Yang Tingting, Zhang Yingyuan, Zhou Tong, Wang Yaqin, Wang Lu, Yang Jing, Shang Yizi, Chen Feng, Hei Pengfei
Department of Environmental Science, College of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China.
Guizhou Academy of Testing and Analysis, Guiyang 550000, China.
J Environ Manage. 2024 Jun;360:121096. doi: 10.1016/j.jenvman.2024.121096. Epub 2024 May 17.
Macrophyte overgrowth in eutrophic lakes can hasten the decline of shallow water bodies, yet the impact of macrophyte deposition on sediment phosphorus (P) accumulation in the ice-on season remains unclear. Comparative analyses of P variations among 13 semi-connected sub-lakes in Wuliangsu Lake in China, a typical MDE lake, considered external flow and macrophyte decomposition as driving forces. Sediment P fractions and water total phosphorus (TP) were analyzed at 35 sampling points across three ice-on season stages, along with macrophyte TP content to assess debris contributions. Our findings reveal that phosphorus accumulation occurs during the ice-on season in the MDE lake, with an average TP content increase of 16 mg/kg. However, we observed a surprisingly small sediment nutrient accumulation ratio (ΔTP/ΔTN=0.006) compared to macrophyte nutrient levels before decomposition. Further analysis of the dominant species, Potamogeton pectinatus, indicates that a significant portion (55%) of macrophyte phosphorus is released before the ice-on season. This highlights the critical importance of timing macrophyte harvesting to precede the phosphorus leaching process, which has implications for lake management and ecosystem restoration efforts. Additionally, our research demonstrates similar transformations among different sediment fractions as previously reported. Macrophyte debris decomposition likely serves as the primary source of Residual P (Res-P) or TP accumulation. In addition, Ca-bound P (Ca-P) generally showed a decrease, which mainly caused by its transformation to Fe/Al-bound P (Fe/Al-P), Exchange-P (Ex-P), and sometimes to Res-P. However, we emphasize the significant impacts of flow dynamics on Ca-P transport and transformations. Its hydrodynamic action increases water dissolved oxygen, which accelerates the transformation of Ca-P to more easily released Fe/Al-P and Ex-P. Furthermore, hydrodynamic transport also leads to upstream Ca-P transport to downstream. This underscores the necessity of considering flow dynamics when estimating phosphorus variations and formulating phosphorus restoration strategies.
富营养化湖泊中的大型植物过度生长会加速浅水水体的衰退，然而在冰封期大型植物沉积对沉积物磷（P）积累的影响仍不清楚。在中国典型的大型植物主导型富营养化湖泊乌梁素海的13个半连通子湖泊中，通过比较分析，将外部水流和大型植物分解视为驱动力。在冰封期的三个阶段，对35个采样点的沉积物磷组分和水体总磷（TP）进行了分析，并结合大型植物的TP含量来评估残骸的贡献。我们的研究结果表明，在大型植物主导型富营养化湖泊的冰封期会发生磷积累，TP含量平均增加16毫克/千克。然而，与大型植物分解前的养分水平相比，我们观察到沉积物养分积累率出奇地低（ΔTP/ΔTN = 0.006）。对优势物种龙须眼子菜的进一步分析表明，在冰封期之前，很大一部分（55%）的大型植物磷会被释放出来。这突出了在磷淋溶过程之前进行大型植物收获的关键重要性，这对湖泊管理和生态系统恢复工作具有重要意义。此外，我们的研究表明，不同沉积物组分之间存在与先前报道类似的转化。大型植物残骸分解可能是残余磷（Res-P）或TP积累的主要来源。此外，钙结合磷（Ca-P）总体上呈现下降趋势，这主要是由于其向铁/铝结合磷（Fe/Al-P）、交换性磷（Ex-P）的转化，有时也会转化为Res-P。然而，我们强调水流动力学对Ca-P迁移和转化的重大影响。其水动力作用增加了水体溶解氧，加速了Ca-P向更易释放的Fe/Al-P和Ex-P的转化。此外，水动力输运还导致上游的Ca-P向下游输运。这强调了在估算磷变化和制定磷恢复策略时考虑水流动力学的必要性。
