Phycology

Our current knowledge of the cyanobacterial diversity in Egypt is still underestimated During our routine study on Egyptian cyanobacteria, two interesting and morphologically cryptic strains were isolated from streams of Bahr Yussef and Qarun Lake, one of the oldest lakes in the world, located at the Faiyum depression, Egypt. We applied the polyphasic approaches, combining the state-of-the-art morphotaxonomy, 16S rRNA gene phylogenies, and ecological preferences to precisely unravel the taxonomic positions of these two cyanobacterial strains. Based on a combination of their morphotaxonomic traits and 16S rRNA phylogenetic assessment, we identified them as Alkalinema pantanalense (Leptolyngbyaceae, Leptolyngbyales) and Roholtiella edaphica (Nostocaceae, Nostocales). Both species are considered new cyanobacterial records for Egypt and the African continent based on the available literature. From an ecological standpoint, both species are eutraphentic, where they could tolerate relatively elevated concentrations of NO₃⁻, NH₄⁺ (in particular for R. edaphica), and silicates, reflecting eutrophication signs in the ecosystems they colonize. This study adds to the limited molecular information available on the Egyptian cyanobacteria, and also highlights the need for re-investigation of Egyptian cyanobacteria, using polyphasic approaches, to better understand their taxonomy and ecology. Full article

Rhodomelaceae is the largest red algae family, with 158 genera and more than 1000 described nominal species. In particular, Acanthophora (Rhodomelaceae) is a red alga with erect thalli that arises from stoloniferous branches or holdfast discs, with cylindrical main axes and spine-like branchlets. The life cycle of members of this genus has been partially described; however, the female gamete (carpogonium) has not been described. Here, we present a complete description of each stage in the life cycle of Acanthophora. Thalli of this species were collected from 27 localities in the Gulf of Mexico between 2021 and 2024 and placed in a 5% formaldehyde solution in seawater. Reproductive structures were measured and characterized under stereo and optical microscopes. A total of 62 thalli were collected, of which 10 were carposporophytes, 12 male gametophytes, 1 female gametophyte, 16 vegetative thalli, and 23 tetrasporophytic thalli. A detailed description of the shape and size of the reproductive structures is presented. We documented carpogonium for the first time. The evidence here presented contributes to the description of the life cycle of the genus Acanthophora, in which structures forgotten in current works are recovered, which is of great help in the comparative phycology of the Rhodomelaceae family and Ceramiales order. Full article

Pelagic Sargassum impacts the Caribbean and West Africa since 2011, disrupting economies and bringing major environmental, social, and health concerns. Avenues explored to valorise this biomass include the production of liquid biofertilisers and biostimulants. There has been less emphasis on the production of compost and mulch, and on their impact on plant growth. Therefore, the effects of compost and mulch prepared from rinsed and unrinsed Sargassum on corn, tomato, and pepper were investigated in this study. The elemental composition of soil, compost, mulch, and plant samples was also assessed to investigate the potential transfer of metals and metalloids from the compost and mulch to different parts of the plants (roots, leaves, and fruits). Sargassum-derived composts exhibited less effects on seed germination compared to mulch. Significant differences (p ≤ 0.05) between treatments were observed for seedling growth parameters (height, shoot diameter, and number of leaves). Post-harvest parameters were mixed with the leaf area index and the root-to-shoot ratios varied significantly between treatments but not moisture content. Variations in elemental concentrations were observed between the different parts of the plants and evaluated against established nutritional recommendations and toxicity thresholds. This study provides foundational insights for optimising pelagic Sargassum-based compost and mulch preparation to support plant growth. Full article

Microalgae biotechnology is increasingly applied across diverse fields, from food and medicine to energy and environmental protection, with strain selection being crucial for both target product accumulation and scalability potential. In this study, we for the first time assess the scalability of two new promising green microalgae strains, Neochlorella semenenkoi IPPAS C-1210 and Desmodesmus armatus ARC-06, in 5-L flat-panel photobioreactors. The growth characteristics of each culture, along with their biochemical composition and CO₂ utilization efficiency, were examined and compared to the well-studied model strain Chlorella sorokiniana IPPAS C-1. While C-1 achieved the highest biomass concentration (7.1 ± 0.4 g DW L⁻¹ by day 8) and demonstrated superior specific productivity (1.5 ± 0.1 g DW L⁻¹ d⁻¹) and CO₂ utilization efficiency (average 25.4%, peaking at 34% on day 3), ARC-06 accumulated the highest starch content (51% of DW), twice that of C-1. Strain C-1210 showed intermediate performance, reaching 6.8 ± 0.8 g DW L⁻¹ biomass with a CUE of 22.7%, whereas ARC-06 had the lowest CUE (12.8%). These results, combined with proposed cultivation optimization strategies, provide a foundation for scaling up N. semenenkoi and D. armatus production in industrial flat-panel PBR systems. Full article

Transparent Exopolymer Particles (TEP) play a key role in the marine carbon cycle, facilitating the aggregation and exportation of organic matter. TEP production is particularly relevant during Harmful Algal Blooms (HABs), where dinoflagellates like Lingulaulax polyedra can release significant amounts of exudates. Temperature is a crucial environmental factor that influences HAB dynamics and physiological processes of bloom-forming species, affecting exudate composition and abundance. This study investigates the influence of temperature and nutrient availability on the production of organic exudates in L. polyedra cultures. TEP, Particulate Organic Carbon (POC), and Particulate Organic Nitrogen (PON) concentrations were analyzed under controlled laboratory conditions. Batch cultures were maintained at temperatures of 17, 20, and 25 °C, with two nutrient regimes (low and high nitrate and phosphate concentrations). Exudates were quantified using colorimetric and spectrophotometric methods. We found that temperature and nutrient availability significantly influence exudate production. The highest TEP concentration was recorded at 25 °C in cells cultivated under low-nutrient conditions, whereas POC exhibited a notable increase at 20 °C. ANOVA revealed that TEP and POC were the primary drivers of variability among treatments. These findings reveal that temperature is important in the regulation of L. polyedra exudate production. The role of this variable on organic matter cycling and bloom dynamics in marine ecosystems is discussed. Full article

The application of marine algae-derived biostimulants offers a sustainable approach to improving plant performance in aromatic and medicinal crops. This study investigated the effects of four macroalgal extracts and two commercial biostimulant products on the growth, physiology, and essential oil production of Lavandula angustifolia cultivated under greenhouse conditions at CREA, Pescia (Italy). Treatments included extracts from Ascophyllum nodosum (France and Greenland), Laminaria digitata (Iceland), Sargassum muticum (Italy), two commercial formulations (a seaweed-based and an amino acid-based biostimulant), and a control receiving only standard fertilization. Over a 10-week period, plants were evaluated for multiple parameters: plant height, leaf number and area, SPAD index (chlorophyll content), above- and below-ground biomass, flower production, microbial activity in the growth substrate, and essential oil yield. Algae extracts, particularly those from A. nodosum (Greenland) and S. muticum (Venice), significantly enhanced most parameters compared to the control and commercial products. These treatments yielded higher biomass, greater chlorophyll retention, increased flower number, and improved essential oil content. Rhizosphere microbial counts were also elevated, indicating a positive interaction between algae treatments and substrate biology. The study highlights the multifunctional nature of marine algae, whose complex composition of bioactive compounds appears to promote plant growth and secondary metabolism through multiple pathways. The superior performance of cold- and temperate-climate algae suggests a relationship between environmental origin and biostimulant efficacy. Compared to commercial inputs, the tested algae extracts showed broader and more consistent effects. These findings support the integration of macroalgae-based biostimulants into sustainable lavender cultivation strategies. Further research is recommended to optimize formulations, validate field performance, and explore synergistic effects with beneficial microbes or organic inputs. Full article

Urban wastewater is composed of nutrients such as nitrogen and phosphorus, organic matter, heavy metals, pathogens, and micropollutants. If untreated, these contribute to eutrophication and environmental degradation. Microalgae-based bioremediation offers a sustainable solution, showing promise for pollutant removal and high-value bioproduct generation. This study evaluates the efficacy of Galdieria sulphuraria ACUF 427 in treating urban wastewater, with a focus on nutrient removal and phycocyanin production at different optical densities (OD 2, OD 4, and OD 6). Nutrient removal rates (RRs) were analysed for ammonium nitrogen (N-NH₄⁺), ammonia nitrogen (N-NH₃), phosphate phosphorus (P-PO₄³⁻), and chemical oxygen demand (COD). The RR for N-NH₄⁺ increased with optical density, reaching 7.49 mg/L/d at an optical density of 6. Similar trends were observed for N-NH₃ and P-PO₄³⁻, with peak removal at OD 6. COD removal remained high across all ODs, though differences between OD 4 and OD 6 were not statistically significant. Significant variations (p < 0.05) in nutrient removal were noted across the ODs, except for COD between OD 4 and OD 6. Biomass growth and phycocyanin production were significantly higher in the wastewater compared to the control (Allen Medium), with the most effective performance observed at an optical density (OD) of 6. Maximum growth rates were 0.241 g/L/d at OD 6, 0.178 g/L/d at OD 4, and 0.120 g/L/d at OD 2. These results highlight the potential of G. sulphuraria as an agent for wastewater bioremediation and the production of high-value compounds, particularly at elevated cell densities, where we achieved superior nutrient removal and biomass production. Full article

Phytoplankton–mesozooplankton interactions play a central role in shaping Black Sea food web dynamics, yet their trophic coupling has been insufficiently investigated in policy-relevant frameworks. This systematic review of 86 peer-reviewed studies (1987–2025) synthesizes research trends, limitations, and knowledge gaps in the field. The analysis reveals a clear dominance of work on plankton community structure (81%), whereas topics such as modeling and scenario analysis (7%), ecosystem assessment (7%), and bloom dynamics and seasonality (5%) remain comparatively underrepresented. Post-2020 publications indicate a promising shift toward scenario-based frameworks, gelatinous zooplankton impacts, and trait-based indicators, although functional integration remains fragmented. Keyword co-occurrence and network analyses revealed a concentration on nutrient–phytoplankton–zooplankton pathways, while other themes—such as bioluminescence and redoxcline dynamics—appeared only marginally represented in the literature we analyzed. To support ecosystem-based management under the Marine Strategy Framework Directive (MSFD), we highlight three priorities: improving NPZD-type models, using trophic efficiency metrics, and standardizing plankton indicators across the region. Strengthening the mechanistic understanding of planktonic trophic linkages is critical for improving food web assessments and adaptive marine governance in the Black Sea. Full article

Anthropogenic warming of the world’s oceans is not just an environmental crisis, but may result in a significant threat to human health. The combination of a warming ocean and increased human activity in coastal waters sets the stage for increased pathogenic Vibrio–human interaction. Warming patterns due to climate change have already been related to the emergence of Vibrio outbreaks in temperate and cold regions. Seafoods, including seaweeds, are uniquely poised to contribute to global food and nutrition security. In recent years there has been a resurgence of interest in seaweeds due to their many uses, high nutritional value, and ability to provide ecosystem services such as habitat provision, carbon and nutrient uptake, and coastal protection. However, some seaweed species can be a reservoir for harbouring pathogenic Vibrio, and illnesses like gastroenteritis have recently been associated with foods prepared with seaweeds. In this study, we investigated the impact of elevated water temperatures on abundances of the major human pathogens Vibrio parahaemolyticus, Vibrio alginolyticus, and Vibrio vulnificus/cholerae on seaweed and in coastal waters. Three seaweed species, Fucus serratus, Palmaria palmata, and Ulva spp., were exposed to temperature treatments (16 °C and 20 °C) to assess the effects of mean-temperature rise on Vibrio parahaemolyticus, Vibrio alginolyticus, and Vibrio vulnificus/cholerae colonisation. Colony-forming units (CFUs) on seaweed surfaces and in surrounding water were counted. F. serratus and P. palmata showed significantly higher Vibrio abundances at higher temperatures compared with Ulva spp.; however, temperature did not significantly affect abundances of tested Vibrio species in surrounding waters. These results indicate that certain seaweed species may serve as major hotspots for human pathogenic bacteria in warmer conditions, with implications for human health. Full article

This study explores the enhancement of fluoride adsorption using biochar derived from the brown macroalga Sargassum polycystum, which was treated with iron oxide (Fe₃O₄). The macroalgal biomass underwent pyrolysis at 400 °C, followed by Fe₃O₄ impregnation, to improve surface functionality and create active sites for fluoride ion binding. Various factors affecting fluoride removal were systematically examined. A maximum fluoride removal effectiveness of 90.2% was attained under ideal circumstances (pH 2, 60 mg adsorbent dose, 30 mg/L fluoride concentration, and 150 min contact duration). Adsorption isotherm analysis showed that the Langmuir model provided a better fit (R² = 0.998) than the Freundlich model (R² = 0.941), with a maximum adsorption capacity (qₘ) of 3.41 mg/g, indicating monolayer adsorption on a homogeneous surface. Kinetic modeling revealed that the pseudo-second-order model best described the adsorption process (R² = 0.9943), suggesting chemisorption as the dominant mechanism, while the intraparticle diffusion model also showed a good fit (R² = 0.9524), implying its role in the rate-limiting step. Surface complexation, facilitated by the enhanced surface area and porosity of the iron-modified biochar, was identified as the primary mechanism of fluoride ion interaction. This study highlights the potential of Fe₃O₄-modified macroalgal biochar as an effective and sustainable solution for fluoride remediation in contaminated water sources. Full article

Type 2 diabetes mellitus (T2DM) is recognized as a multifactorial health disorder associated with various complications. This paper presents a bibliometric analysis of type 2 diabetes mellitus and natural active substances. Currently, the research field in this area is on an upward trajectory, with major research hotspots focusing on pathogenesis, pharmacological activities, the gut microbiota, and lipid metabolism. Algae-derived natural active substances, namely astaxanthin, extracellular polysaccharide from Porphyridium cruentum (EPS-P), and β-carotene, all exhibit high antioxidant properties and safety, along with favorable hypoglycemic effects. Therefore, their therapeutic intervention effects on type 2 diabetes mellitus were evaluated through in vitro experiments. Compared with the model group, astaxanthin, β-carotene, and Porphyridium cruentum polysaccharide (EPS-P) improved various indicators by at least 24.17%, 7.7%, and 6.7%, respectively. All three substances could, to a certain extent, enhance glucose consumption, glycogen content, and pyruvate activity, as well as improve and restore the condition of IR-HepG2 cells. The order of intervention efficacy was astaxanthin, followed by β-carotene, and then Porphyridium cruentum polysaccharide (EPS-P). These findings provide a scientific basis for the biomedical applications of algae-derived natural products. Full article

This study evaluated the effects of different storage conditions, varying in light exposure, relative humidity (RH), and packaging materials, on the physicochemical stability of Lobosphaera sp. biomass, the retention of bioactive compounds, and the bioactivity of its extracts. Under light and 75% RH, the biomass absorbed moisture over time, reaching 0.779 ± 0.003 g/g dry weight (DW) after three months. This was accompanied by a decline in luminosity, chroma, and hue values. In contrast, samples stored under other conditions showed minimal changes, indicating that high humidity, combined with light exposure, compromises biomass stability. Packaging in metalized polyethylene terephthalate (PETmet/PE) effectively preserved the water content, color, and carotenoid levels during a two-month storage period. Bioactive compounds extracted via hydroethanolic ultrasound-assisted extraction yielded 15.48 ± 1.35% DW. Total phenolic content (TPC) of the extracts declined over time in both PETmet/PE and low-density polyethylene (LDPE) packaging, though the decrease was less pronounced in PETmet/PE. Antioxidant activity, assessed via the ABTS assay, remained stable, regardless of storage duration or packaging. Antimicrobial activity of the extract decreased over time but remained more effective against Gram-positive bacteria (Staphylococcus aureus, Bacillus cereus, and Listeria monocytogenes), with PETmet/PE packaging better preserving antimicrobial efficacy than LDPE. These findings underscore the importance of optimized storage conditions and packaging for maintaining the quality and bioactivity of Lobosphaera sp. biomass and its extracts. Full article

Cyanobacteria (also called blue-green algae)-based dietary supplements are commonplace, but cyanobacteria-enhanced foods, such as spirulina crackers, are just appearing on New Zealand supermarket shelves. While much research has been devoted to consumer attitudes towards macro-algae-based products, little research has been devoted to micro-algae-based or cyanobacteria-enhanced consumer products. The current study, following the Capability–Opportunity–Motivation to Behaviour theory, examines likely consumer drivers of favouring or disfavouring spirulina crackers. These drivers include food neophilia, food neophobia, perception of sustainability and health-related product attributes, involvement with algae and an exploratory driver, snacking behaviour. Fully supported drivers (related to increased favour and decreased disfavour) included food neophilia and perception of sustainability and health-related product attributes. Algae involvement was only related to increased favour, and food neophobia was not supported. Surprisingly, snacking behaviour was related to increased disfavour of spirulina crackers. Both theoretical and managerial implications are offered. Full article

The demand for sustainable animal production is increasing. Microalgae such as Chlorella and Spirulina show promise as sustainable and functional ingredients in animal (poultry) feed. However, little is known about consumer perceptions regarding the use of algae in broiler diets and potential effects of algae on chicken meat. Residents of Flanders (Belgium) were surveyed to evaluate consumer knowledge, attitudes and willingness to buy chicken meat produced with algae-supplemented feed. Demographic data were collected, and both descriptive and inferential statistics were applied to assess influencing factors (n = 275 respondents who purchase chicken meat). While most respondents (69.6%) had tasted macroalgae (seaweed), only 11.4% and 24.6% indicated having tasted Chlorella and Spirulina before, respectively. Health, taste and safety were the most important drivers for consuming algae. Meat quality was the most important factor when purchasing chicken meat, while organic production was least valued. Regarding algae-fed chicken, 72.5% expressed willingness to purchase meat labeled as such, and 83.7% would buy algae-fed chicken regardless of its color. Sustainability beliefs significantly influenced willingness to accept a yellower meat color (β = 0.42 to 0.66, p < 0.001). Educational level and age also played a role, with higher-educated consumers showing greater acceptance. The influence of age was also related to the price of the meat, with consumers over 30 expressing a greater willingness to pay more than young people (under 30). Despite limited general knowledge about microalgae, the consumers surveyed are open to the idea of algae-fed chicken meat, particularly when it is framed as more sustainable. Clear ingredient labeling and consumer education may further support market acceptance. Full article

High ash content in algal biomass limits its suitability for biofuel production by reducing combustion efficiency and increasing fouling. This study presents a green deashing strategy using nitrilotriacetic acid (NTA) and deionized (DI) water to purify Scenedesmus algae, which was selected for its high ash removal potential. The optimized sequential treatment (DI, NTA chelation, and DI+NTA treatment at 90–130 °C) achieved up to 83.07% ash removal, reducing ash content from 15.2% to 3.8%. Elevated temperatures enhanced the removal of calcium, magnesium, and potassium, while heavy metals like lead and copper were reduced below detection limits. CHN analysis confirmed minimal loss of organic content, preserving biochemical integrity. Unlike traditional acid leaching, this method is eco-friendly after three cycles. The approach offers a scalable, sustainable solution to improve algal biomass quality for thermochemical conversion and supports circular bioeconomy goals. Full article

Salinity serves as a critical environmental factor influencing the physiological and morphological characteristics of Spirulina, a filamentous cyanobacterium used for food production and commercial purposes. This study examined a Spirulina strain’s responses to different salinity levels (10–45 ppt) through three independent laboratory experiments that determined growth, productivity, and size structure. Growth across salinity treatments was assessed by monitoring optical density in 24-well microplates over 20 days and estimating specific growth rates using a logistic growth model. Primary productivity under different salinity and light conditions was measured using light and dark bottle experiments to calculate gross primary productivity (GPP) and to estimate photosynthetic efficiency through linear regression of GPP against light intensity. The size structure was assessed through tube-based experiments and image analysis, with organism sizes categorized and analyzed to identify salinity-induced patterns in filament structure. The study demonstrated that the Spirulina strain achieved its greatest growth at 10 ppt yet produced the highest photosynthetic efficiency between 27 and 45 ppt because it reallocated energy during salinity stress. The morphological analysis revealed that the Spirulina strain produced medium-sized filaments between 400 and 799 µm at elevated salinity levels, and our analysis confirmed substantial variations in size structure. The Spirulina strain demonstrates both physiological and morphological plasticity when exposed to salinity changes. The cultivation of the Spirulina strain at 27 ppt provides conditions that support moderate growth, enhanced productivity, and manageable morphological shifts while using its natural salinity tolerance to improve the efficiency and scalability of production for diverse biotechnological applications. Full article

Conservation units (CUs) play a fundamental role in maintaining and conserving biodiversity, and are important in preserving streams, reducing impacts from human activities and increasing water availability beyond the boundaries of the reserves. However, knowledge about the phytoplankton biodiversity of ecosystems in CUs is scarce. This study evaluated how environmental integrity alters microphytoplankton communities in extractive CUs and their surroundings in the southwestern Brazilian Amazon. Our results demonstrated that the streams exhibited distinct physicochemical and hydrological characteristics, representing spatially heterogeneous environments. Differences in habitat integrity values altered species composition in streams within and outside conservation units. Local beta diversity (LCBD) was negatively influenced by habitat integrity, indicating that sites with greater habitat integrity did not always present a greater number of unique species. The species Trachelomonas hispida, Gyrosigma scalproides and Spirogyra sp. were the ones that contributed the most to beta diversity. However, the phytoplankton species that contributed most to beta diversity were not always associated with streams with greater integrity, indicating that even environments that are less intact play a relevant role in maintaining species richness and beta diversity of microphytoplankton. Factors such as habitat integrity, pH, temperature and dissolved oxygen were the main influencers of microphytoplankton in the streams. Thus, the streams of both CUs and their surroundings, despite their physical–chemical and hydrological differences, effectively contribute to the high richness and beta diversity of regional microphytoplankton. Full article

The nutrient-rich composition of seaweeds and lichens makes them well-suited for agricultural applications. Their use as alternatives to synthetic fertilizers contributes to sustainable agricultural production, enabling farmers to adopt ecological practices while maintaining or increasing crop productivity. This review aims to highlight the status and trends of research, along with a literature analysis on the application of these biomasses in sustainable agriculture. A bibliometric analysis was performed based on two databases (Scopus and Web of Science) to overview the main research topics regarding the use of biomasses studied in agriculture, thus providing useful information for future research. The biochemical composition and agricultural applications of these biomasses have been highlighted. The analysis shows that these biomasses are rich of nutrient compounds, revealing their roles and mechanisms of action on the chemical, nutritional properties, and soil microbial activities and their effect on plant growth, using various extraction and application methods. It also highlighted the potential of seaweeds for protection against biotic and abiotic stresses. In light of all the data presented in this review, it is possible to stimulate farmers’ interest in using seaweeds and lichens as natural fertilizers, with a focus on sustainable and ecological agriculture mainly in developing countries. Full article

Bangiales are photosynthetic organisms that grow in the intertidal zone, a region characterized by fluctuating environmental conditions. The order comprises genera exhibiting two different morphological variations, filamentous and foliose. It was recently demonstrated that the filamentous alga ‘Bangia’ sp. ESS1 possesses the intrinsic ability to “memorize” an experience of prior heat stress to enhance its survival under subsequent, normally lethal, high-temperature conditions via the acquisition of heat stress tolerance. Here, we investigated whether foliose red algae can similarly memorize heat stress to acquire thermotolerance. When Pyropia yezoensis thalli were primed with non-lethal, high-temperature treatments (22 and 25 °C) for 7 days, vegetative cells subsequently triggered with a normally lethal temperature of 30 °C showed dramatically increased survival rates, indicating that P. yezoensis can acquire heat stress tolerance via exposure to non-lethal high temperatures. In addition, when 22 °C-primed thalli were incubated at 15 °C for recovery, vegetative cells survived subsequent incubation at 30 °C; their survival rates varied depending on the duration of recovery. These findings indicate that, like filamentous red algae, the foliose species P. yezoensis memorizes heat stress to acquire tolerance to recurrent thermostress. The identification of heat stress memory in foliose Bangiales lays a foundation for improving the heat stress tolerance of these important algae, supporting the sustainability of the nori mariculture industry. Full article