First Report of Agroathelia rolfsii Causing Southern Blight on Lippia (Phyla canescens) in Guangzhou, China.

Lippia (Phyla canescens) is a fast-growing, mat-forming, and prostrate perennial plant well adapted to infertile, high-saline, and drought environments (Leigh, et al. 2004). It arrived in China from Japan as a flowering ground cover in 2001 (Cai, et al. 2004). In June 2022, southern blight appeared in our nursery of the Floriculture Research Institute of Guangdong Academy of Agricultural Sciences. High temperature and damp environment are major factors for this disease. The symptoms of top-layer plants were not easily detected, but they were slightly yellowed. A yellowish-brown water-soak lesion appeared on the stems and lowest leaves exposed to soil. White mycelium appeared in the middle stage. Finally, the surface plants showed water-soak decay, and a mass of beige to black-brown rapeseed-shaped sclerotia appeared on the residue and surrounding soil; these plants died. Sclerotia and mycelia were collected from disease tissue, and after surface sterilization, sclerotia was cultured on potato dextrose agar (PDA) at 28±2°C in an incubator without light. Eight fungal isolates with similar colony morphologies were consistently isolated by purifying from different sampling areas. The isolates exhibited obvious septa and a clamp connection structure within the white mycelium. The average growth rate was 26.86±0.06 mm/day. Numerous white granular sclerotia were produced on the mycelium 6 days later. The sclerotia with a diameter of 1.24±0.07mm (n=189) gradually changed from diage to yellow to brown. A typical strain B1 was selected for further identification, targeting its 18S rRNA and LSU rRNA sequences (Yang, et al. 2011; Xue, et al. 2019). Its 18S rRNA sequence (GenBank Accession No. OR517233, 1626 bp) is 99.63% and 99.57% identical to Athelia rolfsii (AY665774, 1179bp; KC670714, 1775bp; JF819726, 1781bp). Its LSU rRNA sequence (OR539570, 757 bp) is 99.87% identical to Agroathelia rolfsii (OR526537, 904 bp). For Athelia rolfsii, a synonym of Agroathelia rolfsii, by combining the morphological characteristics and molecular identification, the isolate pathogen B1 was confirmed to be Agroathelia rolfsii (the teleomorph of Sclerotium rolfsii). To fullfill Koch's postulates, we inoculated the mycelial plugs to healthy lippia stems and leaves which has grown for one year, with PDA plugs free of mycelium as the control. All the plants were kept in a greenhouse at 28±2°C with a 14-h photoperiod and 80% relative humidity. Each treatment was repeated thrice and vaccinated with 6 points. At 7 d following inoculation, all plants inoculated with B1 showed typical symptoms, but the control group was asymptomatic, and sclerotia appeared 17d after inoculation. Using the same protocol mentioned above, pathogenic fungal was reisolated only from treated groups, but not from the control group. Chose three of the pathogens for 18S rRNA and LSU rRNA sequencing, the results showed 100% identity to B1, the same as its microstructure. There are few reports about the disease on P. canescens. Sosa (2007) investigated the pathogens on P. canescens in Argentina, 16 fungi were found but no A. rolfsii. Sclerotium rolfsii were identified on P. nodiflora or P. lanceolata (Michaux) Greene in America (Farr, et al. 1989). To our knowledge, this is the first report in China. Because this pathogen has wide-ranging hosts and causes serious damage, the results from this study will offer guidance for the prevention and treatment of this disease.

Using rice straw-augmented ecological floating beds to enhance nitrogen removal in carbon-limited wastewater.

Agricultural biomass used as solid carbon substrates in ecological floating beds (EFBs) has been proven to be applicable in nitrogen removal for carbon-limited wastewater treatment. However, the subtle interactions among plants, rhizosphere microorganisms, and supplementary carbon sources have not been thoroughly studied. This study combined rice straw mats with different aquatic macrophytes in EFBs to investigate denitrification efficiency in carbon-limited eutrophic waters. Results showed that rice straw significantly enhanced the nitrogen removal efficiency of EFBs, while enriching nitrogen-fixing and denitrifying bacteria (such as Rhizobium, Rubrivivax, and Rhodobacter, etc.). Additionally, during the denitrification process in EFBs, rice straw can release humic acid-like fraction as electron donors to support the metabolic activities of microorganisms, while aquatic macrophytes provide a more diverse range of dissolved organic matters, facilitating a sustainable denitrification process. These findings help to understand the synergistic effect of denitrification processes within wetland ecosystems using agricultural biomass.

Deep Learning-Assisted Spectrum-Structure Correlation: State-of-the-Art and Perspectives.

Spectrum-structure correlation is playing an increasingly crucial role in spectral analysis and has undergone significant development in recent decades. With the advancement of spectrometers, the high-throughput detection triggers the explosive growth of spectral data, and the research extension from small molecules to biomolecules accompanies massive chemical space. Facing the evolving landscape of spectrum-structure correlation, conventional chemometrics becomes ill-equipped, and deep learning assisted chemometrics rapidly emerges as a flourishing approach with superior ability of extracting latent features and making precise predictions. In this review, the molecular and spectral representations and fundamental knowledge of deep learning are first introduced. We then summarize the development of how deep learning assist to establish the correlation between spectrum and molecular structure in the recent 5 years, by empowering spectral prediction (i.e., forward structure-spectrum correlation) and further enabling library matching and de novo molecular generation (i.e., inverse spectrum-structure correlation). Finally, we highlight the most important open issues persisted with corresponding potential solutions. With the fast development of deep learning, it is expected to see ultimate solution of establishing spectrum-structure correlation soon, which would trigger substantial development of various disciplines.

Multi-modal nanoprobe-enabled biosensing platforms: a critical review.

Nanomaterials show great potential for applications in biosensing due to their unique physical, chemical, and biological properties. However, the single-modal signal sensing mechanism greatly limits the development of single-modal nanoprobes and their related sensors. Multi-modal nanoprobes can realize the output of fluorescence, colorimetric, electrochemical, and magnetic signals through composite nanomaterials, which can effectively compensate for the defects of single-modal nanoprobes. Following the multi-modal nanoprobes, multi-modal biosensors break through the performance limitation of the current single-modal signal and realize multi-modal signal reading. Herein, the current status and classification of multi-modal nanoprobes are provided. Moreover, the multi-modal signal sensing mechanisms and the working principle of multi-modal biosensing platforms are discussed in detail. We also focus on the applications in pharmaceutical detection, food and environmental fields. Finally, we highlight this field's challenges and development prospects to create potential enlightenment.

Response strategies of stem/leaves endophyte communities to nano-plastics regulate growth performance of submerged macrophytes.

Research on the toxicity effects of nano-plastics on submerged macrophytes has been increasing over the past several years. However, how the endophytic bacteria of submerged macrophytes respond to nano-plastics remains unknown, although they have been widely shown to help terrestrial plants cope with various environmental stressors. Here, a microcosm experiment was performed to unravel the effects of high concentration of nano-plastics (20 mg/L) on three submerged macrophyte (Vallisneria natans, Potamogeton maackianus, Myriophyllum spicatum) and their endophytic bacterial communities. Results indicated that nano-plastics induced antioxidative stress in plants, but significantly reduction in relative growth rate (RGR) only occurred in V. natans (from 0.0034 to -0.0029 day-1), accompanied by change in the stem/leaves endophyte community composition. Further analysis suggested nano-plastics caused a reduction in environmental nutrient availability and the proportion of positive interactions between endophyte communities (43%), resulting in the lowest RGR of V. natans. In contrast, endophytes may help P. maackianus and M. spicatum cope with nano-plastic stress by increasing the proportion of positive correlations among communities (70% and 75%), leaving their RGR unaffected. Collectively, our study elucidates the species-specific response strategies of submerged macrophyte-endophyte to nano-plastics, which helps to reveal the different phytoremediation potential of submerged macrophytes against nano-plastic pollution.

1D Gradient-Weighted Class Activation Mapping, Visualizing Decision Process of Convolutional Neural Network-Based Models in Spectroscopy Analysis.

Being characterized by the self-adaption and high accuracy, the deep learning-based models have been widely applied in the 1D spectroscopy-related field. However, the "black-box" operation and "end-to-end" working style of the deep learning normally bring the low interpretability, where a reliable visualization is highly demanded. Although there are some well-developed visualization methods, such as Class Activation Mapping (CAM) and Gradient-weighted Class Activation Mapping (Grad-CAM), for the 2D image data, they cannot correctly reflect the weights of the model when being applied to the 1D spectral data, where the importance of position information is not considered. Here, aiming at the visualization of Convolutional Neural Network-based models toward the qualitative and quantitative analysis of 1D spectroscopy, we developed a novel visualization algorithm (1D Grad-CAM) to more accurately display the decision-making process of the CNN-based models. Different from the classical Grad-CAM, with the removal of the gradient averaging (GAP) and the ReLU operations, a significantly improved correlation between the gradient and the spectral location and a more comprehensive spectral feature capture were realized for 1D Grad-CAM. Furthermore, the introduction of difference (purity or linearity) and feature contribute in the CNN output in 1D Grad-CAM achieved a reliable evaluation of the qualitative accuracy and quantitative precision of CNN-based models. Facing the qualitative and adulteration quantitative analysis of vegetable oils by the combination of Raman spectroscopy and ResNet, the visualization by 1D Grad-CAM well reflected the origin of the high accuracy and precision brought by ResNet. In general, 1D Grad-CAM provides a clear vision about the judgment criterion of CNN and paves the way for CNN to a broad application in the field of 1D spectroscopy.

Bacterial community are more susceptible to nanoplastics than algae community in aquatic ecosystems dominated by submerged macrophytes.

As a ubiquitous emerging pollutant, microplastics can interact with algal and bacterial communities in aquatic ecosystems. Currently, knowledge on how microplastics influence algae/bacteria is mostly limited to toxicity tests using either monocultures of algae/bacteria or specific algal-bacterial consortium. However, information on the effect of microplastics on algal and bacterial communities in natural habitats is not easily available. Here, we conducted a mesocosm experiment to test the effect of nanoplastics on algal and bacterial communities in aquatic ecosystems dominated by different submerged macrophytes. The community structure of algae and bacteria suspended in the water column (planktonic) and attached to the surface of submerged macrophytes (phyllospheric) were identified, respectively. Results showed that both planktonic and phyllospheric bacteria were more susceptible to nanoplastics, and these variations driven by decreased bacterial diversity and increased abundance of microplastic-degrading taxa, especially in aquatic systems dominated by V. natans. The community composition of both algae and bacteria were influenced to varying degrees by nanoplastics and/or plant types, but RDA results showed that only bacterial community composition was strongly correlated with environmental variables. Correlation network analysis showed that nanoplastics not only reduced the intensity of associations between planktonic algae and bacteria (average degree reduced from 4.88 to 3.24), but also reduced proportion of positive correlations (from 64% to 36%). Besides, nanoplastics also decreased the algal/bacterial connections between planktonic and phyllospheric habitats. Our study elucidates the potential interactions between nanoplastics and algal-bacterial community in natural aquatic ecosystems. These findings suggest that in aquatic ecosystems, bacterial community are more vulnerable to nanoplastics and may serve as a protective barrier for algae community. Further research is needed to reveal the protective mechanism of bacteria against algae at the community level.

Individual and combined toxicity of microplastics and diuron differs between freshwater and marine diatoms.

Microplastics are considered as the emerging pollutants, which not only directly affect aquatic organisms, but also causes combined pollution by adsorbing other pollutants. Diuron, as one of the most widely used herbicides, is frequently monitored in the aquatic environment for its adverse effects on aquatic organisms. However, little is known about the combined toxicity of microplastics and diuron to aquatic organisms, especially diatoms. In this study, freshwater diatom (Cyclotella meneghiniana) and marine diatom (Skeletonema costatum) were selected to study the individual and combined toxicity of microplastics (polystyrene, 0.6- 1.0 µm) and diuron. Experimental concentrations of microplastics and diuron were set at 50 mg/L and 100 µg/L, respectively, which have been shown to significantly inhibit the growth of aquatic organisms. Results suggested that both single microplastics and single diuron significantly inhibited the growth of the two diatoms, while significant SOD and MDA increase were only found in single diuron exposure. For diatoms exposed to individual microplastics, the microplastic particles adsorbed inside Cyclotella sp. and those aggregated around Skeletonema sp. were the major factor inhibiting the growth of diatom, respectively. According to the independent action model, the combined toxicity for both diatoms were all antagonistic. The adsorption behavior of microplastics to diuron alleviated the intracellular damage to diatoms caused by diuron, and the oxidative stress induced by diuron mitigated the physical damage to diatoms caused by microplastics. Collectively, our findings suggest that the co-existence of microplastics and diuron may affect their respective toxicity to diatoms. The mechanism of this "cross-phenomenon" between microplastics and diuron and their combined toxicity to different aquatic organisms need to be further studied.

Seasonality and Species Specificity of Submerged Macrophyte Biomass in Shallow Lakes Under the Influence of Climate Warming and Eutrophication.

Climate warming and eutrophication caused by anthropogenic activities strongly affect aquatic ecosystems. Submerged macrophytes usually play a key role in shallow lakes and can maintain a stable clear state. It is extremely important to study the effects of climate warming and eutrophication on the growth of submerged macrophytes in shallow lakes. However, the responses of submerged macrophytes to climate warming and eutrophication are still controversial. Additionally, the understanding of the main pathways impacting submerged macrophytes remains to be clarified. In addition, the influence of seasonality on the growth responses of submerged macrophytes to climate warming and eutrophication requires further elucidation. In this study, we conducted a series of mesocosm experiments with four replicates across four seasons to study the effects of rising temperature and nutrient enrichment on the biomass of two submerged macrophytes, Potamogeton crispus and Elodea canadensis. Our results demonstrated the seasonality and species specificity of plant biomass under the influence of climate warming and eutrophication, as well as the main explanatory factors in each season. Consistent with the seasonal results, the overall results showed that E. canadensis biomass was directly increased by rising temperature rather than by nutrient enrichment. Conversely, the overall results showed that P. crispus biomass was indirectly reduced by phosphorus enrichment via the strengthening of competition among primary producers. Distinct physiological and morphological traits may induce species-specific responses of submerged macrophytes to climate warming and eutrophication, indicating that further research should take interspecies differences into account.

Algal migration and nutrient enrichment contribute to patterns in phytoplankton versus epiphyton communities.

Algal dominance between phytoplankton and epiphyton plays an essential role in predicting shallow lake shifts between clear-water and turbid-water states. However, compared to resources competition, studies on algal life-form shifts between phytoplankton and epiphyton have traditionally received less interest, as few studies have focused on algal communities in both habitats concurrently. We conducted a 4 × 3 factorial design microcosm experiment to explore the mutual feedback relationship between phytoplankton and epiphyton. The initial algal life-form (epiphytic algae and phytoplanktonic algae alone or together) and nutrients enrichment (ambient, enrichment with N and P alone or together) were manipulated. After 28 days of incubation, the results suggested that the nutrient effects on the phytoplankton and epiphyton communities differed among the three different initial algal life-forms. A significant competitive advantage of phytoplankton was found even in treatments containing only epiphytic algae as the initial algal community. The contribution of nutrient enrichment to phytoplankton abundance (13%) was similar to that of epiphyton abundance (11%). In the mutual influence between two algal communities, epiphyton was likely to be a beneficiary as the phytoplankton community contributed 15% of the variance in epiphyton abundance. In addition, significant algal life-form shifts between phytoplankton and epiphyton only occurred in treatments containing one algal life-form, but not in treatments containing both algal life-forms at the beginning of the experiment. Our results emphasized the competitive advantage of phytoplankton in utilizing nutrient resources in the water column of shallow lakes. Moreover, we demonstrated that algal life-form shift was an adaptive behavior closely correlated with environmental variation. These results will provide broader insights to explore algal succession between phytoplankton and epiphyton in shallow lakes. To better understand the mutual influence mechanism between two algal life-forms under different nutrient conditions, research on multiple short time-scales based on algal migration is needed in the future.

Fabrication of a Cu Nanoparticles/Poly(ε-caprolactone)/Gelatin Fiber Membrane with Good Antibacterial Activity and Mechanical Property via Green Electrospinning.

To improve the antibacterial effect of a poly(ε-caprolactone)/gelatin (PCL/Gt) composite, Cu nanoparticles (Cu NPs) were synthesized as an antibacterial agent, and a Cu NPs/PCL/Gt fiber membrane was thus fabricated via green electrospinning. The results showed that the Cu NPs/PCL/Gt fiber membrane with a uniform and complete structure exhibited high porosity and water absorption, favorable hydrophilicity, good mechanical and thermal properties, and satisfactory antibacterial activity. The easy preparation and good comprehensive property implied the great potential application of the Cu NPs/PCL/Gt fiber membrane in various fields (e.g., wound dressing and antibacterial clothing). In addition, the synthesis in this work would offer a promising approach for the preparation of a metal nanoparticle/polymer fiber material with good antibacterial property.

Effects of submerged vegetation on sediment nitrogen-cycling bacterial communities in Honghu Lake (China).

Sediment nitrogen (N) cycling is an important biological removal process for N permanently and driven by N-cycling microbial community. There is a growing interest in interactions between submerged vegetation (SV) and sediment N-cycling bacterial community, because of the close link between rooted aquatic plants and the sediment microbes. However, the effects of SV on the sediment N-cycling bacterial community are still controversial. Furthermore, the discrimination of direct and indirect effects of SV on the N-cycling bacterial community remains unclear. Here, we investigated the biomass and species richness of SV and determined the corresponding environment factors (water quality and sediment properties) in Honghu Lake (China). We also used functional genes as markers to unveil the bacterial diversity and community composition and abundance in lake sediments. Our results showed that biomass and species richness of SV affected the composition, diversity and abundance of sediment N-cycling bacterial communities through improving lake water quality and sediment properties. With the increasing richness and abundance of SV, the diversity of most N-cycling bacterial assemblages including nitrifying, denitrifying and DNRA bacteria decreased, while the abundance increased. However, the anammox bacterial assemblage in sediments showed inverse trends. Sediment carbon vs. nitrogen (C:N) ratio negatively affected the abundance of amoA and nirS + nirK + nosZ bacterial assemblages. Additionally, due to the presence of SV, positive interactions among N-cycling bacterial assemblages were found, such as amoA and nrfA bacterial assemblages. Overall, our findings confirmed the significant effects of SV on the N-cycling bacterial community structure and abundance. Moreover, the direct effects of SV on the N-cycling bacterial community and the indirect effects through altering the sediment C were clarified in our study. Our results casted a new light on the negative effects of high C:N ratio. From the study, we made a conclusion that the better SV develops, the greater nitrogen removal occurs in lake sediments.

Warming Effects on Periphyton Community and Abundance in Different Seasons Are Influenced by Nutrient State and Plant Type: A Shallow Lake Mesocosm Study.

Periphyton plays an important role in lake ecosystems processes, especially at low and intermediate nutrient levels where periphyton contribution to primary production can be similar to or exceed that of phytoplankton. Knowledge of how periphyton responds to key drivers such as climate change and nutrient enrichment is, therefore, crucial. We conducted a series of mesocosm experiments over four seasons to elucidate the responses of periphyton communities to nutrient (low and high, TN-0.33 mg L-1 TP-7.1 µg L-1 and TN-2.40 mg L-1 TP-165 µg L-1, respectively), temperature (ambient, IPCC A2 scenario and A2 + 50%) and plant type (two submerged macrophytes with different morphological structural complexity: Potamogeton crispus and Elodea canadensis, and their corresponding plastic imitations with similar size and structure). We found a noticeable seasonality in the abundance and composition of periphyton. In spring and summer, periphyton abundances were significantly higher in the turbid-high-nutrient state than in the clear-low-nutrient state, and in summer they were notably higher at ambient temperature than in climate scenario A2 and A2 + 50%. In contrast, periphyton abundances in autumn and winter were not influenced by nutrient and temperature, but they were notably higher on plants with a more complex morphological structure than simple ones. The genus composition of periphyton was significantly affected by nutrient-temperature interactions in all seasons and by plant type in winter. Moreover, periphyton functional composition exhibited noticeable seasonal change and responded strongly to nutrient enrichment and temperature rise in spring, summer, and autumn. Our results suggest that the effect of warming on periphyton abundance and composition in the different seasons varied with nutrient state and host plant type in these mesocosms, and similar results may likely be found under field conditions.

Cetylpyridinium bromide/montmorillonite-graphene oxide composite with good antibacterial activity.

In this study, a cetylpyridinium bromide (CPB)/montmorillonite-graphene oxide (GM) composite (GM-CPB) was prepared by loading CPB in a carrier of GM. The chemical structure, elemental composition, morphology, thermogravimetric analysis, antibacterial activity, sustained release property and cytotoxicity were analyzed. The loading rate of CPB in a GM carrier was higher than that of the graphene oxide (GO) carrier under the same loading condition. The antibacterial activity and sustained release performance of GM-CPB were also better than that of GO-CPB; furthermore, GM-CPB showed lower cytotoxicity than CPB.

Graphene Oxide-IPDI-Ag/ZnO@Hydroxypropyl Cellulose Nanocomposite Films for Biological Wound-Dressing Applications.

In this work, we proposed a feasible approach to prepare multifunctional composite films by introducing a nanoscaled filler into a polymer matrix. Specifically, thanks to isophorone diisocyanate (IPDI) acting as a coupling agent, the hydroxyl groups and carboxyl groups on the surface of graphene oxide (GO) and the hydroxyl groups on the surface of silver-coated zinc oxide nanoparticles (Ag/ZnO) are covalently grafted, forming GO-IPDI-Ag/ZnO (AGO). The prepared AGO was then introduced into the hydroxypropyl cellulose (HPC) matrix to form AGO@HPC nanocomposite films by solution blending. AGO@HPC nanocomposite films exhibited improved mechanical, anti-ultraviolet, and antibacterial properties. Specifically, a tensile test showed that the tensile strength of the prepared AGO@HPC nanocomposite film with the addition of as low as 0.5 wt % AGO was increased by about 16.2% compared with that of the pure HPC film. In addition, AGO@HPC nanocomposite films showed a strong ultraviolet resistance and could effectively inactivate both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria at a low loading of AGO, and rapid sterilization plays a crucial role in wound-healing. In vivo results show that the AGO@HPC release of Ag+ and Zn2+ stimulates the immune function to produce a large number of white blood cells and neutrophils, thereby producing the synergistic antibacterial effects and accelerated wound-healing. Therefore, our results suggest that these novel AGO@HPC nanocomposite films with improved mechanical, anti-ultraviolet, and antibacterial properties could be promising candidates for antibacterial packaging, biological wound-dressing, etc. The abuse of antibiotics has brought about serious drug-resistant bacteria, and our nanofilm antibacterial does not entail such problems. In addition, local administration reduces the possibility of changing the body's immune system and organ toxicity, which greatly increases the safety.

Montmorillonite-Modified Reduced Graphene Oxide Stabilizes Copper Nanoparticles and Enhances Bacterial Adsorption and Antibacterial Activity.

To increase antibacterial activity and reduce the cytotoxicity of copper nanoparticles (CuNPs), we used reduced graphene oxide with montmorillonite to support CuNPs and fixed CuNPs on reduced graphene oxide to synthesize the hybrid montmorillonite-reduced graphene oxide copper nanoparticles (MMT-rGO-CuNPs). The synthesized MMT-rGO-CuNPs complex showed a stronger antibacterial activity against Gram-positive bacteria S. aureus than Gram-negative E. coli. This may be due to the protective effect of the outer membrane of E. coli, as well as the fact that the MMT-rGO-CuNPs complex adsorbs S. aureus more strongly than E. coli. The hybrid molecule's antibacterial efficacy is the combined result of the synergistic effects of electrostatic adsorption and copper ion sterilization ability. At the same time, the MMT-rGO-CuNPs complex exhibits a lower cytotoxicity than PVP-CuNPs and provides a biocompatible composite material with a reduced cytotoxicity.

Multielement stoichiometry of submerged macrophytes across Yunnan plateau lakes (China).

Stoichiometric homeostasis of element composition is one of the central concepts of ecological stoichiometry. We analyzed concentrations of macroelements (C, N, P, Ca, K, Mg, S), microelements (Cu, Fe, Mn, Mo, Ni, Zn) and beneficial elements (Na, Se, Si) in submerged macrophytes, water and sediments across 20 Yunnan plateau lakes. We predicted that tissue element composition in submerged macrophytes is affected by lake trophic level and taxonomy, and submerged macrophytes have weak stoichiometric homeostasis for all above 16 elements. Canonical discriminant analyses successfully discriminated among trophic level groups and taxa groups. Of all the elements, C, N, P and S most effectively discriminated among trophic level groups across 20 lakes, revealing lake trophic level mostly affect tissue macroelement composition in submerged macrophytes; while Ca, K and Se most effectively discriminated among submerged macrophytes taxa groups, suggesting taxonomy mostly affect compositions of macroelements and beneficial elements in submerged macrophytes. In addition, the stoichiometric homeostatic coefficient of 1/HCa:C for all five taxa of submerged macrophytes were less than zero, suggesting submerged macrophytes in Yunnan plateau lakes have strong Ca stoichiometric homeostasis. Our findings, not only broaden the knowledge of multielement stoichiometric homeostasis, but also help to choose most appropriate lake management strategy.

Metal accumulation by submerged macrophytes in eutrophic lakes at the watershed scale.

Metal concentrations (Al, Ba, Ca, K, Li, Mg, Na, Se, Sr and Ti) in submerged macrophytes and corresponding water and sediments were studied in 24 eutrophic lakes along the middle and lower reaches of the Yangtze River (China). Results showed that these eutrophic lakes have high metal concentrations in both water and sediments because of human activities. Average concentrations of Al and Na in tissues of submerged macrophytes were very high in sampled eutrophic lakes. By comparison, Ceratophyllum demersum and Najas marina accumulated more metals (e.g. Ba, Ca, K, Mg, Na, Sr and Ti). Strong positive correlations were found between metal concentrations in tissues of submerged macrophytes, probably because of co-accumulation of metals. The concentrations of Li, Mg, Na and Sr in tissues of submerged macrophytes significantly correlated with their corresponding water values, but not sediment values.

Bioaccumulation of heavy metals by submerged macrophytes: looking for hyperaccumulators in eutrophic lakes.

To directly select submerged macrophytes with high accumulation capability from the field, 24 eutrophic lakes along the middle and lower reaches of the Yangtze River were investigated in the study. These eutrophic lakes have large amounts of heavy metals in both water and sediments because of human activities. The results showed that Najas marina is a hyperaccumulator of As and Cd, Ceratophyllum demersum is a hyperaccumulator of Co, Cr, and Fe, and Vallisneria natans is a hyperaccumulator of Pb. Strong positive correlations were found between concentrations of heavy metals in tissues of submerged macrophytes, probably because of coaccumulation of heavy metals. However, for most heavy metals, no significant correlations were found between submerged macrophytes and their surrounding environments. In conclusion, N. marina, C. demersum, and V. natans are good candidate species for removing heavy metals from eutrophic lakes.