富营养化湖泊中浮游病毒控制藻类生产力和调节细菌死亡率的生态功能研究

Viruses play crucial roles in the ecology and biogeochemistry of aqautic ecology by infecting the microorganism host(alga and bacterium).The ecological function of virioplankton(EFV) is a new research hot in recent years. By infecting the microorganism host(alga and bacterium), planktonic virus could mediate the abundance and diversity of its host, regulate bloom and red tide in the development and termination, reduce the primary production and influence the global biogeochemical cycle. However, the roles of virioplankton as regulators have been a focus of numerous studies in marine environments, yet remain much less studied in freshwater bodies ,especially in eutrophic lakes. Thus, EFV research in eutrophic lakes is urgent and may provide an insight in understanding the mechanism of eutrophication and the outbreake of HAB(harmful algal bloom). Taking eutrophication for research background ,we plans to carry out the research work using Donghu Lake (Wuhan City) as an ideal object what with different trophic levels inner the lake. The essential step of the study is as follows:Firstly, after a relatively long-term field survey, the influence of virioplankton on primary production and bacteria mortality in various trophic levels as well as the rapid change of the FIC(frequency of infected cells) during the periods of algal bloom forming will be elucidated, in addition, the the key parameters that can embody the EFV in eutrophic waters will be identified.Subsequently , the key parameters identified basing on microcosms in lab scale and in the field enclosures will be used for study in detail under the controllable conditions, upon which the key EFV in eutrophic waters could be inferred. Finally, by combinating statistical models and theoretical models, the interaction between eutrophication and EFV as well as the long-term change trend of EFV during the development of eutrophication could be deduced.

海洋中浮游病毒具有调节宿主种群丰度和多样性、控制赤潮消长、影响海洋初级生产力和生物地球化学循环等重要作用，目前开始重视对其生态学功能的研究，但是淡水浮游病毒的相关研究明显弱于海洋，对在富营养化湖泊中的认识几乎为零。开展湖泊中浮游病毒生态学功能的研究，对于阐释富营养化机理和藻类水华暴发机制具有重要意义。项目在前期工作基础上，拟以武汉东湖为研究对象，首先通过现场调查，定量阐述不同营养水平湖区中浮游病毒调节湖泊初级生产力和细菌致死率的差异，高精度解析水华消长期浮游病毒对水华藻类感染率的变化，识别表征浮游病毒生态功能的关键指标；然后，通过微宇宙和中宇宙的研究，在可控条件下细致研究上述关键指标在不同营养水平水体中及水华消长期的变化，阐述富营养化湖泊中浮游病毒的重要生态学功能；最后，将统计模型与机理模型相结合，推演湖泊富营养化与浮游病毒生态功能变化的相互影响以及富营养化进程中其功能变化的长期趋势

以武汉东湖为研究对象，以浮游病毒调节湖泊初级生产力和细菌致死率为重点，研究浮游病毒的生态学功能。研究结果表明浮游病毒丰度、裂解率、溶原诱导率存在明显的时空分布变化，温度对浮游病毒丰度、裂解率和溶原率都存在显著影响，而营养水平对浮游植物溶原率、浮游细菌裂解率存在明显影响。从不同富营养化水平的湖区分离得到了3株感染湖生蓝丝藻（Limnothrix planktonica）的噬藻体，这是首次关于感染湖生蓝丝藻（L. Planktonica）裂性噬藻体的报道。这3株噬藻体的形态特殊之处在于其20面体头部以下有一个明显的“颈部”结构，该形态的噬藻体（噬菌体）尚未见报道。实验室条件下研究了营养盐输入、二氧化碳浓度升高等对噬藻体感染力的影响。结果显示噬藻体PP对宿主藻的感染力会随着营养水平的提高而明显增强，并推测噬藻体在水体富营养化的进程中发挥着调控藻类种群更替的作用。当磷供应充分时，噬藻体的吸附率、成功感染率和释放量均随着大气二氧化碳浓度的升高而升高；而当磷限制明显时，吸附率、成功感染率和释放量却随着大气二氧化碳浓度的升高而降低。 此外，噬藻体感染席藻的潜伏期会在磷限制明显时随着大气二氧化碳浓度的升高而明显缩短，但在磷供应较充分时不受大气二氧化碳浓度升高的影响。这一结果说明，在营养较充分时大气二氧化碳浓度升高能刺激噬藻体的感染力，但在营养限制明显时大气二氧化碳浓度的升高却能削弱噬藻体的感染力，即在未来二氧化碳浓度升高的大背景下，富营养化水体中噬藻体的感染力将增加，但贫营养水体中噬藻体的感染力将降低。