微囊藻和栅列藻的垂直迁移及生态学意义

本研究在自制沉降柱中,检测铜绿微囊藻(Microcystis aeroginosa)和斜生栅列藻(Scenedesmus obliquus)不同生长时期的细胞群体在不同光照条件下的垂直迁移。本文首次提出藻密度衰减系数(K)的概念、拟合方法和生态学意义,并根据等细胞密度沉降面的沉降速率来计算细胞沉降速率(Vc),以这两个参数来衡量细胞的沉降特性,对细胞垂直迁移研究的方法进行了的探索。结果表明,两种藻细胞群体在三个生长时期和四种光照条件的沉降特性表现已定的差异。栅列藻细胞密度的衰减系数(K)最小值为-0.0021cm^-1(上浮),最大值为0.0065cm^-1(下沉);微囊藻的K最小值为-0.0029cm^-1(上浮),最大值为0.0036cm^-1(下沉)。两种藻沉降曲线的指数拟合的R²大多在0.6以上,说明K值是一个较好的衡量细胞群体沉降特性的参数,细胞密度与深度的关系较好地服从指数规律。细胞沉降速度V的最大值(4.681cm·h^-1,下沉)出现在栅列藻的指数期,最大上浮速率-1.790cm·h^-1,出现在微囊藻的稳定期。本文得到的活体藻细胞群体的垂直迁移特性差异的实验数据,说明该实验方法的适用性和两种藻沉降特性差异的可检测性。本文讨论了水华优势种形成与藻细胞群体迁移特性之间的关系。

Vertical migration of Microcystis and Scenedesmus and its ecological significance

The vertical migration of cell of two algal species (Microcystis aeroginosa and Scenedesmus obliquus), represented by attenuation coefficient (K) and sinking velocity (V), was studied in self-made sinking column. Results showed that the property in vertical migration of these two species were different in 4 irradiation intensities and 3 growth phases. For Scenedesmus obliquus colony, the K_min is -0.0021 cm^-1 (migrating upward) and the K_max is 0.0065 cm^-1 (sinking downward),and the value of relative parameter is-0.0029 cm^-1and 0.0036 cm^-1 for Microcystis colony respectively. Most values of R² of exponential simulation was more than 0.6, which showed R² can reflect the property of cell sinking and the variation of cell density according to depth exponentially. The maxim of sinking velocity (V_max), 4.681cm·h^-1 (downward), was obtained in Scenedesmus colony in exponential phase, and the V_min of migration velocity,-1.790 cm·h^-1 (upward) was present in stable phase of Microcystis colony. The data gained in this study may be a direct evidence to explain the mechanism of population domination of Microcystis spp.