三峡水库微型生物食物网中的各功能群生态学研究

The Three Gorges project on the Yangtze River has attracted worldwide attention, and its impacts on ecological environment can be profound and long. Numerous studies have shown that algal bloom occurred in tributary of Three Gorges became more and more serious. After impoundment water level to 175 m , the tributary estuary and bays have apparently physical structure of stagnant water stratification which are similar to river estuary and gulf. But it's need to be verified if the microbial food webs theory of gulf, which indicated that microbial food webs led to high efficient mass circulation is suitable to be used in the tributary estuary and bay of Three Gorge reservior. We take the eutrophicated tributary estuary and bay of Three Gorge reservior as object, study on the effects of the functional groups in the microbial food webs on mass circulation efficiency from ecological perspective. By field investigation and rapid monitoring, on the basis study on ecological indicators such as trophic type, particle-size spectra, biomass spectra and biological type, we could isolate and access the functional groups that efficently utilize and rapid response to dissolved organic matter. At the same time, laboratory experiments are carried out to analyze the relationship between functional group with dissolved organic matter. This study is an exploration of the mass circulation and energy flow in food webs, and a research for the causes and mechanism of algal blooms of three gorges reservoir, which could deepen the understanding of the ecosystem and provide scientific basis for the eutrophication treatments in the Three Gorges reservoir.

长江三峡工程举世瞩目，其对生态环境的影响深刻而久远，诸多研究表明三峡蓄水后支流藻类水华现象日趋严重。三峡水库蓄水175米后，支流入库河口和库湾显然具备了与河口、海湾类似的"滞水分层"结构，关于海湾的微型生物食物网导致物质高效循环理论是否适合于三峡水库支流入库河口和库湾尚待验证。本课题以三峡水库富营养化支流入库河口和库湾作为研究对象，从生态学角度对导致物质高效循环的微型生物食物网中的功能群进行研究。通过现场调查和快速监测，获取对可溶性有机物高效利用和快速反应的功能群，对其营养类型、粒径谱、生物量谱、生物类型等生态学指标进行研究；同时开展室内实验，分析功能群与可溶性有机物之间的关系。本研究是对三峡水库食物网物质循环和能量流动、水华成因和机理的探索，可加深人类对三峡水库生态系统的了解，为三峡水库富营养化的提供科学依据。

项目选择三峡水库支流澎溪河、大宁河和香溪河作为研究区域开展微型生物食物网（MFW）中的各功能群生态学研究。研究结果如下：.1、三峡水库MFW由细菌、单细胞藻类和不同功能群的原生动物组成，形成了一个既有生产者、又有消费者和分解者的完整食物网结构。细菌检出30门，第一优势类群为变形菌门；原生动物检出94种，食菌兼食藻者功能群种类最多，占35.1%，其次是食菌者功能群占28.7%，二者所占比例达到63.8%，成为MFW中最重要的一环。.2、三峡水库粒径分布和密度粒径谱常数在春、夏季呈现时空异质性，且不同水深的粒径谱斜率呈明显线性相关趋势（斜率随水深0m-16m从-1.84逐级递减至到-3.28），但秋季粒径谱常数的垂直变化不明显，且粒径谱常数变动与水深不呈线性相关，表明秋季微型生物群落结构的垂直变动趋势被改变。.3、三峡蓄水及调度对MFW各功能群的影响明显。藻类在三条支流都呈现出蓄水期比泄水期密度和生物量同时显著下降的规律，原生动物蓄水期种类、密度和生物量也同时显著下降。春季泄水期和夏季低水位运行期比例最高的变形菌则到秋季蓄水期较少。厚壁菌则相反，秋季蓄水期急剧增加成为数量最多的细菌类群。.4、在三峡水库的泄水期、低水位时期和蓄水期，粒径谱斜率的中位值依次为：-3.22、-3.51、-2.58，粒径谱截距依次为：4.96、5.28、3.85。三峡水库秋季蓄水期粒径谱斜率最高，而粒径谱截距最低，表明秋季个体较大的微型生物比例相对较高，且生物密度相对较低。而春季泄水期正相反，个体小的微型生物比例较高。粒径谱常数（斜率和截距）很好地反映了微型生物群落对水库调度运行的响应。.5、影响三峡水库细菌空间分布的主要环境因子为叶绿素、TN和磷酸盐。叶绿素对澎溪河细菌的影响较为明显，磷酸盐对香溪河细菌的影响较大，而大宁河支流主要受TN的影响。蓄水期原生动物食菌者数量与优势类群芽孢杆菌的数量密切相关，细菌数量增加，食菌者原生动物的数量也随之增加。.总之，三峡水库MFW物质循环主要通过细菌至食菌原生动物进行，水库调度对MFW的影响较大，粒径谱分析可以成为研究MFW的一个新的手段。本项目对微型生物的功能群及粒径谱的研究，有助于深入了解三峡水库MFW结构，探索MFW物质循环机理，加深人类对三峡水库生态系统的了解，为三峡水库富营养化的治理提供科学依据。