低光低温联合作用对铜绿微囊藻复苏能力的影响

运用正交实验设计方法研究了低温低光联合作用对铜绿微囊藻(Microcystis aeruginosa FACHB 905,以下称905)生长与光合活性的影响.采用比色法测定了铜绿微囊藻细胞叶绿素、类胡萝卜素的含量及组成比例,同时使用植物效率分析仪(Water-PAM)测定了905细胞的光合活性,并通过回复培养验证了其光合作用回复的能力.结果表明,相对于正常培养条件,低温低光对M.aeruginosa的生长均有不同程度的抑制作用,在9℃各处理组中,M.aeruginosa基本无法生长,因此可推测905细胞生长的温度阈值应高于9℃.在12℃各处理组中,光强为影响905细胞生长的主要因子,12℃、100 lx能促进其初期的生长,据此推测这一条件可能为微囊藻复苏的起始条件.15℃、100 lx处理组中,藻生长最快,生物量(以叶绿素a计)最大值为0.88 mg/L左右,分别为其他处理组的2～17倍;并且在15℃各处理组中,905细胞在"微光"(100 lx)处理组中叶绿素含量,电子传递速率及最大光量子产量均高于"低光"(500 lx)处理组,显示出相对于"低光"条件,铜绿微囊藻对"微光"的适应性更强.而回复培养的数据显示,9℃和12℃处理组样品在5 d内能迅速恢复其生长与光合活性,并最终与15℃处理组样品同样,荧光量子产量最终保持在0.55～0.6左右,并能稳定生长.研究结果对揭示铜绿微囊藻对湖泊底泥中越冬环境条件的耐受阈值及复苏的起始条件有重要意义.

Recruitment Ability of Microcystis aeruginosa Under Low Light-Low Temperature Combination

The responses of growth and PS II activities in Microcystis aeruginosa (FACHB 905) have been studied under a condition of low light-temperature combination use orthogonal experiment method. The contents and proportions of chlorophyll and carotenoid were determined by colorimetry, the PS II activities were assayed with a Water-PAM, and also, the photosynthesis recovery of M. aeruginosa was verified via reculture under a normal condition. The results showed that recruitment of M. aeruginosa should not be triggered since it could hardly grow under the temperature of 9 degrees C. Under 12 degrees C, the growth was greatly affected by the light intensity. 12 degrees C & 100 lx combination was considered to be the threshold value to induce recruitment of Microcystis due to the physiological responses in growth and photosynthetic system. The growth of alga was obviously inhibited in all samples. However, the biomass under 15 degrees C & 100 lx combination was the largest, which reached about 0.88 mg/L, and it was about 2-17 times compared to the other samples, respectively. We also found FACHB 905 could persist longer under low light intensity (100 lx) than a relative higher intensity (500 lx) under 15 degrees C, since the chlorophyll content, electron transfer rate and yield were relative higher in combination. Reculture of M. aeruginosa was conducted after a 20 d study, samples under the temperatures of 9 degrees C & 12 degrees C recovered soon in growth characters and PS II activities during 5 days. Meanwhile, all the samples of FACHB 905 reached a rather stable growing status, with a fluorescence quantum yield about 0.55-0.6, like other normal cultured samples finally. The present results should be important to determine the tolerance threshold and even to reveal the probable mechanisms in overwintering and recruitment of M. aeruginosa from lake sediments.