湖北长湖蓝藻季节动态及其驱动因子分析

Seasonal Dynamics and Driving Forces of Cyanobacteria Populations in Changhu Lake,Hubei Province

长湖是调控长江中游地区生态平衡重要的湿地生态系统,为了解长湖蓝藻季节动态并进一步探究蓝藻与环境因子的相关关系,根据其湖形特征设置5个采样点,于2020年4月至2021年3月对长湖蓝藻及水环境进行了逐月采样调查与分析。结果显示,调查期间共检出蓝藻18种(属),主要优势种为棒胶藻属(Rhabdogloea sp.)、惠氏微囊藻(Microcystis wesenbergii)和假鱼腥藻属(Pseudanabaena sp.)。二维非度量多维尺度(NMDS)分析显示,长湖蓝藻生物量季节变化明显,5、6、8月的蓝藻生物量较高,为6.88~15.50 mg/L,占浮游植物总生物量的24.0%~43.8%;冬季和初春较低,为0.13~0.29 mg/L,占浮游植物总生物量的0.5%~2.8%。逐步回归分析显示,气温、气压、总磷、降雨量和溶解氧是影响蓝藻的重要因子,共解释了蓝藻生物量变化的70.0%。结构方程模型展示了环境因子与蓝藻生物量的关系,气温和溶解氧的上升可促进蓝藻生长,而气压、总磷和降雨量正好相反,环境因子可直接或间接地通过改变湖泊的湖沼学特征影响蓝藻生物量。研究结果可为长湖蓝藻水华防控提供参考依据。

The Changhu Lake wetland ecosystem is critical for regulating the ecological balance of the middle Yangtze River,and plays an important role in maintaining ecological stability in the Hanjiang and Yangtze River basins.In this study,we analyzed the seasonal dynamics of cyanobacte-ria populations and its relationship with environmental factors in Changhu Lake.Our objectives were to evaluate the risk of cyanobacteria bloom occurrence and provide scientific data to support the prevention and control of cyanobacteria blooms and eutrophication in lakes of the middle Yang-tze River region.From April 2020 to March 2021,water samples were collected monthly at five sampling sites in Changhu Lake for phytoplankton identification and measurements of biomass and density.Physicochemical parameters of Changhu Lake were determined as samples were collected,and included WT,DO,TN,TP,Chl-a.A total of 18 cyanobacteria species(genera)were identified during the study period and the dominant species were Rhabdogloea sp.,Microcystis wesenbergii and Pseudanabaena sp.Nonmetric multidimensional scaling(NMDS)analysis showed an obvious seasonal variation of cyanobacteria biomass in Changhu Lake,with the highest biomass(6.88-15.50 mg/L)recorded in May,June,and August and the lowest(0.13-0.29 mg/L)in winter and early spring,accounting for 24.0%-43.8%and 0.5%-2.8%of the total phytoplankton biomass.Stepwise regression analysis indicated that air temperature,air pressure,precipitation,TP and DO were the primary environmental factors affecting cyanobacteria biomass,explaining 70.0%of the total bio-mass variance.The structural equation model(SEM)demonstrated the relationship of environmental factors and cyanobacterial biomass,and indicated that the rise of air temperature and dissolved oxy-gen boosted the growth of cyanobacteria species,while air pressure,precipitation and TP had the opposite effect.To summarize,environmental factors directly and indirectly affect cyanobacteria bio-mass by altering limnological conditions.