Cyanobacteria Blooms Research Articles

The Role of Climate Change in the Proliferation of Freshwater Harmful Algal Blooms in Inland Water Bodies of the United States

Abstract Harmful algae and cyanobacteria blooms are increasing in frequency and intensity in freshwater systems due to anthropogenic impacts such as nutrient loading in watersheds and engineered alterations of natural waterways. There are multiple physical factors that affect the conditions in a freshwater system that contribute to optimal habitats for harmful algae and toxin-producing cyanobacteria. A growing body of research shows that climate change stressors also are impacting water-body conditions that favor harmful algae and cyanobacteria species over other phytoplankton. The overgrowth of these organisms, or a “bloom,” increases the opportunity for exposure to toxins by humans, companion animals, livestock, and wildlife. As waters warm and precipitation patterns change over time, exposure to these blooms is projected to increase. Hence, it is important that states and tribes develop monitoring and reporting strategies as well as align governmental policies to protect their citizens and ecosystems within their jurisdiction. Currently, the policies and approaches taken to monitor and report on harmful algae and cyanobacteria blooms vary widely among states, and it is undetermined if any tribes have specific policies on harmful algae blooms. This paper synthesizes research on algal blooms in inland freshwater systems of the United States. This review examines how climate change contributes to trends in bloom frequency or severity and outlines approaches that states and tribes may use to monitor, report, and respond to harmful algae and cyanobacteria blooms. Significance Statement Inland bodies of freshwater supply drinking water for humans and animals, water for irrigating crops, habitats for aquatic species, places of cultural significance for Indigenous peoples, and other important functions. Many of these bodies of water have been polluted with runoff from industry, including agriculture, and already support harmful algal blooms during warm conditions. Hot extremes associated with climate change are expected to increase the occurrence and duration of harmful algal blooms, and in some places, initiate blooms where none have been recorded previously. These toxic blooms are harmful to people, companion animals, livestock, and wildlife. It is important to review the interconnections among biological, climate, and water systems to monitor blooms and alert the public about their toxin production.

Hydraulic control on sedimentation processes and bottom sediments chemistry of Sulejów Reservoir in Poland

Abstract The Sulejów reservoir is one of the largest reservoirs in Poland and is exposed to a large flux of nutrients from both point and diffuse sources, which leads to an excessive amount of eutrophication and cyanobacteria bloom. The underlying inspiration for this paper was to use a 1D HEC-RAS hydrodynamic model to improve the knowledge of sedimentation conditions and the chemistry of bottom sediments in the context of reservoir eutrophication and algae bloom. Field sampling was performed, and chemical concentrations of Total Organic Carbon, Total Phosphorus, and Cadmium were measured in samples from bottom sediments. The deepest parts of the reservoir and the presence of sediment traps coincide with the highest concentrations of organic carbon, nutrients, and heavy metals. The paper has shown that reservoir hydrodynamic modelling and precise bathymetry maps provide very valuable information that can be used for the interpretation of bottom sediment chemistry patterns and for understanding the conditions of sedimentation.

An Improved ResNet50 for Environment Image Classification

With the drastic changes in the ecological environment, the issue of blue-green algae blooms has become increasingly common, significantly affecting human habitats. Real-time image data extraction and classification via deep learning models play a critical role in detecting blue-green algae in water bodies and facilitating subsequent alerts and interventions. However, current research in this field faces several challenges. Firstly, traditional convolutional methods struggle to effectively extract features such as textures and outlines from images. Secondly, the target and background areas in captured images often share similar environments, leading to classification errors. Addressing these issues, this paper initially enhances the feature representation capabilities of the ResNet50 architecture by integrating a detail feature extraction module. Subsequently, a binary mask image fusion method is proposed to direct the model’s focus towards learning features of water regions. Our constructed model shows improved classification performance on real-time camera data compared to other classification models.

Introducing fluorescent probe technology for detecting microcystin-LR in the water and cells

BackgroundFor a long time, the environment hazards caused by cyanobacteria bloom and associated microcystins have attracted attention worldwide. Microcystin-LR (MC-LR) is the most widely distributed and most toxic toxin. At present, numerous MC-LR detection methods exist many drawbacks. Therefore, a quick and accurate method for identifying and detecting MC-LR is crucial and necessary. In this work, we strived to introduce a novel fluorescence assay to detect MC-LR in the water and cells. ResultsAccording to the special spatial configuration and physicochemical properties of MC-LR, we designed and constructed six fluorescent probes. The design concepts of the probes were exhaustively elaborated. MC-YdTPA, MC-YdTPE, MC-RdTPA, and MC-RdTPE could show significant fluorescence enhancement in MC-LR solution. Significantly, MC-YdTPA, MC-YdTPE, and MC-RdTPA could also response well in the cells treated with MC-LR, demonstrating these fluorescent probes’ values. The recognition mechanism between probes and MC-LR were also deeply explored: (1) The polyphenylene ring structure of probes may have nested or hydrogen bond weak interaction with the ring structure of MC-LR. (2) The probes can generate a reaction to the hydrogen ions ionized by MC-LR. SignificanceWe proposed the novel ideas for designing MC-LR probes. This research can provide valuable experiences and important assistance in synthesizing MC-LR fluorescent probes. We expect that this work may bring new ideas to develop fluorescent probes for researching MC-LR in vivo and in vitro.

Resolving phytoplankton pigments from spectral images using convolutional neural networks

AbstractMotivated by the need for rapid and robust monitoring of phytoplankton in inland waters, this article introduces a protocol based on a mobile spectral imager for assessing phytoplankton pigments from water samples. The protocol includes (1) sample concentrating; (2) spectral imaging; and (3) convolutional neural networks (CNNs) to resolve concentrations of chlorophyll a (Chl a), carotenoids, and phycocyanin. The protocol was demonstrated with samples from 20 lakes across Scotland, with special emphasis on Loch Leven where blooms of cyanobacteria are frequent. In parallel, samples were prepared for reference observations of Chl a and carotenoids by high‐performance liquid chromatography and of phycocyanin by spectrophotometry. Robustness of the CNNs were investigated by excluding each lake from model trainings one at a time and using the excluded data as independent test data. For Loch Leven, median absolute percentage difference (MAPD) was 15% for Chl a and 36% for carotenoids. MAPD in estimated phycocyanin concentration was high (102%); however, the system was able to indicate the possibility of a cyanobacteria bloom. In the leave‐one‐out tests with the other lakes, MAPD was 26% for Chl a, 27% for carotenoids, and 75% for phycocyanin. The higher error for phycocyanin was likely due to variation in the data distribution and reference observations. It was concluded that this protocol could support phytoplankton monitoring by using Chl a and carotenoids as proxies for biomass. Greater focus on the distribution and volume of the training data would improve the phycocyanin estimates.

Microcystin-LR-induced autophagy via miR-282–5p/PIK3R1 pathway in Eriocheir sinensis hepatopancreas

With the intensifying climate warming, blue-green algae blooms have become more frequent and severe, releasing environmental hazards such as microcystin that pose potential threats to human and animal health. Autophagy has been shown to play a crucial role in regulating immune responses induced by environmental hazards, enabling cells to adapt to stress and protect against damage. Although microcystin-LR (MC-LR) has been identified to affect autophagy in mammalian, its impact on aquatic animals has been poorly studied. To investigate the toxicological effects of MC-LR in aquatic ecosystems, we constructed a microRNA profile of acute MC-LR stress in the hepatopancreas of the Chinese mitten crab. Interestingly, we found the MC-LR exposure activated autophagy in the hepatopancreas based on the following evidence. Specifically, mRNA expression level of ATG7, Beclin1 and Gabarap was significantly up-regulated, autophagy regulatory pathways were significantly enriched, and numerous autolysosomes and autophagosomes were observed. Additionally, we found that miR-282–5p and its target gene PIK3R1 played important regulatory roles in autophagy by in vivo and in vitro experiments. Overexpression of miR-282–5p mimicked MC-LR-induced autophagy by inhibiting PIK3R1 expression, while miR-282–5p silencing inhibited autophagy by promoting PIK3R1 expression. Altogether, our findings suggest that MC-LR increases miR-282–5p, which then targets inhibition of PIK3R1 to stimulate autophagy. This study focused on the stress response regulatory mechanisms of juvenile crabs to toxic pollutants in water, offering a potential target for alleviating the toxicity of MC-LR. These findings lay a foundation for reducing the toxicity of MC-LR and environmental hazards in organisms.

Understanding the dynamics of Microcystis bloom: Unraveling the influence of suspended solids through proteomics and metabolomics approaches

Light plays a crucial role in blue-green algae bloom formation in lakes, while suspended solids (SS) influence underwater light intensity. This study investigates the integrated effects of SS concentrations (0–125 mg/L) on Microcystis aeruginosa in natural conditions. Results show that SS inhibits cyanobacterial growth above 100 mg/L, with 25–75 mg/L favoring bloom formation. Proteomic analysis reveals differential protein involvement in ribosomes, ABC transporters, cofactor biosynthesis, and photosynthesis pathways at 25 mg/L SS. SS concentrations within the range of 25–125 mg/L significantly impact the metabolism of algal cells, resulting in an increase in lipid metabolism and a decrease in the biosynthesis of secondary metabolites in cyanobacteria. These coordinated biochemical adaptations play a vital role in the survival of cyanobacteria in challenging environmental conditions. Employing a multi-omics approach enhances our comprehension of how M. aeruginosa responds to SS and the underlying molecular mechanisms, thereby contributing to our understanding of cyanobacteria outbreaks. This underscores the importance of monitoring SS concentrations in lakes as a proactive measure for future control of cyanobacteria dominance.

Symptom frequency and exposure to a cyanobacteria bloom in Florida

This investigation was undertaken to characterize health effects associated with a major bloom of blue-green algae due to the proliferation Microcystis aeruginosa that occurred in Florida in 2018. Cyanobacteria produce multiple toxins, including the potent hepatotoxic microcystins (MCs), that have been reported to cause illness in exposed persons worldwide. Widespread exposure to toxins released by blue-green algae during the 2018 bloom was shown by the presence of MCs in the nasal passages of 95 percent of the individuals studied previously in south Florida (Schaefer et al., 2020). The current analyses were conducted to determine whether self-reported symptoms were associated with activity patterns, direct contact with water, residential, recreational, and occupational exposure. The 125 persons who participated in the initial study reported an average of 4.94 (± 4.87) symptoms. Those reported most commonly included rhinorrhea, sneezing, headache, sore throat and dry cough. Respiratory symptoms were reported by 74%, ocular symptoms by 62%, and gastrointestinal symptoms by 35% of respondents. Residential and recreational exposures were associated with increased risks of respiratory, gastrointestinal, or ocular symptoms in univariate and adjusted multivariable analyses. Residential exposure was significantly associated with increased reporting of dry cough (p = 0.03), dyspnea (p < 0.01) and wheezy respirations (p = 0.04). Among persons reporting gastrointestinal symptoms, nausea (p = 0.02) and abdominal pain (p < 0.01) were significantly associated with residential exposure. Recreational exposure was significantly associated with sore throat and eye irritation. The findings add to the evidence that exposure to cyanobacteria at concentrations encountered during an algal bloom is associated with a diverse array of symptoms and that inhalation of aerosols constitutes an important exposure pathway.

Management of the Risk of Blue-Green Algae Blooms in the Iskar Dam for Drinking Water Quality of Sofia City

The introduction of systems for ensuring quality and safe drinking water and risk management is the World Health Organization (WHO) good practice introduced as a legislative requirement for all water supply organizations (Directive EU 2020/2184) on the quality of water intended for human consumption. A specific object of this research is the implemented risk assessment and management system, part of the drinking water safety plan for Sofia city. The water supply system from the water source to the end user, operated by Sofiyska voda JSC and part of Veolia, was analyzed. The hazards and risk events were reviewed for each component of the system—the catchment, water source, supply water pipes, drinking water treatment plants (DWTPs) and distribution water network. The results of the risk evaluation show that the risk of an algal bloom falls from medium risk, with a value of 36 in 2018. This risk was new for the Iskar Dam—the main water source for Sofia city. The purpose of the current study is to analyze the risk of blue-green algae blooming and the potential release of toxins in the Iskar Dam. A data analysis of phytoplankton counts, temperature of the water in the dam, precipitation, algal diversity and quantity of microcystins for a period of three years shows that there is a low probability of algae blooming. The concentration of microcystin LR was below 0.6 µg/L and of microcystin YR was below 0.1 µg/L. The highest phytoplankton count was 70,000 cells/mL in 2018, and it decreased to 30,000 cells/mL in 2020. The impact of the risk of “blue-green algae blooms in the Iskar Dam” is assessed as moderate (3) and that has not changed between 2018 and 2022. The likelihood of occurrence of this risk decreased from possible (3) to unlikely (2) after risk reassessment, and the current control effectiveness changed from weakly controlled (4) in 2018 to well controlled (2) in 2022, because more risk management actions were included in Sofiyska voda JSC. The results of the risk evaluation show that the risk of an algal bloom falls into the low-risk category with a value of 12, after measures were considered and a reassessment. As a preventive measure for better management and risk minimization, it is necessary to continue monitoring the phytoplankton count, species composition, concentration of algae toxins (microcystin LR) and nutrients in raw water from the Iskar Dam. This research has added value to the global database for surface water sources intended for human consumption and is focuses on a potential problem, valid for agricultural as well as for urban territories rich in diffused sources of pollution. The specific risk evaluation and management steps could be used and adapted by other water supply companies.

Allelopathy of p-coumaric acid on Limnothrix sp., a bloom-forming cyanobacteria

Cyanobacteria blooms caused by water eutrophication are an urgent problem worldwide, and the frequency and scale of blooms with filamentous cyanobacteria are increasing continuously as the intensification of global warming. Plant secondary metabolite p-coumaric acid (p-CA) has biological properties such as scavenging free radicals, anti-inflammation, anti-tumor, and antibacterial, and have allelopathic effects on terrestrial plants, but its allelopathy on algae is less studied. In this study, the low concentration of p-CA (113 mg/L) can promote the growth of Limnothrix sp., while the high concentration (>127 mg/L) can significantly inhibit algae growth in a dose-dependent manner, reaching 99.55 % inhibition rate at the concentration of 153 mg/L. About 150 mg/L p-CA led to the destruction of algae cell structure, leakage of intracellular material, reduced photosynthetic pigments and protein content, inhibited photosynthesis, and stressed antioxidant system. Untargeted metabolomic analysis showed that 189 metabolites of Limnothrix sp. were significantly differentially expressed under the treatment of p-CA, and the metabolic pathways related to antioxidant stress and cell membranes were disrupted. In general, the above results indicate that p-CA is an effective allelochemical for inhibiting the growth of Limnothrix sp. and provide a new idea for the development of p-CA as a botanical agent for the control of cyanobacterial bloom.

Remote estimation of phycocyanin concentration in inland waters based on optical classification

In recent years, under the dual pressure of climate change and human activities, the cyanobacteria blooms in inland waters have become a threat to global aquatic ecosystems and the environment. Phycocyanin (PC), a diagnostic pigment of cyanobacteria, plays an essential role in the detection and early warning of cyanobacterial blooms. In this context, accurate estimation of PC concentration in turbid waters by remote sensing is challenging due to optical complexity and weak optical signal. In this study, we collected a comprehensive dataset of 640 pairs of in situ measured pigment concentration and the Ocean and Land Color Instrument (OLCI) reflectance from 25 lakes and reservoirs in China during 2020–2022. We then developed a framework consisting of the water optical classification algorithm and three candidate algorithms: baseline height, band ratio, and three-band algorithm. The optical classification method used remote sensing reflectance (Rrs) baseline height in three bands: Rrs(560), Rrs(647) and Rrs(709) to classify the samples into five types, each with a specific spectral shape and water quality character. The improvement of PC estimation accuracy for optically classified waters was shown by comparison with unclassified waters with RMSE = 72.6 μg L−1, MAPE = 80.4 %, especially for the samples with low PC concentration. The results show that the band ratio algorithm has a strong universality, which is suitable for medium turbid and clean water. In addition, the three-band algorithm is only suitable for medium turbid water, and the line height algorithm is only suitable for high PC content water. Furthermore, the five distinguished types with significant differences in the value of the PC/Chla ratio well indicated the risk rank assessment of cyanobacteria. In conclusion, the proposed framework in this paper solved the problem of PC estimation accuracy problem in optically complex waters and provided a new strategy for water quality inversion in inland waters.

Seasonal and interannual responses of blue-green algal taxa and chlorophyll to a monsoon climate, flow regimes, and N:P ratios in a temperate drinking-water reservoir

Blooms of blue-green algae (BGA) threaten drinking water safety and ecosystems worldwide. Understanding mechanisms and driving factors that promote BGA proliferation is crucial for effective freshwater management. This study tested the response of BGA growth to environmental variations driven by nutrients (N and P), N:P ratios, and flow regime depending on the influence of the Asian monsoon intensity and identified the critical regulatory factors in a temperate drinking-water reservoir, using weekly interval samplings collected during 2017–2022. The hydrodynamic and underwater light conditions experienced significant changes in summers due to high inflows and outflows associated with intense rainfalls, and these conditions strongly influenced the proliferation of BGA and total phytoplankton biomass (as estimated by chlorophyll-a [CHL-a]) during summer monsoons. However, the intense monsoon resulted in the post-monsoon blooms of BGA. The monsoon-induced phosphorus enrichment, facilitated through soil washing and runoff, was crucial in promoting phytoplankton blooms in early post-monsoon (September). Thus, the monomodal phytoplankton peak was evident in the system, compared to the bimodal peaks in North American and European lakes. Strong water column stability in the weak monsoon years depressed phytoplankton growth and BGA, suggesting the importance of the intensity of monsoon. The low N:P ratios and longer water residence time increased BGA abundance. The predictive model of BGA abundance accounted for the variations largely (Mallows' Cp = 0.39, adjusted R2 = 0.55, p < 0.001) by dissolved phosphorus, N:P ratios, CHL-a, and inflow volume. Overall, this study suggests that monsoon intensity was the key triggering factor regulating the interannual BGA variations and facilitated the post-monsoon blooms through increased nutrient availability.

Effects of Cyanobacterial Harmful Algal Bloom Toxin Microcystin-LR on Gonadotropin-Dependent Ovarian Follicle Maturation and Ovulation in Mice.

Cyanobacterial harmful algal blooms (CyanoHABs) originate from the excessive growth or bloom of cyanobacteria often referred to as blue-green algae. They have been on the rise globally in both marine and freshwaters in recently years with increasing frequency and severity owing to the rising temperature associated with climate change and increasing anthropogenic eutrophication from agricultural runoff and urbanization. Humans are at a great risk of exposure to toxins released from CyanoHABs through drinking water, food, and recreational activities, making CyanoHAB toxins a new class of contaminants of emerging concern. We investigated the toxic effects and mechanisms of microcystin-LR (MC-LR), the most prevalent CyanoHAB toxin, on the ovary and associated reproductive functions. Mouse models with either chronic daily oral or acute intraperitoneal exposure, an engineered three-dimensional ovarian follicle culture system, and human primary ovarian granulosa cells were tested with MC-LR of various dose levels. Single-follicle RNA sequencing, reverse transcription-quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, western blotting, immunohistochemistry (IHC), and benchmark dose modeling were used to examine the effects of MC-LR on follicle maturation, hormone secretion, ovulation, and luteinization. Mice exposed long term to low-dose MC-LR did not exhibit any differences in the kinetics of folliculogenesis, but they had significantly fewer corpora lutea compared with control mice. Superovulation models further showed that mice exposed to MC-LR during the follicle maturation window had significantly fewer ovulated oocytes. IHC results revealed ovarian distribution of MC-LR, and mice exposed to MC-LR had significantly lower expression of key follicle maturation mediators. Mechanistically, in both murine and human granulosa cells exposed to MC-LR, there was reduced protein phosphatase 1 (PP1) activity, disrupted PP1-mediated PI3K/AKT/FOXO1 signaling, and less expression of follicle maturation-related genes. Using both invivo and in vitro murine and human model systems, we provide data suggesting that environmentally relevant exposure to the CyanoHAB toxin MC-LR interfered with gonadotropin-dependent follicle maturation and ovulation. We conclude that MC-LR may pose a nonnegligible risk to women's reproductive health by heightening the probability of irregular menstrual cycles and infertility related to ovulatory disorders. https://doi.org/10.1289/EHP12034.

Mutual links between microcystins-producing cyanobacteria and plankton community in clear and brown northern lakes

This work studies the composition and abundances of phytoplankton and zooplankton and their relationships during cyanobacteria bloom (mainly Dolichospermum lemmermannii) in two subarctic oligotrophic lakes, a clear deep lake (Krivoe) and a brown shallow lake (Krugloe). Cyanobacteria bloom (D. lemmermannii) was observed four times during 7–10 days in both lakes: late July, late August, September 2019, and late September 2020. The toxicity of cyanobacteria was determined by the presence of cyanotoxins in water and plankton biomass. Microcystins (mostly LR, RR, and other structure variants) were found in every case of visible blooms (July–September of 2019–2020) in the shallow lake and only once in the deep lake. Despite the nutritious food items (cryptomonads), the presence and dominance of colony-forming microalgae (Botryococcus brauni) and filamentous cyanobacteria in both lakes consisted of a low-efficient food base for grazers. A high abundance of toxic microcystins in the shallow lake with dystrophic features led to the specific composition of zooplankton with the prevalence of the selective grazers, copepod Eudiaptomus graciloides, and cladoceran Ceriodaphnia pulchella adapted to cyanotoxins. In a clear deep lake, where toxic variants of microcystins were low or not detected during the cyanobacteria bloom, the omnivorous rotifer Asplanchna priodonta and small grazer Bosmina longirostris reached high abundance. This study confirms close relationships between cyanobacteria and zooplankton communities.

Harvesting of microcells from cyanobacteria-laden water by energy-efficient electro-flocculation-flotation with aluminum hydrates

Electrocoagulation-flotation (ECF) is able to effectively harvest microcells from eutrophicated drinking water reservoirs to reduce algogenic organic matter (AOM) during cyanobacteria blooming. However, ECF needs high current density (CD) and prolonged reaction time with inevitable high-energy consumption. This study aimed to investigate a novel electrocoagulation-flocculation-flotation (EFF) process, with 10 min EC reaction and 15 min flocculation followed by 10 min flotation, for Microcystis aeruginosa (MA) cell harvesting from water as well as AOM reduction with Al hydrates at various CD and pH conditions. The results have shown that significant MA cell separation and dissolved organic carbon (DOC) reduction by EFF occurred at pH 8 with 5 mA/cm2, accounting for 95 % and 56 %, respectively. At such a condition, the formation of dominant colloidal Al species (Alc) governed the EFF to promote cells and AOM destabilization by strong sweep flocculation along with weak charge neutralization by polymeric Al species (Alb). Moreover, the pronounced reduction in soluble microbial product-like (SMPL) substances could be further improved by up to 60 % with EFF. It was also found that EFF required only 2.07 × 10−2 kWh/kg in energy input and served energy saving ~63 % less than that by prolonged ECF at similar MA cell separations. It concluded that EFF was an energy-efficient technique to fast separate and harvest microcells from MA-laden water and AOM reduction with low energy input for practical application in drinking water treatment.

Ultrasensitive electrochemical phosphate detection by pyridine–zinc(II) complex

Phosphorous is an important environmental health parameter as the availability of phosphorus within water systems plays an essential role in the prevalence of harmful algal blooms (cyanobacteria blooms). Currently, phosphates are detected using sensitive chromatographic and colorimetric techniques; however, major disadvantages stem from the lack of anion selectivity in samples with complex matrices, as well as the high cost of analysis. Electrochemical techniques utilizing self-assembled monolayers can provide a cheaper yet sensitive method of detection. This work explores the modification of a gold working electrode using pyridine–zinc(II) complexes. The implementation of self-assembled monolayers allows for an ultrasensitive and selective method of indirect detection of the H2PO4 − species, ranging in concentrations between 0.0 and 1.2 fmol/L phosphate. Electrochemical techniques such as cyclic voltammetry and square-wave voltammetry were explored for their phosphate-detection abilities, with detection limits of 4.0 × 10−16 and 9.0 × 10−17 mol/L H2PO4 −, respectively. X-ray photoelectron spectroscopy measurements were also taken to confirm the modification of the electrode. The selectivity of this sensor towards phosphate anions was successfully explored for this sensor in the presence of potential interfering agents (sulfate, chlorine, carbonate, fluoride, nitrite, and hypochlorite ions), and applicability of sensor was also explored through the detection of phosphate in a tap and lake water sample.

Floating Islands for Urban Resilience Aquatic Resources Management in the Tropics: Win-Win-Win Strategies for Eutrophication Control, Aquafarming and Waterborne Green Transport System

Various wastes from ever rising populations, widespread use of fertilizers, pesticides, antibiotics, pharmaceuticals, hormones for intensified agriculture, aquaculture, livestock farming, direct sewage discharge have been the major drivers of excess phosphorus responsible for eutrophication in inland freshwaters. Reduction of nitrogen did not prove effective for eutrophication control, while multiple lines of evidence indicate that phosphorus control works best to mitigate eutrophication in freshwaters. More specifically, it is the N:P ratio that modulates the types of algal bloom as NP ratio &gt; 16:1 favours the bloom of harmful blue green algae and the reverse for green algae. Although there are different physical, chemical and biological methods used for phosphorus removal, the constructed floating islands have proved immense potentials to remove phosphorus mediated through plant-microbe uptake mechanism to restore clean habitat for sustainable development. The current challenge of the conversion of numerous valuable lakes, reservoirs, wetlands, rivers into wastewater systems unacceptable for fish farming and other economic driven activities can be confronted with win- win- win strategies of environmentally safe and sustainable solutions of floating landmass for agriculture, bio-reclamation of eutrophic lakes and rivers, a farming in these water and urban resilience waterborne green transport system across small to medium scale rivers. It is that floating islands made of selective powerful plants and microbes can be installed not only in the confined polluted lakes and reservoirs, but this facility can be extended to rivers of different dimensions for clean up as well as a network of waterborne public transport in the form of environmentally- safe passage boat, water taxi across the rivers. This is of special significance in small to medium scale rivers in India, Bangladesh and other rich countries in Asia not only for public transport and fish farming as well. However, multidimensional technological approaches and strategies with innovative cutting edge technical nature based solutions are most welcome to achieve the success of such giant holistic functionality project.

Impactos de eventos extremos de precipitação na qualidade da água: uma análise cienciométrica em escala global

Abstract: Aim This study aims to evaluate temporal patterns of extreme events related to precipitation on a global scale, identifying their main impacts and if there are climatic zones more susceptible to these phenomena using a scientometric approach. Methods A systematic review was conducted on scientific papers published between 1991 and July 2020, obtained from the Scopus and Thomson ISI Web of Science databases. Keywords related to precipitation extreme events and their effects on planktonic communities and freshwater ecosystems' water quality were used in the search. Results The analysis revealed a significant increase in publications, particularly from 2014 onwards, following the release of reports by the Intergovernmental Panel on Climate Change (IPCC) and the American Meteorological Society (AMS). These reports highlighted the increasing frequency of these climatic events and their potential for causing damage to humanity. In this review, we focused on extreme weather events related to precipitation such as droughts, rains, and floods. These events, due to their sudden volumetric changes, lead to immediate physical and chemical alterations in the water column. The main impacts of these extreme events on aquatic ecosystems include increased nutrient concentrations (mainly phosphorus and nitrogen), contamination by micropollutants, cyanobacteria blooms, and loss of biodiversity. Conclusions The scientometric analysis indicates that extreme weather events associated with precipitation have a detrimental effect on water quality and aquatic biodiversity, exacerbating the eutrophication process in freshwater systems.

Nitrous oxide emission and its influencing factors at the cyanobacteria-dominated lake

湖泊等内陆水体是大气N₂O潜在的重要排放源,也是全球N₂O收支估算的重要组成部分。目前全球湖泊普遍面临富营养化和蓝藻暴发等问题,明晰藻型湖泊N₂O排放强度及其环境影响因子对准确估算湖泊N₂O排放和预测其未来变化至关重要。本研究选择太湖藻型湖区为研究对象,同时选取人为活动影响较小的湖心区作为对比区域,基于2011年8月至2013年8月为期2年的逐月连续观测,探讨藻型湖区N₂O排放特征及其影响因素。结果表明,藻型湖区呈现极强的N₂O排放,其排放通量为(4.88±3.05) mmol/(m²·d),是参考区域(湖心: (2.10±4.31) mmol/(m²·d))的2倍多。此外,在藻型湖区中不同点位N₂O排放差异显著,受河流外源输入影响,近岸区是N₂O的热点排放区,其年均排放通量高达10.93 mmol/(m²·d)。连续观测表明N₂O排放具有显著的季节变化模式,但在不同区域调控N₂O排放时间变化的因子有所不同。其中,近岸区N₂O排放主要受氮负荷影响,其他区域N₂O排放变化受水温和氮负荷等多因子影响。氮素富集是藻型湖区N₂O高排放的直接原因,水体氮负荷可以作为N₂O排放热点的重要指示因子。但藻型湖泊N₂O排放极其显著的时空变异等在未来研究中应得到更多关注。;Inland lakes potential emit large nitrous oxide (N₂O) to atmosphere and play significant role in global N₂O budget estimation. Widespread global increase in lake phytoplankton blooms have been found, identifying the N₂O flux and its influencing factors at the cyanobacteria-dominated lake is essential to being able to accurate estimate the N₂O emissions from lakes and predict future change. In order to identify N₂O flux characteristics and its influencing factors in the cyanobacteria-dominated zone of Lake Taihu, the N₂O emission was observed based on the two-year field measurements. Results showed the annual mean N₂O flux from the cyanobacteria-dominated zone ((4.88±3.05) mmol/(m²·d)) was about twice higher than that in the central zone with less cyanobacteria blooms ((2.10±4.31) mmol/(m²·d)). Meanwhile, the N₂O emissions varies spatially within the cyanobacteria-dominated zone, peak N₂O emission (10.93 mmol/(m²·d)) occurred in littoral zone due to the large external loadings input via river discharge. Continuous filed measurement showed that the N₂O emission varied seasonally, but the factors influencing the seasonal patterns varied among sub-zones. Generally, the temporal variation of N₂O emission were regulated by N loadings in littoral zone, and were regulated by multiple environment variables, such as temperature and N loadings, in Meiliang Bay and the central zone. High nitrogen loadings contributed to large N₂O emission from cyanobacteria-dominated zone, indicating that N loadings can be used as proxy of N₂O emission from lakes. Considering significant temporal and spatial variation of N₂O emission from cyanobacteria-dominated zones, more attention should be paid in future research.

High capacity for a dietary specialist consumer population to cope with increasing cyanobacterial blooms

We present a common-garden experiment to examine the amphipod Monoporeia affinis, a key deposit-feeder in the Baltic Sea, a low diversity system offering a good model for studying local adaptations. In the northern part of this system, the seasonal development of phytoplankton is characterized by a single diatom bloom (high nutritional quality), whereas in the south, the diatom bloom is followed by a cyanobacteria bloom (low nutritional quality) during summer. Therefore, the nutrient input to the benthic system differs between the sea basins. Accordingly, the amphipod populations were expected to be dietary specialists in the north and generalists in the south. We tested this hypothesis using a combination of stable isotope tracers, trophic niche analyses, and various endpoints of growth and health status. We found that when mixed with diatomes, the toxin-producing cyanobacteria, were efficiently incorporated and used for growth by both populations. However, contrary to expectations, the feeding plasticity was more pronounced in the northern population, indicating genetically-based divergence and suggesting that these animals can develop ecological adaptations to the climate-induced northward cyanobacteria expansion in this system. These findings improve our understanding regarding possible adaptations of the deposit-feeders to increasing cyanobacteria under global warming world in both limnic and marine ecosystems. It is possible that the observed effects apply to other consumers facing altered food quality due to environmental changes.