Journal Of Phycology[JOURNAL]
Sun
200 papers
Integrative taxonomy of Harveylithon (Corallinales, Rhodophyta) reveals three new species from Korea and expanded diversity in the northwestern Pacific.
Kim GW, Jeong SY, Won BY … +2 more , Fredericq S, Cho TO
J Phycol · 2026 Jul · PMID 42400203 · Publisher ↗
Non-geniculate coralline genus Harveylithon includes 12 species worldwide. In this study, we propose three new species, Ha. koreanum sp. nov., Ha. longiforme sp. nov., and Ha. planiforme sp. nov., based on integrative mo...
Non-geniculate coralline genus Harveylithon includes 12 species worldwide. In this study, we propose three new species, Ha. koreanum sp. nov., Ha. longiforme sp. nov., and Ha. planiforme sp. nov., based on integrative molecular and morphological analyses. These three new species share the diagnostic morphological characters of Harveylithon, including a monomerous, non-coaxial thallus construction with perithallial cells oriented perpendicularly to the surface; a hypothallial layer composed of rectangular cells aligned parallel to the substratum; and the presence of trichocytes occurring singly, in pairs, or in clusters. Our phylogenetic analyses of a concatenated four-gene data set (COI + rbcL + psbA + SSU rRNA) clearly resolved the three new species within Harveylithon, each forming a well-supported and distinct lineage. The topologies of the individual-gene phylogenies based on the psbA and the SSU rRNA genes were largely congruent and supported these relationships, whereas phylogenetic trees based on the rbcL and COI genes did not recover Harveylithon as monophyletic, with Dawsoniolithon species nested within the Harveylithon clade. Interspecific sequence divergences between new species and their congeners were 6.3%-13.7% for the COI gene, 0.8%-9.8% for the psbA gene, and 1.8%-14.6% for the rbcL gene. Harveylithon koreanum sp. nov. and Ha. planiforme sp. nov. are currently known from only Jeju Island in Korea, whereas Ha. longiforme sp. nov. was identified from both Jeju Island, Korea, and India, indicating that it may have a broad Indo-Pacific distribution. In addition, we newly generated the psbA gene sequence from the generitype, Ha. rupestre (TRH A3-149) and incorporated it into our molecular data set to stabilize the phylogenetic circumscription of the genus.
Mysticladia gen. nov. (Cladophorales, Ulvophyceae): A new genus encompassing two long-recognized Cladophora species from the South Atlantic Ocean.
Brito JOF, Carneiro VAR, Cassano V … +3 more , da Silva DM, Moura CWN, Gama WA
J Phycol · 2026 Jul · PMID 42400193 · Publisher ↗
The genus Cladophora (Cladophorales, Ulvophyceae) has a long history of taxonomic challenges due to morphological plasticity and incongruence between traditional classifications and molecular phylogenies. Here, we propos...
The genus Cladophora (Cladophorales, Ulvophyceae) has a long history of taxonomic challenges due to morphological plasticity and incongruence between traditional classifications and molecular phylogenies. Here, we propose Mysticladia gen. nov. to accommodate species previously assigned to Cladophora but phylogenetically placed within the Siphonocladus clade. Analyses of concatenated SSU + LSU rDNA gene sequences from specimens collected along the Brazilian coast revealed that populations morphologically identified as C. prolifera and C. aokii form a distinct and phylogenetically distant clade from Cladophora sensu stricto. Genetic divergence and morphological comparisons supported the recognition of two new cryptic species: Mysticladia nigra sp. nov. and M. edisonii sp. nov. Both seemingly restricted to the southwestern Atlantic. These species are morphologically indistinguishable from their closest relatives but distinguishable by DNA sequences. Additionally, we transfer C. prolifera, C. aokii, and C. coelothrix to Mysticladia. Our findings broaden the widespread cryptic diversity within the Cladophorales and emphasize the critical need for molecular analyses across populations in this group, including those already and correctly identified based on morphology alone. Such efforts are essential for elucidating cryptic lineages and species boundaries in simple filamentous green algae, where phenotypic plasticity often disguises true evolutionary relationships.
Selective grazing in the heterotrophic dinoflagellate Oxyrrhis marina: Effects of prey type, size, temperature, and nutrient limitation.
Liang D, Zhang Y, Li H … +3 more , Sun J, Li Z, Xiang H
J Phycol · 2026 Jun · PMID 42376767 · Publisher ↗
Protists are the main consumers of phytoplankton in the marine environment, playing pivotal roles in the carbon cycle and nutrient regeneration. Heterotrophic dinoflagellates, which have been extensively studied, are the...
Protists are the main consumers of phytoplankton in the marine environment, playing pivotal roles in the carbon cycle and nutrient regeneration. Heterotrophic dinoflagellates, which have been extensively studied, are the linking hubs for microbial food loops and classical food chains. In particular, Oxyrrhis marina has been used as a model predator in laboratory studies. Designed experiments were conducted to explore the effects of biological factors (prey type, particle size) and abiotic factors (temperature, nutrient limitation) on its growth and ingestion. Oxyrrhis marina had the ability to consume various algae, including Chromalveolata, Haptophyta, Chlorophyta, Bacillariophyta, and Ochrophyta. When prey had diameters ranging from 7.4 to 13 μm, O. marina exhibited the highest ingestion rates, growth rates, and cell volume. With increases in temperature, the ingestion rate, growth rate, and productivity of O. marina increased significantly, but the cell volume decreased dramatically. Compared to ingesting phosphorus-restricted prey, ingesting nitrogen-restricted prey significantly increased the ingestion rate, growth rate, and cell volume of O. marina. Nitrogen-restricted (phosphorus-restricted) O. marina preferred to select prey that contained more nitrogen (phosphorus) elements to regulate nutritional imbalance. The purpose of this study is to provide a theoretical foundation for understanding the selective ingestion of the heterotrophic dinoflagellate O. marina and its impact on the community structure of plankton.
Impact of the invasive diatom species Cymbella janischii on riverine microbial biofilm communities and a potential role of bacterially produced zeatin.
Arguelles EDLR, Mugikura K, Sato S
J Phycol · 2026 Jun · PMID 42376710 · Publisher ↗
The diatom Cymbella janischii is an invasive species in Japan, causing nuisance blooms by forming thick mats in rivers. To date, there are no documented studies on the microbiome associations in C. janischii mats or the...
The diatom Cymbella janischii is an invasive species in Japan, causing nuisance blooms by forming thick mats in rivers. To date, there are no documented studies on the microbiome associations in C. janischii mats or the processes that drive bloom formation. This study used metabarcoding of diatoms, bacteria, and fungi to identify key species and assess the effects of C. janischii blooms on the benthic microbial communities. C. janischii blooms reduced diatom and bacterial species diversity, while fungal diversity remained stable. In addition, the diatom Nitzschia paleacea and the bacterium Flavobacterium sp. were observed to co-occur and vary in abundance, indicating a possible ecological link that may affect mat structure or function. Metagenomic predictions of bacterial functions showed that compared to benthic stones without visible C. janischii mats, mat-associated bacteria had enriched pathways related to the metabolism of carbohydrates, nucleotides, and amino acids, along with zeatin biosynthesis. Zeatin is a cytokinin phytohormone that stimulates plant growth and development. In vitro exposure of C. janischii to varying zeatin concentrations confirmed its growth-promoting effects, inducing cell proliferation and stalk formation. This study shows that zeatin stimulates the growth of C. janischii. The findings of this study provide new insights into microbiome diversity, identifying key taxa associated with C. janischii mats to help better understand bloom formation.
Spore priming by coastal upwelling in the intertidal kelp Lessonia spicata.
Parada GM, Martinez Mosqueira EA, Broitman BR
J Phycol · 2026 Jun · PMID 42365437 · Publisher ↗
The kelp populations of two cryptic species of Lessonia inhabiting the intertidal zone of the southeastern Pacific are vulnerable to local extinction and range contraction by being exposed to large-scale thermal extremes...
The kelp populations of two cryptic species of Lessonia inhabiting the intertidal zone of the southeastern Pacific are vulnerable to local extinction and range contraction by being exposed to large-scale thermal extremes and strong harvesting by artisanal fisheries. Our study explored the effect of variable ocean temperature conditions on the germination of spores, a critical stage for post-disturbance persistence of local populations, including harvesting. Over a 15-month experimental period, we collected reproductive tissues from 10 tagged sporophytes of a wild local population of L. spicata in Central Chile (~33.5° S) and measured germination success. Reproductive activity closely tracked the presence of low (<14°C) ocean temperatures at the study site. Mean spore germination was over 80% from late Austral fall to late spring and sharply declined and became more variable under the warmer ocean conditions of summer and early fall. Unexpectedly, a mid-summer mesoscale upwelling event cooled seawater below 14°C, and spore germination success increased from <50% to up to 90%. Across the study period, germination showed a significant negative correlation with seawater temperature, down to a lag of 4 days prior to the collection of reproductive tissue. These results suggest both a temperature threshold and a temporal scale for spore priming in L. spicata, providing support to earlier hypotheses positing spatial heterogeneity in the upwelling regime as the leading driver of speciation in the Lessonia complex. Together, our results provide an important evolutionary insight for the conservation, restocking, and management of the Lessonia complex.
Environmental constraints on freshwater red algae in Estonian streams: Insights from long-term observations and machine-learning models.
Piirsoo K, Vilbaste S, Pall P … +1 more , Olli K
J Phycol · 2026 Jun · PMID 42340333 · Publisher ↗
The division Rhodophyta (red algae) includes an inconspicuous and often overlooked component of benthic freshwater biota. In many cases, freshwater red algae are considered indicators of good ecological status, yet their...
The division Rhodophyta (red algae) includes an inconspicuous and often overlooked component of benthic freshwater biota. In many cases, freshwater red algae are considered indicators of good ecological status, yet their environmental preferences remain poorly understood. Species richness is low globally, and the distribution of many taxa remains poorly known. Here, we report the occurrence of 12 taxa of benthic red algae in 272 Estonian streams, based on 734 sampling sites and 1263 sampling occasions. The aim of this study is to identify the key environmental drivers of freshwater red algae occurrence and to evaluate their potential as indicators of water quality. Red algae were recorded in 20% of the samples. The influence of 37 environmental variables on the occurrence of red algae was assessed using machine-learning algorithms (random forest and gradient boosting trees). Hydrological and hydrochemical variables were by far the most important variable groups, followed by bottom substrate, watershed land cover and land use, and geological bedrock type. Among the hydrochemical variables, biological oxygen demand was the single most important predictor, indicating a high sensitivity of freshwater red algae to labile organic pollution. In contrast, the effect sizes of mineral and total nutrients were lower and more nuanced, suggesting that freshwater red algae are not particularly sensitive indicators of eutrophication. Some division-level responses may have been obscured by contrasting species-specific patterns. Species-level effects were often difficult to verify using machine-learning approaches due to low occurrence frequencies.
Klebsormidiophyceae sister genomes reveal multicellularity and stress adaptations.
Ma J, Huo R, Bai S … +1 more , Huang J
J Phycol · 2026 Jun · PMID 42333967 · Publisher ↗
Klebsormidium and Interfilum are two closely related genera in the charophyte group Klebsormidiophyceae. Members of Klebsormidium are usually multicellular whereas those of Interfilum are unicellular. The genome of K. ni...
Klebsormidium and Interfilum are two closely related genera in the charophyte group Klebsormidiophyceae. Members of Klebsormidium are usually multicellular whereas those of Interfilum are unicellular. The genome of K. nitens has been sequenced using second-generation sequencing technology, but the assembled scaffolds are frequently fragmented. In this study, we re-sequenced the genomes of K. nitens using PacBio platform and obtained 15.8 Gb long reads. We also sequenced the genome of I. paradoxum and obtained 13 Gb long reads. The I. paradoxum genome assembly (81.7 Mb) included 59 contigs with N50 of 1.9 Mb, and the K. nitens assembly (132.9 Mb) included 188 contigs with N50 of 2.1 Mb. A total of 20,425 and 15,103 protein-coding genes were annotated in K. nitens and I. paradoxum, respectively. Comparative genome analyses identified 2805 gene families specific to Klebsormidiophyceae, which are enriched in gene ontology (GO) categories related to jasmonic acid (JA) biosynthesis and rRNA catabolism. Twenty-seven gene families, enriched in RNA-DNA hybrid ribonuclease activity and transmitter-gated ion channel activity, were found to have expanded in the last common ancestor of I. paradoxum and K. nitens. Several genes related to cell wall structure, including galactosyltransferase (GALT), were absent in I. paradoxum. We also found that approximately 50% of abiotic stress-related genes (e.g., late embryogenesis abundant, LEA genes) are present in land plants. The generation of K. nitens and I. paradoxum genomes and transcriptome data provides additional resources to understand the origin and evolution of land plants.
The evolutionary ecology of reproduction in the red alga Palmaria palmata: Insights from an atypical life cycle.
Baud A, Valero M, Mauger S … +3 more , Krueger-Hadfield SA, Potin P, Destombe C
J Phycol · 2026 Jun · PMID 42333960 · Publisher ↗
Unlike other red algae, the perennial species Palmaria palmata exhibits pronounced sexual dimorphism with a microscopic female gametophytic phase that does not produce cystocarps. To investigate how these unique features...
Unlike other red algae, the perennial species Palmaria palmata exhibits pronounced sexual dimorphism with a microscopic female gametophytic phase that does not produce cystocarps. To investigate how these unique features of its life cycle influence its reproductive mode, we analyzed the relative proportion of macroscopic individuals (tetrasporophytes vs. male gametophytes) across multiple geographic scales and between intertidal and subtidal habitats along the western coast of France (892 individuals collected from 17 locations). Because female gametophytes are microscopic and cannot be directly sampled in the field, their frequencies were inferred under two alternative hypotheses: (H1) assuming an equal sex ratio (i.e., the proportion of females equal to males) and (H2) assuming the proportion of females equals tetrasporophytes, given that tetrasporophytes develop directly on a female gametophyte. Under H1, our results predict a demographic advantage of tetrasporophytes over gametophytes. Moreover, tetrasporophytes were significantly more abundant in intertidal than in subtidal zones, likely reflecting their greater resilience to environmental fluctuations. Conversely, under H2, the sex ratio was significantly biased toward female gametophytes and the estimated proportion of tetrasporophytes was lower than that of gametophytes. In addition, the relative contribution of self-fertilization and clonal reproduction were assessed using 11 microsatellite markers. These findings confirm that this species reproduces mainly sexually and suggest that sexual dimorphism may limit selfing and enhance the survival of the tetrasporophyte, which develops directly on the female, thereby compensating for the absence of cystocarps. Overall, our results provide valuable insights into the reproductive strategies and adaptive potential of this commercially important alga.
Complete organellar genomes of Cystophora brownii: Insights into mitochondrial and plastid structure and evolution in brown algae.
Edgeloe JM, Starko S, Wood GV … +3 more , Pessarrodona A, Minne AJP, Wernberg T
J Phycol · 2026 Jun · PMID 42333737 · Publisher ↗
Cystophora (order Fucales) is one of the most diverse genera of habitat-forming brown algae and is endemic to temperate reefs of Australia and New Zealand. Species in this genus form complex habitat structures that suppo...
Cystophora (order Fucales) is one of the most diverse genera of habitat-forming brown algae and is endemic to temperate reefs of Australia and New Zealand. Species in this genus form complex habitat structures that support diverse marine communities and contribute to coastal productivity. However, Cystophora spp. are highly sensitive to environmental stress, and recent declines across parts of their historical range highlight their vulnerability to ocean warming. Despite their ecological importance, genomic resources for Cystophora remain scarce, limiting insight into their evolutionary history, adaptive capacity, and resilience to environmental change. Here, we sequenced, assembled, and annotated the complete plastid and mitochondrial genomes of the widespread species Cystophora brownii using PacBio HiFi long-read sequencing. We characterized organellar genome architecture and gene content, conducted comparative analyses with other Fucalean taxa, and reconstructed phylogenetic relationships within the Fucales. The mitochondrial genome is 36,047 bp and contains 66 conserved genes (GenBank accession PZ196221). The plastid genome is 124,536 bp and contains 171 conserved genes, including two inverted repeat regions (GenBank accession PX975689). Comparative analyses indicate conserved gene content, order, and structure relative to other Fucalean organellar genomes. Maximum likelihood phylogenetic analyses robustly place C. brownii within the Fucales with strong support, resolving it as sister to the remaining Sargassaceae, suggesting an early divergence within the family that may date to the Miocene. These genomic resources provide a foundation for resolving the evolutionary placement of Cystophora and advancing studies of organellar genome evolution in brown algae.
Heat stress induces organelle alterations in Macrocystis pyrifera gametophytes.
Harden M, Koos DS, Arzuyan K … +4 more , Kovalev M, Lansford R, Alberto F, Nuzhdin S
J Phycol · 2026 Jun · PMID 42311204 · Publisher ↗
Kelp, brown macroalgae in the order Laminariales, provide ecosystem services vital to ocean biodiversity. However, kelp forests worldwide are declining due to abiotic stressors such as ocean warming. In this study, we pr...
Kelp, brown macroalgae in the order Laminariales, provide ecosystem services vital to ocean biodiversity. However, kelp forests worldwide are declining due to abiotic stressors such as ocean warming. In this study, we present results from high-resolution confocal microscopy and in vivo imaging system imaging using protocols developed to visualize kelp gametophyte cells exposed to heat-stress treatments. Imaging revealed chloroplast mislocalization, fragmentation, and subsequent loss of chloroplasts in heat-stressed gametophyte cells. Additionally, nuclei exhibited fragmentation and a progressive loss of fluorescent signal, and the associated microbiome proliferated under various heat-stress treatments. Notably, because brown algae possess a continuous outer membrane that connects the nuclear envelope and the chloroplast envelope, these observations suggest a cellular vulnerability underlying thermal sensitivity in brown macroalgae. Finally, by comparing heat-stress tolerant and heat-stress sensitive genotypes, we found that genotypes with higher heat tolerance exhibited substantially fewer abnormalities compared to sensitive ones.
Holdfast adhesion in the kelp Alaria marginata: Cell wall polysaccharides and phenolics.
Roy-Musor MR, Agoawike C, Samuels AL … +1 more , Martone PT
J Phycol · 2026 Jun · PMID 42305052 · Publisher ↗
Adhesion is a critical process in the survival of seaweeds, especially in wave-swept environments. Kelp (Laminariales) sporophytes secrete adhesives from specialized rhizoid cells to anchor themselves to the substrate an...
Adhesion is a critical process in the survival of seaweeds, especially in wave-swept environments. Kelp (Laminariales) sporophytes secrete adhesives from specialized rhizoid cells to anchor themselves to the substrate and withstand immense forces applied by waves. Although the composition of macroalgal adhesive has been described primarily in the Fucales, the current adhesive model is incomplete, and similarities between kelp and fucoid adhesives are unknown. Moreover, the cellular organization of the attachment interface of kelps is poorly understood. In this study, we examined the composition of rhizoid cells and adhesive from developing holdfasts of the kelp Alaria marginata using brightfield, fluorescence, and scanning electron microscopy. Rhizoid cells form a thick, intertwined mat cemented with adhesive. We provide the highest resolution immunofluorescent analysis of kelp adhesives to date using confocal microscopy: Kelp adhesives are composed of fucose-containing sulfated polysaccharides (FCSPs) and alginate, dominated by BAM3 and BAM4 epitopes. Holdfast adhesives are biochemical extensions of the cell wall with distinct composition from the wall proper. This work advances our basic understanding of kelp adhesion and highlights gaps in our current understanding of adhesive composition, raising questions, for example, about the roles of phenolics and proteins. Biochemical and histological methods presented here set the stage for future examination of the developmental, ecological, and evolutionary dynamics of adhesion.
Dinoflagellate responses to nutrients and mangrove leaf organic matter in the bioluminescent Mangrove Lagoon, St. Croix, U.S. Virgin Islands.
Pinckney JL, Zimberlin M, Greenfield DI
J Phycol · 2026 Jun · PMID 42305047 · Publisher ↗
Bioluminescent bays (biobays) are uncommon coastal ecosystems featuring dense populations of dinoflagellates, often found in mangrove-ringed lagoons with long water retention times and high organic matter (OM) levels. Al...
Bioluminescent bays (biobays) are uncommon coastal ecosystems featuring dense populations of dinoflagellates, often found in mangrove-ringed lagoons with long water retention times and high organic matter (OM) levels. Although mangroves are associated with high dinoflagellate abundance, it remains uncertain how inorganic nutrients compare with mangrove-derived organic matter in shaping phytoplankton communities. We performed short-term in situ bioassays in Mangrove Lagoon, St. Croix, U.S. Virgin Islands, to compare phytoplankton community responses to additions of inorganic nutrients (N and P) and senescent mangrove leaf additions. Phytoplankton composition was assessed using high-performance liquid chromatography (HPLC) pigment analysis combined with CHEMTAX, and data were analyzed with compositional and centered log-ratio principal component analyses (CLR-PCAs). Nutrient additions primarily increased total phytoplankton biomass and favored diatom-dominated communities, consistent with N limitation, but did not significantly alter community composition. Conversely, adding senescent mangrove leaves consistently shifted the community toward higher abundances of peridinin-containing dinoflagellates, without significantly increasing the abundance of other phytoplankton groups. Multivariate analysis showed that leaf additions shifted the community along a continuous compositional spectrum rather than creating distinct assemblages. These findings suggest that OM (leachate) from senescent mangrove leaves, rather than inorganic N and P enrichment alone, is a plausible mechanism for promoting dinoflagellate dominance in Mangrove Lagoon. Our results underscore the potential role of mangrove OM input in sustaining dinoflagellate-dominated environments in some tropical lagoons, demonstrating a mechanism by which mangroves may regulate phytoplankton community composition in adjacent waters.
Redescription and neotypification of Alexandrium minutum Halim-the type species of Alexandrium-from its type locality in Alexandria, Egypt, with insights into ribotype biogeography and toxicity.
Huang S, Gu H, Krock B … +4 more , Shams El-Din NG, Moestrup Ø, Cochet E, Mertens K
J Phycol · 2026 Jun · PMID 42300811 · Publisher ↗
Alexandrium minutum Halim, the generitype species of the toxigenic Alexandrium, was described from a 1958 bloom in the Eastern Harbour, Alexandria (Egypt), but has never been re-examined with modern methods from the type...
Alexandrium minutum Halim, the generitype species of the toxigenic Alexandrium, was described from a 1958 bloom in the Eastern Harbour, Alexandria (Egypt), but has never been re-examined with modern methods from the type locality. Here, we establish a monoclonal strain (TIO1796) by cyst germination from Alexandria's port sediment and a second strain (TIO1816) from plankton samples from the Gulf of Suez. Cell morphology of both cultured strains and plankton samples was examined using scanning electron and light microscopy. The plate formula of A. minutum was identified as Po, *4', 6'', 6C, 9S, 5''', 2p, 1''''. Our results confirmed the consistent presence of a ventral pore and a variable connection between Po and 1'. Molecular phylogenetic analyses based on LSU rRNA gene and ITS rRNA region sequences revealed four ribotypes (A-D) of A. minutum. The LSU rRNA gene and ITS rRNA region sequences of both strains were identical and belong to the widespread ribotype A ("Global/Mediterranean clade"). The other ribotypes are restricted to the Asia-Pacific region. Strain TIO1796 (type locality) was non-toxic regarding paralytic shellfish toxin (PST < 0.024 pg · cell), whereas TIO1816 produced GTX1/4-dominated toxins (0.48 pg PST · cell). These results (i) anchor the name A. minutum to ribotype A via neotypification of strain TIO1796, (ii) document a PST-producing A. minutum in the Red Sea, and (iii) provide evidence supporting that A. minutum constitutes a cryptic species complex analogous to the A. tamarense species complex. The historical decline of A. minutum blooms in Alexandria since the 1990s correlates with near-absent cyst banks in recent sediments.
Growth and development of Griffithsia heteroclada under varying light intensity and cell type conditions.
Lyu J, Zhao P, Liu J … +4 more , Park J, Lee H, Wang Y, Han T
J Phycol · 2026 Jun · PMID 42249632 · Full text
To investigate the effects of internal and external factors on the growth and development of Griffithsia heteroclada, the optimal culture medium and conditions were first established. Subsequently, individual apical cell...
To investigate the effects of internal and external factors on the growth and development of Griffithsia heteroclada, the optimal culture medium and conditions were first established. Subsequently, individual apical cell (Ca), rhizoid cell (Cr), shoot cell (Cs), and nodal cell (Cn) were cultured under varying light intensities. The findings indicated that the most suitable culture media for G. heteroclada are Provasoli-enriched seawater and Tropic Marin, with optimal culture conditions comprising an irradiance of 60 μmol photons · m · s, a salinity of 25, a temperature of 25°C, and a pH of 8. Any single cell could regenerate into a new plant, but regeneration varied by cell type, with the promoting effect being most pronounced in the order of Cn = Cs > Cr ≥ Ca. High light intensity inhibited energy transfer from accessory pigments to reaction centers in Ca and Cr, thereby diminishing their light capture capacity and photosynthetic efficiency. Fresh weight is deemed an appropriate biomass indicator for G. heteroclada, and the cell enlargement rate is considered a suitable growth indicator. Developmental indicators include cell number, division rate, branch number, and branch initiation time, while cell length, branching rate, elongation rate, and area are not suitable.
Ecophysiological study of green microalgae isolated from the grit crust of the Atacama Desert.
Glaser K, Kuschel F, Prelle LR … +2 more , Jung P, Karsten U
J Phycol · 2026 Jun · PMID 42246649 · Full text
Terrestrial algae play a critical, yet often overlooked, role in the functioning of biological soil crusts (biocrusts), which are considered microecosystems, particularly in extreme environments. This study investigated...
Terrestrial algae play a critical, yet often overlooked, role in the functioning of biological soil crusts (biocrusts), which are considered microecosystems, particularly in extreme environments. This study investigated the ecophysiological traits of green algae isolated from the grit crust-a unique biocrust type reported a few years ago in the coastal Atacama Desert (National Park Pan de Azúcar), Chile. We assessed photosynthetic performance, temperature tolerance, and desiccation recovery in four strains: Pseudochlorella signiensis strain C11, Lobosphaera incisa strain LC2, and two strains of Klebsormidium elegans, C12 and C14. The results revealed significant interspecific variation, with P. signiensis exhibiting the highest photosynthetic capacity and both Klebsormidium strains demonstrating efficient light utilization. Desiccation recovery at very low relative air humidity was limited across all species, potentially reflecting the influence of frequent fog events in the coastal region of the Atacama, which result in a moderate air humidity. This study fills a critical knowledge gap regarding terrestrial algal ecology in South America and highlights the physiological traits enabling algal survival in one of the world's most extreme environments, providing insights into the resilience of biocrust communities in the face of environmental change.
Kelp gametophytes upregulate photosynthetic bicarbonate (HCO ) utilization in response to irradiance and temperature.
Stodder K, Edwards M, Kim JH
J Phycol · 2026 Jun · PMID 42240961 · Publisher ↗
Microscopic stages play an integral role in the kelp life cycle and ultimately determine settlement patterns of adult populations. Kelp gametophytes often exhibit broader thermal tolerances than adults and may enable the...
Microscopic stages play an integral role in the kelp life cycle and ultimately determine settlement patterns of adult populations. Kelp gametophytes often exhibit broader thermal tolerances than adults and may enable the persistence of kelp forests under stressful conditions that adult sporophytes cannot survive. However, physiological responses to moderate increases in temperature can be complex in kelps and may depend on the ability to obtain sufficient inorganic carbon for photosynthesis. While most kelps use carbon concentrating mechanisms (CCMs) to convert abundant HCO to CO for use in photosynthesis when CO is limited, little is known about CCM functioning in their microscopic life stages. To better understand the role of CCMs in kelp gametophyte physiology, we measured steady-state net and gross photosynthesis and external carbonic anhydrase (eCA)-mediated CCM usage in gametophytes of two forest-forming kelp species, Macrocystis pyrifera and Pelagophycus porra, under different irradiance and temperature conditions. Both species used eCA-mediated CCMs to support 5%-40% of their photosynthetic carbon demand and increased HCO usage in response to elevated irradiance and temperature. Our results suggest that M. pyrifera and P. porra gametophytes adjust their inorganic carbon use efficiency to acclimate to environments with varying irradiance and temperature, which may enhance photosynthetic performance and survival across depth gradients.
Chloroplast and mitochondrial genomes of Sphaerosorus coelastroides Pascher (Xanthophyceae) from Central Appalachia, Clinch River, Virginia, United States.
Collins GS, Matthews RA, Cahoon AB
J Phycol · 2026 Jun · PMID 42223988 · Publisher ↗
This report describes the isolation and culture of Sphaerosorus coelastroides from the plankton of a freshwater river in the central Appalachian mountain chain. This alga was first observed in a dry freshwater riverbed i...
This report describes the isolation and culture of Sphaerosorus coelastroides from the plankton of a freshwater river in the central Appalachian mountain chain. This alga was first observed in a dry freshwater riverbed in Central Europe in 1908 and, since then, has been included in Xanthophyceae surveys from nearly all continents with temperate climates. Differential interference microscopic analysis of our isolate revealed cell sizes ranging from 10.2 to 19 μm in diameter occurring in groups of two to 32 cells with a mucilage layer that changed thickness depending upon the phase of the life cycle. Chloroplasts were light green, and confocal fluorescence microscopy revealed three or more per cell. Genetic markers were sequenced, annotated, and deposited into GenBank, and include the 18S nuclear rRNA gene (PX102079) and completed chloroplast (PV826133) and mitochondrial (PV826132) genomes. Phylogenetic analyses using 18S and rbcL gene sequences revealed that this isolate was closely related to S. composita, the only other known species from this genus. This isolate was deposited into the UTEX Culture Collection of Algae, making it the only strain of this alga available for phycological study at this time.
Seaweed community dynamics on the Konkan coast: Implications of variation in environmental factors.
Imchen T, Akshay KP
J Phycol · 2026 Jun · PMID 42223987 · Publisher ↗
This study investigated seaweed diversity across 21 rocky intertidal sites along the Konkan coast, on the west coast of India. A total of 107 species were documented; Rhodophyta (red algae) were the most dominant (43.9%)...
This study investigated seaweed diversity across 21 rocky intertidal sites along the Konkan coast, on the west coast of India. A total of 107 species were documented; Rhodophyta (red algae) were the most dominant (43.9%), followed by Chlorophyta (green algae, 29%) and Phaeophyceae (brown algae, 27.1%). High species diversity (H') and even distribution were observed at the Alibaug-Murud and Sandkhol stations. Specifically, Sandkhol hosted the highest richness of Phaeophyceae (15 species), whereas Kunkeshwar exhibited the highest Rhodophyta richness (24 species). The greatest Chlorophyta richness (12 species) was recorded at Anjuna, Kunkeshwar, and Alibaug-Murud. Environmental factors, including salinity, pH, light intensity, and nutrients showed significant spatio-seasonal variations (p < 0.01). Nutrient-rich conditions were observed to promote the growth of opportunistic, fast-growing species, which may outcompete and inhibit slower growing taxa, thereby altering overall diversity. Salinity and nutrient levels emerged as the predominant variables correlated with community structure. Notably, ~71% of species were common to both pre-monsoon and post-monsoon seasons. Furthermore, this study indicates that increased variability in factors such as nutrients may promote the dominance of opportunistic macroalgae.
Effects of rapid and sustained changes in light and salinity on Heterosigma akashiwo (Raphidophyceae).
D'Souza NA, Hebner CJ, Stauffer BA
J Phycol · 2026 Jun · PMID 42223984 · Publisher ↗
The euryhaline raphidophyte Heterosigma akashiwo is a harmful algal bloom (HAB) species found worldwide, including in coastal waters that experience inputs of freshwater from large river systems. Heterosigma akashiwo can...
The euryhaline raphidophyte Heterosigma akashiwo is a harmful algal bloom (HAB) species found worldwide, including in coastal waters that experience inputs of freshwater from large river systems. Heterosigma akashiwo can tolerate salinities ranging from 6 to 30; however, H. akashiwo ecophysiology under covarying salinity and light regimes that represent the gradients of sediment-laden, freshwater inputs that are common in coastal waters are unknown. This research describes the responses of H. akashiwo to rapid and sustained changes in light and salinity at levels expected in estuarine and coastal regions impacted by large river inputs. We monitored changes in growth, cell size, and chlorophyll a in cultures exposed to nine salinity-light environments over 7 and 14 days and in exposed cultures returned to their original environment through rapid or incremental shifts. Heterosigma akashiwo grew at all salinity and light levels tested. Growth was primarily influenced by light following rapid salinity-light shifts but was driven by both salinity and light during incremental shifts back to the original conditions. Cell sizes were influenced by both light and salinity. Heterosigma akashiwo could sustain growth in nonideal conditions following rapid environmental changes but showed contractions in niche over longer timelines. Heterosigma akashiwo growth also returned to, or surpassed, baseline levels following removal of the two stressors. These results indicate that H. akashiwo can rapidly adapt to a wide variety of salinity-light environments and could therefore be a dominant HAB species in these river-influenced environments in the future, where such environmental fluctuations are expected.
Nanoscale elemental mapping reveals the effect of light and temperature on Gephyrocapsa huxleyi coccoliths.
Flavin C, Marchitto T, Pattammattel A … +3 more , Chu YS, Chatterjee A, Toney MF
J Phycol · 2026 Jun · PMID 42216894 · Publisher ↗
Coccolithophores produce vast quantities of stable calcium carbonate coccoliths, occupying the distinctive position as one of the most productive calcifying organisms on Earth. Gephyrocapsa huxleyi, the most abundant spe...
Coccolithophores produce vast quantities of stable calcium carbonate coccoliths, occupying the distinctive position as one of the most productive calcifying organisms on Earth. Gephyrocapsa huxleyi, the most abundant species of coccolithophores across modern oceans, plays an important role in the biological carbon pump and may serve as inspiration for nature-based carbon capture and sequestration technologies. Despite intensive study into G. huxleyi, the biological mechanisms of coccolith synthesis remain unclear. Here, we employ synchrotron X-ray fluorescence to quantitatively map elemental incorporation (calcium, Ca; strontium, Sr; sulfur, S; iron, Fe; and silicon, Si) into G. huxleyi coccoliths at 40-nanometer resolution. Trace elements play a role in determining the thermodynamic stability of coccolith carbonate sequestration and may provide insight into unknown mechanisms of coccolithogenesis. Although the coccolith Sr/Ca ratio has been widely applied as a paleoceanographic proxy, understanding of the Sr/Ca phenomena is limited. Our results confirm that Sr/Ca is temperature dependent but challenge the hypothesis that growth rate is a primary determinant. We find that increased light irradiance led to an ~30% decrease in calcium incorporated into the coccoliths. Surprisingly, X-ray fluorescence spectra and mapping revealed evidence of sulfur, at approximately three times the concentration of Sr, embedded in and around the calcite matrix, suggesting that G. huxleyi coccoliths may play an expanded role in the global sulfur cycle. Based on our elemental maps, we postulate that sulfur is active in the intracellular coccolith vesicle and plays a direct role in formation of G. huxleyi coccoliths.
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