Microcystin

50-day's free access https://authors.elsevier.com/a/1dnnLB8ccr0ST ........................................................................................................................................... Cyanobacteria are notorious for producing harmful algal blooms that present an ever-increasing serious threat to aquatic ecosystems worldwide, impacting the quality of drinking water and disrupting the recreational use of many water bodies. Remote sensing techniques for the detection and quantification of cyanobacterial blooms are required to monitor their initiation and spatiotemporal variability. In this study, we developed a novel semi-analytical approach to estimate the concentration of cyanobacteria-specific pigment phycocyanin (PC) and common phytoplankton pigment chlorophyll a (Chl a) from hyperspectral remote sensing data. The PC algorithm was derived from absorbance-concentration relationship, and the Chl a algorithm was devised based on a conceptual three-band structure model. The developed algorithms were applied to satellite imageries obtained by the Hyperspectral Imager for the Coastal Ocean (HICO™) sensor and tested in Lake Kinneret (Israel) during strong cyanobacterium Microcystis sp. bloom and out-of-bloom times. The sensitivity of the algorithms to errors was evaluated. The Chl a and PC concentrations were estimated with a mean absolute percentage difference (MAPD) of 16% and 28%, respectively. Sensitivity analysis shows that the influences of backscattering and other water constituents do not affect the estimation accuracy of PC (~2% MAPD). The reliable PC/Chl a ratios can be obtained at PC concentrations above 10 mg m−3. The computed PC/Chl a ratio depicts the contribution of cyanobacteria to the total phytoplankton biomass and permits investigating the role of ambient factors in the formation of a complex planktonic community. The novel algorithms have extensive practical applicability and should be suitable for the quantification of PC and Chl a in aquatic ecosystems using hyperspectral remote sensing data as well as data from future multispectral remote sensing satellites, if the respective bands are featured in the sensor.

Studies on phytoplankton in some Greek lakes (Vegoritis, Volvi, Mikri Prespa, Doirani and Kastoria) have shown that prolonged cyanobacterial blooms can occur, lasting up to 8 months, which are dominated by potentially toxic species (Moustaka-Gouni and Nikolaidis 1990; Moustaka-Gouni 1993; Tryfon and Moustaka-Gouni 1997; Temponeras et al. 2000; Vardaka et al. 2000).

Cyanobacterial harmful algal bloom (CyanoHAB) proliferation is a global problem impacting ecosystem and human health. Western Lake Erie (WLE) typically endures two highly toxic CyanoHABs during summer: a Microcystis spp. bloom in Maumee Bay that extends throughout the western basin, and a Planktothrix spp. bloom in Sandusky Bay. Recently, the USA and Canada agreed to a 40% phosphorus (P) load reduction to lessen the severity of the WLE blooms. To investigate phosphorus and nitrogen (N) limitation of biomass and toxin production in WLE CyanoHABs, we conducted in situ nutrient addition and 40% dilution microcosm bioassays in June and August 2019. During the June Sandusky Bay bloom, biomass production as well as hepatotoxic microcystin and neurotoxic anatoxin production were N and P co-limited with microcystin production becoming nutrient deplete under 40% dilution. During August, the Maumee Bay bloom produced microcystin under nutrient repletion with slight induced P limitation under ...

Coagulation and flocculation processes could reduce particulate algal cells efficiently , but they are not so performant in dealing with solubilized algal organic matter in potable water factories. This work reviews the main findings found in recent publications. Many techniques used in the water treatment industry encounter the problem of microalgae lysis, toxin release, and degradation. Indeed, chemical coagulants such as alum and pre-oxidation injecting chlorine can trigger demolition to algal cell integrity leading to the release of intracellular organic matter. As suggestion, chlorination could be decreased to the disinfection (i.e., before sand filtration) averting pre-disinfection and keeping the post-disinfection. Moreover, algae recuperation instead of its removal in drinking water treatment plants remains an encouraging outlook especially if the surface water arrives from dams where algae blooms happen usually. Algae remain a sustainable energy resource with a huge capacity for CO 2 fixation. The micro-algae could be developed in photo-bioreactors or in open ponds. A fresh attracting domain of investigation would be fast and simultaneous algal biodiesel production with drinking water treatment in the biodiesel production/water treatment plant without chemicals use.

Cyanobacterial harmful algal bloom (CyanoHAB) proliferation is a global problem impacting ecosystem and human health. Western Lake Erie (WLE) typically endures two highly toxic CyanoHABs during summer: a Microcystis spp. bloom in Maumee Bay that extends throughout the
western basin, and a Planktothrix spp. bloom in Sandusky Bay. Recently, the USA and Canada agreed to a 40% phosphorus (P) load reduction to lessen the severity of the WLE blooms. To investigate phosphorus and nitrogen (N) limitation of biomass and toxin production in WLE CyanoHABs, we conducted in situ nutrient addition and 40% dilution microcosm bioassays in June and August 2019. During the June Sandusky Bay bloom, biomass production as well as hepatotoxic microcystin and neurotoxic anatoxin production were N and P co-limited with microcystin production becoming nutrient deplete under 40% dilution. During August, the Maumee Bay bloom produced microcystin
under nutrient repletion with slight induced P limitation under 40% dilution, and the Sandusky Bay bloom produced anatoxin under N limitation in both dilution treatments. The results demonstrate
the importance of nutrient limitation effects on microcystin and anatoxin production. To properly combat cyanotoxin and cyanobacterial biomass production in WLE, both N and P reduction efforts should be implemented in its watershed.

Toxic cyanobacterial blooms in urban lakes present serious health hazards to humans and animals and require effective management strategies. Managing such blooms requires a sufficient understanding of the controlling environmental factors. A range of them has been proposed in the literature as potential triggers for cyanobacterial biomass development and cyanotoxin (e.g. microcystin) production in freshwater systems. However, the environmental triggers of cyanobacteria and microcystin variability remain a subject of debate due to contrasting findings. This issue has raised the question of whether the relevance of environmental triggers may depend on site-specific combinations of environmental factors. In this study, we investigated the site-specificity of environmental triggers for cyanobacterial bloom and microcystin dynamics in three urban lakes in Western Australia. Our study suggests that cyanobacterial biomass, cyanobacterial dominance and cyanobacterial microcystin content variability were significantly correlated to phosphorus and iron concentrations. However, the correlations were different between lakes, thus suggesting a site specific effect of these environmental factors. The discrepancies in the correlations could be explained by differences in local nutrient concentration. For instance, we found no correlation between cyanobacterial fraction and total phosphorous (TP) in the lake with the highest TP concentration, while correlations were significant and negative in the other two lakes. In addition, our study indicates that the difference of the correlation between total iron (TFe) and the cyanobacterial fraction between lakes might have been a consequence of differences in the cyanobacterial community structure, specifically the presence or absence of nitrogen-fixing species. In conclusion, our study suggests that identification of significant environmental factors under site-specific conditions is an important
strategy to enhance successful outcomes in cyanobacterial
bloom control measures.

Eutrophication of surface waters caused by toxic cyanobacteria such as Microcystis aeruginosa leads to the release of secondary metabolites called Microcystins (MCs), which are heptapeptides with adverse effects on soil microbiota, plants, animals, and human health. Therefore, to avoid succumbing to the negative effects of these cyanotoxins, various remediation approaches have been considered. These techniques involve expensive physico-chemical processes because of the specialized equipment and facilities required. Thus, implementing eco-technologies capable of handling this problem has become necessary. Indeed, multi-soil-layering (MSL) technology can essentially meet this requirement. This system requires little space, needs simple maintenance, and has energy-free operation and high durability (20 years). The performance of the system is such that it can remove 1.16 to 4.47 log10 units of fecal contamination from the water, 98% of suspended solids (SS), 92% of biological oxygen de...

Zebra mussel invasion of northern American lakes during the last century may play an important role in the occurrence of toxic cyanobacteria blooms. Herein, large-scale data from the USEPA National Lake Assessment (> 1,000 lakes) were used to study the potential linkage between zebra mussels, cyanobacteria community composition, and cyanotoxin levels in the lakes. ANOVA Based on Dissimilarities tests (Adonis) showed that there was a significant difference in cyanobacterial communities between lakes located in areas with and without established zebra mussel populations. Meanwhile, significantly higher microcystin levels and cyanobacteria abundance were observed, but lower concentrations of phosphorous in lakes located in areas with established zebra mussels. Structural equation modeling was used to confirm and estimate the effect of zebra mussels on microcystin concentrations via different pathways. The results suggest three potential pathways whereby zebra mussels influence microcystin production: 1) altering phosphorous concentration; 2) increasing cyanobacteria abundance; and 3) shifting cyanobacteria community structure. The total effect of zebra mussel establishment resulted in an overall 1.40 times net increase in microcystin level, which presumably resulted from three contributing factors: 1) a 1.06 times increase through an increased cyanobacteria abundance; 2) a 1.53 times increase through a selective force, resulting in increased cyanobacteria toxicity; and 3) a 0.86 times decrease in microcystin level through total phosphorus decrease. The study suggested the important potential role of zebra mussel invasion in altering cyanobacterial composition and influencing microcystin levels in the US lakes.

Cyanobacteria are a source of potent toxins among which the microcystin (a hepatotoxic peptide encoded by the mcy gene cluster of Microcystis spp.) is a frequent cause of poisoning in inland waters worldwide. Although the molecular basis of microcystin production is known, its role is still unknown. It was suggested that microcystin production have a metabolic cost that could be offset by some benefit (e.g. protection from grazing). We check that: i) microcystin-producing and non-producing strains occurs simultaneously in the Microcystis spp. blooms, ii) evolutionary forces (mutation, genetic drift) control frequencies of microcystin production and non-production strains, and iii) microcystin producing strains have diminished fitness compared with non-producing strains. We employ evolutionary game theory to explain the maintaining of microcystin-producing genotypes in natural populations of Microcystis spp. A two-strategy (to produce or not microcystin), two-players game of cooperat...

... fish had enlarged livers, which is a symptom of possible algal poisoning (Moyo 1997). In Harare, cases of gastrointestinal infections and liver cancer have risen over 300% and 400%, respectively, between 1991 and 2001. Documented cases of gastroenteritis rose from < 100 ...

Background: Uniquely synthesised titanium dioxide (TiO2) with high-energy {001} exposed facets denoted HF8 was used for the photocatalytic degradation of microcystin-LR (MC-LR) under ultraviolet irradiation at 365 nm.

Methods: The influence of various conditions including environmental pH, nutrient anions, TiO2 dose, and MC-LR concentration was studied, and concentration of MC-LR measured using liquid chromatography-tandem mass spectrometry.

Results: Within 120 min, 72.6% of an environmentally relevant MC-LR concentration (120 µg/L) was degraded under pH conditions ranging from 3 to 11. Stability tests revealed no loss of TiO2 activity after four applications of the same dose, indicating its stability, reusability, and potential to be re-used for sustainable remediation of MC-LR in eutrophic waters. Mechanism studies suggested that the reaction obeyed the pseudo-first-order equation and that hydroxyl radicals are the major reactive intermediate contributing to the reaction. The structure elucidation of intermediates suggested that hydroxylation and bond cleavage between the Adda chain and Mdha site could be the initiation of reactions in the degradation of MC-LR by HF8 TiO2.

Conclusion: The results present a fast, sustainable, and practical method using modified TiO2 to improve MC-LR remediation.

Keywords: Degradation, Microcystin-LR, Photocatalysis, Titanium dioxide

Blooms of cyanobacteria or blue-green algae are known to have caused poisoning in fish, waterfowl, animals and man. One of the toxins responsible for this is the hepatotoxin microcystin-LR which has been found to occur in blooms present intermittently in sources used for domestic water supplies. Three sets of experiments were undertaken to investigate the acute toxicity of microcystin-LR in mice and rats by the oral and intraperitoneal routes, the potential for effects on foetal development in the mouse, and the effects of repeated oral dosing over 13 weeks in the mouse. The results of this work were as follows: (1) Microcystin-LR is 30-100 times less toxic via oral ingestion than via intraperitoneal injection; (2) Microcystin-LR is not a selective developmental toxicant in the mouse. There was a No Observed Adverse Effect Level (NOAEL) of 600 microg kg(-1) bodyweight per day given on days 6-15 of pregnancy for any form of developmental toxicity; (3) There was a clear NOAEL for tissue damage in the liver of 40 microg kg(-1) bodyweight per day of microcystin-LR. Using this data, a value of 1 microg l(-1) microcystin-LR would be an appropriate guideline value for drinking water.

This study evaluated the effects of [d-Leu¹]Microcystin-LR variant by the exposure of tadpole to unialgal culture NPLJ-4 strain. The Tadpole was placed in aquariums and exposed to culture or disrupted cells. For 16 days, 5 individuals were removed every 2 days, and tissue samples of liver, skeletal muscle, and intestinal tract were collected for histopathology and bioaccumulation analyses. After exposure, those surviving tadpoles were placed in clean water for 15 days to evaluate their recovery. A control without algae and toxins was maintained in the same conditions and exhibited normal histology and no tissue damage. In exposed tadpoles, samples were characterized by serious damages that similarly affected the different organs, such as loss of adhesion between cells, nucleus fragmentation, necrosis, and hemorrhage. Samples showed signs of recovery but severe damages were still observed. Neither HPLC-PDA nor mass spectrometry analysis showed any evidence of free Microcystins bioacc...

Cyanobacterial harmful algal bloom (CyanoHAB) proliferation is a global problem impacting ecosystem and human health. Western Lake Erie (WLE) typically endures two highly toxic CyanoHABs during summer: a Microcystis spp. bloom in Maumee Bay that extends throughout the western basin, and a Planktothrix spp. bloom in Sandusky Bay. Recently, the USA and Canada agreed to a 40% phosphorus (P) load reduction to lessen the severity of the WLE blooms. To investigate phosphorus and nitrogen (N) limitation of biomass and toxin production in WLE CyanoHABs, we conducted in situ nutrient addition and 40% dilution microcosm bioassays in June and August 2019. During the June Sandusky Bay bloom, biomass production as well as hepatotoxic microcystin and neurotoxic anatoxin production were N and P co-limited with microcystin production becoming nutrient deplete under 40% dilution. During August, the Maumee Bay bloom produced microcystin under nutrient repletion with slight induced P limitation under ...