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The over proliferation of harmful cyanobacteria and their cyanotoxins resulted in damaged aquatic ecosystem, polluted drinking water and threatened human health. Cyanophages are a kind of viruses that exclusively infect cyanobacteria, which is considered as a potential strategy to deal with cyanobacterial blooms. Nevertheless, the infecting host range and/or lysis efficiency of natural cyanophages is limited, rising the necessity of constructing non-natural cyanophages via artificial modification, design and synthesis to expand their host range and/or efficiency. The paper firstly reviewed representative cyanophages such as P60 with a short latent period of 1.5 h and S-CBS1 having a burst size up to 200 PFU/cell. To explore the in-silico design principles, we critically summarized the interactions between cyanophages and the hosts, indicating modifying the recognized receptors, enhancing the adsorption ability, changing the lysogeny and excluding the defense of hosts are important for artificial cyanophages. The research progress of synthesizing artificial cyanophages were summarized subsequently, raising the importance of developing genetic manipulation technologies and their rescue strategies in the future. Meanwhile, Large-scale preparation of cyanophages for bloom control is a big challenge. The application prospects of artificial cyanophages besides cyanobacteria bloom control like adaptive evolution and phage therapy were discussed at last. The review will promote the design, synthesis and application of cyanophages for cyanobacteria blooms, which may provide new insights for the related water pollution control and ensuring hydrosphere security. [Display omitted] [ABSTRACT FROM AUTHOR]

Cyanobacteria are ubiquitously distributed in water on the Earth. It has long been known that the cyanobacterial bloom in aquaculture ponds can cause acute and massive deaths of shrimp. However, the long-term and chronic effects of the cyanobacterial bloom on shrimp are still poorly understood. In this study, the immune state of white pacific shrimp, Litopenaeus vannamei , surviving a naturally occurring cyanobacterial bloom was investigated and tracked for 70 d. Compared with the control, the growth of shrimp suffering high concentrations of cyanobacteria was obviously postponed. In these shrimp, the activities of the NF-κB, JAK/STAT and P38 MAPK immune signaling pathways and the expression of many antimicrobial peptide genes were down-regulated, whereas the expression of C-type lectins was significantly up-regulated. Although the mRNA level of lysozyme was reduced, the expression of the invertebrate-type lysozyme gene was increased. Furthermore, the concentration of hemocytes in hemolymph was greatly decreased, but the phagocytic activity of hemocytes was increased. These suggested that the cyanobacterial bloom has significant and complex influences on the immune system of shrimp, and in turn, alteration of the immune state could be a factor by which few shrimp can survive the cyanobacterial bloom. Thus, the current study could help further understand the interactions between the aquaculture water environment and the immune system of shrimp. [ABSTRACT FROM AUTHOR]

In the present study, the feasibility of using sulfate radicals generated by coupling ferrous ions and persulfate as a transition metal and oxidant, respectively, was investigated for the removal of Microcystis aeruginosa . The results show that the Fe 2+ /S 2 O 8 2− process was effective for the removal of Microcystis aeruginosa and influenced by operating parameters, such as the mass ratio of Fe 2+ and S 2 O 8 2− , persulfate dosage, initial solution pH, and reaction time. The mass ratio of Fe 2+ and S 2 O 8 2− and concentration of persulfate noticeably impacted the Microcystis aeruginosa removal efficiency, with the mass ratio of Fe 2+ and S 2 O 8 2− having a more significant effect than the persulfate dosage. The chlorophyll a removal rate of Microcystis aeruginosa reached 95.38% under the following optimum orthogonal conditions: a mass ratio of Na 2 S 2 O 8 /FeSO 4 of 2:1, a Na 2 S 2 O 8 dosage of 25 mg/L, a pH of 4, and a reaction time of 60 min. Both sulfate and hydroxyl radicals generated from the Fe 2+ -activated persulfate system were responsible for the inhibition of Microcystis aeruginosa cell growth and reproduction through destruction of the cellular structure, degradation of cell inclusions and inhibition of photosynthesis. This study indicated that the application of Fe 2+ -activated persulfate oxidation is a feasible method for treating cyanobacterial blooms. [ABSTRACT FROM AUTHOR]

Antibiotics are normally regarded as safe to aquatic ecosystems when their contamination concentrations are lower than the toxic threshold. This study observed the hazard of ciprofloxacin, sulphamethoxazole and their binary mixture to the aquatic environment at environmentally relevant concentrations lower than the toxic threshold, due to the stimulation on the bloom of Microcystis aeruginosa. The enhanced growth of M. aeruginosa, coupled with elevated photosynthesis activity, was exerted by 50-200 ng/L of ciprofloxacin, 100-200 ng/L of sulphamethoxazole and 20-100 ng/L of the binary antibiotic mixture. Stimulated production and release of microcystins were observed at even lower concentrations. The upregulation of transcription-related proteins, cell division-related proteins, a gas vesicle protein, a global nitrogen regulator (ntcA), two microcystin synthetases (mcyC and mcyH) and ATP-binding cassette transporters provided direct proteomic evidence for the regulation of target antibiotics on M. aeruginosa bloom. Cytochrome P450 was an essential component involved in stress responses and antibiotic biodegradation. Proteomic responses to antibiotic exposure presented a shift in the energy metabolism of M. aeruginosa towards the excitation of photosynthesis, an increase of carbohydrate biosynthesis and the inhibition of carbohydrate catabolism. Superoxide dismutase, enolase and D1 protein were candidate target proteins of different antibiotics in M. aeruginosa. The antibiotic mixture showed a greater hazard than single antibiotics, and a safe threshold of 5 ng/L was suggested for each target antibiotic under the coexistence condition. [ABSTRACT FROM AUTHOR]

Although cyanobacterial blooms can change microbial communities, it is still unclear what impact such harmful blooms will have on denitrifying bacteria, the drivers of the removal of excessive nitrogen from water. In order to clarify the impact, populations of denitrifying bacteria, with periodic proliferation and dominance of cyanobacteria in a eutrophic shallow lake located in southeast China, were investigated using quantitative real-time polymerase chain reaction (qPCR) and 454-pyrosequencing based on the copper-containing nitrite reductase (nirK) gene, cytochrome cd1-containing nitrite reductase (nirS) gene and nitrous oxide reductase (nosZ) gene. Samples were collected periodically during a three-month period when the cyanobacterial density gradually increased. In the qPCR analyses, abundances ofnirK,nirSandnosZwere intensely positively correlated with the biomass of cyanobacteria. Moreover, 454-pyrosequencing revealed that the community composition of denitrifying bacteria shifted with the increase in cyanobacterial density. These results indicated that the shifts of the community composition of denitrifying bacteria might be related to cyanobacterial blooms, which could potentially lead to alterations of denitrification in eutrophic water. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms may stimulate epiphytic nitrification and denitrification in the water column. To validate this hypothesis, a 4-week floating mesocosms experiment that involved a cyanobacterial decay-growth-decay period was conducted at Lake Taihu. In addition to conventional methods for detecting the physical and chemical properties, quantitative real-time PCR was used to identify the nitrification and denitrification genes (archaeal and bacterial amoA, nirS and nirK). Treatment with cyanobacteria led to removal of about 3.62 mg N L total nitrogen, 40% of which was organic nitrogen, indicating a nitrogen transformation and removal mechanism was present in the system. Variations in the biogeochemical properties suggested that remineralization and coupling nitrification and denitrification by epiphytic and pelagic microorganisms was the primary pathway through which organic nitrogen was removed. The results of this study revealed that algal blooms can accelerate nitrogen removal efficiency, which may be the primary reason that nitrogen is limited in summer in Lake Taihu. [ABSTRACT FROM AUTHOR]

In order to illuminate the characteristics of excreting alkaline phosphatase (AP) by cyanobacteria and verify the feasibility of alkaline phosphatase activity (APA) as the indicator of soluble reactive phosphorus (SRP) deficiency, daily investigation in situ was conducted during a complete process of cyanobacterial bloom in the Xiaojiang River, a tributary of Three Gorges Reservoir. Changes of phytoplankton communities, SRP, chlorophyll a (Chl a), physic-chemical parameters and APA were screened. The complete process of cyanobacterial bloom could be divided into two stages. In the bloom stage, Microcystis sp. dominated the phytoplankton communities, water temperature (WT), dissolved oxygen (DO) and the total APA (APAT) kept a high level and Chl a displayed an ascending trend and reached the peak. APA>3.0µM occupied the main proportion of the total APA (APAT) and showed the significant positive relationship with SRP (p<0.05). In the bloom decaying stage, the predominant species was Anabaena sp., the values of WT, DO, Chl a, APAT and APA>3.0µM declined and lower than that in the bloom stage; APA>3.0µM still occupied the main proportion of APAT and showed the significant negative relationship with SRP (p<0.05). It was proved that AP was mainly excreted by phytoplankton and there were at least two different AP excreting mechanisms in cyanobacteria, APA was not reasonable treated as the indicator of SRP deficiency when Microcystis sp. dominated the phytoplankton communities. [ABSTRACT FROM AUTHOR]

Cyanobacterial bloom formation is dependent on nutrient levels and meteorological conditions. In this study, we elucidated the effects of extreme weather events (EWEs, heavy rainfall and strong winds) on the cyanobacterial blooms in Lake Taihu in recent years based on an analysis of the meteorological, nutrient, and bloom area data from 2007 to 2015. The levels of total phosphorus (TP) and total nitrogen (TN) decreased by 42.5% and 31.2%, respectively, in the water of Lake Taihu over the past nine years. However, the frequency and intensity of cyanobacterial blooms did not significantly decrease. A total of 50.5% of the extended blooms (>300 km 2 ) were associated with EWEs from 2007 to 2015, 36.2% of which were due to heavy rainfall and 38.3% of which were due to strong winds (25.5% were due to both). Interestingly, the frequency of the EWE-induced extended blooms significantly increased after 2012. Principal component analysis (PCA) showed that this frequency correlated positively with EWE-induced nutrient increases in the water, indicating that the complement from nutrient increases induced by EWE allow cyanobacterial cells to reach high biomass under relatively low nutrient condition. Our results suggest that EWEs play a more important role in extended bloom formation after the nutrient levels in shallow lakes are reduced. [ABSTRACT FROM AUTHOR]

Long-term interannual (1991-2013) and monthly (1999-2013) data were analyzed to elucidate the effects of meteorological factors and nutrient levels on phytoplankton biomass in the cyanobacteria-dominated Waihai basin of Lake Dianchi. The interannual ln(chl. a) exhibited positive correlations with the mean air temperature, mean minimum air temperature, and mean maximum air temperature; in addition, a positive relationship between Δln(chl. a) and ΔTP was observed throughout the period. Additionally, ln(chl. a) exhibited a positive correlation with the TP concentration, negative correlations with the sunshine hours and wind speed during the dry season, and positive correlations with the TN and TP concentrations during the rainy season. Furthermore, TP was the most influential factor affecting cyanobacterial bloom dynamics throughout the entire period and during the dry season, and TN and TP were the most important factors during the rainy season, as determined by relative importance analysis. The results of this study based on interannual analysis demonstrated that both meteorological factors and nutrient levels have important roles in controlling cyanobacterial bloom dynamics. The relative importance of these factors may change according to precipitation patterns. Thus, climate change regulation and eutrophication management should be considered in strategies for bloom control. Decreasing the TP load should be prioritized throughout the entire period and during the dry season, and decreasing the TN and TP loads should be considered initially during the rainy season. In addition, further studies of more frequent and complete data acquired over a longer period of time should be conducted in the future. [ABSTRACT FROM AUTHOR]

Modified soils (MSs) are being increasingly used as geo-engineering materials for the sedimentation removal of cyanobacterial blooms. Cationic starch (CS) has been tested as an effective soil modifier, but little is known about its potential impacts on the treated water. This study investigated dissolved organic matters in the bloom water after algal removal using cationic starch modified soils (CS-MSs). Results showed that the dissolved organic carbon (DOC) could be decreased by CS-MS flocculation and the use of higher charge density CS yielded a greater DOC reduction. When CS with the charge density of 0.052, 0.102 and 0.293 meq/g were used, DOC was decreased from 3.4 to 3.0, 2.3 and 1.7 mg/L, respectively. The excitation–emission matrix fluorescence spectroscopy and UV 254 analysis indicated that CS-MS exhibits an ability to remove some soluble organics, which contributed to the DOC reduction. However, the use of low charge density CS posed a potential risk of DOC increase due to the high CS loading for effective algal removal. When CS with the charge density of 0.044 meq/g was used, DOC was increased from 3.4 to 3.9 mg/L. This study suggested, when CS-MS is used for cyanobacterial bloom removal, the content of dissolved organic matters in the treated water can be controlled by optimizing the charge density of CS. For the settled organic matters, other measures ( e.g. , capping treatments using oxygen loaded materials) should be jointly applied after algal flocculation. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms in freshwaters have become one of the most widespread of environmental problems and threaten water resources worldwide. Previous studies on cyanobacteria in Lake Taihu often collected samples from one site (like Meiliang Bay or Zhushan Bay) and focused on the variation in patterns or abundance of Microcystis during the blooming season. However, the distribution of cyanobacteria in Lake Taihu shows differing pattern in various seasons. In this study, water samples were collected monthly for one year at five sites in Lake Taihu with different trophic status and a physicochemical analysis and denaturing gradient gel electrophoresis (DGGE) were conducted. DGGE fingerprint analysis showed that Microcystis (7/35 bands) and Synechococcus (12/35 bands) were the two most dominant genera present during the study period at all five sites. Cyanobium (3/35 bands) was the third most common genus which has seldom been previously reported in Lake Taihu. Redundancy analysis (RDA) indicated that the cyanobacterial community structure was significantly correlated with NO-N, COD, and NH-N in the winter and spring, whereas it was correlated with water temperature in the summer and autumn. Limiting the nutrient input (especially of N and C loading) in Lake Taihu would be a key factor in controlling the growth of different genera of cyanobacteria. [ABSTRACT FROM AUTHOR]

Microcystis occurs as colonies in the natural environment but disaggregates into single cells in laboratory cultures. In order to explore the mechanism of how Microcystis forms colonies, the zeta potentials of Microcystis cells from the laboratory and the field were studied, and the hydrophobicity of Microcystis colonies in different sizes was investigated in Lake Taihu. The incubation experiment indicated that the zeta potentials of Microcystis cells were affected by growth phase and species. The absolute values in exponential phase were lower than those in stationary phase, suggesting that the cells with rapid growth easily formed colonies due to more instability on the cell surface. The values of Microcystis aeruginosa were higher than those of Microcystis flos-aquae, which confirmed that M. aeruginosa prevailed in waters for a longer time and at a larger size compared with M. flos-aquae. In another aspect, the absolute zeta potentials of Microcystis spp. at pH 7.0 decreased from spring to autumn in the field; the values in spring were higher than those in summer, suggesting that a large-sized Microcystis colony would more easily form in summer. Additionally, differences in hydrophobicity exist among Microcystis colonies of various sizes. The surface hydrophobicity of colonies in the <20 μm size class was higher than that of larger colonies. This characteristic allowed small colonies to easily form large colonies to survive better. These results would be helpful to understand the mechanism of the bloom formation, especially the colony formation, in Microcystis. [ABSTRACT FROM AUTHOR]

Cyanobacteria can produce toxic metabolites known as cyanotoxins. Common and frequently investigated cyanotoxins include microcystins (MCs), nodularin (NOD) and saxitoxins (STXs). During the summer of 2011 extensive cyanobacterial growth was found in several fishponds in Serbia. Sampling of the water and fish (common carp, Cyprinus carpio ) was performed. Water samples from 13 fishponds were found to contain saxitoxin, microcystin, and/or nodularin. LC–MS/MS showed that MC-RR was present in samples of fish muscle tissue. Histopathological analyses of fish grown in fishponds with cyanotoxin production showed histopathological damage to liver, kidney, gills, intestines and muscle tissues. This study is among the first so far to report severe hyperplasia of intestinal epithelium and severe degeneration of muscle tissue of fish after cyanobacterial exposure. These findings emphasize the importance of cyanobacterial and cyanotoxin monitoring in fishponds in order to recognize cyanotoxins and their potential effects on fish used for human consumption and, further, on human health. [ABSTRACT FROM AUTHOR]

Global warming and eutrophication accelerated Microcystis blooms, causing water quality deterioration. Cyanocides produced by cyanobactericidal bacteria have attracted substantial attention for controlling Microcystis blooms owing to their environmental friendliness. However, their application is still in the early stages, highlighting the need for the discovery of novel cyanocides. Herein, we isolated and purified a novel macrocyclic tambjamine produced by Paucibacter aquatile DH15, named paucibactin A. The cyanocidal activity of paucibactin A (1 μg/mL) against Microcystis (106 cells/mL) was 81.6% after 24 h of exposure. Paucibactin A killed Microcystis by destroying its structural integrity, photosynthetic and antioxidant systems, and macromolecules. The expression of the key genes involved in these fundamental processes in Microcystis was downregulated after paucibactin A treatment. In a microcosm study, paucibactin A (1 μg/mL) exhibited selective cyanobactericidal activity against Microcystis and Dolichospermum but not against other cyanobacteria. However, 87.4% of paucibactin A was degraded by photolysis in 24 h. Cyanobactericidal processes promoted the growth of eukaryotic microalgae, possibly by altering the competitive relationship and inducing changes in the bacterial community and interaction network. Collectively, our findings suggest that paucibactin A could be an effective cyanobactericidal compound for controlling Microcystis and Dolichospermum blooms. [Display omitted] • The first report of a macrocyclic tambjamine with cyanobactericidal activity. • Paucibactin A is a novel cyanocide for controlling both Microcystis and Dolichospermum blooms. • Paucibactin A destroys photosystems and induces oxidative stress in Microcystis. • Paucibactin A is degraded quickly after bloom removal, leaving no secondary pollution. [ABSTRACT FROM AUTHOR]

Cyanobacterial bloom challenges the aquatic ecosystem and ecological restoration is an effective approach for cyanobacterial bloom control, but the change of aquatic community after ecological restoration is still unclear. Dianchi Lake is an eutrophic lake with frequent cyanobacterial blooms in China, and recent ecological restoration projects in Caohai (north part) have a satisfactory performance. In this study, we collected 249 water samples at 23 sites from Dianchi Lake to explore the relationships between water physicochemical variables and aquatic microbial communities. Water physicochemical variables in Waihai (south part) intensively changed along time, whereas those in Caohai did not. Photoautotrophic communities were significantly divergent between Caohai and Waihai. Waihai had a lower diversity of photoautotrophic community, containing higher abundance of Cyanophyceae (89.9%) than Caohai (42.7%). Nutrient level and Cyanophyceae only exhibited strong correlations in Wahai (p < 0.05). Redundancy analysis and microbial ecological network suggested that microbial communities in Caohai had a higher stability. Deterministic process dominated the microbial assembly (50–80% for bacteria and >90% for photoautotrophs), and particularly in Caohai. Our results unraveled that the structure and assembly of bacterial and photoautotrophic communities significantly changed after ecological restoration, offering valuable suggestions that photosynthetic diversity should be focused for other ecological restoration projects. [Display omitted] • Similar bacterial communities between Waihai and Caohai. • Significant difference in photoautotrophs between Waihai and Caohai. • More stochastic processes for microbial assembly in Waihai than Caohai. • Higher microbial stability in Caohai after ecological restoration. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms, usually dominated by Microcystis aeruginosa , pose a serious threat to global freshwater ecosystems owing to their production and release of various harmful secondary metabolites. Detection of the chemicals in M. aeruginosa exudates using metabolomics technology revealed that phytosphingosine (PHS) was one of the most abundant compounds. However, its specific toxicological mechanism remained unclear. CNE-2 cells were selected to illustrate the cytotoxic mechanism of PHS, and it was determined to cause excessive production of reactive oxygen species and subsequently damage the mitochondrial structure. Mitochondrial membrane rupture led to matrix mitochondrial membrane potential disintegration, which induced Ca2+ overload and interrupted ATP synthesis. Furthermore, rupture of the mitochondrial membrane induced the opening of the permeability transition pore, which caused the release of proapoptotic factors into the cytoplasm and the expression of apoptosis-related proteins Bax, Bcl-2, cytochrome-c and cleaved caspase-3 in CNE-2 cells. These events, in turn, activated the mitochondrially mediated intrinsic apoptotic pathway. A mitochondrial repair mechanism, namely, PINK1/Parkin-mediated mitophagy, was then blocked, which further promoted apoptosis. Our findings suggest that more attention should be paid to the ecotoxicity of PHS, which is already listed as a contaminant of emerging concern. [Display omitted] [ABSTRACT FROM AUTHOR]

• Water blooms caused by Cyanobacteria have become more and more frequent. • We assessed the effect of blooms on diversity in hypertrophic shallow lakes. • The species diversity of non-cyanobacteria was not affected negatively by the bloom. • The functional richness and dispersion were only marginally significantly affected. • Applied methods are not sensitive to reflect the diversity of subordinated species. Under increasing pressure of climatic change and anthropogenic eutrophication, water blooms, i.e. the formation of high phytoplankton biomass of a single or a few species, have become more and more frequent in lake ecosystems that is caused mostly by Cyanobacteria. The dynamics of phytoplankton under a cyanobacterial pressure may provide important information about what a competitive advantage of Cyanobacteria have over eukaryotic microalgae. The research, therefore focused on the relationship between cyanobacterial blooms and the accompanying species in hypertrophic shallow lakes where nutrients are in excess. The following hypotheses were selected for testing: i) Cyanobacterial blooms negatively affect the species richness and diversity of phytoplankton assemblages in the studied hypertrophic lakes. ii) Cyanobacterial blooms negatively affect the multi-trait functional diversity of phytoplankton assemblages in the studied hypertrophic lakes. iii) The formation of a cyanobacterial bloom causes a shift in the species and trait composition of phytoplankton assemblages. It was found that the species diversity of non-cyanobacterial assemblages was not affected negatively by increasing density of Cyanobacteria. Cyanobacterial biomass negatively affected the functional richness and functional dispersion of the assemblages, but both relationships were only marginally significant. Some temporal shift was detected in the community weighted mean values of width, colonial ability of accompanying microalgae, and also in flagellatedness and mixotrophic ability. We conclude that Cyanobacterial blooms basically alter dominance relations in the phytoplankton and reduce availability of light in waters. However, it does not necessarily coincide with the elimination of other taxa and reduction their species numbers or diversity. The formerly published data on the decrease in species richness can be likely explained by methodological deficiencies, which are responsible for reduced detectability of species. To better understand the seasonal dynamics and resilience of phytoplankton assemblages in hypertrophic water bodies the development of new methodologies by which diversity and succession of subordinate species can be evaluated is required. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) emission of fresh invertebrates has too long been neglected in eutrophic lakes, although the sediments these animals inhabit are presumably hot spots of N2O emission. Thus, the experiment in this research was designed to gain insight into the influence of cyanobacterial degradation on the N2O emission by fresh water invertebrates (Chironomus plumosus). The presence of decaying cyanobacteria in Lake Taihu decreased the N2O emission rate of Chironomus plumosus larvae from the larvae body by almost 400% for the larvae as a whole. The N2O emission rate decreased by 350% based on readings from studies of their gut, which was mostly due to stimulation of intestinal complete denitrification. The quantitative PCR results showed that intestinal gene abundance of nirK, nosZ (encoding the copper nitrite reductase and N2O reductase, respectively) were significantly increased with the presence of decaying cyanobacteria. In contrast nirS (encoding the cytochrome cd1 heme nitrite reductase) and the total bacteria decreased. In the gut of Chironomus plumosus, the diversity and richness of nosZ and nirK were lower with the cyanobacteria. Phylogenetic analysis of the intestinal function genes (nosZ and nirK) showed that the nosZ- and nirK-type denitrifying bacterial sequences were related to different phylotypes. Hence, additional cyanobacteria increased the abundance, but decreased the richness and diversity of intestinal nitrate-reducing bacteria, probably by providing more carbon source in the gut. The data obtained in this study elucidates that the decaying cyanobacteria decreased the emissions of N2O by the aquatic invertebrates in freshwater sediment and could serve as a valuable resource for nitrogen removal affecting greenhouse gas emissions.

The occurrence of cyanobacterial blooms in summer are frequently accompanied by the succession of phytoplankton communities in freshwater. However, little is known regarding the roles of viruses in the succession, such as in huge reservoirs. Here, we investigated the viral infection characteristics of phytoplankton and bacterioplankton during the summer bloom succession in Xiangxi Bay of Three Gorges Reservoir, China. The results indicated that three distinct bloom stages and two successions were observed. From cyanobacteria and diatom codominance to cyanobacteria dominance, the first succession involved different phyla and led to a Microcystis bloom. From Microcystis dominance to Microcystis and Anabaena codominance, the second succession was different Cyanophyta genera and resulted in the persistence of cyanobacterial bloom. The structural equation model (SEM) showed that the virus had positive influence on the phytoplankton community. Through the Spearman's correlation and redundancy analysis (RDA), we speculated that both the increase of viral lysis in the eukaryotic community and the increase of lysogeny in cyanobacteria may contributed to the first succession and Microcystis blooms. In addition, the nutrients supplied by the lysis of bacterioplankton might benefit the second succession of different cyanobacterial genera and sustain the dominance of cyanobacteria. Based on hierarchical partitioning method, the viral variables still have a marked effect on the dynamics of phytoplankton community, although the environmental attributes were the major factors. Our findings suggested that viruses played multiple potential roles in summer bloom succession and may help the blooms success of cyanobacteria in Xiangxi Bay. Under the background of increasingly serious cyanobacterial blooms worldwide, our study may have great ecological and environmental significance for understanding the population succession in phytoplankton and controlling the cyanobacterial blooms., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Peng, Jiao, Gao, Xiong, Zhao, Yang and Liao.)

The succession amongst different cyanobacteria genera remains understudied and poorly understood as much of the focus has been on mono-specific blooms. The spring-summer succession between Aphanizomenon flos- aquae and Microcystis and its underlying mechanism were investigated from 2009 to 2012 in hypereutrophic Dianchi Lake in China. Regularly, A. flos- aquae grows rapidly and forms bloom in March at water temperatures around 15°C, followed by Microcystis blooming around 18°C in April. Since 2010, the pattern of succession has changed, featuring an increase of Microcystis but decrease of A. flos- aquae biovolume, leading to near disappearance of A. flos- aquae in 2012. Coincidently, there was a sharp increase of nitrogen concentration in 2010, going up to 5.67 mg/l in 2011, and a big increase in the mass ratio of TN to TP from 13.6 in 2009 to 21.1 in 2011. We hypothesized that temperature is the most influential factor governing the initiation of rapid growth and succession between A. flos- aquae and Microcystis, while increase of TN and/or ratio of TN to TP may trigger the decline and disappearance of A. flos- aquae, time of recruitment, and the population dynamics of Microcystis. Our findings are not only meaningful to the understanding of the cyanobacterial bloom mechanism but also to the management of shallow eutrophic lakes. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms occur annually in Lake Taihu, causing large ecological and economic losses. As part of efforts to enhance the strategies explored to control cyanobacterial blooms, an algicidal bacterium, F6, was isolated from Lake Taihu and then identified as a Stenotrophomonas species by 16S rDNA sequence analysis. The results showed that Stenotrophomonas F6 exhibited strong algicidal activity against dominant cyanobacterial bloom-forming species in Lake Taihu, mainly via excretion of extracellular algicidal compounds. The algicidal compounds were subsequently extracted with ethyl acetate, purified by high-performance liquid chromatography (HPLC) and identified as cyclo-(Gly-Pro) and hydroquinone by gas chromatography-mass spectrometry (GC-MS) and H nuclear magnetic resonance (NMR) analysis. Cyclo-(Gly-Pro) exerted a strong algicidal effect against Microcystis aeruginosa 9110 with a 50 % effective concentration (EC) value of 5.9 mg L, but had no algicidal effect on Synechococcus sp. BN60. Hydroquinone showed stronger algicidal activity against both M. aeruginosa 9110 and Synechococcus sp. BN60, with EC values of 0.96 and 5.6 mg L, respectively. Through characterization of algicidal process, the algicidal activity of Stenotrophomonas F6 was found to be dependent on the concentration of algicidal compounds, and the secreted algicidal compounds could be detected only when the cell density of F6 was above a threshold of 2-4 × 10 CFU mL. Taken together, these results suggest that the algicidal bacterium F6 and its two algicidal compounds have the potential for use as bio-agents for controlling cyanobacterial blooms in Lake Taihu. [ABSTRACT FROM AUTHOR]

The bloom-containing water bodies may have an impact due to cyanotoxins production on other microorganisms and aquatic plants. Where such water is being used for crops irrigation, the presence of cyanotoxins may also have a toxic impact on terrestrial plants and their rhizosphere microbiota. For that purpose, PCR-based 454 pyrosequencing was applied to phylogenetically characterize the bacterial community of Medicago sativa rhizosphere in response to cyanotoxins extract. This analysis revealed a wide diversity at species level, which decreased from unplanted soil to root tissues indicating that only some populations were able to compete for nutrients and niches in this selective habitat. Gemmatimonas , Actinobacteria , Deltaproteobacteria and Opitutae mainly inhabited the bulk soil, whereas, the root-adhering soil and the root tissues were inhabited by Gammaproteobacteria and Alphaproteobacteria . The proportion of these populations fluctuated in response to cyanotoxins extract exposure. Betaproteobacteria proportion increased in the three studied compartments, whereas Gammaproteobacteria proportion decreased except in the bulk soil. This study revealed the potential toxicity of cyanotoxins extract towards Actinobacteria , Gemmatimonas , Deltaproteobacteria , and Gammaproteobacteria , however Clostridia , Opitutae and bacteria related with Betaproteobacteria , were stimulated denoting their tolerance. Altogether, these data indicate that crop irrigation using cyanotoxins containing water might alter the rhizosphere functioning. [ABSTRACT FROM AUTHOR]

This study aimed to explain how the changes in certain hydrological, meteorological and physicochemical factors influence the cell density of the cyanobacteria Microcystis aeruginosa in the Nakdong River. Occurrence patterns of M. aeruginosa were analyzed between 1993 and 2010 (N=96) using a selforganizing map. The cell density of M. aeruginosa was sensitive to certain meteorological, hydrological and physicochemical factors. In addition, our clustering analysis results identified specific limnological features under different environmental conditions. Cluster 1 suggested that high rainfall and increased river flow, dam discharge, total phosphorous and phosphate concentrations were associated with low M. aeruginosa cell density (June-July; monsoon season). However, cluster 2 suggested low irradiance since water temperature decreases with irradiation time, and thus low M. aeruginosa cell density (April-June and after November). Finally, cluster 3 was indicative of high water temperature and irradiance, increased irradiation time, low phosphate and nitrate concentrations, and high M. aeruginosa cell density (August, after the monsoon season). Taken together, these results suggest that rainfall, river flow, water temperature and nutrient concentration (i.e., phosphates and nitrates) were the primary factors that affected cyanobacterial bloom occurrence in the Nakdong River. M. aeruginosa blooms can be suppressed by employing an integrated water resource management program that accommodates meteo-hydrological factors along with the effective control of exogenous nutrient sources. [ABSTRACT FROM AUTHOR]

Anthropogenic lake eutrophication can allow toxic cyanobacteria (blue-green algae) to grow uncontrollably, resulting in harmful algal blooms with potentially serious economic and health-related impacts. Development of monitoring methods for predicting bloom events is an important goal of monitoring programs and is one of the fundamental interests to those examining the ecology of aquatic ecosystems. Implementation of new monitoring methods complies with the provisions of national and community laws for the protection and restoration of good chemical and ecological status of water reservoirs and dependent ecosystems, and allows for the fulfilment of obligations of legislation policy of European Union (WFD 2000/60/EC) and Polish Water Law Acts, and The Environmental Protection Law. Our paper investigates a comparison between aerial remote sensing methods and currently used technology, and presents advantages of the proposed monitoring as an accurate, flexible, cheap, and fast method of detecting and predicting eutrophication and therefore cyanobacteria bloom in water reservoirs, taking into account the complexity and dynamics of an ecosystem. The article also states that aerial remote sensing technology represents an innovative tool strongly supporting traditional methods for continuous monitoring application and an early warning system against algal bloom. Therefore, it is reasonable to continue remote sensing methods development in order to precisely determine the cyanobacteria blooms in lakes. It is also necessary to improve satellite algorithms and the use of both satellite images and those taken from unmanned aerial vehicles (UAVs) and manned planes. [ABSTRACT FROM AUTHOR]

In order to get insight into the impacts of UVC/H 2 O 2 on Microcystis aeruginosa , physiological and morphological changes as well as toxicity were detected under different UVC/H 2 O 2 treatments. In the presence of sole UVC or H 2 O 2 , the net oxygen evolution rate decreased significantly ( p < 0.05) since activity of photosystem II (PSII) was inhibited. Meanwhile, increase of intracellular reactive oxygen species (ROS), degradation of microcystin (MC) and ultrastructure destructions were observed. Under sole UVC treatment, no changes happened in the activity of photosystem I (PSI), but the degradation of D1 protein was observed. Under sole H 2 O 2 treatment, an increase of malondialdehyde, aggregation of D1 protein and deformation of the thylakoid membrane were observed. ROS content under H 2 O 2 treatment was about 5 times than that under UVC treatment. Combined use of UVC and H 2 O 2 , as well as 20 mJ cm −2 UVC and 60 μM H 2 O 2 , showed high synergetic effects. Obvious damage to membrane systems, the marked degradation of MC and inhibition of the photosystems were observed. It could be deduced that UVC worked on intracellular membrane components directly and the damaged oxygen-evolving complex, which was followed by the D1 protein degradation. H 2 O 2 oxidised the membrane lipids via an ROS-mediated process, with thylakoid injury and the aggregation of D1 protein being the lethal mechanisms, and both PSII and PSI being the attacking targets. With regard towards the effective inactivation of M. aeruginosa and high removal of MC, UVC/H 2 O 2 proposed a novel practical method in controlling cyanobacterial blooms. [ABSTRACT FROM AUTHOR]