环境因子对三峡库区铜绿微囊藻(Microcystis aeruginosa)群体形成影响及其形态特征

摘要

为揭示微囊藻群体形成机理,为有效防治水华暴发提供依据,以三峡库区铜绿微囊藻(Microcystis aeruginosa)为研究对象,研究N、P浓度,Ca2+浓度,光强,温度对铜绿微囊藻生长、胞外多糖(EPS)合成和群体微囊藻形成的影响,并对比分析了单细胞和群体微囊藻的形态特征.研究发现当N≤100 mg/L、P≤5 mg/L时,铜绿微囊藻生物量和EPS合成量随着N、P浓度增加而增加;适宜浓度的Ca2+(65 mg/L)有利于藻生长,EPS产量随着Ca2+浓度增加而降低,过高浓度的Ca2+在刺激微囊藻细胞分泌EPS的同时可能会促进其溶解,Ca2+和EPS均对微囊藻群体形成起桥架粘结作用;光照和温度对EPS合成有一定促进作用,且其促进效果均高于N、P和Ca2+作用,20℃是同时满足微囊藻生长及EPS合成的最有利条件.群体细胞比单细胞周围的胶质鞘更加明显和清晰,多糖胶鞘表面有许多Ca2+晶体,从微观角度可以确定Ca2+在EPS合成及群体形成中起着重要作用.%To reveal Microcystis aeruginosa colony formation mechanism and provide the basis for effectively controlling the algae blooming in the Three Gorges Reservoir region, impacts of N, P concentrations, Ca2+concentration, light intensity and temperature on the growth, extracellular polysaccharides synthesis and colony formation of the M. aeruginosa were investigated, and the mor-phological characteristics of single cells and M. aeruginosa groups were compared. The results showed that the biomass of M. aerug-inosa and EPS concentration increased with the increasing of N, P concentrations. The optimal Ca2+concentration for the growth of M. aeruginosa was 65 mg/L, and the EPS content decreased with the increasing of Ca2+concentration. High Ca2+concentrations might stimulate the cells to secrete the EPS and simultaneously promote the EPS to be dissolved. Both Ca2+ and EPS took the re-sponsibility for the colony formation of M. aeruginosa as the bridge bond action. Light and temperature played a role on the synthesis of the EPS, which were stronger than the promoting effects of N, P and Ca2+concentrations. 20℃ was the most favorable tempera-ture conditions for the Microcystis growth and EPS synthesis. The surrounding gelatinous sheath of cells group was more obvious and clearer than the single cell. Many Ca2+ crystals on the sheath surface of polysaccharide gums were observed. Thus, Ca2+ played an important role in EPS synthesis and colony formation.