Phycology, Volume 4, Issue 4 (December 2024) – 6 articles

Selenium (Se)-enriched microalgae are emerging as new food or agricultural resources. Thus far, the microalgae tested for Se accumulation or biofortification are still very limited. Here, we investigated the effects of selenite on the growth of three terrestrial microalgae (Vischeria sp. WL1, Chlorella sp. WL1, and Nostoc flagelliforme) and their total Se accumulation levels. The three microalgae were previously collected at the same location and show great application potential but differ in classification and growth speed. Three concentrations (10, 20, and 40 mg/L) of selenite were used for treatment. The former two species could resist 40 mg/L selenite but the last one could not. At the relatively optimal concentration (20 mg/L selenite), their specific growth rates were 0.09, 0.10, and 0.05 μ day⁻¹, respectively. Vischeria sp. WL1 could accumulate 3.3 mg/g dry weight (DW) Se after 16 days of cultivation; N. flagelliforme could accumulate 5.6 mg/g DW Se after 24 days of cultivation. Chlorella sp. WL1 accumulated a relatively lower amount of Se, being 0.74 mg/L DW after 18 days of cultivation, but its more rapid growth would be beneficial to saving production costs. These results indicate that three microalgae are capable of functioning as excellent carriers for Se nutrients. This study will contribute to enriching the microalgal resource pool for Se biofortification in food and agricultural areas. Full article

Coastal areas are the most biologically productive and undoubtedly among the most complex ecosystems. Algae are responsible for most of the gross primary production in these coastal regions. However, despite the critical importance of algae for the global ecosystem, the biodiversity of many algal groups is understudied, partially due to the high complexity of morphologically identifying algal species. The current study aimed to take advantage of the recently developed technology for biotic community assessment through the high-throughput sequencing (HTS) of environmental DNA (eDNA), known as the “eDNA metabarcoding”, to characterize littoral algal communities in the Northern Gulf of Mexico (NGoM). This study demonstrated that eDNA metabarcoding, based on the universal plastid amplicon (UPA) and part of the large nuclear ribosomal subunit (LSU) molecular markers, could successfully differentiate coastal biotic communities among littoral zones and geographical locations along the shoreline of the NGoM. The statistical significance of separation between biotic communities was partially dependent on the dissimilarity calculation metric; thus, the differentiation of algal community structure according to littoral zones was more distinct when phylogenetic distances were incorporated into the diversity analysis. Current work demonstrated that the relative abundance of algal species obtained with eDNA metabarcoding matches previously established zonation patterns for these species. In addition, the present study detected molecular signals of 44 algal species without previous reports for the Gulf of Mexico, thus providing an important, molecular-validated baseline of species richness for this region. Full article

Genomic and chemical analysis has revealed that numerous species of filamentous cyanobacteria harbor complex secondary metabolisms tailored to their particular ecological niche. The metabolomic analysis of strains and environmental samples from benthic cyanobacterial mats (BCMs) from coral reefs has the potential to expand the library of marine cyanobacteria-derived natural products. In this study, cyanobacterial strains were obtained from phytobenthos collected from coral reefs in Abrolhos, Brazil and Ishigaki, Japan. Phylogenetic analysis of isolates shows high similarity to previously described members of benthic mats and also suggests the geographic expansion of the Adonisia lineage. Chemical analysis by untargeted liquid chromatography-high resolution mass spectrometry and data processing via MZmine and FBMN-GNPS confirmed the presence of a wide diversity of secondary metabolites. In addition, similarity analysis applying the newly developed tool DBsimilarity indicated the broad coverage of various biosynthetic and chemical classes of compounds previously reported for cyanobacteria. This report is one of the first applications of untargeted metabolomics workflow and similarity network construction for groups of marine filamentous cyanobacteria isolated from benthic mats on corals reefs. Full article

Seaweed is a great source of biologically active metabolites which could prove interesting in cosmeceutical applications. In this study, seven Icelandic seaweed species (Ascophyllum nodosum, Alaria esculenta, Laminaria hyperborea, Laminaria digitata, Saccharina latissima, Palmaria palmata, and Schizymenia jonssonii) were screened for total polyphenol content, antioxidant properties, and inhibition of skin-degrading enzymes. Antioxidant assays included DPPH (2,2-diphenyl-1-picrylhydrazyl), reducing power, and ORAC (oxygen radical absorbance capacity). In most assays, A. nodosum extracts were the most active. A. nodosum extracts also showed the strongest inhibition of the skin-degrading enzymes elastase and collagenase at low concentrations, demonstrating its skin-protective qualities. To further investigate the activity, A. nodosum was subsequently extracted with solvents with increasing polarity into seven different extracts. Compared to other extracts, the extracts obtained by extraction with acetone and methanol showed the highest activity in all assays. Extracts obtained with room-temperature water and 85 °C water also demonstrated moderate to high activities. The outcomes of this study support the potential utilization of the brown seaweed A. nodosum as a source of natural ingredients in cosmeceuticals. Full article

Microalgae represent a valuable renewable resource for biofuel production due to their high lipid content, rapid growth rates, and non-competition with food resources. Both freshwater species like Chlorella and marine species such as Dunaliella, Tetraselmis, and Nannochloropsis are among the most commonly utilized candidates. This review provides a comprehensive overview of current cultivation and harvesting methodologies for microalgae in the context of biofuel production, emphasizing sustainable aviation fuel and biohydrogen. It synthesizes recent findings, technological advancements, and practical implementations to enhance the productive and economic viability of microalgae-based biofuels, highlighting their potential as a sustainable renewable energy source. Among the biofuels, sustainable aviation fuel and biohydrogen stand out as significant contributors to reducing greenhouse gas emissions. Technologies such as the oil-to-jet process and Fischer–Tropsch synthesis are being optimized to convert algal lipids into high-quality fuels. Biohydrogen offers several advantages, including the potential for negative CO₂ emissions and compatibility with existing hydrogen infrastructure. Despite the challenges associated with the high costs of cultivation and processing, advances in biotechnological methods and process engineering promise to overcome these barriers. This review highlights the importance of continued research and development to maximize the potential of microalgal biofuels in achieving sustainable energy goals and contributing to global efforts in mitigating climate change. Full article

Codium tomentosum holds a variety of bioactive compounds, high nutritional value and health benefits, which makes it a valuable natural resource for the food, cosmetic and pharmaceutical industries. Currently, C. tomentosum is farmed at a small-scale targeting niche markets, and further expansion of production is limited by a lack of optimised propagation and cultivation methods. This study aims to identify the conditions required to control key production parameters including gametogenesis, gamete release and suitable culture conditions for the early stages of development of C. tomentosum. Wild specimens of C. tomentosum were collected on the Aguçadoura shore, north of Portugal. Gametogenesis was successfully induced in infertile specimens cultured under a short-day photoperiod (8 h:16 h; L:D). Gamete release was optimised through a combination of hydric shock and ultrasounds, with the highest gamete yield obtained after a 2 h 30 min desiccation period, followed by re-hydration and a series of three ultrasounds. Germlings, precursors of the adult C. tomentosum, grew faster when cultured under a lower light intensity (20 μmol m⁻² s⁻¹) compared to higher intensities (40 and 60 μmol m⁻² s⁻¹) in every light spectrum; additionally, the growth of germlings exposed to the lowest light intensity was significantly higher under white, red and green light spectra compared to blue light. The results on key production parameters constitute an important contribution to the establishment of nursery protocols based on sexual reproduction for aquaculture of the species. Full article