Health hazards for terrestrial vertebrates from toxic cyanobacteria in surface water ecosystems

Dynamics of toxic genotypes of Microcystis aeruginosa complex (MAC) through a wide freshwater to marine environmental gradient

Bloom-forming species belonging to Microcystis aeruginosa complex (MAC) are the most commonly reported worldwide. MAC blooms are composed by toxic and non-toxic genotypes and the environmental conditions favouring the dominance of toxic genotypes are still a matter of debate among the scientific community. In this study, we evaluated the distribution of toxic MAC genotypes along a seasonal cycle and over an environmental gradient spanning 800km, from a eutrophic freshwater reservoir in Río Uruguay to marine water in the outer limit of Río de la Plata. Abundance of four mcy genes, mcyB, mcyD, mcyE and mcyJ was determined by qPCR and used as a proxy of abundance of toxic MAC genotypes. All the mcy genes were detected through the seasonal cycle at all sampling sites, being systematically higher in the freshwater reservoir and decreasing towards the marine site. The highest toxic genotype abundance was found during the austral summer months. According to generalized linear regressions and random forest models, temperature and conductivity were the most relevant explanatory variables. This suggests that although toxic MAC genotypes grow optimally in freshwater, they are also able to tolerate the high-salinity and low temperature conditions found in estuarine and marine waters. This ability to resist harsh conditions impose a health risk and a management challenge. To our knowledge, this is the first report addressing several mcy genes in a broad gradient that includes a wide array of different environmental conditions.

Using H2O2 treatments for the degradation of cyanobacteria and microcystins in a shallow hypertrophic reservoir

Toxins produced by cyanobacteria in freshwater ecosystems constitute a serious health risk worldwide for humans that may use the affected water bodies for recreation, drinking water, and/or irrigation. Cyanotoxins have also been deemed responsible for loss of animal life in many places around the world. This paper explores the effect of H₂O₂ treatments on cyanobacteria and microcystins in natural samples from a hypertrophic reservoir in microcosm experiments. According to the results, cyanobacteria were more easily affected by H₂O₂ than by other phytoplanktonic groups. This was shown by the increase in the fractions of chlorophyll-a (a proxy for phytoplankton) and chlorophyll-b (a proxy for green algae) over total phytoplankton pigments and the decrease in the fraction of phycocyanin (a proxy for cyanobacteria) over total phytoplankton pigments. Thus, while an overall increase in phytoplankton occurred, a preferential decrease in cyanobacteria was observed with H₂O₂ treatments over a few hours. Moreover, significant degradation of total microcystins was observed under H₂O₂ treatments, while more microcystins were degraded when UV radiation was used in combination with H₂O₂. The combination of H₂O₂ and ultraviolet (UV) treatment in natural samples resulted in total microcystin concentrations that were below the World Health Organization limit for safe consumption of drinking water of 1 μg/L. Although further investigation into the effects of H₂O₂ addition on ecosystem function must be performed, our results show that the application of H₂O₂ could be a promising method for the degradation of microcystins in reservoirs and the reduction of public health risks related to the occurrence of harmful algal blooms.

Enhanced thermal destruction of toxic microalgal biomass by using CO2

This work confirmed that dominant microalgal strain in the eutrophic site (the Han River in Korea) was Microcystis aeruginosa (M. aeruginosa) secreting toxins. Collected and dried microalgal biomass had an offensive odor due to microalgal lipid, of which the content reached up to 2±0.2wt.% of microalgal biomass (dry basis). This study has validated that the offensive odor is attributed to the C3-6 range of volatile fatty acids (VFAs), which was experimentally identified by the non-catalytic transformation of triglycerides (TGs) and free fatty acids (FFAs) in microalgal biomass into fatty acid methyl esters (FAMEs). In particular, this study mechanistically investigated the influence of CO2 in the thermal destruction (i.e., pyrolysis) of hazardous microalgal biomass in order to achieve dual purposes (i.e., thermal disposal of hazardous microalgal biomass and energy recovery). The influence of CO2 in pyrolysis of microalgal biomass was identified as 1) the enhanced thermal cracking behaviors of volatile organic compounds (VOCs) from the thermal degradation of microalgal biomass and 2) the direct gas phase reaction between CO2 and VOCs. These identified influences of CO2 in pyrolysis of microalgal biomass significantly enhanced the generation of CO: the enhanced generation of CO in the presence of CO2 was 590% at 660°C, 1260% at 690°C, and 3200% at 720°C. In addition, two identified influences of CO2 (i.e., enhanced thermal cracking and direct gas phase reaction) occurred simultaneously and independently. The identified gas phase reaction in the presence of CO2 was only initiated at temperatures higher than 500°C, which was different from the Boudouard reaction. Lastly, the experimental work justified that exploiting CO2 as a reaction medium and/or chemical feedstock will provide new technical approaches for controlling syngas ratio and in-situ air pollutant control without using catalysts.

Molecular tools to detect anatoxin-a genes in aquatic ecosystems: Toward a new nested PCR-based method

Over the last few decades, cyanobacterial mass occurrence has become a recurrent feature of aquatic ecosystems. This has led to ecosystem exposure and health hazards associated with cyanotoxin production. The neurotoxin anatoxin-a and its homologs can be synthesized by benthic cyanobacterial species in lotic systems, but also by planktonic lacustrine species such as Dolichospermum (also known as Anabaena). However, only a few studies have focused on anatoxin-a occurrence and its biosynthesis genes in freshwater lakes. The initial aim of this study was to evaluate the molecular tools available in the literature to detect anatoxin-a biosynthesis genes in lacustrine environments. Having tested different sets of PCR primers, we found that that some sets of primers, such as anxC, were too specific and did not amplify anatoxin-a biosynthesis genes in all producing strains. On the other hand, some sets of primers, such as atxoa, seemed not to be specific enough, amplifying numerous non-specific bands in environmental samples, especially those from sediments. Furthermore, anaC and anaF amplification exhibited different band intensities during electrophoresis, suggesting a high variation in number of gene copies between samples. As a result, we proposed a new nested PCR-based method which considerably improved the amplification of the anaC gene in our environmental samples, eliminating non-specific bands and weak detections. Using this tool, our study also highlighted that anatoxin-a genes are widely distributed throughout freshwater lakes. This suggests the need for further ecological investigations into anatoxin-a in these ecosystems.

Spatial and temporal variation in microcystin occurrence in wadeable streams in the southeastern United States

Despite historical observations of potential microcystin-producing cyanobacteria (including Leptolyngbya, Phormidium, Pseudoanabaena, and Anabaena species) in 74% of headwater streams in Alabama, Georgia, South Carolina, and North Carolina (USA) from 1993 to 2011, fluvial cyanotoxin occurrence has not been systematically assessed in the southeastern United States. To begin to address this data gap, a spatial reconnaissance of fluvial microcystin concentrations was conducted in 75 wadeable streams in the Piedmont region (southeastern USA) during June 2014. Microcystins were detected using enzyme-linked immunosorbent assay (limit = 0.10 µg/L) in 39% of the streams with mean, median, and maximum detected concentrations of 0.29 µg/L, 0.11 µg/L, and 3.2 µg/L, respectively. Significant (α = 0.05) correlations were observed between June 2014 microcystin concentrations and stream flow, total nitrogen to total phosphorus ratio, and water temperature; but each of these factors explained 38% or less of the variability in fluvial microcystins across the region. Temporal microcystin variability was assessed monthly through October 2014 in 5 of the streams where microcystins were observed in June and in 1 reference location; microcystins were repeatedly detected in all but the reference stream. Although microcystin concentrations in the present study did not exceed World Health Organization recreational guidance thresholds, their widespread occurrence demonstrates the need for further investigation of possible in-stream environmental health effects as well as potential impacts on downstream lakes and reservoirs. Environ Toxicol Chem 2016;35:2281-2287. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US Government work and, as such, is in the public domain in the United States of America.

Mass Development of Diazotrophic Cyanobacteria (Nostocales) and Production of Neurotoxic Anatoxin-a in a Planktothrix (Oscillatoriales) Dominated Temperate Lake

In spite of extensive studies on multispecies toxigenic cyanobacterial blooms, they are still difficult to eliminate, and factors regulating their succession and toxin production remain still to discover. A 4-year study revealed periodical mass development of diazotrophic Nostocales such as Dolichospermum spp. (previously Anabaena), Aphanizomenon gracile and expansive Cuspidothrix (previously Aphanizomenon) issatschenkoi in a lake affected by perennial blooms of Planktothrix agardhii (Oscillatoriales). Compared to Oscillatoriales, Nostocales reached the highest total biomass (up to 16 mg L^-1) and contributed nearly 33-85 % to the total biomass of filamentous cyanobacteria at higher water temperatures (average values 17.5-22.6 °C) and higher ratio (11.8-14.1) of dissolved inorganic nitrogen to dissolved inorganic phosphorus (DIN/DIP). Species structure of Nostocales changed considerably from year to year as indicated by the Jaccard similarity index (0.33-0.78). Concentrations of intracellular anatoxin-a (ANTX) ranged from 0.03 to 2.19 μg L^-1 of the lake water, whilst extracellular toxin reached up to 0.55 μg L^-1. The highest positive correlations were found between the intracellular ANTX and the biomass of Dolichospermum spp. (R² = 0.73) and C. issatschenkoi (R² = 0.43-0.65). Our study suggests that ANTX production by Dolichospermum depended mainly on water temperature, whereas that by C. issatschenkoi was related to water conductivity and DIN/DIP ratio. P-PO₄ concentrations also seemed to be important. The relatively short-term mass development of neurotoxic Nostocales is an additional threat to shallow, highly eutrophic water bodies continuously affected by Oscillatoriales blooms and may be controlled mainly by the DIN/DIP ratio. ANTX should be considered as a pollutant of freshwaters.

The influence of microcystin-LR on fish phagocytic cells

The in vitro influence of microcystin-LR (MC-LR) on rainbow trout phagocytic cell functions was studied. The cells isolated from the fish blood were exposed on MC-LR at the concentrations of 1, 5, 10, 20 μg/mL. The viability of the cells after 2, 4 and 24 hour incubation with MC-LR was studied as well as phagocytic cell ability measured as zymozan particle phagocytosis and metabolic activity measured as respiratory burst activity. The toxin caused time- and dose-dependent viability decrease, the strongest after cell exposure on 10 and 20 μg/mL and observed only after 24 hours incubation when 1 μg/mL was applied. The phagocytic ability was elevated in the presence of MC-LR at the dose of 5 μg/mL. MC-LR had also modulatory influence on respiratory burst activity. While the two lower doses caused the stimulation of the parameter, the two higher ones diminished superoxide anion production in the triggered cells. The results show the potency of the toxin to influence the fish phagocytic cell functions. Human & Experimental Toxicology (2007) 26: 603—607.

Distribution and Habitat Specificity of Potentially-Toxic Microcystis across Climate, Land, and Water Use Gradients

Toxic cyanobacterial blooms are a growing threat to freshwater bodies worldwide. In order for a toxic bloom to occur, a population of cells with the genetic capacity to produce toxins must be present together with the appropriate environmental conditions. In this study, we investigated the distribution patterns and phylogeny of potentially-toxic Microcystis (indicated by the presence and/or phylogeny of the mcyD and mcyA genes). Samples were collected from the water column of almost 60 water bodies across widely differing gradients of environmental conditions and land use in Israel. Potentially, toxic populations were common but not ubiquitous, detected in ~65% of the studied sites. Local environmental factors, including phosphorus and ammonia concentrations and pH, as well as regional conditions such as the distance from built areas and nature reserves, were correlated with the distribution of the mcyD gene. A specific phylogenetic clade of Microcystis, defined using the sequence of the mcyA gene, was preferentially associated with aquaculture facilities but not irrigation reservoirs. Our results reveal important environmental, geospatial, and land use parameters affecting the geographic distribution of toxinogenic Microcystis, suggesting non-random dispersal of these globally abundant toxic cyanobacteria.

Genotypes of ITS region of rRNA in Microcystis (Cyanobacteria) populations in Erhai Lake (China) and their correlation with eutrophication level

Previous studies on spatiotemporal changes of Microcystis genotypes have shown that the existence and succession of dominant genotypes always occur in eutrophicated freshwater bodies. However, few studies have focused on the correlation between genotype composition and eutrophication level. In the present study, clone libraries of the internal transcribed spacer (ITS) of rrn operon were sequenced from Microcystis populations in Erhai Lake, a subtropical plateau lake in the preliminary eutrophication stage. The genotype composition of the Microcystis populations was highly variable at spatiotemporal scales, and 473 ITS genotypes were identified from the 800 ITS sequences obtained. However, no significantly dominant ITS genotypes existed in the lake. Comparison of Erhai Lake with four major lakes in China, namely, Taihu, Chaohu, Gucheng, and Shijiu Lakes, showed that the Microcystis ITS genotypes and genetic diversity were negatively correlated with eutrophication level. Extensive comparison of the Microcystis ITS genotypes from waters worldwide revealed that 440 ITS genotypes were unique to Erhai Lake, and no obvious phylogenetic correlations can be detected among the dominant genotypes from different water bodies. The high genetic diversity of the Microcystis populations in Erhai Lake may have resulted from the effect of the early stage of eutrophication.

Separation of Microcystin-LR by Cyclodextrin-Functionalized Magnetic Composite of Colloidal Graphene and Porous Silica

Microcystin-LR belongs to the family of microcystins produced by cyanobacteria and known to be the most toxic of this family. Existence of cyanobacteria in water bodies leads to the contamination of drinking water with microcystin-LR and thus their separation is essential for an advanced water purification system. Here we report functional nanocomposite-based selective separation of microcystin-LR from contaminated water. We have synthesized cyclodextrin-functionalized magnetic composite of colloidal graphene and porous silica where the cyclodextrin component offers host-guest interaction with microcystin-LR and the magnetic component offers easier separation of microcystin-LR from water. High surface area and large extent of chemical functional groups offer high loading (up to 18 wt %) of cyclodextrin with these nanocomposites, and the dispersible form of the nanocomposite offers easier accessibility of cyclodextrin to microcystin-LR. We have shown that microcystin-LR separation efficiency is significantly enhanced after functionalization with cyclodextrin, and among all the tested cyclodextrins, γ-cyclodextrin offers the best performance. We have also found that graphene-based nanocomposite offers better performance over porous silica-based nanocomposite due to better accessibility of cyclodextrins for interaction with microcystin-LR. The proposed graphene-based functional nanocomposite is environment friendly, reusable, and applicable for advanced water purification.

Comparative genomics reveals diversified CRISPR-Cas systems of globally distributed Microcystis aeruginosa, a freshwater bloom-forming cyanobacterium

Microcystis aeruginosa is one of the most common and dominant bloom-forming cyanobacteria in freshwater lakes around the world. Microcystis cells can produce toxic secondary metabolites, such as microcystins, which are harmful to human health. Two M. aeruginosa strains were isolated from two highly eutrophic lakes in China and their genomes were sequenced. Comparative genomic analysis was performed with the 12 other available M. aeruginosa genomes and closely related unicellular cyanobacterium. Each genome of M. aeruginosa containing at least one clustered regularly interspaced short palindromic repeat (CRISPR) locus and total 71 loci were identified, suggesting it is ubiquitous in M. aeruginosa genomes. In addition to the previously reported subtype I-D cas gene sets, three CAS subtypes I-A, III-A and III-B were identified and characterized in this study. Seven types of CRISPR direct repeat have close association with CAS subtype, confirming that different and specific secondary structures of CRISPR repeats are important for the recognition, binding and process of corresponding cas gene sets. Homology search of the CRISPR spacer sequences provides a history of not only resistance to bacteriophages and plasmids known to be associated with M. aeruginosa, but also the ability to target much more exogenous genetic material in the natural environment. These adaptive and heritable defense mechanisms play a vital role in keeping genomic stability and self-maintenance by restriction of horizontal gene transfer. Maintaining genomic stability and modulating genomic plasticity are both important evolutionary strategies for M. aeruginosa in adaptation and survival in various habitats.

Affinity and efficacy of copper following an algicide exposure: application of the critical burden concept for Lyngbya wollei control in Lay Lake, AL

Accurate predictions of nuisance algae responses to algicide exposures are needed to guide management decisions. Copper sorption and responses of Lyngbya wollei (Farlow ex Gomont) Speziale and Dyck were measured in the laboratory and two areas in Lay Lake (AL, USA) to treatments of Captain(®) XTR (SePRO Corporation; chelated copper algicide) and a sequential treatment of GreenClean(®) Liquid (BioSafe Systems, LLC; peroxygen algicide) combined with Hydrothol(®) 191 (United Phosphorus, Inc.; endothall algicide) followed by Captain XTR. Measured filament viability in laboratory exposures predicted Captain XTR alone could control L. wollei in Lay Lake, with 2 mg Cu/g algae EC75. This produced a targeted field treatment of 9.7 kg Cu/ha which was divided into three applications of 0.3 mg Cu/L as Captain XTR in the treatment areas. Laboratory and field experiments indicated treatments of Captain XTR alone and the combination treatment resulted in comparable copper sorption and responses of L. wollei. Copper adsorbed greater to L. wollei in laboratory experiments than in the treated areas of Lay Lake with comparable exposures (2 mg Cu/g L. wollei). However, responses and infused copper were similar and correlated in laboratory experiments and treated areas of Lay Lake indicating infused copper is critical for governing toxicity. Laboratory exposures as mg Cu/g algae accurately predicted the necessary algicide exposure required to attain the critical burden of infused copper and elicit desired responses of L. wollei in treated areas of Lay Lake.

Harmful algal bloom characterization at ultra-high spatial and temporal resolution using small unmanned aircraft systems

Harmful algal blooms (HABs) degrade water quality and produce toxins. The spatial distribution of HAbs may change rapidly due to variations wind, water currents, and population dynamics. Risk assessments, based on traditional sampling methods, are hampered by the sparseness of water sample data points, and delays between sampling and the availability of results. There is a need for local risk assessment and risk management at the spatial and temporal resolution relevant to local human and animal interactions at specific sites and times. Small, unmanned aircraft systems can gather color-infrared reflectance data at appropriate spatial and temporal resolutions, with full control over data collection timing, and short intervals between data gathering and result availability. Data can be interpreted qualitatively, or by generating a blue normalized difference vegetation index (BNDVI) that is correlated with cyanobacterial biomass densities at the water surface, as estimated using a buoyant packed cell volume (BPCV). Correlations between BNDVI and BPCV follow a logarithmic model, with r²-values under field conditions from 0.77 to 0.87. These methods provide valuable information that is complimentary to risk assessment data derived from traditional risk assessment methods, and could help to improve risk management at the local level.

Successional change in microbial communities of benthic Phormidium-dominated biofilms

Benthic cyanobacterial blooms are increasing worldwide and can be harmful to human and animal health if they contain toxin-producing species. Microbial interactions are important in the formation of benthic biofilms and can lead to increased dominance and/or toxin production of one or few taxa. This study investigated how microbial interactions contribute to proliferation of benthic blooms dominated by the neurotoxin-producing Phormidium autumnale. Following a rainfall event that cleared the substrate, biofilm succession was characterised at a site on the Hutt River (New Zealand) by sampling every 2-3 days over 32 days. A combination of morphological and molecular community analyses (automated ribosomal intergenic spacer analysis and Illumina™ MiSeq sequencing) identified three distinct phases of succession in both the micro-algal and bacterial communities within P. autumnale-dominated biofilms. Bacterial composition shifted between the phases, and these changes occurred several days before those of the micro-algal community. Alphaproteobacteria and Betaproteobacteria dominate in the early phase; Alphaproteobacteria, Betaproteobacteria, Sphingobacteria and Flavobacteria in the mid-phase; and Sphingobacteria and Flavobacteria in the late phase. Collectively, the results suggest that succession is driven by bacteria in the early stages but becomes dependent on micro-algae in the mid- and late stages of biofilm formation.

Human illnesses and animal deaths associated with freshwater harmful algal blooms-Kansas

Freshwater harmful algal bloom (FHAB) toxins can cause morbidity and mortality in both humans and animals, and the incidence of FHABs in the United States and Kansas has increased. In 2010, the Kansas Department of Health and Environment (KDHE) developed a FHAB policy and response plan. We describe the epidemiology of FHAB-associated morbidity and mortality in humans and animals in Kansas. Healthcare providers and veterinarians voluntarily reported FHAB-associated cases to KDHE. An investigation was initiated for each report to determine the source of exposure and to initiate public health mitigation actions. There were 38 water bodies with a confirmed FHAB in 2011. There were 34 reports of human and animal FHAB-associated health events in 2011, which included five dog deaths and hospitalization of two human case patients. Five confirmed human illnesses, two dog illnesses and five dog deaths were associated with one lake. Four human and seven dog cases were exposed to the lake after a public health alert was issued. Public health officials and FHAB partners must ensure continued awareness of the risks to the public, educate healthcare providers and veterinarians on FHAB-related health events and encourage timely reporting to public health authorities.

Impact of environmental factors on the regulation of cyanotoxin production

Cyanobacteria are capable of thriving in almost all environments. Recent changes in climatic conditions due to increased human activities favor the occurrence and severity of harmful cyanobacterial bloom all over the world. Knowledge of the regulation of cyanotoxins by the various environmental factors is essential for effective management of toxic cyanobacterial bloom. In recent years, progress in the field of molecular mechanisms involved in cyanotoxin production has paved the way for assessing the role of various factors on the cyanotoxin production. In this review, we present an overview of the influence of various environmental factors on the production of major group of cyanotoxins, including microcystins, nodularin, cylindrospermopsin, anatoxins and saxitoxins.

Comparison of cyanobacterial microcystin synthetase (mcy) E gene transcript levels, mcy E gene copies, and biomass as indicators of microcystin risk under laboratory and field conditions

Increased incidences of mixed assemblages of microcystin-producing and nonproducing cyanobacterial strains in freshwater bodies necessitate development of reliable proxies for cyanotoxin risk assessment. Detection of microcystin biosynthetic genes in water blooms of cyanobacteria is generally indicative of the presence of potentially toxic cyanobacterial strains. Although much effort has been devoted toward elucidating the microcystin biosynthesis mechanisms in many cyanobacteria genera, little is known about the impacts of co-occurring cyanobacteria on cellular growth, mcy gene expression, or mcy gene copy distribution. The present study utilized conventional microscopy, qPCR assays, and enzyme-linked immunosorbent assay to study how competition between microcystin-producing Microcystis aeruginosa CPCC 299 and Planktothrix agardhii NIVA-CYA 126 impacts mcyE gene expression, mcyE gene copies, and microcystin concentration under controlled laboratory conditions. Furthermore, analyses of environmental water samples from the Missisquoi Bay, Quebec, enabled us to determine how the various potential toxigenic cyanobacterial biomass proxies correlated with cellular microcystin concentrations in a freshwater lake. Results from our laboratory study indicated significant downregulation of mcyE gene expression in mixed cultures of M. aeruginosa plus P. agardhii on most sampling days in agreement with depressed growth recorded in the mixed cultures, suggesting that interaction between the two species probably resulted in suppressed growth and mcyE gene expression in the mixed cultures. Furthermore, although mcyE gene copies and McyE transcripts were detected in all laboratory and field samples with measureable microcystin levels, only mcyE gene copies showed significant positive correlations (R(2) > 0.7) with microcystin concentrations, while McyE transcript levels did not. These results suggest that mcyE gene copies are better indicators of potential risks from microcystins than McyE transcript levels or conventional biomass proxies, especially in water bodies comprising mixed assemblages of toxic and nontoxic cyanobacteria.

Detection of free and covalently bound microcystins in different tissues (liver, intestines, gills, and muscles) of rainbow trout (Oncorhynchus mykiss) by liquid chromatography-tandem mass spectrometry: method characterization

So far only a few publications have explored the development of extraction methods of cyanotoxin extracted from complex matrices. With regard to cyanobacterial microcystins (MCs), the data on the contamination of the flesh of aquatic organisms is hard to compare and very limited due to the lack of validated methods. In recent years, evidence that both free and bound fractions of toxin are found in these tissues has highlighted the need to develop effective methods of quantification. Several techniques do exist, but only the Lemieux oxidation has so far been used to investigate complex tissue matrices. In this study, protocols based on the Lemieux approach were adapted for the quantitative chemical analysis of free MC-LR and MMPB derived from bound toxin in the tissues of juvenile trout gavaged with MC-LR. Afterwards, the NF V03 110 guideline was used to characterize the protocols elaborated and evaluate their effectiveness.

Epidemiology of cancers in Serbia and possible connection with cyanobacterial blooms

Cyanobacteria produce toxic metabolites known as cyanotoxins. These bioactive compounds can cause acute poisoning, and some of them may promote cancer through chronic exposure. Direct ingestion of and contact with contaminated water is one of the many exposure routes to cyanotoxins. The aim of this article was to review the incidence of 13 cancers during a 10-year period in Serbia and to assess whether there is a correlation between the cancer incidences and cyanobacterial bloom occurrence in reservoirs for drinking water supply. The types of cancers were chosen and subjected to epidemiological analyses utilizing previously published data. Based on the epidemiological and statistical analysis, the group of districts in which the incidences of cancers are significant, and may be considered as critical, include Nišavski, Toplički, and Šumadijski district. A significantly higher incidence of ten cancers was observed in the three critical districts as compared to the remaining 14 districts in Central Serbia. These elevated incidences of cancer include: brain cancer, heart, mediastinum and pleura cancer, ovary cancer, testicular cancer, gastric cancer, colorectal cancer, retroperitoneum and peritoneum cancer, leukemia, malignant melanoma of skin, and primary liver cancer. In addition, the mean incidence of five chosen cancers was the highest in the three critical regions, then in the rest of Central Serbia, while the lowest values were recorded in Vojvodina. Persistent and recurrent cyanobacterial blooms occur during summer months in reservoirs supplying water to waterworks in the three critical districts. People in Central Serbia mainly use surface water as water supply (but not all the water bodies are blooming) while in Vojvodina region (control region in this study) only groundwater is used. Among the 14 "noncritical" districts, reservoirs used for drinking water supply have been affected by recurrent cyanobacterial blooms in two districts (Rasinski and Zaječarski), but the waterworks in these districts have been performing ozonation for more than 30 years. We propose that the established statistical differences of cancer incidences in Serbia could be related to drinking water quality, which is affected by cyanobacterial blooms in drinking water reservoirs in certain districts. However, more detailed research is needed regarding cyanobacterial secondary metabolites as risk factors in tumor promotion and cancerogenesis in general.

Temporal shifts in cyanobacterial communities at different sites on the Nakdong River in Korea

The studies of cyanobacterial blooms resulting from eutrophication or climate change and investigation of changes in the cyanobacterial community in freshwater environments are critical for the management of drinking water. Therefore, we investigated the cyanobacterial communities at 6 sites along the Nakdong River in South Korea from May 2012 to October 2012 by using high-throughput sequencing techniques and studied their relationship with various geochemical factors at sampling sites. Diverse genera (total of 175 genera) were detected within the cyanobacteria, and changes in their compositions were analyzed. The genus Prochlorococcus predominated in the May samples, especially in those obtained from the upstream part of the river, whereas the relative abundance of Microcystis and Anabaena increased with increase in water temperature. The relationship between the cyanobacterial community and environmental factors was analyzed by canonical correlation analysis, and the correlation between harmful cyanobacteria and chemical factors was analyzed by nonmetric multidimensional scaling ordination. Various environmental factors such as dissolved oxygen, pH, electric conductivity, temperature were found to affect the cyanobacterial communities in the river. The results of this study could help in the management of freshwater environments and in maintenance of drinking water quality.

Toxicological evaluation of microcystins in aquatic fish species: current knowledge and future directions

Microcystins (MCs) are algal toxins produced intracellularly within the algal cells, and are subsequently released into the aquatic systems. An increase in the frequency and intensity of occurrence of harmful algal blooms has directed the global attention towards the presence of MCs in aquatic systems. The effects of MCs on fish have been verified in a number of studies including histological, biochemical and behavioral effects. The toxicological effects of MCs on different organs of fish are related to the exposure route (intraperitoneal injection, feeding or immersion), the mode of uptake (passive or active transport) as well as biotransformation and bioaccumulation capabilities by different organs. This paper reviews the rapidly expanding literature on the toxicological evaluation of MCs in fish from both field studies and controlled laboratory experimental investigations, integrates the current knowledge available about the mechanisms involved in MC-induced effects on fish, and points out future research directions from a cross-disciplinary perspective. In addition, the need to carry out systematic fish toxicity studies to account for possible interactions between MCs and other environmental pollutants in aquatic systems is discussed.

The importance of small colonies in sustaining Microcystis population exposed to mixing conditions: an exploration through colony size, genotypic composition and toxic potential

Microcystis is a toxic colony-forming cyanobacterium, which can bloom in a wide range of freshwater ecosystems. Despite the ecological advantage of the colonial form, few studies have paid attention to the size of Microcystis colonies in the field. With the aim of evaluating the impact of a fluctuating physical environment on the colony size, the genotypic composition and the toxic potential of a Microcystis population, we investigated five different colony size classes of a Microcystis bloom in the Grangent reservoir (France). By sequencing the internal transcribed spacer of the ribosomal operon, we evidenced changes in the genetic structure among size classes in response to environmental change. While similar genotypes were seen in every size class in stable conditions, new dominant genotypes appeared in the smallest colonies (< 160 μm) concomitantly with mixing conditions, strongly suggesting the importance of these colonies in response to disturbances. Moreover, these small colonies played a major role in microcystin production during this bloom, since very high microcystin contents (> 1 pg.cell.(-1)) were found in their cells. These findings indicate that the colony size distribution of a Microcystis population in response to disturbance could be an adaptive strategy that may explain its ecological success in freshwater ecosystems.

A review on cylindrospermopsin: the global occurrence, detection, toxicity and degradation of a potent cyanotoxin

Cylindrospermopsin is an important cyanobacterial toxin found in water bodies worldwide. The ever-increasing and global occurrence of massive and prolonged blooms of cylindrospermopsin-producing cyanobacteria poses a potential threat to both human and ecosystem health. Its toxicity is associated with metabolic activation and may involve mechanisms that adversely affect a wide variety of targets in an organism. Cylindrospermopsin has been shown to be cytotoxic, dermatotoxic, genotoxic, hepatotoxic in vivo, developmentally toxic, and may be carcinogenic. Human exposure may occur through drinking water, during recreational activities and by consuming foods in which the toxin may have bioaccumulated. Drinking water shortages of sufficient quality coupled with growing human pressures and climate variability and change necessitate an integrated and sustainable water management program. This review presents an overview of the importance of cylindrospermopsin, its detection, toxicity, worldwide distribution, and lastly, its chemical and biological degradation and removal by natural processes and drinking water treatment processes.

Differences in microcystin production and genotype composition among Microcystis colonies of different sizes in Lake Taihu

The cyanobacterium Microcystis, which occurs as colonies of different sizes under natural conditions, can produce toxic microcystins (MCs). To monitor the toxicity and assess the risk of Microcystis blooms in Lake Taihu, it is important to investigate the relationship between MC production and Microcystis colony size. In this study, we classified Microcystis collected from Zhushan Bay of Lake Taihu during blooms into four classes with size of <50 μm, 50-100 μm, 100-270 μm and >270 μm and studied their differences in MC production and genetic structure. The results showed that colonies with size of <50, 50-100, 100-270 and >270 μm produced 12.2 ± 11.2%, 19.5 ± 7.9%, 61.3 ± 12.6%, and 7.0 ± 9.6% of total MC, respectively. The proportion of cell density of colonies with size of 50-100, 100-270 and >270 μm was positively correlated with MC concentration during blooms, while that of colonies with size of <50 μm was negatively correlated. The MC cell quota tended to be higher during blooms in colonies with larger size except that of colonies with size of 100-270 μm was higher than that of colonies with size of >270 μm from June 11 to September 16. Colonies with size of <50 μm showed the highest proportion of the less toxic MC congener MC-RR, and colonies with size of >100 μm showed higher proportion of the most toxic MC congener MC-LR than colonies with size of <100 μm. Real-time PCR indicated that larger colonies had higher proportion of potential toxic genotype. Principal component analysis of PCR-denaturing gradient gel electrophoresis profile showed that cpcBA and mcyJ genotype compositions were different between colonies with size of <50 μm and colonies with size of >50 μm, and cpcBA genotype composition was also different among colonies with size of 50-100 μm, 100-270 μm and >270 μm. These results indicated that MC cell quota and congener composition were different in Microcystis colonies with different sizes in Lake Taihu during blooms, and the differences in MC production in colonies with different size resulted chiefly from the difference in their genotype composition. Therefore, the authorities of water quality monitoring and drinking water supply service in Lake Taihu should be alert that the toxicity of Microcystis colony with different size was different during blooms, and the high abundance of colonies larger than 50 μm could be an indicator of relatively high bloom toxicity.

Spatial and thematic distribution of research on cyanotoxins

Cyanobacteria in surface water are well known for their ability to form toxic blooms responsible for animal mortality and human poisoning. Accompanying major progress in science and technology, the state of knowledge of cyanotoxins has dramatically increased over the last two decades. The bibliometric approach applied in this study shows the evolution of research and identifies major gaps to be filled by future work. Although the publication rate has gradually increased from one hundred to three hundred articles per year since the 1990s, half of the literature available focuses on microcystins and another quarter on saxitoxins. Other cyanotoxins such as beta-N-methylamino-l-alanine or cylindrospermopsin remain vastly disregarded. Moreover, most of the publications deal with toxicity and ecology while other research areas, such as environmental and public health, require additional investigation. The analysis of the literature highlights the main journals for the communication of knowledge on cyanotoxins but also reveals that 90% of the research is originated from only ten countries. These countries are also those with the highest H-index and average number of citation per article. Nonetheless, the ranking of these countries is significantly altered when the amount of publications is normalized based on the population, the number of universities, the national gross domestic product or the government revenue. However, the lower amount of publications from Eastern Europe, Africa and South America could also reflect the lack of monitoring campaigns in these regions. This lack could potentially lead to the underestimation of the prevalence of toxic cyanobacterial blooms and the diversity of toxins worldwide.

State of knowledge and concerns on cyanobacterial blooms and cyanotoxins

Cyanobacteria are ubiquitous microorganisms considered as important contributors to the formation of Earth's atmosphere and nitrogen fixation. However, they are also frequently associated with toxic blooms. Indeed, the wide range of hepatotoxins, neurotoxins and dermatotoxins synthesized by these bacteria is a growing environmental and public health concern. This paper provides a state of the art on the occurrence and management of harmful cyanobacterial blooms in surface and drinking water, including economic impacts and research needs. Cyanobacterial blooms usually occur according to a combination of environmental factors e.g., nutrient concentration, water temperature, light intensity, salinity, water movement, stagnation and residence time, as well as several other variables. These environmental variables, in turn, have promoted the evolution and biosynthesis of strain-specific, gene-controlled metabolites (cyanotoxins) that are often harmful to aquatic and terrestrial life, including humans. Cyanotoxins are primarily produced intracellularly during the exponential growth phase. Release of toxins into water can occur during cell death or senescence but can also be due to evolutionary-derived or environmentally-mediated circumstances such as allelopathy or relatively sudden nutrient limitation. Consequently, when cyanobacterial blooms occur in drinking water resources, treatment has to remove both cyanobacteria (avoiding cell lysis and subsequent toxin release) and aqueous cyanotoxins previously released. Cells are usually removed with limited lysis by physical processes such as clarification or membrane filtration. However, aqueous toxins are usually removed by both physical retention, through adsorption on activated carbon or reverse osmosis, and chemical oxidation, through ozonation or chlorination. While the efficient oxidation of the more common cyanotoxins (microcystin, cylindrospermopsin, anatoxin and saxitoxin) has been extensively reported, the chemical and toxicological characterization of their by-products requires further investigation. In addition, future research should also investigate the removal of poorly considered cyanotoxins (β-methylamino-alanine, lyngbyatoxin or aplysiatoxin) as well as the economic impact of blooms.

Clinical marine toxicology: a European perspective for clinical toxicologists and poison centers

Clinical marine toxicology is a rapidly changing area. Many of the new discoveries reported every year in Europe involve ecological disturbances--including global warming--that have induced modifications in the chorology, behavior, and toxicity of many species of venomous or poisonous aquatic life including algae, ascidians, fish and shellfish. These changes have raised a number of public issues associated, e.g., poisoning after ingestion of contaminated seafood, envenomation by fish stings, and exposure to harmful microorganism blooms. The purpose of this review of medical and scientific literature in marine toxicology is to highlight the growing challenges induced by ecological disturbances that confront clinical toxicologists during the everyday job in the European Poison Centers.

Temporal and seasonal variation in acetylcholinesterase activity and glutathione-S-transferase in amphipods collected in mats of Lyngbya wollei in the St-Lawrence River (Canada)

Mats of filamentous algae Lyngbya wollei cover large areas on top of the sediments along the St-Lawrence River. Like most cyanobacteria, L. wollei produce toxins, named lyngbyatoxin (LYNGTX), an analog of saxitoxin. In order to verify the neurotoxic potential of these filamentous cyanobacteria, we collected amphipods within local vegetation at three sites in summer months: a site rich in L. wollei (Lake St-Louis [LSL]) and two urban sites composed of macrophytes but devoid of L. wollei mats (Richelieu River [RICH] and L'Assomption River [ASSO] outlets). The body weight of each amphipod was measured, and the neurotoxicity was estimated with the measurement of acetylcholinesterase (AChE) and glutathione-s-transferase (GST) activities. Levels of protein-bound phosphates were also evaluated, to rule out contamination by Microcystis sp. The results showed that the activity of acetylcholinesterase measured in amphipods in ASSO and RICH was lower than the activity found in amphipods collected in L. wollei mats in LSL. In addition, amphipods found in L. wollei mats at the LSL site have significantly higher GST activity than those located at the two devoid sites, RICH and ASSO. No significant change was observed for protein-bound phosphate levels. This study suggests that the presence of L. wollei triggers potential toxicity.

Artificially-born "killer" lake: phytoplankton based water quality and microcystin affected fish in a reconstructed lake

Lake Karla (Greece) is an example of a lake ecosystem which was dried in 1960's and now is restored, facing various anthropogenic pressures, whereas it is also listed in the network of Greek protected areas in terms of its conservation value. The objective of the present study was to determine the presence of microcystins (MCYST) in the lake water and their accumulation in tissues of the commercial fish species Cyprinus carpio, along with the highlighting of phytoplankton community and general limnological features of Lake Karla, a newly reconstructed lake, the first year of its refilling. MCYST concentrations in water and fish tissues were determined by an enzyme-linked immunosorbent assay (ELISA). Results suggest that Lake Karla has undergone a progressive cultural eutrophication with frequent cyanobacterial blooms. The most dominant species in lake's phytoplankton were Anabaenopsis elenkinii, Sphaerospermopsis and Planktothrix agardhii. MCYST concentrations were detected in water samples comparable to those reported for other eutrophicated Mediterranean lakes while considerable amounts of MCYST were detected in the tissues of the species C. carpio in the following order: liver>kidney>brain>intestine>muscles. The presence of prominent cyanobacterial blooms dominated by toxic species highlights the need to undertake eutrophication control measures so as to avoid further toxicological problems.

Metal dyshomeostasis and inflammation in Alzheimer's and Parkinson's diseases: possible impact of environmental exposures

A dysregulated metal homeostasis is associated with both Alzheimer's (AD) and Parkinson's (PD) diseases; AD patients have decreased cortex and elevated serum copper levels along with extracellular amyloid-beta plaques containing copper, iron, and zinc. For AD, a putative hepcidin-mediated lowering of cortex copper mechanism is suggested. An age-related mild chronic inflammation and/or elevated intracellular iron can trigger hepcidin production followed by its binding to ferroportin which is the only neuronal iron exporter, thereby subjecting it to lysosomal degradation. Subsequently raised neuronal iron levels can induce translation of the ferroportin assisting and copper binding amyloid precursor protein (APP); constitutive APP transmembrane passage lowers the copper pool which is important for many enzymes. Using in silico gene expression analyses, we here show significantly decreased expression of copper-dependent enzymes in AD brain and metallothioneins were upregulated in both diseases. Although few AD exposure risk factors are known, AD-related tauopathies can result from cyanobacterial microcystin and β-methylamino-L-alanine (BMAA) intake. Several environmental exposures may represent risk factors for PD; for this disease neurodegeneration is likely to involve mitochondrial dysfunction, microglial activation, and neuroinflammation. Administration of metal chelators and anti-inflammatory agents could affect disease outcomes.

Cyanotoxins: characteristics, production and degradation routes in drinking water treatment with reference to the situation in Serbia

Cyanobacteria are members of phytoplankton of the surface freshwaters. The accelerated eutrophication of freshwaters, especially reservoirs for drinking water, by human activity has increased the occurrence and intensity of cyanobacterial blooms. They are of concern due to their ability to produce taste and odors compounds, a wide range of toxins, which have a hepatotoxic, neurotoxic, cytotoxic and dermatotoxic behavior, being dangerous to animal and human health. Therefore, the removal of cyanobacteria, without cell lysis, and releasing of intracellular metabolites, would significantly reduce the concentration of these metabolites in the finished drinking water, as a specific aim of the water treatment processes. This review summarizes the existing data on characteristics of the cyanotoxins, their productions in environment and effective treatment processes to remove these toxins from drinking water.

Cylindrospermopsin: water-linked potential threat to human health in Europe

Cylindrospermopsin (CYN) is a secondary metabolite produced by several cyanobacteria species. Its potential effect on human health includes liver, kidneys, lungs, spleen and intestine injuries. CYN can be cyto- and genotoxic to a variety of cell types. Occurrence and expansion of species able to synthesize CYN in European water bodies has been recently reported and raised awareness of potential harm to human health. Therefore, surface water of different human use should be monitored for the presence of toxic species of blue-green algae. This paper aims to describe the distribution of CYN producers in Europe and the potential effects of the toxin on human health according to the current state of knowledge.

Effects of microcystin-containing cyanobacterial extract on hematological and biochemical parameters of common carp (Cyprinus carpio L.)

The aim of the study was to assess the effects of a cyanobacterial extract containing microcystins (MCs) on selected hematological and biochemical parameters in common carp (Cyprinus carpio L.), as well as to determine the accumulation of toxins in fish tissues. The fish were immersed for 5 days in water containing toxins at a final concentration of 12 μg/L of microcystin LR equivalent. Microcystin LR residues were detected in fish liver, reaching 207, 238 and 260 ng/g f.w. of the tissues taken 24 h, 72 h and 5 days after the end of intoxication, respectively. The most substantial changes were found in fish plasma, including increases in creatine kinase, lactate dehydrogenase, ammonia, glucose, aspartate aminotransferase and alanine aminotransferase levels. A decline of about 50% in lysozyme activity was observed by the end of the experimental period. Moreover, a marked increase in ceruloplasmin activity was detected 24 h after the end of intoxication with a subsequent decrease in its activity after 72 h and 5 days. This study concludes that not only consumption of food containing toxins but also MCs dissolved in water may pose a threat to fish health. Additionally, detected changes in lysozyme and ceruloplasmin activity may have distinct effects in fish resistance against pathogens or oxidative stress, which should be taken into account in the future studies.

Kinetic and mechanistic study of microcystin-LR degradation by nitrous acid under ultraviolet irradiation

Degradation of microcystin-LR (MC-LR) in the presence of nitrous acid (HNO(2)) under irradiation of 365nm ultraviolet (UV) was studied for the first time. The influence of initial conditions including pH value, NaNO(2) concentration, MC-LR concentration and UV intensity were studied. MC-LR was degraded in the presence of HNO(2); enhanced degradation of MC-LR was observed with 365nm UV irradiation, caused by the generation of hydroxyl radicals through the photolysis of HNO(2). The degradation processes of MC-LR could well fit the pseudo-first-order kinetics. Mass spectrometry was applied for identification of the byproducts and the analysis of degradation mechanisms. Major degradation pathways were proposed according to the results of LC-MS analysis. The degradation of MC-LR was initiated via three major pathways: attack of hydroxyl radicals on the conjugated carbon double bonds of Adda, attack of hydroxyl radicals on the benzene ring of Adda, and attack of nitrosonium ion on the benzene ring of Adda.

Evidence of the cost of the production of microcystins by Microcystis aeruginosa under differing light and nitrate environmental conditions

The cyanobacterium Microcystis aeruginosa is known to proliferate in freshwater ecosystems and to produce microcystins. It is now well established that much of the variability of bloom toxicity is due to differences in the relative proportions of microcystin-producing and non-microcystin-producing cells in cyanobacterial populations. In an attempt to elucidate changes in their relative proportions during cyanobacterial blooms, we compared the fitness of the microcystin-producing M. aeruginosa PCC 7806 strain (WT) to that of its non-microcystin-producing mutant (MT). We investigated the effects of two light intensities and of limiting and non-limiting nitrate concentrations on the growth of these strains in monoculture and co-culture experiments. We also monitored various physiological parameters, and microcystin production by the WT strain. In monoculture experiments, no significant difference was found between the growth rates or physiological characteristics of the two strains during the exponential growth phase. In contrast, the MT strain was found to dominate the WT strain in co-culture experiments under favorable growth conditions. Moreover, we also found an increase in the growth rate of the MT strain and in the cellular MC content of the WT strain. Our findings suggest that differences in the fitness of these two strains under optimum growth conditions were attributable to the cost to microcystin-producing cells of producing microcystins, and to the putative existence of cooperation processes involving direct interactions between these strains.

Spatial heterogeneity of cyanobacterial communities and genetic variation of microcystis populations within large, shallow eutrophic lakes (Lake Taihu and Lake Chaohu, China)

Cyanobacteria, specifically Microcystis, usually form massive blooms in eutrophic freshwater lakes. Cyanobacterial samples were collected from eight sites of both Lake Taihu and Lake Chaohu in late summer to determine the diversity and distribution pattern of cyanobacteria and Microcystis in large, shallow, entropic lakes with significant spatial heterogeneity and long-term Microcystis bloom. Molecular methods based on denaturing gradient gel electrophoresis and clone library analysis were used. A similar heterogeneous distribution pattern of cyanobacteria in both lakes was observed. Most parts of these two lakes with high trophic level were dominated by Microcystis. However, in the regions with low trophic levels as well as low concentrations of chlorophyll a, Synechococcus occupied a considerable percentage. Different morphospecies and genotypes dominated the bloom-forming Microcystis populations in these two lakes. Microcystis viridis and Microcystis novacekii were dominant in Lake Chaohu, whereas Microcystis flos-aquae was dominant in Lake Taihu. Only 2 of thel3 Microcystis operational taxonomic units were shared between these two lakes. Analysis of molecular variance based on 16S to 23S internal transcribed spacer sequences indicated the significAnt genetic differentiation of Microcystis between these two lakes (F(ST) = 0.19, p < 0.001). However, only 19.46% of the genetic variability was explained by the population variation between lakes, whereas most (80.54%) of the genetic variability occurred within the lakes. Phylogenetic analysis revealed no phylogeographic structure of Microcystis population in these two lakes, as illustrated by their cosmopolitan nature. Our results revealed that spatial heterogeneity within lakes has more impact on the cyanobacterial diversity than geographical isolation in a local scale.

Tailored microarray platform for the detection of marine toxins

Currently, there are no fast in vitro broad spectrum screening bioassays for the detection of marine toxins. The aim of this study was to develop such an assay. In gene expression profiling experiments 17 marker genes were provisionally selected that were differentially regulated in human intestinal Caco-2 cells upon exposure to the lipophilic shellfish poisons azaspiracid-1 (AZA1) or dinophysis toxin-1 (DTX1). These 17 genes together with two control genes were the basis for the design of a tailored microarray platform for the detection of these marine toxins and potentially others. Five out of the 17 selected marker genes on this dedicated DNA microarray gave clear signals, whereby the resulting fingerprints could be used to detect these toxins. CEACAM1, DDIT4, and TUBB3 were up-regulated by both AZA1 and DTX1, TRIB3 was up-regulated by AZA1 only, and OSR2 by DTX1 only. Analysis by singleplex qRT-PCR revealed the up- and down-regulation of the selected RGS16 and NPPB marker genes by DTX1, that were not envisioned by the new developed dedicated array. The qRT-PCR targeting the DDIT4, RSG16 and NPPB genes thus already resulted in a specific pattern for AZA1 and DTX1 indicating that for this specific case qRT-PCR might a be more suitable approach than a dedicated array.