水中主要阳离子对铜绿微囊藻生长及多糖的影响

通过室内培养试验,在65μmol·m-2·s-1光照度和12 h∶12 h光暗比下,模拟野外水体中铜绿微囊藻（Microcystis aeruginosa）的生长,研究了水中主要阳离子Ca、Mg、K、Na质量浓度的变化对铜绿微囊藻生长以及多糖的影响。依据自然水体中Ca、Mg、K、Na的实际浓度水平结合已有研究得到的抑制浓度,试验分别设定了5个质量浓度梯度的培养基,其中Ca质量浓度梯度为0、10、20、50、100 mg·L-1,Mg质量浓度梯度为0、2、5、10、20 mg·L-1,K质量浓度梯度为5、10、20、50、100 mg·L-1,Na质量浓度梯度为18、30、50、100、200 mg·L-1。试验测定的生理生化指标包括培养周期内每天铜绿微囊藻的藻细胞密度和对数生长期内铜绿微囊藻溶解性胞外多糖（sEPS）、固着性胞外多糖（bEPS）和胞内多糖（IPS）的含量。试验结果表明：低质量浓度的Ca对微囊藻的生长没有明显影响,高质量浓度的Ca（〉50 mg·L-1）会抑制铜绿微囊藻的生长但同时铜绿微囊藻合成多糖总量（TPS）会增加,Ca质量浓度的增大对铜绿微囊藻胞外多糖的分泌呈现先促进后抑制的趋势,并在刺激铜绿微囊藻细胞分泌多糖的同时会促进其溶解。Mg缺失时,铜绿微囊藻的生长会受到显著的抑制,较高质量浓度的Mg（〉5 mg·L-1）也会抑制铜绿微囊藻的生长但同时铜绿微囊藻合成多糖总量（TPS）会增加,Mg在适宜质量浓度（5 mg·L-1）会抑制多糖分泌、防止多糖溶解。K离子质量浓度的变化对微囊藻的生长无明显影响但铜绿微囊藻TPS的量呈现先增加后减少的趋势,K对多糖的分泌并没有显著影响,但对多糖的溶解呈现先促进后抑制的作用。Na离子质量浓度的变化对铜绿微囊藻的生长以及合成TPS的量均无明显影响,Na质量浓度增大对多糖的分泌的影响与Ca的一致,但影响的程度明显小于Ca的影响,其质量浓度的增加对多糖的溶解过程有轻微的促进作用。

Effect of major cations in water on the growth and polysaccharide contents of Microcystis aeruginosa

Effects of major cations （calcium, magnesium, potassium, sodium） on the growth and polysaccharide content of Microcystis aeruginosa were studied under 65 μmol m2 s-1 illumination and ratio of light and dark of 12 h ： 12 h. Five levels of the cations were set according to their concentrations in wild water and inhibitory concentration obtained from existing research. The concentration gradient of Ca is 0, 10, 20, 50, 100 mg.L-1, Mg is 0, 2, 5, 10 and 20 mg.L-1, K is 5, 10, 20, 50, 100 mg L-1 and Na is 18 30, 50, 100, 200 mg.L-1. The Microcystis aeruginosa cell density was analyzed daily during the culture period and at the logarithmic phase. Polysaccharide content （soluble extracellular polysaccharide, sEPS; bound extracellular polysaccharide, bEPS; intracellular polysaccharide, IPS） was measured. Results showed that low concentration of Ca has no significant effect on the growth of M. aeruginosa. With the increase of Ca （〉50 mg.L-1） concentration, the contents of total polysaccharide （TPS） were increased while the growth of M. aeruginosa was inhibited. The increases of Ca concentration promote the secretion of polysaccharide at first and then inhibit it as the concentration of Ca continues to increase. It stimulated the secretion of polysaccharide while facilitating its dissolution. The absence of Mg notably inhibits the growth of M. aeruginosa. With the increase of Mg （〉5 mg L-1） concentration, the contents of TPS were increased while the growth of M. aeruginosa was inhibited. An appropriate concentration of Mg （5 mg. L-1） can inhibit the secretion and dissolution of polysaccharides. The concentrations of K had negligible effects on the growth of M.. aeruginosa and polysaccharide secretion. Furthermore, the contents of TPS increased as the K concentrations increased from 0 to 10 mg L-1, but it then decreased while the K concentration went up from 10 to 100 mg.L-1. With the increase of K concentration, the amount of dissolved polysaccharide increased initially but decreased subsequently. The concentrations of Na had negligible effects on the growth of M. aeruginosa and the contents of TPS. The increase of Na concentration affect the secretion of polysaccharide in accordance with the Ca, but the impact was significantly less than the influence of Ca. The increase of Na concentration slightly promote the dissolution of polysaccharide.