汉江下游干支流浮游植物群落特征及其对水质的指示评价

浮游植物群落的动态变化可以全面、真实地反映水质的优劣,有利于了解水体污染状况的发展趋势。为及时掌握汉江下游水质变化,基于2019年3—12月汉江下游干流及主要支流浮游植物和水体理化指标监测数据,分析了浮游植物群落结构特征,并通过冗余分析研究了影响浮游植物群落结构的主要环境因子,同时运用浮游植物群落特征对汉江下游水质进行了综合评价。研究结果表明,在汉江下游干流及主要支流共鉴定出浮游植物7门110种,硅藻在种类组成上占绝对优势,以直链藻和冠盘藻为主。不同区域的浮游植物优势种存在差异:在汉江下游干流,硅藻门直链藻的优势度最大(0.19);在引江济汉运河,绿藻门球衣藻的优势度最大(0.14);在汉北河,蓝藻门伪鱼腥藻的优势度最大(0.24)。结合早年调查结果,汉江下游浮游植物密度近年来呈现先上升后下降的变化趋势。浮游植物密度和生物量受多种环境因子的影响,与水温呈显著正相关,与总磷、总氮、磷酸盐、氨氮和硅酸盐呈显著负相关。汉江下游干流、引江济汉运河、汉北河Shannon-Wiener指数分别为2.15、2.16、2.37,水质评价结果均为β-中污染;Pielou均匀度指数分别为0.77、0.80、0.74,水质评价结果均为轻度污染;Margalef物种丰富度指数分别为1.24、1.07、1.54,水质评价结果均为α-中污染。综合评价显示,2019年3—12月,汉江下游干流及主要支流整体处于中度污染状态。

Phytoplankton Assemblage Characteristic and Its Indication on Water Quality in the Lower Reaches of the Hanjiang River

The dynamics of phytoplankton community can reflect water quality comprehensively and truly,which is conducive to understand the development of water pollution tendency.In order to keep up on the water quality dynamics in the lower reaches of Hanjiang River,this study analyzed the characteristics of phytoplankton community structure and the relationships between phytoplankton community composition and environmental variables using redundancy analysis and then evaluated the water quality based on phytoplankton community characteristics according to the investigation data of phytoplankton and water physical and chemical indexes in the main stream and tributaries of the lower reaches of Hanjiang River during March-December 2019.The results showed that 110 species of phytoplankton belonging to 7 phyla were identified,and Bacillariophyta were the dominant taxonomic group,mainly composed of Melosira sp.and Stephanodiscus sp.in both of the mainstream and main tributaries of the lower reaches of Hanjiang River.The dominant species of phytoplankton differed in different regions,which was Melosira sp.(Bacillariophyta)(0.19,McNaughton dominance-index)in the mainstream of the lower reaches of Hanjiang River,Chlamydomonas globosa(Chlorophyta)(0.14)in Yangtze-Hanjiang River Canal,and Pseudoanabaena sp.(Cyanophyta)(0.24)in Hanbei River.Compared with the results of earlier surveys,phytoplankton density in lower reaches of Hanjiang River increased first and then declined.Phytoplankton density and biomass were affected by various environmental factors,and were positively correlated with water temperature,and negatively correlated with total phosphorus,total nitrogen,phosphate,ammonia and silicate.In the three investigated regions(the mainstream of the lower reaches of Hanjiang River,Yangtze-Hanjiang River Canal and Hanbei River),the Shannon-Wiener diversity index was 2.15,2.16 and 2.37,respectively,suggestingβ-medium pollution of all.The Pielou evenness index was 0.77,0.80 and 0.74,respectively,suggesting mild pollution of all.The Margalef richness index was 1.24,1.07 and 1.54,respectively,suggestingα-medium pollution of all.The comprehensive evaluation indicated a moderate-pollution state for the mainstream and main tributaries of the lower reaches of Hanjiang River during March-December 2019.