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In samples of harmful algal blooms (HABs), seawater can contain a high abundance of microorganisms and elemental ions. Along with the hardness of the walls of key HAB dinoflagellates such as Prorocentrum triestinum, this makes RNA extraction very difficult. These components interfere with RNA isolation, causing its degradation, in addition to the complex seawater properties of HABs that could hinder RNA isolation for effective RNA sequencing and transcriptome profiling. In this study, an RNA isolation technique was established through the modification of the Trizol method by applying the Micropestle System on cell pellets of P. triestinum frozen at −20 °C, obtained from 400 mL of culture with a total of 107 cells/mL. The results of the modified Trizol protocol generated quality RNA samples for transcriptomics sequencing, as determined by their measurement in Analyzer Agilent 4150. [ABSTRACT FROM AUTHOR]

Marine toxins produced by marine organisms threaten human health and impose a heavy public health burden on coastal countries. Lately, there has been an emergence of marine toxins in regions that were previously unaffected, and it is believed that climate change may be a significant factor. This paper systematically summarizes the impact of climate change on the risk of marine toxins in terms of changes in seawater conditions. From our findings, climate change can cause ocean warming, acidification, stratification, and sea-level rise. These climatic events can alter the surface temperature, salinity, pH, and nutrient conditions of seawater, which may promote the growth of various algae and bacteria, facilitating the production of marine toxins. On the other hand, climate change may expand the living ranges of marine organisms (such as algae, bacteria, and fish), thereby exacerbating the production and spread of marine toxins. In addition, the sources, distribution, and toxicity of ciguatoxin, tetrodotoxin, cyclic imines, and microcystin were described to improve public awareness of these emerging marine toxins. Looking ahead, developing interdisciplinary cooperation, strengthening monitoring of emerging marine toxins, and exploring more novel approaches are essential to better address the risks of marine toxins posed by climate change. Altogether, the interrelationships between climate, marine ecology, and marine toxins were analyzed in this study, providing a theoretical basis for preventing and managing future health risks from marine toxins. [ABSTRACT FROM AUTHOR]

This study used satellite remote sensing to investigate trends in harmful algal blooms (HABs) over the last 21 years, focusing on four regions within the Laurentian Great Lakes: western Lake Erie, Green Bay, Saginaw Bay, and western Lake Superior. HABs in the water column were identified from remote sensing-derived chlorophyll concentrations, and surface HAB scums were classified based on the Normalized Difference Vegetation Index (NDVI) band ratio index. Using imagery from the Moderate Resolution Imaging Spectroradiometer sensor on the Aqua satellite (MODIS-Aqua) from 2002 to 2022, we generated daily estimates of the HAB and surface scum extents for each region, which were then averaged to generate mean annual extents. We observed a significant decline in the Saginaw Bay mean annual HAB extents over the 21-year study period. Otherwise, no significant changes were observed over this period in any region for either the HAB or surface scum mean annual extents, thus suggesting that HABs are not increasing in the Great Lakes. Despite the lack of increasing trends, the blooms are still recurring annually and causing a negative impact on the nearby communities; thus, we believe that it is crucial to continue studying Great Lakes HABs to monitor the impact of current and future abatement strategies. [ABSTRACT FROM AUTHOR]

In Western Europe, the incidence of DST is likely the highest globally, posing a significant threat with prolonged bans on shellfish harvesting, mainly caused by species of the dinoflagellate genus Dinophysis. Using a time series from 2014 to 2020, our study aimed (i) to determine the concentration of D. acuminata in water at which shellfish toxin levels could surpass the regulatory limit (160 µg OA equiv kg−1) and (ii) to assess the predictability of toxic events for timely mitigation actions, especially concerning potential harvesting bans. The analysis considered factors such as (i) overdispersion in the data, (ii) distinct periods of presence and absence, (iii) the persistence of cells, and (iv) the temporal lag between cells in the water and toxins in shellfish. Four generalized additive models were tested, with the Tweedie (TW-GAM) model showing superior performance (>85%) and lower complexity. The results suggest existing thresholds currently employed (200 and 500 cells L−1) are well-suited for the Portuguese coast, supported by empirical evidence (54–79% accuracy). The developed algorithm allows for thresholds to be tailored on a case-by-case basis, offering flexibility for regional variations. [ABSTRACT FROM AUTHOR]

Advancements in data availability, including high frequency, near real-time multiparameter sensors, laboratory analysis, and in-situ and remote observations, have driven the development of machine learning (ML) models for applications such as toxic Harmful Algal Bloom (HABs) monitoring. However, the performance of ML predictions is influenced by both model uncertainties due to inherent model structures and errors associated with input dataset measurements. For example, measurement uncertainty arises from sample collection, sensor drift and laboratory analysis and sample handling errors. While impacts of model uncertainty are commonly addressed using probabilistic approaches, the effect of measurement uncertainty is less studied due to the limited availability of detailed measurement information. This study focuses on assessing the impact of measurement uncertainty on the ML prediction of chlorophyll-a concentration as an index of HABs in a mesotrophic lake. Using randomized subsets of input measured datasets that mimic possible chlorophyll-a concentration distributions, the study built 1000 Random Forest (RF) and Support Vector Regression (SVR) models. An independent measured dataset was used to validate the ensemble models, allowing for model performance evaluation and the creation of prediction intervals to measure the propagated uncertainty. Our findings showed that the model predictions have MAE that ranged between 0.16 μg/l and 5.19 μg/l, and RMSE ranging between 0.20 μg/l and 7.39 μg/l. The highest uncertainty coverage of 0.71 was observed in the RF model without chlorophyll-a sensor values as a predictor. The study found that the training dataset sizes due to the high frequency and manually sampled nature influence how much measurement uncertainty is covered. The results of this study demonstrate how well ML models can capture various HABs patterns when given diverse measurement variables. Our findings will give researchers insightful information on how to lessen the impact of measurement uncertainty when using ML models as decision-support tools for HABs management.

One of the main threats to freshwater resources is pollution from anthropogenic activities such as rapid urbanization and excessive agricultural nutrient runoff. Remote sensing technologies have been effectively used in monitoring and mapping rapid changes in the marine environment and assessing the overall health of freshwater ecosystems. The main goal of this study is to comparatively evaluate the performance of index-based and classification-based approaches in mapping dense floating algal blooms observed in Lake Burdur using Sentinel-2 imagery. For index-based mapping, algae-specific indices, namely the Floating Algae Index (FAI), Adjusted Floating Algae Index, Surface Algal Blooms Index (SABI), and Algal Blooms Detection Index (ABDI), were used. At the same time, pixel- and object-based Random Forest (RF), eXtreme Gradient Boosting (XGBoost), and Long Short-Term Memory Network (LSTM) were utilized for classification-based algal mapping. For this purpose, seven Sentinel-2 images, selected through time series analysis performed on the Google Earth Engine platform, were used as the primary dataset in the application. The results show that high-density floating algae formations can be detected over 99% by both indices and classification-based approaches, whereas pixel-based classification is more successful in mapping low-density algal blooms. When two-class thematic maps representing water and floating algae classes were considered, the maps produced by index-based FAI using an appropriate threshold value and the classification-based RF algorithm reached an overall accuracy of over 99%. The highest algae density in the lake was observed on July 13, 2021, and was determined to be effective in ~ 45 km2 of the lake's surface. [ABSTRACT FROM AUTHOR]

Cloud computing offers an excellent platform for sharing information and services among departments, partners, customers, and other parties. To ensure the effectiveness of a cloud deployment, it is imperative that resources and data are available in a secure and efficient manner. The protection of personally identifiable information (PII) is a critical requirement for many organizations in order to prevent unauthorized disclosure of that information. In spite of the fact that private information may not be stored within an authorized organization, it can still be protected. It has been shown in recent literature that anonymity can be used to preserve PII privacy. The current methodology for anonymous access is based on certificates rather than subject identity or attribute-based encryption. Identity-based access control is inflexible and violates privacy laws. Access to a certificate can be linked using a certificate that poses a risk of re-identification. The types of objects that can be encrypted by attributes are limited. To preserve the privacy of attributes set of subject and object, we extend the attribute-based access control (ABAC) model by expressing privacy requirements with anonymous access. It inherits several characteristics from ABAC, including fine-grained authorizations, unlimited object types, policy flexibility, and object privacy. ABAC-PA2 uses homomorphic attribute-based signature (HABS), a secure anonymous access framework that enhances ABAC's identity-less and incorporates privacy-preserving principles by assigning privacy levels to resources. [ABSTRACT FROM AUTHOR]

Ocean acidification (OA) driven by eutrophication, riverine discharge, and other threats from local population growth that affect the inorganic carbonate system is already affecting the eastern Gulf of Mexico. Long-term declines in pH of ~ -0.001 pH units yr-1 have been observed in many southwest Florida estuaries over the past few decades. Coastal and estuarine waters of southwest Florida experience high biomass harmful algal blooms (HABs) of the dinoflagellate Karenia brevis nearly every year; and these blooms have the potential to impact and be impacted by seasonal to interannual patterns of carbonate chemistry. Sampling was conducted seasonally along three estuarine transects (Tampa Bay, Charlotte Harbor, Caloosahatchee River) between May 2020 and May 2023 to obtain baseline measurements of carbonate chemistry prior to, during, and following K. brevis blooms. Conductivity, temperature and depth data and discrete water samples for K. brevis cell abundance, nutrients, and carbonate chemistry (total alkalinity, dissolved inorganic carbonate (DIC), pCO2, and pHT were evaluated to identify seasonal patterns and linkages among carbonate system variables, nutrients, and K. brevis blooms. Karenia brevis blooms were observed during six samplings, and highest pCO2 and lowest pHT was observed either during or after blooms in all three estuaries. Highest average pH and lowest pCO2 were observed in Tampa Bay. In all three estuaries, average DIC and pHT were higher and pCO2 was lower during dry seasons than wet seasons. There was strong influence of net community calcification (NCC) and net community production (NCP) on the carbonate system; and NCC: NCP ratios in Tampa Bay, Charlotte Harbor, and the Caloosahatchee River were 0.83, 0.93, and 1.02, respectively. Linear relationships between salinity and dissolved ammonium, phosphate, and nitrate indicate strong influence of freshwater inflow from river input and discharge events on nutrient concentrations. This study is a first step towards connecting observations of high biomass blooms like those caused by K. brevis and alterations of carbonate chemistry in Southwest Florida. Our study demonstrates the need for integrated monitoring to improve understanding of interactions among the carbonate system, HABs, water quality, and acidification over local to regional spatial scales and event to decadal time scales. [ABSTRACT FROM AUTHOR]

The City of Wichita Falls (CWF) Cypress Environmental Laboratory (CEL) established an integrated monitoring program in response to extreme taste and odor (T&O) events in 2016. The program uses field monitoring with sondes, sensory analysis to describe types of odors, water quality bench testing, algae/cyanobacteria identification and enumeration by flow-imaging microscopy, actinomycetes culturing, T&O detection by gas chromatography-mass spectrometry (GC-MS), cyanotoxin screening by quantitative polymerase chain reaction (qPCR), and cyanotoxin detection by fluorometry. To date, the CEL had detected 16 T&O events prior to finished tap being discharged to the distribution system. This has allowed utility staff to take proactive measures to mitigate events, which has virtually eliminated consumer T&O complaints. This article provides a brief history of T&O analysis, means to monitor and mitigate blooms, T&O compounds, and cyanotoxins, and measures the effectiveness of the CEL's monitoring program by evaluating each T&O event, and specifically geosmin. HIGHLIGHTS Poor water quality aesthetics undermine consumer confidence.; An integrated approach to monitoring is the key to providing the most complete water quality understanding.; Sensory analysis cannot be replaced by analytical techniques.; Monitoring programs should be consistently evaluated and updated.; Integrated monitoring programs can effectively reduce customer complaints.;

In samples of harmful algal blooms (HABs), seawater can contain a high abundance of microorganisms and elemental ions. Along with the hardness of the walls of key HAB dinoflagellates such as Prorocentrum triestinum, this makes RNA extraction very difficult. These components interfere with RNA isolation, causing its degradation, in addition to the complex seawater properties of HABs that could hinder RNA isolation for effective RNA sequencing and transcriptome profiling. In this study, an RNA isolation technique was established through the modification of the Trizol method by applying the Micropestle System on cell pellets of P. triestinum frozen at −20 °C, obtained from 400 mL of culture with a total of 107 cells/mL. The results of the modified Trizol protocol generated quality RNA samples for transcriptomics sequencing, as determined by their measurement in Analyzer Agilent 4150.

Harmful algal blooms are important threats to reservoir condition. Over a 15-year period, we sampled five Argentinian reservoirs to identify the responsible species for harmful algal blooms and determine the water quality factors driving their occurrence. These reservoirs exhibit diverse morphological and hydrological characteristics and are distributed across varying climatic zones. Cyanobacterial blooms included an array of species, including toxin producers such as Raphidiopsis raciborskii, Aphanizomenon gracile, and Microcystis aeruginosa. In contrast, dinoflagellate blooms were predominantly characterized by Ceratium. The cyanobacterial blooms primarily occurred in the shallower reservoirs located in warmer regions, whereas dinoflagellate blooms occurred where temperatures were lower. The most intense blooms occurred during the summer, and although cyanobacterial and chlorophyte blooms co-occurred, they never coexisted with dinoflagellate blooms. We identified cyanotoxins in the reservoirs over the past three years, a phenomenon previously unreported in the region. Given that these reservoirs are drinking water sources for human populations, ongoing and systematic monitoring is needed to protect public health. Controlling the proliferation of algae and cyanobacteria in reservoirs requires resource management at the watershed level, and in the case of the Itiyuro and El Limon, requires binational management with Bolivia. [ABSTRACT FROM AUTHOR]

The coastal ocean is experiencing changes in its physical and chemical properties that strongly affect planktonic metabolism assemblages and, in some cases, favor the occurrence of harmful algal blooms (HABs). Here we analyze the variations in phytoplankton biomass, gross and net primary production (NCP) as well as community respiration (CR) at two nearshore sampling sites (P1 and P2) located at a Mediterranean beach where high biomass HABs are recurrent. At P1, the most exposed site, phytoplankton chlorophyll was generally low, whereas dinoflagellates outbreaks of the genus Gymnodinium and Alexandrium were recurrent during summer at P2 spanning for 10–20 days. During bloom episodes, NCP increased up to 10-fold (>80 mmol O2 m−3 day−1). Contrastingly, variation in CR only reached an average of 1.8-fold the rates of non-bloom conditions. Remarkably, although the enhanced NCP:CR ratio suggests net autotrophic population growth, production per unit biomass at P1 and P2 was not significantly different. Our results indicate that although summer conditions favor the necessary primary production enhancement leading to HAB occurrences, the short-term dynamics driving high biomass episodes are not driven by metabolic variations but instead are governed by subtle accumulative processes of some flagellate species in the nutrient-rich nearshore environment. [ABSTRACT FROM AUTHOR]

This study used satellite remote sensing to investigate trends in harmful algal blooms (HABs) over the last 21 years, focusing on four regions within the Laurentian Great Lakes: western Lake Erie, Green Bay, Saginaw Bay, and western Lake Superior. HABs in the water column were identified from remote sensing-derived chlorophyll concentrations, and surface HAB scums were classified based on the Normalized Difference Vegetation Index (NDVI) band ratio index. Using imagery from the Moderate Resolution Imaging Spectroradiometer sensor on the Aqua satellite (MODIS-Aqua) from 2002 to 2022, we generated daily estimates of the HAB and surface scum extents for each region, which were then averaged to generate mean annual extents. We observed a significant decline in the Saginaw Bay mean annual HAB extents over the 21-year study period. Otherwise, no significant changes were observed over this period in any region for either the HAB or surface scum mean annual extents, thus suggesting that HABs are not increasing in the Great Lakes. Despite the lack of increasing trends, the blooms are still recurring annually and causing a negative impact on the nearby communities; thus, we believe that it is crucial to continue studying Great Lakes HABs to monitor the impact of current and future abatement strategies.

Ocean acidification (OA) driven by eutrophication, riverine discharge, and other threats from local population growth that affect the inorganic carbonate system is already affecting the eastern Gulf of Mexico. Long-term declines in pH of ~ -0.001 pH units yr-1 have been observed in many southwest Florida estuaries over the past few decades. Coastal and estuarine waters of southwest Florida experience high biomass harmful algal blooms (HABs) of the dinoflagellate Karenia brevis nearly every year; and these blooms have the potential to impact and be impacted by seasonal to interannual patterns of carbonate chemistry. Sampling was conducted seasonally along three estuarine transects (Tampa Bay, Charlotte Harbor, Caloosahatchee River) between May 2020 and May 2023 to obtain baseline measurements of carbonate chemistry prior to, during, and following K. brevis blooms. Conductivity, temperature and depth data and discrete water samples for K. brevis cell abundance, nutrients, and carbonate chemistry (total alkalinity, dissolved inorganic carbonate (DIC), pCO2, and pHT were evaluated to identify seasonal patterns and linkages among carbonate system variables, nutrients, and K. brevis blooms. Karenia brevis blooms were observed during six samplings, and highest pCO2 and lowest pHT was observed either during or after blooms in all three estuaries. Highest average pH and lowest pCO2 were observed in Tampa Bay. In all three estuaries, average DIC and pHT were higher and pCO2 was lower during dry seasons than wet seasons. There was strong influence of net community calcification (NCC) and net community production (NCP) on the carbonate system; and NCC : NCP ratios in Tampa Bay, Charlotte Harbor, and the Caloosahatchee River were 0.83, 0.93, and 1.02, respectively. Linear relationships between salinity and dissolved ammonium, phosphate, and nitrate indicate strong influence of freshwater inflow from river input and discharge events on nutrient concentrations. This study is a first step towards connecting observations of high biomass blooms like those caused by K. brevis and alterations of carbonate chemistry in Southwest Florida. Our study demonstrates the need for integrated monitoring to improve understanding of interactions among the carbonate system, HABs, water quality, and acidification over local to regional spatial scales and event to decadal time scales.

Harmful algal blooms are important threats to reservoir condition. Over a 15-year period, we sampled five Argentinian reservoirs to identify the responsible species for harmful algal blooms and determine the water quality factors driving their occurrence. These reservoirs exhibit diverse morphological and hydrological characteristics and are distributed across varying climatic zones. Cyanobacterial blooms included an array of species, including toxin producers such as Raphidiopsis raciborskii, Aphanizomenon gracile, and Microcystis aeruginosa. In contrast, dinoflagellate blooms were predominantly characterized by Ceratium. The cyanobacterial blooms primarily occurred in the shallower reservoirs located in warmer regions, whereas dinoflagellate blooms occurred where temperatures were lower. The most intense blooms occurred during the summer, and although cyanobacterial and chlorophyte blooms co-occurred, they never coexisted with dinoflagellate blooms. We identified cyanotoxins in the reservoirs over the past three years, a phenomenon previously unreported in the region. Given that these reservoirs are drinking water sources for human populations, ongoing and systematic monitoring is needed to protect public health. Controlling the proliferation of algae and cyanobacteria in reservoirs requires resource management at the watershed level, and in the case of the Itiyuro and El Limón, requires binational management with Bolivia.

Cyanobacterial blooms are a global concern prone to causing environmental and economic damages and are tightly linked to anthropogenic nutrient inputs. Likewise, microplastic pollution has also become globally ubiquitous inevitably co-occurring with blooms. However, little is known on how microplastics influence cyanobacterial physiologically and how potential physiological changes can affect their buoyancy, ultimately impacting their fate, and transport, including deposition during bloom events. Interactions of environmental relevant concentrations of high-density polyethylene microplastics (MPs) (0–0.4 mg/mL) and temperatures (2.5–32.5 °C) were evaluated to assess the effects of MPs on interactions of cyanobacteria Anabaena variabilis’s growth, total organic carbon concentrations, extracellular polymeric substances (EPS) production, and MP deposition. Microplastics both stimulated and inhibited A. variabilis growth depending on the concentration. Lower MPs concentrations (0.1–0.2 mg/L) increased A. variabilis growth while higher MP concentrations (>0.3 mg/mL) impeded it across all temperatures studied. Carbon sources leached from MPs may have been a contributing factor to the increased growth at lower MPs concentration, while higher MPs concentration potentially shaded A. variabilis inhibiting its growth. Shading may have induced stress which corresponded with an observed increase in EPS production by A. variabilis when exposed to MP. Extracellular polymeric substances generation activated under adverse circumstances (MPs 0.4 mg/mL) enhanced MP deposition. Overall, our findings indicate that MPs play an important role in cyanobacterial blooms, and that these blooms may enhance MPs deposition.

Harmful Algal Blooms (HABs) are becoming increasingly common in freshwater and coastal waters around the world. Eutrophication and the impairment of water quality due to the toxins produced by HABs are especially concerning for water bodies used as a drinking water supply. Freshwater systems are becoming more susceptible to HABs due to anthropogenic nutrient loading from nonpoint sources and from the influence of climate change, which results in increased water temperatures and precipitation. This paper focuses on Skaneateles Lake, one of New York's Finger Lakes that has recently begun to experience HABS. Here, we use the InVEST Nutrient Delivery Ratio (NDR) Model to demonstrate a novel approach to stakeholder engagement in assessing the potential impact of different land management options on annual nutrient loads. Through these stakeholder-informed scenarios, we find that the use of riparian buffers offers the most efficient pathway to reducing nutrient loading to the Lake.

The non-natural mineralization of CaCO3 with special structures or morphologies is generated during the migration of crude oil and is the main form of scale in alkaline/surfactant/polymer (ASP) flooding in oilfields, adversely affecting oil recovery and causing environmental pollution. To date, the mineralization of aragonite superstructures and the role of heavy alkyl-benzene sulfonate (HABS) in mineralization are still unclear. In this work, aragonite-based superstructures of CaCO3 crystals were obtained in an O/W emulsion with HABS to help deepen the understanding of the diversified growth of CaCO3 scaling in oilfields. As a result, rosette-like, bouquet-like, and dumbbell-shaped CaCO3 crystals with vaterite–aragonite, aragonite, and calcite–aragonite phases were formed with 200 mg/L HABS concentration at 45 °C for 60 min and spherical vaterite phase stabilized at a high HABS concentration (800 mg/L and 1000 mg/L). Rhombohedral calcite content experienced a fluctuation of about 40% as the HABS concentration varied. Needle-like and bundle-like aragonite precipitates were generated with increasing temperatures from 65 °C to 85 °C. Thus, HABS affects the nucleation and growth of the precipitated CaCO3 solid, leading to modifications in the structure and morphology of the crystals. The synergistic effect between HABS and temperature can regulate ion pairs with the calcium ions and block sites that are essential to the incorporation of new solutes into the crystal lattice, which leads to the heterogeneous nucleation of vaterite and aragonite on calcite, forming aragonite-based superstructures in kerosene emulsion. This work may enrich the understanding of CaCO3 mineralization in oilfields, and also provide a novel strategy for manufacturing organic–inorganic composites. [ABSTRACT FROM AUTHOR]

The armoured dinoflagellate Alexandrium can be found throughout many of the world's temperate and tropical marine environments. The genus has been studied extensively since approximately half of its members produce a family of potent neurotoxins, collectively called saxitoxin. These compounds represent a significant threat to animal and environmental health. Moreover, the consumption of bivalve molluscs contaminated with saxitoxin poses a threat to human health. The identification of Alexandrium cells collected from sea water samples using light microscopy can provide early warnings of a toxic event, giving harvesters and competent authorities time to implement measures that safeguard consumers. However, this method cannot reliably resolve Alexandrium to a species level and, therefore, is unable to differentiate between toxic and non-toxic variants. The assay outlined in this study uses a quick recombinase polymerase amplification and nanopore sequencing method to first target and amplify a 500 bp fragment of the ribosomal RNA large subunit and then sequence the amplicon so that individual species from the Alexandrium genus can be resolved. The analytical sensitivity and specificity of the assay was assessed using seawater samples spiked with different Alexandrium species. When using a 0.22 µm membrane to capture and resuspend cells, the assay was consistently able to identify a single cell of A. minutum in 50 mL of seawater. Phylogenetic analysis showed the assay could identify the A. catenella, A. minutum, A. tamutum, A. tamarense, A. pacificum, and A. ostenfeldii species from environmental samples, with just the alignment of the reads being sufficient to provide accurate, real-time species identification. By using sequencing data to qualify when the toxic A. catenella species was present, it was possible to improve the correlation between cell counts and shellfish toxicity from r = 0.386 to r = 0.769 (p ≤ 0.05). Furthermore, a McNemar's paired test performed on qualitative data highlighted no statistical differences between samples confirmed positive or negative for toxic species of Alexandrium by both phylogenetic analysis and real time alignment with the presence or absence of toxins in shellfish. The assay was designed to be deployed in the field for the purposes of in situ testing, which required the development of custom tools and state-of-the-art automation. The assay is rapid and resilient to matrix inhibition, making it suitable as a potential alternative detection method or a complementary one, especially when applying regulatory controls. [ABSTRACT FROM AUTHOR]

Background: Harmful algal blooms (HABs) of the toxic dinoflagellate Karenia brevis impact the overall ecosystem health. Methods: K. brevis cell counts were extracted from Harmful Algal BloomS Observing System (HABSOS) in situ data and matched with 0.25º resolution environmental information from the Copernicus database to generate spatio-temporal maps of HABs in the Gulf of Mexico (GoM) between 2010 and 2020. The data was used to analyze the relationship between spatial and temporal variability in the presence/absence of K. brevis blooms (≥100,000 cells/L) and biotic and abiotic variables using Generalized Additive Models (GAM). Results: The variability of blooms was strongly linked to geographic location (latitude and salinity), and temporal variables (month and year). A higher probability of K. brevis blooms presence was predicted in areas with negative sea surface height (SSH) values, silicate concentration (0, 30-35 mmol. m -3), sea surface temperature of 22-28 oC, and water currents moving south-westward (225º). The smooth effect of each environmental variable shows a bimodal pattern common in semi-enclosed basins such as GoM. The spatial predictions from the model identified an important permanent area in (1) Southwest Florida (25.8-27.4 o latitude), and four seasonally important areas, (2) North Central Florida (3) Central West Florida, (4) Alabama on Gulf Shores and (5) Mississippi with higher bloom probabilities during the fall to winter season (November-January). Results also suggest that HABs can extend until ≥ 300 km offshore; starting to form in March and reaching a peak in September, and were swept to the coastal area during fall and winter. This suggests the role of upwelling and water circulation in GoM for the accumulation of cells and HABs. Information on the spatio-temporal dynamics of K. brevis blooms and understanding the environmental drivers are crucial to support more holistic spatial management to decrease K. brevis blooms incidence in bodies of water.

Pyrodinium bahamense blooms reaching and exceeding 105 cells L-1 occur nearly every summer in Tampa Bay, Florida, USA. These high biomass blooms can reduce light penetration, degrade water quality, and deplete dissolved oxygen. In addition, this alga produces potent neurotoxins (saxitoxins) that can accumulate in filter-feeding shellfish and cause paralytic shellfish poisoning in humans if contaminated shellfish are consumed. Variability in toxicity of two alternate life history stages (vegetative cells and resting cysts) of P. bahamense can have implications for resource management. Here we discuss the saxitoxin composition and concentration observed in vegetative cells and resting cysts of P. bahamense collected from Tampa Bay. Analysis of bloom samples and cysts collected from Tampa Bay confirmed the presence of three saxitoxin congeners: decarbamoylsaxitoxin (dcSTX), gonyautoxin 5 (GTX5), and saxitoxin (STX) and showed that in general, vegetative cells in this area may be more toxic than resting cysts. In samples collected on 10 days throughout a laboratory growth experiment on a single isolate, the average total cellular toxin was 0.2 ± 0.02 pmol cell-1. In contrast, the average total cellular toxin in vegetative cells from bloom samples collected from 9 locations during peak bloom was 0.02 ± 0.002 pmol cell-1 and the concentration in resting cyst from one sediment sample 0.003 pmol cyst-1. [ABSTRACT FROM AUTHOR]

Harmful Algal Blooms (HABs) persist in many water bodies around the world and pose adverse health and economic impacts to the affected communities. Small Unmanned Aerial Vehicles (UAVs) have recently been applied as a cost‐effective tool for HABs monitoring. In this study, HABs in two small lakes in Southern Illinois (Carbondale Reservoir and the Campus Lake of Southern Illinois University) were monitored using UAVs and biomass concentrations in lake waters. By analyzing vegetation indices derived from multispectral UAV images and chlorophyll‐a concentrations in the two lakes, statistical regression models were established for each waterbody. The model relates spectral characteristics of the lake water to its algae biomass. It was found that normalized difference vegetation index (NDVI) and blue‐to‐green band ratio are the best‐fit indices to the variation in chlorophyll‐a in Carbondale Reservoir and the Campus Lake, respectively. The findings in this study can be used for monitoring HABs using UAVs in these lakes in the future. [ABSTRACT FROM AUTHOR]

HABs pose a threat to coastal ecosystems, the economic sector and human health, and are expanding globally. However, their influence on copepods, a major connector between primary producers and upper trophic levels, remains essentially unknown. Microalgal toxins can eventually control copepod survival and reproduction by deterring grazing and hence reducing food availability. We present several 24-h experiments in which the globally distributed marine copepod, Acartia tonsa, was exposed to different concentrations of the toxic dinoflagellate, Alexandrium minutum, grown under three N:P ratios (4:1, 16:1 and 80:1), with the simultaneous presence of non-toxic food (the dinoflagellate Prorocentrum micans). The different N:P ratios did not affect the toxicity of A. minutum, probably due to the low toxicity of the tested strain. Production of eggs and pellets as well as ingested carbon appeared to be affected by food toxicity. Toxicity levels in A. minutum also had an effect on hatching success and on the toxin excreted in pellets. Overall, A. minutum toxicity affected the reproduction, toxin excretion and, to an extent, the feeding behavior of A. tonsa. This work indicates that even short-term exposure to toxic A. minutum can impact the vital functions of A. tonsa and might ultimately pose serious threats to copepod recruitment and survival. Still, further investigation is required for identifying and understanding, in particular, the long-term effects of harmful microalgae on marine copepods. [ABSTRACT FROM AUTHOR]

Cyanobacteria blooms in the Baltic Sea have been studied for years due to their toxicity, which negatively affects all biota, along with the influence of these floating colonies on surface fluxes. However, mapping these blooms is still a challenge since their high dynamics, wide coverage, and specific radiometric footprint hinder atmospheric correction and negatively affect the quality of satellite images. In this study, we assessed the use of an alternative approach called the cyanobacteria index (CI), which is based on the reflectance spectral shape and which does not require comprehensive atmospheric correction. We demonstrated a close relationship between the positive CI values, indicating the presence of blooms, and the concentration of phycocyanin, the marker pigment of filamentous cyanobacteria in the Baltic Sea. We proved that the CI index could efficiently identify cyanobacteria-dominated blooms where colonies floated near the surface. Therefore, this index represents a valuable complement to the previous monitoring methods, suitable for extreme bloom events. The analysis of a time series of satellite images obtained between 2002 and 2018 using the CI index revealed the elongation of the bloom season, which may have been a consequence of the water temperature remaining within the cyanobacteria's tolerance range for a longer time. [ABSTRACT FROM AUTHOR]

Spiny‐surfaced species of Prorocentrum form harmful algal blooms, and its taxonomic identity is obscure due to the size and shape variability. Molecular phylogenies reveal two major clades: one for P. cordatum with sequences mainly retrieved as P. minimum, and the other for P. shikokuense with sequences also retrieved as P. dentatum and P. donghaiense. Several closely related clades still need to be characterized. Here, we provide nuclear SSU and LSU rRNA genes, and nuclear ITS region (ITS1‐5.8S gene‐ITS2) sequences of the strain CCMP3122 isolated from Florida (initially named P. donghaiense) and strains Prorocentrum sp. RCC6871–2 from the Ross Sea, Antarctica. We describe Prorocentrum thermophilum sp. nov. based on the strain CCMP3122, a species also distributed in the open waters of the Gulf of Mexico, New Zealand, and the Arabian Gulf; and Prorocentrum criophilum sp. nov. based on the strain RCC6872, which is distributed in the Antarctic Ocean and Arctic Sea. Prorocentrum thermophilum is roundish (~14 μm long, ~12 μm wide), with an inconspicuous anterior spine‐like prolongation under light microscopy, valves with tiny, short knobs (5–7 per μm2), and several (<7) large trichocyst pores (~0.3 μm) in the right valve, as well as smaller pores (~0.15 μm). Prorocentrum criophilum is round in valve view (~11 μm long, 10 μm wide) and asymmetrically roundish in lateral view, the periflagellar area was not discernible under light microscopy, valves with very tiny, short knobs (6–10 per μm2), and at least 12 large pores in the right valve. Other potentially undescribed species of spiny‐surfaced Prorocentrum are discussed. [ABSTRACT FROM AUTHOR]

(1) Background: Harmful algal blooms (HABs) can negatively impact marine ecosystems, but few studies have evaluated the microbial diversity associated with HABs and its potential role in the fates of these proliferations. (2) Methods: Marine prokaryotic diversity was investigated using high-throughput sequencing of the 16S rRNA gene during the bloom declines of two dinoflagellates detected in the summer of 2019 along the northern and southern Tunisian coasts (South Mediterranean Sea). The species Gymnodinium impudicum (Carthage, Tunis Gulf) and Alexandrium minutum (Sfax, Gabes Gulf) were identified using microscopy and molecular methods and were related to physicochemical factors and prokaryotic compositions. (3) Results: The abundance of G. impudicum decreased over time with decreasing phosphate concentrations. During the G. impudicum bloom decay, prokaryotes were predominated by the archaeal MGII group (Thalassarchaeaceae), Pelagibacterales (SAR11), Rhodobacterales, and Flavobacteriales. At Sfax, the abundance of A. minutum declined with decreasing phosphate concentrations and increasing pH. At the A. minutum peak, prokaryotic communities were largely dominated by anoxygenic phototrophic sulfur-oxidizing Chromatiaceae (Gammaproteobacteria) before decreasing at the end of the survey. Both the ubiquitous archaeal MGII group and Pelagibacterales were found in low proportions during the A. minutum decay. Contrary to the photosynthetic Cyanobacteria, the photo-autotrophic and -heterotrophic Rhodobacterales and Flavobacteriales contents remained stable during the dinoflagellate bloom decays. (4) Conclusions: These results indicated changes in prokaryotic community diversity during dinoflagellate bloom decays, suggesting different bacterial adaptations to environmental conditions, with stable core populations that were potentially able to degrade HABs. [ABSTRACT FROM AUTHOR]

The present study assessed the effective use of biochar, a pyrogenous organic material derived from plant or animal waste, for the adsorption of two potent HAB toxins namely, Microcystin-LR (MCLR) and Saxitoxin (STX) through a combination of dosage. kinetic, equilibrium, initial pH, and competitive adsorption experiments. Characterized results of biochar displayed promising adsorption potentials in the form of high carbon stability (H/C = 0.02, O/C = 0.11), well-defined pore network (SBET = 261.06 in2/g), decorated surface functionality (oxygen-containing groups 941.33 klinol/g), and positive surface charge. The results suggest excellent adsorption capabilities of biochar for the removal of MCLR and STX, with STX reporting higher adsorption capacities (622.53 - 3507.46 kig/g). STX removal required a minimal dosage of 0,02 g/L, while MCLR reinoval needed 0.4 g/L for > 90 %. Similarly, a shorter contact time was required for STX removal compared to MCLR for > 90 % of toxin removed from water. Initial pH study revealed that for MCLR acidic conditions favored higher uptake while STX favored basic conditions. Kinetic studies revealed that the Elovich model to be most suitable for both toxins. while STX also showed suitable fittings for Pseudo First and Pseudo Second Order in individual toxin systems. Similarly. for the Elovich model the most suited kinetic model for both toxins in presence of each other. Isotherm studies confirmed the Langmuir-Freundlich model as the best fit for both toxins. These results suggest adsorption mechanisms such as electrostatic attraction. hydrogen bonding. hydrophobic interactions, ir-Tr interactions, dispersive interactions. and pore filling. [ABSTRACT FROM AUTHOR]

Spatial–temporal variability of phytoplankton community and potentially harmful species in the Golden Horn Estuary (Sea of Marmara) was investigated from October 2018 to September 2019 together with some environmental factors. A total of 148 phytoplankton taxa were identified during the study period. Among these, 134 taxa (90.5%) consisted of diatoms (71 taxa, 48%) and dinoflagellates (63 taxa, 42.5%), while 14 taxa (9.5%) were other groups. Seventeen species were recorded for the first time in the study area. Species richness was highest in October, while it was lowest in August. The species diversity (H') varied according to sampling stations. Cell abundances were higher especially in the middle and upper estuary in spring and summer than in autumn and winter. The abundance of diatoms and euglenophyceans was highest in spring, while the abundance of raphidophycean and cryptophycean was highest in summer. Temperature was correlated positively with total abundance (P < 0.01), but negatively with species diversity (H') (P < 0.01). Several dense algal blooms causing discolouration in surface water occurred in spring and summer. A total of 12 microalgae species known as potentially toxic were detected during this study period. Among these, dinoflagellates Alexandrium cf. tamarense and Dinophysis infundibulum were recorded for the first time in the study area. The increase in species diversity and richness in the upper estuary, and the decrease in frequency of bloom events compared with the previous years indicated the changes in environmental conditions in this study period. Findings showed that phytoplankton might be used as an indicator of the changing environmental conditions in such ecosystems. [ABSTRACT FROM AUTHOR]

Red tides have many harmful effects on offshore ecosystem and even human health, which has become a global marine environmental problem. In recent years, the occurrence of red tides has become more frequent and extensive in the offshore area of China. As one of the important sea areas in northern China, the north of Shandong Peninsula is also facing the impact of red tides. Relevant data and information on red tides outbreaks around the north of Shandong Peninsula (This study refers to the coastal area of Yantai) from 2000 to 2019 were collected in this study, and then, the comprehensive human activity intensity model was constructed. It was found that the occurrence of red tides in this area had a certain aggregation on both temporal and spatial scales, and the reason was related to nearshore human activities. Different types of land cover in coastal zone had a more significant impact on the occurrence of red tides. The types of water and structures had a certain correlation with the occurrence of red tides. [ABSTRACT FROM AUTHOR]

Quantifying the abundance of Chattonella species is necessary to effectively manage the threats from ichthyotoxic raphidophytes, which can cause large-scale mortality of aquacultured fish in temperate waters. The identification and cell counting of Chattonella species have been conducted primarily on living cells without fixation by light microscopy because routine fixatives do not retain their morphological features. Species belonging to the Chattonella marina complex, including C. marina and C. marina var. ovata, had high genetic similarities and the lack of clear morphological delimitations between the species. To estimate the abundance of C. marina complex in marine plankton samples, we developed a protocol based on the droplet digital polymerase chain reaction (ddPCR) assay, with C. marina complex-specific primers targeting the internal transcribed spacer (ITS) region of the rDNA. Cell abundance of the C. marina complex can be determined using the ITS copy number per cell, ranging from 25 ± 1 for C. marina to 112 ± 7 for C. marina var. ovata. There were no significant differences in ITS copies estimated by the ddPCR assay between environmental DNA samples from various localities spiked with the same number of cells of culture strains. This approach can be employed to improve the monitoring efficiency of various marine protists and to support the implementation of management for harmful algal blooms, which are difficult to analyze using microscopy alone. [ABSTRACT FROM AUTHOR]

Harmful Algal Blooms (HABs) have been classified depending on the causative organism and its impacts: non-toxic HAB (microalgae capable of affecting tourism and causing oxygen deficiency, which generates mortality of marine organisms), toxic HAB (microalgae capable of transferring toxins to the food chain), and ichthyotoxic HAB (microalgae capable of generating mechanical damage in fish). HABs represent a worldwide problem and have apparently increased in frequency, intensity, and geographic distribution at different latitudes. This review details the occurrence of HAB events in the Southeast Pacific, Chile, over a 65-year period, analysing two of the three types of HAB described: toxic and ichthyotoxic HABs. For this, we conducted a review from many different scientific sources and from the written press and social media, that have mentioned HAB events in the country. In Chile, the microalgae involved in HAB events are dinoflagellate (52%), diatoms (33%) and silicoflagellate (10%), with a total of 41 species and/or genera described in the literature. A total of 501 HAB events were recorded in Chile between 1956 and 2021, where 240 (47.9%), 238 (47.5%), 14 (2.7%), 8 (1.5%) and 1 (0.2%) event were caused by diatoms, dinoflagellate, silicoflagellate, raphidophycean and haptophyte, respectively. An apparent increase in the frequency of HAB events is observed since the first record in 1956, with a maximum of 46 events during the years 2017 and 2019. The highest incidence in fish is caused by the group of silicoflagellate, raphidophycean and haptophyte (23 events), where 10 events caused mortalities in salmon with an incidence rate of 43.4%. Unlike what is observed with diatoms and dinoflagellate, the events associated with these groups are less frequent, but hold a much higher salmon mortality rate. During the last 65 years, HAB's geographic extent shows an apparent trend to increase south-to-north. However, the identification of events is closely linked to the areas where much of the country's aquaculture is located and, therefore, it could be biased. In turn, it is observed that the apparent increase in HAB events could be associated with a greater monitoring effort after major events (e.g., after the 2016 HAB event). On the other hand, it is also recognized a lack of knowledge about harmful algae throughout the Chilean Humboldt Current system, particularly in the northern regions, such as Atacama and Coquimbo. Therefore, the total number of blooms that have occurred in fjords and channels, particularly those that have caused minor economic impacts for artisanal fishermen and the salmon and mussel farming sector, might be underestimated. [ABSTRACT FROM AUTHOR]

• Grand Lake St Marys (Ohio) is characterized by nearly year-round cyanobacterial blooms that often produce high levels of toxins, historically ranking among the highest for public drinking water intakes in the United States. • This study documents and models changes in phytoplankton biomass, community structure, and toxicity over a 3-year period of hydrologic extremes (heavy rain and drought). • Results from the dry year in this study show that external nutrient load reductions and resulting can positively impact phytoplankton community structure, biodiversity, and toxicity in the same year, rather than being outweighed by legacy nutrients. • Applying NH 4 + turnover (to represent a more accurate estimate of N availability) to model microcystins in situ offers a significant improvement in model accuracy at high biomass but low toxin concentrations. Grand Lake St. Marys (GLSM) is a large, shallow, hypereutrophic lake situated in an agricultural watershed with high-nutrient, non-point source runoff. The resulting harmful algal blooms (HABs) are typically dominated by Planktothrix , which can produce microcystin, a potent cyanobacterial toxin that has varied in concentration over the past decade. Some drivers of bloom biomass and toxicity in GLSM are described, but recent years (2019–2022) have exhibited anomalous combinations of winter ice cover and spring runoff, suggesting that additional factors contribute to variability in HAB severity and toxicity. 2020 and 2022 were typical water years, with normal tributary runoff volumes occurring primarily in late winter and spring after either little to no ice cover (2019–2020) or heavy/prolonged ice cover (2021–2022). However, 2021 exhibited prolonged winter ice and low winter/spring runoff. 2020 and 2022 were typical bloom years, with near monoculture, Planktothrix -dominated biomass (11 to 405 μg/L total chlorophyll) and high total concentrations of microcystins (<0.3 to 65 μg/L). However, the first half of 2021 exhibited lower biomass (18 to 65 μg/L chlorophyll a) and toxin concentrations (0.4 to 2.0 μg/L). While biomass returned to bloom levels when external tributary loading increased, ammonium uptake and regeneration rates and microcystin concentrations remained low throughout 2021 (in contrast to other years). Overall, potential ammonium uptake rates strongly correlated with chlorophyll and microcystin concentrations (Bayesian R2 = 0.59; 95% CI = 0.44 to 0.65). Phytoplankton diversity was higher in 2021 than other years, especially in spring/early summer, with increased dinoflagellates and diatoms in spring, followed by a mixed cyanobacterial assemblage in summer. These results suggest that lower external nutrient loads can drive immediate positive impacts on water quality, such as reduced HAB biomass and toxicity and higher phytoplankton diversity, even in hypereutrophic, shallow lakes. [ABSTRACT FROM AUTHOR]

Advancements in data availability, including high frequency, near real-time multiparameter sensors, laboratory analysis, and in-situ and remote observations, have driven the development of machine learning (ML) models for applications such as toxic Harmful Algal Bloom (HABs) monitoring. However, the performance of ML predictions is influenced by both model uncertainties due to inherent model structures and errors associated with input dataset measurements. For example, measurement uncertainty arises from sample collection, sensor drift and laboratory analysis and sample handling errors. While impacts of model uncertainty are commonly addressed using probabilistic approaches, the effect of measurement uncertainty is less studied due to the limited availability of detailed measurement information. This study focuses on assessing the impact of measurement uncertainty on the ML prediction of chlorophyll-a concentration as an index of HABs in a mesotrophic lake. Using randomized subsets of input measured datasets that mimic possible chlorophyll-a concentration distributions, the study built 1000 Random Forest (RF) and Support Vector Regression (SVR) models. An independent measured dataset was used to validate the ensemble models, allowing for model performance evaluation and the creation of prediction intervals to measure the propagated uncertainty. Our findings showed that the model predictions have MAE that ranged between 0.16 μg/l and 5.19 μg/l, and RMSE ranging between 0.20 μg/l and 7.39 μg/l. The highest uncertainty coverage of 0.71 was observed in the RF model without chlorophyll-a sensor values as a predictor. The study found that the training dataset sizes due to the high frequency and manually sampled nature influence how much measurement uncertainty is covered. The results of this study demonstrate how well ML models can capture various HABs patterns when given diverse measurement variables. Our findings will give researchers insightful information on how to lessen the impact of measurement uncertainty when using ML models as decision-support tools for HABs management. [Display omitted] • ML prediction of HABs is affected by errors in measured water quality datasets. • Chlorophyll-a prediction as index of HABs was assessed using subsets of measured data. • Ensemble RF and SVR models were used to generate chlorophyll-a prediction intervals. • Variation in datasets influences the ability of HABs ML models to reduce measurement uncertainty effect. [ABSTRACT FROM AUTHOR]

BackgroundAlexandrium pacificum is a dinoflagellate species notorious for its rapid growth resulting in large-scale blooms. This study aimed to investigate the molecular mechanisms of A. pacificum under laboratory-simulated rapid growth conditions from the perspective of H3K4me3 modification regulation.Methods and resultsWestern blot was used to detect the modification abundance of H3K4me3 in A. pacificum cultured under different conditions, including high light (HL), high nitrogen (HN), and f/2 medium (control, CT), in the rapid growth exponential phase. The results showed that the modification abundance of H3K4me3 under HL or HN was greater than that under CT. Chromatin immunoprecipitation-sequencing was used to explore the acting genes of H3K4me3 under different conditions for the first time. Nitrogen metabolism and endocytosis were significantly associated with H3K4me3 regulation under HL. Furthermore, H3K4me3 was also significantly associated with the vitamin metabolism pathway under HN.ConclusionsThese findings demonstrate that H3K4me3 plays a potentially important role in the regulation of the rapid growth of A. pacificum. Such knowledge of a histone modification regulatory network in this dinoflagellate, lays a necessary foundation for future research in related fields.

The occurrence of HABs is known to be affected by multiple environmental factors such as temperature, salinity, nutrients, light, water chemistry, and biological activity. This study aimed to study the possibility of early warning for Cochlodinium polykrikoides blooms in southern Korean waters using qPCR and metabarcoding analysis. We were able to detect C. polykrikoides via a sensitive technique, and confirmed the early warning potential of C. polykrikoides by quantitative PCR. To identify the microbial organisms related to the bloom caused by C. polykrikoides, metabarcoding analysis was conducted using 18 water samples collected from bloom sites in southern Korean waters between 2018 and 2019. Although there was no single group that could explain the successive blooms of C. polykrikoides, four taxa, including Gamma proteobacteria (0.588, p < 0.01), Verrucomicrobia (0.874, p < 0.01), Cyanobacteria (0.975, p < 0.01), and Cryptophyta, were related to C. polykrikoides blooms. When the HABs that occurred were caused by C. polykrikoides, although there were sites where the cells of C. polykrikoides were not detected, similar functions of the microbial communities operated in all southern Korean coastal waters. We identified that the phytoplankton community structure was divided into three or four, using metabarcoding analysis by sampling years. [ABSTRACT FROM AUTHOR]

The Hartbeespoort Dam is a discharge point of a catchment that is characterized by urbanization, mining, industrial, and agricultural activities. These activities coupled with fluxes of heavily polluted wastewater from informal settlements, wastewater treatment works, as well as runoff from golf courses have led to the development of recurring harmful algal blooms (HABs). The predominant cyanobacteria scum that is largely covering the Dam water is toxic to fish and poses serious public health risks. Phosphorus is the limiting nutrient in terrestrial aquatic systems and excess concentration in the waters usually results in eutrophication. The productivity level in Hartbeespoort Dam is also a function of total phosphorous (TP) level, showing a positive correlation with chlorophyll-a, an index for phytoplankton which are predominantly HABs in this Dam. Analysis of long-term in situ water quality data (1980–2020) show that TP is not the only driver, changes in surface water temperatures also affect the productivity level, especially, when TP levels are below a threshold of approximately 0.4 mg/L. Chlorophyll-a was retrieved from current generation high resolution satellite (Landsat and Sentinel) at 5-year interval. Standard band ratio-based ocean color model applied to satellite data produced an accuracy of R2 = 0.86 and RMSE of 5.56 µg/L. Time series analysis of in situ and satellite data show similar trends including capturing the effect of biocontrol on productivity levels between the late 1980s and the early 1990s, after which productivity increased with an increased flux of TP. Since 2015, the average annual surface temperature in the Dam has decreased leading to the decline in productivity level despite increasing levels of TP. The spatial dynamics of the HABs is a function of the discharges levels of the various rivers draining into the Dam as well as its geometry. Relatively higher concentrations are observed near river discharges and in areas of restricted water circulation. [ABSTRACT FROM AUTHOR]

Harmful algal bloom events (HABs) of the raphidophyte, Heterosigma akashiwo, have increased in frequency and severity in some South African estuaries and have been observed in conjunction with substantial fish kills. The impact of H. akashiwo on wild fish populations is still unclear, despite being responsible for massive economic losses in the aquaculture industry globally. Thus, histopathological techniques were used to assess the impacts of H. akashiwo HABs on three species of Mugilidae (Chelon richardsonii, Mugil cephalus and Chelon dumerili) during an in situ cage study (stocking density of < 0.75 kg m−3) in the agriculturally influenced Sundays Estuary, which has predictable spring/summer blooming periods of H. akashiwo. It was hypothesised that fishes kept in mesocosms situated in the bloom area of the estuary would have higher blood plasma cortisol and glucose levels and have more deleterious gill alterations than fishes kept adjacent to the bloom area. Blood plasma cortisol, glucose and gill histological and morphological indices were similar between the HAB and control treatments but differed between bloom phases. The proportion of secondary lamellae available for gas exchange (PAGE index) was lower during trials that were in a hypereutrophic bloom phase (> 60 Chl-a µg.L−1) compared to the accumulation and decay phases. Gill histological alterations (HIGill index) were also more pronounced during the same trials. This study emphasises the need for further research including a toxicology study on the H. akashiwo strain, now common in some South African estuaries, to gain knowledge on the mechanisms by which H. akashiwo causes fish kills in order to protect the ecosystem services that estuaries provide. [ABSTRACT FROM AUTHOR]

Increasing global population has resulted in increased urbanization of coastal areas across the globe. Such an increase generates many challenges for sustainable food production and food security. The development of aquaculture has proven to be an extremely good option to ensure food security (uninterrupted supply and good quality of food) by many countries, especially those with urban areas affected by space limitations such as Singapore. However, the implementation of aquaculture is not without its challenges and impacts to the environment, with Harmful Algal Blooms (HABs) being one of the major concerns in coastal waters. In this review we analyze the development of the aquaculture industry with respect to HABs in Singapore and compare it to similar urban areas such as Hong Kong (SAR China), Salalah (Oman), Cape Town (South Africa), Valencia (Spain), Rotterdam (The Netherlands), Tampa bay (USA), Vancouver (Canada), and Sydney (Australia). Along with HABs, the abovementioned urban areas face different challenges in sustainably increasing their aquaculture production with respect to the economy and geography. This review further assesses the different production and monitoring strategies that have been implemented to counter these challenges while sustainably increasing production. The ongoing COVID-19 pandemic has affected the world with lockdowns and border closures resulting in logistical difficulties in seafood trade which has further accentuated the dependencies on food import. We conclude that the challenges faced by urban areas for sustainable achievement of food security through development of the aquaculture industry can be effectively managed through proper planning, management and collaboration of knowledge/skills on an international level. [ABSTRACT FROM AUTHOR]

Harmful algal blooms (HABs) pose a significant ecological threat and economic detriment to freshwater environments. In order to develop an intelligent early warning system for HABs, big data and deep learning models were harnessed in this study. Data collection was achieved utilizing the vertical aquatic monitoring system (VAMS). Subsequently, the analysis and stratification of the vertical aquatic layer were conducted employing the "DeepDPM-Spectral Clustering" method. This approach drastically reduced the number of predictive models and enhanced the adaptability of the system. The Bloomformer-2 model was developed to conduct both single-step and multistep predictions of Chl-a, integrating the " Alert Level Framework" issued by the World Health Organization to accomplish early warning for HABs. The case study conducted in Taihu Lake revealed that during the winter of 2018, the water column could be partitioned into four clusters (Groups W1-W4), while in the summer of 2019, the water column could be partitioned into five clusters (Groups S1-S5). Moreover, in a subsequent predictive task, Bloomformer-2 exhibited superiority in performance across all clusters for both the winter of 2018 and the summer of 2019 (MAE: 0.175-0.394, MSE: 0.042-0.305, and MAPE: 0.228-2.279 for single-step prediction; MAE: 0.184-0.505, MSE: 0.101-0.378, and MAPE: 0.243-4.011 for multistep prediction). The prediction for the 3 days indicated that Group W1 was in a Level I alert state at all times. Conversely, Group S1 was mainly under an Level I alert, with seven specific time points escalating to a Level II alert. Furthermore, the end-to-end architecture of this system, coupled with the automation of its various processes, minimized human intervention, endowing it with intelligent characteristics. This research highlights the transformative potential of integrating big data and artificial intelligence in environmental management and emphasizes the importance of model interpretability in machine learning applications.

ABSTRACT: This paper presents the first results of a new way of using MODIS (Moderate Resolution Imaging Spectroradiometer) sensor data to visualize phytopigment inconstancy in the near-surface layer of water basins. Other sensors of this class alike, the MODIS spectral resolution is too low to reproduce the minimums of reflectance Rrs caused by phytopigments in water. However, MODIS is remarkable for the presence of a channel at 469 nm combined with channels at 412, 443, 488, 531, 547, and 555 nm. This makes it possible to distinguish the spectral limits of preferential light absorption by chlorophyll a (412–469 nm) and by accessory pigments (469–555 nm). These capabilities were realized thanks to spectral pixel indexation (SPI) of MODIS images of the sea surface. The SPI boils down to the fact that a user determines the presence of pigment minima in spectra of every image pixel, finds the sum of the wavelengths of these minima as a WRM code and assigns it to the image pixel as one of its attributes. WRM code = 100 is assigned to pixels free of the minima. Such indexation makes it possible to examine the inconstancy of phytopigments on the background of aquatic environment variability. Application of SPI approach to MODIS images of the Gulf of Mexico and the Baltic Sea made it possible to reveal new patterns of phytopigment dynamics during HABs events.

The non-natural mineralization of CaCO3 with special structures or morphologies is generated during the migration of crude oil and is the main form of scale in alkaline/surfactant/polymer (ASP) flooding in oilfields, adversely affecting oil recovery and causing environmental pollution. To date, the mineralization of aragonite superstructures and the role of heavy alkyl-benzene sulfonate (HABS) in mineralization are still unclear. In this work, aragonite-based superstructures of CaCO3 crystals were obtained in an O/W emulsion with HABS to help deepen the understanding of the diversified growth of CaCO3 scaling in oilfields. As a result, rosette-like, bouquet-like, and dumbbell-shaped CaCO3 crystals with vaterite–aragonite, aragonite, and calcite–aragonite phases were formed with 200 mg/L HABS concentration at 45 °C for 60 min and spherical vaterite phase stabilized at a high HABS concentration (800 mg/L and 1000 mg/L). Rhombohedral calcite content experienced a fluctuation of about 40% as the HABS concentration varied. Needle-like and bundle-like aragonite precipitates were generated with increasing temperatures from 65 °C to 85 °C. Thus, HABS affects the nucleation and growth of the precipitated CaCO3 solid, leading to modifications in the structure and morphology of the crystals. The synergistic effect between HABS and temperature can regulate ion pairs with the calcium ions and block sites that are essential to the incorporation of new solutes into the crystal lattice, which leads to the heterogeneous nucleation of vaterite and aragonite on calcite, forming aragonite-based superstructures in kerosene emulsion. This work may enrich the understanding of CaCO3 mineralization in oilfields, and also provide a novel strategy for manufacturing organic–inorganic composites.