Differences in nutrition condition and algae population in different areas of Poyang Lake

Abstract

在平水期、丰水期和枯水期对鄱阳湖典型天然碟形湖、人控湖汊和主湖区进行了水质、藻类和蓝藻毒素等对比调查，结果表明鄱阳湖各个湖区的水质与藻类种群等差异较大，蓝藻毒素浓度和底泥中铁含量的分布具有一定关联性.在各水文季节蓝藻均为人控湖汊藻类的主要优势种之一.平水期鄱阳湖藻类生物量（叶绿素a浓度）与水体的pH呈正相关关系，与采样点的水深呈负相关关系，碟形湖区水体营养盐浓度和藻类细胞密度均较其他湖区水体低.丰水期各湖区的水质差异相对较小，碟形湖藻类细胞密度仍低于其他湖区，但蓝藻已成为各湖区的优势种，该时期藻类生物量与水体总磷浓度及浊度呈正相关关系.枯水季鄱阳湖各水体藻类生物量与水体总氮浓度、铵态氮浓度及电导率呈正相关关系，碟形湖与主湖区发生了完全分离，水体流动性差，暴发蓝藻水华的风险较高.高温丰枯季节鄱阳湖水体蓝藻毒素浓度与底泥铁含量呈现一定的相关分布关系，底泥铁含量高的地方，其水体蓝藻毒素浓度通常比较高，应警惕鄱阳湖流域富铁红壤流失带来的湖区蓝藻水华风险加剧后果.上述研究结果将为鄱阳湖水环境的预警和污染控制提供科学指导.;Shallow dished lakes, isolated bays and the main water body of Poyang Lake were studied during common water period, flood period and drought period. The water, phytoplankton and dissolved microcystin samples were collected and analyzed. Results showed that in all periods, water quality and algae population varied greatly among the three areas. Dissolved microcystin concentration correlated well with Fe content in the sediment. Cyanobacteria was the dominant specie in the isolated bays during all periods. In common water period, algae biomass was positively correlated with pH and negatively correlated with water depth. Nutrient concentrations and algae cell density in the shallow dished lakes were much lower than those of the other water bodies. In flood period, algae biomass was positively correlated with total phosphorus concentration and turbidity while variance of water quality among different water bodies was relatively small. Cyanobacteria, especially Microcystis, became the dominant specie in all water bodies, while algae cell density and biomass in the shallow dished lakes were the lowest. In drought period, shallow dished lakes were isolated from the main water body of Poyang Lake with very poor water mobility, which may increase the risk of algae bloom. Algae biomass was positively correlated with total nitrogen, ammonia nitrogen and water conductivity. In both flood and drought periods with high temperature condition, dissolved microcystin concentration correlated well with Fe content in the sediment. This indicated that Fe may promote microcystin production and Fe enriched red soil erosion around Poyang Lake may exacerbate the risk of algae bloom. The present study can provide some guidance for water pollution control and aquatic environment risk warning of Poyang Lake.