Aquatic plants are the main primary producers and an important part of the aquatic ecosystem. Seasonal flooding broke out in July 2020 in the middle and lower reaches of the Yangtze River, resulting in continued high water levels in lakes connected to the Yangtze River. To study the impact of extreme flooding on aquatic vegetation cover, we utilized two methods (surveying and remote sensing image data) to determine the changes in the aquatic vegetation cover of Shengjin Lake, one of the lakes connected to the Yangtze River, during the wet season from 2018 to 2020. The results showed that the dominant aquatic plant species before the flood in July 2020 were the emergent plant Zizania caduciflora, the floating plant Trapa incisa, the submerged plant Ceratophyllum demersum and Vallisineria natans. The area covered by aquatic vegetation in 2018–2019 showed a slight upward trend, increasing from 24.94 to 25.94 km2. In April 2020, the aquatic vegetation cover was 25.53 km2, and after the flooding in July 2020, the aquatic vegetation cover decreased sharply to 1.36 km2, which was mainly composed of emergent plant Z. caduciflora in the nearshore. No recovery of the dominant aquatic plant species, the floating plant T. incisa and other submerged plants, was seen during the monitoring of water level decline from September to December 2020. Winter wetland plants were not significantly affected by flooding. The results of the study provide a theoretical basis for the maintenance mechanism of aquatic vegetation and lake management in Shengjin Lake.
Many reports have demonstrated that the removal of aquaculture purse seine is conducive to the restoration of aquatic vegetation and the improvement in water quality, but less attention has been paid to the effects on phytoplankton. This paper addressed the response of phytoplankton community structure to aquatic vegetation restoration after purse seine removal in Caizi Lakes. The results showed that the average dissolved oxygen (from 7.43 ± 0.25 mg/L to 9.12 ± 0.49 mg/L) and Secchi depth (from 28.40 ± 6.20 cm to 47.61 ± 14.62 cm) in the water column of the Caizi Lakes increased after the restoration of aquatic vegetation, while the average concentrations of total nitrogen (from 2.00 ± 0.16 mg/L to 1.34 ± 0.18 mg/L) and total phosphorus (from 0.15 ± 0.02 mg/L to 0.06 ± 0.01 mg/L) decreased. After the restoration of the aquatic vegetation, the cell density of phytoplankton declined from 21.04 ± 4.57 × 106 cells/L to 12.74 ± 3.63 × 106 cells/L, and the biomass fell from 18.13 ± 3.57 mg/L to 9.72 ± 2.55 mg/L. We also observed that Shannon–Wiener diversity, Margalef and Pielou indices of phytoplankton surged by 66.50%, 46.20% and 84.68%, respectively. Because this study demonstrated that aquatic vegetation could alleviate the eutrophication, it can provide guidance for the restoration and protection of the aquatic ecosystem.
Aquatic vegetation has been restored since the removal of seine nets from the lake surface of Shengjin Lake in 2018. Through four seasons of phytoplankton sampling surveys from 2019–2020, we analyzed spatial and temporal changes in phytoplankton communities, water quality, and aquatic plant recovery in conjunction with previous research literature to reveal the response mechanisms of phytoplankton community structure to rapidly recovering aquatic vegetation. The results showed that the Secchi depth increased (0.4 m to 0.7 m), the concentration of total phosphorus decreased (0.053 mg/L to 0.41 mg/L), the species of aquatic plants (5 species to 16 species), phytoplankton species (210 species to 254 species) and cell density increased after the removal of the seine. Since the removal of the seine of Shengjin Lake, the aquatic vegetation cover has exceeded 80%, the phytoplankton biodiversity has increased, and the water quality has recovered to II-III water status. Our results show that aquatic plants improve water quality through direct and indirect effects and influence phytoplankton community structure together with the water environment, which can provide guidance for the restoration situation of the middle and lower reaches of the Yangtze River through-river lake ecosystems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.