Harmful Cyanobacterial Blooms Research Articles

Comparison of Bacterial Assemblages Associated with Harmful Cyanobacteria under Different Light Conditions.

Harmful cyanobacterial blooms in freshwater ecosystems are closely associated with changes in the composition of symbiotic microbiomes, water quality, and environmental factors. In this work, the relationship between two representative harmful cyanobacterial species (Anabaena sp. and Microcystis sp.) and their associated bacterial assemblages were investigated using a 16S rRNA-based meta-amplicon sequencing analysis during a large-scale cultivation of cyanobacteria under different light conditions with limited wavelength ranges (natural light, blue-filtered light, green-filtered light, and dark conditions). During the cultivation periods, the growth pattern of cyanobacteria and bacterial composition of the phycosphere considerably varied in relation to light restrictions. Unlike other conditions, the cyanobacterial species exhibited significant growth during the cultivation period under both the natural and the blue light conditions. Analyses of the nitrogenous substances revealed that nitrogen assimilation by nitrate reductase for the growth of cyanobacteria occurred primarily under natural light conditions, whereas nitrogenase in symbiotic bacteria could also be activated under blue light conditions. Sphingobium sp., associated with nitrogen assimilation via nitrogenase, was particularly dominant when the cell density of Microcystis sp. increased under the blue light conditions. Thus, cyanobacteria could have symbiotic relationships with ammonium-assimilating bacteria under light-limited conditions, which aids the growth of cyanobacteria.

Year-long monitoring of phytoplankton community, toxigenic cyanobacteria, and total microcystins in a eutrophic tropical dam supplying the Mexico megacity

The Valle de Bravo dam is an important source of drinking water supply for the Mexico City Conurbation (>26 million inhabitants) and is also a hotspot for nautical sports, recreational fishing, and tourism. However, anthropogenic pressures in the upper reaches of the basin have led to increased eutrophication and numerous harmful cyanobacterial blooms (HCBs). To determine the effect of abiotic variables on the characteristics of the phytoplanktonic community, as well as their influence on the diversity of toxigenic cyanobacteria and related cyanotoxins, we evaluated monthly variations in environmental factors, phytoplankton biovolume and composition and total microcystins in Valle de Bravo dam during the year of 2019. Overall, 75 phytoplanktonic species were identified, mostly belonging to the divisions Cyanobacteria, Chlorophyta, and Bacillariophyta. Cyanobacteria presented the highest biomass throughout the year, with water temperature and rainfall being the best correlated factors. The highest concentrations of total microcystins were recorded from July to September (maximum of 71 μg L−1), associated with the dominance of species such as M. smithii, M. aeruginosa, M. viridis M. flos-aquae, Aphanocapsa planctonica, and Dolichospermum crassum, and environmental factors such as rainfall, total dissolved solids, water temperature, and specific trace metals. In all months except December, the total cyanobacterial biovolume was above the World Health Organization alert level two, indicating potentially high risks to human health. The predominance of cyanobacteria and high biovolumes classified water quality as poor to very poor during most of the year. To avoid the development of HCBs in this dam, the contribution of nutrients by the tributary rivers and sewage must be controlled, since the poor-quality conditions of the water threaten the aquatic biota, the sports and recreation activities and affect the potable water supply.

Urbanization and seasonality strengthens the CO2 capacity of the Red River Delta, Vietnam

Tropical rivers are dynamic CO2 sources. Regional patterns in the partial pressure of CO2 (pCO2) and relationships with other a/biotic factors in densely populated and rapidly developing river delta regions of Southeast Asia are still poorly constrained. Over one year, at 21 sites across the river system in the Red River Delta (RRD), Vietnam, we calculated pCO2 levels from temperature, pH, and total alkalinity and inter-linkages between pCO2 and phytoplankton, water chemistry and seasonality were then assessed. The smaller, more urbanized, and polluted Day River had an annual median pCO2 of 5000 ± 3300 µatm and the larger Red River of 2675 ± 2271 µatm. pCO2 was 1.6 and 3.2 times higher during the dry season in the Day and Red rivers respectively than the rainy season. Elevated pCO2 levels in the Day River during the dry season were also 2.4-fold higher than the median value (2811 ± 3577 µatm) of calculated and direct pCO2 measurements in >20 sub/tropical rivers. By further categorizing the river data into Hanoi City vs. other less urban-populated provinces, we found significantly higher nutrients, organic matter content, and riverine cyanobacteria during the dry season in the Day River across Hanoi City. Forward selection also identified riverine cyanobacteria and river discharge as the main predictors explaining pCO2 variation in the RRD. After accounting for the shared effects (14%), river discharge alone significantly explained 12% of the pCO2 variation, cyanobacteria uniquely a further 21%, while 53% of the pCO2 variance was unexplained by either. We show that the urbanization of rivers deltas could result in increased sources of riverine pCO2, water pollution, and harmful cyanobacterial blooms. Such risks could be mitigated through water management to increase water flows in problem areas during the dry season.

The combined impact of low temperatures and shifting phosphorus availability on the competitive ability of cyanobacteria

In freshwater systems, cyanobacteria are strong competitors under enhanced temperature and eutrophic conditions. Understanding their adaptive and evolutionary potential to multiple environmental states allows us to accurately predict their response to future conditions. To better understand if the combined impacts of temperature and nutrient limitation could suppress the cyanobacterial blooms, a single strain of Microcystis aeruginosa was inoculated into natural phytoplankton communities with different nutrient conditions: oligotrophic, eutrophic and eutrophic with the addition of bentophos. We found that the use of the bentophos treatment causes significant differences in prokaryotic and eukaryotic communities. This resulted in reduced biodiversity among the eukaryotes and a decline in cyanobacterial abundance suggesting phosphorus limitation had a strong impact on the community structure. The low temperature during the experiment lead to the disappearance of M. aeruginosa in all treatments and gave other phytoplankton groups a competitive advantage leading to the dominance of the eukaryotic families that have diverse morphologies and nutritional modes. These results show cyanobacteria have a reduced competitive advantage under certain temperature and nutrient limiting conditions and therefore, controlling phosphorus concentrations could be a possible mitigation strategy for managing harmful cyanobacterial blooms in a future warmer climate.

A Virtual Sensing Concept for Nitrogen and Phosphorus Monitoring Using Machine Learning Techniques.

Harmful cyanobacterial bloom (HCB) is problematic for drinking water treatment, and some of its strains can produce toxins that significantly affect human health. To better control eutrophication and HCB, catchment managers need to continuously keep track of nitrogen (N) and phosphorus (P) in the water bodies. However, the high-frequency monitoring of these water quality indicators is not economical. In these cases, machine learning techniques may serve as viable alternatives since they can learn directly from the available surrogate data. In the present work, a random forest, extremely randomized trees (ET), extreme gradient boosting, k-nearest neighbors, a light gradient boosting machine, and bagging regressor-based virtual sensors were used to predict N and P in two catchments with contrasting land uses. The effect of data scaling and missing value imputation were also assessed, while the Shapley additive explanations were used to rank feature importance. A specification book, sensitivity analysis, and best practices for developing virtual sensors are discussed. Results show that ET, MinMax scaler, and a multivariate imputer were the best predictive model, scaler, and imputer, respectively. The highest predictive performance, reported in terms of R2, was 97% in the rural catchment and 82% in an urban catchment.

Developing cyanobacterial bloom predictive models using influential factor discrimination approach for eutrophic shallow lakes

Harmful cyanobacterial blooms damage aquatic ecosystems and pose a threat to human health. To identify key factors causing cyanobacterial blooms in eutrophic shallow lakes, we analyzed cyanobacterial and physicochemical water samples of 12 sites collected monthly from December 2012 to December 2019 in Dianshan Lake. We found that the rapid growth of cyanobacteria was limited by a temperature threshold. When the air temperature was below 18 °C, the sampled physicochemical factors could not make difference in cyanobacterial abundance regardless the values of these parameters. However, when the air temperature was above 18 °C, the measured physicochemical factors played important roles in influencing cyanobacterial abundance. We developed a data-driven predictive model for cyanobacterial blooms based on seven-year data from Dianshan Lake using multiple logistic regression. Such a model could be easily used to predict cyanobacterial blooms. Our weight analysis of model parameters indicated that dissolved substances other than TN and TP are the key factor determining cyanobacterial blooms in nitrogen and phosphorus rich shallow freshwater lakes once air temperature is above 18 °C. Eutrophic shallow lakes are prone to cyanobacterial blooms, and unwashed data analysis may mask key factors determining cyanobacterial blooms, which obscures the prediction of cyanobacteria blooms. Our results are helpful to uncover the real causes of the blooms of eutrophic shallow lakes in China and elsewhere, and hence improve the understanding and management in controlling cyanobacterial blooms.

Reporting of Freshwater Cyanobacterial Poisoning in Terrestrial Wildlife: A Systematic Map.

Simple SummaryHarmful cyanobacterial blooms (cyanoHABs) have been reported globally, threatening human and animal health. They are encouraged by the warming climate and agricultural pollution creating nutrient-rich, warm environments, ideal for cyanobacterial proliferation. The cyanotoxins produced by these blooms have caused poisonings in many wildlife species; however, these cases are severely underreported, and many are likely missed. The aim of this systematic map was to collate, organise, and characterise all existing reports of cyanotoxin poisonings in terrestrial wildlife. We conducted a search of the published literature using online databases, yielding a total of 45 cases detailing incidents involving terrestrial wildlife. There is no current standard method for the reporting and diagnosis of cyanotoxin intoxication cases, and we provide recommendations on this to include both clinical diagnostic tools and investigative chemistry techniques. Less than half of all cases employed robust methods of detection and diagnosis based on our recommendations. Most cases were investigated after poisonings had already occurred, and only nine reports mentioned any effort to mitigate the effects of harmful cyanobacteria on terrestrial wildlife. This systematic map details terrestrial wildlife cyanotoxin intoxications from a diagnostic perspective, identifying how reporting can be improved, leading to more successful mitigation and investigative efforts in the future.Global warming and over-enrichment of freshwater systems have led to an increase in harmful cyanobacterial blooms (cyanoHABs), affecting human and animal health. The aim of this systematic map was to detail the current literature surrounding cyanotoxin poisonings in terrestrial wildlife and identify possible improvements to reports of morbidity and mortality from cyanotoxins. A systematic search was conducted using the electronic databases Scopus and Web of Science, yielding 5059 published studies identifying 45 separate case reports of wildlife poisonings from North America, Africa, Europe, and Asia. Currently, no gold standard for the diagnosis of cyanotoxin intoxication exists for wildlife, and we present suggested guidelines here. These involved immunoassays and analytical chemistry techniques to identify the toxin involved, PCR to identify the cyanobacterial species involved, and evidence of ingestion or exposure to cyanotoxins in the animals affected. Of the 45 cases, our recommended methods concurred with 48.9% of cases. Most often, cases were investigated after a mortality event had already occurred, and where mitigation was implemented, only three cases were successful in their efforts. Notably, only one case of invasive cyanobacteria was recorded in this review despite invasive species being known to occur throughout the globe; this could explain the underreporting of invasive cyanobacteria. This systematic map highlights the perceived absence of robust detection, surveillance, and diagnosis of cyanotoxin poisoning in wildlife. It may be true that wildlife is less susceptible to these poisoning events; however, the true rates of poisoning are likely much more than is reported in the literature.

New insights into the production of fucoxanthin by mixotrophic cultivation of Ochromonas and Microcystis aeruginosa

Fucoxanthin (Fx) has attracted great interest due to its remarkable biological activities such as antioxidant and anti-obesity, and its increasing demands in biopharmaceutical and cosmetic fields. However, its commercial production is limited by low yield and high cost. In this study, we isolated and identified a species of golden algae (Ochromonas sp.) capable of engulfing Microcystis aeruginosa (M. aeruginosa) and accumulating Fx. After 72 h mixotrophic cultivation of Ochromonas sp. and M. aeruginosa, the algal culture changed from green to yellow–brown, and the content of Fx and the daily production rate were up to 11.58 mg g−1, and 1.315 mg L-1 d-1, respectively. The utilization rate of M. aeruginosa was 527.27 fg cell−1. This study will not only provide a new thought to produce Fx in an efficient, low-cost, and sustainable way but an innovative method for the control and treatment of harmful cyanobacterial blooms from eutrophic freshwaters as well.

Nitrogen fixation contribution to nitrogen cycling during cyanobacterial blooms in Utah Lake.

Nitrogen (N) cycling is an essential process in lake systems and N-fixation is an important component of it. Recent studies have also found that nitrate reduction through heterotrophic denitrification in lake systems did not prevent harmful cyanobacterial blooms, but instead, may have favored the dominance of N2-fixing cyanobacteria. The overall objective of this study was to estimate nitrogen fixation rates and the expressions of associated nitrogenase (nif gene) functional gene at several sites at different occasions in freshwater Utah Lake. For comparison purposes, one time sampling was also conducted in the brackish Farmington Bay of Great Salt Lake (GSL). The microbial ecology of the top 20-cm of surface water was investigated to assess the dominant cyanobacterial communities and N-related metabolisms. Our study revealed that Dolichospermum and Nodularia were potential N2-fixers for Utah Lake and brackish Farmington Bay, respectively. The in situ N2-fixation rates were 0-0.73nmolN hr-1L-1 for Utah Lake and 0-0.85nmolN hr-1L-1 for Farmington Bay, and these rates positively correlated with the abundance and expressions of the nif gene. In addition, nitrate reduction was measured in sediment (0.002-0.094mgN VSS-1 hr-1). Significantly positive correlations were found among amoA, nirS and nirK abundance (R=0.56-0.87, p<0.05, Spearman) in both lakes. An exception was the lower nirK gene abundance detected at one site in Farmington Bay where high ammonium retentions were also detected. Based on a mass balance approach, we concluded that the amount of inorganic N loss through denitrification still exceeded the N input by N2-fixation, much like in most lakes, rivers, and marine ecosystems. This indicates that N cycling processes such as denitrification mediated by heterotrophic bacteria contributes to N-export from the lakes resulting in N limitations.

Compounds to mitigate cyanobacterial blooms affect growth and toxicity of Microcystis aeruginosa

Numerous products and techniques are used to combat harmful cyanobacterial blooms in lakes. In this study, we tested nine products, the phosphate binders Phoslock® and Aqual-PTM, the coagulant chitosan, the phosphorus binder and coagulant aluminum salts (aluminum sulphate and sodium aluminate), the copper-based algicides SeClear, Captain® XTR and CuSO4·5H2O, the antibiotic Streptomycin and the oxidant hydrogen peroxide (H2O2) on their efficiency to manage the cyanobacterium Microcystis aeruginosa (M. aeruginosa). To this end, 7 days of laboratory experiments were conducted and effects were determined on chlorophyll-a, photosystem II efficiency (PSII), soluble reactive phosphorus (SRP) and intracellular and extracellular microcystin (MC) concentrations. The algicides, chitosan and H2O2 were the most powerful in reducing cyanobacteria biomass. Biomass reductions compared to the controls yielded: Chitosan (99.8%) > Hydrogen peroxide (99.6%) > Captain XTR (98.2%) > SeClear (98.1%) > CuSO4·5H2O (97.8%) > Streptomycin (86.6%) > Phoslock® (42.6%) > Aqual-PTM (28.4%) > alum (5.5%). Compounds that caused the largest reductions in biomass also strongly lowered photosystem II efficiency, while the other compounds (Phoslock®, Aqual-PTM, aluminum salts) had no effect on PSII, but strongly reduced SRP. Intracellular MC concentration followed the biomass patterns, extracellular MC was generally lower at higher doses of algicides, chitosan and H2O2 after one week. Recovery of PSII was observed in most algicides and chitosan, but not at the highest doses of SeClear and in all streptomycin treatments. Our results revealed that M. aeruginosa can be killed rapidly using several compounds, that in some treatments already signs of recovery occurred within one week. P fixatives are efficient in reducing SRP, and thus acting via resource suppression, which potentially may provide an addition to fast-acting algicides that kill most of the cells, but allow rapid regrowth as sufficient nutrients remain.

Tidal water exchanges can shape the phytoplankton community structure and reduce the risk of harmful cyanobacterial blooms in a semi-closed lake

Tidal water exchanges can shape the phytoplankton community structure and reduce the risk of harmful cyanobacterial blooms in a semi-closed lake

Immobilization of Microbes for Biodegradation of Microcystins: A Mini Review.

Harmful cyanobacterial blooms (HCBs) frequently occur in eutrophic freshwater ecosystems worldwide. Microcystins (MCs) are considered to be the most prominent and toxic metabolites during HCBs. MCs may be harmful to human and animal health through drinking water and recreational water. Biodegradation is eco-friendly, cost-effective and one of the most effective methods to remove MCs. Many novel MC-degrading bacteria and their potential for MCs degradation have been documented. However, it is a challenge to apply the free MC-degrading bacterial cells in natural environments due to the long-term operational instability and difficult recycling. Immobilization is the process of restricting the mobility of bacteria using carriers, which has several advantages as biocatalysts compared to free bacterial cells. Biological water treatment systems with microbial immobilization technology can potentially be utilized to treat MC-polluted wastewater. In this review article, various types of supporting materials and methods for microbial immobilization and the application of bacterial immobilization technology for the treatment of MCs-contaminated water are discussed. This article may further broaden the application of microbial immobilization technology to the bioremediation of MC-polluted environments.

Development of a Potentially New Algaecide for Controlling Harmful Cyanobacteria Blooms Which is Ecologically Safe and Selective.

Harmful cyanobacterial blooms (HCBs) caused by Microcystis aeruginosa are of great concern as they negatively affect the aquatic environment and human health. Chemical methods could rapidly eradicate HCBs and have been used for many decades. However, many chemical reagents are not recommended to eliminate HCBs in the long term, given the possible destructive and toxic effects of the chemicals employed on non-target aquatic organisms. We developed a new algaecide, 2-((1,3,4-thiadiazol-2-yl)thio)-N-(4-chlorophenyl) acetamide (Q2), to control harmful cyanobacteria while being environmentally friendly and selective. In our study, Q2 effectively inhibited cyanobacterial growth, especially of M. aeruginosa, but did not affect eukaryotic algae in test concentrations. A critical mechanism was revealed by transcriptome and metagenomic results showing that Q2 affects multiple cellular targets of cyanobacteria for HCB control, including the destruction of organelles, damage in the photosynthesis center, as well as inhibition of gas vesicle growth, and these changes can be highly relevant to the decrease of quorum-sensing functional KEGG pathways. Furthermore, Q2 did not affect the microbial composition and could recover the disrupted aquatic functional pathways in a short period. This is different from the impact on ecosystem functioning of the traditionally used harmful algaecide diuron. All these results verified that Q2 could be friendly to the aquatic environment, providing a new directional choice in managing HCBs in the future.

Mitigation of Cyanobacteria Isolated from Tri An Reservoir Using Local Soils

Cyanobacterial blooms in eutrophic waters pose serious threats to public health, water quality, and ecological management worldwide. Mitigation of the problem is essential to maintain stainable development. In this study, the effectiveness of local soils collected from the Tri An Reservoir (TAR) lakeside in the removal of cyanobacteria Microcystis aeruginosa was investigated. The organic matter content and clay mineral were characterized and used for the experiment. Cell density, percentage of growth inhibition, and changes in cell morphology were observed and used at endpoints of the experiment. The three soil samples named TA1, TA2, and TA3 were characterized with a high proportion of illit, montmorillonit, and kaolinite, respectively. Our results indicated that different soil compositions generated different inhibition on the growth of M. aeruginosa. Exposure to the soil high in kaolinite (52.1%) at a dose of 500 mg/L completely inhibited M. Aeruginosa growth, while the soil contained a high amount of montmorillonit (42.3%) inhibited only 38.4% of the growth of M. aeruginosa. The half-maximal effective concentration (EC50) values of the TA1, TA2, and TA3 soil samples were 351.6 mg/L, 668.9 mg/L, 201.3 mg/L, respectively. Our results suggested that soil rich in kaolinite can be used to prevent harmful cyanobacterial blooms in inland waters.

Downstream Transport of Geosmin Based on Harmful Cyanobacterial Outbreak Upstream in a Reservoir Cascade.

Understanding water quality events in a multiple-impoundment series is important but seldom presented comprehensively. Therefore, this study was conducted to systematically understand the explosion event of geosmin (GSM) in the North Han River (Chuncheon, Soyang, Euiam, and Cheongpyeong Reservoirs) and Han River (Paldang Reservoir), which consists of a cascade reservoir series, the largest drinking water source system in South Korea. We investigated the spatiotemporal relationship of harmful cyanobacterial blooms in the upstream reservoir (Euiam) with the water quality incident event caused by the GSM in the downstream reservoir (Paldang) from January to December 2011. The harmful cyanobacterial bloom occurred during August–September under a high water temperature (>20 °C) after a heavy-rainfall-based flood runoff event. The high chlorophyll-a (Chl-a) concentration in the upper Euiam Reservoir was prolonged for two months with a maximum concentration of 1150.5 mg m−3, in which the filamentous Dolichospermum circinale Kütz dominated the algal community at a rate of >99%. These parameters remarkably decreased (17.3 mg Chl-a m−3) in October 2011 when the water temperature decreased (5 °C) and soluble reactive phosphorus was depleted. However, high and unprecedented GSM concentrations, with a maximum value of 1640 ng L−1, were detected in the downstream reservoirs (Cheongpyeong and Paldang); the level was 11 times higher than the value (10 ng L−1) recommended by the World Health Organization. The concentrations of GSM gradually decreased and had an adverse effect on the drinking water quality until the end of December 2011. Our study indicated that the time lag between the summer–fall cyanobacterial outbreak in the upstream reservoir and winter GSM explosion events in the downstream reservoirs could be attributed to the transport and release of GSM through the effluent from hydroelectric power generation in this multiple-reservoir system. Therefore, we suggest that a structural understanding of the reservoir cascade be considered during water quality management of drinking water sources to avoid such incidents in the future.

Efficient photocatalytic inactivation of Microcystis aeruginosa via self-floating Ag3VO4/BiVO4 hydrogel under visible light

In this work, a facile separation of self-floating Ag3VO4/BiVO4 hydrogel (ABVH) photocatalyst was constructed via the freeze-thaw method for the inactivation of Microcystis aeruginosa. The as-synthesized photocatalyst exhibited excellent photocatalytic performance, resulting in the degradation efficiency of chlorophyll a reaching approximately 99.6% within 4 h under visible light. The cell morphology, intracellular organic matter (IOM), extracellular organic matter (EOM), and antioxidant system were severely disrupted during the photocatalytic process. The inactivation mechanism could be ascribed to the ·OH and h+ generated by hydrogel photocatalyst under visible light irradiation. Furthermore, five repetitive experiments and cyclic compressive stress-strain tests demonstrated that the as-prepared hydrogel possessed excellent reusability and mechanical strength properties. Besides, the hydrogel photocatalyst showed excellent potential for the removal of M. aeruginosa in the presence of natural organic matter (NOM). Overall, the synthesized self-floating hydrogel photocatalyst may offer a novel insight into the control of harmful cyanobacterial blooms.

The role of internal nitrogen loading in supportingnon‐N‐fixing harmful cyanobacterial blooms in the water column of a large eutrophic lake

AbstractWestern Lake Erie cyanobacterial harmful algal blooms (cyanoHABs) occur every summer as a result of anthropogenic nutrient loading. Although the physiological importance of nitrogen (N) in supporting bloom biomass and toxin production is established, the role of internal N recycling in the water column to support bloom maintenance is not as well understood. Over three field seasons (2015–2017), we collected water from western Lake Erie and employed bottle incubations with15N‐ammonium () enrichments to determine regeneration and potential uptake rates in the water column. Potential uptake rates followed spatial and seasonal patterns, with greatest rates measured nearest the Maumee River inflow and during peak bloom months (August and September). Regeneration followed a similar spatial pattern but was greatest in early summer (June and July) and supported ~ 20–60% of potential demand during the height of the bloom. Basin‐wide internal regeneration during the April–October period could supply at 60–200% of annual external N loading to the western basin. These results help explain how non‐N‐fixing cyanoHABs in Lake Erie and other large, eutrophic lakes continue producing biomass and N‐rich toxins long after spring nutrient loads are exhausted or transported to other areas. Internal N loads are ultimately driven by external N loads; in low precipitation years, external nutrient loads result in smaller blooms, producing less substrate for subsequent internal N loads. Overall, these findings, along with others, confirm that both internal and external N loading must be considered when evaluating cyanoHAB management strategies.

Impact of climate change on catchment nutrient dynamics: insights from around the world

This study is a meta-analysis of global articles on hydrological nutrient dynamics to determine trends and consensus on: (1) the effects of climate change-induced hydrological and temperature drivers on nutrient dynamics and how these effects vary along the catchment continuum from land to river to lake; (2) the convergence of climate change impacts with other anthropogenic pressures (agriculture, urbanization) in nutrient dynamics; and (3) regional variability in the effects of climate change on nutrient dynamics and water-quality impairment across different climate zones. An innovative web crawler tool was employed to help critically synthesize the information in the literature. The literature suggests that climate change will impact nutrient dynamics around the globe and exacerbate contemporary water-quality challenges. Nutrient leaching and overland flow transport are projected to increase globally, promoted by extreme precipitation. Seasonal variations in streamflow are expected to emulate changing precipitation patterns, but the specific local impacts of climate change on hydrology and nutrient dynamics will vary both seasonally and regionally. Plant activity may reduce some of this load in nonagricultural soils if the expected increase in plant uptake of nutrients prompted by increased temperatures can compensate for greater nitrogen (N) and phosphorus (P) mineralization, N deposition, and leaching rates. High-temperature forest and grass fires may help reduce mineralization and microbial turnover by altering N speciation via the pyrolysis of organic matter. In agricultural areas that are at higher risk of erosion, extreme precipitation will exacerbate existing water-quality issues, and greater plant nutrient uptake may lead to an increase in fertilizer use. Future urban expansion will amplify these effects. Higher ambient temperatures will promote harmful cyanobacterial blooms by enhancing thermal stratification, increasing nutrient load into streams and lakes from extreme precipitation events, decreasing summer flow and thus baseflow dilution capacity, and increasing water and nutrient residence times during increasingly frequent droughts. Land management decisions must consider the nuanced regional and seasonal changes identified in this review (realized and predicted). Such knowledge is critical to increasing international cooperation and accelerating action toward the United Nations’s global sustainability goals and the specific objectives of the Conference of Parties (COP) 26.

Transcriptome Analysis Reveals the Algicidal Mechanism of Brevibacillus laterosporus against Microcystis aeruginosa through Multiple Metabolic Pathways.

It is widely accepted that eutrophication has played an important role in the formation of harmful cyanobacterial blooms in recent decades, which impacts water quality and ecological environment and causes huge economic losses. Algicidal bacteria have a promising application prospect in controlling cyanobacterial blooms in aquaculture water. Here, the process of the algicidal bacterium Brevibacillus laterosporus strain Bl-zj acting on Microcystis aeruginosa was explored using transcriptome analysis to elucidate the algicidal mechanism. The results of the co-culture of bacterium and alga showed a strong alga-lysing effect of B. laterosporus against M. aeruginosa with an extreme morphology deformation of the algal cells. A total of 2744 differentially expressed genes of B. laterosporus were identified, which were mainly involved in the metabolism of amino acid, carbohydrate, and lipid. In the co-cultured group, the expression of genes mainly enriched in valine, leucine and isoleucine degradation, and fatty acid degradation were significantly increased. However, the expression of the genes related to ribosome were mainly inhibited. Transcriptome analysis showed that B. laterosporus obtained ATP and energy by the degradation of valine, leucine, isoleucine, and fatty acids, and destroyed algal cells by efflux pump transporters, secretion of hydrolytic enzymes, antibiotics, proteases, and other secondary metabolites, resulting in algal death and achieving the algicidal effect.

River phosphorus cycling during high flow may constrain Lake Erie cyanobacteria blooms

Cyanobacterial harmful blooms have been increasing worldwide, due in part to excessive phosphorus (P) losses from agriculture-dominated watersheds. Unfortunately, cyanobacteria bloom management is often complicated by uncertainty associated with river P cycling. River P cycling mediates P exports during low flow but has been assumed to be unimportant during high flows. Thus, we examined interactions between dissolved reactive phosphorus (DRP) and suspended sediment P during high flows in the Maumee River network, focusing on March–June Maumee River DRP exports, which fuel recurring cyanobacteria blooms in Lake Erie. We estimate that during 2003–2019 March to June high flow events, P sorption reduced DRP exports by an average of 13–27%, depending upon the colloidal-P:DRP ratio, decreasing the bioavailability of P exports, and potentially constraining cyanobacteria blooms by 13–40%. Phosphorus sorption was likely lower during 2003–2019 than 1975–2002 due to reductions in suspended sediment loads, associated with soil-erosion-minimizing agricultural practices. This unintended outcome of erosion management has likely decreased P sorption, increased DRP exports to Lake Erie, and subsequent cyanobacteria blooms. In other watersheds, DRP–sediment P interactions during high flow could have a positive or negative effect on DRP exports; therefore, P management should consider riverine P cycles, particularly during high flow events, to avoid undermining expensive P mitigation efforts.