Phycology

Oyster-associated microbiomes represent a dynamic interface between marine hosts and their environment, yet the diversity, evolution, and functional potential of their associated cyanobacteria remain poorly understood. For microbial organisms, such as cyanobacteria, survival requires adaptation to several environmental pressures, including higher metal concentrations and osmotic stress. To investigate these adaptations, two cyanobacterial strains, CENA647 and CENA648, were isolated from oyster surfaces sampled along the Amazon coast. Genomic analysis and untargeted metabolomics were conducted to investigate the taxonomy and functional potential of these strains. Both genomes exhibited high completeness (>99.2%) and low contamination (<2.2%). The total lengths differed, with 8.3 Mbp for CENA647 and 6.5 Mbp for CENA648. The genome size correlated with the number of identified coding regions: 7593 for CENA647 and 5541 for CENA648. Phylogenetic analysis highlights their taxonomic relationships within cyanobacteria adapted to fluctuating salinity, including the first description of the genus Thainema in South America. Comparative genome mining revealed extensive genetic repertoires associated with osmoregulation and metal resistance, consistent with adaptation to oyster-associated environments. Both strains shared predicted metabolites annotated in the metabolomes, with a wide range of compound classes, including amino acids, terpenes, fatty acids, and peptides, as well as several unannotated molecular features. Overall, our findings expand current knowledge of oyster-associated cyanobacteria and highlight their metabolic diversity in the Amazon region, as well as genomic traits that may be associated with adaptation to dynamic estuarine environments. Full article

Phytoplankton are the major primary producers in the Southern Ocean, are important to global nutrient cycles, and are at the base of marine food webs. Polar ecosystems are unique in their extended periods of darkness in the winter, and prolonged darkness has the potential to exert selection that affects diatom population composition if there is differential survival in the dark, the variation in population growth rates in subsequent light periods, or both. We tested whether prolonged darkness has the potential to exert within-species selection on a model polar diatom species by exposing five strains of the polar diatom Porosira glacialis to prolonged darkness at two different temperatures in the laboratory. We measured population survival in the dark, growth rate upon re-illumination, and between-strain variability in these traits. We found a pronounced decline in survival and growth rate with time spent in the dark, as well as important intraspecific variation in the tested strains. Declines in survival and growth were exacerbated at a higher temperature. Our results show that the darkness of polar night can exert intraspecific selection in a common Southern Ocean diatom. Full article

Sargassum fusiforme is a commercially important macroalga in Eastern Asia. To support the conservation and restoration of S. fusiforme populations, we investigated its predominant reproductive mode using a population genetics approach. Two sampling schemes were employed: random sampling of 80 samples at > 1 m intervals across four sites, and quadrat sampling of 207 samples using 50 cm × 50 cm quadrats subdivided into 10 cm grids at two sites. Clonemates were identified based on the microsatellite genotypes. In random sampling, only three clonal pairs were detected. In the quadrat sampling, each quadrat contained 4–7 genets, with an average extent of 23.2 ± 14.3 cm (standard deviation) and a maximum of 70.7 cm. The genetic indices (Pareto β, inbreeding coefficient, variance of inbreeding coefficient, genotypic richness, and synthetic linkage disequilibrium) suggested higher clonality at Site B than at Site D. Contemporary gene flow analysis indicated that over 65% of sexual recruitment was limited to within the quadrats, whereas at least 10% extended over meters to kilometers. Taken together, these results suggest that S. fusiforme disperses its offspring both sexually and clonally on a small scale and sexually on a larger scale. Full article

Perennially ice-covered lakes in the McMurdo Dry Valleys, Antarctica, are shaped by permanent stratification, extreme oligotrophy, and salinity gradients, yet these features are vulnerable to climate-driven hydrologic change. Because phytoplankton and associated bacteria regulate carbon flow and nutrient cycling, understanding how algal–bacterial consortia respond to disturbance is key to predicting ecosystem change. We used enrichment cultures from Lakes Bonney and Fryxell to test responses to nutrient deprivation and salinity alteration, two perturbations relevant to climate-driven changes in hydrologic connectivity and expansion of open water moats. Autotrophic enrichments lacking added organic carbon were used to enrich algal–bacterial consortia dependent on photosynthetically derived substrates. Community responses were assessed with 16S rRNA amplicon sequencing of size-fractionated samples, allowing comparison of particle-associated and planktonic communities. Short-term nutrient limitation produced only limited shifts in community composition, indicating resistance to transient nutrient stress. However, bacterial communities were strongly structured by size fraction: particle-associated assemblages separated clearly from planktonic communities and were enriched in taxa linked to algal surfaces and polysaccharide-rich microhabitats, including Flavobacteriales, Sphingobacteriales, Rhizobiales, and Rhodobacterales. Salinity perturbation drove stronger restructuring of bacterial communities, with shallow Lake Bonney enrichments showing greater sensitivity than deeper communities. These findings suggest that algae-associated bacterial communities help structure Antarctic algal enrichment cultures and may influence microbial responses to climate-linked disturbance. Full article

Spirulina, a cyanobacterium recognized for its nutritional and environmental advantages, has emerged as a potential ingredient for sustainable diets. Consumer acceptance remains limited despite its benefits, particularly due to sensory challenges and limited prior awareness. This study aimed to investigate knowledge, consumption patterns, and attitudes toward Spirulina among a Brazilian sample. A cross-sectional online questionnaire distributed via social media and public spaces yielded 933 valid responses, categorized into three groups based on prior awareness and consumption history. Results indicated limited prior awareness and low consumption, with more than half of consumers having tried Spirulina only once. Education, income, generation, and health-related behaviors were associated with knowledge and consumption, although most effect sizes were small. Knowledge of Spirulina was concentrated on nutritional attributes, whereas environmental and technological attributes were less widely recognized. Health and environmental benefits were most often rated as increasing willingness to consume Spirulina, while self-reported barriers included taste, smell, and issues related to powdered and capsule forms. Preferred applications were in familiar food categories such as baked goods and powdered mixes. These findings indicate that Spirulina occupies a niche position among respondents and suggest the relevance of sensorially acceptable formulations, tailored communication strategies, and inclusive educational efforts. Full article

The article proposes a methodology for the valuation of ecosystem services rendered by benthic vegetation. The methodology is based on the integration of biotope mapping and characterization, quantitative assessment of macrophyte phytomass stocks, and aggregated unit values of ecosystem services. The coastal zone of the natural monument “Coastal Aquatic Complex (CAC) near the Dzhangul landslide coast” was selected as a model water area. The study area is distinguished by high species diversity of benthic vegetation, the occurrence of species with conservation status, and low anthropogenic pressure. Five biotopes were identified and described, their macrophyte phytomass stocks were quantified, and their spatial distribution within the natural monument was analyzed. According to the calculated data, the total value of ecosystem services provided by macrophytobenthos within the boundaries of the natural monument “CAC near the Dzhangul landslide coast” amounted to USD 2,805,430.32. The largest contribution to this value is made by biotopes of block-boulder deposits dominated by Ericaria crinita and Gongolaria barbata (USD 2,319,641.52), followed by biotopes with a mosaic growth of these species together with Nereia filiformis and the attached form of Phyllophora crispa (USD 397,884.16). The quantitative results obtained may be applied to substantiate compensation payments, assess the effectiveness of investments in environmental protection frameworks, and support integrated coastal zone management. Full article

To boost the local microalgae sector, Switzerland needs to better understand the current state of the industry, which is not fully represented in the existing literature. Only by identifying the strengths and weaknesses of the Swiss microalgae industry, will the country be able to develop strategies toward a strong and sustainable sector in the future. This work provides the first structured assessment of Switzerland’s fragmented and poorly documented microalgae sector through desktop research and an online survey of the country’s microalgae stakeholders. First, research articles with Swiss authors and patents with Swiss applicants were mapped. Then, a survey consisting of 8 questions was designed to gather information about the location, purpose, employees, production capacity, activities, and installations of 42 organizations with a research and/or commercial focus. The growing number of organizations working with microalgae in Switzerland is dominated by small companies (<50 employees) that provide services rather than biomass or bioproducts. Microalgae biomass production is about 2 tons DW per year and is also dominated by small-scale producers (<100 kg DW per year). One third of Swiss companies that sell microalgae-based products produce their own biomass abroad or purchase from abroad. Our findings highlight the growth potential of the Swiss microalgae sector. This systematic summary of research interests, technological innovations, and current market parameters is the first step toward future improvements in the sector. Full article

Gongolaria barbata has undergone a major decline along the Romanian Black Sea coast due to historical winter events of the 1970s and ongoing anthropogenic pressures and is currently listed as Critically Endangered in the Romanian List of Endangered Marine Species, highlighting the need for ex situ culture to support restoration and long-term preservation of this habitat-forming species. This study evaluates how different substrate types (travertine, shale and ceramic) influence early thallus development in G. barbata, and attachment and growth dynamics, and establishes an ex situ culture procedure tailored to Black Sea conditions. Germling-based culture was carried out under controlled conditions, with salinity maintained at 17.1 ± 0.5 PSU and seawater temperature at 19.0 ± 0.8 °C. After 216 days of ex situ culture, thalli reached comparable sizes across all substrates, with mean heights between 5 and 7 cm and maximum values ranging from 12 to over 20 cm. Thallus development progressed steadily across all substrates, each supporting comparable growth, a finding relevant for restoration, aquaculture, and large-scale cultivation. All tested hard substrates sustained early development, with travertine producing slightly more robust thalli and stronger holdfasts, highlighting its potential for future restoration initiatives along the Romanian Black Sea coast. Full article

Rivers have always been essential to humankind. They are used for many purposes and, as a result, have been heavily modified. Human impacts, many of them still poorly understood, interfere with river ecosystems, making them vulnerable to disturbances. Amongst these, mega events along riverbanks are listed. We studied the effects of the “FM4 Frequency Festival,” which attracted more than 200,000 visitors, on microalgae in the channelized section of the River Traisen in St. Pölten, the capital of Lower Austria. During the festival, phosphorus, dissolved organic carbon, and chloride increased significantly during the whole study period compared with before and after. Although the overall epilithic biomass remained unchanged during the festival period, the phytobenthos community experienced an increase in taxonomic richness downstream of the festival area. Both the Shannon diversity (mean ± SD = 2.89 ± 0.34) and Pielou’s evenness (mean ± SD = 0.73 ± 0.08) did not differ significantly between the sampling dates before, during, and after the festival. We found a shift towards Achnanthidium minutissimum as the dominant species during the festival. Diatoma ehrenbergii, which is sensitive to nutrient enrichment and organic pollution, disappeared during the event. Overall, the biofilm shifted towards a community dominated by heterotrophs during the festival, likely due to high organic loading. Pelagic microalgae experienced a rise in the total taxa number during the festival, which was partly caused by resuspension of phytobenthos. Our results reflect significant impacts from visitors to the Traisen ecosystem. Not only short-term changes in the hydrochemical environment but also mechanical disturbances of the phytobenthos caused by visitors were demonstrated. We suggest continuous monitoring to verify that such events will not have long-term impacts on the system. Full article

Dulce (Palmaria palmata) is a high-value macroalga that is increasingly being cultivated, with strong potential for waste valorisation in nutrient-rich aquaculture systems (RASs). This study evaluated P. palmata growth in, and nutrient uptake from, commercial Atlantic salmon RAS effluent. A 12-week bench-scale experiment cultivated wild-collected P. palmata (average 10 g fresh weight, FW). These were grown in 1 L glass beakers at three effluent dilutions (25%, RAS25; 50%, RAS50; 100%, RAS100) and in seawater (SW) using 10 replicates. The water samples were analysed for ammonium nitrogen (NH₄-N), nitrate nitrogen (NO₃-N), and orthophosphate (PO₄-P) using a spectrophotometer. RAS25 and RAS50 exhibited 100% survival and maintained a dark red colour, with RAS50 achieving the highest specific growth rate (0.49 ± 0.13% day⁻¹), significantly higher than that of SW and RAS25. In contrast, RAS100 led to complete disintegration by 4–8 weeks with significant colour degradation. SW also exhibited reduced colour and 50% mortality by week 12. Sori’s presence was highest in RAS25/RAS50 (up to 80% at week 8 in RAS50), low in SW (10%), and absent in RAS100. The NH₄-N uptake was notably 3× higher than that of NO₃-N (0.16 vs. 0.05 mg g FW⁻¹ day⁻¹), without differences among the groups. The PO₄-P uptake was significantly higher for RAS50 (0.07 mg g FW⁻¹ day⁻¹) than for RAS100. P. palmata performed best in the diluted RAS effluents, as undiluted conditions led to acute tissue disintegration; the nitrogen and phosphorus uptake from the RAS effluents demonstrates significant potential for nutrient valorisation. Full article

Cyanobacteria inhabit ecosystems ranging from oligotrophic deserts to eutrophic lakes, yet it remains unclear whether distantly related species dominate in disparate habitats, share common genomic features, or show divergent specialization. Here, we established a comparative framework of Microcoleus vaginatus, the pioneer stabilizer of biocrusts, and Microcystis aeruginosa, a major cause of freshwater blooms worldwide. Our dataset comprises 504 high-quality cyanobacterial genomes, including 132 M. vaginatus, 148 M. aeruginosa, and 224 reference taxa, for analyses of genome architecture, functional repertoires, and genomic plasticity. Both focal lineages showed signatures of extensive horizontal gene transfer and shared a small set of conserved orthologous groups, annotated as FAD-dependent oxidoreductases, manganese efflux, and class II aldolases. Nevertheless, the two lineages followed distinct genomic strategies. M. vaginatus expands regulatory breadth and stress-resilience gene families, whereas M. aeruginosa shows evidence of genome streamlining and rapid nutrient exploitation. Notably, we hypothesize that aquatic M. vaginatus strains retain ancestral terrestrial genomic features while gradually acquiring potential aquatic-specific adaptations. Together, these results reveal a two-tier architecture associated with cyanobacterial dominance and provide a testable hypothesis for how cyanobacterial lineages may respond to global change pressures. Full article

Seaweeds are sustainable, nutrient-rich resources with potential for use in the development of functional foods. Fermentation represents a powerful biotechnological approach to enhance the nutritional, sensory and bioactive profile of seaweed-based products. This review synthesizes the literature published between 2010 and 2025, addressing recent advances in seaweed pre-treatment technologies, fermentation processes and their integration into diverse food matrices, together with associated health benefits. The diversity of seaweeds applied in fermentation, dominated by brown algae, is examined alongside key pre-treatment strategies, ranging from conventional approaches to emerging technologies including ultrasound, high-pressure processing and assisted fermentation, with emphasis on their impact on fermentability and bioactive recovery. The role of microbial groups is critically discussed in relation to their metabolic contributions and functional outcomes. Overall, fermented seaweed-enriched foods emerge as promising innovations in functional food development, with antioxidant activity being the most consistently reported benefit. Seaweed versatility is evidenced by its incorporation into a wide range of fermented products, including miso, beverages, dairy alternatives and sauces. Key future research directions include optimizing microbial–seaweed interactions, exploring under-investigated pre-treatment technologies such as freezing, and elucidating the mechanisms linking fermentation to heavy metal reduction, with the ultimate goal of improving process control, product quality and consumer acceptance. Full article

Whether exogenous vitamin K1 (VK1) promotes microalgal growth is unknown. This study reports for the first time that Bacillus megaterium can promote the growth of Chlorella pyrenoidosa, an effect possibly mediated by VK1. To confirm this finding and clarify the corresponding mechanism, the effects of exogenous VK1 on the growth and lipid production of C. pyrenoidosa were studied. The results showed that the microalgal cell density, chlorophyll a content, lipid content, and lipid productivity increased by 117%, 90%, 291%, and 247%, respectively, following the addition of 0.3 g/L exogenous VK1. Additionally, the microalgal Fv/Fo, Fv/Fm, and Fm/Fo were also improved by the VK1, indicating that VK1 promoted microalgae growth by increasing microalgal photosynthesis activities. The microalgal genes of lipid synthesis, including the acetyl-CoA carboxylase gene, malonyl-transferase gene, 3-oxoacylsynthase I gene, and 3-oxoacyl-[acyl-carrier-protein] synthase II gene, were all up-regulated by VK1 at the transcript level, revealing the promotion mechanism of VK1 on microalgal lipid production. Moreover, the total phosphorus utilization of the C. pyrenoidosa reached nearly 100%, indicating its excellent phosphorus utilization ability. The results are beneficial for exploring a more effective technology of utilizing C. pyrenoidosa for biofuel production and provide a new perspective on understanding the interaction mechanism between bacteria and microalgae. Full article

This study investigated the use of Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) as a cost-effective analytical approach for screening the bioactivity of green algal extracts. Samples of five Caulerpa species—C. ashmeadii, C. paspaloides, C. cupressoides, C. verticillata, and C. prolifera—were collected from Dzilam, Yucatán, Mexico, across seven seasonal campaigns. Sequential extraction was performed using solvents of increasing polarity: hexane, dichloromethane, acetone, and methanol. After solvent evaporation, extracts were analyzed via ATR-FTIR, and Total Phenolic Content (TPC) and Trolox Equivalent Antioxidant Capacity (TEAC) were quantified. Statistical analysis (PERMANOVA) revealed that the type of solvent accounted for most of the variance (61.6%), while species and collection date contributed minimally. Infrared (IR) band assignments highlighted functional groups associated with lipids, such as terpenes, and carbohydrates. K-means clustering enabled the subdivision of less polar extracts, notably grouping numerous samples from C. verticillata. Classification models comparing full-spectrum and IR band datasets showed that Partial Least Squares Discriminant Analysis (PLS-DA) with full-spectrum data achieved the best performance. TPC showed a positive correlation with absorption at 1730.8 cm⁻¹, which is associated with ester-containing metabolites. Although ATR-FTIR effectively distinguished extraction solvents, it was less sensitive to subtle biological variation among Caulerpa. However, the method remains a practical tool for rapid screening, with spectral data supporting solvent-based classification. Reduction of salt content prior to extraction may minimize interference in both FTIR measurements and biological assays. Full article

Microalgae are valuable biotechnological resources due to their high productivity and their capacity to synthesize compounds with nutritional and antioxidant functions. However, in the Santa Elena Peninsula (Ecuador), their use in aquaculture is limited to commercial strains. In this study, native microalgae were isolated and evaluated for their nutritional value in aquaculture. Samples were collected at five coastal sites, cultivated under controlled conditions, and characterized using optical microscopy and SEM, identified at the molecular level through the 28S rRNA gene, and their biochemical profiles were analyzed, including carotenoid quantification. The isolates were identified as PM-UPSE-006 (Tetradesmus obliquus), PM-UPSE-007 (Conticribra weissflogii), PM-UPSE-016 (Halamphora coffeiformis), PM018 (Dunaliella sp.), and PM-UPSE-022 (Chlorella vulgaris), with T. obliquus and H. coffeiformis being recorded for the first time in the peninsula. The highest growth rates were observed in T. obliquus, Dunaliella sp., and C. vulgaris, while Dunaliella sp. and C. vulgaris stood out for their protein content (57.28% DM and 55.37% DM), T. obliquus for carbohydrates (40.5% DM), and H. coffeiformis, Dunaliella sp., and C. vulgaris for carotenoids (0.53–1.60% DM). These results demonstrate their ex situ adaptability, competitive growth, and noteworthy biochemical profiles, establishing them as promising biotechnological resources for sustainable aquaculture. Full article

Porphyra sensu lato is a promising source of natural photoprotective and antioxidant compounds for cosmeceutical applications. This study evaluated the geographical and temporal variability of bioactive compounds in Porphyra and Pyropia spp. from Chile and Spain and assessed their applicability in topical photoprotective formulations. Antioxidant capacity, soluble polyphenols, phycobiliproteins, and mycosporine-like amino acids (MAAs) were quantified in different species, collection sites, and sampling periods. In parallel, selected Pyropia elongata extracts were incorporated into water-in-oil creams, alone or combined with vegetable oils and physical UV filters, and in vitro SPF/UVAPF values were determined using the PMMA plate transmittance method. Marked variability was observed among species, sites, and collection dates. In P. elongata, total MAAs ranged approximately from 3 to 6 mg.g⁻¹ DW, while porphyra-334 was the dominant MAA, accounting for about 70–100% of total MAAs across samples. A positive correlation was found between soluble polyphenol concentration and ABTS antioxidant activity. In the formulations, Pyropia extracts increased absorbance mainly in the UVB–UVA range and improved SPF and UVA-related protection, particularly when combined with karanja and calophyll oils and physical filters. These results support Porphyra sensu lato biomass as a flexible natural reservoir for developing sustainable bio-based photoprotective products. Full article

Recent studies of understudied habitats, particularly caves, have revealed previously unrecognised cyanobacterial diversity. In this study, we used a metabarcoding approach to assess cyanobacterial communities in lampenflora developing in the most visited sections of Stopić Cave, Serbia. Two visually distinct lampenflora types were analysed: aerophytic lampenflora on exposed surfaces and submerged lampenflora within retained water, along with key environmental parameters. A wide range of Cyanobacteria was detected, including cave-adapted, rock-dwelling, atmophytic taxa from various habitats (deserts, thermal and saline environments), as well as species typically associated with freshwater and saline environments. Notably, many of the documented taxa have only recently been described. Dominant Cyanobacteria (>10%) included those assigned to Cyanothece aeruginosa, Loriellopsis cavernicola, Marileptolyngbya sina, Neochroococcus gongqingensis, Pseudocyanosarcina phycocyania, Scytonema hofmanii and Thainema salinarum, while representatives of the genera Chalicogloea, Crocosphaera, Dulcicalothrix, Gloeothece, Kovacikia, Timaviella, and Trichocoleus each contributed ≥1% of the community. In addition, Vampirovibrio chlorellavorus, a representative of Candidatus Melainabacteria, the non-photosynthetic relative of Cyanobacteria and an obligate parasite of Chlorella species, was detected in all aerophytic lampenflora. Full article

Cyanobacterial species in the Arabian Peninsula region display a diverse range of potential biotechnological application. This review summarizes the cyanobacteria diversity found in the Peninsula region, the bioactive compounds found in these species, and the several health benefits and applications. The Arabian Peninsula region comprises a wide range of cyanobacteria with representatives from the orders Oscillatoriales, Chroococcales, Stigonematales, and Nostocales. These microorganisms produce specialized metabolites such as photosynthetic pigments, pigment–protein complexes, lipopeptides, phenolic compounds, and unique secondary metabolites. Many of the metabolites offer beneficial biological functions including antioxidants, antibacterial, anti-cancer, anti-inflammatory antiviral, and neuroprotective ones. In addition to the medical-related practices, cyanobacteria in the Peninsula region might have several other applications. Other probable uses include their potential bioremediation capability to remove pollutants or heavy metals, as a potential biohydrogen source for renewable energy, and as biofertilizers and soil enhancement to support sustainable agriculture; other useful applications include bioplastics production (polyhydroxyalkanoates), soil microbiota improvement, and methane reduction. The review highlights the potential diverse biotechnological applications of Arabian Peninsula cyanobacteria toward bioremediation, bioplastics, ecosystem regeneration, biofertilizers, bioenergy, and agro-sustainability, as well as human health. This review highlights the importance of the further exploration and exploitation of these resourceful microorganisms for sustainable development in the Arabian Peninsula region. Full article

The diversity of cyanobacteria from the semi-arid region of Rajasthan, India, remains vastly unexplored and warrants systematic investigation. We isolated two cyanobacterial strains (SN2022/33 & AT2016/25) of non-heterocytous, filamentous cyanobacterium from samples of sandy soil biological crusts and investigated them using a polyphasic approach. Based on 16S rRNA gene sequence identity, both strains formed a distinct lineage, with 16S sequence identity (p-distance) < 95% to the closest sister genera Trichocoleus, Venetifunis, Trichothermofontia, and Pinocchia. Analyses of 16S-23S Internal Transcribed Spacer (ITS) secondary structures (D1-D1′, BoxB, and V3 helixes) yielded substantial differences from phylogenetically associated taxa. Morphologically, both strains corresponded to members of the family Trichocoleusaceae (Leptolyngbyales), with tapered filaments and conical-pointed end cells. Most significantly, this taxon exhibited a form of true branching, with prolific unilateral or bilateral extrusions, something that had previously been the exclusive purview of members of the Nostocaceae. The combined evidence from conventional and molecular studies supports the recognition of the isolates as a novel taxon hereby described as Edaphifilum ginni gen. et sp. nov., in accordance with the International Code of Nomenclature (ICN) for Algae, Fungi, and Plants. Full article