Cyanotoxin management and human health risk mitigation in recreational waters

Effects of the Toxic Non-Protein Amino Acid β-Methylamino-L-Alanine (BMAA) on Intracellular Amino Acid Levels in Neuroblastoma Cells

The cyanobacterial non-protein amino acid (AA) β-Methylamino-L-alanine (BMAA) is considered to be a neurotoxin. BMAA caused histopathological changes in brains and spinal cords of primates consistent with some of those seen in early motor neuron disease; however, supplementation with L-serine protected against some of those changes. We examined the impact of BMAA on AA concentrations in human neuroblastoma cells in vitro. Cells were treated with 1000 µM BMAA and intracellular free AA concentrations in treated and control cells were compared at six time-points over a 48 h culture period. BMAA had a profound effect on intracellular AA levels at specific time points but in most cases, AA homeostasis was re-established in the cell. The most heavily impacted amino acid was serine which was depleted in BMAA-treated cells from 9 h onwards. Correction of serine depletion could be a factor in the observation that supplementation with L-serine protects against BMAA toxicity in vitro and in vivo. AAs that could potentially be involved in protection against BMAA-induced oxidation such as histidine, tyrosine, and phenylalanine were depleted in cells at later time points.

Self-optimization of training dataset improves forecasting of cyanobacterial bloom by machine learning

Data-driven model (DDM) prediction of aquatic ecological responses, such as cyanobacterial harmful algal blooms (CyanoHABs), is critically influenced by the choice of training dataset. However, a systematic method to choose the optimal training dataset considering data history has not yet been developed. Providing a comprehensive procedure with self-based optimal training dataset-selecting algorithm would self-improve the DDM performance. In this study, a novel algorithm was developed to self-generate possible training dataset candidates from the available input and output variable data and self-choose the optimal training dataset that maximizes CyanoHAB forecasting performance. Nine years of meteorological and water quality data (input) and CyanoHAB data (output) from a site on the Nakdong River, South Korea, were acquired and pretreated via an automated process. An artificial neural network (ANN) was chosen from among the DDM candidates by first-cut training and validation using the entire collected dataset. Optimal training datasets for the ANN were self-selected from among the possible self-generated training datasets by systematically simulating the performance in response to 46 periods and 40 sizes (number of data elements) of the generated training datasets. The best-performing models were screened to identify the candidate models. The best performance corresponded to 6-7 years of training data (∼18 % lower error) for forecasting 1-28 d ahead (1-28 d of forecasting lead time (FLT)). After the hyperparameters of the screened model candidates were fine-tuned, the best-performing model (7 years of data with 14 d FLT) was self-determined by comparing the forecasts with unseen CyanoHAB events. The self-determined model could reasonably predict CyanoHABs occurring in Korean waters (cyanobacteria cells/mL ≥ 1000). Thus, our proposed method of self-optimizing the training dataset effectively improved the predictive accuracy and operational efficiency of the DDM prediction of CyanoHAB.

Perceived Intensification in Harmful Algal Blooms Is a Wave of Cumulative Threat to the Aquatic Ecosystems

Simple Summary

Harmful algal blooms (HABs) are a serious threat to aquatic environments. The intensive expansion of HABs across the world is a warning signal of environmental deterioration. Global climatic change enforced variations in environmental factors causing stressed environments in aquatic ecosystems that favor the occurrence, distribution, and persistence of HABs. Perceived intensification in HABs increases toxin production, affecting the ecological quality as well as serious consequences on organisms including humans. This review outlines the causes and impacts of harmful algal blooms, including algal toxicity, grazing defense, management, control measures, emerging technologies, and their limitations for controlling HABs in aquatic ecosystems.

Abstract

Aquatic pollution is considered a major threat to sustainable development across the world, and deterioration of aquatic ecosystems is caused usually by harmful algal blooms (HABs). In recent times, HABs have gained attention from scientists to better understand these phenomena given that these blooms are increasing in intensity and distribution with considerable impacts on aquatic ecosystems. Many exogenous factors such as variations in climatic patterns, eutrophication, wind blowing, dust storms, and upwelling of water currents form these blooms. Globally, the HAB formation is increasing the toxicity in the natural water sources, ultimately leading the deleterious and hazardous effects on the aquatic fauna and flora. This review summarizes the types of HABs with their potential effects, toxicity, grazing defense, human health impacts, management, and control of these harmful entities. This review offers a systematic approach towards the understanding of HABs, eliciting to rethink the increasing threat caused by HABs in aquatic ecosystems across the world. Therefore, to mitigate this increasing threat to aquatic environments, advanced scientific research in ecology and environmental sciences should be prioritized.

A Long-Term Study on the Effect of Cyanobacterial Crude Extracts from Lake Chapultepec (Mexico City) on Selected Zooplankton Species

Many urban lakes in Mexico City such as Lake Chapultepec are infested with high densities of cyanobacteria, particularly Microcystis. We tested the effect of cyanotoxins from cyanobacterial crude extracts on the demographic variables of zooplankton. The rotifers Brachionus havanaensis and Brachionus calyciflorus, and the cladocerans Ceriodaphnia dubia and Moina macrocopa were used for the assays. Temperature effects on the response of B. calyciflorus and 2 clones of M. macrocopa were tested. We hypothesized that with an increase in cyanotoxin concentration and temperature there would be an increase in the adverse effect on the test species and that the clone of Moina previously exposed to cyanobacteria from Lake Chapultepec would be more resistant to the cyanotoxins. Demography experiments showed that B. havanaensis was more sensitive than C. dubia. The negative effect of the cyanobacterial crude extract on B. calyciflorus was greater at 30 °C than at 20 °C or 25 °C. The strain of M. macrocopa isolated from Lake Chapultepec was more resistant to the cyanotoxins than the strain that had not been previously exposed to the cyanobacteria. The present study indicated that cyanobacteria in Lake Chapultepec are highly toxic and, considering the recreational use of this lake, should be controlled. Environ Toxicol Chem 2020;39:2409-2419. © 2020 SETAC.

Cyanotoxin impact on microbial-mediated nitrogen transformations at the interface of sediment-water column in surface water bodies

Harmful cyanobacterial blooms produce lethal toxins in many aquatic ecosystems experiencing eutrophication. This manuscript presents results on the effects of cyanotoxins on the aerobic microbial communities residing at the interface of sediments and water columns with the ammonia-oxidizing bacteria (AOB) as the model microbial community. Microcystin-LR (MC-LR), a heavily researched cyanotoxin variant, was used as the model cyanotoxin. To measure cyanotoxin influence on the activity of nitrifying microbial communities, an enriched culture of AOBs collected from an ongoing partial nitrification-nitritation reactor was examined for its exposure to 1, 5 and 10 μg/L of MC-LR. The nitritation kinetics experiment demonstrated MC-LR's ability at 1, 5, and 10 μg/L concentrations to prevent ammonium oxidation with statistically significant differences in nitritation rates between the blanks and spiked samples (One-way ANOVA, p < 0.05). Significantly decreased dissolved oxygen (DO) consumption during oxygen update batch tests demonstrated toxin's influence on AOB's oxidizing capabilities when exposed to even lower concentrations of 0.75, 0.5, and 0.25 μg/L of MC-LR in a separate set of experiments. Based on competitive kinetics, the MC-LR inhibition coefficient-the concentration needed to produce half-maximum inhibition of the mixed community AOBs was determined to be 0.083 μg/L. The stress tests proved the recovery of nitritation to some extent at lower MC-LR concentrations (1 and 5 μg/L), but significant irreversible inhibition was recorded when the AOB population was exposed to 10 μg/L MC-LR. The comparisons of amoA gene expressions corresponded well with nitrifying kinetics. All concentrations of MC-LR spiking were determined to produce a discernible impact on the AOB nitritation rate by either destroying the bacterial cell or immediately inhibiting the amoA gene expression.

Remediation of Eutrophic Aquatic Ecosystems: Evaluation of Phosphorus Adsorption by Sawdust

A wide range of anthropogenic activities have caused various problems to the aquatic environment, leading to economic, social, and environmental losses. The use of materials for the recovery of water quality is very important due to the water scarcity scenario present in different parts of the world. The use of sawdust as an organic adsorbent for P removal in eutrophic environments attempts to address both water quality preservation and possible application of the organic adsorbent as fertilizer for agricultural practices. This use will result in important contributions to the water and food security. In this work, we performed laboratory experiments to study P adsorption and to evaluate possible adsorption of metals and emerging contaminants by sawdust. The experiments were carried out in 36 microcosms (glass jars), using 50% of the flasks as treatments (containing bags with sawdust) and the rest of the flasks as control (water and sediment without sawdust). For future application of sawdust as a fertilizer it is important to be aware of the presence of possible pathogenic microorganisms, thus the presence of helminth eggs was determined in the sawdust. The results showed the tendency of P adsorption by the biosorbent; maximum adsorption occurred at 214 d (41 μg P g^-1 ), after the P desorption occurred. No helminth eggs or emerging contaminants and toxic metal were detected in the sawdust after its use as biosorbent, providing an important subsidy regarding the use of the biosorbent as soil fertilizer. Integr Environ Assess Manag 2019;00:1-12. © 2019 SETAC.

First Detection of Microcystin-LR in the Amazon River at the Drinking Water Treatment Plant of the Municipality of Macapá, Brazil

Human poisoning by microcystin has been recorded in many countries, including Brazil, where fatal cases have already occurred. The Amazon River is the main source of drinking water in municipalities such as Macapá, where there is no monitoring of cyanobacteria and cyanotoxins. This study investigated the presence of cyanobacteria and cyanotoxins in samples from a drinking water treatment plant (DWTP) that catches water from the Amazon River. The toxin analyses employed ELISA, LC/MS, and molecular screening for genes involved in the production of cyanotoxins. The sampling was carried out monthly from April 2015 to April 2016 at the intake (raw water) and exit (treated water) of the DWTP. This study reports the first detection of microcystin-LR (MC-LR) in the Amazon River, the world's largest river, and in its treated water destined for drinking water purposes in Macapá, Brazil. The cyanobacterial density and MC-LR concentration were both low during the year. However, Limnothrix planctonica showed a density peak (± 900 cells mL-1) in the quarter of June-August 2015, when MC-LR was registered (2.1 µg L-1). Statistical analyses indicate that L. planctonica may produce the microcystin.

Economic impact of harmful algal blooms on human health: a systematic review

Harmful algal blooms (HABs) damage human activities and health. While there is wide literature on economic losses, little is known about the economic impact on human health. In this review, we systematically retrieved papers which presented health costs following exposure to HABs. A systematic review was conducted up to January 2019 in databases such as ScienceDirect and PubMed, and 16 studies were selected. Health costs included healthcare and medication expenses, loss of income due to illness, cost of pain and suffering, and cost of death. Two categories of illness (digestive and respiratory) were considered for health costs. For digestive illness cost, we found $86, $1,015 and $12,605, respectively, for mild, moderate and severe cases. For respiratory illness, costs were $86, $1,235 and $14,600, respectively, for mild, moderate and severe cases. We used Quality-Adjusted Life Years (QALYs) to access the loss of well-being due to illness caused by HABs. We found that breathing difficulty causes the most loss of QALYs, especially in children, with a loss of between 0.16 and 0.771 per child. Having gastroenteritis could cause a loss of between 2.2 and 7.1 QALYs per 1,000 children. Misleading symptoms of illness following exposure to HABs could cause bias in health costs estimations.

Enhanced real-time cyanobacterial fluorescence monitoring through chlorophyll-a interference compensation corrections

In situ fluorometers can be used as a real-time cyanobacteria detection tool to maintain safe drinking and recreational water standards. However, previous studies into fluorometers have established issues arising mainly from measurement inaccuracies due to green algae interference. Therefore, this study focusses on developing correction factors from a systematic study on the impact of green algae as an interference source. This study brings a novel technique where the chlorophyll-a (Chl-a) and phycocyanin measurements are used to correct the fluorometer output for interference bias; four fluorometers were tested against three key cyanobacterial species and the relationship between phycocyanin output, green algae and cyanobacteria concentrations were investigated. Good correlation (R² > 0.9, p-value < 0.05) was found between the fluorometer phycocyanin output and increasing green algae concentration. The optimal correction method was selected for each of the fluorometer and cyanobacteria species pairs by validating against data from the investigation of green algae as an interference source. The correction factors determined in this study reduced the measurement error for almost all the fluorometers and species tested by 21%-99% depending on the species and fluorometer, compared to previous published correction factors in which the measurement error was reduced by approximately 11%-81%. Field validation of the correction factors showed reduction in fluorometer measurement error at sites in which cyanobacterial blooms were dominated by a single species.

The first detection of potentially toxic Microcystis strains in two Middle Atlas Mountains natural lakes (Morocco)

Aguelmam Azizgza (LAZ) and Dayet Afourgah (DAF) are two Moroccan natural lakes located in a humid hydrographic basin of the Middle Atlas Mountains. Both are considered important reservoirs of plant and animal biodiversity. In addition, they are extensively used for recreational and fishing activities and as a water source for irrigation of agricultural crops. Recurrent cyanobacteria scum episodes in the two water bodies have been reported, Microcystis being the main genus in the scums. Here, we report on the toxic potential of three Microcystis aeruginosa strains isolated from those lakes: Mic LAZ and Mic B7 from LAZ and Mic DAF isolated from DAF. The toxic potential was checked by their microcystin (MC) content and the presence of mcy genes involved in MC synthesis. The identification and quantification of MC variants were performed by high-performance liquid chromatography-photo-diode array. The detection of mcy genes was achieved by whole-cell multiplex PCR that allowed the simultaneous amplification of DNA sequences corresponding to specific mcy regions. MC content of cultured cells, as MC-LR equivalents per gram cell biomass, was slightly higher in Mic LAZ (ca. 860) than in Mic B7 (ca. 700) and Mic DAF (ca. 690). Four MC variants were identified in the three isolates: MC-WR, MC-RR, MC-DM-WR, and MC-YR. The presence of toxic Microcystis strains in the two studied lakes may be regarded as an environmental and health hazard, especially during periods of bloom proliferation. It would be recommended the use of two complementary techniques, as those utilized herein (HPLC and mcy detection) to alert on highly probable toxicity of such lakes.

Biosorbent, a promising material for remediation of eutrophic environments: studies in microcosm

Eutrophication is considered a global environmental problem that causes economic and biodiversity loss. Together with excess phosphorus in some aquatic environments, there is the depletion of phosphate rock deposits, which can directly affect fertilizer production and therefore global food security. Thus, the present work aimed to study a new remediation technique for eutrophic environments that enables the recovery of these environments through phosphorus adsorption in sawdust, creating the possibility to apply the phosphorus-enriched material as an agricultural fertilizer. The study was conducted in 36 microcosm flasks with water and sediment samples from a eutrophic reservoir in Ibirité/MG. The experiment was carried out using 18 control flasks and 18 others as treatment, consisting of water and eutrophic environment sediment and, additionally, two bags, containing 10 g of sawdust in each bag. The phosphorus adsorption on sawdust was more intense after 49 days of immersion in the microcosm, and reductions of 90% in the concentration of reactive soluble phosphorus were observed in the water column of the microcosm treatment at 159 days of the experiment. Based on the results, it can be concluded that, although the phosphorus concentration adsorbed on sawdust (16.2 μg g^-1) is considered low, the use of the biosorbent is a particularly promising technique for remediation of eutrophic environments, as well as the possible reuse of the adsorbed phosphorus as a fertilizer in agriculture.

Assessing the Contribution of the Environmental Parameters to Eutrophication with the Use of the "PaD" and "PaD2" Methods in a Hypereutrophic Lake

Lake Pamvotis (Greece) is a shallow hypereutrophic lake with a natural tendency to eutrophication. Several restoration measures were applied, but with no long-term success. To examine the causes for this an Artificial Neural Network (ANN) was created in order to simulate the chlorophyll-a (Chl-a) levels and to investigate the role of the associated environmental parameters. The ANN managed to simulate with good correlation the simulated Chl-a and can be considered as a reliable predictor. The relative importance of the environmental parameters to the simulated Chl-a was calculated with the use of the "Partial Derivatives" ("PaD") sensitivity method. The water temperature (WT) and soluble reactive phosphorus (SRP) had the highest relative importance, with values of 50% and 17%, respectively. The synergistic effect of the paired parameters was calculated with the use of the "PaD2" algorithm. The SRP-WT paired parameter was the most influential, with a relative contribution of 22%. The ANN showed that Lake Pamvotis is prone to suffer the effects of climatic change, because of the major contribution of WT. The ANN also revealed that combined nutrients reduction would improve water quality status. The ANN findings can act as an advisory tool regarding any restoration efforts.

Procedures to Investigate Waterborne Illness

Humanity could not survive without a reliably clean, safe, and steady flow of drinking water. Since the early 1900s when typhoid fever and cholera were frequently causes of waterborne illness in developed countries, drinking water supplies have been protected and treated to ensure water safety, quality, and quantity. Having access to safe drinking water has always been one of the cornerstones of good public health. Not only safe water is limited to drinking water, but recreational water can also be a source for waterborne illness—both from treated waters such as in swimming pools, whirlpools, or splash pads and from non-treated surface waters such as lakes, rivers, streams and ponds. Recreational waters may cause illness not only from ingestion of pathogens, but also when in contact with eyes, ears, or skin. Some pathogens in water can be acquired by inhalation of aerosols from water that is agitated or sprayed such as in humidifiers, fountains, or misting of produce. This poses a potential risk to those exposed, particularly if they are immunocompromised.

Bloom Dynamics of Cyanobacteria and Their Toxins: Environmental Health Impacts and Mitigation Strategies

Cyanobacteria are ecologically one of the most prolific groups of phototrophic prokaryotes in both marine and freshwater habitats. Both the beneficial and detrimental aspects of cyanobacteria are of considerable significance. They are important primary producers as well as an immense source of several secondary products, including an array of toxic compounds known as cyanotoxins. Abundant growth of cyanobacteria in freshwater, estuarine, and coastal ecosystems due to increased anthropogenic eutrophication and global climate change has created serious concern toward harmful bloom formation and surface water contamination all over the world. Cyanobacterial blooms and the accumulation of several cyanotoxins in water bodies pose severe ecological consequences with high risk to aquatic organisms and global public health. The proper management for mitigating the worldwide incidence of toxic cyanobacterial blooms is crucial for maintenance and sustainable development of functional ecosystems. Here, we emphasize the emerging information on the cyanobacterial bloom dynamics, toxicology of major groups of cyanotoxins, as well as a perspective and integrative approach to their management.

Increased risk of exposure to microcystins in the scum of the filamentous cyanobacterium Aphanizomenon flos-aquae accumulated on the western shoreline of the Curonian Lagoon

Concentration of toxic cyanobacteria blooms on the downwind shore of high recreational amenity water bodies with largely increases the risk of exposure to cyanotoxins. In this study analysis of phytoplankton structure, cyanotoxin composition and concentration was performed on cyanobacteria scum material, high- and low-density bloom samples in the Curonian Lagoon. We found that the concentration of cyanotoxins in the scum material increased from ∼30 to ∼300-fold compared to bloom samples. In Microcystis aeruginosa dominated samples microcystin-LR was present at the highest concentration, while the dominance of Planktothrix agardhii was associated with the occurrence of dmMC-RR as the major microcystin variant. The toxicological potential of cyanobacterial scums in the Curonian Lagoon is emphasized, and management by removal of these scums is proposed.

The influence of water quality variables on cyanobacterial blooms and phytoplankton community composition in a shallow temperate lake

Cyanobacterial blooms and their detrimental effects on water quality have become a worldwide problem. Vancouver Lake, a tidally influenced shallow temperate freshwater lake in Washington state, U.S.A., exhibits annual summer cyanobacterial blooms that are of concern to local resource managers. Our objectives were to describe changes in phytoplankton community composition in Vancouver Lake over seasonal, annual, and interannual time scales, and to identify strong water quality predictors of phytoplankton community structure, with an emphasis on cyanobacterial blooms, from 2007 through 2010. Cluster analysis, indicator species analysis, and non-metric multidimensional scaling were used to identify significantly different phytoplankton community groupings and to determine which environmental factors influenced community changes. From 2007 through 2009, depletion of NO3-N followed by elevated PO4-P concentration was associated with increased biomass and duration of each cyanobacterial bloom. Time-lag analysis suggested that NO3-N availability contributed to interannual changes within the summer phytoplankton community. Specifically, in summer 2010, a distinct cyanobacteria community was not present, potentially due to increased NO3-N and decreased PO4-P and NH4-N availability. Our study provides a comprehensive assessment of species-level responses to water quality variables in a shallow non-stratifying temperate lake, contributes to a better understanding of phytoplankton dynamics, and may aid in predicting and managing cyanobacterial blooms.