草型湖泊与藻型湖泊沉积物有机质性质调控磷释放行为的机理研究

Lake eutrophication is one of the world environmental problems, the deposition of organic matter in lakes of different trophic levels will significantly changes sediment phosphorus balance. Centring on scientific issues of the difference of sediment phosphorus release between macrophyte-flourishing lakes and algae-predominant lakes, and taking macrophyte-flourishing lakes (Lake Yandong and grass area of Lake Qingling) and algae-predominant lakes (Lake Chaohu and breeding area of Lake Qingling) as the research object, the difference of phosphorus release patterns between this two type of lakes was explored, and the process and mechanisms of sediment performing the function of phosphorus source to phosphorus sink, and to phosphorus source in different stage from growth to extinction of waterweeds in macrophyte-flourishing lakes was revealed; using field investigation, combined with indoor culture experiment, the difference of mineralization of organic matter, decomposition, and reduction ability, and its relationship with phosphorus release, and the different influence on phosphorus adsorption behavior in sediment of macrophyte-flourishing lakes and algae-predominant lakes were comparatively studied. Finally, the mechanism of organic matter composition regulating sediment phosphorus release behavior was revealed. The implementation of this research will be helpful to further clarify the biogeochemical mechanism and the different forms of phosphorus release from sediments in macrophyte-flourishing lakes and algae-predominant lakes, reveal the reasons for maintaining poor nutrition state of macrophyte-flourishing lake, enrich the mechanism of positive feedback of eutrophication in eutrophic lake, and provide scientific basis for the restoration of eutrophic lakes. Therefore, it has important theoretical and practical significance.

湖泊富营养化是世界性环境问题之一，不同营养类型湖泊底层有机质的沉积将明显改变沉积物磷的收支。围绕草型和藻型湖泊沉积物磷释放差异性这一重要科学问题，申请者拟选取季节性不同水草占优势的水体－青菱湖水草区和苦草为优势种的严东湖与藻型湖泊（区）巢湖和青菱湖养殖区为实验对象，探究草型和藻型湖泊沉积物磷释放模式的差异，揭示草型湖泊不同水草生长到消亡不同阶段，沉积物磷源和磷汇功能转换的过程与机理；并野外调查与室内模拟相结合，比较研究不同性质有机质矿化能力、可分解性和还原能力的差异及其与磷释放的关系，以及对磷吸附行为的不同影响。最终揭示有机质性质调控沉积物磷释放行为的机理。本项研究的实施有助于深入阐明沉积物磷释放的生物地球化学机制及其在草型和藻型湖泊的独特表现形式，揭示草型湖泊维持贫营养状态，而藻型湖泊富营养化程度以正反馈形式加速的机理，同时为富营养化湖泊的修复提供科学依据，因而具有重要的理论与实践意义。

湖泊富营养化是世界性环境问题之一，主要表现为植物营养元素磷的激增导致浮游植物的过量生长和氧的锐减，从而引起湖泊生态系统发生一系列剧变，而不同营养类型湖泊磷再生模式及潜在机制差异显著。以严东湖、青菱湖和巢湖为对象，系统分析了表层水和间隙水各形态氮和磷浓度浓度，沉积物碳、氮、磷和铁化合物含量，沉积物胞外酶活性、磷吸附行为、磷溶菌丰度、总微生物和磷功能微生物等。研究结果表明，处于不同稳态的湖泊，磷供应途径和潜在机制截然不同。在高氮磷含量的富营养化湖泊，铁结合态磷的厌氧释放和高释放潜能导致间隙水和表层水中磷的积累，并诱导藻华种类由蓝藻向绿藻转变。在处于由水生植物向藻类过渡后期的湖泊，磷溶菌驱动的有机磷水解和钙结合态磷的解离对湖泊磷的再生具有重要作用。在处于由水生植物向藻类过渡早期的湖泊，外源磷输入是主要的磷供应方式。在以大型水生植物占优势的湖泊中，磷供应不足。多种营养循环特别是碳、氮、磷、氧、铁循环的偶联可有效增加磷再生途径的多样化和再生强度。不同稳态磷功能微生物丰度、群落组成及其功能也不同，可以解释不同稳态下磷再生模式的不同。此外，不同稳态下磷再生途径的不同主要归因于有机质结构和数量的不同。本研究厘清了不同营养类型湖泊磷供应途径和潜在机制，可为富营养化湖泊的修复提供科学依据，具有重要的理论与实践意义。