2013年春夏季天津近岸海域浮游植物的群落结构

Phytoplankton Community Structure in the Tianjin Nearshore Waters during the Summer and Autumn of 2013

于2013年春季（6月）和夏季（8月）对渤海湾天津近岸海域的浮游植物和环境因子进行了综合调查,共发现浮游植物4门、72种,其中6月39种,8月63种,主要由硅藻和甲藻组成,优势种以硅藻为主,仅有少量的蓝藻和裸藻;6月的优势种是硅藻门的窄隙角毛藻（Chaetoceros affinis）、星脐圆筛藻（Coscinodiscus asteromphalus）及圆筛藻（Coscinodiscus spp.）;8月的优势种是硅藻门的丹麦细柱藻（Leptocylindrus danicus）、尖刺拟菱形藻（Pseudonitzschia pungens）、中肋骨条藻（Skeletonema costatum）。6月浮游植物细胞密度为2.14×10^4-836.67×10^4个/L,平均值为129.31×10^4个/L;8月浮游植物细胞密度为6.83×10^4-16 042.50×10^4个/L,平均值为2 461.63×10^4个/L;在调查海域的各采样点中,细胞密度均以硅藻占比最大,分别占浮游植物细胞总密度的99%和95%以上,浮游植物细胞密度的分布趋势与硅藻细胞密度分布趋势基本一致。6月各采样点浮游植物Shannon-Wiener多样性指数（H＇）为0.96-3.69,平均值为2.87;均匀度指数（J）为0.28-0.95,平均值为0.71;丰富度指数（d）为0.60-1.21,平均值为0.88。8月的H＇为0.01-3.58,平均值为1.48;J为0.002-0.86,平均值为0.33;d为0.65-1.37,平均值为0.91。典范对应分析（canonical correspondence analysis;CCA）浮游植物分布与环境因子之间的关系,影响渤海湾浮游植物分布的关键因子是水温、盐度、溶解氧、亚硝酸盐、硅酸盐。

Tianjin is a coastal city of the western Bohai Sea. Rapid economic growth, especially in the port area, has increased pollutant loads discharged to nearshore waters and led to more severe environmental deterioration in recent years. Bohai Bay is a typictal semi-closed bay, and low exchange with the open waters has caused the accu- mulation of nutrients and resulted in the frequent occurrence of red tides. The phytoplankton community is sensitive to the environmental change and widely used to assess the status of coastal aquatic ecosystems. In June and August of 2013, phytoplankton and water samples were collected in the Tianjin nearshore waters at 15 sites. The phyto- plankton community structure was analyzed and the physical - chemical parameters of the water were determined to provide basic data on the coastal ecosystem. Canonical correspondence analysis （CCA） was used to analyze the re- lationship between the phytoplankton community and environmental variables in order to predict community succes- sion and establish the level of pollution control necessary to protect the environment of this region. Phytoplankton was collected with a type III plankton net towed vertically from the bottom to the surface at each sampling site, fixed with 1.5% Lugol＇s solution and preserved with 5% formaldehyde. The identification and counting of the phyto- plankton was conducted under an Olympus BX51 microscope. Water temperature, pH, dissolved oxygen and salini- ty were measured in situ with a multifunctional water quality analyzer, transparency was measured with a secchi disk, and soluble reactive phosphorus （SRP）, nitrite nitrogen （NO2-N）, nitrate nitrogen （NO3-N）, ammonia ni- trogen （NH4-N） and silicates（ SiO3 ） were measured in the laboratory. A total of 72 phytoplankton species were re- corded in the two seasons, 39 in summer and 63 in autumn. The phytoplankton community was composed primarily of Bacillariophyta and Dinophyta, with Bacillariophyta dominating, and fewer species of Cyanophyta and Eugleno- phyta. In June, the Bacillariophyta species Chaetoceros affinis, Coscinodiscus asteromphalus and Coscinodiscus spp. dominated. In August, the prevalent species were the Bacillariophyta species Leptocylindrus danicus, Pseudo- nitzschia pungens and Skeletonema costatum. Phytoplankton abundance ranged from 2. 14×10^4 to 836. 67×10^4 cells/L in June, with an average of 129.31 ×10^4 cells/L. In August, the abundance ranged from 6.83×10^4 to 16 042.50 ×10^4 cells/L with an average of 2 461.63×10^4 cells/L. Bacillariophyta accounted for 〉99% of the to- tal phytoplankton in June and 〉 95% in August at all sampling sites. The distribution of phytoplankton density and Bacillariophyta density were identical. In June, the mean values （ range in parentheses） for Shannon-Wiener diver- sity index （H＇）, Pielou index （J） and Margalef index（d） were 2.87 （0.96 -3.69）, 0.71 （0.28 -0.95） and 0.88 （0.60 - 1.21 ）, respectively. In August, the mean values for H＇, J and d were 1.48 （0.01 - 3.58）, 0.33 （0. 002 -0. 86） and 0.91 （0.65 - 1.37）, respectively. CCA results indicate that water temperature, salinity, dissolved oxygen, nitrite nitrogen and silicates were the leading environmental variables influencing the phytoplank- ton community distribution.