Effects of Wind Mixing in a Stratified Water Column on Toxic Cyanobacteria and Microcystin-LR Distribution in a Subtropical Reservoir

We analyzed the effects of stratification changes due to wind on the vertical cyanobacteria distribution and microcystin-LR concentrations in a reservoir and assessed the implications for water management. Under stratified conditions, the highest microcystin concentrations (up to 4.16 µg/L) and toxic cyanobacteria biovolume occurred in the epilimnion (~?1 m). The lowest microcystin concentrations were between 0.02 and 1.28 µg/L and occurred in the hypolimnion (~?20 m). A cold front passage associated with high wind velocities induced water column mixing, promoting the redistribution of microcystin-LR and cyanobacteria throughout the water column and increasing their concentrations in deeper zones. Microcystin-LR concentration was positively correlated with cyanobacteria biovolume (r?=?0.747) and chlorophyll a concentration (r?=?0.798). Changes in thermal profile due to wind would imply a greater challenge for drinking water treatment plants, since high cyanobacterial and microcystin concentrations could reach deep-water intakes.     

Toxic cyanobacteria and their toxins in standing waters of Kenya: implications for water resource use

Phytoplankton biodiversity studies in Kenya's standing waters were carried out between 2001 and 2003. Toxin producing cyanobacteria were recorded in twelve water bodies. Microcystis and Anabaena were the most common species in freshwaters while Anabaena and Anabaenopsis were common in alkaline saline lakes. Seven lakes with cyanobacteria blooms and a hot spring had detectable levels of microcystins and anatoxin-a. Cell bound microcystins (LR equivalents) concentration ranged from 1.6-19800 microgg(-1) Dry Weight (DW) while anatoxin-a varied from below the limit of detection to 1260 microgg(-1) DW. In alkaline-saline lakes, microcystins and anatoxin-a were also present in stomach contents and liver samples of dead flamingos. Monoculture strains of A. fusiformis from Lakes Sonachi and Bogoria had detectable levels of microcystins while anatoxin-a was present in strains isolated from Lakes Sonachi, Bogoria and Nakuru. Two freshwater sites, Nyanza Gulf (L. Victoria) and Lake Baringo recorded cyanotoxin concentration exceeding WHO'S upper limit of 1.0 microgl(-1) for drinking water. The results confirm that cyanotoxins could have played a role in the mortality of flamingos in Lakes Bogoria and Nakuru. The implications of these findings on water resource use, measures to be taken to reduce the risk of exposure and eutrophication control steps to reduce cyanobacteria bloom formation are considered in this paper.     

上海市供水系统微囊藻毒素LR含量调查

目的　调查上海市供水系统中微囊藻毒素LR(MC- LR)的污染状况及常规水处理工艺对MC- LR的去除效果。方法　运用高效液相色谱法 (HPLC)检测有代表性的水源、水厂及出厂水样中MC LR的含量。结果　源水中MC- LR浓度随采样点及采样季节变化 ,在夏末秋初易形成污染高峰 ,最高达 2 . 38μg L。混凝沉淀、加氯消毒对去除毒素有一定的效果 ,而过滤则效果不明显 ,在出厂水中也能检测到MC- LR ,最高达1. 2 7μg L。结论　夏秋季节上海市供水系统源水受到以MC- LR为代表的蓝藻毒素的污染 ,郊区源水污染较重 ,常规水处理工艺不能有效地去除水中的微囊藻毒素。     

First Report of a Microcystin-Containing Bloom of the Cyanobacteria <Emphasis Type="Italic">Microcystis</Emphasis> spp. in Lake Oubeira,Eastern Algeria

Lake Oubeira has been used as the main source of drinking water for many communities in the East of Algeria. In this lake, nutrient loading coupled with year-round warm weather favors the growth of cyanobacteria, several of which can produce cyanotoxins, especially the potent liver toxins called microcystins (MCYSTs). The present study evaluated microcystin levels and characterized the different microcystin variants present in the raw water during a 17-month period (April 2000–September 2001), as measured by protein phosphatase inhibition assays and by matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) mass spectrometry, respectively. The results showed that microcystin concentrations in the lake water varied between 3 and 29,163 g microcystin-LR equivalent per liter. The microscopic examination of the phytoplankton samples showed the dominance of the Microcystis genus in the cyanobacterial bloom. The highest MCYST concentration was observed in August 2001, at 29,163 g/l. Therefore, the highest total MCYST content per phytoplankton biomass was found in August 2001, with 4,590 g MCYST-LR equivalents/g dried bloom material. Analysis of the field bloom extract by MALDI-TOF mass spectrometry demonstrated the presence of four variants of microcystins: microcystin-LR (MCYST-LR), microcystin-YR (MCYST-YR), microcystin-RR (MCYST-RR), and a demethylated variant of MCYST-LR (D-MCYST-LR).     

Diversity and distribution of cyanobacterial toxins in the Italian subalpine lacustrine district

Nine lakes (Garda, Maggiore, Como, Iseo, Lugano, Idro, Pusiano, Ledro, and Levico) located in the Italian subalpine lacustrine district were chosen for a comparative study of the diversity and distribution of cyanobacterial toxins. All nine lakes are known to host different toxic cyanobacteria, mainly Planktothrix rubescens. An analytical protocol has been used, based on LC-MS technique, for determining 20 different toxins (14 microcystins, 2 nodularins, anatoxin-a and 3 cylindrospermopsins). In the investigation, microcystins were found in all lakes on all sampling dates. Anatoxin-a could be detected in 6 lakes, but it was only present in 4 lakes on all sampling dates (lakes Garda, Iseo, Como, and Maggiore). Nodularins and cylindrospermopsins were not detected at all. The number of microcystins detected in the survey was 9, but 4 were the most abundant (dmRR, YR, dmLR, and LR); they were differently distributed among the lakes, thus providing each lake a unique toxic potential. Statistical analysis showed positive correlations between total microcystin concentrations and eutrophication indicators and also between anatoxin-a concentrations and water temperature, suggesting that anthropic and climate-related stressors can have different impacts on the presence of different cyanotoxins.     

Effect of ozonation on the removal of cyanobacterial toxins during drinking water treatment

Water treatment plants faced with toxic cyanobacteria have to be able to remove cyanotoxins from raw water. In this study we investigated the efficacy of ozonation coupled with various filtration steps under different cyanobacterial bloom conditions. Cyanobacteria were ozonated in a laboratory-scale batch reactor modeled on a system used by a modern waterworks, with subsequent activated carbon and sand filtration steps. The presence of cyanobacterial toxins (microcystins) was determined using the protein phosphatase inhibition assay. We found that ozone concentrations of at least 1.5 mg/L were required to provide enough oxidation potential to destroy the toxin present in 5 X 10(5 )Microcystis aeruginosa cells/mL [total organic carbon (TOC), 1.56 mg/L]. High raw water TOC was shown to reduce the efficiency of free toxin oxidation and destruction. In addition, ozonation of raw waters containing high cyanobacteria cell densities will result in cell lysis and liberation of intracellular toxins. Thus, we emphasize that only regular and simultaneous monitoring of TOC/dissolved organic carbon and cyanobacterial cell densities, in conjunction with online residual O(3) concentration determination and efficient filtration steps, can ensure the provision of safe drinking water from surface waters contaminated with toxic cyanobacterial blooms.     

Assessing potential health risks from microcystin toxins in blue-green algae dietary supplements

The presence of blue-green algae (BGA) toxins in surface waters used for drinking water sources and recreation is receiving increasing attention around the world as a public health concern. However, potential risks from exposure to these toxins in contaminated health food products that contain BGA have been largely ignored. BGA products are commonly consumed in the United States, Canada, and Europe for their putative beneficial effects, including increased energy and elevated mood. Many of these products contain Aphanizomenon flos-aquae, a BGA that is harvested from Upper Klamath Lake (UKL) in southern Oregon, where the growth of a toxic BGA, Microcystis aeruginosa, is a regular occurrence. M. aeruginosa produces compounds called microcystins, which are potent hepatotoxins and probable tumor promoters. Because M. aeruginosa coexists with A. flos-aquae, it can be collected inadvertently during the harvesting process, resulting in microcystin contamination of BGA products. In fall 1996, the Oregon Health Division learned that UKL was experiencing an extensive M. aeruginosa bloom, and an advisory was issued recommending against water contact. The advisory prompted calls from consumers of BGA products, who expressed concern about possible contamination of these products with microcystins. In response, the Oregon Health Division and the Oregon Department of Agriculture established a regulatory limit of 1 microg/g for microcystins in BGA-containing products and tested BGA products for the presence of microcystins. Microcystins were detected in 85 of 87 samples tested, with 63 samples (72%) containing concentrations > 1 microg/g. HPLC and ELISA tentatively identified microcystin-LR, the most toxic microcystin variant, as the predominant congener.     

微囊藻毒素无害化处理的研究进展

富营养化湖泊中的微囊藻毒素对环境和人类健康的危害已成为全球关注的重大环境问题之一。而常用的水处理工艺难以将其彻底去除,开发用于处理微囊藻毒素的新技术越来越迫切。本文就微囊藻毒素无害化处理的研究进展作综述。     

The adsorption of cyanobacterial hepatoxins as a function of soil properties

Cyanobacterial hepatotoxins present a risk to public health when present in drinking water supplies. Existing removal strategies, although efficient, are not economically viable or practical for remote Australian communities and developing nations. Bank filtration is a natural process and a potential low cost, toxin removal strategy. Batch studies were conducted in 12 texturally diverse soils to examine the soil properties influencing the adsorption of the cyanobacterial hepatotoxins, microcystin-LR and nodularin. Sorption isotherms were measured. Freundlich and linear isotherms were observed for both toxins with adsorption coefficients not exceeding 2.751 kg(-1) for nodularin and 3.81 kg(-1) for microcystin. Significant positive correlations were identified between hepatotoxin sorption and clay and silt contents of the soils. Desorption of toxins was also measured in three different soils. Pure nodularin and microcystin-LR readily desorbed from all soils.     

Human fatalities from cyanobacteria: chemical and biological evidence for cyanotoxins

An outbreak of acute liver failure occurred at a dialysis center in Caruaru, Brazil (8 degrees 17' S, 35 degrees 58' W), 134 km from Recife, the state capital of Pernambuco. At the clinic, 116 (89%) of 131 patients experienced visual disturbances, nausea, and vomiting after routine hemodialysis treatment on 13-20 February 1996. Subsequently, 100 patients developed acute liver failure, and of these 76 died. As of December 1996, 52 of the deaths could be attributed to a common syndrome now called Caruaru syndrome. Examination of phytoplankton from the dialysis clinic's water source, analyses of the clinic's water treatment system, plus serum and liver tissue of clinic patients led to the identification of two groups of cyanobacterial toxins, the hepatotoxic cyclic peptide microcystins and the hepatotoxic alkaloid cylindrospermopsin. Comparison of victims' symptoms and pathology using animal studies of these two cyanotoxins leads us to conclude that the major contributing factor to death of the dialyses patients was intravenous exposure to microcystins, specifically microcystin-YR, -LR, and -AR. From liver concentrations and exposure volumes, it was estimated that 19.5 microg/L microcystin was in the water used for dialysis treatments. This is 19.5 times the level set as a guideline for safe drinking water supplies by the World Health Organization.     

Analysis of microcystins in freshwater samples using high performance liquid chromatography and an enzyme-linked immunosorbent assay

Blooms of non-toxin producing and toxin producing cyanobacteria are often observed in lakes, reservoirs and slowly flowing eutrophic freshwater. Microcystin congeners are the most important group of cyanobacterial toxins and determination of the microcystin concentration is necessary in order to assess the health risk when such waters are used for recreational purposes. The most widely used standard method for analysis of microcystins is high-performance liquid chromatography (HPLC). But this technique is time-consuming and needs a special expensive equipement. Therefore a commercially available microcystin enzyme-linked immunosorbent assay (ELISA) could be an alternative. However, when performed as recommended by the manufacturer, the ELISA is not suitable for a valid quantitative analysis. We have therefore modified the microcystin extraction method and the ELISA protocol and have been able to use the ELISA for a quantitative analysis comparable to that of the widely recommended HPLC method. The modified ELISA provides a relatively simple and highly sensitive approach for the quantitative analysis of microcystins in freshwater. Results can be obtained within two to three days after sampling.     

远洋船舶水舱藻类污染调查

探讨远洋船舶水舱里藻与藻类毒素污染的现状,用显微镜作藻类计数分类,用间接ELISA法测藻类毒素.30艘远洋船舶水舱里检出饮水舱微囊藻毒素阳性19份,阳性率63.33%,浓度范围20.4～348.7ng/L;压载舱微囊藻毒素阳性26份,阳性率86.67%,浓度范围32.0～139.8ng/L.饮用水和压舱水都未发现藻类生长.追踪污染来源,来发现毒素污染与饮水或压舱水装载地有关联.结果提示远洋船舶水舱存在藻类毒素污染,可能是长期积累过程,水舱须定期清洗与监测,以免污染环境及影响船员身体健康.     

Vulnerability of Quebec drinking-water treatment plants to cyanotoxins in a climate change context

Cyanobacteria are a growing concern in the province of Quebec due to recent highly publicised bloom episodes. The health risk associated with the consumption of drinking water coming from contaminated sources was unknown. A study was undertaken to evaluate treatment plants' capacity to treat cyanotoxins below the maximum recommended concentrations of 1.5 μg/L microcystin-LR (MC-LR) and the provisional concentration of 3.7 μg/L anatoxin-a, respectively. The results showed that close to 80% of the water treatment plants are presently able to treat the maximum historical concentration measured in Quebec (5.35 μg/L MC-LR equ.). An increase, due to climate change or other factors, would not represent a serious threat because chlorine, the most popular disinfectant, is effective in treating MC-LR under standard disinfection conditions. The highest concentration of anatoxin-a (2.3 μg/L) measured in natural water thus far in source water is below the current guideline for treated waters. However, higher concentrations of anatoxin-a would represent a significant challenge for the water industry as chlorine is not an efficient treatment option. The use of ozone, potassium permanganate or powder activated carbon would have to be considered.     

微囊藻毒素毒理学的研究进展

水体富营养化现象日益严重及藻类水华的频繁暴发已成为全球广泛关注的环境问题.而微囊藻毒素(Microcystin,MCs)是在蓝藻水华污染中出现频率最高、造成危害最严重的一种环七肽肝毒素.目前,蓝藻水华的研究主要集中在MCs对水产动物及哺乳动物造成的伤害.大量研究表明,作为肝毒素的MCs具有稳定性,不但能够在生物链中积累...     

Relationship Between Cyanobacterial Biomass and Total Microcystin-LR Levels in Drinking and Recreational Water

Cyanobacterial biomass, chlorophyll-a, and microcystin-LR levels were monitored in drinking and recreational water in Seoul, South Korea and three satellite cities from Oct 2006 to Aug 2007. Total microcystin-LR was the sum of particulate and dissolved microcystin. Except during cold periods, toxic cyanobacteria, including Anabaena flos-aquae, were found at all sites. The total microcystin-LR levels were below guideline danger levels (<1.0 μg/L) except one time (1.27 μg/L in October), whereas chl-a (111.7 μg/L) and cell levels (2.6 × 10⁵ cells/mL) were at ‘vigilance’ and ‘alert’ levels for drinking water and at ‘guidance’ level for recreational water, respectively. Discrepancies in these parameters may thus lead to frequent unnecessary alerts, thereby increasing water management costs.     

Microcystins (cyanobacterial toxins) in surface waters of rural Bangladesh: pilot study

In Bangladesh the exposure of millions of inhabitants to water from (shallow) tube wells contaminated with high geogenic loads of arsenic is a major concern. As an alternative to the costly drilling of deep wells, the return to the use of surface water as a source of drinking water is considered. In addition to the well-known hazards of water borne infectious diseases associated with the use of surface water, recently the potential public health implications of toxic cyanobacteria have been recognized. As a first step towards a risk assessment for cyanotoxins in Bangladesh surface waters, seston samples of 79 ponds were analysed in late summer 2002 for the presence of cyanobacteria and microcystins (MCYST), the most frequently detected cyanobacterial toxins worldwide. Microcystins could be detected in 39 ponds, mostly together with varying abundance of potentially microcystin-producing genera such as Microcystis, Planktothrix and Anabaena. Total microcystin concentrations ranged between <0.1 and > 1,000 microg l(-1), and more than half of the positive samples contained high concentrations of more than 10 microg l(-1). The results clearly show that concentrations of microcystins well above the provisional WHO guideline value of 1 microg l(-1) MCYST-LR can be frequently detected in Bangladesh ponds. Thus, an increasing use of surface water for human consumption introduces a risk of replacing one health hazard by another and therefore needs to be accompanied by cyanotoxin hazard assessments.     

Effects of cyanobacterial toxins and cyanobacterial cell-free crude extract on germination of alfalfa (Medicago sativa) and induction of oxidative stress

Cyanobacterial toxins have adverse effects on both terrestrial and aquatic plants. Microcystins are cyclic heptapeptides and an important group of cyanotoxins. When lake water contaminated with cyanobacterial blooms is used for spray irrigation, these toxins can come in contact with agricultural plants. During the exposure to these toxins, reactive oxygen species can form. These reactive oxygen species have a strong reactivity and are able to interact with other cellular compounds (lipids, protein, and DNA). Plants have antioxidative systems that will limit the negative effects caused by reactive oxygen species. These systems consist of enzymes, such as superoxide dismutase, catalase, and ascorbate peroxidase, and nonenzymatic substances, such as reduced glutathione or vitamins. The aim of the present study was to investigate the effects of cyanobacterial toxins (microcystins and anatoxin-a) and cyanobacterial cell-free crude extract on alfalfa (Medicago sativa) seedlings. Inhibition of germination and root growth was observed with toxin concentrations of 5.0 microg/L. Also, oxidative damage, such as lipid peroxidation, was detected after the exposure of alfalfa seedlings to the toxin. Reactive oxygen detoxifying enzymes were elevated, showing a marked response in alfalfa to oxidative stress caused by the exposure to cyanobacterial metabolites that might influence the growth and development of these plants negatively.     

Cyanobakterientoxine bei der Uferfiltration

Cyanobacterial toxins are substances produced by cyanobacteria or blue-green algae. They can occur in surface waters worldwide and have to be reliably removed when using affected surface waters as a drinking water source. Bank filtration has been used for 150 years for drinking water (pre-)treatment. It utilizes natural elimination processes like sorption and degradation in the sub-surface. Retention of cells on the sediment surface is the most prominent process for eliminating these primarily cell-bound toxins. Middle to coarse grained sands eliminated more than 99.9 % of intracellular toxins within the first 10 cm of flow path. Elimination of extracellular microcystin during underground passage is mainly due to biodegradation. Reversible adsorption processes do not reduce the total load but lead to longer contact times for extended biodegradation. Laboratory experiments showed that the sediment structure, i.e. high clay/silt and organic content, is crucial for maximum adsorption. However, redox conditions play an important role for degradation rates: under aerobic conditions half-lives of less than one day occurred frequently, whereas anoxic conditions resulted in lag phases of one day and more, as well as in half lives of more than 25 days. Field experiments showed that temperature is crucial for degradation velocity under natural conditions.Under optimal conditions 10 d residence time are sufficient to reduce microcystin concentrations to values below the WHO guidelines value for drinking water (1 microg/L). Under sub-optimal conditions a residence time of up to 90 days may be necessary.     

Microcystin-producing blooms--a serious global public health issue

The investigation on microcystin topics is increasing due to the related ecological and public health risks. Recent investigation confirms a gap in establishing global patterns relating a particular environment to the bloom occurrence of a species and the production of certain microcystin variants. All the results concerning the environmental effects on the microcystin synthesis of one species must be checked in the light of genome diversity. Thus, the poisoning risks of a bloom depend on the strain causing toxicity. To be more effective, specific water treatment methods are required for blooms of different microcystin producing species (such as colonial and filamentous cyanobacteria found in stratified and unstratified water bodies, respectively). With the increasing number of new microcystin variants discovered, the development of new rapid, inexpensive and sensitive enough monitoring methods to promptly screen simultaneously a great diversity of toxins and also check their toxic effects is becoming necessary.     

饮用水源中的微囊藻毒素与大肠癌发病的关系

目的：研究不同类型饮用水源中的微囊藻毒素与大肠癌发病的关系。方法 在浙江省海宁市的８个乡镇,对近２０年的共４０８例大肠癌患进行一生中饮水情况的调查,并分别采集井水、自来水、池塘水及河浜水的水样,用间接竞争酶联免疫方法测定微囊藻毒素的含量。结果：饮用池塘水及河浜水的大肠癌发病率均明显高于饮用水和自来水的发病率,经与饮用井水相比,饮用自来水,河浜水及池塘水的相对危险度分别为１．８８、７．９４和７．７