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This work represents the first study of its kind that was conducted to evaluate changes in lipid metabolic networks following a balneation exposure of adult zebrafish to MCLR (microcystin-leucine-arginine) and MCRR (microcystin-arginine-arginine) at a sublethal dose (10 μg L(-1)) for a period of 30 days. Following the exposure to MCLR and MCRR, gills, liver, intestine, and brain tissues were harvested for metabolite extraction. Extracted metabolites were detected using qTOF-LC-MS (time-of-flight-liquid chromatography-mass spectrometry). Metabolites were identified using Kegg pathways. The identified metabolites are shown on lipid biochemical maps to demonstrate major perturbations in the metabolic machinery. Results showed that most of the metabolic pathways under the lipid class were affected in different tissues of zebrafish following the exposure to MCLR and MCRR (10 μg L(-1) for 30 days). The kind and flux of metabolic perturbations varied among different tissues of the organs after the exposure to MCLR and MCRR with the tissues of gills being the most affected. Among the various lipid pathways, cholesterol synthesis was affected significantly as observed from the highest number of perturbed metabolites in that pathway. Cholesterol is responsible for synthesis of steroid hormones and bile acids, which have been recognized as endocrine signaling molecules. Disruption in the synthesis of these compounds following MCLR/MCRR exposure suggests that MCs are capable of causing endocrine disruption among aquatic organisms even under sublethal conditions. Apart from cholesterol synthesis, various other metabolic pathways belonging to the class of essential fatty acids and lipid oxidation were also observed to be perturbed following a balneation exposure of zebrafish to MCLR/MCRR.

Microcystins (MCs) are algal toxins produced intracellularly within the algal cells, and are subsequently released into the aquatic systems. An increase in the frequency and intensity of occurrence of harmful algal blooms has directed the global attention towards the presence of MCs in aquatic systems. The effects of MCs on fish have been verified in a number of studies including histological, biochemical and behavioral effects. The toxicological effects of MCs on different organs of fish are related to the exposure route (intraperitoneal injection, feeding or immersion), the mode of uptake (passive or active transport) as well as biotransformation and bioaccumulation capabilities by different organs. This paper reviews the rapidly expanding literature on the toxicological evaluation of MCs in fish from both field studies and controlled laboratory experimental investigations, integrates the current knowledge available about the mechanisms involved in MC-induced effects on fish, and points out future research directions from a cross-disciplinary perspective. In addition, the need to carry out systematic fish toxicity studies to account for possible interactions between MCs and other environmental pollutants in aquatic systems is discussed., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Graphene oxide (GO) was employed in the present study for removal of two commonly occurring algal toxins, microcystin-LR (MC-LR) and microcystin-RR (MC-RR), from water. The adsorption performance of GO was compared to that of commercially available activated carbon. Further, adsorption experiments were conducted in the presence of other environmental pollutants to understand the matrix effects of contaminated water on the selective adsorption of MC-LR and MC-RR onto GO. The environmental pollutants addressed in this study included different anions (nitrate NO3-, nitrite NO2-, sulphate SO4(2-), chloride (Cl(-)), phosphate PO4(3-) and fluoride (F(-))) and cations (sodium (Na(+)), potassium (K(+)), magnesium (Mg(2+)) and calcium (Ca(2+))). GO showed very a high adsorption capacity of 1700 μg/g for removal of MC-LR and 1878 μg/g for MC-RR while the maximum adsorption capacity obtained with the commercial activated carbon was 1481.7 μg/g and 1034.1 μg/g for MC-LR and MC-RR, respectively. The sorption kinetic experiments revealed that more than 90% removal of both MC-LR/RR was achieved within 5 min for all the doses studied (500, 700 and 900 μg/L). GO could be reused as an adsorbent following ten cycles of adsorption/desorption with no significant loss in its adsorption capacity., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Microcystins (MCs) interact with environmental contaminants as well as various other congeners of the MC family in the natural environment and with antioxidants in the exposed organisms. These interactions are likely to modify the toxicological behavior of MCs at the cellular level. The present study was conducted to determine the toxicological response of extracellular MCs in aquatic systems under environmentally relevant conditions. Microcystin-leucine-arginine (MCLR) and microcystin-arginine-arginine (MCRR) were introduced at different concentrations in a single-component (MCLR or MCRR) or dual-component (MCLR and MCRR) system to zebrafish embryos in the presence of inorganic elements (Hg, As, Pb, and Cd) and nutrient species (NO3 (-) , PO4 (3-) , and Cl(-1) ). Hatchability, heart rate, and mortality of zerbrafish embryos were monitored together with changes in the activity of glutathione-S-transferase (GST) to evaluate their response on exposure to MCLR and MCRR. There was a significant reduction in all these parameters at higher doses of MCLR and MCRR (>100 ng/mL), implying bioaccumulation of these MCs in embryos and adverse effects on early development stages of the fish. It was further observed that PO4 (3-) and Cl(-) enhanced the toxic effects of MCLR and MCRR while NO3 (-) attenuated their toxic effects. In contrast, all 4 toxic elements together increased the toxicity of MCLR and MCRR to embryos compared with their single-component counterparts. Thus, the toxic effects of MCs depend not only on their relative environmental concentrations, but also on those of other environmental pollutants and the levels of antioxidants in exposed organisms., (Copyright © 2013 SETAC.)

Introduction: Microcystins (MCs; cyclic heptapeptides) are produced by freshwater cyanobacteria and cause public health concern in potable water supplies. There are more than 60 types of MCs identified to date, of which MC-LR is the most common found worldwide. For MC-LR, the WHO has established a threshold value of 1 μg L(-1) for drinking water. The present MCs removal methods such as coagulation, flocculation, adsorption, and filtration showed low efficiency for removing dissolved MC fraction from surface waters to the stipulated limit prescribed by WHO based on MC health impacts. The search for cost-effective and efficient removal method is still warranted for remediation of dissolved MC-LR-contaminated water resources., Materials and Methods: Molecularly imprinted polymer (MIP) adsorbent has been prepared using non-covalent imprinting approach. Using MC-LR as a template, itaconic acid as a functional monomer, and ethylene glycol dimethacrylate as a cross-linking monomer, a MIP has been synthesized. Computer simulations were used to design effective binding sites for MC-LR binding in aqueous solutions. Batch binding adsorption assay was followed to determine binding capacity of MIP under the influence of environmental parameters such as total dissolved solids and pH., Results and Discussion: The adsorptive removal of MC-LR from lake water has been investigated using MIPs. The MIP showed excellent adsorption potential toward MC-LR in aqueous solutions with a binding capacity of 3.64 μg mg(-1) which is about 60% and 70% more than the commercially used powdered activated carbon (PAC) and resin XAD, respectively. Environmental parameters such as total organic carbon (represented as chemical oxygen demand (COD)) and total dissolved solids (TDS) showed no significant interference up to 300 mg L(-1) for MC-LR removal from lake water samples. It was found that the binding sites on PAC and XAD have more affinity toward COD and TDS than the MC-LR. Further, the adsorption capacity of the MIP was evaluated rigorously by its repeated contact with fresh lake water, and it was found that the adsorption capacity of the MIP did not change even after seven adsorption/desorption cycles. The contaminated water of MC-LR (1.0 μg L(-1)) of 3,640 L could be treated by 1 g of MIP with an estimated cost of US $1.5., Conclusions: The adsorption capacity of the MIP is 40% more than commercially used PAC and resins and also the polymer showed reusable potential which is one of the important criteria in selection of cyanotoxins remediation methods.

The present study was carried out to examine the dose-response of microcystin-LR (MC-LR) and microcystin-RR (MC-RR) toxicity in adult Danio rerio (zebrafish) under balneation conditions at various time points. The differential responses of superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione-S-transferase (GST) as biomarkers were assessed for oxygen mediated toxicity in liver, gills, intestine and brain tissues of zebrafish exposed to dissolved MC-LR and MC-RR (0.1-10.0 μgl(-1)). To investigate the time related response of biomarkers, fish were sampled after 4, 7 and 15 days of exposure. Responses varied (i) between MC-LR and MC-RR (for certain groups), (ii) for different enzymes at all time points, and (iii) for different tissues. In general, most of the enzymes followed a bell shaped curve, with an abrupt increase in activity at a particular concentration. It was observed that upon exposure to MC-LR and MC-RR, some enzymes showed an adaptive response after the first time point wherein the enzyme activity increased in some tissues. The increase in enzyme activity is suggestive of their cellular and metabolic adaptations to the continued stress and toxin exposure. Enzyme activities in general increased at lower concentrations (≤ 5.0 μgl(-1)) and decreased at higher concentrations (≥ 5.0 μgl(-1)). An abrupt change in enzyme activities was observed at a particular concentration in all the tissue enzymes. For GPx and GR, there was a differential response in the case of fish exposed to MC-LR and MC-RR, which could be due to the difference in toxicity potentials of these cyanotoxins. In general, initial stress conditions were observed in most of the tissue enzymes following the exposure to microcystins (MCs). This observation suggests that MCs found in trace levels are likely to have deleterious effects on aquatic organisms and can trigger a variety of biochemical responses depending on their specific toxicity., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Cyanobacterial toxins are considered as an emerging threat to natural water reservoirs and drinking water supplies. When they are ingested, these toxins are responsible for human and animal poisonings. The main goal of water quality monitoring programs is to predict harmful algal blooms and maintain the water quality of drinking water supplies. The current methods used for routine monitoring are not able to detect all the types and variants of cyanotoxins. The authors review the current state of the knowledge in detecting cyanotoxins in the environmental water samples and provides a comparative evaluation of methods ranging from conventional biological and analytical methods to recently advancing molecular and biosensor approaches in terms of their capabilities. In addition, the recent advances made in the area of cyanotoxins detection by molecular methods and biosensor-based technologies are discussed for their practical applications in terms of their use in a total analysis system. [ABSTRACT FROM PUBLISHER]

Abstract: A cloud point extraction method has been developed using an ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate, BMiM PF6) for the determination of a widely studied cyanotoxin (microcystin leucine–arginine, MCLR) in natural waters. Extraction parameters such as sample pH, extraction temperature, extraction time, the amount of ionic liquid and the amount of extraction volume were investigated and optimized to achieve the maximum extraction efficiency. The results obtained indicated a good linearity with the correlation coefficient of 0.995 over the range of 0.5–50μgL−1. The relative standard deviation (RSD) of the method was 7.5% (n =6). The calculated method detection limit was 0.03μgL−1 (n =6). The practical applicability of the technique was demonstrated by analyzing water samples (n =9) collected from three different sites in local reservoirs. [ABSTRACT FROM AUTHOR]