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Background and aims: Male Populus cathayana individuals alleviate the stress-induced damage on females when both sexes of plant individuals grow together compared with the female-female competition relationship. However, it is still largely unknown how microbiota associated with roots are regulated by intra- and inter-sexual plant competition that affect the plant ecology, such as the ability to mitigate stressors. Methods: Bacterial communities in the rhizosphere and root endosphere were investigated in intra-sexual competition male-male, female-female and inter-sexual competition male-female of the dioecious species P. cathayana under different availabilities of water. Results: Female P. cathayana individuals were more strongly subjected to competition from a same sex neighbor and suffered more severe damage by drought compared with the males in male-male competition. More carbon deprived from roots was assimilated by soil microorganisms in female-female competition than male-female and male-male competitions under conditions of adequate water. Changes in neighbor effect were a driving force in regulating the bacterial community in the rhizosphere and endosphere. This study found that male-male, female-female and male-female competitions recruited large numbers of unique operational taxonomic units and largely influenced bacterial β-diversity. Moreover, the inter-sexual competition highly increased the association between species of the bacterial network. Male neighbors favored colonization of the female roots by the growth promoting taxa Streptomyces and Phyllobacterium. Conclusions: It was emphasized that the beneficial roles of males in alleviating the drought-induced damage on females was associated with root microbiota, which were impacted by the sexual identity of neighbor under drought. [ABSTRACT FROM AUTHOR]

The stick number and the edge length of a knot type in the simple hexagonal lattice (sh-lattice) are the minimal numbers of sticks and edges required, respectively, to construct a knot of the given type in sh-lattice. By introducing a linear transformation between lattices, we prove that for any given knot both values in the sh-lattice are strictly less than the values in the cubic lattice. Finally, we show that the only non-trivial 1 1 -stick knots in the sh-lattice are the trefoil knot ( 3 1 ) and the figure-eight knot ( 4 1 ). [ABSTRACT FROM AUTHOR]

Background: Dioecious plants have coevolved with diverse plant microbiomes, which are crucial for the fitness and productivity of their host. Sexual dimorphism in morphology, physiology, or gene expression may relate to different microbial compositions that affect male and female fitness in different environments. However, sex-specific impacts on ecological processes that control the microbiome assembly are not well known. In this study, Populus cathayana males and females were planted in different nitrogen conditions. It was hypothesized that males and females differently affect bacterial and fungal communities in the rhizosphere soil, roots, old leaves, and young leaves. Physiological traits and transcriptome profiles of male and female plants were investigated to reveal potential mechanisms that control the microbiome assembly. Results: Our results showed strong niche differentiation that shapes microbial communities leading to a rapid loss of diversity along a decreasing pH gradient from the rhizosphere soil to leaves. Sex had different impacts on the microbial assembly in each niche. Especially fungal endophytes showed great differences in the community structure, keystone species, and community complexity between P. cathayana males and females. For example, the fungal co-occurrence network was more complex and the alpha diversity was significantly higher in young female leaves compared to young male leaves. Transcriptome profiles revealed substantial differences in plant-pathogen interactions and physiological traits that clearly demonstrated divergent internal environments for endophytes inhabiting males and females. Starch and pH of young leaves significantly affected the abundance of Proteobacteria, while tannin and pH of roots showed significant effects on the abundance of Chloroflexi, Actinobacteria, and Proteobacteria, and on the bacterial Shannon diversity. Conclusion: Our results provided important knowledge for understanding sexual dimorphism that affects microbial assemblies, thus advancing our understanding of plant-microbiome interactions. 6fJBNPXyfja-eHSN4N3z_Q Video Abstract [ABSTRACT FROM AUTHOR]

Background: Dioecious plants have coevolved with diverse plant microbiomes, which are crucial for the fitness and productivity of their host. Sexual dimorphism in morphology, physiology, or gene expression may relate to different microbial compositions that affect male and female fitness in different environments. However, sex-specific impacts on ecological processes that control the microbiome assembly are not well known. In this study, Populus cathayana males and females were planted in different nitrogen conditions. It was hypothesized that males and females differently affect bacterial and fungal communities in the rhizosphere soil, roots, old leaves, and young leaves. Physiological traits and transcriptome profiles of male and female plants were investigated to reveal potential mechanisms that control the microbiome assembly. Results: Our results showed strong niche differentiation that shapes microbial communities leading to a rapid loss of diversity along a decreasing pH gradient from the rhizosphere soil to leaves. Sex had different impacts on the microbial assembly in each niche. Especially fungal endophytes showed great differences in the community structure, keystone species, and community complexity between P. cathayana males and females. For example, the fungal co-occurrence network was more complex and the alpha diversity was significantly higher in young female leaves compared to young male leaves. Transcriptome profiles revealed substantial differences in plant-pathogen interactions and physiological traits that clearly demonstrated divergent internal environments for endophytes inhabiting males and females. Starch and pH of young leaves significantly affected the abundance of Proteobacteria, while tannin and pH of roots showed significant effects on the abundance of Chloroflexi, Actinobacteria, and Proteobacteria, and on the bacterial Shannon diversity. Conclusion: Our results provided important knowledge for understanding sexual dimorphism that affects microbial assemblies, thus advancing our understanding of plant-microbiome interactions. 6fJBNPXyfja-eHSN4N3z_Q Video Abstract [ABSTRACT FROM AUTHOR]

Deciduous and evergreen trees differ in their responses to drought and nitrogen (N) demand. Whether or not these functional types affect the role of the bacterial community in the N cycle during drought remains uncertain. Two deciduous tree species (Alnus cremastogyne, an N2‐fixing species, and Liquidambar formosana) and two evergreen trees (Cunninghamia lanceolata and Pinus massoniana) were used to assess factors in controlling rhizosphere soil bacterial community and N cycling functions. Photosynthetic rates and biomass production of plants, 16S rRNA sequencing and N‐cycling‐related genes of rhizosphere soil were measured. The relative abundance of the phyla Actinobacteria and Firmicutes was higher, and that of Proteobacteria, Acidobacteria, and Gemmatimondaetes was lower in rhizosphere soil of deciduous trees than that of evergreen. Beta‐diversity of bacterial community also significantly differed between the two types of trees. Deciduous trees showed significantly higher net photosynthetic rates and biomass production than evergreen species both at well water condition and short‐term drought. Root biomass was the most important factor in driving soil bacterial community and N‐cycling functions than total biomass and aboveground biomass. Furthermore, 44 bacteria genera with a decreasing response and 46 taxa showed an increased response along the root biomass gradient. Regarding N‐cycle‐related functional genes, copy numbers of ammonia‐oxidizing bacteria (AOB) and autotrophic ammonia‐oxidizing archaea (AOA), N2 fixation gene (nifH), and denitrification genes (nirK, nirS) were significantly higher in the soil of deciduous trees than in that of the evergreen. Structural equation models explained 50.2%, 47.6%, 48.6%, 49.4%, and 37.3% of the variability in copy numbers of nifH, AOB, AOA, nirK, and nirS, respectively, and revealed that root biomass had significant positive effects on copy numbers of all N‐cycle functional genes. In conclusion, root biomass played key roles in affecting bacterial community structure and soil N cycling. Our findings have important implications for our understanding of plants control over bacterial community and N‐cycling function in artificial forest ecosystems. [ABSTRACT FROM AUTHOR]

The conglomerate reservoir in Mahu sag, located in the northwest margin of Junggar basin, China, is of low porosity and permeability. Hydraulic fracturing is necessary to improve oil production efficiency. However, the influence of strong reservoir heterogeneity and large difference in gravel content on mechanical properties still needs study. In this study, uniaxial compression tests were conducted on the conglomerate in which the gravel diameter ranges from 2 to 26 mm. In these tests, a large number of micro-fractures were found to be generated evenly around gravels. Additionally, we found that as the gravel content increased, the uniaxial compressive strength and elastic modulus of conglomerate decreased, and the plasticity characteristics increased. The experimental results show that the gravel content is the key factor determining the mechanical properties of the conglomerate. When gravel content is less than the critical content (~ 14.61–31.72%), at which the brittle–plastic transition of rocks exists, the macro-mechanical properties are mainly influenced by the cementing material. When gravel content is greater than the critical gravel content (~ 78.50%), failure is determined by the Hertz contact stress among the gravels. When gravel content is between (~ 14.61–31.72%) and (~ 78.50%), Orowan additional stress is the main factor determining the mechanical mechanism of rock failure. This failure is closely related to gravel content and cementation strength between the gravel and matrix. Highlights: The gravel content is the key factor of the mechanical properties of conglomerate. As the gravel content increases, the uniaxial compressive strength and elastic modulus of conglomerate decrease. The micro fracture of rock is distributed around the gravel, which is closely related to the interaction between gravel and matrix. [ABSTRACT FROM AUTHOR]

Unconventional oil and gas reservoirs are normally characterized by low porosity and low permeability and need to be hydraulically fractured to produce fracture networks and achieve the potential for economic production. Reservoir rocks are generally characterized by bedding planes, which have a significant impact on fracture propagation. In this study, a double torsion experiment was used to simulate tensile fracture propagation during hydraulic fracturing. The effect of bedding planes on fracture toughness, fracture morphology, and propagation rate in shale and tight sandstone was studied. Micromechanical mechanisms were analyzed through a microindentation experiment. The results show that as the angle between bedding and a pre-cut plane increases, fracture toughness first decreases and then increases, while the subcritical fracture propagation rate first increases and then decreases. The inflection point for this behavior occurs at an angle of 30° between the bedding and pre-cut plane. The shape of the tensile fractures is mainly influenced by the micromechanical properties of the adjacent bedding plane. When the ratio of elastic modulus between adjacent beds is 0.67, fractures propagate along the bedding plane, while at a ratio of 0.79, fractures extend through the bedding plane. These findings indicate that the angle between bedding and artificial planes as well as the difference in micromechanical properties of adjacent bedding planes are important to judge whether hydraulic fractures can penetrate or spread along a bedding plane. Highlights: As the angle between bedding and a pre-cut plane increases, fracture toughness first decreases and then increases, while the subcritical fracture propagation rate first increases and then decreases. The shape of the tensile fractures is mainly influenced by the micromechanical properties of the adjacent bedding plane. When the ratio of elastic modulus between adjacent beds is 0.67, fractures propagate along the bedding plane, while at a ratio of 0.79, fractures extend through the bedding plane. [ABSTRACT FROM AUTHOR]

Sexual dimorphism occurs regarding carbon and nitrogen metabolic processes in response to nitrogen supply. Differences in fixation and remobilization of carbon and allocation and assimilation of nitrogen between sexes may differ under severe defoliation. The dioecious species Populus cathayana was studied after two defoliation treatments with two N levels. Males had a higher capacity of carbon fixation because of higher gas exchange and fluorescence traits of leaves after severe long-term defoliation under deficient N. Males had higher leaf abscisic acid, stomatal conductance and leaf sucrose phosphate synthase activity increasing transport of sucrose to sinks. Males had a higher carbon sink than females, because under N-deficient conditions, males accumulated >131.10% and 90.65% root starch than males in the control, whereas females accumulated >40.55% and 52.81%, respectively, than females in the control group. Males allocated less non-protein N (NNon-p) to leaves, having higher nitrogen use efficiency (photosynthetic nitrogen use efficiency), higher glutamate dehydrogenase (GDH) and higher leaf GDH expression, even after long-term severe defoliation under deficient N. Females had higher leaf jasmonic acid concentration and NNon-p. The present study suggested that females allocated more carbon and nitrogen to defense chemicals than males after long-term severe defoliation under deficient N. [ABSTRACT FROM AUTHOR]

Agricultural straw is abundant worldwide, but efficient production of lactic acid from straw is still challenging. In this paper, Trichoderma viride R16 was cultivated using corncob as the substrate in a fed‐batch process, after which the enzymes from T. viride R16 broth were analyzed through protein mass spectrometry and used for lactic acid production. Dioxygenase activity was found in the T. viride R16 enzymes, and 0.2 g/L phenolics (vanillin, 4‐hydroxybenzaldehyde, syringaldehyde) was degraded during enzyme production. Lactic acid production and yield from NH3‐H2O2 pretreated and washed corncob were increased by more than 24% and total phenolics was significantly lower using T. viride R16 enzymes compared with commercial enzymes in batch and fed‐batch fermentation. These characteristics of T. viride R16 support industrial applications with efficient in situ detoxification of phenolic inhibitors without adding an extra step during lactic acid production from pretreated agricultural straw using simultaneous saccharification and fermentation. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

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In this work, sediments were treated with calcium nitrate, aluminum sulfate, ferric sulfate, and Phoslock®, respectively. The impact of treatments on internal phosphorus release, the abundance of nitrogen cycle-related functional genes, and the growth of submerged macrophytes were investigated. All treatments reduced total phosphorus (TP) and soluble reactive phosphorus (SRP) in interstitial water, and aluminum sulfate was most efficient. Aluminum sulfate also decreased TP and SRP in overlying water. Treatments significantly changed P speciations in the sediment. Phoslock® transformed other P species into calcium-bound P. Calcium nitrate, ferric sulfate, and Phoslock® had negative influence on ammonia oxidizers, while four chemicals had positive influence on denitrifies, indicating that chemical treatment could inhibit nitrification but enhance denitrification. Aluminum sulfate had decreased chlorophyll content of the leaves of submerged macrophytes, while ferric sulfate and Phoslock® treatment would inhibit the growth of the root. Based on the results that we obtained, we emphasized that before application of chemical treatment, the effects on submerged macrophyte revegetation should be taken into consideration. [ABSTRACT FROM AUTHOR]

Effects of laser irradiation on photosystem II (PS II) photochemical efficiencies, growth, and other physiological responses of Microcystis aeruginosa were investigated in this study. Results indicate that laser irradiation (wavelengths 405, 450, 532, and 650 nm) could effectively inhibit maximal PS II quantum yield (Fv/Fm) and maximal electron transport rates (ETR) of M. aeruginosa, while saturating light levels (E) of M. aeruginosa did not change significantly. Among the four tested wavelengths, 650 nm laser (red light) showed the highest inhibitory efficiency. Following 650 nm laser irradiation, the growth of M. aeruginosa was significantly suppressed, and contents of cellular photosynthetic pigments (chlorophyll a, carotenoid, phycocyanin, and allophycocyanin) decreased as irradiation dose increased. Meanwhile, laser irradiation enhanced the enzyme activities of superoxide dismutase (SOD) and peroxidase (POD) in M. aeruginosa cells. Lower irradiation doses did not change the intracellular microcystin contents, but higher dose irradiation (>1284 J cm) caused the release of microcystin into the culture medium. Transmission electron microscope examination showed that the ultrastructure of M. aeruginosa cells was destructed progressively following laser irradiation. Effects of laser irradiation on M. aeruginosa may be a combination of photochemical, electromagnetic, and thermal effects. [ABSTRACT FROM AUTHOR]

Presence of plastic debris in marine and freshwater ecosystems is increasingly reported. Previous research suggested plastic debris had a strong affiliation for many pollutants, such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and heavy metals. In this study, the sorption behavior of pharmaceuticals and personal care products (PPCPs), including carbamazepine (CBZ), 4-methylbenzylidene camphor (4MBC), triclosan (TCS), and 17α-ethinyl estradiol (EE2), to polyethylene (PE) debris (250 to 280 μm) was investigated. The estimated linear sorption coefficients ( K) are 191.4, 311.5, 5140, and 53,225 L/kg for CBZ, EE2, TCS, and 4MBC, and are related to their hydrophobicities. Increase of salinity from 0.05 to 3.5 % did not affect the sorption of 4MBC, CBZ, and EE2 but enhanced the sorption of TCS, likely due to the salting-out effect. Increase of dissolved organic matter (DOM) content using Aldrich humic acid (HA) as a proxy reduced the sorption of 4MBC, EE2, and TCS, all of which show a relatively strong affiliation to HA. Results from this work suggest that microplastics may play an important role in the fate and transport of PPCPs, especially for those hydrophobic ones. [ABSTRACT FROM AUTHOR]

Parabens are extensively used as preservatives and bactericides in personal care and other consumer products, and are commonly found in wastewater and surface water as contaminants. However, few data are currently available on the ecotoxicity of parabens. Periphyton biofilm, a widely distributed microbial aggregate of ecological importance in aquatic environment, is frequently used for water quality monitoring, ecological restoration, and toxicity assessment. In this work, the effects of butyl paraben on the development and microbial composition of periphyton biofilm was studied in a laboratory experiment for 32 days using flow through channels. No effect was observed at the environmental relevant concentration level (0.5 μg L) during the experiment. At the highest tested concentration level (5000 μg L), following effects were noted: (1) inhibition on algae growth at the end of the experiment as indicated by the chlorophyll a and total biovolume; (2) inhibition of photosynthetic efficiency on day 24 as suggested by the maximal Photosystem II quantum yield (Fv/Fm); (3) decrease of the algal diversity on day 24 and 32 as reflected by the Pielou and Shannon-Weiner indices. Bacteria were less sensitive than algae in the periphyton biofilm, which showed no difference at all tested concentration levels as illustrated by the Biolog EcoPlates™ analysis. Therefore, we conclude that environmental residues of butyl paraben have a very low risk to periphyton in aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Occurrence of five endocrine-disrupting chemicals (EDCs)-bisphenol-A (BPA), triclosan (TCS), 17α-ethinyl estradiol (EE2), benzophenone-3, and 4-methylbenzylidene camphor-were monitored in East Lake, the largest urban lake in China. Other than EE2, all selected EDCs were detected at least once in the lake water with concentrations ≤89.1 ng/L. EDCs were detected with greater occurrence in spring than in other seasons. In lake sediment, TCS was detected at the greatest concentration (30.9 ng g), whereas BPA and EE2 were not detected. Spatial distribution of the EDCs in the lake water and the lake sediment showed similar patterns, and greater EDC residuals were found from those sites with known wastewater input. The linear adsorption coefficients ( K) varied from 17.9 to 1,017 L kg and were related to the octanol-water partition coefficient ( K) values of the compounds. Photodegradation was a major process removing the EDCs from the lake water, and the presence of dissolved organic material and NO in the lake water can accelerate the photodegradation process. Degradation of the EDCs in the lake sediment was relatively slow and occurred mainly due to the microbial processes. All compounds were found more persistent under anoxic conditions than under oxic conditions. [ABSTRACT FROM AUTHOR]

Diethyldithiocarbamate and 2-mercaptoethanol modifiers were compared for the preconcentration of mercury species in water by C18solid phase extraction (SPE). The recovery values of mercury species were determined by high performance liquid chromatography–atomic fluorescence spectrometry. The eluent type, pH, chloride ion concentration, humic acid concentration, and storage time were evaluated to compare the preconcentration efficiency. L-cysteine was employed to elute the mercury compounds. Less eluent was needed for 2-mercaptoethanol modified SPE than for diethyldithiocarbamate modified SPE at an L-cysteine concentration of 0.12%. Diethyldithiocarbamate modified SPE could be used over a wider pH range and higher humic acid concentrations, whereas 2-mercaptoethanol modified SPE was less affected by the chloride concentration. Both modified SPE systems stored mercury species for 5 days, but diethyldithiocarbamate modified SPE could be stored longer. Diethyldithiocarbamate SPE provided limits of detections of 3.5, 2.5, and 4 ng · L−1and average recoveries of 90.78 ± 3.37%, 96.79 ± 5.12%, and 84.88 ± 5.37% for mercury(II), methylmercury, and ethylmercury, respectively. The relative standard deviation was less 6.5%. For 2-mercaptoethanol modified SPE, the limits of detection were 1.4, 1, and 1.6 ng · L−1and the recoveries were of 87.66 ± 8.45%, 86.70 ± 2.61%, and 91.31 ± 6.98% for mercury(II), methylmercury, and ethylmercury, respectively, with a relative standard deviation below 9.7%. Water should be characterized for its physical and chemical characteristics before mercury preconcentration to choose the most suitable method. [ABSTRACT FROM AUTHOR]

Adsorption and degradation processes of triclosan (TCS) were studied in the laboratory using field-collected sediments of different physicochemical properties. Batch equilibrium experiment indicated that adsorption isotherms were fitted well to both linear and Freundlich model with linear sorption coefficients ( K) varied from 147 to 1,425 mL μg. The sediment with a higher organic carbon content and a lower pH value had the greatest adsorption capability. Degradation experiment showed that triclosan was relatively stable in water with calculated half-life values ranged from 89 to 161 days. No degradation in sterilized water suggested that the loss of triclosan was due to biological processes. Degradation was more rapid in water-sediment system than in water, and the calculated half-life value in water-sediment systems ranged from 32 to 62 days. Methylation of triclosan was observed in all studied sediments, but the amount of methyl-triclosan (M-TCS) accounted for less than 5 % of the degradated TCS. [ABSTRACT FROM AUTHOR]

Qinghai Lake, situated on the Qinghai-Tibet plateau, is the largest lake in China. In this study, the water and sediment quality were investigated in Qinghai Lake, three sublakes, and five major tributaries. Both Na and Cl were found to be the major ions present in Qinghai Lake and the three sublakes, while Ca and HCO dominated the tributaries. Compared with historical data from the 1960s, the concentrations of NH, NO, and soluble reactive silica have increased considerably, likely caused by increased human activities in the area. Compared to the historical data, chemical oxygen demand has increased and lake water transparency has decreased, likely related to an increase in nutrient levels. Relatively high concentrations of total nitrogen (TN) and total phosphorus (TP) were observed in Qinghai Lake sediments, although P fraction types and low water concentrations of these two indicate low possibility of transfer into the water column. The ratios of C/N suggest that the organic matter in the sediments are primarily from autochthonous sources. TN and total organic carbon in the sediment cores increased slowly up the core while TP and total inorganic carbon have been fairly constant. [ABSTRACT FROM AUTHOR]

The effectiveness of a novel and low-cost adsorbent, iron-modified bamboo charcoal (BC-Fe), for arsenic removal from aqueous systems was evaluated in this study. The BC-Fe was synthesized by loading iron onto bamboo charcoal via soaking in a ferric salt solution. The BC-Fe possessed a porous structure with a surface area of 277.895 m/g. The adsorption characteristics of arsenic onto BC-Fe were further investigated at various pHs, contact times, arsenic concentrations, and adsorbent doses in batch tests. The corresponding optimum equilibrium pH ranges for As(III) and As(V) removal were 4-5 and 3-4, respectively. The equilibrium times for As(III) and As(V) adsorption were 30 and 35.5 h, respectively. The arsenic removal was strongly dependent on the initial adsorbate concentration and adsorbent dosage. The maximum arsenic removal capacities of BC-Fe under the experimental conditions were 7.237 and 19.771 mg/g for As(III) and As(V), respectively. The pseudo-second-order kinetic model and Freundlich isotherm explained the kinetic and equilibrium of both the As(III) and As(V) adsorbent processes, respectively. Based on these results, the BC-Fe developed in this study is a promising material for the treatment of arsenic-contaminated water. [ABSTRACT FROM AUTHOR]

Continuous viscosity of the sugar melt ranged from the superheated to the supercooled, was measured with a rotating viscometer. The thermal properties of sugars have been investigated by differential scanning calorimetric and thermogravimetry. The melt fragility and the fragility of the supercooled liquid have been calculated. This study indicated that, for the whole sugar system, the melt fragility and the fragility of the supercooled liquid separately show negative linear relations with the glass-forming ability and can be used as indicators of this property. In an individual sugar system, the fragility of the supercooled liquid has a direct proportion to melt fragility, which depends on the different inherent characteristic temperatures. [ABSTRACT FROM PUBLISHER]

Our previous data have shown that inorganic arsenic concentrations were high in Dianchi Lake, China, where Microcystis blooms often occur. To explore the relationship between arsenic and the growth of Microcystis, the effects of arsenite [As(III)] and arsenate [As(V)] on the growth and toxin production of M. aeruginosa strain FACHB 905 were tested. Results showed that M. aeruginosa FACHB 905 was tolerant to inorganic arsenic and its growth was not inhibited when the concentration of As(III) was below 10 mol L or that of As(V) below 10 mol L. Total microcystin production was stimulated in the presence of 10 mol L As(III) and the response of this M. aeruginosa strain to As(III) seemed to be a typical inverted U-shaped hormesis. The content increase of microcystin-LR per cell indicated that the toxicity was enhanced as M. aeruginosa FACHB 905 was exposed to As(V). Considering the relatively high concentration of inorganic arsenic in Dianchi Lake (139 μg L in epilimnetic water), the origin of the M. aeruginosa strain, inorganic arsenic favors survival of M. aeruginosa FACHB 905 and may stimulate its microcystin production and cellular toxicity. [ABSTRACT FROM AUTHOR]

To assess the ecological impact of arsenic pollution during cyanobacterial blooms, As speciation and cyanobacterial growth in phosphate-modified Microcystis aeruginosa cultures treated with arsenate were investigated under laboratory conditions. Marked growth inhibition was observed when arsenate was added. The inhibition effect of 1 mMarsenate was lower than that of 10mMarsenate. Increasing phosphate supply (0–175 mM) in the medium decreased the inhibition of As. In the medium, arsenate, arsenite, and dimethylarsenicals (DMA) occurred under phosphate-deprivation (0mM) and phosphate-excess (175 mM) conditions. However, only arsenate andDMAwere detected under phosphate-limited (1 mM) and phosphate-rich (10 mM) conditions. Moreover, arsenite andDMA concentrations had significantly positive correlation with the biomass production of M. aeruginosa in the existence of phosphate. Arsenic speciation was more significantly affected by phosphate levels than arsenate concentrations. Recovery of total As content in M. aeruginosa culture medium increased with the increasing phosphate supply. The duration of arsenate contamination in the culture of M. aeruginosa had no influence on the variation of As species but affected the concentration of them in the medium under the phosphateexcess condition. This demonstrated that the effect of M. aeruginosa on As speciation was not related to the duration of As contamination under the phosphate-excess condition. [ABSTRACT FROM AUTHOR]

Periphyton biofilms are natural mixtures comprised of photoautotrophic and heterotrophic complex microorganisms. In this work, the inhibition effects of periphyton biofilms on cyanobacterial blooms were studied in pilot and field trials. Results show that the cyanobacterial species responsible for the blooms had an upper nutrient concentration threshold, below which it could not effectively compete with other organisms in the periphyton. The disappearance of the cyanobacterial blooms was due to the allelopathy between the cyanobacteria and periphyton biofilm. In particular, it was found that the periphyton biofilm could produce water-soluble allelochemicals such as indole and 3-oxo-α-ionone to significantly inhibit the growth of the cyanobacteria. These allelochemicals are able to damage the thylakoid membranes of the cyanobacteria, interrupt the electron transport in photosystem II, decrease effective quantum yields, and eventually lead to the failure of photosynthesis. A comprehensive discussion on the ecological consequences of these findings is also presented. This work demonstrates the potential of periphyton biofilm to be used as an environmentally friendly ecological engineering solution for (i) the control of cyanobacterial blooms and (ii) a transitional means for the construction of beneficial conditions for ecosystem restoration. In addition, this work provides significant insights into the competitive relationships between algae and biofilms. [ABSTRACT FROM AUTHOR]

From June 2004 to December 2004, Lake Dianchi, which had large scale of cyanobacterial blooms was investigated in order to study P-fractionation in the suspended matter and the sediment. The investigation improves our understanding of phosphorus in Lake Dianchi and the relationship between phosphorus and cyanobacterial blooms. It contributes to the available literature on the behavior of P in hypertrophic lakes. The distribution of P-fractions in Lake Dianchi was not uniform from northwest to south, but was closely related to the trophic status of the whole lake. The concentrations of total phosphorus, labile P (NH4Cl-P), Organic P (NaOH-NRP) and loss on ignition in suspended matter were positively correlated with the strength of cyanobacterial blooms. Total phosphorus in suspended matter was relatively stable for almost half an year and closely related to Chl. a concentration. The main content of organic phosphorus is in the cyanobacterial blooms. The concentrations of phosphorus bound to metal oxides and carbonates (NaOH-SRP and HCl-P) in sediment were similar to NaOH-SRP and HCl-P in the corresponding suspended matter. The latter two forms of P in suspended matter were not affected by cyanobacterial blooms, indicating that the inorganic phosphorus is derived from the sediment after resuspension from the sediment due to wind and wave action. The contribution of the different P-fractions to TP in sediment and in suspended matter indicates that NH4Cl-P in the suspended matter is an important buffer for maintaining dissolved phosphorus in water. [ABSTRACT FROM AUTHOR]

The different pools in the sediment from two bays with different scales of cyanobacterial bloom were studied to assess the trophic status. With large scale of cyanobacterial bloom in Haigeng bay the concentrations of different phosphorus fractions were higher than the corresponding concentrations in Macun bay, and especially WSP and AAP are the most evident, which indicates that there are more available and potential available phosphorus in Haigeng bay. The adsorption experiment also shows that the sediment in Haigeng bay is more saturated than that in Macun bay. Haigeng bay can be faced with the more serious ecological danger. Furthermore the death and deposit of a mass of algae can contribute to phosphorus released from sediment and help to the breakout of newborn cyanobacterial blooms. [ABSTRACT FROM AUTHOR]

Toxic metals introduced into aquatic environments by human activities accumulation in sediments. A common notion is that the association of metals with acid volatile sulfides (AVS) affords a mechanism for partitioning metals from water to solid phase, thereby reducing biological availability. However, variation in environmental conditions can mobilize the sediment-bound metal and result in adverse environmental impacts. The AVS levels and the effect of AVS on the fate of Cu, Cd, Zn, Ni in sediments in the the Changjiang River, a suboxic river with sandy bottom sediment and the Donghu Lake, a anoxic lake with muddy sediment in China, were compared through aeration, static adsorption and release experiments in laboratory.Sipsisotherm equation, kinetic equation and grade ion exchange theory were used to describe the heavy metal adsorb and release process. The results showed that AVS level in the lake sediment are higher than that of the river. Heavy metals in the overlying water can transfer to sediments incessantly as long as the sediment remains undisturbed. The metal release process is mainly related to AVS oxidation in lake sediment while also related to Org-C and Fe-Mn oxyhydroxide oxidation in river sediment. The effect of sulfides on Zn and Ni is high, followed by Cd, and Cu is easy bound to Org-C. AVS plays a major role in controlling metals activity in lake sediment and its presence increase the adsorption capacity both of the lake and river sediments. [ABSTRACT FROM AUTHOR]