• 关键词：蓝藻水华  颗粒物粒径  垂向分布  太湖  数值模拟

• 基金项目：国家自然科学基金（No. 42071299， U2102207）； 江苏省林业科技创新与推广项目（No.LYKJ［2019］32）

• 李俊达
• 南京师范大学虚拟地理环境教育部重点实验室，南京 210023

• 李云梅
• 南京师范大学虚拟地理环境教育部重点实验室，南京 210023;江苏省地理信息资源开发与利用协同创新中心，南京 210023

• 吕恒
• 南京师范大学虚拟地理环境教育部重点实验室，南京 210023;江苏省地理信息资源开发与利用协同创新中心，南京 210023

• 董宪章
• 南京师范大学虚拟地理环境教育部重点实验室，南京 210023

• 蔡小兰
• 南京师范大学虚拟地理环境教育部重点实验室，南京 210023

• 曾帅
• 南京师范大学虚拟地理环境教育部重点实验室，南京 210023

• 摘要：蓝藻垂向运动的表征对于理解浅水富营养化湖泊中蓝藻水华的形成过程至关重要.本研究以太湖为研究区，通过野外实验观测，分析蓝藻生物量及颗粒物粒径分布的垂向变化特征，结合一维蓝藻平流运动模型，研究在不同扰动强度和群体粒径下的蓝藻垂向运动规律.结果表明，在低风速条件下（风速小于3 m·s^-1），太湖水体中蓝藻生物量在垂向上分布不均匀，其垂直分布剖线在水表或水柱某一深度形成峰值.当水华发生时，直径> 75 μm的蓝藻群体主要聚集在水表，其剖线在水下形成不明显的峰值；在水华未发生时，75~175 μm直径范围内的蓝藻群体主要聚集在水深1.2 m处，175~250 μm直径范围内的大粒径蓝藻群体仍聚集在水表.垂向运动模拟表明，直径> 100 μm的蓝藻群体随光照变化在水柱中进行周期性上浮下沉运动，直径< 100 μm的蓝藻群体，由于垂向迁移速度较小，在弱扰动条件下聚集在真光层深度附近.不同粒径蓝藻群体的垂向运动规律不同，导致蓝藻生物量垂直剖线在水表和水下形成两类特征峰.

• Abstract：Characterization of cyanobacterial vertical movement is essential to understand the process of cyanobacteria bloom formation in shallow eutrophic lakes. Lake Taihu， which is characterized by frequent cyanobacterial blooms， was reasonably selected as our study area. Here， we characterize the vertical distribution characteristics of cyanobacteria under different turbulence intensity and colony sizes in Lake Taihu based on field experimental observations and one-dimensional advection movement model. The results show that the vertical distribution of cyanobacteria biomass was not uniform with cyanobacterial biomass peak appearing in the water surface or at a certain depth in the water column when the wind speed is low （wind speed< 3 m·s^-1）. For the bloom areas， the diameter of cyanobacteria colonies is larger than 75 μm and there is a small cyanobacterial biomass peak at a certain water depth. For non-bloom areas， cyanobacteria colonies with the diameter between 75~175 μm mainly appeared at the water depth of 1.2 m， while cyanobacteria colonies with the diameter ranging from 175 to 250 μm mainly concentrated in the water surface. The vertical movement simulations show that cyanobacteria colonies with diameters> 100 μm float demonstrated periodic floating and sinking movements with the changes of light. When the diameters< 100 μm， cyanobacteria gathered near the euphotic zone under the weak disturbance condition. The two types of characteristic peaks of the cyanobacteria biomass vertical profile at the water surface and at a certain water depth could be attributed to the differences in the movement characteristics of cyanobacteria colonies with varied particle sizes.

• Key words：cyanobacterial blooms  particle size  vertical distribution  Taihu Lake  numerical simulation

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