赣江中下游浮游植物群落结构及其水质生物学评价

Phytoplankton Community Structure and Biological Evaluation of Water Quality in the Middle and Lower Ganjiang River

为了探究赣江中下游浮游植物群落结构的季节变化,为渔业资源可持续利用、水质监测及生物多样性保护提供参考,2016年10月(秋季)、2017年1月(冬季)、4月(春季)和7月(夏季),对赣江中下游浮游植物群落结构进行季度调查。结果表明,赣江中下游共记录浮游植物5门、55属、95种。其中,绿藻门44种,占总浮游植物种类的46.0%;硅藻门29种,占30.5%;蓝藻门15种,占16.0%。浮游植物密度为82.3×104~906.0×104个/L,平均值为315.0×104个/L。生物量为0.43~1.26mg/L,平均值为0.69mg/L。赣江支流浮游植物的平均密度和生物量(546.0×104个/L,1.07mg/L)均高于干流(212.0×104个/L,0.52mg/L)。干流主要优势种为小席藻(Phormidium tenue)、颗粒直链藻(Melosira granulata)、卵形隐藻(Cryptomonas ovata)和尖尾蓝隐藻(Chroomonas acuta);支流主要优势种为小席藻、微小平裂藻(Merismopedia tenuissima)、四尾栅藻(Scenedesmus quadricauda)和水华束丝藻(Aphanizomenon flos-aquae)。浮游植物Shannon-Wiener多样性指数(H′)和Margalef丰富度指数(D)的年均值分别为1.87和0.94,干流的H′值高于支流,而干流的D值低于支流。研究显示,赣江中下游水域均受到不同程度的污染,干流的污染程度比支流更为严重。

Phytoplankton is the primary producer in aquatic ecosystems and plays an important role in maintaining the ecological balance.Thus,phytoplankton community structure is an important indicator of water quality.In this study,we explored the seasonal variation of phytoplankton community structure in the middle and lower reaches of Ganjiang River,aiming to provide a reference for sustainable utilization of fishery resources,water quality evaluation and biodiversity protection.Samples were collected at 13sampling stations in both the main stream and tributaries during October 2016,and January,April and July 2017.Sample analyses focused on phytoplankton density,dominant species and species diversity.A total of 95species,belonging to 55genera and 5phyla,were collected and Chlorophyta(44species)dominated,followed by Bacillariophyta(29species)and Cyanophyta(15species),accounting respectively for 46.0%,30.5%and 16.0%of the total species.The ranges of phytoplankton density and biomass were 82.3×104-906.0×104 cells/L and 0.43mg/L-1.26mg/L,with average values of 315.0×104 cells/L and 0.69mg/L.The annual density and biomass of phytoplankton in tributaries(546.0×104 cells/L,1.07mg/L)were higher than in the main stream(212.0×104 cells/L,0.52mg/L).Dominant species in the main stream were Phormidium tenue,Melosira granulata,Cryptomonas ovata and Chroomonas acuta,while tributaries were dominated by P.tenue,Merismopedia tenuissima,Scenedesmus quadricauda and Aphanizomenon flos-aquae.The mean values of the Shannon-Wiener diversity index and Margalef abundance index of the phytoplankton community in the middle and lower Ganjiang River were 1.87and 0.94,respectively.The Shannon-Wiener diversity index in the main stream was higher than that in tributaries,while the Margalef abundance index in the main stream was lower.Our results indicate that water quality in the middle and lower Ganjiang River is influenced by varying degrees of pollution and that pollution is heavier in the main stream than in tributaries.