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.

Keywords: Internal loading; Lake restoration; Nitrogen and phosphorus cycling genes; Submerged macrophyte; Water-sediment system.

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沉积物中氮和磷的释放，即所谓的内源性营养负荷，在决定湖泊富营养化状态及其生态恢复时间方面起着关键作用。恢复沉水植被被认为是一种改善湖泊富营养化的有效措施。然而，关于沉水植被恢复对湖底-水体系统中氮和磷存储及转化机制的影响尚未进行系统的研究。本研究构建了物种丰富度分别为两种或五种的两个沉水植物群落，并在植物生长的三个阶段（5月、7月和10月）监测了植物-水体-沉积物系统的理化特性、氮磷动态变化以及沉积物微生物群落结构与功能的变化。研究结果表明，沉水植被的存在有效减少了底-水系统中的氮和磷负荷，包括它们的化学形态、活性浓度及释放通量。同时，恢复沉水植物改变了沉积物微生物群落组成及其氮磷循环功能。在恢复后，固氮、有机氮代谢、硝酸盐还原以及氨氧化相关的功能基因丰度平均下降了2.95%。相反，参与反硝化和氮限制响应调节的基因丰度增加了20.24%，而与磷循环过程有关的基因丰度则提高了7.29%。此外，不同物种丰富度的沉水植物群落对湖泊氮磷负荷以及沉积物微生物群落结构和功能的影响各不相同，这主要与沉水植物的生活周期阶段相关。这些发现强调了沉水植被在维持湖底营养平衡及沉积物微生物群落方面的重要作用，为研究沉水植被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。

关键词：内源性负荷；湖泊修复；氮磷循环基因；沉水植物；水-底系统。

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