微囊藻水华与浮游细菌的关系及其机制

Phytoplankton is the major primary producers of eutrophication lakes, whereas bacterioplankton play an important role in energy flow and material circulation in aquatic ecosystems, such as lakes. However, at present, little is known about whether there is a species-specific relationship between Microcystis and bacterioplankton in Microcystis blooms dominanted lake ecosystems. In this proposed study, we will focus on the relationship between bacterioplankton and Microcystis blooms. Combined methods including the field investigation, in situ microcosms experiment, lab-scale simulation experiment will be applied to carry out this study, in which Meiliang Bay in the northern part of Lake Taihu where cyanobacterial blooms (especially Microcystis blooms) frequently occur, will be selected for field experiment. We will first analyze bacteria community compositions during the occurrences of different cyanobacteria blooms. Then, by combining DNA-based stable isotope probing (SIP) and high-throughput pyrosequencing, we will examine the bacterioplankton-Microcystis relationship and its action mechanism during the occurrence, accumulation and breakdown phases of Microcystis blooms, which may leads differences in the concentrations of dissolved organic carbon, dissolved oxygen and grazing. Furthermore, we will try to reveal the key bacteria community involved in decomposition of Microcystis biomass. The obtained results will help us to deepen our understanding of structure and function of lake ecosystems, better understand the mechanism of maintaining regime of Microcystis blooms, and contribute to the theory of interspecific relationships and functional groups.

浮游藻类是富营养化湖泊中主要的初级生产者，而浮游细菌在湖泊等水生生态系统的物质循环和能量流动中发挥着重要作用，然而目前尚不清楚在微囊藻水华占优势的湖泊生态系统中微囊藻与浮游细菌间是否存在种属特异性的关系。本项目以太湖易发生蓝藻水华，尤其微囊藻水华的北部湖区- - 梅梁湾为研究对象，借助稳定同位素探针和高通量测序技术，采用野外监测、原位模拟和实验室控制试验相结合的方法，在明确不同种类蓝藻水华对浮游细菌群落结构影响的基础上，进一步从微囊藻水华发生、堆积、分解过程中水体溶解性有机物、溶解氧和捕食作用变化的特异性三方面，揭示微囊藻水华对浮游细菌群落结构的影响机制，探明参与微囊藻水华分解的关键浮游细菌种类或类群。上述研究的开展将有助于深入认识湖泊生态系统的结构与功能，对于了解微囊藻水华稳定态系统的维持机制具有重要理论价值，同时也将丰富种间关系、功能群等生态学理论。

浮游藻类是富营养化湖泊中主要的初级生产者，而浮游细菌在湖泊等水生生态系统的物质循环和能量流动中发挥着重要作用，揭示藻类与浮游细菌之间的关系及其作用机制是了解湖泊生态功能的关键。本项目以太湖易发生蓝藻水华，尤其微囊藻水华的北部湖区——梅梁湾为研究对象，采用野外监测、原位模拟和室内控制试验相结合的方法，从微囊藻水华发生、堆积、分解过程中水体溶解性有机物、溶解氧和捕食作用变化的特异性三方面，揭示微囊藻水华对浮游细菌群落结构的影响机制。. 研究发现，1-3月，微囊藻（Microcystis spp.）和席藻（Phormidium spp.）、针杆藻（Synedra）和星杆藻（Asterionella）是梅梁湾的优势浮游藻类；6-10月微囊藻成为唯一的优势藻类且形成了水华。典范对应分析（Canonical correspondence analysis）表明藻类alpha多样性是影响浮游细菌群落结果组成的关键性环境因子；高通量测序分析发现，微囊藻与隶属于Micrococcineae的OUT 54、隶属于Burkholderiales OUT 16存在显著性负相关关系，与OUTs 2 and 8 (Actinomycetales) 存在显著性正相关关系；针杆藻（Synedra）与OTUs 1和21 (Actinomycetales)、OUT 33（Planctomycetales）、OUT 40（Rhodobacterales）、OUT 13（Sphingomonadales）、OUT 19（Xanthomonadales）存在显著性正相关关系，与OUTs 3和 42（unclassified bacteria）存在显著性负相关关系。这些结果表明浮游细菌与浮游藻类存在种属特异性关系，即使在同一属内也存在差异。在水华微囊藻堆积过程中，浮游细菌功能基因结构组成发生了变化，且变化因微囊藻浓度的不同而异；高浓度水华微囊藻的添加导致浮游细菌碳分解、厌氧氨氧化、氮吸收、多磷酸盐合成等功能基因的相对含量明显增加；而水华消退后，浮游细菌功能基因结构组成得以恢复。. 上述结果更为深入的阐明了微囊藻水华与浮游细菌种间关系及其机理，有助于深入认识湖泊生态系统的结构与功能，对于了解微囊藻水华稳定态系统的维持机制具有重要理论价值，同时也将丰富种间关系、功能群等生态学理论。