由链式到网式的湖泊“水华”生物控制

The biological control of Lake "bloom" is essentially the process of ecological relationship adjustment between dominant algae and its associated populations, which is actually a kind of food-chain-control. This direct predation or competition control, despite some direct algicidal effects, is apt to ignore the ecological relationships with other correlated populations. Thus, the long-term, stable and system-level ecological effects are difficult to assess. In this study, a series of ecological mesocosms will be built in the "bloom" areas of the Ulansuhai Lake in Inner Mongolia. On the basis of field monitoring, indoor experimental analysis and computer simulation, we construct and quantify the nutrients cycle network model. Using the Ecological network analysis (ENA) method, we judge the key populations that directly and indirectly impact the dominant algae and thus detect important ecological relationships that impact or constrain the growth of the dominant algae. Meanwhile, on the basis of ENA, some indicators including velocity of water flowing, light, temperature and pH value will be analyzed to identify the way and extent that they influence the growth of algae. Based on the above research work, we use the uncertainty analysis to detect the driving factors leading to the changes of ecological relationships. Some biological control measures, based on holistic-level ecological relationship, will be given to provide a reference for ecological restoration of lakes in china.

湖泊“水华”生物控制，实质是水体中优势藻类及其关联种群间生态关系的调整过程，多基于藻类及其相关种群间单一的链式控制关系而实施。这种直接捕食或者竞争式的控制，虽然有直接的抑藻效果，但容易忽略由此带来的与其他相关种群间的生态关系，长期、系统、整体层次的生态效果往往难以评估。本研究聚焦内蒙古乌梁素海“水华”易发区，原位构建一系列大型围隔系统，模拟由食物链过渡到食物网的“水华”生物控制系统，在室外动态监测、室内实验分析和计算机模拟的基础上，构建并量化营养盐循环的网络模型，采用生态网络分析判断直接或者间接影响藻类生长的种群，定量分析影响和制约藻类生长的重要生态关系；基于网络分析判断流速、光照、温度、pH值等因素对藻类生长的影响方式和程度；在上述研究的基础上，采用不确定性分析从系统层次上辨识种群间生态关系变化的驱动因子，提出基于食物网关系的湖泊“水华”生物控制措施，为我国湖泊的生态修复提供参考。

“水华”是湖泊富营养化的直接和集中反映，不仅会引起水质恶化，而且会耗尽水中氧气而造成鱼类死亡、产生藻毒素，对鱼类、人畜饮水安全产生严重危害，最终产生水生生态系统服务削弱甚至消失的严重生态后果。传统的湖泊“水华”生物控制，主要关注优势藻类及其直接关联种群间生态关系，基于藻类及其相关种群间的食物链式关系而开展。这种直接捕食或者竞争式的控制，虽然有直接的抑藻效果，但容易忽略由此带来的与其他相关种群间的生态关系，因而长期的、系统整体层次的生态效果往往难以评估。本研究在内蒙古乌梁素海“水华”易发区开展在原位监测和室内实验分析，构建并量化基于磷营养盐循环的湖泊生态系统网络模型，采用生态网络分析方法判断直接和间接影响藻类生长的种群，定量分析影响和制约藻类生长的关键生态关系。网络分析结果显示：（1）网络视角下的系统流动强度、无论是系统链接还是系统内流动强度均比直接观察的结果明显增大，说明生态系统各功能组之间相互影响十分密切（2）主要功能组之间的生态效用改变，甚至会引起生态关系的变化，说明给于链式的生物控制的间接影响可能被忽视（3）对藻类种群的生长的输入和输出控制由发挥关键控制的功能组由直接的2-3个增加到4-5个功能组，说明水华控制需考虑更多的功能组。（4）基于在上述研究结果提出了系统层次、网络视角的水华控制的方法和建议，也为我国湖泊的生态修复提供新的启示。