中文摘要：

2011年11月25日-12月1日在渤海（37o00＆#39;-40o00＆#39;N，118o00＆#39;-121o00＆#39;E）21个站位进行了水文、化学和生物的综合调查，应用Uterm？hl方法对调查海域的浮游植物群落进行了研究，并将群落数据与环境因子（温度、盐度和营养盐）进行了相关性分析。本次调查共发现浮游植物3门30属65种，主要由硅藻和甲藻组成，还有少量的金藻，生态类型以温带近岸性物种为主，主要优势种为：具槽帕拉藻[Paralia sulcata （Ehrenberg）Cleve]、偏心圆筛藻（Coscinodiscus excentricus Ehrenberg）、梭状角藻[Ceratium fusus（Ehrenberg）Dujardin]、相似曲舟藻（Pleurosigma affine Grunow）、星脐圆筛藻（Coscin原odiscus asteromphalus Ehrenberg）和菱形藻（Nitzschia sp.）等。调查区浮游植物细胞丰度介于0.89＆#215;103~16.4＆#215;103 cells/L，平均值为4.36＆#215;103 cells/L。表层浮游植物细胞丰度分布主要受硅藻刻画，高值区集中在辽东湾南侧和渤海海峡西侧海域，甲藻则主要集中在调查区西部和西北部海域。细胞丰度在水体中的垂直分布为随水深增加先升高后降低。调查区浮游植物群落多样性指数和均匀度指数均在调查区中部海域较高，在外侧海域较低。与历史资料的对比发现，近30年来渤海中部海域浮游植物群落结构由早期的硅藻占绝对优势转化为硅藻和甲藻联合占优。PCA和CCA分析以及与历史资料的对比表明，渤海中部海域营养盐结构的改变可能是造成这种转化的主要原因。

英文摘要：

A comprehensive survey was carried out in the Bohai Sea（37o00’-40o00’N,118o00’-121o00’E）from November 25th to December 1th in 2011. Phytoplankton species composition and abundance were studied by Uterm hl method,and the relationship between phytoplankton community and environmental factors was analyzed. A total of 65 taxa which belong to 30 genera of 3 phyla were identified. The phytoplankton community was mainly composed of Bacillariophyta and Dinophyta,and there were also a few species belonging to Chrysophyta. Most of the ecotypes of phytoplankton species were neritic,and＆amp;nbsp;preponderant species were Paralia sulcata （Ehrenberg） Cleve, Coscinodiscus excentricus Ehrenberg, Ceratium fusus（Ehrenberg）Dujardin,Pleurosigma affine Grunow, Coscinodiscus asteromphalus Ehrenberg and Nitzschia sp., etc. Cell abundance ranged from 0.89＆#237;103 to 16.4＆#237;103 cells/L with an average of 4.36＆#237;103 cells/L. Horizontally, the surface distribution of cell abundance in the survey area was dominated by diatoms, and the high value appeared in the areas to the south of the Liaodong Bay and to the west of the Bohai Strait. The high cell abundance of dinoflagellates mainly appeared in western and northwestern part of the survey area. In the vertical direction, phytoplankton cell abundance increased in the upper water, and then decreased in the bottom water. Both of Shannon-wiener diversity index and Pielou’s evenness index were higher in the central part of the survey area. By comparing the results with historical data, it can be inferred that the shift phytoplankton community of from diatom dominated community to diatom-dinoflagellate dominated community occurred in central Bohai Sea during the last 30 years. PCA and CCA analysis revealed that the change of nutrient structure in central Bohai Sea might be responsible for this community shift.