汉丰湖支流浮游植物群落结构及环境因子影响分析

Phytoplankton Community Structure and Its Correlation with Environmental Factors in Tributaries of Hanfeng Lake

为了准确反映汉丰湖的水环境状况，通过浮游植物监测与环境因子监测相结合，探讨小江中上游汉丰湖入湖支流东河、桃溪河、南河、头道河浮游植物群落结构特征及其与水体理化因子的关系，对水体理化指标和浮游植物进行了采样分析，在东河、南河、桃溪河、头道河各设置3个监测点，于2013年3、6、9、12月各采样1次。结果表明，4条入湖支流共采集鉴定浮游植物8门、84属、218种（含变种），以硅藻（107种）和绿藻（64种）居多，其次是蓝藻（31种），这3类的种数占浮游植物总数的92．7％，其它5门的种类数较少。各支流浮游植物种类数由低到高依次为东河（83种）、桃溪河（100种）、南河（106种）、头道河（120种），其密度均值在105数量级，南河下游浮游植物密度在夏季出现最大峰值，达到1160×10^4个／L，在绝大部分时段均以蓝藻占优势。水体理化指标监测数据显示，汉丰湖4条主要支流的总氮、总磷、pH、溶氧、水温、CODMn和电导率均值分别为1.00～1．61 mg／L、0.03～0．11 mg／L、7．82～8．53、6．65～7．03 mg／L、17．9～20．4℃、2．07～4．57 mg／L、269．25～522．50μS／cm；其中，南河的总氮、CODMn较高，头道河的总磷较高，各支流的水温、溶氧、pH较为接近。浮游植物与环境因子的相关性分析表明，东河的裸藻、桃溪河的绿藻以及头道河的蓝藻密度均与水温显著相关（P＜0．05），南河的硅藻和绿藻密度与水温极显著相关（P＜0．01），东河的甲藻密度与总磷浓度极显著相关（P＜0．01），桃溪河的硅藻和甲藻密度与总磷浓度显著相关（P＜0．05），绿藻密度与总氮浓度显著负相关（P＜0．05），硅藻密度与总氮浓度极显著负相关（P＜0．01）；浮游植物分布及密度主要受水温、总氮和总磷的影响。

Hanfeng Lake （ Kai County, Chongqing） was created in 2008 during the filling of Three Gorges Reser-voir.The four major tributaries of Hanfeng Lake （ the Donghe, Nanhe, Taoxi and Toudao Rivers） contribute 90%of the water volume and play a decisive role in the aquatic ecology of Hanfeng Lake.To better understand the ecol-ogy of Hanfeng Lake and provide a scientific basis for water conservation, the phytoplankton community structure in the lake and environmental factors of the four main tributaries of Hanfeng Lake were investigated during March, June, September and December of 2013.The relationship of the phytoplankton community structure and the envi-ronmental factors were analyzed based on the results of the investigation.Three sampling sites were selected in each river and the phytoplankton sample for qualitative analysis was collected with a No.25 plankton net and preserved with 4%formalin.For quantitative analysis a 1 L water sample was obtained from a mixture of surface, middle and bottom waters from each river, concentrated to 30 mL after settling 48h.The water temperature （ WT） , dissolved oxygen （ DO） , pH and electronic conductivity were determined at sample site using YSI-650 water quality analy-zer, and the total nitrogen （ TN） , total phosphorous （ TP） and chemical oxygen demand （ CODMn ） were measured using standard methods for water and wastewater analysis.A total of 218 phytoplankton species （ including varie-ties） belong to 84 genera and 8 phyla were identified.Bacillariophyta （107 species）, Chlorophyta （64 species） and Cyanophyta （31 species） were the dominant populations, accounting for 92.7%of the phytoplankton species with the species number of the other 5 phyla much lower.The species richness of the four tributaries from low to high was as follows：Donghe River （83 species）, Taoxi River （100 species）, Nanhe River （106 species）, Toudao River （120 speceis） .The phytoplankton density in the main tributaries of Hanfeng Lake averaged at five orders of magnitude, with Cyanophyta dominating most of the time, and a maximum density of 1 160 ×10^4 cells/L occurred during the summer in Nanhe River.Among the four major tributaries, the range of average values for TN, TP, pH, DO, WT, CODMn and conductivity were, respectively, 1.00 -1.61 mg/L, 0.03 -0.11 mg/L, 7.82 -8.53, 6.65-7.03 mg/L, 17.9-20.4℃, 2.07-4.57 mg/L and 269.25-522.50 μS/cm.TN and CODMn were the highest in Nanhe River and TP was the highest in Toudao River while tributary values for WT, DO and pH were similar.The densities of Euglenophyta in Donghe River, Chlorophyta in Taoxi River and Cyanophyta in Toudao River were significantly correlated with WT （P〈0.05） and the correlation was even higher （P〈0.01） with Bacil-lariophyta and Chlorophyta in Nanhe River.The Dinoflagellate density in Donghe River was highly correlated with TP（P〈0.01） and correlation of Bacillariophyta and Dinoflagellate densities in Taoxi River with TP were also sig-nificant （P〈0.05）.The Chlorophyta density in Taoxi River was negatively related to TN（ P〈0.05）, and the density of Bacillariophyta displayed highly significant negative correlation with TN （P〈0.01）.In conclusion, phy-toplankton density and distribution were affected primarily by WT, TN and TP.