三峡水库超微浮游植物群落动态变化规律及对蓝藻水华影响研究

Since the impoundment of the Three Gorges Reservoir, the eutrophication became serious and algal bloom outbreak in tributary of Three Gorges Reservoir, the dynamics and mechanism of cyanobacteria blooms receives significant attention. However, the studies are rarely reported in the picophytoplankton diversity and the correlation between nanophytoplankton(blooming cyanobacteria) and picophytoplankton. The present project will target on Xiangxi River, a tropical tributary of the Three Gorges Reservoir, to study the basic characteristics and dynamic pattern on the morphotypic and genotypic diversity of nanophytoplankton and picophytoplankton and the relationship in species level. At different phases, during the development of blooms, samples will be collected and examined through the Microscope and Sequencing Technology in the typical regions of the tributary. Meanwhile, the cpc-IGS genotypes database will be also constructed. The responses of cyanobacteria blooms to the related picophytoplankton were physiologically and molecularly explored. Isolation of nanocyanobacteria and picophytoplankton strains will be performed using Micropipet method followed by continuous washing, the obtained strains will be subsequently sequenced for cpc-IGS regions. The dominant genotypes and strains will be identified comparing the strains’ sequences with highly frequencies from the field samples. Using the dominant strains/genotypes to study their physiological and metabolic characters under different co-culture picophytoplankton species, it is expected the significant advantageous points of the dominant cyanobacteria genotypes will be demonstrated, therefore the diversity of picophytoplankton and the inner-driving mechanism of cyanobacteria blooms in the Three Gorges Reservoir at the morphology and molecule level can be elucidated in some extent, which could deepen the understanding of the Microbial loop and may provide the scientific basis for the further prevention and control of water blooms.

三峡水库自蓄水以来，主要入库河流蓝藻从无到水华频发的状态。其水华动态及其成因备受关注，但超微浮游植物的动态变化以及微型水华蓝藻与超微浮游植物这两个生态类群之间的相互作用关系目前鲜有报道。为了深入了解超微浮游植物与水华蓝藻的内在耦合关系，认识超微浮游植物对水华暴发的影响。本课题以香溪河为对象，通过显微观察、高通量测序和基因探针技术，明晰不同时期微型水华蓝藻及超微浮游植物形态型和基因型的时空分布格局，分析超微浮游植物与微型蓝藻时空动态在种属水平的相互关系。同时利用藻株分离筛选技术选出典型支流水华蓝藻与超微浮游植物关联基因型类群的藻株，模拟研究不同关联类型，探讨水华蓝藻在水华暴发前期和优势维持期获得优势的内在机制和驱动因子。本研究是结合形态、分子等手段对大型水库中超微浮游植物与水华动态发展的内部驱动机制进行探讨，可加深人类对三峡微食物环的了解，为水体富营养化治理与藻类水华防治提供理论参考。

三峡水库自蓄水以来，主要入库河流蓝藻从无到有，再到水华频发的状态，其水华动态及其成因备受关注。但超微浮游植物的动态变化以及微型水华蓝藻与超微浮游植物这两个生态类群之间的相互作用关系目前鲜有报道。为了深入了解超微浮游植物与水华蓝藻的内在耦合关系，认识超微浮游植物对水华暴发的影响。.1. 从物种数量上来看，香溪河和小江的浮游植物以绿藻门和硅藻门种类最多，其次为蓝藻，小江的物种数稍多于香溪河。香溪河5、6和7月份的浮游植物种类数较高，以绿藻门种类最为丰富。8月份出现了明显的微囊藻水华，物种数目降低，到一月份达到最低水平。而小江在5、6月份微囊藻水华达到最高值，物种数目较低，而7、8月份物种数到达了最高值。从物种多样性看，香溪河4月份香浓指数最低，10月份最高。而小江1月份香浓指数最低，9月份最高，8月份的均一性指数较低。RDA分析结果显示，香溪河和小江浮游植物群落结构变化的驱动因子不同。.2. 水华种微囊藻在香溪河和小江都有形成较为严重的水华，并全年都有检测到超微浮游植物的存在，主要有PC-cells、PE-cells和PPEs，细胞丰度变化趋势显示：超微浮游植物类群与微囊藻丰度具有相反的发展趋势，两者具有负相关关系。主要原因是微囊藻与超微浮游植物与环境因子呈现相反的相关性，蓝藻与营养盐具有显著的正相关，而超微浮游植物与之相反，而与水体温度等具有显著的正相关性。.3. 超微浮游植物的丰度及类群组成并没有受蓄-排水的影响，其全年变化趋势并没受水位高低影响。.4. Miseq测序发现溪河和小江的超微原核浮游植物占总蓝藻的相对丰度分别为48.65%和60.26%，测序所比对的结果只有Synechococcaceae和Pseudanabaenaceae这两个科，很难鉴定到属种水平，原因是基因文库数据不全；超微真核浮游植物主要是隐藻门植物，其它的为真菌类和囊泡虫类。.5. 共现性网络分析发现，在水华发生前，网络结构复杂；而水华发生时，物种呈单一化，网络结构明显变得简单；水华消退后，网络结构又变得复杂。物种间存在对于资源和空间的强烈竞争。