中文摘要：

根据2010年春季（4月）乐清湾的调查结果,分析了该海域浮游生物的种类组成、优势种、丰度、多样性及其对环境因子的影响。共鉴定出浮游植物6门、162种;其中,硅藻144种,占总种数的88.9%,甲藻12种,占总种数的7.4%。浮游动物10类、37种;其中,桡足类19种,占总种数的51.4%。浮游植物和浮游动物的平均丰度分别为38.12×104个/m3和37.26个/m3,其空间分布格局均呈由内湾至外湾逐渐降低。浮游植物优势种为琼氏圆筛藻（Coscinodiscus jonesianus）和中国盒形藻（Biddulphia sinensis）,浮游动物优势种为真刺唇角水蚤（Labidocera euchaeta）和针刺拟哲水蚤（Paracalanus aculeatus）。浮游植物和浮游动物平均Shannon-Weiner多样性指数（H＇）分别为2.35和1.16,浮游生物群落沿环境梯度更替的现象极显著。乐清湾富营养化严重,可溶性无机氮和活性磷酸盐平均浓度分别为0.756mg/L和0.038mg/L。对比历史资料可知,近30年来乐清湾无机氮和磷酸盐呈升高趋势,较1982年同期分别上升112%和131%;同时浮游生物丰度有所下降,且浮游植物优势种有一定程度的变化,但浮游植物群落仍以硅藻为主、甲藻其次,而浮游动物群落仍以桡足类为主。

英文摘要：

The species composition, dominant species, and abundance of plankton were investigated in Yueqing Bay on April 13, 2010. A total of 162 phytoplankton species which belonged to 6 phyla were identified. The phyto- plankton community was mainly composed of Bacillariophyta （ 144 species, 88.9% ） , followed by Pyrrhophyta （ 12 species, 7.4% ）. On the other hand, 37 zooplankton species which belonged to 10 groups were identified, 51.4% of them were Copepoda （19 species）. The average cell abundances of the phytoplankton and zooplankton were 38.12 x 104 cells/m3 and 37.26 cells/m3 , respectively. The spatial distributions of phytoplankton and zooplankton abundances were decline from inner bay to open bay. The dominant species of phytoplankton were Coscinodiscus jo- nesianus and Biddulphia sinensis, and that of zooplankton were Labidocera euchaeta and Paracalanus aculeatus. The average diversity indexes （H＇） of phytoplankton and zooplankton were 2.35 and 1.16, respectively. Moreover, the plankton community in different areas was varied with the changed environmental gradients. Yueqing Bay was seri- ous eutrophication, and the contents of DIN arid DIP were 0. 756 mg/L and 0.038 rag/L, respectively. Compared to the data of May, 1982, DIN and DIP contents increased by 112% and 131%, respectively. The decline of phy- toplankton abundance was observed comparing to the data of 1982, and Copepoda remained the dominant group in community of zooplankton.