Phytoplankton community structure and water ecological assessment in the Three Gorges Reservoir

2020年是长江禁渔开局之年,三峡库区作为长江的重要生态屏障,其水生态环境健康对长江大保护的实施具有重要意义。本文于2020年8月、11月及2021年1月、4月在三峡库区干支流共设置19个断面探究浮游植物群落结构特征,并利用生物量、多样性指数、综合营养状态指数和浮游植物Q指数等多种评价方法评价三峡库区水生态健康并分析其影响因素。结果表明:(1)三峡库区共鉴定出浮游植物8门105属266种,年平均丰度为6.4×104 cells/L,年平均生物量为0.038 mg/L。不同季节优势种组成不同,变异直链藻(Melosira varians Agardh)、骨条藻(Skeletonema spp.)、脆杆藻(Fragilaria spp.)为全年优势种。(2)三峡库区共划分24个功能群,B、D、MP、S1、P、Y为优势功能群。RDA分析表明,电导率、总氮、化学需氧量、总磷、pH、总溶解性固体与三峡库区四季功能群呈现显著关系。(3)相较于丰度、生物量和多样性水质评价结果,浮游植物Q指数更适用于三峡库区水生态评价,显示三峡库区干流水生态环境总体较好,但春、夏两季支流浮游植物丰度、生物量显著升高和浮游植物Q指数的降低在一定程度上影响了干流水生态健康,成为三峡库区面临的主要风险。因此更应充分做好支流水华监测、预警,充分利用干流水生态调度,保障三峡库区水生态环境健康。;The year 2020 is the first of 10-year fishing ban in Yangtze River. As an important ecological barrier River, water environment health Three Gorges Reservoir (TGR) great significance to implementation River protection. Nineteen sites were set main and tributaries TGR (August November) 2021 (January April) explore composition phytoplankton community, multiple assessment methods such as biomass, diversity index, comprehensive trophic status index Q used evaluate area analyze its influencing factors. The results showed that: (1) 266 taxa belonging 105 genera 8 phyla identified,the average annual density was 6.4×104 cells/L biomass 0.038 mg/L. dominant species varied seasonally. Melosira Agardh, Skeletonema spp. Fragilaria all round. (2) classified into 24 functional groups, which B, D, MP, S1, P Y groups. Redundant analysis that Cond, total nitrogen, COD, phosphorus, pH dissolved solid environmental factors affecting groups TGR. (3) Compared with density, quality, more suitable for ecology Results stream generally good. However, significant increases decrease spring summer would affect a certain extent, had become risks area. Therefore, we should make full use monitoring early warning tributary bloom take advantage dispatch ensure whole