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1.
Ecotoxicol Environ Saf ; 208: 111713, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33396044

RESUMO

A novel Microcystis bloom caused by Microcystis densa has occurred in a typical subtropical reservoir every spring and summer since 2012, and it has caused several ecological and economic losses. To determine the environmental factors that influence the growth and physiological characteristics of M. densa, we investigated the variations in physicochemical factors and M. densa cell density from 2007 to 2017. The results showed that the urea-N concentration increased significantly (from 0.02 ± 0.00-0.20 ± 0.01 mg N l-1), whereas other factors did not vary significantly. NO3--N and urea-N concentrations were higher than the NH4+-N concentration during the M. densa bloom. The nitrogen composition changed, and urea-N and NO3--N became a major nitrogen sources in the reservoir. Water temperature and increased urea-N concentrations were the primary factors that influenced variations in M. densa cell density (45.5%, p < 0.05). Laboratory experiments demonstrated that M. densa cultured with urea-N exhibited a higher maximum cell density (9.8 ± 0.5 × 108 cells l-1), more cellular pigments for photosynthesis (chlorophyll a and phycocyanin) and photoprotection (carotenoid), and more proteins than those cultured with NH4+-N and NO3--N. These results suggested that M. densa cultured with urea-N exhibited preferable growth and physiological conditions. Moreover, M. densa exhibited an increased maximum specific uptake rate (0.93 pg N cell-1 h-1) and reduced half-saturation constant (0.03 mg N l-1) for urea-N compared with NH4+-N and NO3--N, suggesting that M. densa preferred urea-N as its major nitrogen source. These results collectively indicated that the increasing urea-N concentration was beneficial for the growth and physiological conditions of M. densa. This study provided ten years of field data and detailed physiological information supporting the critical effect of urea-N on the growth of a novel bloom species M. densa. These findings helped to reveal the mechanism of M. densa bloom formation from the perspective of dissolved organic nitrogen.


Assuntos
Eutrofização , Microcystis/crescimento & desenvolvimento , Nitrogênio/metabolismo , Ureia/metabolismo , Proteínas de Bactérias/metabolismo , Microcystis/metabolismo , Nitratos/análise , Nitratos/metabolismo , Nitrogênio/análise , Nitrogênio/química , Pigmentos Biológicos/metabolismo , Temperatura , Ureia/análise
2.
Environ Pollut ; 271: 116409, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33418289

RESUMO

The gut microbiota has been increasingly recognized to regulate host fitness, which in turn is dependent on stability of community structure and composition. Many biotic and abiotic factors have been demonstrated to shape gut microbiota of cladocerans. However, the interactive effects of these variables on cladocerans fitness due to alteration of gut microbiota and their linkage with life history parameters are poorly understood. Here, we investigated the responses of Daphnia magna gut microbiota to the combined effects of toxic Microcystis aeruginosa and high temperature and its associations with fitness. We found that under good food regime, the temperature has no effect on the composition of the gut microbiota, whereas under high proportion of toxic M. aeruginosa and high temperature conditions, D. magna lost their symbionts. High proportion of toxic M. aeruginosa and high temperature had synergistically negative effects on D. magna performance due to altered gut microbiota. The high abundance of symbiotic Comamonadaceae and good food increased D. magna fitness. The present study illustrates that understanding life history strategies in response to multiple stressors related to changes in the gut microbiota diversity and composition requires integrated approaches that incorporate multiple linked traits and tether them to one another.


Assuntos
Microbioma Gastrointestinal , Traços de História de Vida , Microcystis , Animais , Daphnia , Temperatura
3.
Water Res ; 190: 116747, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33385876

RESUMO

Coagulation-flocculation followed by sedimentation or dissolved air flotation (DAF) are processes routinely used for separating microalgae from water; however, during algae separation then can exhibit inconsistent separation, high coagulant demand, and high operating cost. To circumvent these problems, previous studies reported the development of a novel DAF process in which bubbles were modified instead of particles. While this process was shown to be sustainable and inexpensive, the problem of inconsistent algal separation across species remained. Recent research has suggested that this could be due to the varying concentration and character of algal-derived proteins and carbohydrates within the extracellular organic matter (EOM) and their associated interactions. This hypothesis is tested in the current study using the novel modified-bubble DAF process, which has been highly susceptible to EOM protein and carbohydrate concentrations and character. Biomolecular additives (commercially available proteins and carbohydrates, and algal-extracted proteins) of widely differing molecular weight (MW) and charge were dosed in varying proportions into samples containing either Chlorella vulgaris CS-42/7, Microcystis aeruginosa CS-564/01, or Microcystis aeruginosa CS-555/1 after removing the intrinsic EOM. These cell-rich suspensions were then subject to flotation using cationic bubbles modified with poly(diallyldimethylammonium chloride) (PDADMAC). When additives were dosed independently, separation increased from <5% to up to 62%. The maximum separation was obtained when the dose was double the respective biopolymer concentration measured in the intrinsic EOM for the equivalent species, and, in the case of protein additives, when MW and charge were >50 kDa, and >0.5 meq·g-1, respectively, irrespective of the species tested. When evaluating steric- and charge-based protein-carbohydrate interactions on cell separation by simultaneously dosing high MW and high charge protein- and carbohydrate-additives, enhanced separation of up to 79% was achieved. It is suggested that enhanced cell separation is achieved due to proteins and carbohydrates bridging with cells and forming protein-carbohydrate-cell suprastructures in the presence of a flocculant, e.g. PDADMAC, and this only occurs when the intrinsic EOM comprises proteins and carbohydrates that have high MW (>25 kDa) and charge (>0.2 meq·g-1), and interactions with each other and with the cell surface.


Assuntos
Chlorella vulgaris , Microcystis , Purificação da Água , Carboidratos , Floculação
4.
Ecotoxicol Environ Saf ; 208: 111664, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33396174

RESUMO

Recently, the pollution of microplastics (MPs) in the global freshwater environment has become increasingly problematic, but there are few studies on the freshwater environment risks of MPs. The present study, therefore, has investigated the single and combined effects of MPs and lead (Pb) on the freshwater algal Microcystis aeruginosa. Results showed that Pb-only (>0.05 mg·L-1) promoted the growth of algal cells, while MPs-only (1 mg L-1) resulted in growth inhibition. However, compared with the corresponding concentration of Pb-only groups, the growth of algal cells was promoted in MPs + Pb treatments. MPs-only and Pb-only (0.5 mg L-1) both reduced the content of photosynthetic pigments and affected algal photosynthesis. The MPs-only treatment and MPs + Pb2+ (no pretreatment, 0.5 mg L-1 Pb2+) treatments showed significant cell aggregation. At the same time, MPs-only caused a significant increase in bound extracellular polysaccharides (bEPS), while 0.5 mg L-1 Pb reduced bEPS. Furthermore, under high Pb stress (0.5 mg L-1), the effects of combined MPs and Pb on chlorophyll content, antioxidant enzyme activity (peroxidase (POD), catalase (CAT)), and damage to algal cells were less compared to individual effects, and the combination of MPs and Pb had a synergistic effect on promoting aggregations of M. aeruginosa. These results demonstrate that single and combined effects of MPs and Pb can induce differential responses in the freshwater algal M. aeruginosa, which can have a significant impact on aquatic ecosystems.


Assuntos
Água Doce/microbiologia , Chumbo/toxicidade , Microcystis/efeitos dos fármacos , Microplásticos/toxicidade , Poluentes Químicos da Água/toxicidade , Antioxidantes/metabolismo , Clorofila/metabolismo , Sinergismo Farmacológico , Ecossistema , Água Doce/química , Microcystis/crescimento & desenvolvimento , Microcystis/metabolismo , Fotossíntese/efeitos dos fármacos
5.
Ecotoxicol Environ Saf ; 208: 111575, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33396101

RESUMO

Microplastics (MPs) have aroused widespread concern due to their extensive distribution in aquatic environments and adverse effects on aquatic organisms. However, the underlying toxicity of different kinds of MPs on freshwater microalgae has not been examined in detail. In this study, we investigated the effects of polyvinyl chloride (PVC), polystyrene (PS) and polyethylene (PE) MPs on the growth of Microcystis aeruginosa, as well as on its toxin production and oxidative stress. We found that all three kinds of MPs had an obvious inhibition effect on the growth of M. aeruginosa. Considering the results of antioxidant-related indicators, the activity of superoxide dismutase (SOD) and catalase (CAT), and cell membrane integrity were greatly affected with exposure to PVC, PS and PE MPs. Moreover, the content of intracellular (intra-) and extracellular (extra-) microcystins (MCs) had a noticeable increase due to the presence of PVC, PS, and PE MPs. Finally, according to the comprehensive stress resistance indicators, the resistance of M. aeruginosa to three MPs followed the order: PE (3.701)> PS (3.607)> PVC (2.901). Our results provide insights into the effects of different kinds of MPs on freshwater algae and provide valuable data for risk assessment of different types of MPs.


Assuntos
Microcystis/fisiologia , Microplásticos/toxicidade , Poluentes Químicos da Água/toxicidade , Antioxidantes/metabolismo , Catalase/metabolismo , Água Doce , Microalgas/efeitos dos fármacos , Microcistinas , Microcystis/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Plásticos/toxicidade , Polietileno , Poliestirenos/toxicidade , Cloreto de Polivinila/toxicidade , Superóxido Dismutase/metabolismo
6.
Ecotoxicol Environ Saf ; 211: 111894, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33472108

RESUMO

Enantiomers of chiral fungicides usually display different toxic effects on nontarget organisms in the surrounding environment, although there are rare reports on the enantioselective toxicity of metconazole (MEZ) to aquatic organisms, such as Microcystis flos-aquae (M. flos-aquae). To explore the enantioselective toxicity of MEZ in algae, the impact of various concentrations (0.001, 0.003, 0.01, 0.03 and 0.1 mg/L) of MEZ on M. flos-aquae over 8 days was investigated. Significant differences were observed between the four enantiomers in chlorophyll a (Chl a) contents, carotenoids, photochemical efficiency (Fv/Fm), rapid light-response curves (RLCs), utilization efficiency of light energy (α) and protein contents during treatment time. MEZ can enantioselectively stimulate the chlorophyll fluorescence parameters (RLCs, Fv/Fm and α) and carotenoid and Chl a contents of M. flos-aquae, especially at low concentrations (0.001 or 0.003 mg/L). At high concentrations of 0.03 or 0.1 mg/L, the chlorophyll fluorescence parameters (RLCs, Fv/Fm and α), protein and Chl a contents of M. flos-aquae exposed to cis-enantiomers were lower than those of M. flos-aquae exposed to trans-enantiomers. These observations indicated that the enantiomers of MEZ pose different toxicities to M. flos-aquae, with the cis-enantiomers more toxic than the trans-enantiomers. These results are beneficial for understanding the enantioselective effects of MEZ enantiomers on nontarget organisms and helpful for evaluating their eco-environment risk.


Assuntos
Fungicidas Industriais/toxicidade , Microcystis/fisiologia , Fotossíntese/efeitos dos fármacos , Triazóis/toxicidade , Clorofila A , Microcystis/efeitos dos fármacos , Estereoisomerismo
7.
J Environ Manage ; 281: 111884, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33385902

RESUMO

A new method for algal community restructuring is proposed, where harmful algae growth is inhibited through the addition of remedial nano-agent, while probiotic algae growth is promoted or only affected indistinctively. In this paper, the inhibiting effects of five different nanomaterials on Microcystis aeruginosa (M. aeruginosa) and Cyclotella sp. were studied, and the optimal nanomaterial was served as algae-inhibition ingredient of the remedial agent. The effects of the remedial agent on algal growth and their physiological characteristics were investigated, and the restructuring of algal community in actual water samples was explored. The results indicated that the inhibition ratio of 10 mg/L nm-Cu2O/SiO2 on M. aeruginosa and Cyclotella sp. could reach 293.1% and 82.8% respectively, acting as the best candidate for algae-inhibiting ingredient. After adding the remedial nano-agent made with nm-Cu2O/SiO2, the content of chlorophyll a, protein, and polysaccharides of M. aeruginosa decreased sharply, while the physiological characteristics of Cyclotella sp. were not significantly affected. Besides, the total biomass and proportion of cyanobacteria dropped (P < 0.05), but the Bacillariophyta biomass increased significantly (P < 0.05). The uniformity index, Shannon-Wiener index, and richness index all increased significantly (P < 0.05). Meanwhile, the quality of actual water samples has been improved evidently (P < 0.001). Therefore, the prepared remedial nano-agent in this study can control the harmful algae bloom to a certain extent by restructuring the algal community in eutrophic water bodies.


Assuntos
Diatomáceas , Microcystis , Clorofila A , Proliferação Nociva de Algas , Dióxido de Silício , Água
8.
Environ Pollut ; 271: 116400, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33421845

RESUMO

Freshwater cyanobacteria produce highly toxic secondary metabolites, which can be transported downstream by rivers and waterways into the sea. Estuarine and coastal aquaculture sites exposed to toxic cyanobacteria raise concerns that shellfish may accumulate and transfer cyanotoxins in the food web. This study aims to describe the competitive pattern of uptake and depuration of a wide range of microcystins (MC-LR, MC-LF, MC-LW, MC-LY, [Asp3]-MC-LR/[Dha7]-MC-LR, MC-HilR) and nodularins (NOD cyclic and linear) within the common blue mussel Mytilus edulis exposed to a combined culture of Microcystis aeruginosa and Nodularia spumigena into the coastal environment. Different distribution profiles of MCs/NODs in the experimental system were observed. The majority of MCs/NODs were present intracellularly which is representative of healthy cyanobacterial cultures, with MC-LR and NOD the most abundant analogues. Higher removal rate was observed for NOD (≈96%) compared to MCs (≈50%) from the water phase. Accumulation of toxins in M. edulis was fast, reaching up to 3.4 µg/g shellfish tissue four days after the end of the 3-days exposure period, with NOD (1.72 µg/g) and MC-LR (0.74 µg/g) as the dominant toxins, followed by MC-LF (0.35 µg/g) and MC-LW (0.31 µg/g). Following the end of the exposure period depuration was incomplete after 27 days (0.49 µg/g of MCs/NODs). MCs/NODs were also present in faecal material and extrapallial fluid after 24 h of exposure with MCs the main contributors to the total cyanotoxin load in faecal material and NOD in the extrapallial fluid. Maximum concentration of MCs/NODs accumulated in a typical portion of mussels (20 mussels, ≈4 g each) was beyond greater the acute, seasonal and lifetime tolerable daily intake. Even after 27 days of depuration, consuming mussels harvested during even short term harmful algae blooms in close proximity to shellfish beds might carry a high health risk, highlighting the need for testing.


Assuntos
Cianobactérias , Microcystis , Animais , Microcistinas , Nodularia , Frutos do Mar/análise
9.
Sci Total Environ ; 754: 142362, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33254935

RESUMO

Cyanobacterial toxic blooms are a worldwide problem. The Río de la Plata (RdlP) basin makes up about one fourth of South America areal surface, second only to the Amazonian. Intensive agro-industrial land use and the construction of dams have led to generalized eutrophication of main tributaries and increased the intensity and duration of cyanobacteria blooms. Here we analyse the evolution of an exceptional bloom at the low RdlP basin and Atlantic coast during the summer of 2019. A large array of biological, genetic, meteorological, oceanographic and satellite data is combined to discuss the driving mechanisms. The bloom covered the whole stripe of the RdlP estuary and the Uruguayan Atlantic coasts (around 500 km) for approximately 4 months. It was caused by the Microcystis aeruginosa complex (MAC), which produces hepatotoxins (microcystin). Extreme precipitation in the upstream regions of Uruguay and Negro rivers' basins caused high water flows and discharges. The evolution of meteorological and oceanographic conditions as well as the similarity of organisms' traits in the affected area suggest that the bloom originated in eutrophic reservoirs at the lower RdlP basin, Salto Grande in the Uruguay river, and Negro river reservoirs. High temperatures and weak Eastern winds prompted the rapid dispersion of the bloom over the freshwater plume along the RdlP northern and Atlantic coasts. The long-distance rapid drift allowed active MAC organisms to inoculate freshwater bodies from the Atlantic basin, impacting environments relevant for biodiversity conservation. Climate projections for the RdlP basin suggest an increase in precipitation and river water flux, which, in conjunction with agriculture intensification and dams' construction, might turn this extraordinary event into an ordinary situation.


Assuntos
Cianobactérias , Microcystis , Água Doce , Microcistinas , Rios , América do Sul , Uruguai
10.
Sci Total Environ ; 754: 142076, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-32920391

RESUMO

Individual cell heterogeneity within a population can be critical to its peculiar function and fate. Conventional algal cell-based assays mainly analyze the average responses from a population of algal cells. Therefore, the mechanisms through which changes in population characteristics are driven by the behavior of single algal cells are still not well understood. Algal cells may modulate their physiology and metabolism by changing their morphology in response to environmental stress. In this study, an algal single-cell culture and analysis system was developed to investigate the potential role of morphological changes by algal cells during adaptation to nutrient stress based on a microwell array chip. The surface-to-volume ratio of Microcystis aeruginosa (M. aeruginosa) and the volume of Scenedesmus obliquus (S. obliquus) significantly increased with increasing culture time under nutrient stress. The eccentricity of M. aeruginosa and S. obliquus gradually increased and decreased, respectively, with increasing culture time, indicating that the morphology of M. aeruginosa and S. obliquus became increasingly irregular and regular, respectively, under nutrient stress. There were significant correlations between the morphological characteristics and physiological characteristics of M. aeruginosa and S. obliquus under nutrient stress. In M. aeruginosa, an increased surface-to-volume ratio facilitated a high specific fluorescence intensity, specific Raman intensity, and maximum electron transport rate. In S. obliquus, increased cell volume enhanced nutrient absorption, which facilitated a higher specific growth rate. M. aeruginosa and S. obliquus adopted different adaptation strategies in response to nutrient stress based on morphological changes. These findings facilitate the development of management strategies for controlling harmful cyanobacterial blooms.


Assuntos
Microcystis , Scenedesmus , Aclimatação , Nutrientes
11.
J Environ Sci (China) ; 99: 1-9, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33183685

RESUMO

Freshwater cyanobacterial blooms have drawn public attention because they threaten the safety of water resources and human health worldwide. Heavy cyanobacterial blooms outbreak in Lake Taihu in summer annually and vanish in other months. To find out the factors impacting the cyanobacterial blooms, the present study measured the physicochemical parameters of water and investigated the composition of microbial community using the 16S rRNA gene and internal transcribed spacer amplicon sequencing in the months with or without bloom. The most interesting finding is that two major cyanobacteria, Planktothrix and Microcystis, dramatically alternated during a cyanobacterial bloom in 2016, which is less mentioned in previous studies. When the temperature of the water began increasing in July, Planktothrix appeared first and showed as a superior competitor for M. aeruginosa in NO3--rich conditions. Microcystis became the dominant genus when the water temperature increased further in August. Laboratory experiments confirmed the influence of temperature and the total dissolved nitrogen (TDN) form on the growth of Planktothrix and Microcystis in a co-culture system. Besides, species interactions between cyanobacteria and non-cyanobacterial microorganisms, especially the prokaryotes, also played a key role in the alteration of Planktothrix and Microcystis. The present study exhibited the alteration of two dominant cyanobacteria in the different bloom periods caused by the temperature, TDN forms as well as the species interactions. These results helped the better understanding of cyanobacterial blooms and the factors which contribute to them.


Assuntos
Cianobactérias , Microbiota , Microcystis , Cianobactérias/genética , Lagos , Microcystis/genética , RNA Ribossômico 16S/genética
12.
Ecotoxicol Environ Saf ; 207: 111233, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32916528

RESUMO

Growth of microcystin-producing cyanobacteria in Lake Okeechobee (Florida, USA) and surrounding waters has resulted in adverse health impacts for humans and endangered species, as well as significant economic losses. As these issues worsen, there is growing pressure for efficacious solutions to rapidly mitigate harmful algal blooms (HABs) and protect critical freshwater resources. Applications of USEPA-registered algaecides as management tactics meet many decision-making criteria often required by water resource managers (e.g., effective, scalable, selective), but have not yet been evaluated on a large scale within the Lake Okeechobee waterway. This study was conducted to bolster the peer-reviewed database for available management tactics against microcystin-producing cyanobacteria in waters of this region. Laboratory-scale experiments can be conducted first to minimize uncertainty at larger scales and improve confidence in decision-making. In this study, samples containing microcystin-producing cyanobacteria collected from Lake Okeechobee were exposed to several USEPA-registered algaecides in laboratory toxicity experiments. Responses of target cyanobacteria were measured 3 days after treatment (DAT) in terms of cell density, chlorophyll-a concentrations, and phycocyanin concentrations. Based on responses of the cyanobacteria, minimum effective exposure concentrations were identified for each algaecide. Microcystin release (i.e. proportion of total microcystins in the aqueous phase) was measured and compared 1 DAT among effective exposures. Total microcystin concentrations were measured in effective treatments at 1, 4, and 9 DAT to discern potential for microcystin persistence following exposures to the effective formulations and exposure concentrations. Overall, several formulations including GreenClean Liquid® 5.0, GreenClean Liquid® 5.0 combined with Hydrothol® 191, and the copper-based algaecides evaluated (Algimycin® PWF, Argos, Captain® XTR, Cutrine® Ultra, and SeClear®) achieved significant and similar effects on target cyanobacteria. The chelated copper-based formulations (Algimycin® PWF, Argos, Captain® XTR, and Cutrine® Ultra) resulted in relatively less microcystin release 1 DAT and lesser total microcystin concentrations 4 DAT. At 9 DAT, total microcystin concentrations were significantly lower than in untreated controls in all treatments evaluated. These results provide the necessary comparative performance data for preliminary decision-making and designing additional studies at larger scales. Importantly, the comparative toxicity data and approach provided in this study demonstrate the initial steps for development of site-specific management strategies for Lake Okeechobee and other areas impacted by harmful algal blooms with large spatial and temporal scales.


Assuntos
Cianobactérias/fisiologia , Herbicidas/toxicidade , Microcistinas/metabolismo , Clorofila/análogos & derivados , Clorofila A , Cobre/toxicidade , Sulfato de Cobre/toxicidade , Cianobactérias/efeitos dos fármacos , Florida , Proliferação Nociva de Algas , Lagos/microbiologia , Microcystis , Água
13.
Water Res ; 190: 116735, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33352526

RESUMO

The occurrence of pharmaceuticals and personal care products (PPCPs) in wastewater poses huge environmental threats, even at trace concentrations, and novel approaches are urged due to the inefficiencies of conventional wastewater treatment plants, especially when processing contaminants at high concentrations. Meanwhile, another widespread problem in the aquatic domain is the occurrence of harmful algal blooms (HABs) which cause serious damage to the ecosystem, but have rarely been investigated for possible valorization. This study investigated the possibilities, mechanisms, and effects of toxin release of using a harmful cyanobacterial species, Microcystis aeruginosa (M. aeruginosa), in order to remove the widely used drug, tetracycline, at high concentration. The results were compared with the performance obtained by the use of the hitherto generally-selected chlorophyte alga Chlorella pyrenoidosa (C. pyrenoidosa) for tetracycline concentrations of 10-100 mg L-1. M. aeruginosa exhibited a much more effective and rapid tetracycline removal (over 98.0% removal in 2 days) than did C. pyrenoidosa (36.7%-93.9% in 2 days). A comprehensive kinetic investigation into probable removal pathways indicated that, theoretically, bio-remediation dominated the process by M. aeruginosa (71.6%), while only accounting for 20.5% by C. pyrenoidosa. Both microalgae promoted the hydrolysis of tetracycline under conditions of increased pH and inhibited abiotic photolytic reactions by the shading effect to the water column, when compared with control experiments. Although identical degradation by-products were identified from treatments by both microalgal species, distinct by-products were also confirmed, unique to each treatment. Moreover, the growth of M. aeruginosa biomass exhibited strong tolerance to tetracycline exposure and released significantly lower levels of microcystin-LR, compared with the control systems. This study supports the possibility of reusing HABs species for the effective remediation of antibiotics at high concentrations. We have further suggested possible mechanisms for remediation and demonstrated control of toxin release.


Assuntos
Chlorella , Cianobactérias , Microcystis , Antibacterianos , Ecossistema , Microcistinas
14.
Ecotoxicol Environ Saf ; 209: 111810, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33360217

RESUMO

The number of undesirable environmental impacts of fish feed has been reported widely. Although repeated fish feed exposures are more prospective to occur in water, previous studies were mostly conducted as a single exposure of fish feed. In order to fill these gaps, a 40 days incubator experiment was conducted to explore the effects of fish feed addition scenarios during the lag phase with prometryn on both Microcystis aeruginosa growth and concentrations of nutrients. The maximum algae densities in groups of single exposure were 6.0-26.2% and 8.8-74.4% higher than those in groups of double and triple exposures, respectively (P < 0.05). At the beginning of the experiment, concentrations of nutrients in groups with different feed exposure scenarios were significantly different. The pattern of nutrient limitation showed a transformation from phosphorus limitation to nitrogen limitation generally. Furthermore, the average inhibition rates of algae by prometryn in the case of a single fish feed exposure were 4.6-9.4% lower than those under double exposures, and 22.0-26.8% lower than those under triple exposures (P < 0.05). In addition, algae growth rates have been developed as a function of concentrations of consumed nutrients (R2 = 0.410-0.932). Based on the above results, we concluded that in terms of limiting algae growth multiple low-dosage additions of fish feed were considered as a better addition pattern. By optimizing feed addition scenarios, there is considerable potential to increase the environmental sustainability of aquaculture.


Assuntos
Ração Animal , Herbicidas/toxicidade , Microcystis/efeitos dos fármacos , Prometrina/toxicidade , Animais , Aquicultura/métodos , Peixes , Microcystis/crescimento & desenvolvimento , Nitrogênio/análise , Nutrientes , Fósforo/análise , Estudos Prospectivos , Qualidade da Água
15.
Chemosphere ; 266: 129191, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33310358

RESUMO

The inactivation of bacteriophage MS2 by sodium hypochlorite was investigated to understand the effect of solution chemistry on the disinfection efficacy in the presence of particles. Kaolinite and Microcystis aeruginosa (M. aeruginosa) were used as the models of inorganic and organic particles to simulate high turbidity and algal cells, respectively, in drinking water sources. In both particle-containing solutions, lower pH, the presence of cations (di-valent Ca2+) and natural organic matters (NOM) were regarded as the main factors to influence the aggregation and inactivation of MS2. The results showed that MS2 aggregated in all solutions at pH 3.0, protecting the inner viruses. At pH 7.0, the presence of Na+ cations (0-200 mmol/L) did not affect the inactivation efficacy of MS2, which always followed the order of particles-free ≈ kaolinite > M. aeruginosa. The inactivation efficacy of MS2 in the presence of Ca2+ cations followed the order of kaolinite > particles-free > M. aeruginosa at 0-50 mmol/L Ca2+ cations, while the inactivation efficacy remained almost constant in the range of 100-200 mmol/L Ca2+ cations. By contrast, kaolinite offered not enough protection to adsorbed MS2, but MS2 aggregation decreased disinfection efficacy at a high concentration of Ca2+ cations. Moreover, the presence of humic acid as NOM decreased the inactivation of MS2 more significantly than M. aeruginosa due to the more consumption of free chlorine from humic acids. Therefore, the co-existence of NOM and di-valent Ca2+ cations are potential challenges for the inactivation of viruses by sodium hypochlorite in safe drinking water.


Assuntos
Levivirus , Microcystis , Desinfecção , Caulim , Hipoclorito de Sódio/farmacologia , Inativação de Vírus
16.
Chemosphere ; 267: 129244, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33321278

RESUMO

A single exposure to glyphosate or antibiotic may facilitate cyanobacterial growth at currently reported concentrations due to hormesis. However, the influence of these contaminants on cyanobacteria under combined exposure conditions has not been reported. In this study, proteomic mechanisms for the combined effects of glyphosate and a quaternary antibiotic mixture of amoxicillin, sulfamethoxazole, tetracycline, and ciprofloxacin in a dominant bloom-forming cyanobacterium (Microcystis aeruginosa) were investigated and compared with those for single exposure to glyphosate. The growth rate of M. aeruginosa, photosynthetic activity indicated by Fv/Fm, and microcystin production ability showed a typical U-shaped hormetic dose-response to glyphosate exposure. Upregulated proteins related to photosynthesis and biosynthesis, as well as increased photosynthetic activity, were responsible for the stimulated growth induced by 0.1-5 µg/L glyphosate, while the upregulation of mcyB protein contributed to increased microcystin synthesis in glyphosate-treated cells. The presence of 0.04-0.2 µg/L mixed antibiotics significantly (p < 0.05) enhanced the stimulation effects of glyphosate. Combined exposure to glyphosate and mixed antibiotics promoted microcystin synthesis through the upregulation of six microcystin synthesis regulatory proteins (mcyC, mcyF, mcyG, mcyI, MAE_56520, and ntcA) and stimulated cyanobacterial growth through the upregulation of proteins involved in photosynthesis, cell division, carbon fixation, pentose phosphate, translation, and chlorophyll synthesis. Combined exposure to glyphosate and antibiotic contaminants promoted cyanobacterial growth at no-effect concentrations of single exposure (0.04 µg/L for mixed antibiotics; 0.05, 10 and 100 µg/L for glyphosate), suggesting an increased threat from combined contamination to aquatic ecosystems through promoting the formation of cyanobacterial bloom.


Assuntos
Microcystis , Antibacterianos/toxicidade , Ecossistema , Glicina/análogos & derivados , Microcistinas/toxicidade , Proteômica
17.
Chemosphere ; 263: 127708, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33296998

RESUMO

In water treatment process, Microcystis colonies can be effectively removed by coagulants. However, the use of popular coagulants could cause adverse health effects in humans or increase the amount of sludge. Meanwhile, Microcystis unicells are much more difficult to remove than colonies, due to their small size and dispersed distribution. This study proposed and analyzed the flocculation of Microcystis unicells induced by pH regulation. The particle size, zeta potential, cell viability and integrity, cytochemical changes, and cell-to-cell connections were recorded during pH regulation. Results showed that when pH was adjusted in the range of 2.5 to 2 by HCl (1.2 M), Microcystis unicells aggregated to form flocs as large as 28 µm, which are easy to remove by filtration or sedimentation. The overwhelming majority of cells were intact and inactivated in the optimal pH range (2.5-2). Thus, pH regulation is an environment-friendly and cost-effective method to remove Microcystis unicells, which can be potentially applied to water treatment.


Assuntos
Microcystis , Purificação da Água , Floculação , Humanos , Concentração de Íons de Hidrogênio , Esgotos
18.
Chemosphere ; 263: 128299, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33297241

RESUMO

In the last decades, the use of bisphenol A has attracted global attention resulting from its actions as an endocrine disrupting compound. In this regard, various bisphenol analogues have been manufactured as a replacement for this compound in consumer products. As a result of the high production volumes, different bisphenol analogues are entered into the terrestrial and aquatic environment, which consequently leads to their increasing contamination and may pose serious risk to organisms. Nevertheless, only few studies have reported on the toxic effect of bisphenol analogues on phytoplankton. Therefore, in this study, the anticyanobacterial activity of six bisphenol analogues and their mixture were investigated for the first time. Bisphenol AF, bisphenol B and bisphenol C (14 d, EC50 12.88-54.87 mg L-1) exhibit more toxic effect to both tested species in comparison to bisphenol A (14 d, EC50 55.27-78.96 mg L-1). Moreover, data show that mixture of bisphenol analogues (14 d, EC50 32.32-60.88 mg L-1) exhibit toxic effect similar to or even stronger than that of bisphenol A. The toxic effect of bisphenol analogues, singly and in combination on the growth of both cyanobacteria species was arranged in the following order: bisphenol AF > bisphenol C> bisphenol B> bisphenol A> bisphenol E> bisphenol BP and bisphenol B> bisphenol AF > bisphenol C> bisphenol A> bisphenol E> bisphenol BP for Anabaena variabilis and Microcystis aeruginosa, respectively. This research aims to assure a basic understanding of the toxic effects of bisphenol analogues on cyanobacteria and provides a more comprehensive view on environmental risk assessment.


Assuntos
Anabaena variabilis , Anabaena , Microcystis , Compostos Benzidrílicos , Fenóis
19.
PLoS One ; 15(12): e0244000, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33320886

RESUMO

The aim of this study was to investigate the potential interference of cyanobacterial metabolites, in particular microcystins (MCs), with steroid hormone biosynthesis. Steroid hormones control many fundamental processes in an organism, thus alteration of their tissue concentrations may affect normal homeostasis. We used liquid chromatography-tandem mass spectrometry (LC-MS/MS) to investigate the modulation of 14 hormones involved in the adrenal steroid biosynthesis pathway using forskolin-treated H295R cells, following exposure with either microcystin-LR (MC-LR) alone, a mixture made up of MC-LR together with eight other MCs and nodularin-R (NOD-R), or extracts from the MC-LR-producing Microcystis aeruginosa PCC7806 strain or its MC-deficient mutant PCC7806mcyB-. Production of 17-hydroxypregnenolone and dehydroepiandrosterone (DHEA) was increased in the presence of MC-LR in a dose-dependent manner, indicating an inhibitory effect on 3ß-hydroxysteroid dehydrogenase (3ß-HSD). This effect was not observed following exposure with a MCs/NOD-R mixture, and thus the effect of MC-LR on 3ß-HSD appears to be stronger than for other congeners. Exposure to extracts from both M. aeruginosa PCC7806 and M. aeruginosa PCC7806mcyB- had an opposite effect on 3ß-HSD, i.e. concentrations of pregnenolone, 17-hydroxypregnenolone and DHEA were significantly decreased, showing that there are other cyanobacterial metabolites that outcompete the effect of MC-LR, and possibly result instead in net-induction. Another finding was a possible concentration-dependent inhibition of CYP21A2 or CYP11ß1, which catalyse oxidation reactions leading to cortisol and cortisone, by MC-LR and the MCs/NOD-R mixture. However, both M. aeruginosa PCC7806 and M. aeruginosa PCC7806mcyB- extracts had an opposite effect resulting in a substantial increase in cortisol levels. Our results suggest that MCs can modulate steroidogenesis, but the net effect of the M. aeruginosa metabolome on steroidogenesis is different from that of pure MC-LR and independent of MC production.


Assuntos
17-alfa-Hidroxipregnenolona/metabolismo , 3-Hidroxiesteroide Desidrogenases/antagonistas & inibidores , Desidroepiandrosterona/biossíntese , Inibidores Enzimáticos/farmacologia , Microcistinas/farmacologia , Microcystis/química , Linhagem Celular Tumoral , Família 11 do Citocromo P450/antagonistas & inibidores , Família 21 do Citocromo P450/antagonistas & inibidores , Humanos
20.
PLoS One ; 15(12): e0243582, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33351804

RESUMO

Bloom-forming cyanobacteria dramatically influence nutrient cycling in eutrophic freshwater lakes. The phosphorus (P) assimilation and release of bloom-forming cyanobacteria significantly may also affect the phosphorus source and amounts in water. To understand the phosphorus release process of bloom-forming cyanobacteria below the accumulated surface and sedimentary bloom-forming cyanobacteria, the degradation of bloom-forming cyanobacteria dominated by Microcystis spp. at different cell density in the dark was investigated over a 25-day microcosm experiment. The dissolved inorganic phosphorus (DIP) and dissolved total phosphorus (DTP) contents increased with the increment of cyanobacterial density, and the dark status markedly increased the proportion of DIP in water during the decline period of bloom-forming cyanobacteria. Meanwhile, the process of cyanobacterial apoptosis accompanied by the changes of malondialdehyde (MDA) and phosphatase (AKP) contents, and the increases of superoxide dismutase (SOD) and catalase (CAT) activities of cyanobacteria in the dark, especially in low-density groups (5.23×108 cells L-1), which further affect the physicochemical water parameters. Moreover, the DIP release from high-density cyanobacteria (7.86×107 cells L-1~5.23×108 cells L-1) resulted from the relative abundance of organophosphorus degrading bacteria in the dark. Therefore, the fast decay of cyanobacteria in the dark could accelerate DIP release, the high DIP release amount from accumulated bloom-cyanobacteria provide adequate P quickly for the sustained growth of cyanobacteria.


Assuntos
Cianobactérias/crescimento & desenvolvimento , Eutrofização , Fósforo/metabolismo , Cianobactérias/citologia , Cianobactérias/metabolismo , Lagos/microbiologia , Viabilidade Microbiana , Microcystis/citologia , Microcystis/crescimento & desenvolvimento , Microcystis/metabolismo , Fotoperíodo
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