Journal Of Phycology[JOURNAL]
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200 papers
Genetic structure of sugar kelp in the St. Lawrence Estuary and Gulf (Québec, Canada).
Treillefort M, Le Cam S, Valero M … +7 more , Mauger S, Ruggeri P, Salvo F, Gendron-Lemieux I, Provencher T, Belley R, Dufresne F
J Phycol · 2026 Apr · PMID 41761897 · Full text
The sugar kelp, Saccharina latissima, is cultivated at low scale in Quebec, Canada, and current practice involves seeding meiospores or gametophyte stocks onto spools carrying twine and transferring these to a seaweed fa...
The sugar kelp, Saccharina latissima, is cultivated at low scale in Quebec, Canada, and current practice involves seeding meiospores or gametophyte stocks onto spools carrying twine and transferring these to a seaweed farm site. As the stocks can originate from locations spanning several hundreds of kilometers from the farm sites, such practices could involve genetic contamination and disrupt local adaptations. Assessing genetic structure can inform us of the potential risks associated with these practices. Here, we characterized the genetic diversity and structure of S. latissima from locations in the St. Lawrence Estuary and Gulf at both microsatellite loci (308 sporophytes at 22 loci in 16 sites) and genomic markers (228 sporophytes at 6578 single nucleotide polymorphisms, or SNPs, in 13 sites). Several populations had low heterozygosity values and significant F values at microsatellite loci. No genetic structure was observed among populations with microsatellite loci, but strong genetic structuring was observed with the genomic data. Population structure followed a geographic pattern and was congruent with major currents. Individuals from the wild population in the vicinity of the farm site were genetically distinct from the sporophytes on the growing lines that belong to a genetically distinct group. There was no significant genetic differentiation between wild individuals living in proximity to the farm site and another wild population of the same area. Hence, aquaculture practices have not resulted in changes in the genetic composition of the wild population on a large scale. Our results are important to guide future conservation efforts and the seaweed farming industry.
The hard and soft of it: The role of substrate in patterns of phase dominance and phenology in Gracilaria vermiculophylla.
Krueger-Hadfield SA, Oetterer AP, Kelley DM … +1 more , Ryan WH
J Phycol · 2026 Apr · PMID 41757687 · Full text
Despite the importance of the seasonal timing of events in the life cycle for understanding population dynamics, we lack information on the phenology of most macroalgal species. The red macroalga Gracilaria vermiculophyl...
Despite the importance of the seasonal timing of events in the life cycle for understanding population dynamics, we lack information on the phenology of most macroalgal species. The red macroalga Gracilaria vermiculophylla has become common in both hard- and soft-bottom habitats following its invasion throughout the Northern Hemisphere. In sites with sufficient hard substratum, thalli are fixed by holdfasts to the hard substrate. By contrast, in sites with soft substratum, thalli are free-living and either drift freely or are anchored by the tube-building polychaete Diopatra cuprea. The difference in substrate type has had profound implications on the evolutionary ecology of G. vermiculophylla populations, wherein the life cycle has been disrupted in soft-bottom habitats, leading to tetrasporophytic dominance. To investigate these patterns across seasons, we determined the reproductive state via microscopy and phase via a sex-linked polymerase chain reaction (PCR) assay for >4800 thalli over the course of 3 years at hard and soft bottom sites with fixed and free-living G. vermiculophylla thalli, respectively, along the Eastern Shore of Virginia and in Maryland. At hard-bottom sites, most thalli were reproductive in the summer, and sites were composed of gametophytes and tetrasporophytes, although there was a tetrasporophytic bias. By contrast, soft-bottom sites were overwhelmingly tetrasporophyte-dominated, and fewer thalli were reproductive at any point in the year. Moreover, each soft-bottom site displayed different patterns in the proportion of reproductive thalli, with G. vermiculophylla abundance also fluctuating through time. Phenology surveys are critical for understanding the spread of introduced macroalgae, including the ongoing spread of G. vermiculophylla.
Resolving widespread and endemic dinoflagellates (Symbiodiniaceae) mutualistic with Indo-Pacific octocorals reveals differences in specificity based on host phylogeny.
Butler CC, Turnham KE, Hess A … +1 more , LaJeunesse TC
J Phycol · 2026 Feb · PMID 41725037 · Full text
Endosymbionts in the dinoflagellate family Symbiodiniaceae can form mutualisms with a diverse array of host invertebrates, constituting a widespread and ecologically important family. While those associated with reef-bui...
Endosymbionts in the dinoflagellate family Symbiodiniaceae can form mutualisms with a diverse array of host invertebrates, constituting a widespread and ecologically important family. While those associated with reef-building corals (order Scleractinia) have received considerable research attention, the diversity and ecology of zooxanthellae from soft coral hosts (Octocorallia) have remained understudied and unappreciated. To address this lack of understanding, octocoral zooxanthellae were sampled across the Indo-Pacific and genetic, morphological, ecological, and geographic evidence were utilized to formally characterize five new species in the genus Cladocopium. Four species were associated with hosts in the family Sarcophytidae that horizontally acquire their endosymbionts. Of these new species, C. fabriciae sp. nov. and C. peratum sp. nov. are widespread across the Indo-Pacific whereas C. zanzibariense sp. nov. and C. belauense sp. nov. are known only from their type localities in Zanzibar and Palau, respectively. The fifth species, C. bilineaum sp. nov., occurs in the Pacific and Indian Oceans associated with hosts in the families Xeniidae, which can display either horizontal or vertical mode of transmission and Lemnaliidae, which horizontally transmit their endosymbionts. Because soft coral abundances are increasing with ocean warming across many geographic provinces and in various reef habitats, formal species descriptions of their endosymbionts should facilitate future physiological and ecological research toward a more comprehensive understanding of their natural history and contributions to coral reef ecosystem productivity.
Differential transcriptomic and circadian regulation across giant kelp blades based on relative tissue age.
Chandra MI, Nuzhdin SV, Gracey AY
J Phycol · 2026 Apr · PMID 41721547 · Publisher ↗
Kelps are ecologically and economically important organisms. Kelp biomass generates habitat structure and carbon flux and is increasingly harvested as a sustainable resource. Kelp blades grow through cell proliferation a...
Kelps are ecologically and economically important organisms. Kelp biomass generates habitat structure and carbon flux and is increasingly harvested as a sustainable resource. Kelp blades grow through cell proliferation at the proximal meristem and erode from the distal end, resulting in a spatiotemporal map reflecting tissue development. Diel physiology, such as photosynthesis, respiration, and carbohydrate metabolism, changes across the growing blade, yet the interaction of the circadian clock with age / blade structure has not been explicitly tested. Here, we sampled the proximal and distal ends of giant kelp (Macrocystis pyrifera) blades over 48 h under constant lab conditions to compare differential transcriptomic and circadian regulation across the blade. Gene function was differentially enriched across the blade, with proliferative and protective pathways upregulated in the younger proximal tissue and carbon acquisition and metabolic pathways upregulated in older distal tissue. We identified candidate aging-related genes based on similarities to plant, animal, and fungal senescence-associated genes, which were enriched in the older, distal tissue. While ~13% of analyzed genes displayed consistent circadian regulation across the blade, ~2% displayed altered rhythmic parameters, with consistently lower amplitudes and longer periods in older distal tissue. This is evidence of variable circadian physiology across giant kelp anatomy. The interacting developmental and circadian influences on the giant kelp transcriptome evoked here are integral for understanding the coordination of physiology important to kelp growth and health.
DNA sequencing of Linnaeus's Ulva compressa, U. intestinalis, and U. linza (Ulvaceae, Chlorophyta) and other Ulva type specimens.
Hughey JR, Maggs CA, van der Loos LM … +2 more , Harris SA, Gabrielson PW
J Phycol · 2026 Apr · PMID 41700901 · Publisher ↗
The names published by Linnaeus in Species Plantarum represent the foundation of modern plant taxonomy. Despite their systematic value, very few of Linnaeus's original type specimens have been analyzed using current DNA...
The names published by Linnaeus in Species Plantarum represent the foundation of modern plant taxonomy. Despite their systematic value, very few of Linnaeus's original type specimens have been analyzed using current DNA sequencing technologies. Here, we performed high-throughput sequencing on Linnean and other type specimens of Ulva, a genus of ecological and commercial importance. Chloroplast and mitochondrial genomes were assembled for Linnaeus's U. compressa, U. intestinalis, U. lanceolata, and U. linza as well as Kützing's Phycoseris smaragdina type specimens. Phylogenetic analyses of these data showed that the names U. compressa and U. intestinalis were correctly applied, but U. linza and U. lanceolata were misapplied. Ulva linza is the earliest available name for the European species currently called U. pseudocurvata. The correct name for the globally distributed species previously known as U. "linza" is Ulva smaragdina (Kützing) comb. nov. The names Ulva lanceolata, U. crispata, and Phycoseris olivacea do not represent distinct species, instead being heterotypic synonyms of U. compressa, and P. planifolia is a heterotypic synonym of U. intestinalis. These results demonstrate that genetic characterization of type material can unequivocally resolve longstanding taxonomic debates over scientific names.
To multicellularity and back again: Description of two new coccoid genera (Portococcus gen. nov. and Pseudanabaenococcus gen. nov.) in the basal "filamentous" order Pseudanabaenales, Cyanobacteria.
Strunecký O, Kozlíková-Zapomělová E, Jezberová J … +7 more , Morais J, Lemus MAT, Štenclová L, Johansen JR, Čapková K, Vasconcelos VMO, Mareš J
J Phycol · 2026 Feb · PMID 41700889 · Full text
Despite recent efforts in taxonomic revision of phylogenetically basal photosynthetic cyanobacteria, cryptic diversity and recurrence of simple plesiomorphic morphotypes has continued to appear in phylogenies with poorly...
Despite recent efforts in taxonomic revision of phylogenetically basal photosynthetic cyanobacteria, cryptic diversity and recurrence of simple plesiomorphic morphotypes has continued to appear in phylogenies with poorly characterized "Synechococcus" and "Pseudanabaena" strains. Herein, one of the prominent undefined unicellular lineages was resolved as a monophyletic group of taxa that have lost multicellularity within the otherwise filamentous order Pseudanabaenales. Genome sequencing coupled with the classical polyphasic taxonomic analysis based on the 16S rRNA gene and the ITS rRNA region sequence comparisons, light and transmission electron microscopy, and source habitat record have congruently supported the description of two novel genera, Portococcus, with four new species, and Pseudanabaenococcus, with a single new species. The whole-genome phylogeny was essential for the accurate assessment of phylogenetic relationships between the genera and families and is hereby highly recommended as a new standard integrated in the polyphasic taxonomy of cyanobacteria. Records of the new taxa from a variety of freshwater habitats and one terrestrial cave habitat in geographically distant regions have indicated the need for further investigation to discover the full extent of cryptic diversity in these deep-branching clades. The loss of filamentous forms within the first group in cyanobacterial evolution that had invented it offers an excellent model for future study of the genetic and physiological mechanisms of early prokaryotic multicellularity.
Diversity and seasonal dynamics of the marine diatom family Chaetocerotaceae (Bacillariophyta, Mediophyceae) in Catalan coastal waters (northwest Mediterranean).
Arin L, Reñé A, Timoneda N … +3 more , Gallisai R, Garcés E, Estrada M
J Phycol · 2026 Feb · PMID 41685743 · Full text
The family Chaetocerotaceae includes the genera Chaetoceros and Bacteriastrum, with Chaetoceros being one of the most cosmopolitan, abundant, and diverse diatom genera in the oceans. This study investigated the diversity...
The family Chaetocerotaceae includes the genera Chaetoceros and Bacteriastrum, with Chaetoceros being one of the most cosmopolitan, abundant, and diverse diatom genera in the oceans. This study investigated the diversity and seasonal dynamics of the Chaetocerotaceae in surface waters of two coastal sites along the Catalan coast (Barcelona and Blanes Bay), from 2004 to 2019. A combination of field sample observations, morphological (light and scanning electron microscopy), and molecular (SSU and LSU rDNA gene sequences) analyses of monoclonal cultures, and V4 18S rDNA metabarcoding time-series data from Blanes was used for species identification. The seasonal dynamics of both genera were investigated during two annual cycles at both sites through monthly light microscopy observations and, at Blanes Bay, also through the metabarcoding dataset. A total of 60 species of Chaetoceros and 10 of Bacteriastrum were detected. Based on cell ultramorphology and SSU and LSU rDNA gene phylogenies, two species within the genus Chaetoceros are putatively new to science, although they are not formally described here. The most abundant and frequent taxa were C. tenuissimus, C. socialis, C. vixvisibilis, and the C. curvisetus complex. These species presented similar seasonal trends at both sites, with C. tenuissimus and C. vixvisibilis peaking in late spring and summer, whereas C. socialis was more prevalent in winter. The C. curvisetus complex did not show a clear seasonality although its components were less abundant in summer. These results highlight the value of integrating morphological and molecular approaches to assess the diversity and ecological dynamics of the dominant Chaetoceros species.
An investigation into the efficacy of Biokos® in controlling ciliates in laboratory cultures of Saccharina latissima gametophytes.
Farrugia Drakard V, Fester M, Stekoll MS
J Phycol · 2026 Apr · PMID 41665016 · Full text
A major challenge faced by kelp aquaculture operations is the control of contaminants, including by marine ciliates. Biokos® is a commercially available treatment for ciliate parasites in fish, in which the active ingred...
A major challenge faced by kelp aquaculture operations is the control of contaminants, including by marine ciliates. Biokos® is a commercially available treatment for ciliate parasites in fish, in which the active ingredient is a viscosin-like lipopeptide surfactant. This study aimed to determine whether Biokos® is effective at controlling ciliate contamination in Saccharina latissima cultures without impacting gametophytes. Two experiments were conducted. Biokos® was first added to a live ciliate culture, and mortality was compared to a control. Subsequently, Biokos® was added to a culture of S. latissima gametophytes. The growth, density, and reproduction of gametophytes were compared to a control. Biokos® was highly effective at destroying ciliates within 24 h of treatment. We observed no impact on the vegetative growth of gametophytes. However, Biokos® did reduce gametophyte densities and may have had an impact on adherence. Biokos® also induced higher egg and sporophyte production in female gametophytes, potentially as a response to changes in pH associated with the treatment. There is potential for Biokos® to be effective at controlling ciliate contamination in gametophyte cultures, and at this stage, we would recommend treatment at manufacturer-recommended doses, along with appropriate buffering to maintain the pH of the culture. Further research is recommended on the identity of ciliate species contaminating gametophyte cultures and the response of different kelp species to Biokos®. Additionally, we would recommend that Biokos® now be tested in a commercial hatchery setting to identify impacts on S. latissima throughout the cultivation process and to determine optimal dosing procedures.
Nodosilinea jinyiensis and Nodosilinea qiaokuensis-two novel species of Nodosilinea (Nodosilineaceae, Cyanobacteria) based on a polyphasic approach.
Wei J, Chen J, Li S … +2 more , Li R, Cai F
J Phycol · 2026 Feb · PMID 41657294 · Publisher ↗
Three strains of fine filamentous cyanobacteria were isolated from freshwater lakes in Hubei province, China. A polyphasic analysis based on morphology, ecology, 16S rRNA gene phylogenies, and 16S-23S internal transcribe...
Three strains of fine filamentous cyanobacteria were isolated from freshwater lakes in Hubei province, China. A polyphasic analysis based on morphology, ecology, 16S rRNA gene phylogenies, and 16S-23S internal transcribed spacer (ITS) rRNA region secondary structures was undertaken. Based on the 16S rRNA gene phylogeny, three strains (JYH02, JYH03, and ZYHGY02) are likely new species of Nodosilinea, sharing <98.7% similarity to other species. Furthermore, the ITS rRNA region secondary structures from all three strains were distinct and unique compared with other Nodosilinea species. These results support the establishment of two new species: Nodosilinea jinyiensis sp. nov. and Nodosilinea qiaokuensis sp. nov.
Plastid genome structure and phylogenomics of the freshwater red algal order Batrachospermales (Rhodophyta).
Crowell RM, Lemes Da Silva NM, Paiano MO … +2 more , Vis ML, Necchi O
J Phycol · 2026 Apr · PMID 41641622 · Full text
For the freshwater red algal order Batrachospermales, the number of plastid genomes available is relatively small compared to the number of genera. Fully assembled plastid genomes can provide insights into plastid evolut...
For the freshwater red algal order Batrachospermales, the number of plastid genomes available is relatively small compared to the number of genera. Fully assembled plastid genomes can provide insights into plastid evolution and crucial data for phylogenetic reconstruction. In the present study, 18 plastid genomes were generated for a total of 40 plastid genomes from 38 species representing 18 of the 23 genera. The greatly expanded dataset allowed for comparison of the plastid genome structural characteristics with the other orders in the Nemaliophycidae and inference of the phylogenetic relationships of the genera within the order. Results showed the plastid genomes had either one or two RNA operons, and this variation could be intrageneric. All plastid genomes had the chlB gene with an intron like all Nemaliophycidae but lacked the apcF gene present in all Nemaliophycidae. The loss of the pbsA gene was variable in the Batrachospermales and the Nemaliophycidae. Phylogenetic analysis using a 126-gene concatenated dataset produced a fully supported Batrachospermales. In addition, generally high support for the relationships among the genera resulted in the most robust phylogeny to date. Nevertheless, the phylogeny also highlighted that potentially more data will be needed to resolve the relationship among sections of Nothocladus and other related genera. Overall, the Batrachospermalean genera were split into two well-supported lineages, which had been noted in other studies using plastid and mitochondrial genomes. However, we lack a combination of characters to distinguish these two lineages, as the morphological characters to describe taxa are shared between them.
A phylogenetic classification of diatoms (Bacillariophyta).
Kociolek JP, Ashworth MP, Alverson AJ
J Phycol · 2026 Feb · PMID 41631365 · Publisher ↗
Diatoms are known for their extraordinary species richness, cornerstone roles in aquatic ecosystems, and immense contributions to the global cycling of carbon, oxygen, and silica. For nearly 2 centuries, taxonomic classi...
Diatoms are known for their extraordinary species richness, cornerstone roles in aquatic ecosystems, and immense contributions to the global cycling of carbon, oxygen, and silica. For nearly 2 centuries, taxonomic classifications of diatoms have been based on interpretations of their feature-rich, silica cell walls. These classifications, in turn, have been used to make broad inferences about diatom ecology and evolution, but decades of molecular phylogenetic research have shown that historical and contemporary classification systems do not reflect evolutionary history, severely limiting their utility and insights. We took advantage of recent advances in our understanding of the diatom phylogeny to develop the first entirely natural classification of diatoms, in which only monophyletic groups have been recognized and named. The classification is comprehensive, dividing 431 genera among 68 families, 44 orders, and 10 classes. Among these, seven classes, 13 orders, three families, and one genus are proposed as new. Although the new classification includes many areas of overlap with previous systems, one principal departure is the increased number of classes, which reflects that "centric" and "araphid" diatoms are comprised of multiple lineages recognized here as distinct classes. By providing a more accurate representation of phylogenetic relationships, the proposed classification facilitates clearer communication about all aspects of diatom biology.
Distribution of rickettsial endosymbionts and their possible transmission within the Pleodorina japonica (Volvocales, Chlorophyceae) population.
Nozaki H, Matsuzaki R, Takahashi K … +4 more , Ueki N, Higashiyama T, Kawachi M, Tanabe Y
J Phycol · 2026 Apr · PMID 41626866 · Publisher ↗
The green alga Pleodorina japonica is an interesting volvocine species that harbors abundant rickettsial endosymbionts ("MIDORIKO") within its cytoplasm. However, the diversity and transmission of these endosymbionts wit...
The green alga Pleodorina japonica is an interesting volvocine species that harbors abundant rickettsial endosymbionts ("MIDORIKO") within its cytoplasm. However, the diversity and transmission of these endosymbionts within the species remain unclear. In this study, we examined the presence or absence of "MIDORIKO" and the genetic diversity in 21 culture strains of the host P. japonica population from various localities in Japan. Genomic polymerase chain reactions using "MIDORIKO"-specific primers and 4',6-diamidino-2-phenylindole-staining demonstrated that only five of the 21 strains harbored "MIDORIKO." The 16S ribosomal DNA sequences of "MIDORIKO" from these five strains (1148 bp) were identical to each other and distinct from the sequences of the rickettsial endosymbionts harbored by other algal species and protists, suggesting that "MIDORIKO" from P. japonica is specific to P. japonica. The phylogenetic results for the 21 host strains, which were resolved based on three nuclear genes encoding oxygen-evolving enhancer protein 1, F1F0 ATP synthase subunit beta and actin disagreed significantly. None of the three gene phylogenies supported the close relationship of the five "MIDORIKO"-harboring strains. A recombination test using the three concatenated genes provided strong evidence of recombination. Therefore, gene flow by sexual reproduction has likely occurred in the natural habitats of P. japonica. The transmission of "MIDORIKO" among different P. japonica genotypes could also be considered to occur via sexual reproduction, although it is likely infrequent via that method given the sporadic nature of "MIDORIKO" within the P. japonica population. Although P. japonica exhibits homothallic sexual reproduction, the present genetic data demonstrate that it is undoubtedly a biological species.
Microbiota associated with benthic Sargassum (Fucales, Phaeophyceae): From morphological structures to geographically dispersed populations.
Mendonça IRW, Oliveira MC
J Phycol · 2026 Feb · PMID 41626864 · Publisher ↗
Seaweed-associated microbiota distribution is influenced by factors such as symbiosis, season, life cycle, environmental conditions, and geographic location. This study investigated how microbial communities vary across...
Seaweed-associated microbiota distribution is influenced by factors such as symbiosis, season, life cycle, environmental conditions, and geographic location. This study investigated how microbial communities vary across different parts of benthic Sargassum thalli from nine locations spanning three regions over 600 km apart along Brazil's coast, with sites in each region within 20 km of each other. Using 16S rDNA gene sequencing of the V4 region, we identified 16,802 amplicon sequence variants (ASVs), with 1169 shared across thallus structures and 1100 shared across regions. Our analysis showed that microbial communities varied both along the thallus and between regions, though communities were similar within regions less than 20 km apart. Among thallus structures, the holdfast had the most distinct microbiota, differing from the phylloid and receptacle. This pattern was consistent across Brazil's coastline and has also been observed in studies from Singapore and Portugal. The holdfast microbiota was marked by an unidentified Alphaproteobacteria, along with sulfur-cycling families Desulfocapsaceae and Desulfosarcinaceae. Phylloids and receptacles were mainly associated with photosynthetic cyanobacteria. We also identified shared taxonomic biomarkers across Sargassum species from Asia, Europe, and South America. These results suggest that the microbiota are more influenced by the thallus structure than by geographic location. These consistent patterns across Sargassum species from different continents-Asia, Europe, and South America-support the hypothesis of microbiota specialization within morphological niches.
Genome sequences of Almyronema epifaneia and Thainema salinarum isolated from an intertidal mangrove forest.
Roy AR, Lefler FW, Laughinghouse HD … +3 more , Chakraborty S, de Los Santos Villalobos S, Mukherjee J
J Phycol · 2026 Feb · PMID 41578717 · Publisher ↗
Here, we have presented draft genome sequences from the type strain of Almyronema epifaneia MCC 5313 as well as Thainema salinarum MCC 5402, two filamentous cyanobacteria obtained from the Sundarbans, the largest interti...
Here, we have presented draft genome sequences from the type strain of Almyronema epifaneia MCC 5313 as well as Thainema salinarum MCC 5402, two filamentous cyanobacteria obtained from the Sundarbans, the largest intertidal mangrove forest in the world. AntiSMASH analysis revealed that the two genomes contained distinct biosynthetic gene clusters (BGCs), which may help in supporting their adaptation to the fluctuating intertidal environment. These BGCs encode the production of secondary metabolites such as terpenes, hapalosin, anachelin, bovienimide A, and scytocyclamide. The whole-genome shotgun projects for Almyronema epifaneia MCC 5313 and Thainema salinarum MCC 5402 have been deposited in GenBank under accession numbers GCA_042788235.1 and GCA_052168235.1, respectively.
Enhancing species discovery and description in algal turfs: A case study in the green alga Pseudoderbesia (Bryopsidales).
Hastings A, Cremen C, Courtney M … +2 more , Du Y, Verbruggen H
J Phycol · 2026 Feb · PMID 41556745 · Full text
Algal turfs are assemblages consisting of small marine green, brown, and red algae on the scale of millimeters to a few centimeters. Due to their small size, they have been less intensively studied by macroalgal taxonomi...
Algal turfs are assemblages consisting of small marine green, brown, and red algae on the scale of millimeters to a few centimeters. Due to their small size, they have been less intensively studied by macroalgal taxonomists, and they also fall outside the scope of microalgal taxonomists, who tend to focus on smaller, often unicellular, taxa. They often have a rather simple structure and a tendency to converge onto similar morphologies with creeping and upright axes. Because of all of this, there is a substantial amount of undocumented algal biodiversity in turfs, as has been shown in several molecular surveys. Our aim in this paper was to explore some integrative taxonomic methods that could help accelerate the discovery and description of very small turf species. We focused on Pseudoderbesia, a genus of extremely small green algae from the family Bryopsidaceae. We used a combination of multifocal imaging of field-collected samples, microsample genomics, and culturing to document the Pseudoderbesia biodiversity from Heron Island on the Great Barrier Reef. Algorithmic species delimitation based on rbcL and tufA marker genes indicated that likely six (possibly five) species exist in Pseudoderbesia, but only two have been described. We have formally described the two species discovered at Heron Island as P. luxurians and P. epilithica. The latter was described using a multifocal image as the holotype, following an exception to the nomenclatural code for microscopic algae. We have justified this choice extensively, both based on an interpretation of the code and on the broader conceptual need to name newly discovered species, facilitating their use in science, conservation, and policy.
Characterizing morphology of Egregia menziesii (Laminariales) in California over 2 centuries using historical and contemporary herbarium specimens.
Khen A, Moore KM, Braybrook SA … +3 more , Vroom PS, Miller KA, Smith JE
J Phycol · 2026 Feb · PMID 41556737 · Full text
The canopy-forming feather boa kelp Egregia menziesii exhibits remarkable morphological variability across its geographic range. Regional morphotypes of Egregia were once considered separate species, but they were not de...
The canopy-forming feather boa kelp Egregia menziesii exhibits remarkable morphological variability across its geographic range. Regional morphotypes of Egregia were once considered separate species, but they were not determined to be genetically distinct; instead, their morphology was thought to reflect local physical or environmental conditions. Although morphological variation in Egregia has long been observed and was previously characterized through field surveys in the early 2000s, we revisited this topic using digital morphometrics (i.e., image analysis) of 1624 macroalgal herbarium specimens from California dating back to the 19th century. We observed that the morphology of Egregia (rachis texture, lateral blade shape, and blade or pneumatocyst density) varied along a latitudinal gradient and could be predicted by seawater temperature and wave height. We also identified some region-specific morphological changes in recent decades. Further, the monthly presence or absence of sporophylls in southern-region specimens provided preliminary evidence into the reproductive phenology of Egregia. Herbarium collections are invaluable for studying patterns in morphology because they showcase inter- and intraspecific variability and establish a baseline for comparison through time. Integrating natural historical and contemporary data will be critical for understanding and predicting future trends in the context of ocean warming.
Species delimitation within the Achnanthidium minutissimum complex (Bacillariophyta), based on morphological, molecular, and ecophysiological approaches.
Dani M, Beszteri S, Castellanos AB … +8 more , Schimani K, Skibbe O, Zimmermann J, Soares AR, Griesdorn L, Probst AJ, Kahlert M, Beszteri B
J Phycol · 2026 Feb · PMID 41552949 · Full text
The benthic diatom species Achnanthidium minutissimum belongs to a species complex with a challenging taxonomy. Achnanthidium minutissimum has been reported to be a widespread and abundant species occurring in a broad ra...
The benthic diatom species Achnanthidium minutissimum belongs to a species complex with a challenging taxonomy. Achnanthidium minutissimum has been reported to be a widespread and abundant species occurring in a broad range of freshwater habitats. However, differentiating and delimiting it from other Achnanthidium species is challenging due to the small size and great similarity of the different species, often with overlaps in morphological features. Therefore, reports of the occurrence of these taxa probably come with a large uncertainty due to potential misidentification. To gain a better understanding of the boundaries between species within the A. minutissimum species complex, we applied an integrative taxonomic approach and investigated the congruence between morphological, molecular, and ecophysiological variability among 13 monoclonal strains isolated from Germany, Sweden, and Spitsbergen. In addition to the characterization of valve morphology, we assessed their growth under different temperatures and salt concentrations and compared sequences of the rbcL marker gene as well as of a broad set of homologous loci sampled by genome skimming. Molecular and ecophysiological variability was mostly congruent with scanning electron microscopy-based morphological identification; the main exception was that two pairs of strains identified as A. cf. microcephalum and A. jackii could be distinguished neither in their ecophysiological profiles nor in their DNA sequences. Extending this integrated taxonomic approach to more strains will be beneficial for a better understanding of the morphological, molecular, and niche differentiation among different Achnanthidium species. The added value of the combined morphological-molecular-ecophysiological approach is an improved delineation of morphological features applicable for species differentiation and a better understanding of ecological differentiation.
Organellar genomes of the putative Hawaiian endemic species Gibsmithia punonomaewa (Gigartinales, Rhodophyta): First available genomes for the Dumontiaceae.
Sherwood AR, Paradis S, Presting GG
J Phycol · 2026 Feb · PMID 41517998 · Publisher ↗
We have reported the first mitochondrial (GenBank accession PV035080) and chloroplast (GenBank accession PV035081) genomes for a representative of the gigartinalean family Dumontiaceae (Gibsmithia punonomaewa). High-thro...
We have reported the first mitochondrial (GenBank accession PV035080) and chloroplast (GenBank accession PV035081) genomes for a representative of the gigartinalean family Dumontiaceae (Gibsmithia punonomaewa). High-throughput sequencing yielded both organellar genomes for the holotype specimen of Gibsmithia punonomaewa, a recently described species that is also a putative endemic to the mesophotic zone of the Hawaiian Islands. Gene content and order of the 26,428-bp mitochondrial genome are conserved relative to other available genomes of the Gigartinales. The genome contains 52 genes, including 25 protein-coding sequences (CDSs), 3 rRNAs, and 24 tRNAs, as well as one group II intron in a trnI-GAU tRNA. The chloroplast genome is 185,316 bp in length and contains 236 genes, including 203 CDSs, three rRNAs, and 30 tRNAs, and one group II intron in a trnM-CAU tRNA. Both organellar genomes displayed high synteny compared to close relatives in the order Gigartinales, with unique features restricted to several open reading frames. Phylogenomic analyses of the mitochondrial and chloroplast genomes with other gigartinalean representatives yielded well-resolved phylogenies that supported an early diverging position of the Dumontiaceae within the order Gigartinales.
Lack of genetic support for varieties in Saccharina japonica (Laminariales, Phaeophyceae): Proposal for taxonomic merger.
Akita S, Chizaki K, Hosoyama Y … +5 more , Kawagoe C, Uji T, Fujita D, Vieira C, Mizuta H
J Phycol · 2026 Feb · PMID 41503639 · Publisher ↗
Following the treatment of Saccharina diabolica, S. ochotensis, and S. religiosa as varieties of S. japonica, the same authors reported independent genetic groups corresponding to the original distributions of these spec...
Following the treatment of Saccharina diabolica, S. ochotensis, and S. religiosa as varieties of S. japonica, the same authors reported independent genetic groups corresponding to the original distributions of these species described in 1902. However, other population genetic studies have not supported these genetic groups corresponding to the varieties, and these varietal names have been applied predominantly to the Japanese population, despite S. japonica having a broader distribution in North Korea and the Russian Far East. This study reevaluated the taxonomic validity of these varieties by investigating the presence of corresponding genetic groups within Japan. We collected 475 individuals across its Japanese distribution, assigned them to five groups based on prior research, and genotyped them using 12 simple sequence repeat (SSR) markers. STRUCTURE analysis, discriminant analysis of principal components scatter plots, and isolation by distance analyses did not support the presence of distinct genetic clusters aligning with the described distributions of S. japonica and its varieties. Instead of confirming the previously demonstrated genetic groups, these analyses revealed either two or three large, geographically based genetic clusters or smaller genetic groups composed of neighboring localities. Consequently, this study has proposed the merger of the three varieties into a single species, S. japonica. Furthermore, we have proposed new combinations of several formae under S. japonica as they have retained their previous taxonomic status under Laminaria japonica or L. diabolica. Further research is required to assess the taxonomic validity of these formae.
Enzymatic strategies for phosphorus utilization in periphyton: A study of alkaline phosphatase kinetics in post-mining lakes.
Konopáčová E, Nedoma J, Čapek P … +3 more , Čapková K, Bešta T, Řeháková K
J Phycol · 2026 Feb · PMID 41492248 · Full text
Alkaline phosphatase (AP) plays an important role in phosphorus (P) cycling in aquatic ecosystems, particularly under nutrient limitation. In post-mining lakes of Czechia, periphyton forms extensive mats despite chronic...
Alkaline phosphatase (AP) plays an important role in phosphorus (P) cycling in aquatic ecosystems, particularly under nutrient limitation. In post-mining lakes of Czechia, periphyton forms extensive mats despite chronic P deficiency, suggesting dissolved organic P (DOP) may serve as a key P source. This study examines periphyton's ability to hydrolyze DOP via AP in three post-mining lakes in Czechia, assessing enzyme kinetic models, seasonal variation, and P-acquisition strategies. Seasonal shifts of apparent alkaline phosphatase catalytic efficiency (APCE) in periphyton, determined as the ratio of maximum hydrolysis velocity to Michaelis constant, have indicated that periphyton dynamically adjusts its enzyme activity. Periphyton exhibited rapid DOP turnover (tenths to tens of seconds) but had significantly lower APCE than phytoplankton. This suggests fundamental differences in P-acquisition strategies: Although phytoplankton relies on ambient DOP, periphyton retains and recycles P within its matrix. Retained P can be distributed throughout the periphyton taxa, supporting an idea of metabolic commensalism in periphyton assemblage. Our results underscored the adaptive role of periphyton community in buffering P availability through internal recycling, which, alongside P uptake from the lake water, supports persistence of periphyton in fluctuating P conditions. By sequestering and recycling P internally, periphyton alters lake-wide P dynamics, reduces P availability for phytoplankton, and potentially influences ecosystem productivity. Furthermore, this research has highlighted the limitations of applying simple Michaelis-Menten kinetics to describe complex enzymatic processes in natural ecosystems, emphasizing the need for models that better capture enzymatic heterogeneity and environmental interactions.
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