平水期南洞庭湖浮游植物群落特征及其与水环境因子的关系

Characteristics of Phytoplankton Communities and Their Relationship toWater Environmental Factors in the South Dongting Lake in the NormalWater Period

南洞庭湖是典型的通江型湖泊,每年9月以后,进入平水期,水位下降,洲滩大量显露,水环境发生变化。为了探明平水期南洞庭湖水环境的健康状态,2020年9~10月,在南洞庭湖3个湖区进行样品采集,研究浮游植物群落特征及其与环境因子的关系,并对水质状况进行评价。研究结果表明,平水期在南洞庭湖东南湖、万子湖和横岭湖共检出浮游植物6门35属49种,其中东南湖浮游植物种类数最多,有23属29种;浮游植物平均丰度和平均生物量分别为34.22×10^(4)cells/L和0.54 mg/L,均以横岭湖最高(42.05×10^(4)cells/L和0.61 mg/L);3个湖区浮游植物优势物种均以密集微囊藻(Microcystis densa)为主,东南湖和万子湖浮游植物优势种数量较多,横岭湖最少;Shannon-Wiener多样性指数、Margalef丰富度指数和综合营养状态指数(TLI)范围分别为2.60~2.84、0.64~0.72和61.95~65.74,表明南洞庭湖水体处于中度富营养-β中等污染状态,其中横岭湖污染最为严重;冗余分析表明,水温、高锰酸盐指数和总氮浓度是影响南洞庭湖浮游植物空间分布的主要环境因子。研究结果能够为大型通江湖泊的生态保护与修复以及流域生态系统监测及预警提供数据支撑。

The south Dongting Lake is a typical river-communicating lake.After September every year,it gets into the normal water period,the water level drops,a large number of marshlands are exposed,and the water environment changes.In order to investigate the health status of water environment in the south Dongting Lake during the normal water period,samples were collected in three lake areas from September to October 2020,to study the characteristics of phytoplankton communities and their relationship with environmental factors,and to evaluate the water quality.The results showed that a total of 49 species of phytoplankton belonging to 35 genera and 6 phyla were detected in the Dongnan Lake,the Wanzi Lake,and the Hengling Lake,and the number of phytoplankton species in the Dongnan Lake was the highest,with 29 species of 23 genera.The average abundance of phytoplankton was 34.22×10^(4)cells/L,with the Hengling Lake having the highest value(42.05×10^(4)cells/L).The average biomass of phytoplankton was 0.54 mg/L,with the Hengling Lake having the highest(0.61 mg/L).The dominant species of phytoplankton in the three lakes were mainly Microcystis densa.The Dongnan Lake and the Wanzi Lake had more dominant species of phytoplankton,while Hengling Lake had the least.The Shannon-Wiener diversity index,Margalef richness index and comprehensive trophic level index(TLI)ranged from 2.60 to 2.84,0.64 to 0.72 and 61.95 to 65.74,respectively,indicating that the water body of the south Dongting Lake was in a state of medium eutrophication-βmoderate pollution,with the Hengling Lake being the most severely polluted.Redundancy analysis showed that water temperature,permanganate index and total nitrogen concentration were the main environmental factors affecting the spatial distribution of phytoplankton in the south Dongting Lake.This study provided data support for the ecological protection and restoration of large river-communicating lakes,as well as the monitoring and early warning of watershed ecosystems.