College of Chemistry and Environmental Protection Engineering, Southwest Minzu University, 610041 Chengdu, PR China.
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, PR China.
Sci Total Environ. 2019 Oct 10;686:753-763. doi: 10.1016/j.scitotenv.2019.05.133. Epub 2019 May 15.
Sediment dredging is a controversial technology for lake eutrophication control. A lengthy and holistic assessment is important to understand the effects of a dredging project on a lake ecosystem. In this study, a dredging project was followed for 5 years. To understand the variations of lake ecosystems before, during and after the project, water quality, phytoplankton, zooplankton and benthic animal biomass were monitored; Four subindicators, including eco-exergy (Ex), structural eco-exergy (Ex), buffer capacity of total phosphorus for phytoplankton (β) and trophic level index (TLI) were calculated and developed to an integrated ecosystem health indicator (EHI). The monitoring results showed that the dredging project caused many short-term positive effects such as decreased total nitrogen, total phosphorus, permanganate index and phytoplankton biomass throughout the entire lake water, increased Secchi disk depth in the whole lake and increased benthonic animal biomass in the nondredged regions. However, these positive effects disappeared overtime. Water chemistry and biomass returned to the initial state before dredging. EHI showed that the dredging project caused negative effects on the lake health in the dredged region at first. Subsequently, the health status of the entire lake, including the dredged and nondredged regions, improved until 1-2 years after the project finished. Because of the lack of other timely ecological restoration measures, the lake gradually returned to its initial health status. However, the health status in the dredged regions was only slightly better than before dredging and often worse than that of the nondredged regions. Our study suggested that dredging projects may only cause short-term positive effects on lake ecosystem health. The external interception and dredging ratio were important. A dredging project should be combined with other ecological lake restoration measures when the project has caused positive effects in a lake.
底泥疏浚是湖泊富营养化控制的一项有争议的技术。为了了解疏浚工程对湖泊生态系统的影响，需要进行长期而全面的评估。在本研究中，对一个疏浚工程进行了 5 年的跟踪监测。为了了解项目前后湖泊生态系统的变化，监测了水质、浮游植物、浮游动物和底栖动物生物量；计算并开发了四个子指标，包括生态热能值（Ex）、结构生态热能值（Ex）、总磷对浮游植物的缓冲能力（β）和营养级指数（TLI），以作为综合生态系统健康指标（EHI）。监测结果表明，疏浚工程在整个湖泊范围内短期内产生了许多积极影响，如总氮、总磷、高锰酸盐指数和浮游植物生物量降低，整个湖泊的透明度增加，未疏浚区的底栖动物生物量增加。然而，这些积极影响随着时间的推移而消失。水质和生物量恢复到疏浚前的初始状态。EHI 表明，疏浚工程首先对疏浚区的湖泊健康造成了负面影响。随后，包括疏浚区和未疏浚区在内的整个湖泊的健康状况得到改善，直到项目完成后 1-2 年。由于缺乏其他及时的生态修复措施，湖泊逐渐恢复到初始健康状态。然而，疏浚区的健康状况仅略好于疏浚前，且经常比未疏浚区差。我们的研究表明，疏浚工程可能仅对湖泊生态系统健康产生短期的积极影响。外部截留和疏浚比例是重要的。当疏浚工程在湖泊中产生积极影响时，应将其与其他生态湖泊修复措施结合使用。
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