Apoptotic effect of cyanobacterial extract on rat hepatocytes and human lymphocytes

Toxic cyanobacterial blooms are an increasing problem in Poland. The production of cyanobacterial toxins and their presence in drinking and recreational waters represent a growing danger to human and animal health. This is connected with the increase of cyanobacterial biomass caused by excessive eutrophication of the water ecosystem. There is evidence that cyanobacterial hepatotoxins can act as a potent promoter of primary liver cancer. The apoptotic effect of microcystins in Polish cyanobacterial bloom samples on rat hepatocytes and human lymphocytes was observed using light and fluorescence microscopy, flow cytometry, and electrophoretic analysis. The incubation time needed to observe the first morphological apoptotic changes in hepatocytes was approximately 30 min; however, the characteristic biochemical changes in DNA were not observed even after 120 min. In lymphocyte cultures the morphological changes characteristic for apoptosis were observed after 24 h of incubation and a 48‐h incubation was found to be optimal for analysis of internucleosomal DNA fragmentation, which is one of the main biochemical hallmarks of programmed cell death. These cells are an easily isolated and inexpensive material for medical diagnostics. Therefore the apoptotic changes, together with the clastogenic effect seen in lymphocyte cultures, are proposed as a future analytical method for these toxins. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 225–233, 2001     

Hepatotoxic cyanobacterial blooms in the lakes of northern Poland

The lakes of northern Poland are among the recreational sites most valued by Polish and German holiday makers. Given the socioeconomic importance of these lakes, water quality should be maintained at high levels for such intensive recreational purposes. In 2002 studies of species composition, biomass, and toxin production by phytoplankton and the attendant physicochemical variables were performed in order to assess the risk of cyanobacterial blooms in selected northern lakes: Lakes Jeziorak, Jagodne, Szymoneckie, Szymon, Taltowisko, Siecino, and Trzesiecko. The research showed that total phosphorus (0.1 mg P/L) and total nitrogen (1.5 mg N/L) in the studied lakes almost exceeded the permissible limits for eutrophication of water bodies. Most phytoplankton samples were taken in late summer, when cyanobacteria were expected to reach their highest biomass. At the time of sampling most of the lakes were dominated by oscillatorialean and nostocalean species. Average chlorophyll-a concentration was higher than 10 microg/L in almost all the lakes studied, which corresponded with an average microcystin concentration in the range of 4-5 microg/L. The main microcystins in the analyzed samples were dmMC-RR, MC-RR, MC-YR, and MC-LR. The results demonstrated a potential for intensive cyanobacterial blooms to appear during the summer in northern Polish lakes. The levels of cyanobacteria found in the lakes investigated indicated that toxicity had reached the first-alert level according to World Health Organization recommendations. If microcystin-producing cyanobacteria dominate, with a microcystin concentration of 2-4 microg/L, symptoms of toxicity can appear in the swimmers most sensitive to exposure. Analysis of cyanobacterial assemblages in northern Polish lakes also indicated a significant presence of Aphanizomenon species including a Scandinavian species, A. skujae (Skuja) Kom.-Legn. & Cronb. Future investigations of Polish lakes also should assess neurotoxins and study the biology of their producers. This study was the first attempt to evaluate the potential danger of toxic cyanobacterial blooms in the lakes of northern Poland.     

Effect of different cyanobacterial biomasses and their fractions with variable microcystin content on embryonal development of carp (Cyprinus carpio L.)

While numerous studies focused on the effects of microcystins, the role of other components of complex cyanobacterial water blooms in toxicity is poorly understood. In this study we have evaluated effects of various fractions of cyanobacterial biomass with different composition and microcystin content on embryolarval development of carp (Cyprinus carpio). The following samples (fractions) of four natural water blooms were prepared and tested: complex cyanobacterial biomass, crude aqueous extract of biomass, cellular pellet remaining from aqueous extract, permeate (i.e. microcystin-free fraction prepared during C-18 solid-phase extraction; SPE), and eluate (i.e. fraction prepared by SPE containing mostly microcystins). Complex biomass and the crude aqueous extract (regardless of microcystin content and/or microcystin variants present) in the sample were the most toxic. On the other hand, eluate fractions of all samples containing microcystins in concentrations 8-255 microgL(-1) induced no or only weak toxic effects. Exposures of fish to permeate fractions (with removed microcystins) of two samples dominated by Aphanizomenon sp. and Planktothrix sp. resulted in significant mortality, while other two samples dominated by Microcystis spp. induced minor effects. We have also observed significant inhibition of glutathione S-transferases (GST) at most fractions of the Aphanizomenon sp. and Planktothrix sp. dominated samples. Our data indicate that cyanobacterial water blooms as well complex biomass extracts induce significant embryolarval toxicity in common carp. However, these effects were independent of microcystin content, and the most pronounced effects were observed with the non-Microcystis dominated samples. Therefore, a critical examination of microcystin role in overall ecotoxicology of complex cyanobacterial blooms is needed.     

Is Toxin-Producing Planktothrix sp. an Emerging Species in Lake Constance?

Recurring blooms of filamentous, red-pigmented and toxin-producing cyanobacteria Planktothrix rubescens have been reported in numerous deep and stratified prealpine lakes, with the exception of Lake Constance. In a 2019 and 2020 Lake Constance field campaign, we collected samples from a distinct red-pigmented biomass maximum below the chlorophyll-a maximum, which was determined using fluorescence probe measurements at depths between 18 and 20 m. Here, we report the characterization of these deep water red pigment maxima (DRM) as cyanobacterial blooms. Using 16S rRNA gene-amplicon sequencing, we found evidence that the blooms were, indeed, contributed by Planktothrix spp., although phycoerythrin-rich Synechococcus taxa constituted most of the biomass (>96% relative read abundance) of the cyanobacterial DRM community. Through UPLC–MS/MS, we also detected toxic microcystins (MCs) in the DRM in the individual sampling days at concentrations of ≤1.5 ng/L. Subsequently, we reevaluated the fluorescence probe measurements collected over the past decade and found that, in the summer, DRM have been present in Lake Constance, at least since 2009. Our study highlights the need for a continuous monitoring program also targeting the cyanobacterial DRM in Lake Constance, and for future studies on the competition of the different cyanobacterial taxa. Future studies will address the potential community composition changes in response to the climate change driven physiochemical and biological parameters of the lake.     

The Importance of Lake Sediments as a Pathway for Microcystin Dynamics in Shallow Eutrophic Lakes

Microcystins are toxins produced by cyanobacteria. They occur in aquatic systems across the world and their occurrence is expected to increase in frequency and magnitude. As microcystins are hazardous to humans and animals, it is essential to understand their fate in aquatic systems in order to control health risks. While the occurrence of microcystins in sediments has been widely reported, the factors influencing their occurrence, variability, and spatial distribution are not yet well understood. Especially in shallow lakes, which often develop large cyanobacterial blooms, the spatial variability of toxins in the sediments is a complex interplay between the spatial distribution of toxin producing cyanobacteria, local biological, physical and chemical processes, and the re-distribution of toxins in sediments through wind mixing. In this study, microcystin occurrence in lake sediment, and their relationship with biological and physicochemical variables were investigated in a shallow, eutrophic lake over five months. We found no significant difference in cyanobacterial biomass, temperature, pH, and salinity between the surface water and the water directly overlying the sediment (hereafter ‘overlying water’), indicating that the water column was well mixed. Microcystins were detected in all sediment samples, with concentrations ranging from 0.06 to 0.78 µg equivalent microcystin-LR/g sediments (dry mass). Microcystin concentration and cyanobacterial biomass in the sediment was different between sites in three out of five months, indicating that the spatial distribution was a complex interaction between local and mixing processes. A combination of total microcystins in the water, depth integrated cyanobacterial biomass in the water, cyanobacterial biomass in the sediment, and pH explained only 21.1% of the spatial variability of microcystins in the sediments. A more in-depth analysis that included variables representative of processes on smaller vertical or local scales, such as cyanobacterial biomass in the different layers and the two fractions of microcystins, increased the explained variability to 51.7%. This highlights that even in a well-mixed lake, local processes are important drivers of toxin variability. The present study emphasises the role of the interaction between water and sediments in the distribution of microcystins in aquatic systems as an important pathway which deserves further consideration.     

Identification of microcystins in waters used for daily life by people who live on Tai Lake during a serious cyanobacteria dominated bloom with risk analysis to human health

Tai Lake is the third largest freshwater lake in China with annual cyanobacteria blooms. Microcystins produced by these blooms have serious health risks for populations surrounding the lake, especially for people living on Tai Lake, because they usually drink raw lake water after a simple alum treatment. This study presents data on the detection and identification of microcystins in waters used for daily life by people living on Tai Lake, during the cyanobacterial blooming in July 2007. The health risks from drinking these microcystin-polluted waters were also calculated. The main microcystins detected by high-performance liquid chromatography-electrospray ionization mass spectrometry in the water samples collected from two parts of Tai Lake (Wuli Lake and Meiliang Bay) were MC-LR (4.33-12.27 microg/L), MC-RR (8.36-16.91 microg/L) and MC-YR (1.41-5.57 microg/L). Risk assessment showed that the drinking water simply treated by alum was not safe. The lowest calculated hazards ratios in all water samples was 6.4, which indicated that the risk of microcystins exposure from drinking water was over six times higher than the tolerable daily intake (TDI) recommended by The World Health Organization (WHO). Further studies should be conducted to elucidate the relationships between the epidemiology of people living on Tai Lake and microcystins exposure from drinking water.     

Assessing drinking water treatment systems for safety against cyanotoxin breakthrough using maximum tolerable values

For assessing the safety of drinking water supplies suffering cyanobacterial blooms in their water source, a methodology is proposed which relates the performance of their current treatment train to the quality of the raw water. The approach considers that different treatment trains can remove algal toxins with different efficiency. Maximum Tolerable (MT-) values of the raw water expressed by cell counts or by biovolumes of cyanobacteria were calculated. Three MT-categories were identified by colours; high risk (red), moderate risk (yellow) and no risk (green). Two treatment facilities using a conventional (1) and polishing train (2) were assessed using this methodology. For most of the time during an algal bloom the water quality could be classified as yellow which means short term higher toxin levels in comparison to the guide line in clear water were found. However, the red classification, indicating a high risk for drinking water quality was never reached. The model proposed can be understood as supplement of the common alert level framework, ALF-concept (Chorus and Bartram, Situation Assessment, Planning and Management. London and New York: E & FN Spon. 1999; House et al., Management Strategies for Toxic Blue Green Algae: Literature Review. Australia: CRC for Water Quality and Treatment. 2004).     

Levels of microcystins in two Argentinean reservoirs used for water supply and recreation: differences in the implementation of safe levels

Toxic cyanobacterial blooms are an increasing problem in Argentina. The production of cyanobacterial hepatotoxins (microcystins) and their presence in drinking and recreational waters represent a growing danger to human and animal health. Risk management deals with the probability that a certain exposure to toxins will lead to specific health outcomes. Various model schemes for risk management have been portrayed, most of which have some common elements. These include the need for an information base on which to make decisions. Thus, seasonal variability in the concentrations of total microcystins and cyanobacterial cells was studied in two reservoirs: San Roque and Paso de las Piedras. Both reservoirs are eutrophic water bodies and mainly used to supply drinking water and for recreation. Because San Roque is an important recreational spot, the spatial distribution of microcystins was also investigated. Sampling of the San Roque Reservoir occurred from 1998 to 2000 and of the Paso de las Piedras Reservoir from June to December 2002 (late autumn, winter, and spring). Microcystins were identified by LC-MS, and their concentrations were measured using the enzyme-linked immunosorbent assay. These hepatotoxic compounds were detected in all seasons, and even during winter relatively high concentrations were observed. Concentrations in the San Roque Reservoir varied from undetectable to 920 microg/L. On the contrary, in the Paso de las Piedras Reservoir the concentration remained below 1 microg/L, which is the provisional guideline value proposed by the World Health Organization (WHO; Chorus and Bartram, 1999) for microcystin-LR in drinking water. Comparison of cell number and concentration of total microcystins indicated that the phytoplankton in San Roque Reservoir contained more toxic cyanobacterial strains than did the Paso de las Piedras Reservoir. This indicates that the threshold of 2000 cell/mL proposed by WHO as a alert level should be adjusted: it should be reduced for the San Roque Reservoir, whereas it seems appropriate for the Paso de la Piedras Reservoir.     

Toxic cyanobacterial blooms in reservoirs under a semiarid mediterranean climate: the magnification of a problem

Sicilian reservoirs constitute the most important water resources available on the island. During summer 2001, the intense water utilization of Lake Arancio reservoir reduced the water level significantly, which coincided with the formation of intense blooms formed by the microcystin (MC)-producing cyanobacterium Microcystis aeruginosa. During summer 2003, Lake Arancio was continuously filled and the vertical stratification of the water column was maintained resulting in five to sixfold lower cell numbers of M. aeruginosa. For both years, a significant relationship between MC net production and Microcysytis cell growth was observed, implying that Microcystis cell numbers can be used to infer MC concentrations in water. Unexpectedly, dense blooms of the MC-producing cyanobacterium Planktothrix rubescens occurred during winter 2005/2006 in the reservoirs Lake Pozzillo, Prizzi, Nicoletti, and Garcia but have not been reported earlier. In this season, MC concentrations higher than those recorded in summer were measured, implying that monitoring of Mediterranean drinking water reservoirs needs to be intensified during winter, a season usually considered to be less prone to the formation of cyanobacterial blooms.     

Increase of crustacean sensitivity to purified hepatotoxic cyanobacterial extracts by manipulation of experimental conditions

Toxic cyanobacterial blooms are one of the most common consequences of water eutrophication. Microbiotests with crustaceans are not expensive and are easy to prepare for screening tests. They can be applied in the determination of bioactivity and interaction between toxic substances in water, including hepatotoxins. The principal aim of this study was to modify the standard conditions in the Thamnotoxkit F trade mark and Artoxkit M in order to increase crustacean sensitivity to purified cyanobacterial extracts containing microcystins. The results reported show that exposure time, higher temperature, and presence of DMSO can increase the sensitivity of microbiotests to microcystins. The best sensitivity with the Artemia salina test was achieved after a 48-h exposure at 25 degrees C. The tests using a 24-h exposure at 27 degrees C were the most sensitive for Thamnocephalus platyurus. The test without preincubation with DMSO provided the best correlation of microcystin concentration and LC(50) for Thamnocephalus platyurus and is recommended.     

Elucidating the factors influencing the biodegradation of cylindrospermopsin in drinking water sources

The cyanotoxin cylindrospermopsin (CYN) is produced by several species of cyanobacteria and can be persistent in drinking waters supplies, which is of major concern to water authorities because of its potential to severely compromise human health. Consequently, there is a need to fully understand the persistence of CYN in water supplies, in particular, to determine whether this toxin is readily degraded by endemic aquatic organisms. This study provides insights into the environmental factors that can influence the biodegradation of this toxin in Australian drinking water supplies. Biodegradation of CYN was only evident in water supplies that had a history of toxic Cylindrospermopsis raciborskii blooms. In addition, lag periods were evident prior to the onset of biodegradation; however, repeated exposure of the endemic organisms to CYN resulted in substantial decreases in the lag periods. Furthermore, the concentration of CYN was shown to influence biodegradation with a near linear relationship (R(2) of 0.9549) existing between the biodegradation rate and the initial CYN concentration. Temperature was also shown to affect the biodegradation of CYN, which is important since CYN is now being detected in more temperate climates. The presence of copper-based algicides inhibited CYN degradation, which has significant implications since copper-based algicides are commonly used to control cyanobacterial growth in water bodies. The results from this study indicate that the biodegradation of CYN in natural water bodies is a complex process that can be influenced by many environmental factors, some of which include CYN concentration, temperature, and the presence of copper-based algicides.     

Evaluation of Cyanobacterial Bloom from Lake Taihu as a Protein Substitute in Fish Diet—A Case Study on Tilapia

The utility of cyanobacterial bloom is often hindered by concerns about the toxin content. Over three years of investigation, we found that the toxin content of cyanobacterial bloom in Lake Taihu was always low in June and higher in late summer and autumn. The findings enabled us to compare the effects of diets containing low and high toxic cyanobacterial blooms on the growth and consumption safety of tilapia. There were no negative effects on the growth of tilapia, and the muscle seemed to be safe for human consumption in the treatment of 18.5% low toxic cyanobacterial bloom. Therefore, limitations of the utilization of cyanobacterial biomass can be overcome by selecting low toxic cyanobacterial bloom that can be found and collected in large lakes.     

Evaluating genotoxicity associated with microcystin-LR and its risk to source water safety in Meiliang Bay, Taihu Lake

In recent years cyanobacteria blooms have become a severe problem in Taihu Lake, a large shallow eutrophic lake in China. Microcystins produced by certain genera of cyanobacteria can affect public health in this area because of their acute and chronic toxic effects. In this study, samples of cyanobacteria were collected and extracted by two solvent systems. The extracts were tested with three short-term genotoxicity assays, the ara test, the Ames test, and the SOS/umu test. In addition, temporal variation in the concentrations of microcystin-LR in the water samples was determined and monitored by an ELISA assay. Then the concentration of microcystin-LR in the drinking water was estimated. The risk of microcystin-LR exposure by drinking water was assessed according to tolerable daily intake (TDI). The three genotoxicity assays showed negative results regardless of the solvent system used, and there were clear inconsistencies in the spatiotemporal profiles of genotoxic potential and microcystin concentrations in Taihu Lake. Risk assessment showed that the drinking water from Taihu Lake was not safe from the end of July to the beginning of November because of a high concentration of microcystin-LR. Our study indicated the drinking water from Taihu Lake posed a risk because of the microcystin-LR, although it was neither genotoxic nor associated with genotoxicity of the lake water.     

The Effects of Ferric Sulfate (Fe2(SO4)3) on the Removal of Cyanobacteria and Cyanotoxins: A Mesocosm Experiment

Cyanobacterial blooms are a global concern. Chemical coagulants are used in water treatment to remove contaminants from the water column and could potentially be used in lakes and reservoirs. The aims of this study was to: 1) assess the efficiency of ferric sulfate (Fe₂(SO₄)₃) coagulant in removing harmful cyanobacterial cells from lake water with cyanobacterial blooms on a short time scale, 2) determine whether some species of cyanobacteria can be selectively removed, and 3) determine the differential impact of coagulants on intra- and extra-cellular toxins. Our main results are: (i) more than 96% and 51% of total cyanobacterial cells were removed in mesocosms with applied doses of 35 mgFe/L and 20 mgFe/L, respectively. Significant differences in removing total cyanobacterial cells and several dominant cyanobacteria species were observed between the two applied doses; (ii) twelve microcystins, anatotoxin-a (ANA-a), cylindrospermopsin (CYN), anabaenopeptin A (APA) and anabaenopeptin B (APB) were identified. Ferric sulfate effectively removed the total intracellular microcystins (greater than 97% for both applied doses). Significant removal of extracellular toxins was not observed after coagulation with both doses. Indeed, the occasional increase in extracellular toxin concentration may be related to cells lysis during the coagulation process. No significant differential impact of dosages on intra- and extra-cellular toxin removal was observed which could be relevant to source water applications where optimal dosing is difficult to achieve.     

More and more toxins around–analysis of cyanobacterial strains isolated from Lake Chao (Anhui Province, China)

Lake Chao, China, is highly eutrophicated and experiences recurrent dense cyanobacterial blooms. Its surface water is used as drinking water resource for Hefei city, hence the potential toxicity of those cyanobacteria was of interest. Sixteen isolated strains of Microcystis aeruginosa evidenced that non-toxic, toxic and highly toxic strains coexist in the lake. Microcystin variants within one strain ranged up to 11, the concentration up to 4.799 mg g DW⁻¹. Mass spectrometry analysis confirmed desmethylated microcystin variants.     

Microcystins in potable surface waters: toxic effects and removal strategies

In freshwater, harmful cyanobacterial blooms threaten to increase with global climate change and eutrophication of surface waters. In addition to the burden and necessity of removal of algal material during water treatment processes, bloom‐forming cyanobacteria can produce a class of remarkably stable toxins, microcystins, difficult to remove from drinking water sources. A number of animal intoxications over the past 20 years have served as sentinels for widespread risk presented by microcystins. Cyanobacterial blooms have the potential to threaten severely both public health and the regional economy of affected communities, particularly those with limited infrastructure or resources. Our main objectives were to assess whether existing water treatment infrastructure provides sufficient protection against microcystin exposure, identify available options feasible to implement in resource‐limited communities in bloom scenarios and to identify strategies for improved solutions. Finally, interventions at the watershed level aimed at bloom prevention and risk reduction for entry into potable water sources were outlined. We evaluated primary studies, reviews and reports for treatment options for microcystins in surface waters, potable water sources and treatment plants. Because of the difficulty of removal of microcystins, prevention is ideal; once in the public water supply, the coarse removal of cyanobacterial cells combined with secondary carbon filtration of dissolved toxins currently provides the greatest potential for protection of public health. Options for point of use filtration must be optimized to provide affordable and adequate protection for affected communities. Copyright © 2013 John Wiley & Sons, Ltd.     

The influence of microcystin-LR and hepatotoxic cyanobacterial extract on the water plant Spirodela oligorrhiza

The eutrophication of the Sulejów Reservoir dam in Poland is related to toxicity from cyanobacterial blooms. The main species responsible for hepatotoxic bloom formation is Microcystis aeruginosa. The aim of this study was to evaluate the influence of toxic cyanobacterial extract on the growth and morphology of the water plant Spirodela oligorrhiza, compared with commercial-grade microcystin-LR (MC-LR). It was found that after 96 h of incubation the highest concentration of cyanobacterial extract, containing 0.344 mg MC-LR/L, reduced the number of fronds by about 50% in comparison with the control. The extract effected a reduction in the frond mass and a decrease in chlorophyll (a + b) concentration. A reduction in the number of fronds was also observed after the first 24 h of incubation in the presence of 0.2 and 0.1 microg/L of commercial-grade MC-LR. Changes in activity of constitutive acid phosphatase and RNase after 7 days of incubation with commercial-grade MC-LR were observed. The results confirm the toxicity of cyanobacterial hepatotoxins to Spirodela oligorrhiza, which can be used as a sensitive bioindicator.     

Effects of cyanobacterial biomass and purified microcystins on malformations in Xenopus laevis: teratogenesis assay (FETAX)

Xenopus laevis (African clawed frog) embryos in a 96-h teratogenesis assay (FETAX) were exposed to 0-250 microg/L and 500 microg/L of purified microcystin-LR (MCYST-LR) for the estimation of lethality, as well as to equivalent concentrations of biomass containing MCYST-LR (natural water bloom dominated by Microcystis aeruginosa) and biomass without MCYST-LR (bloom dominated by Microcystis wesenbergii). The highest tested concentrations of purified MCYST-LR caused up to 30% lethality after a 96-h exposure, corresponding to a LC(25) of 380 microg/L. Cyanobacterial biomass containing MCYST-LR caused significant lethality up to 50% at the highest tested concentrations (300 mg/L, i.e., 250 microg/L of MCYST-LR). The estimated 96-h LC(25) values varied from 125 mg/L (biomass containing MCYST-LR) up to 232 mg/L (biomass without MCYST-LR). A statistically significant increase in the number of malformed embryos was observed after exposure to cyanobacterial samples. Purified MCYST-LR at and above 25 microg/L significantly increased the number of malformations, with 53% of surviving embryos malformed in the highest tested concentration, 250 microg/L (EC(25) = 27 microg/L). Exposure to the highest concentration of MCYST-LR containing biomass resulted in more than 60% of the embryos being malformed and an EC(25) of 52 mg/L (i.e., 43 microg of MCYST-LR/L). Cyanobacterial biomass with no natural microcystin also induced substantial malformations-about 50% aberrant embryos at the highest concentration, 300 mg/L (EC(25) = 75 mg/L). External additions of purified MCYST-LR to the biomass that was originally without microcystins resulted in a slight additional increase in the rate of malformations (80% at the highest concentration, 300 mg of biomass plus 250 microg of MCYST-LR per liter). A comparison of lethality and effects on malformations (teratogenic index, TI = LC(25)/EC(25)) showed that all samples had significant teratogenic potential in the FETAX assay (TI(MCYST-LR) = 14; TI for biomass with and without microcystin ranged between 2.4 and 3.1, respectively). We conclude that cyanobacterial water blooms can significantly alter the normal development of amphibian embryos.     

The adsorption of microcystin-LR by natural clay particles.

The microcystin cyanobacterial hepatotoxins represent an increasingly severe global health hazard. Since microcystins are found world wide in drinking water reservoirs concern about the impact on human health has prompted investigations into remedial water treatment methods. This preliminary study investigates the scavenging from water of microcystin-LR by fine-grained particles known to have a high concentration of the clay minerals kaolinite and montmorillonite. The results show that more than 81% of microcystin-LR can be removed from water by clay material. Thus, microcystin-LR is indeed scavenged from water bodies by fine-grained particles and that this property may offer an effective method of stripping these toxins from drinking water supplies.     

Oral toxicity of a bloom of the Cyanobacterium microcystis Aeruginosa administered to mice over periods up to 1 year

Cyanobacterial blooms in lakes have been reported causing livestock deaths and liver injury to human populations. In this study bloom material consisting of Microcystis aeruginosa was collected from a farm water storage after the death of sheep drinking from it. The cyanobacterial cells were lysed and a cell-free extract was provided to mice at a series of dilutions as their only source of drinking water. Mice of both sexes, with controls, were killed at intervals up to 1 yr of administration. Autopsies, histopathological examination, and analyses of plasma lactate dehydrogenase and alanine aminotransferase were carried out. Increased mortality was observed, particularly among males, together with chronic active liver injury and elevated alanine aminotransferase in blood. In control mice and those receiving lower concentrations of extract, hepatic amyloidosis with neutrophil infiltration, and bronchopneumonia, were seen with increasing age. The bronchopneumonia appeared earlier among mice receiving cyanobacterial extract. Four tumors were seen in 71 mice receiving a high concentration of extract for up to 1 yr, none in 150 mice receiving lower concentrations, and 2 in 73 control mice. No effects on male or female fertility, embryonic mortality, neonatal viability, or skeletal development were observed, but 7 out of 73 neonatal mice born to parents given cyanobacterial extract showed reduced brain size. No cases were seen in controls. We conclude that the major toxicity exhibited is liver injury. Further attention is needed for evaluation of carcinogenicity and embryonic damage.