Key Laboratory of Algal Biology of Chinese Academy of Sciences, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
Key Laboratory of Algal Biology of Chinese Academy of Sciences, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Sci Total Environ. 2020 Aug 1;728:138727. doi: 10.1016/j.scitotenv.2020.138727. Epub 2020 Apr 15.
Cyanobacteria of the genus Microcystis produces surface scum that negatively affects water quality in inland waters. This scum layer can be disintegrated and vertically dispersed by external forces (e.g., wind mixing), followed by reformation of surface scum as buoyant Microcystis colonies migrate upward. However, the recovery dynamics of Microcystis surface scum following a strong mixing event have rarely been studied. Here, we used a tank experiment to investigate the process of Microcystis surface scum recovery after a mixing event with focus on dynamics of colonies of different size classes and their contribution to that process. Microcystis colony size distribution and colony volume concentration was measured using a laser in-situ scattering and transmissometry instrument. The dynamics of Microcystis in the water column and upward colony migration velocity were strongly dependent on colony size. Larger colonies (>180 μm) with fast upward migration rates contributed the most to surface scum formation shortly after turbulence subsided. The contribution of slowly migrating smaller colonies to scum formation was observed over notably longer time. The estimated floating velocities of large colonies ranged 0.15 to 0.46 m h depending on colony size and were 5-15 times higher than those of smaller colonies (~0.03 m h). The changes in colony size distribution of Microcystis in the water column reflect the dynamics of surface scum. Analysis of size distribution of Microcystis colonies can be used for better understanding and prediction of Microcystis surface scum development in water bodies.
微囊藻属的蓝藻产生的表面浮渣会对内陆水域的水质产生负面影响。这种浮渣层可以通过外力（例如风混合）分解并垂直分散，然后随着有浮力的微囊藻菌落向上迁移，表面浮渣重新形成。然而，强烈混合事件后微囊藻表面浮渣的恢复动态很少被研究。在这里，我们使用水箱实验来研究混合事件后微囊藻表面浮渣的恢复过程，重点关注不同大小类别的菌落的动态及其对该过程的贡献。使用激光原位散射和透射仪测量微囊藻菌落的大小分布和菌落体积浓度。水柱中微囊藻的动态和向上的菌落迁移速度强烈依赖于菌落大小。沉降后不久，具有快速向上迁移率的较大菌落（>180μm）对表面浮渣的形成贡献最大。较小的菌落（<180μm）的缓慢迁移对浮渣形成的贡献则持续更长的时间。根据菌落大小，大菌落（0.15 至 0.46 m h）的估计浮动速度范围为 0.15 至 0.46 m h，比小菌落（0.03 m h）高 5-15 倍。水柱中微囊藻菌落大小分布的变化反映了表面浮渣的动态。对微囊藻菌落大小分布的分析可用于更好地理解和预测水体中微囊藻表面浮渣的发展。
