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The potential of microplastics to act as a vector for micropollutants of natural or anthropogenic origin is of rising concern. Cyanobacterial toxins, including microcystins, are harmful to humans and wildlife. In this study, we demonstrate for the first time the potential of microplastics to act as vectors for two different microcystin analogues. A concentration of up to 28 times from water to plastic was observed for the combination of polystyrene and microcystin-LF achieving toxin concentrations on the plastic of 142 ± 7 μg g-1. Based on the experimental results, and assuming a worst-case scenario, potential toxin doses for daphnids are calculated based on published microplastic ingestion data. Progressing up through trophic levels, theoretically, the concentration of microcystins in organisms is discussed. The experimental results indicate that adsorption of microcystins onto microplastics is a multifactorial process, depending on the particle size, the variable amino acid composition of the microcystins, the type of plastic, and pH. Furthermore, the results of the current study stressed the limitations of exclusively investigating microcystin-LR (the most commonly studied microcystin congener) as a model compound representing a group of around 250 reported microcystin congeners.

Cyanobacteria and their toxic secondary metabolites present challenges for water treatment globally. In this study we have assessed TiO

The authors would like to thank the Scottish Goverment's Hydro Nation Scholars Programme for funding this research. The authors would like to thank the Engineering and Physical Sciences Research Council (EPSRC) [EP/P029280/1]. Plastics are utilised globally but are of environmental concern due to their persistence. The global presence of microplastics (particles

Cyanobacteria and their toxins are a threat to drinking water safety as increasingly cyanobacterial blooms (mass occurrences) occur in lakes and reservoirs all over the world. Photocatalytic removal of cyanotoxins by solar light active catalysts is a promising way to purify water at relatively low cost compared to modifying existing infrastructure. We have established a facile and low-cost method to obtain TiO

The authors would like to thank the Engineering and Physical Sciences Research Council (EPSRC) [EP/P029280/1], the Coordination for the Improvement of Higher Education Personnel - CAPES [PROEX 20/2016 and PrInt 88887.311806/2018–00], and the Brazilian National Research Council – CNPq [403116/2016–3 and 304164/2017–8] for funding this research. As per EPSRC requirement all data will be made publicly available via the Robert Gordon University's open access repository OpenAIR@RGU. Further, the first author also acknowledges the scholarship from the Brazilian National Research Council - CNPq. To date, the high cost of supplying UV irradiation has prevented the widespread application of UV photolysis and titanium dioxide based photocatalysis in removing undesirable organics in the water treatment sector. To overcome this problem, the use of UV-LEDs (365 nm) for photolysis and heterogeneous photocatalysis applying TiO2 coated glass beads under UV-LED illumination (365 nm) in a pilot scale reactor for the elimination of Microcystis aeruginosa PCC7813 and four microcystin analogues (MC-LR, -LY, -LW, -LF) with a view to deployment in drinking water reservoirs was investigated. UV-A (365 nm) photolysis was shown to be more effective than the UV/TiO2 photocatalytic system for the removal of Microcystis aeruginosa cells and microcystins. During photolysis, cell density significantly decreased over 5 days from an initial concentration of 5.8 × 106 cells mL−1 until few cells were left. Both intra- and extracellular microcystin concentrations were significantly reduced by 100 and 92 %, respectively, by day 5 of the UV treatment for all microcystin analogues. During UV/TiO2 treatment, there was great variability between replicates, making prediction of the effect on cyanobacterial cell and toxin behavior difficult. Postprint Postprint

Many toxic and/or noxious cyanobacteria appear in nature with a filamentous, stacked cell arrangement called trichomes. Although water treatment can be optimized to keep cyanobacterial cells intact and avoid the release of toxic and/or noxious compounds, many physical and chemical stresses encountered during the treatment process may result in trichome truncation, decreasing treatment efficiency by allowing single cells or short trichomes to reach the product water. This makes it possible for harmful/noxious compounds as well as organic matter to enter the distribution system. Investigations in a pilot and three full-scale water treatment plants were carried out in order to elucidate the degree of trichome truncation across different unit processes. It was found that genera (Pseudanabaena, Planktolyngbya) with short trichomes (

To realize the potential of microalgae in the biorefinery context, exploitation of multiple products is necessary for profitability and bioproduct valorization. Appropriate analytical tools are required for growth optimization, culture monitoring, and quality control purposes, with safe, low‐tech, and low‐cost solutions favorable. Rapid, high‐throughput, and user‐friendly methodologies were devised for (a) determination of phycobiliproteins, chlorophylls, carotenoids, proteins, carbohydrates, and lipids and (b) qualitative and quantitative carotenoid profiling using UPLC‐PDA‐MSE. The complementary methods were applied on 11 commercially important microalgal strains including prasinophytes, haptophytes, and cyanobacteria, highlighting the suitability of some strains for coproduct exploitation and the method utility for research and industrial biotechnology applications. The UPLC method allowed separation of 41 different carotenoid compounds in, Rapid, user‐friendly methodologies were devised for the determination of phycobiliprotein, pigment, and macromolecule contents in microalgae, and for qualitative and quantitative carotenoid profiling using liquid chromatography coupled with spectrophotometry and mass spectrometry. Methods were applied to commercially important microalgal strains, demonstrating their application and suitability as tools for quality control, strain selection, and growth optimization purposes within microalgal research and integrated biorefinery settings.

International audience; Primary consumers in freshwater ecosystems, such as the zooplankton organism Daphnia magna, are highly affected by cyanobacteria, both as they may use it as a food source but also by cyanobacterial metabolites present in the water. Here, we investigate the impacts of cyanobacterial metabolites focussing on the environmental realistic scenario of the naturally released mixture without crushing cyanobacterial cells or their uptake as food. Therefore, D. magna were exposed to two concentrations of cell free cyanobacterial spent medium from Microcystis aeruginosa PCC 7806 to represent higher and lower ecologically-relevant concentrations of cyanobacterial metabolites. Including microcystin-LR, 11 metabolites have been detected of which 5 were quantified. Hypothesising concentration and time dependent negative impact, survival, gene expression marking digestion and metabolism, oxidative stress response, cell cycle and molting as well as activities of detoxification and antioxidant enzymes were followed for 7 days. D. magna suffered from oxidative stress as both catalase and glutathione S-transferase enzyme activities significantly decreased, suggesting enzyme exhaustibility after 3 and 7 days. Moreover, gene-expressions of the 4 stress markers (glutathione S-transferase, glutathione peroxidase, catalase and thioredoxin) were merely downregulated after 7 days of exposure. Energy allocation (expression of glyceraldehyde-3-phosphate dehydrogenase) was increased after 3 days but decreased as well after 7 days exposure. Cell cycle was impacted time dependently but differently by the two concentrations, along with an increasing downregulation of myosin heavy chain responsible for cell arrangement and muscular movements. Deregulation of nuclear hormone receptor genes indicate that D. magna hormonal steering including molting seemed impaired despite no detection of microviridin J in the extracts. As a consequence of all those responses and presumably of more than investigated molecular and physiological changes, D. magna survival was impaired over time, in a concentration dependent manner. Our results confirm that besides microcystin-LR, other secondary metabolites contribute to negative impact on D. magna survival and stress response.

Cyanobacterial blooms are increasingly reported worldwide, presenting a challenge to water treatment plants and concerning risks to human health and aquatic ecosystems. Advanced oxidative processes comprise efficient and safe methods for water treatment. Hydrogen peroxide (H2O2) has been proposed as a sustainable solution to mitigate bloom-forming cyanobacteria since this group presents a higher sensitivity compared to other phytoplankton, with no major risks to the environment at low concentrations. Here, we evaluated the effects of a single H2O2 addition (10 mg L−1) over 120 h in mesocosms introduced in a reservoir located in a semi-arid region presenting a Planktothrix-dominated cyanobacterial bloom. We followed changes in physical and chemical parameters and in the bacterioplankton composition. H2O2 efficiently suppressed cyanobacteria, green algae, and diatoms over 72 h, leading to an increase in transparency and dissolved organic carbon, and a decrease in dissolved oxygen and pH, while nutrient concentrations were not affected. After 120 h, cyanobacterial abundance remained low and green algae became dominant. 16S rRNA sequencing revealed that the original cyanobacterial bloom was composed by Planktothrix, Cyanobium and Microcystis. Only Cyanobium increased in relative abundance at 120 h, suggesting regrowth. A prominent change in the composition of heterotrophic bacteria was observed with Exiguobacterium, Paracoccus and Deinococcus becoming the most abundant genera after the H2O2 treatment. Our results indicate that this approach is efficient in suppressing cyanobacterial blooms and improving water quality in tropical environments. Monitoring changes in abiotic parameters and the relative abundance of specific bacterial taxa could be used to anticipate the regrowth of cyanobacteria after H2O2 degradation and to indicate where in the reservoir H2O2 should be applied so the effects are still felt in the water treatment plant intake.

The presence of harmful algal bloom in many reservoirs around the world, alongside the lack of sanitation law/ordinance regarding cyanotoxin monitoring (particularly in developing countries), create a scenario in which the local population could potentially chronically consume cyanotoxin-contaminated waters. Therefore, it is crucial to develop low cost tools to detect possible systems failures and consequent toxin release inferred by morphological changes of cyanobacteria in the raw water. This paper aimed to look for the best combination of convolutional neural network (CNN), optimizer and image segmentation technique to differentiate P. agardhii trichomes before and after chemical stress caused by the addition of hydrogen peroxide. This method takes a step towards accurate monitoring of cyanobacteria in the field without the need for a mobile lab. After testing three different network architectures (AlexNet, 3ConvLayer and 2ConvLayer), four different optimizers (Adam, Adagrad, RMSProp and SDG) and five different image segmentations methods (Canny Edge Detection, Morphological Filter, HP filter, GrabCut and Watershed), the combination 2ConvLayer with Adam optimizer and GrabCut segmentation, provided the highest median accuracy (93.33%) for identifying H2O2-induced morphological changes in P. agardhii. Our results emphasize the fact that the trichome classification problem can be adequately tackled with a limited number of learned features due to the lack of complexity in micrographs from before and after chemical stress. To the authors' knowledge, this is the first time that CNNs were applied to detect morphological changes in cyanobacteria caused by chemical stress. Thus, it is a significant step forward in developing low cost tools based on image recognition, to shield water consumers, especially in the poorest regions, against cyanotoxin-contaminated water.

Cyanobacterial blooms are observed when high cell densities occur and are often dangerous to human and animal health due to the presence of cyanotoxins. Conventional drinking water treatment technology struggles to efficiently remove cyanobacterial cells and their metabolites during blooms, increasing costs and decreasing water quality. Although field applications of hydrogen peroxide have been shown to successfully suppress cyanobacterial growth, a rapid and accurate measure of the effect of oxidative stress on cyanobacterial cells is required. In the current study, H2O2 (5 and 20 mg L−1) was used to induce oxidative stress in Microcystis aeruginosa PCC 7813. Cell density, quantum yield of photosystem II, minimal fluorescence and microcystin (MC-LR, -LY, -LW, -LF) concentrations were compared when evaluating M. aeruginosa cellular stress. Chlorophyll content (determined by minimal fluorescence) decreased by 10% after 48 h while cell density was reduced by 97% after 24 h in samples treated with 20 mg L−1 H2O2. Photosystem II quantum yield (photosynthetic activity) indicated cyanobacteria cell stress within 6 h, which was considerably faster than the other methods. Intracellular microcystins (MC-LR, -LY, -LW and -LF) were reduced by at least 96% after 24 h of H2O2 treatment. No increase in extracellular microcystin concentration was detected, which suggests that the intracellular microcystins released into the surrounding water were completely removed by the hydrogen peroxide. Thus, photosynthetic activity was deemed the most suitable and rapid method for oxidative cell stress detection in cyanobacteria, however, an approach using combined methods is recomended for efficient water treatment management.

Cyanobacteria and their toxic secondary metabolites are a challenge in water treatment due to increased biomass and dissolved metabolites in the raw water. Retrofitting existing water treatment infrastructure is prohibitively expensive or unfeasible, hence 'in-reservoir' treatment options are being explored. In the current study, a treatment system was able to photocatalytically inhibit the growth of Microcystis aeruginosa and remove released microcystins by photocatalysis using titanium dioxide coated, porous foamed glass beads and UV-LEDs (365 nm). A 35% reduction of M. aeruginosa PCC7813 cell density compared to control samples was achieved in seven days. As a function of cell removal, intracellular microcystins (microcystin-LR, -LY, -LW, and -LF) were removed by 49% from 0.69 to 0.35 μg mL

Authors wish to thank EPSRC Global Challenges program for providing the funding for this project (Grant number EP/P029280/1). NS wishes to thank ‘Energy Pioneering Research Program (PRP)’ at QUB. JTSI and JH wish to acknowledge EPSRC Capital for Great Technologies (Grant EP/LP017008/1and EP/R02375/1). Blooms of blue-green algae (cyanobacteria) in water reservoirs frequently produce highly toxic secondary metabolites including microcystins which have resulted in both human and animal fatalities. To tackle this global problem, we present here a viable solution: utilising the photo-catalytic power of TiO2 immobilised on glass beads that are encased in ‘photo-reactor pods’, equipped with UV LEDs, for the photocatalytic destruction of cyanotoxins. These reactor pods are designed in such a way that they can be used continuously with the aid of a power supply to facilitate the photocatalytic process. This process could be used to address one of the Global Challenges: providing safe drinking water around the globe. Postprint

Photocatalysis has been shown to successfully remove microcystins (MC) in laboratory experiments. Most research to date has been performed under ideal conditions in pure or ultrapure water. In this investigation the efficiency of photocatalysis using titanium dioxide was examined in a complex matrix (waste stabilisation lagoon water). A flow-through photocatalytic reactor was used for the photocatalytic removal of four commonly occurring microcystin analogues (MC-YR, MC-RR, MC-LR, and MC-LA). Up to 51% removal for single MC analogues in waste lagoon water was observed. Similar removal rates were observed when a mixture of all four MC analogues was treated. Although treatment of MC-containing cyanobacterial cells of Microcystis aeruginosa resulted in no decline in cell numbers or viability with the current reactor design and treatment regime, the photocatalytic treatment did improve the overall quality of waste lagoon water. This study demonstrates that despite the presence of natural organic matter the microcystins could be successfully degraded in a complex environmental matrix.

International audience; Due to eutrophication, freshwater ecosystems frequently experience cyanobacterial blooms, many of which produce bioactive metabolites that can affect vertebrates and invertebrates life traits. Zooplankton are able to develop tolerance as a physiological response to cyanobacteria and their bioactive compounds, however, this comes with energetic cost that in turn influence Daphnia life traits and may impair populations. Vice versa, it has been suggested that Daphnia are able to reduce cyanobacterial dominance until a certain cyanobacterial density; it remains unclear whether Daphnia metabolites alone influence the physiological state and bioactive metabolites production of cyanobacteria. Hence, this study investigates mutual physiological reactions of toxic Microcystis aeruginosa PCC7806 and Daphnia magna. We hypothesize that a) the presence of D. magna will negatively affect growth, increase stress response and metabolites production in M. aeruginosa PCC7806 and b) the presence of M. aeruginosa PCC7806 will negatively affect physiological responses and life traits in D. magna. In order to test these hypotheses experiments were conducted in a specially designed co-culture chamber that allows exchange of the metabolites without direct contact. A clear mutual impact was evidenced. Cyanobacterial metabolites reduced survival of D. magna and decreased oxidative stress enzyme activity. Simultaneously, presence of D. magna did not affect photosynthetic activity. However, ROS increase and tendencies in cell density decrease were observed on the same day, suggesting possible energy allocation towards anti-oxidative stress enzymes, or other protection mechanisms against Daphnia infochemicals, as the strain managed to recover. Elevated concentration of intracellular and overall extracellular microcystin MC-LR, as well as intracellular concentrations of aerucyclamide A and D in the presence of Daphnia, indicating a potential protective or anti-grazing function. However, more research is needed to confirm these findings.

A simple, rapid UHPLC-MS/MS method has been developed and optimised for the quantitation of microcystins and nodularin in wide variety of sample matrices. Microcystin analogues targeted were MC-LR, MC-RR, MC-LA, MC-LY, MC-LF, LC-LW, MC-YR, MC-WR, [Asp3] MC-LR, [Dha7] MC-LR, MC-HilR and MC-HtyR. Optimisation studies were conducted to develop a simple, quick and efficient extraction protocol without the need for complex pre-analysis concentration procedures, together with a rapid sub 5min chromatographic separation of toxins in shellfish and algal supplement tablet powders, as well as water and cyanobacterial bloom samples. Validation studies were undertaken on each matrix-analyte combination to the full method performance characteristics following international guidelines. The method was found to be specific and linear over the full calibration range. Method sensitivity in terms of limits of detection, quantitation and reporting were found to be significantly improved in comparison to LC-UV methods and applicable to the analysis of each of the four matrices. Overall, acceptable recoveries were determined for each of the matrices studied, with associated precision and within-laboratory reproducibility well within expected guidance limits. Results from the formalised ruggedness analysis of all available cyanotoxins, showed that the method was robust for all parameters investigated. The results presented here show that the optimised LC-MS/MS method for cyanotoxins is fit for the purpose of detection and quantitation of a range of microcystins and nodularin in shellfish, algal supplement tablet powder, water and cyanobacteria. The method provides a valuable early warning tool for the rapid, routine extraction and analysis of natural waters, cyanobacterial blooms, algal powders, food supplements and shellfish tissues, enabling monitoring labs to supplement traditional microscopy techniques and report toxicity results within a short timeframe of sample receipt. The new method, now accredited to ISO17025 standard, is simple, quick, applicable to multiple matrices and is highly suitable for use as a routine, high-throughout, fast turnaround regulatory monitoring tool.

Although some studies have investigated the impact caused by chemicals used on water treatment (coagulants and oxidants) on cyanobacteria integrity, the isolated effect of shear stress during coagulation is still not fully understood. This study evaluated the impact of different velocity gradients, mixing times, and the addition of powdered activated carbon (PAC) on the integrity of Microcystis aeruginosa, Raphidiopsis raciborskii, and Dolichospermum circinale, known producers of toxin and taste and odor (T&O) compounds. No association was found between R. raciborskii cell lysis and velocity gradient, with or without PAC, demonstrating the high resilience of this taxon to shear stress. In contrast, an association was found for M. aeruginosa at the highest velocity gradient evaluated (1000 s−1) and for D. circinale above the lowest velocity gradient studied (600 s−1). After PAC addition, there was a reduction in the chances of finding M. aeruginosa intact cells above velocity gradient 800 s−1 at 45 s, while D. circinale show cell lysis in all the scenarios expect at 600 s−1 and 10 s of agitation. The additional impact of PAC on cell lysis may lead to more release of metabolites and shows the need to adjust the hydraulic conditions in the rapid mixing stage, especially when more “fragile” cyanobacteria are present. Neither cyanobacterial cell size nor morphology was shown to be relevant to shear stress sensitivity, indicating that cell wall composition might have been an important factor in controlling cell lysis.

Background: Microcystins are cyclic peptides containing seven amino acids with the condensation of two terminal amino acids of the linear peptide to form a cyclic compound. The cyclic nature of microcystins suggests that they are highly stable in water across a wide range of pH and temperatures. Microcystins are produced by several blue-green algae (cyanobacteria) including Microcystis, Anabaena, Planktothrix, Oscillatoria and Radiocystis commonly found in freshwater reservoirs in Ghana. Microcystins have very serious health implications on both humans and animals. Known symptoms associated with microcystin poisoning include skin irritation, allergic responses, mucosa blistering, muscular and joint pains, gastroenteritis, pulmonary consolidation, liver and kidney damage and other neurological effects. Methods: In this study, we present results of toxicological analysis conducted on water samples from the Brimsu and Kwanyarko Reservoirs used as sources of drinking water by some parts of the Central Region of Ghana in 2011. HPLC was used to measure microcystin and phytoplankton was identified using an inverted microscope. Results: HPLC analyses of samples gave four variants of microcystin, MC-LR, MC-YR, MC-RR and MC-LA with microcystins ranging from 0.79 μg/L during the intake of water at the Brimsu treatment plant to 0.1 μg/L in the final drinking water products of both reservoirs. Microcystin-LA is a microcystin variant identified in Ghana for the first time. Cyanobacteria diversity was low in both reservoirs. However, biomass was very high and constituted about 84% and 93% of the total algal counts of the water intake for Kwanyarko and Brimsu Reservoirs respectively. Dominant cyanobacteria species found in these reservoirs are Microcystis aeroginosa and Planktothrix agardhii. Conclusions: Due to the chronic effect of these toxins it is recommended that drinking reservoirs with low levels of microcystins must be regularly monitored to keep it free from microcystin to ensure safeguarding human health.

Nodularia spumigena is one of the dominant toxic cyanobacteria which produce blooms in the Baltic Sea, a brackish water body, particularly in late summer. Nodularia spp. are known to produce hepatotoxic nodularins (NODs) and other bioactive peptides such as spumigins and nodulopeptins. In a recent study, three new nodulopeptins with a molecular weight of 899, 901 and 917 Da were characterized from N. spumigena KAC66. To gain further insight into the effects of environmental stress on growth and production of bioactive metabolites in N. spumigena KAC66, two parameters were investigated: temperature and salinity. It was found that growth conditions have a considerable effect on biomass and toxin levels of N. spumigena KAC66. Increasing temperature had a profound effect on NOD production with an increase from 22 to 25 °C resulting in a 50% decrease in intracellular NOD levels. At 30 °C, little or no NOD was detected. In contrast, while concentrations of nodulopeptin 901 decreased with increasing temperature, it was still detectable throughout the growth cycle at elevated temperatures. The light intensity of 13 μmol photons m−2 s−1, 22 °C and 11–20‰ salinity were optimal growth conditions to obtain maximum biomass, intra- and extracellular peptide productions. This is the first report to evaluate the effects of selected environmental parameters on NOD/nodulopeptin 901 productions which ultimately may be helpful to explain the distribution, control of natural blooms and toxin levels of N. spumigena in the Baltic Sea, as well as in laboratory based experiments.

While the intracellular function of many toxic and bioactive cyanobacterial metabolites is not yet known, microcystins have been suggested to have a protective role in the cyanobacterial metabolism, giving advantage to toxic over nontoxic strains under stress conditions. The zooplankton grazer Daphnia reduce cyanobacterial dominance until a certain density, which may be supported by Daphnia exudates, affecting the cyanobacterial physiological state and metabolites&rsquo, production. Therefore, we hypothesized that D. magna spent medium will impact the production of cyanobacterial bioactive metabolites and affect cyanobacterial photosynthetic activity in the nontoxic, but not the toxic strain. Microcystin (MC-LR and des-MC-LR) producing M. aeruginosa PCC7806 and its non-microcystin producing mutant were exposed to spent media of different D. magna densities and culture durations. D. magna spent medium of the highest density (200/L) cultivated for the shortest time (24 h) provoked the strongest effect. D.magna spent medium negatively impacted the photosynthetic activity of M. aeruginosa PCC7806, as well as the dynamics of intracellular and extracellular cyanobacterial metabolites, while its mutant was unaffected. In the presence of Daphnia medium, microcystin does not appear to have a protective role for the strain. On the contrary, extracellular cyanopeptolin A increased in M. aeruginosa PCC7806 although the potential anti-grazing role of this compound would require further studies.

Photocatalysis has been shown to successfully remove microcystins (MC) in laboratory experiments. Most research to date has been performed under ideal conditions in pure or ultrapure water. In this investigation the efficiency of photocatalysis using titanium dioxide was examined in a complex matrix (waste stabilisation lagoon water). A flow-through photocatalytic reactor was used for the photocatalytic removal of four commonly occurring microcystin analogues (MC-YR, MC-RR, MC-LR, and MC-LA). Up to 51% removal for single MC analogues in waste lagoon water was observed. Similar removal rates were observed when a mixture of all four MC analogues was treated. Although treatment of MC-containing cyanobacterial cells of Microcystis aeruginosa resulted in no decline in cell numbers or viability with the current reactor design and treatment regime, the photocatalytic treatment did improve the overall quality of waste lagoon water. This study demonstrates that despite the presence of natural organic matter the microcystins could be successfully degraded in a complex environmental matrix.

Since conventional drinking water treatments applied in different countries are inefficient at eliminating potentially toxic cyanobacterial peptides, a number of bacteria have been studied as an alternative to biological filters for the removal of microcystins (MCs). Here, we evaluated the degradation of not only MCs variants (-LR/DM-LR/-RR/-LF/-YR), but also non-MCs peptides (anabaenopeptins A/B, aerucyclamides A/D) by Paucibactertoxinivorans over 7 days. We also evaluated the degradation rate of MC-LR in a peptide mix, with all peptides tested, and in the presence of M. aeruginosa crude extract. Furthermore, biodegradation was assessed for non-cyanobacterial peptides with different chemical structures, such as cyclosporin A, (Glu1)-fibrinopeptide-B, leucine-enkephalin, and oxytocin. When cyanopeptides were individually added, P. toxinivorans degraded them (99%) over 7 days, except for MC-LR and -RR, which decreased by about 85 and 90%, respectively. The degradation rate of MC-LR decreased in the peptide mix compared to an individual compound, however, in the presence of the Microcystis extract, it was degraded considerably faster (3 days). It was noted that biodegradation rates decreased in the mix for all MCs while non-MCs peptides were immediately degraded. UPLC–QTOF–MS/MS allowed us to identify two linear biodegradation products for MC-LR and MC-YR, and one for MC-LF. Furthermore, P. toxinivorans demonstrated complete degradation of non-cyanobacterial peptides, with the exception of oxytocin, where around 50% remained after 7 days. Thus, although P. toxinivorans was previously identified as a MC-degrader, it also degrades a wide range of peptides under a range of conditions, which could be optimized as a potential biological tool for water treatment.

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., Graphical abstract Image 1, Highlights • MCs/NODs were present in M. edulis tissue, faecal material and extrapallial fluid after 24 h of exposure. • Depuration of MCs/NODs was incomplete after 27 days. • MCs/NODs distributed differently in the experimental system. • Consumption of M. edulis harvested after a short term HAB can pose a human and animal health risk., Accumulation of freshwater cyanotoxins in marine mussels is fast but depuration is slow what could result in high health risk for wildlife and humans, highlighting the need for testing.

Advanced oxidation processes, such as using titanium dioxide (TiO2) photocatalysis, are being developed to reduce or eliminate the toxicity of treated water. In this study, the removal of purified anatoxin-a (ANTX-a), live Dolichospermum flos-aquae cells, and a cell extract of this organism under UV-A/TiO2 photocatalysis, creation of decomposition products and their toxicity were investigated. Total degradation of purified ANTX-a from the initial concentration of 10 mg·L−1 with the addition of TiO2 under UV-A irradiation was achieved in 30 min. Under these conditions several decomposition products were noted with m/z ratio from 156.11 to 216.1. Analysis of the completely degraded ANTX-a sample using Thamnotoxkit F™ toxicity test showed that it was no longer toxic. TiO2 photocatalysis was also efficient in the decomposition of the living cyanobacterial cells. Degradation of their cell structures and degradation of released toxin was also achieved in 30 min. Earlier homogenization of cyanobacteria culture significantly accelerated degradation of ANTX-a to 10 min.

The authors acknowledge the Engineering and Physical Sciences Research Council (EPSRC) for funding this research [EP/P029280/1]. Cyanobacteria and their toxic secondary metabolites are a challenge in water treatment due to increased biomass and dissolved metabolites in the raw water. Retrofitting existing water treatment infrastructure is prohibitively expensive or unfeasible, hence ‘in-reservoir’ treatment options are being explored. In the current study, a treatment system was able to photocatalytically inhibit the growth of Microcystis aeruginosa and remove released microcystins by photocatalysis using titanium dioxide coated, porous foamed glass beads and UV-LEDs (365 nm). A 35% reduction of M. aeruginosa PCC7813 cell density compared to control samples was achieved in seven days. As a function of cell removal, intracellular microcystins (microcystin-LR, -LY, -LW, and -LF) were removed by 49% from 0.69 to 0.35 μg mL−1 in seven days. Microcystins that leaked into the surrounding water from compromised cells were completely removed by photocatalysis. The findings of the current study demonstrate the feasibility of an in-reservoir treatment unit applying low cost UV-LEDs and porous foamed beads made from recycled glass coated with titanium dioxide as a means to control cyanobacteria and their toxins before they can reach the water treatment plant. Postprint

There has been a steady rise in the incidences of algal blooms globally, and worryingly, there is increasing evidence that changes in the global climate are leading to a shift toward cyanobacterial blooms. Many cyanobacterial genera are harmful, producing several potent toxins, including microcystins, for which there are over 90 described analogues. There are a wide range of negative effects associated with these toxins including gastroenteritis, cytotoxicity, hepatotoxicity and neurotoxicity. Although a variety of oxidation based treatment methods have been described, ozonation and advanced oxidation are acknowledged as most effective as they readily oxidise microcystins to non-toxic degradation products. However, most ozonation technologies have challenges for scale up including high costs and sub-optimum efficiencies, hence, a low cost and scalable ozonation technology is needed. Here we designed a low temperature plasma dielectric barrier discharge (DBD) reactor with an incorporated fluidic oscillator for microbubble delivery of ozone. Both technologies have the potential to drastically reduce the costs of ozonation at scale. Mass spectrometry analysis revealed very rapid (

Although desalination by membrane processes is a possible solution to the problem of freshwater supply, related cost and energy demands prohibit its use on a global scale. Hence, there is an emerging necessity for alternative, energy and cost-efficient methods for water desalination. Cyanobacteria are oxygen-producing, photosynthetic bacteria that actively grow in vast blooms both in fresh and seawater bodies. Moreover, cyanobacteria can grow with minimal nutrient requirements and under natural sunlight. Taking these observations together, a consortium of five British Universities was formed to test the principle of using cyanobacteria as ion exchangers, for the specific removal of Na+ and Cl− from seawater. This project consisted of the isolation and characterisation of candidate strains, with central focus on their potential to be osmotically and ionically adaptable. The selection panel resulted in the identification of two Euryhaline strains, one of freshwater (Synechocystis sp. Strain PCC 6803) and one of marine origin (Synechococcus sp. Strain PCC 7002) (Robert Gordon University, Aberdeen). Other work packages were as follows. Genetic manipulations potentially allowed for the expression of a light-driven, Cl−-selective pump in both strains, therefore, enhancing the bioaccumulation of specific ions within the cell (University of Glasgow). Characterisation of surface properties under different salinities (University of Sheffield), ensured that cell–liquid separation efficiency would be maximised post-treatment, as well as monitoring the secretion of mucopolysaccharides in the medium during cell growth. Work at Newcastle University is focused on the social acceptance of this scenario, together with an assessment of the potential risks through the generation and application of a Hazard Analysis and Critical Control Points plan. Finally, researchers in Imperial College (London) designed the process, from biomass production to water treatment and generation of a model photobioreactor. This multimodal approach has produced promising first results, and further optimisation is expected to result in mass scaling of this process.

Shortage of freshwater is a serious problem in many regions worldwide, and is expected to become even more urgent over the next decades as a result of increased demand for food production and adverse effects of climate change. Vast water resources in the oceans can only be tapped into if sustainable, energy-efficient technologies for desalination are developed. Energization of desalination by sunlight through photosynthetic organisms offers a potential opportunity to exploit biological processes for this purpose. Cyanobacterial cultures in particular can generate a large biomass in brackish and seawater, thereby forming a low-salt reservoir within the saline water. The latter could be used as an ion exchanger through manipulation of transport proteins in the cell membrane. In this article, we use the example of biodesalination as a vehicle to review the availability of tools and methods for the exploitation of cyanobacteria in water biotechnology. Issues discussed relate to strain selection, environmental factors, genetic manipulation, ion transport, cell-water separation, process design, safety, and public acceptance.

Investigation of aqueous methanol extracts of the cyanobacterium Nodularia spumigena KAC 66 led to the isolation of the nodulopeptins 899, 901 and 917. The chemical structures were determined using high-resolution NMR and MS-data. The stereochemistry of the amino-acid residues was realized by LC–MS analysis using Marfey’s reagent. The bioactivity of the novel compounds was determined.

The cyanobacterium Nostoc sp. BHU001 is a new isolate from a pond in India. The cyanobacterium produces more than ten peptides including five microcystin (MC) variants, MC-LR, -WR, -AR, -LA and methylated MC-LR, and a new peptide similar to cyanopeptolin. Total MC content determined by ELISA was 25.2 μg g −1 dry wt of the cyanobacterium, dominated by MC-LR (54%). This is the first report of MC producing Nostoc strain from India.

This is the first detailed study on the occurrence of cyanobacterial toxins in India, where we studied five eutrophic, temple ponds in the vicinity of Varanasi city, Uttar Pradesh, which continuously supported blooms of Microcystis sp. for several years. Bloom material from all five ponds was sampled bi-monthly from September 2003 to August 2004. Analysis of extracts by high-performance liquid chromatography (HPLC) indicated that microcystin-RR (MC-RR) was present all year round at high concentrations (311–1540 μg/g, dry weight), posing a significant health hazard especially since all five ponds are widely used for bathing, washing, cattle drinking supply, irrigation and recreation. In addition, there was unusually low temporal variation in concentration of MC-RR in each pond, Characterization of microcystin composition of several bloom samples from this study by HPLC–PDA/MS confirmed that additional microcystins were present in many of the samples. The rarely reported, MC-AR was frequently detected in bloom samples from three of the ponds (Adityanagar, Durgakund and Sankuldhara), where it typically represented 20% of the microcystin pool. MC-WR was frequently found in samples from Adityanagar and Sankuldhara, representing 5–10% of the microcystin pool. MC-LR, along with the previously unreported MC-AHar, each represented approximately 5% of the microcystin pool when present. Bloom samples from each pond had a characteristic microcystin profile, when sampled from 2003 to 2006, suggesting persistent species/strain domination. The perennial and consistent nature of the toxic Microcystis blooms in these ponds is highly unusual, in contrast to the commonly encountered temporal and spatial variation of toxigenic and non-toxigenic species. Laboratory isolates from several ponds were shown to produce microcystins, showing similar microcystin composition to the original bloom material.

Microcystin-LR (MC-LR) was readily biodegraded on addition to six different water samples irrespective of their previous exposure to microcystins. Subsequent studies with water from three of these water bodies confirmed the degradation of MC-LR and also demonstrated the biodegradation of MC-LF, nodularin and mixture of microcystins and nodularin. Rates of degradation of MC-LR, MC-LF and NOD in individual water samples ranged from a half-life of 4 to 18d. Analysis by HPLC-PDA-ESI+ and MALDI MS/MS revealed novel intermediate degradation products of MC-LF and nodularin which included demethylation, hydrolysis, decarboxylation and condensation of the parent compound(s). Our study suggests a possible diversity of micro-organisms and/or pathways which has not been previously observed.

International audience; Freshwater gastropods are increasingly exposed to multiple stressors in the field such as the herbi- cide glyphosate in Roundup formulations and cyanobacterial blooms either producing or not producing microcystins (MCs), potentially leading to interacting effects. Here, the responses of Lymnaea stagnalis to a 21-day exposure to non-MC or MC-producing (33 ug L−1 ) Planktothrix agardhii alone or in combination with the commercial formulation RoundUp® Flash at a concentration of 1 ug L−1 glyphosate, followed by 14 days of depuration, were studied via i) accumulation of free and bound MCs in tissues, and ii) activities of anti-oxidant (catalase CAT) and biotransformation (glutathione-S-transferase GST) enzymes. During the intoxication, the cyanobacterial exposure induced an early increase of CAT activity, independently of the MC content, probably related to the production of secondary cyanobacterial metabolites. The GST activity was induced by RoundUp® Flash alone or in combination with non MC-producing cyanobacte- ria, but was inhibited by MC-producing cyanobacteria with or without RoundUp® Flash. Moreover, MC accumulation in L. stagnalis was 3.2 times increased when snails were concomitantly exposed to MC- producing cyanobacteria with RoundUp®, suggesting interacting effects of MCs on biotransformation processes. The potent inhibition of detoxication systems by MCs and RoundUp® Flash was reversible during the depuration, during which CAT and GST activities were significantly higher in snails previ- ously exposed to MC-producing cyanobacteria with or without RoundUp® Flash than in other conditions, probably related to the oxidative stress caused by accumulated MCs remaining in tissues.

Microcystins and nodularin are toxic cyanobacterial secondary metabolites produced by cyanobacteria that pose a threat to human health in drinking water. Conventional water treatment methods often fail to remove these toxins. Advanced oxidation processes such as TiO2 photocatalysis have been shown to effectively degrade these compounds. A particular issue that has limited the widespread application of TiO2 photocatalysis for water treatment has been the separation of the nanoparticulate powder from the treated water. A novel catalyst format, TiO2 coated hollow glass spheres (Photospheres™), is far more easily separated from treated water due to its buoyancy. This paper reports the photocatalytic degradation of eleven microcystin variants and nodularin in water using Photospheres™. It was found that the Photospheres™ successfully decomposed all compounds in 5 min or less. This was found to be comparable to the rate of degradation observed using a Degussa P25 material, which has been previously reported to be the most efficient TiO2 for photocatalytic degradation of microcystins in water. Furthermore, it was observed that the degree of initial catalyst adsorption of the cyanotoxins depended on the amino acid in the variable positions of the microcystin molecule. The fastest degradation (2 min) was observed for the hydrophobic variants (microcystin-LY, -LW, -LF). Suitability of UV-LEDs as an alternative low energy light source was also evaluated.

A previous pioneering study of freshwater bodies in Sri Lanka revealed the presence of toxic cyanobacteria in three out of four water bodies tested. It was therefore important to perform a more detailed investigation into the presence of cyanobacteria and their toxins throughout Sri Lanka. The country has a long history of well-planned water management with the agricultural economy and drinking water supply still dependent on thousands of man-made tanks. Seventeen reservoirs from different user categories and different climatic zones were selected to study variations in phytoplankton communities with relation to major nutrients, with particular emphasis on cyanobacteria. The study was carried out during a two-year period and heavy growths or blooms of cyanobacteria observed during the study period were tested for microcystins. The results clearly categorised the 17 reservoirs into four groups parallel to the classification based on the user categories of water bodies. Biomass of total phytoplankton, the abundance of cyanobacteria, the dominance of Microcystis spp. and concentration of nitrate (N) and total phosphorous (P) were the lowest in drinking water bodies and the highest in aesthetic water bodies. Irrigation water bodies showed the second lowest values for phytoplankton biomass, and concentration of N and P, while hydropower reservoirs showed the second highest values for the same parameters. The fraction of cyanobacteria in irrigation waters was higher than that in hydropower reservoirs, but surprisingly the dominance of Microcystis spp. was reversed. Possible reasons for these variations are discussed. More than half of the bloom material tested contained microcystins up to 81microgl(-1). Our findings indicate the potential for high-risk situations due to toxigenic cyanobacterial blooms in susceptible freshwaters of Sri Lanka.

Titanium dioxide (TiO 2 ) photocatalysis has been used to initiate the destruction of nodularin, a natural hepatotoxin produced by cyanobacteria. The destruction process was monitored using liquid chromatography–mass spectrometry analysis which has also enabled the identification of a number of the photocatalytic decomposition products. The reduction in toxicity following photocatalytic treatment was evaluated using protein phosphatase inhibition assay, which demonstrated that the destruction of nodularin was paralleled by an elimination of toxicity.

Concern regarding the presence of microcystins in drinking water and their possible contamination in food (e.g., salad vegetables, fish, shellfish) has resulted in the need for reliable methods for the detection and accurate quantification of this class of toxins. Currently, routine analysis of microcystins is most commonly carried out using high-performance liquid chromatography with photodiode array detection (HPLC-PDA), although more sensitive biological assays such as antibody-based ELISAs and protein phosphatase inhibition assays have also proven useful. However, many of these methods have been hindered by the availability of a wide range of purified microcystins. Although over 60 variants have now been reported, only a very small number are commercially available and calibrated standards are not yet obtainable. This has led to the common practice of reporting microcystin-LR equivalence regardless of which variant is present. The increased availability of HPLC with online mass spectral analysis (HPLC-MS) may facilitate more accurate detection of toxin variants but as several microcystins share the same molecular mass, definitive identification can be difficult. A further difficulty in analyzing microcystins is the requirement for sample processing before analysis. Solid phase extraction (SPE) is typically used to enrich environmental concentrations of microcystins, or to eliminate contaminants from complex samples such as animal and plant tissues. Recently, new technologies employing recombinant antibodies and molecularly imprinted polymers have been exploited to develop assays and biosensors for microcystins. These novel detection systems are highly sensitive, often do not require sample processing, and offer a simpler, less expensive alternative to analytical techniques. They have also been successfully employed in solid phase extraction formats for the concentration and clean up of environmental samples before HPLC analysis.

Some cyanobacteria (blue-green algae) are able to produce potent toxins, of which one group are the hepatotoxic peptides, the microcystins and the nodularins. In this study, we report the effect of the non-toxic cyanobacterium Planktothrix agardhii CYA29 and its spent medium on the toxin levels of Microcystis aeruginosa PCC7820 and Nodularia sp. PCC7804. Microcystin levels were elevated when P. agardhii or spent medium were added to cultures of M. aeruginosa PCC7820. This effect was also observed for two nodularin variants in Nodularia PCC7804. However, growth of M. aeruginosa in its own spent medium did not lead to elevated microcystin levels.

Microcystins (cyclic heptapeptides) are produced by a number of freshwater cyanobacteria and cause concern in potable water supplies due to their acute and chronic toxicity. The present study reports the structural characterization of the degradation products of the photocatalytic oxidation of microcystin-LR, so aiding the mechanistic understanding of this process. TiO2 photocatalysis is a promising technology for removal of these toxins from drinking water. However, before it can be adopted in any practical application it is necessary to have a sufficient knowledge of degradation byproducts and their potential toxicity. Liquid chromatography-mass spectrometry analysis demonstrated that the major destruction pathway of microcystin appears to be initiated via three mechanisms: UV irradiation, hydroxyl radical attack, and oxidation. UV irradiation caused geometrical isomerization of microcystin converting the (4E), (6E) of the Adda configuration to (4E), 6(Z) or 4(Z), 6(E). Hydroxyl radical attack on the conjugated diene structure of Adda moiety produced dihyroxylated products. Further oxidation cleaved the hydroxylated 4-5 and/or 6-7 bond of Adda to form aldehyde or ketone peptide residues, which then were oxidized into the corresponding carboxylic acids. Photocatalysis also hydrolyzed the peptide bond on the ring structure of microcystin to form linear structures although this appeared to be a minor pathway.

Microcystins are a family of hepatotoxic peptides produced by freshwater cyanobacteria. Their occurrence in drinking water is of concern since chronic exposure to these toxins causes tumor promotion. It is therefore essential to establish a reliable treatment strategy that will ensure their removal from potable water. We have previously described the rapid destruction of microcystin-LR using TiO2 photocatalysis, however, since there are at least 70 microcystin variants it is essential that the destruction of a number of microcystins be evaluated. In this study the dark adsorption and destruction of four microcystins was followed over a range of pH. All four microcystins were destroyed although the efficiency of their removal varied. The two more hydrophobic microcystins (-LW and -LF) were found to have high dark adsorption (98 and 91% at pH 4) in contrast to microcystin-RR, which was found to have almost no (only 2–3%) dark adsorption across all pH.

A naïve (unimmunized) human semisynthetic phage display library was employed to isolate recombinant antibody fragments against the cyanobacterial hepatotoxin microcystin-LR. Selected antibody scFv genes were cloned into a soluble expression vector and expressed in Escherichia coli for characterization against purified microcystin-LR by competition enzyme-linked immunosorbent assay (ELISA). The most sensitive single-chain antibody (scAb) isolated was capable of detecting microcystin-LR at levels below the World Health Organization limit in drinking water (1 μg liter −1 ) and cross-reacted with three other purified microcystin variants (microcystin-RR, -LW, and -LF) and the related cyanotoxin nodularin. Extracts of the cyanobacterium Microcystis aeruginosa were assayed by ELISA, and quantifications of microcystins in toxic samples showed good correlation with analysis by high-performance liquid chromatography. Immobilized scAb was also used to prepare immunoaffinity columns, which were assessed for the ability to concentrate microcystin-LR from water for subsequent analysis by high-performance liquid chromatography. Anti-microcystin-LR scAb was immobilized on columns via a hexahistidine tag, ensuring maximum exposure of antigen binding sites, and the performance of the columns was evaluated by directly applying 150 ml of distilled water spiked with 4 μg of purified microcystin-LR. The procedure was simple, and a recovery rate of 94% was achieved following elution in 1 ml of 100% methanol. Large-scale, low-cost production of anti-microcystin-LR scAb in E. coli is an exciting prospect for the development of biosensors and on-line monitoring systems for microcystins and will also facilitate a range of immunoaffinity applications for the cleanup and concentration of these toxins from environmental samples.

Microcystins are an increasingly important group of bioactive compounds produced by a number of mainly planktonic cyanobacteria. They are a family of cyclic heptapeptides that cause both acute and chronic toxicity. Purified microcystins are utilised in a range of research applications including toxicological and biochemical studies, development of detection systems and the investigation of water treatment strategies. The commercial availability of purified microcystins is still relatively limited and for many projects the cost of their purchase prohibitive. The purification of microcystins from both bloom material and laboratory cultures is reviewed including a discussion on extraction, separation, and the determination of purity and yield.

Single-chain antibody fragments against the cyanobacterial hepatotoxin microcystin-LR were isolated from a naive human phage display library and expressed in Escherichia coli. In competition enzyme-linked immunosorbent assay (ELISA), the most sensitive antibody clone selected from the library detected free microcystin-LR with an IC(50) value of 4 microM. It was found to cross react with three other microcystin variants - microcystin-RR, microcystin-LW and microcystin-LF - and detected microcystins in extracts of the cyanobacterium Microcystis aeruginosa, found to contain the toxins by high-performance liquid chromatography (HPLC). The quantification of microcystins in these extracts by ELISA and HPLC showed good correlation. Although the antibody isolated in this study was considerably less sensitive than the polyclonal and monoclonal antibodies already available for microcystin detection, phage display technology represents a cheaper, more rapid alternative for the production of anti-microcystin antibodies than the methods currently in use.

While investigating the destruction of the cyanobacterial hepatotoxin microcystin-LR in the presence of phycocyanin pigment via semiconductor photocatalysis, it became apparent that the pigment was catalysing the toxin decomposition. The mechanism of this process in terms of phycocyanin acting as a photo-oxygenation sensitizer via singlet oxygen and superoxide attack is explored. The absorption and fluorescence spectra of phycocyanin have been obtained and data on the properties of the excited state calculated. The established photo-oxygenation sensitizer rose bengal was also used as a catalyst for the photolytic decomposition of microcystin-LR to help elucidate the decomposition mechanism.

The incidence of cyanobacterial blooms in freshwaters, including drinking water reservoirs, has increased over the past few decades due to rising nutrient levels. Microcystins are hepatotoxins released from cyanobacteria and have been responsible for the death of humans as well as domestic and wild animals. Microcystins are chemically very stable and many processes have only limited efficacy in removing them. In this paper we review a range of water treatment methods which have been applied to removing microcystins from potable waters.

1. A sample of adult signal crayfish were taken from a pond with a hepatotoxic bloom of the benthic cyanobacterium Oscillatoria sancta. Cyanobacteria were found in the stomachs of thirty-one out of thirty-two crayfish examined. 2. To examine the effect of hepatotoxic cyanobacteria on crayfish a 14-day feeding trial was carried out with thirty-six animals. There were three treatments: (i) hepatotoxic and (ii) non-toxic Planktothrix agardhii; and (iii) crayfish pellets as a control. 3. High-performance liquid chromatography (HPLC) showed that microcystins (the toxins of P. agardhii) had accumulated in the hepatopancreas of 50% of the animals in the toxic treatment. 4. The cyanobacteria did not appear to have any negative impact on the crayfish. All crayfish survived, remained motile and ate throughout the experiment. 5. During the experiment blood samples were taken and the total number of haemocytes counted. At the end of the experiment glucose concentration and relative wet weight of the hepatopancreas were measured. No differences between crayfish fed on toxic and non-toxic P. agardhii and the controls were found. 6. The fact that microcystin accumulates in the crayfish hepatopancreas indicates that the toxin may be transferred further up the food chain.

Toxic cyanobacteria are increasingly found in drinking water reservoirs, with cells and/or dissolved toxins entering the potable water supply. The most commonly observed group of cyanobacterial toxins is the microcystins, and concern about their impact on human health has prompted investigations into remedial treatment methods. This study investigates the ability of domestic water filters to remove cyanobacterial cells and microcystins from drinking water. Cyanobacterial cell were removed by the filter, but the percentage removal (c. 60% of filamentous cells compared to only 10% of single cells) appeared to be dependent on the colony morphology. The removal of four microcystins was assessed and their percentage removal varied little, although microcystins-LR appeared to be removed to a slightly lesser extent. Toxin concentration and the presence of cell components did not affect the amount of soluble toxin removed from water. The performance of three different brands of water filter was compared, assessing the reproducibility of cartridges and their efficiency when both new and at the manufacturers recommended half-life. All brands of water filters investigated were found to remove a proportion of the soluble microcystin; however, none removed all the toxin in a single passage through the filter.

This paper presents a sampling and extraction procedure for the routine analysis of microcystins. Cyanobacterial cells were filtered through GF/C disks and then extracted in methanol. A drying step was introduced before extraction in order to relate the amount of toxin, detected by photodiode-array–high-performance liquid chromatography to a specific biomass of cyanobacteria. It was discovered that the drying temperature was critical to the recovery of microcystins. This was not observed when dealing with purified microcystins. Thermal decomposition of microcystins apparently occurs in the presence of cell components from cyanobacteria. The efficiency of the extraction procedure for microcystins was also investigated. Three consecutive 60-min extractions were only slightly more efficient than three 30-min extractions. The method was applied to natural samples, and although no obvious cyanobacterial blooms were present at the time of sampling we were able to detect and quantify microcystins presen...

Microcystins were extracted from 7 1 (equivalent to 313 g dry weight) of cyanobacterial scum collected from Rutland Water in Leicestershire, UK in 1989. The resulting aqueous extract was rapidly concentrated on a C18 flash chromatography cartridge and microcystins were eluted using a step gradient. Fractions were collected manually and monitored by UV spectrophotometer and analytical HPLC. Fractions containing microcystins of similar polarity were pooled to give three fractions. Simple isocratic methods for separating each fraction were developed on an analytical column and scaled up to a 15×7.5 cm I.D. column. Closed-loop recycling was used to maximise yield and purity of two hydrophobic microcystins.

Six microcystins were identified in a laboratory culture of the cyanobacterium (blue-green alga) Microcystis aeruginosa PCC 7813 using high-performance liquid chromatography coupled with diode array detection (HPLC-DAD) and mass spectrometry (LC-MS). The toxins were purified and further characterized by amino acid analysis and tandem mass spectrometry (MS-MS). The presence of the previously reported microcystin-LR and microcystin-LY was confirmed. Two further microcystins were characterized as microcystin-LW and microcystin-LF. Another two toxins were partially characterized and are believed to be an analog of microcystin-LR (molecular weight 1008) and microcystin-LM (molecular weight 969). Natural bloom material of M. aeruginosa collected from 2 reservoirs was found to have similar microcystin profiles using HPLC-DAD and LC-MS, indicating the widespread occurrence of these microcystin variants. In addition, the presence of 5 of the microcystins was confirmed in the rumen contents of a lamb by LC-MS and LC-MS-MS, providing the first report of microcystins identified in an animal suspected of being poisoned by cyanobacterial hepatotoxins.