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Cyanobacterial blooms are prevalent globally and present a significant threat to water security. Titanium salt coagulants have garnered considerable attention due to their superior coagulation properties and the absence of metal residue risks. This paper explored the influencing factors in the coagulation process of titanium xerogel coagulant (TXC), the alterations in cell activity during floc storage, and the release of cyanobacterial organic matters, thereby determining the application scope of TXC for cyanobacterial water treatment. The findings indicated that at a TXC dosage of 8 mg Ti/L, the removal rate of Microcystis aeruginosa (M. aeruginosa) exceeded 86% across a pH range of 5–9. The coagulation performance with anions HCO 3 −, CO 3 2− and H 2 PO 4 −/HPO 4 2− was unsatisfactory at concentrations of 10, 20, and 50 mg/L, with corresponding chlorophyll a (Chl-a) levels of 168, 129, and 196 μg/L, respectively. While the presence of Cl−, NO 3 −, SO 4 2−, K+, NH 4 +, Ca2+ and Mg2+ had little influence on the removal efficiency. At sodium alginate (SA) concentration of 6 mg/L, the Chl-a content was 116 μg/L, with humic acid (HA) not affecting M. aeruginosa removal but hindering turbidity reduction, leaving a residual turbidity of 11 NTU. Following TXC treatment, a floc storage study with cyanobacteria-laden surface water showed a decrease in microcystins (MCs) content. The low residual titanium concentration post-TXC coagulation (<0.06 mg/L) and MCs reduction contributed to reduced effluent toxicity, indicating TXC's versatile applicability for treating cyanobacterial-contaminated waters. [Display omitted] • TXC effectively removes Microcystis aeruginosa across a broad pH range. • Common anions reduce Microcystis aeruginosa removal to varying extents. • Polysaccharides impair the removal efficiency of TXC on Microcystis aeruginosa. • Acetylacetone, released from TXC, is capable of removing microcystins. • TXC can serve as an alternative for coagulating cyanobacteria-laden water. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms, which are becoming more frequent in aquatic ecosystems across the globe, pose a significant health threat to the aquatic keystone species, Daphnia magna. Given that D. magna solely rely on innate immunity centered around tumor necrosis factor receptor-associated factor 4 (TRAF4), the aim of this study is to analyze how the TRAF4 gene in D. magna (Dm-TRAF4) participates in the response to cyanobacterial stress. First, TRAF4 sequence was identified bioinformatically in the D. magna genome. Then, Dm-TRAF4 expression levels were measured at different developmental stages of D. magna. Furthermore, the effects of exposure to the toxic cyanobacteria (Microcystis aeruginosa) on Dm-TRAF4 expression was investigated. Structural analysis revealed that Dm-TRAF4 contained several conserved functional domains, including three canonical zinc finger motifs and a MATH domain, indicating its potential role in immune signaling. Moreover, Dm-TRAF4 was evolutionarily more related to the insect sequences than to those of copepods. The expression results showed a significant progressive increase in Dm-TRAF4 expression levels in D. magna from embryonic development to aging stages. Furthermore, when exposed to Microcystis , Dm-TRAF4 expression was markedly downregulated compared to the control. In addition, miR-4443 showed a negative correlation with Dm-TRAF4 expression under the threat of M. aeruginosa in D. magna , indicating that post-transcriptional modification of the TRAF4 gene was involved in D. magna response to M. aeruginosa stress. In conclusion, the current findings provide novel insights into the TRAF4-mediated innate immune response to cyanobacteria pollution in zooplankton. [Display omitted] • The immune-related TRAF4 gene is first characterized in Daphnia magna (Dm-TRAF4). • Cyanobacteria suppress Dm-TRAF4 expression under 6 days of individual exposure. • MiR-4443 expression was negatively with Dm-TRAF4 in cyanobacteria exposure. • The study underscores the importance of TRAF4 in the cyanobacteria immunotoxicity. [ABSTRACT FROM AUTHOR]

The physicochemical properties of aluminum oxide nanoparticles (Al 2 O 3 -NPs or AlNPs) allow them to remain suspended in water for extended periods. Despite this, AlNPs are one of the least studied types of metal nanoparticles and pose a significant risk to aquatic ecosystems. Therefore, it is essential to understand the toxic mechanisms of AlNPs on microalgae and cyanobacteria, as they can have adverse effects on the entire aquatic food web. Our research aimed to assess the toxicity of continuous exposure to low environmentally relevant concentrations of AlNPs on the growth rate, photosynthetic activity, oxidative stress (ROS), and microcystin production (MC-LR) in a phytoplanktonic community (PCC) consisting of Scenedesmus armatus and Microcystis aeruginosa. Both single and community cultures were exposed to 1.0 μg mL-1 AlNPs for 28 days. The results showed a significant 20–40% inhibition of S. armatus population growth in both individual and community cultures after 28 days of exposure. In contrast, M. aeruginosa exhibited increased survival and cell division rates when exposed to nanoparticles, both individually and within the community. Additionally, S. armatus showed a substantial reduction in gross photosynthesis (Pg) and net photosynthesis (Pn), with less inhibition in respiration (R) after 28 days of exposure. Conversely, M. aeruginosa demonstrated higher rates of photosynthetic productivity in all three parameters (Pg, Pn, and R). In the PCC, respiration was inhibited from 14 to 28 days, and both Pg and Pn were also inhibited. Both S. armatus and M. aeruginosa showed 28–31% levels of ROS generation, while the phytoplanktonic community exhibited no significant ROS production. Moreover, the production and release of MC-LR decreased by 8–38% in M. aeruginosa compared to the control strain. These findings underscore the importance of monitoring the use and application of nanomaterials to mitigate their potential toxic effects on aquatic ecosystems. [Display omitted] • Long-term AlNPs exposure oppositely modified μ and photosynthetic balance in both strains. • Pg, Pn and R were similarly oppositely modified by long-term AlNPs exposure in both strains. • Long-term AlNPs exposure on bicultures gives competitive advantage to M. aeruginosa in μ and photosynthetic activity. • ROS production increased in both strains exposed to AlNPs for 28 days but decreased in bicultures. • Exposure to AlNPs for 28 days did not change either MC-LR production or release, but increased in bicultures. [ABSTRACT FROM AUTHOR]

The toxicity of triclosan (TCS) to various aquatic organisms has been demonstrated at environmental concentrations. However, the effects and mechanisms of TCS on toxic cyanobacteria remains largely unexplored. This study investigated the physiological and molecular variations in two representative toxic Microcystis species (M. aeruginosa and M. viridis) under exposure to TCS for 12 d. Our findings demonstrated that the median effective concentration (EC 50) of TCS for both Microcystis species were close to the levels detected in the environment (M. aeruginosa : 9.62 μg L−1; M. viridis : 27.56 μg L−1). An increased level of reactive oxygen species (ROS) was observed in Microcystis , resulting in oxidative damage when exposed to TCS at concentrations ranging from 10 μg L−1 to 50 μg L−1. The photosynthetic activity of Microcystis had a certain degree of recovery capability at low concentrations of TCS. Compared to M. aeruginosa , the higher recovery capability of the photosynthetic system in M. viridis would be mainly attributed to the increased ability for PSII repair and phycobilisome synthesis. Additionally, the synthesis of microcystins in the two species and the release rate in M. viridis significantly increased under 10–50 μg L−1 TCS. At the molecular level, exposure to TCS at EC 50 for 12 d induced the dysregulation of genes associated with photosynthesis and antioxidant system. The upregulation of genes associated with microcystin synthesis and nitrogen metabolism further increased the potential risk of microcystin release. Our results revealed the aquatic toxicity and secondary ecological risks of TCS at environmental concentrations, and provided theoretical data with practical reference value for TCS monitoring. [Display omitted] • Triclosan inhibited the growth and of Microcystis at environmental concentrations. • Triclosan induced dysregulation of genes related to photosynthetic system. • Antioxidant system systems were activated by triclosan. • Triclosan induced increase of microcystins (MCs) synthesis genes and MCs production. [ABSTRACT FROM AUTHOR]

In the present study, algicidal bacteria cultivated in an aqueous medium were utilized as a surface modification agent to develop an efficient adsorbent for the removal of Microcystis aeruginosa. The modification considerably enhanced M. aeruginosa cell removal efficiency. Moreover, the introduction of bio-compounds ensured specificity in the removal of M. aeruginosa. Additionally, the cyanotoxin release and acute toxicity tests demonstrated that the adsorption process using the developed adsorbent is environmentally safe. Furthermore, the practical feasibility of the adsorptive removal of M. aeruginosa was confirmed through cell removal tests performed using the developed adsorbent in a scaled-up reactor (50 L and 10 tons). In these tests, the effects of the adsorbent application type, water temperature, and initial cell concentration on the M. aeruginosa removal efficiency were evaluated. The results of this study provide novel insights into the valorization strategy of biological algicides repurposed as adsorbents, and provide practical operational data for effective M. aeruginosa removal in scaled-up conditions. [Display omitted] • Bacterial bio-compound was utilized as surface modifier for cotton adsorbent. • M. aeruginosa adsorption rate of bio-compound modified adsorbents was increased. • Surface modification of bio-compound increased selectivity for M. aeruginosa control. • Operation factor in adsorption process using developed adsorbent was investigated. • Harmful algal blooms adsorption process using developed adsorbent was environmentally safe. [ABSTRACT FROM AUTHOR]

Harmful cyanobacterial bloom is one of the serious environmental problems worldwide. Microcystis aeruginosa is a representative harmful alga in cyanobacteria bloom. It is of great significance to develop new technologies for the removal of Microcystis aeruginosa and microcystins. The feasibility and mechanism of removing microcystis aeruginosa and degrading microcystins by dielectric barrier discharge (DBD) plasma were studied. The suitable DBD parameters obtained in this study are DBD (41.5 W, 40 min) and DBD (41.5 W, 50 min), resulting in algae removal efficiency of 77.4% and 80.4%, respectively; scanning electron microscope and LIVE-DEATH analysis demonstrate that DBD treatment can disrupt cell structure and lead to cell death; analysis of elemental composition and chemical state indicated that there are traces of oxidation of organic nitrogen and organic carbon in microcystis aeruginosa ; further intracellular ROS concentration and antioxidant enzyme activity analysis confirm that DBD damage microcystis aeruginosa through oxidation. Meanwhile, DBD can effectively degrade the microcystin-LR released after cell lysis, the extracellular microcystin-LR concentration in the DBD (41.5 W) group decreased by 88.7% at 60 min compared to the highest concentration at 20 min; further toxicity analysis of degradation intermediates indicated that DBD can reduce the toxicity of microcystin-LR. The contribution of active substances to the inactivation of microcystis aeruginosa is e aq − > • OH > H 2 O 2 > O 3 > 1O 2 > • O 2 − > ONOO − , while on the degradation of microcystin-LR is e aq − > • OH > H 2 O 2 > O 3 > • O 2 − >1O 2 > ONOO −. The application of DBD plasma technology in microcystis aeruginosa algae removal and detoxification has certain prospects for promotion and application. [Display omitted] • DBD can efficiently remove microcystis aeruginosa. • DBD can degrade microcystin-LR and reduce its toxicity. • Contributions of functional substances (e－aq,.•OH, H 2 O 2 , O 3 , 1O 2, •O－2 and QUOTE ONOO−) were demonstrated. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms can impair drinking water quality due to the concomitant extracellular organic matter (EOM). As copper is often applied as an algicide, cyanobacteria may experience copper stress. However, it remains uncertain whether algal growth compensation occurs and how EOM characteristics change in response to copper stress. This study investigated the changes in growth conditions, photosynthetic capacity, and EOM characteristics of M. aeruginosa under copper stress. In all copper treatments, M. aeruginosa experienced a growth inhibition stage followed by a growth compensation stage. Notably, although chlorophyll-a fluorescence parameters dropped to zero immediately following high-intensity copper stress (0.2 and 0.5 mg/L), they later recovered to levels exceeding those of the control, indicating that photosystem II was not destroyed by copper stress. Copper stress influenced the dissolved organic carbon (DOC) content, polysaccharides, proteins, excitation–emission matrix spectra, hydrophobicity, and molecular weight (MW) distribution of EOM, with the effects varying based on stress intensity and growth stage. Principal component analysis revealed a correlation between the chlorophyll-a fluorescence parameters and EOM characteristics. These results imply that copper may not be an ideal algicide. Further research is needed to explore the dynamic response of EOM characteristics to environmental stress. [Display omitted] • Compensatory growth of M. aeruginosa was confirmed following exposure to copper stress. • Post-copper stress, M. aeruginosa 's chlorophyll-a fluorescence surpassed control. • Low copper concentration (0.05 mg/L) enhance short- and long-term EOM content. • EOM characteristics of M. aeruginosa varied with copper stress intensity and the specific growth stage. [ABSTRACT FROM AUTHOR]

The increasing occurrence of harmful algal blooms (HABs) in freshwater ecosystems detrimentally affect global water environments. Zooplankton's role in controlling HABs is hindered by contaminant exposure, necessitating research into combined stressors' ecological impacts. The response of Daphnia , a freshwater keystone species, to environmental stressors can be influenced by its maternal effects. Here, we investigated the combined effects of the world-widely used insecticide spinetoram and non-toxic HABs species Microcystis aeruginosa on the life-history traits of D. pulex offspring produced from different maternal food conditions. Four maternal groups were established, with each group receiving a specific blend of C. vulgaris (Ch) and M. aeruginosa (Ma) in varying proportions: A (100% Ch), B (90% Ch + 10% Ma), C (80% Ch + 20% Ma), and D (70% Ch + 30% Ma). The offspring from the third brood were gathered, and a 21-day experiment was carried out, involving various feeding groups (AA, AD, BA, BB, CA, CC, DA, and DD). Results demonstrated that grazing on M. aeruginosa by D. pulex induced maternal effects on their offspring, with the continuous exposure group showing an enhanced tolerance to M. aeruginosa. This study also unveiled that spinetoram could interfere with the molting of D. pulex , leading to developmental retardation. The Recovery Group exhibited an intriguing phenomenon: under the influence of both concentrations of the pesticide spinetoram (0.18, 0.35 μg L−1), D. pulex produced more offspring. This might be due to a combined strategy of allocating more energy towards reproduction in response to low-quality food and a potential hormetic effect from low concentrations of spinetoram. Assessing the interplay of combined stressors across multiple generations, encompassing harmful algal blooms (HABs) and environmental pollutants, is essential for predicting population responses to evolving environmental conditions. This understanding is vital for the protection and management of aquatic environments and ecosystems. [Display omitted] • Daphnia pulex grazing on Microcystis aeruginosa shows maternal effects on offspring. • Multigenerational continuous exposure increases the tolerance to M. aeruginosa. • M. aeruginosa and spinetoram jointly affect D. pulex 's survival and development. • Low spinetoram concentrations hinders D. pulex molting but enhance reproduction. [ABSTRACT FROM AUTHOR]

Harmful algal blooms (HABs) due to eutrophication are becoming a serious ecological disaster worldwide, threatening human health and the optimal balance of aquatic ecosystems. The traditional approaches to eradicate HABs yield several drawbacks in practical application, while microbial algicidal technology is garnering mounting recognition due to its high efficiency, eco-friendliness, and low cost. In our previous study, we isolated a bacterium strain Raoultella sp. S1 from eutrophic water with high efficiency of algicidal properties. This study further investigated the flocculation and inactivation efficiency of S1 on Microcystis aeruginosa at different eutrophic stages by customizing the algal cell densities. The supernatant extract of S1 strain exhibited remarkable flocculation and inactivation effects against low (1 × 106 cell/mL)and medium (2.7 × 106 cell/mL)concentrations of algal cells, but unexceptional for higher densities. The results further revealed that algal cells at low and medium counts manifested a more apparent antioxidant defense response, while the photosynthetic efficiency and relative electron transport rate were considerably reduced within 24 h. TEM observations confirmed the disruption of thylakoid membranes and cell structure of algal cells by algicidal substances. Moreover, TMT proteomics revealed alterations in protein metabolic pathways of algal cells during the flocculation and lysis stages at the molecular biological level. This signified that the disruption of the photosynthetic system is the core algicidal mechanism of S1 supernatant. In contrast, the photosynthetic metabolic pathways in the HABs were significantly upregulated, increasing the energy supply for the NADPH dehydrogenation process and the upregulation of ATPases in oxidative phosphorylation. Insufficient energy provided by NADPH resulted in a dwindled electron transport rate, stagnation of carbon fixation in dark reactions, and blockage of light energy conversion into chemical energy. Nonetheless, carbohydrate metabolism (gluconeogenesis and glycolysis) proteins were down-regulated and hampered DNA replication and repair. This study aided in unveiling the bacterial management of eutrophication by Raoultella sp. S1 and further arrayed the proteomic mechanism of algal apoptosis. [Display omitted] • The algicidal effect of Raoultella sp. S1 supernatant for different concentrations of algal cultures was investigated. • The oxidative stress response was least significant in the high-concentration algal culture. • Different concentrations of algal solutions varied in the degree of antioxidant response. • TMT proteomics reveals changes of differential proteins during flocculated and lysed stage. • Damage to the photosynthetic system promotes algal cell apoptosis. [ABSTRACT FROM AUTHOR]

The ecological risks of antibiotics in aquatic environments have raised great concerns worldwide, but the chronic effect of antibiotic contaminants on cyanotoxin production and release remains unclear. This study investigated the long-term combined effects of spiramycin (SP) and ampicillin (AMP) on microcystin (MC) production and release in both unicellular and colonial Microcystis aeruginosa (MA) through semi-continuous exposure test. At exposure concentration of 300 ng L−1, MA growth rates were stimulated till the end of exponential phase accompanied with the up-regulation of photosynthesis-related gene. The exponential growth phases of unicellular and colonial MA were prolonged for 2 and 4 days, respectively. The stimulation rate of growth rate and MC content in unicellular MA were significantly higher than that in colonial MA. The highest concentrations of intracellular MC (IMC) and extracellular MC (EMC) were observed in the binary mixture at equivalent SP/AMP ratio (1:1). The promotion of IMC concentration was in consistent with the stimulated expression of MC-synthesis-related gene and nitrogen-transport-related gene. The malondialdehyde content and activities of superoxide dismutase and catalase in unicellular MA were significantly higher than those in colonial MA. The EMC concentration and the antioxidant responses of both unicellular and colonial MA significantly increased with exposure time. Long-term exposure to mixture of SA and AMP at environmentally relevant concentrations would aggravate the disturbance to aquatic ecosystem balance through the stimulation of MA proliferation as well as the promotion of MC production and release. Image 1 • Stimulated M. aeruginosa growth rate and extended exponential phase were observed. • Higher MC production and release could be related to greater combined toxicity. • Long-term exposure to target antibiotics elevated MC-productivity at genetic level. • Stronger cellular antioxidant defense in colonial MA led to lower MC release. • MC release increased with exposure time due to retarded oxidative membrane damage. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (HP) is a feasible algicide to control cyanobacterial blooms, but its application in the waters with strong reductive power is still a problem. The rapid decomposition rate of HP results in a short residence time in the waters, which renders the failure of bloom mitigation. In this study, the damage of Microcystis aeruginosa (M. aeruginosa) by HP, the optimization method for Microcystis bloom control and its field effects were investigated. Results of microcosm experiments indicated M. aeruginosa was vulnerable to HP. The HP-induced damage was mainly attributed to the impairments of HP detoxification pathways and photosystem. Repetitive additions of HP, which could prolong the residence time, were conducted in the mesocosm experiments. HP concentration ranged from 96 μM to 165 μM for 2 h could successfully mitigate Microcystis bloom, even though HP decomposition rate reached 109 μM per h. Besides the removal of M. aeruginosa , contents of total dissolved nitrogen, total dissolved phosphate, dissolved organic carbon and chromophoric dissolved organic matter in water column increased significantly (p < 0.05). The enrichment of nutrients promoted the growth of chlorophytes but the growth of M. aeruginosa couldn't be observed. The dominant species thrived in the HP-treated waters was Chlamydomonas sp. Results in this study confirmed that HP was a promising algicide for cyanobacterial blooms control. The optimization method further demonstrated that repetitive additions of HP could favor the mitigation of cyanobacterial blooms. • H 2 O 2 is a feasible algaecide in mitigating Microcystis bloom. • Repetitive additions of H 2 O 2 can favor the bloom control. • Enrichment of nutrients after H 2 O 2 treatment promotes the growth of chlorophytes. [ABSTRACT FROM AUTHOR]

Abstract Microcystis aeruginosa can cause harmful algal blooms in freshwaters worldwide. It has already seriously affected human lives and prevented the use of water resources. Therefore, there is an urgent need to develop ecofriendly and effective methods to control and eliminate M. aeruginosa in aquatic environments. In this study, Halobacillus sp. strain H9, a bacterium that showed high M. aeruginosa flocculation activity, was isolated and selected to assess its potential for the removal of M. aeruginosa. The analyses of flocculation activity and mode indicated that the strain H9 induced M. aeruginosa flocculation by secreting active flocculating substance rather than by directly contacting algal cells. A 5% concentration of the H9 supernatant could efficiently flocculate M. aeruginosa cells with a density of up to 5 × 107 cells/mL. Dramatic increases in the zeta potential indicated that charge neutralization could be the mechanism of the flocculation process. The strain H9 flocculated M. aeruginosa with no damage to the algal cell membrane, and did not result in microcystin being released into the surrounding environment. The flocculated algal culture was less toxic to zebrafish larvae, suggesting an environmentally friendly benefit of the H9 supernatant. In addition to M. aeruginosa, the H9 strain was also able to flocculate two other species causing harmful algal blooms, Phaeocystis globose and Heterosigma akashiwo. Furthermore, the flocculation activity of the H9 supernatant was stable at different temperatures and over a wide pH range. These characteristics give the H9 strain great potential for mitigating the influences of harmful algal blooms. Graphical abstract Image 1 Highlights • Strain H9 could remove Microcystis aeruginosa cells effectively by bioflocculation. • The flocculation properties include thermal, pH stability and no extra additive. • Flocculating effect is caused by neutralization of algal cell surface charge. • Flocculated M. aeruginosa culture supernatant is less toxic to zebrafish larvae. [ABSTRACT FROM AUTHOR]

In the present study, to remove harmful cyanobacterial species Microcystis aeruginosa from aqueous phases, adsorption-based strategy was utilized. For this strategy, the surface of cotton fiber was modified using chitosan molecules to develop a highly efficient and ecofriendly adsorbent in removal of Microcystis aeruginosa from aqueous solution. The pristine cotton fiber could not remove M. aeruginosa , while the chitosan-modified cotton (CS-m-Cotton) showed the 95% of cell removal efficiency within 12 h. The surface characteristics of chitosan-modified cotton compared to the pristine cotton fiber was examined by various surface analysis methods. In addition, the pre-treatment of pristine cotton using sodium hydroxide solution was an important factor for enhancement of chitosan modification efficiency on the cotton fiber. The developed chitosan-modified cotton fiber could be reusable for M. aeruginosa cell removal after the simple desorption treatment using ultrasonication in alkaline solution. During the repeated adsorbent regeneration and reuse, the chitosan-modified cotton maintained its M. aeruginosa removal efficiencies (>90%). From the acute toxicity assessment using the chitosan-modified cotton and, the measurements of chemical oxygen demand and microcystin level changes in the M. aeruginosa treatment process using the adsorbent, the environmental safety of the adsorption strategy using the developed adsorbent could be confirmed. Based on our results, the chitosan-modified cotton fiber could be proposed as an efficient and ecofriendly solution for remediation of harmful cyanobacterial species occurring water resources. [Display omitted] • Chemical free adsorbent can be fabricated by chitosan coating on the cotton fiber. • Fabricated CS-m-Cotton showed the high M. aeruginosa removal efficiency. • NaOH solution pretreatment of cotton improves chitosan modification efficiency. • CS-m-cotton could be reused five times for cell treatment even without crosslinking. • CS-m-cotton is non-toxic, and did not increase the COD and cyanotoxin levels. [ABSTRACT FROM AUTHOR]

In recent years, photocatalytic technology has been increasingly used for the treatment of algal blooms in water bodies due to its high efficiency and environmental advantages. However, conventional semiconductor materials suffer from high electron-hole recombination rate, low carrier mobility and weak surface adsorption ability, which made their photocatalytic performance limited. Therefore, the photocatalytic performance of the composites can be improved by coupling another semiconductor material to form a heterojunction to accelerate electron transfer. In this study, a novel composite Ag 3 VO 4 /BiVO 4 (ABV) photocatalyst was successfully prepared by in-situ deposition method for the photocatalytic inactivation of Microcystis aeruginosa (M. aeruginosa) under visible light. The photocatalyst showed excellent photocatalytic activity, and the degradation rate of M. aeruginosa chlorophyll a was up to 99.8% within 4 h under visible light. During the photocatalytic degradation, the morphology of algae cells, the permeability of cell membrane, the organic matter inside and outside the cells, the antioxidant system and the soluble protein were seriously damaged. Moreover, three cycle experiments showed that the prepared ABV photocatalyst had high reusability. Finally, a possible mechanism of M. aeruginosa inactivation was proposed. In general, the synthesized ABV photocatalyst can effectively inactivate cyanobacteria under visible light and provided a new method for M. aeruginosa removal in water. [Display omitted] • Synthesis of Ag 3 VO 4 /BiVO 4 photocatalyst with a simple in situ deposition method. • 99.8% efficiency in photocatalytic algae inactivation was achieved within 4 h. • Ag 3 VO 4 /BiVO 4 was proven to be a highly stable photocatalyst by cycling experiments. • Possible photocatalytic mechanisms of algal removal by Ag 3 VO 4 /BiVO 4 were proposed. [ABSTRACT FROM AUTHOR]

Thallium (Tl) is a priority pollutant regulated by the US EPA. It is also a critical element commonly used in high technology industries; with an increasing demand for semiconductors nowadays, wastewater discharges from manufacturing plants or metal mining activities may result in elevated levels of thallium in receiving water harming aquatic organisms. Regarding the impact of thallium on freshwater algae, little attention has been paid to prokaryotic physiology through various exposure periods. In this bench-scale study, prokaryotic alga Microcystis aeruginosa PCC 7806 was cultured in modified BG11 medium and exposed to Tl+ (TlNO 3) ranging from 250 to 1250 μg/L for 4 and 14 days. Throughout the experiment using flow cytometry assays, algal population, cell membrane integrity, oxidation stress level, and chlorophyll fluorescence were exacerbated following the exposure to 750 μg Tl/L (approximately 4-day effective concentration of Tl+ for reducing 50% of algal population). Potassium and humic acid (HA) (1–5 mg/L) were added to study their influences on the thallium toxicity. With the additions of potassium, thallium toxicities to algal population and physiology were not significantly changed within 4 days, while they were alleviated within 14 days. With the addition of HA at 1 mg/L, cell membrane integrity was significantly attenuated within 4 days; ameliorating effects on algal population and oxidative stress were not observed until day 14. Thallium toxicities on oxidative stress level and photosynthesis activity were exacerbated in the presence of HA at 3–5 mg/L. The study provides useful information for further studies on the mode of toxic action of Tl+ in prokaryotic algae; it also demonstrates the necessity of considering short and long-term exposure durations while incorporating water chemistry into assessment of thallium toxicity to algae. [Display omitted] • Thallium (Tl+) toxicity to prokaryotic alga (cyanobacterium) Microcystis aeruginosa. • Algal population and physiology over 4 and 14-days Tl+ exposures were investigated. • Influences of K+ and humic acid (HA) on Tl+ toxicity varied with exposure time. • Tl + toxicity to algal population was alleviated by long-term exposures to K+ and HA. • Tl + toxicity to some algal physiology was exacerbated by K+ and HA. [ABSTRACT FROM AUTHOR]

Abstract Microcystis aeruginosa is a primary species of toxin-producing cyanobacteria. This study explored the effects of short-term exposure (96 h) to M. aeruginosa on the intestinal microflora variation and immune function of zebrafish. After exposure to different cell concentrations of M. aeruginosa , marked histological variation was observed in the intestine, such as goblet cells proliferation and intestinal desquamation. In addition high-concentration M. aeruginosa treatment (initial concentration: 1.59 × 105 cells mL−1) induced a significant increase in cytokine levels compared with other groups. Low-concentration M. aeruginosa treatment (initial concentration: 0.88 × 105 cells mL−1) promoted the transcription of inflammatory genes, while high-concentration treatment restrained the transcription of these genes. Moreover, M. aeruginosa exposure also changed the intestinal microbial diversity. At the phylum level, bacteria belonging to Proteobacteria were the most abundant in all groups, and Gammaproteobacteria were the dominant bacteria with major changes. Pathogenic microorganisms such as Shewanella, Plesiomonas, Halomonas, Pseudomonas, and Lactobacillus increased greatly after treatment with different cell concentrations of M. aeruginosa. This study indicates that M. aeruginosa induces an increase in zebrafish goblet cells and enhances the inflammatory response, which may produce detrimental effects in zebrafish, resulting in a greater proportion of pathogenic bacteria and intestinal injury. The results of this study will help improve the understanding of the effects of M. aeruginosa on the intestines of aquatic organisms. Highlights • M. aeruginosa exposure increased the number of goblet cells in zebrafish intestine. • M. aeruginosa exposure caused intestinal inflammation in zebrafish. • M. aeruginosa exposure increased the abundance of pathogenic microorganisms in zebrafish intestine. [ABSTRACT FROM AUTHOR]

Abstract Environment-friendly algaecides based on allelopathy have been extensively studied to control harmful algal blooms (HABs). The inhibitory effects of linoleic acid (LA) sustained-release microspheres on different cell densities of Microcystis aeruginosa (M. aeruginosa) at different growth phases were studied. The results showed that the growth of M. aeruginosa could be inhibited within 4 days and the constant inhibitory rate with initial algal density of 8 × 105 cells∙mL−1 (exponential phase) was up to 96% compared with control. The chlorophyll-a content in the treatment group had the same change trend with the algal density and declined significantly at day 20th, which suggested that the microspheres could promote the degradation of chlorophyll-a. The activities of superoxide dismutase (SOD) and catalase (CAT) increased gradually within 5 days but then declined sharply, which indicated that LA microspheres could cause oxidative damage to M. aeruginosa during the process of inhibition and reduce the activities of antioxidant enzymes. In addition, the concentration of oxygen free radical (O 2 −) increased at day 10th and rose constantly, and the content of malodialdehyde (MDA) increased to 2.7 times as much as control at day 20th. Furthermore, the content of protein, nucleic acid and the conductivity in culture solution showed a significant rise. These results showed that algal cell membrane lipid peroxidation occurred and the membrane permeability increased, accompanied by the damage of cell membrane. To sum up, the destruction of algal cell membrane is the main mechanism of LA microspheres inhibiting algal growth. [ABSTRACT FROM AUTHOR]

Abstract H 2 O 2 has been suggested and applied as effective algaecide for harmful cyanobacterial bloom control, however, the transport of exogenous H 2 O 2 into microalgal cells, the subsequent intracellular damage pathway and dose-response variations were little studied. We addressed these questions in a bloom-forming cyanobacterium Microcystis aeruginosa with H 2 O 2 at 0.1–1.5 mM. The results showed that H 2 O 2 at 0.4 mM and above significantly suppressed M. aeruginosa growth for over two weeks, and induced apoptosis-like death in terms of membrane potential dissipation, caspase-3 activation, chromatin condensation, and lysis induction. However, the dose-response effects were not monotonic. H 2 O 2 at 0.7 mM resulted in the severest growth suppression among 0.1–1.5 mM treatments, including the lowest biomass for 74% loss, the highest cell lysis ratio for 79%, and the highest utilization rate of H 2 O 2 for 0.101 mM d−1. Moreover, several evidence point to severer apoptosis-like cell death in 0.7 mM treatments, involving fastest and severest cell lysis, smallest cell size and wrinkled surface and lowest membrane potential. Therefore, the apoptosis-like cell death induced by H 2 O 2 at moderate dosages should be a crucial cause for the non-monotonic dose-response effects on growth suppression. Additionally, intracellular H 2 O 2 level increased rapidly within 20 min after exposure at 0.4 mM and above, directly confirming the transport of exogenous H 2 O 2 into M. aeruginosa cells and the intracellular damages due to subsequent elevation in intracellular oxidative stress. The study demonstrates that H 2 O 2 at moderate dosages could be a promising method for the biomass control, in a fast and efficient way, on M. aeruginosa blooms. Graphical abstract Image 1 Highlights • H 2 O 2 -induced growth suppression on Microcystis was non-monotonic dose-dependent. • H 2 O 2 at moderate dosages induced significant apoptosis-like cell death. • The treatments at H 2 O 2 moderate dosages had a higher utilization efficiency for H 2 O 2. • Exogenous H 2 O 2 was transported into cell and induced intracellular oxidative damage. • Our work is helpful to enhance efficiency in Microcystis bloom control using H 2 O 2. [ABSTRACT FROM AUTHOR]

Abstract The study provided an algal treatment to achieve dual function with antibiotic elimination and CO 2 fixation simultaneously. Two widely used antibiotics, cefradine and amoxicillin were selected as the target compounds. First of all, we assessed the influence of light intensity on algal growth and antibiotic removal efficiency to obtain the optimal light intensity. Secondly, after the algal antibiotic treatment, the CO 2 capture capacities at varied CO 2 volume concentrations were assessed and compared. Significant improvement in the removal efficiency of cefradine occurred when CO 2 was added into the treatment. Change in the content of photosynthetic pigments and the activities of RuBisCO and carbonic anhydrase occurred as the algal responses to the treatment condition. Our results showed that Chlorella pyrenoidosa performed better than Microcystis aeruginosa in both the antibiotic removal efficiency and the CO 2 capture capacity. In the integrated algal treatment, the remove rate of antibiotic has been improved by 30.16% and at the same time, the CO 2 absorption rate has been promoted by 10.94%. Metabolite analyses also revealed the mechanism involved, which proved the crucial role of the algae in the biodegradation of the target antibiotic. Graphical abstract Image 1 Highlights • Antibiotic removal and CO 2 fixation could be achieved simultaneously. • Added CO 2 improved antibiotic removal efficiency in algal treatment. • Photosynthetic pigments and enzymes activity were enhanced in C. pyrenoidosa. • Metabolite analyses proved the crucial role of the algae in biodegradation. [ABSTRACT FROM AUTHOR]

Abstract Microcystins (MCs) are hepatotoxins that have been considered to be a worldwide problem due the effects that they can cause to environmental and human health systems. The Iraí Reservoir, located in the South of Brazil, is used as a water supply and MCs concentrations have been reported in this ecosystem. This study aimed to determine the MCs concentrations in the Iraí Reservoir and to evaluate the MCs depuration time and the health of Geophagus brasiliensis using biomarkers. Water and fish samples were collected in the Iraí Reservoir from August 2015 to May 2016. Phytoplankton and chemical analyses were conducted using water samples and the fish were divided into two groups; the Immediate Group (IMM) and the Depuration Group (DEP). In the IMM group, the blood, liver, muscle, brain and gills were collected, in order to evaluate the genotoxic, biochemical and chemical biomarkers. The DEP group was used in the depuration experiment for 90 days, and after this period the fish were submitted to the same procedure as the IMM group. Our results suggested that fish accumulated MCs and it may have caused oxidative stress, neurotoxicity and molecular damage. Furthermore, MCs concentrations increased during the depuration time and it resulted in molecular damage over the first 30 days. After 90 days, the recovery of the antioxidant system occurred. The depuration started on the 15th day, however, the toxins were still present in the samples. Therefore, the effects and the persistence of MCs are a risk to environmental systems and human health. Highlights • The Iraí Reservoir is contaminated by Microcystins (MCs). • Fish have accumulated MCs above the established limit for human consumption. • Neurotoxicity, oxidative stress, molecular and liver damage were observed in fish. • A recovery of the antioxidant system and molecular damage was present 90 days after. • After the depuration time, MCs were still detected in the muscles of the fish. [ABSTRACT FROM AUTHOR]

Iron is an important trace element in algal growth and water eutrophication. This study focused on the ultrafiltration (UF) membrane fouling mechanism by the intracellular organic matter (IOM) of Microcystis aeruginosa under different iron treatments. The results indicated that the membranes experienced faster flux decline and worse fouling reversibility when the IOM formed under low iron concentrations. In contrast, less IOM membrane fouling was found under normal and high iron concentrations. The mass balances of the dissolved organic carbon (DOC) content implied that the IOM in the low-iron treatment was associated with higher IOM retention and a higher capacity of reversibly deposited organics, whereas more IOM in the high-iron treatment passed through the UF membrane. The IOM in the low-iron treatment was composed of more biopolymer macromolecules, whereas the IOM in the high-iron treatment contained more UV-absorbing hydrophobic organics. The fluorescence excitation-emission matrix (EEM) spectra coupled with peak-fitting analysis implied that the fouling associated with protein-like components was more irreversible in the low-iron treatment than those in the normal- and high-iron treatments. Cake formation combined with intermediate blocking was identified as the main membrane fouling mechanism responsible for the flux decline caused by IOM solutions in the three iron treatments in this study. [ABSTRACT FROM AUTHOR]

Cyanobacterial bloom causes the release of algal organic matter (AOM), which inevitably affects the treatment processes of natural organic matter (NOM). This study works on treating micro-polluted surface water (SW) by emerging coagulant, namely titanium sulfate (Ti(SO 4 ) 2 ), followed by Low Pressure Ultrafiltration (LPUF) technology. In particular, we explored the respective influence of extracellular organic matter (EOM) and intracellular organic matter (IOM) on synergetic EOM-NOM/IOM-NOM removal, functional mechanisms and subsequent filtration performance. Results show that the IOM inclusion in surface water body facilitated synergic IOM-NOM composite pollutants removal by Ti(SO 4 ) 2 , wherein loosely-aggregated flocs were produced, resulting in floc cake layer with rich porosity and permeability during LPUF. On the contrary, the surface water invaded by EOM pollutants increased Ti(SO 4 ) 2 coagulation burden, with substantially deteriorated both UV 254 -represented and dissolved organic matter (DOC) removal. Corresponded with the weak Ti(SO 4 ) 2 coagulation for EOM-NOM removal was the resultant serious membrane fouling during LPUF procedure, wherein dense cake layer was formed due to the compact structure of flocs. Although the IOM enhanced NOM removal with reduced Ti(SO 4 ) 2 dose and yielded mitigated membrane fouling, larger percentage of irreversible fouling was seen than NOM and EOM-NOM cases, which was most likely due to the substances with small molecular weight, such as microcystin, adhering in membrane pores. This research would provide theoretical basis for dose selection and process design during AOM-NOM water treatment. [ABSTRACT FROM AUTHOR]

Previous studies have found that pre-oxidation of manganese salts such as potassium permanganate and potassium manganate can remove algae in water, while existing problems such as excessive oxidation and appearance of chromaticity. In this study, our objective was to induce a Fenton-like reaction by activating sodium percarbonate (SPC) with divalent manganese (Mn(II)) to pre-oxidize algae-contaminated water. The optimal dosage of Mn(II)/SPC was determined by assessing the zeta potential of the algae and the residual Mn(II) in the solution. Moreover, we conducted a characterization of the cells post-reaction and assessed the levels of dissolved organic carbon (DOC). The disinfection by-products (DBPs) (sodium hypochlorite disinfection)of the algae-containing water subsequent to Mn(II)/SPC treatment were measured. Experiments show that Mn(II)/SPC pre-oxidation at optimal dosage acquired 88% removal of algae and less damage to the cell membrane. Moreover, the Mn(II) acted not only as a catalyst but also formed MnO 2 which adsorbed onto the cell surface and facilitated sedimentation. Furthermore, this technology exhibits the capability to effectively manage algal organic matters present in water, thereby mitigating the formation of nitrogen-containing DBPs. These results highlight the potential of Mn(II)/SPC treatment for treating water contaminated with algae, thus ensuring the safety and quality of water resources. [Display omitted] • The 0.2/0.1 mM Mn(II)/SPC dosage is effective on the removal of Microcystis aeruginosa. • By reducing zeta potential and the adsorption of MnO 2 , the algae cells can be coagulated by the Mn(II)/SPC treatment. • The DOC and N-DBPs could be effectively controlled after the Mn(II)/SPC treatment. [ABSTRACT FROM AUTHOR]

Zero-valent nano-iron particles (nZVI) are increasingly present in freshwater aquatic environments due to their numerous applications in environmental remediation. However, despite the broad benefits associated with the use and development of nZVI nanoparticles, the potential risks of introducing them into the aquatic environment need to be considered. Special attention should be focused on primary producer organisms, the basal trophic level, whose impact affects the rest of the food web. Although there are numerous acute studies on the acute effects of these nanoparticles on photosynthetic primary producers, few studies focus on long-term exposures. The present study aimed at assessing the effects of nZVI on growth rate, photosynthesis activity, and reactive oxygen activity (ROS) on the freshwater green algae Scenedesmus armatus and the cyanobacteria Microcystis aeruginosa. Moreover, microcystin production was also evaluated. These parameters were assessed on both organisms singly exposed to 72 h-effective nZVI concentration for 10% maximal response for 28 days. The results showed that the cell growth rate of S. armatus was initially significantly altered and progressively reached control-like values at 28 days post-exposure, while M. aeruginosa did not show any significant difference concerning control values at any time. In both strains dark respiration (R) increased, unlike net photosynthesis (Pn), while gross photosynthesis (Pg) only slightly increased at 7 days of exposure and then became equal to control values at 28 days of exposure. The nZVI nanoparticles generated ROS progressively during the 28 days of exposure in both strains, although their formation was significantly higher on green algae than on cyanobacteria. These data can provide additional information to further investigate the potential risks of nZVI and ultimately help decision-makers make better informed decisions regarding the use of nZVI for environmental remediation. [Display omitted] • Short-term exposures to nZVI decreased freshwater microalgae growth. • nZVI-IC 10 did not affect the M. aeruginosa exponential growth rate at 28-d. • The S. armatus growth recovered after nZVI-IC 10 7-d exposure. • The initial effect on photosynthetic activity decreased after 28 days of exposure. • ROS increased in both species during 28 days of exposure to nZVI-IC 10. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) and per- and polyfluoroalkyl substances (PFASs) have drawn significant attention as emerging threats to aquatic ecosystems. There are currently just a few investigations on the combined toxicity of PFAS and MP on freshwater microalgae. In this research, the combined toxicity of polyvinyl chloride (PVC) and perfluorooctanoic acid (PFOA) to Microcystis aeruginosa was investigated. The results indicated that the combination of these pollutants inhibited the growth of M. aeruginosa and promoted the synthesis and release of Microcystin-LR (MC-LR). Individual and combined exposure caused different responses to cellular oxidative stress. Under the Individual exposure of PFOA, when the concentration was greater than 20.0 mg/L, the catalase (CAT) activity increased significantly, and when it was greater than 100.0 mg/L, the malondialdehyde (MDA) content increased significantly, but there is no significant change under combined exposure. PVC and PFOA exposure also caused physical damage to the algal cells and reduced the content of extracellular polymer substances (EPS) based on analysis of cell morphology. Metabolic analysis revealed that carbohydrate metabolism and amino acid metabolism of the algae were affected. The current study offers a fresh theoretical framework for MPs and PFASs environmental risk evaluations. [Display omitted] • PVC and PFOA significantly inhibit algal growth. • Combined exposure promoted the synthesis and release of Microcystin-LR. • PVC and PFOA triggered oxidative stress and cytomembrane damage. • Metabolomics was used to revealed the effect of PVC and PFOA on M. aeruginosa. [ABSTRACT FROM AUTHOR]

The health of the aquatic ecosystem has recently been severely affected by cyanobacterial blooms brought on by eutrophication. Therefore, it is critical to develop efficient and secure methods to control dangerous cyanobacteria, such as Microcystis aeruginosa. In this research, we tested the inhibition of M. aeruginosa growth by a Scenedesmus sp. strain isolated from a culture pond. Scenedesmus sp. culture filtrate that had been lyophilized was added to M. aeruginosa , and cultivation for seven days, the cell density, chlorophyll a (Chl-a) concentration, maximum quantum yield of photosystem II (Fv/Fm), the activities of superoxide dismutase (SOD), catalase (CAT), and the concentration of malondialdehyde (MDA) and glutathione (GSH) were measured. Moreover, non-targeted metabolomics was carried out to provide light on the inhibitory mechanism in order to better understand the metabolic response. According to the results, M. aeruginosa is effectively inhibited by the lyophilized Scenedesmus sp. culture filtrate at a rate of 51.2%. Additionally, the lyophilized Scenedesmus sp. clearly inhibit the photosystem and damages the antioxidant defense system of M. aeruginosa cells, resulting in oxidative damage, which worsens membrane lipid peroxidation, according to changes in Chl-a, Fv/Fm, SOD, CAT enzyme activities and MDA, GSH. Metabolomics analysis revealed that the secondary metabolites of Scenedesmus sp. significantly interfere with the metabolism of M. aeruginosa involved in amino acid synthesis, membrane creation and oxidative stress, which is coherent with the morphology and physiology outcomes. These results demonstrate that the secondary metabolites of Scenedesmus sp. exert algal inhibition effect by breaked the membrane structure, destroyed the photosynthetic system of microalgae, inhibited amino acid synthesis, reduced antioxidant capacity, and eventually caused algal cell lysis and death. Our research provides a reliable basis for the biological control of cyanobacterial blooms on the one hand, and on other hand supply application of non-targeted metabolome on the study of microalgae allelochemicals. [Display omitted] • The isolated Scenedesmus sp. has an inhibition rate of 51.2% to M. aeruginosa. • The inhibition mainly caused by the damage of cell membrane, photosynthetic and antioxidant defense system. • Amino acid synthesis, membrane creation and oxidative stress were mainly interfered by non-targeted metabolomics analysis. [ABSTRACT FROM AUTHOR]

Sulfoxaflor (SFX) is a fourth-generation neonicotinoid used widely in modern agriculture. Due to its high water solubility and mobility in environment, it is expected to occur in water environment. Degradation of SFX leads to formation of corresponding amide (M474), which in the light of recent studies may be much more toxic to aquatic organisms than the parent molecule. Therefore, the aim of the study was to assess the potential of two common species of unicellular bloom-forming cyanobacteria (Synechocystis salina and Microcystis aeruginosa) to metabolize SFX in a 14-day-long experiment, using elevated (10 mg L−1) and predicted highest environmental (10 μg L−1) concentrations. The results obtained support the occurrence of SFX metabolism in cyanobacterial monocultures, leading to release of M474 into the water. Differential SFX decline in culture media, followed by the presence of M474, was observed for both species at different concentration levels. For S. salina , SFX concentration decreased by 7.6% at lower concentration and by 21.3% at higher concentration; the M474 concentrations were 436 ng L−1 and 514 μg L−1, respectively. Corresponding values for M. aeruginosa were 14.3% and 3.0% for SFX decline; 282 ng L−1 and 317 μg L−1 for M474 concentration. In the same time, abiotic degradation was almost non-existent. Metabolic fate of SFX was then studied for its elevated starting concentration. Uptake of SFX to cells and amounts of M474 released to water fully addressed the decrease in SFX concentration in M. aeruginosa culture, while in S. salina 15.5% of initial SFX was transformed to yet unknown metabolites. The degradation rate of SFX observed in the present study is sufficient to produce a concentration of M474 that is potentially toxic for aquatic invertebrates during cyanobacterial blooms. Therefore, there is a need for more reliable risk assessment for the presence of SFX in natural waters. [Display omitted] • First evidence for sulfoxaflor (SFX) degradation in water by cyanobacteria. • Formation of corresponding SFX-amide (M474) was documented. • Up to 5% of SFX transformed to M474 in a single bloom event. • Increase in toxicity towards aquatic invertebrates is expected. • Risk assessment for SFX in water environment needs to be updated. [ABSTRACT FROM AUTHOR]

Chiral herbicides consist of two or more enantiomers, which usually differ in their biological properties and behave enantioselectively in biochemical process. Scant studies have been published in the past decades to characterize the enantiomers of herbicide lactofen. In this study, a laboratory method was developed to prepare the lactofen enantiomers using normal phase high performance liquid chromatography with an AD-H column, and μg level production yield was achieved in a single run. The two separated enantiomers had purity of ≫99%, with their absolute configurations assigned by experimental and calculated electronic and vibrational circular dichroism. Spectral analyses including semi-empirical rules as well as comparisons with the results of quantum chemical calculations confirmed the molecular configurations of R -lactofen and S -lactofen, in this elution order. The enantioselective bioactivity toward weed ( Echinochloa crusgalli ) and toxicity toward aquatic algae ( Microcystis aeruginosa ) was assessed by measuring their growth rates after the treatments with lactofen enantiomers and racemate. The results showed that R -lactofen affected E. crusgalli more severely, while S -lactofen was more toxic to algae. Using active enantiomer instead of racemate may be more efficient and safe. Therefore, a more comprehensive understanding of the behaviors of chiral enantiomers is a need to improve activity and risk assessment and regulations of chiral compounds. Our work will be helpful to easily prepare single enantiomers from racemic mixtures and to establish effective absolute configurations of the enantiomers. [ABSTRACT FROM AUTHOR]

Mechanical harvest of massive harmful algal blooms is an effective measure for bloom mitigation. Yet subsequent processing of the resulting water from algae water separation after the harvesting becomes a new problem since individual algal cells or small algal aggregates are still present in the water. Here, we proposed a novel approach for effectively flocculating the cyanobacteria Microcystis aeruginosa with a removal efficiency of 97% in 6 h using hydrolyzed urine. Nitrogen and phosphorus were simultaneously reclaimed through struvite formation. The addition of Mg 2+ promoted the flocculation efficiency and nutrient removal as well as the yield of struvite. Ca 2+ could enhance the flocculation efficiency by forming calcium phosphate. During the flocculation process, no significant damage in algal cells was observed. This study provides a novel and sustainable potential for subsequent processing of the resulting water after algae water separation with simultaneous nutrient precipitation and reducing nutrient loads to wastewater treatment plants. [ABSTRACT FROM AUTHOR]

Microcystis aeruginosa , a primary species in cyanobacterial blooms, is ubiquitously distributed in water. Microcystins (MCs) purified from M. aeruginosa can exert reproductive toxicity in fish. However, the effects of M. aeruginosa at environmentally relevant levels on the reproductive and endocrine systems of zebrafish are still unknown. The present study investigated the reproductive and endocrine-disrupting toxicity of M. aeruginosa on female zebrafish ( Danio rerio ) by short-term exposure (96 h). After exposure, marked histological lesions in the liver or gonads, such as nuclear pyknosis and deformation, were observed, and the fertilization rate and hatchability of eggs spawned from treated females were both significantly lower than they were in females in the control group, suggesting the possibility of transgenerational effects of M. aeruginosa exposure. Moreover, M. aeruginosa exposure decreased the concentration of 17β-estradiol (E2) and testosterone (T) in female zebrafish. Interestingly, the vtg1 transcriptional level significantly decreased in the liver, whereas plasma vitellogenin (VTG) protein levels increased. The present findings indicate that M. aeruginosa could modulate endocrine function by disrupting transcription of hypothalamic-pituitary-gonadal-liver (HPGL) axis-related genes, and impair the reproductive capacity of female zebrafish, suggesting that M. aeruginosa causes potential adverse effects on fish reproduction in Microcystis bloom-contaminated aquatic environments. [ABSTRACT FROM AUTHOR]

Pesticide residues and nitrogen overload (which caused cyanobacteria blooms) have been two serious environmental concerns. In particular, chiral pesticides with different structures may have various impacts on cyanobacteria. Nitrogen may affect the behavior between pesticides and cyanobacteria (e.g., increase the adverse effects of pesticides on cyanobacteria). This study evaluated the impacts of Rac- and S-metolachlor on the cell integrity and toxin release of Microcystis aeruginosa cells at different nitrogen levels. The results showed that (both of the configurations: Rac-, S-) metolachlor could inhibit M. aeruginosa cell growth under most conditions, and the inhibition rates were increased with the growing concentrations of nitrogen and metolachlor. However, cyanobacterial growth was promoted in 48 h under environmental relevant condition (1 mg/L metolachlor and 0.15 mg/L nitrogen). Therefore, the water authorities should adjust the treatment parameters to remove possible larger numbers of cyaonbacteria under that condition. On the other hand, the inhibition degree of M. aeruginosa cell growth by S-metolachlor treatments was obviously larger than Rac-metolachlor treatments. S-metolachlor also had a stronger ability in compromising M. aeruginosa cells than Rac-metolachlor treatments. Compared to control samples, more extracellular toxins (12%–86% increases) were detected after 5 mg/L S-metolachlor treatment for 72 h at different nitrogen levels, but the variations of extracellular toxins caused by 5 mg/L Rac-metolachlor addition could be neglected. Consequently, higher concentrations of metolachlor in source waters are harmful to humans, but it may prevent cyanobacterial blooms. However, the potential risks (e.g. build-up of extracellular toxins) should be considered. [ABSTRACT FROM AUTHOR]

In this research, the release and degradation of intracellular microcystin-LR (MC-LR) due to oxidation of Microcystis aeruginosa ( M. aeruginosa ) was examined kinetically. Brief exposure to free chlorine with no measureable oxidant exposure was demonstrated to be sufficient to induce rapid release of intracellular MC-LR from M. aeruginosa . Thus, in a water treatment plant, there is currently no level of prechlorination that can be assumed to be safe, since very low preoxidation prior to filtration and no measureable free chlorine residual may still observe the release and buildup of extracellular MC-LR. Higher chlorine dosages resulting in a measureable exposure or CT (concentration times contact time) cause more rapid release and oxidation of the intracellular toxins. Further, the rate of release of MC-LR with intermediate oxidant dosages were shown to be initially rapid, but then slowed to a lower release rate due to an as yet undetermined mechanism. While free chlorine was reactive with the extracellular MC-LR, the monochloramine resulting from the consumption of the free chlorine by ammonia was not. Consideration of the ammonia concentration and the chlorine dosage relative to the chlorination breakpoint dosages is important for utilities assessing the impact of prechlorination of water containing cyanobacteria. MC-LR, once released, was rapidly oxidized by permanganate resulting in only negligible buildup of extracellular toxins. [ABSTRACT FROM AUTHOR]

N-Phenyl-1-naphthylamine (P 1 NA) and N-Phenyl-2-naphthylamine (P 2 NA) 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 P 1 NA and P 2 NA on Microcystis aeruginosa . According to the results, a dose-response relationship was observed only between P 1 NA concentrations and growth inhibition. The EC 50 (48 h) of P 1 NA calculated from growth inhibition was 16.62 μM, while that of P 2 NA was not detected. When the esterase and photosynthetic activity were applied to evaluate the biotoxicity, it was found that a concentration of 20 μM P 1 NA, P 2 NA 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 P 1 NA exposure concentration increased, but that was not detected when exposure to P 2 NA. The difference substituted position in the molecular structure of P 1 NA and P 2 NA leads to different toxicological properties and only P 1 NA was found highly toxic to M. aeruginosa . The toxicity is due to that only P 1 NA 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. [ABSTRACT FROM AUTHOR]

It has been puzzling whether and how a plant could exert a strong allelopathic inhibition to the target organisms by releasing low concentrations of allelochemicals. Plant allelochemicals have been proposed to be released continuously, however, direct evidence from specific allelochemicals is urgently required. In the present study, the toxicity of allelochemical N -phenyl-1-naphthylamine (NPN) towards the cyanobacterium Microcystis aeruginosa by two different exposure patterns was compared. One was low-dosage repeated exposure (LRE), in which 50 μg L −1 NPN was repeatedly dosed to simulate the continual release of allelochemicals, and the other one was high-dosage single exposure (HSE) as per the routine toxicity assay. The results showed a significant growth inhibition to M. aeruginosa in the LRE group, where the inhibition rate reached above 90% from day 6 to day 9. The cell-membrane damage ratio increased from 64.05% on day 5 up to 96.60% on day 9. PSII photosynthesis activity expressed as Fv/Fm, Φ PSII , NPQ and ETRmax was also thoroughly inhibited in this group. Whereas the growth and PSII photosynthesis activity of M. aeruginosa in the HSE group were inhibited initially, but recovered gradually from day 4 or 5, which was accompanied by a continuous reduction of NPN content in culture solutions. Although NPN content in the LRE group was relatively lower, it remained at a more stable level throughout the experiment. These results indicate that continual release of low-dosage allelochemicals by aquatic plants plays crucial roles in their potent inhibition against cyanobacteria. Low-dosage continual exposure pattern needs to be investigated further. [ABSTRACT FROM AUTHOR]

Copper exposures from algaecide applications in aquatic systems are hypothesized to impede bacterial degradation of microcystin (MC), a cyanobacterial produced hepatotoxin. Despite regulatory implications of this hypothesis, limited data exist on influences of copper-exposures on MC-degrading bacteria and consequent MC-degradation. In this study, influences of copper-algaecide concentrations and formulations on bacterial composition and microcystin-LR (MCLR) degradation were investigated. Microcystis aeruginosa was exposed to four concentrations (0–5.0 mg Cu L −1 ) of three copper-algaecide formulations, and rates and extents of MCLR degradation were measured. In untreated controls and following exposures of 0.1, 0.5, and 1.0 mg Cu L −1 , MCLR concentrations decreased at a rate of ∼41–53 μg MCLR/L d −1 . Following exposure to 5.0 mg Cu L −1 MCLR degradation rates decreased an order of magnitude to ∼3–7 μg MCLR/L d −1 . Bacterial diversity decreased following copper-exposures greater than 0.1 mg Cu L −1 for all formulations. Relative abundance of certain groups of MC-degrading bacteria identified in treatments increased with increasing copper concentration, suggesting they may be less sensitive to copper exposures than other, MCLR and non MC-degrading heterotrophic bacteria present in the assemblage. Results from this study revealed that copper concentration can influence degradation rates of MCLR, however this influence was not significant within copper concentrations currently registered for use (≤1.0 mg Cu L −1 ) of the tested algaecides. Copper formulation did not significantly alter degradation rates or bacterial composition. These data augment our understanding of the influences of copper algaecide-exposures on MCLR degradation, and can be used to inform more accurate risk evaluations and use of copper-algaecides for management of MCLR-producing cyanobacteria. [ABSTRACT FROM AUTHOR]

Oxidation treatment of algae-laden water may cause cells rupture and emission of intracellular organics, thus restricting its further popularization. As a moderate oxidant, calcium sulfite could be slowly released in the liquid phase, thus exhibiting a potential to maintain the cells integrity. To this end, calcium sulfite oxidation activated by ferrous iron was proposed integrated with ultrafiltration (UF) for removal of Microcystis aeruginosa , Chlorella vulgaris and Scenedesmus quadricauda. The organic pollutants were significantly eliminated, and the repulsion between algal cells was obviously weakened. Through fluorescent components extraction and molecular weights distribution analyses, the degradation of fluorescent substances and the generation of micromolecular organics were verified. Moreover, the algal cells were dramatically agglomerated and formed larger flocs under the premise of maintaining high cell integrity. The terminal normalized flux was ascended from 0.048–0.072 to 0.711–0.956, and the fouling resistances were extraordinarily decreased. Due to the distinctive spiny structure and minimal electrostatic repulsion, Scenedesmus quadricauda was easier to form flocs, and its fouling was more readily mitigated. The fouling mechanism was remarkably altered through postponing the formation of cake filtration. The membrane interface characteristics including microstructures and functional groups firmly proved the fouling control efficiency. The reactive oxygen species (i.e., SO 4 •− and 1O 2) generated through the principal reactions and Fe–Ca composite flocs played dominant roles in alleviating membrane fouling. Overall, the proposed pretreatment exhibits a brilliant application potential for enhancing UF in algal removal. [Display omitted] • CaSO 3 activated by Fe(II) was proposed for the removal of various types of algae. • The sustained-release property of CaSO 3 helped to maintain the cells integrity. • The formation of complex flocs positively affected the aggregation of algal cells. • The CaSO 3 /Fe(II) integrated strategy efficiently alleviated membrane fouling. • A mass of oxygen species (i.e., SO 4.•− and 1O 2) were generated in the process. [ABSTRACT FROM AUTHOR]

Deferoxamine (DFB) is a trihydroxamic acid siderophore that chelates with iron (Fe) to form iron-siderophore complexes. The existence of siderophores in nature changes the form of iron and affects the absorption and utilization of iron by organisms. However, the relationship between siderophores and the growth of Cyanobacteria is largely unknown. In this study, the cellular and transcriptomic responses to the addition of DFB were investigated. A high concentration of DFB (12 mg/L) significantly inhibited the growth of Cyanobacteria cells, reduced photosynthetic activity, and induced the production of peroxidase, with the highest inhibition rate of algal growth of 74.82%. These indexes were also affected for the low (3 mg/L) and medium concentration (6 mg/L) groups, but this difference is closely related to the growth stage of Cyanobacteria cells. This may be due to competition between the cell-associated iron-binding part/system and the extracellular Fe (Ⅲ)-DFB ligand. Transcriptome results showed that most of the genes involved in iron uptake and transport were down-regulated, and only the fur gene encoding the iron uptake regulator protein was significantly up-regulated. Most genes related to photosynthesis, glycolysis, and fatty acid metabolism were also down-regulated, while the obvious up-regulation of a few genes may be a complex regulation in response to the down-regulation of most genes. These findings will provide important insights into the effects of siderophores on iron bioavailability in algae. [Display omitted] • Deferoxamine could inhibit the growth of Microcystis aeruginosa. • The expression of related genes involved in photosynthesis were down-regulated. • TransCripts of genes related to iron transport were down-regulated. [ABSTRACT FROM AUTHOR]

Phytochemical is considered an alternative method for cyanobacterial bloom control in aquatic environments. When cyanobacteria are treated with anti-algal materials produced from plant tissues, they tend to exhibit growth inhibition or necrosis of cells. These different anti-algal responses have not been well discussed, and thus, the modes of anti-algal action in cyanobacteria remain obscure. In this study, transcriptomic and biochemical researches were conducted to understand the mechanisms of cyanobacterial growth inhibition and necrosis in harmful cyanobacterial cells exposed to allelopathic materials. The cyanobacteria Microcystis aeruginosa was treated with aqueous extracts of walnut husk, rose leaf, and kudzu leaf. Walnut husk and rose leaf extracts induced mortality of cyanobacterial population with cell necrosis, whereas kudzu leaf extract exhibited poorly grown cells with shrunk size. Through RNA sequencing, it was revealed that the necrotic extracts significantly downregulated critical genes in enzymatic chain reactions for carbohydrate assembly in the carbon fixation cycle and peptidoglycan synthesis. Compared to the necrotic extract treatment, expression of several genes related to DNA repair, carbon fixation, and cell reproduction was less interrupted by the kudzu leaf extract. Biochemical analysis of cyanobacterial regrowth was performed using gallotannin and robinin. Gallotannin was identified as the major anti-algal compound in walnut husk and rose leaf affecting cyanobacterial necrosis, whereas robinin, which is the typical chemical in kudzu leaf, was associated with growth inhibition of cyanobacterial cells. These combinational studies using RNA sequencing and regrowth assays provided evidence supporting the allelopathic effects of plant-derived materials on cyanobacterial control. Furthermore, our findings suggest novel algicidal scenarios with different responses in the cyanobacterial cells depending on the type of anti-algal compounds. [Display omitted] • Allelopathic responses in cyanobacteria exhibited growth inhibition or mortality. • Walnut husk and kudzu leaf possessed rich tannins and robinin, respectively. • Tannic acid was the critical component inducing cyanobacterial cell necrosis. • Robinin affected not necrosis but growth inhibition of cyanobacterial cells. • Allelopathic necrosis caused inhibition of carbon fixation and cell wall synthesis. [ABSTRACT FROM AUTHOR]

Phytoplankton-derived extracellular polymeric substances (EPS) are of vital importance for the biogeochemical cycles of hydrophobic organic pollutants in lake ecosystems. In this study, roles of loosely-bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) in biosorption of phenanthrene (PHE) on a typical cyanobacteria Microcystis aeruginosa were investigated. The results showed that the biosorption of PHE on M. aeruginosa cell varied lasted 24 h, while the binding of PHE to LB-EPS and TB-EPS reached equilibrium within less than 2 h. The equilibrium biosorption capacities of M. aeruginosa cell, LB-EPS and TB-EPS were 6.78, 12.31, and 9.47 μg mg −1 , respectively, indicating that the binding of PHE to EPS was a considerable process involved in biosorption. Fluorescence quenching titration revealed that increasing temperature induced more binding sites in EPS for PHE and the binding process was driven by electrostatic force and hydrophobic interactions. Interestingly, dynamic and static quenching processes occurred simultaneously for the binding of PHE to protein-like substances in EPS, whereas the binding of PHE to humic-like substances belonged to static quenching. The relatively higher contents of proteins in LB-EPS produced a stronger binding capacity of PHE. Overall, the interactions between hydrophobic organic pollutants and cyanobacterial EPS are favorable to the bioaccumulation of hydrophobic organic pollutants in cyanobacteria and facilitate the regulatory function of cyanobacterial biomass as a biological pump. [ABSTRACT FROM AUTHOR]

Microcystin release from algal cells influences use of copper-algaecides in water resources. Accurate data regarding relationships between copper-algaecide exposures and responses of microcystin-producing algae are needed to make informed management decisions. Responses of Microcystis aeruginosa were measured in terms of cellular microcystin-LR (MC-LR), aqueous MC-LR, and chlorophyll- a following exposure to CuSO 4 and copper-ethanolamine. Comparisons were made between treated and untreated samples, and copper formulations. EC 50 s and slopes for M. aeruginosa responses to copper exposures were calculated. Algal responses followed a sigmoidal exposure-response relationship, and cellular MC-LR and chlorophyll- a were negatively related to copper concentrations. Aqueous MC-LR increased with copper concentrations, although the increase in aqueous MC-LR was not proportional to decreases in cellular MC-LR and chlorophyll- a . Cellular MC-LR and chlorophyll a declined at a greater rate than aqueous MC-LR increased. Total MC-LR was less than untreated controls following copper exposure. Differences were measured between copper formulations in terms of aqueous and total MC-LR concentrations at concentrations of 0.5 and 1.0 mg Cu L-1. Aqueous and total MC-LR were greater (10–20%) following exposure to CuSO 4 compared to copper-ethanolamine one day following exposure. The positive relationship between copper concentration and aqueous MC-LR at 0.07–1.0 mg Cu L-1 demonstrates that lower copper concentrations were as effective as higher concentrations in controlling M. aeruginosa while decreasing the total amount of MC-LR, and minimizing the proportion of MC-LR released to the aqueous-phase. Results serve to support more accurate risk evaluations of MC-LR concentrations when M. aeruginosa is exposed to copper-algaecides and when it is untreated. [ABSTRACT FROM AUTHOR]

We investigated the effects of allelochemical ferulic acid (FA) on a series of physiological and biochemical processes of blue-green algae Microcystis aeruginosa , in order to find sensitive diagnostic variables for allelopathic effects. Algal cell density was significantly suppressed by FA (0.31–5.17 mM) only after 48 h exposure. Inhibitions of photosynthetic parameters ( F v / F m and F v ′/ F m ′) occurred more rapidly than cell growth, and the stimulation of non-photochemical quenching was observed as a feed-back mechanisms induced by photosystem II blockage, determining by PAM fluorometry. Inhibitions on esterase activity, membrane potential and integrity, as well as disturbance on cell size, were all detected by flow cytometry with specific fluorescent markers, although exhibiting varied sensitivities. Membrane potential and esterase activity were identified as the most sensitive parameters (with relatively lower EC 50 values), and responded more rapidly (significantly inhibited only after 8 h exposure) than photosynthetic parameters and cell growth, thus may be the primary responses of cyanobacteria to FA exposure. The use of PAM fluorometry and flow cytometry for rapid assessment of those sensitive variables may contribute to future mechanistic studies of allolepathic effects on phytoplankton. [ABSTRACT FROM AUTHOR]