上海河道浮游植物群落结构时空变化特征及影响因素分析

Spatial and Temporal Variation of Phytoplankton Community Structure and Its Influencing Factors in Shanghai River Channels

为探究上海河道浮游植物群落结构时空变化特征及影响因素,于2018年9~10月(秋季)和2019年7~8月(夏季)对上海中心城区、新城镇和农村地区河道总计44个样点的水环境和浮游植物群落结构进行调查.结果表明:①秋季和夏季浮游植物种类均以绿藻门为主,其次为蓝藻和硅藻;浮游植物密度以蓝藻占据绝对优势;浮游植物种类和密度均是夏季>秋季,分别高出24%和2.77倍,硅藻门种类略微上升,而裸藻门种类稍微下降;秋季微囊藻(Microcystis sp.)优势度明显(Y=0.16),而夏季则无占绝对优势的优势种.②各地区浮游植物种数无明显变化;浮游植物密度和蓝藻门密度均呈现农村>新城镇>中心城区的规律,秋季3个地区的浮游植物密度无显著差异(P>0.05),而在夏季农村所有浮游植物和蓝藻门密度显著高于中心城区(P<0.05),分别高出1.82和1.93倍.③蒙特卡洛检验结果表明,影响秋季和夏季浮游植物群落结构的主要因子分别为透明度(SD)、总磷(TP)、总氮(TN)、浊度(Turb)和TN、Turb、SD、pH.冗余分析(RDA)结果表明,秋季新城镇河道浮游植物群落结构主要受Turb、TN和TP的影响,农村河道则主要受SD的影响,而夏季新城镇和农村河道浮游植物均主要受TN、Turb的影响.两次调查时中心城区浮游植物的影响因素均较为复杂.

In order to explore the spatial and temporal characteristics of the phytoplankton community structure and its influencing factors in Shanghai rivers,the water quality and phytoplankton community structure at 44 river channel sites in a central urban area,new town area,and rural area in Shanghai were investigated from September to October 2018(autumn)and July to August 2019(summer).The results showed that:①Chlorophyta was the dominant phyla during the autumn and summer,and was followed by Cyanobacteria and Bacillariophyta.Cyanobacteria dominated the phytoplankton community in terms of density.The number of species and density of phytoplankton were 24%and 2.77 times higher,respectively,than those during the summer and autumn.The dominance of Microcystis sp.was obvious during the autumn(Y=0.16),but there was no absolute dominant species during the summer.②The difference in the number of phytoplankton species among the three regions was not significant,and the density of the total phytoplankton and cyanobacteria species showed a similar spatial pattern:rural area>new town area>central urban area.Additionally,no significant difference was observed in the total phytoplankton and Cyanobacteria density among the three regions during the autumn(P>0.05),whereas it was 1.82 and 1.93 times higher,respectively,in the rural area in comparison to the central urban area during the summer(P<0.05).Montecarlo test results revealed that the main factors affecting the phytoplankton community structure during the autumn were secchi disk transparency(SD),total phosphorus(TP),total nitrogen(TN),and turbidimetry(Turb),whereas these were TN,Turb,SD,and pH during the summer.③The results of a redundancy analysis(RDA)indicated that during the autumn,the phytoplankton in the rivers of the new town area were mainly affected by Turb,TN,and TP,while the rural rivers were mainly affected by SD.During the summer,the phytoplankton in the rivers of the new town and rural areas were mainly affected by TN and Turb.The influencing factors in the central urban area were complex.