客水引流对浅水湖泊生境影响的时间效应及机制

As an emergent hydraulic measure coping with cyanobacterial blooms, allochthonus water diversion has a great influence on the environmental succession of shallow lakes, while this hydraulic measure can quickly improve limnetic water qualities. Until now,little is kown about the short- and long-term variations of ecological elements influenced by the water diversion and their regulating mechanisms in shallow lakes. In this project, autotrophic phytoplankton and heterotrophic bacteria, sensitive to limnic changes, are selected to be the bioindicators, and the engineering of water diversion from Yangtze River to Taihu Lake will be focused on. To provide insight into the effects of water diversion on the occurrence, transportation and assimilation processes of biogenic elements in the lake, the short- and long-term responses of physicochemical characteristics and microbial communities in Lake Taihu will be investigated based on experiments of outside observation, historic data collection, indoor incubation and numerical simulation.The chemical speciations of biogenic elements sensitive to the water diversion will also be explored and selected. For modeling and deducing the dynamics of the ecological effects of water diversion, the special attention will be concentrated on the change of the microbial proliferation and functional activities affected by sensitive biogenic elements like the suspended organic substances. The temporal effect and its regulating mechanism of allochthonus water diversion on the ecological elements in shallow lakes will be revealed, which will provide a benefited guide for the hydraulic ecological restoration on eutrophic shallow lakes.

作为应对水华灾害的应急措施，客水引流工程在快速改善湖泊水质的同时，对浅水湖泊生物生境的演变也有着不容忽视的影响。目前，对客水引流影响下大型浅水湖泊生境要素随时间的短期与长期动态变化规律及其驱动机制还知之甚少。本研究以大型客水引流工程--引江济太工程为例，选取对湖泊环境变化敏感的自养型浮游藻类与异养型细菌为指示微生物，通过野外现场观测、数据资料收集、室内模拟实验与数学模型演算，研究引江济太工程影响下太湖生境理化性质与微生物群落的短期与长期动态响应过程，弄清客水引流对受水湖区生源要素赋存、输移与同化的影响，筛选对客水引流响应敏感的关键生源要素形态。重点研究悬浮有机物等生源要素的形态与含量对微生物增殖与功能活性的影响，推演客水引流对浅水湖泊生境要素影响的动态。项目预期将阐明客水引流对浅水湖泊生境要素影响的时间效应及机制，为富营养化浅水湖泊的水利修复实践提供理论依据。

客水引流工程在快速改善湖泊水质的同时，对浅水湖泊生物生境的演变也有着不容忽视的影响，此前针对客水引流影响下大型浅水湖泊生物生境的时间效应及驱动机制缺乏深入认识。本研究以大型客水引流工程—引江济太工程为例，选取对湖泊环境变化敏感的浮游藻类和细菌为指示生物，通过野外现场观测、室内模拟实验及数据统计分析等综合手段，首先解析了季节性引水影响下受水湖区浮游藻类及理化生境的短期与长期变化过程，发现季节性引水短期内可快速降低受水湖区有机物浓度，显著增加浮游藻类与细菌的多样性，改变不同季节贡湖湾的群落组成，但也增加了受水湖区营养盐富集风险；受引水水量限制，引水产生的短期效应在引水后会有所回复，短期效应较长期累积效应更为显著；其次筛选出受水湖区水体pH、SiO3-Si、TN、NO3-N、TP和CODMn为客水引流敏感理化生源要素形态，揭示了敏感生源要素与受水湖区生物群落演替呈现出多元线性关系，不同季节总藻、蓝藻、硅藻以及绿藻密度与磷素等参数的耦联关系均有所不同；最后弄清了季节性引水外源输入与湖区理化生境改变对湖泊浮游藻类群落演替的定量贡献，引水引起的理化生境干扰对浮游藻类群落变化的贡献率约为23.3%至31.3%。外来物种对贡湖湾浮游藻类多样性增加的潜在贡献率最高，约为15.8%，而理化生境干扰对贡湖湾浮游藻类多样性的贡献率约为12.0%～31.3%。项目成果阐明了重大客水引流工程对浅水湖泊生物生境影响的时间效应及机制，已应用于引江济太工程湖泊生态影响调度实践。