洪泽湖浮游藻类变化动态及影响因素

Seasonal dynamics of and factors in phytoplankton in Hongze Lake

针对2011年7月至2013年10月在洪泽湖11个采样点20次采样获得的湖水表层浮游藻类和水质理化指标数据,采用Shannon-Wiener指数H和优势度指数Y进行数据统计处理,分析洪泽湖浮游藻类时空分布动态及其影响要素。结果表明：洪泽湖浮游藻类共有7门60属144种,主要包括绿藻门66种、硅藻门36种、蓝藻门23种、裸藻门13种。浮游藻类群落具有明显的时空异质性,物种丰富度夏季最高,秋季中等,冬春季最低;西北部（成子湖区）和河流入湖口（溧河洼）高,湖心和河流出湖口（蒋坝）低;浮游藻类细胞密度全湖平均值变幅为157万~604万个/L,夏秋高,冬春--低;成子湖区等静水区高,入湖和出湖口低。浮游藻类组成和细胞密度的时间动态与温度、水位及营养盐（TN、TP等）的季节差异有关,而其空间动态与水动力因素和营养盐（NH3-N）的空间差异有关。建议限制洪泽湖营养盐陆地输入,合理调控洪泽湖水动力,以遏制洪泽湖蓝藻水华的发生。

In order to explore the temporal-spatial pattern of phytoplankton distribution in Hongze Lake and associated factors,we sampled surface water 20 times at 11 sites across the lake from July 2011 to October 2013,and obtained physical and chemical indices of phytoplankton and water quality. We processed the data using the Shannon-Wiener index H and dominance index Y. Then,we found 144 phytoplankton species belonging to 60 genera,and seven phyla（ including 66 species of green algae,36 species of diatoms,23 species of cyanobacteria,and 13 species of euglena）. The phytoplankton distribution presented an obvious spatial-temporal variability. The species richness was at a high level in the summer,at an intermediate level in the autumn,and at low levels in the winter and spring; it exhibited large values in the northwestern part（ Chengzi Lake area） and the inflow area of the lake（ site Lihewa）,and small values in the central area and the outflow area of the lake. The average cell density of phytoplankton ranged from 1. 57 × 106 to 6. 04 × 106 cells / L. The cell density was higher in the summer and autumn,and lower in the winter and spring; it exhibited large values in the Chengzi Lake area and small values at the inflow and outflow areas of the lake. Data analysis shows that the temporal dynamics of the species composition and cell density were significantly associated with the seasonal variations of water temperature,water level,and nutrients（ mainly total nitrogen and total phosphorus）,while the spatial dynamics of the species composition and cell density were correlated with the spatial variations of hydrodynamic factors and nutrients（ particularly ammonia nitrogen）. We suggest restricting nutrient input and modulating the hydrological dynamics of Hongze Lake,in order to prevent algal blooms in the lake.