Algal Blooms Research Articles

Periodically asymmetric responses of deep chlorophyll maximum to light and thermocline in a clear monomictic lake: Insights from monthly and diel scale observations

Deep chlorophyll maximum (DCM), a chlorophyll peak in the water column, has important implications for biogeochemical cycles, energy flow and water surface algal blooms in deep lakes. However, how an observed periodically asymmetric DCM response to environmental variables remains unclear, limiting our in-depth understanding and effective eco-environmental management of deep lakes. Based on both monthly field investigations in 2021 and diel continuous observations in 2021–2023 in clear, monomictic Lake Fuxian, Southwest China, the temporal dynamics and drivers of DCM were examined and periodic features of DCM were found, with a formation period (FP, February–July) and a weakening period (WP, August–December). On the monthly scale, although DCM dynamics were partly attributed to thermocline structures, the role of light penetration depths varied with period. In the FP, the influence of light on DCM was direct, i.e., increased depth and thickness but decreased magnitude. Differently, the influence of light mainly occurred by affecting thermocline structures in the WP, where water quality was another important driver. On the diel scale, light was a major reason for a thicker and lower (magnitude) DCM during day than at night, and the response of DCM to environmental factors between the FP and WP differed also more during day. This periodically asymmetric response of daytime DCM not only being caused by light but possibly also related to other physical factors such as lake surface water temperature, wind speed and precipitation. Bayesian network modelling suggested that water darkening and stratification intensification may promote a shallower, thinner and larger (magnitude) DCM in both FP and WP, but achieving such changes in DCM requires different light and thermocline thresholds. Our findings provide new information valuable for modelling DCM and for predicting the related surface algal blooms in deep lakes under climate change and eutrophication.

A Graphic Review of Studies on Ocean and Mediterranean Sea Environment Quality

With so many studies today on the water quality of the sea, one can hardly comprehend the multitude of topics that arise all over the world. This study provides a few graphic syntheses related to the most frequent words (including their clustering and links), trend topics, the spatial distribution of the researched areas, and the thematic evolution of the research directions over the decades. The most frequent authors’ keywords have a 50% similitude between the ocean studies and the studies related to the Mediterranean Sea; these keywords are part of a causal chain that dominates the marine studies on water quality: nutrients → eutrophication → phytoplankton → chlorophyll → seagrass. The most frequent words in the titles and abstracts of the selected papers from the Web of Science are “concentration” and “species”; in the Mediterranean studies, “chlorophyll” and “temperature” are the most frequent. In close connection with water quality, Zostera marina (eelgrass) and Crassotrea virginica (eastern oyster) prevail at the global scale, while Posidonia oceanica (Neptune grass) is relevant in the Mediterranean space. Some of the most studied water bodies are the South China Sea, San Francisco Bay, Chesapeake Bay, and, in the Mediterranean Sea, the Adriatic, Ionian, Aegean, and Marmara seas. “Climate change” and “remote sensing” are trend topics that shape the current studies on water quality; the increasing sea surface temperature enhances algal blooms—these need to be monitored using satellite imagery for the sustainable evolution of human activities, including aquaculture.

Fluoro-Electrochemistry Based Phytoplankton Bloom Detection and Enumeration; Field Validation of a New Sensor for Ocean Monitoring

Fluoro-Electrochemistry Based Phytoplankton Bloom Detection and Enumeration; Field Validation of a New Sensor for Ocean Monitoring

Interface-assisted synthesized covalent organic framework film for efficient extraction of microcystins in aquatic organisms

Covalent organic framework (COF) film-based solid-phase extraction (F-SPE) has garnered great attention in sample pretreatment. However, harsh synthesis conditions of COF films have severely hindered their potential applications. In this study, a kind of COF (TPB-DMTP) films were fabricated via a liquid-liquid interfacial synthesis method at a mild condition. The obtained films exhibited excellent extraction performance towards microcystins (MCs, an algal toxin) due to their porous structure, high specific surface area and abundant accessible adsorption sites. Coupled TPB-DMTP films-based F-SPE with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), a sensitive and environment-friendly analytical method was established for MCs detection. Under the optimal conditions, this method possessed wide linear ranges (2.0–800.0 pg mL−1) with good linearity (R ≥ 0.9991), low limits of detection (0.8–3.0 pg mL−1) and satisfactory precision (RSDs ≤7.1 %), which then successfully applied for MCs detection in actual aquatic organism samples. Trace amounts of MC-RR (42.4 pg mL−1) and MC-YR (14.6 pg mL−1) were detected in the mussels. The results demonstrate the excellent application potential of COF films in sample pretreatment.

An assessment of N, P, Fe, Zn, Ni and Mo limitation on suspended nutrient diffusing substrates in nearshore areas of Lake Michigan and Lake Erie

In large lakes, metal availability sometimes limits the acquisition of nutrients (nitrogen, N and phosphorus, P) in offshore waters that are relatively isolated from tributaries and sediments. We hypothesize that metals may also be important within harmful algal blooms (HABs). HABs occur where nutrient loads are elevated, but bioassays often indicate that phytoplankton in HABs are N or P limited. Nutrient limitation may be exacerbated by corresponding limitations in several metals (i.e. nickel - Ni, molybdenum - Mo, zinc - Zn, and iron - Fe) that facilitate uptake and transformation of oxidized and organic forms of nutrients, such as urea, nitrate and organic phosphorus. The cyanotoxin microcystin has been hypothesized to have a role in metal management, so metal demand may also influence the toxicity of HABs. Here, we used nutrient diffusing substrates to measure how N, P, Ni, Mo, Zn and Fe amendments influenced the growth and toxicity of periphyton. Periphyton was grown suspended in 10 nearshore sites in Lake Michigan and Lake Erie (5 with and 5 without perennial HABs). Outside of blooms, we found no evidence for metal limitation or co-limitation. However, evidence for metal co-limitation was observed in two HABs sites (Zn in Green Bay and Zn, Mo, Ni and Fe in Sandusky Bay). N, P and Zn amendments all stimulated microcystin content in Maumee Bay. These data indicate that nutrient limitation occurs even within blooms, and the availability of metals may have an influence on growth, community composition and toxicity.

Improvement of water quality through coordinated multi-trophic level biomanipulations: Application to a subtropical emergency water supply lake

Artificial emergency water source lakes have been built in most cities in the middle and lower reaches of the Yangtze River, China, to ensure water safety for residents. However, these new ecosystems are prone to algal blooms or other degraded water quality conditions. A newly built water supply lake in the lower reaches of the Yangtze River was selected as a model system to test whether the coordinated manipulation of fish and submerged macrophyte communities could enhance ecosystem function and quality. The coordinated manipulations spanned a five-year period, aiming to enhance both top-down and bottom-up control of phytoplankton. As a result of these manipulations, the catch per unit effort of small-bodied zooplanktivorous fishes decreased by >95 % from year two and remained low. The coverage and biomass of submerged macrophytes increased year by year. Water transparency increased from 1.07 to 3.33 m. Total phosphorus and total nitrogen showed a decreasing trend (not significant though). The annual mean biomass of Cyanophyta, Chlorophyta and Bacillariophyta decreased from 2.99 to 0.03 mg/L, 3.90 to 0.16 mg/L, and 3.50 to 0.3 mg/L, respectively. The biomass of phytoplankton in different groups decreased in all four seasons. The annual mean biomass of Cladocera and Copepoda remained low. The biomass of Cladocera and Copepoda decreased in summer, fall, and winter. The Ecosystem Health Index - increased from 15.9 to 32.0. The pros and cons of the various top-down and bottom-up control measures employed are discussed. This research presents a valuable case study on the enhancement of ecosystem structure and function in newly constructed emergency water supply lakes and offers insights into the restoration of other subtropical shallow lakes.

Water scarcity and public health concerns in rural India: a case study of Nongpok Sekmai and surrounding villages

This study examines the critical issue of water scarcity and its impact on public health in Nongpok Sekmai and surrounding villages in India. Despite government initiatives to provide universal tap water access by 2024, these villages lack safe drinking water. Traditional sources like open wells are contaminated, and the primary river is drying up due to illegal sand mining and gravel extraction activities upstream. This situation results in a significant public health burden, with villagers facing financial strain due to waterborne diseases and the need to purchase water for basic needs. The study also examines the negative link between on-premise access to safe water and mothers' time spent on water collection. The study highlights the need for a multi-pronged approach. Renewed government efforts to implement the tap water initiative or provide alternative clean water sources like filtration plants or community wells are crucial. Additionally, stricter enforcement is needed to curb illegal mining activities and ensure river sustainability. Furthermore, exploring community-based solutions like rainwater harvesting and raising awareness about waterborne diseases and sanitation practices can empower the population. Addressing this water crisis demands a collaborative effort from the government, local communities, and environmental agencies. This study employed a mixed-methods approach, utilizing visual photographic analysis and community engagement to investigate water contamination in Nongpok Sekmai river, Manipur. The findings highlight key contamination indicators such as turbidity, algae blooms, and floating debris, while also addressing the health and social impacts perceived by the local population.

Exploring controls on the timing of the phytoplankton bloom in western Baffin Bay, Canadian Arctic

In the Arctic Ocean the peak of the phytoplankton bloom occurs around the period of sea ice break-up. Climate change is likely to impact the bloom phenology and its crucial contribution to the production dynamics of Arctic marine ecosystems. Here we explore and quantify controls on the timing of the spring bloom using a one-dimensional biogeochemical/ecosystem model configured for coastal western Baffin Bay. The model reproduces the observations made on the phenology and the assemblage of the phytoplankton community from an ice camp in the region. Using sensitivity experiments, we found that two essential controls on the timing of the spring bloom were the biomass of phytoplankton before bloom initiation and the light under sea ice before sea ice break-up. The level of nitrate before bloom initiation was less important. The bloom peak was delayed up to 20 days if the overwintering phytoplankton biomass was too low. This result highlights the importance of phytoplankton survival mechanisms during polar winter to the pelagic ecosystem of the Arctic Ocean and the spring bloom dynamics.

Fungal Parasite Transmission in a Planktonic Ecosystem Under Light and Nutrient Constraints.

The two main components of the planktonic ecosystem are phytoplankton and zooplankton. Fungal parasites can infect zooplankton and spread between them. In this paper, we construct a dynamic model to describe the spread of fungal parasites among zooplankton. Basic reproduction number for fungal parasite transmission among zooplankton are rigorously derived. The dynamics of this system are analyzed including dissipativity and equilibria. We further explore the effects of ecological factors on population dynamics and the relationship between fungal parasite transmission and phytoplankton blooms. Interestingly, our theoretical and numerical results indicate that a low-light or oligotrophic aquatic environment is helpful in mitigating the transmission of fungal parasites. We also show that fungal parasites on zooplankton can increase phytoplankton biomass and induce blooms.

Detection of Floating Algae Blooms on Water Bodies Using PlanetScope Images and Shifted Windows Transformer Model

The increasing water temperature due to climate change has led to more frequent algae blooms and deteriorating water quality in coastal areas and rivers worldwide. To address this, we developed a deep learning-based model for identifying floating algae blooms using PlanetScope optical images and the Shifted Windows (Swin) Transformer architecture. We created 1,998 datasets from 105 scenes of PlanetScope imagery collected between 2018 and 2023, covering 14 water bodies known for frequent algae blooms. The methodology included data pre-processing, dataset generation, deep learning modeling, and inference result generation. The input images contained six bands, including vegetation indices such as the Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI), enhancing the model’s responsiveness to algae blooms. Evaluations were conducted using both single-period and multi-period datasets. The single-period model achieved a mean Intersection over Union (mIoU) between 72.18% and 76.47%, while the multi-period model significantly improved performance, with an mIoU of 91.72%. This demonstrates the potential of our model and highlights the importance of change detection in multi-temporal images for algae bloom monitoring. Additionally, the padding technique proposed in this study resolved the border issue that arises when mosaicking inference results from individual patches, providing a seamless view of the satellite scene.

Recent Advances in Monitoring Microbial Toxins in Food Samples by HPLC-Based Techniques: A Review

This study examines the significant impact of bacterial, algal, and fungal toxins on foodborne illnesses, and stresses the importance of advanced detection techniques, such as high-performance liquid chromatography (HPLC)-based methodologies. It emphasizes the urgent need for further advancements in these techniques to ensure food safety, as they offer significant benefits, including low detection limits and the ability to be combined with other techniques to detect a wide range of toxins. In this regard, HPLC has emerged as a versatile and sensitive analytical technique for this purpose. Various HPLC methods, often enhanced with detectors such as ultraviolet (UV), fluorescence (FD), and mass spectrometry (MS), have been developed to identify and quantify microbial toxins in a wide variety of food samples. Recent advancements include HPLC-FD methods that utilize the natural fluorescence of certain aflatoxins, improving detection sensitivity. HPLC-MS/MS and UHPLC-MS/MS techniques offer high selectivity and sensitivity, making them suitable for detecting a wide range of toxins in trace quantities. The adaptability of HPLC, combined with innovative detection technologies and sample preparation methods, holds significant potential for enhancing food safety monitoring and reducing the global burden of foodborne diseases.

Unraveling the risks of nAl2O3 on harmful algal blooms: Insights from paralytic shellfish toxins production of Alexandrium tamarense

As one of the commonly used and cost-effective nanomaterials, nanosized aluminum oxide (nAl2O3) posses unique properties and chemical stability. However, its extensive use and resultant dissemination into aquatic ecosystems prompt concerns over the proliferation and repercussions of harmful algal blooms, particularly those caused by dinoflagellates producing toxins. This study investigated the sub-chronic effects of nAl2O3 on growth, physiological activities, and paralytic shellfish toxins (PSTs) production in Alexandrium tamarense. Results showed dose-dependent inhibition in growth (EC50 = 20.6 mg L−1), esterase activity, and photosynthetic efficiency (Fv/Fm) during the sub-chronic exposure (13-day). The internalization of nAl2O3 in microalgal cells and the significant decrease in the total cellular PSTs content were observed under high nAl2O3 concentrations (>40 mg L−1). The study also demonstrated a clear decrease in the content of some derivatives of PSTs (GTX5, C1/2, and GTX2/3) with the increase in nAl2O3 concentrations, accompanied by the induction of an unknown derivative. Excessive ROS production, dissolved Al, and physical inhibition were suggested as potential mechanisms for nAl2O3 toxicity and changes in PSTs toxin profile. Overall, this research enhances our understanding of the potentiated risks and threats on the possible concurrent events of toxic dinoflagellate, such as Alexandrium species and nanoparticles in aquatic environments.

Accumulation and depuration of 4,5-dihydro-KmTx2 from Karlodinium veneficum in the bivalves, Mercenaria mercenaria and Sinonovacula constricta

Bivalves (e.g., clams, oysters, mussels, scallops) are a significant part of the global diet and are harvested for their nutritional value, but as filter feeders they are susceptible to the accumulation of toxins produced by certain species of phytoplankton. Karlotoxins (KmTxs) are a class of amphidinol-like compounds with hemolytic, ichthyotoxic, and cytotoxic properties that have been associated with harmful algal blooms, and the dinoflagellate Karlodinium veneficum uses KmTxs to facilitate prey capture and deter grazing by other organisms. In this work, we examined the accumulation and depuration of 4,5-dihydro-KmTx2, a karlotoxin previously isolated from K. veneficum, in two bivalves with different life habits, i.e., Sinonovacula constricta Lamarck and Mercenaria mercenaria Linnaeus. After both bivalves received K. veneficum GM5 in their feed for a long period of 10 days, 4,5-dihydro-KmTx2 was accumulated considerably in the visceral mass, but there was almost no toxin accumulation in the muscle. The accumulation was more severe for M. mercenaria than S. constricta. The toxin was cleared almost completely from the bivalves 5 days after K. veneficum GM5 was removed from the feed. For both bivalves, the bait microalgae I. galbana slowed both the accumulation and the depuration of the toxin.

Enhancing photosynthesis of microalgae via photoluminescent g-C3N4 accelerated photoelectrons transfer in photosystem

Using photoluminescent (PL) graphitic carbon nitride (g-C3N4) to convert ultraviolet (UV) light into chloroplast absorbed blue or near infrared (NR) is an attractive methodology to facilitate sunlight energy storage and carbon sequestration by microalgae. However, most researches focus on inhibiting water bloom by g-C3N4, applying PL g-C3N4 to promote growth of microalgae is rarely reported. Accordingly, PL g-C3N4 is synthesized by a microwave heating method and co–cultured with Chlorella vulgaris (C. vulgaris) with concentration of 0, 50, and 250 mg/L, named as C. vulgaris-0, C. vulgaris-50, and C. vulgaris-250, respectively, to study effect of PL g-C3N4 on growth of C. vulgaris. Results indicate that there is no significant effect of microwave synthesized g-C3N4 on morphology of microalgae cells, while cell viability and growth rate of C. vulgaris-50 is obviously enhanced. Further analysis indicates that, on the one hand, PL fluorescence at 615 nm enlarges light absorption of microalgae; on the other hand, photogenerated electrons by g-C3N4 accelerate electron transfer in photosystem, subsequently enhancing formation of NADPH and ATP, which is favorable to growth of microalgae. Metabolism analysis illustrates that glucose, fructose, and galactose, involved in glycolysis and photosynthesis, are all up-regulated in C. vulgaris-50 group. This work reveals low concentration of PL g-C3N4 facilitates protein synthesis and energy metabolism through enhancing light absorption and electron transfers, providing a biochemical strategy to enhance carbon sequestration.

Factors shaping pelagic-benthic coupling in the process of settlement in an Arctic fjord

Benthic organisms typically possess a planktonic propagule stage in the form of larvae or spores, which enables them to spread over large distances before settlement, and promotes tight pelago-benthic coupling. However, factors driving dispersal and epibenthos recruitment in shallow hard-bottom Arctic communities are poorly known. We therefore conducted a year-round in situ colonization experiment in Isfjorden (Svalbard), and found out that variation in early-stage epibenthic assemblages was explained by the combination of: abiotic (45.9%) and biotic variables (23.9%), and their interactions (30.2%). The upward-facing experimental plates were dominated by coralline algae, and this is the first study showing that at high latitudes coralline algae Lithothamnion sp. settle in high numbers on available substrates during the polar night in winter. The downward-facing plates, which had much less exposure to light, contained more diverse organisms, with a predominance of polychaetas and bryozoans. However, in summer, the barnacle Semibalanus balanoides outcompeted all the other recruits, as a result of massive occurrence of meroplanktonic Cirripedia larvae, triggered by the phytoplankton bloom. In conclusion, the rate and success of epibenthic settlements were dependent mostly on light availability and temperature, suggesting that larval settlement will be impacted by global warming with some taxa benefitting, while others losing.

Mortality partitioning between viral lysis and microzooplankton grazing in successive phytoplankton blooms using dilution and molecular methods

Phytoplankton play crucial roles in aquatic ecosystems, serving as the foundation of marine food webs and being responsible for ~50% of the world’s oxygen production. Predation by microzooplankton and viral lysis are the major sources of phytoplankton mortality, with the balance between these 2 processes affecting microbial food webs and biogeochemical cycles. However, determining the dominant mortality process in time and space remains an open question. This study investigated microzooplankton grazing and viral lysis rates during a mesocosm experiment in western Norway. High-resolution measurements were determined on phytoplankton groups using flow cytometry to observe changes in mortality rates and carbon flow during phytoplankton blooms. Digital droplet PCR was employed to detect Emiliania huxleyi and Micromonas spp. and associated viruses within environmental samples, to explore its use for determining mortality processes and understanding the impact on the phytoplankton community. The results showed that grazing and viral lysis dominated mortality at different times, with only one significant instance of both processes being observed. Microzooplankton grazing primarily affected picoplankton, while nanoeukaryotes and E. huxleyi were more susceptible to viral lysis. Molecular detection did not always match with abundances or rates determined by flow cytometry; however, it did provide insights into their dynamics throughout the mesocosm. These findings provide insights into the complex interactions between microzooplankton, viruses and phytoplankton communities. Understanding the balance between microzooplankton grazing and viral lysis can contribute to a more comprehensive understanding of carbon flow in aquatic ecosystems, which has significant implications for food webs and biogeochemical cycles.

Effect of carbonaceous materials on phosphorus removal in flow-through packed column systems.

Phosphorus (P) overloading in aquatic environments has long-been recognized as the leading cause of water quality deterioration, harmful algal bloom, and eutrophication. This study investigated P removal performance by five cost-effective carbonaceous materials (CMs) in flow-through packed column systems. These CMs include biochars pyrolyzed from feedstocks of Eucalyptus (E-biochar) and Douglas fir (D-biochar), commercial biochar (C-biochar), iron oxide-coated biochar (Fe-biochar), and commercial activated carbon (AC). The physicochemical properties of CMs, such as specific surface area (SSA), pore volume, pore diameter, elemental composition, and surface charge, were characterized. The packed column experimental results showed that P removal performance followed the order: E-biochar < D-biochar < C-biochar < Fe-biochar < AC. Specifically, the sorption capacity of 1mg/L of P in packed columns was 0.0036mg P/g E-biochar, 0.0111mg P/g D-biochar, 0.0369mg P/g D-biochar, 0.077mg P/g Fe-biochar, and 0.088mg P/g AC, respectively. The largest SSA (1012 m2/g) and pore volume (0.57 cm3/g) of AC accounted for the most outstanding P removal efficiency mainly by physical sorption, while electrostatic interaction explained the high P removal by Fe-biochar (SSA as low as 32.4 m2/g). Our findings provide direct practical implications for effectively removing P in water by cost-effective CMs.

Seasonal Dynamics of Trichodesmium and Phytoplankton Communities in the Eastern Arabian Sea: Winter Vs Spring-inter monsoon

The filamentous marine cyanobacterium Trichodesmium forms extensive blooms in tropical seas, where it plays an important role in nitrogen fixation. This study investigated Trichodesmium-associated phytoplankton in the Eastern Arabian Sea (EAS) during bloom and nonbloom conditions. Trichodesmium blooms over the continental shelf primarily comprised of T. erythraeum and T. thiebautii during the Spring Inter Monsoon (SIM) and T. erythraeum during the Winter Monsoon (WM). T. erythreaum blooms have rarely been reported from the north-east Arabian Sea during WM. Trichomes comprised of 143-1552 cells during the WM, with filaments ranging from 1339 to 13163 µm in length. Non-diazotrophic groups like diatoms and dinoflagellates were associated with Trichodesmium during both seasons within the bloom waters. The study found a novel symbiotic relationship between the heterocystous diazotroph Richelia intracellularis and Nitzschia sicula during WM blooms. This research expands knowledge of lesser-known phytoplankton species and their associations in the EAS.

Efficient simultaneous removal of phosphate and microcystin-LR in water using a novel g-C3N4/calcite composite under dark-visible light cycles

Harmful algal blooms (HABs) associated with the abundant presence of phosphorus and microcystin in natural waters have raised a growing global concern. In this study, an adsorption-photocatalysis strategy was developed using a novel g-C3N4/calcite composite for efficient simultaneous removal of phosphate and microcystin-LR in water under dark-visible light cycles for the first time. The appropriate introduction of calcite into g-C3N4 (i.e., g-C3N4/calcite-1) was efficient in both phosphate adsorption (>78.5 %) and microcystin-LR degradation (>84.3 %) under a dark-visible light cycle of 3:3h at an optimal dosage of 100 mg/L in waters (pH 5–9 and temperature 10–40 °C). The simultaneous removal mechanisms proposed that g-C3N4/calcite-1 adsorbed phosphate via adsorption and precipitation with surface Ca2+, and degraded microcystin-LR via oxidation by photogenerated reactive species (mainly h+ and •OH). The material characterizations and density functional theory (DFT) calculations revealed that the combination of g-C3N4 and calcite could not only change the electric field distributions of calcite and optimize the charge transfer during adsorption to improve its adsorption capacity towards phosphate, but also narrow the band gaps of g-C3N4, promote the electron-hole separation and lower the first-step reaction barrier in oxygen reduction pathway during photocatalysis to enhance its visible-light photocatalytic activity towards microcystin-LR. Collectively, these findings are believed to offer valuable insights on the green material design for water environmental remediation and the underlying mechanism elucidation for simultaneous removal of phosphorus and microcystin in water to achieve effective comprehensive management of HABs.

Satellite-Based Detection of Algal Blooms in Large Alpine Lake Sevan: Can Satellite Data Overcome the Unavoidable Limitations in Field Observations?

Lake Sevan in Armenia is a unique, large, alpine lake given its surface, volume, and geographic location. The lake suffered from progressing eutrophication and, since 2018, massive cyanobacterial blooms repeatedly occurred. Although the lake is comparatively intensely monitored, the feasibility to reliably detect the algal bloom events appeared to be limited by the established in situ monitoring, mostly because algal bloom dynamics are far more dynamic than the realized monitoring frequency of monthly samplings. This mismatch of monitoring frequency and ecosystem dynamics is a notorious problem in lakes, where plankton dynamics often work at relatively short time scales. Satellite-based monitoring with higher overpass frequency, e.g., by Sentinel-3 OLCI with its daily overcasts, are expected to fill this gap. The goal of our study was therefore the establishment of a fast detection of algal blooms in Lake Sevan that operates at the time scale of days instead of months. We found that algal bloom detection in Lake Sevan failed, however, when it was only based on chlorophyll due to complications with optical water properties and atmospheric corrections. Instead, we obtained good results when true-color RGB images were analyzed or a specifically designed satellite-based HAB indicator was applied. These methods provide reliable and very fast bloom detection at a scale of days. At the same time, our results indicated that there are still considerable limitations for the use of remote sensing when it comes to a fully quantitative assessment of algal dynamics in Lake Sevan. The observations made so far indicate that algal blooms are a regular feature in Lake Sevan and occur almost always when water temperatures surpass approximately 20 °C. Our satellite-based method effectively allowed for bloom detection at short time scales and identified blooms over several years where classical sampling failed to do so, simply because of the unfortunate timing of sampling dates and blooming phases. The extension of classical in situ sampling by satellite-based methods is therefore a step towards a more reliable, faster, and more cost-effective detection of algal blooms in this valuable lake.