State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
Water Res. 2023 Sep 1;243:120414. doi: 10.1016/j.watres.2023.120414. Epub 2023 Jul 25.
Increased algal blooms and loss of aquatic vegetation are critical environmental issues associated with shallow lakes worldwide. The increase in organic matter (OM) in both macrophyte-dominated areas (MDAs) and algae-dominated areas (ADAs) has exacerbated these problems. Most OM in water is concentrated as suspended particulate matter (SPM), which eventually migrates to the sediment. However, the detailed origins and fates of OM in water-SPM-sediment systems with coexisting MDAs and ADAs remain unclear. Therefore, in this study, we conducted monthly field investigations in Lake Taihu, focusing on OM-migration patterns in an MDA and an ADA. The C/N mass ratios, δC contents, and OM compositions of the water, SPM, and sediment were analyzed. Our findings revealed that autochthonous sources of OM prevailed in water, whereas terrestrial sources prevailed in SPM and sediment. Rapid decomposition processes of microbial- and algae-derived dissolved OM were discovered along the water-SPM-sediment pathways in both areas. A trend towards a shift from macrophytes to algae in the MDA was also discovered. Overall, the entire lake underwent a burial process of OM in both types of areas, with mineralization mostly occurring during the algal-bloom seasons and more strongly in the ADA. Furthermore, we deduced that a decrease in the OM-burial rate, but an increase in the mineralization rate, might occur after a complete shift from a macrophyte- to an algae-dominated status. Such a shift might change the carbon-cycle process in eutrophic shallow lakes and should be given more attention in future research.
富营养化浅水湖泊中藻类水华暴发和水生植被退化是两个关键的环境问题，而水体和沉积物中大量有机质（OM）的积累则进一步加剧了这两个问题。大型水生植物区（MDA）和藻类区（ADA）中 OM 的增加是造成这一问题的主要原因，水体中的大部分 OM 都以悬浮颗粒物（SPM）的形式存在，最终会向沉积物中迁移。然而，对于 MDA 和 ADA 共存的水 -SPM- 沉积物系统中 OM 的详细来源和归宿仍然不清楚。因此，本研究以 MDA 和 ADA 为研究对象，对太湖进行了为期一年的逐月野外调查，以阐明富营养化浅水湖泊中 OM 的迁移转化过程。对水体、SPM 和沉积物中的 OM 组成、C/N 质量比和 δC 进行了分析。结果表明，MDA 中 OM 主要来源于藻类等自生源，而 SPM 和沉积物中的 OM 主要来源于陆源输入。在 MDA 和 ADA 中，微生物和藻类来源的 DOM 沿着水 -SPM- 沉积物途径快速降解。MDA 中大型水生植物向藻类的演替趋势也十分明显。总体而言，两种类型的区域均发生了 OM 的埋藏过程，且埋藏主要发生在藻类水华季节，ADA 中的埋藏程度更强。此外，我们推测，当 MDA 完全演替为藻类区后，OM 的埋藏速率可能会降低，而矿化速率可能会升高。这种演替可能会改变富营养化浅水湖泊的碳循环过程，值得在未来的研究中给予更多关注。
