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Pond-ditch circulation system (PDCS) is a promising remediation strategy for rural wastewater treatment. Aquatic plants play nonnegligible roles in the nutrient removal of the PDCS. However, mechanisms of root exudates regulating nutrient removal in PDCSs remained unclear. In our study, the PDCS achieved higher total nitrogen (TN) and phosphorus (TP) removal rates (72.7–97.4%) compared to the static system. Protein contents in root exudates of the PDCS ranged from 0.041 to 1.332 mg L−1, showing negative associations with Simpson index. Lactic acid and tartaric acid in the PDCS varied from 0.045 to 0.380 mg L−1 and 0.024 to 5.446 mg L−1, which were tightly linked with TN, TP, and TP removal rates and most sediment properties, especially sediment total nitrogen (STN) and total organic carbon (TOC), and sediment inorganic phosphorus (SIP). Moreover, the top 3 relative dominant genus were Bacillus (0.11%–17.90%), Geobacter (0.35%–12.04%), and Clostridium sensu stricto 1 (0.14%–12.05%), which might be the predominant groups in nutrient removal of PDCSs. RDA results indicated that lactic acid, protein, and amino acids were positively correlated with Geobacter; while Bacillus was significantly affected by water content. Path analysis further demonstrated that the indirect effect of secretion from plant roots on nutrient removal rates was mainly through modulating bacteria diversity and relative abundance. Taken together, root exudates, especially protein, amino acids, and lactic acid, altered rhizosphere microbial relative abundance and diversity, where the impacts were bacterial species-dependent.

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.

Hydrophytes are plants that grow in or on water. Their overgrowth adversely affects the ecosystem because of crowding out other aquatic organisms and polluting the environment with plant residue. In principle, cellulolytic bacteria can be used to degrade hydrophyte biomass. We here isolated and characterized four cellulolytic bacterial strains from Lake Donghu sediments (Wuhan, China) that are rich in organic matter and plant residues. The isolates (WDHS-01 to 04) represent Bacillus, Micromonospora and Streptomyces genera. The bacteria exhibited pronounced endoglucanase activities (from 0.022 to 0.064 U mL–1). They did not extensively degrade the emerged plant Canna indica L. However, in an Hydrilla verticillata (submerged plant) degradation medium, strain WDHS-02 exhibited a high degradation rate (54.91%), endoglucanase activity of 0.35 U mL–1 and the conversion rate of cellulose to reducing sugars of 7.15%. Correlation analysis revealed that bacterial endoglucanase activity was significantly correlated with the degradation rate, and acid detergent lignin, ash and cellulose content of the residual H. verticillata powder. In conclusion, the identified bacteria efficiently decomposed submerged plants without the need for acid–base pretreatment. They expand the set of known cellulolytic bacteria and can be used for natural degradation of submerged plants.

The excessive proliferation of filamentous green algae (FGA) has been considered to be one of the important factors that result in poor growth or even a decline in submerged macrophytes. This study aims to investigate why FGA has stronger growth advantage than that of submerged macrophytes in the co-culture system. Assimilation of nitrogen and phosphorus nutrients, kinetics, and interspecific nutrient competition model were studied to determine the dynamic changes in nutrient assimilation between submerged macrophytes and FGA in a co-culture system with ion depletion technique. The results showed that differences were observed in the assimilation of nitrogen and phosphorus by Vallisneria natans, Ceratophyllum demersum, and Cladophora oligoclona. C. oligoclona was able to assimilate and accumulate much more nitrogen than V. natans and C. demersum, with the content of nitrogen of 5.75% (dry mass). The lower value of Michaelis-Menten constant K m (0.34 mg/L) of C. demersum indicated that C. demersum had a greater affinity for phosphate. The interspecific competition results confirmed that the coexistence of V. natans and C. oligoclona, and C. demersum and C. oligoclona were unstable. Moreover, C. demersum had a stronger competitive ability than V. natans, and it can be used as a pioneer species for the recovery of submerged vegetation in eutrophic lakes.

Microzooplankton plays an important role in controlling the standing crop of phytoplankton and primary production. However, research on microzooplankton grazing has mainly focused on the ocean and only rarely on eutrophic lakes. In this study we investigated plankton community structures, microzooplankton grazing rates (m), and phytoplankton growth rates (mu) in order to explore microzooplankton grazing in 2 eutrophic sub-lakes of West Lake, Hangzhou, China (Waihu and Xilihu). Results showed that Pseudanabaena sp. was dominant in Waihu without submerged macrophytes, and the larger phytoplankton (> 2 mu m) biomass was higher than the picophytoplankton (< 2 mu m) biomass. However, Xilihu with macrophytes growing was mainly composed of diatoms and green algae, and there was no significant difference between larger phytoplankton and picophytoplankton biomass. Furthermore, in West Lake, the values of m (ranging from 1.58 similar to 3.33/d) and mu (ranged from 1.38 similar to 3.05/d) were higher than those in the ocean. The higher m, mu, and relative preference index (RPI) for picophytoplankton in Waihu indicated that microzooplankton had a significant size-selective grazing on picophytoplankton. However, no significant size-selection was found in Xilihu. These different responses of plankton in Waihu and Xilihu might explain why larger phytoplankton occupy a dominant position in eutrophic lakes.

Biomanipulation of filter-feeding bivalves or fish can serve as complementary measures to zooplankton manipulation approach in lakes dominated by large-sized algae. A laboratory grazing experiment was conducted to compare the selective grazing of benthic bivalves (Hyriopsis cumingii) and planktivorous fish (silver carp) on particle size and algae species. Their combination grazing effects were also detected. The results showed that the clearance rates of silver carp were higher than that of H. cumingii, and that silver carp preferred particles in the 30–50 and 50–100 μm size fraction whereas H. cumingii did not show a significant selective grazing on seston size. Furthermore, the differences between the selective grazing of H. cumingii and silver carp on algae species were detected. Some algae species, which had not been digested well by silver carp, were not detected in H. cumingii’s pseudofeces. Similarly, some algal species in the pseudofeces of bivalves were not detected in the feces of fish. Moreover, the combined clearance rates of H. cumingii and silver carp (ranging from 12.14 to 95.99 mL g DW−1 h−1) were higher than that of single filter feeder (0.47 to 10.18 mL g DW−1 h−1). We suggest therefore that when using biomanipulation measures to control large-sized algal overgrowth, a combination of different filter feeders may be a better way considering their collaborative grazing in both particle size and algae species selectivity.

To find suitable wetland plants for constructed wetland-microbial fuel cells (CW-MFCs), four commonly used wetland plants, including Canna indica, Cyperus alternifolius L., Acorus calamus, and Arundo donax, were investigated for their electrogenic performance and physiological changes during non-growing seasons. The maximum power output of 12.82mW/m2 was achieved in the A. donax CW-MFC only when root exudates were being released. The results also showed that use of an additional carbon source could remarkably improve the performance of electricity generation in the C. indica and A. donax CW-MFCs at relatively low temperatures (2-15°C). However, A. calamus withered before the end of the experiment, whereas the other three plants survived the winter safely, although their relative growth rate values and the maximum quantum yield of PSII (Fv/Fm) significantly declined, and free proline and malondialdehyde significantly accumulated in their leaves. On the basis of correlation analysis, temperature had a greater effect on plant physiology than voltage. The results offer a valuable reference for plant selection for CW-MFCs.

Constructed wetland is an efficient way to lower N load from wastewater treatment plants. Here, the nitrogen removal rate and nitrogen balance, as well as the microbial community structure in IVCWs planted with different vegetation for treating reclaimed water were investigated. The results showed that IVCWs planted with vegetation generally achieved a higher TN removal rate than unplanted treatment, especially for Canna indica L. with 10.35% enhancement. Moreover, the microbial process proportion (83.87-87.94%) is the main N removal pathway in IVCW, and vegetation planting could increase 8.16% of it in average. The combination of quantitative polymerase chain reaction (qPCR) and high-throughput sequencing analysis revealed that IVCW planted with Canna indica L. showed the highest microbial abundant and biodiversity. The related denitrification genus Pseudomonas, Acinetobacter, Rhizobium, Bacillus and Rhodopseudomonas might be responsible for the high biological removal rate of nitrogen.

Phosphorous removal in adsorption had been extensively researched; however, the biological dephosphorization process and optimum operating parameters have not been discussed or quantified in Integrated Vertical-flow Constructed Wetlands (IVCWs). In this study, IVCWs planted with different plants were employed to evaluate total phosphorus (TP) treatment performance under different hydraulic retention times (HRTs), in summer and autumn. The results showed that the systems planted with Canna generalis showed the highest TP removal efficiency (77%) under a three-day HRT in autumn. The activities of exopolyphosphatase (PPX) and polyphosphate kinase (PPK) were determined, and it was found that PPK activity was seasonably variable and had been more active in autumn than that in summer (p

Submerged macrophyte restoration was used to combat with lake eutrophication and improve water quality in a subtropical, shallow lake. A consistent investigation for three years about macrophyte, phytoplankton, zooplankton and water quality has been conducted to explore the effect of macrophyte restoration on improving aquatic ecosystem. The results showed that macrophyte biomass and coverage after the restoration were as high as 821 g/m 2 and 55%, respectively, and the dominant species were Ceratophyllum demersum , Myriophyllum verticillatum and Potamogeton crispus . Moreover, chemical oxygen demand (COD), total nitrogen (TN), total suspended solids (TSS) and nitrate nitrogen (NN) significantly decreased yearly, but the changes in total phosphorus (TP) and ammonia nitrogen (AN) were not significant during the investigation. Phytoplankton density and biomass significantly decreased, and the dominant species changed from blue-green algae to green algae. Zooplankton density and biomass, however, significantly increased yearly, and the small-sized dominant species (such as, Keratella cochlearis , Polyarthra trigla , etc.) were gradually replaced by the large-sized species (such as, Asplanchna priodonala , Alona guttata , etc.) during the restoration. In addition, macrophyte was negatively correlated with nutrients, but positively correlated with zooplankton. Phytoplankton was also positively related with TN. These correlations showed that restored macrophytes could decrease nutrition loading in water body, inhibit phytoplankton growth to decrease the risk of algae blooms, and support more large-sized zooplankton to strengthen the top-down control of phytoplankton. Therefore, our results showed that macrophyte restoration is a very potential and effective method to combat with the eutrophication and develop water quality in the eutrophic subtropical lakes, and deserves more attentions in future subtropical/tropical lake managements.

Artificially supported colonization of submerged macrophytes was tested in-situ in Maojiabu, a sublake of West Lake (Hangzhou City, China). Multiple species, including Hydrilla verticillata , Vallisneria natans , Myriophyllum spicatum and Ceratophyllum oryzetorum , were artificially restored in two enclosures that differed in water depth. The multiple species community existed less than a year, but the colonization of Vallisneria natans was successful and reached a biomass of 430.6 g m −2 in the shallow enclosure after one year of succession. Redundancy analysis indicated that plant biomass was most closely correlated with total nitrogen (TN) concentration of the water column, which is the limiting factor for the trophic state of West Lake. Plant biomass was correlated with water depth, though water transparency reached the bottom. The growth of Potamogeton crispus , a species that spontaneously germinated in the wintering stage, was promoted by the macrophyte species that grew before winter. The microbial community characterized by fatty acid methyl esters (FAMEs) showed that the proportion of aerobic microbes and fungi in sediment was closely related with macrophyte biomass, which might be a response of the microbial community to the nutrient demand of macrophyte growth. The results implied that restoration of submerged macrophytes could be enhanced by artificially supported colonization which further modified the microbial community in the sediment. Although the presence of multiple vegetation species could not be sustained at this time, Vallisneria natans is a suitable pioneer species for large-scale ecological engineering in West Lake.

N-Phenyl-1-naphthylamine (P1NA) and N-Phenyl-2-naphthylamine (P2NA) are both widely used as antioxidant and plant secondary metabolites. In this study, growth, esterase, photosynthetic activity and cell membrane integrity were used as biomarkers to compare biotoxicity of P1NA and P2NA on Microcystis aeruginosa. According to the results, a dose-response relationship was observed only between P1NA concentrations and growth inhibition. The EC50 (48 h) of P1NA calculated from growth inhibition was 16.62 μM, while that of P2NA was not detected. When the esterase and photosynthetic activity were applied to evaluate the biotoxicity, it was found that a concentration of 20 μM P1NA, P2NA caused reduction of esterase activity and Fv/Fm of M. aeruginosa to 22.2 and 3.3%, 97.5 and 92.1%, respectively, after 48 h exposure. The percentage of membrane-damaged cells was increased as P1NA exposure concentration increased, but that was not detected when exposure to P2NA. The difference substituted position in the molecular structure of P1NA and P2NA leads to different toxicological properties and only P1NA was found highly toxic to M. aeruginosa. The toxicity is due to that only P1NA can be biotransformed to 1,4-naphthoquinone, which could induce overproduction of intracellular ROS as well as result in oxidative damage and growth inhibition of test organism.

To explore the size-dependent responses of zooplankton to submerged macrophyte restoration, we collected macrophyte, zooplankton and water quality samples seasonally from a subtropical shallow lake from 2010 to 2012. Special attention was given to changes in rotifers and crustaceans (cladocerans and copepods). The rotifers were grouped into three size classes ( 400 μm) to explore their size-related responses to macrophyte restoration. The results showed that during the restoration, the annual mean biomass and macrophyte coverage increased significantly from 0 to 637 g/m2 and 0 to 27%, respectively. In response, the density and biomass of crustaceans and the crustacean-to-rotifer ratio increased significantly, while the rotifer density decreased significantly. Moreover, rotifers showed significant sizedependent responses to macrophyte restoration. Specially, rotifers

The phosphorus reduction in water column was attempted by integrating sediment microbial fuel cells (SMFCs) with the submerged macrophyte Vallisneria spiralis. A comparative study was conducted to treat simulated water rich in phosphate with a control and three treatments: SMFC alone (SMFC), submerged macrophytes alone (macophyte), and combined macrophytes and fuel cells (M-SMFC). All treatments promoted phosphorus flux from the water column to sediments. Maximum phosphorus reduction was obtained in proportion to the highest stable phosphorus level in sediments in M-SMFC. For the initial phosphate concentrations of 0.2, 1, 2, and 4 mg/L, average phosphate values in the overlying water during four phases decreased by 33.3% (25.0%, 8.3%), 30.8% (5.1%, 17.9%), 36.5% (27.8%, 15.7%), and 36.2% (0.7%, 22.1%) for M-SMFC (macrophyte, SMFC), compared with the control. With macrophyte treatment, the obvious phosphorus release from sediments was observed during the declining period. However, such phenomenon was significantly inhibited with M-SMFC. The electrogenesis bacteria achieved stronger phosphorus adsorption and assimilation was significantly enriched on the closed-circuit anodes. The higher abundance of Geobacter and Pseudomonas in M-SMFC might in part explain the highest phosphorus reduction in the water column. M-SMFC treatment could be promising to control the phosphorus in eutrophic water bodies.

Plant is an important part of constructed wetland (CW), while, its potential effect on nitrogen cycling is complicated. Herein, integrated vertical-flow constructed wetland (IVCW) in pilot-scale planted with Arundo donax (Planted System, PS) was constructed to treat swine wastewater. The removal performance of nitrogen in PS, effects of plant on the microbial community structure and nitrogen related function genes were revealed. Results showed that, Arundo donax planting enhanced the removal rate of TN, compared to unplanted IVCWs, the absolute abundance of Pseudomonas, Acinetobacter and Bacillus in PS was significantly increased, as well as the absolute abundance of functional gene (amoA, nxrA, nirK, nirS and nosZ). The denitrification process was mainly occurred in down-flow cell of PS with significantly higher abundant of nirK and nosZ (P 0.05). These findings suggested that Arundo donax planting in IVCWs with zeolite as substrate promoted the growth of denitrifying microorganisms under higher pollutant load. In addition, the increased abundant of nosZ and the ratio of nosZ/∑nir indicating a lower genetic potential for N

Antibiotics and antibiotic resistance genes (ARGs) in swine wastewater have an irreversible impact on the surrounding water and soil ecosystems. Herein, integrated vertical-flow constructed wetlands (IVCWs) were constructed to assess the effects of zeolite and plants on the removal of sulfonamides (SMs), tetracyclines (TCs), and related ARGs (tetW, tetO, tetM, sul I, sul II, and sul III) from digested swine wastewater. The microorganism community structure was also investigated. Results showed that IVCWs with a zeolite substrate and plant system (ZP) exhibited a favorable removal performance for N, antibiotics, and ARGs at 97.9%, 95.0%, and 95.1%, respectively. Moreover, zeolite systems showed higher adsorption of SMs, lower adsorption of TCs. The higher removal rate of antibiotics in ZP systems might be due to the enhanced microbial degradation with the enrichment of Pseudomonas, Acinetobacter, and Bacillus in zeolite. Furthermore, Arundo donax had limited impact on antibiotics removal and was not conducive to the removal of ARGs. The absolute abundances of sul(I), sul(II), sul(III), tet(M), and tet(O) were significantly positively correlated with the absolute abundance of 16S rDNA. However, no significant correlation was found between the concentration of antibiotics and the abundance of related ARGs in the effluent.

During the restoration of eutrophic shallow lakes, submerged macrophyte recovery is often accompanied by an excessive proliferation of filamentous green algae (FGA). This can lead to the recession or even disappearance of the submerged macrophytes in these lakes. However, the use of plant fragments in reproduction and dispersion is an important life history strategy for submerged macrophytes. In this work, it studied apical fragment propagation in Myriophyllum spicatum and its physiological and biochemical responses to the decomposing liquid of Cladophora oligoclona. Myriophyllum spicatum apical fragments showed no new roots or buds when treated with 0.4 times the original decomposing liquid, and their PSII functional parameters were lower than those of the control. In contrast, the relevant sugar content accumulated to 115.26%, and the activities of an energy enzyme (Ca2+/Mg2+-ATPase) and a secondary metabolic-related enzyme (PAL) increased by 490.63% and 28.13%, showing an elevated defense response. These results indicated that the early regeneration of M. spicatum could be hindered by environmental stress, and that this may further affect the reproduction and colonization of these submerged macrophytes.

This paper presents a scientific performance study of the application of the modified aquatic mat pond (MAMP)-integrated vertical-flow constructed wetland (IVCW) coupling process for treating micro-polluted river water using luffa sponge material. In addition, the surface modifications of luffa sponge were investigated. The results showed that luffa sponge functioned well in a bench scale experiment and in a demonstration project, and the main effluent water indexes reached the class IV standard defined by the surface water quality standard of China (GB3838-2002). However, natural luffa sponge is easily hydrolyzed and should be replaced at regular intervals. A microwave-enhanced KH550 (Silane coupling agent gamma-aminopropyltriethoxysilane) coupling method for modifying luffa sponges were performed to reduce the water absorption rate and prolong the engineering service time of the sponge. The results showed that the water absorption rate of the tested luffa sponge fibers was reduced to 22.39% after the fourth set of modifications, and an orthogonal test revealed that the priority order for the factors that affected the modification process was KH550 concentration >microwave reaction time >NAOH concentration > soaking time. The optimal set of modification conditions for luffa sponge fibers was 2% (w/w) NAOH, 1% (w/w) KH550, 30 min of soaking and 180 s of microwave treatment.

In this study, we evaluated the effects of two dominant microfilamentous algae (i.e. Melosira granulata and Oscillatoria sp.), collected from the West Lake, on growth and metabolism of Daphnia magna. Our experiment utilized 13C and 15N dual labeling to calculate the carbon and nitrogen isotopic turnover rates and half-life times in D. magna. The two labeled types of filaments were offered to D. magna as sole food sources or as paired mixtures with the unlabeled Scenedesmus obliquus. Labeled S. obliquus served as the control. Combined results showed that D. magna had a higher grazing rate on Oscillatoria sp. than on M. granulate and a small percentage of unlabeled S. obliquus addition could improve the grazing rate in both filamentous algae, especially for Oscillatoria sp., which had the highest carbon and nitrogen isotopic turnover rates and the lowest half times, even superior to the sole S. obliquus treatment. Our study revealed that D. magna could utilize the two dominant filamentous algae as a food source for their growth and metabolism, and a small percentage addition of S. obliquus could ameliorate the negative impact of these two filamentous algae on D. magna.

The effects of supplementing plant-based carbon sources, fermented tissues of Arundo donax and Pontederia cordata, and a combination of the two plants, on the nitrogen removal efficiency and microbial composition in a vertical flow constructed wetland (VFCW) were examined. The results showed that the addition of the composite carbon source produced the highest removal efficiencies of NH4+-N 91.5%, NO3--N 94.5% and TN 92.8% in VFCW. The detected abundance of amoA, nirS, and nxrA genes indicated that ammonia oxidation bacteria and denitrifying bacteria were more abundant than the nitrite oxidation bacteria. Furthermore, the addition of the composite carbon source significantly promoted the growth of the denitrifying bacteria in VFCW. The results indicated that supplementing the system with plant-based carbon sources achieved partial nitrification and denitrification, as well as classic denitrification in VFCWs. The study suggested that multiple nitrogen removal pathways were required to feasibly and efficiently remove nitrogen.

This investigation demonstrates that programmed cell death (PCD) in a cyanobacterium, Microcystis aeruginosa, resulting from allelopathic stress induced by a submerged macrophyte, Myriophyllum spicatum, in a co-culture system. The hallmarks of PCD, caspase-3-like protease activity, DNA fragmentation, and destruction of cell ultrastructure, as well as intracellular PCD signaling radicals, reactive oxygen species (ROS), and nitric oxide (NO), were measured in M. aeruginosa cells co-cultured with M. spicatum for 7 days. The results showed a dose–response relationship between M. spicatum biomass and M. aeruginosa mortality. A caspase-3-like protease was activated and elevated from day 3. Thylakoid disintegration, cytoplasmic vacuolation, and fuzzy nuclear zone were observed by transmission electron microscopy, and distinct DNA fragmentation was detected in M. aeruginosa cells at a M. spicatum biomass of 6.0 g fresh weight (FW) L−1 during the 7 days. Allelochemicals of total phenolic compounds (TPCs) were determined in co-culture water, and the concentration increased with increasing of M. spicatum biomass and co-culture time. Compared with the level of ROS production in the control group, a significant overproduction of ROS was detected in M. aeruginosa cells in the treatment group, and this was positively correlated with TPC concentration. Furthermore, the level of intracellular NO increased with the percent mortality of M. aeruginosa. The results indicated that a PCD pathway was induced in the cyanobacterium M. aeruginosa when co-cultured with the submerged macrophyte M. spicatum.

The removal efficiency of sediment phosphorus (P) in all fractions with a combined technology of porous ceramic filter media (PCFM) and submerged macrophytes was studied in Donghu Lake, Wuhan, China. The adsorption kinetic models of the sediment P in all fractions on PCFM could be described well by a power function equations (Q(t) = k . t(a), 0 < a < 1). The P removal capacity of the combination of PCFM and Potamogeton crispus, a submerged macrophyte, was higher for all P forms than that of the combination of PCFM and another macrophyte, Vallisneria spiralis. This study suggested that the combination of PCFM and macrophytes could achieve a synergetic sediment P removal because the removal rates of the combinations were higher than the sum of that of PCFM and macrophytes used separately. The combined technology could be further applied to treat internal P loading in eutrophic waters. (C) 2015 Elsevier Ltd. All rights reserved.

Excessive proliferation of filamentous green algae (FGA) has been considered an important factor resulting in the poor growth or even decline of submerged macrophytes. However, there is a lack of detailed information regarding the effect of decaying FGA on submerged macrophytes. This study aimed to investigate whether the decomposing liquid from Cladophora oligoclona negatively affects Hydrilla verticillata turion germination and seedling growth. The results showed that the highest concentrations of decomposing liquid treatments inhibited the turion germination rate, which was the lowest than other treatments, at only 84%. The chlorophyll a fluorescence (JIP test) and physiological indicators (chlorophyll a content, soluble sugars, Ca2+/Mg2+-ATPase and PAL activity) were also measured. The chlorophyll a content in the highest concentration (40% of original decomposing liquid) treatment group decreased by 43.53% than that of the control; however, soluble sugars, Ca2+/Mg2+-ATPase, and PAL activity increased by 172.46%, 271.19%, and 26.43% respectively. The overall results indicated that FGA decay has a considerable effect on submerged macrophyte turion germination and seedling growth, which could inhibit their expansion and reproduction. This study emphasized the need to focus on effects of FGA decomposition on the early growth stages of submerged macrophytes and offered technological guidance for submerged vegetation restoration in lakes and shallow waters.

The removal efficiency of sediment phosphorus (P) with the in-situ synergistic effect of modified bentonite granules (MBG) and Vallisneria spiralis (V. spiralis) in West Lake, Hangzhou, China was investigated for the first time in the study. CMBG-Na10-450 (nitrification (10% Na2CO3)-calcination (450 °C) combined modification) was prepared and characterized, and the removal effects of sediment P of all fractions with CMBG-Na10-450 and V. spiralis in combination and separately were evaluated in batch experiments. Results showed that CMBG-Na10-450 could promote the growth of V. spiralis, and the residual P of the sediment not adsorbed on CMBG-Na10-450 was changed through root oxygenation and nutrition allocation, and then enhanced the extra P adsorption on CMBG-Na10-450. The combination of MBG and V. spiralis exhibited a synergistic removal effect higher than the summation of MBG and V. spiralis applied separately. The results of microcosm experiments showed that the combination of CMBG-Na10-450 and V. spiralis enhanced the function of P metabolism by increasing the special genus that belongs to the family Erysipelotrichaceae.

Increases in the structural complexity of submerged macrophytes are often shown to be linked to higher invertebrate abundance and diversity, but a number of studies have demonstrated, however, that this is not always the case. The objective of this study was to analyze the effects of four macrophyte species with two contrasting architectures (simple architecture with broad leaves: Vallisneria spiralis L. and Potamogeton malaianus Miq. and complex architecture with finely dissected leaves: Ceratophyllum demersum L. and Myriophyllum verticillatum L.) on zooplanktons. We hypothesized that structurally more complex macrophytes would support more zooplanktons and higher diversity, species richness, abundance and biomass, and to test our hypotheses, zooplankton samples within the above-mentioned macrophytes were collected to analyze the variances at different times. Contrary to our expectations, we found that the zooplankton’ responses were independent to the macrophyte architecture. Specially, although finely dissected M. verticillatum could significantly increase total zooplanktons, diversity, species richness, rotifers and cladocerans than the other three macrophytes, the effects of finely dissected C. demersum on these parameters exhibited no significant differences compared to two broad leaved macrophytes (V. spiralis and P. malaianus). Moreover, broad leaved macrophytes even increased more abundance zooplanktons than finely dissected C. demersum. In addition, the effects of macrophytes on zooplanktons also varied with zooplankton species. For example, the four tested macrophytes could significantly increase cladoceran abundance and biomass. Yet for copepods, the density was significantly increased in presence of V. spiralis and C. demersum, but P. malaianus and M. verticillatum did not show significant effects on copepod density. Moreover, all the tested macrophytes except for V. spiralis even significantly suppress copepod biomass. Therefore, our results did not support the hypothesis that structurally complex macrophytes harbor more zooplanktons, and showed that the effects of the investigated macrophytes on zooplanktons were not likely to depend on their architectures, but seemed to rely on complex relationships between macrophyte and zooplankton species.

The performance of bioelectrochemically assisted constructed wetland systems planted with Arundo donax were evaluated at applied voltages of 1, 2, 3 and 5 V. The RGR and Proline (Pro) results implied a positive response at the proper applied voltage. In the 3-V group, the RGR sharply climbed to a maximum over two stages, and the Pro reached a higher level of 256.25 μg/g at the end of the first stage without an additional organic carbon source. This result indicated that A. donax was attempting to adapt the 3-V stress via physiological self-regulation and the growth was nearly unaffected. However, in the 5-V group, the great increase in Pro and withering of the aboveground A. donax showed that the voltage stress had become lethal and the plant was not able to endure it through physiological regulation. In addition, Anodic microbial community compositions accumulating on graphite felts were analyzed via high-throughput sequencing. Results showed that there were two clear clusters at different applied voltages. One cluster was assembled from the anodic region of the 0-V and 1-V groups, and the other was collected from the 2-V and 3-V samples. At the phylum level, Proteobacteria, Firmicutes and Bacteroidetes were the most common phyla among the samples. However, at the genus level, the dominant genera varied with the applied voltage. The relative abundance of Desulfovibrio increased with increased applied voltage. The highest total nitrogen removal rate in the 2-V group was closely related to the high abundance of the Acinetobacter genus. Moreover, Exiguobacterium became dominant only in the 5-V sample, suggesting that this genus strongly depended on the interactive environment of exudes from A. donax and applied voltage.

Six wetland plants were investigated for their effect on the degradation characteristics of chlorpyrifos in nonsterile hydroponic system at constant temperature of 28 degrees C. The results showed that the removal rates of chlorpyrifos in the water of plant systems were 1.265.56% higher than that in the control without plants. Scirpus validus and Typha angustifolia were better than other hygrophytes in elimination of chlorpyrifos. The removal rates of the two systems were up to 88%. Plants of acaulescent group had an advantage over caulescent group in removing chlorpyrifos. Phytoaccumulation of chlorpyrifos was observed, and the order of chlorpyrifos concentration in different plant tissues was root > stem > leaf. It was also found that chlorpyrifos and its metabolite TCP decreased rapidly at the initial step of the experiment.

Aluminate is generally used as a flocculant in water and wastewater treatment processes, but the residual aluminum (Al) may have toxic effects on aquatic organisms when the concentration accumulates beyond a threshold level. The in situ and laboratory tests were conducted to evaluate the impact of residual Al on submerged macrophytes in West Lake, Hangzhou, China, which receives Al flocculant-purified water diverted from the Qiantang River. The responses of Vallisneria natans and Hydrilla verticillata were investigated based on their morphological and physiological parameters in pot culture and aquarium simulation experiments. In the pot culture experiments, the biomass, seedling number, plant height, stolon number, stolon length, and root weight were significantly higher at a site located 150m from the inlet compared with those at a site located 15m from the inlet (P < 0.05), thereby indicating that the residual Al significantly inhibited the morphological development of V. natans and H. verticillata. The variations in the chlorophyll-a, protein, and malondialdehyde contents of the two species in both the pot culture and aquarium simulation experiments also demonstrated that the two submerged macrophytes were stressed by residual Al. V. natans and H. verticillata accumulated 0.052-0.227mg of Al per gram of plant biomass (fresh weight, mg/g FW) and 0.045-0.205mg Al/g FW in the in situ experiments, respectively, where the amounts of Al were significantly higher in the plants in the treatment aquaria during the laboratory experiments than those in the controls. These results may have important implications for the restoration of submerged macrophytes and ecological risk assessments in Al-exposed lakes. It is recommended that the Al salt concentration used for the control of lake eutrophication should be reduced to an appropriate level.

Pyrogallic acid (PA) is used in various industrial and consumer products. The molecular mechanisms underlying PA's toxicity was not fully understood. In this study, toxicity of PA on Microcystis aeruginosa with reactive oxygen species (ROS) generation as an end point was investigated. The results showed an increase in the percentage of cells with loss of membrane integrity and enhanced intracellular ROS production. Exposure to 50mgL(-1) PA for 48h caused the highest percentage of loss of membrane integrity (56.7%), and a 2.54-fold higher intracellular ROS level compared to control. Further investigation revealed that PA caused a dose-dependent increase in DNA strand breaks (DSB) of M. aeruginosa at exposure concentration from 2 to 50mgL(-1). The incubation of cells with ROS scavengers ascorbic acid, N-acetyl-l-cysteine (NAC) and tocopherol markedly alleviated the level of PA-induced DSB. Analysis of PA autoxidized products in culture solution showed that PA was quickly converted to purpurogallin (PG), and PG was further autoxidized to other polyphenolic compounds. PA and PG might participate a futile redox cycle, which mediated ROS production in M. aeruginosa. These results suggested DNA strands and cell membrane were two targets of ROS induced by PA, and oxidative damage was an important mechanism for the toxicity of PA against M. aeruginosa.

An exploratory study on the management of undesirable cyanobacteria blooms with respect to off-flavor problems using an integrated vertical-flow constructed wetland (CW) was performed at a small commercial-scale channel catfish farm from 2004 to 2007. The results of the three-year experiment indicated that water treatment by the CW could reduce the possibility of dominance by undesirable cyanobacteria species that often cause off-flavor problems. A detailed investigation in 2007, showed that the concentrations of geosmin, MIB (2-methylisoborneol), and beta-cyclocitral in the water of the recirculating pond (4.3 ng L(-1), U.D. (undetected) and 0.2 ng L(-1), respectively) treated by the CW were significantly lower than those in the control pond (152.6 ng L(-1), 63.3 ng L(-1) and 254.8 ng L(-1), respectively). In addition, the relationships among the cyanobacteria species, the off-flavor compounds and ten environmental variables were explored by canonical correspondence analysis (CCA). The results showed that Oscillatoria sp., Oscillatoria kawamurae and Microcystis aeruginosa were the main sources of off-flavor compounds in the catfish ponds. The successful manipulation of undesirable cyanobacteria species potentially resulted in lower concentrations of odorous compounds in the water of the recirculating pond. An investigation of the concentrations of geosmin and MIB in catfish fillets showed that the levels of odorous compounds were below the OTC (odor threshold concentration) values in the recirculating pond but were above the OTC values from July to October in the control pond. Water recycling by the CW could potentially be one of the best management practices to control off-flavor occurrences in aquaculture. (C) 2011 Elsevier Ltd. All rights reserved.

Shallow, eutrophic lakes are usually characterized by a turbid state devoid of submerged vegetation subject to human-induced eutrophication. In most cases, it is rather hard to restore a vegetated clear state due to reduced resilience caused by a blend of complicated factors. In this study, we successfully reestablished a plant community in a small hypereutrophic lake over a certain period. In winter and spring with transparency of >55 cm and temperature of

The presence of the odorous compounds, 2-methylisoborneol (MIB) and geosmin, as well as causative microorganisms in brackish intensive cultivation fishponds in Tianjin, China that had a severe earthy-musty odor were evaluated. The results revealed that MIB was the primary odorous compound present in the Tianjin fishponds, with a concentration ranging from 0.53–5302.7 ng·L−1. Furthermore, the concentration of MIB was found to be closely correlated with the gross biomass of actinomycetes in the water, which ranged from 10.67–1528.24 × 106 cfu·ml−1. Therefore, the sequences of the 16 SrRNA and morphological characteristics of the actinomycetes in the brackish fishponds were investigated. The results revealed that the actinomycetes in the brackish fishponds included 9 species of common and dominant actinomycetes belonging to 4 genera. Of these genera, Streptomyces were the dominant species, and Streptomyces, Nocardioides and Micromonospora were the most common species in the fishponds evaluated. Next, the ability of each of the isolated Streptomyces to produce MIB was measured under laboratory culture conditions. Streptomyces Sp2 was found to have a strong ability to produce MIB, which indicates that this strain may be the primary source of the earthy-musty odor reported in brackish intensive cultivation fishponds in Tianjin, China.

The bacterial diversity of activated sludge from submerged membrane bioreactor (SMBR) was investigated. A 16S rDNA clone library was generated, and 150 clones were screened using restriction fragment length polymorphism (RFLP). Of the screened clones, almost full-length 16S rDNA sequences of 64 clones were sequenced. Phylogenetic tree was constructed with a database containing clone sequences from this study and bacterial rDNA sequences from NCB1 for identification purposes. The 90.6% of the clones were affiliated with the two phyla Bacteroidetes (50%) and Proteobacteria (40%), and beta-, -gamma-, and delta-Proteobacteria accounted for 7.8%, 28.1%, and 4.7%, respectively. Minor portions were affiliated with the Actinobacteria and Firmicutes (both 3.1%). Only 6 out of 64 16S rDNA sequences exhibited similarities of more than 97% to classified bacterial species, which indicated that a substantial fraction of the clone sequences were derived from unknown taxa. Rarefaction analysis of operational taxonomic units (orrUs) clusters demonstrated that 150 clones screened were still insufficient to describe the whole bacterial diversity. Measurement of water quality parameter demonstrated that performance of the SMBR maintained high level, and the SMBR system remained stable during this study.