升温对湖泊底泥藻细胞复苏及其生理特性的影响

EFFECTS OF ENHANCED TEMPERATURE ON ALGAE CELLS RECRUITMENT FROM SEDIMENT AND THEIR PHYSIOLOGICAL CHARACTERISTICS

为探讨藻细胞复苏过程中环境因子的作用及其细胞生理特性的变化,在连续升高温度条件下,比较了在不同N:P值的培养基中复苏藻细胞的丰度、藻群落组成动态、藻光合活性变化,同时检测了这一过程中藻细胞中Na+K+-ATPase和Ca2+Mg2+-ATPase活性的变化。结果表明:实验期间共检测到7门,62种藻,表明太湖的底泥可以作为"种源",为藻细胞的复苏提供"种子"。6℃时蓝藻就能够萌发复苏,16℃左右是最适宜藻细胞复苏的温度。在设定的温度范围内,底泥中复苏蓝藻的光合效率随着温度的升高一直增加,表明温度越高越有利于蓝藻从底泥中的萌发和复苏;但是复苏的绿藻和硅藻的光合活性一直处在被抑制状态。低N:P值培养基中复苏的藻细胞丰度远远大于其他2种培养基中复苏的藻细胞丰度,低N:P值能够显著性的激发藻细胞从底泥中的复苏。同时,低N:P比培养液中复苏藻细胞的Na+K+-ATPase和Ca2+Mg2+-ATPase活性都显著高于其他培养液中复苏藻细胞的ATPase活性;16℃时2种ATPase活性的骤然升高与最适宜藻细胞复苏的温度相吻合,而且这个温度提前于复苏藻细胞显著增加的温度(21℃)。此外,复苏藻细胞的比生长速率与Na+K+-ATPase和Ca2+Mg2+-ATPase活性都呈现显著性的线性相关(*P<0.05)。因而,藻细胞中Na+K+-ATPase和Ca2+Mg2+-ATPase活性的恢复和升高,对推动藻细胞从底泥迁移到水柱中的萌发和复苏过程具有重要的意义。

Many reports have suggested that the recruitment of some overwintered phytoplankton in the sediment may be important for the pelagic populations and may even be responsible for bloom formation. However, so far no single overwhelming environmental factor has been reported to trigger the recruitment of algal cells. And no study focused on the variation of Na＋K＋-ATPase and Ca2＋Mg2＋-ATPase activities, which may be of crucial importance for the process of algal recruitment. Besides, the sediment in lakes suffered from algal blooms could be considered as ＂seed bank＂ as many studies reported, could provide ＂seed＂ for the pelagic populations in the lake and is also significance for bloom forma- tion. Therefore, the growth and the photosynthetic activity of the ＂seed＂ triggered by the favorable outside conditions, the variation of Na＋K＋-ATPase and Ca2＋Mg2＋-ATPase activities during the period of algal recruitment, all have critical significance for further research on the process of recruitment. The article mainly focused on the environmental factors and the characteristics of the recruited algal cells, and wanted to study their effects in the process of algal recruitment. Sediment in the experiment was collected from Meili- ang Bay （31±26＇14＇＇ N, 120±11＇04 E） in Lake Taihu suffered from cyanobacaterial blooms. Three media with different N：P ratio （45：1, 29：1, 7：1） based on the BG11 medium were prepared. In the condition of enhancing temperature, the abundance of recruited algal cells and the variation of algal community in the three different media with laying the sediment were detected. What is more, algal cells photosynthetic activity measured with PHYTO-PAM-2000 in the three different media was compared. The variation of Na＋K＋-ATPase and Ca2＋Mg2＋-ATPase activities in the algal cells were also detected using the ATPase kit. The results showed that there were 62 species of algae in the study, belonging to 7 phyla. Therefore, the sediment in Lake Taihu should be considered as ＂seed bank＂, and would provide ＂seed＂ for algal recruitment in the eutrophic lake. The cyanobacteria began to recruit in 6℃ and 16℃ was the optimum temperature for algal cells recruitment. Under experimental conditions, the photosynthetic efficiency of recruited cyanobacterial ceils from sediment increased with the enhancing temperature, which suggested that the higher the temperature the better the recruitment of cyanobacterial cells from sediment. However, the photosynthetic efficiency of recruited Green algae and Diatom were both inhibited. The abundance of recruited algal cells in low N：P ratio medium was much larger than that in the other two media, and low N：P ratio could significantly trigger algal recruitment from sediment. Meanwhile, the Na＋K＋-ATPase and Ca2＋Mg2＋-ATPase activities of recruited algal cells in the low N：P ratio medium were significantly higher than that in the other two media. The rapid increases of the Na＋K＋-ATPase and Ca2＋Mg〉-ATPase activities in 16℃ coincided with the optimum temperature for algal cells recruitment. Furthermore, the specific growth rate of recruited algal cells had sig- nificantly correlation with the Na＋K＋-ATPase and Ca2＋Mg2＋-ATPase activities （＊P〈0.05）. Therefore, the restored and increased activities of both Na＋K＋-ATPase and Ca2＋Mg2＋-ATPase should play important role in algal cells recruitment from the sediment.