Journal Of Phycology[JOURNAL]
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200 papers
A simple and effective protocol for cryopreservation of germplasm of the bull kelp, Nereocystis luetkeana (Phaeophyceae).
Coleman LJM, Read S, Sokhey AK … +1 more , Bisgrove S
J Phycol · 2025 Jun · PMID 40285715 · Full text
Kelps are large brown seaweeds that can form three-dimensional underwater forests that provide food and habitat for a wide diversity of marine organisms. They also provide a wealth of ecosystem services to humans and may...
Kelps are large brown seaweeds that can form three-dimensional underwater forests that provide food and habitat for a wide diversity of marine organisms. They also provide a wealth of ecosystem services to humans and may be able to help combat climate change through blue carbon. However, kelps are currently in decline in many parts of the world, most likely due to rising ocean temperatures, and conservation action is needed quickly to preserve kelp biodiversity. One kelp conservation strategy that needs further development is biobanking, the storage of biological material. In particular, the development of cryopreservation protocols would permit easier storage of large quantities of kelp germplasm under stable conditions. In this paper, we compare the effectiveness of different cryoprotective agents-chemicals that mitigate the damaging effects of freezing on living tissue-for use in cryopreservation of gametophyte tissue of the bull kelp, Nereocystis luetkeana. We observed that when cryopreserved in a solution of 10% ethylene glycol + 9% sorbitol, Nereocystis gametophytes of both sexes showed excellent survivorship 6 weeks after removal from cryogenic conditions. Although kelp cryopreservation protocols still need to be further researched, we believe that these methods have great potential to improve and expand kelp biobanking, and we would encourage the development of protocols for more kelp species as well as more widespread adoption of cryopreservation by existing kelp biobanking efforts.
Corrigendum to "Floridanema gen. nov. (Aerosakkonemataceae, Aerosakkonematales ord. nov., Cyanobacteria) from benthic tropical and subtropical fresh waters, with the description of four new species".
J Phycol · 2025 Apr · PMID 40265495 · Publisher ↗
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A historical review of giant kelp harvesting in Tasmania.
Forbes H, Visch W, Bennett S … +3 more , Sanderson JC, Wright JT, Layton C
J Phycol · 2025 Jun · PMID 40249852 · Full text
Kelps have a long history of human use and exploitation. Knowledge of past harvesting practices offers insights into environmental baselines and the contemporary management and conservation of these critically important...
Kelps have a long history of human use and exploitation. Knowledge of past harvesting practices offers insights into environmental baselines and the contemporary management and conservation of these critically important ecosystems. In Tasmania, Australia, giant kelp (Macrocystis pyrifera) was commercially harvested for alginate production from 1964 to 1973, but those forests have since undergone precipitous declines due primarily to climate change. We reviewed a collection of archival data and sources to describe the history, methods, and scale of this understudied and largely forgotten industry. We calculated that >65,000 tonnes (wet weight) of Macrocystis were harvested from eastern Tasmania over a decade (mean annual harvest = 6531 t), making it one of the largest wild harvest industries to ever exist in the region. However, the industry had challenges finding sufficient biomass to sustain operations, ultimately driving its closure in less than a decade. Feasibility surveys prior to harvesting suggested much greater kelp availability than was ultimately realized, perhaps motivating overexpansion. Against a backdrop of climate change in this ocean warming hotspot, harvest efforts grew wider and more intensive, and during summer months when stocks were lowest, almost all exploitable biomass was harvested. It remains unclear whether harvesting contributed to the decline of Tasmanian Macrocystis forests, but it may have reduced their resilience and exacerbated other stressors, particularly in heavily harvested areas. This historical review provides a rare opportunity to examine the past scale and use of now-endangered Macrocystis forests and also to help inform the contemporary management and conservation of seaweed resources.
Comparative analysis of mitochondrial genomes of Chaetoceros species.
Cui Z, Xu Q, Liu F … +2 more , Wang J, Chen N
J Phycol · 2025 Jun · PMID 40249850 · Publisher ↗
Chaetoceros is one of the most diverse genera of marine planktonic diatoms. Chaetoceros species are common and may become dominant in coastal ecosystems. Many Chaetoceros species can develop harmful algal blooms with neg...
Chaetoceros is one of the most diverse genera of marine planktonic diatoms. Chaetoceros species are common and may become dominant in coastal ecosystems. Many Chaetoceros species can develop harmful algal blooms with negative effects on the aquaculture industry. In this study, we constructed full-length mitochondrial genomes (mtDNAs) for 12 Chaetoceros species, including eight known species and four undescribed species. The sizes of these mtDNAs are generally similar, varying from 34,174 to 39,411 bp. Despite extensive synteny conservation, discrete regions showed high variations, and based on these regions, a specific primer chaetomt1 for Chaetoceros species was designed. The availability of mtDNAs from various Chaetoceros species is not only valuable as a super-barcode for phylogenetic analysis but also important for functional and evolutionary analysis of diatoms.
Remodeling of the terpenoid metabolism during prolonged phosphate depletion in the marine diatom Phaeodactylum tricornutum.
Pruckner F, Morelli L, Patwari P … +1 more , Fabris M
J Phycol · 2025 Jun · PMID 40234016 · Full text
Terpenoids are a diverse class of naturally occurring organic compounds, which derive from five-carbon isoprene units and play crucial roles in physiology, ecological interactions such as defense mechanisms, or adaptatio...
Terpenoids are a diverse class of naturally occurring organic compounds, which derive from five-carbon isoprene units and play crucial roles in physiology, ecological interactions such as defense mechanisms, or adaptation to environmental stresses. In Phaeodactylum tricornutum, some of the most important isoprenoids are sterols and pigments, derived from precursors of the cytosolic mevalonate and the plastidial methyl-erythritol 4-phosphate pathway, respectively. However, the regulation of isoprenoid metabolism in P. tricornutum has not yet been characterized, presenting a major gap in our understanding of its ecological functions and adaptations. By leveraging metabolic, photosynthetic, and transcriptomic analyses, we characterized the dynamic remodeling of the isoprenoid pathways during prolonged nutrient stress in wild-type diatoms. We observed the down-regulation of the methylerythritol 4-phosphate and pigment biosynthesis pathways and the upregulation of key genes in the mevalonate and sterol biosynthesis pathways. At the metabolite level, we observed an overall decrease in pigment and no changes in sterol levels. Using a genetically engineered diatom strain to produce a heterologous monoterpenoid to monitor the availability of one of the main terpenoid precursors, geranyl diphosphate (GPP), we suggest that cytosolic GPP pools increase during prolonged phosphate depletion. Our results have demonstrated how the biosynthesis of isoprenoid metabolites and the pools of prenyl phosphate are vastly remodeled during phosphate depletion. We anticipate that the knowledge generated in this study can serve as a foundation for understanding ecological responses and adaptations of diatoms to nutrient stress, contributing to our broader comprehension of marine ecosystem dynamics and design strategies for producing high-value compounds in diatoms.
Genetic and morphological variation in the genus Zygogonium (Zygnematophyceae, Charophyta) from localities in Europe and North America and description of Z. angustum, sp. nov.
Stancheva R, Lewis LA, Hall J … +3 more , Šoljaková T, Permann C, Holzinger A
J Phycol · 2025 Jun · PMID 40203186 · Full text
The globally distributed genus Zygogonium exhibits a narrow environmental range, with 19 morphologically described species. Its molecular characterization is poor, based on a single accession of the type species Z. erice...
The globally distributed genus Zygogonium exhibits a narrow environmental range, with 19 morphologically described species. Its molecular characterization is poor, based on a single accession of the type species Z. ericetorum from Austria. We examined the genetic variability, morphology, and ultrastructure of field-collected Zygogonium material from different sampling sites in Austria, Norway, Ireland, Scotland, and the United States. Phylogenetic analysis based on partial sequences of the psbC gene distinguished three well-supported groups and one subgroup. AtpB gene sequences collected from a subset of samples also support this result, while rbcL gene data provided lower support. Group 1A contained the type species Z. ericetorum from Obergurgl/Austria and samples from Kühtai/Austria, Norway, and Scotland. The morphology was characterized by wide vegetative filaments (15-31 μm) and the occurrence of aplanospores with purple residue. Group 1B contained Z. cf. ericetorum from Ireland and Ellmau/Austria. Filaments were in a similar size range (12-30 μm) as in group 1A. This group had round unusual akinetes with green or purple content, had one or two chloroplasts, and was surrounded by a thick cell wall; no aplanospores were observed. Group 2 collected from Ireland had narrower filaments (8-12 μm), cells up to six times longer than wide, and contained elongated aplanospores. Therefore, we have described a new species Z. angustum sp. nov. Group 3 contained Z. cf. ericetorum from Norway and the United States, represented by vegetative filaments with an intermediate width (13-20 μm), but no other distinct morphological features. The morphological and genetic variability observed in Zygogonium is possibly related to habitat and ecology.
Critical taxonomic revision of Korean Dictyoteae describing three new species and honoring Haenyeo culture.
Vieira C, Kang JC, Daudinet M … +2 more , Akita S, Kim MS
J Phycol · 2025 Apr · PMID 40186544 · Full text
This study re-evaluates the species diversity and taxonomy of the genera Canistrocarpus, Dictyota, and Rugulopteryx in Korea using an integrative approach combining molecular data and morphological observations. Phylogen...
This study re-evaluates the species diversity and taxonomy of the genera Canistrocarpus, Dictyota, and Rugulopteryx in Korea using an integrative approach combining molecular data and morphological observations. Phylogenetic analyses based on psbA, cox1, and rbcL gene sequences identified nine lineages including eight Dictyota and one Rugulopteryx. Morphological assessments corroborated these molecular findings. Of the seven species listed in recent national checklists, only two were confirmed, while the remaining species were misidentifications. Three novel species are described: Dictyota haenyeosa sp. nov., Dictyota sumbisoria sp. nov., and Dictyota taewakia sp. nov. Additionally, molecular evidence confirmed that the species historically identified as D. dichotoma in Korea corresponds to D. spathulata, a species described from Japan. This revision of Dictyota taxonomy highlights the importance of molecular tools in resolving long-standing misidentifications. The updated checklist for Korean Dictyota and Rugulopteryx includes D. bartayresiana, D. coriacea, D. haenyeosa sp. nov., D. pfaffii, D. spathulata, D. sumbisoria sp. nov., D. taewakia sp. nov., and R. okamurae. The genus Canistrocarpus is absent from the Korean flora. The Korean Dictyota and Rugulopteryx flora is predominantly endemic to the Eastern Asian region (Korea and Japan), with species such as D. coriacea, D. haenyeosa sp. nov., D. spathulata, D. sumbisoria sp. nov., D. taewakia sp. nov., and R. okamurae. Exceptions include the widely distributed, potentially introduced species D. pfaffii and D. bartayresiana, both originally described from the Caribbean. Rugulopteryx okamurae, while endemic to Korea and Japan, has also been introduced to the Atlantic and Mediterranean regions over the past two decades.
Moderate levels of dissolved iron stimulate cellular growth and increase lipid storage in Symbiodinium sp.
Dellisanti W, Murthy S, Bollati E … +2 more , Prehn Sandberg S, Kühl M
J Phycol · 2025 Jun · PMID 40159425 · Full text
Dinoflagellates in the family Symbiodiniaceae are fundamental in coral reef ecosystems and facilitate essential processes such as photosynthesis, nutrient cycling, and calcium carbonate production. Iron (Fe) is an essent...
Dinoflagellates in the family Symbiodiniaceae are fundamental in coral reef ecosystems and facilitate essential processes such as photosynthesis, nutrient cycling, and calcium carbonate production. Iron (Fe) is an essential element for the physiological processes of Symbiodiniaceae, yet its role remains poorly understood in the context of cellular development and metabolic health. Here, we investigated the effect of iron availability-0-100 nM Fe(III)-on Symbiodinium sp. ITS2 type A1 cultures and quantified cellular content using flow cytometry and holotomography. Moderate levels of dissolved Fe (50 nM) enhanced growth rates and cellular content development in Symbiodinium sp., including lipids and proteins. We observed distinct growth patterns, pigment concentrations, and cellular morphology under increasing Fe concentrations, indicating the influence of iron availability on cellular physiology. Nondestructive, label-free holotomographic microscopy enabled single-cell in vivo imaging, revealing higher intracellular lipid accumulation (+57%) in response to 50 nM Fe(III) enrichment. Our findings contribute to a deeper understanding of the relationship between iron availability and Symbiodinium sp. growth and cellular development, with potential implications for coral health and reef resilience in the face of environmental stressors.
Toward understanding the mechanisms of Raphidiopsis raciborskii response to chill/light stress.
Tokodi N, Latkowska E, Klimczak B … +6 more , Kłodawska K, Malec P, Willis A, Kokociński M, Antosiak A, Dziga D
J Phycol · 2025 Jun · PMID 40132033 · Publisher ↗
Cyanobacteria, particularly Raphidiopsis raciborskii, are known for their harmful blooms, posing significant ecological and economic challenges in aquatic ecosystems. This study investigates the strain-specific adaptive...
Cyanobacteria, particularly Raphidiopsis raciborskii, are known for their harmful blooms, posing significant ecological and economic challenges in aquatic ecosystems. This study investigates the strain-specific adaptive mechanisms of five R. raciborskii strains (CS-505, CS-506, UAM/DH-KmRr, UAM/DH-BiRr, and UAM/DH-MRr) under chill/light stress (low temperature and high light intensity), focusing on growth, pigment composition, photosynthetic activity, gene expression, and toxin production. Results revealed that growth rates were significantly reduced under stress for all strains, with the Polish strain UAM/DH-MRr showing the highest resilience. Stress conditions caused a reduced chlorophyll a level and increased carotenoid/Chl a ratio, suggesting photoprotective adaptations. Photosynthetic quantum efficiency (Fv/Fm) declined during chill/light but was recovered post-stress, while electron transport rates (rETR) were not significantly altered. Enhanced respiration and increased photosynthetic oxygen evolution were observed, particularly in CS-506 and UAM/DH-MRr. Principal component analysis (PCA) highlighted pigment content and parameters related to photosynthetic electron transport as key factors influencing response; no variable-specific groupings were observed among strains regarding the broad range of parameters. Gene expression analyses revealed divergent transcriptional regulation of genes involved in photosynthesis and cylindrospermopsin (CYN) biosynthesis, with toxic CS-505 upregulating cyr genes under stress, while CS-506 down-regulated them. Intracellular CYN levels decreased under stress, yet cell quotas increased in CS-505, which warrants further investigation. Our results indicate the complexity of strain-specific responses to chill/light stress and highlight the importance of understanding physiological mechanisms for predicting and managing cyanobacterial blooms in diverse climates.
Microcystin production is important for toxic Microcystis to survive long-term nitrogen starvation.
Lian XY, Qiu GW, Zheng WC … +6 more , Shang JL, Xu HF, Dai GZ, Gan NQ, Zhang ZC, Qiu BS
J Phycol · 2025 Apr · PMID 40119875 · Publisher ↗
Toxic cyanobacterial blooms have expanded and intensified on a global scale. Although microcystins are known as the most abundant cyanotoxins released during cyanobacterial blooms, the physiological role of these toxic s...
Toxic cyanobacterial blooms have expanded and intensified on a global scale. Although microcystins are known as the most abundant cyanotoxins released during cyanobacterial blooms, the physiological role of these toxic secondary metabolites has not been fully resolved. Here, we show that microcystin production is important for toxic Microcystis to maintain carbon metabolism under long-term nitrogen starvation and subsequent recovery. Compared to carbon metabolism in the nonmicrocystin-producing strains, toxic Microcystis could accumulate more carbon reserves under nitrogen limitation, which is important for the survival of cells under stressful conditions. Transcriptomic analysis revealed that the genes involved in microcystin synthesis were significantly up-regulated at the initial recovery phase, indicating their essential role in strengthening glycogen catabolism and fueling recovery. Flow cytometry analysis showed that compared to nontoxic strains, microcystin-producing Microcystis exhibited a higher survival and recovery rate after prolonged nitrogen starvation, which is consistent with the dominance of these species at the early stage of cyanobacterial blooms. The close genetic traits between Microcystis strains suggest that the strategies observed here might be highly conserved. Our results imply that toxic Microcystis establishes a competitive advantage over nontoxic species and provides insights into the seasonal succession of natural Microcystis populations.
Taxonomic review of Tryblionella with special reference to the Apiculatae group-New characters of genus Tryblionella sensu stricto (Bacillariaceae).
Olszyński RM, Górecka E, Trobajo R … +3 more , Gastineau R, Ashworth M, Mann DG
J Phycol · 2025 Apr · PMID 40103222 · Full text
Tryblionella (Bacillariaceae) was described by Smith in 1853, and for many years, the diagnosis of this genus was questionable. Recent molecular analysis based on the rbcL gene marker suggests that Tryblionella is a poly...
Tryblionella (Bacillariaceae) was described by Smith in 1853, and for many years, the diagnosis of this genus was questionable. Recent molecular analysis based on the rbcL gene marker suggests that Tryblionella is a polyphyletic genus with T. apiculata, T. hungarica, and T. gaoana forming a distinct group from other Tryblionella representatives. Therefore, this study aimed to clarify the diagnosis of Tryblionella as a genus. The focus of this study was a selected group of species previously categorized within Grunow's section Apiculatae, which includes the type species T. acuminata. This classification serves as a foundation for conducting morphological and molecular comparisons with taxa of Tryblionella sensu lato, which are likely to represent distinct and highly diverse genera. Our review includes a detailed examination of frustule ultrastructure and ontogeny combined with a new molecular phylogenetic analysis derived from a three-gene concatenated dataset. The results of our research indicated that among Tryblionella, several monophyletic groups of taxa can be distinguished, including Tryblionella sensu stricto (s.s.), by three key characters: a porose valve cross-section; longitudinal valve undulation, where the peak of the undulation is located on the proximal side of the valve; and the presence of an axial sternum with thickened and relief virgae. Tryblionella s.s. taxa share a similar girdle structure: The girdle is graded, except that the first band bears a single row of poroids in the pars exterior and a crenulate margin on the side corresponding to the distal valve mantle.
Applications of environmental DNA monitoring for seaweed reproductive phenology: A case study with giant kelp (Macrocystis pyrifera).
Ward MR, Burridge CP, McCammon S … +3 more , Smolenski A, Hurd CL, Visch W
J Phycol · 2025 Apr · PMID 40103189 · Full text
Monitoring the seasonal reproductive cycles of seaweeds is crucial for effective population and ecosystem management, as well as mariculture seedstock collection. Traditional methods, such as visual monitoring by SCUBA d...
Monitoring the seasonal reproductive cycles of seaweeds is crucial for effective population and ecosystem management, as well as mariculture seedstock collection. Traditional methods, such as visual monitoring by SCUBA diving or snorkeling, are costly, labor-intensive, and limited in temporal and spatial coverage. This study explores substituting these methods with environmental DNA (eDNA) techniques for giant kelp (Macrocystis pyrifera, order Laminariales). This laboratory study aimed to determine the minimum detectable concentration of zoospores and sporophyte tissue needed for detecting the reproductive phenology of M. pyrifera and to assess the ability and sensitivity to discriminate between life stages. The study involved syringe-filtering seawater samples through 0.45-μm pore-size filters before quantitative polymerase chain reaction (qPCR) analysis with species-specific primers. There was a strong positive correlation between zoospore concentration and eDNA copies per μL (ρ = 0.982, p < 0.001), and a weak correlation for sporophyte wet weight (ρ = 0.367, p = 0.134). There was a significant difference between zoospore and zoospore + sporophyte treatments (p = 0.010), indicating the substantial influence of sporophyte tissue on detected eDNA quantity. Sporophyte tissue obscures the zoospore signal, especially at lower zoospore concentrations (<37 zoospores · mL), highlighting that eDNA analysis is suitable for monitoring reproductive peaks and broader patterns in seasonal reproduction cycles of giant kelp when zoospore concentrations are high.
KEIO knockout collection reveals metabolomic crosstalk in Chlorella spp.-Escherichia coli co-cultures.
Tong CY, Tomita H, Miyazaki K … +2 more , Derek CJC, Honda K
J Phycol · 2025 Jun · PMID 40074247 · Publisher ↗
The interdependence between microalgae and bacteria has sparked scientific interest over years, primarily driven by the practical applications of microalgal-bacteria consortia in wastewater treatment and algal biofuel pr...
The interdependence between microalgae and bacteria has sparked scientific interest over years, primarily driven by the practical applications of microalgal-bacteria consortia in wastewater treatment and algal biofuel production. Although adequate studies have focused on the broad interactions and general behavior between the two entities, there remains a scarcity of study on the metabolic role of symbiotic bacteria in promoting microalgal growth. Here, we use the KEIO Knockout Collection, an Escherichia coli gene knockout mutant library, to systematically screen for genes involved in the interdependence of Chlorella sorokiniana and E. coli. By co-cultivating C. sorokiniana and E. coli knockout mutants in 96-well microplates (200 μL medium per well) under white light at 25°C, 31 potential algal growth-promoting and 56 growth-inhibiting genes out of 3985 genes were identified that enhanced (≥1.25-fold) and diminished (≤0.8-fold) the production of algal chlorophyll-a content, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) mapping of these growth-regulating genes suggested a metabolic symbiosis involving bacteria-derived cobalamin (cobU, cobC), biotin (bioB, bioF, bioC, bioD, fabF, fabH), riboflavin (fbp, guaB, gnd, guaA, zwf, purA), and 2,3-butanediol (fumB, adhE, mdh, frdB, pta, sdhC). The effects of these metabolites were further validated by supplementing the agents into the axenic algal cultures; Dose-dependent trends were observed for each metabolite, with a maximum four-fold increase in algal biomass productivity over the control. The specific growth rate of algae was increased by ≥1.27-fold and doubling time was shortened by ≥22.5%. The present results, obtained through genome-wide analyses of interdependence between microalgae and bacteria, reveals multiple interactions between organisms via metabolites.
Cryptic diversity within the Gonyaulax spinifera species complex, its relation to the cyst-defined species Spiniferites bentorii, S. mirabilis and S. membranaceus, with the description of Gonyaulax carbonell-mooreae sp. nov. (Gonyaulacales, Dinophyceae).
Huang S, Mertens KN, Nguyen-Ngoc L … +9 more , Doan-Nhu H, Krock B, Li Z, Luong DQ, Bilien G, Pospelova V, Shin HH, Plewe S, Gu H
J Phycol · 2025 Apr · PMID 40063417 · Publisher ↗
The fossil dinoflagellates Spiniferites bentorii, S. mirabilis, and S. membranaceus are known to inhabit recent sediments and are often used to reconstruct past sea-surface conditions. However, information on their corre...
The fossil dinoflagellates Spiniferites bentorii, S. mirabilis, and S. membranaceus are known to inhabit recent sediments and are often used to reconstruct past sea-surface conditions. However, information on their corresponding motile cells has been rare. We isolated single cysts resembling these fossil species from China and France to yield Gonyaulax spinifera-like cells. Gonyaulax strains were also established from Viet Nam and South Korea by isolating single cells. Both cysts and cells were examined by light and scanning electron microscopy, and their LSU rRNA genes were sequenced. A new Gonyaulax species, G. carbonell-mooreae, was obtained from S. bentorii-like cysts and considered the equivalent of Spiniferites bullatus, dating back to the Campanian. Gonyaulax kunsanensis was related to S. mirabilis-like cysts. A typical S. membranaceus cyst from France yielded cells resembling G. lewisiae but shared only 75% similarity in LSU rRNA gene sequence with those from South Korea. Molecular phylogeny revealed that the pronounced apical boss is systematically significant, whereas the presence of intergonal processes is insignificant. Two ASVs of 18S rRNA V4 region were respectively identified as G. kunsanensis and G. lewisiae from the Tara Oceans metabarcoding data. Gonyaulax kunsanensis has a wide distribution in the Pacific, Indian, and Atlantic Oceans, but G. lewisiae has a restricted distribution. One strain of G. kunsanensis was examined for yessotoxin content using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), but no detectable amounts of toxins were observed. Our results uncover the hidden diversity within the G. spinifera species complex and stress the significance of cyst morphology in the taxonomy of Gonyaulax.
Characterization of the Pyropia katadae plastid genome and comparative analysis within Bangiales species.
Tang X, Yu X, Zhu X … +3 more , Bian K, Meng C, Mao Y
J Phycol · 2025 Apr · PMID 40062743 · Publisher ↗
Bangiales species live in intertidal regions and suffer from stresses from a variable environment, making them suitable research objects for studying how plants adapt to nature. In this study, the plastid genome of Pyrop...
Bangiales species live in intertidal regions and suffer from stresses from a variable environment, making them suitable research objects for studying how plants adapt to nature. In this study, the plastid genome of Pyropia katadae was sequenced and compared with those of 11 previously reported Bangiales species. The Py. katadae plastid genome was 193,531 bp long and contained a single-copy region (LSC) of 149,821 bp, a small single-copy region (SSC) of 34,732 bp, and two direct repeats (DRs) 4489 bp long in between. Furthermore, we compared the plastid genomes of 12 Bangiales species. Among the 12 Bangiales plastid genomes, Bangia fuscopurpurea harbored the largest plastid genome size (196,913 bp), and Py. perforata harbored the smallest (189,789 bp). Phylogenetic analyses of shared genes indicated that Py. katadae clustered with Py. yezoensis into a single clade with a high bootstrap value. An overall high degree of similarity in gene content and arrangement among the Bangiales plastid genomes was observed. The size of the plastid genomes and that of the repeats of Pyropia were positively correlated, demonstrating that the repeats were essential for changes in the plastid genome size over a short evolutionary time. The presence of DR or approximate DR regions in most Bangiales plastid genomes indicates the existence of DR regions in their last common ancestor. The different shortened lengths of identical DR regions showed that each species experienced species-specific evolutionary events, which might cause variations in the sequences and the loss of genes. The two steps of fragment reversal could generate the DRs of Bangiales species from an ancestor in common with Florideophyceae. We identified positive selection sites in eight genes that appeared to be essential for Bangiales species to adapt to diverse environments. Our results provide essential genetic data for an in-depth understanding of the evolution and phylogeny of Bangiales species.
A comparison of calcification mechanisms in haploid and diploid cells of the coccolithophore Calcidiscus leptoporus (Murray & Blackman 1898).
Meyer EM, Taylor AR
J Phycol · 2025 Jun · PMID 40062711 · Full text
Coccolithophores are prominent marine pelagic calcifiers due to their production of calcite coccoliths. Diploid coccolithophores produce heterococcoliths intracellularly, with an organic cellulose baseplate scale acting...
Coccolithophores are prominent marine pelagic calcifiers due to their production of calcite coccoliths. Diploid coccolithophores produce heterococcoliths intracellularly, with an organic cellulose baseplate scale acting as a nucleating substrate. However, coccolith production in the haploid life phase has not been extensively studied. Most haploid coccolithophores produce distinct holococcoliths that were previously thought to be produced in an extracellular space. However, we recently observed intracellular holococcolith production in haploid Coccolithus braarudii. We therefore compared the calcification mechanisms of the 2 N and N phases of Calcidiscus leptoporus, an understudied yet ecologically important species, to better understand ultrastructure features related to calcification and explore aspects of the calcification pathway in each life-history phase. We show that both life phases of C. leptoporus produce coccoliths intracellularly and that holococcoliths are likely nucleating on body scales in a dilated vacuole space rather than within a tightly associated coccolith vesicle (CV) as in diploid heterococcolith production. Both life phases were sensitive to the SERCA CaATPase inhibitor thapsigargin, suggesting conservation in the transcellular Ca transport pathways utilized for intracellular calcification, namely through calcium accumulation in the endoplasmic reticulum. However, the Si analogue germanium led to severe disruption of the CV and coccolith morphogenesis only in the diploid life phase. This work provides strong evidence to support a model of intracellular holococcolith production and clearly demonstrates that calcification in both life phases shares a common cellular pathway. Nevertheless, differences in the spatial arrangement of the CV membrane exert significant control over crystal growth that has profound consequences for coccolith morphology.
Hyposaline conditions impact the early life-stages of commercially important high-latitude kelp species.
Farrugia Drakard V, Hollarsmith JA, Stekoll MS
J Phycol · 2025 Apr · PMID 39985765 · Publisher ↗
This study examines how hyposaline stress impacts the early life-stages of commercial kelp species from Alaska. Kelp are important species both ecologically and commercially and are likely to experience significant impac...
This study examines how hyposaline stress impacts the early life-stages of commercial kelp species from Alaska. Kelp are important species both ecologically and commercially and are likely to experience significant impacts due to ongoing climate change. Climate-driven glacial melt and changing rainfall patterns globally will release large amounts of freshwater into coastal systems in the coming decades. Both bull kelp (Nereocystis luetkeana) and ribbon kelp (Alaria marginata) are high-latitude species of commercial and ecological importance. These species inhabit very different environments: While bull kelp is a subtidal, canopy-forming species, ribbon kelp is an intertidal subcanopy species. In this study, fertile specimens of both were collected from various locations in Alaska and induced to release spores. These were cultivated for 30 days in four salinity treatments: 32, 25, 20, and 13. Both species grew and produced gametophytes in salinities down to a salinity of 20, although A. marginata seems to be better adapted to hyposaline conditions. Below a salinity of 20, we observed several impacts on progression between life stages. The response of gametophyte growth and the production of eggs and sporophytes to different salinities varied both by species and by population. Gametophytes of N. luetkeana grew fastest at a salinity of 32, while those of A. marginata grew fastest between 20 and 25 (Juneau) or 25 and 32 (Kodiak). In terms of egg production, A. marginata displayed significant population-level variation. Juneau individuals produced the same number of eggs regardless of salinity. Kodiak individuals produced fewer eggs in hyposaline conditions. The production of sporophytes from eggs for both species from all locations was unaffected by salinities above 20; however, no sporophytes at all were produced at 13. All of this has implications for commercial production in the hatchery phase, as hyposaline stress may induce N. luetkeana to produce sporophytes faster than in full oceanic salinity. In terms of wild populations, the observed population-level and species-level differences in adaptation to hyposaline conditions suggest that decreased salinities in coastal areas are likely to impact the distribution of these two species over the coming decades.
Seasonality and interannual stability in the population genetic structure of Batrachospermum gelatinosum (Rhodophyta).
Shainker-Connelly S, Stoeckel S, Vis ML … +2 more , Crowell RM, Krueger-Hadfield SA
J Phycol · 2025 Feb · PMID 39954296 · Full text
Temporal population genetic studies have investigated evolutionary processes, but few have characterized reproductive system variation. Yet, temporal sampling may improve our understanding of reproductive system evolutio...
Temporal population genetic studies have investigated evolutionary processes, but few have characterized reproductive system variation. Yet, temporal sampling may improve our understanding of reproductive system evolution through the assessment of the relative rates of selfing, outcrossing, and clonality. In this study, we focused on the monoicous, haploid-diploid freshwater red alga Batrachospermum gelatinosum. This species has a perennial, microscopic diploid phase (chantransia) that produces an ephemeral, macroscopic haploid phase (gametophyte). Recent work focusing on single-time point genotyping suggested high rates of intragametophytic selfing, although there was variation among sites. We expand on this work by genotyping 191 gametophytes sampled from four sites that had reproductive system variation based on single-snapshot genotyping. For this study, we sampled at multiple time points within and among years. Results from intra-annual data suggested shifts in gametophytic genotypes throughout the season. We hypothesize that this pattern is likely due to the seasonality of the life cycle and the timing of meiosis among the chantransia. Interannual patterns were characterized by consistent genotypic and genetic composition, indicating stability in the prevailing reproductive system through time. Yet, our study identified limits by which available theoretical predictions and analytical tools can resolve reproductive system variation using haploid data. There is a need to develop new analytical tools to understand the evolution of sex by expanding our ability to characterize the spatiotemporal variation in reproductive systems across diverse life cycles.
Algal perspectives: The algal phyla.
Delwiche CF
J Phycol · 2025 Feb · PMID 39950333 · Full text
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Three reference genomes for freshwater diatom ecology and evolution.
Roberts WR, Alverson AJ
J Phycol · 2025 Apr · PMID 39930529 · Full text
Diatoms are an important component of marine and freshwater ecosystems. Although the majority of described diatom species live in freshwater systems, genome sequencing efforts have focused primarily on marine species. Ge...
Diatoms are an important component of marine and freshwater ecosystems. Although the majority of described diatom species live in freshwater systems, genome sequencing efforts have focused primarily on marine species. Genomic resources for freshwater species have the potential to improve our understanding of diatom ecology and evolution, particularly in the context of major environmental shifts. We used long- and short-read sequencing platforms to assemble reference genomes for three freshwater diatom species, all in the order Thalalassiosirales, which are abundant in the plankton of oceans, lakes, reservoirs, and rivers worldwide. We targeted three species that cover the breadth of phylogenetic diversity in the cyclostephanoid clade of Thalassiosirales: Cyclostephanos tholiformis (JALLPB020000000), Discostella pseudostelligera (JALLBG020000000), and Praestephanos triporus (JALLAZ020000000). The reference genome for D. pseudostelligera was considerably smaller (39 Mb) than those of both P. triporus (73 Mb) and C. tholiformis (177 Mb). Long-read sequencing allowed for the assembly of scaffold-level genomes, including regions rich in repetitive DNA. Compared to short-read assemblies, long-read assemblies increased the contig N50 length as much as 37-fold and reduced the number of contigs by more than 88%. Transcriptome-guided annotation of the protein-coding genes identified between 10,000 and 12,000 genes. This work provides further demonstration of the value of long-read sequencing and provides novel genomic resources for understanding the ecology and evolution of freshwater diatoms.
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