抚仙湖超微型浮游藻类群落结构空间分布特征

2016年7月对抚仙湖进行采样调查，研究抚仙湖超微型浮游藻类（超微藻）的空间分布特征及关键影响因子。结果表明，抚仙湖超微藻平均丰度为（8.58±3.25）×10³个/mL，其中超微蓝藻丰度显著高于超微真核藻。超微藻丰度在沿岸带较高，敞水区相对较低，北部最深点低于南部最深点；垂直方向上，超微藻丰度在水下10 m处达到最大值，随着深度的增加丰度逐渐下降。通过方差膨胀因子分析和建模得到超微藻丰度和环境因子的相关关系，水体的浊度、pH以及总磷对超微真核藻丰度有显著影响，而超微蓝藻的丰度主要是受到总磷的影响。结合流式细胞分选和高通量测序得到了抚仙湖超微真核藻的群落结构特征，主要是金藻纲、硅藻纲、甲藻纲等，其中金藻纲占绝对优势。在空间上，不同湖区和不同深度超微真核藻的群落组成也存在差异：表层水体以金藻纲、硅藻纲、甲藻纲为主；而在深层水体中超微真核藻的多样性降低，金藻纲为优势种。超微藻作为贫营养湖泊初级生产力的主要贡献者，对其组成和分布的研究有助于更全面的认识抚仙湖生态系统结构和功能。

The spatial distribution of the community structure of picophytoplankton in Lake Fuxian

The spatial distribution of picophytoplankton and the community structure of eukaryotic picophytoplankton were investigated in Lake Fuxian in July 2016. The results showed that average cell density of picophytoplankton (APP) was 8.58×10³ cells/mL, and picocyanobacteria (PCY) was abundant than photosynthetic picoeukaryotes (PPEs). Horizontally, picophytoplankton was more numerous in the littoral regions than in the pelagic regions. Its density was lower in the deepest region of the north lake than the deepest region of the south lake. Vertically, the abundance of picophytoplankton was the highest at the depth of 10 m, and declined with the depth. The analysis results based on variance inflation factor (VIF) and modelling indicated that turbidity, pH and total phosphorus had significant impacts on the abundance of photosynthetic picoeukaryotes. While the abundance of picocyanobacteria was mainly affected by total phosphorus. The community structure of PPEs was achieved by using the combination of flow cytometric sorting and high-throughput sequencing. In Lake Fuxian, the PPEs was mainly composed of Chrysophyceae, Bacillariophyceae, Dinophyceae, in which Chrysophcyeae was prevalent. PPEs showed more diversified in the surface water than in the deep water, being composed of Chrysophcyeae, Dinophyceae and Bacillariophyceae in the surface water, but being merely dominant by Chrysophyceae in the deep water. As the most important primary producer in oligotrophic lake, the study on the community structure of picophytoplankton would be helpful to understand the ecological structure and function of Lake Fuxian.