Cyanobacteria Concentrations Research Articles

Integrated workflow for interpretation of satellite imageries using machine learning to assess and monitor algal blooms in Utah Lake, USA

An integrated workflow is developed to estimate the spatial distribution of harmful algal blooms, especially cyanobacteria concentrations in inland water bodies. The methodology comprises satellite data extraction and preprocessing for atmospheric and water surface corrections, identifying feature importance, in-situ sample collection, training and testing of machine learning algorithms, and prediction. Six input bands are selected using feature importance algorithms from 12 original bands of Sentinel-2 satellite imagery. In-situ sample data that are synchronous with Sentinel-2 image capture time were obtained from a public database. These models are evaluated and compared using spider plots of different error calculations. The workflow developed in this study and the predicted spatial concentration of harmful algal blooms across the lake can be used to improve warning and advisory systems for the public and avoid exposure. The incorporation of other parameters such as water temperature, nutrient concentrations, and surface wind speed could improve the machine-learning models.

Monitoring and forecasting cyanobacteria risk for a drinking water plant in Spain

Abstract Cyanobacterial harmful algal blooms are a critical risk for public health since the release of cyanotoxins can reach hazardous levels in drinking water. In this study, a cost-effective monitoring programme has been developed and applied by a Spanish water operator to detect cyanobacteria presence in a drinking water plant reservoir; a total of 65 phytoplankton genera and seven cyanobacterial taxa were identified. Based on these monitoring data, different analysis techniques such as classification trees have been used to identify the potential situations of risk and to forecast cyanobacteria evolution in surface water. As a result, a new operational risk management plan has been developed and applied by the water operator since 2019. The main improvements concern the classification of the situations of risk in six groups (from low to very high, according to chlorophyl-a and cyanobacteria concentrations), the planning of the actions required under each situation (monitoring, management practice and treatment), and the use of the risk forecast to perform some of these actions from 2–3 days in advance. The methodology can be replicated to other case studies to facilitate the management of cyanobacteria risk and comply with the requirements of the revised European Drinking Water Directive adopted in 2020.

Simulated impacts of climate change on Lake Simcoe water quality

ABSTRACT Lake Simcoe has undergone eutrophication and hypoxia since the 1960s. Climate change, leading to enhanced summer thermal stratification, has been identified as a key stressor. In this study, we modeled the impacts of climate change on hydrodynamics and biogeochemistry in Lake Simcoe by applying a 1-dimensional (vertical) model forced with A2 and B1 scenario outputs from a global climate model over 2000–2100. The model was calibrated in 2008 and validated in 2009, with maximum root mean square error (RMSE) of modelled temperature between 1.5 and 3.0 °C and dissolved oxygen RMSE between 0.5 and 2.5 mg L−1. Phytoplankton chlorophyll a was simulated with RMSE between 1.25 µg L−1 (large diatoms) and ∼0.5 µg L−1 (other groups). Interannual variability in spring water temperature and length of stratification were related to changes in the North Atlantic and Artic Oscillation indices, respectively. Under A2 and B1 forcing, the duration of stratification will increase by 45 and 38 days in summer between spring and fall turnover, respectively. The extended stratified period leads to a reduction in hypolimnetic dissolved oxygen from 3–7 to <3 mg L−1, thereby reducing the quality of cold-water fish habitat and increasing internal phosphorus loading from the benthos. These internal loads, combined with increased water temperatures, lead to increased cyanobacteria concentrations, beginning around 2070.

Acute health effects associated with satellite-determined cyanobacterial blooms in a drinking water source in Massachusetts

BackgroundThe occurrence of cyanobacterial blooms in freshwater presents a threat to human health. However, epidemiological studies on the association between cyanobacterial blooms in drinking water sources and human health outcomes are scarce. The objective of this study was to evaluate if cyanobacterial blooms were associated with increased emergency room visits for gastrointestinal (GI), respiratory and dermal illnesses.MethodsSatellite-derived cyanobacteria cell concentrations were estimated in the source of drinking water for the Greater Boston area, during 2008–2011. Daily counts of hospital emergency room visits for GI, respiratory and dermal illnesses among drinking water recipients were obtained from an administrative record database. A two-stage model was used to analyze time-series data for an association between cyanobacterial blooms and the occurrence of illnesses. At the first stage, predictive autoregressive generalized additive models for Poisson-distributed outcomes were fitted to daily illness count data and daily predictive variables. At the second stage, residuals from the first stage models were regressed against lagged categorized cyanobacteria concentration estimates.ResultsThe highest cyanobacteria concentration (above the 75th percentile) was associated with an additional 4.3 cases of respiratory illness (95% confidence interval: 0.7, 8.0, p = 0.02, n = 268) compared to cyanobacteria concentrations below the 50th percentile in a two-day lag. There were no significant associations between satellite derived cyanobacterial concentrations and lagged data on GI or dermal illnesses.ConclusionThe study demonstrated a significant positive association between satellite-derived cyanobacteria concentrations in source water and respiratory illness occurring 2 days later. Future studies will require direct measures of cyanotoxins and health effects associated with exposure to cyanobacteria-impacted drinking water sources.

Toolbox for the sampling and monitoring of benthic cyanobacteria

Benthic cyanobacteria are a nuisance because they produce highly potent toxins and taste and odour compounds. Despite this, benthic cyanobacteria remain far less studied than their planktonic counterparts. For example, little is known about their growth or the seasonality of their secondary metabolite production. Moreover, sampling and monitoring techniques commonly used for the survey of planktonic species are not necessarily applicable to benthic forms. This study aimed to develop and validate a new sampling device for the routine monitoring of benthic mats. Molecular monitoring techniques were established and validated on environmental samples collected in a South Australian reservoir (SA-L2). A total of eight qPCR assays were applied to samples in order to track seasonal variations in cyanobacteria concentrations and associated secondary metabolite production. Next Generation Sequencing was utilised to conduct a microbial community composition analysis and to select the most appropriate substrate material for the sampling of benthic cyanobacteria. The concentration of the secondary metabolites geosmin and 2-methyl-isoborneol were quantified using High-Performance Liquid Chromatography, and concentrations of key nutrients (N, P) were quantified in water samples. The sampling device designed proved efficient and easy to use in the field. The qPCR assay designed for the amplification of the cyanobacterial MIB synthase had a high efficiency with a minimum limit of quantification of 4 cell-equivalents per reaction and identified a potential source of MIB in SA-L2 Reservoir. The peak season for benthic growth and secondary metabolite production was observed in spring. Proportionally, 35% of the variability in water geosmin concentrations can be explained by benthic actinobacterial and cyanobacterial activity, showing that freshwater benthic mats represent a significant source of taste and odour compounds.

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.

A novel Eulerian approach for modelling cyanobacteria movement: Thin layer formation and recurrent risk to drinking water intakes

Toxic cyanobacteria (CB) blooms are being reported in an increasing number of water bodies worldwide. As drinking water (DW) treatment can be disrupted by CB, in addition to long term management plans, short term operational decision-making tools are needed that enable an understanding of the temporal variability of CB movement in relation to drinking water intakes. In this paper, we propose a novel conservative model based on a Eulerian framework and compare results with data from CB blooms in Missisquoi Bay (Québec, Canada). The hydrodynamic model considered the effects of wind and light intensity, demonstrated that current understanding of cell buoyancy in relation to light intensity in full-scale systems is incomplete and some factors are yet to be fully characterized. Factors affecting CB buoyancy play a major role in the formation of a thin surface layer that could be of ecological importance with regards to cell concentrations and toxin production. Depending on velocities, wind contributes either to the accumulation or to the dispersion of CB. Lake recirculation effects have a tendency to create zones of low CB concentrations in a water body. Monitoring efforts and future research should focus on short-term variations of CB throughout the water column and the characterization of factors other than light intensity that affect cell buoyancy. These factors are critical for understanding the risk of breakthrough into treatment plants as well as the formation of surface scums and subsequent toxin production.

Climate Change Impacts on Harmful Algal Blooms in U.S. Freshwaters: A Screening-Level Assessment.

Cyanobacterial harmful algal blooms (CyanoHABs) have serious adverse effects on human and environmental health. Herein, we developed a modeling framework that predicts the effect of climate change on cyanobacteria concentrations in large reservoirs in the contiguous U.S. The framework, which uses climate change projections from five global circulation models, two greenhouse gas emission scenarios, and two cyanobacterial growth scenarios, is unique in coupling climate projections with a hydrologic/water quality network model of the contiguous United States. Thus, it generates both regional and nationwide projections useful as a screening-level assessment of climate impacts on CyanoHAB prevalence as well as potential lost recreation days and associated economic value. Our projections indicate that CyanoHAB concentrations are likely to increase primarily due to water temperature increases tempered by increased nutrient levels resulting from changing demographics and climatic impacts on hydrology that drive nutrient transport. The combination of these factors results in the mean number of days of CyanoHAB occurrence ranging from about 7 days per year per waterbody under current conditions, to 16-23 days in 2050 and 18-39 days in 2090. From a regional perspective, we find the largest increases in CyanoHAB occurrence in the Northeast U.S., while the greatest impacts to recreation, in terms of costs, are in the Southeast.

Treatment challenge of a cyanobacterium Romeria elegans bloom in a South Australian wastewater treatment plant – a case study

ABSTRACTA bloom of the non-toxic cyanobacterium Romeria elegans in waste stabilisation ponds (WSPs) within Angaston waste water treatment plant (WWTP) has posed an unprecedented treatment challenge for the local water utility. The water from the WSPs is chlorinated for safety prior to reuse on nearby farmland. Cyanobacteria concentrations of approximately 1.2 × 106 cells mL−1 increased the chlorine demand dramatically. Operators continuously increased the disinfectant dose up to 50 mg L−1 to achieve operational guideline values for combined chlorine (0.5-1.0 mg L−1) prior to reuse. Despite this, attempts to achieve targeted combined chlorine residual (CCR) failed. In this study, samples from the waste stabilisation pond at Angaston WWTP were chlorinated over a range of doses. Combined chlorine, disinfection by-product formation, cyanobacteria cell concentration, Escherichia coli inactivation, as well as dissolved organic carbon and free ammonia were monitored. This study shows that, in the occurrence of cyanobacterial blooms, CCR does not directly suggest pathogen removal efficiency and is therefore not an ideal parameter to evaluate the effectiveness of disinfection process in WWTP. Instead, E. coli removal is a more direct and practical parameter for the determination of the efficiency of the disinfection process.

Response of Daphnia's antioxidant system to spatial heterogeneity in Cyanobacteria concentrations in a lowland reservoir.

Many species and clones of Daphnia inhabit ecosystems with permanent algal blooms, and they can develop tolerance to cyanobacterial toxins. In the current study, we examined the spatial differences in the response of Daphnia longispina to the toxic Microcystis aeruginosa in a lowland eutrophic dam reservoir between June (before blooms) and September (during blooms). The reservoir showed a distinct spatial pattern in cyanobacteria abundance resulting from the wind direction: the station closest to the dam was characterised by persistently high Microcystis biomass, whereas the upstream stations had a significantly lower biomass of Microcystis. Microcystin concentrations were closely correlated with the cyanobacteria abundance (r = 0.93). The density of daphniids did not differ among the stations. The main objective of this study was to investigate how the distribution of toxic Microcystis blooms affects the antioxidant system of Daphnia. We examined catalase (CAT) activity, the level of the low molecular weight antioxidant glutathione (GSH), glutathione S-transferase (GST) activity and oxidative stress parameters, such as lipid peroxidation (LPO). We found that the higher the abundance (and toxicity) of the cyanobacteria, the lower the values of the antioxidant parameters. The CAT activity and LPO level were always significantly lower at the station with the highest M. aeruginosa biomass, which indicated the low oxidative stress of D. longispina at the site with the potentially high toxic thread. However, the low concentration of GSH and the highest activity of GST indicated the occurrence of detoxification processes at this site. These results demonstrate that daphniids that have coexisted with a high biomass of toxic cyanobacteria have effective mechanisms that protect them against the toxic effects of microcystins. We also conclude that Daphnia's resistance capacity to Microcystis toxins may differ within an ecosystem, depending on the bloom's spatial distribution.

Phytoplankton composition modifies predator-driven life history evolution in Daphnia

Organisms experience competing selective pressures, which can obscure the mechanisms driving evolution. Daphnia ambigua is found in lakes where a predator, the alewife (Alosa pseudoharengus) either does (anadromous) or does not (landlocked) migrate between marine and freshwater. We previously reported an association between alewife variation and life history evolution in Daphnia. However, differences in alewife migration indirectly influence phytoplankton composition for Daphnia. In ‘anadromous lakes’, Daphnia are present in the spring and experience abundant high-quality green algae. Intense predation by young-of-the-year anadromous alewife quickly eliminates these Daphnia populations by early summer. Daphnia from ‘landlocked lakes’ and lakes without alewife (‘no alewife lakes’) are present during the spring and summer and are more likely to experience high concentrations of sub-optimal cyanobacteria during the summer. To explore links between predation, resources, and prey evolution, we reared third-generation laboratory-born Daphnia from all lake types on increasing cyanobacteria concentrations. We observed several significant ‘lake type × resource’ interactions whereby the differences among lake types depended upon cyanobacteria concentrations. Daphnia from anadromous lakes developed faster, were larger at maturation, produced more offspring, and had higher intrinsic rates of increase in the absence of cyanobacteria. Such trends disappeared or reversed as cyanobacteria concentration was increased because Daphnia from anadromous lakes were more strongly influenced by the presence of cyanobacteria. Our results argue that alewife migration and phytoplankton composition both play a role in Daphnia evolution.

Effect of nutrient media on photobiological hydrogen production by Anabaena variabilis ATCC 29413

This study reports a factor 5.5 increase in hydrogen production by Anabaena variabilis ATCC 29413 using Allen–Arnon medium compared with BG-11 and BG-110 media. The results were obtained with a flat panel photobioreactor made of acrylic and operated in two stages at 30∘C. Stage 1 aims at converting carbon dioxide into biomass by photosynthesis while Stage 2 aims at producing hydrogen. During Stage 1, the photobioreactor was irradiated with 65μmol/m2/s (14W/m2) of light and sparged with a mixture of air (95% by volume) and carbon dioxide (5% by volume). During Stage 2, irradiance was increased to 150μmol/m2/s (32W/m2) and the photobioreactor was sparged with pure argon. The parameters continuously monitored were (1) the cyanobacteria concentration, (2) the pH, (3) the dissolved oxygen concentration, (4) the nitrate and (5) the ammonia concentrations in the medium, and (6) the hydrogen concentration in the effluent gas. The three media BG-11, BG-110, and Allen–Arnon were tested under otherwise similar conditions. The maximum cyanobacteria concentrations during Stage 2 were 1.10 and 1.17kgdrycell/m3 with BG-11 and Allen–Arnon media, respectively, while it could not exceed 0.76kgdrycell/m3 with medium BG-110. Moreover, the heterocyst frequency was 5%, 4%, and 9% for A.variabilis grown in BG-11, BG-110, and Allen–Arnon media. The average specific hydrogen production rates were about 8.0×10-5 and 7.2×10-5kgH2/kgdrycell/h (1 and 0.9LH2/kgdrycell/h at 1atm and 30∘C) in media BG-11 and BG-110, respectively. In contrast, it was about 4.5×10-4kgH2/kgdrycell/h (5.6LH2/kgdrycell/h at 1atm and 30∘C) in Allen–Arnon medium. The maximum light to hydrogen energy conversion efficiencies achieved were 0.26%, 0.16%, and 1.32% for BG-11, BG-110, and Allen–Arnon media, respectively. The larger heterocyst frequency, specific hydrogen production rates, efficiencies, and cyanobacteria concentrations achieved using Allen–Arnon medium were attributed to higher concentrations of magnesium, calcium, sodium, and potassium in the medium. Finally, presence of vanadium in Allen–Arnon medium could have induced the transcription of vanadium based nitrogenase which is capable of evolving more hydrogen than molybdenum based one.

Abundance and cellular characteristics of marine Synechococcus spp. in the dilution zone of the Changjiang (Yangtze River, China)

Concentrations of the marine cyanobacterium Synechococcus were estimated in the dilution zone of the Changjiang (Yangtze River, China) using epifluorescence microscopy while cell size and photosynthetic pigment content were measured with flow cytometry. Cyanobacteria concentrations (10 2–10 3 cell ml −1 in winter and 10 2–10 5 cell ml −1 in summer) increased in the offshore direction and reached their maximum at the most marine stations in winter and at stations of intermediate salinities (25–30 g l −1) in summer. In the latter season, concentrations in excess of 10 4 cell ml −1 developed in the surface layer when the euphotic depth increased beyond 10 m as a result of suspended matter sedimentation. Cell concentrations fell by an order of magnitude below the thermocline in comparison to the surface layer and the highest values were associated with the saline waters of the Taiwan Current. In summer Synechococcus cell size (as measured by light scattered at 90° angle) was the smallest in the region of maximum cell concentration, probably in relation to the high population growth rate there. Cell phycoerythrin content (measured by fluorescence) was related to light availability and to a lesser extent to inorganic nitrogen concentration.