Abstract The potentially toxigenic genus Pseudo-nitzschia from Antarctic waters is currently a subject of active research. Morphological observations of net phytoplankton samples from the Weddell Sea revealed the diatom Pseudo-nitzschia chiniana . The cells examined show the distinctive morphological features consistent with the original description of P. chiniana , which allowed confident identification of this species. However, our specimens differed from the original description by exhibiting a wider variation in poroid and striae ultrastructure. This finding is the first record of P. chiniana from the Antarctic waters and the tenth species of this genus found in the region.
Abstract Microalgae are increasingly recognized as pivotal agents in addressing the intertwined challenges of climate change, food security, and energy transition. Their extraordinary physiological diversity and evolutionary capacity position them at the nexus of natural biogeochemical regulation and engineered sustainability solutions. This review explores how microalgal physiology, spanning carbon fixation, nutrient cycling, and stress metabolism, supports their roles in circular bioeconomy systems and global sustainability initiatives. We highlight how physiological efficiency and physiological flexibility underpin the potential of microalgae for CO 2 capture, wastewater valorization, biofuel production, and high-value bioproduct synthesis. Yet, we also emphasize the importance of integrating physiological constraints, ecological feedbacks, and adaptive potential into the design of sustainable cultivation systems. Bridging cellular mechanisms with global-scale processes will be essential to ensure the evolutionary stability and environmental safety of future algal technologies. Building on John Raven’s foundational insights into photosynthetic energetics and resource acquisition, we advocate for an integrative framework linking algal physiology, evolution, and sustainability science to realize the “microalgae imperative” for a sustainable Anthropocene.
Rising ocean temperatures threaten kelp forests, especially Macrocystis pyrifera, an ecologically dominant species in temperate marine ecosystems. We tested whether chimerism, i.e., the fusion of genetically distinct individuals, improves thermal tolerance in juvenile M. pyrifera from the central coast of Peru. Juveniles were grown at 15, 18, 21, and 24 degrees C for 14 days in controlled conditions. As temperatures rose, growth and survival declined, but putative chimeric juveniles persisted and grew at 24 degrees C (39 % survival), while non-chimeric juveniles failed above 21 degrees C. Our results indicate that chimerism might enhance thermal tolerance in kelps, suggesting potential relevance for restoration and cultivation under climate change.
Abstract The Falkland Islands and South Georgia can be found at similar latitudes in the South Atlantic, yet they are on opposite sides of the Antarctic Convergence and show distinctly different features in terms of climate and biodiversity. While the Falkland Islands are cold-temperate and located in shallow waters on the southern Patagonian Shelf, South Georgia is a remote Subantarctic island with multiple glaciers that discharge into its bays and fjords. This review addresses the lack of a synopsis in the recent literature. It covers the biogeographic features of both the Falkland Islands and South Georgia as well as the exploration history and current state of knowledge of their seaweed diversity, including alien seaweed species, seaweed ecology, pathogens and potential uses.
The rare southern Australian rhodophyte, previously known as Ptilota (?) hannafordii Harvey 1862, is morpho-anatomically re-examined and the new genus Sgouracanthus and tribe Sgouracantheae are proposed to accommodate it. Thalli of Sgouracanthus hannafordii may reach 38 cm in length and grow individually in the sublittoral zone (to 33 m depth) attached to rock and macroalgae, although most records are from drift specimens bearing debris and grit among its curly and spiny branches. Sgouracanthus exhibits whorl-branches of determinate growth bearing procarps on their basal cells, which characterizes basal members of Ceramioideae, but the new genus is here classified in the Wrangeliaceae on account of oblique apical divisions, dense cortication, lack of gland cells, elongate spermatangial heads, polysporangia, a distinctive fusion cell, and multinucleate vegetative cells. In addition, Sgouracanthus develops a single auxiliary cell and tetrahedrally divided subspherical tetrasporangia, characters found in members of both groups. The taxonomic analysis supports a position near Spongoclonium and Dasythamniella, which is in agreement with a gene phylogeny based on the nuclear small subunit rDNA.
The biochemical composition of 11 green, 10 brown, and 9 red seaweeds collected from Caramoan, Camarines Sur, Philippines, was measured. Total soluble carbohydrates (TSC), total phenolic content (TPC), and protein content (PC), presented as percent (%) fresh weight (FW), were measured colorimetrically. Red seaweeds had the highest TSC (0.962 +/- 0.080 %), while the highest TPC (0.047 +/- 0.004 %) and PC (1.783 +/- 0.065 %) were noted in brown and green seaweeds, respectively. TSC was highest in Gelidiella acerosa (2.054 +/- 0.098 %) and Chaetomorpha linum (1.364 +/- 0.064 %). The highest TPC was recorded in Hormophysa cuneiformis (0.103 +/- 0.011 %) and Padina sp. (0.102 +/- 0.009 %), while the highest PC was found in Halimeda discoidea (2.768 +/- 0.076 %) and Halimeda macroloba (2.694 +/- 0.012 %). Fleshy seaweeds had higher TSC (0.672 +/- 0.058 %) and TPC (0.042 +/- 0.002 %), while calcifying seaweeds had higher PC (1.702 +/- 0.052 %). PCA revealed that seaweed biochemical composition can be distinguished by their taxonomic group and functional form. Our findings suggest that seaweeds from Caramoan with good nutritive content present opportunities for further research on their potential applications for human (e.g., functional foods, nutra- and pharmaceutical importance) and non-human products (e.g., animal feeds and plant nutrition).
Eucheumatoid production in the Philippines has declined despite rising global demand for carrageenan. Single-stream carrageenan processing generates 65-70 % waste, including liquid spent wash (LSW), a KOH-based effluent produced during the alkaline treatment of seaweeds during semi-refined carrageenan extraction. This study evaluated LSW as a biostimulant in the tissue culture of Eucheuma denticulatum and Kappaphycus striatus. A single batch of LSW was filtered, centrifuged to obtain the liquid fraction, and adjusted to pH 7.38 before application at 0.5, 1, 2, and 3 ml l(-1) over a 45-day culture period. LSW characterization showed soluble nutrients and bioactive compounds, while calcium and magnesium were below detectable limits, likely due to precipitation under strongly alkaline conditions. Explants tolerated all treatments, with survival and shoot formation remaining high, though responses were more stable in E. denticulatum than in K. striatus. Shoot length increased at moderate supplementation (0.5-2 ml l(-1); up to 10 mm), while excessive input (3 ml l(-1)) reduced elongation. Chlorophyll-a content increased with LSW concentration, though pigment levels do not correlate with growth performance. This study provides the first evidence of LSW as a waste-derived biostimulant for eucheumatoid tissue culture, demonstrating its potential to enhance regenerative performance while valorizing processing waste and supporting more sustainable aquaculture practices.
Lithophyllum is a highly diverse and widely distributed genus of non-geniculate coralline algae. Despite its ecological importance, a comprehensive taxonomic treatment of Lithophyllum species in Korea remains lacking, primarily due to substantial unresolved cryptic diversity within the genus. In this study, we describe Lithophyllum jejuensis based on an integrated taxonomic approach combining molecular phylogenetic analyses with detailed morpho-anatomical observations of specimens from Korea. Phylogenetic analyses of plastid markers (psbA and rbcL) resolved L. jejuensis as a distinct lineage. Morpho-anatomically, the species exhibits a multilayered, encrusting growth form with successive applanate branches, bistratose margins, and predominantly palisade basal (hypothallial) cells. Lithophyllum jejuensis resembles L. prototypum (originally described from the U.S. Virgin Islands), but differs from the holotype in having widely triangular tetrasporangial conceptacle pore canals that taper toward the thallus surface. Additionally, L. jejuensis can be distinguished from Korean L. neo-okamurae and L. okamurae by an exclusively adherent, encrusting growth form with applanate branches, bistratose margins composed of palisade cells, and larger tetrasporangial conceptacle chamber dimensions. These results reaffirm the importance of integrative taxonomy in elucidating the cryptic diversity of Korean Lithophyllum.
This study reports the first confirmed record of Halophila nipponica in the Philippines through DNA barcoding, extending its known distribution beyond Japan, Korea, and Malaysia. Specimens were collected from two coastal sites in Batangas, Philippines, with and without direct influence from submarine groundwater discharge at 4-8 m depth. This discovery highlights the importance of molecular tools in delineating taxa with few distinguishing morphological characters. More DNA barcoding work is necessary to catalogue the true seagrass species identity and to assess their total diversity, which is important for their protection and conservation.
This paper compiles and contextualises the existing known relationships that the Yaghan, or Yamana, peoples had with Macrocystis pyrifera, the giant kelp so abundant in Fuegian waters. It utilises Reverend Thomas Bridges' Yamana-English dictionary, compiled during the 1800s, as primary ethnohistorical source to structure and weave together mentions of kelp in other ethnographical sources for the area, and material culture insights from the extensive archaeological work carried out in the area of the Onashaga, or Beagle Channel. Notes about compared ethnophycological relations from elsewhere in the world are included when relevant, to suggest certain common themes in the environmental perception of kelp forests in sub-polar areas.
Mangroves are important hotspots of fungal diversity. Although the Philippines is home to a significant number of mangrove species, the identification of their associated endophytic fungi remains limited, with most studies focusing on foliar endophytes. This study provides the first comprehensive morphological and phylogenetic characterization of endophytic fungi from mangrove roots in the Philippines. A total of 25 endophytic fungal isolates were obtained from three mangrove hosts, Avicennia marina, Bruguiera cylindrica, and Rhizophora stylosa, in Nogas Island, Antique, Philippines. The isolates were classified into 10 morphospecies and identified using BLASTn searches in NCBI and phylogenetic inference based on several DNA markers, including internal transcribed spacer regions of ribosomal DNA (ITS), nuclear large subunit ribosomal DNA (LSU), RNA polymerase II second largest subunit (rpb2), beta-tubulin (tub), and translation elongation factor 1-alpha (tef-1 alpha). Ten species of endophytic fungi belonging to Ascomycota and Basidiomycota were identified, representing one new species (Amphisphaeria endophytica sp. nov.), six new geographic records, and 10 new host records. Morphological descriptions and phylogenetic analyses for each identified species are detailed in this study.
To expand knowledge of Pseudo-nitzschia in the Southern Ocean, we describe the morphological and molecular characteristics of two recently described species, Pseudo-nitzschia meridionalis and Pseudo-nitzschia glacialis, using field samples collected from the Weddell Sea and adjacent waters. In the ITS1-5.8S rDNA-ITS2 phylogenetic tree, our specimens clustered with previously studied strains of P. meridionalis and P. glacialis with high branch support. The specimens we obtained differed from the original description of P. meridionalis by exhibiting a wider variation in poroid ultrastructure (division into 2-4 parts vs. 1-3 parts). For P. glacialis, we identified poroids that were either simple, undivided, or divided into 1-3 parts at the stria edges. The morphological description of P. glacialis can thus be supplemented as follows: the ultrastructure of the striae and poroids was variable; striae were predominantly biseriate and, less frequently, of a transitional type (shifting from 2 to 1 row of poroids); these correspondingly contained simple undivided poroids and poroids divided into 1-3 parts on the stria edges. Information about the distribution P. meridionalis and P. glacialis has been updated.
The Falkland Islands are an archipelago just north of the Antarctic Convergence on the Patagonian Shelf, with a rich diversity of seaweeds showing affinities to both Patagonia and the Subantarctic. This paper presents an identification key and detailed illustrated descriptions for the brown algae of the region, based upon a series of recent expeditions by the authors and the available literature.
The abundance of Caribbean seagrass meadows has declined due to multiple human-induced stressors and the recent introduction of the invasive seagrass species Halophila stipulacea, a native to the Red Sea and Indo-Pacific regions. To investigate how environmental factors influence the interaction between the native Caribbean seagrasses and the invasive Halophila, a 13-month study was conducted in four seagrass meadows along the coast of Culebra, Puerto Rico. These meadows had varying environmental conditions and different levels of Halophila invasion. At each site, we monitored water movement, temperature, solar radiation, sedimentation rate, and five allometric measurements of seagrass; seagrass coverage, canopy height, shoot density, and above/below-ground biomass at 3-month intervals. The environmental factors varied over time and by site. Thalassia was the most common native seagrass species found at three sites. Halophila was present in all study sites but showed no direct impact on the native seagrasses. Water motion emerged as the most significant factor influencing allometric measures, affecting these characteristics positively or negatively, depending on the specific metric rather than the seagrass species.
This study examined the taxonomic diversity and biochemical composition of Ulva spp., a macroalga that was collected from eight sites along the Boka Kotorska Bay shoreline (Montenegro). The aim was to determine whether site-specific or interspecific variation influences the biochemical traits of Ulva populations. Species were identified through morphological features supported by tufA sequencing. Elemental composition, ash, amino acids, and fatty acids were quantified to assess biochemical heterogeneity. Carbon ranged from 19.8-27.4 %, nitrogen 1.3-4.0 %, and sulfur 2.4-5.6 % DW. Ash content varied widely (25.4-48.9 %), while total amino acids (TAA) spanned 0.02-0.05 mu g mg-1. Essential amino acids (%EAA = 28.7-73.7 %) and branched-chain amino acids (%BCAA = 26.3-80.1 %) showed pronounced divergence. Total fatty acids differed significantly among samples, peaking in sample S3 (1,287 +/- 29 mu g mg-1) and were lowest in sample S6 (260 +/- 8 mu g mg-1). Palmitic acid (C16:0) dominated all samples (171-578 mu g mg-1). These differences indicate that local environmental and taxonomic factors jointly influence Ulva biochemical composition. The intra-Bay variability highlights the adaptive potential of Ulva populations and their promise as sustainable sources of biomolecules. Future studies integrating multi-marker taxonomy, seasonal monitoring, and environmental characterization are recommended to clarify the drivers of this biochemical heterogeneity.
Isotope tracing experiments can be used to trace organic material flow through the ecosystem by artificially adding labelled biomass into a system. The advantage of this process is the direct control of carbon and nitrogen addition to the system for measuring uptake rates by consumers, which can substantially reduce the uncertainties associated with food web models. This article details and discusses the steps involved in successfully culturing and isotopically enriching ( 13 C and 15 N) juvenile sporophytes of two common North Atlantic kelp species (Laminariales): Saccharina latissima and Laminaria digitata . A first successful isotopic enrichment study of S. latissima , as well as the first inclusion of 15 N enrichment for L. digitata , are detailed. This protocol provides a comprehensive description of the stable isotope enrichment process in two kelp species, potentially serving as a foundation for its application in other macroalgal taxa.
Sub-Antarctic coastal ecosystems are characterized by a high diversity of intertidal and subtidal macroalgae. Recent studies in this region have advanced knowledge of their composition and distribution, as well as adding new species records. During scientific diving expeditions in Isla Grande de Tierra del Fuego, we documented the subtidal brown macroalga Microzonia velutina, representing a new record for Chile and an additional record for Argentina. Field surveys were conducted at three sites, located in Aguirre Bay (Argentina) and In & uacute;til Bay (Chile). Specimens were identified based on external and internal thallus anatomy, following diagnostic criteria established in studies along the Argentine Atlantic coast. The species occurred at depths of 3-6 m in subtidal habitats dominated by giant kelp forests (Macrocystis pyrifera). Diagnostic features included a fan-shaped thallus less than 3 cm in size, olive-brown coloration, uniseriate filaments bearing unilocular ovoid sporangia, occurring singly or in clusters. This finding expands the known distribution of M. velutina into sub-Antarctic ecosystems, highlighting Isla Grande de Tierra del Fuego, an important biogeographic region for macroalgal diversity. Future research should investigate the life cycle of the species and apply molecular approaches to clarify its phylogenetic position and evolutionary origins.
We report the first molecular record of Phyllodictyon robustum, a tropical turf-forming green alga previously known only from the Pacific coasts of Mexico and Panama, in Korean waters (Hongdo, 3-5 m depth). Morphological analysis revealed key diagnostic features, including an erect thallus (2-6 cm), polygonal calcium oxalate crystals with dentate margins, lenticular cells, and reproductive structures with multiple raised pores. Molecular phylogenetic analyses using LSU rDNA, ITS, and SSU rRNA sequences confirmed its taxonomic identity, grouping Korean specimens with populations from Mexico and Panama. Haplotype network analysis indicated closer genetic affinity to Panamanian samples. These findings highlight the importance of an integrated taxonomic approach for tracking macroalgal biogeography and monitoring climate-driven range expansions and long-distance dispersal whether natural or human-mediated.
Species of Dictyota with dentate margins exhibit notable diversity and a broad distribution across the Greater Caribbean. Oceanic islands such as Saint Kitts (Lesser Antilles) and the Archipelago of San Andr & eacute;s (Colombia) play a key role in expanding our understanding of these taxa. In this study, we report Dictyota canariensis as a new record for both countries and confirm the presence of Dictyota ciliolata and Dictyota jamaicensis using molecular and morphological evidence. Phylogenetic analyses based on psbA and cox1 sequences support the identity of these species, and the cox1 haplotype network reveals some geographic structure. Overall, our findings underscore the value of molecular data in addressing taxonomic complexity and highlight the importance of oceanic islands in shaping the regional diversity of dentate Dictyota species in the Caribbean basin.
