夏、冬季南海北部浮游植物群落特征

Characteristics of phytoplankton community in the northern South China Sea in summer and winter

对2009年7月19日—8月16日和2010年1月6—30日南海北部(18°—23.5°N、109°—120°E)两个航次的浮游植物样品应用Utermhl方法进行了分析鉴定。结果如下:夏季样品鉴定浮游植物4门72属150种,浮游植物细胞丰度范围为(0.16—6001.78)×103个/L,平均细胞丰度为26.49×103个/L,硅藻的平均细胞丰度为25.81×103个/L,主要优势种属有铁氏束毛藻(Trichodesmium thiebautii)、菱形海线藻(Thalassionema nitzschioides)、柔弱伪菱形藻(Pseudo-nitzschia delicatissima)及裸甲藻(Gymnodinium spp.)等;冬季样品鉴定浮游植物4门58属168种,浮游植物细胞丰度范围为(0.08—37.52)×103个/L,浮游植物平均细胞丰度为2.69×103个/L,硅藻的平均细胞丰度为2.49×103个/L,主要优势物种为菱形海线藻、伏氏海线藻(Thalassionema frauenfeldii)及短刺角毛藻(Chaetoceros messanensis)等;夏季调查区5m层浮游植物细胞丰度的平面分布由近岸到外海迅速减少,高值区主要在广东东部近岸及海南东部近岸;冬季则在珠江口近岸和海盆区出现较高值。两次调查中,浮游植物细胞丰度在浅水站位(<200m)远高于深水站位(>200m);较冬季相比,夏季浮游植物平均细胞丰度偏高,但物种丰富度却略偏低。夏、冬季浮游植物的香农-威纳多样性指数平均值分别为2.12和2.36,Pielou均匀度指数平均值分别为0.79和0.81。两个航次调查中,浮游植物细胞丰度均与盐度表现出显著性负相关性;在冬季还与磷酸盐浓度表现出显著性负相关性。

Two cruises were carried out in the northern South China Sea （18°-23.5°N, 109°-120°E） in summer （19th July to 16th August, 2009） and winter （6＇h to 30th January, 2010）. Phytoplankton samples were analyzed and 150 taxa belonging to 72 genera of 4 classes were identified by UtermiJhl method in summer samples. The cell abundance of phytoplankton ranged 0.16-6001. 78 × 103 cells/L, the average cell abundance was 26.49 × 103 cells/L, in which Bacillafiophyta accounted for 25.81 × 103 cells/L. The dominant species in summer were Trichodesmium thiebautii, Thalassionema nitzschioides,Pseudo-nitzschia delicatissima and Gymnodinium spp. etc. 168 taxa belonging to 58 genera of 4 classes were identified in winter samples, the average cell abundance was 2.69 × 103 cells/L, cell abundance of phytoplankton ranged in which Bacillariophyta abundance was 0. 08-37. 52 × 103 cells/L, the 2.49 × 103 cells/L. The dominant species in winter were Thalassionema nitzschioides, Thalassionema frauenfeldii and Chaetoceros messanensis, etc. The average cell abundance of phytoplankton in the 5m layers reduced rapidly from coastal zone to open sea in summer, and ahigh abundance value of phytoplankton occurred in coastal seawaters of east of Guangdong Province and east of Hainan Provence, while a high value of phytoplankton cell abundance occurred in Pearl River Estuary and sea basin in winter. In general, phytoplankton cell abundance was lower at deep-water stations （〉200m） than at shallow water stations （〈200m） during this two cruises. The average cell abundance of phytoplankton in summer was higher, but species richness was lower than that in winter. The average Shannon-Wiener diversity index of phytoplankton community were 2.12 and 2.36 in this two cruises, average Pielou index were 0.79 and 0.81, respectively. Pearson Correlate Analysis of phytoplankton cell abundance with environmental factors showed that the phytoplankton cell abundance correlated negatively （in 0.01 level） to the salinity in this two cruises and negatively correlated （in 0.01 level） to phosphate concentration in winter.