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Submerged plants and related disturbances can affect both the phosphorus (P) release and the microbial communities in sediments. In this study, a sediment resuspension system was constructed, and P variability characteristics influenced by Vallisneria natans (V. natans) and the response mechanism of the microbial community were studied. The results indicated that the total phosphorus (TP) content increased from 678.875 to 1019.133 mg/kg and from 1126.017 to 1280.679 mg/kg in sediments and suspended solids (SSs) during the sediment resuspension process, respectively. Organic P (OP) increased by 127.344 mg/kg and 302.448 mg/kg in sediments and SSs after the disturbance, respectively. The microbial communities in the sediments and the leaves of V. natans had higher Chao values after the disturbance, while Shannon values decreased after the disturbance compared to the control in SSs. Proteobacteria had the highest abundance with the value of 51.1% after the disturbance in the sediments and SSs, and the abundance values of Proteobacteria in rhizomes and leaves of V. natans could reach 73.2% on average. Chloroflexi, Acidobacteria, and Firmicutes were also the main phyla in the sediment resuspension system. Sodium hydroxide extractable P (NaOH-P) in sediments could reduce the bioavailability of this P fraction under disturbance conditions. The decrease in the abundance of Bacteroidetes and Nitrospirae indicated that they were more sensitive to the disturbance, and the rotational speed changed the survival conditions for the Bacteroidetes and Nitrospirae. The response mechanism of microbial community during the sediment resuspension process could reflect the influence of the microbial community on the changing characteristics of P and could provide a theoretical foundation for P control at the micro level. [ABSTRACT FROM AUTHOR]

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Vallisneria spinulosa Yan (V.spinulosa Yan) with good ability of water purification is often used for ecological restoration of polluted water bodies. However, it is difficult to survive in turbid water bodies due to the low lighting condition. This study explored the feasibility of introducing artificial underwater light source into water bodies with high turbidity to strengthen the water restoration by V.spinulosa Yan. Addition of underwater light source promoted the clonal reproduction ability of V.spinulosa Yan, thus enhancing the removal loads of total nitrogen (TN), total phosphorus (TP), and nitrate nitrogen ( NO 3 − - N ) by 1.60–3.43 × 10−2, 1.49–3.49 × 10−3, and 0.80–2.06 × 10−2 g m−2 d−1, respectively. Underwater light source significantly reduced the abundance of microbial community on V.spinulosa Yan leaves, as well as most nitrifying bacteria (Nitrosomonadaceae) and denitrifying bacteria (Nitrospira, Comamonadaceae, and Rhodocyclaceae) in the system. But the attachment of some Cyanophyta (Chloroplast and Cyanobacteria) and Photosynthetic bacteria (Rhodobacter) onto the leaves and the growth of Methyloligellaceae in water and sediments were promoted. Nitrogen and phosphorus removal by the growth system of V.spinulosa Yan without underwater light source mainly depended on the biological processes by functional bacteria, while the absorption and co-assimilation effect of V.spinulosa Yan with underwater light source. [ABSTRACT FROM AUTHOR]

In aquatic ecological restoration projects, V. natans (Vallisneria natans (Lour.) Hara), a species of submergent plant, after being transplanted often experiences a poor growing condition and a lengthy adaption period, however, brassinolides possess considerable effectiveness of plant development and metabolism according to available research reports. In an attempt to employ a phytohormone soaking pre-treatment method to study the effect of brassinolides' effect on V. natans development, a laboratory experiment was conducted probing into the influencing factors: brassinolides dosage (0, 0.25, 0.5, 1, 2 and 4 mg/L) and soaking time (10, 20, and 40 minutes). The results showed that the pre-treatment with brassinolide facilitated the improvement to some extent of biomass, plant height, number of leaves, number of tillers, and chlorophyll of V. natans, and that the effect of soaking solution concentration was more pronounced than immersion time; it appeared that under the condition of above three soaking intervals the biomass of V. natans increased to the maximum at the solution concentration of 0.5 mg/L; however, 10 min soaking time gave rise to biggst boosting effect, and from the perspective of plant height indicator, as the soaking time was 10 min brassinolide of 0.25-2 mg/L concentration had a notable positive effect on the plant height of V. natans (P<0.05). In terms of chlorophyll indicators, it was the best condition that the content of chlorophyll a and chlorophyll b of V. natans was boosted when brassinolide concentration ranged 0.5-1 mg/L and soaking time was 10 min. In accordance with the experimental data obtained and considering economic cost and time cost, it is recommended that prior to the transplantation V. natans be soaked with brassinolide at a concentration of 0.5 mg/L for 10 min, in this way the problem of V. natans colonizationcan could be successfully solved. Finally, it is expected that the experimental results could provide theoretical references for the quick recovery of submerged macrophytes in aquatic environment. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Guangxi Normal University - Natural Science Edition is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Perfluorinated compounds (PFCs) are persistent organic contaminants that are highly toxic to the environment and bioaccumulate, but their ecotoxic effects on aquatic plants remain unclear. In this study, the submerged plant Vallisneria natans was treated with short-term (7 days) and long-term (21 days) exposures to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) at concentrations of 0, 0.01, 0.1, 1.0, 5.0, and 10 mg/L, respectively. The results showed that both high concentrations of PFOA and PFOS inhibited the growth of V. natans and triggered the increase in photosynthetic pigment content in leaves. The oxidative damage occurred mainly in leaves, but both leaves and roots gradually built up tolerance during the stress process without serious membrane damage. Both leaves and roots replied to short-term stress by activating superoxide dismutase (SOD), catalase (CAT) and polyphenol oxidase (PPO), while peroxidase (POD) was involved under high concentration stress with increasing exposure time. Leaves showed a dose–effect relationship in integrated biomarker response (IBR) values under short-term exposure, and the sensitivity of roots and leaves to PFOS was higher than that of PFOA. Our findings help to increase knowledge of the toxic effects of PFCs and have important reference value for risk assessment and environmental remediation of PFCs in the aquatic ecosystem. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) were typical environmental contaminants that accumulated continuously in sediment. Microbial degradation is the main way of PAH degradation in the natural environment. Therefore, expanding the available pool of microbial resources and investigating the molecular degrading mechanisms of PAHs are critical to the efficient control of PAH-polluted sites. Here, a strain (identified as Xanthobacteraceae bacterium) with the ability to degrade pyrene was screened from the rhizosphere sediment of Vallisneria natans. Response surface analysis showed that the strain could degrade pyrene at pH 5–7, NaCl addition 0–1.5%, and temperature 25–40 °C, and the maximum pyrene degradation (~ 95.4%) was obtained under the optimum conditions (pH 7.0, temperature 28.5 °C, and NaCl-free addition) after 72 h. Also, it was observed that the effect of temperature on the degradation ratio was the most significant. Furthermore, eighteen metabolites were identified by mass spectrometry, among which (2Z)-2-hydroxy-3-(4-oxo-4H-phenalen-3-yl) prop-2-enoic acid, 7-(carboxymethyl)-8-formyl-1-naphthyl acetic acid, phthalic acid, naphthalene-1,2-diol, and phenol were the main metabolites. And the degradation pathway of pyrene was proposed, suggesting that pyrene undergoes initial ortho-cleavage under the catalysis of metapyrocatechase to form (2Z)-2-hydroxy-3-(4-oxo-4H-phenalen-3-yl) prop-2-enoic acid. Subsequently, this intermediate was progressively oxidized and degraded to phthalic acid or phenol, which could enter the tricarboxylic acid cycle. Furthermore, the pyrene biodegradation by the strain followed the first-order kinetic model and the degradation rate changed from fast to slow, with the rate remaining mostly slow in the later stages. The slow biodegradation rate was probably caused by a significant amount of phenol accumulation in the initial stage of degradation, which resulted in a decrease in bacterial activity or death. [ABSTRACT FROM AUTHOR]

This study aims to assess the ecological restoration effects of Vallisneria natans in a multitrophic level ecosystem. The water-purification effects of two hierarchical configuration modes of V. natans-Bellamya aeruginosa and V. natans-B. aeruginosa-Hyriopsis cumingii were studied. Results show that a V. natans and B. aeruginosa configuration ratio of 15:2 stabilizes water quality at Grade IV (TN ≤ 1.5 mg/L, TP ≤ 0.3 mg/L), and increasing B. aeruginosa density significantly reduces total phosphorus. The V. natans, B. aeruginosa, and H. cumingii configuration at 15:2:10 stabilizes water at Grade III (TN ≤ 1.0 mg/L, TP ≤ 0.2 mg/L), with a positive correlation between H. cumingii density and chlorophyll-a removal. Furthermore, the filtration and biocycling actions of B. aeruginosa (snails) and H. cumingii (mussels) significantly reduce levels of Total Nitrogen (TN), Total Phosphorus (TP), and Ammonium (NH4+-N) in water, thus enhancing the self-purification capacity of the water bodies. However, the bioturbation effect of H. cumingii can temporarily increase phosphorus release from sediments, leading to a short-term rise in TP concentration in the water. Overall, the study concludes that multitrophic level ecosystems are effective in purifying water quality and offer significant ecological restoration benefits. This research provides crucial data support for future construction and ecological restoration projects involving multitrophic level approaches in China's rivers and lakes. [ABSTRACT FROM AUTHOR]

Background: Macrophytes may modify benthic biodiversity and biogeochemistry via radial oxygen loss from roots. This condition contrasts sediments anoxia, allows roots respiration, and facilitates aerobic microbial communities and processes in the rhizosphere. Simultaneously, the rhizosphere can stimulate anaerobic microorganisms and processes via exudates or by favoring the build-up of electron acceptors as nitrate. As eutrophication often results in organic enrichment in sediments and large internal nutrients recycling, an interesting research question is to investigate whether plants maintain the capacity to stimulate aerobic or anaerobic microbial communities and processes also under elevated organic pollution. Methods: A manipulative experiment was carried out under laboratory-controlled conditions. Microcosms containing bare sediments and sediments transplanted with the macrophyte Vallisneria spiralis L. were created. The effect of the plant was investigated on sediments with moderate (8%) and elevated (21%) organic matter content, after an acclimatization period of 30 days. Chemical and physical parameters, microbial community composition and the potential rates of nitrification, denitrification and nitrate ammonification were measured at two different depths (0–1 and 1–5 cm) after the acclimatization period to evaluate the role of roots. Results: Vallisneria spiralis grew and assimilated pore water nutrients at the two organic matter levels and vegetated sediments had always nutrient-depleted porewaters as compared to bare sediments. Nitrifying microbes had a lower relative abundance and diversity compared to denitrifying bacteria. However, regardless of the organic content, in vegetated sediments nitrifiers were detected in deeper horizons as compared to bare sediments, where nitrification was confined near the surface. In contrast, potential denitrification rates were not affected by the presence of roots, but probably regulated by the presence of nitrate and by root-dependent nitrification. Potential nitrate ammonification rates were always much lower (< 3%) than potential denitrification rates. Conclusions: Vallisneria spiralis affects N-related microbial diversity and biogeochemistry at moderate and elevated organic matter content, smoothing bottom water–pore water chemical gradients and stimulating nitrification and nitrogen loss via denitrification. These results suggest the possibility to deploy V. spiralis as a nature-based solution to counteract eutrophication in freshwater systems impacted by high loads of organic matter, for example, downstream of wastewater treatment plants. [ABSTRACT FROM AUTHOR]

In shallow eutrophic lakes, submersed macrophytes are significantly influenced by two main factors: light availability and benthic fish disturbance. Plant foraging is one of the most crucial aspects of plant behavior. The present study was carried out to effects of light regimes and fish disturbance on the foraging behavior of Vallisneria natans in heterogeneous sediments. V. natans was cultivated in heterogeneous sediments with four treatments: high-light regime (H), high-light regime with benthic fish (HF), low-light regime (L), and low-light regime with benthic fish (LF). We use plant trait network analysis to evaluate the relationships between traits in heterogeneous sediments. We found the plant foraging intensity was positively correlated with trait network modularity. The biomass of stem, maternal plant biomass ratio, and ramet number were the hub traits of plant growing in heterogeneous habitats. Although the plant relative growth rate (RGR) was positively correlated with foraging intensity, the hub traits had closer links with plant RGR than foraging intensity. Light regime and benthic fish indirectly affected the plant foraging intensity by changing the chlorophyll a content and pH of overlying water. Overall, our analysis provides valuable insights into plant foraging behavior in response to environmental changes. [ABSTRACT FROM AUTHOR]

Microbial respiration determines the accumulation of reduced solutes and negative redox potential in organic sediments, favoring the mobilization of dissolved inorganic phosphorus (DIP), generally coprecipitated with Fe oxyhydroxides. Macrophytes releasing oxygen from the roots can contrast DIP mobility via the oxidation of anaerobic metabolism end-products. In this work, the submerged macrophyte Vallisneria spiralis was transplanted into laboratory microcosms containing sieved and homogenized organic sediments collected from a contaminated wetland. Sediments with and without plants were incubated under light and dark conditions for oxygen and DIP fluxes measurements and pore water characterization (pH, oxidation-reduction potential, DIP, dissolved Mn, and Fe). Bare sediments were net DIP sources whereas sediments with V. spiralis were weak DIP sources in the dark and large sinks in light. V. spiralis radial oxygen loss led to less negative redox potential and lower Fe, Mn, and DIP concentrations in pore water. Roots were coated by reddish plaques with large amounts of Fe, Mn, and P, exceeding internal content. The results demonstrated that at laboratory scale, the transplant of V. spiralis into polluted organic sediments, mitigates the mobility of DIP and metals through both direct and indirect effects. This, in turn, may favor sediment colonization by less-tolerant aquatic plants. Further in situ investigations, coupled with economic analyses, can evaluate this potential application as a nature-based solution to contrast eutrophication. [ABSTRACT FROM AUTHOR]

Constructed wetland systems employing submerged macrophytes are increasingly utilized for treating municipal and industrial wastewater, as well as odoriferous and eutrophic water bodies. However, the pollutant removal efficiency of these systems needs further enhancement. In this study, we examined the impact of the gas-to-water ratio on the treatment efficiency of the constructed wetland of Vallisneria. We also examined the extracellular polymeric substances (EPSs) of the floating biofilm and the structure of the microbial community in this system. Our findings showed that the gas-to-water ratio significantly affects the total nitrogen (TN) removal rate within the Vallisneria wetlands, with an optimum removal at a gas-to-water ratio of 15:1, while the removal efficiencies for chemical oxygen demand (COD), NH4+-N, and total phosphorus (TP) remain relatively unaffected. Increased gas-to-water ratios corresponded to a notable decrease in biofilm EPSs. High-throughput sequencing analysis demonstrated a shift in biofilm-denitrifying bacteria from anoxic heterotrophic to aerobic denitrifiers, alongside a significant rise in the abundance of denitrifying bacteria, whereas excessively high gas-to-water ratios inhibited the growth of these bacteria. A gas-to-water ratio of 15:1 constituted the optimal condition for ecological restoration of the water body within the Vallisneria wetland systems. These results could contribute to the optimization of submerged-macrophyte constructed wetland system design and the enhancement of treatment efficiency.

The modified material at the bottom of lakes plays a key role when restoring and reconstructing the ecology of waterbodies. However, the effects of different substrate types on the growth and development of submerged plants and rhizosphere microorganisms remain unclear. Therefore, this study analyzed the effects of five substrates (attapulgite, biochar, cinder, maifanite, and quartz sand) on the growth and rhizosphere microorganisms of Vallisneria natans (Lour.) Hara (V. natans). The results showed that during the culture period, the mean plant height of V. natans peaked in the maifanite group (26.75 cm), the mean leaf number peaked in the biochar group (12.13), and the mean root activity peaked in the cinder group (83.42 U g−1 min). There was no significant difference in the total chlorophyll content among the groups during culture (P > 0.05). The malondialdehyde content of V. natans leaves in all groups, except quartz sand group, peaked early in the culture period (10 days). Moreover, the superoxide dismutase activity of the five groups increased first and then decreased; however, the catalase activity in the maifanite group decreased significantly compared with the levels in the other groups (P<0.05). This indicates that maifanite supplementation can accelerate the adaptation of V. natans to changes in the environment. After the addition of substrate, the species of dominant bacteria in the rhizosphere remained nearly unchanged, but their relative abundance was different. Specifically, the relative abundance of Desulfobacterota increased in each group, peaking at 9.77% in the maifanite group. This study showed that different substrates had different growth-promoting effects on submerged plants, with maifanite exerting the greatest effect. The findings provide a technical reference for selecting the best substrate improver for in situ ecological restoration. [ABSTRACT FROM AUTHOR]

Low light intensity and high sediment organic matter (SOM) conditions coexist recurrently in aquatic ecosystems, which affects submerged macrophyte re-habilitation. In this greenhouse study, four light intensity levels (10% [natural light intensity], 30%, 60%, and 100%) and three initial SOM loads (11% [measured as the loss on ignition], 17%, and 25%) were applied to explore the effects of their interactions on the growth of Vallisneria natans (V. natans). Two-way ANOVA revealed the effects of interactions between light intensity and SOM load on the growth characteristics of V. natans. Multiple linear regression models indicate that the dry weights and root lengths exhibited a single maximum as the SOM load increased. The inhibitory effect of the sediment on the growth of V. natans could be alleviated by increasing the light intensity in a certain SOM range. However, the inhibited growth of V. natans was not alleviated by enhancing the light intensity at a 25% SOM load. We explored a potential mechanism for this phenomenon based on ammonium (NH4+) toxicity regulation. Structural equation modeling indicates that enhanced light intensity could directly reduce sediment NH4+ contents or reduce them indirectly by decreasing the abundances of bacterial functional genes associated with NH4+ formation. Subsequently, lower sediment NH4+ content increased the plant dry weight, thereby facilitating the removal of nitrogen and phosphorus from the sediment. Therefore, enhancing the light intensity over a wide range of SOM loads resulted in the restoration of submerged macrophytes, whereas reducing SOM loads could be performed in high SOM conditions to improve the restoration of submerged macrophytes. [ABSTRACT FROM AUTHOR]

Aquatic macrophytes in inland lakes provide a wide range of ecosystem services. Management efforts to restore aquatic macrophytes for ecosystem recovery need comprehensive understanding of the interaction between growth and nutrient removal efficiency. In contrasting hydrodynamic environments, we examined the growth and phosphorus accrual of two common submerged (Vallisneria natans) and emergent (Acorus calamus) macrophytes. Both biomass and nutrient storage of two macrophytes were observed with significant increases during the incubation period, suggesting the great potential of selected macrophytes in suppressing eutrophication in shallow lakes. Experimental results showed very opposite impacts of flowing water on two macrophyte types. The flowing water was observed to restrain submerged macrophyte's growth and nutrient accrual, but oppositely to stimulate the emergent type. Specifically, our study demonstrated an average reduction of 33.7% in individual plant biomass and 11.4% in nutrient inventory of V. natans, but an overall increase of 27.2% in biomass and 50.0% in nutrient inventory for A. calamus in flowing-water environments. We estimated a total removal of 470-ton phosphorus assuming the complete comeback of aquatic macrophytes in Lake Taihu, as much as 22% of the annual external loading. The results from this study could inform management of aquatic macrophytes at local and lake-wide scales. [ABSTRACT FROM AUTHOR]

The aim of the study was to know the chemical properties of some algae,Enteromorpha and Cladophora,and some selected aquatic plants,Typha domingensis,Ceratophylum demersum, Vallisneria eriaspiralis, Sodium, potassium and calcium at different times of the seasons.Cladophora alga showed the highest percentage in water contentwhich amounted to (89.50%), proteins (41.13%)and calcium (2.06%)while Enteromorpha algae showed the highest percentage in dry matter which amounted to (88.72%), carbohydrates (62.40%)and sodium (7.89%). As for the plants,clear significant differences appeared in the different seasons, as the results showed that the highest value of water content in the spring season was in each of Typha(85.42), Vallisneria(95.81) while the rest of the seasons did not show significant differences between them.As for the dry matter, the highest value was in the winter season in Typha (25.33)and Vallisneria (9.56).The spring season was characterized by having the highest percentage of carbohydrates in each of Typha(73.61) and Ceratophylum(44.98),And the highest percentage of proteins in the summer season was in each of Typha (12.62) and Ceratophylum (22.13) .The highest percentage of sodium in the spring was in Typha(0.37) and Ceratophylum(1.39) .The highest percentage of potassium in the summer was in all of Ceratophylum(6.35)andVallisneria(6.08).The summer season was characterized by containing the highest percentage of calcium in all of Ceratophylum (0.83) and Vallisneria (2.62). [ABSTRACT FROM AUTHOR]

Plant genetic diversity differs in habitat's oscillations, especially species distributed under heterogeneous environmental conditions. Freshwater ecosystems are vulnerable to biotic and abiotic impacts, which affect the genetic and epigenetic variations in aquatic plants. The extent of environmental heterogeneous attributes can be examined based on genetic and epigenetic variations. Such variations under environmental gradient can provide evidence for understanding the correlations between rapid environmental changes and species evolution. In this study, we performed amplified fragment polymorphism length and methylated‐sensitive amplified polymorphism analysis to depict the genetic and epigenetic variations of Vallisneria natans in a subtropical lake. Results showed that this species maintained a relatively high genetic diversity (mean HE = 0.320, I = 0.474, PPL = 85.93%) and epigenetic variation (mean eHE = 0.282, eI = 0.428, ePPL = 83.91%). Water body temperature and chlorophyll a density were positively correlated to the genetic and epigenetic variations. The clonal generates of V. natans depicted a relative high methylation level and shew ancestral scenario between the genet and the second clonal generation. These findings revealed that species diversity is unevenly distributed under environmental heterogeneity, even at a fine geographic scale. Environmental characteristics in relation to temperature and chlorophyll a should be considered in the analysis of the genetic and epigenetic variations. Additionally, epigenetic variations between genets and ramets should be considered with caution when applied to analysis of other aquatic species. [ABSTRACT FROM AUTHOR]

In shal low eutrophic lakes, submersed macrophytes are essential for maintaining a clear water state and they are significantly affected by benthic fish disturbance, light availability, and sediment types. We conducted a mesocosm experiment with benthic fish (Misgurnus anguillicaudatus), two light regimes, and submerged macrophyte (Vallisneria natans) growing in two sediment types to investigate the ecological effects of benthic fish and light regimes on water quality and the growth of submersed macrophyte. Our findings indicated that the benthic fish increased the concentrations of total nitrogen, total phosphorus, and total dissolved phosphorus in the overlying water. The effects of benthic fish on ammonia–nitrogen (NH4+-N) and chlorophyll a (Chl-a) contents were related to light regimes. Fish disturbance indirectly promoted the growth of macrophytes growing in sand by increasing NH4+-N content in overlying water. However, the increasing Chl-a content stimulated by fish disturbance and high light regime reduced the growth of submersed macrophytes growing in clay due to shading. Macrophytes with different sediments had different strategies coping with light. Plants growing in sand responded to low light mainly by adjusting the leaf and root biomass allocation, whereas plants growing in clay responded to low light by physiologically adjusting the soluble carbohydrate content. The findings of this study might help restore lake vegetation to some degree, and using nutrient-poor sediment might be an appropriate method to avoid the detrimental effects of fish-mediated disturbances on the growth of submerged macrophytes. [ABSTRACT FROM AUTHOR]

The increase of nitrogen and phosphorus causes eutrophication in water bodies. Using submerged plants to decrease the pollution from water bodies is an effective way. In this research, three common submerged plants (Vallisneria natans, Hydrilla verticillata, and Ceratophyllum demersum) and their combinations were used to purify eutrophic water. The control treatment did not contain any plants. The removal effects and dynamic regulations of the three plants with their combinations of nutrients (such as nitrogen and phosphorus) in water were analyzed. All three species and their combinations above could grow in the eutrophic water and efficiently remove aquatic nutrients. All the treatment groups had a higher pollutant removal rate for total nitrogen (TN) and total phosphorus (TP) than that of the blank control. In these treatment groups, treatment F (50 g Vallisneria natans plus 50 g Ceratophyllum demersum) had the highest removal rate of TP at 57.53%; treatment B (100 g Vallisneria natans) had the best removal rate of TN at 92.04 %. Among these plants and their combinations, Vallisneria natans and Ceratophyllum demersum showed better purification ability; the combination of these two submerged plants and the combination of three submerged plants were more applicable for the restoration of eutrophic water. [ABSTRACT FROM AUTHOR]

After comparing the removal effect of Vallisneria natans on Cu2+, Zn2+, Cd2+, Pb2+, and the responses of chlorophyll fluorescence parameters at low, medium and high concentration levels, our results showed that:(1) Among the four heavy metals, Vallisneria natans has the best removal effect on Cu2+ and the highest absorption of Zn2+. The maximum absorption of Cu2+, Zn2+,Cd2+ and Pb2+ by bitter grass were 4.21, 25.3, 0.231 and 0.509 μg/g respectively, the attenuation ratio of the medium mass concentration group of Cu2+ was the highest (47.33%),and that of the low mass concentration group of Zn2+, Cd2+, Pb2+ was the highest (33.13%, 29.2%, 45.7%);(2) Under heavy metal stress, the chlorophyll a content of Vallisneria natans in the Cu2+ and Zn2+ high mass concentration groups decreased less than that in the Cd2+ and Pb2+ high mass concentration groups, and the order of the decrease in chlorophyll b content was Zn2+ >Cu2+ >Cd2+ >Pb2+, and the high mass concentration group decreased significantly. (3) The maximum photochemical efficiency (Fv/Fm) and potential photochemical efficiency (Fv/F0) of Vallisneria natans increased in different degrees under Cu2+ and Zn2+ stress, but decreased significantly under Cd2+ and Pb2+ stress. The photochemical quenching coefficient (Qp), non-photochemical quenching efficiency (Qn) and the quantum yield of regulatory energy dissipation (YNPQ) all decreased with the increase of heavy metal mass concentration, in which the decrease of Qp in Zn2+, Cu2+, Cd2+, Pb2+ mass concentration groups decreased in turn, while the effective quantum yield (YⅡ) increased with the increase of heavy metal mass concentration. In general, Vallisneria natans is more suitable for removing Cu2+ and Zn2+ in water. The research results may lay a foundation for the ecological restoration of heavy metal polluted rivers. [ABSTRACT FROM AUTHOR]

Microorganism is an important part of freshwater ecosystem and its community composition is closely related to water environment. Five experimental groups were set up in the laboratory to simulate the population structure of the ecosystem by planting the evergreen submersible plant Vallisneria natans and introducing Bellamya aeruginosa, Hyriopsis cumingii and Carassius auratus. In this paper, the effects of different aquatic organisms on bacterial community structure were explored by constructing a multi-trophic freshwater ecosystem. The results showed that the dominant bacteria groups in the freshwater ecosystem were Proteobacteria, Actinobacteriota, Bacteroidota and Cyanobacteria. The existence of snails, mussels and fish greatly reduced the number of Cyanobacteria in the water, which could effectively control the overreproduction of Cyanobacteria. The bacterial Shannon index was higher in Vallisneria natans and Vallisneria natans-Bellamya aeruginosa-Hyriopsis cumingii, but lower in Vallisneria natans-Bellamya aeruginosa and Vallisneria natans-Bellamya aeruginosa-Hyriopsis cumingii-Carassius auratus. RDA results showed that there were significant differences in the abundance of microbial communities among different systems. The introduction of different aquatic organisms and the content of DO are the direct factors affecting the change of microbial community, and the change of nutrient concentration is mainly dependent on the interaction between aquatic organisms and microorganisms, which is an indirect factor affecting the change of microbial community. In conclusion, the construction of multi-trophic ecosystem can not only improve the water quality, but also increase the diversity of bacteria in the water, change the community structure of bacteria in the water, and make it more healthy and stable. [ABSTRACT FROM AUTHOR]

The submerged plant Vallisneria natans can provide an attachment matrix and habitat for diverse microorganisms and plays an important role in maintaining the structure and function of the shallow lake ecosystem. However, little is known about how V. natans-related microorganism components, especially bacteria, adapt to specific plant compartments. In this study, we investigated the assembly and network of bacterial communities living in different plant compartments (sediment, rhizosphere, rhizoplane, root endosphere, and leaf endosphere) associated with V. natans by 16S rRNA gene sequencing. The results showed that the diversity and network complexity of the bacterial community in the sediment was significantly higher than that in other plant compartments. The bacterial community composition showed that the dominant phyla were Proteobacteria, Bacteroidetes, Actinobacteria, Firmicutes, Desulfobacterota, and Chloroflexi, among which Proteobacteria were extremely abundant in all samples, and there were notable differences in bacterial community composition related to plant compartments. Different networks based on sediment and plant compartments showed distinct co-occurrence patterns and exhibited distinct topological features. Additionally, functional predictions from FAPROTAX indicate that the predominant biogeochemical cycle function of the V. natans-related bacterial community is to participate in the carbon and nitrogen cycle. These results strongly suggested how the microbial community adapted to different plant compartments and provided theoretical and technical data for isolating beneficial bacteria from macrophytes in the future. [ABSTRACT FROM AUTHOR]

Bisphenol A (BPA) is considered a contaminant of emerging concern and interferes with the normal activities of living organisms. The toxicity of BPA is evident in animals and terrestrial plants. However, the response of aquatic plants to low BPA concentrations is still unclear. In the present study, effects of varying BPA loadings (targeting at 0.01, 0.1, and 1 mg/L) on the growth and reproductive traits of the dioecious annual submerged macrophyte Vallisneria natans were assessed through a 5-month experiment. The results showed that BPA inhibited the elongation of V. natans leaves but resulted in an increase in leaf number and ramet number under the highest BPA loading treatment (targeting at 1 mg/L). In addition, detectable biochemical changes in the total carbon and soluble sugar contents were found, which both were significantly higher at the highest BPA loading treatment. However, the total biomass did not alter significantly after the BPA treatments, indicating that BPA did not induce direct toxic effects on the growth of V. natans. At the highest BPA loading treatment, female individuals of V. natans allocated less number for ramet than male ones, showing a clear sexual dimorphism. No significant differences between the five treatments were found for the flower or fruit traits, while the germination rate was significantly inhibited for the seeds collected from the highest BPA loading treatment. In conclusion, V. natans tolerated low concentrations of BPA by making a trade-off between ramet (leaf) number and leaf elongation, as well as modulating the total carbon and soluble sugar contents. However, serious consequence of decline in seed viability implied that the impact of BPA on plant reproduction were usually underestimated. [ABSTRACT FROM AUTHOR]

The main aim of this research was to determine the physiological response of the submerged macrophyte Vallisneria natans (V. natans) to black water with a foul odor. V. natans was chosen as the experimental plant species to investigate the morphological response and ecophysiological adaptation methods in response to varying light depths and black-odorous water. V. natans was planted in tap water (D), two types of black-odorous water (E and F), and under three distinct light conditions (low light, medium light, and high light). In the high-light condition with black-odorous water (E), the biomass content of V. natans declined from 1.78 g on the 14th day to 1.49 g on the 28th day, demonstrating that the black-odorous water inhibited the growth of V. natans. Under the stress of black-odorous water, the chlorophyll content of V. natans increased greatly in the early period but reduced during the latter experimental period. However, on the 21st day, maximum chlorophyll content of 1.30 mg/g (E) and 1.18 mg/g (F) was observed. In addition, the malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activity was monitored and reported under black-odorous water stress in V. natans. The experimental results of this work demonstrated conclusively that odorous black water exerts a certain stress on the physiological development of V. natans. Future research should incorporate the evaluation of several plant species and vary the process and environmental conditions to produce field-relevant, dependable results. [ABSTRACT FROM AUTHOR]

Outbreaks of periphytic algae, including filamentous algae, have been observed after submerged macrophyte restoration and are common in early stages. Dynamic changes in the periphytic algae community on Vallisneria natans and artificial V. natans were investigated in situ, and their characteristics were compared on the two substrates. The results showed that more periphytic algae species occurred on V. natans (77 taxa) than on artificial V. natans (66 taxa) (F = 2.089, p = 0.047). The cell density and chlorophyll a (Chl. a) content of periphytic algae were 3.42–202.62-fold and 2.07–15.50-fold higher on the artificial substrate than on V. natans, respectively. Except for Lyngbya perelagans (i.e., the only common dominant periphytic algae species on the two substrates), the dominant species on V. natans were Cocconeis placentula and Ulothrix tenerrima, while those on the artificial substrate were Stigeoclonium aestrivale, Oscillatoria tenuis and Achnanthes minutissima. The cell density of periphytic algae was significantly affected by the total phosphorus (TP) and NO3−-N and electric conductivity on V. natans, and by TP and NH4+-N on artificial V. natans. The malondialdehyde content of V. natans was significantly correlated with the periphytic algae biomass. V. natans was more affected by periphytic algae during its slow-growing period, and the contribution order of stress to V. natans was diatoms > cyanobacteria > green algae. Our findings might contribute to the understanding the effect of substrate specificity on periphytic algae communities, and have important implications for the restoration of submerged plants in eutrophic lakes. [ABSTRACT FROM AUTHOR]

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Background: Resource translocation among interconnected ramets can improve the growth performance of the recipient ramets and influence soil properties and microbial communities in the rooting zone. However, scanty attention has been paid to the effect of this clonal integration on soil biotic and abiotic characteristics of neighboring species around the recipient ramets. Methods: We conducted a soil heterogeneous experiment in which the mother ramet of the ramet pair for Vallisneria natans was planted in a high-nutrient patch, and the daughter ramet was planted in a low-nutrient patch with conspecific neighbors V. natans or heterospecific neighbors Myriophyllum spicatum. The stolons between ramet pairs were severed or left intact. Results: Our results showed that effects of clonal integration on growth of the daughter ramet depend on the identity of neighboring species. Overall growth of neighbors V. natans was not affected by clonal integration, while growth of neighbors M. spicatum was greatly reduced. Soil properties and microbial community composition (especially bacteria) in the rhizosphere of neighboring plants were significantly influenced by clonal integration, and these effects were more obvious in the rhizosphere of neighbor V. natans than those in the rhizosphere of neighbors M. spicatum. Conclusion: Our study suggests that clonal integration may play a vital role in facilitating nutrient cycling, modifying habitat heterogeneity and affecting interspecific interactions and even the community structure. [ABSTRACT FROM AUTHOR]

The red alga Compsopogon caeruleus can generally be found in tropical and subtropical waters worldwide. In addition to its natural habitats, this species may be found in waters that receive abnormally hot water, e.g., from powerhouses. To date, the presence of C. caeruleus has not been observed in thermally polluted lacustrine ecosystems in Poland, which has a moderate climate. The thalli of this red alga were found growing on Vallisneria spiralis in Licheńskie Lake. Importantly, this paper presents a previously unknown relationship between the temperature (20, 25, 30, 35, and 40°C) and oxygen requirements of C. caeruleus (based on ex situ measurements of O2 consumption by thalli). Surprisingly, 35°C can be the optimum temperature for C. caeruleus, and this temperature is higher than the values reported by some previous thermal analyses by approximately 10°C. Additionally, we reviewed and mapped the distribution of this nonnative and mesophilic red alga in natural / seminatural water ecosystems in Europe. Finally, we propose that the occurrence of C. caeruleus mature thalli can be a novel, simple and easy-to-recognize bioindicator of artificially and permanently heated waters in moderate climate zones by a regular discharge of postindustrial water. [ABSTRACT FROM AUTHOR]

To study the response of the Vallisneria natans morphological and physiology to water level change, seedlings were placed in a submerged condition at depths ranging from 50 cm to 135 cm and set the rising and declining water levels respectively (0.2 cm/d, 0.5 cm/d, 0.8 cm/d, 1.1 cm/d, 1.4 cm/d, 1.7 cm/d). After 50 days of simulation experiment, we observed the effects on plant height, the number of blades, root activity, biomass, chlorophyll a (Chl a), chlorophyll b (Chl b), chlorophyll (a + b) (Chl a + b), carotenoid (Car), soluble protein (SP) and soluble sugar (SS) of V. natans under different water level change rates. The results showed that (1) plant height and the number of blades showed an overall upward trend under the condition of high-rate water level change, while the low-rate change of water level showed a trend of first rising and then decreasing. (2) the root activity of 0.5–1.7 cm/d groups increased with the test time at rising water level, and the declining water level showed a trend of increasing and then decreasing. The total biomass showed an upward trend with the extension of the test time. (3) Chl a, Chl b, Chl (a + b), and Car showed a multi-peak downward trend with the extension of the test time. (4) the response of SP and SS to the test time showed a trend of first increase and then decrease with water level changes. In conclusion, our study demonstrates that the morphological and physiology of V. natans could adapt to water level changes, but it could be stressed if the water level exceeded the suitable range. [ABSTRACT FROM AUTHOR]

Water regime plays a determinant role in plant community development and patterns of plant zonation in wetlands. The waters located in the middle reach of the Yangtze River (China) have experienced a large decrease in wetland area from human activities for a long time, especially after the hydrological drought events in recent years. This outdoor study was conducted to clarify the morphological responses and reproductive strategy of Vallisneria spinulosa to water depth gradients (0.6 m, 1.0 m, 1.5 m) and to drawdown (down to 0.3 m). In static water, water depth of 1.0 m was the best condition for V. spinulosa to grow, manifested as high biomass of vegetative parts, tubers and sexual structures. However, V. spinulosa growing in water depth of 1.5 m was able to adapt to the decline in water depth in autumn, expressed as increased ramet number, stolon weight and belowground biomass. The low water depth of 0.6 m produced small plants with slight vegetative biomass and drawdown produced more tuber biomass. The drawdown caused a decline in vegetative ratio of V. spinulosa. Moreover, it caused an increase in clonal ratio at water levels of 1.5 m and 0.6 m, and a decline in sexual ratio at water levels of 1.5 m and 1.0 m. The results show that under the condition of relatively large fluctuations in water level, V. spinulosa will reduce the allocation of sexual biomass and increase the allocation of clonal biomass in order to cope with environmental changes so that it can proliferate better. Thus, water level changes have a great influence on the growth and reproduction of V. spinulosa. [ABSTRACT FROM AUTHOR]

The problem of seasonal drought has intensified in recent years. Unfortunately, dry seasons can lead to poor water quality due to nitrogen (N) accumulation, which, in turn, may result in the gradual decline or even disappearance of submerged plants. This outdoor study was conducted to determine the morphological, biomass responses and C/N metabolism of Vallisneria spinulosa to the high N content and low water level. We used two N contents (i.e., low and high) and three simulated water levels (i.e., gradual water level increase from 60 cm to 150 cm over four periods (C), low water level of 60 cm maintained for three periods followed by an abrupt increase to 150 cm in the fourth period (CE) and low water levels of 60 ± 30 cm maintained for three periods followed by an abrupt increase to 150 cm in the fourth period (E)). For the low N content, low water levels for CE and E treatments caused increased ramet number and biomass of V. spinulosa. However, for the high N content, the low water levels did not cause such big changes in V. spinulosa. High N contents demonstrated a remarkably negative influence on the biomass of each organ (included leaf, stolon, root and tuber) of V. spinulosa and flowering ramet number. For C water level, the high N content caused an increase in free-amino acid (FAA) content in stolons and leaves, and no difference in soluble carbohydrate (SC) content. For E water level, there was no significant increase in FAA content of V. spinulosa under high N treatment; furthermore, there was no significant change in SC content under high N treatment except for leaves. In conclusion, low water levels exacerbated the damage to V. spinulosa caused by high nitrogen level. [ABSTRACT FROM AUTHOR]

Seed germination is a critical process in the seed life cycle, especially for annual submerged macrophytes Vallisneria natans which is a model species for the restoration of degraded shallow lakes. Fresh seeds of V. natans have a very high germination rate but with no significant responses to the aggregation effect; meanwhile, these recalcitrant seeds quickly lose seed viability under dry storage. This study aims to explore the response of seed germination of V. natans after dry storage to aggregation effect by several microcosm experiments. We observed that seed aggregation has a significant positive effect on germination, and among the seven experimental densities between 10 ∼ 640 seeds, higher seed densities resulted in significantly enhanced germination. In contrast, daily removal of germinated seeds led to a significant decrease in the overall germination rate, suggesting that germinated seeds may secrete chemicals that promote the germination of ungerminated seeds. However, further experiments indicated that ethylene and gibberellins had no noticeable impact on seed germination, which was consistent with additional experiment results from spectrophotometer and high-throughput targeted metabolomics. We concluded that the promoting effect of aggregation on the seed germination of V. natans may be an adaptation of this species to its natural habitat but detailed mechanisms warranted further study. • Germination of Vallisneria natans seeds after long-term dry storage was investigated. • Seed density above ∼300 seeds per petri dish promoted seed germination. • Germinated seeds facilitate the germination process. • The functional chemicals that promote germination were unknown. [ABSTRACT FROM AUTHOR]

The efficiency and mechanism in the reduction of internal phosphorus loading from sediment by Vallisneria natans combined with iron- and zirconium-modified bentonites (abbreviated as FeBT and ZrBT, respectively) were studied, and the responses of the microbial communities in sediments to Vallisneria natans combined with FeBT and ZrBT were also explored. ZrBT had stronger phosphate adsorption ability than FeBT. The greatest phosphate adsorption capacities for FeBT and ZrBT in the simultaneous presence of common ions can attain 1.60 and 4.29 mg P/g, respectively, and those for the loaded iron in FeBT and zirconium in ZrBT can attain 55.2 mg P/g Fe 2 O 3 and 164 mg P/g ZrO 2 , respectively. The combined utilization of FeBT and Vallisneria natans and that of ZrBT and Vallisneria natans can effectively lower the releasing risk of phosphorus from sediment into the overlying water (OW), and the combined use of ZrBT and Vallisneria natans had a higher controlling efficiency than that of FeBT and Vallisneria natans. The passivation of diffusion gradient in thin film (DGT)-labile phosphorus in the sediment layer was vital to the control of phosphorus release from sediment by Vallisneria natans combined with FeBT and ZrBT. The bacterial communities in the sediments under the conditions of FeBT + Vallisneria natans and ZrBT + Vallisneria natans can exert well ecological functions. This work indicates that the combined utilization of ZrBT and Vallisneria natans is a better method to lower the releasing risk of phosphorus from sediment into OW than that of FeBT and Vallisneria natans. [Display omitted] • Maximum P adsorption capacity for loaded Fe in FeBT attained 55.2 mg P/g Fe 2 O 3. • Maximum P adsorption capacity for loaded Zr in ZrBT attained 164 mg P/g ZrO 2. • Vallisneria natans (VN) was combined with FeBT/ZrBT to control internal P release. • Inactivation of DGT-labile P in sediment was vital to internal P release control. • ZrBT + VN has high potential in control of P release from sediment. [ABSTRACT FROM AUTHOR]

In this study, by setting two different water level environments, rising and falling, we investigated the characteristics of changes in the antioxidant enzyme system and the degree of cell membrane peroxidation of Vallisneria natans under different intensities of water level fluctuations. The results showed that (1) Peroxidase (POD) and Superoxide dismutase (SOD) showed a trend of increasing first and then decreasing under the rising water level and a multi-peak decreasing trend under the falling water level. Catalase (CAT) generally showed a trend of increasing first and then decreasing during the change in water level. The activity of POD and SOD were higher in the water level with low fluctuation intensity, and CAT was higher in the water level with high fluctuation intensity. (2) Malondialdehyde (MDA) and the production rate of superoxide anion (O2 - ) showed a trend of rising first and then decreasing under the rising water level and a multi-peak decreasing trend under the falling water level. Overall, fluctuating water levels can produce growth stresses on V. natans, and in response to these stresses, the antioxidant enzyme system of V. natans produces a series of antioxidant protection mechanisms to maintain normal plant growth. [ABSTRACT FROM AUTHOR]

Clonal integration benefits clonal plants by buffering environmental stress and increasing resource extraction efficiency. However, the number of connected ramet generations that benefit from clonal integration in a clonal system has received relatively little attention. A pot experiment was conducted to evaluate the extent of physiological integration within the clonal system of Vallisneria natans consisting of a mother ramet and three sequentially connected offspring ramets. Mother ramets were grown in full sunlight, and offspring ramets were heavily shaded with limited light availability. Stolons between mother ramets and offspring ramets were severed or connected, but connection among the three offspring ramets remained. The photosynthetic ability of unshaded mother ramets of V. natans was significantly enhanced, but their biomass accumulation was greatly reduced when connected to shaded offspring ramets. Clonal integration significantly increased biomass accumulation, C and N availabilities, extracellular enzyme activities and microbial biomass of the first ramet generation (adjacent ramet), but not later ramet generations. Our results indicate that support from the mother ramet of V. natans may be limited to the adjacent offspring ramet in a clonal system under severe light stress, implying an effect of ramet generation. Our results contribute to a better understanding of the hierarchy and segmentation of clonal plants. These findings suggest that the extent of clonal integration plays a vital role in ecological interactions of the ramet population. [ABSTRACT FROM AUTHOR]

The characteristics of propagules markedly impact the germination and plant growth of submerged macrophytes. Vallisneria spinulosa S.Z. Yan is a common submerged macrophyte and has been widely used in lake restoration projects. The responses of tuber germination and plant growth to different tuber sizes and burial depths are not well known for this species and may vary with light intensity. In this study, the tuber germination and plant growth of V. spinulosa germinated from two levels of tuber sizes (large and small) and two different burial depths in the sediment (5 and 15 cm) were tested at two light intensities (high and low) by measuring morphological and physiological traits. Although light intensity, tuber size and burial depth did not affect the tuber germination, they significantly influenced the morphological and physiological traits of the plants. Light intensity had the greatest effect on plant growth, followed by tuber size, while burial depth had the least effect. High light, large tuber and shallow burial depth favoured the plant growth performance (plant biomass, ramet and leaf numbers). The growth performance of plants germinated from small tubers was more susceptible to changes in light intensity and burial depth. Soluble carbohydrate and free amino acid contents were negatively and starch content positively correlated with the morphological traits. The study highlights the importance of tuber size and burial depth for plant growth as well as their interactions with light, which should be considered when determining lake management and restoration strategies. [ABSTRACT FROM AUTHOR]

The estimation of the protein content and amino acid composition under the influence of metal nanoparticles (Mn, Cu, Zn, Ag) for seven species of aquatic macrophytes: Limnobium laevigatum (Humb. & Bonpl.ExWilld.), Pistia stratiotes L., Salvinia natans L., Elodea canadensis Michx., Najas guadelupensis (Spreng.) Magnus, Vallisneria spiralis L. and Riccia fluitans L. was conducted. The plants were exposed during 7 days on the experimental solutions of metal nanoparticles at the rate of 1 g of plant per 100 ml of the mixture of stock colloidal solutions of metal nanoparticles (Mn - 0.75 mg/l, Cu - 0.37 mg/l, Zn - 0.44 mg/l, Ag+, Ag2O - 0.75 mg/l) diluted 200 times. In the five investigated species, reduction of the protein content was observed. However, this indicator remained stable only in P. stratiotes (52 mg/ml) and, conversely, increased in V. spiralis (46 mg/ml to 51 mg/ml). The content of the studied amino acids in N. guadelupensis decreased by 46% (from 112.05 mmol/g to 60.15 mmol/g), in R. fluitans - by 44% (from 104.06 mmol/g to 58.25 mmol/g), in S. natans - by 23% (from 90.08 mmol/g to 69.59 mmol/g), in E. canadensis - by 10% (from 143.92 mmol/g to 129.4 mmol/g), and in P. stratiotes as well as in L. laevigatum - by 8% (from 210.65 mmol/g to 193.77 mmol/g and with 155.0 mmol/g to 142.60 mmol/g), but in V. spiralis, on the contrary, increased by 7% (from 91.31 mmol/g to 97.59 mmol/g). Changes in the composition and content of amino acids for each species of aquatic plant were analyzed. It was suggested that the studied plants, which belong to different families, have different defense mechanisms, according to which the amino acid composition of plants varies. [ABSTRACT FROM AUTHOR]

For investigating the response of chlorophyll fluorescence characteristics under single and combined of Cu or Zn stress, Vallisneria natans was selected as the experimental subject. V. natans was cultured 21 days under six concentration levels of Cu or Zn. The results showed that Fv/Fm, Fv/Fo, Y (II) and qP increased, and other indicators were almost unchanged in low- concentration treatment (Cu≤0.4mg/L, Zn≤4.0mg/L, Cu+Zn≤0.2+2.0 mg/L). V. natans could still maintain normal growth within such a range of heavy metal concentration, and it could maintain relatively a high photosynthetic activity. When heavy metal concentration was higher than the above concentration, the photosynthetic activity was inhibited. Fv/Fm, Fv/Fo, Y (II) and qP decreased gradually with the increasing stress concentration and stress time, while Y(NO), Y (NPQ), and qN showed different degrees of increase. The combined stress of Cu and Zn had a synergistic effect on the photosynthetic activity. V. natans can be used for ecological restoration of polluted water with low concentration of Cu and Zn. [ABSTRACT FROM AUTHOR]

Restoration of genetic diversity to levels that ensure long-term species persistence is an important management strategy in degraded systems. Unfortunately, genetic data are lacking for many species such that practitioners must make management decisions for data-deficient areas using information from other parts of a species' range. For such a management approach to be reliable, genetic diversity needs to be structured similarly. To determine if this is the case, we compared genetic structure in the submersed aquatic plant species Vallisneria americana across similar salinity gradients in three major tidal rivers in eastern North America (the Potomac, Hudson, and Kennebec) using 10 microsatellite markers. The Potomac supported high genotypic diversity, and no barriers between sampled sites were identified. Migrant analysis suggested that moving restoration stock within 22 km would fall within natural dispersal distances and thus create low risks, if augmentation were sought for sites where potential inbreeding was detected. The Hudson supported low genotypic diversity. No inbreeding was detected in the Kennebec or the Hudson, but dispersal barriers and recent bottlenecks were observed. These differences in genetic structure among rivers could limit broad adoption of management guidelines based solely on genetic data from one part of this species' range. Such guidelines could risk moving restoration stock across barriers in the unsampled rivers, altering the species' genetic architectures and potentially its natural resilience. Despite the allure of applying science-based generalities to restoration practice, locally relevant data and stock may often be needed for restoration efforts to maintain self-sustaining systems. [ABSTRACT FROM AUTHOR]

• Effect of vermiculite on Vallisneria spiralis and sediment microenvironment. • A certain amount vermiculite accelerate the growth of Vallisneria spiralis. • Diversity and richness of microbial communities in vermiculite group were increased. • PCA demonstrated 5% and 10% group improved the sediment conditions. • Vermiculite can be applied to ecological restoration projects in eutrophic lakes. Ecological restoration is one of the hot technologies for the reconstruction of eutrophic lake ecosystems in which the restoration and propagation of submerged plants is the key and difficult step. In this paper, the effect of vermiculite on the growth process of Vallisneria spiralis and sediment microenvironment were investigated, aiming to provide a theoretical basis for the application of vermiculite in aquatic ecological restoration. Results of growth indexes demonstrated that 5% and 10% vermiculite treatment groups statistically promote the growth of Vallisneria spiralis compared to the control. Meanwhile, the results of ecophysiological indexes showed that photosynthetic pigment, soluble sugar content, superoxide dismutase (SOD), and catalase (CAT) activity of 5% and 10% group were increased compared with the control while the malondialdehyde (MDA) content exhibited the opposite result (p < 0.05), which illustrated that vermiculite can improve the resistance of plants and delay the aging process of Vallisneria spiralis. In addition, result of PCA (Principal Component Analysis) demonstrated 5% and 10% group has improved the sediment physical conditions and create more ecological niche for microorganisms directly, and then promoted the growth of plants. The dissolution results showed that vermiculite can dissolve the constant and trace elements needed for plant growth. Furthermore, the addition of vermiculite increased the diversity of microorganisms in the sediments, and promoted the increase of plant growth-promoting bacteria and phosphorus-degrading bacteria. This study could provide a technique reference for the further application of vermiculite in the field of ecological restoration. [Display omitted] [ABSTRACT FROM AUTHOR]

Research on aquatic plant viruses is lagging behind that of their terrestrial counterparts. To address this knowledge gap, here we identified viruses associated with freshwater macrophytes, a taxonomically diverse group of aquatic phototrophs that are visible with the naked eye. We surveyed pooled macrophyte samples collected at four spring sites in Florida, USA through next generation sequencing of RNA extracted from purified viral particles. Sequencing efforts resulted in the detection of 156 freshwater macrophyte associated (FMA) viral contigs, 37 of which approximate complete genomes or segments. FMA viral contigs represent putative members from all five major phyla of the RNA viral kingdom Orthornavirae. Similar to viral types found in land plants, viral sequences identified in macrophytes were dominated by positive-sense RNA viruses. Over half of the FMA viral contigs were most similar to viruses reported from diverse hosts in aquatic environments, including phototrophs, invertebrates, and fungi. The detection of FMA viruses from orders dominated by plant viruses, namely Patatavirales and Tymovirales, indicate that members of these orders may thrive in aquatic hosts. PCR assays confirmed the presence of putative FMA plant viruses in asymptomatic vascular plants, indicating that viruses with persistent lifestyles are widespread in macrophytes. The detection of potato virus Y and oat blue dwarf virus in submerged macrophytes suggests that terrestrial plant viruses infect underwater plants and highlights a potential terrestrial-freshwater plant virus continuum. Defining the virome of unexplored macrophytes will improve our understanding of virus evolution in terrestrial and aquatic primary producers and reveal the potential ecological impacts of viral infection in macrophytes. [ABSTRACT FROM AUTHOR]

Enrofloxacin (ENR) is a member of quinolones, which are extensively used in livestock farming and aquaculture to fight various bacterial diseases, but its residues are partially transferred to surface water and affect the local aquatic ecosystem. There are many studies on the effect of ENR on the growth of a single aquatic species, but few on the level of the aquatic community. Epiphytic algae, which are organisms attached to the surface of submerged plants, play an important role in the absorption of nitrogen and phosphorus in the ecological purification pond which are mainly constructed by submerged plants, and are commonly used in aquaculture effluent treatment. Enrofloxacin (ENR) is frequently detected in aquaculture ponds and possibly discharged into the purification pond, thus imposing stress on the pond ecosystem. Here, we performed a microcosm experiment to evaluate the short-term effects of pulsed ENR in different concentrations on the epiphytic algal communities growing on Vallisneria natans. Our results showed an overall pattern of "low-dose-promotion and high-dose-inhibition", which means under low and median ENR concentrations, the epiphytic algal biomass was promoted, while under high ENR concentrations, the biomass was inhibited. This pattern was mainly attributed to the high tolerance of filamentous green algae and yellow-green algae to ENR. Very low concentrations of ENR also favored the growth of diatoms and cyanobacteria. These results demonstrate a significant alteration of epiphytic algal communities by ENR and also spark further research on the potential use of filamentous green algae for the removal of ENR in contaminated waters because of its high tolerance. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of water flow on the growth and physiological indicators of the submerged macrophyte, Vallisneria natans, and the bacteria and algae community composition on its epiphytic biofilm-covered leaves. The authors set up a simulated flowing water laboratory experiment testing high nitrogen (N) and phosphorus (P) concentrations. Total chlorophyll and dissolved oxygen (DO) was significantly enhanced, and turbidity was reduced, thereby accelerating the growth of V. natans. These experiments were compared to another set of observations on a static group. The accumulation of malonaldehyde (MDA) in the dynamic groups was significantly higher than that in the static group. As an antioxidant stress response, the total superoxide dismutase (T-SOD) was also induced in plants exposed to nutrient-rich flowing water. The results of 16S rRNA high-throughput sequencing analyses showed that the water flow increased the bacteria community diversity of biofilm-producing bacteria with N and P removing bacteria, carbon cycle bacteria, and plant growth-promoting rhizobacteria on the epiphytic biofilm. This research determined that water flow alleviates the adverse effects of eutrophication when V. natans grows in water containing high N and P concentrations. Water flow also inhibits the growth of cyanobacteria (also referred to as blue-green algae) in epiphytic biofilm. The ecological factor of water flow, such as water disturbance and aeration measures, could alleviate the adverse effect of eutrophic water by providing a new way to restore submerged macrophytes, such as V. natans, in eutrophic water. [ABSTRACT FROM AUTHOR]

Ammonium (NH4-N) produces a paradoxical effect on submersed macrophytes because it is not only the preferred nitrogen source for the growth of plants but also threatens the growth of plants at high concentration. Whether short-term and smallscale physiological toxicity experiments at an individual level can reflect the effects of high ammonium on populations of submersed macrophytes in natural conditions is still unclear. In this study, an 18-month experiment was conducted in six 600 m2 ponds subjected to different levels of ammonium loading. The effects of high ammonium on populations of canopy-forming Myriophyllum spicatum and rosette-forming Vallisneria natans were explored. The results showed that M. spicatum and V. natans populations can develop high cover and height at high ammonium concentration (7 mg/L) at shortterm exposures, and V. natans may be tolerant to 18 mg/L ammonium concentration. However, the cover of M. spicatum and the height of both species were inhibited at 2.4 mg/L at long-term exposures. The height of M. spicatum was two to six times higher than that of V. natans across all treatments and control by the end of the experiment, and the cover of M. spicatum was 7-11 times higher than that of V. natans in most NH4-N loading treatments, except the cover of M. spicatum in the highest NH4-N loading treatment with 18 mg/L NH4-N. The rosette-forming V. natans resists ammonium stress by slow growth (shoot elongation) to reduce consumption, while canopy-forming species resist ammonium stress by shoot elongation and canopy development to capture light. Although increasing ammonium concentration may induce severe stress on M. spicatum, the morphological characteristics of this species may, to some extent, release the plants from this stress. Our present study indicates that the negative effects of ammonium stress on the development of populations increased with exposure duration, and the submersed macrophyte community with stronger ability for light capture and dispersal may resist high ammonium stress. Nevertheless, in strongly ammonium-enriched systems, competition and succession cannot be neglected. [ABSTRACT FROM AUTHOR]

Trait‐based methods are key to understanding the biodiversity–productivity relationship (BPR) of macrophyte communities. Community‐weighted mean traits (i.e., community trait structure) have been proven to have more influence on macrophyte community productivity than species richness. However, the underlying mechanism by which community trait structure variation affects macrophyte community productivity along an environmental gradient is still not well understood.A mesocosm experiment was used to investigate how community trait structure shapes macrophyte community productivity along the water depth gradient. Three submerged macrophyte species (Myriophyllum spicatum, Vallisneria natans and Potamogeton malaianus) were assembled into all possible combinations (one, two and three species per community) at three different water depths (1, 2.5 and 4 m). We fitted the relationships between community‐weighted mean traits and community productivity, and between species richness and community productivity as a comparison. We compared functional traits under different water depths and species composition at the species and community levels and disentangled the community trait structure into species turnover and intraspecific trait variability effects.The results showed that community trait structure had various influences on macrophyte community productivity, which was based on traits per se. However, species richness had a non‐significant impact on macrophyte community productivity. Water depth had a significant impact on most traits of the three species at the species level, whereas both water depth and species composition had significant impacts on community trait structure which was mainly affected by intraspecific trait variability along the water depth gradient.Our findings highlight the importance of considering intraspecific trait variability and species turnover under water depth gradients to understand the relationship between trait‐based biodiversity and productivity. [ABSTRACT FROM AUTHOR]

A 60 days growth trial was conducted with fry of Hypselobarbus pulchellus for evaluating the effect of incorporation of two aquatic plants Azolla microphylla and Vallisneria spiralis at 30, 60 and 90% levels in the diet on growth and survival. The fry (average weight 23.07 ± 0.96 mg and average length 1.57 ± 0.24 cm) were stocked at 12 numbers per tank and fed to satiation with one of the experimental diets (three diets each with azolla and vallisneria) or a control diet. Water quality parameters analysed at fortnightly intervals did not show significant difference between treatments (p >.05). The mean final weight of fish reduced in groups fed diets with azolla and vallisneria incorporated beyond 60% and 30% respectively (p <.05). While the mean final length of fish fed azolla diets did not differ among the treatments, it gradually reduced in groups fed diets with increasing levels of vallisneria incorporation (p >.05). The condition factor and survival did not vary between treatments (p >.05). The study indicates the possible incorporation of azolla up to 60% and vallisneria up to 30% as feed ingredients in the diet for H. pulchellus during fingerling raising. [ABSTRACT FROM AUTHOR]

Lanthanum-modified bentonite (LMB) has remarkable efficacy on eutrophication control, but the reduced bioavailable phosphorus and formed anaerobic horizon from LMB may be harmful to submerged macrophytes. We conducted this study to explore the influence of LMB on Hydrilla verticillata and Vallisneria natans in mixed-species plantings. The concentrations of TP, TDP, SRP, and TDN in the LMB treatments were lower than the Control, but the Chl a concentration in the HLMB treatment (850 g m−2) was higher than the Control by 63%. There were no differences of V. natans growth among the treatments. For H. verticillata, its biomass, RGR, height, branch number, root number, and length in the LLMB treatment (425 g m−2) were lower than the Control by 48%, 22%, 13%, 34%, 33%, and 8%, respectively. In addition, the biomass of H. verticillata was 62%, the RGR was 32%, the height was 19%, the branch number was 52%, the root length was 40%, and the root number was 54% lower in the HLMB treatment than those in the Control. In summary, LMB had negative effects on submerged macrophytes with underdeveloped roots. Submerged macrophytes with more developed roots are preferred when using combined biological–chemical methods for water restoration. [ABSTRACT FROM AUTHOR]

Sediment cadmium contamination poses risks to aquatic ecosystems. Phytoremediation is an environmentally sustainable method to mitigate cadmium contamination. Submerged macrophytes are affected by cadmium stress, but plant growth-promoting rhizobacteria (PGPR) can restore the health status of submerged macrophytes. Herein, we aimed to reduce sediment cadmium concentration and reveal the mechanism by which the combined application of the PGPR Enterobacter ludwigii and the submerged macrophyte Vallisneria natans mitigates cadmium contamination. Sediment cadmium concentration decreased by 21.59% after submerged macrophytes were planted with PGPR, probably because the PGPR colonized the rhizosphere and roots of the macrophytes. The PGPR induced a 5.09-fold increase in submerged macrophyte biomass and enhanced plant antioxidant response to cadmium stress, as demonstrated by decreases in oxidative product levels (reactive oxygen species and malondialdehyde), which corresponded to shift in rhizosphere metabolism, notably in antioxidant defence systems (i.e., the peroxidation of linoleic acid into 9-hydroperoxy-10E,12Z-octadecadienoic acid) and in some amino acid metabolism pathways (i.e., arginine and proline). Additionally, PGPR mineralized carbon in the sediment to promote submerged macrophyte growth. Overall, PGPR mitigated sediment cadmium accumulation via a synergistic plant microbe mechanism. This work revealed the mechanism by which PGPR and submerged macrophytes control cadmium concentration in contaminated sediment. [Display omitted] • The study proposed a strategy for mitigating sedimentary cadmium. • PGPR inoculation maximized the accumulation of cadmium in submerged macrophytes. • PGPR may help submerged macrophytes overcome carbon constraints. [ABSTRACT FROM AUTHOR]

[Display omitted] • LMA capping combined with macrophyte (Vallisneria natans) enhanced the immobilization of P in sediments. • A new sediment–water interface was generated after LMA capping, which promoted the growth of Vallisneria natans roots. • Mobile P in black odorous sediments had the highest reduction rates when capping with LMA. As a kind of phosphorus (P) inactivating agent, lanthanum-modified attapulgite (LMA) has effectively been used for controlling the release of P from sediments. However, the effects of LMA on sediments from different types of ecological environments, especially in the rhizosphere of macrophyte, have not yet been studied. In this study, sediments from black-odor rivers (Black-S), cyanobacteria blooms-dominated lake (Algal-S) and macrophyte-dominated lake (Phytic-S) were collected for laboratory-scale microcosmic experiments. The results indicated that LMA had a good inactivation effect on mobile P (sum of Labile-P, Fe-P and organic-P) in three types of sediments, and significantly reduced soluble and labile P in pore water. The rates of reduction of mobile P in Black-S and Algal-S were much higher than that in Phytic-S. LMA capping generated a new sediment water interface, which significantly promoted the growth of roots, the release of oxygen from Vallisneria natans , and the secretion of organic acids to improve the rate of utilization of P in sediments. Meanwhile, the addition of LMA increased the relative abundance of Sideroxydans in the rhizosphere of Vallisneria natans. The study provides a new insight into the applications of LMA capping combined with macrophyte in the restoration of sediments obtained from different ecological settings. [ABSTRACT FROM AUTHOR]

[Display omitted] • Underwater light source obviously affected the microecosystem of V. spinulosa Yan. • Removal loads of TN and TP were enhanced by 61.5 and 8.5 mg m−2 d-1, respectively. • Growth of leaf and root of V. spinulosa Yan were obviously improved. • Abundance of Methylocystis , Dechloromonas was reduced but Clostridium was increased. • Metabolism of carbohydrate, lipid, and energy of V. spinulosa Yan were promoted. Submerged macrophytes are effective in ecological restoration of water bodies polluted by nitrogen and phosphorus, and its restoration capacity depends on underwater illumination condition. This study explored the influencing mechanism of illumination on Vallisneria spinulosa Yan (V. spinulosa Yan) for water restoration. Addition of underwater light source increased the total nitrogen, ammonia nitrogen, total phosphorus, and phosphate removal loads of the V. spinulosa Yan growth system by 61.5, 39.2, 8.5, and 5.0 mg m−2 d-1, respectively. Meanwhile, the growth of V. spinulosa Yan was obviously promoted, even with high water turbidity. Although the biological nitrogen removal processes were inhibited by adding underwater light source, the growth of V. spinulosa Yan can be significantly improved, thus enhancing the efficiency of water purification via the absorption of nitrogen and phosphorus by V. spinulosa Yan. This study provides a theoretical foundation and technical support for application of submerged macrophytes in ecological water restoration. [ABSTRACT FROM AUTHOR]