根据2006年7月对长江口外海域67个站点的大面积综合调查结果,分析了浮游植物的优势种、细胞丰度和叶绿素a转换生物量的分布特征.硅藻细胞丰度占绝对优势,其中以菱形海线藻和中肋骨条藻数量最大.各站点浮游植物细胞丰度范围1.42～448.25×106 cell/m3,平均值为90.47×106cell/m3.通过细胞体积生物量转换法,计算了2006年夏季长江口外海区浮游植物的叶绿素a转换生物量,平均值为4.41 mg Chl.a/m3,各站点间变幅较大,范围从0.02到34.08 mg Chl.a/m3.长江口外海区夏季的浮游植物生物量在冲淡水区最高,江苏外海居中,而近河口区和台湾暖区最低.转换生物量大于4.0 mg Chl.a/m3的高值区位于冲淡水区(3 m层)盐度为28.0的等值线两侧,且处于NH3-N和P的低值区.悬浮物浓度、温盐、水体稳定度和营养盐是影响长江口外海域浮游植物分布的主要环境因子.在本次调查期间长江口外海不存在氮营养盐限制,冲淡水区存在明显的P营养盐限制,台湾暖流区存在潜在的Si营养盐限制.%The distribution characteristics of dominant phytoplankton species and their cell abundance and cell volume conversion biomass off the Changjiang Estuary were analyzed based on a comprehensive survey conducted at 67 stations during July, 2006. The cell abundance of Diatom was dominant, which mostly consists of Thalassionema nitzschioides and Skeletonema costaturn. The cell abundance ranged from 1.42 × 106 to 448.25 × 106 cell/ma and the average value was 90. 47 × 106 cell/m3 for all of the stations.Phytoplankton conversion biomass of Chlorophyll-a was calculated by cell volume measurement. The average Chlorophyll-a biomass was 4.41 mg Chi. a/ms, with a range from 0.02 to 34.08 mg Chi. a/m3. Based on conversion biomass, dominant diatoms were Coscinodiscus jonesianus, Coscinodiscus radiatus Ehrenberg and Thalassionerna nitzschioides, and dominant dinoflagellates were Peridiniurn conicurn, Ceratiun fusus,Ceratium tripos and Ceratium furca. The trend and magnitude of the conversion biomass distribution were similar to those of the Chlorophyll-a distribution of SeaWiFS monthly ocean color data. This area could be divided into 4 parts according to phytoplankton conversion biomass: the dilute plume area is the highest biomass area; the estuary area and Taiwan Warm Current area are the lowest biomass areas;and the area off Jiangsu Coast current area is the middle biomass area. The area of conversion biomass more than 4.0 mg Chl. a/m3 corresponded well to the salinity contour 28.0 adjacent to the area of Changjiang river plume and areas with low NH3-N and P.
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