Effects of extreme flooding on aquatic vegetation cover in Shengjin Lake, China

AbstractAquatic 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 plantZizania caduciflora, the floating plantTrapa incisa, the submerged plantCeratophyllum demersumandVallisineria 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 plantZ. caduciflorain the nearshore. No recovery of the dominant aquatic plant species, the floating plantT. incisaand 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.