中文摘要：

报道了2008—2009年4季度海南西部近岸浮游植物群落的周年动态并探讨其主要关联因素。165份样品经鉴定共有浮游植物4门74属155种（含5变型和2变种）,周年平均丰度为（6.36±4.75）×103cells/L。硅藻在物种组成和丰度上均占绝对优势,其次为甲藻,蓝藻（束毛藻）在7月增殖。主要优势种为菱形海线藻（Thalassionema nitzschioides）、奇异棍形藻（Bacillaria paradoxa）、具槽帕拉藻（Paralia sulcata）、旋链角毛藻（Chaetoceros curvisetus）、笔尖根管藻（Rhizosolenia styliformis）、束毛藻（Trichodesmium spp.）、海洋原甲藻（Prorocentrum micans）等。物种组成的季节差异较大,10月浮游植物种类贫乏,1月次之,4月、7月最丰富。丰度10月最高,季节差异并不明显。束毛藻在4月、7月呈斑块状群聚分布。浮游植物周年平均丰度并不高（〈1.0×104cells/L）。不同季节优势种有明显的交错和变化,菱形海线藻、奇异棍形藻、具槽帕拉藻为全年优势种。浮游植物物种多样性指数和均匀度都表现出较高的值,均匀度与多样性指数的季节变化特点基本一致,群落多样性高的季节物种均匀度也好。物种多样性指数指示调查区水体遭受污染程度低,水质状况优。调查区各季节的浮游植物丰度与温度之间无显著的相关关系,1月丰度与盐度则呈密切负相关关系。10月浮游植物丰度与无机氮（DIN）呈密切的正相关关系。7月浮游植物丰度与活性磷酸盐（PO4-P）呈密切的负相关关系。浮游动物对浮游植物的摄食压力直接影响到后者的丰度变动,并伴随着海区生态系统的相关复杂现象及生物学过程的作用。

英文摘要：

Annual variation of phytoplankton community in coastal waters at western Hainan Island and its related af- fecting factors were analyzed based on four cruise surveys of four seasons carried out in 2008 and 2009. A total of 155 species （including 5 forms and 2 varieties） belonging to 74 genera of 4 classes were identified in 165 samples, in which diatoms were predominant in the species composition and the cell abundance. Dinoflagellates contributed the second major group. Cyanobacteria abundance increased in July. The dominant species were Thalassionema nitzschioides, Ba- cillaria paradoxa, Paralia sulcata, Chaetoceros curvisetus, Rhizosolenia styliformis, Trichodesmium spp., Prorocentrum micans, etc. Among them, Thalassionema nitzschioides, Bacillaria paradoxa and Paralia sulcata were dominant in four seasons. The species composition showed a significant seasonal change while phytoplankton cell abundance did not. Phytoplankton species were lower in October than in January, while richer in April and July. The annual average cell abundance of phytoplankton was （6.36±4.75）×103 cells/L （n=165）, and the peak cell abundance appeared in October. The phytoplankton abundance of each season reduced from near-shore waters to offshore. Patch distribution of Tricho- desmium spp. were obvious in April and July. The diversity index was almost coincident with that of the Pielou evenness index. The high values of both index suggested that the phytoplankton community was in stability and the water quality was healthy in western Hainan Island. Pearson Correlate Analysis of phytoplankton cell abundance with environmental factors indicated that the phytoplankton abundance non-correlated to water temperature, correlated positively to the abio-notrogen in October, and negatively correlated to the salinity in January and to the abio-phosphate in July. The feeding stress from zooplankton directly affected annual variation of the cell abundance of phytoplankton along with influences of biological relationship even of ecosyst