鄱阳湖丰水期氮素分布特征及其对藻类的影响

Nitrogen Distribution and Its Influence on the Algae Community of Poyang Lake in the Wet Season

为了探讨湖泊富营养化过程中水体氮浓度的时空分布格局及其对藻类的影响,于2017年7月在鄱阳湖主湖区布设45个采样点,对浮游藻类数量和氮素含量进行监测,运用单因素方差分析法和皮尔逊相关系数法对数据进行分析。结果表明,丰水期鄱阳湖主湖区各采样点的总氮、硝酸盐氮、氨氮的平均浓度分别为0.54~1.26、0.06~1.01、0.08~0.30 mg/L,外源输入及环境条件对氮素浓度分布产生了一定影响;藻类密度与总氮、硝酸盐氮浓度表现为显著负相关性,与氨氮浓度相关性不明显,南部湖区的总氮和硝酸盐氮浓度高于其他湖区,平均浓度为1.10 mg/L和0.75 mg/L,但藻类密度较低,均值为1.0×10^(6)个/L;西部湖区的氮素浓度较低,总氮和硝酸盐氮浓度均值为0.59 mg/L和0.18 mg/L,藻类密度最高值为3.5×10^(6)个/L。中营养水域占主湖区的44%,富营养水域占56%,东部和西部湖区是鄱阳湖富营养化风险较高的区域。

Nitrogen is one of the primary nutrients for algae growth.Therefore,changes in nitrogen content directly affect the reproduction and growth of algae.In this study,we explored the spatial and temporal distribution pattern of nitrogen levels in Poyang Lake during wet season and analyzed its relationship with algae and the lake eutrophication process,aiming to provide theoretical evidence for controlling the eutrophication of Poyang Lake.A systematic investigation of algae density and nitrogen content in Poyang Lake was carried out at 45 sampling sites in July 2017:Sites 1-12 located in the western area of Poyang Lake;Sites 13-33 located in the southern area of Poyang Lake;Sites 33-45 located in the eastern area of Poyang Lake.One-way ANOVA was used for the significance analysis and the Pearson correlation coefficient method was used to analyze the relationship between water environmental parameters.Results show that total nitrogen,nitrate nitrogen and ammonia nitrogen in the main lake area of Poyang Lake were affected by exogenous inputs and,during the wet season,their concentration ranges were 0.54-1.26,0.06-1.01,and 0.08-0.30 mg/L,respectively.The highest values of total nitrogen(1.26 mg/L)and nitrate nitrogen(1.01 mg/L)occurred in the southern area of the lake,and the lowest values(0.54 mg/L and 0.06 mg/L,respectively)occurred in the western area of the lake.The concentration of ammonia nitrogen decreased from south to north,within a relatively small range.The spatial distribution of algal density followed the pattern:western area>eastern area>southern area.Algal density was not significantly related to the concentration of ammonia nitrogen,but the negative correlation of algal density with total nitrogen and nitrate nitrogen concentrations was significant.The concentrations of the total nitrogen and nitrate nitrogen in the southern area of Poyang Lake were higher,averaging 1.10 mg/L and 0.75 mg/L,respectively,while algae density was lower,averaging 1.0×10^(6) ind/L.In western Poyang Lake nitrogen levels were lower,with average values for total nitrogen and nitrate nitrogen of 0.59 mg/L and 0.18 mg/L,respectively,while algal density was higher,averaging 3.5×10^(6) ind/L.Based on algae densities,we concluded that 44%of Poyang Lake is mesotrophic,56%is eutrophic and that the eastern and western areas of the lake are at a high risk of eutrophication.