Microcystin Concentrations Research Articles

The volatilome reveals microcystin concentration, microbial composition, and oxidative stress in a critical Oregon freshwater lake.

Toxins produced by cyanobacterial blooms in freshwater lakes are a serious public health problem. The conditions leading to toxin production are unpredictable, thereby requiring expensive sampling and monitoring programs globally. We explored the potential of volatile organic compounds (VOCs) to indicate microcystin presence and concentration and microbial community composition in Upper Klamath Lake, Oregon. Elastic net regularization regression selected 24 of 229 detected m/z + 1 values (corresponding to unique VOCs) in models predicting microcystin contamination. These models outperformed regression models based only on environmental parameters, including chlorophyll, pH, and temperature. Several m/z + 1 values selected by elastic net were putatively identified as saturated fatty aldehydes, which defend cyanobacteria against oxidative stress. Elastic net also identified unique sets of m/z + 1 values that predicted the relative abundance of the dominant bacterial phyla, classes, and cyanobacterial genera. VOCs appear to reveal the physiological status of cyanobacteria during toxic blooms and may be a key component of lake monitoring strategies. IMPORTANCE Harmful algal blooms are among the most significant threats to drinking water safety. Blooms dominated by cyanobacteria can produce potentially harmful toxins and, despite intensive research, toxin production remains unpredictable. We measured gaseous molecules in Upper Klamath Lake, Oregon, over 2 years and used them to predict the presence and concentration of the cyanotoxin, microcystin, and microbial community composition. Subsets of gaseous compounds were identified that are associated with microcystin production during oxidative stress, pointing to ecosystem-level interactions leading to microcystin contamination. Our approach shows potential for gaseous molecules to be harnessed in monitoring critical waterways.

Prediction of Cyanotoxin Episodes in Freshwater: A Case Study on Microcystin and Saxitoxin in the Lobo Reservoir, São Paulo State, Brazil

Freshwater reservoirs constitute an important source of drinking water, but eutrophication and higher temperatures increase the risk of more frequent blooms of cyanobacteria, including species that produce toxins. To improve the prediction of cyanotoxin episodes, we studied the annual occurrence of potential microcystin (MC) and saxitoxin (STX)-producing cyanobacteria in the Lobo reservoir, São Paulo State, Brazil. Relationships among environmental variables, cyanobacterial biomass, numbers of the mcyE and sxtA genotypes (genes encoding production of MC and STX, respectively), and concentrations of MC and STX were determined to address variables applicable for monitoring and predicting the dynamics of cyanobacteria and cyanotoxins in the reservoir. Microscopy confirmed the presence of potentially toxin-producing cyanobacteria at all sampling times, and qPCR detection showed the occurrence of both mcyE and sxtA in most samples. Concentrations of MC and STX were generally low (MC 0–1.54 µg L−1; STX 0.03–0.21 µg L−1). The highest MC level exceeded the recommended limit for human intake of 1 µg L−1. The abundance of the mcyE and sxtA genes, as well as the toxin concentrations, were positively correlated with the biomass of Phormidium and Raphidiopsis. Among environmental variables, the abundance of potential toxic cyanobacteria was mainly affected by P limitation (high TN:TP ratios). Our data show that detection of the mcyE and sxtA genotypes serves as a useful and reliable predictor of toxin episodes but might be combined with chemical toxin detection to form an environmental toolbox for cyanotoxin monitoring.

Quantitative relationships among high-throughput sequencing, cyanobacteria toxigenic genotype abundance and microcystin occurrence in bathing waters

Toxin-producing cyanobacteria pose significant threats to human and animal health if exposed during recreational activities in bathing waters. To better safeguard public health and reduce health risks during the bathing season, an effective monitoring and management strategy is required. Molecular tools used to monitor toxigenic cyanobacteria have been evaluated on the basis of the efficiency and applicability of the method used to (i) establish an early-warning monitoring strategy for EU bathing water sites using both targeted quantitative polymerase chain reaction (qPCR) and non-targeted high-throughput sequencing (HTS) genotype analysis and (ii) to compare the toxigenic potential of cyanobacteria with actual microcystin (MC) occurrence and concentrations. For this purpose, 16 bathing water sites were monitored according to the bathing water directive (BWD) of the European Union (EU) during the bathing season of the summer of 2020 in eastern Austria. The cyanobacterial community composition was analyzed through HTS and qPCR by targeting the microcystin synthetase B gene (mcyB), which indicates MC synthesis within the genera Microcystis and Planktothrix. Within the genus Microcystis, which was identified as the primary MC producer, the mcyB genotypes formed stable subpopulations that increased linearly in correlation with the total Microcystis population. Notably, the HTS cell equivalents assigned to Microcystis and Planktothrix correlated with the corresponding qPCR estimates of genotype abundance, which serves as a confirmation of the suitability of (semi)-quantitative sequencing through HTS. In addition to the elevated trophic state, reduced transparency, increasing water temperatures, as well as cyanobacterial HTS read numbers and Microcystis cell number equivalents per mL estimated through qPCR, were associated with positive MC samples. Therefore, in combination with the monitoring of standard environmental parameters, the use of HTS and qPCR techniques is considered highly useful to ensure the timely identification of health risks to recreational users, as mandated by the BWD.

The harmful cyanobacterium Microcystis aeruginosa PCC7806 is more resistant to hydrogen peroxide at elevated CO2

Rising atmospheric CO2 can intensify harmful cyanobacterial blooms in eutrophic lakes. Worldwide, these blooms are an increasing environmental concern. Low concentrations of hydrogen peroxide (H2O2) have been proposed as a short-term but eco-friendly approach to selectively mitigate cyanobacterial blooms. However, sensitivity of cyanobacteria to H2O2 can vary depending on the available resources. To find out how cyanobacteria respond to H2O2 under elevated CO2, Microcystis aeruginosa PCC 7806 was cultured in chemostats with nutrient-replete medium under C-limiting and C-replete conditions (150 ppm and 1500 ppm CO2, respectively). Microcystis chemostats exposed to high CO2 showed higher cell densities, biovolumes, and microcystin contents, but a lower photosynthetic efficiency and pH compared to the cultures grown under low CO2. Subsamples of the chemostats were treated with different concentrations of H2O2 (0–10 mg·L−1 H2O2) in batch cultures under two different light intensities (15 and 100 μmol photons m−2·s−1) and the response in photosynthetic vitality was monitored during 24 h. Results showed that Microcystis was more resistant to H2O2 at elevated CO2 than under carbon-limited conditions. Both low and high CO2-adapted cells were more sensitive to H2O2 at high light than at low light. Microcystins (MCs) leaked out of the cells of cultures exposed to 2–10 mg·L−1 H2O2, while the sum of intra- and extracellular MCs decreased. Although both H2O2 and CO2 concentrations in lakes vary in response to many factors, these results imply that it may become more difficult to suppress cyanobacterial blooms in eutrophic lakes when atmospheric CO2 concentrations continue to rise.

Year-Round Presence of Microcystins and Toxin-Producing Microcystis in the Water Column and Ice Cover of a Eutrophic Lake Located in the Continuous Permafrost Zone (Yakutia, Russia).

This study aimed to test the hypothesis of the year-round presence of toxigenic Microcystis and cyanotoxins in the water and ice of the shallow eutrophic Lake Ytyk-Kyuyol located in the continuous permafrost zone. Three independent approaches-mass-spectrometry, molecular methods and light microscopy-were applied in the study. The cyanobacterial biomass ranged from 1.0 × 10-4 to 4.8 mg L-1. Microcystis flos-aquae and M. aeruginosa were the dominant morphospecies in plankton throughout the observation. In environmental DNA, the presence of M. aeruginosa was supported and mcy gene regions responsible for microcystin biosynthesis were detected through a BLAST (Basic Local Alignment Search Tool) search and phylogenetic estimation based on newly obtained 16S rRNA, 16S-23S ITS rRNA, mcyA and mcyE nucleotide sequences. The intracellular microcystin concentration ranged from <0.1 to 803 ng L-1, and the microcystin quota in the Microcystis biomass was extremely low. For the first time, it was shown that Microcystis cells containing mcy genes and microcystins presented permanently in the water column, both during the ice-free period and under ice, as well as inside thick ice covers within 7 months of severe winter. We hypothesized that minor pelagic and ice populations of Microcystis could participate in increasing cell density in the spring. However, further studies are needed to confirm the viability of the overwintering Microcystis colonies in the water and inside the ice of Lake Ytyk-Kyuyol.

Microbial communities in aerosol generated from cyanobacterial bloom-affected freshwater bodies: an exploratory study in Nakdong River, South Korea.

Toxic blooms of cyanobacteria, which can produce cyanotoxins, are prevalent in freshwater, especially in South Korea. Exposure to cyanotoxins via ingestion, inhalation, and dermal contact may cause severe diseases. Particularly, toxic cyanobacteria and their cyanotoxins can be aerosolized by a bubble-bursting process associated with a wind-driven wave mechanism. A fundamental question remains regarding the aerosolization of toxic cyanobacteria and cyanotoxins emitted from freshwater bodies during bloom seasons. To evaluate the potential health risk of the aerosolization of toxic cyanobacteria and cyanotoxins, the objectives of this study were as follows: 1) to quantify levels of microcystin in the water and air samples, and 2) to monitor microbial communities, including toxic cyanobacteria in the water and air samples. Water samples were collected from five sites in the Nakdong River, South Korea, from August to September 2022. Air samples were collected using an air pump with a mixed cellulose ester membrane filter. Concentrations of total microcystins were measured using enzyme-linked immunosorbent assay. Shotgun metagenomic sequencing was used to investigate microbial communities, including toxic cyanobacteria. Mean concentrations of microcystins were 960 μg/L ranging from 0.73 to 5,337 μg/L in the water samples and 2.48 ng/m3 ranging from 0.1 to 6.8 ng/m3 in the air samples. In addition, in both the water and air samples, predominant bacteria were Microcystis (PCC7914), which has a microcystin-producing gene, and Cyanobium. Particularly, abundance of Microcystis (PCC7914) comprised more than 1.5% of all bacteria in the air samples. This study demonstrates microbial communities with genes related with microcystin synthesis, antibiotic resistance gene, and virulence factors in aerosols generated from cyanobacterial bloom-affected freshwater body. In summary, aerosolization of toxic cyanobacteria and cyanotoxins is a critical concern as an emerging exposure route for potential risk to environmental and human health.

Harmful algal bloom aerosols and human health.

Harmful algal blooms (HABs) are increasing across many locations globally. Toxins from HABs can be incorporated into aerosols and transported inland, where subsequent exposure and inhalation can induce adverse health effects. However, the relationship between HAB aerosols and health outcomes remains unclear despite the potential for population-level exposures. In this review, we synthesized the current state of knowledge and identified evidence gaps in the relationship between HAB aerosols and human health. Aerosols from Karenia brevis, Ostreopsis sp., and cyanobacteria were linked with respiratory outcomes. However, most works did not directly measure aerosol or toxin concentrations and instead relied on proxy metrics of exposure, such as cell concentrations in nearby waterbodies. Furthermore, the number of studies with epidemiological designs was limited. Significant uncertainties remain regarding the health effects of other HAB species; threshold dose and the dose-response relationship; effects of concurrent exposures to mixtures of toxins and other aerosol sources, such as microplastics and metals; the impact of long-term exposures; and disparities in exposures and associated health effects across potentially vulnerable subpopulations. Additional studies employing multifaceted exposure assessment methods and leveraging large health databases could address such gaps and improve our understanding of the public health burden of HABs.

Forecasting microcystin concentrations in Lake Erie using an Eulerian tracer model

Cyanobacteria biomass models are routinely used in Lake Erie to predict the occurrence and location of algal blooms. However, current forecasts do not predict the microcystin toxins produced by these blooms. In this study, we used an extensive dataset of microcystin concentrations to generate weekly distribution maps in Lake Erie for the summers of 2018 and 2019. Using a 3D Eulerian tracer model (ETM) initialized with these maps, we simulated microcystin transport over 7 days, under two conditions: (1) the initial microcystin is mixed within the surface-mixed layer; (2) the initial microcystin is distributed throughout the entire water column. Two scenarios were tested for each condition: one incorporating microcystin production rates into hydrodynamic transport and one excluding them. Model performance was evaluated against weekly sample data in predicting whether microcystin concentrations surpassed specific thresholds (0.3, 1.0, 5.0, 10.0, and 20.0 µg/L), and in predicting trend directionality over each week. Overall, the ETM with hydrodynamics alone captured the transport of microcystins and predicted microcystin concentrations in 69% of the simulations. Incorporating microcystin production into the model increased the accuracy of forecasts by an additional 10%. Moreover, models with microcystin production successfully predicted microcystin concentrations greater than 5 μg/L during a large bloom, high-microcystin year (2019), while incorrectly forecasting concentrations above 5 μg/L during a small bloom year (2018). With limited data to initialize the ETM, no single model configuration consistently outperformed others. It is necessary to consider the full range of model configurations when utilizing their outputs for making management decisions.

Differential effects of nitrate and ammonium on the growth of algae and microcystin production by nitrogen-fixing Nostoc sp. and non-nitrogen-fixing Microcystis aeruginosa.

Cyanotoxins produced by cyanobacteria are a significant threat to human health. However, their responses to nitrogen (N) supplies could differ between N-fixing and non-N-fixing species, which has been poorly understood. This study aimed to compare the responses of the non-N-fixing Microcystis aeruginosa and N-fixing Nostoc sp. to varying concentrations of nitrate and ammonium. This comparison had been conducted by analyzing chlorophyll-a contents, maximum quantum efficiencies of photosystem II, microcystin production, and related gene expressions. Our findings revealed that nitrate substantially stimulated the growth of both M. aeruginosa and Nostoc sp. with biomass increase by 366.2 ± 56.5 and 93.0 ± 14.0%, respectively, at 16 mg-N/L. In contrast, high ammonium concentrations suppressed their growth. Furthermore, the intracellular concentration of microcystins produced by M. aeruginosa was higher under high nitrate. Extracellular microcystins showed an opposite trend to increases in nitrate and ammonium. Ammonium increases the production and releases microcystin from Nostoc sp. N metabolism genes showed a similar trend with toxin formation genes, which were up-regulated under the high N treatments. This study provides valuable insights into the impacts of N supplies on growths of N- and non-N-fixing cyanobacteria, as well as microcystin production, which helps to develop effective strategies for managing cyanobacterial blooms.

Long-term tracking robust removal of Microcystis-dominated bloom and microcystin-pollution risk by luteolin continuous-release microsphere at different nitrogen levels—Mechanisms from proteomics and gene expression

Luteolin continuous-release microsphere (CRM) has promising algicidal effect against Microcystis, but how nitrogen (N) level impacted CRM effects on Microcystis growth and microcystins (MCs) pollution was never tracked along long term. This study revealed that luteolin CRM exerted long-term and robust inhibitory effects on Microcystis growth and MC-pollution by sharply decreasing extracellular and total MCs content at each N level, with growth inhibition ratio of 88.18%–96.03%, 92.91%–97.17% and 91.36%–95.55% at 0.5, 5 and 50 mg/L N, respectively, during day 8–30. Further analyses revealed that CRM-stress inhibited transferase, GTPase and ATPase activities, ATP binding, metal ion binding, fatty acid biosynthesis, transmembrane transport and disrupted redox homeostasis to pose equally robust algicidal effect at each N level. At lower N level, CRM-stress tended to induce cellular metabolic mode towards stronger energy supply/acquisition but weaker energy production/consumption, while triggered a shift towards stronger energy production/storage but weaker energy acquisition/consumption as N level elevated, thus disturbing metabolic balance and strongly inhibiting Microcystis growth at each N level. Long-term robust algicidal effect of CRM against other common cyanobacteria besides Microcystis was evident in natural water. This study shed novel insights into inhibitory effects and mechanisms of luteolin CRM on Microcystis growth and MC-pollution in different N-level waters.

Model Code for manuscript "Forecasting Microcystin Concentrations in Lake Erie Using a Eulerian Tracer Model"

Model Code for manuscript "Forecasting Microcystin Concentrations in Lake Erie Using a Eulerian Tracer Model"

Microcystin congeners in Lake Erie follow the seasonal pattern of nitrogen availability

Cyanobacteria harmful algal blooms produce many toxic secondary metabolites called cyanotoxins. The most studied group of cyanotoxins are microcystins (MC), with over 300 congeners reported. MC-LR is the most studied congener because of its abundance and toxicity. Recent toxicology studies suggest that more hydrophobic MC congeners such as MC-LA, MC-LF, and MC-LW may be less abundant but up to seven times more toxic than MC-LR, whereas, MC-RR's toxicity is only one-fifth that of MC-LR. Hence, understanding the environmental stressors that change the MC congener profile is critical to assessing the negative impact on environmental and human health. A two-year field and experimental study investigated seasonal and spatial changes of MC congener profiles in the western basin of Lake Erie. Both studies showed that nitrogen enrichment favored the production of nitrogen-rich MC-RR (C49H75N13O12). The field study showed that nitrogen depletion favored the low-nitrogen MC-LA (C46H67N7O12). MC-LR (a medium N level, C49H75N10O12) accounted for ∼30% to 50% of the total MC concentration and was stable across nitrogen concentrations. Using the relative toxicity and concentrations of each MC congener, both LC-MS/MS and ELISA overestimated the toxicity early bloom (July) and underestimated it late bloom (September). On 24 July 2019, highly toxic MC-LW and MC-LF were detected at nearshore stations with relative toxicity exceeding drinking water standards. This study demonstrated that the less toxic, high nitrogen MC-RR dominated under nitrogen-replete conditions in the early season, whereas the more toxic, less nitrogen MC-LA dominated under nitrogen-limited conditions later in the season.

Effect of Microcystin on Growth and Development of Some Agricultural Plants Seedlings

A marked correlation between the abundance of M. aeruginosa blooms and high temperature, pH, N and P content of the pond water was observed during studies. Extract of M. aeruginosa showed toxicity to mice and showed the absorption maximum at 236 nm. Co-chromatography and HPLC analysis using standard microcystin showed that the compound present in MT-2 is identical to standard microcystin-LR. Intraperitoneal administration of crude and purified toxins of M. aeruginosa caused death of mice after 40-45 min. Microcystin content in water was also determined and revealed the presence of microcystin-LR in both the ponds Laxmikund and Durgakund respectively. The impact of partially purified microcystin was studied on plants system. Germination percent, growth and antioxidative activity of four plants (rice, cauliflower, mustard and onion). A drastic inhibition in percent germination was observed in mustard, cauliflower and onion seeds was observed in the presence of 2.5µg/ml microcystin. However, there was no significant effect of this concentration of MC on seed germination in rice. Growth (evaluated in terms of shoot and root length, fresh weight and total chlorophyll content) of all four plant seedlings was also significantly affected at the same concentration of microcystin. During antioxidative studies, significant increase in activity of SOD, POD and CAT was observed in the presence of different concentrations of microcystin in seedlings of all plants tested.

Microcystins and Cyanobacterial Contaminants in the French Small-Scale Productions of Spirulina (Limnospira sp.).

Spirulina is consumed worldwide, in the form of food or dietary supplements, for its nutritional value and health potential. However, these products may contain cyanotoxins, including hepatotoxic microcystins (MCs), produced by cyanobacterial contaminants. The French spirulina market has the particularity of being supplied half-locally by approximately 180 small-scale spirulina production farms. Data about this particular production and possible contaminations with other cyanobacteria and MCs are scarce. Thus, we collected the results of MC analyses and total cyanobacteria counts, carried out between 2013 and 2021, from 95 French spirulina producers who agreed to share their data. These data consisted of MC concentrations determined with an enzyme-linked immunosorbent assay (ELISA) using 623 dry spirulina samples and 105 samples of spirulina cultures. In addition, potentially unsafe samples of dry spirulina were further investigated through mass spectrometry, as duplicate analysis. We confirmed that the situation of the French spirulina production stayed within the safe regulatory level in terms of MC levels. On the other hand, the inventory of cyanobacterial contaminants, based on 539 count results, included 14 taxa. We present their prevalence, interannual evolution and geographical distribution. We also suggested improvements in cultivation practices to limit their propagation.

Evaluation of the Effects of Different Phosphorus Sources on Microcystis aeruginosa Growth and Microcystin Production via Transcriptomic Surveys

Microcystis aeruginosa (M. aeruginosa) is a dominant species among frequent cyanobacterial blooms and is well known for its toxin-producing ability. Phosphorus (P) is a typical growth-limiting element for M. aeruginosa. Although alterations in physiological reactions have been documented in response to various P sources, the underlying molecular processes and transcriptional patterns remain poorly understood. This study evaluated the physiological and molecular responses of M. aeruginosa to different P sources. The growth of M. aeruginosa was promoted by both dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP) at a concentration of 0.4 mg/L with an initial cell density of 1.50 (±0.05) × 106 cells/mL. The cell density reached 1.38 (±0.05) × 107 cells/mL in the DIP group on day 14, a value which was higher than that in the DOP group. Most photosynthesis genes had higher levels of upregulated expression in the DIP group. For instance, gene psbA was upregulated by 0.45 Log2Fold Change (Log2FC). In the DOP group, it is interesting that the Pi (PO4-P) concentration increased to 0.09 mg/L on day 14. Meanwhile, the expression of the gene encoding alkaline phosphatase-like protein was significantly upregulated, with a value of 1.56 Log2FC, and the alkaline phosphatase concentration increased in the DOP group. The intracellular microcystin (IMC) concentration decreased with time in both groups. However, the concentration of extracellular microcystins (EMCs) increased with incubation time in both groups. Phosphorus participates in the regulation of microcystin synthesis, mainly by regulating ATP synthesis. Based on the physiological and molecular investigations in this study, the results provide crucial insights into the physiological adaptations and the role of P in modulating harmful algal bloom formation, microcystin synthesis, and potential molecular responses of M. aeruginosa.

Survival and Accumulation of Microcystins in a Native Amphipod Shredder, Gammarus Pulex under Environmentally Relevant Cyanotoxin Exposure

Microcystin release in freshwaters is a major public health and ecological threat, affecting survival and trophic interactions across food web components. Although bioaccumulation has been suggested to represent an important pathway for microcystin uptake and trophic transfer across different food web compartments, it is rarely known how microcystin exposure may affect survival and accumulation among lower trophic levels under environmentally realistic scenario. Therefore, in this study, survival and microcystin accumulations in the UK native amphipod species, Gammarus pulex were monitored during a 96-hour static acute toxicity experiment. Animals were exposed to a range of environmentally relevant microcystin concentrations (0.01–10μg/L) across two treatment types, purified MC-LR and crude extract of microcystin-producing Microcystis aeruginosa. Survival of G. pulex individuals across the two treatments showed no evidence of significant difference from the control. Microcystin concentrations observed in G. pulex exposed to the purified MC-LR and crude extract ranged from (12.8 – 27.5) ng/g of MC-LR and (5.6-12.8) ng/g of MC-LR respectively. Microcystin concentrations measured in animals showed strong positive correlations with toxin concentrations in the experimental media across the two treatments, suggesting G. pulex can bioaccumulate microcystins, therefore may represent a potential vector for microcystin exposure to higher food web consumers. These results highlight the fact that exposure of benthic food web components to environmental microcystin concentrations may constitute an important route of toxin transfer within freshwater food webs.

Microcystins at the tap: A closer look at unregulated drinking water contaminants

AbstractThis case study compared microcystins in tap water from 18 public water systems (PWSs) and 46 households with private intakes or nearshore wells (called self‐supplied water systems [SSWS]) from Clear Lake, California during a major cyanobacterial bloom in 2021. Microcystin concentrations were below the US EPA health advisory (HA; 0.3 μg/L) for PWS with Clear Lake intakes and for SSWS drawing from wells. However, for SSWS with Clear Lake intakes (intake SSWS), 24 of 79 microcystin samples collected were at or above the HA (maximum 3.9 μg/L). Further, microscopy showed that 20 of 28 tap samples (post‐treatment) from intake SSWS contained either cyanobacteria or algal cells. This demonstrates that robust multi‐barrier treatment systems at PWS reliably removed microcystins, while the less sophisticated treatment systems at intake SSWS were compromised during a major cyanobacterial bloom. Intake SSWS should consider alternative sources of drinking water, including physically connecting to an adjacent PWS or drilling a well.

Microcystin concentrations and congener composition in relation to environmental variables across 440 north-temperate and boreal lakes

Understanding the environmental conditions and taxa that promote the occurrence of cyanobacterial toxins is imperative for effective management of lake ecosystems. Herein, we modeled total microcystin presence and concentrations with a broad suite of environmental predictors and cyanobacteria community data collected across 440 Canadian lakes using standardized methods. We also conducted a focused analysis targeting 14 microcystin congeners across 190 lakes, to examine how abiotic and biotic factors influence their relative proportions. Microcystins were detected in 30 % of lakes, with the highest total concentrations occurring in the most eutrophic lakes located in ecozones of central Canada. The two most commonly detected congeners were MC-LR (61 % of lakes) and MC-LA (37 % of lakes), while 11 others were detected more sporadically across waterbodies. Congener diversity peaked in central Canada where cyanobacteria biomass was highest. Using a zero-altered hurdle model, the probability of detecting microcystin was best explained by increasing Microcystis biomass, Daphnia and cyclopoid biomass, soluble reactive phosphorus, pH and wind. Microcystin concentrations increased with the biomass of Microcystis and other less dominant cyanobacteria taxa, as well as total phosphorus, cyclopoid copepod biomass, dissolved inorganic carbon and water temperature. Collectively, these models accounted for 34 % and 70 % of the variability, respectively. Based on a multiple factor analysis of microcystin congeners, cyanobacteria community data, environmental and zooplankton data, we found that the relative abundance of most congeners varied according to trophic state and were related to a combination of cyanobacteria genera biomasses and environmental variables.

Microcystins Exposure Associated with Blood Lipid Profiles and Dyslipidemia: A Cross-Sectional Study in Hunan Province, China

Increasing evidence from experimental research suggests that exposure to microcystins (MCs) may induce lipid metabolism disorder. However, population-based epidemiological studies of the association between MCs exposure and the risk of dyslipidemia are lacking. Therefore, we conducted a population-based cross-sectional study involving 720 participants in Hunan Province, China, and evaluated the effects of MCs on blood lipids. After adjusting the lipid related metals, we used binary logistic regression and multiple linear regression models to examine the associations among serum MCs concentration, the risk of dyslipidemia and blood lipids (triglyceride (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C)). Moreover, the additive model was used to explore the interaction effects on dyslipidemia between MCs and metals. Compared to the lowest quartile of MCs exposure, the risk of dyslipidemia [odds ratios (OR) = 2.27, 95% confidence interval (CI): 1.46, 3.53] and hyperTG (OR = 3.01, 95% CI: 1.79, 5.05) in the highest quartile was significantly increased, and showed dose-response relationships. MCs were positively associated with TG level (percent change, 9.43%; 95% CI: 3.53%, 15.67%) and negatively associated with HDL-C level (percent change, -3.53%; 95% CI: -5.70%, -2.10%). In addition, an additive antagonistic effect of MCs and Zn on dyslipidemia was also reported [relative excess risk due to interaction (RERI) = -1.81 (95% CI: -3.56, -0.05)], and the attributable proportion of the reduced risk of dyslipidemia due to the antagonism of these two exposures was 83% (95% CI: -1.66, -0.005). Our study first indicated that MCs exposure is an independent risk factor for dyslipidemia in a dose-response manner.

Growth, antioxidant response and microcystin production by Microcystis aeruginosa exposed to the surfactant perfluorooctanesulfonic acid (PFOS)

ABSTRACT The surfactant perfluorooctanesulfonic acid (PFOS) is used in various products, but its impact on aquatic organisms like cyanobacteria is poorly understood. PFOS was tested for acute toxicity on the cyanobacterium Microcystis aeruginosa in terms of growth, photosynthetic pigment content, antioxidant response and microcystin production. When exposed to PFOS, the cyanobacterium was sensitive to it, showing significant inhibition of growth and reduction of pigment content. At the same time, exposure to PFOS resulted in a two-fold increase of the content of total carbohydrates and soluble proteins in the cells of M. aeruginosa. There was a significant increase in MDA and H2O2 levels in cells exposed to PFOS, but not in a concentration-dependent manner. Microcystin content tended to increase in PFOS-exposed cyanobacterial cells, although this change was not statistically significant (p > 0.05). These findings suggest that when surfactants like PFOS are used in large quantities or concentrations, they could adversely affect Microcystis populations in the aquatic environment.