Phycology

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

Microalgae have garnered increasing attention as promising sources of diverse natural anti-inflammatory compounds, including carotenoids, phenolics, and unsaturated fatty acids. In this study, we aimed to examine the anti-inflammatory properties of the methanol extract of Nannochloropsis sp. G1-5 (NG15), a strain of marine microalgae isolated from the southern West Sea of the Republic of Korea. Pigment and metabolite analyses revealed that the extract contained various carotenoids and polyunsaturated fatty acids alongside significant quantities of phenolic and flavonoid compounds, which are known to have anti-inflammatory activities. Cytotoxicity assays confirmed that the extract was non-toxic to RAW 264.7 macrophage cells at concentrations up to 1 mg/mL. Upon lipopolysaccharide (LPS) stimulation of the macrophage cells, the NG15 extract significantly inhibited nitric oxide (NO) production in a dose-dependent manner up to 81%. In addition, the NG15 extract reduced the expression of iNOS, COX-2, TNF-α, and IL-6 in the LPS-stimulated cells. These findings suggest that NG15 methanol extract exerts anti-inflammatory effects primarily through the suppression of NO generation without inducing cytotoxicity. Overall, these results underscore NG15 as a promising natural resource for the development of non-toxic and effective anti-inflammatory agents with potential applications in the biomedical and cosmeceutical industries. Full article

Incorporating microalgae into integrated biotechnologies facilitates rational resource management. Cultivation of microalgae in various types of wastewater offers a number of advantages: safe disposal of liquid waste, restoration of water resources, and the production of valuable products. This study presents a comparative analysis of the growth and biomass productivity of various algal strains in an unsterilized fish processing plant wastewater. Desmodesmus sp. EE-M8 demonstrated the most efficient growth, with a biomass yield of 2.21 ± 0.09 g L⁻¹. The average biomass yield obtained during the growth of Chlorella vulgaris SB-M4, Chlorella sp. EE-P5, Micractinium inermum EE-M2, and Tetradesmus obliquus EZ-B11 ranged from 1.42 to 1.96 g L⁻¹. Ammonium, phosphate, and sulfate ions were completely utilized from the wastewater during algal growth. In addition, the bacterial community structure of wastewater was found to change drastically toward the dominance of Alphaproteobacteria during the microalgal growth. The algal strains (in combination with bacterial partners) used to determine their biostimulant potential demonstrated a positive effect on the germination of garden cress seeds. These findings demonstrate that incorporating algae into the wastewater purification process will reduce the negative impact on the environment and produce valuable biomass for various purposes. Full article

Microalgae are increasingly recognized as promising biostimulants for sustainable agriculture, yet their potential remains underexplored due to the complexity of biostimulant activity and the vast diversity of species. Efficient standardized screening approaches are therefore needed. In this study, a high-throughput screening platform assessed the biostimulant activity of five microalgal species (Limnospira platensis, Chlorella vulgaris, Dunaliella salina, Microchloropsis gaditana, and Isochrysis galbana) in Arabidopsis thaliana. The system enabled full life-cycle assessment of A. thaliana under optimal and drought stress conditions, incorporating three application methods (soil amendment, irrigation, foliar spray) and a wide concentration range of 0.01–0.5 g/L. Biostimulant efficacy depended strongly on concentration and application method. Irrigation-based applications generally enhanced drought tolerance but delayed bolting and flowering. The highest concentration inhibited germination and root elongation, likely due to bioactive compound toxicity rather than salinity or pH. L. platensis exhibited broad activity across environmental conditions, while I. galbana likewise showed wide-ranging effects, including enhanced generative growth. In contrast, D. salina and M. gaditana primarily improved drought tolerance, and C. vulgaris acted mainly under optimal conditions. These findings highlight the value of A. thaliana to accommodate rapid biostimulant screening and identify both novel and established microalgae for further validation in crops. Full article

Alaska’s kelp farming industry is expanding, with Alaria marginata (ribbon kelp) emerging as a promising crop. This species is valued for its food-grade applications, yet little is known about its cultivation performance. We tested the effects of five line-spacing treatments (0.31–1.83 m) on blade phenotype and yield under farmed conditions. Wider spacings produced longer, wider, and thicker blades. Sporophytes at 1.23 m and 1.83 m spacings were most likely to exceed 200 cm in length, while most blades were half that length for treatments closely spaced. Yield per meter was lowest at 0.31 m spacing (~2 kg m⁻¹) but exceeded 3 kg m⁻¹ in all wider treatments, with 1.23 m and 1.83 m spacings showing a probability of producing 6 kg or more. Results aligned with those of other kelp studies assessing line spacing on kelp performance. This work highlights the importance of aligning cultivation practices with market demands for either biomass or blade quality. The study was limited to one site and one growing season. Nonetheless, findings provide an initial framework for optimizing A. marginata cultivation in Alaska. Full article

This study describes the results of integrative analysis of cyanobacterial communities in waterbodies of Moscow, Russia. 16S rRNA V3–V4 metabarcoding and light microscopy are implemented to investigate the diversity, abundance, and distribution of cyanobacteria, including the representatives of potentially toxigenic taxa—Anabaena, Aphanizomenon, Dolichospermum, Microcystis, and Planktothrix. High convergence is observed between microscopy and metabarcoding data for dominant genera, including Microcystis and Planktothrix. Sequence verification reveals total (100%) similarity between previously isolated toxigenic strains (e.g., Microcystis aeruginosa CBMC403m and CBMC523m) and corresponding highly abundant ASVs. In addition, current study ascertains the efficiency of metabarcoding for detection of rare cyanobacterial taxa missed by microscopy. We hereby acknowledge the limitations of V3–V4 16S rRNA-based metabarcoding approach for region species-level resolution and distinguishing potentially toxigenic taxa of cyanobacteria. At the same time, our findings validate metabarcoding as a rapid and reliable tool for monitoring of CyanoHABs in urban water ecosystems. Full article

Coastal lagoons are recent geological formations, crucial biodiversity hot-spots, and fragile ecosystems which provide several ecosystem services. These areas are strongly affected by nutrient inputs, which can lead to eutrophication and algal blooms. We identified nine Italian coastal lagoons with a surface area greater than 10 km². Most of them were previously classified in a poor ecological condition. Therefore, we used remote sensing, in particular Sentinel-2 images, to assess the trophic state of these areas over time from 2015 until 2025. Automatic products of chlorophyll-a (Chl-a), total suspended matter (TSM), and water transparency (kd_z90max) were derived. Chl-a concentrations indicated predominantly eutrophic conditions, ranging from 0.44 (Mare Piccolo) to 80.81 mg·m⁻³ (Comacchio). Comacchio and Cabras showed persistently high Chl-a values and low transparency, while Mare Piccolo was characterized by high transparency and oligotrophic conditions. Varano and Cabras showed a significant increase in Chl-a (p < 0.05) coupled with an increase in TSM (p < 0.01) and decline in transparency in Varano (p < 0.05). Most other lagoons showed no long-term trends but remained in eutrophic–hypereutrophic states. Therefore, the Italian coastal lagoons studied are vulnerable areas to environmental degradation. Many of the lagoons showed persistent eutrophic conditions and no long-term recovery trends. However, among the lagoons, there were heterogeneous ecological conditions, ranging from oligotrophic (Mare Piccolo) to chronically hypereutrophic (Comacchio, Cabras). Water clarity was mainly affected by suspended solids; however, in some cases, there was a key role in primary production (algal blooms). Sentinel-2 data proved effective for monitoring spatial and temporal variability in coastal lagoon water quality, offering a valuable tool for environmental management and early detection of degradation trends. Full article

The Gulf of Mexico is a marginal sea recognized as one of the world’s Large Marine Ecosystems. It is characterized by significant climate variability that influences phytoplankton communities. In this paper we investigated the phytoplankton assemblages in the Campeche Canyon, located in the Southern Gulf of Mexico, during a “Nortes” storm season. Additionally, we assessed the role of hydrographic conditions and circulation patterns in species distribution. The assessment was based on in situ observations collected during a multidisciplinary research cruise conducted in February 2011. High-resolution hydrographic data were gathered using a CTD sonde, and water samples were collected at various depths for phytoplankton cell analysis. The findings revealed a deep thermocline at a depth of 90 m, with a deep chlorophyll-a maximum (DCM) occurring below 75 m. The circulation pattern in the area was dominated by a dipole eddy, consisting of both cyclonic and anticyclonic movements, which created strong currents at the edges. The species composition varied by depth; a total of 77 species were identified in the surface waters, while the DCM exhibited a richness of 81 species. In the surface waters, dinoflagellates were the most abundant group, comprising 41 species, whereas diatoms were more prevalent in the DCM, with 44 species identified. In terms of abundance, dinoflagellates were more prevalent at both depths, with concentrations reaching up to 12,000 cells L⁻¹. The most abundant species identified included the ciliate Mesodinium rubrum, the cyanobacteria Trichodesmium hildebrandtii, the diatoms Asteromphalus cleveanus and Pseudo-nitzschia multistriata, the dinoflagellates Lingulaulax polyedra and Blepharocysta denticulata, and the silicoflagellate Dictyocha fibula. Analysis of the horizontal distribution patterns of phytoplankton species revealed that species tend to aggregate in areas with strong currents. These findings enhance our understanding of phytoplankton dynamics in the Campeche Canyon, particularly during climatic seasons when in situ observations are limited due to challenging navigation conditions caused by “Nortes” storms. Full article

The overview of charophytes in Bosnia and Herzegovina has been updated after 35 years through a revision of existing specimens in the BEOU Charophyte Collection, verification and listing of known vouchers in other herbarium collections, and a detailed review of the available literature covering the period from 1848 to 2024. According to all available data, 18 species and three genera of charophytes are found in 122 sites in Bosnia and Herzegovina. Chara papillosa Kütz. and C. subspinosa Rupr. are newly reported species in Bosnia and Herzegovina. Chara vulgaris L., C. contraria A. Braun ex Kütz., C. globularis Thuill., C. gymnophylla (A. Braun) A. Braun, and C. squamosa Desf. are the most frequently recorded. The Dinaric Mountains mixed forests are the most representative and species-rich ecoregion. Most charophytes were recorded before 1930 and after 1980, with a clear discrepancy between the sites documented in these periods. Bosnia and Herzegovina has the lowest charophyte species richness compared to neighbouring countries. We strongly encourage further revision of available collections and continued systematic field research, which will enable the preparation of the Red List and the formal protection of species and habitats. Full article