water. Consequently, the zooplankton communities in these two waters were significantly different. In spring, the abundance and diversity of the communities were larger in NB than in NC. In NC, Sinocalanus sinicus was the only dominant species; while in NB, there were several dominate species, among which, Labidocera euehaeta was most important. In summer, the diversity of the communities in NC and NB was quite similar, but the species richness and total abundance of zooplankton were less in NC than in NB. The zooplankton in NC was made up of olio-haline communities, and that in NB was composed of brackish species, e. g. , Schmackeria poplesia and Tortanus vermieulus. In autumn, similar to those in spring, the abundance and diversity of the communities were larger in NB than in NC. As usual, in NC, S. sinieus was the most important species; while in NB, the zooplankton was composed of neritie community （ Paracalanus parvus, P. aculeatus, L. euchaeta, and Calanus sinicus, etc. ）. In winter, the species richness and diversity were the lowest, and there were no obvious difference between the zooplankton communities in NC and NB. It was concluded that water salinity, water temperature, and their combination were the key factors determining the characters of the mesozooplanktonic communities. Water temperature mainly affected the seasonal alteration of the domin