水动力条件下微囊藻群体分解物对微囊藻群体形成的作用和机制

Microcystis aeruginosa colony, a main form of the algae in cyanobacterial blooms, plays an important role in waterblooms in eutrophicated lakes, while the mechanism of colony formation in Microcystis aeruginosa was not clear yet. The present study confirmed that it was influenced by the predation of zooplanktones and some abiotic factors (illumination, nutrients, calcium ion, etc), while the influence of hydrodynamic force was paid very little attention. The applicant observed that colony formation in Microcystis aeruginosa on the condition of hydrodynamic force, and analysed the relationship between colony characteristic and hydrodynamic force. At the beginning of the research we discovered that the large Microcystis aeruginosa colony in raw water nutrient of Taihu lake on the condition of hydrodynamic force, meanwhile was related to the density of Microcystis aeruginosa colony, the season and etc. Based on this preliminary study, we assumed that microcystis cells would generate colony inductors and accumulate as growing; on the condition of hydrodynamic force Microcystis aeruginosa colony decomposer effect the property of cell membrance and participate in the bridging and junction between cells, which might be a new formation mechanism of Microcystis aeruginosa colony. To confirm this hypothesis, the influence of the secretions on the formation of Microcystis aeruginosa colony, junction between Microcystis aeruginosa cells and membrane property was studied at three levels (colonies, cell-cells and cell membrane) based on quantification of hydrodynamic force and the application of attenuated total reflection infrared spectroscopy (ATR-FTIR), liquid chromatography-mass spectrography (LC-MS), and Zeta potential analysis technology. This project would study the mechanism of colony formation in Microcystis aeruginosa with a new perspective and provide a scientice basis for the treatment of water-blooms.

微囊藻群体是富营养化湖泊蓝藻水华主要存在形式并着起重要作用，但微囊藻群体形成机制尚未阐明。目前研究多认为与浮游动物摄食和非生物因子（光照、营养盐和钙离子）有关。申请人首次观察到微囊藻细胞在水动力作用下形成群体，并分析微囊藻群体与水动力之间的关系。在前期研究中，我们发现在水动力作用下原水培养液中微囊藻细胞形成大群体，与培养液中微囊藻群体密度和季节有关。我们推测微囊藻群体内含有群体感应物并随生长繁殖积累，在水动力作用下微囊藻群体分解物影响藻细胞膜性质并参与群体中细胞-细胞架桥连接，这可能是微囊藻群体形成的一个新机制。为证实这一假说，我们将在定量化水动力基础上，采用衰减全反射红外光谱，液相色谱质谱和Zeta电位分析等技术，从群体特征-细胞与细胞-细胞膜三个层次，观测微囊藻细胞形成群体特征，细胞膜性质和群体中细胞-细胞连接物。本课题将新的视角阐明微囊藻群体形成机制，并为治理蓝藻水华提供科学依据。

随着水体富营养化加剧，蓝藻水华暴发频率和范围增加，是国内外富营养化水体中常见的水环境问题，在我国更为突出。天然水体中蓝藻水华主要以群体的形式存在，铜绿微囊藻群体形成机理仍不清楚。.本研究在有机玻璃环形槽中控制水体流速开展室内培养实验，采用声学多普勒流速仪测定流场，通过能谱分析计算得到能量耗散，最小漩涡尺寸(ηKolmogrov)，剪切力和应变率等水动力特征参数值；通过微颗粒模拟，原水条件培养和钙镁离子条件实验，观察微藻群体形态，细胞膜性质和ζ电位等参数，推导水动力作用下铜绿微囊藻分解物对微囊藻群体形成的影响及机理，为防治蓝藻水华提供科学依据。.本项目完成的主要工作和取得的主要成果有：.(1) 进行了水动力定量化分析。使用声学多普勒流速仪测定水体流场，计算得到流动水体能量耗散，内部最小漩涡尺度和剪切力等内部特征参数；.(2) 在水动力作用下开展了聚苯乙烯胶球颗粒和铜绿微囊藻颗粒群体形成研究。研究得到水动力作用提高微颗粒群体形成，在流速为25cm/s，剪切力和Kolmogrove长度分别为0.0447 Pa和149.22μm时，群体最大所含细胞数为12-13个，较天然水体中群体形态存在较大差异；.(3) 在水动力作用下开展原水，单细胞分解产物和群体分解产物对微囊藻群体形成影响研究。得到群体分解产物对微囊藻细胞群体形成影响更大，最大群体达650个，群体特征显著，微囊藻群体细胞膜主要由醛基，羧基，羟基和氨基等官能团组成，为微囊藻细胞相互链接提供基质，群体形成具有较好的稳定性和疏水性，在流速为25cm/s时更利于群体的形成。.(4) 在水动力作用下开展钙镁离子，过滤不同孔径原水和不同放置时间原水对微囊藻群体形成的影响研究。在流速为15cm/s的水动力条件下，钙镁离子影响微囊藻群体的形成，当钙镁离子浓度超过20mg/L和5mg/L时，钙镁离子对微囊藻群体形成影响较小。过104微米原水培养液中微囊藻群体最大细胞数，平均群体所含细胞数和群体细胞数所占比例分别为220个，17个和超过70%，原水中影响微囊藻群体形成的物质将发生降解，降低对微囊藻群体形成的作用。