State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, No. 73 East Beijing Road, Nanjing 210008, China.
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, No. 73 East Beijing Road, Nanjing 210008, China.
Water Res. 2022 Oct 1;224:119067. doi: 10.1016/j.watres.2022.119067. Epub 2022 Sep 7.
In shallow lakes, eutrophication leads to a shift of the macrophyte-dominated clear state towards an algae-dominated turbid state. Phosphorus (P) is a crucial element during this shift and is usually concentrated in the suspended particulate matter (SPM) in water. However, the dominant processes controlling internal P release in the algae- (ADA) and macrophyte-dominated (MDA) areas under the influence of P-concentrated SPM remains unclear. In this study, we conducted monthly field observations of P exchange across the sediment-water interface (SWI) with the deposition of SPM in the ADA and MDA of Lake Taihu. Results revealed that both algae- and macrophyte-originated SPM led to the depletion of oxygen across the SWI during summer and autumn. Redox-sensitive P (Fe-P) and organic P (Org-P) were the dominant mobile P fractions in both areas. High fluxes of P across the SWI were observed in both areas during the summer and autumn. However, the processes controlling P release were quite different. In MDA, P release was mostly controlled by a traditional Fe-P dissolution process influenced by the coupled cycling of iron, sulfur, and P. In the ADA, Org-P control was intensified with the deterioration of algal bloom status, accompanied with the dissolution of Fe-P. Evidence from the current study revealed that the dominant process controlling the internal P release might gradually shift from Fe-P to a coupled process of Fe-P and Org-P with the shift of the macrophyte- to an algae-dominated state in shallow eutrophic lakes. The differentiated processes in the MDA and ADA should be given more attention during future research and management of internal P loadings in eutrophic lakes.
在浅水湖泊中，富营养化会导致以大型水生植物为主的清澈状态向以藻类为主的浑浊状态转变。磷（P）是这一转变过程中的关键元素，通常集中在水中的悬浮颗粒物（SPM）中。然而，在受富含 P 的 SPM 影响下，藻类（ADA）和大型水生植物（MDA）占主导地位的区域内，控制内部 P 释放的主要过程仍不清楚。在这项研究中，我们对太湖 ADA 和 MDA 中 SPM 的沉积对 P 交换的影响进行了每月的实地观测。结果表明，夏季和秋季，藻类和大型水生植物来源的 SPM 都会导致 SWI 缺氧。在这两个区域，氧化还原敏感磷（Fe-P）和有机磷（Org-P）是主要的可移动磷组分。夏季和秋季，SWI 都有高通量的 P 通过。然而，控制 P 释放的过程却大不相同。在 MDA 中，P 的释放主要由受铁、硫和 P 循环耦合影响的传统 Fe-P 溶解过程控制。在 ADA 中，Org-P 的控制随着藻类水华状况的恶化而加剧，同时伴随着 Fe-P 的溶解。本研究的证据表明，在浅水富营养湖中，从大型水生植物向藻类占主导地位的状态转变过程中，控制内部 P 释放的主导过程可能逐渐从 Fe-P 转变为 Fe-P 和 Org-P 的耦合过程。在未来对富营养湖内部 P 负荷的研究和管理中，应更加关注 MDA 和 ADA 的不同过程。
