Microcystis Flos-aquae Research Articles

Influence of algal organic matter in the in-situ flotation removal of Microcystis using positively charged bubbles

Positively charged bubbles efficiently capture and remove negatively charged algal cells without relying on coagulation-flocculation. However, the efficiency is notably influenced by the presence of algal organic matter (AOM). This study investigated the impact of AOM composition on flotation performance by analyzing AOM from various growth phases of Microcystis flos-aquae. The results indicated that low-concentration AOM (<5 mg C L-1), particularly the high molecular weight (>30 kDa) fractions containing high percentages of protein during the exponential growth phase, significantly improved the flotation efficiency by >18%. A high-speed camera system illustrates the pivotal role of low-concentration protein-containing AOM in forming network structures that enhance cell capture. These protein-driven network structures, which enhance the flotation efficiency, provide valuable insights into the development of effective in-situ algal bloom prevention techniques.

Effects of suspended particles in the Jinjiang River Estuary on the physiological and biochemical characteristics of Microcystis flos-aquae.

The effects of different concentrations (100, 150, 200, 250mg/L) and different particle sizes (0-75μm, 75-120μm, 120-150μm, 150-500μm) on the soluble protein content, superoxide dismutase (SOD) and catalase (CAT) activity, malondialdehyde (MDA) content, chlorophyll a (Chla) content, and photosynthetic parameters of Microcystis flos-aquae were studied, and the mechanism of the effect of suspended particulate matter on the physiology and biochemistry of Microcystis flos-aquae was discussed. The results showed that the soluble protein content of Microcystis flos-aquae did not change noticeably after being stressed by suspended particles of different concentrations/diameters. The SOD activity of Microcystis flos-aquae first increased and then decreased with increasing suspended particulate matter concentrations. The SOD activity of Microcystis flos-aquae reached 28.03 U/mL when the concentration of suspended particulate matter was 100mg/L. The CAT activity of Microcystis flos-aquae increased with increasing concentrations of suspended particles and reached a maximum value of 12.45 U/mg prot in the 250mg/L concentration group, showing a certain dose effect. Small particles had a more significant effect on SOD, CAT, and MDA in Microcystis flos-aquae than large particles. The larger the concentration was and the smaller the particle size was, the stronger the attenuation of light and the lower the content of Chla. Both the maximum quantum yield of PSII (Fv/Fm) and the potential photosynthetic activity of PSII (Fv/F0) of Microcystis flos-aquae increased at first and then decreased under different concentrations/sizes of suspended particles. The relative electron transfer rate gradually returned to a normal level over time. There was no significant difference in the initial slope (α) value between the treatment group and the control group, and the maximum photo synthetic rate (ETRmax) and the semilight saturation (Ik) decreased.

Parallel filtration for solid-liquid separation: A case study of highly-efficient algal removal under parallel configuration driven by magnetic force

In traditional membrane filtration systems, the perpendicular permeate flow to the membrane surface causes the retentate to block the membrane pores, which results in an unavoidable cake resistance, thus making it difficult to achieve high filtration flux. In this study, a novel parallel filtration configuration driven by magnetic force was proposed for the removal of Microcystis flos-aquae. The results showed that the filtration flux under parallel filtration configuration reached 750,000 L⋅m−2⋅h−1 which is 3 times higher than the highest flux (280,000 L⋅m−2⋅h−1) reported in previous literature for algal removal. The permeate flow did not need to cross the cake layer, and the “pore size” of the filter chamber can be as high as 10 cm, thus resulting in negligible resistance (2.1 × 101 m−1) and higher filtration flux compared to traditional vertical filtration. For the magnetic-driven parallel filtration, the use of cationic polyacrylamide after polyaluminum chloride coagulation and magnetic particles (MPs) spiking was necessary. Increasing the MPs size and dosage further improved the filtration performance. Moreover, excessive flow velocity would affect the capture probability of algae-MPs aggregates by the magnetic field, which can be overcome by enhancing the magnetic field strength. We have developed a parallel filtration configuration for highly-efficient solid-liquid separation with simple and sustainable processes, which have the potential for rapid, efficient and large-scale applications in product purification, contaminant removal, and resource recycling in the future.

Cyanobacteria of Ukraine: Actual Diversity, Trends of Taxonomic Changes, Features of Zonal and Ectopic Distribution

Presenting the results of a critical taxonomic revision of the list of cyanobacteria of Ukraine and the analysis of their zonal, ecological and typological distribution. The list includes 766 species from 150 genera. They belong to the class &lt;i&gt;Cyanophyceae&lt;/i&gt; Schaftner, four subclasses, 7 orders and 46 families. The subclass &lt;i&gt;Oscillatoriophycideae&lt;/i&gt; (4 orders, 21 families, 65 genera, 333 species) is characterized by the greatest species and taxonomic diversity. The leading orders are &lt;i&gt;Synechococcales&lt;/i&gt; (34.1&amp;#37;), &lt;i&gt;Nostocales&lt;/i&gt; (26.8&amp;#37;) and &lt;i&gt;Oscillatoriales&lt;/i&gt; (25.5&amp;#37;). Genera &lt;i&gt;Phormidium&lt;/i&gt; K&amp;#252;tz. ex Gomont (7.3&amp;#37; of species), &lt;i&gt;Leptolyngbya&lt;/i&gt; Anagn. et Kom&amp;#225;rek (5.4&amp;#37;), &lt;i&gt;Calothrix&lt;/i&gt; C. Agardh ex Bornet et Flahault (3.8&amp;#37;) and &lt;i&gt;Oscillatoria&lt;/i&gt; Vaucher ex Gomont (3.7&amp;#37;) lead in species richness. The obtained results are significantly different from the generalized data on the species and taxonomic diversity of cyanobacteria of Ukraine as of 2005. The growth of generic and species diversity is partly related to nomenclature and taxonomic changes; 7 genera and 50 species are new floristic records, revealed using molecular methods. The distribution of cyanobacteria on the territory of Ukraine has specific features. The highest diversity and uniqueness of species composition is characteristic of the Steppe zone of Ukraine: 539 species from 124 genera of &lt;i&gt;Cyanophyceae.&lt;/i&gt; Of these, 101 species and 11 genera were recorded only within this zone. The ecological spectrum of Ukrainian cyanoflora consists of freshwater (66.3&amp;#37;), marine (14.5&amp;#37;), and terrestrial (9.5&amp;#37;) species, as well as species with a wide ecological range (7.3&amp;#37;), brackish water (4.1&amp;#37;) and eurytopic (1.4&amp;#37;) species. The representation of species in different habitat types varies widely. Most species were found in rivers (56.5&amp;#37; of the total list), lakes (38.0&amp;#37;), ponds (34.6&amp;#37;) and reservoirs (29.4&amp;#37;). Among continental water bodies, swamps have the most peculiar species composition (9.8&amp;#37; of species are found only here). Floodplain water bodies have the least specific species composition (0.5&amp;#37;). Among non-aquatic habitats, the largest number of species was found in soils (excluding saline): 179 species from 55 genera, 15.6&amp;#37; of species occur only in this type of habitats. In the Ukrainian sectors of the Black and Azov seas, 228 species from 80 genera of cyanobacteria were found, of which 41 species (17.9&amp;#37;) were not registered in other types of habitats. 43 species are widely distributed in water bodies and soils of Ukraine. They include the water bloom agents&lt;i&gt; Dolichospermum spiroides&lt;/i&gt; (Kleb.) Wacklin et al., &lt;i&gt;Microcystis flosaquae&lt;/i&gt; (Wittrock) Kirchn. and &lt;i&gt;M. viridis&lt;/i&gt; (A.Braun in Rabenh.) which most often occur in reservoirs of the plain part of Ukraine.

Ціанобактерії України: актуальне різноманіття, тенденції таксономічних змін, особливості зонального та ектопічного поширення

The paper presents the results of a critical taxonomic revision of the list of cyanobacteria of Ukraine and the analyzis of their zonal, ecological and typological distribution. The list includes 766 species from 150 genera. They belong to the class Cyanophyceae Schaftner, four subclasses, 7 orders and 46 families. The subclass Oscillatoriophycideae (4 orders, 21 families, 65 genera, 333 species) is characterized by the greatest species and taxonomic diversity. The leading orders are Synechococcales (34.1%), Nostocales (26.8%) and Oscillatoriales (25.5%). Genera Phormidium Kütz. ex Gomont (7.3% of species), Leptolyngbya Anagn. et Komárek (5.4%), Calothrix C.Agardh ex Bornet et Flahault (3.8%) and Oscillatoria Vaucher ex Gomont (3.7%) lead in species richness. The obtained results are significantly different from the generalized data on the species and taxonomic diversity of cyanobacteria of Ukraine as of 2005. The growth of generic and species diversity is partly related to nomenclature and taxonomic changes; 7 genera and 50 species are new floristic records, revealed including using molecular methods. The distribution of cyanobacteria on the territory of Ukraine has specific features. The highest diversity and uniqueness of the species composition is characteristic of the Steppe zone of Ukraine: 539 species from 124 genera of Cyanophyceae. Of these, 101 species and 11 genera were recorded only within this zone. The ecological spectrum of Ukrainian cyanoflora consists of freshwater (66.3%), marine (14.5%), terrestrial (9.5%) species, as well as species with a wide ecological amplitude (7.3%), brackish water (4.1%) and eurytopic (1.4%) species. The representation of species in different habitat types varies widely. Most species were found in rivers (56.5% of the total list), lakes (38.0%), ponds (34.6%) and reservoirs (29.4%). Among continental water bodies, swamps have the most peculiar species composition (9.8% of species are found only here). Floodplain water bodies have the least specific species composition (0.5%). Among non-aquatic habitats, the largest number of species was found in soils (excluding saline): 179 species from 55 genera, 15.6% of species occur only in this type of habitats. In the Ukrainian sectors of the Black and Azov seas, 228 species from 80 genera of cyanobacteria were found, of which 41 species (17.9%) were not registered in other types of habitats. 43 species are widespread in Ukraine. They include the water bloom agents Dolichospermum spiroides (Kleb.) Wacklin et al., Microcystis flosaquae (Wittrock) Kirchn. and M. viridis (A.Braun in Rabenh.) which most often occur in reservoirs of the plain part of Ukraine.

Effects of Ginkgo biloba extract on growth, photosynthesis, and photosynthesis-related gene expression in Microcystis flos-aquae.

The inhibitory effect of plants on algae offers a new and promising alternative method for controlling harmful algal blooms. Previous studies showed that anti-algal effects might be obvious from extracts of fallen leaves from terrestrial plants, which had great potential for cyanobacterial control in field tests. To investigate the anti-algal activities and main algicidal mechanisms of Ginkgo biloba fallen leaves extracts (GBE) on Microcystis flos-aquae, the cell density, photosynthetic fluorescence, and gene expression under different concentrations of GBE treatments were tested. GBE (3.00 g L-1) showed a strong inhibitory effect against M. flos-aquae with an IC50 (96h) of 0.79 g L-1. All the inhibition rates of maximal quantum yield (Fv/Fm), effective quantum yield (Fq'/Fm'), and maximal relative electron transfer rate (rETRmax) were more than 70% at 96 h at 3.00 g L-1 and more than 90% at 6.00 g L-1. Further results of gene expression of the core proteins of PSII (psbD), limiting enzyme in carbon assimilation (rbcL), and phycobilisome degradation protein (nblA) were downregulated after exposure. These findings emphasized that photosynthetic damage is one of the main toxic mechanisms of GBE on M. flos-aquae. When exposed to 12.00 g L-1 GBE, no significant influence on the death rate of zebrafish or photosynthetic activity of the three submerged plants was found. Therefore, appropriate use of GBE could control the expansion of M. flos-aquae colonies without potential risks to the ecological safety of aquatic environments, which means that GBE could actually be used to regulate cyanobacterial blooms in natural waters.

Removal of cyanobacteria using novel pre-pressurized coagulation: The effect of cellular properties and algogenic organic matter characteristics

• Pre-pressurized coagulation reduces coagulant dosage for M. flos-aquae removal. • Changes in cell properties/AOM characteristics after pre-pressurization is studied. • Pre-pressurization ruptures mucilaginous sheath and raises coagulation efficiency. • Exposure to more electronegative functional groups promotes the cell-CPAM binding. Pressurization pretreatment is reported as a novel pretreatment method for the coagulation removal of Microcystis sp . from eutrophicated water, as less coagulant is required than without pressurization. However, how cellular properties and algogenic organic matter (AOM) characteristics change with pressurization pretreatment and thus reduce the coagulant dose are still not understood. Using Microcystis flos-aquae in Lake Taihu, this study analyzed the changes in cellular morphology, size distribution, and charge density, as well as the changes in concentration and composition of cell-based protonated functional groups. Coagulation experiments using different combinations of cells and AOM with/without pressurization pretreatment showed that the changes in cell surface properties played a bigger role in coagulation enhancement than AOM. The enhancement of the coagulation efficiency of M. flos-aquae with pressurization pretreatment is related to the rupture of the mucilaginous sheath and subsequent exposure of cells with more active functional groups, the content of phosphodiester, carboxyl and phosphoryl functional groups on the surface of M. flos-aquae cells increased by 55%, 29% and 203%, respectively. Thus increasing the binding sites between M. flos-aquae cells and cationic polyacrylamide (CPAM). As a result, with pressurization pretreatment, the dose of CPAM was reduced from 5 mg L −1 to 0.8 mg L −1 for the same removal efficiency of 90%. These results may help us understand the mechanism by which pressurization treatment impacts M. flos-aquae coagulation and thus provide a new perspective for the low-cost and sustainable removal of cyanobacterial blooms.

Effects of extracellular organic matter on chitosan coagulation-microfiltration harvesting of Microcystis flos-aquae

Extracellular organic matter (EOM) is considered an important cause of membrane fouling when harvesting Microcystis cells using filtration technology. Coagulation pre-treatment has increasingly been applied as an effective method to alleviate membrane fouling. However, the effects and mechanisms of EOM on coagulation-microfiltration of Microcystis cells remain unclear. This study investigated the coagulation-microfiltration performance of EOM-free and EOM-containing Microcystis flos-aquae and explored the effect mechanisms of EOM from the perspective of floc characteristics and deposited algal cake structure. The results showed that the presence of EOM decreased the average flux from 4256.4 L/(m2·h) to 3378.4 L/(m2·h) at the optimal chitosan dosage of 15.11 mg/g. Electrostatic adsorption and/or bridging between carboxyl and amino/hydroxyl groups in EOM and chitosan resulted in a loose floc structure and high compressibility of the cake layer, thus reducing the filtration performance. In addition, interception of EOM in the cake layer contributed to membrane fouling during coagulation-microfiltration. These results revealed the mechanism by which EOM hinders coagulation-filtration performance, which would be helpful for the development of efficient coagulation-filtration-based microalgal harvesting techniques.

Novel Algicides against Bloom-Forming Cyanobacteria from Allelochemicals: Design, Synthesis, Bioassay, and 3D-QSAR Study.

Simple SummaryDue to the frequent outbreaks of cyanobacteria bloom worldwide, research on novel algicides has attracted more and more attention. At present, allelochemicals have been reported as promising natural algicides. However, current studies mainly focus on the parent compounds, and the structural modification of original allelochemicals has been rarely involved. In this study, phenolic acid derivatives were innovatively synthesized as potential algicides, and lead compounds with excellent activity were found. For instance, upon the algicidal activity on Aphanizomenon flos-aquae, the EC50 of the best active compound 18 reached 0.63 µM (0.17 mg/L), while the EC50 values of previously reported allelochemicals have been basically at the mg/L level. The result indicates that the algicides reported in this study are more efficient at inhibiting cyanobacteria with lower effective concentrations than most previously reported compounds. Moreover, 3D-QSAR models were constructed and provided a theoretical guidance for further structure optimization of compounds to achieve better algicidal activity.Cyanobacteria bloom caused by water eutrophication has threatened human health and become a global environmental problem. To develop green algicides with strong specificity and high efficiency, three series of ester and amide derivatives from parent allelochemicals of caffeic acid (CA), cinnamic acid (CIA), and 3-hydroxyl-2-naphthoic acid (HNA) were designed and synthesized. Their inhibitory effects on the growth of five harmful cyanobacterial species, Microcystis aeruginosa (M. aeruginosa), Microcystis wesenbergii (M. wesenbergii), Microcystis flos-aquae (M. flos-aquae), Aphanizomenon flos-aquae (Ap. flos-aquae), and Anabaena flos-aquae (An. flos-aquae), were evaluated. The results revealed that CIA esters synthesized by cinnamic acid and fatty alcohols showed the best inhibition effect, with EC50 values ranging from 0.63 to >100 µM. Moreover, some CIA esters exhibited a good selectivity in inhibiting cyanobacteria. For example, the inhibitory activity of naphthalen-2-yl cinnamate was much stronger on Ap. flos-aquae (EC50 = 0.63 µM) than other species (EC50 > 10 µM). Three-dimensional quantitative structure–activity relationship (3D-QSAR) analysis was performed and the results showed that the steric hindrance of the compounds influenced the algicidal activity. Further mechanism study found that the inhibition of CIA esters on the growth of M. aeruginosa might be related to the accumulation of malondialdehyde (MDA).

Continuous hydrodynamic mixing weakens the dominance of Microcystis: evidences from microcosm and lab experiments.

Hydrodynamic mixing is one of the important environment factors in determining phytoplankton community compositions. Here the influences of continuous hydrodynamic mixing on abundance, morphology, and dominance of Microcystis were investigated in microcosm and lab experiments. Our research results showed that Cyanophyta contributed 57.16% to the total biomass in control, but Chlorophyta was the dominant group in continuous hydrodynamic mixing (CHM) group, contributing 76.54% to the total biomass in the microcosm experiment. The average number of Microcystis in control was 1.95 folds in CHM group. However, the mean abundance of Scenedesmus quadricauda and Pseudanabaena limnetica in CHM was 2.47 and 2.97 folds in control. In the lab experiment, the average number of Microcystis flos-aquae in control was 2.97 folds in CHM group. The mean size of M. flos-aquae colony in control (34.65 μm) group were significantly bigger than that in the CHM (26.78 μm) group. This research results demonstrated that continuous hydrodynamic mixing weakened the dominance of Microcystis, but was beneficial for the others algae (S. quadricauda and P. limnetica) and is helpful in understanding the effect of hydrodynamic mixing on Microcystis blooms in freshwater ecosystem.

Cyanobacteria, cyanotoxins, and their histopathological effects on fish tissues in Feh\xe9rv\xe1rcsurg\xf3 reservoir, Hungary

Cyanobacteria are important members of lake plankton, but they have the ability to form blooms and produce cyanotoxins and thus cause a number of adverse effects. Freshwater ecosystems around the world have been investigated for the distribution of cyanobacteria and their toxins and the effects they have on the ecosystems. Similar research was performed on the Fehérvárcsurgó reservoir in Hungary during 2018. Cyanobacteria were present and blooming, and the highest abundance was recorded in July (2,822,000 cells/mL). The species present were Aphanizomenon flos-aquae, Microcystis flos-aquae, Microcystis wesenbergii, Cuspidothrix issatschenkoi, Dolichospermum flos-aquae, and Snowella litoralis. In July and September, the microcystin encoding gene mcyE and the saxitoxin encoding gene sxtG were amplified in the biomass samples. While a low concentration of microcystin-RR was found in one water sample from July, analyses of Abramis brama and Carassius gibelio caught from the reservoir did not show the presence of the investigated microcystins in the fish tissue. However, several histopathological changes, predominantly in gills and kidneys, were observed in the fish, and the damage was more severe during May and especially July, which coincides with the increase in cyanobacterial biomass during the summer months. Cyanobacteria may thus have adverse effects in this ecosystem.

Molecular detection of some toxogenic cyanobacteria in Tigris River in Baghdad-Iraq.

Cyanobacteria and their pollution are being increasingly commonly reported worldwide that cause a serious hazard to environmental and human health. Cyanotoxin was the most algal toxin reported to be produced by several orders of cyanobacteria. This study aimed to provide a technique to detect cylindrosprmopsin and saxitoxin biosynthesis genes in the river. In November, December 2019, and January 2020. Cyanobacteria were isolated from freshwater of Tigris River and identified by compound microscope also conventional PCR. Five isolates of cyanobacteria that successfully amplified a gene fragment from the phycocyanin were found in all cyanobacteria (Microcystis flosaquae, Microcystis sp, anabaena circinalis, nostoc commune and westiellopsis prolifica) and all isolates successfully amplified aoaC gene to detecting the cylidrospemopsin and the saxitoxin. Our results concluded that PCR assay can be used for early detection of cylidrospemopsin and the saxitoxin producing cyanobacteria in river water that useful to stations responsible for the preparation of drinking water to public.

Enantioselective effects of the fungicide metconazole on photosynthetic activity in Microcystis flos-aquae

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.

Intermittent disturbance combined N and P adding favor colony size and abundance of Microcystis flos-aquae

Nutrients and disturbance are both important environmental factors in the freshwater ecosystem. Here we present data on the effects of intermittent disturbance (ID), nitrogen and phosphorus adding (+N+P), and intermittent disturbance combined N and P adding (ID+N+P) on colony size and abundance of Microcystis flos-aquae in lab experiments. Results showed that the mean colony sizes of M. flos-aquae in ID+N+P group were1.68, 1.56, 1.17 times that in the control, +N+P, ID groups, respectively. Moreover, the average number of M. flos-aquae in ID+N+P group were 1.47, 1.19, 1.42 times those in the control, +N+P, ID groups, respectively. The average concentration of EPS (extracellular polysaccharides) in ID and ID+N+P group was significantly higher than those in control and +N+P groups. Results demonstrated that intermittent disturbance combined N and P adding promoted colony size and abundance of M. flos-aquae. These results suggest that intermittent disturbance combined N and P adding plays an important role in the formation of Microcystis blooms in freshwater ecosystems.

Limno-ecological assessment of lentic ecosystems in the western Mediterranean basin (Turkey) using phytoplankton indices.

Great attention has been given to freshwater ecosystems worldwide due to the increased exploitation of water resources and the degradation of water quality. This study was aimed to demonstrate the phytoplankton-stressor interactions using multivariate approaches and assess the ecological conditions of 28 sampling stations of 12 lentic ecosystems (five lakes and seven reservoirs) in the western Mediterranean basin using phytoplankton indices in dry and rainy seasons 2018. Freshwater and brackish water systems were separately ordinated by canonical correspondence analysis. The brackish ecosystems were under pressures of Ar (arsenic), N-N[Formula: see text] (nitrite), Ca (calcium), EC (electrical conductivity), Cl (chloride), B (boron), etc., whereas shallow freshwater ecosystems were associated with total organic carbon. These factors had significant effects on phytoplankton distribution among lentic ecosystems on the basin. Ecological associations of phytoplankton assemblages varied in the western Mediterranean basin during the study. Pseudanabaena catenata and Palatinus apiculatus, considered tolerant taxa, are associated with higher Ar, EC, and V (vanadium) while Desmodesmus abundans and Microcystis flos-aquae are related to total organic carbon. The modified PTI (phytoplankton trophic index) had the highest correlation coefficient value. Scores of the PTI varied from 2.02 in Çavdır Reservoir to 2.59 in Lake Kocagöl. Results of phytoplankton indices indicated that two (Gölhisar and Yazır) lakes and two (Yapraklı and Çavdır) reservoirs were classified as Good, and three lakes and five reservoirs were classified as Moderate condition. Other predicted classifications (high, poor, and bad) by phytoplankton metrics were not represented. The modified PTI could be a suitable phytoplankton metric for assessing the ecological status of lentic ecosystems in the Mediterranean system according to its highest correlation coefficient value. Overall, the results of this limno-ecological study demonstrated that responses of phytoplankton taxa to explanatory factors provide crucial ecological information about their ecology and to estimate the ecological status of lentic ecosystems.

The effect of plant extracts on growth and photosynthetic fluorescence characteristics of Microcystis flos-aquae.

The cyanobacteria Microcystis flos-aquae can cause harmful algal blooms in waterbodies, which threaten the normal functioning of aquatic ecosystems and human health. Some plant extracts are considered as promising algaecides. In this study, the effects of ten plant extracts (Cinnamomum camphora, Ginkgo biloba, Firmiana platanifolia, Salix babylonica, Euphorbia humifusa, Erigeron annuus, Solidago canadensis, Alternanthera philoxeroides, Thalia dealbata and Eichhornia crassipes) against M. flos-aquae were investigated. The results showed that all ten plant extracts had a significant inhibitory effect on M. flos-aquae growth after 96 h (P < 0.01). The inhibition rates of S. babylonica, E. humifusa, S. canadensis and A. philoxeroides were over 70.00%. Furthermore, the E. humifusa extract had the best inhibitory effect on the photosynthesis of M. flos-aquae, with the effective quantum yield of photosystem II and maximal relative electron transport rate decreasing by 97.50% and 97.00%, respectively, after 96 h. Additionally, the E. humifusa extract was found to be non-toxic to non-target organisms such as Brachydanio rerio and Vallisneria spiralis within 96 h. This study contributes to the existing knowledge and data of freshwater cyanobacteria blooms, and provides insights for their control and the restoration of freshwater systems affected by cyanobacteria blooms.

Diphenamid photodegradation using Fe(III) impregnated N-doped TiO2/sulfite/visible LED process: Influence of wastewater matrix, kinetic modeling, and toxicity evaluation

Sulfite-based photocatalysis has been recently employed as a promising technology for the treatment of organic pollutants via the generation of reactive radicals. In this contribution, the effect of wastewater matrix constituents and toxicity evaluation were systematically investigated in the FeIII impregnated N-doped TiO2 (FeN–TiO2)/sulfite/visible LED (Vis LED) process in the presence of diphenamid (DPA) as a model organic pollutant. The results showed that the presence of HCO3−, SO42−, NO3−, and F− had no detrimental effect on DPA degradation. Conversely, the presence of Cr(VI), NO2−, Cl−, and Br− caused a stronger retardation effect. The effect of natural organic matter such as humic acid (HA) was inert at normal concentrations. Interestingly, the retardation effect of inorganic ions can be quantified at any given ion concentration based on the linear correlations between the DPA decay (first-order kinetic constants) and concentration of ion species. Toxicity tests on Synechocystis sp., Microcystis flos-aquae, and Nostoc sp. algae revealed that higher toxicity was noticed at 240 min treatment time accompanied by lower toxicity with prolonging the treatment time for all selected algae except for Microcystis flos-aquae. In addition, novel two-phase mathematical models were successfully proposed to predict the accumulation of intermediates depending on their evolution profile.

Probing the changes of carotenoids in Microcystis flosaquae under environmental perturbations by two‐dimensional Raman correlation spectroscopy

AbstractRaman mapping spectra of Microcystis flosaquae (M. flosaquae) subjected to environmental perturbations were used to study the correlations among the characteristics of M. flosaquae by two‐dimensional (2‐D) Raman correlation spectroscopy. Overlapping Raman characteristics of the carotenoids in M. flosaquae and their differences in algal growths were shown in the 2‐D synchronous and asynchronous correlation spectra. The asynchronous correlation Raman spectra demonstrated the accumulation of carotenoids in M. flosaquae under normal culture condition and environmental perturbations. High light flux obviously led to the accumulation of β‐carotene in M. flosaquae in comparison with normal culture condition. The results showed that 2‐D Raman correlation spectroscopy can be used to analyze the correlation of complex changes of the Raman characteristics of M. flosaquae induced by different environmental conditions to assess the accumulation of the carotenoids in algae and to predict the algal growth phases.

Inhibition of Scenedesmus quadricauda on Microcystis flos-aquae.

Allelopathy by hydrophytes can be utilized to control algal blooms. This study was conducted to investigate the allelopathic effect (inhibition) of Scenedesmus quadricauda on Microcystis flos-aquae. When M. flos-aquae was co-cultured with S. quadricauda, the secretion of high-MW biopolymer by M. flos-aquae was inhibited by S. quadricauda. We further identified the allelochemicals and found that 4-tert-butylpyrocatechol (TBC) was the main active ingredient that could inhibit the growth of M. flos-aquae. When the dose of TBC was larger than 0.2 mg/L, almost all of the M. flos-aquae died. Additionally, TBC was found to suppress the growth of M. flos-aquae by disturbing the synthesis and secretion of proteins and polysaccharides and harming the chlorophyll to affect the light harvesting of algal cells. Therefore, TBC has the potential for use as a potential and promising algaecide to restrain the biomass of M. flos-aquae.

Algal uptake of hydrophilic and hydrophobic dissolved organic nitrogen in the eutrophic lakes

Dissolved organic nitrogen (DON) derived from sediments plays an active role in biogeochemical cycling of nutrients in aquatic ecosystems. Sediments from four eutrophic lakes were studied using three-dimensional fluorescence excitation-emission matrix (3DEEM) spectra and supelite XAD-8 macroporous resin separation to investigate the bioavailability of hydrophilic and hydrophobic DON to algae (Microcystis flos-aquae (Wittr.) Kirchner). The results showed that the average loss of DON was <6.0% after dividing DON into hydrophilic and hydrophobic components, demonstrating the utility of XAD-8 resin separation in the study of DON components from lake sediments. The 3DEEM analysis showed that hydrophobic and hydrophilic DON comprised humic- and protein-like materials, respectively. During the incubation period, the bioavailability of hydrophilic DON, which accounted for 59.3%–80.4% of total DON, stimulated algal growth, suggesting that hydrophilic DON was the primary source of organic nitrogen for algae. In contrast, hydrophobic DON increased algal density by only 31.8% of that observed for hydrophilic DON, and had a small (accounted for 20.0%–26.6% of total DON) effect on algal growth over the short-term. The significant differences in algal growth between the two types of DON suggested that they should be considered separately in the eutrophic lake restorations.