The release of nitrogen and phosphorus from sediments, known as internal nutrient loading, plays a crucial role in determining the eutrophic state of lakes and the timeframe for their ecological recovery. The restoration of submerged macrophytes is considered an effective measure to improve lake eutrophication. However, the impact of submerged macrophytes restoration on the storage and transformation mechanisms of nitrogen and phosphorus in lake sediment-water systems has not yet been systematically studied. This study constructed two submerged macrophyte communities with species richness of either two or five and monitored the physicochemical characteristics, nitrogen and phosphorus dynamics, and the structural and functional changes of sediment microbiomes in the plant-water-sediment system during three growth stages of the plants (May, July, and October). Our results demonstrated that the presence of submerged vegetation effectively reduced the nitrogen and phosphorus loads in the sediment-water system, encompassing their chemical forms, active concentrations, and release fluxes. Simultaneously, the restoration of submerged vegetation altered the composition of sediment microbial communities and the nitrogen and phosphorus cycling functions. Following the restoration, the abundance of functional genes associated with nitrogen fixation, organic nitrogen metabolism, nitrate reduction, and nitrification exhibited an average decrease of 2.95 %. In contrast, the abundance of genes involved in denitrification and nitrogen limitation response regulation increased by 20.24 %, while those related to phosphorus cycling processes showed a 7.29 % increase. Additionally, submerged macrophyte communities with varying richness differentially affected lake nitrogen and phosphorus loads, as well as the structure and function of sediment microbiomes, primarily related to the life cycle stages of the submerged macrophytes. These findings highlight the crucial role of submerged plants in maintaining lake nutrient balance and sediment microbiomes, providing valuable insights into how the restoration of submerged vegetation affects nutrient cycling in aquatic ecosystems.

中文翻译：

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水下植被的恢复调节微生物群落，以减少沉积物-水系统中的氮和磷负荷


沉积物中氮和磷的释放，称为内部营养负荷，在决定湖泊的富营养化状态及其生态恢复的时间框架方面起着至关重要的作用。恢复沉水植物被认为是改善湖泊富营养化的有效措施。然而，水下大型植物恢复对湖泊沉积物-水系统中氮和磷的储存和转化机制的影响尚未得到系统研究。本研究构建了 2 个物种丰富度为 2 或 5 的沉水大型植物群落，监测了植物 3 个生育阶段（5 月、7 月和 10 月）植物-水-沉积物系统中的理化特性、氮磷动力学以及沉积物微生物组的结构和功能变化。我们的结果表明，淹没植被的存在有效地降低了沉积物-水系统中的氮和磷负荷，包括它们的化学形式、活性浓度和释放通量。同时，沉水植被的恢复改变了沉积物微生物群落的组成和氮磷循环功能。恢复后，与固氮、有机氮代谢、硝酸盐还原和硝化相关的功能基因丰度平均下降了 2.95 %。相比之下，参与反硝化和氮限制反应调节的基因丰度增加了 20.24 %，而与磷循环过程相关的基因丰度增加了 7.29 %。 此外，具有不同丰富度的沉没大型植物群落对湖泊氮和磷负荷以及沉积物微生物组的结构和功能产生差异，主要与沉没大型植物的生命周期阶段有关。这些发现强调了沉水植物在维持湖泊养分平衡和沉积物微生物组方面的关键作用，为沉水植被的恢复如何影响水生生态系统中的养分循环提供了宝贵的见解。