Phycology

Taxonomic clarity within the genus Antithamnion is critical for understanding its molecular phylogeny and biodiversity. Here we report Antithamnion hubbsii for the first time from the Korean coast. This finding highlights the need to re-evaluate its relationship with the previously reported, morphologically very similar A. nipponicum in this region, raising the question of whether the newly identified A. hubbsii represents a local variant of A. nipponicum or a recently introduced invasive species via nearby ports. Specimens collected from Gangneung were analyzed using plastid-encoded rbcL and psaA genes, confirming their identity as A. hubbsii. Morphological features such as indeterminate lateral axes, oppositely arranged pinnae and pinnules, and distinctive adaxial gland cells supported this identification. Molecular analyses revealed minimal divergence between A. hubbsii and A. nipponicum (1–3 bp in rbcL, none in psbA), and contrasting results from different species delimitation methods. Phylogenetic analyses nevertheless placed the Korean specimens in a strongly supported A. hubbsii/A. nipponicum clade. Taken together, our results suggest that the North American invasive A. nipponicum and the Korean A. hubbsii may represent a single species with broad intraspecific variation. Definitive resolution will require molecular analyses of the type specimens of both taxa. Full article

Colaconema daviesii has been described as an epi-endophyte of red algae. However, it has also been observed in vitro to colonize thalli of Macrocystis pyrifera, a giant kelp classified as a foundational organism of coastal marine ecosystems. This study aimed to determine, through co-cultivations, how C. daviesii affects the early stages of M. pyrifera, specifically gametophyte and sporophyte development. Determined were growth, oogonia formation, and gametophyte fertility, as well as sporophyte growth rate and survival. The results showed that the presence of C. daviesii negatively altered oogonia production and gametophyte fertility. Moreover, the survival of young sporophytes in co-cultures decreased. These findings demonstrate that the early developmental stages of M. pyrifera could be susceptible to infestation by a filamentous red alga, with negative consequences on fitness. Full article

This study uses industrial wastewater from an aluminum factory to evaluate the phycoremediation efficiency of two green microalgal strains, Dictyosphaerium sp. and Tetradesmus obliquus. The industrial wastewater contained high levels of pollutants, including COD, ammonium, nitrate, phosphate, and heavy metal ions (Al³⁺, Cu²⁺, Cr³⁺, Zn²⁺, Mn²⁺, Cd²⁺). Four biomass conditions were tested: free-living cells (active living cells), immobilized cells (entrapped within alginate), dried biomass (non-living dried cells), and acid-treated dried biomass (chemically modified for enhanced adsorption). Both strains demonstrated significant pollutant removal, with living biomass (free and immobilized) achieving the highest nutrient and organic pollutant removal, and non-living biomass (dried and acid-treated) being more efficient for rapid heavy metal removal. Tetradesmus obliquus showed superior performance across most parameters, while Dictyosphaerium sp. exhibited the highest aluminum removal (99.4%, reducing Al from 481.2 mg/L to 10.2 mg/L). These findings highlight the potential of microalgae-based approaches and support species-specific strategies for cost-effective and sustainable phycoremediation of industrial wastewater. Full article

Harmful algal blooms (HABs) caused by toxic species such as Pseudo-nitzschia hasleana pose significant risks to marine ecosystems and human health. This study investigates the effects of heating rate on the fluorescence temperature curves (FTCs) of P. hasleana and compares them with non-toxic species (Phaeodactylum tricornutum and Picochlorum maculatum) to design a reliable detection method. An increasing heating rate leads to a change in the temperature spectrum of the fluorescence of the studied algae and to increasing differences between them. During the study, the FTCs were measured in the temperature range of 20–80 °C and at heating rates of 1, 2, 3, and 6°/min. The results showed that P. hasleana exhibited a distinct local fluorescence maximum at 45–55 °C when heated at a rate of 3 °C/min or more, which was absent in non-toxic species. Additionally, rapid heating (6 °C/min) preserved fluorescent pigment–protein complexes, yielding four-fold higher fluorescence intensity at 70–80 °C compared to slower rates. There were no such changes for the microalgae P. maculatum and P. tricornutum. The results of this study make it possible to increase the efficiency of detecting hazardous microalgae using non-invasive optical monitoring methods. These findings demonstrate that controlled heating protocols can enhance the species-specific identification of toxic microalgae, offering a practical tool for early HAB detection. Full article

Sustainable plant-based materials are becoming more popular as a substitute for those of animal origin for the encapsulation of compounds. Among different techniques, microencapsulation is widely used to protect bioactives and keep them intact to reach the desired target area. In this work, microencapsulation of oils by spray-drying using alternative vegan materials was proposed to mitigate oxidative degradation of oils. The determination of the best combination and ratio for different vegan wall materials (pectin, inulin, pea protein, and modified corn starch) was first developed using high-oleic sunflower oil enriched with β-carotene. In terms of efficiency, the best wall materials were pectin and inulin (P:I) in a 1:1 ratio, achieving 67.26 ± 0.78%. This ratio also obtained the best morphological results for shape and size studied by SEM (scanning electron microscopy) and DLS (dynamic light scattering). Additionally, the antioxidant activity of the oil enriched with β-carotene was studied, obtaining an IC5O of 0.15 mg/mL. Moreover, when Schizochytrium sp. was used instead of sunflower oil, as a docosahexaenoic acid (DHA)-enriched plant-based oil, the best results were also obtained for the P:I mixture, but at a ratio of 1:5. In all cases, the preservation of fatty acid profiles was achieved, giving insights for the potential use of alternative materials. The synergy between the use of antioxidants and encapsulation provides an effective method to avoid oxidation of edible oils. This work demonstrates the possibility of encapsulating carotenoid-enriched microalgae oil with vegan materials, improving its stability and bioavailability. Full article

Arthrospira platensis extract is incorporated into sunscreen formulations for its beneficial and UV-protective properties on cultured human cells. However, its effects have not yet been assessed on non-target organisms such as endosymbiotic microalgae in coral tissue. To evaluate its effects, we investigated the photophysiology of the cultured dinoflagellate Cladocopium goreaui using PAM fluorometry (RLC, OJIP) after a 5-day exposure to different extract concentrations. Our results show that, through a hormetic effect, A. platensis enhances the performance index (Pi_Abs) at 0.018 mg L⁻¹ by increasing the number of active reaction centers (RC/ABS) and improving electron transfer efficiency (φEo, ψEo) along the electron transport chain. Conversely, beyond 108.8 mg L⁻¹, negative impacts appear on PSII, increasing the apparent antenna size (ABS/RC) and impairing the oxygen-evolving complex (K-peak), ultimately reducing the maximum relative electron transport rate (rETR_m). This relative toxicity, obtained only for the highest concentrations, supports its potential incorporation into cosmetic formulations. This study contributes to improving the ecotoxicity assessment of cosmetic products on non-target organisms. Full article

Microalgae are photosynthetic microorganisms that could be used as potential microbial cell factories by directly converting CO₂ into valuable bioproducts and biofuels. This study aims to improve the production of biofuel from the isolated green alga Chlorella sp., in terms of an increase in its lipid content and its conversion to fatty acid methyl esters (FAMEs) when the cells are grown under the influence of phosphorus (P) limitation and heavy metal addition. The results show that the highest content of lipids, at 68.9%, was achieved within one day under 0% P with a 17 µM cobalt addition. Moreover, supplementation with a low Pb concentration increased cell growth even under P limitation, but under this condition, its lipid content was decreased after seven days of growth. The lipids of Chlorella sp. were transesterified to produce FAMEs. The overall biodiesel properties of the obtained FAMEs were of acceptable quality according to the standards (ASTM and EN). Additionally, the energy conversion from light energy to lipids was shown to be in the range of 10–16% conversion efficiency within seven days. Hence, the physiological modification of Chlorella sp. culture by phosphorus limitation coupled with the addition of a low concentration of heavy metals enabled the improvement of lipid content, with the subsequent transesterification resulting in the production of biodiesel with acceptable quality. Full article

There has been an increasing interest in studying species of the thecate dinophysoid dinoflagellates, especially the genera Dinophysis and Phalacroma, all around the world. Abundant net phytoplankton material collected from coasts of the western coast of Baja California, the central Mexican Pacific (including the Gulf of California), and the Gulf of Mexico was analyzed, and the diversity and morphology of planktonic species of dinophysoids were studied in certain detail by LM and SEM. Particular morphological characteristics, which can be critical, such as the structure of the cingulum and cingular lists, union of sulcal lists, and theca ornamentation, were observed using SEM. Seventy-five (75) taxa (73 species and two varieties) were found and identified, which belong to the following 10 genera: Amphisolenia, Citharistes, Dinofurcula, Dinophysis, Histioneis, Metaphalacroma, Ornithocercus, Oxyphysis, Phalacroma, and Pseudophalacroma. We also included the following four new records: three for the Mexican Pacific (Amphisolenia brevicauda, A. deltiana, and Phalacroma stenopterygium) and one for the Gulf of Mexico (Phalacroma ornamentatum). Descriptions, illustrations, measurements, and distribution data are provided for each species. Taxonomical remarks concerning synonymies of species of the genus Phalacroma were added. Phalacroma whittingiae (Balech) Esqueda-Lara et Hernández-Becerril nov. comb. is a new taxonomic proposal. Full article

HCBs (Harmful Cyanobacterial Blooms) are increasing in freshwaters across the globe, particularly at lower latitudes. In Southern Europe, a decrease in annual precipitation and an increase in drought periods have enhanced the occurrence of HCBs, impacting both freshwater ecosystems and human health. This review gathers information on isolated cyanobacterial strains with the potential to form cyanobacterial blooms or to be toxic that have been reported over the past half-century in Portugal. Strains of Microcystis aeruginosa are the most represented ones, many of them microcystin producers. Toxic M. aeruginosa strains have been isolated from lakes (Mira, Barrinha de Mira, and Blue), river sections (Tâmega and Guadiana), and reservoirs (Torrão, Vilar, Montargil, Patudos, Caia, Monte da Barca, Corgas, and Magos). Many other strains from potentially toxic species are listed, namely from Aphanizomenon gracile, Aphanizomenon flos-aquae, Sphaerospermopsis aphanizomenoides, Cuspidothrix issatschenkoi, Dolichospermum flos-aquae, Dolichospermum circinalis, Chrysosporum bergii, Raphidiopsis raciborskii or Planktothrix agardhii. Many of the isolated strains were able to produce cyanotoxins such as microcystins, saxitoxins, cylindrospermopsin, or anatoxin. Most isolates belong to the Portuguese culture collections ESSACC (Estela Sousa e Silva Algal Culture Collection); LEGE-CC (Blue Biotechnology and Ecotoxicology Culture Collection); and ACOI (Coimbra Collection of Algae). Despite many strains already having associated molecular data corroborating a correct identification, a large number of strains are still lacking DNA-based information for phylogenetic affiliation. The present checklist is intended to facilitate access to information regarding strains of potentially toxic cyanobacterial species from Portugal in order to contribute to a better understanding of species-specific HCBs at both regional and global scales. Full article

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