To explore the influence of the decomposition of aquatic macrophytes on water quality in eutrophicated aquatic ecosystems and the interacting environmental factors that trigger nitrogen (N) and phosphorus (P) dynamics, a suburban pond with floating-leaved macrophytes (Pond A) as well as another nearby newly dug pond without any obvious aquatic macrophytes (Pond B) were studied. N and P levels together with a series of parameters relating to biomass, water and sediments were monitored during a period of 84 d that covered the entire decomposition process of plants. The results show that the decomposition of aquatic macrophytes can be divided into two phases, with the first phase having a faster decomposition rate and the second phase, a slower one. With the decomposition of biomass, the dissolved oxygen (DO), oxidation-reduction potential (ORP), and pondus hydrogenii (pH) of the water body increased, whereas the permanganate index (COD_Mn) decreased. Significantly higher levels of total phosphorus in both water and sediment (TP_W and TP_S) were detected in Pond A with macrophytes; TP_W increased quickly during the first phase of biomass decomposition but decreased in the second phase, and TP_S remained relatively stable during the first phase but increased slowly in the second phase. Total nitrogen in both water and sediment (TN_W and TN_S) was also significantly higher in Pond A but remained relatively stable. A structural equation model revealed that the decomposition of aquatic macrophytes, could, directly and indirectly, influence N and P cycles in an aquatic ecosystem through the regulation of pH and DO. Our study indicate that the decomposition of biomass exerted a greater influence on P than on N. Besides the direct release of P from decaying biomass, which caused a significant increase of P in water body, changes of DO and ORP and the subsequent redox state of the whole system during the process also indirectly affected the deposition and dissolution of P between sediment and water. P was the decisive factor that caused endogenous eutrophication in ponds containing aquatic macrophytes.

中文翻译：

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富营养化池塘的原位监测揭示了由浮叶大型植物分解引发的氮和磷的复杂动态

为探索水生植物分解对富营养化水生生态系统水质的影响以及触发氮（N）和磷（P）动态的相互作用环境因素，一个带有浮叶植物的郊区池塘（池塘 A）以及研究了附近另一个没有任何明显水生大型植物的新挖池塘（池塘 B）。在涵盖植物整个分解过程的 84 天期间，监测 N 和 P 水平以及与生物量、水和沉积物相关的一系列参数。结果表明，水生植物的分解可分为两个阶段，第一阶段分解速度较快，第二阶段分解速度较慢。随着生物质的分解，溶解氧（DO）、氧化还原电位（ORP）、_Mn ) 减少。在有大型植物的池塘 A 中检测到水和沉积物（TP _W和_{T S}）中的总磷含量显着更高；TP _W在生物质分解的第一阶段迅速增加，在第二阶段下降，TP _S在第一阶段保持相对稳定，但在第二阶段缓慢增加。水和沉积物中的总氮（TN _W和 TN _S) 在池塘 A 中也明显较高，但保持相对稳定。结构方程模型表明，大型水生植物的分解可以通过调节 pH 和 DO 直接和间接影响水生生态系统中的 N 和 P 循环。我们的研究表明，生物质分解对磷的影响大于对氮的影响。除了腐烂的生物质直接释放磷导致水体中磷的显着增加外，DO和ORP的变化以及随后的氧化还原状态整个过程中的整个系统也间接影响了沉积物和水之间P的沉积和溶解。P是引起大型水生植物池塘内源性富营养化的决定性因素。