汉江中下游浮游植物群落结构及水质评价

南水北调中线工程调水后,汉江中下游水华频发引起社会关注。为掌握调水后汉江中下游浮游植物的群落结构特征,于2017年11月、2018年2月、4月和8月在汉江中下游的8个断面对浮游植物进行了定量调查。调查结果显示:共鉴定浮游植物163种,群落组成以硅藻门(Bacillariophyta)、绿藻门(Chlorophyta)为主,其次是蓝藻门(Cyanophyta)。浮游植物优势种主要为硅藻门的梅尼小环藻(Cyclotella meneghiniana)、颗粒直链藻最窄变种(Melosira granulata var.)、变异直链藻(Melosira varians)、颗粒直链藻(Melosira granulata),隐藻门的卵形隐藻(Cryptomonas ovata),蓝藻门的弯曲颤藻(Oscillatoria sp.)和伪鱼腥藻(Pseudoanabaena sp.),且都有较高的优势度。浮游植物密度和生物量的季节变化范围分别为0. 33×106cells/L～1. 82×106cells/L和0. 49 mg/L～7. 38 mg/L。基于Shannon-Weaver多样性指数和Pielou均匀度指数以及优势种评价法对汉江中下游的水质进行评价,判断汉江中下游水质整体处于中污状态。

Phytoplankton community structure and water quality evaluation in the middle and lower reaches of the Hanjiang River

The frequent occurrence of water blooms in the middle and lower reaches of the Hanjiang River has aroused public concern after the diversion of water from the middle route of the South-to-North Water Diversion Project. In order to understand the characteristics of phytoplankton community structure in the middle and lower reaches of Hanjiang River after water diversion, quantitative investigations of phytoplankton were carried out in November 2017, February, April and August 2018 at 8 sections in the middle and lower reaches of Hanjiang River. 163 species of phytoplankton were identified, of which the community is mainly composed of Bacillariophyta and Chlorophyta, followed by Bacillariophyta. The main dominant species were Cyclotella meneghiniana, Melosira granulata var., Melosira varians, Melosira granulata, Cryptomonas ovata, Oscillatoria sp., and Pseudoanabaena sp., whose dominance indexes are higher than others. The phytoplankton density and biomass ranged from 0.33×10⁶ to 1.82×10⁶ cells/L and from 0.49 to 7.38mg/L, respectively. Based on the evaluation method of Shannon Weaver diversity index, Pielou evenness index and dominant species, it is concluded that the water quality of the middle and lower reaches of the Hanjiang River is in a medium pollution state.