引水调控对富营养化浅水湖泊生境演变的影响

Cyanobacterial blooms induced by limnic eutrophication harmfully endanger the lake ecosystems. While water diversion, as an emergent hydraulic measure coping with the ecological disaster, can quickly improve water qualities of eutrophic lakes, amounts of external water can also have a great influence on the original lake ecological environments. Until now, in large, eutrophic, shallow lakes, little is known about environmental successions of the hydrological, physicochemical and biological elements and their coupling relationships under the influence of water diversion. In this project, bacteria, sensitive to limnic changes, is selected to be the bioindicator of aquatic organisms, and the engineering of water diversion from Yangtze River to Taihu Lake will be focused on. To provide insight into the direct and indirect effects of water diversion on the lake ecosystems, the field observation and indoor simulation experiments will be conducted for revealing effect of water diversion on the spatio-temporal patterns of the hydrological, physicochemical variables, bacterial abundance, diversity, community structure and their coupling relationships. The special attention will be concentrated on the responses of Taihu Lake microcosms to different lake current speeds induced by water diversion and water trophic levels. The impact mechanism of water diversion on spatio-temporal successions of the hydrological, physicochemical and biological elements in shallow eutrophic lakes will be displayed, which will provide a benefit guide for the hydraulic ecological restoration on eutrophic shallow lakes.

富营养化所导致的蓝藻水华灾害严重影响湖泊生态系统的健康。作为应对水华灾害的应急措施，引水调控可快速改善湖泊水质，但大量的外来原水也会对受水湖泊原有的生态环境产生很大的影响。目前，对引水调控影响下大型富营养化浅水湖泊的水文、理化和生物环境的演变规律以及三者之间的相互关系还知之甚少。本研究以大型引水工程--引江济太工程为例，选取对湖泊环境变化敏感的生物--细菌作为指示生物，通过野外调查与室内模拟实验，研究引水调控影响下太湖的水文、理化参数以及细菌的丰度、多样性与群落结构的时空分布格局，分析水文、理化和生物要素时空演变规律间的耦联关系，探讨引水调控对受水湖泊的直接和间接生态效应。重点研究太湖微生态系统对引水引起的湖流流速和引水的营养水平的响应。项目预期将阐明引水调控对富营养化浅水湖泊水文、理化和生物要素时空演变的影响机制，为富营养化浅水湖泊的水利修复实践提供理论依据。

引水调控工程在应对水华灾害和改善水质方面有着重要作用，但其对湖泊的生态环境也有着不容忽视的影响。本研究以引江济太工程为背景，通过野外调查手段，研究了引水调控工程影响下太湖贡湖湾的水环境参数和细菌群落结构的时空分布特征，剖析了敏感水环境参数与生物群落变动间的定量耦联关系；同时，结合室内模拟实验，探明了引水流量对受水湖泊微生态系统的影响，弄清了引水要素改变对湖泊生物和生境的影响机制。主要研究结果如下：.（1）风向对贡湖湾水体交换的影响较大，东风、北风、东南风，尤其是东北风时进行引水可有效改善贡湖湾湖流分布，有利于缓解蓝藻堆积等风险。贡湖湾水体TN、TP、NO3-N、SiO3-Si、CODMn、Chl a以及TOC含量对引水响应敏感，引水期营养盐含量从望虞河入湖口至湖心区递减，有机污染含量（CODMn、Chl a、TOC）则呈递增趋势。夏、冬、秋季引水均会增加湖湾水质综合污染指数，但也影响藻型生态系统稳定性，有效降低湖湾有机污染。.（2）引水期贡湖湾细菌群落结构与望虞河和长江入河口更为相似，贡湖湾放线菌门相对比例的增加与望虞河引水密切相关，非引水期贡湖湾细菌群落结构更接近太湖湖心水域。不同季节引水期细菌丰度与水体pH、TN、NO3-N、TP、SRP、CODMn等理化参数定量耦联关系不同，引水期贡湖湾污染物浓度降低对细菌丰度的影响明显。.（3）太湖微生态系统的理化环境与细菌丰度对望虞河引水要素响应敏感。30天的引水模拟过程中，不同流量处理组间湖泊水体理化参数与细菌丰度差异显著。短期引水期间，引水流量与河湖水体成分的浓度差以及湖泊水体浓度变化之间存在定量关系，引水不同阶段（初期、中期和后期）相互间的定量关系也不同。引水对湖泊水生态影响不仅有外源输入的直接作用，还包括湖泊水体理化环境改变后对生物产生的间接作用，生物生境的改变对湖泊水生态的影响更为重要。