蓝藻水华表征指标及驱动因子的多样性增加了研究人员、湖泊管理部门对于蓝藻水华扩张驱动因素的困惑, 本研究通过整合太湖蓝藻水华长尺度研究的成果, 将蓝藻水华扩张区分为时间扩张、空间扩张和生物量扩张3个方面, 分析各自的驱动因子, 系统阐述了当下太湖蓝藻水华的扩张和驱动因素.太湖蓝藻水华的时间扩张呈现由夏季集中发生向春季和秋冬季节扩张的趋势, 导致春季蓝藻水华发生的提前, 以及年度峰值的推迟;空间扩张呈现由西北太湖向湖心和东部湖区、乃至全湖扩张的趋势;太湖蓝藻生物量自2003年以后一直呈现缓慢增加的趋势.蓝藻水华时间扩张的驱动因素相对独立, 主要受气象因子的影响, 风速和日照时间是主要驱动因子, 风速降低和日照时间延长均有助于蓝藻水华时间的扩张;空间扩张和生物量扩张则受气象因子和富营养化的双重影响, 其中影响水华空间扩张的因子较多, 富营养化和气象因素的主次难以确定, 一般偶发性大面积蓝藻水华受气象因子驱动, 而频发性大面积蓝藻水华主要受营养盐空间分布影响;影响蓝藻生物量扩张的主要驱动因素为总磷, 另外氮磷比、水下可利用光和风速的变化也在一定程度上驱动了太湖蓝藻生物量的扩张.目前表征蓝藻水华强度通常利用空间扩张或生物量扩张指标, 但是均具有一定局限性, 相互间也缺乏可比性, 各指标用于长尺度趋势研究更为可靠, 短尺度比较受方法缺陷影响较大, 应进一步开发表征水华蓝藻总存量的指标以统一空间扩张和生物量扩张.%The diversity in proxies and drivers of cyanobacterial blooms expansion increased the confusion of understanding for cyanobacterial blooms expansion to scientists and lake managers. This study integrated the previous studies about long-term variation of cyanobacterial blooms in Lake Taihu, and divided the expansion into three aspects: temporal expansion, spatial expansion and biomass expansion, and discussed their trend and drivers. In time, the occurrence of cyanobacterial blooms shows the trend towards spring and autumn/winter from summer. The onset time of cyanobacterial blooms advances, and the annual peak delays. In space, cyanobacterial blooms expands towards center and east of the lake from the north and west. The cyanobacterial biomass increases gradually since 2003. Wind speed and sunshine hours are the primary factors influencing the temporal expansion. Decreasing wind speed and increasing sunshine hours favor the temporal expansion. The drivers for the spatial expansion are relative complicated, and difficult to disentangle the primary factors from nutrient and climate variables. Generally, the occasional large-area cyanobacterial blooms are driven by wind speed and wind direction, and the frequent large-area blooms are driven by nutrient. Total phosphorus is the primary factor driving the variation of cyanobacterial biomass, following by the ratio of total nitrogen to total phosphorus, underwater available light and wind speed. At present, the cyanobacterial blooms area and biomass usually are used to indicate the blooms intensity, both of which are inaccurate due to the defect of methods. Their proxies are reliable for long-term study, but seriously affected by defect of methods when they are used in short-term study. Therefore, it is necessary to build a new proxy as a substitution for bloom area and biomass to show the total cyanobacterial biomass in the whole lake. In addition, reducing phosphorus loading and decreasing phosphorus concentration are the main task of controlling cyanobacterial blooms in Lake Taihu.
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