Fate of the Toxic Cyclic Heptapeptides, the Microcystins, from Blooms of Microcystis (Cyanobacteria) in a Hypertrophic LAKE1 (original) (raw)
Related papers
Environmental Pollution, 2019
Cyanotoxins from toxic blooms in lakes or eutrophic reservoirs are harmful to several organisms including zooplankton, which often act as vectors of these secondary metabolites, because they consume cyanobacteria, bioaccumulate the cyanotoxins and pass them on along the food chain. Microcystins are among the most commonly found cyanotoxins and often cause zooplankton mortality. Although cyanobacterial blooms are common and persistent in Mexican water bodies, information on the bioaccumulation of cyanotoxins is scarce. In this study we present data on the bioaccumulation of cyanotoxins from Planktothrix agardhii, Microcystis sp., Cylindrospermopsis raciborskii and Dolichospermum planctonicum blooms in the seston (suspended particulate matter more than 1.2 µm) by zooplankton and fish (tilapia (Oreochromis niloticus) and mesa silverside (Chirostoma jordani) samples from Lake Zumpango (Mexico City). The cyanotoxins were extracted from the seston, zooplankton and fish tissue by disintegration using mechanical homogenization and 75% methanol. After extraction, microcystins were measured using an ELISA kit (Envirologix). Concentration of microcystins expressed as equivalents, reached a maximum value of 117 µg g-1 on sestonic samples; in zooplankton they were in the range of 0.0070 to 0.29 µg g-1. The dominant zooplankton taxa include Acanthocyclops americanus copepodites, Daphnia laevis and Bosmina longirostris. Our results indicate twice the permissible limits of microcystins (0.04 µg Kg-1 d-1) for consumption of cyanobacterial products in whole fish tissue of Chirostoma jordani. The data have been discussed with emphasis on the importance of regular monitoring of water bodies in Mexico to test the ecotoxicological impacts of cyanobacterial blooms and the risk that consumption of products with microcystins could promote.
Annales de Limnologie - International Journal of Limnology, 2011
Eutrophication of freshwater lakes has led to blooms formed by cyanobacteria often associated with toxins harmful to livestock and humans. Environmental conditions that favor toxin production during cyanobacterial blooms are, however, not well understood. Moreover, the ability to use cyanobacteria quantity to assess the level of threat associated with toxin production is a topic of discussion. The purpose for this study was to examine Planktothrix agardhii dynamics in a shallow, temperate hypertrophic lake and to determine the factors that affect microcystin production. In addition, the relationship between P. agardhii morphology and microcystin production was examined. The study spanned 2 years, and we documented a perennial P. agardhii bloom that contributed up to 99% of the total biomass. Intracellular microcystins were primarily detected throughout the study, with the highest concentration in October. Microcystin concentrations ranged from 3.4 to 71.2 mg.L x1 , and they had a strong, positive correlation with P. agardhii biomass. In contrast, the levels of weight-specific microcystin were relatively stable throughout the entire study, ranging from 0.23 to 1.18 mg.mg x1. We also found that environmental factors, such as water temperature, phosphate level, ammonium nitrogen and transparency, were the most related to microcystin production. Furthermore, a significant relationship between filament morphology and toxin concentration suggested that there were different morphotypes within the toxic and non-toxic populations of P. agardhii. Our study showed that P. agardhii biomass and filament morphology may be useful characteristics for the identification of threats associated with cyanotoxins.
Bioaccumulation of microcystins
Lago de Patzcuaro is a historically important freshwater fishery in Mexico. The lake is presently characterized by a persistent bloom of cyanobacteria, specifically dominated by recognized producers of toxic microcystins (MCYSTs). We evaluated MCYSTs in sestonic and dissolved fractions of the water column, as well as representative fish species (silversides, Chirostoma spp.; Goodea sp.; and carp, Cyprinus carpio) obtained from local markets and small commercial catches during the bloom. Samples were evaluated primarily by enzyme-linked immunosorbent assay (ELISA), and secondarily by protein phosphatase (PPase) inhibition assay and liquid chromatography-mass spectrometry (LC-MS). Sestonic MCYST concentration (0.02–0.36 mg/L) generally correlated inversely with distance from the bloom, supporting the bloom as the source of the toxin. Several MCYST variants, including MC-LR, -LA and -LY, as well as didemethyl variants, were identified by LC-MS/MS analysis. All three species of fish bioaccumulated MCYSTs in relevant tissues, and toxin content correlated with trophic level, with highest and lowest levels measured in phytoplanktivorous and zooplanktivorous representatives, respectively. Detection of MCYST in silversides and Goodea sp. is particularly relevant because both are consumed in their entirety, including viscera (e.g., liver) known to primarily accumulate MCYST. These results indicate that Lago de Patzcuaro is indeed characterized by a toxigenic bloom, and that commercially important fish species from the lake accumulate toxic MCYST in tissues relevant to human consumption. As such, this system may represent an ideal model of the trophic transfer of MCYSTs and its relevance to human and environmental health.
Microbial Ecology, 1998
Cyanobacterial blooms were sampled at five locations in Lake Grand-Lieu on seven different occasions during May-October 1994. Strains of Microcystis aeruginosa and Anabaena circinalis were isolated from the samples. Microcystins were detected in freeze-dried field samples and the isolated strains by HPLC. The toxins were present in the blooms sampled between June and October. The microcystin content in the blooms varied with site and time, from undetectable concentrations to 0.23 mg g −1 . The highest concentrations of microcystin were found in blooms sampled in September. Microcystin-LR and microcystins with retention times close to the retention time of [Dha 7 ]microcystin-RR (probably varieties of microcystin-RR) were found in the field samples. Sixteen of the 98 isolated M. aeruginosa strains and 2 of the 24 A. circinalis strains produced microcystins. The total amount of microcystins varied from undetectable concentrations to 5.06 mg g −1 in the M. aeruginosa isolates, and from undetectable concentrations to 1.86 mg g −1 in the A.
Investigating the Mechanism Behind the Release of Microcystins in Freshwater Cyanobacteria
The frequency and distribution of toxic cyanobacterial blooms are increasing globally, creating the need for a better understanding of the processes involved in toxic secondary metabolite production. Microcystins (MCs) are potent hepatotoxins produced by a wide range of bloom-forming cyanobacteria genera such as Microcystis and Planktothrix. Although the release of MCs to the extracellular environment has long been considered a by-product of cell lysis and death, several studies suggest the presence of a mechanism that actively transports these toxins outside the cell membrane. The aim of the present study was to find evidence for a link between cell lysis and concentrations of extracellular MCs. A dual-fluorescence cell viability assay using the nucleic acid stain SYTOX Green was optimised for use on Microcystis and Planktothrix. A SYTOX Green concentration of 1 µM, and an incubation time of 30 minutes, yielded a bright and even fluorescent signal that readily identified lysed cell...
Ecotoxicology and environmental safety, 2017
Cyanobacterial blooms and cyanotoxins occur in freshwater lakes and reservoirs all over the world. Bacterial degradation of microcystins (MC), hepatotoxins produced by several cyanobacterial species, has also been broadly documented. However, information regarding MC biodegradation in European water bodies is very limited. In this paper, the occurrence and identification of MC biodegradation products was documented for 21 European lakes and reservoirs, many of which have well-documented cyanobacterial bloom histories. Varying cyanobacterial abundance and taxonomical composition were documented and MC producers were found in all the analysed samples. Planktothrix agardhii was the most common cyanobacterial species and it formed mass occurrences in four lakes. MC biodegradation was observed in 86% of the samples (18 out of 21), and four products of dmMC-LR decomposition were detected by HPLC and LC-MS methods. The two main products were cyclic dmMC-LR with modifications in the Arg-Asp...
Cyanobacterial Composition and Microcystin Accumulation in Catfish Pond
2014
Cyanobacterial blooms frequently occur in catfish ponds, but the potential effects of its secondary metabolites on cultured animals in ponds and human beings remain largely unknown. In the present study, high chlorophyll-a levels (1.28-2.06 mg/L) indicated massive phytoplankton blooms in the studied ponds, with a maximum density of 52 × 106 cells/L of potentially toxic cyanobacteria, composed mainly of Microcystis aeruginosa, Oscillatoria spp., Lyngbya sp., Pseudanabaena spp., Anabaena spp., Anabaenopsis sp., and Cylindrospermopsis sp. However, microcystins were not detected by liquid chromatography-mass spectrometry in samples of water and fish. Instead, microcystin-RR in phytoplankton was estimated to be between 0.014 and 0.202, and correlated positively with the density of Anabaena spp. (r=0.33, p<0.05), alkalinity (r=0.37, p<0.05), and ammonia (r=0.48, p<0.01). Microcystin was not detected in the fish in this study, but microcystin accumulation was found in 43% of analy...
Archives of Environmental Contamination and Toxicology, 2006
Toxic cyanobacterial blooms are a worldwide problem, causing serious water pollution and public health hazard to humans and livestock. The intact cells as well as the toxins released after cellular lysis can be responsible for toxic effects in both animals and humans and are actually associated with fish kills. Two fish cell lines-PLHC-1 derived from a hepatocellular carcinoma of the topminnow Poeciliopsis lucida and RTG-2 fibroblast-like cells derived from the gonads of rainbow trout Oncorhynchus mykiss were exposed to several concentrations of extracts from a natural cyanobacterial bloom and a Microcystis aeruginosa-isolated strain. After 24 hours, morphologic and biochemical changes (total protein content, lactate dehydrogenase leakage, neutral red uptake, methathiazole tetrazolium salt metabolization, lysosomal function, and succinate dehydrogenase [SDH] activity) were investigated. The most sensitive end point for both cyanobacterial extracts in PLHC-1 cells was SDH activity, with similar EC 50 values (6 lM for the cyanobacterial bloom and 7 lM for the isolated strain). RTG-2 cells were less susceptible according to SDH activity, with their most sensitive end point lysosomal function with an EC 50 of 4 lM for the M. aeruginosa-isolated strain and 72 lM for the cyanobacterial bloom. The lysosomal function was stimulated at low concentrations, although SDH activity increased at high doses, indicating lysosomal and energetic alterations. Increased secretion vesicles, rounding effects, decreased cell numbers and size, hydropic degeneration, esteatosis, and apoptosis were observed in the morphologic study. Similar sensitivity to the M. aeruginosa-isolated strain was observed in both cell lines, whereas the cyanobacterial bloom was more toxic to the PLHC-1 cell line. A common consequence of the eutrophication of inland waters is the overgrowth of cyanobacteria (blue-green algae) causing ''cyanobacterial blooms.'' These cyanobacteria can produce toxins and release them to the water as a consequence of their lysis, thus becoming an important water-quality problem in many countries where toxic cyanobacterial blooms have been reported (Moreno et al. 2003a; Nasri et al. 2004). Microcystins (MCs) are the most commonly found group of cyanotoxins. These hepatotoxins are produced by several genera of cyanobacteria, including Microcystis, Nodularia, Oscillatoria, Anabaena, and Nostoc spp. (Carmichael 1994). MCs are heptapeptides with a basic cyclic structure (D-Ala-L-X-erythro-b-mehtyl-D-iso-Asp-L-Y-Adda-D-iso-Glu-N-methylde-hydro-Ala). The residue, Adda, a characteristic cyanobacterial b-amino acid, refers to 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid, and X and Y represent the variable amino-acid residues in the cyclic structure (Dawson 1998). MCs are known to affect many organisms from microalgae to mammals (Figueiredo et al. 2004; Montagnolli et al. 2004) and are associated with fish kills (Carbis et al. 1997; Zimba et al. 2001). Moreover, freshwater fish as well as other aquatic organisms could not only be damaged by cyanobacterial toxins but are also able to bioaccumulate them (Magalhaes et al. 2003; Mohamed et al. 2003), thus making the ingestion of contaminated food a human health risk. The toxicity of cyanobacterial blooms has been investigated traditionally by exposing rodents to MCs from extracts of these blooms and then monitoring their survival, behavior, and histopathology (Teneva et al. 2002). Aune and Berg (1986) were among the first investigators to suggest the use of isolated rat hepatocytes for quick and inexpensive investigation of the toxicity of cyanobacterial blooms. Recently, this model system was shown to correlate particularly well with the content of MCs (Heinze et al. 2001). Nevertheless, inasmuch as the hepatocytes assay still requires the killing of animals, screening cyanobacterial extracts for their impact on cells might be more easily performed using established cell lines (Teneva et al. 2002). The use of cell lines has become particularly attractive in recent years because of the development of techniques applicable to multiwell plate readers and because of the increased availability of cell cultures originating from nonmammalian animals, such as fish, which allow cyanobacterial extracts to be evaluated with respect to environmental
Annales de Limnologie - International Journal of Limnology, 2013
Nutrient release from lake sediments may increase concentrations of harmful algal toxins -such as microcystins -by stimulating blooms of toxigenic cyanobacteria. This hypothesis is supported by a series of experiments in which intact cores of sediment were incubated under different environmental conditions, after which the water overlying the sediments was harvested as a culture medium for growing a toxic strain of the common cyanobacterium Microcystis. Both littoral and profundal sediments from Lake Kinneret, the largest freshwater lake in Israel, released substantial amounts of dissolved phosphorus (1.0 and 4.0 mg.m x2 .d x1 , respectively) and nitrogen (44.2 and 24.3 mg.m x2 .d x1 , respectively) under simulated summer conditions in the laboratory. In comparison, nutrient fluxes from sediments under simulated winter conditions were considerably smaller or negative. The addition of nutrient-rich overlying water harvested from profundal sediments, and to a lesser extent from littoral sediments, increased both chlorophyll a and microcystin concentrations in Microcystis cultures. In contrast, when Microcystis cells were inoculated in natural surface waters only, the cultures did not grow or produce microcystins, and soon collapsed. This study provides experimental evidence of a link between internal nutrient loading from sediments and microcystin concentrations in freshwaters, and demonstrates how environmental factors may indirectly exert control over toxin concentrations in freshwater lakes.