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This study presents research on the possibility of using lake macrophytes to create diagnostic and classification tools for trophically and morphologically diverse lakes. The diagnostic role of macrophytes was determined on the basis of the spatial and functional interrelationships of the various macrophyte groups, which include emergent, submerged, and floating species. In addition, an effort was made to reveal the morphometric features of the lakes that significantly affect the development of the distinguished macrophyte groups. The research was carried out comprehensively in the lakes of the Łęczna-Włodawa Lake District, a unique natural area due to the richness of hydrogenic areas. The lakes in the area are undergoing constant and rapid changes (despite the introduction of various forms of protection), which is reflected in the decreasing number of lakes and their eutrophication. Moreover, stoneworts, which are indicators of clean water, are disappearing from the lakes. The presence of specific groups of macrophytes led to the classification of these lakes as ecologically stable, meaning they are resistant to change and sustainable over time. The depth and surface area of the lakes were identified as the key morphometric features that most significantly influence the growth of macrophytes in eutrophic lakes, which were the most abundant in the study area. By analysing the consistent characteristics of macrophytes and lakes, four distinct classes were identified: emergent macrophyte dominated lakes, submerged macrophyte dominated lakes, low macrophyte density lakes, high macrophyte density lakes. The proposed classification can serve as a diagnostic framework for lakes, helping to identify them and improve our understanding of the changes occurring within these ecosystems.

Eutrophication of water bodies causes the disappearance of submerged macrophytes and frequent blooms of phytoplankton, which leads to changes in the underwater light environment in the aspect of light intensity and light quality. However, compared with underwater light intensity, only few studies have been concentrated in the effect of light quality on submerged macrophytes. The effect of light quality on plants is heterogeneous, and there are two absorption peaks in red and blue wavelengths. Thus, we carried out a mesocosm experiment to study the effects of a series of red and blue light ratios (red/blue light ratio = 1/8, 1/4, 1/1, 4/1, and 8/1) on two submerged macrophyte species, Hydrilla verticillata and Vallisneria natans . We hypothesized that functional traits (growth strategy, morphological, photosynthetic, and nutritional traits) of submerged macrophytes will be modified by different red/blue light ratios. With the increase of red/blue light ratio, plant height of the two submerged macrophytes decreased, while tillers number increased. We could not completely verify our hypothesis, but we found species-specific differences. The leaf area of H. verticillata under 8/1 red/blue light ratio was significantly higher than that under 1/8 red/blue light ratio, whereas the leaf area of V. natans under 4/1 red/blue light ratio was lower than that under 1/8 red/blue light ratio. Our results are helpful to understand the disappearance mechanism of submerged macrophytes in eutrophic lakes and devise more appropriate measures for the recovery of submerged macrophytes.

Aquatic ecosystems provide vital services, and macrophytes play a critical role in their functioning. Conceptual models indicate that in shallow lakes, plants with different growth strategies are expected to inhabit contrasting habitats. For shallow peat lakes, characterized by incohesive sediments, roles of growth forms, life-history strategies and environmental factors in determining the occurrence of aquatic vegetation remain unknown. In a field survey, we sampled 64 points in a peat lake complex and related macrophyte occurrence to growth forms (floating-leaved rooted and submerged), life-history strategies for overwintering (turions, seeds, rhizomes) and environmental factors (water depth, fetch, and porewater nutrients). Our survey showed that macrophyte occurrence relates to water depth, wind-fetch, and nutrients, and depends on growth form and life-history strategies. Specifically, rooted floating-leaved macrophytes occur at lower wind-fetch/shallower waters. Submerged macrophytes occur from low to greater wind-fetch/water depth, depending on life-history strategies; macrophytes with rhizomes occur at greater wind-fetch/depth relative to species that overwinter with seeds or turions. We conclude that growth form and life-history strategies for overwintering predict macrophytes occurrence regarding environmental factors in peat lakes. Therefore, we propose an adapted model for macrophyte occurrence for such lakes. Altogether, these results may aid in species-selection to revegetate peat lakes depending on its environment.

Macroalgae drive the largest CO₂ flux fixed globally by marine macrophytes. Most of the resulting biomass is exported through the coastal ocean as detritus and yet almost no field measurements have verified its potential net sequestration in marine sediments. This gap limits the scope for the inclusion of macroalgae within blue carbon schemes that support ocean carbon sequestration globally, and the understanding of the role their carbon plays within distal food webs. Here, we pursued three lines of evidence (eDNA sequencing, Bayesian Stable Isotope Mixing Modeling, and benthic-pelagic process measurements) to generate needed, novel data addressing this gap. To this end, a 13-month study was undertaken at a deep coastal sedimentary site in the English Channel, and the surrounding shoreline of Plymouth, UK. The eDNA sequencing indicated that detritus from most macroalgae in surrounding shores occurs within deep, coastal sediments, with detritus supply reflecting the seasonal ecology of individual species. Bayesian stable isotope mixing modeling [C and N] highlighted its vital role in supporting the deep coastal benthic food web (22–36% of diets), especially when other resources are seasonally low. The magnitude of detritus uptake within the food web and sediments varies seasonally, with an average net sedimentary organic macroalgal carbon sequestration of 8.75 g C·m⁻²·yr⁻¹. The average net sequestration of particulate organic carbon in sediments is 58.74 g C·m⁻²·yr⁻¹, the two rates corresponding to 4–5% and 26–37% of those associated with mangroves, salt marshes, and seagrass beds, systems more readily identified as blue carbon habitats. These novel data provide important first estimates that help to contextualize the importance of macroalgal-sedimentary connectivity for deep coastal food webs, and measured fluxes help constrain its role within global blue carbon that can support policy development. At a time when climate change mitigation is at the foreground of environmental policy development, embracing the full potential of the ocean in supporting climate regulation via CO₂ sequestration is a necessity.

Aim: Spatial extent is inherently related to the potential roles of the main mechanisms structuring metacommunities. We examined the effects of varying spatial extent (ecological province, region and subregion) on the environmental and spatial components of variation in lake macrophyte communities. We also studied these effects separately for three macrophyte functional groups. Location: The US state of Minnesota. Methods: We examined average and heterogeneity differences in macrophyte community composition and environmental variation among the subregions of Minnesota using canonical analysis of principal coordinates (CAP) and homogeneity of multivariate dispersion (PERMDISP), respectively. We further used partial redundancy analysis (pRDA) to decompose variation in macrophyte community composition between environmental variables and spatial location at each spatial extent and geographical region. Spatial variables were derived using principal coordinates of neighbour matrices (PCNM) analysis. Results: CAP and PERMDISP analyses showed that the subregions differed both in average community composition and in the heterogeneity of community composition for all macrophyte taxa, for emergent and submerged macrophytes, but not for non-rooted macrophytes. We did not, however, find significant differences in overall environmental heterogeneity among the subregions. Variation partitioning using pRDAs showed that species sorting is more important than spatial processes for macrophytes, although these patterns were relatively weak. There was, however, much regional specificity, with the environmental and spatial fractions of community composition varying widely at different spatial extents, among different geographical regions and among functional groups. Contrary to our initial expectations, we did not find increasing spatial structuring and decreasing environmental control with increasing spatial extent. Main conclusions: Our findings indicate that, in macrophyte metacommunities, the relative contribution of spatial processes and environmental control varies rather unpredictably with spatial extent and geographical region. Our findings are thus of importance in advancing metacommunity ecology by showing that drawing wide-ranging conclusions based on a single spatial extent or a single geographical region may be unwise.

Fluxes of carbon dioxide (CO2) and methane (CH4) in shallow lakes are strongly affected by dominant primary producers which mostly has been studied in temperate and boreal regions. We compared summer CO2 and CH4 fluxes (diffusion and ebullition) in littoral and pelagic zones of three subtropical shallow lakes with contrasting regimes: clear-vegetated, phytoplankton-turbid, and sediment-turbid, and assessed fluxes in different seasons in the clear-vegetated system. Significant differences among the lakes occurred only for CH4 fluxes. In the sediment-turbid lake we found undersaturated CH4 concentrations were below atmospheric equilibrium, implying CH4 uptake (< 0 mg m−2 day−1), likely due to low availability of organic matter. Differences between zones occurred in the clear-vegetated and phytoplankton-turbid lakes, with higher total CH4 emissions in the littoral than in the pelagic zones (mean: 4342 ± 895 and 983 ± 801 mg m−2 day−1, respectively). CO2 uptake (< < 0 mg m−2 day−1) occurred in the littoral of the phytoplankton-turbid lake (in summer), and in the pelagic of the clear-vegetated lake even in winter, likely associated with submerged macrophytes dominance. Our work highlights the key role of different primary producers regulating carbon fluxes in shallow lakes and points out that, also in the subtropics, submerged macrophyte dominance may decrease carbon emissions to the atmosphere.

Macrophytes play important roles in maintaining ecosystem health and stability of shallow lakes. Better understanding of their long-term dynamics has important theoretical and practical significance for both lake ecosystem restoration and eutrophication control. However, the knowledge about the historical status and changing patterns of macrophytes in China’s shallow lakes is still controversial and lacks systematic research. Here, we reviewed and synthesized the published records of submerged macrophytes from 14 typical shallow lakes in the eastern plain covering the past 100 years. The results suggest that submerged macrophytes have experienced three clear stages of change: rare period (the 1900s-the 1950s), growth period (the 1950s-the 1980s), and recession period (the 1980s-now). This finding is different from the traditional understanding that submerged macrophytes were abundant in the early 20th century and have been degrading since then. On this basis, we proposed the possible evolution pattern (less-more-less) of submerged macrophytes in the eastern plain lake region over the past 100 years, which provides new perspectives about the long-term evolution process of macrophytes in shallow lakes. Furthermore, we found that the decline of submerged macrophytes during the regime shift shows a gradual process at the interdecadal scale; this finding contradicts the classical regime shift theory that macrophytes decline sharply during the critical transition. This study has important theoretical value for the restoration of the eastern plain lakes in China from “turbid lake” to “clear lake”, especially for establishing the historical reference condition and restoration path of macrophytes.

Functional traits of individuals and not just species can regulate ecological interactions with biotic and abiotic environments, yet how individual-level functional diversity (FD ind ) mediates the environmental effects on community properties (e.g., interaction patterns, connectivity and productivity) remains largely unexplored. Here, we assembled 4432 individuals from 30 macrophyte species across 26 lakes in south China and measured six functional traits -shoot height, specific leaf area, lamina thickness, leaf dry mass content, stem diameter and stem dry mass content—for each individual. We estimated FD ind for macrophyte community in each plot using trait probability density framework. Path analysis revealed that functional richness promoted negative interactions (the absolute value of negative: positive cohesion as proxy of community interaction patterns) and thus community productivity at lower total phosphorus (TP) and shallower water, while functional divergence/redundancy reduced negative interaction and thus community productivity at shallower water, lower TP and higher altitude. Functional evenness decreased community productivity at higher TP and deeper water. Functional dissimilarity reduced community connectivity (total cohesion) and thus community productivity at deeper water and higher altitude. Our results highlight that FD ind could modify the environmental effects (from local to regional) on the interaction patterns, network connectivity and productivity of macrophyte community.

Spatial heterogeneity plays a crucial role in the coexistence of species. Despite recognition of the importance of self-organization in creating environmental heterogeneity in otherwise uniform landscapes, the effects of such self-organized pattern formation in promoting coexistence through facilitation are still unknown. In this study, we investigated the effects of pattern formation on species interactions and community spatial structure in ecosystems with limited underlying environmental heterogeneity, using self-organized patchiness of the aquatic macrophyte Callitriche platycarpa in streams as a model system. Our theoretical model predicted that pattern formation in aquatic vegetation – due to feedback interactions between plant growth, water flow and sedimentation processes – could promote species coexistence, by creating heterogeneous flow conditions inside and around the plant patches. The spatial plant patterns predicted by our model agreed with field observations at the reach scale in naturally vegetated rivers, where we found a significant spatial aggregation of two macrophyte species around C. platycarpa. Field transplantation experiments showed that C. platycarpa had a positive effect on the growth of both beneficiary species, and the intensity of this facilitative effect was correlated with the heterogeneous hydrodynamic conditions created within and around C. platycarpa patches. Our results emphasize the importance of self-organized patchiness in promoting species coexistence by creating a landscape of facilitation, where new niches and facilitative effects arise in different locations. Understanding the interplay between competition and facilitation is therefore essential for successful management of biodiversity in many ecosystems.

Background and aims Harvesting can regulate the overgrowth of submerged macrophytes and affect interspecific competition. However, the effects of harvesting on the growth and competition of submerged macrophytes with different growth forms, remains unclear. Methods Simulation experiments were conducted to study the morphological and physiological indicators, competition intensity, and received light intensity of rosette-forming Vallisneria natans ( V.natans ) under different harvesting intensities of canopy-forming Hydrilla verticillata ( H.verticillata ). Results V. natans had greater plant height and larger leaf area at a medium-intensity (harvest 30% and 45% of the plant height) harvesting than at other intensities. Medium-intensity harvesting was the most conducive to the accumulation of chlorophyll, whereas high-intensity (harvest 60% and 75% of the plant height) harvesting had the lowest chlorophyll content and highest malondialdehyde content in V. natans . Interspecific competition was observed between H. verticillata and V. natans , and the medium harvesting intensity of H. verticillata conferred a competitive advantage to V. natans . Harvesting H. verticillata affect the growth of V. natans by increasing the underwater light intensity, with a greater harvest intensity corresponding to stronger light intensity received by V. natans . Light conditions were the most suitable for the growth of V. natans under medium-intensity harvesting. Conclusions Medium-intensity harvesting not only improved the recovery of H. verticillata but also increased the competitiveness of V. natans , thus promoting the growth of V. natans . Therefore, in practice, medium-intensity harvesting can be applied to the regulation of H. verticillata and V. natans .