研究期间（2011年—2013年）洋山港近岸水域浮游植物的主要组成类群为硅藻，占浮游植物总密度的66％～83％。硅藻中的中肋骨条藻（ Skeletonema costatum）为绝对优势种（ Y≥0.1），其次是具槽帕拉藻（ Paralia sul-cata），其他主要优势种包括近岸低盐性种类扁圆卵形藻（ Cocconeis placentula）、具边线形圆筛藻（ Coscinodiscus mar-ginato-lineatus）和格氏圆筛藻（ C．granii），以及广布性种类尖刺伪菱形藻（ Nitzschia pungens）和菱形海线藻（ Thalas-sionema nitzschioides）。冬季的优势种类较多，种类个数皆大于10；优势种种类最少的季节是夏秋季，种类个数在2～6之间。总磷总氮浓度的季节变化明显，夏季浓度较高，冬季浓度较低。方差分析显示，3年间的浮游植物密度差异显著（P＜0.05，F（2，69）＝6.22），3年的浮游植物平均密度变化无稳定规律与港口潮汐变化有关。 Pearson相关性分析显示，硅藻密度与悬浮物、总磷呈极显著正相关（P＜0.01），洋山港海域的浮游植物密度受到磷营养盐影响极大。自20世纪80年代以来，洋山港浮游植物密度剧烈上升，20世纪80年代至20世纪90年代平均密度增幅高达103倍，20世纪90年代至2000年增幅约102倍，2000年后虽然增幅有所降低但密度仍在上升，约10倍。甲藻的优势种类数量增多且组成发生改变，硅藻的优势种类个体偏小型化。结合历史数据表明，洋山港浮游植物密度的升高及群落结构的改变与港口水质富营养、营养盐结构不平衡及磷营养盐不足密切相关。%Diatom was the dominant taxa of phytoplankton with a total phytoplankton density of 66%-83% during the study period (2011-2013).Skeletonema costatum was the dominant species in diatom taxa (Y≥0.1), and the following dominant species was Para-lia sulcata.The other major dominant species were nearshore protosalt species , including Cocconeis placentula, Coscinodiscus marginato-lineatus, C.granii, Nitzschia pungens and Thalassionema nitzschioides.There were more dominant species in winter , whose species num-ber were greater than 10, whereas those were less in summer and autumn with a species number of 2-6.The seasonal variations of total nitrogen and total phosphorus concentrations were significant with a higher level in summer and lower level in winter .Analysis of variance indicated the difference of phytoplankton density between three years was significant (P<0.05, F(2, 69) =6.22).The monthly average density of phytoplankton change each year without stable rule was related to the tidal changes in harbor .Pearson correlation analysis showed the diatom density had significant positive correlation with suspended solids and total phosphorus ( P<0.01) , thus phytoplankton density was affected by phosphorus greatly .Since the 1980s the density of phytoplankton increased significantly and the increasing rate of phytoplankton density was up to 103, 102 and 10 in 1980s, 1990s and after 2000s, respectively.The number of dominant species in dino-flagellates was increased and the species composition was also changed while the size of dominant species in diatom was minimized gradu -ally.Compared to the historical data , the increment of phytoplankton density and the change of community structure were closely associat -ed with eutrophication , imbalance of nutrient structure and phosphorus deficiency in Yangshan port .
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