Unraveling the ecological mechanisms of Aluminum on microbial community succession in epiphytic biofilms on Vallisneria natans leaves: Novel insights from microbial interactions.

The extensive use of aluminum (Al) poses an escalating ecological risk to aquatic ecosystems. The epiphytic biofilm on submerged plant leaves plays a crucial role in the regulation nutrient cycling and energy flow within aquatic environments. Here, we conducted a mesocosm experiment aimed at elucidating the impact of different Al concentrations (0, 0.6, 1.2, 2.0 mg/L) on microbial communities in epiphytic biofilms on Vallisneria natans. At 1.2 mg/L, the highest biofilms thickness (101.94 µm) was observed. Al treatment at 2.0 mg/L significantly reduced bacterial diversity, while micro-eukaryotic diversity increased. Pseudomonadota and Bacteroidota decreased, whereas Cyanobacteriota increased at 1.2 mg/L and 2.0 mg/L. At 1.2 and 2.0 mg/L. Furthermore, Al at concentrations of 1.2 and 2.0 mg/L enhanced the bacterial network complexity, while micro-eukaryotic networks showed reduced complexity. An increase in positive correlations among microbial co-occurrence patterns from 49.51% (CK) to 57.05% (2.0 mg/L) was indicative of augmented microbial cooperation under Al stress. The shift in keystone taxa with increasing Al concentration pointed to alterations in the functional dynamics of microbial communities. Additionally, Al treatments induced antioxidant responses in V. natans, elevating leaf reactive oxygen species (ROS) content. This study highlights the critical need to control appropriate concentration Al concentrations to preserve microbial diversity, sustain ecological functions, and enhance lake remediation in aquatic ecosystems.

Revealing the response characteristics of periphyton biomass and community structure to sulfamethoxazole exposure in aquaculture water: The perspective of microbial network relationships.

The widespread application of sulfonamide antibiotics in aquaculture has raised concerns about their adverse environmental impacts. Periphyton plays a crucial role in the aquatic ecosystem. In this study, we examined sulfamethoxazole (SMX) effects on the community structure and interactions of periphyton in simulated aquaculture water. Our findings indicated that the total biomass of periphyton decreased, while the biomass of periphytic algae and the secretion of extracellular polymeric substances (EPS) increased at 0.7 × 10-3 mg/L. Under higher SMX concentrations (5 mg/L and 10 mg/L), periphyton growth was severely inhibited, the microbial community structure of periphyton were sharply altered, characterized by the cyanobacteria growth suppression and decrease in the diversity index of community. Furthermore, elevated SMX concentrations (5 mg/L and 10 mg/L) increased the ratio of negative relationships from 45.4% to 49.4%, which suggested that high SMX concentrations promoted potential competition among microbes and disrupted the microbial food webs in periphyton. The absolute abundance of sul1 and sul2 genes in T2 and T3 groups were 2-3 orders of magnitude higher than those in control group after 30 days of SMX exposure, which elevated the risk of resistance gene enrichment and dissemination in the natural environment. The study contributes to our understanding of the detrimental effects of antibiotic pollution, which can induce changes in the structure and interaction relationship of microbial communities in aquaculture water.

Gastrodin protects porcine sertoli cells from zearalenone-induced abnormal secretion of glial cell line-derived neurotrophic factor through the NOTCH signaling pathway.

Zearalenone (ZEA) is a prevalent mycotoxin found in moldy diets and is associated with reproductive dysfunction. However, the molecular underpinning of ZEA in impairment of spermatogenesis remains largely unknown. To unveil the toxic mechanism of ZEA, we established a co-culture model using porcine Sertoli cells and porcine spermatogonial stem cells (pSSCs) to investigate the impact of ZEA on these cell types and their associated signaling pathways. Our findings showed that low concentration of ZEA inhibited cell apoptosis, while high concentration induced cell apoptosis. Furthermore, the expression levels of Wilms' tumor 1 (WT1), proliferating cell nuclear antigen (PCNA) and glial cell line-derived neurotrophic factor (GDNF) were significantly decreased in ZEA treatment group, while concurrently upregulating the transcriptional levels of the NOTCH signaling pathway target genes HES1 and HEY1. The addition of the NOTCH signaling pathway inhibitor DAPT (GSI-IX) alleviated the damage to porcine Sertoli cells caused by ZEA. Gastrodin (GAS) significantly increased the expression levels of WT1, PCNA and GDNF, and inhibited the transcription of HES1 and HEY1. GAS also efficiently restored the decreased expression levels of DDX4, PCNA and PGP9.5 in co-cultured pSSCs suggesting its potential in ameliorating the damage caused by ZEA to Sertoli cells and pSSCs. In conclusion, the present study demonstrates that ZEA disrupts pSSCs self-renewal by affecting the function of porcine Sertoli cell, and highlights the protective mechanism of GAS through the regulation of the NOTCH signaling pathway. These findings may offer a novel strategy for alleviating ZEA-induced male reproductive dysfunction in animal production.

[Characteristics of Phytoplankton Communities and Key Impact Factors in Three Types of Lakes in Wuhan].

To reveal the characteristics and key impact factors of phytoplankton communities in different types of lakes, sampling surveys for phytoplankton and water quality parameters were conducted at 174 sampling sites in a total of 24 lakes covering urban, countryside, and ecological conservation areas of Wuhan in spring, summer, autumn, and winter 2018. The results showed that a total of 365 species of phytoplankton from nine phyla and 159 genera were identified in the three types of lakes. The main species were green algae, cyanobacteria, and diatoms, accounting for 55.34%, 15.89%, and 15.07% of the total number of species, respectively. The phytoplankton cell density varied from 3.60×106-421.99×106 cell·L-1, chlorophyll-a content varied from 15.60-240.50 µg·L-1, biomass varied from 27.71-379.79 mg·L-1, and the Shannon-Wiener diversity index varied from 0.29-2.86. In the three lake types, cell density, Chla, and biomass were lower in EL and UL, whereas the opposite was true for the Shannon-Wiener diversity index. NMDS and ANOSIM analysis showed differences in phytoplankton community structure (Stress=0.13, R=0.048, P=0.2298). In addition, the phytoplankton community structure of the three lake types had significant seasonal characteristics, with chlorophyll-a content and biomass being significantly higher in summer than in winter (P<0.05). Spearman correlation analysis showed that phytoplankton biomass decreased with increasing N:P in UL and CL, whereas the opposite was true for EL. Redundancy analysis (RDA) showed that WT, pH, NO3-, EC, and N:P were the key factors that significantly affected the variability in phytoplankton community structure in the three types of lakes in Wuhan (P<0.05).

Aluminum phytotoxicity induced structural and ultrastructural changes in submerged plant Vallisneria natans.

Aluminum (Al) is a concentration-dependent toxic metal found in the crust of earth that has no recognized biological use. Nonetheless, the mechanism of Al toxicity to submerged plants remains obscure, especially from a cell/subcellular structure and functional group perspective. Therefore, multiple dosages of Al3+ (0, 0.3, 0.6, 1.2, and 1.5 mg/L) were applied hydroponically to the submerged plant Vallisneria natans in order to determine the accumulation potential of Al at the subcellular level and their ultrastructural toxicity. More severe structural and ultrastructural damage was determined when V. natans exposed to ≥ 0.6 mg/L Al3+. In 1.2 and 1.5 mg/L Al3+ treatment groups, the total chlorophyll content of leaves significantly reduced 3.342, 3.838 mg/g FW, some leaves even exhibited chlorosis and fragility. Under 0.3 mg/L Al3+ exposure, the middle-age and young leaves were potent phytoexcluders, whereas at 1.5 mg/L Al3+, a large amount of Al could be transferred from the roots to other parts, among which the aged leaves were the most receptive tissues (7.306 mg/g). Scanning/Transmission electron microscopy analysis displayed the Al-mediated disruption of vascular bundle structure in leaf cells, intercellular space and several vegetative tissues, and demonstrated that Al in vacuole and chloroplast subcellular segregation into electron dense deposition. Al and P accumulation in the roots, stolons and leaves varied significantly among treatments and different tissues (P < 0.05). Fourier transform infrared spectroscopy of plant biomass also indicated possible metabolites (amine, unsaturated hydrocarbon, etc.) of V. natans that may bind Al3+. Conclusively, results revealed that Al3+ disrupts the cellular structure of leaves and roots or binds to functional groups of biological tissues, thereby affecting plant nutrient uptake and photosynthesis. Findings might have scientific and practical significance for the restoration of submerged vegetation in Al-contaminated lakes.

Potential effects of Cladophora oligoclora Decomposition: Microhabitat variation and Microcystis aeruginosa growth response.

Excessive proliferation of filamentous green algae (FGA) is a new ecological problem in lake systems that have not yet reached a steady state. However, knowledge on how FGA decomposition affects the physical and chemical properties of microhabitats, and whether FGA decomposition stimulates the growth of harmful microalgae in the same niche and promotes the formation of harmful algal blooms remains unclear. In this study, we investigated the decomposing effect of a typical FGA, Cladophora oligoclora, on the density and photosynthetic capacity of Microcystis aeruginosa. C. oligoclora decomposition was characterized under different conditions, namely, unshaded and aerobic, unshaded and anoxic, shaded and anaerobic, and shaded and anoxic, which represented different environmental states in the sedimentation process of decaying C. oligoclora mats from water surface to sediment. The shaded and anaerobic treatment significantly decreased the dissolved oxygen and pH of the culture medium by 66.48 % and 7.21 %, respectively, whereas the conductivity and total organic carbon increased by 71.17 and 70.19 times compared with the control group, respectively. This indicated that the decomposing C. oligoclora deposited at the bottom under dark and anaerobic conditions in natural waters had the greatest impact on the lake environment. Further, the cell density of M. aeruginosa was higher than that in the control group with low concentration (10 % of decomposing solution), whereas the cell density and photosynthetic activity decreased significantly at high concentration of the decomposing solution. Fatty acids and phenolic acids were identified as the main Cyanobacteria-inhibiting active substances in the organic acid components of the decomposing solution. Furthermore, phenol, 4-methyl- and indole compounds were active organic lipophilic compounds in the residue and solution of decomposing C. oligoclora were difficult to degrade. Our findings will be valuable for understanding the succession relationships between FGA and cyanobacteria, which have the same niche in lake ecosystems.

Long-term study of ecological restoration in a typical shallow urban lake.

We investigated the long-term effects (6 years) of sediment improvement and submerged plant restoration of a subtropical shallow urban lake, Hangzhou West Lake China. To reveal the lake ecosystems variations, we analyzed the sediment properties, submerged macrophyte characteristics, sediment microorganisms, and benthic macroinvertebrate communities from 2015 to 2020. The ecological restoration project decreased sediment TP and OM, increased submerged macrophyte biomass and sediment microbial diversity, and improved the benthic macroinvertebrate communities in the restored area. The sediment TP decreased from 2.94 mg/g in 2015 to 1.33 mg/g in 2020. The sediment OM of the restored area decreased from 27.44 % in 2015 to 8.08 % in 2020. Principal component analysis (PCA) confirmed that the restoration improved the sediment conditions, making it suitable for the growth of submerged macrophytes, and then sped up the restoration and reconstruction of the lake ecosystem. These results have significant implications on the ecological management of shallow lakes.

Effect of submerged plant coverage on phytoplankton community dynamics and photosynthetic activity in situ.

Restoration of submerged plants in eutrophic lakes can reduce nutrients and phytoplankton biomass in the water body. However, the effect of submerged plants on phytoplankton communities and their photosynthetic activity in situ are still poorly understood. Here, we studied the response of phytoplankton community structure and fluorescence parameters to different submerged plants coverage, the relationship of phytoplankton community and fluorescence parameters with submerged plants coverage and water physicochemical parameters were analysed in sampling area of Hangzhou West Lakes. The results showed that the coverage and biomass of submerged plants were negatively correlated with nitrogen and phosphorus contents in water body but positively correlated with total phenol content. The ratio of nitrogen to phosphorus in the study site changed greatly (32.25-124.54). In spring and summer, Oscillatoria and Leptolyngbya (Cyanophyta) were the dominant species, while in autumn and winter, the dominant species were Cyclotella (Chlorophyta), and Melosira and Cymbella (Bacillariophyta). Compared with Chlorophyta and Bacillariophyta, fluorescence parameters of Cyanophyta were more sensitive to total phosphorus, N:P ratio, total phenols, pH, and electric conductivity. Fluorescence parameters of Chlorophyta and Bacillariophyta were only affected by underwater light. Total phosphorus (TP) and N:P had a negative effect on the maximum photochemical electron yield of Cyanophyta. Furthermore, Cyanophyta was inhibited by total phenols from submerged plants. When phytoplankton were under stress, photochemical electron yield decreased significantly, whereas non-photochemical quenching increased. The structural equation model showed that the coverage of submerged plants might indirectly affect the fluorescence parameters of Cyanophyta by affecting nitrogen, phosphorus, and total phenol contents in the water body. These findings contribute to the understanding of the mechanisms underlying the impact of submerged plant restoration on phytoplankton community dynamics in subtropical eutrophic shallow lakes and provide a theoretical basis for the management of lakes.

[Spatial Distribution Characteristics of Phosphorus Fractions and Release Risk in Sediments of Honghu International Importance Wetland].

According to a spatial distribution analysis of phosphorus in sediments from Honghu Wetland, it was found that TP content in sediments at the mouth of Honghu Lake was 781.31-1955.84 mg·kg-1 and the average value was(1287.21±437.28)mg·kg-1. TP content in sediments in the open water area was 438.33-1554.04 mg·kg-1, with an average value of(718.10±238.15)mg·kg-1. The TP content of sediments in lake inlet was significantly higher than that of sediments in the open water area(P<0.05), and that in the enclosed aquaculture was higher than in the open water area, although no significant difference was observed (P>0.05). The TP content of sediments to the northwest and northeast of Honghu Lake was higher than that to the southwest of Honghu Lake, and the TP content of sediments in The Four-lake main canal was significantly higher than that of Luoshan main canal(P<0.05). The phosphorus input in the Four-lake main canal may be the main source of phosphorus in Honghu Lake sediments. The phosphorus fraction composition in sediments from different sampling sites were significantly different. Fe/Al-P and Ca-P were the main forms of phosphorus in sediments from the lake inlet, while OP and Ca-P were the main forms of phosphorus in sediments from the open water area. The variation in spatial phosphorus form composition was related to the influence of human activity and the distribution of aquatic plants. Fe/Al-P and OP contents were used to estimate the content of biological available phosphorus (BAP) in evaluated sediments, and the proportion of BAP in TP was used to estimate the risk of phosphorus release in Honghu sediments. BAP/TP was 39.8%-69%, with an average of(56.5±7.23)%, indicating a high risk of phosphorus release. OP and BAP were significantly correlated with TP in overlying water(P<0.01), and the correlation between BAP and phosphate in the overlying water was the highest. The results showed that phosphorus concentration in the overlying water may be related to the release of Fe/Al-P and OP into water bodies.

The changing characteristics of phytoplankton community and biomass in subtropical shallow lakes: Coupling effects of land use patterns and lake morphology.

The community composition and biomass of phytoplankton in shallow lakes are impacted by many environmental factors including water quality physicochemical parameters, land use in the watershed, and lake morphology. However, few studies have simultaneously evaluated the relative importance of these factors on the effect of community composition and biomass of phytoplankton. The relative importance of the water quality physicochemical parameters (water temperature [WT], total nitrogen [TN], total phosphorus [TP], pH, dissolved oxygen [DO], electrical conductivity [EC], turbidity and Secchi depth [SD]), land use (built-up land, farmland, waters, forest, grassland, and unused land) in the watershed, and lake morphology (area and depth) on the composition and biomass of phytoplankton communities were assessed in 29 subtropical shallow lakes in Wuhan, China, during different seasons from December 2017 to November 2018. The results showed that phytoplankton in all 29 lakes was mainly composed of Cyanophyta, Chlorophyta, and Bacillariophyta. Phytoplankton abundance was highest in summer and lowest in winter. We analyzed the relative importance of the three groups of variables to the community composition of the phytoplankton by variance decomposition. The results showed that the three groups of environmental variables had the highest explanation rate (> 80%) for the composition of the phytoplankton community in summer and autumn, and the explanation rates in spring and winter were 42.1% and 39.8%, respectively. The water quality physicochemical parameters were the most important variables affecting the composition of phytoplankton communities, followed by land use in the watershed. Through generalized additive model and structural equation model analysis, we found that the land use and lake morphology had minimal direct impact on the Chl-a and cell density of phytoplankton, mainly by altering the TN, TP, turbidity, SD, DO, and EC, which indirectly affected phytoplankton. WT and nutrients were still the main predictors of phytoplankton abundance. Built-up land was the main source of nitrogen and phosphorus in lakes. Correlation analysis found that forest and grassland had positive impacts on reducing lake nitrogen and phosphorus contents. This showed that increasing grassland and forest in the watershed could reduce the pollutants entering the lake. Our findings will contribute to water quality management and pollution control for subtropical shallow lakes.

Potential ecological implication of Cladophora oligoclora decomposition: Characteristics of nutrient migration, transformation, and response of bacterial community structure.

During decay, the sediment microenvironment and water quality are severely affected by excessive proliferation of harmful algae such as filamentous green algae (FGA). The frequency of this FGA is increased through global warming and water eutrophication. In the present study, the degradation processes of a common advantage FGA Cladophora oligoclora and its effect on nitrogen and phosphorus nutrient structure and bacterial community composition at the sediment-water interface were investigated by stable isotope labelling and high-throughput sequencing. The results showed that the decomposition process of C. oligoclona was fast, stable, and difficult to degrade. The changes in sediment δ15N values reached 66.68 ‰ on day 40, which indicated that some of the nitrogen had migrated to the sediment from C. oligoclona litter. TN and NH4+-N in the overlying water rapidly increased between days 0-10, NH4+-N rose to 78.21% of TN on day 40, resulting in severe pollution of ammonia in the overlying water. The nitrogen forms and contents in the sediment are mainly derived from the increasing ammonia nitrogen release. The TP and IP in the overlying water increased to the highest concentrations of 6.68±0.64, 6.59±0.79 mg·L-1 during the decomposition process, respectively, resulting in the migration of phosphate to the sediments with increasing phosphorus content. The abundance of the main dominant bacterial communities, such as Acinetobacter (0.08%-62.48%) and Pseudomonas (0.13%-20.36%) in sediments and overlying water has changed significantly. The correlation analysis results suggested that the phosphorus was mainly related to the bacterial community in the overlying water, while the various forms of nitrogen demonstrated a high relevance with the bacterial community in the sediment. Our research results will be valuable in evaluating the potential ecological risk of FGA decomposition and provide scientific support for shallow lake management and submerged vegetation restoration.

Combined Effects of Allelopathic Polyphenols on Microcystis aeruginosa and Response of Different Chlorophyll Fluorescence Parameters.

Polyphenols are allelochemicals secreted by aquatic plants that effectively control cyanobacteria blooms. In this study, sensitive response parameters (including CFPs) of Microcystis aeruginosa were explored under the stress of different polyphenols individually and their combination. The combined effects on M. aeruginosa were investigated based on the most sensitive parameter and cell densities. For pyrogallic acid (PA) and gallic acid (GA), the sensitivity order of parameters based on the EC50 values (from 0.73 to 3.40 mg L-1 for PA and from 1.05 to 2.68 mg L-1 for GA) and the results of the hierarchical cluster analysis showed that non-photochemical quenching parameters [NPQ, q N, q N(rel) and q CN] > photochemical quenching parameters [YII, q P, q P(rel) and q L] or others [F v/F m, F' v /F' m, q TQ and UQF(rel)] > cell densities. CFPs were not sensitive to ellagic acid (EA) and (+)-catechin (CA). The sensitivity order of parameters for M. aeruginosa with PA-GA mixture was similar to that under PA and GA stress. The quantitative (Toxicity Index, TI) and qualitative (Isobologram representation) methods were employed to evaluate the combined effects of PA, GA, and CA on M. aeruginosa based on cell densities and NPQ. TI values based on the EC50 cells suggested the additive effects of binary and multiple polyphenols, but synergistic and additive effects according to the EC50 NPQ (varied from 0.16 to 1.94). In terms of NPQ of M. aeruginosa, the binary polyphenols exhibited synergistic effects when the proportion of high toxic polyphenols PA or GA was lower than 40%, and the three polyphenols showed a synergistic effect only at the ratio of 1:1:1. Similar results were also found by isobologram representation. The results showed that increasing the ratio of high toxic polyphenols would not enhance the allelopathic effects, and the property, proportion and concentrations of polyphenols played an important role in the combined effects. Compared with cell densities, NPQ was a more suitable parameter as evaluating indicators in the combined effects of polyphenols on M. aeruginosa. These results could provide a method to screen the allelochemicals of polyphenols inhibiting cyanobacteria and improve the inhibitory effects by different polyphenols combined modes.

Spatial and seasonal variation of water parameters, sediment properties, and submerged macrophytes after ecological restoration in a long-term (6 year) study in Hangzhou west lake in China: Submerged macrophyte distribution influenced by environmental variables.

Submerged macrophyte restoration is the key stage in the reestablishment of an aquatic ecosystem. Previous studies have paid considerable attention to the effect of multiple environmental factors on submerged macrophytes. Meanwhile, few studies have been conducted regarding the spatial and seasonal characteristics of water and sediment properties and their long-term relationship with submerged macrophytes after the implementation of the submerged macrophytes restoration project. On a monthly basis, we monitored the spatial and seasonal variation in water parameters, sediment properties, and the submerged macrophyte characteristics of West Lake in Hangzhou from August 2013 to July 2019. From these measurements, we characterized the relationship between environmental factors and submerged macrophytes. Water nutrient concentrations continuously decreased with time, and the accumulation of sediment nutrients was accelerated as the submerged macrophyte communities developed on a long-term scale. The results indicated that the difference in water parameters was due to seasonal changes and land-use types in the watershed. The differences in the sediment properties were mainly attributed to seasonal changes and changes in the flow field. Redundancy analysis showed that the influence of water nutrients on the submerged macrophyte distribution was greater than that of sediment nutrients. The result also suggested that the developed root system, high stoichiometric homeostasis coefficients of P, and compensation ability of substantial leaf tissue may lead to a large distribution of Vallisneria natans in West Lake in Hangzhou. The correlation of water parameters and sediment properties with submerged macrophytes for a long time was very important as the restoration was achieved. To ensure the stability of the aquatic ecosystem after performing the submerged macrophyte restoration, a greater emphasis must be placed on reestablishing the entire ecosystem, including the restoration of aquatic animals and fish stocks. We expect these findings to serve as a reference for researchers and government agencies in the field of aquatic ecosystem restoration.

The promotion effects of silicate mineral maifanite on the growth of submerged macrophytes Hydrilla verticillata.

The effects of maifanite on the physiological and phytochemical process of submerged macrophytes Hydrilla verticillate (H.verticillata) were investigated for the first time in the study. The growth index: plant biomass, root length, plant height and leaf spacing, and physiological and phytochemical indexes: chlorophyll, soluble protein, malondialdehyde (MDA), peroxidase (POD), superoxide dismutase (SOD) content and vitality of the roots of H.verticillata were tested. The results found that maifanite can significantly promote the growth of H.verticillata. The modified maifanite were more conducive to plant growth compared with the raw maifanite, and the MM1 group had the best growth promoting effect. The physiological and phytochemical indexes showed that maifanite can delay the aging process of H.verticillata (P < 0.05). The possible reasons for promoting H.verticillata growth were that maifanite can provide excellent propagation conditions for plant rhizosphere microorganisms, contains abundant major and microelements, and improve the sediment microenvironment. This study may provide a technique for the further application of maifanite in the field of ecological restoration.

Response of Vallisneria natans to aluminum phytotoxicity and their synergistic effect on nitrogen, phosphorus change in sediments.

Increasing aluminum (Al) use and its effects on aquatic systems have been a global issue, however the Al impacts on submerged plants and their ecological functions were poorly understood. Aquatic simulation experiments were performed to study Al-toxicity on the germination and seedling morphological and physiological characteristics of Vallisneria natans, and investigate their synergistic effect on nitrogen (N), phosphorus (P) change and microbial community in sediment. The seeds germination characteristics, growth and physiological parameters of seedlings, including root activity, were significantly affected by alum treatments and the inhibition levels increased with Al3+ concentration. The Al accumulation in roots and leaves were significantly different. Al3+ concentration above 0.3 mg/L showed toxic to V. natans. TN, TP, IP, Fe/Al-P contents in sediments varied markedly under co-existence of Al and V. natans. Additionally, the relative abundance of sediment microbial community related to N, P cycle was effected. Results concluded that the increasing aquatic Al-concentration inhibits growth and propagation of submerged plants and the ecological restoration effect, and exerts synergistic effect with submerged plants on N, P components in sediments. Such findings were helpful for Al ecological evaluation, and were instructive for the submerged plants restoration in shallow eutrophic lakes with Al input.

Synergistic control of internal phosphorus loading from eutrophic lake sediment using MMF coupled with submerged macrophytes.

Sediment phosphorus (P) is the main source of endogenous P for lake eutrophication. An in-situ combined technology for determination the removal effect of sediment P in all fractions was first developed using the novel modified maifanite (MMF) and submerged macrophytes in this study. MMF was synthesized using an acidification process (2.5 mol/L H2SO4) and then a calcination (400 °C) method. The morphology and structure of MMF were characterized by XRD, SEM, XPS, and BET. We tested the removal effects of sediment P by MMF and submerged macrophytes in combination and separately. The results demonstrated that the synergistic removal capacity of sediment P using MMF coupled with submerged macrophytes was higher than the sum of them applied separately. MMF could promote the submerged macrophytes growth and enhance the adsorption of extra P on MMF through root oxygenation and nutrient allocation. The microcosm experiment results showed that sediment from fMMF+V. spiralis exhibited the most microbial diversity and abundance among the sediment. The combination of MMF and submerged macrophytes increased the Firmicutes abundance and decreased the Bacteroidetes. These results indicated that adsorption-biological technology can be regarded as a novel and competitive technology to the endogenous pollution control in eutrophic shallow lakes.

Effects of maifanite on growth, physiological and phytochemical process of submerged macrophytes Vallisneria spiralis.

The restoration of submerged plants is critical for the reconstruction of eutrophic lake ecosystems. The growth of submerged plants is influenced by many factors. For the first time in this study, the effects of silicate-mineral maifanite supplement on the growth, physiological and phytochemical process of Vallisneria spiralis (V. spiralis) were investigated by an outdoor PVC barrel experiment, to provide a technical reference for further applications in aquatic ecological restoration. The results show that the maifanite could significantly promote the growth of V. spiralis. Specifically, the biomass, height, number of leaves, leaf width, root length, and root activity of V. spiralis in the maifanite-supplemented group were better than those of the control (P < 0.05). Moreover, the modified maifanite group performed better than the raw maifanite group (P < 0.05). The photosynthetic pigment, root activity, and the malondialdehyde and peroxidase activity of the maifanite-treated V. spiralis were better than those of the control to some extent. It was found that maifanite contained abundant major and trace elements, which are required for the growth of V. spiralis. It is concluded that maifanite is beneficial to the growth of V. spiralis and can be further applied to the ecological restoration of eutrophic lakes.

Aluminum distribution heterogeneity and relationship with nitrogen, phosphorus and humic acid content in the eutrophic lake sediment.

Increasing amount of aluminum (Al) gets into aquatic ecosystem through anthropogenic activity, but the knowledge about Al migration and relationships with sediments possessing different physico-chemical properties in eutrophic lakes is limited. Here, the Al migration rule and relationships with sediment nutritions in the Hangzhou West Lake, China was investigated, where a certain amount of residual Al-salts can enter because of the pre-treatment of the Qiantang River diversion project every day. Results revealed the obvious spatial distribution heterogeneity of Al in sediment vertical direction and horizontal direction following water flow. The Al content in sediment ranged 0.463-1.154 g kg-1 in Maojiabu Lake, and ranged 9.862-40.442 g kg-1 in Xiaonanhu Lake. Higher Al content distributed in upper layer sediment in lake with more disturbance. Total nitrogen (TN) contents were higher 0.917-3.387 mg g-1 and 0.627-0.786 mg g-1 in upper layer sediment than that in lower layer in Maojiabu Lake and Xiaonanhu Lake, respectively. Total phosphorus (TP) content ranged 0.779-2.580 mg g-1, in which IP and Fe/Al-P contributed 24.9-80.8% and 17.0-51.6%, respectively. Correlations between Al content with nutrition, humic acid (HA) etc. of sediment regionally varied in Maojiabu and Xiaonanhu Lake. Spatial distribution of Al-salt in eutrophic lakes closely related with the physico-chemical characteristics of nutrients, humus, human disturbance and water division parameters. Results provides new insight into Al-salts migration and references for Al-risk evaluating in eutrophic lakes.

Investigation on the adsorption of phosphorus in all fractions from sediment by modified maifanite.

Sediment phosphorus (P) removal is crucial for the control of eutrophication, and the in-situ adsorption is an essential technique. In this study, modified maifanite (MMF) prepared by acidification, alkalization, salinization, calcination and combined modifications, respectively, were first applied to treat sediment P. The morphology and microstructure of MMF samples were characterized by X-ray fluorescence (XRF), Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM) and Brunauer-Emmett-Teller (BET). Various adsorption parameters were tested, such as dosage of maifanite, time, operation pH and temperature. The adsorption mechanisms were also investigated and discussed. Results showed that CMMF-H2.5-400 (2.5 mol/L H2SO4 and calcined at 400 °C) exhibited the highest P adsorption capacity. Thus, it was selected as the in-situ adsorbent material to control the internal P loading. Under the optimal conditions of dynamic experiments, the adsorption rates of TP, IP, OP, Fe/Al-P and Ca-P by CMMF-H2.5-400 were 37.22%, 44.41%, 25.54%, 26.09% and 60.34%, respectively. The adsorption mechanisms analysis revealed that the adsorption of P onto CMMF-H2.5-400 mainly by ligand exchange. Results of this work indicated that the modification treatment could improve the adsorption capacity of maifanite, and CMMF-H2.5-400 could be further applied to eutrophication treatment.

Sensitive detection of oxidative DNA damage in cyanobacterial cells using supercoiling-sensitive quantitative PCR.

Supercoiling-sensitive quantitative PCR (ss-qPCR) is a sensitive technique to detect DNA damage in cultured animal cells and cultured/clinical human cells in vitro. In this study, we investigated whether the ss-qPCR method can be applied as a sensitive means to detect oxidative DNA damage in unicellular organisms. We used the model cyanobacterium Synechococcus elongatus PCC 7942 as a test organism and H2O2 as an exogenetic oxidative toxicant. Results showed that a significant increase in the plasmid DNA damage of S. elongatus PCC 7942 was induced by H2O2 in a dose- and time-dependent manner. The sensitivity of ss-qPCR in detecting DNA damage of the cyanobacterium was higher than the cell inhibition method (up to 255 times) as calculated from the slopes of fitted curves in the tested sub-toxic concentration range of 1-5 mM H2O2. Ss-qPCR also detected repairable low-intensity DNA damage in the cyanobacterium when DNA repair inhibitors were used. The detection limit of modified ss-qPCR was one tenth of that of previous methods. We also observed that ss-qPCR can be used to detect genomic DNA conformation change of cyanobacterium exposed to H2O2. Thus, this method will provide a powerful technical support for investigating the mechanisms of cyanobacterial DNA damage by environmental factors, especially intracellular reactive oxygen species enhancement-related factors.