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Carex communities in most Yangtze-disconnected lakes have been degraded severely due to alterations in water level fluctuations. To explore the feasibility of restoring the lakeshore Carex communities through ecological regulation of water level, the present study selected the Yangtze-connected Qili Lake (the lakeshore was dominated by Carex) and the Yangtze-disconnected Wuchang Lake (the lakeshore was dominated by Zizania latifolia) as model systems, and analyzed the lakeshore seed bank characteristics and seed-related quantitative, morphological, and germination traits of three representative Carex species. According to the results, although Carex seed density in the Qili Lake seed bank was obviously higher than that in Wuchang Lake, their contribution to the total seed density in both lakes was extremely low, with no significant difference between the two lakes. The results indicate that restoration of the degraded Carex communities using existing seed bank in Yangtze-disconnected lakes exclusively through water level regulation is not feasible. In addition, the seed densities of aboveground parts of Carex cinerascens, Carex dimorpholepis, and Carex argyi in Qili Lake were 6.9 × 10 4 , 45.1 × 10 4 , and 3.6 × 10 4 seeds/m 2 , respectively, which can provide high numbers of seeds continuously for lakeshore Carex restoration. The results of seed germination experiments showed that light, burial depth, and their interaction had significant effects on seed germination of the three species, whereas water condition had a significant effect only on C. dimorpholepis seed germination. The average germination rates of the three Carex species were 16.63 %, 19.06 %, and 7.78 %, respectively. However, considering the high seed densities in the aboveground parts of the three species, there are considerable numbers of seeds that can be used for Carex restoration. Therefore, the restoration of Carex communities in lakeshore zones of Yangtze-disconnected lakes is still possible if water level regulation can be combined with natural or artificial seed supplementation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Macrozoobenthos and submerged macrophytes interact closely. However, studies in China have focused on the middle and lower reaches of the Yangtze River, where shallow lakes are concentrated, rather than on temperate lakes. To clarify the responses of taxonomic and functional groups of macrozoobenthos in temperate lakes to changes in submerged macrophyte biomass (B Mac ) on a large scale, 19 temperate lakes within Baiyangdian Lake were investigated in this study. The B Mac differed greatly across the 19 lakes, and Potamogeton crispus was the dominant species. According to the B Mac , the 19 lakes were divided into 4 groups. One-way analysis of variance and Pearson correlation analysis showed that the water environmental parameters were different among the 4 groups, and the B Mac was significant correlated with all the physical and chemical parameters of water bodies (except for water depth). Forty-one taxa of macrozoobenthos were identified in the 19 lakes, with oligochaetes, Hirudinea, gastropods, crustaceans, chironomid larvae, and aquatic insects (excluding chironomid larvae) represented by 9, 1, 4, 2, 19, and 6 species, respectively. Chironomid larvae and oligochaetes dominated by density, and gastropods and chironomid larvae dominated by biomass. Canonical correspondence analysis showed that the B Mac was the most important factor affecting the macrozoobenthos community structure in group 1 to group 4. Macrozoobenthos with low pollution tolerance values were mainly found in areas with high B Mac , while species with high pollution tolerance values were mainly distributed in areas with low B Mac and high nutrient contents. Different taxonomic and functional groups of macrozoobenthos responded differently to changes in B Mac . As B Mac increased, density and biomass of oligochaetes and chironomid larvae tended to decrease, while those of gastropods and aquatic insects tended to first decrease and then increase. Collectors had more species than any other functional group in group 1 to group 4. As B Mac increased, density and biomass of collectors gradually decreased, while density of predators, shredders, and scrapers tended to first decrease and then increase., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Aquatic vegetation in lakes along the middle and lower reaches of the Yangtze River has been seriously degraded by human disturbances such as river-lake disconnection and water eutrophication. Chaohu Lake is a typical lake with reservoir-like water-level fluctuations (WLFs). Since a sluice was built in 1962, the coverage of aquatic vegetation in Chaohu Lake has been very low (0.77%). In this study, field investigations of the aquatic vegetation and seed bank of Chaohu Lake were conducted, and aboveground vegetation diversity was found to be low. Forty-eight species were recorded, of which submerged, floating-leaved, and emergent macrophytes were 1, 5, and 10, respectively. Currently, artificially planted Phragmites australis and Salix communities have become the main community types. A total of 18 aquatic macrophytes were identified in the seed bank, of which the number of submerged, floating-leaved, and emergent macrophytes and hygrophytes were 2, 2, 3, and 11, respectively; the seed density was 2.05, 2.05, 16.93, and 9.30 ind./m 2 , respectively. The seed density of aquatic macrophytes was much lower in Chaohu Lake than in the lakes with quasi-natural WLFs, and the seeds were mainly distributed in the estuary area. Only two emergent macrophyte species (Typha) germinated in the open water area. Spearman correlation analysis showed that the distance to bank was the main environmental factor that affected aquatic macrophyte diversity and seed density in the seed bank. It is not feasible to promote the natural reconstruction and restoration of aquatic macrophytes in Chaohu Lake by decreasing the water level or increasing water transparency, but the area near the estuary can be identified as a priority restoration area (PRA) for aquatic macrophytes. Artificial transformation of the micro-topography can be used to guide some hydrochorous seeds in the tributaries to the PRA and restore aquatic vegetation in the local area., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Plant roots in lakeshore areas can directly determine the survival of the aboveground plant parts. However, most current studies are focused on the aerial shoots, and less attention has been paid to the functions of the roots. In order to evaluate the effects of water level fluctuations (WLFs) on root architectural and morphological traits of plants in lakeshore areas, field investigations were conducted seasonally in three subtropical floodplain lakes with different types of WLFs. The results showed that both the pH and moisture contents of the soils were significantly different in all seasons among the three lakes, while the total nitrogen and total phosphorus in the soils only showed significant differences in certain seasons. Significant differences were also found in the two architectural trait parameters (root length density and root branching number) and three morphological trait parameters (root tissue density, root surface area, and root volume), all of which (except for root tissue density) were highest in the Dahuchi lake that experiences intermittent WLFs, and lowest in the Chaohu Lake with reservoir-like WLFs. With increasing lakeshore elevation gradients, we found that root length density, root branching number, root surface area, and root volume in the three lakes changed significantly, and all these root trait parameters increased first and then decreased. However, no significant differences were found for the above four root traits in the three lakes over the different seasons. Spearman correlation analyses indicated that both the hydrological and physicochemical factors were strongly correlated with the architectural and morphological root trait parameters, and the duration of submergence (duration) was the most important factor, judging from the correlation coefficients (R). The results of stepwise multiple regression further indicated the duration was the key factor affecting plant root traits. Based on the results of this study, we suggest that the WLFs in reservoir-like lakes should be changed in order to improve the ecological functions of the lakeshore.

To understand the health status of aquatic ecosystem in Lake Erhai, the community structure of benthic animals was investigated based on 27 samples from 11 typical monitoring sections in March, June, September and December 2021, and the benthic index of biotic integrity (B-IBI) assessment system was also established. The results showed that Lake Erhai contains 56 genera and species of benthic animals, which refers to 4 phyla, 6 classes, 28 families and 54 genera. The assessment system of B-IBI for Lake Erhai consists mainly of the total number of classification units, proportion of chironomid individuals, and BMWP index, which obtained by range test, discriminatory power and Pearson correlation screen. The health status of aquatic ecosystem in Lake Erhai can divide into five grades according to ratio scoring method, i.e., >2.61, 2.10~2.61, 1.82~2.10, 1.42~1.82 and <1.42, representing health, sub-health, fair, poor and very poor health status, respectively. Based on above method and standard, the health of aquatic ecosystem for Lake Erhai in 2021 is fair status. Specifically, five, six, five, nine and two sampling sites were in health, sub-health, fair, poor and very poor health status, accounting for 18.5%, 22.2%, 18.5%, 33.3% and 7.4% of the total sites, respectively. [ABSTRACT FROM AUTHOR]

To address the issues of submerged vegetation restoration in the deep-water area of Baiyangdian Lake, a type of suspended ecological bed was developed, which was constructed with aquatic plants, ropes and supporting poles. The depth of a suspended ecological bed could be adjusted based on the water level. From July to November 2019, the phytoplankton community structure in the water around the suspended beds was continually monitored, and the effects of the submerged plants present in the suspended beds on the phytoplankton community structure in the deep-water area of the lake were studied. The results showed that Myriophyllum spicatum L. grew well in the suspended beds, with 95% survival after 60 d. The maximum biomass was reached in 55 d, and the water surface coverage reached 23%. There were 71 species of phytoplankton belonging to seven phyla in the water surrounding the suspended ecological beds. Over half (36 species) were members of Prochlorophyta, and the average density and biomass of phytoplankton gradually decreased month by month. The proportion of cyanobacteria in the community showed a downwards trend, while the proportions of other phytoplankton phyla showed upwards trends. The annual average Shannon–Wiener diversity index was 0.88, the annual average Pielou evenness index was 0.32, and the annual average Margalef richness index was 1.21. The Shannon–Wiener diversity index and Pielou's evenness index both showed increasing trends. This comprehensive analysis shows that planting submerged plants in suspended beds can improve the phytoplankton community structure of the surrounding water and increase the biodiversity of phytoplankton, making this an effective measure for restoring submerged vegetation in algae-dominated northern lakes. [ABSTRACT FROM AUTHOR]

Vegetation communities in floodplain lakes are adapted to natural water regimes. Construction of sluices or dams between rivers and their floodplain lakes will inevitably lead to great changes in plant communities. In order to evaluate the effects of water level fluctuations (WLFs) on lakeshore vegetation in floodplain lakes of the Yangtze River, a field investigation was conducted in two river-disconnected lakes (Wuchang Lake and Shengjin Lake) and one river-connected lake (Shimen Lake). The results showed that plant species richness was highest in the disconnected Shengjin Lake with intermediate amplitude of WLFs, and lowest in the connected Shimen Lake. Species composition differed among the three lakes and the two disconnected lakes with more similar WLFs exhibiting the greatest similarity. Six plant communities were classified using TWINSPAN. Multivariate analyses showed that the amplitude of WLFs was the most important factor in determining the distribution of lakeshore plants, followed by relative elevation and duration of submergence. Our results provide an eco-hydrological basis for plant restoration in the Yangtze floodplain lakes. We suggest that fluctuating amplitude should be increased in lakes with small WLFs, and small habitats with various hydrological regimes should be created in lakes with large WLFs. [ABSTRACT FROM AUTHOR]

Submerged vegetation is essential for maintaining a clear water state in shallow lakes. To determine the optimal submerged macrophyte coverage required to improve water quality, field investigations and a simulation experiment were carried out in a sub-lake of Baiyangdian Lake, China. The effects of two seasons and five submerged macrophyte coverage gradients (0 [C-0], 25 [C-25], 50 [C-50], 75 [C-75], and 90% [C-90]) were examined in the field study, while the five submerged macrophyte coverage gradients were examined in an 80-day simulation experiment. In the field study, plant coverage, season, and their interaction all had a significant effect on most physicochemical parameters. Compared with C-0, the Secchi depth and pH of the water were higher, while the total nitrogen and total phosphorus concentrations were lower when submerged vegetation was present. Lowest values of total nitrogen, total phosphorus, and conductivity all appeared under C-50. Meanwhile, in the simulation experiment, the total nitrogen content decreased by 76.43, 90.98, 88.28 and 84.32%, and the total phosphorus content decreased by 85.15, 88.48, 87.76 and 79.00% at C-25, C-50, C-75 and C-90 compared with C-0, respectively. Moreover, plant coverage and time had a significant effect on all eight physiochemical parameters. There were no significant differences in the total nitrogen content among C-50, C-75 and C-90, but values were significantly lower than at C-0 and C-25. In contrast, the total phosphorus content was significantly higher at C-0 than all other groups, and the lowest value was observed at C-50. Overall, these findings suggest that 50% is the optimal submerged macrophyte coverage for improvements in water quality in temperate shallow lakes. • Field and simulation results suggest that submerged macrophytes improve water quality. • Coverage affected the physicochemistry of the water in the field and simulation. • Submerged macrophyte coverage of 50% was optimal. • Above 50% coverage, no further improvements in water quality were observed. [ABSTRACT FROM AUTHOR]

• 85 plant species from 6 Yangtze floodplain lakes were classified into 8 guilds based on 7 functional traits. • Amplitude of WLFs and duration of submergence significantly affected LPG distribution. • The biomass of two indictor guilds can be used to evaluate the alterations in WLFs. • Morphological parameters of LPGs showed no significant linear relationships with the increase in WLFs. River–lake disconnection has led to alterations in natural water level fluctuations (WLFs) in lakes along the middle and lower reaches of the Yangtze River to various extents. To predict the effects of altered WLFs on lakeshore vegetation, lakeshore herbaceous plant guilds (LPGs) in six Yangtze floodplain lakes were classified in this study. The lakeshore herbaceous plant distribution pattern, main influencing factors, and responses of different LPGs to altered WLFs were analyzed. A total of 130 plant species were identified from the six lakes. With the increase in the amplitude of WLFs, the total species number in the six lakes showed a hump–shaped trend, whereas the lakeshore herbaceous plant coverage showed a positive correlation. The Qili Lake with the largest WLFs had the lowest species number and highest plant coverage. The species numbers, average biomass, and coverage of lakeshore herbaceous plants in all the six lakes were obviously higher in spring than in autumn. The lakeshore herbaceous plants in the six lakes were classified into eight guilds. Small differences in pH, organic matter, total nitrogen, and total phosphorus were detected in the substrate among the eight LPGs, but obvious differences in soil moisture content and duration and depth of submergence were observed. The canonical correspondence analysis showed that the main environmental factors affecting the distribution of different LPGs in the six lakes in spring and autumn were the amplitude of WLFs and duration of submergence. The regression analyses showed that the biomass of perennial mesophyte with erect stem guild and perennial hygrophyte with well–developed rhizome guild responded sensitively to alterations in the amplitude of WLFs and duration of submergence, and the guilds could be considered as indicator groups at a regional scale. Morphological parameters such as plant height, stem diameter, leaf thickness, and specific leaf area of the eight LPGs showed no significant linear relationships with the increase in WLFs. The use of these parameters in the evaluations of alterations in WLFs needs to be further analyzed. [ABSTRACT FROM AUTHOR]