Phycology, Volume 6, Issue 1 (March 2026) – 33 articles

The present study investigated the community composition and dynamics of freshwater biofouling on fiberglass inland waterway vessel (IWV) models coated with two commercial antifouling paints deployed in the Danube River (Serbia) for a total of five months. Biofouling was characterized using visual observations, in situ optical microscopy, the rapid ATP bioluminescence method, dry biomass measurements, and analyses of phototrophic and fungal communities. Based on the results, Hard Racing TecCel demonstrated the highest suppression of biofouling, with the lowest biomass accumulation and reduced algal diversity. At all stages of biofouling, diatoms dominated the phototrophic community, comprising 123 taxa. Achnanthidium minutissimum and Gomphonella olivacea were shown to be persistent hull colonizers, while Cyanobacteriophyta and Chlorophyta had reduced presence. Overall, the results highlight a slower progression of freshwater biofouling compared to marine systems and emphasize the need for the development of tailored antifouling strategies for IWVs to reduce environmental impact and operational costs. Full article

Obesity is a chronic systemic disorder frequently associated with multiorgan complications of inflammatory and metabolic origin. This study aimed to evaluate the histoprotective effects of Sargassum muticum, an invasive brown seaweed harvested from the Moroccan Atlantic coast, in cafeteria diet-induced obese rats. Thirty-five Wistar rats were divided into five groups: standard control, obese control (cafeteria diet), two obese groups treated with Sargassum muticum at 10% and 20%, and one group treated with orlistat at 30 mg/kg. After eight weeks, tissue samples were collected for a histopathological analysis. In untreated obese rats, histological examination revealed multiple abnormalities, including submucosal edema, vascular congestion, gastric inflammatory infiltration, pulmonary hemorrhage and lipid vacuoles, as well as hepatic, cardiac, pancreatic, and testicular lesions. Treatment with S. muticum, particularly at 20%, markedly improved these alterations, characterized by a significant reduction in inflammatory infiltration, vascular congestion, lipid vacuolization, and tissue degeneration, together with improved preservation of tissue architecture. These effects were superior to those observed with orlistat. The anti-inflammatory, antioxidant, and metabolic properties of S. muticum are likely due to its richness in bioactive compounds, notably phlorotannins, fucoxanthin, and sulfated polysaccharides. These findings confirm the therapeutic potential of S. muticum in preventing histopathological complications of obesity and pave the way for translational studies and potential nutraceutical applications in human obesity management. Full article

Urban water bodies serve as biodiversity hot spots in a human-influenced landscape. We studied the backwater “Alte Donau” (Vienna, Austria), which has been the subject of ongoing management and restoration efforts. We aimed to capture short-term variations in the planktonic and benthic algal community during a vegetation period with a specific focus on Gloeotaenium loitlesbergerianum with its primary distribution in tropical regions. In total, 196 algal taxa were identified, indicating a high and balanced species diversity. Although the waterbody is shallow and densely colonized by macrophytes, phytoplankton and microphytobenthos exhibited significant differences in composition, particularly in spring. Less pronounced differences during summer were probably caused by macrophyte harvesting combined with recreational activities. We found a clear seasonal pattern with spring characterized by blooms of Ochrophyta, followed by a shift towards green algae, Dinophyta, and Cyanobacteria during summer and autumn. We found high variability in spring samples, whereas summer and autumn samples showed increasing similarity. Temperature, silicate, and alkalinity were the primary environmental factors structuring algal community composition. G. loitlesbergerianum was detected during warmer months from May through October across a temperature range of 14 to 28 °C, with highest abundances >20 °C. Warmer water and altered nutrient regimes not only stress native populations but also promote the establishment of new species such as G. loitlesbergerianum, accelerating community shifts. Therefore, sustained monitoring, targeted macrophyte restoration, and effective nutrient management are crucial for preserving both water quality and biodiversity in such systems. Full article

The emerging Arthrospira industry in Ordos utilizes alkaline resources, the discharge of aquaculture wastewater from which may potentially influence the surrounding aquatic environment. Water quality and phytoplankton communities were systematically monitored at three representative ponds in both the green (H-1) and yellow ponds (H-2) of Lake Hammatai (three sites per pond) during April, June, August, and October of 2017 and 2018. Our results showed that phytoplankton biomass and abundance in Lake Hammatai were relatively low compared to other saline–alkaline lakes. The phytoplankton community was primarily dominated by Arthrospira spp. and Chlamydomonas spp. A low TN/TP ratio, together with elevated organic nitrogen concentrations, appeared to jointly facilitate the dominance of Arthrospira spp. Both lake water and wastewater were characterized by Na⁺ as the dominant cation, along with high concentrations of HCO₃⁻ and CO₃²⁻. Redundancy analysis (RDA) identified Na⁺, K⁺, Cl⁻, and HCO₃⁻ as the key environmental factors shaping algal community structure. These findings reveal the potential effects of aquaculture effluent on phytoplankton communities and water chemistry in alkaline lakes, offering insights into the response of fragile ecosystems to anthropogenic disturbances and informing targeted management strategies. Full article

Coastal ecosystems of the tropical Atlantic and the Mexican Caribbean have experienced recurrent massive influxes of pelagic brown macroalgae, Sargassum natans and Sargassum fluitans, generating severe environmental, social, and economic impacts. While the accumulation of this biomass poses a significant waste management challenge, it also represents an underexploited renewable resource aligned with circular economy and sustainability principles. This study investigated the valorisation of Sargassum spp. through comprehensive physicochemical characterisation and multiple value-added applications. The biomass collected in Tulum, Quintana Roo, Mexico, was analysed to determine its chemical composition, including lignin, holocellulose, α-cellulose, ash, and moisture content, using standardised methods of the Technical Association of the Pulp and Paper Industry (TAPPI). For mechanical testing, methods from the American Society for Testing and Materials (ASTM) were used. The biomass was subjected to controlled pretreatment and thermochemical conversion processes. Evaluated valorisation pathways included: (1) taxonomic identification and physicochemical characterisation, (2) polymer composites, (3) reinforcement in construction materials such as unfired clay bricks, and (4) biochar and activated carbon production for contaminant adsorption. The results demonstrated that Sargassum spp. biomass can be transformed from an environmental nuisance into a multifunctional, high-value biomaterial, providing scalable solutions that mitigate waste disposal challenges and contribute to climate and resource sustainability. Full article

Biochar-based catalysts have emerged as sustainable alternatives for biodiesel production, achieving high yields (up to 99%) from various feedstocks. This study aimed to utilize Spirulina-derived biochar as a bifunctional green catalyst for biodiesel synthesis from waste cooking oil (WCO) through transesterification and assess its green performance metrics. Biochar synthesized by carbonization (324 °C) was modified with calcium and sulfuric acid, featuring dual acid-base sites. Energy dispersive spectra revealed impregnation of calcium (11.11%) compared to the raw biomass (2.34%), followed by peaks of methoxy group and methylene group, and with methylene and β-carbonyl protons shown by nuclear magnetic spectroscopy. Thus, the biochar catalyst tested on WCO achieved a 93.27% yield under optimized conditions (65 °C, 1:15 methanol-to-oil ratio, 3% catalyst, 3.5 h) via central composite design. Catalyst reusability was maintained over four cycles with an average biodiesel yield (90%). Further, green metrics validate their eco-friendliness with a single-cycle reaction mass efficiency (RME) of 60.8%. When the initial catalyst mass is amortized over four cycles, the cumulative biodiesel yield per initial catalyst input reaches the equivalent of 243% of a single-batch theoretical yield (catalyst productivity = 3.12 g FAME/g catalyst). E-Factor at 0.67 (reduced to 0.17) and mass intensity at 1.68 (down to 0.42), contrasting with business-as-usual scenarios such as sulfuric acid catalysis (RME 70.0%, E-Factor 0.25) using 8.85 g H₂SO₄ vs. ~5 g H₂SO₄/kg biochar. Our results demonstrate that bio-based catalysts minimize non-benign inputs, supporting a circular economy from algal waste. Full article

The Albufera of Valencia is a shallow, hypertrophic Mediterranean coastal lagoon. Since the 1970s, the lagoon has undergone substantial ecological deterioration, marked by the decline of macrophyte beds and the predominance of phytoplankton. The objective of this study was to monitor key water quality variables over a 10-year period (2015–2025) to assess the persistence of eutrophication and the current ecological status of the lagoon. For this purpose, a remote sensing approach was applied using the Sentinel-2 constellation, complemented by newly developed algorithms specifically calibrated with ten years of in situ field data (2016–2025). This approach was employed to estimate variables such as the chlorophyll-a (Chl-a) concentration as an indicator of phytoplankton biomass, suspended solids (S.S.), and Secchi disk depth (Z_SD). An analysis of temporal trends from 2017 to 2025 revealed a progressive system deterioration. The concentrations of both chlorophyll-a and suspended solids exhibited a statistically significant increasing trend (p < 0.01). Moreover, in line with these findings, water transparency (Z_SD) decreased significantly (p < 0.001). Thus, there has been a progressive deterioration in the trophic status and ecological quality of the lagoon over the last decade, despite prior management interventions. The results from this research highlight the need to implement more effective conservation strategies, such as regulating nutrient inputs and increasing the water renewal time in the lagoon. Full article

Microalgae are emerging as a key biological platform for the production of important metabolites, environmental monitoring, and water treatment. However, despite their significant potential for a variety of industrial applications, several challenges associated with the efficiency of their cultivation hinder their widespread use. Here, focus was placed on the freshwater organism, Micractinium inermum strain EE-M2, to study the growth and accumulation of pigments, proteins, lipids, and starch under various strategies of increased inorganic carbon supply and ammonium nutrition conditions. NaOH and NaHCO₃ were tested as pH control agents. Combinations of constant sparging with atmospheric air enriched with CO₂ (finally 2.0% CO₂, v/v) and NaHCO₃ addition showed a slight increase in algal biomass productivity, but the metabolic profiles were indistinguishable from those obtained with pH regulation using NaOH. Decreasing the CO₂ concentration from 2.0% to 0.5% significantly reduced the final biomass yield and productivity of this strain (in a batch process). Also, the present study showed the feasibility of continuous cultivation of M. inermum to produce marketable biomass and metabolites. Under two cultivation strategies, batch and continuous, the alga effectively accumulated pigments (up to 2.7% of dry weight), proteins (up to 37.3%), lipids (up to 23.3%), and starch (up to 22.5%), indicating its biotechnological value. Overall, the obtained results demonstrate that M. inermum strain EE-M2 is a robust and fast-growing microalgal strain suitable for both laboratory and industrial cultivation. Full article

The mitigation of toxic cyanobacterial blooms is a much-researched and ongoing challenge. Seasonal influences, microbial diversity, and the wide range of cyanotoxins known to be associated with cyanobacterial blooms add layers of complexity to these environmental threats. Strategies to remediate blooms must avoid inducing widespread cell lysis and the release of cyanotoxins, which would compound rather than address the problem. Bacterial isolates have been found to be effective in bloom mitigation and can impact the diversity associated with the bloom. The present study reports on the exposure of non-axenic cultures of colonial Microcystis sp. and filamentous Oscillatoria sp. isolated from dams in South Africa to low ratios of four antagonistic bacterial isolates for 4 days. TEM was used to assess ultrastructural changes, HPLC to determine the relative concentrations of microcystin-LR and RR, and next-generation sequencing (NGS) to explore possible shifts in diversity from control samples as a result of exposure to the biological control bacterial isolates used. Ultrastructurally, Microcystis showed greater signs of stress than cells of Oscillatoria, with isolate 1 (Aeromonas lacus) having the least effect overall, whilst Isolate B (Lysinibacillus) and 3Y (Pseudomonas sp.) induced cell lysis in Microcystis. All isolates reduced the concentration of the toxic microcystin-LR, while the -RR variant often increased after 4 days. Minimal diversity shifts were noted in Microcystis-treated cultures, whilst those of Oscillatoria showed a greater diversity shift, indicating an increase in families containing isolates linked to bloom decline. Full article

Macroalgae are essential components of marine ecosystems, supporting biodiversity, primary productivity, and the functioning of coastal habitats. In the northeast Atlantic Macaronesian archipelagos (Azores, Madeira, Selvagens, Canary Islands, Cabo Verde), they hold significant ecological and economic value and have recently emerged as key indicators of environmental change. This oceanic region faces increasing pressure from multiple stressors, including climate change, invasive species, habitat degradation, and other anthropogenic impacts, driving shifts in coastal ecosystems and the simplification of structurally complex habitats such as marine forests. To assess the current state of knowledge on Macaronesian macroalgae and identify gaps relevant to conservation and management, we conducted a systematic literature review following PRISMA guidelines. Our results show strong but uneven foundational knowledge, with the Azores and Canary Islands accounting for roughly 80% of publications. Research is dominated by fundamental studies in ecology and taxonomy, while applied research (e.g., resource exploitation, aquaculture, toxicology, and climate-change impacts) remains limited. Red algae and a few dominant orders (Ceramiales, Fucales, Dictyotales) are well represented, whereas green algae and less conspicuous taxa are understudied. Future research should expand geographic coverage, broaden taxonomic scope using molecular tools, strengthen applied research, standardize monitoring frameworks, and align scientific output with management needs. Full article

Efficient inorganic carbon supply is a common limitation in microalgal cultivation, particularly in waste-derived media such as anaerobic digestate. Carbonic anhydrase (CA) accelerates the interconversion of CO₂ and bicarbonate and may therefore enhance carbon utilisation under conditions where inorganic carbon is abundant but not readily available. In this study, crude CA-containing extracts (aCA) were prepared from Scenedesmus-dominated algal biomass, and CA activity was quantified using an esterase assay (EAA). Although EAA activities varied depending on biomass pretreatment (0.15–0.47 U g⁻¹ DW), the physiological response to extract addition was consistent. In batch cultures of Chlorella sorokiniana grown in diluted digestate, aCA supplementation increased the specific growth rate (SGR) by 21–82%. In contrast, stimulation in a mineral medium was minimal, indicating that the benefit of aCA addition is most apparent under reduced inorganic carbon availability. In semi-continuous cultivation, repeated extract addition sustained a higher biomass productivity over time (rather than a specific growth rate). These results demonstrate that crude microalgal extracts containing CA can improve growth performance in digestate-based cultures and may offer a simple, low-cost approach to enhancing inorganic carbon utilisation in waste-integrated algal production systems. Full article

Light and antioxidant systems play a crucial role in the life activities of algal cells. This study investigates the algicidal efficacy of hydrogen peroxide (H₂O₂) against the harmful algal bloom (HAB)-forming dinoflagellate Prorocentrum donghaiense Lu, with a focus on the modulating roles of light conditions and iron ion environments. Within 180 min, dark-adapted cells showed 78% greater viability loss than light-exposed ones, and Fe₃O₄ nanoparticles synergistically enhanced H₂O₂ inhibition. Imaging and cytometry confirmed cell damage, including membrane rupture. Mechanistically, H₂O₂ penetrated cells, induced severe oxidative stress, suppressed photosynthesis, and compromised membrane integrity. Darkness likely exacerbated toxicity by depleting antioxidant reserves. This study elucidates an apoptosis-like pathway underlying H₂O₂-induced cell death and highlights the critical influence of ambient light on treatment efficiency. These findings reveal an apoptosis-like death pathway and highlight ambient light’s critical role, suggesting that optimized nighttime H₂O₂ application with nanomaterial synergists could improve HAB control strategies. Full article

This research assesses a triphasic extraction technique for the sequential retrieval of C-phycocyanin (C-PC) and polyhydroxybutyrate (PHB) from a thermotolerant Potamosiphon sp. strain. A two-stage design-of-experiments methodology was employed (Minimum Run Resolution V factorial design involving six variables, followed by a central composite design (CCD)) to optimize the chosen region. In the factorial stage, PHB ranged from 109.396 to 168.995 mg/g, and the model was significant (F = 22.63, p < 0.0001). Freeze-milling and vortexing were identified as critical elements, underscoring the importance of the t-butanol × (NH₄)₂SO₄ interaction for phase selectivity. The CCD concentrating on freeze-milling and vortex cycles yielded a robust quadratic model (F = 78.18, p < 0.0001), forecasting a peak PHB yield of 191.82 mg/g at six freeze-milling cycles and three vortex cycles (desirability 0.921), while maintaining t-butanol at 19.9 mL, t-butanol concentration at 94.7% (v/v), (NH₄)₂SO₄ at 49.9% (w/v), and vortex duration at 1.2 min. Ten separate trials validated the model’s accuracy, yielding an observed PHB of 191.5 mg/g, which closely matched the model’s prediction. The platform facilitates an integrated downstream process in which C-PC is recovered under moderate conditions before triphasic partitioning. This enables the simultaneous valorization of pigment, lipophilic fraction, and biopolymer inside a unified cyanobacterial biorefinery process. Full article

Heterotrophic nanoflagellates (HNANs) are central components of the microbial loop, transferring carbon from bacteria to higher trophic levels and facilitating nutrient recycling. While many HNANs are free-swimming, some exhibit enhanced feeding efficiency when attached to surfaces, including diatom frustules. Here, we describe the attachment behavior of a novel interception-feeding HNAN affiliated with the order Bicosoecida to centric diatoms common in North Carolina coastal waters. Using growth experiments, live observations, and time-lapse microscopy, we quantified attachment frequency and assessed its influence on diatom growth for three diatom species: Coscinodiscus sp., Odontella sp., and Rhizosolenia sp. HNAN attachment differed significantly among diatom taxa: Coscinodiscus sp. hosted the highest and most sustained numbers per frustule, whereas after normalizing for surface area, Rhizosolenia sp. exhibited the highest attachment efficiency. Diatom peak growth was 1.2 to 2.1-fold higher and occurred earlier in HNAN co-cultures than in controls, indicating microbial recycling by the HNAN stimulated growth. These findings highlight the nuanced ecological role attached HNANs might play as they exploit diatom-associated boundary layers to enhance bacterial encounter rates. The growth trajectories in our lab experiments suggests that attachment behavior in situ can play a role in driving diatom bloom dynamics and, therefore, play an important role for carbon cycling. Full article

Microalgae and cyanobacteria represent promising, sustainable resources for agricultural applications, particularly as biofertilisers, biostimulants, and biological plant protection agents. Their biomass can improve nutrient use efficiency, support plant growth and yield, and enhance soil structure and microbial activity, while cyanobacteria additionally contribute through biological nitrogen fixation, reducing reliance on synthetic fertilisers. The integration of microalgal cultivation with closed-loop systems, such as wastewater treatment plants or biogas facilities, enables nutrient recovery, production of value-added biomass, and mitigation of greenhouse gas emissions. This review synthesises current knowledge on the biochemical composition, functional properties, and mechanisms of action of microalgal and cyanobacterial biomass in relation to these established agricultural applications. In addition, prevailing research trends, selected technological and organisational constraints, and implementation challenges are discussed. Particular attention is given to emerging application contexts, including bioregenerative life support systems (BLSS) for space agriculture, where microalgae and cyanobacteria can contribute to oxygen production, nutrient recycling, and edible biomass generation. Species such as Chlorella vulgaris, Arthrospira platensis, and Scenedesmus obliquus demonstrate tolerance to microgravity, radiation, and limited light conditions, supporting their potential use in closed, self-sufficient cultivation systems. Although numerous reviews have addressed individual agricultural applications of microalgae and cyanobacteria, a more integrative perspective that connects biological functionality with broader technological, regulatory, and implementation contexts remains valuable. The present review contributes to this perspective by consolidating established agronomic uses and extending the discussion toward selected emerging applications, thereby providing a structured framework for future research and development in sustainable terrestrial and extraterrestrial agriculture. Full article

Conventional wastewater treatment methods often rely on energy-intensive physical and chemical processes that are costly and may generate secondary pollution. These limitations have prompted the exploration of more sustainable alternatives. Among them, phycoremediation, particularly using microalgae, has emerged as a promising strategy for mitigating environmental pollution. Microalgae possess unique capabilities to sequester heavy metals, assimilate nutrients, and degrade emerging contaminants while simultaneously producing valuable biomass. The efficacy of microalgal bioremediation can be enhanced through omics-based approaches, which enable these biological agents to convert toxic compounds into non-toxic forms and improve ecosystem health. Additionally, forming microalgae–microorganism consortia can enhance process efficiency and cost-effectiveness. This review highlights multi-pronged strategies for pollutant mitigation in wastewater, focusing on environmentally and economically viable microalgal cultivation systems. It also identifies research gaps and discusses the potential for biomass valorization into economically important products. Full article

Microalgae have emerged as sustainable biofactories producing diverse bioactive compounds with significant applications in nutrition and cosmetics. Their high metabolic versatility makes them promising alternatives to conventional resources for addressing global challenges such as malnutrition, food insecurity, and environmental degradation. This review provides an integrated perspective on microalgal bioactives, highlighting their role in functional foods, dietary supplements, and maternal and infant nutrition, as well as their incorporation into cosmetic formulations for anti-aging, photoprotection, hydration, and microbiome support. Mechanistic insights reveal antioxidant, anti-inflammatory, and extracellular matrix-preserving effects, alongside UV absorption and barrier reinforcement. The review also discusses their biochemical diversity, mechanisms of action, safety, regulatory considerations, and emerging technologies for formulation and delivery. AI-driven and machine-learning approaches using microalgae for cosmetic and nutritional applications have also been discussed. Overall, microalgae serve as a cornerstone for next-generation nutraceuticals and cosmeceuticals, aligning with sustainability and circular-economy principles. Full article

The kelp genus Eisenia Areschoug is represented by two species in the Southeast Pacific: Eisenia cokeri, distributed in Peru and Chile, and E. gracilis, endemic to Peru. However, the taxonomic distinction between these species has long been questioned, and it remains unclear whether E. cokeri is conspecific with the Northeast Pacific species E. arborea. To address these issues, we conducted an integrative taxonomic assessment combining morphological analyses, molecular phylogenetics, and molecular species delimitation approaches. Sampling for morphological and molecular analyses was carried out in subtidal zones at five localities along the Peruvian coast, and an additional locality in Chile was included for molecular analyses where E. cokeri was documented. Peruvian Eisenia species exhibited consistent morphological differentiation, including differences in thallus size, holdfast diameter, stipe modifications (e.g., longitudinal division and pseudostipe formation), frond division, frond margins, and surface roughness, as supported by morphometric analyses. Phylogenetic reconstructions based on mitochondrial and chloroplast markers, together with concordant results from multiple species delimitation methods (ABGD, GMYC, and bPTP), consistently recovered three independent evolutionary lineages corresponding to E. cokeri, E. gracilis, and a distinct lineage of Eisenia from the Desventuradas Islands (Chile). Our results confirm the taxonomic distinctiveness of E. cokeri and E. gracilis, demonstrate that E. cokeri is genetically distinct from E. arborea, and reveal the presence of a previously unrecognized lineage of Eisenia in the Southeast Pacific. These findings refine species boundaries within the genus and provide a robust framework for the management and conservation of these endemic, foundation, habitat-forming species. Full article

The valorization of nutrient-rich institutional effluents represents a promising route for sustainable algal biotechnology. This study investigates the potential of canteen wastewater (CW) as an alternative culture medium for Spirulina platensis, integrating wastewater treatment with high-value carotenoid and lipid production. Growth performance, biochemical composition, and nutrient removal efficiencies were systematically evaluated in 2 L photobioreactors under optimized conditions. Spirulina cultured in 75% CW under 180 μmol photons m⁻² s⁻¹ achieved a biomass productivity of 0.071 g L⁻¹ day⁻¹, nearly three-fold higher than the synthetic BG-11 control (0.023 g L⁻¹ day⁻¹). Nutrient remediation was highly efficient, with 92.12% nitrate and 90.05% phosphate removal, effectively reducing effluent concentrations below discharge limits. Biochemical profiling revealed that wastewater-grown biomass contained 54.3% protein and 7.85% lipids, with a remarkable carotenoid yield of 21.81 mg g⁻¹ DW—significantly higher than the control (6.85 mg g⁻¹ DW). Mechanistic analysis suggests that the balanced nutrient stoichiometry (C:N:P ≈ 30:4:1) and mixotrophic conditions enhanced biomass quality while mitigating ammonia toxicity. This study demonstrates the first integrated application of canteen wastewater for dual-purpose bioremediation and pigment-rich biomass production, establishing a scalable circular bioeconomy framework for institutional waste management. Full article

The convergence of food insecurity, water scarcity, and environmental degradation has intensified the global search for sustainable agricultural models. Integrated Microalgal–Aquaponic Systems (IAMS) have emerged as a novel multi-trophic platform that unites aquaculture, hydroponics, and microalgal cultivation into a closed-loop framework for resource-efficient food production and water recovery. This critical review synthesizes empirical findings and engineering advancements published between 2008 and 2024, evaluating IAMS performance relative to traditional agriculture and recirculating aquaculture systems (RAS). Reported under controlled laboratory and pilot-scale conditions, IAMS have achieved nitrogen and phosphorus recovery efficiencies exceeding 95% while potentially reducing water consumption by up to 90% compared to conventional farming. The integration of microalgal photobioreactors enhances nutrient retention, may contribute to internal carbon capture, and enables the generation of diversified co-products, including biofertilizers and protein-rich aquafeeds. Nevertheless, significant barriers to commercial scalability persist, including the biological complexity of maintaining multi-trophic synchrony, high initial capital expenditure (CAPEX), and regulatory ambiguity regarding the safety of waste-derived algal biomass. Technical challenges such as photobioreactor upscaling, biofouling control, and energy optimization are critically discussed. Finally, the review evaluates the alignment of IAMS with UN Sustainable Development Goals 2, 6, and 13, and outlines future research priorities in techno-economic modeling, automation, and policy development to facilitate the transition of IAMS from pilot-scale innovations to viable industrial solutions. Full article

Understanding the molecular basis of heat tolerance in microalgae is crucial for developing resilient strains for industrial biotechnology. This study identified two desert Chlorella strains, XDA024 (thermotolerant) and XDA121 (heat-sensitive), through short-term thermal screening. The thermotolerant strain XDA024 survived exposure to 50 °C for 3 h, whereas XDA121 succumbed within 1 h at 40 °C. Physiological analyses revealed that the superior heat resistance of XDA024 was associated with enhanced activities of key antioxidant enzymes, including superoxide dismutase, catalase, and peroxidase, which effectively mitigated oxidative damage, alongside an elevated proline content contributing to osmoregulation. Transcriptomic profiling under acute heat stress (45 °C, 3 h) revealed that the unique thermotolerance of XDA024 was underpinned by the upregulation of genes related to photosystem stability and lipid synthesis, processes supported by activated calcium signaling and antioxidant pathways. In contrast, XDA121 exhibited significant downregulation of photosynthesis-related genes and promoted lipid degradation, resulting in membrane instability. Exogenous application of phosphatidylethanolamine (PE) and monoethanolamine (MEA) markedly increased the survival rate of XDA121 by more than threefold, primarily by alleviating membrane damage through enhanced membrane integrity and modulated antioxidant enzyme activities. These findings indicate that thermotolerance in desert Chlorella (Chlorophyta) is governed by the integrated coordination of antioxidant defense mechanisms, lipid metabolism, and photosystem protection. This research provides crucial insights and practical strategies for engineering heat-resistant microalgal strains for sustainable biofuel and bioproduct production. Full article

Macroalgae are increasingly recognized as a valuable source of nutrients and bioactive compounds for animal nutrition, including for aquatic species. However, the complex structure of the macroalgal cell wall limits the accessibility of intracellular components, restricting their use in feeds. To overcome this limitation, macroalgal hydrolysis using various technological treatments has been tested, often employing a low solid-to-water ratio, which complicates downstream processing due to phase separation. In contrast, high-solids loading hydrolysis has the advantage of producing a single and consolidated fraction, simplifying subsequent processing and application. The present study assessed the effectiveness of high-solids loading water or alkaline (0.5 and 1N NaOH) autoclaving for 30 or 60 min, applied alone or followed by sequential enzymatic hydrolysis, using a xylanase-rich enzymatic complex aimed at promoting cell wall disruption and increasing the extractability of intracellular components in the red macroalga Palmaria palmata with minimal free water. The 1N NaOH treatment for 30 min decreased neutral and acid detergent fiber while increasing Folin–Ciocalteu total phenolic content (GAE) (expressed as gallic acid equivalent) and the water-soluble protein fraction and decreased crude protein, indicating enhanced extractability of these components. Microscopic examination showed relatively mild structural changes on the surface of P. palmata after high-solids loading alkaline (1N NaOH) autoclaving for 30 min. Following alkaline or water treatment, the enzymatic complex hydrolysis further increased the Folin–Ciocalteu total phenolic content (GAE), with minimal effects on NDF, ADF, or crude protein. Overall, these results showed that high-solids loading alkaline autoclaving, with or without subsequent enzymatic hydrolysis, effectively disrupts P. palmata cell walls and induces substantial modifications while simplifying processing by avoiding phase separation. Full article

Microalgae can modify their metabolic pathways as a response to environmental stimuli such as light, temperature, salinity, and nutrient availability, which critically influence the synthesis of lipids and other biomolecules. While extensive studies have focused on the impact of these environmental variables on the accumulation of valuable compounds such as polyunsaturated fatty acids (PUFAs) and triacylglycerols (TAGs), information on the biosynthesis of specialized metabolites, including long-chain hydroxy fatty acids (LCHFAs), long-chain diols (LCDs), and long-chain alkenols (LCAs) is scarce. These metabolites are thought to contribute to the structural integrity of cell walls in certain microalgae, such as Nannochloropsis spp. (Eustigmatophyceae), where they make up a biopolymer known as algaenan. This study investigates how varying light intensities affect the production of LCHFAs, LCDs, and LCAs in Nannochloropsis oceanica over a 12 h light/dark cycle. Our findings provide insights into the lipid biosynthetic pathways in microalgae, revealing that light strongly drives the production of LCHFAs, whereas LCDs and LCAs are less light-dependent and show more variable responses to different light intensities. Full article

Inflammation plays a central role in the pathogenesis of numerous diseases through the excessive production of nitric oxide (NO), prostaglandins, and pro-inflammatory cytokines. Although bromophenols from marine algae and various phenolic compounds exhibit strong anti-inflammatory activity, the biological properties of brominated vanillin derivatives remain largely unexplored. This study aimed to investigate the anti-inflammatory effects of 2-bromo-5-hydroxy-4-methoxybenzaldehyde (2B5H4M), a brominated vanillin derivative structurally similar to marine bromophenols, in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. 2B5H4M significantly reduced LPS-induced NO and PGE₂ production by suppressing the protein and mRNA expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). It also downregulated the expression of pro-inflammatory cytokines, including TNF-α, IL-1β, and IL-6. Mechanistically, 2B5H4M inhibited the phosphorylation and degradation of IκB-α, thereby preventing NF-κB nuclear translocation, and reduced the phosphorylation of ERK and JNK. These findings demonstrate that 2B5H4M exerts potent anti-inflammatory effects by simultaneously blocking NF-κB and MAPK signaling pathways. Although not algae-derived, the structural resemblance of 2B5H4M to marine bromophenols highlights its potential as a marine-inspired reference compound. This work suggests that 2B5H4M may serve as a promising lead scaffold for developing new phenolic anti-inflammatory agents and provides a foundation for future mechanistic and in vivo studies. Full article

Microalgae are sustainable sources of bioactive compounds with broad hepato-protective potential. This review synthesizes evidence for five major classes—carotenoids such as astaxanthin and fucoxanthin, polysaccharides such as paramylon and fucoidan, phycobiliproteins such as phycocyanin, omega-3 fatty acids, and phenolic extracts—linking their actions to key liver injury mechanisms. Preclinically, these compounds enhance antioxidant defenses, improve mitochondrial function, suppress inflammatory signaling, regulate lipid metabolism, modulate the gut–liver axis, and inhibit hepatic stellate cell activation, thereby attenuating fibrosis. Consistent benefits are observed in models of non-alcoholic and alcoholic fatty liver disease, drug-induced injury, ischemia–reperfusion, and fibrosis, with marked improvements in liver enzymes, oxidative stress, inflammation, steatosis, and collagen deposition. Emerging evidence also highlights their roles in regulating endoplasmic reticulum stress and ferroptosis. Despite their promise, translational challenges include compositional variability, a lack of standardized quality control, limited safety data, and few rigorous human trials. To address these challenges, we propose a framework integrating multi-omics and AI-assisted strain selection with specification-driven quality control and formulation-aware designs—such as lipid carriers for carotenoids or rational combinations like fucoxanthin with low-molecular-weight fucoidan. Future priorities include composition-defined randomized controlled trials in non-alcoholic fatty liver disease, alcoholic liver disease, and drug-induced liver injury; harmonized material specifications; and multi-constituent interventions that synergistically target oxidative, inflammatory, metabolic, and fibrotic pathways. Full article

A strain of aeroterrestrial green microalgae Coelastrella rubescens IBSS-156, isolated from an epilithic lichen, has been previously shown to efficiently produce green biomass and accumulate significant amounts of secondary carotenoids. In this study, using a two-stage batch culture, we analyzed time-course changes in variable chlorophyll a (Chl a) fluorescence parameters. Additionally, regression models were developed to correlate autofluorescence signals with spectrophotometric measurements of Chl a and total carotenoid content. Maximum quantum efficiency of photosystemII (F_v/F_m) remained high throughout the vegetative stage. At the end of this stage, under nutrient-limited conditions, the relative electron transport rate (rETR) declined to half its peak value during exponential growth. Stress induced a strong response in the algal photosynthetic apparatus during the early red stage. Within the first three days, F_v/F_m and rETR remained extremely low, but both increased sharply by day 5. During secondary carotenoid accumulation, fluorescence parameters remained at 70–80% of the vegetative-stage maximum, followed by a sharp decline toward the end of the red stage. Therefore, changes in variable fluorescence parameters can serve as markers of C. rubescens cellular physiology during biotechnological cultivation, denoting the completion of specific stages. Flow cytometry and pigment assay regression enabled real-time monitoring of C. rubescens biomass and carotenoids. Full article

Achillea fragrantissima is a medicinal herb valued for its essential oils and bioactive compounds. Microalgae, such as Spirulina platensis and Chlorella vulgaris, show considerable promise as natural biostimulants due to their high levels of protein, minerals, vitamins, and fatty acids. The individual or compound effects of S. platensis and C. vulgaris on the growth, photosynthetic pigments, and essential oil composition of A. fragrantissima in vitro were measured in this study. According to chemical analysis, S. platensis contains large amounts of protein and several minerals, including phosphorus, manganese, and iron. Conversely, C. vulgaris showed a higher percentage of carbohydrates, lipids, phytol, aldehydes, and fatty acid esters. The combination of 1.0 g·L⁻¹ S. platensis and 0.5 g·L⁻¹ C. vulgaris tended to stimulate callus formation. Meanwhile, the 0.5 g·L⁻¹ C. vulgaris treatment enhanced shoot and leaf development and increased total photosynthetic pigment content. Analysis of essential oils from A. fragrantissima produced under different treatments demonstrated that combined treatments with S. platensis and C. vulgaris had greatly improved the valuable bioactive substances, such as phytol, oleic acid, 2H-pyran, and thymine. These results show the effectiveness of using S. platensis and C. vulgaris extracts as eco-friendly biostimulants. Full article

The use of biostimulants has emerged as a promising strategy for enhancing seed vigor, germination, and seedling growth. This is due to the composition of beneficial substances considered as biostimulants that modulate plant physiology and metabolism. In this context, the interest in biostimulants is growing and the use of microalgal extracts is becoming more widespread. This study aims to assess the effect of Chlorococcum sp. aqueous extracts on the germination indices and the biometric and biochemical parameters of sesame (Sesamum indicum L.). Chlorococcum sp. culture exhibited favorable growth characteristics, including high productivity, specific growth rate, and short generation time. Furthermore, analysis of the extract demonstrated that it contains a high concentration of biomolecules, which suggests significant biostimulant potential. Importantly, the results also showed a significant improvement in germination indices as well as in biochemical parameters and photosynthetic pigments in seeds treated with the highest extract concentration (2 g/L). Furthermore, improvement in biometric parameters, including radicle length as well as fresh and dry weight, was observed at low extract concentration (0.1 and 0.5 g/L). Additionally, no phytoinhibitory effects were detected. Overall, the application of microalgal aqueous extract highlights a strong potential as a sustainable and cost-effective alternative to conventional synthetic chemical fertilizers, thereby promoting the development of an environmentally friendly agricultural practice of sesame cultivation. Full article

The mucilage phenomenon consists of the appearance of large gelatinous aggregates floating in the water column. In summer 2024, this event has reappeared in the Northern Adriatic Sea (NAS) on a large scale. This study provides an integrated characterization of the microalgal community within mucilage aggregates and surrounding waters in two NAS areas (Gulf of Trieste and Conero Riviera) using light microscopy (LM), metabarcoding (MB) based on ribosomal 18S V4 and V9 markers, and scanning electron microscopy (SEM) for selected taxa identification. Mucilage aggregates acted as dynamic microbial hotspots, hosting a rich diatom community, with abundances 1–2 orders of magnitude higher than in the surrounding water. Dominant diatom species were Cylindrotheca closterium, Nitzschia spp., Nitzschia gobbii, and Thalassionema nitzschioides. Some phytoflagellates (e.g., Tetraselmis spp.) and dinoflagellates (e.g., Karlodinium veneficum, Pseliodinium fusus, and Wangodinium sinense) were detected exclusively by MB, while LM and SEM revealed species missed by other approaches. Gonyaulax fragilis, one of the species indicated as an important mucus producer, was present at the onset and throughout the phenomenon, as detected by LM and MB. The integrated approach improves knowledge of microalgal communities in NAS mucilage. Full article

The industrial cultivation of microalgae for high-value products faces significant challenges, particularly in maintaining long-term, cost-effective operations. Semi-continuous cultivation presents a promising solution to this problem. In this study, the green alga Chlorella sorokiniana IPPAS C-1 was cultivated in a flat-panel 5 L photobioreactor under optimized conditions, with three biological replicates. We evaluated batch mode against three semi-continuous dilution fractions (50%, 75%, and 87.5%). The 75% dilution fraction demonstrated superior performance, achieving the highest biomass productivity with an average specific productivity of 1.36 g DW L⁻¹ day⁻¹ over seven harvest cycles. Furthermore, this regime ensured stable biochemical composition—including proteins, lipids, carbohydrates, and pigments—as well as a consistent lipid profile and sustained photosynthetic activity throughout the cultivation. These findings are useful for the development of scalable and efficient technological protocols for the industrial production of Chlorella in flat-panel photobioreactors. Full article