根据2014年8月(夏季)、2014年11月(秋季)、2015年1月(冬季)和2015年5月(春季)对连云港邻近海域的网采浮游植物的调查,共鉴定出浮游植物8门68属155种(含变种、变型),主要由硅藻(115种)和甲藻(30种)组成.冬季细胞丰度(230.13×104 cells/m3)显著高于春(24.67×104 cells/m3)、夏(119.78×104 eells/m3)、秋(90.25×104 cells/m3)三季,优势种主要有密连角毛藻(Chaetoceros densus)、中肋骨条藻(Skeletonema costatum)、三叶原甲藻(Prorocentrum triestinum)、卡氏角毛藻(Chaetoceros castracanei)和微小细柱藻(Leptocylindrus minimus)等.浮游植物群落参数(种类数、细胞丰度、Shannon-Wiener多样性、Margalef丰富度、Pielou均匀度等指数)和环境因子(温度、盐度、pH值、DO、COD和营养盐)均存在季节显著差异.聚类、多维尺度和相似性分析结果也表明,浮游植物群落组成季节差异显著.冗余分析表明,浮游植物群落的主要影响因子为营养盐、悬浮物、盐度和COD.结合历史数据分析表明,浮游植物优势种由硅藻占主要优势演替为硅藻和甲藻联合占优势.营养盐结构已有较大变化:硝酸盐浓度急剧升高,由20世纪80年代的1.30 μmol/dm3升至2014 ～2015年的24.58 μmol/dm3;磷酸盐浓度也由20世纪80年代的0.19 μmol/dm3升至2014 ～2015年的0.48 μmol/dm3;N/P由8.3升高至91.9.%This paper presents the seasonal community composition of net-collected phytoplankton near the sea area of Lianyungang.The samples were collected in January (winter),April (spring),August (summer) and November (autumn) in 2014 ～2015.A total of 8 phyla,68 genera,and 155 species were recorded including 115 diatom species and 30 dinoflagellate species,and other rare species such as Euglenophyta,Chrysophyta,Cryphophyta,Cyanophyta,Chlorophyta and Xanthophyta.The phytoplankton abundances in winter (230.13 × 104 eells/m3) was significantly higher than those in spring (24.67 × 104 cells/m3),summer (119.78 × 104 cells/m3) and autumn (90.25 × 104 cells/m3).Chaetoceros densus,Skeletonema costatum,Prorocentrum triestinum,C.castracanei,and Leptocylindrus minimus were the main dominant species.Both the phytoplankton community parameters (abundance,species number,Shannon-Wiener diversity,Pielou evenness,and Margalef richness index) and the environmental variables (temperature,salinity,pH value,DO,suspended solids,COD,DIN,and PO43--P levels) are seasonally different.The seasonal and spatial distributions of net-collected phytoplankton community are significantly different according to the results of cluster,multidimensional scaling and similarity analysis.Redundancy analysis shows that nutrition (DIN and PO43--P),salinity,DO,and COD are the main factors influencing phytoplankton community in turn.Since 1980s,the environmental factors in the study area had changed obviously:concentrations of NO3--N dramatically increased from 1.30 μmol/dm3 in 1983 ～ 1984 to 24.58 lμ moL/dm3 in 2014 ～ 2015;and N:P ratio also increased from 8.3 in 1983 ～ 1984 to 91.9 in 2014 ～ 2015.The community structure has also experienced variation since 1980s.Combined with the historical data,we found that the dominant species of phytoplankton are shifting from diatoms alone to dinoflagellates and diatoms.
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