草型清水态维持与长效运行的营养盐响应机制——以滇池大型围隔试验为例

为探究湖泊水体生态修复工程中草型清水态维持与长效运行的营养盐响应机制,利用滇池草海建立的大型原位试验围隔,采用非参数突变点分析法(nCPA)及临界指示物种分析法(TITAN),探究了叶绿素a、浊度、透明度和浮游植物的营养盐阈值.结果表明,草型清水态维持与长效运行较为成功的围隔,其藻类的叶绿素a含量虽然明显较低,但在夏季时蓝藻门仍占绝对优势.原位生态围隔叶绿素a响应TN的阈值为1.423mg/L,响应TP的阈值为0.103mg/L.水体透明度响应TN的阈值为1.684mg/L,响应TP的阈值为0.103mg/L.各围隔总磷含量的平均值均大于或等于0.226mg/L,B1、B3、B8围隔后期处于清水态,其TN平均值都低于或等于1.42mg/L, B5、A1、A2、A3、A4围隔后期处于浊水态,其TN平均值都高于或等于1.78mg/L.这表明在滇池水华重灾区实施水体生态修复工程时,应首要考虑TN的影响,在TP含量严重超出阈值的情况下,如果TN处于一个较低水平,也能维持湖泊水体草型清水态的长效运行,并实现湖泊水体由藻型浊水态向草型清水态的转换.

The responding mechanism of nutrient concentration on the maintenance and long-term operation of macrophytes-dominated clear water state: A case study of a large experimental enclosure in Dianchi Lake

In order to explore the responding mechanism of nutrient concentration on the maintenance and long-term operation of macrophytes-dominated clear water state in lake ecological restoration projects, a large in-situ test enclosure was set up in Caohai, Dianchi Lake. Using the in-situ mesocosms via nonparametric change-point analysis (nCPA) and thresholds indicator taxa analysis (TITAN), nutrient thresholds of chlorophyll a, turbidity, transparency and phytoplankton community were studied. Even in a more successful and long-term clear state enclosure with lower chlorophyll a, the cyanobacteria still absolutely dominated in summer. TN and TP thresholds of the ecological restoration enclosure for chlorophyll a were 1.423 and 0.103mg/L, whereas TN and TP thresholds for transparency were 1.684 and 0.103mg/L, respectively. The mean values of TP in all enclosures was greater than or equal to 0.226mg/L. In the later period, B1, B3, B8 enclosures were in clear water state with the mean values of TN lower than or equal to 1.42mg/L, whereas B5, A1, A2, A3, A4enclosures were in turbid water state with all mean values of TN greater than or equal to 1.78mg/L. These results showed that TN should be primarily considered for the ecological restoration at area with heavy cyanobacteria blooms. When TP concentration severely exceeds the threshold, concentration of TN then becomes the limiting factor, and if kept at low level, the long-term operation of macrophytes-dominated clear water state could still be maintained to achieve the transition from phytoplankton-dominated turbid water state to macrophytes-dominated clear water state.