Effect of light intensity on growth of <i>Microcystis flos-aquae</i> colonies size

Abstract

大量微囊藻群体的形成和聚集是微囊藻水华形成的重要条件.光照强度是影响微囊藻生长的重要因素之一.为了了解光照强度对水华微囊藻(Microcystis flos-aquae)群体大小增长的影响,以太湖微囊藻水华优势种之一的水华微囊藻作为研究对象,开展了不同光照强度对水华微囊藻群体大小增长的影响研究.共设置5个不同光强处理组,依次为G1:2000 lx;G2:4000 lx;G3:8000 lx;G4:16000 lx;G5:变化光照强度(模拟野外光强).实验期间,G1~G5组大于100细胞群体的平均大小分别为255、480、630、763和662 cells/群体.胞外多糖含量分析显示水华微囊藻形成的群体越大,胞外多糖含量越高.结果表明,低光照强度不利于太湖水华微囊藻群体大小的增长,而变化光照强度和高光照强度有利于水华微囊藻群体大小的增长.研究结果解释了太湖夏季野外变化光照强度和高光照强度有利于微囊藻水华形成的原因.;The formation and accumulation of massive Microcystis colonies was an important prerequisite in Microcystis blooms formation. Light intensity was an essential ecological factor affecting the growth of Microcystis. To understand the effect of light intensity on growth of Microcystis colonies size, a study was conducted on the effect of different light intensity on the colony size growth of Microcystis flos-aquae which was one of the dominant species of Microcystis bloom in Lake Taihu. In this study, five different light intensity treatments were set up as follows:G1:2000 lx; G2:4000 lx; G3:8000 lx; G4:16000 lx; G5:change light (simulating light intensity changes in the field). During the experiment, the average size of colony (above 100 cells) of M. flos-aquae in G1-G5 were 255, 480, 630, 763 and 662 cells/colony, respectively. The analysis of extracellular polysaccharides showed that extracellular polysaccharides concentration increased with the increase of M. flos-aquae colony size. Our results showed that low light intensity was disadvantage for the growth of M. flos-aquae colony size. However, high light intensity and variation of light intensity were advantage for the growth of M. flos-aquae colony size. This study explained why light intensity changed in the field and high light intensity were in favor of the formation of Microcystis bloom in summer in Lake Taihu.