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This study aimed to test the hypothesis of the year-round presence of toxigenic Microcystis and cyanotoxins in the water and ice of the shallow eutrophic Lake Ytyk-Kyuyol located in the continuous permafrost zone. Three independent approaches—mass-spectrometry, molecular methods and light microscopy—were applied in the study. The cyanobacterial biomass ranged from 1.0 × 10−4 to 4.8 mg L−1. Microcystis flos-aquae and M. aeruginosa were the dominant morphospecies in plankton throughout the observation. In environmental DNA, the presence of M. aeruginosa was supported and mcy gene regions responsible for microcystin biosynthesis were detected through a BLAST (Basic Local Alignment Search Tool) search and phylogenetic estimation based on newly obtained 16S rRNA, 16S–23S ITS rRNA, mcyA and mcyE nucleotide sequences. The intracellular microcystin concentration ranged from <0.1 to 803 ng L−1, and the microcystin quota in the Microcystis biomass was extremely low. For the first time, it was shown that Microcystis cells containing mcy genes and microcystins presented permanently in the water column, both during the ice-free period and under ice, as well as inside thick ice covers within 7 months of severe winter. We hypothesized that minor pelagic and ice populations of Microcystis could participate in increasing cell density in the spring. However, further studies are needed to confirm the viability of the overwintering Microcystis colonies in the water and inside the ice of Lake Ytyk-Kyuyol. [ABSTRACT FROM AUTHOR]

This study aimed to test the hypothesis of the year-round presence of toxigenic Microcystis and cyanotoxins in the water and ice of the shallow eutrophic Lake Ytyk-Kyuyol located in the continuous permafrost zone. Three independent approaches—mass-spectrometry, molecular methods and light microscopy—were applied in the study. The cyanobacterial biomass ranged from 1.0 × 10−4 to 4.8 mg L−1. Microcystis flos-aquae and M. aeruginosa were the dominant morphospecies in plankton throughout the observation. In environmental DNA, the presence of M. aeruginosa was supported and mcy gene regions responsible for microcystin biosynthesis were detected through a BLAST (Basic Local Alignment Search Tool) search and phylogenetic estimation based on newly obtained 16S rRNA, 16S–23S ITS rRNA, mcyA and mcyE nucleotide sequences. The intracellular microcystin concentration ranged from −1, and the microcystin quota in the Microcystis biomass was extremely low. For the first time, it was shown that Microcystis cells containing mcy genes and microcystins presented permanently in the water column, both during the ice-free period and under ice, as well as inside thick ice covers within 7 months of severe winter. We hypothesized that minor pelagic and ice populations of Microcystis could participate in increasing cell density in the spring. However, further studies are needed to confirm the viability of the overwintering Microcystis colonies in the water and inside the ice of Lake Ytyk-Kyuyol.

• Urea is metabolized by the microbial consortium in Lake Taihu. • Urea supports the growth of Microcystis indirectly at a rate comparable to NH 4 +. • Urea fate depends on light conditions (natural light vs. dark). • Heterotrophic bacteria are the dominant organisms affecting urea cycling in Lake Taihu. Lake Taihu, the third largest freshwater lake in China, suffers from harmful cyanobacteria blooms caused by Microcystis spp., which do not fix nitrogen (N). Reduced N (i.e., NH 4 +, urea and other labile organic N compounds) is an important factor affecting the growth of Microcystis. As the world use of urea as fertilizer has escalated during the past decades, an understanding of how urea cycling relates to blooms of Microcystis is critical to predicting, controlling and alleviating the problem. In this study, the cycling rates of urea-N in Lake Taihu ranged from non-detectable to 1.37 μmol N L−1 h−1 for regeneration, and from 0.042 μmol N L−1 h−1 to 2.27 μmol N L−1 h−1 for potential urea-N removal. The fate of urea-N differed between light and dark incubations. Increased 15NH 4 + accumulated and higher quantities of the removed urea-15N remained in the 15NH 4 + form were detected in the dark than in the light. A follow-up incubation experiment with 15N-urea confirmed that Microcystis can grow on urea but its effects on urea dynamics were minor, indicating that Microcystis was not the major factor causing the observed fates of urea under different light conditions in Lake Taihu. Bacterial community composition and predicted functional gene data suggested that heterotrophic bacteria metabolized urea, even though Microcystis spp. was the dominant bloom organism. [ABSTRACT FROM AUTHOR]

In this present study, ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate (IL)) modified pencil graphite electrode (IL-PGEs) was developed for electrochemical monitoring of DNA hybridization related to Microcystis spp. (MYC). The characterization of IL-PGEs was performed using microscopic and electrochemical techniques. DNA hybridization related to MYC was then explored at the surface of IL-PGEs using differential pulse voltammetry (DPV) technique. After the experimental parameters were optimized, the sequence-selective DNA hybridization related to MYC was performed in the case of hybridization between MYC probe and its complementary DNA target, noncomplementary (NC) or mismatched DNA sequence (MM), or and in the presence of mixture of DNA target: NC (1:1) and DNA target: MM (1:1).

In this present study, ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate (IL)) modified pencil graphite electrode (IL-PGEs) was developed for electrochemical monitoring of DNA hybridization related to Microcystis spp. (MYC). The characterization of IL-PGEs was performed using microscopic and electrochemical techniques. DNA hybridization related to MYC was then explored at the surface of IL-PGEs using differential pulse voltammetry (DPV) technique. After the experimental parameters were optimized, the sequence-selective DNA hybridization related to MYC was performed in the case of hybridization between MYC probe and its complementary DNA target, noncomplementary (NC) or mismatched DNA sequence (MM), or and in the presence of mixture of DNA target: NC (1:1) and DNA target: MM (1:1). [ABSTRACT FROM AUTHOR]

Freshwater algal blooms have become a growing concern world-wide. They are caused by a high level of cyanobacteria, predominantly Microcystis spp. and Cylindrospermopsis raciborskii, which can produce microcystin and cylindrospermopsin, respectively. Longtime exposure to these cyanotoxins may affect public health, thus reliable detection, quantification, and enumeration of these harmful algae species has become a priority in water quality management. Traditional manual enumeration of algal bloom cells primarily involves microscopic identification which limited by inaccuracy and time-consumption.With the development of molecular techniques and an increasing number of microbial sequences available in the Genbank database, the use of molecular methods can be used for more rapid, reliable, and accurate detection and quantification. In this study, multiplex polymerase chain reaction (PCR) and real-time quantitative PCR (qPCR) techniques were developed and applied for monitoring cyanobacteria Microcystis spp. and C. raciborskii in the Macau Storage Reservoir (MSR). The results showed that the techniques were successful for identifying and quantifying the species in pure cultures and mixed cultures, and proved to be a potential application for water sampling in MSR. When the target species were above 1 million cells/L, similar cell numbers estimated by microscopic enumeration and qPCR were obtained. Further quantification in water samples indicated that the ratio of the estimated number of cell by microscopy and qPCR was 0.4-12.9 for cyanobacteria and 0.2-3.9 for C. raciborskii. However, Microcystis spp. was not observed by manual enumeration, while it was detected at low levels by qPCR, suggesting that qPCR is more sensitive and accurate. Thus the molecular approaches provide an additional reliable monitoring option to traditional microscopic enumeration for the ecosystems monitoring program. [ABSTRACT FROM AUTHOR]

Toxic cyanobacterial blooms and biological invasions are major threats to freshwater systems worldwide. While usually dealt with independently, the two threats can interact to produce synergistic or antagonistic outcomes. The aim of this survey is to analyse interactions between the cyanobacterium Microcystis spp. and the Asian invasive mussel Limnoperna fortunei., On the basis of 9 years of observational data in a large subtropical reservoir ( Salto Grande, Argentina- Uruguay), we analyse causal relationships between recurring summer-early autumn blooms of Microcystis spp. and recruitment by L. fortunei. Reproduction of the mussel was interrupted during dry summers ( January- April), coinciding with periods of peak Microcystis spp. growth and low water discharge (which favours build-up of algal biomass). On the other hand, wet summers with high discharge rates were characterised by low Microcystis spp. densities and high numbers of L. fortunei larvae in the water column., Of the seven South American waterbodies investigated, Salto Grande was the only one with very marked cyanobacterial blooms and where larval numbers decrease to near zero during January- April; in all others, reproduction peaks in January- April., The assumption that microcystin-producing algae are responsible for these troughs during periods when elsewhere larvae are very abundant was reinforced by experimental results indicating that microcystin- LR is highly toxic to the mussel's larvae, eliminating 58-100% of animals in 48 h at 10-20 μg L−1., Paradoxically, high concentrations of microcystin in water are probably partly due to L. fortunei's own activity, which enhances growth of Microcystis spp. through modification of nutrient concentrations, selective grazing of solitary Microcystis spp. cells over colonial ones and production of chemical cues that trigger the formation of colonies., These interactions have important implications for the management of biofouling of industrial raw cooling water facilities by the byssate mussels, as well as policies oriented at curtailing the spread of the invasive bivalve. [ABSTRACT FROM AUTHOR]

Highlights: [•] A simple approach to produce H2 from Taihu Lake Microcystis spp. blooms is described. [•] Efficient H2 production occurred in the dark and was inactivated by light. [•] Efficient H2 production resulted from reduced O2 content and enhanced H2ase activity. [•] A post-treatment strategy is proposed to turn algal bloom waste into useful products. [ABSTRACT FROM AUTHOR]

Iron (Fe) is an essential micronutrient for algal growth and can be a potential limiting nutrient in aquatic system, especially regions that exhibits nitrogen (N) limitation. Using short-term nutrient addition bioassays, we evaluated the potential role that iron might play in modifying the response of Microcystis spp. to the anthropogenic phosphorus (P) and N enrichment in hypereutrophic Lake Taihu, the third largest freshwater lake in China. Three nutrient enrichment experiments involving additions of N (as NO) and P (as PO) with and without Fe were conducted during 2009-2010 in Meiliang Bay, a region characterized by summer cyanobacterial ( Microcystis spp.) blooms, and East Taihu, a region largely free of cyanobacterial blooms and dominated by macrophytes. In Meiliang Bay, Fe addition alone did not significantly increase Microcystis spp. biomass. However, Fe addition occasionally increased the stimulatory effect of N and P additions on Microcystis spp., indicating that Fe was not a primary limiting nutrient for Microcystis spp. growth. Occasionally Fe was co-limiting with N and P in this region. In East Taihu, the addition of Fe alone significantly stimulated Microcystis spp. growth, while addition of N and/or P had no effects on growth, indicating that Fe was a primary limiting nutrient in East Taihu. The combined addition of Fe and N resulted in a growth response similar to Fe alone, while combined addition of Fe and P yielded greater biomass increases than the addition of Fe alone. This indicated that in East Taihu, N was not limiting and Fe and P supplies facilitated Microcystis spp. growth. These results reflect differential availabilities and limitations of N, P, and Fe in distinct regions of Taihu. The potential role of Fe in eutrophication dynamics of large, regionally complex lakes like Taihu requires further attention. [ABSTRACT FROM AUTHOR]

Harmful algal bloom (HAB) events threaten human health, living marine resources, and ecosystem health. Their occurrence has increased in frequency, duration, and severity over the last several decades. Preventing, controlling, o:r mitigating the impacts of HABs requires the development of permanent, operational ocean observing systems that continuously provide the data and information necessary for rapid detection and timely forecasts of changes in ecosystem states. Key elements of such observing systems are observations and modeling that must be efficiently linked via data management and communication networks. Building the observing system begins by integrating existing assets, is followed by incorporation of new technologies and knowledge, and is guided by the data and information needs of decision makers. User needs are particularly important for development of operational forecast models and new sensors for measuring required biological (e.g., HAB species abundance) and chemical (e.g., concentrations of HAB toxins) variables in near realtime. This article describes operational observing system requirements for a HAB forecasting system and current efforts by Regional Associations to develop these observing systems for targeted species in their respective regions. [ABSTRACT FROM AUTHOR]

Abstract: A batch anaerobic test was conducted to evaluate the effects of inoculum/substrate ratios (ISRs) on the methane yield and orthophosphate release from the anaerobic digestion of Microcystis spp. The results demonstrated an obvious influence on methane yield and orthophosphate release by ISR. The maximum methane yield decreased from 140.48 to 94.42mL/gVS when the ISR decreased from 2.0 to 0.5. The highest maximum methane yield calculated from Ørskov equation was 153.66mL/gVS at ISR value of 1.0. The values of pH, ammonia and volatile fatty acids (VFAs) corroborated the appropriate stability of this anaerobic process. [Copyright &y& Elsevier]

Microcystis spp. blooms have occurred annually in western Lake Erie since about 1995. Microcystis produce a group of toxins known as microcystins which can be harmful to livestock and to humans. In this study, surface water samples were collected from six sites during six sampling events from July to October in 2007. In situ environmental data (e.g. pH, temperature) and laboratory analyses (e.g. nutrients) were carried out to characterize the six sites. The Microcystis spp. density ranged from 10² to 107 cells/ml. Microcystin-LR concentration of 20 of all 36 samples were below the detection limit (0.15-5 ppb), while the microcystin-LR concentration in the 16 remaining samples ranged from 0.5 to 3 x 10³ μg per gram dry weight. The aim of this research was to investigate the relationships between sampling location, environmental parameters, Microcystis spp. concentration, and microcystin-LR concentration. The results suggest that temperature, nutrient concentration, turbidity, and wind speed and direction ( P < 0.05) are factors which affected Microcystis spp. density. Sampling site 8M, located 13m from the Maumee River, provided an advantage for Microcystis spp. growth, presumably due to intermediate water depth (5.5 m) combined with impact from the river. No relationship was found between Microcystis spp. density and microcystin-LR concentration. Temperature, nutrient concentration and DO ( P < 0.05) were associated with the production of microcystin-LR. [ABSTRACT FROM AUTHOR]

The blue - green alga Microcystis was grown under continuous culture in the presence of chromium (VI), cadmium (II) and copper (II), as single metal species and as mixtures of two or three metals in a laboratory-scale system. The present work used artificial wastewater with low free ion activities due to the presence of a strong chelating agent EDTA but with total concentrations not appropriate for acceptable environments. Chromium (VI) and cadmium (II) had a positive interaction that increased the removal percentages of both these metals; the work, however, could not detect any interaction with copper (II). Microcystis was able to remove all the tested metals to some extent (24 - 76%), but bivalent metals were not removed as efficiently as reported in batch cultures. Chromium (VI) was more efficiently removed in continuous cultures than in batch culture, because the uptake of chromate could be favoured by actively growing algae. The work demonstrated the efficiency of Microcystis in metal removal from single bimetallic as well as multimetallic conditions. Since Microcystis is a nuisance and bloom-forming cyanobacteria, its biotechnological exploitation in metal removal at the field scale should follow an eco-sustainable approach. [ABSTRACT FROM AUTHOR]

One of the most severe problems associated with eutrophication of urban freshwater ecosystems is the occurrence of increasingly frequent blooms of toxic cyanobacteria. Cyanotoxins might accumulate in the trophic web, producing diverse intoxication symptoms and chronic effects that are difficult to diagnose and prevent. High mortality of domestic animals and fish has been reported previously under these prevailing conditions. This study investigates the taxonomic composition of phytoplankton assemblages in Sheldon Lake during the summer of 2004, a year after the completion of a restoration project on the lake. The study analysed the physical and chemical changes caused by urban run-off and artificial mixing, as well as the usefulness of microcystin molecular markers derived from the mcy gene cluster for the detection of toxic cyanobacterial strains in environmental samples from Sheldon Lake. This study clearly demonstrates that the artificial mixing rate alone was insufficient to cause a transition to a well-mixed aquatic system, and that cyanobacteria remained dominant throughout the summer months. The presence of toxic cyanobacterial strains was confirmed with the use of molecular markers that detected the presence of the mcy gene cluster responsible for the production of toxin by Microcystis spp. This approach might have a great potential use in the routine analyses of urban aquatic ecosystems. It also might make toxicity monitoring more feasible, allowing for the early application of corrective actions, especially for cases such as Sheldon Lake, which is a public recreational focal point. [ABSTRACT FROM AUTHOR]

Benthic stages of the annual life cycle of the meroplanktonic cyanobacteriumMicrocystisspp. in relation to microcystin (MCYST) dynamics in sediments of a shallow lake (Quitzdorf Reservoir, Germany) were investigated. Based on changes in the absolute abundance of benthicMicrocystis, the annual life cycle was subdivided into four phenological stages: reinvasion, pelagic growth, sedimentation, and overwintering. Habitat-coupling processes, such as reinvasion of the pelagic zone in spring as well as autumnal sedimentation, were particularly triggered by changes in water temperature. During reinvasion substantial losses ofMicrocystiswere detected. Only a minor part of benthicMicrocystis(about 3%) formed the inoculum for pelagic growth. Between 65% and 85% of the benthicMicrocystisstock disappeared during the reinvasion phase. Because these colonies were neither detected within the sediments nor in the pelagic inoculum, it was concluded that they were subjected to decay. The occurrence of extracellular MCYSTs in the pelagic zone during this period, which cannot solely originate from the pelagicMicrocystispopulation, supports this conclusion. Dynamics of benthicMicrocystisand MCYSTs were characterized by almost identical successions with a decrease during reinvasion, an increase during sedimentation, and remarkable invariability throughout pelagic growth and overwintering. It can be deduced that MCYSTs are preserved within benthic resting stages ofMicrocystisbecause they could play a role during overwintering or reinvasion. [ABSTRACT FROM AUTHOR]

• Microcystis dominates more freshwater cyanoHABs than R. raciborskii (78 % vs. 18 %). • M. aeruginosa and R. raciborskii growth models were calibrated from laboratory data. • R. raciborskii was predicted with higher growth rate for most light and temperature. • Growth rates measured in cultures need reconsideration in cyanoHAB prediction. Predicting algal population dynamics using models informed by experimental data has been used as a strategy to inform the management and control of harmful cyanobacterial blooms. We selected toxic bloom-forming species Microcystis spp. and Raphidiopsis raciborskii (basionym Cylindrospermopsis raciborskii) for further examination as they dominate in 78 % and 17 %, respectively, of freshwater cyanobacterial blooms (cyanoHABs) reported globally over the past 30 years. Field measurements of cyanoHABs are typically based on biomass accumulation, but laboratory experiments typically measure growth rates, which are an important variable in cyanoHAB models. Our objective was to determine the usefulness of laboratory studies of these cyanoHAB growth rates for simulating the species dominance at a global scale. We synthesized growth responses of M. aeruginosa and R. raciborskii from 20 and 16 culture studies, respectively, to predict growth rates as a function of two environmental variables, light and temperature. Predicted growth rates of R. raciborskii exceeded those of M. aeruginosa at temperatures ≳ 25 °C and light intensities ≳ 150 μmol photons m−2 s-1. Field observations of biomass accumulation, however, show that M. aeruginosa dominates over R. raciborskii , irrespective of climatic zones. The mismatch between biomass accumulation measured in the field, and what is predicted from growth rate measured in the laboratory, hinders effective use of culture studies to predict formation of cyanoHABs in the natural environment. The usefulness of growth rates measured may therefore be limited, and field experiments should instead be designed to examine key physiological attributes such as colony formation, buoyancy regulation and photoadaptation. Improving prediction of cyanoHABs in a changing climate requires a more effective integration of field and laboratory approaches, and an explicit consideration of strain-level variability. [ABSTRACT FROM AUTHOR]