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The freshwater red alga Batrachospermum gelatinosum has a well‐documented distribution spanning historically glaciated and unglaciated eastern North America. This alga has no known desiccation‐resistant propagule; thus, long‐distance dispersal events are likely rare. We predicted strong genetic structure among drainage basins and admixture among sites within basins. We predicted greater genetic diversity at lower latitude sites because they likely serve as refugia and the origin of northward, post‐Pleistocene range expansion. We used 10 microsatellite loci to investigate genetic diversity from 311 gametophytes from 18 sites in five major drainage basins: South Atlantic Gulf, Mid‐Atlantic, Ohio River, Great Lakes, and Northeast. Our data showed strong genetic partitioning among drainage basins and among sites within basins, yet no isolation by distance was detected. Genetic diversity varied widely among sites and was not strictly related to latitude as predicted. The results from B. gelatinosum provide strong support that each stream site contributes to the unique genetic variation within the species, potentially due to limited dispersal and the prevailing reproductive mode of intragametophytic selfing. Simulations of migration suggested post‐Pleistocene dispersal from the Mid‐Atlantic. Batrachospermum gelatinosum potentially persisted in refugia that were just south of the ice margins rather than in the southernmost part of its range. Research of other taxa with similar ranges could determine whether these results are generally applicable for freshwater red algae. Nevertheless, these results from B. gelatinosum add to the growing literature focused on the patterns and genetic consequences of post‐Pleistocene range expansion by eastern North American biota. [ABSTRACT FROM AUTHOR] more...

Environmental racism may be among the explanations for why we are facing the worst socioenvironmental crisis in the history of humanity, led by a state of climate emergency that could result in an ecocidal genocide of planetary dimensions. Unfoldings of environmental racism even reach towards nature when it is considered subject of rights. Among the marine ecosystems less considered in these discussions are rhodolith beds—reef habitats of red coralline algae, also called maerl beds. When dealing with the feasibility of oil exploration in the Amazon mouth region, an area dominated by extensive rhodolith beds, the Brazilian Association of Petroleum Geologists broadcast live a geologist quoted as saying (transcript follows) '... what there is (at the mouth of the Amazon) are coralline algae called rhodoliths, which are common, anywhere in Brazil, and are things, errrrr (with hand gestures and facial expression with negative or pejorative sense), ugly like that, they're not nice at all, (...) and even the rhodolith reefs are dead reefs, dead'. As a result, now, the region is facing the real possibility of extensive oil exploitation. This opinion of a limited aesthetical perspective of which nature is important demands urgent public recognition. Policies that foster rhodolith bed conservation needs, explaining their wealth of valuable contributions to society, must be introduced in formal education, dialoguing with children, young people and adults. Multilateral United Nation forums, during the Ocean Decade, can provide ways to speed up this process, combating different forms of environmental racism and speciesism, buying some time and creating opportunities to establish rhodolith bed conservation as a natural world heritage. [ABSTRACT FROM AUTHOR] more...

SUMMARY The species Gelidium divaricatum was originally described from Hong Kong by G. Martens (1866). Mexico did not have any records of this species until the present study. The species was found from a study for which the research objective is to evaluate specimens of Gelidium collected in Bahía de La Paz, Baja California Sur (the entrance to the Gulf of California) using morphological and molecular techniques, including the rbcL marker. Phylogenetic analyses using the rbcL marker revealed that the studied specimens are in the same clade of G. divaricatum from the type locality with their sequence differences being less than 0.3%, indicating that the specimens are the same species as G. divaricatum. This is the first record of the species for Mexico. The most important morphological difference was the branching pattern, which was irregular to pinnate in the Hong Kong specimens, whereas it was simple or irregular in the Mexican thalli. [ABSTRACT FROM AUTHOR] more...

Rhodoliths are non‐geniculate, free‐living coralline red algae that can accumulate on the seafloor and form structurally complex habitats supporting highly biodiverse communities termed rhodolith beds. Limited understanding of key rhodolith kinetical attributes and how they scale with environmental variability limits ability to predict changes in rhodolith bed distribution and abundance in a globally changing ocean climate. We carried out two experiments in an oscillatory wave tank to test the effects of (1) rhodolith (Boreolithothamnion glaciale) density and wave velocity on rhodolith displacement and abrasion over a hard substratum and (2) rhodolith density on rhodolith displacement and the stability of underlying sediment. We established that on a hard substratum, (1) a threshold wave velocity of ~0.3 m s−1 is required to induce noticeable displacement in average‐sized rhodoliths and (2) rhodolith abrasion increases (quasi‐linearly) with wave velocity up to this threshold. We also showed that (3) for a same rhodolith density, rhodolith displacement is at least two times smaller on a sedimentary than hard substratum and (4) the loss of sediment underneath rhodoliths decreases (quasi‐linearly) with an increase in rhodolith density. Rates documented and strong scaling with changes in water motion and rhodolith density indicate that relatively small changes in the density of rhodoliths or hydrodynamic forces can quickly destabilize rhodolith bed frameworks and underlying sediment. These rates can be used to develop predictive models of change in rhodolith bed distribution and abundance that can in turn inform development of more accurate, science‐based rhodolith bed conservation strategies. [ABSTRACT FROM AUTHOR] more...

The global flows of cultivated seaweed were estimated for the year 2019 using a combination of literature review, assumptions, and simple conservation of mass calculations. Red seaweeds were found to be the largest contributors to the hydrocolloids industry, for both food and non‐food applications. Carrageenan‐containing species were found to be the largest contributors to both food (62%) and non‐food (55%) hydrocolloids and are the primary source for water gels, which make up 27% of non‐food hydrocolloids, followed by pet food (16%), toothpaste (6%), and others (6%). Carrageenan also accounts for almost all meat products, which make up 35% of the food hydrocolloid industry, and dairy products, which make up 26%. Agar‐containing seaweeds are used in confections (10% of food hydrocolloids), baking (9%), and other (2%) and make up 15% of non‐food hydrocolloids. Porphyra (nori) is cultivated for direct consumption and makes up 23% of direct food consumption. Cultivated brown seaweeds were found to comprise Laminaria/Saccharina for alginate production (30%), Laminaria/Saccharina for direct consumption (44%), and Undaria for direct consumption (16%). About half of the alginates produced make up 18% of food hydrocolloids, and the other half is used in non‐food hydrocolloids comprising technical grades (28% of non‐food) and animal feed (3%). The results are discussed in the context of emerging markets for seaweed and the potential for seaweeds as a substitute for staple foods, and the environmental impact of seaweed farming is explored through a review of life cycle assessment studies. [ABSTRACT FROM AUTHOR] more...

Bioplastic is an emerging candidate for replacing traditional fossil‐based plastics due to its fewer carbon emissions, ease of recycling, and high degradability. Current research has shown that bioplastics benefit many applications, such as packaging, kitchenware, drug delivery, and sensors. However, high electrical resistance and poor stability of bioplastic are barriers to electronic components in robotic, bionic, and exoskeleton applications. Here, we introduce a novel bioplastic application as a strain sensor to estimate elbow angles for controlling exoskeletons. This study utilized extracted agar from red algae as the matrix, incorporating various concentrations of carbon nanotube (CNT) as a filler. The results were remarkable, with the increase in filler concentration not only improving strain from 0.8 to 1.1 but also stress from 35.2 to 45.8 kPa, surpassing commercial plastic by approximately two times. The optimized sensors have a response time of 0.16 s, a recovery time of 0.25 s, and stability over 10,000 cycles. Furthermore, the CNT‐bioplastic sensor is seamlessly integrated with the exoskeleton. Our work is a significant step toward using bioplastic in electronic applications. [ABSTRACT FROM AUTHOR] more...

Neoporphyra haitanensis, a red alga harvested for food, thrives in the intertidal zone amid dynamic and harsh environments. High irradiance represents a major stressor in this habitat, posing a threat to the alga's photosynthetic apparatus. Interestingly, N. haitanensis has adapted to excessive light despite the absence of a crucial xanthophyll cycle‐dependent photoprotection pathway. Thus, it is valuable to investigate the mechanisms by which N. haitanensis copes with excessive light and to understand the photoprotective roles of carotenoids. Under high light intensities and prolonged irradiation time, N. haitanensis displayed reduction in photosynthetic efficiency and phycobiliproteins levels, as well as different responses in carotenoids. The decreased carotene contents suggested their involvement in the synthesis of xanthophylls, as evidenced by the up‐regulation of lycopene‐β‐cyclase (lcyb) and zeaxanthin epoxidase (zep) genes. Downstream xanthophylls such as lutein, zeaxanthin, and antheraxanthin increased proportionally to light stress, potentially participating in scavenging reactive oxygen species (ROS). When accompanied by the enhanced activity of ascorbate peroxidase (APX), these factors resulted in a reduction in ROS production. The responses of intermediates α‐cryptoxanthin and β‐cryptoxanthin were felt somewhere between carotenes and zeaxanthin/lutein. Furthermore, these changes were ameliorated when the organism was placed in darkness. In summary, down‐regulation of the organism's photosynthetic capacity, coupled with heightened xanthophylls and APX activity, activates photoinhibition quenching (qI) and antioxidant activity, helping N. haitanensis to protect the organism from the damaging effects of excessive light exposure. These findings provide insights into how red algae adapt to intertidal lifestyles. [ABSTRACT FROM AUTHOR] more...

Mazzaella, a genus with no genomic resources available, has extensive distribution in the cold waters of the Pacific, where they represent ecologically and economically important species. In this study, we aimed to sequence, assemble, and annotate the complete mitochondrial and chloroplast genomes from two Mazzaella spp. and characterize the intraspecific variation among them. We report for the first time seven whole organellar genomes (mitochondria: OR915856, OR947465, OR947466, OR947467, OR947468, OR947469, OR947470; chloroplast: OR881974, OR909680, OR909681, OR909682, OR909683, OR909684, OR909685) obtained through high‐throughput sequencing for six M. laminarioides sampled from three Chilean regions and one M. membranacea. Sequenced Mazzaella mitogenomes have identical gene number, gene order, and genome structure. The same results were observed for assembled plastomes. A total of 52 genes were identified in mitogenomes, and a total of 235 genes were identified in plastomes. Although the M. membranacea plastome included a full‐length pbsA gene, in all M. laminarioides samples, the pbsA gene was split in three open reading frames (ORFs). Within M. laminarioides, we observed important plastome lineage‐specific variations, such as the pseudogenization of the two hypothetical protein‐coding genes, ycf23 and ycf45. Nonsense mutations in the ycf23 and ycf45 genes were only detected in the northern lineage. These results are consistent with phylogenetic reconstructions and divergence time estimation using concatenated coding sequences that not only support the monophyly of M. laminarioides but also underscore that the three M. laminarioides lineages are in an advanced stage of divergence. These new results open the question of the existence of still undisclosed species in M. laminarioides. [ABSTRACT FROM AUTHOR] more...

Four species of the genus Wrangelia are presently known from the western Atlantic Ocean: W. argus, W. bicuspidata, W. penicillata, and W. gordoniae, with the first three historically being reported from Bermuda. Morphological and molecular barcode (COI‐5P) and phylogenetic analyses used in this study (SSU, LSU, rbcL) indicated eight species groupings of Wrangelia in Bermuda, excluding two of the historically recognized species, retaining only W. argus while adding seven new species, of which six are formally described. What had been historically reported as W. penicillata from Bermuda was shown to be distinct from Mediterranean Sea specimens (type locality) and was shown to be a mixture of W. hesperia sp. nov. and W. incrassata sp. nov. Along with these two, three other new species (W. laxa sp. nov., W. ryancraigii sp. nov., and W. secundiramea sp. nov.) have complete rhizoidal cortication tightly covering axial cells of indeterminate axes below the apices, distinguishing them from the two local incompletely corticated congeners W. argus and W. abscondita sp. nov., the latter a morphologically cryptic sister species with W. bicuspidata from the Caribbean Sea. Only one of the new species, W. ryancraigii, has thus far been observed in the mesophotic zone off the Bermuda platform, and it is morphologically cryptic with the euphotic zone's W. laxa. [ABSTRACT FROM AUTHOR] more...

The use of macroalgae for food has been extensive in Asia historically. However, there has been a renewed interest at present in macroalgae due to its recognition as a potential carbon capture agent and a blue carbon donor besides their utility in biofuel production. Bioplastics is an umbrella term for a wide variety of polymers that can be either biobased or biodegradable, or both. Macroalgal polysaccharides and their inherent film‐forming capacity are exploited in the bioplastics industry and macroalgal polysaccharide‐based biofilms are extensively used in food packaging due to their compatibility and ease of production. Commercial macroalgae‐based bioplastics production is ongoing, with research dedicated to the development of biodegradable/compostable biofilms suitable for the food packing and biomedicine sector. This review aims to provide an overview of the polysaccharides of macroalgae that can be used to form biofilms and bioplastics. Different methods for biofilm formation are discussed along with summarizing the effect of plasticizers, the method of film formation, and biodegradability. The major source of marine macroalgal polysaccharaides are agar, alginate, carrageenan, laminarin, fucoidan, and ulvan. Different groups of macroalgae are utilized for the production of polysaccharide derived bioplatics, namely, brown algae (Padina pavonica, Ascophyllum nodosum, Laminaria japonica, Rugulopteryx okamurae, Sargassum natans, Sargassum siliquosum, Jolyna laminarioides, Gracilaria salicornia), green algae (Ulva fasciata, Halimeda opuntia, Codium fragile, Ulva intestinalis, Ulva lactuca, Ulva rigida), and red algae (Eucheuma cottonii, Porphyra sp., Kappaphycus alvarezii, Gracilaria corticata). The outcome of the review reveals that there is a vast scope for macroalgal polysaccharide‐derived bioplastics for a sustainable environment. [ABSTRACT FROM AUTHOR] more...

SUMMARY: Lithophyllum is a cosmopolitan coralline algal genus with 12 species currently recognized in Japan based on modern morpho‐anatomical taxonomic concepts primarily characterized by having uniporate tetrasporangial and bisporangial conceptacles, the presence of secondary pit‐connections between cells of adjacent filaments and a dimerous thallus construction with a single basal layer of predominantly non‐palisade cells. In the present study, we describe Lithophyllum nagaokaense sp. nov. based on a combination of molecular and morpho‐anatomical data of specimens from the temperate waters of Japan. The new species forms both attached epilithic thalli and free‐living rhodoliths. Phylogenetic analyses of psbA, rbcL and COI markers resolved L. nagaokaense as an independent species. Morpho‐anatomically, L. nagaokaense resembles Lithophyllum johansenii, originally described from Australia, but distinguished from the latter by the absence of enlarged angular cells occluding pore canals of tetrasporangial conceptacle chambers. Lithophyllum nagaokaense shared a fruticose morphology with Lithophyllum kaiseri, Lithophyllum kuroshioense, Lithophyllum neo‐okamurae, Lithophyllum okamurae, and Lithophyllum pygmaeum from Japan. Of these, L. nagaokaense is the most similar to L. neo‐okamurae in having attached and free‐living thalli with encrusting and warty to lumpy growth forms bearing knobby protuberances that are dichotomously branched or anastomosing. The new species is distinct from other Japanese fruticose species collectively by five tetrasporangial conceptacle chamber characters and the absence of trichocytes. A taxonomic key for identifying Japanese fruticose species is provided. This is the fifth Lithophyllum species and the third rhodolith‐forming species verified by DNA sequencing to be found in Japan. [ABSTRACT FROM AUTHOR] more...

Seaweed polysaccharides are natural biomacromolecules with unique physicochemical properties (e.g., good gelling, emulsifying, and film‐forming properties) and diverse biological activities (e.g., anticoagulant, antioxidant, immunoregulatory, and antitumor effects). Furthermore, they are nontoxic, biocompatible and biodegradable, and abundant in resources. Therefore, they have been widely utilized in food, cosmetics, and pharmaceutical industries. However, their properties and bioactivities sometimes are not satisfactory for some purposes. Modification of polysaccharides can impart the amphiphilicity and new functions to the biopolymers and change the structure and conformation, thus effectively improving their functional properties and biological activities so as to meet the requirement for targeted applications. This review outlined the modification methods of representative red algae polysaccharides (carrageenan and agar), brown algae polysaccharides (fucoidan, alginate, and laminaran), and green algae polysaccharides (ulvan) that have potential food applications, including etherification, esterification, degradation, sulfation, phosphorylation, selenylation, and so on. The improved functional properties and bioactivities of the modified seaweed polysaccharides and their potential food applications are also summarized. [ABSTRACT FROM AUTHOR] more...

Pyropia nereocystis is an annual northeastern Pacific‐bladed bangialean species whose macroscopic stage epiphytized the annual canopy forming bull kelp Nereocystis luetkeana. I examined three in situ facets of these epiphyte‐host dynamics in the central California region: (1) spatial and temporal variation in the presence of P. nereocystis epiphytes as a function of host density, (2) the relationship between individual host morphology and epiphytic P. nereocystis biomass, and (3) the ecophysiological growth ramifications for subtidal transplants of both life stages of P. nereocystis. Swath canopy surveys and whole host collections were conducted at five sites between November 2017 and February 2019. Additionally, transplants of P. nereocystis gametophytes and sporophytes were conducted across multiple subtidal depths. I observed temporal changes in the proportions of hosts epiphytized by P. nereocystis, with differences in seasonal persistence of P. nereocystis among sites and between years. Biomass of P. nereocystis was positively correlated with individual host stipe length, stipe surface area, and the primary principal component (PC) of stipe morphometrics denoted by principal component analysis (PCA). Gametogenesis in P. nereocystis epiphytes was spatially heterogeneous and limited for the 2018–2019 cohort due to comprehensive removal of hosts by the February 2019 sampling period. Transplants of P. nereocystis gametophytes yielded similar growth responses among depths, and sporophyte (conchocelis) transplant areal growth was positively correlated with transplant depth. These findings detail spatiotemporal complexity and multi‐scale (individual, site, and whole region) phenological nuances for central Californian P. nereocystis epiphytes. [ABSTRACT FROM AUTHOR] more...

As a polysaccharide extracted from marine red algae, carrageenan has the advantages of biodegradability, nontoxicity and water solubility over petroleum‐based plastics for use as films and coatings for keeping food fresh. Aqueous solutions of carrageenan can be cast into films on plates and then made into food packaging bags, as well as coated directly onto food surfaces, all of which are referred to as 'wraps'. To overcome the inherent limitations of carrageenan as a packaging material, physical and chemical modifications have been studied. The mechanical, thermal, barrier and antibacterial properties of modified carrageenan make it widely applicable for extending the shelf life of food products and monitoring its freshness. The research progress of carrageenan‐based wraps in recent years has been reviewed in terms of preparation methods, physicochemical properties, gelation mechanisms and applications, and the factors affecting the drying rate of them have been analysed. Finally, applications and future research directions of carrageenan are summarized and discussed to provide useful guidelines for further research. [ABSTRACT FROM AUTHOR] more...

Horizontal genetic transfer (HGT) is a common phenomenon in eukaryotic genomes. However, the mechanisms by which HGT‐derived genes persist and integrate into other pathways remain unclear. This topic is of significant interest because, over time, the stressors that initially favoured the fixation of HGT may diminish or disappear. Despite this, the foreign genes may continue to exist if they become part of a broader stress response or other pathways. The conventional model suggests that the acquisition of HGT equates to adaptation. However, this model may evolve into more complex interactions between gene products, a concept we refer to as the 'Integrated HGT Model' (IHM). To explore this concept further, we studied specialized HGT‐derived genes that encode heavy metal detoxification functions. The recruitment of these genes into other pathways could provide clear examples of IHM. In our study, we exposed two anciently diverged species of polyextremophilic red algae from the Galdieria genus to arsenic and mercury stress in laboratory cultures. We then analysed the transcriptome data using differential and coexpression analysis. Our findings revealed that mercury detoxification follows a 'one gene‐one function' model, resulting in an indivisible response. In contrast, the arsH gene in the arsenite response pathway demonstrated a complex pattern of duplication, divergence and potential neofunctionalization, consistent with the IHM. Our research sheds light on the fate and integration of ancient HGTs, providing a novel perspective on the ecology of extremophiles. [ABSTRACT FROM AUTHOR] more...

Unitary and modular sessile organisms both dominate in marine benthic communities, commonly preyed upon by the same generalist predators. The differences between unitary and modular defensive strategies may underlie the ways generalist predators control community structure, but this has never been empirically examined. We hypothesize that the individual size of an omnivorous mesopredatory shrimp affects the relative vulnerability of unitary and modular prey and hence translates into community structure. In a short‐term laboratory microcosm experiment, we assessed the effect of the shrimp individual size on an epibiotic assemblage of red algae blades initially dominated by three species of modular bryozoans and a unitary serpulid tubeworm. We found that the individual size of a shrimp determines its effect on the prey community composition. Large shrimp stronger than small shrimp increased the proportion of unitary tubeworms among the epibionts surviving predation. While large shrimp reduced the proportions of all the three dominant bryozoan species, small shrimp, in contrast, mostly increased the proportion of a bryozoan species with the smallest modules and largest colonies. This bryozoan, like the tubeworms, demonstrated a higher survival rate with larger individual (colony) size. Yet, against large shrimp this bryozoan was outperformed by the largest tubeworms almost immune to predation. Partial predation by small shrimp modestly improved survival of the largest bryozoan colonies. Thus, relative vulnerability of unitary and modular prey is determined by the predator individual size. Our findings clarify the complex way the size structures of generalist consumers and their prey shape communities by affecting the species‐specific relative performance of modular and unitary organisms. The demography of a foundation species and the competitive hierarchy can have additional effects by altering the balance of predation and competition. [ABSTRACT FROM AUTHOR] more...

Summary: Plant glycosyl hydrolases (GHs) play a crucial role in selectively breaking down carbohydrates and glycoconjugates during various cellular processes, such as reserve mobilization, pathogen defense, and modification/disassembly of the cell wall.In this study, we examined the distribution of GH genes in the Archaeplastida supergroup, which encompasses red algae, glaucophytes, and green plants.We identified that the GH repertoire expanded from a few tens of genes in early archaeplastidians to over 400 genes in modern angiosperms, spanning 40 GH families in land plants. Our findings reveal that major evolutionary transitions were accompanied by significant changes in the GH repertoire. Specifically, we identified at least 23 GH families acquired by green plants through multiple horizontal gene transfer events, primarily from bacteria and fungi. We found a significant shift in the subcellular localization of GH activity during green plant evolution, with a marked increase in extracellular‐targeted GH proteins associated with the diversification of plant cell wall polysaccharides and defense mechanisms against pathogens.In conclusion, our study sheds light on the macroevolutionary processes that have shaped the GH repertoire in plants, highlighting the acquisition of GH families through horizontal transfer and the role of GHs in plant adaptation and defense mechanisms. [ABSTRACT FROM AUTHOR] more...

To date (1 November 2023), the online database AlgaeBase has documented 50,589 species of living algae and 10,556 fossil species here referred to four kingdoms (Eubacteria, Chromista, Plantae, and Protozoa), 14 phyla, and 63 classes. The algae are the third most speciose grouping of plant‐like organisms after the flowering plants (≈382,000 species) and fungi (≈170,000 species, including lichens) but are the least well defined of all the botanical groupings. Priority is given to phyla and class names that are familiar to phycologists and that are nomenclaturally valid. The most species‐rich phylum is the Heterokontophyta to which 18 classes are referred with 21,052 living species and which is dominated by the diatoms in three classes with 18,673 species (16,427 living; 2239 fossil). The next most species‐rich phyla are the red algae (7276 living), the green algae (6851 living), the blue‐green algae (Cyanobacteria, 5723 living), the charophytes (4950 living, including the Charophyceae, 511 species living, and the Zygnematophyceae, 4335 living species), Dinoflagellata (2956 living, including the Dinophyceae, 2828 extant), and haptophytes (Haptophyta 1722 species, 517 living). [ABSTRACT FROM AUTHOR] more...

The impacts of global change—from shifts in climate to overfishing to land use change—can depend heavily on local abiotic context. Building an understanding of how to downscale global change scenarios to local impacts is often difficult, however, and requires historical data across large gradients of variability. Such data are often not available—particularly in peer reviewed or gray literature. However, these data can sometimes be gleaned from casual records of natural history—field notebooks, data sheet marginalia, course notes, and more. Here, we provide an example of one such approach for the Gulf of Maine, as we seek to understand how environmental context can influence local outcomes of region‐wide shifts in subtidal community structure. We explore a decade of hand‐drawn algal cover maps around Appledore Island made by Dr. Art Borror while teaching at the Shoals Marine Lab. Appledore's steep wave exposure gradient—from exposed to the open ocean to fully protected—provides a living laboratory to test interactions between global change and local conditions. We then recreate Borror's methods two and a half decades later. We show that overfishing‐driven urchin outbreaks in the 1980s were slowed or stopped by wave exposure and benthic topography. Similarly, local variation appears to have curtailed current invasions by filamentous red algae. Last, some formerly dominant kelps have disappeared over the past 40 years—an observation verified by subtidal surveys. Global change is altering life in the seas around us. While underutilized, solid natural history observations stand as a key resource for us to begin to understand how global change will translate to the heterogeneous mosaic of life in a future Gulf of Maine and other ecosystems around the world. [ABSTRACT FROM AUTHOR] more...

Summary: The kinetic properties of Rubisco, the most important carbon‐fixing enzyme, have been assessed in a small fraction of the estimated existing biodiversity of photosynthetic organisms. Until recently, one of the most significant gaps of knowledge in Rubisco kinetics was marine macrophytes, an ecologically relevant group including brown (Ochrophyta), red (Rhodophyta) and green (Chlorophyta) macroalgae and seagrasses (Streptophyta). These organisms express various Rubisco types and predominantly possess CO2‐concentrating mechanisms (CCMs), which facilitate the use of bicarbonate for photosynthesis. Since bicarbonate is the most abundant form of dissolved inorganic carbon in seawater, CCMs allow marine macrophytes to overcome the slow gas diffusion and low CO2 availability in this environment. The present review aims to compile and integrate recent findings on the biochemical diversity of Rubisco and CCMs in the main groups of marine macrophytes. The Rubisco kinetic data provided demonstrate a more relaxed relationship among catalytic parameters than previously reported, uncovering a variability in Rubisco catalysis that has been hidden by a bias in the literature towards terrestrial vascular plants. The compiled data indicate the existence of convergent evolution between Rubisco and biophysical CCMs across the polyphyletic groups of marine macrophytes and suggest a potential role for oxygen in shaping such relationship. [ABSTRACT FROM AUTHOR] more...

Rhodelphidia is a recently discovered phylum within the supergroup Archaeplastida, comprising only two known representatives (Rhodelphis marinus and Rhodelphis limneticus). Despite its close phylogenetic relatedness to red algae, Rhodelphidia differ markedly by being nonphotosynthetic eukaryotrophic flagellates with gene‐ and intron‐rich genomes. Here, we describe a new freshwater Rhodelphidia species, Rhodelphis mylnikovi sp. n., strain Rhod‐M. It shows clear morphological differences with the two other Rhodelphis species, including larger cell body size, presence of two contractile vacuoles, short and blunt pseudopodia, absence of cysts, and tendency to cannibalism. 18S rRNA‐based phylogenetic analysis placed it sister to the freshwater species R. limneticus. [ABSTRACT FROM AUTHOR] more...

Given sea ice's importance in global climate regulation, fully understanding the role of natural temperature and atmospheric patterns like the Arctic Oscillation (AO), North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO) in its variability is critical. While instrumental AMO and reliable AO records are available since the mid‐1800s and 1958, respectively, satellite sea‐ice concentration data sets start only in 1979, limiting the shared timespan to study their interplay. Growth increments of the coralline algae, Clathromorphum compactum, can provide sea‐ice proxy information for years prior to 1979. We present a seasonal 210‐year algal record from Lancaster Sound in the Canadian Arctic Archipelago capturing low frequency AMO/NAO variability and high frequency interannual AO/NAO prior to 2000. We suggest that sea‐ice variability here is strongly coupled to these large‐scale climate processes, and that sea‐ice cover was greater and the AO more negative in the early and late 19th century compared to the 20th. Plain Language Summary: Arctic sea‐ice variability is dually related to air/ocean temperatures and dynamic forces (wind patterns and ocean currents). While long‐term basin‐averaged temperature trends (i.e., Atlantic Multidecadal Oscillation) tend to influence variability over decades, cyclical wind patterns (e.g., Arctic Oscillation), may instead influence it seasonally and interannually. When the Atlantic Multidecadal and/or Arctic Oscillation (AMO/AO) are in a positive phase, warmer air and winds tend to export sea‐ice out of the Arctic, and vice‐versa during negative phases. Unfortunately, the span of the satellite sea‐ice cover record is too short to study long‐term sea‐ice variability driven by these patterns. Therefore, proxy records are required to fill this gap. The tree‐ring‐like growth bands of an Arctic coralline red algae have produced multi‐centennial proxy sea‐ice cover records. We present a 210‐year algal sea‐ice proxy record, showing a relationship with instrumental AMO (1861–present) and AO records (1958–2000). It also suggests that the AO was more negative and sea‐ice cover was greater during the 19th century in comparison to the 20th century. Due to sea‐ice's role in global climate at different timescales, this record can be utilized to tune climate models or constrain the relative influence of internal forcing on sea‐ice behavior. Key Points: Annual algal growth increment widths (sea ice cover proxy) correlate most strongly with summer Arctic Oscillation (AO) trendsAbrupt width increases in the early 1800s and 1920s capture sea‐ice cover decreases in phase with or slightly lagging behind +AMO phasesThe algal proxy record from Lancaster Sound captures +AO‐related sea‐ice export into the Canadian Arctic Archipelago [ABSTRACT FROM AUTHOR] more...

Over the last 2 decades, routine collections in the Hawaiian Archipelago have expanded to mesophotic reefs, leading to the discovery of a new red algal genus and species, here described as Anunuuluaehu liula gen. et sp. nov. This study provides a detailed genus and species description and characterizes chloroplast and mitochondrial organellar genomes. The new genus, Anunuuluaehu, shares many characteristics with the family Phyllophoraceae and shows close similarities to Archestennogramma and Stenogramma, including habit morphology, nemathecia forming proliferations at the outer cortex with terminal chains of tetrasporangia, and carposporophytes with multi‐layered pericarps. The single species in this genus exhibits distinctive features within the Phyllophoraceae: the presence of single‐layer construction of large medullary cells and the development of long, tubular gonimoblastic filaments. Multi‐gene phylogenetic analyses confirmed it as a unique, monophyletic lineage within the family. Cis‐splicing genes, interrupted by intron‐encoded proteins within group II introns, are present in both the chloroplast and mitochondrial genomes of A. liula. Notably, a specific region of the coxI group II intron exhibits similarity to fungal introns. Anunuuluaehu liula is presumed to be endemic to the Hawaiian Archipelago and thus far is known to live solely at mesophotic depths from Hōlanikū to Kaho'olawe ranging from 54 to 201 m, which is the deepest collection record of any representative in the family. Overall, this study enhances our understanding of the genomic and taxonomic complexities of red algae in mesophotic habitats, emphasizing the significance of continued research in this area to uncover further insights into evolutionary processes and biogeographic patterns. [ABSTRACT FROM AUTHOR] more...

Cryptic diversity is common among marine macroalgae, with molecular tools leading to the discovery of many new species. To assign names to these morphologically similar species, the type and synonyms have to be examined, and if appropriate, new species must be described. The turf‐forming red alga Polysiphonia scopulorum was originally described from Rottnest Island, Australia, and subsequently widely reported in tropical and temperate coasts based on morphological identifications. A recent study of molecular species delineation revealed a complex of 12 species in Australia, South Africa, and Europe. These species are placed in a taxonomically unresolved lineage of the tribe Polysiphonieae. The aim of this study was to resolve the genus‐ and species‐level taxonomy of this complex and related species using molecular and morphological information. Three morphologically indistinguishable species of the complex were found at the type locality of P. scopulorum, preventing a straightforward assignment of the name to any of the molecular lineages. Therefore, we propose a molecularly characterized epitype. Polysiphonia caespitosa is reinstated for the only species found in its type locality in South Africa. We describe seven new species. Only one species of the complex can be morphologically recognized, with the other eight species indistinguishable based on morphometric analysis. The studied complex, together with another seven species currently placed in Polysiphonia and two Bryocladia species, formed a clade distinct from Polysiphonia sensu stricto. Based on observations of Bryocladia cervicornis (the generitype), we describe our seven new species in the genus Bryocladia and transfer another nine species from Polysiphonia to Bryocladia. [ABSTRACT FROM AUTHOR] more...

Different marine seaweed species have been shown to harbour specific bacterial communities, however, the extent to which vertical symbiont transmission from parents to offspring contributes to host‐specificity is unclear. Here we use fluorescence and electron microscopy as well as 16S rRNA gene‐based community analysis to investigate symbiont transmission in members of the three major seaweed groups (green Chlorophyta, red Rhodophyta and brown Phaeophyceae). We found seaweeds employ diverse strategies to transfer symbionts to their progeny. For instance, the green Ulva australis does not appear to have the capacity for vertical transmission. In contrast, the brown Phyllospora comosa adopts a non‐selective vertical transmission. The red Delisea pulchra demonstrates weak selectivity in symbiont transmission, while the brown Hormosira banksii exhibits a strongly selective symbiont transfer. Mucilage on the gametes appears to facilitate vertical transmission and transferred bacteria have predicted properties that could support early development of the seaweeds. Previous meta‐analysis has indicated that vertical transmission is rare in aquatic compared to terrestrial environments, however, our results contribute to the growing evidence that this might not be the case and that instead vertical transmission with various degrees of symbiont selection occurs in the ecologically important group of seaweeds. [ABSTRACT FROM AUTHOR] more...

SUMMARY: The rare red algal genus Neoabbottiella from the Russian Pacific coast was taxonomically re‐examined. Currently, Neoabbottiella is assigned to the Halymeniales; however, some features of the reproductive anatomy cast doubt on the correctness of assigning the genus to Halymeniaceae sensulato. We investigated the phylogenetic affinities of Neoabbottiella using four DNA markers (nuclear LSU and SSU rDNA, rbcL and COI‐5P). Neoabbottiella failed to group with any families of the Halymeniales, but it was nested in a highly supported clade containing representatives of the genus Schmitzia (Calosiphoniaceae incertae sedis). Reproductive anatomy and post‐fertilization development also separate Neoabbottiella from the Halymeniaceae. The main characteristics distinguishing Neoabbottiella from the Halymeniales include the intercalary position of the auxiliary cell, the contact of the connecting filament with the auxiliary cell via the lateral process, the origin of the initial gonimoblast cell from the connecting filament at a distance from the auxiliary cell and a lack of a pericarp of branched ampullar filaments. These traits bring Neoabbottiella close to its genetic sister genus Schmitzia, making the classification of Neoabbottiella at the family and order levels difficult. The eventual taxonomic classification of Neoabbottiella awaits the input of data of other species of Schmitzia as well as Calosiphonia, the type genus of the Calosiphoniaceae; thus, Neoabbottiella should be provisionally excluded from the Halymeniales and considered as incertae sedis in the Rhodymeniophycidae. Further, the results of the present study showed that Neoabbottiella is monotypic; Neoabbottiella decipiens should be recognized as a synonym of the generitype Neoabbottiella araneosa. [ABSTRACT FROM AUTHOR] more...

Non‐native species (NNS) might become invasive and threaten biodiversity, economy and public health. Therefore, it is essential that their invasiveness risk be quantified to support conservation measures.The Azores, located in the mid‐northern Atlantic, is the crossroad of macroalgal native distributions and also present almost three times the global ratio of macroalgae reported as NNS.Aquatic Species Invasiveness Screening Kit, a decision‐support tool consisting of 49 questions for the Basic Risk Assessment (BRA) and six for the Climate Change Assessment (CCA), was applied to the 42 marine macroalgae classified as NNS in the Azores.The results indicate that 21 species pose a medium risk of becoming invasive, and 15 present a high risk under current climate conditions (BRA scores only). The combined BRA + CCA scores show that Laurencia dendroidea poses a high risk instead of a medium risk.Thirty‐three Rhodophyta species were screened, with 10 (BRA) and 11 (BRA + CCA) classified as high risk. All four Chlorophyta species ranked as high risk. Only one of the five Ochrophyta species was classified as high risk, namely Rugulopteryx okamurae, one of the most invasive species in European waters.High‐risk species are present in all islands, likely spread by the continuous maritime traffic between islands. Six of the high‐risk species are restricted to single islands (BRA and BRA + CCA scores), and efforts should be made to contain their further expansion. Asparagopsis armata, a species introduced in Europe in the 1920s, is the only high‐risk species present in all islands.Conservation measures for prevention, monitoring and control of NNS are proposed for the different islands of the Azores, including regulation of introduction pathways, prospection of areas with high risk of invasion, risk screening, eradication and containment of NNS. The involvement of stakeholders and maritime workers is also recommended. [ABSTRACT FROM AUTHOR] more...

Porolithon is one of the most ecologically important genera of tropical and subtropical crustose (non‐geniculate) coralline algae growing abundantly along the shallow margins of coral reefs and functioning to cement reef frameworks. Thalli of branched, fruticose Porolithon specimens from the Indo‐Pacific Ocean traditionally have been called P. gardineri, while massive, columnar forms have been called P. craspedium. Sequence comparisons of the rbcL gene both from type specimens of P. gardineri and P. craspedium and from field‐collected specimens demonstrate that neither species is present in east Australia and instead resolve into four unique genetic lineages. Porolithon howensis sp. nov. forms columnar protuberances and loosely attached margins and occurs predominantly at Lord Howe Island; P. lobulatum sp. nov. has fruticose to clavate forms and free margins that are lobed and occurs in the Coral Sea and on the Great Barrier Reef (GBR); P. parvulum sp. nov. has short (<2 cm), unbranched protuberances and attached margins and is restricted to the central and southern GBR; and P. pinnaculum sp. nov. has a mountain‐like, columnar morphology and occurs on oceanic Coral Sea reefs. A rbcL gene sequence of the isotype of P. castellum demonstrates it is a different species from other columnar species. In addition to the diagnostic rbcL and psbA marker sequences, the four new species may be distinguished by a combination of features including thallus growth form, margin shape (attached or unattached), and medullary system (coaxial or plumose). Porolithon species, because of their ecological importance and sensitivity to ocean acidification, need urgent documentation of their taxonomic diversity. [ABSTRACT FROM AUTHOR] more...

Macroalgae have been a key ecological component of marine ecosystems since the Proterozoic period and are common fossil forms in Cambrian Burgess Shale‐type Lagerstätten. However, in most cases, it is difficult to place these early fossil algae into modern groups because little distinctive morphology is preserved. Here, we describe a new form of macroalgae, Qingjiangthallus cystocarpium gen. & sp. nov., from the Qingjiang biota of South China. The new taxon is represented by 546 specimens remarkably preserved with characteristics that allow a phylogenetic placement into crown groups of red algae. Centimeter‐sized thalli resemble members of the extant Rhodymeniophycidae (a subclass of the class Florideophyceae), and hence suggest a florideophycean affinity, which indicates that ahnfeltiophycidaen and rhodymeniophycidaen algae may have diverged at least 518 Ma, accordant with estimations of molecular studies. The presence of possible cystocarps on Qingjiangthallus thalli suggests that evolutionary innovation of a triphasic life cycle in red algae may have occurred no later than the Early Cambrian. The branching patterns and branch width of Qingjiangthallus are consistent with the coarsely dichotomously branched morphogroup, which was previously present in the Ediacaran, Ordovician, and afterward, but absent in the Cambrian. [ABSTRACT FROM AUTHOR] more...

In this study, the nutritional and phytochemical components of red seaweed, Gracilariopsis longissima, were assessed in relation to the effects of various drying methods (freeze, oven, and sun). Gracilariopsis longissima's proximate composition differed significantly (P < 0.05) among the three drying techniques, with freeze-dried samples having significantly greater protein (30.63 ± 0.90% dry weight) and lipids (1.49 ± 0.05% dry weight) contents. Except for phosphorus and sulfur, the mineral concentrations were likewise considerably greater in the freeze-dried samples. The total amino acids (30.48 ± 0.06% dry weight) and fatty acids contents were substantially greater (P < 0.05) in the freeze-dried samples. In freeze-dried samples, the levels of essential amino acids (18.92 ± 0.02% dry weight) and unsaturated fatty acids (54.08 ± 0.07%) were substantially greater (P < 0.05). When compared to oven- and sun-dried samples, the total phenolic content (88.70 ± 2.19 mg GAE/g dry weight) and the flavonoid content (71.46 ± 2.17 mg QE/g dry weight) of freeze-dried samples was also substantially higher. Among the three distinct drying techniques used, the freeze-drying technique kept G. longissima's higher nutritional and phytochemical components. [ABSTRACT FROM AUTHOR] more...

Summary: Rhodophyta (or red algae) are a diverse and species‐rich group that forms one of three major lineages in the Archaeplastida, a eukaryotic supergroup whose plastids arose from a single primary endosymbiosis. Red algae are united by several features, such as relatively small intron‐poor genomes and a lack of cytoskeletal structures associated with motility like flagella and centrioles, as well as a highly efficient photosynthetic capacity. Multicellular red algae (or macroalgae) are one of the earliest diverging eukaryotic lineages to have evolved complex multicellularity, yet despite their ecological, evolutionary, and commercial importance, they have remained a largely understudied group of organisms. Considering the increasing availability of red algal genome sequences, we present a broad overview of fundamental aspects of red macroalgal biology and posit on how this is expected to accelerate research in many domains of red algal biology in the coming years. [ABSTRACT FROM AUTHOR] more...

Algal carbon‐to‐nitrogen (C:N) and carbon‐to‐phosphorus (C:P) ratios are fundamental for understanding many oceanic biogeochemical processes, such as nutrient flux and climate regulation. We synthesized literature data (444 species, >400 locations) and collected original samples from Tasmania, Australia (51 species, 10 locations) to update the global ratios of seaweed carbon‐to‐nitrogen (C:N) and carbon‐to‐phosphorus (C:P). The updated global mean molar ratio for seaweed C:N is 20 (ranging from 6 to 123) and for C:P is 801 (ranging from 76 to 4102). The C:N and C:P ratios were significantly influenced by seawater inorganic nutrient concentrations and seasonality. Additionally, C:N ratios varied by phyla. Brown seaweeds (Ochrophyta, Phaeophyceae) had the highest mean C:N of 27.5 (range: 7.6–122.5), followed by green seaweeds (Chlorophyta) of 17.8 (6.2–54.3) and red seaweeds (Rhodophyta) of 14.8 (5.6–77.6). We used the updated C:N and C:P values to compare seaweed tissue stoichiometry with the most recently reported values for plankton community stoichiometry. Our results show that seaweeds have on average 2.8 and 4.0 times higher C:N and C:P than phytoplankton, indicating seaweeds can assimilate more carbon in their biomass for a given amount of nutrient resource. The stoichiometric comparison presented herein is central to the discourse on ocean afforestation (the deliberate replacement of phytoplankton with seaweeds to enhance the ocean biological carbon sink) by contributing to the understanding of the impact of nutrient reallocation from phytoplankton to seaweeds under large‐scale seaweed cultivation. [ABSTRACT FROM AUTHOR] more...

Parasitic red algae are an interesting system for investigating the genetic changes that occur in parasites. These parasites have evolved independently multiple times within the red algae. The functional loss of plastid genomes can be investigated in these multiple independent examples, and fine‐scale patterns may be discerned. The only plastid genomes from red algal parasites known so far are highly reduced and missing almost all photosynthetic genes. Our study assembled and annotated plastid genomes from the parasites Janczewskia tasmanica and its two Laurencia host species (Laurencia elata and one unidentified Laurencia sp. A25) from Australia and Janczewskia verruciformis, its host species (Laurencia catarinensis), and the closest known free‐living relative (Laurencia obtusa) from the Canary Islands (Spain). For the first time we show parasitic red algal plastid genomes that are similar in size and gene content to free‐living host species without any gene loss or genome reduction. The only exception was two pseudogenes (moeB and ycf46) found in the plastid genome of both isolates of J. tasmanica, indicating potential for future loss of these genes. Further comparative analyses with the three highly reduced plastid genomes showed possible gene loss patterns, in which photosynthetic gene categories were lost followed by other gene categories. Phylogenetic analyses did not confirm monophyly of Janczewskia, and the genus was subsumed into Laurencia. Further investigations will determine if any convergent small‐scale patterns of gene loss exist in parasitic red algae and how these are applicable to other parasitic systems. [ABSTRACT FROM AUTHOR] more...

A cryptogenic, invasive‐like red macroalga, Chondria tumulosa, was first observed in 2016 forming thick mats on the forereef of Manawai Atoll within Papahānaumokuākea Marine National Monument. Subsequent expeditions revealed an increased abundance of this alga. In 2021, unattached C. tumulosa was observed forming a network of dark, meandering accumulations throughout the atoll's inner lagoon. High‐resolution satellite imagery revealed that these accumulations became visible in 2015 (length: ~0.74 km; area: ~0.88 km2) and increased 56‐fold in length and 115‐fold in area by 2021 (length: 41.32 km; area: 101.34 km2). An exponential expansion rate of ~16.02 km · y−1 (length), ~44.75 km2 · y−1 (area). This study presents the comprehensive temporal and spatial expansion of C. tumulosa accumulations for Manawai Atoll since its discovery, providing ecologist and resource managers with a proxy to gauge the overall abundance trend of this invasive‐like alga. [ABSTRACT FROM AUTHOR] more...

Phylogenetic analyses of rbcL gene sequences and of concatenated rbcL, psbA, and nuclear SSU rRNA gene sequences resolved the generitype of Lithothamnion, L. muelleri, in a clade with three other southern Australian species, L. kraftii sp. nov., L. saundersii sp. nov., and L. woelkerlingii sp. nov. Cold water boreal species currently classified in Lithothamnion and whose type specimens have been sequenced are transferred to Boreolithothamnion gen. nov., with B. glaciale comb. nov. as the generitype. The other species are B. giganteum comb. nov., B. phymatodeum comb. nov., and B. sonderi comb. nov., whose type specimens are newly sequenced, and B. lemoineae comb. nov., B. soriferum comb. nov., and B. tophiforme comb. nov., whose type specimens were already sequenced. Based on rbcL sequences from the type specimens of Lithothamnion crispatum, L. indicum, and L. superpositum, each is recognized as a distinct species and transferred to the recently described Roseolithon as R. crispatum comb. nov., R. indicum comb. nov., and R. superpositum com. nov., respectively. To correctly assign species to these three genera based only on morpho‐anatomy, specimens must have multiporate conceptacles and some epithallial cells with flared walls. The discussion provides examples demonstrating that only with phylogenetic analyses of DNA sequences can the evolution of morpho‐anatomical characters of non‐geniculate corallines be understood and applied at the correct taxonomic rank. Finally, phylogenetic analyses of DNA sequences support recognition of the Hapalidiales as a distinct order characterized by having multiporate tetra/bisporangial conceptacles, and not as a suborder of Corallinales whose tetra/bisporangial conceptacles are uniporate. [ABSTRACT FROM AUTHOR] more...

The coastline is a heterogeneous and highly dynamic environment influenced by abiotic and biotic variables affecting the temporal stability of genetic diversity and structure of marine organisms. The aim of this study was to determine how much the genetic structure of four species of marine Bangiales vary in time and space. Partial sequences of the cytochrome oxidase I (COI) gene obtained from two Pyropia (Py. sp. CHJ and Py. orbicularis) and two Porphyra (P. mumfordii and P. sp. FIH) species were used to compare the effect of the 40° S/41° S biogeographic break (spatial‐regional scale) and the one of the Valdivia River discharges (spatial‐local scale) and determine their temporal stability. Four seasonal samplings were taken during 1 year at five sites, one site located in Melinka (Magallanes province) and four sites along the coast of Valdivia (Intermediate area), on both sides of the river mouth. Results showed a strong genetic spatial structure at regional scale (ΦST > 0.4) in Py. sp. CHJ, Py. orbicularis, and P. mumfordii, congruent with the 41° S/42° S biogeographic break. A potential barrier to gene flow, related to the Valdivia River discharge, was detected only in P. mumfordii. In P. sp. FIH, spatial genetic structure was not detected at any scale. The genetic structure of all four species is stable throughout the year. The potential effect of main currents and river discharge in limiting the transport of Bangiales spores are discussed. We propose that both a restricted propagule dispersal and the formation potential for persistent banks of microscopic stages could lead to a temporally stable spatial partitioning of genetic variation in bladed Bangiales. [ABSTRACT FROM AUTHOR] more...

Meiosis and syngamy generate an alternation between two ploidy stages, but the timing of these two processes varies widely across taxa, thereby generating life cycle diversity. One hypothesis suggests that life cycles with long‐lived haploid stages are correlated with selfing, asexual reproduction, or both. Though mostly studied in angiosperms, selfing and asexual reproduction are often associated with marginal habitats. Yet, in haploid‐diploid macroalgae, these two reproductive modes have subtle but unique consequences whereby predictions from angiosperms may not apply. Along the western Antarctic Peninsula, there is a thriving macroalgal community, providing an opportunity to explore reproductive system variation in haploid‐diploid macroalgae at high latitudes where endemism is common. Plocamium sp. is a widespread and abundant red macroalga observed within this ecosystem. We sampled 12 sites during the 2017 and 2018 field seasons and used 10 microsatellite loci to describe the reproductive system. Overall genotypic richness and evenness were high, suggesting sexual reproduction. Eight sites were dominated by tetrasporophytes, but there was strong heterozygote deficiency, suggesting intergametophytic selfing. We observed slight differences in the prevailing reproductive mode among sites, possibly due to local conditions (e.g., disturbance) that may contribute to site‐specific variation. It remains to be determined whether high levels of selfing are characteristic of macroalgae more generally at high latitudes, due to the haploid‐diploid life cycle, or both. Further investigations of algal life cycles will likely reveal the processes underlying the maintenance of sexual reproduction more broadly across eukaryotes, but more studies of natural populations are required. [ABSTRACT FROM AUTHOR] more...

The Cyanidiophyceae, an extremophilic red algal class, is distributed worldwide in extreme environments. Species grow either in acidic hot environments or in dim light conditions (e.g., "cave Cyanidium"). The taxonomy and classification systems are currently based on morphological, eco‐physiological, and molecular phylogenetic characters; however, previous phylogenetic results showed hidden diversity of the Cyanidiophyceae and suggested a revision of the classification system. To clarify phylogenetic relationships within this red algal class, we employ a phylogenomic approach based on 15 plastomes (10 new) and 15 mitogenomes (seven new). Our phylogenies show consistent relationships among four lineages (Galdieria, "cave Cyanidium", Cyanidium, and Cyanidioschyzon lineages). Each lineage is distinguished by organellar genome characteristics. The "cave Cyanidium" lineage is a distinct clade that diverged after the Galdieria clade but within a larger monophyletic clade that included the Cyanidium and Cyanidioschyzon lineages. Because the "cave Cyanidium" lineage is a mesophilic lineage that differs substantially from the other three thermoacidophilic lineages, we describe it as a new order (Cavernulicolales). Based on this evidence, we reclassified the Cyanidiophyceae into four orders: Cyanidiales, Cyanidioschyzonales, Cavernulicolales ord. nov., and Galdieriales ord. nov. The genetic distance among these four orders is comparable to, or greater than, the distances found between other red algal orders and subclasses. Three new genera (Cavernulicola, Gronococcus, Sciadococcus), five new species (Galdieria javensis, Galdieria phlegrea, Galdieria yellowstonensis, Gronococcus sybilensis, Sciadococcus taiwanensis), and a new nomenclatural combination (Cavernulicola chilensis) are proposed. [ABSTRACT FROM AUTHOR] more...

Introduced seaweeds and undescribed species often remain undetected because marine regional floras are as yet poorly understood. DNA sequencing facilitates their detection, but databases are incomplete, so their improvement will continue to lead the discovery of these species. Here we aim to clarify the taxonomy of two turf‐forming red algal Australian species that morphologically resemble the European Aphanocladia stichidiosa. We also aim to elucidate whether either of these species could have been introduced in Europe or Australia. We studied their morphology, analyzed 17 rbcL sequences of European and Australian specimens, examined their generic assignment using a phylogeny based on 24 plastid genomes, and investigated their biogeography using a taxon‐rich phylogeny including 52 rbcL sequences of species in the Pterosiphonieae. The rbcL sequences of one of the Australian species were identical to A. stichidiosa from Europe, considerably expanding its known distribution. Unexpectedly, our phylogenetic analyses resolved this species in the Lophurella clade rather than in Aphanocladia and the new combination L. stichidiosa is proposed. The other Australian species is described as L. pseudocorticata sp. nov. Although L. stichidiosa was originally described in the Mediterranean ca. 70 years ago, our phylogenetic analyses placed it in a lineage restricted to the southern hemisphere, showing that it is native to Australia and introduced to Europe. This study confirms that further work using molecular tools is needed to characterize seaweed diversity, especially among the poorly explored algal turfs, and showcases the usefulness of phylogenetic approaches to uncover introduced species and to determine their native ranges. [ABSTRACT FROM AUTHOR] more...

Compromised light quantity on the seabed affects the composition and resilience of marine forests and the maintenance of ecosystem services. However, the response of macroalgal assemblages to changes in the quality (spectral composition) of light as compared to the quantity alone is poorly understood. Here, we bridge radiative transfer modeling and algal physiology to simulate the underwater light environment and explore macroalgal responses to spectral attenuation by various coastal water constituents. We considered three groups of macroalgal taxa (class Phaeophyceae and, phyla Chlorophyta and Rhodophyta) for which we developed a "synthetic envelope" of spectrally resolved action spectra using 1 million radiative simulations. We found that brown algae were more efficient at harvesting light across the whole spectrum at low attenuation (< 0.2 m−1) when depths were greater than 10 m, whereas green algae dominated shallower depths than 10 m for low to high attenuation values. Finally, red algae made best use of the available light at relatively higher attenuation values (> 0.2 m−1) and deeper depths. We also demonstrated that the brown and green algal taxa showed higher photosynthetic efficiencies when attenuation was dominated by particulate matter rather than by phytoplankton or detrital matter. Our results shed new light on the "Complementary Chromatic Adaptation" hypothesis by confirming that algal pigmentation matters under a subset of scenarios, particularly at the limits of light availability in coastal waters. This study paves the way for identifying competitive thresholds in macroalgal communities by using satellite‐derived ocean color products to identify regions and depths of potential optical transitions. [ABSTRACT FROM AUTHOR] more...

Model organism research has provided invaluable knowledge about foundational biological principles. However, most of these studies have focused on species that are in high abundance, easy to cultivate in the lab, and represent only a small fraction of extant biodiversity. Here, we present three examples of rare algae with unusual features that we refer to as "algae obscura." The Cyanidiophyceae (Rhodophyta), Glaucophyta, and Paulinella (rhizarian) lineages have all transitioned out of obscurity to become models for fundamental evolutionary research. Insights have been gained into the prevalence and importance of eukaryotic horizontal gene transfer, early Earth microbial community dynamics, primary plastid endosymbiosis, and the origin of Archaeplastida. By reviewing the research that has come from the exploration of these organisms, we demonstrate that underappreciated algae have the potential to help us formulate, refine, and substantiate core hypotheses and that such organisms should be considered when establishing future model systems. [ABSTRACT FROM AUTHOR] more...

The carrageenophyte red alga Sarcothalia radula (Gigartinaceae), referred to under its earlier name Gigartina radula, is one of eight species considered a safe source of the refined hydrocolloid and food additive carrageenan and is also reported to be a source of compounds of interest in a variety of other commercial applications. While the latter name has been applied to carrageenophyte red algae from many parts of the Southern Hemisphere as well as in the northeast Pacific, the identity of the type material and the type locality have remained unclear. The location of the type specimen of Fucus radula could not be found. We discuss available information about the probable collection location and present arguments for the collection to have been made during Cook's second voyage to southern New Zealand. Both a lectotype and epitype are designated. [ABSTRACT FROM AUTHOR] more...

Summary: Iron (Fe) is essential for virtually all organisms, being irreplaceable because of its electrochemical properties that enable many biochemical processes, including photosynthesis. Besides its abundance, Fe is generally found in the poorly soluble form of ferric iron (Fe3+), while most plants uptake the soluble form Fe2+. The model angiosperm Arabidopsis thaliana, for example, captures Fe through a mechanism that lowers rhizosphere pH through proton pumping that increases Fe3+ solubility, which is then reduced by a membrane‐bound reductase and transported into the cell by the zinc‐regulated, iron‐regulated transporter‐like protein (ZIP) family protein AtIRT1. ZIP proteins are transmembrane transporters of divalent metals such as Fe2+, Zn2+, Mn2+, and Cd2+. In this work, we investigated the evolution of functional homologs of IRON‐REGULATED TRANSPORTER 1/ZIP in the supergroup Archaeplastida (Viridiplantae + Rhodophyta + Glaucophyta) using 51 genomes of diverse lineages. Our analyses suggest that Fe is acquired through deeply divergent ZIP proteins in land plants and chlorophyte green algae, indicating that Fe2+ uptake by ZIP proteins evolved independently at least twice throughout green plant evolution. Our results indicate that the archetypical IRON‐REGULATED TRANSPORTER (IRT) proteins from angiosperms likely emerged before the origin of land plants during early streptophyte algae terrestrialization, a process that required the evolution of Fe acquisition in terrestrial subaerial settings. [ABSTRACT FROM AUTHOR] more...

Holocarpic oomycetes have been neglected over several decades, until interest in these organisms has recently resurged. One of the most widespread genera of holocarpic oomycetes is Pontisma, parasitic to red seaweeds throughout all oceans. Recently, the genus Sirolpidium (parasitic to green algae) was found to be congeneric with Pontisma. This hinted at a high pathogenic versatility and prompted the screening of other macroalgae on the coastline of Iceland. During this survey a parasite of the brown algae Pylaiella littoralis was found, which formed anisolpidium‐like thalli, but produced biflagellate zoospores. Phylogenetic investigations revealed that the parasite was placed in the genus Pontisma. In reconstructions based on partial nrSSU sequences, it grouped with some sequences of parasitoids of the diatom genus Licmophora, but the more variable mitochondrial cox2 sequences were divergent. Based on phylogenetic evidence and the unique parasitism of brown algae, the parasitoid is described as Pontisma blauvikense in this study. Pontisma blauvikense is the fourth oomycete species parasitic to Pylaiella, which is also parasitised by Euychasma dicksonii and two Anisolpidium species. For a better understanding of the ecology and evolution of holocarpic oomycetes, further research is necessary to investigate the host spectrum of Pontisma in general and Pontisma blauvikense in particular. [ABSTRACT FROM AUTHOR] more...

Phycobilisomes, the light‐harvesting complexes of cyanobacteria and red algae, are a resource for photosynthetic, photonic and fluorescence labeling elements. They cover an exceptionally broad spectral range, but the complex superstructure and assembly have been an obstacle. By replacing in Synechocystis sp. PCC 6803 the biliverdin reductases, we studied the role of chromophores in the assembly of the phycobilisome core. Introduction of the green‐absorbing phycoerythrobilin instead of the red‐absorbing phycocyanobilin inhibited aggregation. A novel, trimeric allophycocyanin (Dic‐APC) was obtained. In the small (110 kDa) unit, the two chromophores, phycoerythrobilin and phytochromobilin, cover a wide spectral range (550 to 660 nm). Due to efficient energy transfer, it provides an efficient artificial light‐harvesting element. Dic‐APC was generated in vitro by using the contained core‐linker, LC, for template‐assisted purification and assembly. Labeling the linker provides a method for targeting Dic‐APC. [ABSTRACT FROM AUTHOR] more...

Partial rbcL sequences from type specimens of three of the earliest described Corallina species showed that C. arbuscula (type locality: Unalaska Island, Alaska, USA) and C. pilulifera (type locality: Okhotsk Sea, Russia) are synonymous, with C. pilulifera as the taxonomically accepted name and that C. vancouveriensis (type locality: Botanical Beach, Vancouver Island, Canada) is a distinct species. To identify molecular species limits and clarify descriptions and distributions of C. pilulifera and C. vancouveriensis, we sequenced and analyzed portions of one mitochondrial and two plastid genes from historical and recent collections. The single‐gene phylogenetic reconstructions support the recognition of both species as distinct, as well as two additional species, C. hakodatensis sp. nov. and C. parva sp. nov., which are sister to, and often morphologically indistinguishable from C. pilulifera and C. vancouveriensis, respectively. DNA sequence data currently illustrate that C. pilulifera is found in the cold northern Pacific waters from the Okhotsk Sea of Russia to Hokkaido, Japan, eastward across the Aleutian Islands to Knoll Head, Alaska, and as far south as Nanaimo, British Columbia. Corallina vancouveriensis is distributed as far west as Attu Island in the Aleutian Islands to Sitka, Alaska, and southeasterly at numerous sites from British Columbia to the north of Point Conception, California, USA. The cryptic species C. hakodatensis and C. parva occur sympatrically with their sister species but with narrower ranges. The complex phylogenetic relationships shown by the single gene trees recommend Corallina as a model genus to explore coralline algal biogeography, evolution, and patterns of speciation. [ABSTRACT FROM AUTHOR] more...

The Cyanidiales are a group of mostly thermophilic and acidophilic red algae that thrive near volcanic vents. Despite their phylogenetic relationship, the reduced genomes of Cyanidioschyzon merolae and Galdieria sulphuraria are strikingly different with respect to pre‐mRNA splicing, a ubiquitous eukaryotic feature. Introns are rare and spliceosomal machinery is extremely reduced in C. merolae, in contrast to G. sulphuraria. Previous studies also revealed divergent spliceosomes in the mesophilic red alga Porphyridium purpureum and the red algal derived plastid of Guillardia theta (Cryptophyta), along with unusually high levels of unspliced transcripts. To further examine the evolution of splicing in red algae, we compared C. merolae and G. sulphuraria, investigating splicing levels, intron position, intron sequence features, and the composition of the spliceosome. In addition to identifying 11 additional introns in C. merolae, our transcriptomic analysis also revealed typical eukaryotic splicing in G. sulphuraria, whereas most transcripts in C. merolae remain unspliced. The distribution of intron positions within their host genes was examined to provide insight into patterns of intron loss in red algae. We observed increasing variability of 5′ splice sites and branch donor regions with increasing intron richness. We also found these relationships to be connected to reductions in and losses of corresponding parts of the spliceosome. Our findings highlight patterns of intron and spliceosome evolution in related red algae under the pressures of genome reduction. [ABSTRACT FROM AUTHOR] more...

The parental care of the nests and the embryonic and larval development of the labrisomid blenny Labrisomus philippii (Teleostei: Labrisomidae) were described for the first time. In situ underwater recordings were done on nests deposited at 2‐m depth at Pisagua and Sarmenia, northern Chile. The nests were composed by a mass of adhered eggs, exclusively on red algae covers (Rhodophyta) outside the crevices used by the adult and guarded by the male. Males utilized ~90% of the time taking care of the nest, defending it from predators (other fish and crustaceans), and keeping it clean. For the observation of larvae, egg masses were extracted from the nests and incubated in the laboratory. Eggs are spheroid, 1.09–1.23 mm in size, with filaments originating from a central thallus in the basal pole, small perivitelline space and granular yolk, with numerous small oil droplets. Larvae hatched at an average size of 5.06 ± 0.10 mm body length (BL), with a functional mouth, and a round yolk‐sac of 0.09 mm3. Larvae are elongated, slightly laterally compressed, with a round and moderate head and a short snout. They have preopercular spines and 35 myomeres; melanophores are located on the cleithrum symphysis, over the head, along the base of the anal fin, between pterygiophores of the dorsal ray fin, and in the ventral margin of the gut. During development, larvae grew at 0.28 mm d−1. Finally, this research helped to increase knowledge on early‐life history traits of this coastal fish inhabiting rocky shores along the south Pacific Ocean. [ABSTRACT FROM AUTHOR] more...

In degraded coral reef ecosystems, allelopathic macroalgae have received increasing attention from marine ecologists because their secondary metabolites (also known as allelochemicals) kill corals that grow adjacent to them and weaken the recovery of degraded reefs. One well‐known coral‐killing macroalga is the calcareous red seaweed Galaxaura. However, our knowledge of how coral reef fishes interact with allelopathic algae like Galaxaura is very limited. Here, we documented novel observations of feeding interactions of 17 species of coral reef fishes (herbivorous and carnivorous) with the filamentous Galaxaura divaricata on degraded lagoon patch reefs in Dongsha Atoll (South China Sea). Video analyses showed that territorial farming damselfishes (i.e., Dischistodus perspicillatus, D. prosopotaenia, Hemiglyphidodon plagiometopon, Pomacentrus grammorhynchus, P. adelus, and Neoglyphidodon nigroris) and juvenile parrotfishes (Scarus schlegeli, S. ghobban, S. rivulatus, and Chlorurus spilurus) likely used G. divaricata as a feeding substratum. Further, microscopic analyses revealed that the filamentous surface of G. divaricata harbored a wealth of epiphytic microalgae, such as filamentous cyanobacteria (i.e., Leptolyngbya, Lyngbya, Rivularia, Oscillatoria, and Stigonema), diatoms (i.e., Synedra, Nitzschia, Mastogloia, and Pleurosigma), and filamentous red algae (i.e., Heterosiphonia), suggesting that these fishes targeted the nutrient‐rich microscopic epiphytes rather than the nutrient‐poor host. Juvenile benthic carnivores (i.e., Labridae, Parupeneus multifasciatus, and Meiacanthus grammistes) form feeding assemblages with roving parrotfishes to feed on small invertebrates (i.e., amphipods, copepods, isopods, gastropods, and polychaetes) associated with G. divaricata. Given that coral reef fishes appear to target the epiphytes associated with Galaxaura rather than the alga itself, these observations thus substantiate the threat posed by the overgrowth of G. divaricata to coral recovery in degraded reef systems due to the lack of natural grazers. [ABSTRACT FROM AUTHOR] more...

The aqueous extract of red algae was used for bio-inspired manufacturing of cobalt oxide nanoparticles (Co3O4NPs) and for antioxidant, antibacterial, hemolytic potency, and anticancer activity. Typical, characterization techniques include UV-Vis, SEM, EDAX, TEM, FTIR, XRD, and TGA. Using an X-ray diffraction assay, the size of the Co3O4NPs crystal was determined to range from 23.2 to 11.8 nm. Based on TEM and SEM pictures, biosynthesized Co3O4NPs' had a homogeneous spherical morphology with a 28.8 to 7.6 nm average diameter. Furthermore, Co3O4NPs biological properties were investigated, including determining the antibacterial potency using the zone of inhibition (ZOI) method and determining the minimal inhibitory concentration (MIC). The antibacterial activity of Co3O4NPs was higher than that of the ciprofloxacin standard. Alternatively, scavenging of DPPH free radical investigation was carried out to test the antioxidant capacitance of Co3O4NPs, revealing significant antioxidant ability. The biosynthesized Co3O4NPs have a dose-dependent effect on erythrocyte viability, indicating that this technique is harmless. Furthermore, bioinspired Co3O4NPs effectively against HepG2 cancer cells (IC50: 201.3 μg/ml). Co3O4NPs would be a therapeutic aid due to their antioxidant, antibacterial, and anticancer properties. [ABSTRACT FROM AUTHOR] more...