Phycology doi: 10.3390/phycology6030091

Authors: Julia Nevzorova Denis Davydov

The Murmansk Region (the Russian Arctic) faces severe environmental degradation due to heavy metal (HM) pollution from copper–nickel smelting, resulting in vast industrial barrens with elevated concentrations of copper (Cu) and nickel (Ni). Conventional phytostabilization methods are often ineffective or costly, necessitating alternative bioremediation strategies. This study evaluates the potential of microalgae and cyanobacteria for revegetating HM-contaminated substrates. Six strains of Nostoc-like morphotypes and three green microalgae were tested for Cu2+ tolerance (0.5–15 mg/L). While most strains exhibited growth inhibition at ≥3 mg/L Cu2+, Atlanticothrix sp. KPABG-154445, isolated from Tolbachik Volcano, showed positive growth at 2 mg/L Cu2+ under the tested conditions and recovering metabolic activity post-exposure. In sorption experiments, non-viable biomass achieved 68% Cu2+ removal at 2 mg/L, outperforming actively growing cultures. A microcosm experiment using copper-spiked nepheline slime (simulating mining waste) revealed Atlanticothrix sp. KPABG-154445’s ability to colonize nutrient-poor substrates, forming biocrusts covering 42% of the surface within one month, even under Cu2+ contamination (10 mg/kg). These findings highlight cyanobacteria, particularly strains such as KPABG-154445, as promising agents for the bioremediation of Arctic industrial barrens, leveraging their dual capacity for heavy metal tolerance and biocrust formation.

Phycology doi: 10.3390/phycology6030090

Authors: Ahmed H. Elaswad Maiya Al-Maawali Ahmed A. Al-Alawi Haytham Ali Huda Al-Barashdi Khalid Al-Subhi Mohamed Al-Wahaibi Michael J. Wynne

DNA barcoding is a reliable technique for seaweed identification. However, high concentrations of sulfated polysaccharides and secondary metabolites hinder the extraction of DNA templates of suitable quality. Therefore, this study assessed four DNA extraction protocols (CTAB, commercial kit, HotSHOT, and DNAzol Direct) using two red seaweed species (Laurencia dendroidea and Hypnea sp.) and two barcoding genes (18S rRNA and rbcL). The results showed significant differences (p < 0.05) in DNA yield (μg/mg), DNA purity (A260/A280), and DNA concentration (ng/μL) among protocols. A significant protocol × seaweed interaction was also observed. DNAzol and HotSHOT provided the highest overall DNA yields (2.390 ± 0.080 and 2.234 ± 0.212 μg/mg, respectively), followed by CTAB (0.123 ± 0.011 μg/mg) and the commercial kit (0.007 ± 0.001 μg/mg). The commercial kit had the highest PCR and DNA sequencing success, followed by HotSHOT, DNAzol, and CTAB. Importantly, DNA concentration and purity did not always correlate with PCR and sequencing success. Considering performance, cost, and processing time, HotSHOT appeared to be the most practical method for Laurencia and Hypnea. This study addresses an important gap in the molecular identification of red seaweeds and provides information for selecting appropriate DNA extraction methods for seaweed barcoding

Phycology doi: 10.3390/phycology6030089

Authors: Xinyan Wu Xin Li Mengya Song Jie Yu Yuanpei Jin Yunhao Wang Bo Xie

Microalgal growth-promoting bacteria (MGPBs) represent a promising strategy to enhance biomass productivity, yet the mechanistic basis of these mutualistic interactions remains poorly understood. Here, we isolated a new MGPB, Cupriavidus oxalaticus MEYA8, and characterized its mutualistic interaction with the model microalga Chlamydomonas reinhardtii. Co-cultivation at an optimal MEYA8: Chlamydomonas ratio greatly enhanced microalgal cell density and chlorophyll content, which reached 2.1-fold and 1.6-fold those of the control, respectively, with markedly improved photosynthetic efficiency across both photosystems. Transwell assays confirmed that this promotion is mediated by diffusible metabolites rather than direct cell contact. Metabolites and multi-omics analyses revealed that MEYA8 can produce compounds similar to indole-3-acetic acid (IAA) and is adapted to the microalgal phycosphere by preferentially utilizing organic acids and amino acid derivatives. In response, Chlamydomonas upregulated proteins involved in photosynthetic electron transport, energy metabolism, and nitrogen assimilation, consistent with the observed enhancement in photosynthetic performance. These findings suggest a metabolically reciprocal interaction model: MEYA8 supplies diffusible growth-promoting factors such as IAA-like compounds to enhance Chlamydomonas photosynthesis and growth, while Chlamydomonas provides organic substrates that sustain bacterial proliferation. Our work provides new insights into algal–bacterial mutualism and may provide a new microbial resource for engineering microalgal and beneficial bacterial consortia.

Phycology doi: 10.3390/phycology6030088

Authors: Máté Tibor Aszalós Milán Riba Sándor Gonda István Bácsi

Interactions between cyanobacteria and eukaryotic algae are traditionally viewed as favoring cyanobacteria, which are often the dominant competitors in freshwater ecosystems. However, increasing evidence suggests that eukaryotic algae also possess effective chemical defenses capable of suppressing cyanobacterial proliferation. In this study, the anti-cyanobacterial potential of a methanolic biomass extract of the green microalga Chlorella vulgaris against the bloom-forming cyanobacterium Microcystis aeruginosa was investigated. Optical density measurements revealed the inhibition of cyanobacterial growth, with extract concentrations of 0.4–1.6 mg mL−1 significantly reducing biomass accumulation. The lowest concentration (0.2 mg mL−1) stimulated the accumulation of phycobiliproteins, whereas concentrations of 0.8–1.6 mg mL−1 significantly decreased phycobiliprotein content, indicating progressive physiological impairment. The results suggest that the highest extract concentration applied may also cause alteration in phosphate acquisition. Lipid profiling of the Chlorella biomass showed that 97% of the extractable lipids consisted of methanol-soluble fatty acids, with C18 fatty acids predominating among the 20 identified compounds. These metabolites are reported to possess allelopathic activity and therefore represent plausible contributors to the observed inhibition. These findings support that anti-cyanobacterial activity may represent a widespread ecological trait of Chlorella and potentially other green microalgae, providing a promising foundation for environmentally friendly cyanobacterial bloom management.

Phycology doi: 10.3390/phycology6030087

Authors: Jing Liu Leshi Li Yan Yan Ming Du Jiangxin Wang

The pet food industry is undergoing a significant transformation, driven by the growing trend of companion animal humanization and increasing concerns over the environmental sustainability of conventional protein and lipid sources. Consumers now seek diets that not only meet basic nutritional requirements but also offer preventive health benefits. Microalgae, including Arthrospira (Spirulina, a kind of cyanobacterium), Chlorella, Schizochytrium, and Euglena gracilis, have emerged as versatile biological platforms capable of addressing both functional and sustainability challenges. These microorganisms produce high-quality proteins, omega-3 long-chain polyunsaturated fatty acids (particularly docosahexaenoic acid, DHA), natural pigments, and immunomodulatory polysaccharides. This review synthesizes findings from peer-reviewed studies on the application of microalgae in pet nutrition, covering dogs, cats, and aquatic companion animals. We examine how algal ingredients influence gut microbiota, for instance, by enriching beneficial genera such as Turicibacter and Peptococcus, enhance vaccine responses and mucosal immunity, support cognitive function in aging pets, and contribute to weight management. Particular attention is given to Euglena gracilis and its paramylon (β-1,3-glucan), a pathogen-associated molecular pattern that engages the Dectin-1 pathway to train innate immunity and has demonstrated antiviral activity through host defense mechanisms. The review also surveys the patent landscape, highlighting trends in palatability enhancement, hypoallergenic formulations, and novel delivery formats. Key challenges remain, including ingredient standardization, safety validation, palatability optimization, and consumer acceptance. We outline a translational roadmap that prioritizes well-designed clinical trials in target species and processing methods that preserve bioactivity. Collectively, the evidence positions microalgae, and Euglena gracilis in particular, as promising candidates for next-generation functional pet foods that deliver health benefits alongside ecological sustainability.

Phycology doi: 10.3390/phycology6030086

Authors: Hajime Haneji Shin Haneji Satoshi Managaki Brigitta I. van Tussenbroek

Using multivariate analysis in three zones of the Great Atlantic Sargassum Belt (GASB), we found close associations between the density of sargassum, dust deposition, and surface iron concentration on the sea surface during 2002–2010, before the appearance of the GASB in 2011. Combined with a statistical analysis of dust depositions during 1980–2023 in these zones, the results imply increases in each, concomitant with the behavior of the GASB in recent times, such as its appearance in 2011 in the northern tropical Atlantic and its reach in the Mexican Caribbean in 2015. Given indications that sargassum growth is limited by iron and the close association between dust deposition and iron concentration in the sea surface, we infer that the increase in dust deposition, which is generated mainly in the African Sahara and Sahel deserts, may have contributed to the sargassum growth in the GASB. Although the results of this study showed statistical significance, they remain hypothetical due to the lack of field data. Further surveys measuring chemical compositions and stable isotope rates of samples of Saharan dust, phytoplankton, and sargassum may explain the relevance of dust deposition to the development of the GASB.

Phycology doi: 10.3390/phycology6030085

Authors: Aleksandr Yakoviichuk Irina Maltseva Angelika Kochubey Svetlana Cherkashyna Ekaterina Lysova Evilina Sheludko Maxim Kulikovskiy Yevhen Maltsev Svetlana Maltseva

Microalgae represent a promising raw material for the bioeconomy and biotechnology. One of the key factors regulating their metabolism is light. However, the traditional approach to cultivation, aimed at maximising biomass productivity due to high lighting intensity, contradicts the principles of energy efficiency. In addition, the responses of soil microalgae to the spectral composition of light remain poorly understood, which creates a gap in fundamental knowledge. The Pleurastrum insigne CAMU MZ–Ch4 soil strain is a potent producer of valuable compounds. Physico-chemical and instrumental analysis, including spectrophotometric, chromatographic and gravimetric techniques, were used to determine the productive and biochemical parameters of the strain. It was shown that blue and red light with intensities of 90 and 150 µmol m−2 s−1 are optimal in absolute terms for the growth and CO2 biofixation, green light for the accumulation of pigments and antioxidants, and low-intensity red light is the most energy efficient for the synthesis of lipids and other metabolites. Based on calculations of product-specific energy intensity, it was demonstrated that the “more light = more product” strategy increases metabolite energy intensity. Maximum bioeconomic efficiency (the minimum cost of electricity to produce a unit of a metabolite) is achieved with low intensity of red and blue light.

Phycology doi: 10.3390/phycology6030084

Authors: Alonso Cartuche Ernesto Delgado-Fernández Nikolay Aguirre Roberth Yaguana Camilla Schulz Eduardo A. Lobo Ángel Benítez

Water pollution can compromise the ecological integrity of freshwater habitats, thereby exposing freshwater communities to sources of pollution such as wastewater and agricultural and industrial discharges. Diatoms are key organisms because of their role as primary producers; thus, they have been regularly used as bioindicators to assess water quality. The diatom assemblages were collected from the surface of small stones in four rivers (El Carmen, Jipiro, San Simón, and Curitroje) across three zones defined according to a land-use gradient (high, medium, and low). A total of 54 diatom species were recorded. The El Carmen stream showed the highest total richness (29 species), followed by Curitroje (21), Jipiro (19), and San Simón (11). The results revealed significant changes in diatom richness, abundance, diversity indices, trophic index (IT) and community structure associated with both stream and zone. Following a similar pattern, temperature, conductivity, TDS (total dissolved solids), and pH also strongly influenced community composition. Achnanthidium subatomus, Sellaphora lanceolata, Odontidium mesodon were indicators of the high zone and show a general preference for zones characterized by conserved riparian vegetation, fast, clear and oxygenated water. On the other hand, Gomphonema reichardtii, Rhopalodia musculus, Gomphonema clavatulum, Gomphonema subclavatum, Gomphonema variostriatum, Eunotia incisa were indicators of a low zone with heavy organic pollution, water pollution, and environmental changes in temperature, conductivity, TDS and pH.

Phycology doi: 10.3390/phycology6030083

Authors: Taif Muthanna Mohammed Hamdan

Freshwater phytoplankton communities are currently being influenced by ongoing climate change. This study aimed to investigate the effects of warming and dissolved inorganic carbon (DIC) on chlorophyll-a concentration and physicochemical variables in a freshwater ecosystem in mesocosm conditions. A 21-day experiment was conducted using freshwater collected from the Tigris River. Four treatments were established: control, warming (+3 °C), DIC, and DIC + 3 °C, with three replicates for each treatment. Chlorophyll-a, DIC, water temperature, pH, dissolved oxygen (DO), nitrate (NO3−), and phosphate (PO43−) were measured throughout the experiment. The results showed that chlorophyll-a concentration increased under warming and DIC treatments. The combined treatment (DIC + 3 °C) showed the highest chlorophyll-a concentration. Water temperature was significantly higher in the warming treatment compared to DIC treatment. In addition, pH, DO, nitrate, and phosphate varied among treatments and over time. Overall, the combined effects of warming and DIC were greater than those of the individual treatments. These findings indicate that warming and increased inorganic carbon availability may play an important role in influencing chlorophyll-a concentration, carbon cycling, nutrient dynamics, and water quality in freshwater ecosystems.

Phycology doi: 10.3390/phycology6030082

Authors: Fatima Ezzahra Kabbali Youness Kadil Se Jeong Kim Jihane Ait Benbella Hasnaa Bazhar Ikram Ghicha Fatiha Bousselham Ibtihal Segmani Afaf Banid Nor-Eddine Rezzoum Mohamed Benazzouz Imane Rahmoune Houda Filali Mi Kyeong Lee Touria Ould Bel Lahcen

Sargassum muticum is an invasive brown macroalga that has rapidly expanded along the Moroccan Atlantic coast, posing ecological challenges while representing an abundant marine biomass with potential biotechnological value. This study investigated the biochemical composition and metabolic properties of Moroccan S. muticum through compositional analysis, in vivo metabolic evaluation, and molecular docking. Proximate analysis revealed a carbohydrate-rich composition with moderate protein content, together with photosynthetic pigments and nutritionally relevant minerals. In a cafeteria diet-induced rat model, dietary supplementation with S. muticum significantly attenuated body weight gain, improved adiposity-related indices, reduced serum total cholesterol, triglycerides, LDL cholesterol, and C-reactive protein levels, and increased HDL cholesterol. To obtain mechanistic insight, molecular docking analysis was performed using representative phlorotannins reported from Sargassum species. Among the compounds evaluated, dieckol showed the highest docking scores toward key metabolic targets, including AMP-activated protein kinase and peroxisome proliferator-activated receptor gamma. Although these in silico findings do not demonstrate biological activation, they provide preliminary mechanistic support for the observed in vivo effects. Overall, the results highlight the potential of S. muticum for sustainable valorization as a functional marine bioresource.

Phycology doi: 10.3390/phycology6030081

Authors: Jian Zhou Qianqian Li

The evolution of plant cell walls was critical for land colonization, yet its genetic basis remains incompletely understood. Charophyte green algae are the closest relatives of land plants and provide key insights into the origins of cell wall biosynthesis. Here, we conducted a genome-wide analysis of the CesA/Csl superfamily in the charophyte alga Chara braunii to investigate the evolutionary origins of plant cell wall formation. Thirty genes were identified and classified into three major clades: CesA, CslA, and CslC. CesA genes were exclusively associated with primary cell wall lineages, with no homologs of secondary wall-specific CesA4/CesA7/CesA8, indicating an early origin of cellulose biosynthesis followed by later functional specialization. In contrast, Csl genes were restricted to the CslA and CslC subfamilies, suggesting that diversification of hemicellulose biosynthesis occurred after the divergence of charophytes and land plants. Expression and promoter analyses revealed clade-specific regulatory patterns and stress-responsive expression, and the quantitative RT-PCR validated that CesA, CslA, and CslC genes respond differentially to NaCl and ABA treatments, with CslA genes strongly induced by ABA and CslC genes preferentially by salt. Together, these findings are consistent with a stepwise model of cell wall evolution and suggest that C. braunii may represent an important intermediate stage in the transition to land plants.

Phycology doi: 10.3390/phycology6030080

Authors: Jonathan Deven Chandrawati Putri Wulandari Muslim Mahardika Aini Zuhra Abdul Kadir Gunawan Setia Prihandana

The global crisis of expanded polystyrene (EPS) waste and the rising demand for affordable water purification technologies necessitate the development of sustainable, high-performance filtration materials. This study reports the successful upcycling of post-consumer Styrofoam into functional nanocomposite membranes reinforced with nano-activated carbon (nAC). Fabricated via nonsolvent-induced phase separation (NIPS) with nAC concentrations ranging from 0 to 0.4 wt.%, the membranes were evaluated to determine the synergistic effects of nanoparticle loading on morphology and transport phenomena. Scanning electron microscopy (SEM) revealed a stable asymmetric architecture characterized by a dense selective skin layer and a porous support structure. The integration of nAC significantly enhanced both surface hydrophilicity and structural porosity. The 0.3 wt.% nAC loading yielded optimal results, achieving a minimum water contact angle of 70.03° and a maximum porosity of 93.17%. Consequently, hydraulic permeability reached a peak of 35.66 LMH/bar, an approximate 223% improvement over the pristine EPS baseline. Performance evaluations utilizing Spirulina platensis as a model biomass demonstrated an absolute rejection efficiency of 100% and a turbidity reduction to 0 NTU across all composite variations, confirming robust size-exclusion capabilities. These findings demonstrate that incorporating nAC effectively transforms recycled Styrofoam into a high-value, sustainable filtration medium, offering a highly efficient and low-cost solution for cyanobacteria harvesting and environmental remediation.

Phycology doi: 10.3390/phycology6030079

Authors: Paolo Bailo Chiara Carsana Maria Garreffa Stefano Tambuzzi Matteo Marchesi Paola Primignani Andrea Piccinini Riccardo Zoja Guendalina Gentile

Forensic diagnosis of drowning remains challenging because postmortem findings are often supportive rather than pathognomonic. The classical diatom test has long been used as an ancillary tool, but its interpretation remains controversial because of contamination, false positives, environmental ubiquity, and heterogeneous analytical workflows. This PRISMA-ScR scoping review mapped emerging diatom-based and adjacent aquatic biological approaches proposed beyond the classical test, with emphasis on analytical innovation, forensic applicability, and medico-legal validation. Scopus, PubMed, and Web of Science Core Collection were searched for literature published between 2014 and 2026. After deduplication and screening, 165 studies were included. The literature covered targeted molecular and environmental-biological approaches, drowning-site inference, automated image analysis and scanning electron microscopy (SEM)/automated scanning electron microscopy (Auto-SEM) workflows, quantitative and tissue-to-medium comparisons, alternative substrates, contamination assessment, and medico-legal interpretation. Most evidence consisted of controlled experimental or comparative validation studies and case-based forensic applications; no study was classified as multicenter, externally validated, or operationally mature Level 5 evidence. Emerging approaches may strengthen drowning investigations by improving detection, comparison, quantification, and workflow reproducibility. However, they should currently be regarded as adjunctive tools rather than standalone proof of drowning or precise site attribution. Harmonized protocols, standardized environmental reference sampling, explicit contamination controls, external validation, and fit-for-purpose medico-legal interpretation remain central priorities.

Phycology doi: 10.3390/phycology6030078

Authors: Thierry Tonon Artemisa Gonçalves Joelma Silva Gomes Diana Semedo Lindsay C. Stringer Leonardo D. Gomez Edita Magileviciute

Since 2011, Caribbean and West African countries have experienced the deposit of millions of tonnes of the pelagic brown seaweed sargassum. While these algal blooms are well documented in the Caribbean, less information is available on the occurrence, monitoring and composition of sargassum biomass in West Africa. Cabo Verde (CV), one of the volcanic archipelagos of the Macaronesia region, has experienced sargassum beaching events since 2022, with 2025 being the worst year so far. In this study, high quantities of biomass that were beached in December 2025 (>100 tonnes) were determined in two locations in Santiago—CV’s largest island. Additionally, samples taken in 2024 were analysed to explore the potential valorisation of pelagic sargassum in CV. Elemental composition, amino acid profiling and calculation of NPK ratio suggested that this biomass could be processed for applications towards sustainable agriculture, providing benefits for local development. However, processes would have to include low cost and efficient pre-treatment(s) to manage the content of toxic elements (arsenic, cadmium, and lead). The development of sargassum-derived products for soil amelioration and improvement of crop production could contribute to strengthening communities and empowering local women’s groups, who play key roles in Cabo Verdean agriculture and rural economy.

Phycology doi: 10.3390/phycology6030077

Authors: Zubeidat Precious Ahmed Elizabeth Abdulmalik Besna Armando Daniel Abdullahi Kusogi Abdullahi Suleiman Dauda Sadiya Awala Samuel Abraham Gana Yisa Jerry Tersoo Agee Ibrahim Yusuf Okpanachi Mathias Ahii Chia

Among cyanobacterial genera, Microcystis spp. dominate aquatic systems and form harmful algal blooms (HABs) under favorable environmental conditions, such as temperature and nitrogen availability. Numerous studies have examined the effects of these drivers on biomass accumulation and microcystins (MCs) production; however, their findings have been inconsistent, with some reporting positive, negative, or neutral correlations. To address this, we synthesized existing data using multilevel meta-analysis. A total of 143 effect sizes were extracted from 18 independent laboratory studies and used to evaluate three main relationships, (i) temperature, nitrate, and biomass; (ii) temperature, nitrate, and microcystin concentration; (iii) biomass and microcystin; while microcystin compartments (intracellular, extracellular, and total microcystin) were used as moderators to determine whether they explain variations in observed patterns. Temperature and nitrate showed positive correlations with biomass accumulation, with nitrate having a stronger effect. However, they showed a weak correlation with microcystin production, with temperature having no statistically significant effect and nitrate showing a moderate positive correlation. Biomass exhibited a consistent positive correlation with microcystin production across all studies, suggesting that it plays a significant role in toxin accumulation. Microcystin compartmentalization revealed that correlation between biomass and microcystins differed by compartment. Extracellular and total microcystin levels showed a stronger correlation with biomass than intracellular microcystin levels. The heterogeneity observed across studies suggests that microcystin production is not only influenced by environmental factors and biomass accumulation but also by differences in genetics, physiology, and toxin compartment dynamics among Microcystis species.

Phycology doi: 10.3390/phycology6030076

Authors: Ivana Trbojević Vanja Milovanović Željko Savković Olga Jakovljević Gordana Subakov Simić Miloš Mrvaljević Miloš Jović Roman Romanov

The rare charophyte species Chara corfuensis, which has an almost exclusively Mediterranean distribution, was recorded for the first time in two small waterbodies in southern Serbia, deep inland and far from the coast. Habitat characteristics were described in detail, as was the morphometry of the collected specimens, which corresponded well with literature data. In particular, reproductive structures—oospores and gyrogonites—were analyzed in detail, as the previous data on oospores was scarce and none existed for gyrogonites. The genetic profile of the Serbian specimens was determined based on DNA barcoding of the matK and rbcL plastid genes, confirming their taxonomic identity and showing close evolutionary relationships with most species of the subsection Hartmania.

Phycology doi: 10.3390/phycology6030075

Authors: Wanida Pan-utai Naraporn Phomkaivon Thidarat Pantoa Hataichanok Kantrong Prapat Kosawatpat Sarn Settachaimongkon

The red macroalga Halymenia durvillei is a cultivated tropical biomass with potential for aqueous recovery of phycoerythrin (PE)-containing fractions. This study investigated the effects of biomass-to-solvent ratio, extraction temperature, extraction time, and extraction cycle on PE concentration, PE extraction yield, PE purity index, soluble protein yield, phenolic- and flavonoid-equivalent responses, and antioxidant capacity in crude aqueous extracts from sun-dried H. durvillei. Aqueous phosphate-buffered extraction was evaluated at 1:25 and 1:50 w/v, −20 to 35 °C, and 24–48 h, under one or two extraction cycles. The condition 1:25 w/v, 35 °C, 48 h, cycle 1 was the most favorable for PE concentration, PE extraction yield, PE purity index, and soluble protein yield, indicating enhanced recovery of PE-containing proteinaceous fractions from the dried algal matrix. By contrast, selected 1:50 w/v conditions enhanced total phenolic and flavonoid-equivalent and antioxidant responses. These findings show that PE recovery and antioxidant-associated co-extractives followed different extraction response patterns and were not co-optimized under the same condition. The extracts should be regarded as crude PE-containing aqueous proteinaceous fractions, with further purification and compound-level characterization required before specific pigment-grade or functional ingredient applications.

Phycology doi: 10.3390/phycology6030074

Authors: Mauricio J. Machado Fernanda R. Jacinavicius Rafael B. Dextro Anderson M. T. Feitosa Lucas S. Silva Francisco A. S. Alves Ernani Pinto Marli F. Fiore Maria Paula C. Schneider

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.

Phycology doi: 10.3390/phycology6030073

Authors: Patrícia Mrázek Sinéad Collins

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.

Phycology doi: 10.3390/phycology6030072

Authors: Sota Minamiguchi Takeaki Hanyuda Yuta Jozawa Natsu Maeda Hiroyuki Mizuta Toshiki Uji Shingo Akita

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.

Phycology doi: 10.3390/phycology6030071

Authors: Bradley Krzysiak Rachael M. Morgan-Kiss

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.

Phycology doi: 10.3390/phycology6030070

Authors: Renata Nolasco Braga-Souto Anna Rafaela Cavalcante Braga

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.

Phycology doi: 10.3390/phycology6030069

Authors: Tatiana Pankeeva Nataliya Mironova Aleksandra Nikiforova Vladimir Tabunshchik

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.

Phycology doi: 10.3390/phycology6030068

Authors: Daniel Kurpan Alexandra Baumeyer Brahier

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.

Phycology doi: 10.3390/phycology6020067

Authors: Oana Alina Marin Florin Timofte Olivier De Clerck

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.

Phycology doi: 10.3390/phycology6020066

Authors: Michael Schagerl Astrid Harjung Nikola Krlovic Victor Aigner

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.

Phycology doi: 10.3390/phycology6020065

Authors: Vasco C. Mota Alyssa L. Bolcan Imen Hamed Tor H. Evensen Philip James

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.

Phycology doi: 10.3390/phycology6020064

Authors: Jingyi Wei Hua Li Xiaoyu Guo Yunzhu Wang Chunxiang Hu

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.

Phycology doi: 10.3390/phycology6020063

Authors: Geraldo Filipe Nhapulo Catarina Prista Maria Cristiana Nunes Isabel Sousa

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.

Phycology doi: 10.3390/phycology6020062

Authors: Yixin Yan Wanchuan Xing Yaming Ge Xiaoling Zhang Ye Chen Junzhi Liu

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.

Phycology doi: 10.3390/phycology6020061

Authors: Priscila Vázquez-García Héctor Arturo Peniche Pavía Julio Enrique Oney-Montalvo Rosa Yazmin Us-Camas William Santiago González-Gómez Luis Alberto Rosado-Espinosa Emanuel Hernández-Núñez

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.

Phycology doi: 10.3390/phycology6020060

Authors: Janeth I. Galarza Jimmy Villón Claudio A. Álvarez Bryan Pillacela María Soledad Romero Macarena Mellado Alexis Hernández-Pérez Rosario Díaz Gonzalo Álvarez

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.

Phycology doi: 10.3390/phycology6020059

Authors: Débora Tomazi Pereira Julia Vega José Bonomi Barufi Nathalie Korbee Félix L. Figueroa

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.

Phycology doi: 10.3390/phycology6020058

Authors: Slađana Popović Željko Savković Miloš Stupar Olga Jakovljević

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.

Phycology doi: 10.3390/phycology6020057

Authors: Safiya Al Shmali Razan Zadjali Khalid Al Hashimi Maha Al Khalili Syed Ariful Haque Nasser Al Habsi

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.

Phycology doi: 10.3390/phycology6020056

Authors: Anuj Kumar Tomer Sonam Sonam Nidhi Pareek Shaubhik Anand Prashant Singh Dale A. Casamatta Pawan K. Dadheech

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.

Phycology doi: 10.3390/phycology6020055

Authors: Miguel F. Romero-Gutiérrez Bernardo Águila Ricardo Miranda-González Ana E. Escalante Roberto Garibay-Orijel

Soil algae are important photoautotrophs, yet drivers of their diversity in peri-urban landscapes and across soil horizons remain poorly resolved. We used ITS2 metabarcoding to profile eukaryotic algal and fungal communities in 34 samples from Mexico City’s peri-urban conservation soils. Samples represented three Soil Systems: agricultural mineral soil, forest mineral soil, and forest litter, collected in two boroughs (Xochimilco and Tlalpan). We inferred amplicon sequence variants (ASVs), then alpha diversity and Bray–Curtis turnover were analyzed against edaphic and stoichiometric variables using random forests and PERMANOVA, and compared algal with fungal turnover. We recovered 662 algal ASVs spanning eight classes dominated by Trebouxiophyceae and Chlorophyceae. Litter was the richest and most distinct compartment with a high prevalence and abundance of lichen-associated taxa, whereas mineral soils were dominated by Chlorophyceae. Random forests ranked N/P ratio as the top predictor of both diversity indices. PERMANOVA indicated that the Soil System explained the largest single fraction of turnover. Algal and fungal turnover were positively correlated in mineral soils. Together, soil management practices, vertical compartmentalization and measured edaphic gradients were associated with community differences. These results point to potential algal management practices that could enhance peri-urban soil conservation and agroecological productivity.

Phycology doi: 10.3390/phycology6020054

Authors: Tabitha J. Carr Maureen E. Wakefield Gary S. Caldwell

Augmenting aquaculture feeds with black soldier fly (Hermetia illucens L.) larvae is an emerging solution to the industry’s fishmeal and fish oil dependence. However, the larva’s nutritional plasticity often results in bioaccumulation of metals from the rearing substrates. Larvae can be nutritionally enriched with microalgae, but research investigating growth impacts and metals uptake are lacking. In this study, a Stichococcaceae algae strain that is used to phycoremediate effluent from commercial anaerobic digesters was investigated as a rearing substrate. Larvae were reared on chicken feed enriched with stepped ratios of algae and spent coffee grounds (a reference waste feed). Growth, survival and metals content (ICP-OES) were recorded when 10% of larvae were prepupal. Survival was >98.5% across all treatments with a trend of increased growth with microalgal inclusion, and no significant impact of metals on growth. Metals uptake as determined by a bioaccumulation factor was significantly lower in the highest algae treatment compared to the coffee-only treatment. Larvae consistently accumulated cadmium and lead whereas arsenic bioaccumulation was only observed in three treatments. Cadmium had the highest bioaccumulation factor (up to 4.06) and arsenic the lowest (down to 0.41). Larvae did not exceed current European Union maximum metal ions levels for inclusion into aquafeeds. These findings highlight the potential of using Stichococcaceae to enrich black soldier fly larvae, offering a dual sustainable solution for wastewater remediation and aquaculture feed provision.

Phycology doi: 10.3390/phycology6020053

Authors: Ana Milićević Olga Jakovljević Željko Savković Vanja Milovanović Vesna Karadžić Marija Pećić Slađana Popović

Thermomineral springs provide stable thermal and geochemical regimes that promote the development of dense phototrophic biofilms dominated by cyanobacteria. Phototrophic communities were investigated across eight thermomineral springs in Serbia (six in eastern and two in central Serbia) using an integrated morphological, ecological, and molecular approach. Biofilms were sampled in 2024 from contrasting microhabitats (submerged, overflow, and splash/aerosol-exposed zones) and biomass was assessed through chlorophyll a (Chl a) quantification. Cyanobacterial taxa were identified via light microscopy using standard taxonomic keys and simple trichal morphotypes represented the highest diversity; Leptolyngbya showed the broadest distribution, while heterocytous taxa (Calothrix) were rare. A total of 73 cyanobacterial taxa were recorded across the eight investigated springs, with richness ranging from 1 to 33 taxa per locality; the highest richness was observed in Brestovac (33 taxa), followed by Šarbanovac (28) and Nikoličevo (22). Molecular characterization (16S rRNA) of nine cultured isolates revealed multiple filamentous cyanobacterial lineages, including Elainella (Oculatellales) and Wilmottia-related clades, while several isolates showed “Leptolyngbya-like” BLASTn affinities but phylogenetically separated clustering. Overall, the results indicate that Serbian thermomineral springs host diverse cyanobacteria-dominated biofilms shaped by local physical and chemical gradients and microhabitat structure and represent promising reservoirs of thermotolerant strains for further biotechnological use.

Phycology doi: 10.3390/phycology6020052

Authors: Mixue Jiang Man Chen Kai Chen Hongxia Wang Tianli Li Xiaonan Zhang Lirong Song Denis V. Tikhonenkov Yingchun Gong

Poterioochromonas is a typical mixotrophic chrysophyte that plays an important ecological role in natural aquatic environments and has received particular attention from morphological and ecological perspectives over the last few decades because of its peculiar mode of feeding and relevance for practical applications. However, the taxonomic classification of this genus remains controversial, and the true extent of its diversity remains largely unknown. Here, we use a complementary approach of culturing, morphological and phylogenetic analyses, and sequence database mining to address this issue. We collected 16 cultures of Poterioochromonas to determine the essential morphological characteristics and clarify the taxonomy and phylogeny of the genus. Our results confirmed that all Poterioochromonas strains produce lorica, which is the diagnostic character for the genus. We suggest that the shape of the lorica cup and the morphology of the cyst could be used as diagnostic characteristics to differentiate different species within the genus. Molecular phylogenetic analysis based on the SSU rDNA and rbcL gene sequences confirmed the monophyly of Poterioochromonas, which is subdivided into heterotrophic and mixotrophic clades. Comparative analysis of six molecular markers revealed that the COI gene is the most sensitive for distinguishing both inter- and intraspecific relationships. An exhaustive screening of the NCBI GenBank database and publicly available amplicon sequencing datasets revealed 100 SSU rDNA gene sequences for Poterioochromonas. The results showed that many soil-derived environmental sequences grouped with heterotrophic Poterioochromonas and indicated that the heterotrophic representatives of the genus are abundant in the soil environment. The results also revealed that many environmental sequences did not group with any reference sequences of known species, indicating that the genus Poterioochromonas is much more diverse than previously thought. This study contributes to a clearer taxonomic and distributional framework for Poterioochromonas, thereby facilitating future basic and applied research on this genus and similar mixotrophic chrysophytes.

Phycology doi: 10.3390/phycology6020051

Authors: Subhasini Sahoo Debajyoti Saha Pallavi Saxena Anupam Kundu Sasmita Das Maheswari Behera Ruchi Pathania Lakshmi Singh

Plant pathogens can result in massive crop destruction globally, thereby increasing starvation, while conventional or synthetic pesticides are harmful to the environment and human health. The urgent need for sustainable and eco-friendly disease management strategies has driven interest in natural biocontrol agents. Ulva sp. produce a sulfated polysaccharide named ulvan, which serves as a multifunctional biostimulant with pronounced antibacterial, antiviral, and antifungal properties against a broad spectrum of phytopathogens. Its complex anionic structure plays a dual role by directly inhibiting pathogen growth through cell membrane disruption and biofilm suppression, while simultaneously inducing plant defense mechanisms through reactive oxygen species (ROS) signaling and activation of pathogenesis-related (PR) proteins. Recent advances in ulvan extraction, purification, structural analysis, and inhibitory mechanisms of phytopathogens are discussed in this review. Furthermore, the biodegradability and biocompatibility of ulvan highlight its potential applications beyond agriculture, including biomedical and sustainable biomaterial development. By comprehensively analyzing the bioactivity spectrum and mechanistic pathways of ulvan, this review proposes strategic approaches for integrating ulvan into environmentally friendly plant disease management systems, supporting its role in advancing a circular bioeconomy.

Phycology doi: 10.3390/phycology6020050

Authors: Domenico Prisa Aristidis Matsoukis Aftab Jamal Damiano Spagnuolo Lorenzo Maria Ruggeri

Algae rarely occur as solitary phototrophs in nature or engineering; instead, they are embedded in complex bacterial consortia that control their physiology, productivity and ecological performance. The phycosphere, a microscale niche rich in algal exudates, promotes extensive metabolic exchange and chemical signaling, defining these associations. Bacteria capitalize on the dissolved organic carbon released by algae, providing growth supporting molecules such as vitamins, trace metals, and siderophores, as well as regenerated inorganic nutrients. Bidirectional beneficial interactions range from obligate mutualism to facultative commensalism and antagonism, depending on environmental context and community membership. Bacterial partners can stimulate algal growth, morphogenesis, and stress tolerance, as well as modulating defense and programmed cell death during the decline and bloom succession of algae resulting from algicidal taxa. Metabolic cooperation, QS signaling, extracellular enzyme activity, and chemically induced gene expression produce the exometabolome in the phycosphere, which in turn reprograms gene expression in all partners. Recent advances in multi-omics toolboxes, single-cell isotopic analyses, and microfluidics have greatly enhanced our understanding of the functional and spatiotemporal orientation of algal microbiomes. Ecologically, algal–bacterial interactions manage the phytoplankton community structure, control HABs, and modulate carbon and nutrient fluxes in both marine and freshwater realms. Biotechnologically, engineered algal–bacterial consortia are a promising tool for enhancing biomass production, stabilizing large-scale cultivation, improving wastewater treatment, and upgrading biofuels and fine chemicals. Despite these notable research advances, the context- and species-dependent complexity of multispecies interactions remains a major obstacle to their practical modeling and scalable implementation. Integrative research frameworks that combine molecular, ecological, and bioengineering approaches are urgently needed to unlock the full potential of sustainable applications in the future.

Phycology doi: 10.3390/phycology6020049

Authors: Paulina Montserrat Serrano-Espinosa Angel Valdez-Ortiz Manuel García-Ulloa Aracely Evangelina Chávez-Piña José P. Tejeda-Miramontes Hervey Rodríguez-González

Aquafeed formulations often rely on lipid sources that supply n-3 fatty acids but are vulnerable to oxidation, highlighting the need for ingredients that clarify how n-3 delivery and oxidative stability interact. Biomass from Dunaliella tertiolecta and Tetraselmis chuii were chemically characterized to examine this relationship using fatty acid profiles, lipid quality indices, and antioxidant activity. Dunaliella contained α-linolenic acid as its main n-3 fatty acid (27.19% of total FA), whereas Tetraselmis contained eicosapentaenoic acid (5.94%) and minor docosahexaenoic acid (0.77%). These differences produced distinct peroxidizability index values: 82.5 in Dunaliella and 101.4 in Tetraselmis, reflecting the contrasting susceptibilities of their lipid fractions to oxidation. Antioxidant measurements also diverged; Dunaliella showed higher reducing activity (FRAP: 200.33 mg TE g−1 db), while Tetraselmis exhibited greater DPPH activity (69.62 mg TE g−1 db) and flavonoid content (25.73 mg EEPC g−1 db). The combination of high EPA with higher PI in Tetraselmis and lower PI with stronger reducing capacity in Dunaliella highlights the conditions under which each biomass may influence n-3 availability and oxidative stability in formulated feeds. These results establish a functional decision framework for selecting and combining microalgal ingredients based on trade-offs between HUFA delivery and oxidative stability in aquafeed formulation.

Phycology doi: 10.3390/phycology6020048

Authors: Trinidad de Evan Carlos Navarro Marcos Eduarda Molina-Alcaide Margarita Novoa-Garrido Ying Yen Julia E. Fernández-Yepes María Dolores Carro

Brown seaweed Alaria esculenta has potential as a sustainable feed for ruminants, but it deteriorates quickly after harvesting. This study evaluated silage as a preservation method and analyzed its effects on nutritive value and anti-methanogenic properties. Four treatments were tested: no additive, formic acid, lactic acid bacteria (LAB), and pre-wilting at 30% dry matter plus LAB (PLAB). Chemical composition and in vitro fermentation using sheep rumen fluid were analyzed. Ensiling reduced fiber components and polyphenols but did not affect gross energy, and increased gas production and total volatile fatty acids, indicating improved fermentability, especially in PLAB treatment. However, overall nutritive value remained lower than that of alfalfa hay and concentrate. Methane production increased after ensiling due to higher fermentation levels. Despite this, the methane-to-VFA ratio in all the seaweed samples was about one-third of that of conventional feeds, indicating anti-methanogenic properties. No differences in this ratio were found between fresh and ensiled seaweed, indicating that these anti-methanogenic properties were preserved. Overall, ensiling is a viable method to stabilize A. esculenta, improving its fermentability and maintaining its capacity to reduce methane emissions, although its nutritional value remains relatively low compared to traditional ruminant feeds.

Phycology doi: 10.3390/phycology6020047

Authors: Kemal Salam Ramadhan Budi Arifvianto Muslim Mahardika Ario Sunar Baskoro Norihisa Miki Tutik Sriani Gunawan Setia Prihandana

The rapid proliferation of microalgae in aquatic systems poses significant environmental and public health challenges, particularly in regions lacking adequate water treatment facilities. This study reports a sustainable approach for microalgae removal through the development of low-cost membranes derived from expanded polystyrene (EPS) waste and modified with polyethylene glycol (PEG) as a pore-forming agent. Membranes were fabricated via non-solvent-induced phase separation with PEG loadings of 0–20 wt.% and characterized in terms of morphology, porosity, wettability, and hydraulic performance. Filtration efficiency was evaluated using Spirulina platensis as a model microalga. Incorporation of PEG (up to 15 wt.%) enhanced membrane porosity (77–84%), improved hydrophilicity (water contact angle reduced from 68° to 48°), and increased water flux (10.98–39.2 L·m−2·h−1), while maintaining complete microalgal rejection (100%). Optimized membranes exhibited asymmetric finger-like structures, contributing to improved permeability.

Phycology doi: 10.3390/phycology6020046

Authors: German L. López-Barrera Janet B. García-Martínez René Yepes-Callejas

This study integrates a Systematic Literature Review (PRISMA 2020) with a bibliometric analysis to examine how global research on microalgae biotechnology has incorporated innovation management, technology transfer, and dynamic capabilities. A total of 418 records were retrieved from Scopus and Web of Science for the period 2015–2025, of which 133 studies met the inclusion criteria after deduplication and screening based on an adapted PICO framework. Bibliometric indicators were generated using Bibliometrix (R) and VOSviewer (version 1.6.20) to identify publication trends, leading countries, collaboration networks, and thematic structures. The results suggest a progressive shift from predominantly techno-biological research toward approaches that emphasize technology maturity, innovation processes, and organizational capabilities. Three main analytical outcomes were identified: (i) studies addressing dynamic capabilities related to organizational learning and strategic reconfiguration (14.1%); (ii) research focused on technology readiness levels (TRL) and technology adoption, reflecting the transition from laboratory-scale research to pilot and industrial implementation (22.9%); and (iii) analyses of innovation ecosystems highlighting university–industry collaboration, governance mechanisms, and bioeconomy-oriented policies (17.7%). Nevertheless, approximately 22% of the literature remains exclusively technical, indicating a persistent disciplinary bias. By integrating innovation management, technology transfer, and dynamic capabilities as complementary analytical lenses, this review develops a comprehensive framework for understanding how microalgae biotechnology contributes to the consolidation of sustainable bioeconomy-oriented innovation ecosystems. The findings underscore the potential of technology governance and TRL-based management to bridge the gap between scientific research and industrial deployment.

Phycology doi: 10.3390/phycology6020045

Authors: Albaris B. Tahiluddin Aldimar S. Bara Adzhar M. Abduhasad Nurizna T. Jumaide

Seaweed cultivation is a primary economic driver in Tawi-Tawi, Philippines, yet the industry faces significant challenges regarding the physiological integrity of propagules during inter-island transit. This study evaluated the effects of varying transportation durations (0, 12, 24, 36, and 48 h) on the specific growth rate (SGR), occurrence of ice-ice disease, and dry biomass yield of Kappaphycus striatus over a 30-day cultivation period using a modified fixed-off-bottom method. The results demonstrated that transportation duration significantly influenced SGR at Day 10 and Day 30 (p < 0.05), whereas no significant differences were observed at Day 20. The control group (0 h transport) exhibited the highest growth performance (4.61 ± 0.18% day−1 at Day 10), whereas the lowest growth was recorded in the 48 h treatment group at Day 30 (0.93 ± 0.49% day−1). Pathological assessment indicated that ice-ice disease occurrence was highly significant during the initial recovery phase (Days 1–7) and at Day 20 (p < 0.05). Specifically, propagules subjected to 48 h transport reached 100% disease incidence within the first four days post-transplant, while the 36 h group reached 96.67%, highlighting acute transport-induced stress. Although the 48 h group exhibited significantly higher initial ice-ice spot counts (p < 0.05), statistical differences diminished between Day 10 and Day 30, suggesting a degree of physiological resilience and recovery capacity. Ultimately, prolonged transportation exceeding 24 h induced severe dehydration stress, resulting in a 62.7% reduction in SGR by Day 30 compared to the control. These findings suggest that seedling transport should be optimized within a 24 h window to preserve thallus vigor and maximize sustainable yields. Future research should investigate post-transport recovery protocols to mitigate the effects of unavoidable shipping delays.

Phycology doi: 10.3390/phycology6020044

Authors: Thiago Holanda Basilio Bianca Rodrigues Ramalhete Nunes Angélica Neto Daisa Hakbart Bonemann Danielle Tapia Bueno Mutue T. Fujii Iago Alonso Ana Teresa Lima Weber Adão Rodrigues Junior Eduardo Schiettini Costa Renato Rodrigues Neto

Seaweeds are photosynthetic organisms with ecological, social, and economic significance, and they serve as effective bioindicators in marine ecosystems. This study assessed trace element concentrations in beach-cast seaweeds collected from four beaches along the Espírito Santo coast in southeastern Brazil—an area impacted by mining-related contamination. Samples of Zonaria tournefortii (J.V. Lamouroux) Montagne and Sargassum natans (Linnaeus) Gaillon, gathered during low tide (July–August 2022), were analyzed for 15 elements. Statistical analysis using the Kruskal–Wallis test revealed significant interspecific differences in the accumulation of several metals. Aluminum (Al), iron (Fe), and magnesium (Mg) were the most abundant (>100 mg/kg), while minor elements (<100 mg/kg) included barium (Ba), arsenic (As), zinc (Zn), vanadium (V), nickel (Ni), chromium (Cr), copper (Cu), lead (Pb), cobalt (Co), cadmium (Cd), silver (Ag), and mercury (Hg). Elemental profiles exceeded those reported in other global regions and closely resembled iron ore tailings. Most elements had relatively higher concentrations on the beaches of Imigrantes, in the north of the state. These findings are the first for beach-cast seaweeds in this region, suggesting that this contamination indicates the legacy of the mining industry from southeastern Brazil.

Phycology doi: 10.3390/phycology6020043

Authors: Moin Uddin Abu Sadeque Md. Selim Uttam Kumar Roy Khatun-A-Jannat Esha Sabrina Zaman Seema Shamsun Nahar Tamanna Mst. Umme Habiba Md. Mozammel Haque S. A. Masudul Hoque Kasim Sakran Abass Md. Morshedur Rahman

Ruminants significantly contribute to global methane (CH4) emissions, necessitating the development of dietary mitigation strategies. This study evaluated five Bangladeshi seaweeds (brown, red, and green types) from Saint Martin Island for their anti-methanogenic potential through phenotypic identification, proximate analysis, and in vitro fermentation assessment. Significant interspecies variation was (p < 0.001) observed in dry matter (DM: 82.1–99.9%), acid detergent fiber (ADF: 17.4–24.9%), neutral detergent fiber (NDF: 29.6–43.6%), and dry matter degradability (DMD: 43.9–58.7%), while crude protein (CP) remained consistent (p = 0.574). After 48 h of fermentation, total gas (1.3–22.1 mL/g DM) and CH4 yield (0.04–1.6 mL/g DM) varied markedly (p < 0.01). DMD was strongly correlated with total gas and CH4 production. Crucially, both ADF and NDF showed a positive correlation with total gas and CH4 production. However, NDF displayed a weak positive correlation with DMD. These findings suggest atypical fiber fraction dynamics, contrasting with terrestrial forages. Supplementation effects of two red seaweeds, SW-4 (Gracilaria parvispora) and SW-5 (Asparagopsis taxiformis), on Napier grass were assessed at 5% and 10% inclusion levels. SW-5 reduced CH4 by 52.7% when co-fermented with Napier grass at a 10% inclusion level for 48 h, whereas SW-4 showed no significant effect. These results highlight SW-5 as a promising dietary supplement to reduce enteric CH4 in ruminants, suggesting further in vivo validation for optimal use.

Phycology doi: 10.3390/phycology6020042

Authors: Aleksandr Popik Sergei Voznesenskii Andrei Leonov Anton Zinov Tatiana Orlova

Harmful algal blooms (HABs) pose a serious threat to public health, aquaculture, and coastal ecosystems, making the development of tools for their rapid and specific detection a high priority. Laser-induced fluorescence (LIF) spectroscopy enables the assessment of characteristic photosynthetic pigments, offering a pathway to automated, high-throughput monitoring systems. Here, we investigate the temperature dependency of LIF spectra in the range of 20–80 °C to establish stable fluorescence fingerprints for the harmful microalgae Alexandrium catenella. Critically, we demonstrate that the relationship between temperature and both fluorescence intensity and spectral position remains consistent over 35 days of cultivation, independent of culture age. We performed complementary flow cytometric and pigment analyses (HPLC) to characterize the culture’s physiological state. Over the 35-day period, cell concentration increased 20-fold, while cell size, granularity, and fluorescence spectra remained stable. A transient decrease in fluorescence intensity observed on day 10 coincided with a drop in peridinin concentration, confirming the link between the spectral signal and pigment composition. Obtained results validate the use of this fluorescence fingerprint for the reliable identification of A. catenella without prior knowledge of the culture’s age—a key advantage for field applications. Furthermore, these fingerprints remained clearly distinguishable even when the culture was diluted with seawater to just 3% of its original volume, underscoring the potential sensitivity of this approach for early warning systems.

Phycology doi: 10.3390/phycology6020041

Authors: Aleksandra B. Rakonjac Tijana Z. Veličković Kristina A. Markeljić Nevena B. Đorđević Snežana B. Simić

Bodanella lauterborni W.M. Zimmermann and Heribaudiella fluviatilis (Areschoug) Svedelius are members of brown algae (Phaeophyceae) that exclusively inhabit freshwater habitats. Heribaudiella fluviatilis is the most frequently reported freshwater brown alga, widely distributed in the Northern Hemisphere. In contrast, B. lauterborni, one of the rarest algae globally, has been reported in only four glacial Alpine lakes and has not been observed in nature for nearly 50 years. Since 2019, the species has been considered locally extinct at its type locality, and its presence in the other three lakes is also questionable. Here, we report the occurrence of B. lauterborni in three springs on the Vlasina Plateau (Southeast Serbia), being the first finding of the species in Southeast Europe and the fifth discovery globally in environmental conditions not previously described for the species. We also provide detailed data on the morphology, ecology, and biogeography of B. lauterborni and H. fluviatilis. Additionally, we report the non-obligate association Hildenbrandio rivularis-Heribaudielletum fluviatilis discovered in two rivers. Our findings significantly expand the known ecological and geographical range of phaeophytes, highlighting Southeast Europe as a refugium for freshwater Phaeophyceae biodiversity.

Phycology doi: 10.3390/phycology6020040

Authors: Katerina Mladenova Tsvetelina Batsalova Dzhemal Moten Balik Dzhambazov Detelina Belkinova Ivanka Teneva

Different cyanobacterial species have been shown to be a valuable source of biologically active compounds with immunomodulatory activity. To date, little is known about members of the genus Tolypothrix (Cyanophyceae). Therefore, the present study focuses on five Tolypothrix strains (T. tenuis PACC 5497, T. tenuis PACC 8648, T. distorta SAG 1482-2, T. distorta CCALA 194, Tolypothrix sp. PACC 5501) that were not previously evaluated for specific morphological characteristics and immunomodulatory potential toward human immune cells. Cyanobacterial cultures were studied by light and transmission electron microscopy (TEM). Peripheral blood leukocytes were isolated from patients with inflammatory conditions and treated ex vivo with Tolypothrix non-polar extract fractions. Following treatment, the cells were analyzed by flow cytometry, and cytokine concentrations in culture supernatants were quantified by ELISA. Light microscopy observations showed that the cultures established from four of the strains have morphological features that correspond to T. tenuis Kützing (1843) ex Bornet et Flahault 1887 and T. distorta Kützing (1843) ex Bornet et Flahault. TEM analyses indicated parietal arrangement of cellular thylakoids in all strains, but T. distorta CCALA194 and Tolypothrix sp. PACC 5501 also displayed fascicular thylakoid arrangement. Immunophenotypic analyses revealed significantly increased proportions of T, NK, and B lymphocytes in leukocyte cultures treated with Tolypothrix extracts compared to the untreated controls. The concentrations of proinflammatory cytokines were lower in the culture medium of treated cells, while levels of the anti-inflammatory cytokine interleukin-10 remained stable, except in cultures treated with T. distorta SAG 1482-2 extract. The present study provides the detailed morphological characteristics of five strains of the genus Tolypothrix and indicate that non-polar extract fractions derived from the strains exert immunomodulatory effects on human leukocytes.

Phycology doi: 10.3390/phycology6020039

Authors: Aly Castillo María Celeiro Marta Lores Kristina Perišić Krunoslav Aladić Stela Jokić

The present study provides an exhaustive exploration of twelve macroalgal species from the Adriatic Sea, including seven brown algae (Ericaria amentacea, Fucus virsoides, Cutleria multifida, Cystoseira compressa, Cystoseira corniculata, Gongolaria barbata and Padina pavonica), three green algae (Codium adhaerens, Codium vermilara and Ulva lactuca), and two red algae (Scinaia furcellata and Asparagopsis taxiformis). Matrix solid-phase dispersion (MSPD) was applied as the extraction technique, using generally recognized as safe (GRAS) solvents. The bioactive profile of the extracts was assessed through the quantification of total phenolic content (TPC) and antioxidant activity. Among the three phyla, U. lactuca, F. virsoides and S. furcellata exhibited the highest TPC (0.8, 26 and 3.0 mgGAE·g−1) and antioxidant activity (1.9, 38 and 7.5 mgTE·g−1), respectively. Targeted HPLC-MS/MS analysis enabled the identification of nineteen phenolic compounds across all taxa. Chlorophyta showed a characteristic profile enriched in coumarins, benzaldehydes and flavanones, including the selective detection of 7-hydroxycoumarin in species with higher antioxidant potential. Additionally, compounds such as chlorogenic, rosmarinic and caffeic acids exhibited taxon-specific distributions that may explain differences in antioxidant activity. Complementary untargeted ultra-high performance liquid chromatography quadrupole time-of-flight (UHPLC-QToF) metabolomics analysis provided broader coverage, revealing eighty metabolites spanning phenolics, sugars, organic acids, lipids, amino acids and their derivatives. Notably, the proposed detection of fatty acid esters of hydroxy fatty acids (FAHFAs) represents the first report of these compounds in macroalgae, alongside a pronounced presence of sulphated phenolics. Overall, these findings provide a robust baseline on the bioactivity and chemical composition of Adriatic macroalgae, highlighting their value as a natural source of functional compounds.

Phycology doi: 10.3390/phycology6020038

Authors: Nataliya Mironova Tatiana Pankeeva Aleksandra Nikiforova Vladimir Tabunshchik

A comparative analysis of the long-term dynamics of phytobenthos on the Black Sea coast from 1964 to 2020 has been conducted. The aim of the work was to assess changes in species composition, quantittive characteristics, and distribution of bottom vegetation under the influence of natural and anthropogenic factors. The research was carried out at three transects using standard hydrobotanical methods and analysis of climatic data. The results revealed significant structural reorganization of the communities: a decrease in the proportion of key brown algae (Ericaria crinita and Gongolaria barbata) by the middle of the observation period with partial recovery by 2020, an overall increase in biomass and species diversity, and increased role of epiphytes and green algae. An expansion of the depth range of the phytal zone and an increase in the presence of the deep-water species Phyllophora crispa were established. The main drivers of the transformation are increased anthropogenic pressure and climate change, which aligns with global trends. The obtained data are important for developing measures to preserve coastal ecosystems and can be used in monitoring the ecological state of the aquatic area. A promising direction for further research is the quantitative assessment of the role of the macrophytobenthos in this area in carbon sequestration.

Phycology doi: 10.3390/phycology6020037

Authors: José António Mestre Prates Mohamed Ezzaitouni Tarik Chileh-Chelh Rosalía López-Ruiz José Luis Guil-Guerrero

Macroalgae are increasingly recognised as promising sources of bioactive compounds with nutritional and functional relevance. This study investigated the biochemical composition of selected green, brown, and red marine macroalgae from the Mediterranean coast sampled at different seasons, focusing on fatty acid profiles, carotenoid composition, phenolic and flavonoid contents, antioxidant activity, and multivariate biochemical structuring. Fatty acid distributions were determined by Gas Chromatography (GC)-Flame Ionisation detector (FID), carotenoids were quantified and profiled by Liquid Chromatography–Mass Spectrometry (LC-MS), and total phenolic content, total flavonoid content, and antioxidant capacity (ABTS•+ and DPPH• methods) were assessed using standard spectrophotometric assays. Principal component analysis was applied to evaluate relationships among biochemical variables and taxonomic patterns. Brown macroalgae tended to exhibit more complex and enriched biochemical profiles, containing high proportions of long-chain n-3 polyunsaturated fatty acids, particularly eicosapentaenoic acid, elevated total carotenoid contents dominated by fucoxanthin, the highest total phenolic and flavonoid contents, and antioxidant activities. Green macroalgae were characterised by fatty acid profiles rich in saturated and C18 polyunsaturated fatty acids, while carotenoid compositions were dominated by lutein and siphonoxanthin. Red macroalgae exhibited comparatively simpler lipid and pigment patterns, characterised by palmitic acid and zeaxanthin as dominant components and lower total carotenoid levels. Principal component analysis revealed taxonomic structuring, with brown algae clearly separated from green and red groups, while seasonal differences were minor. Antioxidant activity closely clustered with carotenoids and total phenolic content, suggesting their combined contribution to radical-scavenging capacity. Overall, brown species appear as promising candidates for functional foods and nutraceutical applications.

Phycology doi: 10.3390/phycology6020036

Authors: Nataly Quiroz-González Luis Gabriel Aguilar-Estrada Ma. Guadalupe Rivas-Acuña Heidi Arleth Pérez-Ávalos Oscar Ochoa-Rodríguez Luz Elena Mateo-Cid Catalina Mendoza-González Hilda P. León-Tejera

Phycological knowledge in Mexico has primarily focused on intertidal zones, coral reefs, and, to a much lesser extent, mangroves. In mangroves, there are isolated studies on various areas of the country, and in many cases, references are made to the macroalgae that grow in association with them, incidentally as part of floristic inventories for a given area. Therefore, the present study aimed to compile existing information on macroalgae associated with mangrove roots in seven ecoregions throughout Mexico. The search was integrative using Google Scholar, Scopus, and Web of Science with different keywords; only records of algae growing on mangrove roots were considered. The literature review includes information on the composition, species richness, their distribution across Mexican marine ecoregions, and their morphofunctional groups. A systematic literature review from 1972 to 2024 identified 40 studies with data on macroalgae found on mangrove roots. The final phycofloristic inventory recorded 155 taxa, distributed among 67 genera, 39 families, 19 orders, and three phyla. The most representative orders were Ceramiales and Cladophorales, and the families with the greatest number of taxa were Rhodomelaceae and Cladophoraceae. This checklist provides a baseline for future taxonomic and biogeographic studies of mangrove-associated macroalgae.

Phycology doi: 10.3390/phycology6020035

Authors: Andrés F. Barajas-Solano Antonio Zuorro Roberto Lavecchia Janet B. García-Martínez Jefferson E. Contreras-Ropero Nestor A. Urbina-Suarez German L. Lopez-Barrera

Harvesting and drying are critical post-harvest operations in microalgal biomass processing because they strongly influence biomass conditioning and the subsequent recoverability of major macromolecular fractions. Accordingly, this study evaluated and optimized harvesting and drying conditions to identify processing windows associated with carbohydrate, protein, and lipid responses in Chlorella sp. (UFPS012). An I-optimal design was applied to assess drying temperature (40–60 °C), drying time (18–30 h), equipment (oven vs. food-grade dehydrator), and harvesting method (chemical flocculation vs. electroflotation). Subsequently, temperature and time were optimized using a central composite design while keeping electroflotation and the food-grade dehydrator fixed. The harvesting method was consistently significant across responses, whereas drying factors showed metabolite-dependent effects. During the screening stage, carbohydrates were mainly influenced by drying time and harvesting method, proteins by drying time and equipment, and lipids by drying temperature, equipment, and harvesting method. In the optimization stage, the fitted quadratic models showed high goodness of fit (R2 = 0.9778–0.9959), and the desirability function identified a compromise condition at 56.78 °C and 41.28 h. Under these conditions, the model predicted approximately 155.0 mg/L of total carbohydrates, 368.4 mg/L of total proteins, and 15.2 mg/L of total lipids. Process validation showed no significant difference between predicted and observed values for proteins, whereas carbohydrates and lipids differed significantly. In parallel, the moisture ratio approached zero at approximately 2460 min, consistent with the late stage of drying. Overall, electroflotation, coupled with food-grade dehydration, defined a laboratory-scale post-harvest configuration for the simultaneous conditioning of Chlorella biomass for multi-metabolite recovery. Future studies should evaluate specific energy demand, techno-economic feasibility, alternative drying technologies, and other Chlorella-relevant high-value compounds such as carotenoids.

Phycology doi: 10.3390/phycology6020034

Authors: Andrei Mironov Anton Glushchenko Natalia Tseplik Yevhen Maltsev Sergei Genkal Maxim Kulikovskiy

This is an investigation of molecular phylogeny and morphology of the genus Cymbosellaphora (Bacillariophyceae, Cymbellales). For this study, a strain of Cymbosellaphora geisslerae isolated from the Plotnikova River (Kamchatka Territory, Russia) was studied using light, scanning, and transmission electron microscopy, as well as molecular methods. Phylogenetic analysis based on 18S rDNA and rbcL gene sequences revealed that Cymbosellaphora geisslerae belongs to the order Cymbellales and forms an alliance with representatives of genera Gomphonella and Reimeria. The results of molecular study are supported by morphology. In the course of molecular analysis, we discuss the diversity of valve morphology across Cymbosellaphora, Gomphonella, Reimeria and related genera. As a result, a new type of pore occlusions, typical for Cymbosellaphora, is proposed, the diagnoses of the genus Cymbosellaphora and the species Cymbosellaphora geisslerae are emended, and the epitypification of this species is made. Most importantly, our data indicates that the concepts of areolae morphology and pore occlusions structure in the order Cymbellales might require critical evaluation.

Phycology doi: 10.3390/phycology6010033

Authors: Sanja Šovran Ana Knežević Danijela Vidaković Slađana Popović Milan Kalajdžić Nikola Unković

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

Phycology doi: 10.3390/phycology6010032

Authors: Fatima Ezzahra Kabbali Nisrine Bennani Guebessi Malak Sadry Youness Kadil Imane Rahmoune Houda Filali Touria Ould Bel Lahcen

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

Phycology doi: 10.3390/phycology6010031

Authors: Lena Sax Michael Schagerl

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

Phycology doi: 10.3390/phycology6010030

Authors: Donghui Gong Jiemei Zhao Zhizhong Wang Ziqing Guo Wenxue Wei Yan Wang Pengxiang Zhang Jie Bi

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

Phycology doi: 10.3390/phycology6010029

Authors: Juan Jesús Reyes Valdez Eduardo Alberto López Maldonado Tomás Lozano Ramírez Minerva Ana María Zamudio Aguilar Yarazett Hernández Castillo Luisiana Morales Zamudio

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

Phycology doi: 10.3390/phycology6010028

Authors: Kavitha Munisamy Sambasivam Chitra Devarajulu Susanth Sunil Kumar Rathika Sivasurendar Thirumalaisamy Eluri Bhavani Shankar Sudharsanam Abinandan

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

Phycology doi: 10.3390/phycology6010027

Authors: Juan Víctor Molner Juan Miguel Soria Noelia Campillo-Tamarit Rebeca Pérez-González Xavier Sòria-Perpinyà Manuel Muñoz-Colmenares

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

Phycology doi: 10.3390/phycology6010026

Authors: Elvira E. Ziganshina Ayrat M. Ziganshin

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

Phycology doi: 10.3390/phycology6010025

Authors: Luyanda Lindelwa Ndlela James Wesley-Smith Paul Johan Oberholster Monique Smit

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

Phycology doi: 10.3390/phycology6010024

Authors: David Milla-Figueras Ander Larrea Ester A. Serrão Pedro Afonso

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

Phycology doi: 10.3390/phycology6010023

Authors: Maja Berden-Zrimec Domen Lazar Domen Trontelj Elli Maria Barampouti Sofia Mai Dimitris Malamis Robert Reinhardt

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

Phycology doi: 10.3390/phycology6010022

Authors: Pengyu Liang Ziqing Zhong Qilin Zheng

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

Phycology doi: 10.3390/phycology6010021

Authors: Andrés F. Barajas-Solano

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

Phycology doi: 10.3390/phycology6010020

Authors: Gabrielle Corradino Astrid Schnetzer

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

Phycology doi: 10.3390/phycology6010019

Authors: Izabela Świca Joanna Kazimierowicz Marcin Dębowski

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

Phycology doi: 10.3390/phycology6010017

Authors: Khalifa S. H. Eldiehy Yasmeen G. Haraz Ibrahim S. Alkhazi Malek Alrashidi Mansoor Alghamdi Norhan M. Elbanhawy Omar Mohammad Atta

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

Phycology doi: 10.3390/phycology6010018

Authors: Amritpreet Kaur Minhas Suchitra Gaur Sharon Sunny Chaturya Paladugu Gokare Aswathanarayana Ravishankar Leonel Pereira Ranga Rao Ambati

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

Phycology doi: 10.3390/phycology6010016

Authors: Patricia Carbajal Natalia Arakaki Diego Márquez-Corigliano Florence Tellier

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

Phycology doi: 10.3390/phycology6010015

Authors: Charith Akalanka Dodangodage Geethaka Nethsara Gamage Induwara Arsith Wijesekara Jagath C. Kasturiarachchi Thilini A. Perera Dilan Rajapakshe Rangika Umesh Halwatura

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

Phycology doi: 10.3390/phycology6010014

Authors: Charith Akalanka Dodangodage Jagath C. Kasturiarachchi Induwara Arsith Wijesekara Thilini A. Perera Dilan Rajapakshe Rangika Halwatura

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.

Phycology doi: 10.3390/phycology6010013

Authors: Nuerbiye Yisimayi Liping Yang Mingyang Sun Xinyue Tang Lingna Chen Aisajiang Tuheti Shanjiang Ai Yongkun Chen

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.

Phycology doi: 10.3390/phycology6010012

Authors: Catarina Ramos-Oliveira Marta Ferreira Isabel Belo Aires Oliva-Teles Helena Peres

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.

Phycology doi: 10.3390/phycology6010011

Authors: Martina Blasio Adele Cutignano Angela Sardo Stefan Schouten Sergio Balzano

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.

Phycology doi: 10.3390/phycology6010010

Authors: Junseong Kim Seong-Yeong Heo Eun-A Kim Nalae Kang Soo-Jin Heo

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.

Phycology doi: 10.3390/phycology6010009

Authors: Wentao Sun Ming Du Guoming Shen Dongming Lai Jiangxin Wang

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.

Phycology doi: 10.3390/phycology6010008

Authors: Irina Mansurova Nataliya Dantsyuk Irina Chubchikova Elena Bocharova Olga Krivenko

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 (Fv/Fm) 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, Fv/Fm 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.

Phycology doi: 10.3390/phycology6010007

Authors: Hind Salih Alrajeh Fadia El Sherif Salah Khattab

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.

Phycology doi: 10.3390/phycology6010006

Authors: Khaoula Abid Maryem Minhaj Amer Chabili Imane El Ateri Mohammed Loudiki Najat Manaut Mountasser Douma

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.

Phycology doi: 10.3390/phycology6010005

Authors: Marika Ubaldi Francesca Neri Giorgia Montali Tiziana Romagnoli Aurora Tomasini Federica Cerino Timotej Turk Dermastia Patricijia Mozetič Janja Francé Camilla Spoto Stefano Accoroni Cecilia Totti

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.

Phycology doi: 10.3390/phycology6010004

Authors: David A. Gabrielyan Maria A. Sinetova Boris V. Gabel Alexander K. Gabrielian Alexander Y. Starikov Roman A. Voloshin Alexandra Markelova Grigoriy A. Savinykh Natalia V. Shcherbakova Dmitry A. Los

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.

Phycology doi: 10.3390/phycology6010003

Authors: Hanbi Moon Jaoon Young Hwan Kim

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.

Phycology doi: 10.3390/phycology6010002

Authors: Svetlana S. Bulynina Elvira E. Ziganshina Artem D. Terentev Ayrat M. Ziganshin

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.

Phycology doi: 10.3390/phycology6010001

Authors: Bram Vangenechten Tom Bernaerts Floris Schoeters Sabine Van Miert Barbara De Coninck Johan Ceusters

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.

Phycology doi: 10.3390/phycology5040089

Authors: Schery Umanzor Alexandra Meyer Zach Stamplis Alf Pryor

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.

Phycology doi: 10.3390/phycology5040088

Authors: Elena Kezlya Elina Mironova Ekaterina Voyakina Sergey Kravchenko Andrei Mironov Vasilii Kuzmin Ekaterina Chernova Anton Iurmanov Yevhen Maltsev Maxim Kulikovskiy

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.

Phycology doi: 10.3390/phycology5040087

Authors: Viola Pagliani Elena Arnau-López Noelia Campillo-Tamarit Manuel Muñoz-Colmenares Juan Miguel Soria Juan Víctor Molner

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.

Phycology doi: 10.3390/phycology5040086

Authors: Elizabeth Durán-Campos David Alberto Salas-de-León María Adela Monreal-Gómez Erik Coria-Monter

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.

Phycology doi: 10.3390/phycology5040085

Authors: Ivana Trbojević Roman Romanov Vanja Milovanović Gordana Subakov Simić Mihajlo Stanković Ermin Mašić Jelena Blaženčić

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.

Phycology doi: 10.3390/phycology5040084

Authors: Charith Akalanka Dodangodage Hirasha Premarathne Jagath C. Kasturiarachchi Thilini A. Perera Dilan Rajapakshe Rangika Umesh Halwatura

Conventional petroleum-based protective coatings release high levels of volatile organic compounds (VOCs) and contribute to resource depletion, urging the development of environmentally responsible alternatives. Among the bio-based candidates, microalgae and Cyanobacteriophyta have recently gained attention for their ability to produce diverse biopolymers and pigments with intrinsic protective functionalities. However, existing literature has focused mainly on algal biofuels and general biopolymers, leaving a major gap in understanding their application as sustainable coating materials. This review addresses that gap by providing the first integrated assessment of algae-based protective coatings. It begins by defining abiotic and biotic surface degradation mechanisms, including microbiologically influenced corrosion, to establish performance benchmarks. The review then synthesizes recent findings on key algal components, including alginate, extracellular polymeric substances (EPS), and phycocyanin, linking biochemical composition to functional performance, techno-economic feasibility, and industrial scalability. It evaluates their roles in adhesion strength, UV stability, corrosion resistance, and antifouling activity. Reported performance metrics include adhesion strengths of 2.5–3.8 MPa, UV retention above 85% after 2000 h, and corrosion rate reductions of up to 40% compared with polyurethane systems. Furthermore, this study introduces the concept of carbon-negative, multifunctional coatings that simultaneously protect infrastructure and mitigate environmental impacts through CO2 sequestration and pollutant degradation. Challenges involving biomass variability, processing costs (>USD 500/ton), and regulatory barriers are critically discussed, with proposed solutions through hybrid cultivation and biorefinery integration. By bridging materials science, environmental engineering, and sustainability frameworks, this review establishes a foundation for transforming algae-based coatings from laboratory research to scalable, industrially viable technologies.

Phycology doi: 10.3390/phycology5040083

Authors: Han-Yang Yeh Yi-Jung Chen Po-Chien Lin Jane Wungen-Sani Fan-Hua Nan Zhi-Cheng Huang Meng-Chou Lee

Non-geniculate crustose coralline algae (NCA) are important in algal reef ecosystems, yet their physiological responses to turbidity and sediment burial remain insufficiently understood. We examined how six turbidity levels (0–300 mg L−1) and four sediment deposition depths (0–3 cm) affected two dominant species, Sporolithon sp. and Phymatolithon sp. Under turbidity treatments, for Sporolithon sp., Fv/Fm was lowest at 0 mg L−1 (0.43 ± 0.01) and highest at 250 mg L−1 (0.62 ± 0.01). ETRmax increased markedly under 150 mg L−1 (17.94 ± 0.27) but declined under 300 mg L−1 (5.33 ± 0.19). In Phymatolithon sp., turbidity levels of 150–250 mg L−1 produced consistently higher Fv/Fm values (0.58–0.60) and the lowest ETRmax occurred at 300 mg L−1 (5.71 ± 0.34). Sediment burial caused strong early reductions in photosynthetic performance. In Sporolithon sp., all burial depths except 0 cm caused significant Fv/Fm declines within five days (decrease to 0.46). After 45 days, ETRmax ranged from 9.28 ± 0.38 at 0 cm to 4.02 ± 0.11 at 3 cm, with intermediate values at 1 and 2 cm. Phymatolithon sp. showed rapid declines in Fv/Fm at all depths (1 to 3 cm) before partial recovery after 15–20 days. Overall, moderate turbidity (150–250 mg L−1) provided protective light attenuation, whereas sediment deposition imposed strong early physiological stress. The contrasting responses of the two species highlight different adaptive strategies for surviving low-light and sediment-rich environments.

Phycology doi: 10.3390/phycology5040082

Authors: Maria Rafaele Oliveira Bezerra da Silva Bruna Emanuelle Gomes do Nascimento Maria Eduarda Moura Mendes Rayane Oliveira Bezerra da Silva Silvana de Fátima Ferreira da Silva Romero Marcos Pedrosa Brandão Costa Daniela de Araújo Viana Marques

Due to the scarcity of sustainable inputs for photosynthetic microorganisms’ biotechnology, the search for natural substrates such as coconut water has gained prominence. This by-product is a substrate rich in macro- and micronutrients, as well as endogenous phytohormones that support microbial growth. In this context, this study aimed to use it as an alternative cultivation medium for Limnospira platensis (Gomont), formerly known as Arthrospira platensis, a high-value cyanobacterium. We evaluated growth parameters, phycocyanin concentration, purity, and biomass yield cultivated in coconut water and in SAG1x medium, a modified Zarrouk medium. Over 35 days of cultivation, both media efficiently supported cyanobacterial growth. In coconut water, the specific growth rate was 0.305 d−1, the maximum growth rate was 0.629 d−1, and the productivity was 0.256 g L−1 d−1. In SAG1x medium, the values obtained were 0.240 d−1, 0.676 d−1, and 0.218 g L−1 d−1, respectively. Phycocyanin obtained from cultivation in SAG1x medium presented food-grade purity (OD620/OD280 ratio > 0.7), while in coconut water, it was 0.6. The pigment concentration and yield in SAG1x (19.1 mg/L and 34.3%, respectively) also slightly exceeded those obtained with coconut water (14.3 mg/L and 25.5%, respectively). Despite this, the data reinforce the potential of coconut water as a viable and economically competitive alternative to conventional media for L. platensis production.

Phycology doi: 10.3390/phycology5040081

Authors: Widyah Budinarta Nur Ajijah Anastasia Aliesa Hermosaningtyas

The agro-industrial sector in Indonesia produces significant amounts of nutrient-rich waste and wastewater, which pose environmental risks but also present opportunities for valorization within a circular bioeconomy. Microalgae provide a promising solution for transforming these wastewaters into valuable products such as biomass for bioenergy, biofertilizers, or pigments, all while helping to remediate pollutants. This review synthesizes current knowledge on the use of major Indonesian agro-industrial effluents, specifically palm oil mill effluent (POME), byproducts from cassava and sugarcane, and soybean residues, as substrates for microalgal biomass production and cultivation. Furthermore, various cultivation strategies are summarized, including autotrophic, heterotrophic, and mixotrophic methods, as well as the use of open ponds, photobioreactors, and hybrid systems. These cultivation processes influence biomass yield, metabolite production, and nutrient removal. Reported studies indicate high removal efficiencies for organic loads, nitrogen, and phosphorus, along with considerable production of lipids, proteins, pigments, and biofuels. Yet, effluent pretreatment, concerns about heavy metal and pathogen contamination, high downstream processing costs, and biosafety issues remains as challenges. Nonetheless, the application of microalgal cultivation into Indonesia’s agro-industrial wastes treatment can provide the dual benefits of waste mitigation and resource recovery, helping to advance climate goals and promote rural development.