Submerged aquatic vegetation (SAV) plays a vital role in improving water quality and providing essential habitats for diverse aquatic fauna in floodplain lakes. However, in large floodplain systems, the spatiotemporal dynamics and underlying drivers of SAV remain poorly understood, largely due to monitoring challenges posed by complex topography, highly variable water levels, and diverse vegetation communities. To address this knowledge gap, we developed a novel remote sensing approach that integrates multi-temporal imagery from the water-level drawdown period with differential submergence responses of wetland vegetation types. This method effectively overcomes detection difficulties under high water levels and minimises interference from inundated emergent vegetation. Applying this approach, we analysed long-term changes in SAV extent in Poyang Lake, the largest floodplain lake in China, and used generalised additive models to identify key environmental drivers, with a particular focus on hydrology and water transparency. Our results revealed a substantial and persistent collapse of SAV in Poyang Lake, declining from 655 +/- 288 km(2) during 2001-2009 to 44 +/- 31 km(2) during 2020-2023, accompanied by reduced variability and slower recovery, indicating a loss of natural dynamic resilience. This collapse was primarily driven by hydrological alterations, including more frequent extreme floods linked to climate change and earlier water-level recession caused by hydraulic engineering and sand mining. Reduced water transparency further intensified SAV losses. This study enhances understanding of SAV dynamics and their drivers in large, hydrologically complex lakes, while also providing a transferable monitoring framework for other floodplain lakes. These findings offer critical insights for conservation and adaptive management strategies aimed at sustaining these vulnerable ecosystems.

Aquatic macrophyte responses and adaptation to water depth and nutrient gradients are of critical importance for understanding the functional ecology of lakes and their restoration when degraded. However, the role of plant trait networks (PTNs), a powerful tool for decoding trait-environment-function relationships, in mediating these adaptations remains unclear, particularly across species and community scales. We conducted cross-scale PTN analyses at species and community levels for aquatic macrophytes, integrating assessments of phylogenetic signals and hierarchical environmental filtering. At species level, aquatic macrophytes exhibited two complementary PTN-based adaptive strategies: trait compartmentalization to enhance stress tolerance and trait integration to optimize resource utilization. Notably, local environmental conditions (rather than phylogenetic signals) dominated the pattern of PTN metrics, highlighting the primacy of immediate habitat constraints over evolutionary relatedness in driving species-specific adaptations. At community level, environmental filtering operated hierarchically, acting sequentially by water depth, nutrient availability, and lake morphology. PTNs further mediated the trade-off between community diversity and productivity, providing a mechanistic link between abiotic filtering and ecosystem function. Our findings advance network theory in functional ecology by extending its application to aquatic systems, bridging longstanding gaps between terrestrial and aquatic PTN research, and offering actionable guidance for eutrophic lake restoration (e.g., by targeting PTN-linked core traits related to nutrient adaptation). Overall, our work provides a cross-scale framework for understanding PTN mediated adaptation of aquatic macrophytes and its implications for ecosystem management.

Local fish diversity in lakes has severely declined in the last century under the effects of climate change and human activities. Thus, examining the underlying factors and implementing appropriate measures are crucial for preventing further aquatic biodiversity losses. Environmental DNA (eDNA) metabarcoding represents a promising tool for improving fish population monitoring. While spatiotemporal variations of fish eDNA in lentic ecosystems have become a research focus, effective monitoring techniques remain limited. Therefore, this study used eDNA metabarcoding to monitor the diversity and spatiotemporal distribution of fish in Erhai Lake, China. Water samples from the shore, nearshore, and midline were collected from 2020 to 2021 during summer and autumn. Thirty-six taxa, including 5 native (one endangered species, Schizothorax taliensis) and 31 non-native taxa, were detected. Seasonal and spatial differences in fish community structure were observed. The seasonal distribution was primarily influenced by water temperature and nutrient status, while the spatial distribution was affected by water depth. Most fish species found in the lake were detected in shoreline samples, suggesting that shoreline sampling is a cost-effective strategy for monitoring fish diversity. These findings confirmed that fine-scale spatial sampling and eDNA metabarcoding represent effective tools for monitoring fish diversity and spatiotemporal distribution in lakes.

Nutrient pulses caused by heavy rainfall or agricultural runoff can increase the loss of phosphorus from land to adjacent waters, threatening aquatic ecosystems. Using in-situ enclosure experiments that simulated a single moderate PO4-P pulse (0.05 mg P/L), we tested how the macrophytes at different coverage levels (0-100%) regulate water quality, ecosystem resilience, and eutrophication processes. The system's buffering capacity and resilience were significantly positively correlated with submerged macrophytes coverage (SMC). High SMC enclosures exhibited lower nutrient levels, curbed algal growth, and sustained clear-water conditions, whereas systems with sparse macrophytes retained relatively higher nutrients and algal biomass, along with a greater eutrophication risk. Suspended solids, turbidity, and Chl-a were more sensitive to increases in SMC, meaning SMC enhancement improved these parameters more effectively and visibly than nutrients. Structural equation modeling suggested that submerged macrophytes offered more pathways to improve water quality at higher coverage levels, yet the actual mechanisms remain to be tested by direct measurements of pH, ORP, Ca-P and Fe-P interactions. Furthermore, a critical threshold of 39% SMC (95% CI: 20%-54%) was inferred to inhibit eutrophication, and maintaining coverage above this level is crucial to buffer single moderate P pulses, but the threshold may vary with plant species, lake type, and pulse magnitude and frequency.

Submerged macrophytes play a crucial role in lake ecosystems, and their survival is dependent upon their ability to cope with variable environmental stress. Therefore, studying the plastic response of submerged macrophytes' resource allocation and functional traits to the environment may provide insights helpful for ecological restoration practices. In September 2021, a field survey was conducted in the Erhai Lake, where samples of Ottelia acuminata, and functional traits and biomass allocation in relation to water depth were measured. The study found that O. acuminata exhibited large intraspecific variations to adapt to environmental stress, and the average intraspecific variation was 55.86

Climate change is driving more frequent extreme rainfall events, which in turn trigger nutrient pulse events. These events can degrade water quality and reduce biodiversity in receiving water bodies. While submerged macrophytes are critical for stabilising aquatic ecosystems during such nutrient pulses, differences in macrophyte composition and coverage may affect their functional effectiveness. This study simulated nutrient pulse events by conducting in situ mesocosm experiments to investigate the effects of different macrophytes composition (single-species community [Vallisneria natans] vs. multi-species community [V. natans + Hydrilla verticillata + Potamogeton wrightii]) and coverage levels (0%, 30%, 40%, 50% and 60%) on system buffering capacity and stability. Additionally, we identified the coverage thresholds required for stabilising aquatic ecosystems under pulse loading conditions. Higher submerged macrophyte coverage significantly reduced TN, TP, Chl-a concentrations and water turbidity, with a critical threshold of 50% macrophyte coverage for optimal nutrient pulse mitigation. Compared with mixed communities, monocultures of V. natans showed better nutrient buffering capacity, with TN and TP removal efficiencies increased by 1.93 and 1.49 times at 50% coverage. Selecting appropriate submerged macrophyte coverage and suitable community compositions is crucial for improving ecological restoration efforts, especially in reducing nutrient disturbances and maintaining long-term aquatic ecosystem stability.

Biological invasions in freshwater ecosystems are increasingly severe, posing significant threats to ecosystem health and economic development. Hydrilla verticillata (L.f.) Royle and Elodea densa (Planch.) Casp. are two of the most aggressive invasive submerged macrophytes worldwide, and often regarded as similar species due to their growth forms and habitat requirements, although there are few field coexistence records. Hydrilla verticillata is a native species in the large plateau Lake Erhai, where the non-native E. densa has been documented since 2017. This study aims at exploring the colonisation process of E. densa as well as its niche overlap and interspecific interactions with native H. verticillata in Lake Erhai. A continuous seven-year field investigation was conducted in Lake Erhai. Four indicators were used to assess the population distribution of H. verticillata and E. densa, including occurrence frequency, biomass, relative abundance and relative niche breadth. The logistic growth model was applied to analyse population dynamics. The Gaussian model was used to characterise their distribution with water depths. A stability index was employed to evaluate variations in measured indices across different water depths. Indicators of niche overlap and interspecific association were used to describe the coexistence and interactions between the two species. Elodea densa established several stable populations in Lake Erhai after years of colonisation and naturalisation, primarily colonising deeper areas of the lake than H. verticillata. Elodea densa tended to thrive at depths of around 4.0 m, whereas H. verticillata typically grew at depths from 2.0 to 3.0 m. Hydrilla verticillata demonstrated greater stability across varying water depths than E. densa. Niche overlap between the two species was minimal. Our findings indicated that in this large plateau lake, native H. verticillata exhibited higher competitiveness than alien E. densa. There was a distinct niche difference in water depths between H. verticillata and E. densa, which prevented competitive exclusion. The two species achieved stable coexistence at a lake-wide scale. This study provided the first field evidence for coexistence between two globally recognized invasive species, showing that in habitats with sufficient environmental gradients and filtering pressures, submerged macrophytes similar in taxonomy and appearance could avoid competitive exclusion by occupying different ecological niches, leading to stable coexistence.

1. An understanding of how biodiversity confers ecosystem stability is crucial in managing ecosystems under major environmental changes. Multiple biodiversity drivers can stabilize ecosystem functions over time. However, we know little about how local environmental conditions can influence these biodiversity drivers, and consequently how they indirectly shape the ecological stability of ecosystems. 2. We hypothesized that environmental factors can have opposite influences (i.e., not necessarily either positive or negative) on the temporal stability of communities in different environmental ranges depending on the biodiversity drivers involved. We tested this novel hypothesis by using data from a 4-year-long field study of submerged macrophyte across a water depth gradient in 8 heterogeneous bays of Erhai lake (with total sample size of 30,071 quadrats), a large lentic system in China. 3. Results indicate that a unimodal pattern of stability in temporal biomass measurements occurred along the water-depth gradient, and that multiple biodiversity drivers (the asynchrony in species dynamics, and the stability of dominant species) generally increased the temporal stability of aquatic primary producers. However, the effect of water depth either increased or decreased the stability of biomass according to the environmental conditions associated with sites along the water depth gradient. 4. Synthesis. These results reveal the influence of local environmental conditions on the biodiversity drivers of stability may help predict the functional consequences of biodiversity change across different scenarios of environmental change.

Understanding how biodiversity and community functional traits preserve lake ecosystem multidimensional stability under global environmental changes is crucial for sustaining the vital ecosystem services we depend on. Based on sediment nutrient gradient experiments and three‐year seasonal monitoring of macrophyte communities in Erhai Lake, southwest China, spanning pre‐ and post‐algal bloom periods, we explored how species diversity and a key community functional trait (stoichiometric homeostasis) affect multiple dimensions (temporal stability, resistance, resilience and recovery) and facets (function, composition, diversity and functional trait) of stability of macrophyte communities following algal blooms. Generally, we found that species diversity and stoichiometric homeostasis of phosphorus ( H P ) had positive relationships with functional and compositional temporal stability, resistance and recovery, indicating that ecosystems with high species diversity and community H P are more resistant and stable in response to external algal bloom disturbances. However, species diversity and community H P had no positive or even negative relationships with resilience, suggesting that high biodiversity with high‐ H P species‐dominated ecosystems is not beneficial for the rapid recovery from disturbances, probably due to the slow growth and reproduction rate of high‐ H P species. In addition, we found strong positive correlations between functional and compositional stability across the four dimensions of stability, while the stability of species diversity and the key functional trait ( H P ) exhibited complex relationships, implying the difficulty of optimizing multiple dimensions and facets of stability simultaneously. Synthesis . Our work demonstrated that macrophyte species diversity and community H P are critical in determining the multiple dimensions and facets of stability in response to disturbances, which provides new insights for predicting the responses of macrophyte‐dominated lake ecosystems to the current increasing frequency of algal blooms.

Aquatic macrophytes are fundamental structural components in freshwater ecosystems. Understanding the distribution pattern of macrophyte communities is crucial for the management and restoration of freshwater ecosystems. In this study, the community composition, biomass, as well as interspecific interactions of macrophytes were investigated across a finely-divided depth gradient from 0.5 m to 5.5 m with 0.5 m intervals in a large plateau lake. Results revealed that biomass and alpha-diversity of macrophyte community followed hump-shaped patterns peaking at intermediate depths, while beta-diversity exhibited a U-shaped pattern with minimal turnover at 2.95 m. Niche overlap increased with increasing depth, indicating heightened spatial co-occurrence under low-light conditions. Interspecific associations shifted from facilitation under high filtering pressure (shallow disturbed and deep light-limited zones) to competition at optimal depths (2.0-3.0 m), where resource competition intensified despite high productivity and diversity. Neutral overall species associations at 1.0-2.5 m and 5.5 m indicated either balanced positive/negative species interactions or stochastic coexistence. The instability of species coexistence at these depths highlights the vulnerability of macrophyte communities to environmental shifts (e.g., water level, light availability). By demonstrating water depth's role as a habitat filter, our findings underscore the necessity to involve depth-mediated interspecific interaction into freshwater restoration strategies.

Climate change intensifies nutrient pulses through extreme rainfall and agricultural runoff, yet the buffering capacity of submerged macrophytes against such disturbances remains unquantified. Through a large-scale enclosure experiment simulating ammonium pulses (1.24 mg/L NH4-N), we tested how submerged macrophytes coverage (SMC, 0-100%) modulates water quality, ecosystem resilience, and regime shifts (from clear to turbid). The system's buffering capacity and resilience stability increased significantly with SMC, whereas its recovery stability decreased. High SMC (>50%) accelerated NH4-N removal (96 h vs 168 h in controls), suppressed phytoplankton blooms (Chl-a increase: 102.5% vs 237.4%), and sustained clear water. Conversely, low and medium SMC (<50%) did not prevent transitions to algal-dominated states. Furthermore, NH4-N stress was inversely correlated with SMC, and persistently high NH4-N at low SMC increased macrophyte degradation risk. Structural equation modeling revealed that macrophytes-mediated nutrient competition and light stabilization underpinned these effects. Additionally, we identify a critical SMC threshold (39-51%) to mitigate pulse impacts─a finding urgently needed to guide lake restoration in a changing climate. This work bridges the gap between pulse ecology and adaptive management, offering actionable strategies for SDG 6 (Clean Water) and 13 (Climate Action).

Lake Erhai is an important lake on the Yunnan-Guizhou Plateau, which has experienced pollution and treatment in recent years. Since 2017, the high-level protection and management have been carried out in the entire Lake Erhai basin, resulting in spatiotemporal changes in the external pollution and water quality. To analyze the influencing factors of external pollution on the water quality of Lake Erhai, this study conducted monthly water quality monitoring in eight major bays, as well as in the central of the northern, middle, and southern parts of Lake Erhai from 2017 to 2022. The concentrations of total nitrogen, total phosphorus, chlorophyll- a and water transparency were measured in the water column. The eutrophication was evaluated by the trophic level index( TLI). The results showed that: 1) The TLI decreased from the northern area to southern area, in agreement with the higher nutrients input of rivers in the northern part of the lake. 2) During the period from 2017 to 2022, the trophic index decreased significantly in the southern area of Lake Erhai and decreased slightly in the middle area, while increased in the northern area, indicating that the pollution control was more effective in the southern and middle areas than in the northern area. 3) the trophic index was higher in the wet season than in the dry season, and the seasonal variation of TLI was higher in the northern area than in the middle and southern areas. 4) It is important for the control of phosphorus input into the lake, particularly for the northern area of Lake Erhai basin and/or in the flooding season, as well as the phosphorus concentration in the lake water.

Rebuilding a clear-water state dominated by submerged macrophytes is essential for addressing eutrophication, yet the impact of benthic fish on water quality is complex. We conducted two experiments to explore the interaction of submerged plants and benthic fish on the water quality. Experiment I investigated the water clearing effects of submerged macrophytes with varying coverage (from 0% to 40%) before and after the removal of benthic fish. Experiment II explored the impacts of benthic fish at different densities on aquatic ecosystems with and without submerged macrophytes. The results showed that an increase in submerged macrophytes coverage significantly enhanced the reduction of some major water quality parameters. We assert that the coverage of submerged macrophytes should not be lower than 40% to establish and sustain a clear-water state in shallow lakes. However, benthic fish significantly weaken the ability of submerged macrophytes to improve water quality. Surprisingly, the presence or absence of macrophytes may reverse the role of benthic fish in freshwater ecosystems. When macrophytes are present, benthic fish can cause water quality to deteriorate. Conversely, when macrophytes are absent, benthic fish with a density of ≤ 10 g/m3 can restrict the growth of phytoplankton by directly consuming algae or by disturbing sediments to increase turbidity, thereby potentially improving water quality. But the detrimental effects of benthic fish with higher densities may gradually outweigh their benefits to water clarity. Therefore, the percentage of submerged macrophyte cover in combination with the density of benthic fish play crucial roles in shaping the ecological effects of benthic fish and overall ecosystem dynamics. These findings underscore the importance of understanding ecosystem interactions and have practical implications for the management of shallow lakes.

The impact of global warming on plant abundance has been widely discussed, but it remains unclear how warming affects plant physiological traits, and how these traits contribute to the abundance of aquatic plants. We explored the adjustments in physiological traits of two common aquatic plant species (Potamogeton crispus L. and Elodea canadensis Michx.) and their links to plant abundance in three temperature treatments by determining twelve physiological traits and plant abundance over an 11-month period in outdoor mesocosms. This mesocosms facility has been running uninteruptedly for 16 years, rendering the plants a unique opportunity to adapt to the warming differences. We found that 1) warming reduced the starch storage in winter for P. crispus and in summer for E. canadensis while increased the nitrogenous substances (e.g., TN, FAA, and proline) in winter for P. crispus. 2) For E. canadensis, TC, starch, SC, and sucrose contents were higher in summer than in winter regardless of warming, while TC, SC, and sucrose contents were lower in summer for P. crispus. 3) Warming decreased the association strength between physiological traits and plant abundance for P. crispus but enhanced it for E. canadensis. 4) E. canadensis showed increased interaction strength among physiological traits under warming, indicating increased metabolic exertion in the response to warming, which contributed to the reduction in abundance. Trait interaction strength of P. crispus was reduced under warming, but with less impact on plant abundance compared with E. canadensis. Our study emphasizes that warming alters the network of plant physiological traits and their contribution to abundance and that different strengths of susceptibility to warming of the various plant species may alter the composition of plant communities in freshwater ecosystems.

Monitoring underwater vegetation is vital for evaluating lake ecosystem health. Automated data collection and analysis play key roles in achieving large-scale, high-precision, and high-frequency monitoring. While technologies such as unmanned vessels have made data collection more efficient, challenges persist in the analysis process, particularly in addressing the varied needs of different lake environments. Supervised AI methods can automatically identify underwater vegetation but are heavily reliant on labeled datasets. In practice, models trained on public datasets often struggle with generalization due to differences in vegetation types, collection environments, and equipment, resulting in discrepancies between training and testing datasets. Moreover, traditional dataset construction methods that rely on manual annotation are time-consuming and costly, limiting their scalability and application. This study aims to overcome these challenges by proposing an unsupervised method for automatically classifying underwater vegetation data, aiming to reduce manual annotation efforts and construct unbiased datasets at lower costs with greater efficiency. Compared with existing unsupervised, self-supervised, and unsupervised domain adaptation methods, this method introduces two key innovations: 1) a two-step dimensionality reduction method that combines pre-trained model and manifold learning to extract key features and 2) a multialgorithm voting mechanism to increase classification confidence. These features enable high-accuracy classification without prior data annotation. Experiments show 97.32 % accuracy on public dataset and 92.43 % and 96.15 % accuracy on private datasets from Erhai Lake and Wuhan East Lake, respectively, surpassing supervised methods and matching manual classification. Additionally, it drastically reduces the annotation effort, requiring only approximately 20 labeled images to classify thousands of points. By integrating unmanned vessel technology, this approach provides an efficient, cost-effective solution for large-scale, high-frequency underwater vegetation monitoring across diverse lakes.

IntroductionWater depth (WD) and snail abundance (SA) are two key factors affecting the growth of submersed aquatic plants in freshwater lake ecosystems. Changes in WD and SA drive changes in nutrients and other primary producers that may have direct or indirect effects on submersed plant growth, but which factor dominates the impact of both on aquatic plants has not been fully studied.MethodsTo investigate the dominant factors that influence aquatic plant growth in plateau lakes, a one-year field study was conducted to study the growth of three dominant submersed macrophyte (i.e., Vallisneria natans, Potamogeton maackianus, and Potamogeton lucens) in Erhai Lake.ResultsThe results show that, the biomass of the three dominant plants, P.maackianus, is the highest, followed by P.lucens, and V.natans is the lowest. Meanwhile, periphyton and snails attached to P.maackianus are also the highest. Furthermore, WD had a positive effect on the biomass of two submersed macrophyte species of canopy-type P.maackianus and P.lucens, while it had a negative effect on rosette-type V.natans. Snail directly inhibited periphyton attached on V.natans and thereby increasing the biomass of aquatic plants, but the effect of snails on the biomass of the other two aquatic plants is not through inhibition of periphyton attached to their plants.DiscussionThe dominant factors affecting the biomass of submersed macrophyte in Erhai Lake were determined, as well as the direct and indirect mechanisms of WD and snails on the biomass of dominant submersed macrophyte. Understanding the mechanisms that dominate aquatic plant change will have implications for lake management and restoration.

The preservation of biodiversity is crucial for sustaining ecosystem functioning, and recently the ongoing loss of biodiversity in lake ecosystems due to human activities has raised significant concerns. This study aimed to assess the impact of human activities on the biodiversity of aquatic plants through long-term empirical evidence. By comparing species composition and genetic diversity of submerged macrophyte within last decade, this research focused on the long-term changes of submerged macrophyte biodiversity resulting from human disturbances and restoration efforts. Three plateau lakes - Lake Erhai, Lake Fuxianhu, and Lake Jianhu - were selected as study sites, exhibiting varying biodiversity alterations in response to different levels of human disturbance and restoration activities. The oligotrophic Lake Fuxianhu demonstrated a stable level of both biodiversity levels, and the eutrophic Lake Jianhu exhibited a significant reduction in species diversity and genetic diversity. Meanwhile, the strong restoration measures in Lake Erhai between the 2010s and the 2020s effectively safeguard species diversity and alleviate declines in genetic diversity due to eutrophication during the last decade. We also found that improper use of alien species and the transplantation of clones of aquatic plant may pose ecological risks to biodiversity. Given the importance of aquatic plant re-establishment for the long-term recovery of plateau lakes, conservation strategies could prioritize large-scale propagation of aquatic plant materials through local seed banks.

Macrophytes with different growth forms exhibit diverse functional traits and ecological functions. In natural sub-deep lakes, there are often large differences in water quality between nearshore areas with macrophytes and open water areas. However, it remains unclear whether this phenomenon can be attributed to differences in plant growth forms. Therefore, we conducted continuous monitoring for four years, both before and after the implementation of an ecological restoration project, to explore whether the change in plant growth forms caused differences in water quality between the nearshore and open water areas. The results showed that implementing ecological restoration projects proved highly effective in improving the local environment, including water physicochemical properties and biological components, in the implementation area. First, the ecological restoration project greatly altered the plant community structure in the nearshore area before and after restoration. After restoration, there was a significant increase in the biomass and distribution area of noncanopy-forming plants (including erect and rosette-forming plants), while the opposite effect was observed for canopy-forming plants. Second, the transition of macrophyte community growth forms enhanced the stability of both macrophyte communities and water physicochemical parameters. Furthermore, the reduction in canopy-forming plants facilitated a more efficient water body exchange, resulting in greater homogeneity in water quality between the nearshore and open water areas. Overall, the presence of canopy-forming plants can hinder water body exchange due to large canopy formations on the water surface. In light of these findings, it is recommended that ecological restoration projects in natural lakes should consider the functional group composition of macrophytes.

Intense precipitations caused by global climate change will result in the occurrence of greater frequencies and longer durations of flooding, influencing the survival and yields of wetland plants. Alisma orientale (Samuel.) Juz., an important traditional medicine with edible scape and inflorescence, naturally grows in wetlands and artificially cultivates in paddy fields prone to flood in China. However, we lack understanding of the effect of complete submergence on A. orientale. Here, experiments with four durations of complete submergence including 5 days (ds), 10 ds, 15 ds and 20 ds followed by 20 ds recovery were performed. In the submergence experiments, the number of, length of and biomass of surviving leaves and the total biomass and new blade biomass were measured; in recovery experiments, number and length of surviving leaves were measured. A. orientale grew out longer new leaves during complete submergence, with a dramatic decline in the biomass of both the leaves and tubers as well as the total biomass at the ends of the submergence experiments. The A. orientale plants had a high survival rate after submergence. The duration of submergence did not influence the time for A. orientale needed to start regrowing. At the end of recovery period, the submerged A. orientale plants generated more leaves, had more surviving leaves, had shorter new leaves and a shorter total length of surviving leaves than the control plants. This study highlights that A. orientale plants can resist at least 20 ds of complete submergence caused by flooding and regrow rapidly after submergence and improves our understanding of the flooding tolerance mechanisms of A. orientale plants.

The effect of biodiversity on ecosystem productivity has been a controversial issue in ecological research. The species richness–productivity relationship is highly variable in natural ecosystems, with a positive relationship being one of the most commonly observed relationships. Previous regional studies from terrestrial ecosystems have demonstrated that environmental gradients can regulate the species richness–productivity relationship. However, how this relationship varies in freshwater ecosystems across spatial environment gradients remains unclear. In this study, we propose that the species richness–productivity relationship can be modulated by the water depth. Here, we surveyed the submerged macrophyte community structure by establishing 24 transects and 642 quadrats in Erhai Lake, Yunnan Plateau, China. Our findings highlight that the species richness–productivity relationship gradually changed from slightly positive to strongly positive as the environment became more light-limited with the increasing water depth, supporting the stress-gradient hypothesis. The results from this study provide new insights into the biodiversity–ecosystem functioning relationships and in managing lake macrophyte communities and productivity.