浅水湖泊生物可利用磷多介质转化与浮游植物生长响应机制

Phosphorus (P) is recognized as the key limiting factor for phytoplankton growth and in lake systems. In recent years, the variation characteristics of bioavailable P (BAP) and the response mechanisms of phosphatase have gained increasing attention. In general, shallow lakes are highly susceptible to wind-induced disturbance. The transformation and transportation of phosphorus between water and sediment is of frequent and complicated. However, few studies about the characteristics and influence mechanisms of BAP transportation and transformation among multi-mediums (overlying water, sediment, organisms) in shallow lakes, and research about the origin, activity and ecological significance of phosphatase is also scarcely reported. With regard to the above concerns, this project takes Lake Taihu as the research object, and the observation of BAP distribution will be carried out during four life phases of phytoplankton (recovery period, growth period, assemblage period and dormancy period). It focuses on the distribution and concentration levels of BAP among multi-mediums. And also, laboratory flume experiments of the mechanisms of BAP transportation among multi-mediums under different hydrodynamic conditions are also investigated by microcosmic measures(ion chromatography, liquid chromatography, nuclear magnetic resonance,etc.). Meanwhile, the origin, activity features and ecological significance of phosphatase in the process of algae blooms are analyzed with the enzyme-labeled fluorescence , which could reveal the coupling relationship between phosphatase activity and typical phytoplankton growth with their ecotype conditions. The aims of this project is to provide theoretical support for the study of algal bloom mechanisms and water eutrophicaiton control in shallow lakes.

磷是湖泊水体中浮游植物生长等过程的关键限制性因子。近年来，生物可利用磷变化特征及磷酸酶响应机理方面的研究逐渐受到重视。浅水湖泊受风浪扰动，水体与沉积物间磷迁移交换频繁复杂，当前关于生物可利用磷在上覆水、沉积物和生物体内多介质迁移转化及影响机制方面的研究较少，磷酸酶多介质分布、来源特征及浮游植物生长积累的指示意义研究还不系统。本项目以太湖为研究对象，在藻类复苏期、生长期、积聚爆发期和休眠期开展生物可利用磷的多介质分布特征观测研究；通过室内水槽实验，结合微观实验手段（包括离子色谱、液相色谱、核磁共振等），揭示不同水动力条件下生物可利用磷多介质迁移转化规律及影响机制；同时借助胞外酶荧光标记(FLEA)等技术分析藻类水华发生过程中磷酸酶的多介质分布、活性特征及生态学意义，阐释磷酸酶活性与典型浮游植物生长及生境条件间的耦合关系。项目研究为把控藻类水华发生过程和科学治理湖泊富营养化提供理论支持。

项目以大型浅水湖泊太湖及流域典型湖荡为研究对象，调查了水华发生不同时期上覆水、沉积物和浮游植物中生物可利用磷的分布特征、多介质间迁移转化规律，结果表明可酶解有机磷是水体生物可利用磷的重要潜在来源，且浮游植物磷的含量分布变化与上覆水体磷含量保持较高的时空变化特征。其次，探索了不同环境因素下藻种对不同形态磷的利用过程和效率变化，发现上覆水营养盐浓度、pH、水体温度、水体扰动、种间竞争、磷形态等环境因素能够明显影响生物可利用磷在藻、水、沉积物间迁移转化过程。同时，本项目结合野外调查和室内培养研究分析了不同区域、不同时期氮磷营养盐输入对浮游植物生长响应、群落结构及磷循环过程的变化。结果表明氮磷输入对促进浮游植物生长具有一定的作用范围。此外，采用荧光标记等技术分析了磷酸酶活性的来源和分布特征，探明了生物可利用磷和磷酸酶活性与水华发生过程的耦合响应关系，揭示了浮游植物的的酶学响应机制和环境指示意义。