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Human Health Risk Assessment Related to Cyanotoxins Exposure

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Human Health Risk Assessment Related to Cyanotoxins Exposure

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Abstract

This review focuses on the risk assessment associated with human exposure to cyanotoxins, secondary metabolites of an ubiquitous group of photosynthetic procariota. Cyanobacteria occur especially in eutrophic inland and coastal surface waters, where under favorable conditions they attain high densities and may form blooms and scums. Cyanotoxins can be grouped according to their biological effects into hepatotoxins, neurotoxins, cytotoxins, and toxins with irritating potential, also acting on the gastrointestinal system. The chemical and toxicological properties of the main cyanotoxins, relevant for the evaluation of possible risks for human health, are presented. Humans may be exposed to cyanotoxins via several routes, with the oral one being by far the most important, occurring by ingesting contaminated drinking water, food, some dietary supplements, or water during recreational activities. Acute and short-term toxic effects have been associated in humans with exposure to high levels of cyanotoxins in drinking and bathing waters. However, the chronic exposure to low cyanotoxin levels remains a critical issue. This article identifies the actual risky exposure scenarios, provides toxicologically derived reference values, and discusses open issues and research needs.

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... Cyanotoxin hepatotoxicity causes inhibition of serine/threonine protein phosphatases and affects the regulation of cellular protein hyperphosphorylation [10]. Neurotoxicity results in neuromuscular blockade [11], anti-acetylcholinesterase activity, anti-phosphatase activity, postsynaptic cholinergic agonist activity, and also affects protein kinase C activators. ...
... Neurotoxins usually have acute effects on vertebrates, with rapid paralysis of the peripheral skeletal and respiratory muscles. Other symptoms include loss of coordination, twitching, irregular gill movement, tremors, altered swimming, and convulsions before death due to respiratory arrest [7,11]. ...
... They are chemically unstable and degrade in water by photolysis. Therefore, they accumulate to a lesser extent in the tissues of aquatic organisms [11]. Anatoxin-a(s) (Figure 2b) is an N-hydroxyguanidine methyl phosphate ester and is the only known natural organophosphate. ...
Article
Cyanobacteria are the most ancient phytoplankton that first appeared at least 2.5 billion years ago and have a prolonged evolutionary history. They can form impenetrable and toxic blooms in aquatic ecosystems such as freshwater and marine environments. Cyanobacterial blooms produce cyanotoxins that endanger ecosystem functioning and deteriorate water quality used for recreation, drinking, and in fisheries, thus, adversely affecting human health and the economy. Some bloom-producing genera are Aphanizomenon, Planktothrix, Cylindrospermopsis, Nodularia, Trichodesmium, Dolichospermum, and Microcystis. They increase turbidity and suppress submerged aquatic vegetation. Due to the microbial bloom-mediated environmental degradation, oxygen scarcity might occur, inducing hypoxia and anoxia, and resulting in the death of fish and benthic invertebrates. Several cyanotoxins cause many diseases related to digestion, liver, and neurological disorders when ingested by birds and mammals, including humans. Global changes resulting from human impacts like eutrophication, rising CO 2 levels, and global warming are major driving forces for the enhancement of cyanobacterial blooms in many aquatic systems worldwide. Various management strategies such as nutrient load reduction, hydrodynamic changes, and chemical and biological controls have been used to reduce bloom occurrence and proliferation of cyanobacteria. In this chapter, we have discussed the approaches regarding the understanding of how global changes affect cyanobacterial blooms and also suggested effective prediction and management strategies.
... A large number of freshwater cyanobacteria (e.g. Microcystis, Anabaena, Planktothrix (Oscillatoria), Nostoc, Hapalosiphon, Anabaenopsis) produces a variety cyanotoxins that can contaminate drinking water and recreational waters, and can result in the deaths of domestic animals and wildlife (Briand et al. 2003;Funari and Testai 2008;Stewart et al. 2008). The majority of cyanotoxins target the nervous system (neurotoxins), the liver (hepatotoxins) or the skin (dermatoxins) (Sivonen and Jones 1999). ...
... Lastly, we investigated the interactions between cyanobacterial blooms and hydrogen peroxide dynamics. Funari, E., & Testai, E. (2008). Human health risk assessment related to cyanotoxins exposure. ...
... A variety of freshwater cyanobacteria produce harmful toxins, known as cyanotoxins, which constitute a global health-risk for humans through the impairment of recreational activities and drinking water. Cyanotoxins have also caused the deaths of domestic animals and wildlife (Briand et al. 2003;Funari and Testai 2008;Stewart et al. 2008). Under favorable light and nutrient conditions, toxic cyanobacteria can form thick scums in the surface water, which inhibit the photosynthesis of benthic aquatic plants and cause hypoxia (Paerl et al. 2001). ...
Thesis
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Hydrogen peroxide is widely recognized as the most stable of the reactive oxygen species (ROS) produced by abiotic, biotic and sediments in natural waters. By mediating redox transformations, hydrogen peroxide may directly or indirectly affect aquatic ecosystems. It might be particularly important in the biology and ecology of harmful freshwater cyanobacteria blooms which are increasingly occurring in nutrient-rich freshwater bodies. Environmental interactions between cyanobacteria and natural hydrogen peroxide could play a large role in cyanobacterial blooms, but little is known about these interactions. To better understand the interactions of hydrogen peroxide and cyanobacteria, we determined the hydrogen peroxide level in the presence and absence of cyanobacterial blooms. Also, we aimed to understand the ecological significance of hydrogen peroxide production by cyanobacteria in the waters of southwest Florida, a subtropical zone which experiences strong sunlight and heavy precipitations in the rainy season. In this study, hydrogen peroxide concentrations were determined using a fast response amperometric hydrogen peroxide microsensor in 24 freshwater bodies. Our results indicated that rainwater contains higher hydrogen peroxide levels (0-92.9 µM) than freshwater bodies under cyanobacterial bloom conditions (0-5.3 µM). To determine the potential biodegradation of hydrogen peroxide during sample transportation in the dark (opaque containers), water samples were passed through 0.2 µm filters immediately after sampling and compared with unfiltered water samples in the laboratory. We found the filtered water samples retained higher concentrations of hydrogen peroxide than non-filtered samples; and we determined the mean biodegradation rate of hydrogen peroxide was 44.7 ±10.6 nmol/h in unfiltered water. We also determined the baseline hydrogen peroxide concentrations and microscale depth profiles (10-60 mm) of hydrogen peroxide using a recently developed hydrogen peroxide microsensor. The hydrogen peroxide concentrations were higher at M. aeruginosa bloom sites compared to control sites and higher in locations exposed to sunlight than in shaded locations. In addition, micro-profiles showed extremely high hydrogen peroxide concentrations (3.3 to 20.9 µM) in the uppermost layer of the lake water in cyanobacterial blooms. All together, we found hydrogen peroxide hotspots in fresh waterbodies in a subtropical region that were generated by both abiotic and biotic factors. In addition, we found extremely high hydrogen peroxide concentrations in cyanobacterial bloom sites compared to reported values from other freshwater systems which could have a large effect on the aquatic microbial community.
... MC variants cause a variety of acute toxicities depending on the present substituents; the LD 50 value ranges from 50 to >1200 µg/kg BW via i.p injection in rodents [24]. A tenfold increase can be observed in acute toxicity of MC-LR vs. MC-RR via an i.p exposure by a single amino acid change. ...
... Likewise, an in-vivo study indicated that >32 µg/kg BW of MC-LR via i.p injections could inhibit PP1 and PP2A [26], which is similar to the no-effect concentrations reported by various studies. The lowest doses of MC-LR via oral administration could also cause hepatic toxicity (LOAEL, = 500 µg/kg BW) [24]. ...
... The LOAEL (200 µg/kg BW/day) could induce mild liver damage in a small number of treated animals, while all the animals developed hepatic lesions after exposure to 1 mg/kg BW/day as the highest tested dose, similar to MC-LR known effects. However, Funari and Testai reported a higher NO-AEL value (333 µg/ kg BW/day) in mice considering toxicokinetic differences by the sub-chronic administration of extracts, containing MC-LR per OS similar to human exposure route, although the risk of interference with other cyanobacterial components exists [24,27]. Alterations in hepatic metabolism, along with the lack of changes in other toxicity and histological markers, were observed by omics tolls in rats receiving lower doses of MC-LR for seven days via gavage [28]; however, further studies are required to obtain more conclusive results. ...
Article
Different biological methods based on bioactivity are available to detect cyanotoxins, including neurotoxicity, immunological interactions, hepatotoxicity, cytotoxicity, and enzymatic activity. The mouse bioassay is the first test employed in laboratory cultures, cell extracts, and water bloom materials to detect toxins. It is also used as a traditional method to estimate the LD50. Concerning the ease of access and low cost, it is the most common method for this purpose. In this method, a sample is injected intraperitoneally into adult mice, and accordingly, they are assayed and monitored for about 24 hours for toxic symptoms. The toxin can be detected using this method from minutes to a few hours; its type, e.g., hepatotoxin, neurotoxin, etc., can also be determined. However, this method is nonspecific, fails to detect low amounts, and cannot distinguish between homologues. Although the mouse bioassay is gradually replaced with new chemical and immunological methods, it is still the main technique to detect the bioactivity and efficacy of cyanotoxins using LD50 determined based on the survival time of animals exposed to the toxin. In addition, some countries oppose animal use in toxicity studies. However, high cost, ethical considerations, low-sensitivity, non-specificity, and prolonged processes persuade researchers to employ chemical and functional analysis techniques. The qualitative and quantitative analyses, as well as high specificity and sensitivity, are among the advantages of cytotoxicity tests to investigate cyanotoxins. The present study aimed at reviewing the results obtained from in-vitro and in-vivo investigations of the mouse bioassay to detect cyanotoxins, including microcystins, cylindrospermopsin, saxitoxins, etc.
... Cyanobacteria (CB) are ubiquitously distributed in both terrestrial and aquatic systems, covering the range from deserts to tropical rain forests, to alpine and subsurface soils, and from the ultraoligotrophic open ocean to hypereutrophic lakes (Buratti et al., 2017). Global climate change, anthropogenic activities and eutrophication leads to the rapid growth of cyanobacterial species (a large group of photosynthetic prokaryotes), which results in the formation of algal blooms and scums (Funari and Testai, 2008;Zanchett and Oliveira-Filho, 2013;Buratti et al., 2017;Zerrifi et al., 2019;Habtemariam et al., 2021). Lysis of harmful algal bloom (HAB) forming cyanobacterial cells, often emits their toxic secondary metabolites -cyanotoxins (CTX). ...
... Total MCs concentration, in sample s1 and s2, was 453.89 μg/L and 61.63 μg/L respectively for extracellular MCs; and 189.29 μg/L and 112.34 μg/L respectively for intracellular MCs. CTX exposure induces several different toxicological effects to livestock and human beings; and a large number of scientific investigations have already addressed the potential toxicities of CTX on aquatic and human health (Funari and Testai, 2008;Zanchett and Oliveira-Filho, 2013;Buratti et al., 2017;Kubickova et al., 2019;Svircev et al., 2019). Underlying mechanisms, responsible for inducing different toxic effects of CTX in animals and human, has also been described by many authors (Buratti et al., 2017). ...
Article
Cyanotoxins (CTX) and micro/nanoplastics (M/NP) are ubiquitously distributed in every environmental compartment. But the distribution, abundance and associated ecological risks of CTX are still poorly understood in soil system. On the other hand, M/NP could serve as vectors for persistent organic/inorganic pollutants in the natural environment through the sorption of pollutants onto them. Thus, co-occurrence of CTX and M/NP in soils suggests the sorption of CTX onto M/NP. So, major aim of this review is to understand the relevance of CTX and M/NP in soils as co-contaminants, possible interactions between them and ecological risks of CTX in terms of phytotoxicity. In this study, we comprehensively discuss different sources and fate of CTX and the sorption of CTX onto M/NP in soil system, considering the partition coefficient of different phases of soil and mass balance. Phytotoxicity of CTX, CTX mixture and co-contaminants has also been discussed with insights on the mechanism of action. This study indicates the need for the evaluation of sorption between co-contaminants, especially CTX and M/NP, and their phytotoxicity assessment using environmentally relevant concentrations.
... Dados da literatura reportam o mesmo padrão de aumento de biomassa algal associados às condições mais rasas, eutróficas e túrbidas em reservatórios do semiárido brasileiro (Huszar et al. 2000;Costa et al. 2009;Dantas et al. 2011e Soares et al., 2013. Funari;Testai, 2008). Enquanto as cianobactérias são geralmente relacionadas à condição de estabilidade térmica, as Chlorophyceaes são frequentemente associadas à desestratificação, coincidindo com a maior disponibilidade de nutrientes provenientes da ressuspensão do sedimento (Gentil et al., 2008). ...
... Dados da literatura reportam o mesmo padrão de aumento de biomassa algal associados às condições mais rasas, eutróficas e túrbidas em reservatórios do semiárido brasileiro (Huszar et al. 2000;Costa et al. 2009;Dantas et al. 2011e Soares et al., 2013. Funari;Testai, 2008). Enquanto as cianobactérias são geralmente relacionadas à condição de estabilidade térmica, as Chlorophyceaes são frequentemente associadas à desestratificação, coincidindo com a maior disponibilidade de nutrientes provenientes da ressuspensão do sedimento (Gentil et al., 2008). ...
... Regarding TP concentration, all reservoirs are eutrophic, which explains the high density of Cyanobacteria, with the dominance of potentially toxin-producing genera (e.g., Anabaenopsis, Aphanizomenon, Coelosphaerium, Dolichospermum, Microcystis, Oscillatoria, Phormidium, Planktothrix, and Raphidiopsis), already reported in several areas around the world [12,13,[131][132][133][134][135][136][137]. Therefore, in all reservoirs, high-risk situations were identified, especially considering the identified taxa are potential producers of different toxins, namely microcystins, anatoxins, anatoxin-a, cylindrospermopsins, and saxitoxins [137]. ...
... Water from reservoirs is often used for irrigation through illegal direct extractions, animal watering, and other domestic uses. Some authors point out that continuous exposure to contaminated water, even with low concentrations of cyanotoxins, may also pose a risk of chronic health effects [21,131,142]. Furthermore, there are risks associated with other routes of exposure, such as aerosols, during recreational activities, or from direct or indirect contact with contaminated water [142,143]. ...
Article
Full-text available
Reservoirs provide valuable services to human beings, especially in arid, semi-arid, and Mediterranean regions affected by water scarcity. The present effort aims to study the environmental descriptors of variation and the main factors influencing phytoplankton composition, structure, and diversity in five reservoirs in Santiago Island, Cape Verde, a region affected by water availability. Five campaigns took place from 2016 to 2020 to sample phytoplankton and measure environmental variables according to standard analytical methodologies. Environmental results (17 water physicochemical variables, air temperature, and precipitation) revealed that reservoirs differ in the geological influence variables. The high levels of P and N in water seem to be related to Land Use/Land Cover and are responsible for water-quality degradation. Cyanobacteria dominated the phytoplankton community and posed high risk levels, especially considering that the identified taxa are potential producers of different toxins. Taxa responsible for this dominance were not the same in all reservoirs, emphasizing the dominant role of local habitat factors on community composition and diversity. Overall, the results reveal the importance of defining integrated management plans/strategies for the set of five studied reservoirs, since the processes influencing variation in the phytoplankton community are temporal-scale dependent, with similar biogeographic patterns.
... Regarding TP concentration, all reservoirs are eutrophic, which explains the high density of Cyanobacteria, with the dominance of potentially toxin-producing genera (e.g., Anabaenopsis, Aphanizomenon, Coelosphaerium, Dolichospermum, Microcystis, Oscillatoria, Phormidium, Planktothrix, and Raphidiopsis), already reported in several areas around the world [12,13,[131][132][133][134][135][136][137]. Therefore, in all reservoirs, high-risk situations were identified, especially considering the identified taxa are potential producers of different toxins, namely microcystins, anatoxins, anatoxin-a, cylindrospermopsins, and saxitoxins [137]. ...
... Water from reservoirs is often used for irrigation through illegal direct extractions, animal watering, and other domestic uses. Some authors point out that continuous exposure to contaminated water, even with low concentrations of cyanotoxins, may also pose a risk of chronic health effects [21,131,142]. Furthermore, there are risks associated with other routes of exposure, such as aerosols, during recreational activities, or from direct or indirect contact with contaminated water [142,143]. ...
Article
Reservoirs provide valuable services to human beings, especially in arid, semi-arid, and Mediterranean regions affected by water scarcity. The present effort aims to study the environmental descriptors of variation and the main factors influencing phytoplankton composition, structure, and diversity in five reservoirs in Santiago Island, Cape Verde, a region affected by water availability. Five campaigns took place from 2016 to 2020 to sample phytoplankton and measure environmental variables according to standard analytical methodologies. Environmental results (17 water physicochemical variables, air temperature, and precipitation) revealed that reservoirs differ in the geological influence variables. The high levels of P and N in water seem to be related to Land Use/Land Cover and are responsible for water-quality degradation. Cyanobacteria dominated the phytoplankton community and posed high risk levels, especially considering that the identified taxa are potential producers of different toxins. Taxa responsible for this dominance were not the same in all reservoirs, emphasizing the dominant role of local habitat factors on community composition and diversity. Overall, the results reveal the importance of defining integrated management plans/strategies for the set of five studied reservoirs, since the processes influencing variation in the phytoplankton community are temporal-scale dependent, with similar biogeographic patterns.
... This classification concerns toxin-producing cyanobacteria. As toxin analyses have not been carried out during this activity, identification of toxin-producing cyanobacteria was based on previous studies [16] [17] [27] [28]. Thus, according to Bernard [17], they were grouped into three families according to the cyanotoxic effects: hepatotoxins (main target organ: the liver), neurotoxins (target organ: the nervous system) and dermatotoxins (target organ: the skin). ...
... Cyanotoxins can be present in drinking water, depending on their concentration in surface waters and the effectiveness of the treatment method [41]. In countries without adequate water treatment, the population may be exposed to intracellular toxins and dissolved cyanotoxins [28]. These cyanobacterial toxins are structurally diverse and cause numerous health problems in humans and animals [ [77]. ...
... All of these factors in fish farming ponds and lakes are inter-related and require careful and constant monitoring to avoid contamination and/or degradation of the environment. Special attention must be paid to cyanobacteria blooms, which are symptomatic of eutrophication in productive lakes, since they may produce cyanotoxins (Funari and Testai, 2008;Semyalo et al., 2010) which are toxic to vertebrates and can affect human health through direct contact or consumption of contaminated water, fish or plants. Caging aquaculture may also cause other impacts on aquatic environments, such as the destruction of natural habitats and alterations in the structure and dynamics of local organisms, as well as trophic changes (Agostinho et al., 2008;Strictar-Pereira et al., 2010;Dias et al., 2012). ...
Article
Contaminants of emerging concern (CECs) are ubiquitous in aquatic environments across all continents and are relatively well known in the developed world. However, few studies have investigated their presence and biological effects in low- and middle-income countries. Here, we provide a first survey of CEC presence in the Volta River, Ghana and examine microbial consequences of anthropogenic activities along this economically and ecologically important African river. Water and sediment samples were taken by boat or from shore at 14 sites spanning 118 km of river course from the Volta estuary to the Akosombo dam. Sample extracts were prepared for targeted analysis of antimicrobial CECs, N,N-diethyl-meta-toluamide (DEET), and perfluorochemicals (PFAS, water only). Concurrent samples were extracted to characterize the microbial community and antibiotic resistant genes (ARGs). Antibiotics and PFAS (☐PFAS: 2-20 ng/L) were found in all water samples, however, their concentration were usually in the low ng/L range and lower than reported for other African, European, and North American studies. DEET was present in all samples. The number of different genes detected (between one and ten) and total ARG concentrations varied in both water (9.1×10-6 to 8.2×10-3 ) and sediment (2.2×10-4 to 5.3×10-2 ), with increases in gene variety at sites linked to urban development, sand mining, agriculture, and shellfish processing. Total ARG concentration spikes in sediment samples were associated with agriculture. No correlations between water quality parameters, CEC presence, and /or ARGs were noted. The presence of CECs in the Lower Volta River highlights their global reach. The overall low concentrations of CECs detected is encouraging and coupled with mitigation measures, can stymy future CEC pollution in the Volta River. This article is protected by copyright. All rights reserved.
... Many cyanotoxins have multiple variants with a range of toxicities (Welker and von Döhren, 2006). Several studies have reported the negative health and ecological effects of cyanotoxins (Carmichael, 1992;Funari and Testai, 2008). Therefore, Brazil and several other countries have set national standards for cyanotoxins in drinking and recreational waters (Hudnell, 2008). ...
... Compounds of toxic properties are also a very interesting group. These allow microorganisms to survive under extreme conditions and fight for their position in a given environment, but they pose serious threats to human health and the environment [90]. The bioaccumulation and bioconcentration of toxins inside aquatic organisms can be a serious problem here, which results in the introduction of toxins (e.g., neurotoxins) to the organisms representing the next stages of the food chain. ...
Article
Full-text available
Cyanobacteria constitute an interesting group of photosynthetic microorganisms due to their morphological and genetic diversity that is related to their extremely long evolution process, which created the need for them to adapt to immensely heterogeneous environmental conditions. Cyanobacteria grow in salt and fresh waters as well as on the surface of soils and rocks. The diverse cell structure is characterized by the fact that they occur in many morphological forms, from small single cells through to larger ones as well as branches, threads, or spirals. Taking into account the presence of cyanobacteria in virtually all possible conditions and places on Earth, cyanobacteria represent an unexplored potential that is worth investigating. This review presents the possibilities of using algae in chosen areas of biotechnology: e.g., as biocatalysts or in industries such as the pharmaceutical industry. It covers the characteristics of secondary metabolites along with their division and the potential of using them as sources of effective drugs for many diseases. It presents an overview of the possibilities of using cyanobacteria in biotransformation processes. These processes are of great importance in the case of, for example, the neutralization of municipal, industrial, or chemical waste, the amount of which is constantly growing every year, and they are also an easier and cheaper path to obtain chemical compounds.
... Indeed, these toxins can reach animals and humans through a variety of pathways (Codd et al., 2020) such as: (1) through consumption of fish, and particularly shellfish (filter feeders), that have absorbed these contaminants; (2) through inhalation from aerosols, such as in cases where crops are irrigated with contaminated water, from recreational activities (swimming, boating, waterboarding, etc.) (Backer et al., 2010), from dried scum on the shore, and from arid environments following rainfall (Metcalf et al., 2012); (3) through the consumption of crops irrigated with contaminated water, which can absorb the toxins (Lee et al., 2017); (4) through dermal contact; and (5) intravenously (Carmichael et al., 2001). Mild infections can lead to unpleasant symptoms, such as diarrhea, vomiting, fever and headache, just to name a few, while severe infections can cause blistering of the mouth, pneumonia, confusion, respiratory paralysis and death (Funari and Testai, 2008). Since their first observation in the 1800s, where the rapid death of stock animals at a freshwater lake in Australia was investigated and attributed to cyanobacteria (Francis, 1878), harmful and toxic blooms have been increasing in number and severity (Gobler, 2020;Lewitus et al., 2012). ...
Chapter
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Fertilizers are at the foundation of our modern society, without which we would not be able to feed and sustain a majority of the world population. Of the major macronutrients necessary for agriculture, which include nitrogen (N), phosphorus (P) and potassium (K), nitrogen is essential for healthy plant growth, being vital for the production of amino-acids and proteins. For this reason, nitrogen is by far the most produced and applied fertilizer around the world, generally in the form of urea and ammonium salts, as well as through organic fertilizers such as manures, composts and digestates. Luckily, in the early 1900's, the Haber-Bosch process was developed, allowing for the production of synthetic nitrogen fertilizers on an industrial scale; a process that is still responsible for over 96% of the world's synthetic nitrogen production. However, despite the unimaginable benefits of nitrogen fertilizers on humanity, there have also been some significant impacts worldwide, notably ecologically and environmentally. Such impacts include soil acidification, eutrophication, nutrient runoff , reduced biological diversity, and substantial greenhouse gas (GHG) emissions. This chapter aims at exploring the environmental and ecological impact of nitrogen fertilizers, discussing the impact of their production and application to land.
... Microcystin (MCs) are toxins produced by cyanobacteria ( Blue-green algae )from water environment that can induce acute and chronic effects on humans and animals after ingestion /contact with contaminated water (Funari and Testai , 2008;Codd,1995;Dawson, 1998;Pouria et al, 1998), or concentration in plant tissue and inhibition of growth (Mmitrovic et al.2005) and can potentially transfer in to human and animals via food chains (Crush et al.2008). Microcystins are structurally drives cyclic heptopeptides that are primarily considered as heptotoxins (WHO,2008) although the gastrointestinal tract, kidney and other organs are also susceptible to mediated damage (Falconer,1996 ;Al-Sultan and Al-Ali , 2010 ;Al-Ali et al., 2011 ). ...
... The exposure of humans to cyanotoxins is usually related to the ingestion of contaminated drinking water (Funari & Testai, 2008;Pouria et al., 1998), and it has been reported worldwide (Gaget et al., 2017;Tamele & Vasconcelos, 2020;Vu et al., 2020;WHO, 2017). More specifically, 14 episodes of massive cyanotoxin poisoning in humans and animals were recorded in South America, with the highest number of episodes in Brazil and Argentina (Svirčev et al., 2019). ...
Article
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While the presence of microcystin-LR (MC-LR) in raw water from eutrophic reservoirs poses human health concerns, the risks associated with the ingestion of MC-LR in drinking water are not fully elucidated. We used a time series of MC-LR in raw water from tropical urban reservoirs in Brazil to estimate the hazard quotients (HQs) for non-carcinogenic health effects and the potential ingestion of MC-LR through drinking water. We considered scenarios of MC-LR removal in the drinking water treatment plants (DWTPs) of two supply systems (Cascata and Guarapiranga). The former uses coagulation/flocculation/sedimentation/filtration/disinfection, while the latter has an additional step of membrane ultrafiltration, with contrasting expected MC-LR removal efficiencies. We considered reference values for infants (0.30 μg L−1), children/adults (1.60 μg L−1), or the population in general (1.0 μg L−1). For most scenarios for Cascata, the 95% upper confidence level of the HQ indicated high risks of exposure for the population (HQ > 1), particularly for infants (HQ = 30.910). The water treatment in Cascata was associated to the potential exposure to MC-LR due to its limited removal capacity, with up to 263 days/year with MC-LR above threshold values. The Guarapiranga system had the lowest MC-LR in the raw water as well as higher expected removal efficiencies in the DWTP, resulting in negligible risks. We reinforce the importance of integrating raw water quality characteristics and treatment technologies to reduce the risks of exposure to MC-LR, especially for vulnerable population groups. Our results can serve as a starting point for risk management strategies to minimize cases of MC-LR intoxication in Brazil and other developing countries.
... It is estimated that over 75% of cyanobacterial blooms result in the production of a wide range of toxic secondary metabolites, called cyanotoxins, limiting the use of available water resources [6,7]. Among cyanobacterial toxins, microcystins (MCs) are the most widespread and worrisome class of cyanotoxins, which have attracted the attention of many researchers worldwide [8,9]. ...
Article
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Over the last years, the use of artificial lakes and ponds to irrigate agricultural crops has been intensified and cultivation methods have been diversified. Hydroponics is a type of hydroculture which usually involves growing plants in an inert substrate, by using nutrient-enriched water to support plant growth. However, irrigating plants in hydroponic-based culture must be accompanied by monitoring the quality of irrigation water. The human health risks involved are mainly related to the proliferation of microcystin-producing cyanobacteria that contaminate water used for irrigation purposes. Strawberry (Fragaria vulgaris L.) is a widely cultivated plant of an increased economically importance worldwide. Its fruits provide essential elements for human nutrition; therefore, the study of its sensitivity to microcystins (MCs) is of paramount importance. The objective of this study was to evaluate the effects of MCs in irrigation water on the growth, physiology, and antioxidant defense system in F. vulgaris. In this study, strawberry seedlings at the three-leaf stage were grown in pots containing perlite under controlled conditions. Plants were exposed to a crude extract of Microcystis aeruginosa bloom at different concentrations of MCs (1, 5, 10, and 20 μg/L) for 60 days of exposure. The results showed that the highest concentrations of 10 and 20 μg/L induced a decrease in growth parameters. They resulted in root/shoot length decrease as well as number of leaves, roots/leaves dry and fresh weight. Furthermore, MCs reduced chlorophyll/carotenoid content, stomatal conductance, fluorescence, and total protein content of strawberry plants. At the same time, a significant increase in Malondialdehyde (MDA) (an indicator of lipid peroxidation), polyphenol, and sugar content were recorded in strawberry plants exposed to MCs at 5, 10, and 20 μg/L compared with the control. Additionally, superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), Polyphenoloxydase (PPO), and ascorbate peroxidase (APX) activities significantly increased in plants under MCs exposure. The oxidative stress was higher in plants exposed to 10 and 20 μg/L of MCs from the second harvest (after 60 days of exposure) compared to those from the first harvest (after 30 days). Overall, the results obtained in this study indicate an increasingly negative effect of MCs on strawberry plants grown in hydroponics even at concentrations (10 and 20 µg/L). This effect is more damaging on the roots after exposure (60 days).
... DAT has also been found toxic to humans by laboratory exposure to ethanol solutions containing 0.5 µg-5 mg/ml DAT, suggesting aerosolisation and/or volatilisation (74.) It is important to note that these are relatively crude toxicity estimates for LA and DAT compared to more advanced dose-response and dose-translation toxicological modelling (19, 31,24,81). Such estimations are anticipated using these advanced toxicological models outside of the scope of this project. ...
Research
Executive Summary Coastal algal blooms (CABs) of the cyanobacterium Lyngbya majuscula (Moorea producens) have been associated with negative health impacts in individuals exposed to bloom biomass. These include respiratory and ocular and dermal irritation, acute dermatitis, burning sensation on skin and mucous membranes, headache, nausea and diarrhoea. In order to assess health risks associated with CABs of the potentially toxic cyanobacterium L. majuscula; levels, distribution and mobility of two indicator toxins (lyngbyatoxin A [LA], debromoaplysiatoxin [DAT]) were investigated using biomass collected from Moreton Bay bloom events. Toxin distribution in; as well as leaching, adsorption, aerosolisation, volatilisation and aqueous partitioning properties from; biomass were examined. Levels of both toxins were significantly higher than previously reported in the literature. Toxin in biomass exceeded the lowest levels estimated to produce adverse dermal health effects based on the individual toxins alone in 85-100% (LA) and 15-60% (DAT - North Deception Bay only) of samples, dependent on adverse effect level estimate. Toxin distribution within individual biomass was evaluated and found to be highly variable. Sample storage conditions were also evaluated, with substantial leaching of LA from biomass into associated container liquid found during heated and refrigerated storage. This suggests potential for leaching of concentrated toxin-bearing liquid from wet, composting or stockpiled biomass, and possible exposure in the marine environment to leached rather than cell-associated toxin(s). Leaching of both toxins from biomass via seawater into underlying sand was demonstrated. However, LA was leached much more effectively than DAT. Drying biomass prior to leaching substantially increased levels leached. The majority of seawater-leached toxin was found adsorbed to underlying sand. Determination of sand (Kd) and lipid-surrogate (Kow) partition coefficients indicated both LA and DAT are hydrophobic, with strong partitioning behaviour to sand from both seawater and distilled water. Low-level aerosolisation of L. majuscula filaments via wind-driven sea spray onto glass capture surfaces was demonstrated for suspended biomass using a bubble-wind chamber. Aerosolisation of filaments from static, dried biomass was not found in this study. Emission of volatile compounds from L. majuscula was demonstrated, largely associated with marine anaerobic degradative fermentative and sulphur cycling processes rather than specific L. majuscula-produced secondary metabolite toxins. Potential health impacts associated with exposure to above-threshold levels of these volatiles are similar to symptoms reported by those presumptively exposed to vapours (volatiles) associated with L. majuscula CAB biomass. Current recommendations regarding handling and disposal of L. majuscula bloom material biomass appear adequate to protect the health of the public and mitigation staff, with additional recommendations provided. Health risk assessments should consider the results of this study concerning: potential levels of toxins in bloom material; associated exposure limits; toxin mobility/partitioning; generation of aerosols/volatiles; and use of indicator toxin monitoring in risk assessment(s). Bloom material sampling, preservation and toxin analysis considerations are discussed and recommendations presented. A health risk assessment matrix, and risk assessment and control register template are provided.
... Without discussing the details of the medical literature on the effects of water pollution on human health, we briefly summarize some references of the main human health effects of the pollutants: nitrogen and phosphorus (Qasemi et al., 2018); pesticides (Kim et al., 2017); cyanotoxins and mycotoxins (Funari and Testai, 2008;Zain, 2011;Malakar et al., 2019). Foodborne pathogens include a broad range of bacteria, viruses and parasites. ...
Article
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Water is a factor input for many food system activities such as agriculture, food processing and consumption. However, food system activities also affect water resources. Moreover, the shift in focus of food security in Low- and Middle-Income Countries (LMICs) from producing enough staple foods toward healthy diets stimulates local production of fresh food such as fruit, vegetables and fish even in water scarce regions. To secure local production, polluted water is used for food production, processing and consumption, which might jeopardize human health. However, scientific evidence is still scattered and fragmented. The aim of this study is to systematically investigate the empirical tested impacts of water quality on the food system activities and vice versa. Using a comprehensive framework, we sketch the inter-relationships between water quality and food systems based on a literature study. Food system activities included food production (crop production, livestock and aquaculture), food processing, and food consumption. Multiple contaminants were incorporated such as nitrogen, phosphorus, pesticides, pathogens, cyanotoxins, and heavy metals. Moreover, we considered different water sources such as groundwater, surface water, wastewater and coastal water. We found that food system activities contaminate water in several ways, and these differ between food system activity and type of food produced. The impact of water quality on the food system depends on the food produced, the type of contaminant and techniques of food preparation. In addition, food is contaminated in multiple ways along the food system. Irrigation with polluted water may sound familiar, but polluted water is sometimes also used in food processing (cleaning of equipment or food products), and in food preparation (at home or by street vendors). Hygiene in food consumption is crucial to prevent fecal-oral transmission. However, water, sanitation and hygiene (WASH) received little attention in relation to food consumption. If local production of fresh food is encouraged to improve food security, all aspects of water quality should be analyzed to avoid undesirable consequences.
... Finally, global change-driven eutrophication and elevated temperatures lead to an increased growth of cyanobacteria, which can produce toxins (e.g. cyanotoxins), with known negative impacts on human health (Catherine et al., 2013;Funari and Testai, 2008;Zanchett and Oliveira-Filho, 2013). ...
Article
Mountains are an essential component of the global life-support system. They are characterized by a rugged, heterogenous landscape with rapidly changing environmental conditions providing myriad ecological niches over relatively small spatial scales. Although montane species are well adapted to life at extremes, they are highly vulnerable to human derived ecosystem threats. Here we build on the manifesto ‘World Scientists' Warning to Humanity’, issued by the Alliance of World Scientists, to outline the major threats to mountain ecosystems. We highlight climate change as the greatest threat to mountain ecosystems, which are more impacted than their lowland counterparts. We further discuss the cascade of “knock-on” effects of climate change such as increased UV radiation, altered hydrological cycles, and altered pollution profiles; highlighting the biological and socio-economic consequences. Finally, we present how intensified use of mountains leads to overexploitation and abstraction of water, driving changes in carbon stock, reducing biodiversity, and impacting ecosystem functioning. These perturbations can provide opportunities for invasive species, parasites and pathogens to colonize these fragile habitats, driving further changes and losses of micro- and macro-biodiversity, as well further impacting ecosystem services. Ultimately, imbalances in the normal functioning of mountain ecosystems will lead to changes in vital biological, biochemical, and chemical processes, critically reducing ecosystem health with widespread repercussions for animal and human wellbeing. Developing tools in species/habitat conservation and future restoration is therefore essential if we are to effectively mitigate against the declining health of mountains.
... Similarly, skin contact with blooms can cause severe dermatitis, and inhaling suspended particle droplets of cyanotoxified water can aggravate pre-existing respiratory diseases such as asthma [34]. Generally, the most common way to get cyanotoxins is to drink contaminated water or ingest edible aquatic organisms, including fish, shellfish, and seaweed contaminated with biotoxins due to the biomagnification process [35]. ...
... Cyanotoxins significantly threaten aquatic ecosystems (e.g., causing fish poisoning and fish/waterfowl/mammalian mortality) and potentially contaminate municipal drinking water, posing serious public health risks (Backer and Miller, 2016;Brooks et al., 2017;Ferrão-Filho and Kozlowsky-Suzuki, 2011;Grattan et al., 2016;Landsberg, 2002). Ingestion of cyanotoxins can cause acute and chronic toxicity effects on the human liver, kidney, lung, nervous tissues, gastrointestinal tract, and immune systems (Buratti et al., 2017;Funari and Testai, 2008;Kubickova et al., 2019;Vu et al., 2020;Zanchett and Oliveira-Filho, 2013). Therefore, authorities shut down municipal water supplies when serious HCBs occur in drinking water sources (e.g., the 2014 drinking water crisis in Toledo, Ohio, USA, caused by a Microcystis bloom in Lake Erie) (Pelley, 2016;Steffen et al., 2017;Wynne and Stumpf, 2015). ...
Article
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Freshwater harmful cyanobacterial blooms (HCBs) potentially produce excessive cyanotoxins, mainly microcystins (MCs), significantly threatening aquatic ecosystems and public health. Accurately predicting HCBs is thus essential to developing effective HCB mitigation and prevention strategies. We previously developed a novel early-warning system that uses cyanotoxin-encoding genes to predict cyanotoxin production in Harsha Lake, Ohio, USA, in 2015. In this study, we evaluated the efficacy of the early-warning system in forecasting the 2016 HCB in the same lake. We also examined potential HCB drivers and cyanobacterial community composition. Our results revealed that the cyanobacterial community was stable at the phylum level but changed dynamically at the genus level over time. Microcystis and Planktothrix were the major MC-producing genera that thrived in June and July and produced high concentrations of MCs (peak level 10.22 μg·L-1). The abundances of the MC-encoding gene cluster mcy and its transcript levels significantly correlated with total MC concentrations (before the MC concentrations peaked) and accurately predicted MC production as revealed by logistic equations. When the Microcystis-specific gene mcyG reached approximately 1.5 × 103 copies·mL-1 or when its transcript level reached approximately 2.4 copies·mL-1, total MC level exceeded 0.3 μg L-1 (a health advisory limit) approximately one week later (weekly sampling scheme). This study suggested that cyanotoxin-encoding genes are promising predictors of MC production in inland freshwater lakes, such as Harsha Lake. The evaluated early-warning system can be a useful tool to assist lake managers in predicting, mitigating, and/or preventing HCBs.
... Aquatic organisms can be affected during growth, reproduction, and embryonic development, making them more susceptible to contaminants in water (Zhang et al., 2008). In addition, the hepatotoxic, neurotoxic, and cytotoxic effects of cyanotoxins (Funari and Testai, 2008), extracts of cyanobacteria were shown to have estrogenic activity in human breast carcinoma cell line MVLN in vitro (Jonas et al., 2015;Stepankova et al., 2011;Sychrova et al., 2012). Among cyanotoxins, microcystin-LR and nodularin-R were found to play an endocrine-disrupting role in vivo and inducing estrogenic activity in cultured mammalian cells (Oziol and Bouaïcha, 2010). ...
Article
Cylindrospermopsin (CYN) is a cytotoxin, and its documented effects in mammals include damage to several organs. CYN also has hormone-disrupting properties, including estrogenic activity, progesterone production inhibition, and apoptosis induction. While CYN has been reported to exert reproductive toxicity in mice, little is known about its effect on fish reproductive function. Using ex vivo organ culture, we investigated the direct action of CYN on the male reproductive system. Isolated zebrafish testis was exposed to 250, 500, and 1000 µg/L CYN for 24 h and 7 d, followed by histo-morphological analysis. The results demonstrate that exposure to CYN led to a decrease in cell types from all three phases of spermatogenesis in zebrafish testis. There were also significant changes in fshr, lhr, and igf3 transcript levels, as well as testosterone secretion following exposure to CYN. In summary, this study provides novel information on the adverse effects of CYN on testicular spermatogenesis and male reproduction in zebrafish. These results provide a framework for a better understanding of CYN toxicity and the mechanism underlying the adverse action of CYN on male reproduction in fish.
... Cyanobacterial bloom is among the most common and serious forms of algal blooms in freshwater ecosystems, and in many cases are harmful to aquatic life (Zamyadi et al. 2012;Bartram and Chorus 1999). The water hypoxia and producing a variety of toxic secondary metabolites are the most important disorders that can be expected from some cyanobacterial blooms in their habitats (Funari & Testai 2008;Paerl and Otten 2013;Patterson and Larsen 1994). In addition, some cyanobacterial blooms such as Microcystis blooms, may have a direct negative impact on diatoms and green algae due to allelopathy (Wang et al. 2016). ...
Article
Aras Dam Lake is a strategic aquatic ecosystem in Iran and there are reports of toxic phytoplankton blooms in this reservoir. This study was performed to determine the effect of meteorological variables on the formation and expansion of toxic phytoplankton communities in Aras dam reservoir. The data of this project have been obtained using field studies and satellite data (MODIS and Sentinel-2). Sampling to determine the composition of phytoplankton communities in the area was carried out seasonally in two time periods from 2003 to 2014, and environmental assessments were also performed based on meteorological and satellite data over an 18-year period (2003-2020). The Chlorophyll-a content was obtained from MODIS and correlated with meteorological data. The statistical analysis showed that the highest coefficient of determination is related to the correlation of chlorophyll-a and Evaporation (R 2 = 0.86). Also, the relative root mean square error is equal to 18%, 18.1% and 21.2% for the chlorophyll-a -SST, chlorophyll-a -wind and chlorophyll-a -Evaporation relations, respectively. Moreover, in a supplementary study, correlation between the chlorophyll-a content with selected meteorological variables including evaporation, wind speed and water surface temperature were investigated seasonally. The results showed that the trend of changes in chlorophyll-a content with three considered variables are parabolic functions and chlorophyll-a -Evp (R 2 = 0.86, MAPE = 15.2%) model indicates better performance. The results also showed that the eutrophication rate of the reservoir during lockdown period increased in comparison with the same time at pre-pandemic period, which can be related to increase of incoming waste loads in this reservoir. Graphical abstract:
... Humans can be exposed to these toxins by different routes, and among them, the oral route, through the intake of contaminated water and food, is the most important. Nevertheless, parenteral, inhalation and dermal exposure may also happen [2]. ...
Article
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Cyanotoxins are secondary metabolites produced by different types of cyanobacteria. Among them, Cylindrospermopsin (CYN) and Microcystins (MCs) stand out due to their wide geographical distribution and toxicity in various organs, including the kidney, which is involved in their distribution and elimination. However, the renal toxicity caused by CYN and MCs has hardly been studied. The aim of this work was to assess the cytotoxicity effects caused by CYN and MC-LR in the renal cell line HEK293, and for the first time, the influence of CYN on the gene expression of selected genes in these cells by quantitative real-time PCR (qRT-PCR). CYN caused an upregulation in the gene expression after exposure to the highest concentration (5 µg/mL) and the longest time of exposure (24 h). Moreover, shotgun proteomic analysis was used to assess the molecular responses of HEK293 cells after exposure to the individuals and combinations of CYN + MC-LR. The simultaneous exposure to both cyanotoxins caused a greater number of alterations in protein expression compared to single toxins, causing changes in the cellular, lipid and protein metabolism and in protein synthesis and transport. Further studies are needed to complete the toxicity molecular mechanisms of both CYN and MC-LR at the renal level.
... They can disrupt the dynamics of aquatic ecosystems by reducing water clarity and leading to hypoxia and therefore death of fish and benthic invertebrates following the degradation of cyanobacterial blooms. The production of toxins may disrupt irrigated crops (Mhlanga et al. 2006), recreational uses and may constitute an acute health risk (Funari and Testai 2008) by inducing digestive or neurological diseases. ...
... High doses of MC-LR causes rupture of mitochondrial membrane and damage to the hepatic architecture with enormous intrahepatic hemorrhaging McDermott et al., 1998]. MC-LR treated mice showed increased liver weight due to massive intrahepatic hemorrhage and pooling of blood in the liver [Funari and Testai 2008b]. Elevation of serum activity of enzymes indicates that hepatocellular damage has been previously reported in both acute and chronic toxicity studies [Dawson 1998]. ...
Article
Full-text available
Environmental toxicants like microcystins are known to adversely impact liver physiology and lead to the increased risk for abnormal liver function and even liver carcinoma. Chaga mushroom (Inonotus obliquus) is reported for various properties mainly antibacterial, antiallergic, anti-inflammatory, antioxidant, and anticancer properties. This study was aimed to assess the effect microcystin (MC-LR) on histopathology of liver in mice and a preventive measure by using aqueous extract of Inonotus obliquus (IOAE). Adult Balb/c mice were administered with MC-LR at 20 μg/kg body weight, per day, intraperitoneal (i.p.) for 4 weeks. IAOE was treated to one group of MC-LR mice at 200 mg/kg body weight, per oral, for 4 weeks. Histological staining for liver structural details and biochemical assays for functions were assessed. The results of the study showed that MC-LR drastically reduced the body weight of mice which were restored close to the range of control by IAOE treatment. MC-LR exposed mice showed 1.9, 1.7 and 2.2-fold increase in the levels of SGOT, SGPT and LDH which were restored by IOAE treatment as compared to control (one-fold). MC-LR exposed mice showed reduced level of GSH (19.83 ± 3.3 μM) which were regained by IOAE treatment (50.83 ± 3.0 μM). Similar observations were noted for catalase activity. Histological examinations show that MC-LR exposed degenerative changes in the liver sections which were restored by IAOE supplementation. The immunofluorescence analysis of caspase-3 counterstained with DAPI showed that MC-LR led to the increased expression of caspase-3 which were comparatively reduced by IAOE treatment. The cell viability decreased on increasing the concentration of MC-LR with 5% cell viability at concentration of 10 μg MC-LR/mL as that of control 100% Cell viability. The IC50 was calculated to be 3.6 μg/ml, indicating that MC-LR is chronic toxic to AML12 mouse hepatocytes. The molecular docking interaction of NF-κB-NIK with ergosterol peroxidase showed binding interaction between the two and showed the plausible molecular basis for the effects of IAOE in MC-LR induced liver injury. Collectively, this study revealed the deleterious effects of MC-LR on liver through generation of oxidative stress and activation of caspase-3, which were prevented by treatment with IOAE.
... The role of cyanotoxins within cyanobacterial blooms may be to impede predation or could function as signaling compounds within the community (DeMott et al., 1991;Codd, 1995;Penn et al., 2014;Rastogi et al., 2014;Huisman et al., 2018). As stated, some of these byproducts have quite damaging effects on aquatic life; however, their effects on mammalian health have drawn the most attention Azevedo et al., 2002;Funari and Testai, 2008). Two well-known classes of these cyanotoxins are anatoxin-a and microcystins which target the nervous system and liver, respectively (Carmichael, 1992;Beltran and Neilan, 2000). ...
Preprint
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For millennia, cyanobacteria have evolved strategies for acclimatization to dynamic environments- this requires a molecular response system. Phosphate is essential for cellular integrity and metabolism, yet inorganic phosphate is often the limiting nutrient for most aquatic environments. This study characterizes two periplasmic phosphate-binding proteins, namely SphX and SphZ, which are essential for the functional response of the SphS-SphR signal transduction system in Synechocystis sp. PCC 6803 and incorporates both into a model. SphX offers a competitive role so as to ensure inorganic phosphate is not depleted from the environment at a faster rate than is necessary for metabolism and, therefore, hinders luxury uptake; whereas, SphZ, encoded by sll0540, is the auxiliary sensor necessary for the SphS response under phosphate limitation in tandem with a protein complex association with the phosphate-specific transport 2 system and the negative regulator, SphU. Cross-regulation between the pho regulon and the photosynthetic apparatus is presented as well as a parameterized analysis for low-temperature fluorescence emission spectroscopy.
... The first visual signs of cyanobacterial expansion appeared within days of the start of the sampling period, and due to their high growth rate, they soon dominated the other organisms in the planktonic community for an extremely long period-125 days. As well as being photoautotrophic, cyanobacteria are known to employ a range of ecophysiological strategies to outcompete eukaryotic algae and ensure their mass dominance in phytoplankton, such as the presence of gas vesicle aggregates, rapid cell division, the use of specific metabolic pathways, making them independent of aqueous forms of nitrogen, and finally the ability to accumulate P and trace metals [38][39][40]. ...
Article
Full-text available
Algal blooms are an emerging problem. The massive development of phytoplankton is driven partly by the anthropogenic eutrophication of aquatic ecosystems and the expansion of toxic cyanobacteria in planktonic communities in temperate climate zones by the continual increase in global temperature. Cyanobacterial harmful algal blooms (CyanoHABs) not only disturb the ecological balance of the ecosystem, but they also prevent the use of waterbodies by humans. This study examines the cause of an unusual, persistent bloom in a recreational, flow-through reservoir; the findings emphasize the role played by the river supplying the reservoir in the formation of its massive cyanobacterial bloom. Comprehensive ecosystem-based environmental studies were performed, including climate change investigation, hydrochemical analysis, and bio-assessment of the ecological state of the river/reservoir, together with monitoring the cyanobacteria content of phytoplankton. Our findings show that the persistent and dominant biomass of Microcystis was related to the N/P ratio, while the presence of Aphanizomenon and Dolichospermum was associated with the high-temperature end electric conductivity of water. Together with the increase in global temperature, the massive and persistent cyanobacterial bloom appears to be maintained by the inflow of biogenic compounds carried by the river and the high electric conductivity of water. Even at the beginning of the phenomenon, the reservoir water already contained cyanobacterial toxins, which excluded its recreational use for about half the year.
... They can disrupt the dynamics of aquatic ecosystems by reducing water clarity and leading to hypoxia and therefore death of fish and benthic invertebrates following the degradation of cyanobacterial blooms. The production of toxins may disrupt irrigated crops (Mhlanga et al. 2006), recreational uses and may constitute an acute health risk (Funari and Testai 2008) by inducing digestive or neurological diseases. ...
Article
Full-text available
The African continent hosts some of the largest freshwater systems worldwide, characterized by a large distribution and variability of surface waters that play a key role in the water, energy and carbon cycles and are of major importance to the global climate and water resources. Freshwater availability in Africa has now become of major concern under the combined effect of climate change, environmental alterations and anthropogenic pressure. However, the hydrology of the African river basins remains one of the least studied worldwide and a better monitoring and understanding of the hydrological processes across the continent become fundamental. Earth Observation, that offers a cost-effective means for monitoring the terrestrial water cycle, plays a major role in supporting surface hydrology investigations. Remote sensing advances are therefore a game changer to develop comprehensive observing systems to monitor Africa’s land water and manage its water resources. Here, we review the achievements of more than three decades of advances using remote sensing to study surface waters in Africa, highlighting the current benefits and difficulties. We show how the availability of a large number of sensors and observations, coupled with models, offers new possibilities to monitor a continent with scarce gauged stations. In the context of upcoming satellite missions dedicated to surface hydrology, such as the Surface Water and Ocean Topography (SWOT), we discuss future opportunities and how the use of remote sensing could benefit scientific and societal applications, such as water resource management, flood risk prevention and environment monitoring under current global change.
... The most commonly occurring cyanobacteria HABs (cyanoHABs) include members of the genera Microcystis, Dolichospermum (formerly Anabaena), and Aphanizomenon, among others [1][2][3]. CyanoHABs are capable of negatively affecting local ecosystems and drinking water resources in a variety of ways, most notably via the production of antagonistic toxins and taste and odor compounds [4][5][6]. The frequency, duration, and geographic range of cyanoHABs are increasing in many systems due ...
Article
Full-text available
Harmful algal blooms (HABs) are naturally occurring phenomena, and cyanobacteria are the most commonly occurring HABs in freshwater systems. Cyanobacteria HABs (cyanoHABs) negatively affect ecosystems and drinking water resources through the production of potent toxins. Furthermore, the frequency, duration, and distribution of cyanoHABs are increasing, and conditions that favor cyanobacteria growth are predicted to increase in the coming years. Current methods for mitigating cyanoHABs are generally short-lived and resource-intensive, and have negative impacts on non-target species. Cyanophages (viruses that specifically target cyanobacteria) have the potential to provide a highly specific control strategy with minimal impacts on non-target species and propagation in the environment. A detailed review (primarily up to 2020) of cyanophage lifecycle, diversity, and factors influencing infectivity is provided in this paper, along with a discussion of cyanophage and host cyanobacteria relationships for seven prominent cyanoHAB-forming genera in North America, including: Synechococcus, Microcystis, Dolichospermum, Aphanizomenon, Cylindrospermopsis, Planktothrix, and Lyngbya. Lastly, factors affecting the potential application of cyanophages as a cyanoHAB control strategy are discussed, including efficacy considerations, optimization, and scalability for large-scale applications.
... Traditionally, ingestion of water or dermal contact with bloom-affected waters were considered significant pathways of concern, with bloom advisories helping limit exposure (Merel et al., 2013;Buratti et al., 2017). However, it is apparent that cyanotoxins are now spreading through water, air, and food, making risk management difficult and bloom advisories less effective (Funari and Testai, 2008). Those abiding water advisory regulations remain at risk from air and food pathways. ...
Article
Management of cyanobacteria has become an increasingly complex venture. Cyanobacteria risks have amplified as society moves forward in an era of accelerated global changes. The cyanobacteria management “pendulum” has progressively shifted from prevention to mitigation, with management considerations often put forth after bloom formation. A universal system (i.e., one-size-fits-all management) fails to provide a management path forward due to the inherent complexities of each lake. A tailored management plan is needed: the right species at the right time in the right place (i.e., the three Rs). The three Rs represent a customizable management strategy that is flexible and informed by advances in scientific understanding to lower cyanobacteria-associated risks. Identifying thresholds in risk tolerance, where thresholds are defined by community collectives, is essential to frame cyanobacteria management targets and to decide on what management interventions are warranted.
... saxitoxins and microcystins) in fish samples collected from different lakes having blooms of blue green algae and in water. It has been shown that it caused human health risk to population [40] [41]. ...
Article
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Cyanotoxins are chemical compounds produced by cyanobacterial mats grown in aquatic ecosystems. These may threaten human health and aquatic organisms. Extraction of these toxins is usually associated with many difficulties due to their concentration in aquatic ecosystems. This study is designed to provide suitable and effective extraction procedures that can effectively extract low concentration cyanotoxin from water and bacterial cells. The methodology is based on collecting raw material of cyanobacterial mats from naturally growing sites such as Wadi Gaza along with 16 liters of aquatic surrounding media. The materials were left in the Lab for 24 - 48 h for stabilization of the mats. The floating mats were collected using special funnel and allowed to air drying. The aqueous phase was extracted by liquid/liquid extraction using solvent mixture (hexane + ethylacetate 10% w:w), and by liquid solid extraction using several types of organoclays complexes. The solid phase was extracted by acetone and ultrasonic device. Results showed some difficulties were associated with liquid/liquid extraction whereas effective and easy extraction procedures were obtained by liquid solid extraction using either organoclay complex or activated charcoal. In contrast combination of both solid materials did not show improvement in the extracted cyanotoxin. Thus we recommend the use of organoclays or activated charcoal separately for extracting cyanotoxin. Further improvement of extraction can be tailored by using a specific organoclay complex that has some similarity in the chemical structure between the pre-adsorbed organic cation to the clay mineral and the chemical structure of cyanotoxin.
... They also detected other strains that are able to degrade toxins or organic compounds such as Sphingomonas. The secondary metabolites produced by cyanobacteria might affect water quality and be harmful for plants, animals and humans [60,61]. High-throughput DNA sequencing can be used to discover new bacterial taxa which can degrade toxins or organic compounds and provide instructions to manage freshwater ecosystems. ...
Article
Full-text available
Changing ecological communities in response to anthropogenic activities and climate change has become a worldwide problem. The eutrophication of waterbodies in freshwater and seawater caused by the effects of human activities and nutrient inputs could result in harmful algae blooms (HABs), decreases water quality, reductions in biodiversity and threats to human health. Rapid and accurate monitoring and assessment of aquatic ecosystems are imperative. Environmental DNA (eDNA) analysis using high-throughput sequencing has been demonstrated to be an effective and sensitive assay for detecting and monitoring single or multiple species in different samples. In this study, we review the potential applications of eDNA approaches in controlling and mitigating eutrophication and HABs in freshwater and marine ecosystems. We use recent studies to highlight how eDNA methods have been shown to be a useful tool for providing comprehensive data in studies of eutrophic freshwater and marine environments. We also provide perspectives on using eDNA techniques to reveal molecular mechanisms in biological processes and mitigate eutrophication and HABs in aquatic ecosystems. Finally, we discuss the feasible applications of eDNA for monitoring biodiversity, surveying species communities and providing instructions for the conservation and management of the environment by integration with traditional methods and other advanced techniques.
... They also detected other strains that are able to degrade toxins or organic compounds such as Sphingomonas. The secondary metabolites produced by cyanobacteria might affect water quality and be harmful for plants, animals and humans [60,61]. High-throughput DNA sequencing can be used to discover new bacterial taxa which can degrade toxins or organic compounds and provide instructions to manage freshwater ecosystems. ...
Article
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Trapa japonica was observed to have inhibiting effects and could be used as a potential environment-friendly control strategy for cyanobacterial blooms in freshwater. However, the changes and effecting mechanisms in eukaryotic and prokaryotic communities by T. japonica are not yet clear. In this study, the effects of T. japonica on microbial communities were assessed in Lake Qionghai and Lake Erhai by 18S rRNA and 16S rRNA amplicon sequencing, respectively. The results showed that T. japonica can improve biodiversity and change the microbial community structures to varying degrees in both lakes. The alpha diversity indexes of microbial communities (e. g., Shannon, Sobs, Ace and Chao 1) were higher in the water inhabited by T. japonica (TJ group) than the water uninhabited by T. japonica (control) (P < 0.05). The PCoA results suggested that the microbial community compositions differed between the two groups (PERMANOVA P = 0.001). In Lake Qionghai, the relative abundances of dominant taxa and nutrients level showed little differences between the two groups. These may result from the homogenous water condition in Lake Qionghai. While the genera Cyanobium_PCC-6307, the majority of Cyanobacteria, decreased significantly in TJ group than control according to 16S rRNA gene sequencing. In Lake Erhai, environmental variables were distinctly affected by T. japonica, which was found to drive Cryptophyceae to become the main taxa through taxonomic analysis of 18S rRNA. Based on 16S rRNA gene sequencing, T. japonica reduced the relative abundance of Cyanobacteria, such as Planktothrix_NIVA-CYA_15 and Cyanobium_PCC-6307, by enriching cyanobactericidal bacteria and growth-inhibiting bacteria (e.g., Limnohabitans and Flavobacterium) and changing environmental parameters. Our results revealed that T. japonica acts in shaping microbial communities in lakes on the community level, shedding new lights on eutrophication mitigation, one of the most serious global ecological problems we are facing.
... Over a hundred such cyanotoxins are now recognized, broadly categorized based on their mode of action into three major groups affecting the skin (dermatoxins), the nervous system (neurotoxins) and the liver (hepatotoxins) (Roegner et al., 2014;Sanseverino et al., 2017). The most commonly encountered and monitored of these cyanotoxins are microcystins (MC), a family of hepatotoxic short peptides produced by several cyanobacterial species, and more specifically, an isomer known as MC-LR often produced by Microcystis aeruginosa (Funari and Testai, 2008;Testai et al., 2016). The high acute toxicity of MC-LR, combined with its carcinogenic properties, has led the World Health Organization to define a maximal daily intake of 0.04 μg MC-LR per kg body weight and to recommend that its concentration in water used for drinking or recreational purposes be kept below 1 μg/L (World Health Organization, 2011), a recommendation adopted as a regulatory standard by many countries (Chorus, 2012). ...
Article
Fouling of aquatic systems by harmful microalgal and cyanobacterial species are an environmental and public health concern. Microalgal bioreactors are engineered ecosystems for the cultivation of algal biomass to meet the increasing demand for alternative protein sources and algae-derived products. Such bioreactors are often open or semi-open ponds or raceways that are prone to contamination by contaminant photosynthetic microorganisms, including harmful cyanobacterial species (HCBs). HCBs affect the quality of products through the accumulation of off-flavours, reducing their acceptance by consumers, and through the production of several different toxins collectively known as cyanotoxins. The density of cultured species within the bioreactor environment creates difficulty in detecting low concentrations of contaminant cells, and there is currently no technology enabling rapid monitoring of contaminations. The present study demonstrates the potential of Low-Resolution Raman Spectroscopy (LRRS) as a tool for rapid detection of low concentrations of HCBs within dense populations of the spirulina (Arthrospira platensis) cultures. An LRRS system adapted for the direct measurement of raw biomass samples was used to assemble a database of Raman spectral signatures, from eight algal and cyanobacterial strains. This dataset was used to develop both quantitative and discriminative chemometric models. The results obtained from the chemometric analyses demonstrate the ability of the LRRS to detect and quantify algal and cyanobacterial species at concentrations as low as 103 cells/mL and to robustly discriminate between species at concentrations of 104 cells/mL. The LRRS and chemometric analyses were further able to detect the presence of low concentrations (103 cells/mL) of contaminating species, including the toxic cyanobacterium Microcystis aeruginosa, within dense (>107 cells/mL) spirulina cultures. The results presented provide a first demonstration of the potential of LRRS technology for real-time detection of contaminant species within microalgal bioreactors, and possibly for early detection of developing harmful algal blooms in other aquatic ecosystems.
Article
Harmful cyanobacterial blooms are increasing and becoming a worldwide concern as many bloom-forming cyanobacterial species can produce toxic metabolites named cyanotoxins. These include microcystins, saxitoxins, anatoxins, nodularins, and cylindrospermopsins, which can adversely affect humans, animals, and the environment. Different methods to assess these classes of compounds in vitro and in vivo include biological, biochemical, molecular, and physicochemical techniques. Furthermore, toxic effects not attributable to known cyanotoxins can be observed when assessing bloom material. In order to determine exposures to cyanotoxins and to monitor compliance with drinking and bathing water guidelines, it is necessary to have reliable and effective methods for the analysis of these compounds. Many relatively simple low-cost methods can be employed to rapidly evaluate the potential hazard. The main objective of this mini-review is to describe the assessment of toxic cyanobacterial samples using in vitro and in vivo bioassays. Newly emerging cyanotoxins, the toxicity of analogs, or the interaction of cyanobacteria and cyanotoxins with other toxicants, among others, still requires bioassay assessment. This review focuses on some biological and biochemical assays (MTT assay, Immunohistochemistry, Micronucleus Assay, Artemia salina assay, Daphnia magna test, Radionuclide recovery, Neutral red cytotoxicity and Comet assay, Enzyme-Linked Immunosorbent Assay (ELISA), Annexin V-FITC assay and Protein Phosphatase Inhibition Assay (PPIA)) for the detection and measurement of cyanotoxins including microcystins, cylindrospermopsins, anatoxin-a, saxitoxins, and nodularins. Although most bioassay analyses often confirm the presence of cyanotoxins at low concentrations, such bioassays can be used to determine whether some strains or blooms of cyanobacteria may produce other, as yet unknown toxic metabolites. This review also aims to identify research needs and data gaps concerning the toxicity assessment of cyanobacteria.
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Muitos corpos hídricos têm sido degradados devido à interferência humana. A poluição causada pelas atividades antrópicas vem comprometendo a qualidade da água e promovendo eventos de eutrofização, afetando toda estrutura trófica do ambiente, podendo assim acarretar na proliferação de cianobactérias tóxicas. Nesse sentido, o conhecimento sobre esses organismos é de grande importância, principalmente em corpos hídricos com usos múltiplos. Esta pesquisa representa uma revisão de trabalhos publicados envolvendo qualidade ambiental e ecolotoxicologia aquática, tendo como foco estudos relacionados às cianobactérias e cianotoxinas. Para o trabalho foram analisados livros textos e artigos publicados entre 2010 e 2020 em periódicos nacionais e internacionais. Na literatura publicada nos últimos anos são apresentadas as principais metodologias envolvidas na detecção e remoção de cianotoxinas, além de bioensaios ecotoxicológicos. Fica evidente a importância do tratamento de efluentes e controle das fontes de poluição difusas e pontuais no ecossistema promovendo a melhoria da qualidade da água e controle de cianobactérias.ABSTRACTCyanobacteria play an important role among producers in aquatic ecosystems, however when associated with eutrophication they become an ecological and public health problem. The problem involving cyanobacteria is the blooming of potentially toxic strains. The present work aims to present and discuss the problems related to the proliferation of cyanobacteria in limnological environments, and its consequences for dynamics in the environment and effects on environmental health. In this sense, knowledge about these organisms is of great importance, especially in water bodies with multiple uses. This research represents a review of published works involving environmental quality and aquatic ecotoxicology, focusing on studies related to cyanobacteria and cyanotoxins. For the present work, textbooks and articles published between 2010 and 2020 in national and internationaljournals were analyzed. In the literature published in recent years, the main methodologies involved in the detection and removal of cyanotoxins are presented, in addition to ecotoxicological bioassays. The study of cyanobacteria and their metabolites comprises an area of interest that reaches a greater dimension when impacts on the quality of water supply are evident, thus the importance of treating effluents and controlling pollution sources in the ecosystem is evident, promoting improvement and maintenance the quality of the water bodies.
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Microcystin-LR (MC-LR) has been identified to pose an increasing threat to the male reproductive system in vivo and in vitro studies with the objects like mammal animals, amphibians, aquatic organisms, etc. This review demonstrates the latest research advances of the male reproductive toxicity induced by MC-LR in detail, which mainly consists of two aspects, namely pathological injuries to testis and prostate, as well as the endocrine disruption. Apart from the direct toxicity to the male reproductive system, we also underline the transgenerational reproductive toxicity that prenatal exposure may pass on to male offspring. This review also demonstrates the interactive effects between MC-LR and other compounds, including synergistic effects with some toxicants and antagonistic effects with some medicine or chemical modification. In terms of the mechanisms of MC-LR-induced toxicity, we mainly focus on the epigenetic modification and non-coding RNAs (ncRNAs)-related mechanisms which have provided a new perspective.
Chapter
The hierarchically structured biominerals with excellent functions are produced by the regulation of organisms via biomineralization. The organic matrix and molecules regulate the inorganic mineralization to fabricate the delicate structural materials with the optimized properties. Inspired by natural biomineralization process, may biomimetic tactics have been developed for applications for materials and biomedicines, such as collagen re-mineralization, tooth and bone repairs. Biomineralization always highlights the control of inorganic materials by using organisms; reversely, the mineralized materials can also regulate or improve the living organisms. By conferring materials on to organism, the rationally designed organism-material hybrids can be created artificially, which are featured by their improved or new functions such as cell protection, bioenergy production, vaccine modification and cell treatment. Such a combination follows a materials-based biological modification, which would contribute a more comprehensive view of biomineralization as well as a new window for biological inorganic chemistry.
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Although groundwater is an important source for drinking and irrigation water worldwide, particularly in arid countries, they have been paid little attention to their contamination with microcystins (MCs) compared to surface water. Our study is the fourth one reporting existence of MCs in groundwater due to surface-water and groundwater interaction. Dissolved MCs in groundwater were found with higher concentrations in summer (0.1 to 0.84 μg L⁻¹) than in winter (0–0.06 μg L⁻¹), in association with MCs detected in nearby surface Nile water. The chronic daily intake (CDI) of MCs for both adults and children (0–0.003 μg kg⁻¹ body weight d⁻¹) in groundwater were lower than the chronic reference dose (RfD, 0.003 μg kg⁻¹ body weight d⁻¹) during winter, with hazard quotient less than 1. Conversely, CDI values exceeded the reference dose during summer for both adults (0.005–0.024 μg kg⁻¹ body weight d⁻¹) and children (0.012–0.05 μg kg⁻¹ body weight d⁻¹), with hazard quotient greater than 1. This indicates that MCs concentrations in these groundwater wells might pose adverse health effects to both adults and children during summer, but not during winter. The study provides evidence for the risk of cyanotoxins in groundwater close to cyanobacteria-contaminated surface water. Therefore, regular monitoring for cyanotoxins in groundwater supplies used for drinking-water should be undertaken when cyanobacteria bloom events are noted in nearby surface waters.
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Freshwater phytoplankton blooms are increasing in prevalence and there are conflicting views on whether trace metals limit growth of key species and thus bloom formation. The Taupō Volcanic Zone (TVZ), New Zealand, was formed by multiple eruptions of a super-volcano which emitted rhyolitic tephra leaving lakes depleted in trace metals. This provides an opportunity to test the potential of trace metal limitation on freshwater phytoplankton growth under nanomolar concentrations. Growth responses of two algal species isolated from Lake Taupō, Dolichospermum lemmermannii (cyanobacteria) and Fragilaria crotonensis (diatom), to six biologically important trace metals (manganese, iron, zinc, cobalt, copper and molybdenum) were examined in culture experiments. These were conducted at three trace metal concentrations: (1) ambient, (2) two-times ambient, and (3) ten-times ambient concentrations in Lake Taupō. Elevated concentrations of iron significantly increased growth rates and maximum cell densities in D. lemmermannii, whereas no significant concentration dependence was observed for other trace metals. Fragilaria crotonensis showed no significant growth response to elevated concentrations of trace metals. These results highlight the importance of iron as a growth limiting nutrient for cyanobacteria and indicate that even small (twofold) increases in Fe concentrations could enhance cyanobacteria growth rates in Lake Taupō, potentially causing cyanobacterial blooms.
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In the context of increasing occurrences of toxic cyanobacterial blooms worldwide, their monitoring in Belgium is currently performed by regional environmental agencies (in two of three regions) using different protocols and is restricted to some selected recreational ponds and lakes. Therefore, a global assessment based on the comparison of existing datasets is not possible. For this study, 79 water samples from a monitoring of five lakes in Wallonia and occasional blooms in Flanders and Brussels, including a canal, were analyzed. A Liquid Chromatography with tandem mass spectrometry (LC-MS/MS) method allowed to detect and quantify eight microcystin congeners. The mcyE gene was detected using PCR, while dominant cyanobacterial species were identified using 16S RNA amplification and direct sequencing. The cyanobacterial diversity for two water samples was characterized with amplicon sequencing. Microcystins were detected above limit of quantification (LOQ) in 68 water samples, and the World Health Organization (WHO) recommended guideline value for microcystins in recreational water (24 µg L−1) was surpassed in 18 samples. The microcystin concentrations ranged from 0.11 µg L−1 to 2798.81 µg L−1 total microcystin. For 45 samples, the dominance of the genera Microcystis sp., Dolichospermum sp., Aphanizomenon sp., Cyanobium/Synechococcus sp., Planktothrix sp., Romeria sp., Cyanodictyon sp., and Phormidium sp. was shown. Moreover, the mcyE gene was detected in 75.71% of all the water samples.
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In addition to obvious negative effects on water quality in eutrophic aquatic ecosystems, recent work suggests that cyanobacterial harmful algal blooms (CHABs) also impact air quality via emissions carrying cyanobacterial cells and cyanotoxins. However, the environmental controls on CHAB-derived aerosol and its potential public health impacts remain largely unknown. Accordingly, the aims of this study were to 1) investigate the occurrence of microcystins (MC) and putatively toxic cyanobacterial communities in particulate matter ≤ 2.5 μm in diameter (PM2.5), 2) elucidate environmental conditions promoting their aerosolization, and 3) identify associations between CHABs and PM2.5 concentrations in the airshed of the Chowan River-Albemarle Sound, an oligohaline, eutrophic estuary in eastern North Carolina, USA. In summer 2020, during peak CHAB season, continuous PM2.5 samples and interval water samples were collected at two distinctive sites for targeted analyses of cyanobacterial community composition and MC concentration. Supporting air and water quality measurements were made in parallel to contextualize findings and permit statistical analyses of environmental factors driving changes in CHAB-derived aerosol. MC concentrations were low throughout the study, but a CHAB dominated by Dolichospermum occurred from late June to early August. Several aquatic CHAB genera recovered from Chowan River surface water were identified in PM2.5 during multiple time points, including Anabaena, Aphanizomenon, Dolichospermum, Microcystis, and Pseudanabaena. Cyanobacterial enrichment in PM2.5 was indistinctive between subspecies, but at one site during the early bloom, we observed the simultaneous enrichment of several cyanobacterial genera in PM2.5. In association with the CHAB, the median PM2.5 mass concentration increased to 8.97 μg m⁻³ (IQR = 5.15), significantly above the non-bloom background of 5.35 μg m⁻³ (IQR = 3.70) (W = 1835, p < 0.001). Results underscore the need for highly resolved temporal measurements to conclusively investigate the role that CHABs play in regional air quality and respiratory health risk.
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The invasive nature of cyanotoxin-producing cyanobacteria and the adverse effects concerning their toxic impacts have gained heightened scientific attention of late. The persistence of cyanotoxins in irrigation water leads to bioaccumulation in plants, the development of phytotoxic effects, and the threat of groundwater contamination. The accumulation of cyanotoxins in plants is caused by several factors leading to severe toxic effects, including reduced plant growth and seed germination, enhanced oxidative stress, lowered rate of mineral uptake, decreased photosynthetic efficiency, and loss of chlorophyll content. The uptake and accumulation of cyanotoxins in plants can be concentration-dependent, as reported in a myriad of studies. Even though several studies have reported phytotoxic effects of cyanotoxin contamination, field-related studies reporting phytotoxic effects are particularly inadequate. Paradoxically, at realistic conditions, some plants are reported to be tolerant of cyanotoxins. Furthermore, the breadth of adverse impacts of cyanotoxins on human health is significant. Cyanotoxins cause major health effects including cancer, oxidative stress, organelle dysfunction, DNA damage, and enzyme inhibition. This review intends to present compelling arguments on microcystins (MCs), cylindrospermopsins (CYN), β-N-methylamino-L-alanine (BMAA), and anatoxin-a (ANTX-a), their uptake and accumulation in crop plants, phytotoxic effects on plants, and potential health implications to humans. The accumulation of cyanotoxins implants cultivated as food crops, resulting in phytotoxic effects and adverse impacts on human health are serious issues that require scientific inputs to be addressed.
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Health risks of chronic exposure to microcystins (MCs), a family of aquatic contaminants produced mainly by cyanobacteria, are critical yet unsolved problems. Despite a few epidemiological studies, the metabolic profiles of humans exposed to MCs remain unknown, hindering the deep understanding of the molecular toxicity mechanisms. Here, sensitive nuclear magnetic resonance (NMR)- and liquid chromatography−mass spectrometry (LC−MS)-based metabolomics were applied to investigate the serum metabolic profiles of humans living near Lake Chao, where toxic cyanobacterial blooms occur annually. MCs were positively detected in 92 of 144 sera by ultra-high-pressure liquid chromatography−tandem mass spectrometry (UPLC−MS/MS) with a median concentration of 0.016 μg/L. The estimated daily intake (0.15−0.27 μg MC-LReq/day) was less than the tolerable daily intake (TDI, 2.4 μg MC-LR for 60 kg adults) recommended by the World Health Organization (WHO). Obvious disruptions of the amino acid metabolism were confirmed and played important roles in renal impairments associated with serum MC burdens. Chronic oral exposure of mice to 30 μg MC-LR/kg body mass, which is less than the no observed adverse effect level, also led to obvious renal lesions and metabolic dysfunction. These observations provide the first evidence of metabolic disturbance of humans exposed to MCs and indicate that the WHO’s TDI value determined traditionally should be lessened to protect human health effectively.
Chapter
Algal blooms, especially blue-green algae, are globally aquatic ecosystems and cause a gradual degeneration of the water's self-purification function. High temperatures and growing nutrient loads lead to excessive growth of algae. These mass developments affect water quality because they produce toxins and reduce oxygen concentration, sometimes leading to the death of fish and other aquatic organisms. In contrast, some fungal parasites help to slow down algal growth. The blooms can become sick when for instance, infected by fungal parasites. It has been found that these infections kill the algal blooms and make them easier to consume for their natural predators. Because of attributes, strategies to control algal development by organisms can be partitioned into two: techniques dependent on single-species microorganisms and techniques dependent on microbial aggregates, and four sorts: techniques for the fast decline of algal cells thickness (e.g., alga-bacterium and alga-parasite bio-flocculation), a hindrance to unsafe algal development, lysis of harmful algal growth (for example algicidal microorganisms, organisms, and actinomycete), and techniques dependent on microbial aggregates (periphytons and biofilms)—an integrative process of “flocculation-lysis-degradation-nutrients regulation. Harmful algal bloom possessions on water systems persuaded researchers to analyze appropriate methods to impede and regulate them. This chapter is designed to determine the fungal mechanism to control the huge mess of algal blooms affecting the environment and living organisms' health.
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Clean, fresh, and safe drinking water is essential to human health and well-being. Occasionally, biological contaminants taint surface water quality used for human consumption and recreation. Microcystins (MCs) and nodularins (NODs) are toxic monocyclic peptides produced by cyanobacteria in fresh and brackish water. These secondary metabolites can reach hazardous concentrations, impairing surface drinking water supplies and thereby increasing the risk of exposure to consumers. Inconsistent screening of MCs and NODs is not uncommon in drinking water systems and no provisional guidance value has been established in Florida to protect community and public health. We performed a case study of two Florida lakes supplying drinking water to adjacent communities for the purpose of monitoring MCs and NODs over the potential peak algae bloom season (June-August). An indirect competitive enzyme-linked immunosorbent assay (icELISA) was employed to analyze concentrations of total MCs and NODs in environmental water samples from Lake Manatee and Lake Washington. Toxin concentrations were similar in each lake, averaging 0.19 μg/L. The highest toxin concentration (0.46 μg/L) was reported in Lake Manatee at Site 15, a location where other toxin concentrations demonstrated statistical significance with toxins detected at Sites 6 (p = 0.014) and 8 (p = 0.011). Inferential analyses from the Kruskal-Wallis H Test revealed a statistically significance difference in toxin concentrations by sampling month within the two Floridian drinking water systems (p < 0.001). Furthermore, phosphate and nitrite concentrations strongly correlated with total MCs and NODs in each lake (p < 0.01). Although results indicate a low probable health risk from cyanotoxins, more research is needed to understand the intrinsic nature of MCs and NODs by examining their prevalence, distribution, and dynamics in surface drinking water supplies serving nearby communities.
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Aquatic animals are exposed to various cyanobacterial products released concomitantly to the environment by decaying blooms. Although there exist results on the toxicity of cyanobacterial extracts little is known on the influence of pure oligopeptides or their mixtures and elucidated mechanisms of behavioral toxicity in zooplanktonic organisms. Therefore, the aim of the present study was to assess the effects of single and mixed pure cyanobacterial oligopeptides: microginin FR-1 (MG-FR1), anabaenopeptin-A (ANA-A) and microcystin-LR (MC-LR) at various concentrations on the swimming behavior and catecholamine neurotransmitter activity, muscular F-actin structure, DNA nuclear content and cell viability of a model rotifer Brachionus calyciflorus. Swimming behavior was analyzed with the use of video digital analysis. Fluorescent microscopy imaging was used to analyze neuromotoric biomarkers in the whole organisms: neuromediator release (by staining with EC517 probe), muscle F-actin filaments (by staining with blue phalloidin dye). DNA content and cytotoxicity was also determined by Hoechst 34580 and propidium iodide double staining, respectively. The results showed that single oligopeptides inhibited all the tested endpoints. The binary mixtures induced synergistic interaction on swimming speed except for MG-FR1 +MC-LR which was nearly additive. Both binary and ternary mixtures also synergistically degraded F-actin and triggered cytotoxic effects visible in the whole organisms. Antagonistic inhibitory effects of all the binary mixtures were found on catecholamine neurotransmitter activity, however the ternary mixture induced additive toxicity. Antagonistic effects of both binary and ternary mixtures were also noted on nuclear DNA content. The results of the study suggest that both depression of neurotransmission and impairment of muscle F-actin structure in muscles may contribute to mechanisms of Brachionus swimming speed inhibition by the tested single cyanobacterial oligopeptides and their mixtures. The study also showed that natural exposure of rotifers to mixtures of these cyanobacterial metabolites may result in different level of interactive toxicity with antagonistic, additive synergistic effects depending on the variants and concentrations present in the environment.
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When administered to mice, either orally or intraperitoneally, extracts of the cyanobacterium Cylindrospermopsis raciborskii strain AWT 205 induced dose-dependent liver and kidney damage. Liver damage was generally centrilobular, becoming more severe and generalized as the dose increased. Damaged hepatocytes were characterized by increased cellular vacuolation, intercellular spaces, and darker nuclear and cytoplasmic staining. Kidney damage was characterized by a reduction in the number of erythrocytes in the glomerulus and an increase in the space around the glomerulus, increased diameter of the tubule lumina, proximal tubule epithelial necrosis, and the presence of proteinaceous material in the distal tubules. Transmission electron microscopy of the same tissue revealed epithelial cell necrosis in the proximal tubules, suggesting the material accumulating in the distal tubules was in part cell debris from this necrosis. The nature, location, and time course of histological damage were similar for oral and intraperitoneal administration, with maximum damage being observed 2-3 days after treatment. The LD50 (24 h) for intraperitoneally administered Cylindrospermopsis preparations ranged from 50 to 110 mg dry weight of lysed cells per kilogram, whereas the LD50 (7 days) ranged between 20 and 65 mg/kg depending upon the batch examined. In contrast, oral administration of 1400 mg/kg, while inducing clear histological damage, was not fatal to any of the animals used in the study. The extent of comparative severity of damage to the liver and kidneys caused by different batches of Cylindrospermopsis of similar cylindrospermopsin content varied considerably, implying the presence of more than one toxin.
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An enzyme-linked immunosorbent assay (ELISA) was developed for direct quantitation of microcystins (MCs), a group of freshwater cyanobacterial toxins. An anti-MC monoclonal antibody exhibiting broad cross-reactivity to major MC derivatives was used. The detection limit and linear range of the ELISA standard curve with microcystin-(leucine-arginine) (MCLR), a variant of MCs, were 20 and 20-500 pg/mL, respectively. For analysis of MC released from cyanobacterial cells, water sample filtered through a glass fiber filter was applied directly to ELISA. For analysis of total MC (released MC plus intracellular MC), intracellular toxin was extracted by freeze-thawing twice before filtration. Mean recovery of MCLR added to tap water and toxin-free environmental water was 101%, with a coefficient of variation (CV) of 7.3% at toxin levels of 20-500 pg/mL. Mean recovery of MCLR added to toxin-free cyanobacterial extracts was 93%, with a CV of 12.5% at toxin levels of 50-500 pg/mL. At 20 pg/mL, an increasing matrix effect on assay variance was observed; therefore, both released MC and total MC were measured in the range 50-500 pg/ mL. Comparative studies with a liquid chromatographic (LC) method showed that the ELISA gives a reliable correlation with LC for analysis of MC in water extracts of natural blooms and cultured cyanobacterial cells (r = 0.98). The ELISA was applied to water samples collected from lakes and ponds in Japan. In 4 of 13 and 12 of 17 samples, 81-800 pg released MC/mL and 64-94 000 pg total MC/mL were detected, respectively. By LC separation followed by the ELISA analysis, the presence of MCLR, microcystin-arginine-arginine, and microcystin-tyrosine-arginine were confirmed in 4 ELISA-positive samples selected randomly. The newly developed ELISA is a reliable and powerful method for mass monitoring of MC levels in environmental water.
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The cyanobacteria are photosynthetic prokaryotes possessing the ability to synthesize chlorophyll a and at least one phycobilin pigment; typically water acts as the electron donor during photosynthesis, leading to the release of oxygen. They are by far the largest group of photosynthetic prokaryotes, as judged by their widespread occurrence, frequent abundance, and morphological diversity. Not only are they represented at the present day in most types of illuminated environment, except for those at lower pH values, but they have one of the longest geological records (Schopf and Walter, 1982). Much of the earth’s original atmospheric oxygen was probably formed by organisms quite similar to modern cyanobacteria (Knoll, 1985) and they are still responsible for a considerable proportion of photosynthetic oxygen evolution in the oceans.
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The continuing increase in numbers of toxic algal species coupled with increased incidences of blooms of these species presents a constant threat to public health worldwide. Traditionally, only filter‐feeding molluscs that concentrate these toxic algae are considered in monitoring programs for paralytic (PSP), diarrhetic (DSP), neurotoxic (NSP), and amnesic (ASP) shellfish poisons; however, increasing attention is being paid to higher‐order consumers such as carnivorous gastropods and crustaceans. This review summarizes data on accumulation of phycotoxins by “non‐target”; species frequently consumed by humans, and stresses the importance of including such species in routine monitoring programs, especially in regions where nontraditional spedes are being harvested.
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Reemerging health problem in Madagascar : mass food poisoning following seafoods consumption. Epidemiological, clinical and toxicological aspects of outbreaks notified from January 1993 to January 1998". During these 5 last years, 19 outbreaks of mass seafoods poisoning were notified at the malagasy Health Ministry. This public health problem, which the administration had forgotten during still 30 years, had mobilised the Health Ministry since 1994 to plan monitoring and primary prevention measures. The marine animals which caused this problem are multiple : sharks, turtles, fishes and mollusca. Poisoning by sharks consumption were most frequent : they give predominant neurological signs. The clinical status varies from serious situation as in Manakara outbreak in 1993 with a lethality of about 30% to mild forms which recall rather the ciguatera as in outbreak of Toliara in 1997 with no death. In the majority of outbreaks, marine toxins were isolated. Popisoning by turtles con,sumption were not rare. Two turtles species were essentially found : Eretmochelys imbricata and Chelonia mydas. In half outbreaks, mucous and neurological signs considered as pathognomonical signs in chelonitoxism were found. Poisoning by fishes consumption were less frequent. They were caused by different species. Baudruche fish (Arothron sp) is fish known for its toxicity risk named clupeotoxism; the outbreak of Antalaha permitted to approach the toxin that could be palytoxin. The crimson snapper (Lutjanus erythropterus, Lutjanidae) gives a clinical status that could evoke the ciguatera. In these poisoning by fishes consumption, none of the clinical status was evocative of scombroïd poisoning. Poisoning by mollusca consumption were rare. Clinical status could evoke saxitoxin and lyngbia toxins poisoning outbreaks. Mots-clés : Food poisoning - Marine toxins - Sharks - Turtle - Fishes - Mollusca - Ichtyotoxism - Chelonitoxism - MADAGASCAR.
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Cyanobacteria possess many adaptations to develop population maxima or “blooms” in lakes and reservoirs. A potential consequence of freshwater blooms of many cyanobacterial species is the production of potent toxins, including the cyclic hepatotoxins, microcystins (MCs). Approximately 70 MC variants have been isolated. Their toxicity to humans and other animals is well studied, because of public health concerns. This review focuses instead on the production and degradation of MCs in freshwater environments and their effects on aquatic organisms. Genetic research has revealed the existence of MC-related genes, yet the expression of these genes seems to be regulated by complex mechanisms and is influenced by environmental factors. In natural water bodies, the species composition of cyanobacterial communities and the ratio of toxic to nontoxic species and strains are largely responsible for total toxin production. Cyanobacteria play vital roles in aquatic food webs, yet production, accumulation, and toxicity patterns of MCs within aquatic food webs remain obscure.
Article
Cylindrospermopsin is a powerful hepatotoxin produced by the cyanobacterium Cylindrospermopsis raciborskii . It is considered a potential threat to livestock, wildlife, and humans, and is the suspected cause of an outbreak of hepatoenteritis on Palm Island, Queensland, Australia, and various stock poisoning incidents around Australia. In this study, the stability of cylindrospermopsin was investigated using different parameters, including visible and UV light, sunlight, temperature and pH. Cylindrospermopsin decomposes rapidly (half‐life of 1.5 h) when exposed to sunlight in an algal extract solution; however, no decomposition was recorded in pure cylindrospermopsin and Milli‐Q water solutions. Cylindrospermopsin decomposes slowly in temperatures ranging from 4 to 50°C at pH 7. After 10 weeks at 50°C, cylindrospermopsin had degraded to 57% of the original concentration. This degradation was accompanied by an increase in another compound which is believed to be structurally related to cylindrospermopsin. Boiling does not cause a significant degradation of cylindrospermopsin within 15 min. Initial investigations indicate that cylindrospermopsin is degraded slowly under artificial light ranging from 42, 29, and 9 μE m⁻¹ s⁻¹ and in darkness. Degradation of cylindrospermopsin was not affected by changes in pH. Experiments were performed in sterile conditions. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 155–161, 1999
Article
When administered to mice, either orally or intraperitoneally, extracts of the cyanobacterium Cylindrospermopsis raciborskii strain AWT 205 induced dose‐dependent liver and kidney damage. Liver damage was generally centrilobular, becoming more severe and generalized as the dose increased. Damaged hepatocytes were characterized by increased cellular vacuolation, intercellular spaces, and darker nuclear and cytoplasmic staining. Kidney damage was characterized by a reduction in the number of erythrocytes in the glomerulus and an increase in the space around the glomerulus, increased diameter of the tubule lumina, proximal tubule epithelial necrosis, and the presence of proteinaceous material in the distal tubules. Transmission electron microscopy of the same tissue revealed epithelial cell necrosis in the proximal tubules, suggesting the material accumulating in the distal tubules was in part cell debris from this necrosis. The nature, location, and time course of histological damage were similar for oral and intraperitoneal administration, with maximum damage being observed 2–3 days after treatment. The LD50 (24 h) for intraperitoneally administered Cylindrospermopsis preparations ranged from 50 to 110 mg dry weight of lysed cells per kilogram, whereas the LD50 (7 days) ranged between 20 and 65 mg/kg depending upon the batch examined. In contrast, oral administration of 1400 mg/kg, while inducing clear histological damage, was not fatal to any of the animals used in the study. The extent of comparative severity of damage to the liver and kidneys caused by different batches of Cylindrospermopsis of similar cylindrospermopsin content varied considerably, implying the presence of more than one toxin. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 143–150, 1999
Article
Blooms of cyanobacteria are known to have caused poisoning in fish, waterfowl, animals and man. One of the low molecular weight toxins responsible for this is the neurotoxin anatoxin-a which has been detected in reservoirs used for domestic water supplies. While the acute behaviour of this alkaloid is clear, there is uncertainty regarding the effects on man of ingestion of anatoxin-a at low levels over longer periods. In order to assess this risk, a series of in vitro and in vivo experiments were undertaken to investigate the pharmacology, sub-acute toxicity, and the teratogenicity of anatoxin-a in the mouse. The results of this work were as follows: (1) Pharmacological screening studies confirmed that anatoxin-a is a potent nicotinic agonist which can produce neuromuscular blockade and death by respiratory arrest. Recovery from a single sub-lethal dose is rapid and complete; (2) Repeated sub-lethal oral administration over 28 days in the mouse did not produce any reliable evidence of treatment-related toxicity; (3) From a preliminary screening study anatoxin-a does not appear to be a developmental toxicant in the mouse. These results indicate that a guideline value for anatoxin-a in drinking water of 1 μg l⁻¹ would provide an adequate margin of safety.
Article
The intact Adda was isolated from microcystin-LR by a microbial degradation using an isolated Sphingomonas strain, B-9. The reaction of microcystin-LR with cell extract of this strain proceeded smoothly to give the final degradation product by way of two intermediates, linearized microcystin-LR and a tetrapeptide. The purified Adda that was structurally characterized using various spectral data did not show the toxicity to mice or inhibition to protein phosphatase activity in contrast to the native toxin.
Article
In a laboratory-scale trial, we studied the removal of saxitoxins from water by ozone, granular activated carbon (GAC) and H2O2, and considered the implications of residual toxicity for compliance with the Australian drinking water standards. Cell-free extracts of Anabaena circinalis were added to raw, untreated drinking water obtained from a water supply reservoir to provide a toxicity of 30 mug (STX equivalents) l(-1). Ozone alone, or in combination with H2O2, failed to destroy the highly toxic STX and GTX-2/3, and only partially destroyed dc-STX, and the low-toxicity C-toxins and GTX-5. In all cases, the toxicity of the water was reduced by less than 10%. GAC removed all of the STX, dc-STX and GTXs, but only partially removed the C-toxins. However, the residual toxicity was reduced to the suggested Australian drinking water guideline concentration of 3 mug (STX equivalents) l(-1) without O-3 pre-treatment. Modelling the spontaneous chemical degradation of residual C-toxins following treatment shows that residual toxicity Could increase to 10 mug l(-1) after 11d due to formation of dc-GTXs and would then gradually decay. In all, residual toxicity would exceed the Australian drinking water guideline concentration for a total of 50d.
Article
A peptide which on hydrolysis was shown to consist of equimolar amounts of L-methionine, L-tyrosine, D-alanine, D-glutamic acid, erythro β-methyl aspartic acid and methylamine was isolated from a bloom of Microcystis aeruginosa. The peptide was shown to be toxic to mice, rats and sheep when administered orally or intraperitoneally (LD50 in mice = 0.056 mg/kg i.p.). The liver was the target organ, by electron microscopy changes could first be observed 15 minutes after injection; death, which followed within 1-3 hours, was due to the massive pooling of blood in the liver, following destruction of the sinusoids. Repeated inoculations of mice with sublethal doses of the peptide led to hepatocyte necrosis. In vitro, the purified toxin was shown to have no haemagglutination activity, it also had no specific effect on major metabolic functions. Incubation of freshly isolated hepatocytes with the peptide toxin caused the cells to lose their spherical shape and to become deformed; characteristic protrusions on the surface of the cells could be seen by light as well as by electron microscopy. The deformation could first be seen 5 minutes after addition of toxin to hepatocytes, and it increased with time. The response was also dose dependent; 30 ng/ml was sufficient to cause the deformation of half the cells. The affected hepatocytes did not release aspartate aminotransferase into the suspension medium, nor did they show increased trypan blue uptake or cell lysis. This rapid, in vitro effect will facilitate the study of the mechanism of action of the peptide toxin from Microcystis aeruginosa.
Chapter
Inflammation is an essential host response to the invasion of tissues by pathogens, and plays a profound role in health and disease. The presence of bacteria in mammalian tissues elicits an inflammatory, response, which involves a complex series of reactions, including increased blood vessel permeability, exudation of fluids, and migration of leucocytes into the inflammatory focus, which results in phagocytosis and killing of the micro-organisms. The response is very rapid and is initially mediated by innate immune reactions, which do not usually require an adaptive response. In most instances inflammatory response leads to the elimination of the microorganisms without producing clinically detectable signs of inflammation. In severe infections, however, inflammatory reactions may contribute to pathological processes that culminate in multiple organ failure, shock and death. One of the critical roles of innate immunity is to recognize the microbial invaders. This is the basic concept underlying innate immunity. Given the impressive recent development in the understanding of the mechanisms of innate immunity, in this chapter attention is focused on molecules such as LBP, CD14 and Toll-like receptors, which play a central role in innate immunity.