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Sargassum species play a key role in habitat formation in tropical and subtropical regions; however, species identification has been hampered by the phenological plasticity exhibited in response to environmental conditions and life history. Molecular phylogenetics has challenged taxa circumscriptions and proven critical in delimiting species in this genus. Yet, the Atlantic species of Sargassum remain poorly understood, and recent studies have shown low molecular diversity between the species in the NW Atlantic. Here, we expand the taxon sampling to the NE Atlantic to assess the diversity of Sargassum in the Atlantic basin, based on a comprehensive morphological and multigene approach. We selected genes commonly used in delineating species in this genus (ITS2, rbcLS, cox3, mtsp) and explored additional markers (cox2, nad6, psbC, clpC, atpB) to infer the phylogenetic relationships between the morphospecies observed in the NE Atlantic. Phylogenetic analyses using single‐gene and multigene alignments including 185 new sequences confirmed the low molecular diversity and supported the distinction of a single clade in Sargassum section Sargassum of N Atlantic benthic species. In contrast, morphological analysis resulted in the identification of 10 species and three new morphospecies that we described here but opt not to equate to species until further molecular evidence is available. Our results were congruent with previous findings from the NW Atlantic and highlight the morphological and ecological diversity of Sargassum in the Atlantic. These results suggest a recent colonization and incipient speciation of Sargassum in the Atlantic basin and showcase the need of further high‐throughput analyses. [ABSTRACT FROM AUTHOR]

Seaweed cultivation, including kelp species, is rapidly expanding in many regions. A widely assumed co-benefit of seaweed farming is increased local carbon sequestration rates (thereby contributing to climate change mitigation), although direct field-based measurements of carbon assimilation and release are largely lacking. We quantified growth, erosion and dislodgement rates of farmed Saccharina latissima in Porthallow Bay (Cornwall, UK) throughout a typical cultivation season to provide insights into the carbon sequestration potential of small-scale kelp farms. Blade elongation rates increased from ~ 1.3 cm day−1 to ~ 2.3 cm day−1 in March–April, before declining to 1.4 cm day−1 by May. Meanwhile, erosion rates remained low, ranging from ~ 0.5 to ~ 0.8 cm day−1. Dislodgement rates decreased from 20% of plants in January–February to 5% in April–May. Rates of carbon accumulation and loss increased from January to May, related to an increase in standing stock. Conservative first-order estimates suggest that the farm captures 0.14 t C ha−1 y−1, of which up to 70% is released into the environment as particulate organic carbon. Based on previous estimates of carbon burial and storage rates, the farm may sequester 0.05 t CO2e ha−1 y−1. These values suggest that scaling-up European kelp farming should be motivated by other co-benefits, such as low-carbon product alternatives, job creation and potential biodiversity gains, and not be solely driven by a perceived meaningful increase in carbon sequestration. Importantly, further information needs to be obtained from a variety of cultivation sites to develop a better understanding of carbon dynamics associated with kelp farms. [ABSTRACT FROM AUTHOR]

Volatile fatty acids (VFA) and reducing sugars (RS) are widely used as platform molecules in biorefineries, facilitating the production of valuable biofuels and chemicals. From an environmental, economic and social perspective, third generation biomass, including macroalgae beach-cast, represents an innovative and optimal solution for the production of these commodities. This study explores the impact of ultrasound pretreatment on the invasive macroalga Rugulopteryx okamurae, aiming to produce RS and VFA through enzymatic hydrolysis and dark fermentation. Several ultrasound conditions were tested: amplitudes (0, 70-100 %), suspension volumes (300, 600 mL), and algal concentrations (4-8 %). Optimal results emerged with 100 % amplitude, 300 mL volume, and 4 % (w/v) algal concentration, leading to the maximum COD solubilization of 61.5 mg COD g-biomass-1. For enzymatic hydrolysis, the pretreated sample achieved maximum RS concentrations (0.124 g-RS g-biomass-1) with half the enzyme dosage required by the non-pretreated alga (25 vs 50 FPU g-biomass-1), implying significant economic benefits for large-scale processes. The kinetic model proposed by Romero-Vargas et al. aligned perfectly with the experimental data, obtaining higher values of all the kinetic parameters for the pretreated sample. Dark fermentation showed substantial increases in organic matter solubilization and VFA production (10.36 mg-HAc g-biomass-1) post ultrasound pretreatment: 21.1 % higher solubilization and 9.4 % increased VFA compared to non-pretreated biomass. The resulting VFA composition comprised 73 % acetic acid, 13 % propionic acid, and 8 % butyric acid. Utilization of chemical agents during sonication may further enhance overall processing yields. [ABSTRACT FROM AUTHOR]

Interest in farming kelps has grown beyond using kelp for food, feed or biofuels. There is considerable interest in generating biomass from seaweed for use in bioplastics and other products that would substitute for petroleum-derived products. For these uses to be viable, large amounts of biomass are needed. Very large kelp farms can be expensive to build and maintain, leading to the need to optimize the biomass per unit area. Although close spacing of growlines can lead to poor growth, a viable approach may be to grow two species of kelps together: one that hangs down and one that is buoyant, growing up. This system would increase the spacing in three dimensions. In Alaska, Saccharina latissima is commonly grown hanging down from longlines. One of the buoyant Alaskan kelps is Nereocystis luetkeana. Because there are commercial uses for wild-harvested Nereocystis in Alaska, we undertook a preliminary trial in Kodiak, Alaska, that grew both Saccharina and Nereocystis in the same longline array. Closely spaced lines were seeded the first week of February 2023 and set at 3 m below the surface. The arrays were harvested in late June 2023. Total yields were greatest on the combined arrays, followed by the Nereocystis only and Saccharina only arrays. Despite having 45% fewer grow-lines, the total yield of the Nereocystis on the combined arrays was statistically similar to the Nereocystis only arrays. These results may have significance for large scale macroalgal production. [ABSTRACT FROM AUTHOR]

To assess the potential effects of future climate change on Undaria pinnatifida cultivation in the Seto Inland Sea, Japan, we developed an individual-based growth model for the U. pinnatifida sporophyte. Initially, we validated the model's performance using field observation data. The simulation results replicated temporal variations in the total lengths of sporophytes at two stations with differing oceanographic conditions. Subsequently, we conducted numerical simulations of sporophyte growth in the Seto Inland Sea during the 1990s and projected outcomes for the 2090s under four emission scenarios of the Representative Concentration Pathway (RCP 2.6, 4.5, 6.0, and 8.5). The majority of areas exhibited decreased sporophyte growth in the 2090s compared to the 1990s, except for the eastern area under the RCP 2.6 scenario. This decline was attributed to delayed cultivation start times associated with ocean warming and reduced dissolved inorganic nitrogen concentrations. Interestingly, the impacts of ocean warming on U. pinnatifida cultivation were not uniformly negative. In addition to adverse effects, there were positive effects that accelerated growth rates in low-temperature winter areas. Sensitivity analyses revealed that the balance between positive and negative impacts varied geographically; moreover, the contrasts were enhanced with higher RCP scenarios. Simulations for climate change adaptation using a high-temperature tolerant cultivar indicated that yield losses could be mitigated, even under the RCP 8.5 scenario. Despite uncertainties in the simulation results, such as future management of nutrient loads and herbivore feeding damages, our projections underscore the potential sustainability and future viability of U. pinnatifida aquaculture in the Seto Inland Sea. [ABSTRACT FROM AUTHOR]

Edible brown seaweeds of the genus Sargassum have the potential to be utilized as nutrient-rich food components yielding beneficial health effects upon consumption. This study aimed to characterise Sargassum crassifolium for its phytochemical content and antioxidant capacity followed by its utilization as a dry powder in wheat noodles as a flour replacement. Sargassum crassifolium dehydrated powder contained considerable amounts of total phenols (1.13±0.05 mg GAE g-1 DW), flavonoids (21.07±0.79 mg RE g-1 DW), fucoidan (2.9±0.48 mg g-1 DW), fucoxanthin (0.963±0.00 µg g-1 DW), carotenoids (1.88±0.002 µg g-1 DW) and tannins (1.88±0.002 mg g-1 DW), while displaying significant DPPH (2,2-diphenyl-picrylhydrazyl hydrate) radical scavenging activity (23.20±1.73%). The use of 2.5% S. crassifolium as a flour replacement enhanced the sensory properties, nutrient composition and phytochemical content of the noodles. The DPPH radical scavenging activity of 2.5% S. crassifolium noodles (19.88±1.56%) in the cooked form was significantly higher than that of the control noodles containing no seaweed (13.29±2.02%). The results of this study revealed that S. crassifolium can be successfully incorporated in noodles to yield acceptable products that have improved nutrient content and potential functionality. [ABSTRACT FROM AUTHOR]

The traditional and local edible brown algae Ecklonia cava subspp. kurome (EK) and stolonifera (ES) are rich in minerals, phlorotannins (brown algal polyphenols), and water-soluble dietary fibres (alginate, laminaran, and fucoidans). These dried powders increase not only alginate- and laminaran-degrading Bacteroides acidifaciens- and B. intestinalis-like bacteria but also Faecalibaculum. To elucidate the effect of EK and ES ingredients, other than dietary fibres, on gut microbiota, 100 mL of ethanolic/aqueous extract solutions (EK-S, ES-S; final solvent was distilled water) were prepared from 100 g of dried samples. EK-S and ES-S contained total phenolic contents of 160 and 120 μmol phloroglucinol equivalent mL-1, respectively. A diet containing 5% (v/w) EK-S or ES-S was fed to ICR mice for 14 days. Amplicon sequencing of the 16S rDNA (V4) gene revealed that EK-S and ES-S increased Faecalibaculum abundance 2-fold and more, and this was the predominant genus (37–38%) in mice. However, the abundances of B. acidifaciens- and B. intestinalis-like bacteria did not increase. Akkermansia muciniphila-like bacteria were higher in EK-S-fed mice. Faecalibaculum and Akkermansia are regarded as desirable gut commensals correlated with anti-inflammatory and immunomodulatory effects on the host's health. These results suggest that phlorotannins have beneficial functional effects on indigenous gut bacteria responsible for host health. [ABSTRACT FROM AUTHOR]

Eisenia (order Laminariales) is a genus of warm-tolerant kelps found in the Northern and Southern Hemispheres of the East Pacific, as well as in the North West Pacific, where species form beds in rocky bottoms along the sea coast from the intertidal and subtidal zones. There are seven recognized species in the genus, including the endemic and vulnerable E. galapagensis. Despite some remarkable morphological variations, Eisenia species are characterized by two twisted stipe-like parts arising from the main stipe. Genetic data have recently contributed to the understanding of Eisenia systematics; however, additional studies on E. desmarestioides, E. cokeri, and E. gracilis are needed. Aside from economic benefits, Eisenia farming has various other essential benefits, such as resource sustainability and ecosystem benefits, which are especially important in climate change scenarios. Spore-based cultivation has been reported only for E. arborea, E. bicyclis, and E. nipponica (formerly known as E. arborea sensu Arasaki). This kelp is widely consumed in Korea and Japan and utilized as a raw material for alginate production and feed for abalone cultures. Because of its nutritional composition and mineral concentration, Eisenia is also a potential food source outside Asia. Moreover, various pharmacological applications of Eisenia have been reported, particularly those related to antioxidant, antidiabetic, and anti-inflammatory properties. Phlorotannins (brown algal polyphenols) derived from E. bicyclis are linked to these bioactivities. In this work, we present a comprehensive synthesis of the current state of knowledge on Eisenia, offering insights into its taxonomy, distribution, ecology, cultivation, and various applications. [ABSTRACT FROM AUTHOR]

The Subantarctic brown alga Cladochroa chnoosporiformis had been collected only on one occasion by Carl Skottsberg in 1907 from Port Philomel, West Falkland, Falkland Islands, resulting in its formal taxonomic description. Due to the lack of reports since then, doubts remained about its existence and identity. Within the framework of this study, Cladochroa was rediscovered 106 years after its original description at its type locality, confirming its existence and the morphological features described by Skottsberg. The re-collection enabled molecular studies on field material and isolated cultures. Sequences of nrDNA, rbcL, and 5′-COI suggest that C. chnoosporiformis is conspecific with Utriculidium durvillei, which has nomenclatural priority. However, the morphologies of C. chnoosporiformis and U. durvillei are significantly different. Utriculidium may be the gametophyte generation of Cladochroa, or hitherto unknown factors cause highly different morphologies without alternating generations. [ABSTRACT FROM AUTHOR]

The state of Espírito Santo has one of the greatest diversities of macroalgae along the Brazilian coast. Beach-cast seaweeds are a frequent phenomenon and exhibit great diversity. This study assessed stranded macroalgae's composition and reproductive status to evaluate their potential for sustainable use by the local community. Monthly collections were carried out from March to November 2022, covering the rainy and dry seasons, on five beaches in Espírito Santo: three in the north and two in the south. At each beach, two 50 m transects were set up parallel to the coastline over the stranded algae patches, one near the wave-breaking zone during low tide and another around high tide, and three 1 × 1 m quadrants were randomly selected in each transect. All material within each quadrant was collected, resulting in six samples per beach. We identified 81 taxa, including 54 Rhodophyta, 16 Ulvophyceae and 11 Phaeophyceae. The taxon composition was relatively consistent across the studied regions, with the rainy season exhibiting the greatest species richness. Seventeen of the identified taxa had reproductive structures, although only four consistently presented these structures. Our results suggest that removing stranded macroalgae does not significantly impact their role as propagule sources. [ABSTRACT FROM AUTHOR]

The state of Espírito Santo has one of the greatest diversities of macroalgae along the Brazilian coast. Beach-cast seaweeds are a frequent phenomenon and exhibit great diversity. This study assessed stranded macroalgae’s composition and reproductive status to evaluate their potential for sustainable use by the local community. Monthly collections were carried out from March to November 2022, covering the rainy and dry seasons, on five beaches in Espírito Santo: three in the north and two in the south. At each beach, two 50 m transects were set up parallel to the coastline over the stranded algae patches, one near the wave-breaking zone during low tide and another around high tide, and three 1 × 1 m quadrants were randomly selected in each transect. All material within each quadrant was collected, resulting in six samples per beach. We identified 81 taxa, including 54 Rhodophyta, 16 Ulvophyceae and 11 Phaeophyceae. The taxon composition was relatively consistent across the studied regions, with the rainy season exhibiting the greatest species richness. Seventeen of the identified taxa had reproductive structures, although only four consistently presented these structures. Our results suggest that removing stranded macroalgae does not significantly impact their role as propagule sources.

Abstract Background Organellar genomes have become increasingly essential for studying genetic diversity, phylogenetics, and evolutionary histories of seaweeds. The order Dictyotales (Dictyotophycidae), a highly diverse lineage within the Phaeophyceae, is long-term characterized by a scarcity of organellar genome datasets compared to orders of the brown algal crown radiation (Fucophycidae). Results We sequenced the organellar genomes of Padina usoehtunii, a representative of the order Dictyotales, to investigate the structural and evolutionary differences by comparing to five other major brown algal orders. Our results confirmed previously reported findings that the rate of structural rearrangements in chloroplast genomes is higher than that in mitochondria, whereas mitochondrial sequences exhibited a higher substitution rate compared to chloroplasts. Such evolutionary patterns contrast with land plants and green algae. The expansion and contraction of the inverted repeat (IR) region in the chloroplast correlated with the changes in the number of boundary genes. Specifically, the size of the IR region influenced the position of the boundary gene rpl21, with complete rpl21 genes found within the IR region in Dictyotales, Sphacelariales and Ectocarpales, while the rpl21 genes in Desmarestiales, Fucales, and Laminariales span both the IR and short single copy (SSC) regions. The absence of the rbcR gene in the Dictyotales may indicate an endosymbiotic transfer from the chloroplast to the nuclear genome. Inversion of the SSC region occurred at least twice in brown algae. Once in a lineage only represented by the Ectocarpales in the present study and once in a lineage only represented by the Fucales. Photosystem genes in the chloroplasts experienced the strongest signature of purifying selection, while ribosomal protein genes in both chloroplasts and mitochondria underwent a potential weak purifying selection. Conclusions Variations in chloroplast genome structure among different brown algal orders are evolutionarily linked to their phylogenetic positions in the Phaeophyceae tree. Chloroplast genomes harbor more structural rearrangements than the mitochondria, despite mitochondrial genes exhibiting faster mutation rates. The position and the change in the number of boundary genes likely shaped the IR regions in the chloroplast, and the produced structural variability is important mechanistically to create gene diversity in brown algal chloroplast.

Sargassum hemiphyllum var. chinense, a prevalent seaweed along the Chinese coast, has economic and ecological significance. However, systematic positions within Sargassum and among the three orders of Phaeophyceae, Fucales, Ectocarpales, and Laminariales are in debate. Here, we reported the organellar genomes of S. hemiphyllum var. chinense (34,686-bp mitogenome with 65 genes and 124,323 bp plastome with 173 genes) and the investigation of comparative genomics and systematics of 37 mitogenomes and 22 plastomes of Fucales (including S. hemiphyllum var. chinense), Ectocarpales, and Laminariales in Phaeophyceae. Whole genome collinearity analysis showed gene number, type, and arrangement were consistent in organellar genomes of Sargassum with 360 SNP loci identified as S. hemiphyllum var. chinense and two genes (rps7 and cox2) identified as intrageneric classifications of Sargassum. Comparative genomics of the three orders of Phaeophyceae exhibited the same content and different types (petL was only found in plastomes of the order Fucales and Ectocarpales) and arrangements (most plastomes were rearranged, but trnA and trnD in the mitogenome represented different orders) in genes. We quantified the frequency of RNA-editing (canonical C-to-U) in both organellar genomes; the proportion of edited sites corresponded to 0.02% of the plastome and 0.23% of the mitogenome (in reference to the total genome) of S. hemiphyllum var. chinense. The repetition ratio of Fucales was relatively low, with scattered and tandem repeats (nine tandem repeats of 14–24 bp) dominating, while most protein-coding genes underwent negative selection (Ka/Ks < 1). Collectively, these findings provide valuable insights to guide future species identification and evolutionary status of three important Phaeophyceae order species. [ABSTRACT FROM AUTHOR]

Brown algae (Phaeophyceae) dominate intertidal and shallow subtidal areas globally, where larger species form extensive underwater forests. These structurally complex and highly productive habitats enhance local biodiversity and support food webs in coastal areas through secondary production, thereby shaping local oceanography and ecology. Macroalgal aquaculture is an important and growing sector, where approximately 40% of all cultivated algae belong to Phaeophyceae. However, both cultured and natural brown algae have been under increasing pressure due to climate-driven factors, such as ocean warming, eutrophication, and herbivore outbreaks. We conducted a comprehensive literature review on abiotic (temperature, light intensity, and UV radiation, nutrients, water motion, salinity, and substrata and sediment) and biotic (bacteria, viruses, fungi, eukaryotic endophytes and endoparasites, epiphytes, and grazers) stressors and illnesses in marine brown macroalgae, as well as brown algae defense mechanisms, and discuss how these parameters may affect the production of a sustainable crop for the aquaculture industry under future climate change scenarios. [ABSTRACT FROM AUTHOR]

To improve the quality and quantity of seaweed mariculture harvests, seedlings are frequently introduced from regions geographically apart from cultivation sites. The effects of such introduction have been insufficiently studied, despite increasing demands on seaweed cultivation as a measure against global warming. We here evaluated the degree of cryptic invasion occurring through mariculture using a brown algal species, Undaria pinnatifida. Cultivated materials used in the Seto Inland Sea, Japan, were introduced from northern Japan in the 1970s. Based on the clear genetic structure among Japanese Undaria populations, we compared mitochondrial haplotypes between wild populations and cultivated materials in the Seto Inland Sea. All cultivated materials analyzed had haplogroups native to northern Japan. Multiple haplogroups were observed in the wild populations, especially those in the eastern Seto Inland Sea, which is exceptional considering the reported genetic structure. Some northern Japan haplotypes were observed both in cultivated materials and wild individuals. A northern Japan haplogroup was predominant at several sites near Undaria-cultivation sites. These results strongly suggested that cryptic invasion through Undaria mariculture occurred here, although its ecological impact remains unclear. There is a clear risk of invasion by mariculture seedlings from other regions, even when native conspecific populations are present. [ABSTRACT FROM AUTHOR]

A type III polyketide synthase (SfuPKS2) from the edible seaweed Sargassum fusiforme was cloned and biochemically characterized. SfuPKS2 can only accept octanoyl-CoA (C8) and neither other long-chain fatty acyl-CoAs, nor non-fatty acyl-CoAs synthesized in this study as the substrate. In addition, in incubation with octanoyl-CoA, only a single product peak was observed, giving rise to the triketide α-pyrone derivative. To understand the substrate specificity of SfuPKS2, we constructed a structural model and performed docking analysis to reveal amino acid residues critical for enzyme-substrate binding. Putative key residues were then mutated experimentally and the impact on protein function was assessed by incubating the mutant with octanoyl-CoA. We found that key amino acids governing enzyme activity and specificity included Ser171, His236, Phe254, and Ile377. Mutations on these amino acids generally resulted in altered interactions with the substrate and thus the enzyme activity. In summary, our work provided mechanistic insight on how the selectivity toward the substrate is achieved in SfuPKS2. [ABSTRACT FROM AUTHOR]

Biostimulants such as seaweed extracts are widely used to stimulate plant growth and crop productivity under optimal or stressful conditions, constituting a sustainable strategy to mitigate the impacts of abiotic stress on plant performance. In this study, a growth experiment was conducted to evaluate the effects of an aqueous extract from the seaweed Padina gymnospora on the physiological, biochemical, and molecular characteristics of Solanum lycopersicum under salt stress. The experiment included four treatments: 1) control plants, 2) plants irrigated with 300 mM NaCl solution, 3) plants treated with the P. gymnospora extract, and 4) plants treated with the P. gymnospora extract and irrigated with 300 mM NaCl solution. Salt stress increased the activity of antioxidant enzymes (catalase and superoxide dismutase) and resulted in the overaccumulation of the osmolyte proline and flavonoids while enhancing photosynthetic performance and chlorophyll content. In addition, treatment with P. gymnospora extract increased total reducing sugars and phenols in salt-stressed plants, which was correlated with DPPH and ABTS antioxidant activity. The induction of stress-responsive genes, such as SlHB7, SlSOD1, SlRD29, and SlHKT, appears to be a major factor modulating the responses to P. gymnospora extract application in tomato plants. The results of this study demonstrate that the application of P. gymnospora to tomato plants attenuated the damage caused by salt stress. It is essential to continue studying the potential of seaweed extracts to mitigate stress in plants, given the promising agricultural applications of these novel biostimulants. [ABSTRACT FROM AUTHOR]

Since 2012 the Moroccan Atlantic coast has witnessed the introduction of the brown alien seaweed Sargassum muticum with a high invasive potential presenting environmental and economic risks. This study evaluates the effect of seasons and location on the biochemical composition of S. muticum. Proteins, carbohydrates, lipids, pigments, minerals, and heavy metals were studied during four seasons from spring 2019 to autumn 2020 at four sites along the Moroccan Atlantic coast: El Jadida, Saada (SA), Sidi Bouzid (SB), Moulay Abdallah (MA) and Jorf Lasfar (JL). MA presents the highest protein content (12.5% dw) during spring and the highest level of lipid and carbohydrate content during summer (1.8% dw and 41.5% dw respectively). The highest chlorophyll a content was found in JL and MA sites with (21.6 and 21.45 mg mL-1, respectively) during winter. Maximum chlorophyll c and carotenoids were found at SA with (2.27 and 9.71 mg mL-1, respectively) during winter. In all locations and during all seasons, the mineral profile was rich in essential minerals such as magnesium, manganese, zinc, iron, selenium, and lithium. Levels of toxic metals Al and Pb were lower than in previous studies whereas Cd and As were slightly higher than the legislation limits for dry seaweeds. Therefore, in this context, some strategies of S. muticum valorisation should be favoured such as bioenergy, bioplastic or biostimulant over others such as human food and animal feed. [ABSTRACT FROM AUTHOR]

Soybean is essential for food security worldwide and water restriction is a rising challenge for its production. In this scenario the use of natural sources such as Ascophyllum nodosum extracts (ANE) which contribute to the better adaptation of plants to environmental stresses, gains relevance. Nonetheless, understanding the metabolic effect of ANE according to the time of application could be better explored, such as, if the application before or during the stress occurrence can trigger different metabolic responses. Thus, this work aimed to identify the physiological and biochemical effects of foliar application of ANE at different times, in soybean plants subjected to water restriction. The experiment was carried out in pots with plants at the vegetative stage, subjected to foliar sprays of ANE in the following treatments: (i) application of ANE at adequate humidity with 80% of the substrate water holding capacity (WHC); (ii) application of ANE three days before the humidity reached 50% of the substrate WHC; (iii) application of ANE on the day that WHC reached 50% (established as drought stress condition); (iv) positive control without application of ANE and WHC 50%; (v) absolute control, without application of ANE and without water restriction. The results allow to point out that ANE application three days before drought stress improved nitrate reductase enzyme activity, chlorophyll and proline content, decrease lipid peroxidation and presented more effective improvement of peroxidase enzyme activity; while application at stress condition resulting in more effective reduction of stomata resistance, long term expressive proline content increment, more effective improvement of superoxide dismutase and catalase enzymes activity and reduce chlorophyll degradation. This works results also could help to answer some field practice questions, such as; it is worth applying ANE when plants are already under drought stress. Ascophyllum nodosum extracts (ANE) applied three days before drought stress (A) improved nitrate reductase enzyme activity (NR), proline (PR) and chlorophyll content (Chl), decreased lipid peroxidation (LP) and presented more effective improvement of peroxidase enzyme activity (POD). Application at stress condition (B) resulting in more effective reduction of stomata resistance (SR) and chlorophyll (Chl) degradation, long term proline content increment (PR), more effective improvement of superoxide dismutase (SOD) and catalase (CAT) enzymes activity. [ABSTRACT FROM AUTHOR]

Seaweeds must be stabilised shortly after harvesting to avoid rapid deterioration. To handle large amounts harvested during a short period, freezing and frozen storage until utilisation or further processing is one of the methods used industrially. The aim of this study was to assess the effects of different freezing and thawing procedures on Alaria esculenta by analysis of the chemical composition of the seaweed and the drip loss expelled during thawing. Thawing of industrially frozen A. esculenta resulted in a drip loss of 57% of wet weight. The drip loss had a dry matter content of 7% of wet weight, of which 71% was mineral content. Analysis showed that, of the dry matter excluding ash, alanine, aspartic acid, and mannitol were the main components lost to the drip loss. Experiments with a second batch of A. esculenta looking at quick and slow freezing and thawing showed that quick freezing resulted in a significantly lower drip loss than slow freezing; 20% compared to up to 42% of wet weight. Dry matter and mineral content of the drip loss of these samples were all around 6% of wet weight and 31% of dry weight. For some applications it might be of interest to reduce the concentration of potentially toxic elements such as iodine and heavy metals, but due to a high loss of other biomass this was not very effectively done by freezing and thawing. For preservation purposes, quick freezing is the best alternative to retain seaweed biomass. [ABSTRACT FROM AUTHOR]

Bio-fabrication of silver nanoparticles (AgNPs) was performed using the extracts of the brown seaweed Dictyota ciliolata (DC) and the resultant AgNPs were characterized by biophysical and chemical techniques. A prominent absorbance peak observed at 417 nm in the UV-Vis spectroscopy confirmed the presence of AgNPs. The FTIR spectrum revealed the presence of various functional groups at 2988.16, 1763.58, 1375.96, 1242.9 and 1055.84 cm-1 which indicates their involvement in the stabilization of nanoparticles. XRD analysis showed the crystalline nature of DC-AgNPs. SEM analysis confirmed the presence of particles with an agglomerated clusters of micro flakes-like structure with the size range of 10 –120 nm. The weight percentage of elemental silver was determined as 54.96 % using the EDX analysis. DC-AgNPs showed potent larvicidal toxicity on the larvae of Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus at first, second and third instars as well as against pupae stages when compared to the aqueous extract of D. ciliolata (DC-AE). The eco-toxicity assessment of the DC-AgNPs showed only very low toxicity against the non-target species, Artemia salina. The study results show the efficacy of the brown seaweed, D. ciliolata for the cost-effective and eco-friendly synthesis of AgNPs and their potential against mosquito-vectors. [ABSTRACT FROM AUTHOR]

Herpes viruses (HSV) are among the most common viruses that infect humans. They cause blisters and inflammation of the oral and genital mucosa as well as severe symptoms such as blindness, hearing impairment and fatal encephalitis. Although acyclovir (ACV) and its derivatives are highly effective in treating recurrent lytic infections, the emergence of resistant strains remains a concern. In this study, the in vitro anti-herpetic activity of a hydroalcoholic extract obtained from the brown seaweed Sargassum fluitans, collected from strandings in Cuba, was evaluated. The hydroalcoholic extract was not cytotoxic in Vero cells (CC50 >5000 µg mL-1) and inhibited replication of HSV-1 (ACV-susceptible and -resistant) and HSV-2 (ACV-resistant) strains with EC50 of 271.66, 403.62 and 14.99 µg mL-1 respectively. In addition, first studies about mechanism of action were evaluated with ACV-sensitive HSV-1 model. The extract showed strong inhibition when pre-incubated with the virus and when the extract and virus were added simultaneously on the cells. The protection of Vero cells during the post-infection assay was very effective up to 1 h. A high resolution UPLC/MS-MS analysis detected 139 compounds, of which 44 were identified. In silico analysis was performed to determine the putative interaction sites of two flavones of interest identified in the extract with the viral glycoprotein D (gD). Molecular docking analysis revealed that takakin and tectorigenin mainly interact with the gD protein active center through hydrophobic interactions (Leu44, Pro50, Thr174, Lys169, Tyr208, Gln209) while hydrogen bonding interactions are less abundant (Ser43, Asp46, Lys169, Tyr208). This research represents a contribution to the valorization of S. fluitans as a source of anti-herpetic compounds in the context of recurrent and abundant seaweed strandings. [ABSTRACT FROM AUTHOR]

The colour produced by an object's microstructure rather than by pigments is generally called structural colour. Various macroalgae have some mechanisms of structural colouration. The presence of structural colour in the brown algae is well known in the Dictyotales and Fucales but has recently been reported in the Sporochnales where Sporochnus dotyi has structures in the terminal assimilatory filaments (trichothallic hairs) that produce a pronounced green iridescence. Based on observations by light microscopy, the structural colour of this species was caused by iridescent bodies, 10–15 µm in diameter, within the cells of assimilatory filaments. In contrast, another Sporochnus species known as S. radiciformis in Japan (S. radiciformis auct. japon.) also contains iridescent bodies of 6–10 µm diameter in the assimilatory filaments, but no significant structural colour was observed. In epi-illumination observations using red, green and blue LED light sources, iridescent bodies of S. dotyi showed stronger reflection of green compared with red and blue, whereas the reflections were similar among those colours in S. radiciformis. Transmission electron microscopy (TEM) using a rapid freezing method revealed that homogeneous globules 130–160 nm in diameter were tightly packed inside the iridescent bodies of S. dotyi, whereas the sizes of the globules were markedly irregular in iridescent bodies of S. radiciformis. Therefore, we conclude that the structural colouration of S. dotyi is caused by the interference and diffraction of incident light caused by the crystal lattice-like structure of tightly packed and regularly arranged globules of homogeneous size in the iridescent bodies, which is similar to the mechanism causing iridescence in opal. A similar opal-like structure of iridescent bodies causing structural colouration was recently reported in Ericaria selaginoides, but that of S. dotyi lacked the dynamic shift of the globules shown in E. selaginoides that resulted in a change of the wavelength of reflected light. Structural colouration, previously known only in Dictyotales and Fucales in Phaeophyceae, is newly reported in Sporochnales. Green structural colour of Sporochnus dotyi is caused by the iridescent bodies within trichothallic hairs. Iridescent bodies of S. dotyi includes densely packed homogeneous globules, whereas they are markedly irregular in size in S. radiciformis auct. japon. which lacks structural colour. [ABSTRACT FROM AUTHOR]

Loej coast situated near Mangrol of Saurashtra region, Arabian Sea, Gujarat is supported by diverse flora and fauna. The present study aimed to document seaweed diversity and distribution along intertidal region of Loej coast by using belt transect sampling method from October 2021 to March 2022. From the study area, a total of 56 seaweed species belonging to 3 phyla, 3 classes, 16 orders, 25 families and 36 genera were recorded. Out of these 12 species were green seaweed, 14 species were brown and 30 species were red seaweed. Maximum number of species diversity was reported from class Rhodophyceae. Dictyotales (16%, species) was found to be dominant order followed by Gigartinales (14%, species); Ceramiales (11%, species). Among 25 families, Dictyotaceae was the dominant family reported with 14 species. Distribution study observed vertical distribution from the seashore side to the seaside of green, brown and red seaweed. Also, horizontal distribution of green seaweed and red seaweed were seen in the upper intertidal area and in the lower intertidal area, respectively. In species distribution behaviour, out of 56 species of seaweed; 8 species show aggregated behaviour, 10 species show the regular distribution and 38 species show random aggregation behaviour. Ulva lactuca was most abundantly and frequently found species with maximum density during the whole study period. During the present study, diversity indices like species diversity index (H') indicate healthy diverse seaweed fauna. Species richness index/Margalef's diversity index (D) was in the range of 3.37-4.81. Maximum species richness was reported in winter month February and minimum species richness in October. Pielou's evenness index (J) showed that seaweed species were unevenly distributed. [ABSTRACT FROM AUTHOR]

Environmental changes associated with rapid climate change in the Arctic, such as the increased rates of sedimentation from climatic or anthropogenic sources, can enhance the impact of abiotic stressors on coastal ecosystems. High sedimentation rates can be detrimental to nearshore kelp abundance and distribution, possibly due to increased mortality at the spore settlement stage. Spore settlement and viability of the Arctic kelp Laminaria solidungula were examined through a series of lab‐based sedimentation experiments. Spores were exposed to increasing sediment loads in three experimental designs simulating different sedimentation scenarios: sediment deposition above settled spores, settlement of spores on sediment‐covered substrate, and simultaneous suspension of spores and sediments during settlement. Spore settlement was recorded upon completion of each experiment, and gametophyte abundance was assessed following a growth period with sediments removed to examine short‐term spore viability via a gametophyte‐to‐settled‐spore ratio. In all three types of sediment exposure, the addition of sediments caused a 30%–40% reduction in spore settlement relative to a no‐sediment control. Spore settlement decreased significantly between the low and high sediment treatments when spores were settled onto sediment‐covered substrates. In all experiments, increasing amounts of sediment had no significant effect on spore viability, indicating that spores that had settled under different short‐term sediment conditions were viable. Our results indicate that depending on spore‐sediment interaction type, higher rates of sedimentation resulting from increased sediment loading could affect L. solidungula spore settlement success with potential impacts on the long‐term persistence of a diverse and productive benthic habitat. [ABSTRACT FROM AUTHOR]

Kelp growers and the food industry, as well as food researchers, are currently finding methods for controlling the iodine content of kelp intended for food as this is one of the major obstacles to entering a profitable market. Kelps are rich sources of dietary iodine since iodine is up-concentrated in algal tissue and utilized as an inorganic antioxidant during exposure to stress. As kelp contains much more iodine than any other food source, it is warranted to reduce the amount of iodine in the biomass prior to consumption, since both iodine deficiency and excess can cause health problems. Iodine is typically removed post-harvest using traditional methods such as blanching. In the present work, we attempted to utilize inherent stressors, i.e., intermediate storage (3 days) with high light exposure and low turnover of water, to reduce the iodine content prior to processing. Furthermore, we assessed the effect on subsequent blanching, comparing samples stored in tanks and not stored samples. The iodine content was slightly reduced when comparing storage to no storage, but in most cases not significantly so. However, after subsequent blanching, there was a pronounced added reduction for stored samples (87 % reduction) compared to not stored samples (80 % reduction). Although the differences are smaller than we expected, our research shows that using post-harvest intermediate storage of kelp may alter the iodine content post-processing. Fine-tuning the stressors and conditions could lead to new possibilities for iodine reduction. [ABSTRACT FROM AUTHOR]

The importance of seaweed as a possible supplement or an alternative protein source for Asian seabass (Lates calcarifer) has been recently recognized by several studies. In the present study, Asian seabass with an initial mean body weight of 29.00 ± 1.00 g has been used as a model organism to establish the effects of dietary Sargassum ilicifolium and Padina australis, as partial substitution of fish meal on growth performance, body composition, hemato-immunlogical response, digestive enzymes and immune and growth-related genes. Three diets were formulated in which fish meal (FM) was replaced by S. ilicifolium (SIM 6) and P. australis meal (PAM 6) at 6% (SIM 6 & PAM 6, respectively) whereas in the control diet (C), FM was not replaced with macroalgae. Asian seabass juveniles were fed for six weeks with experimental diets. At the end of the experiment, growth and feed utilization parameters in PAM 6 were significantly higher than those of the control group (p < 0.05). The P. australis dietary inclusion showed differences significantly in red blood cell (RBC), hemoglobin (Hb), hematocrit (Hct), white blood cell (WBC), lymphocytes, neutrophils, and cholesterol contents (p < 0.05). It was observed that the levels of total protein and triglyceride in fish fed SIM 6 significantly increased compared to the other groups (p < 0.05). The skin mucus total immunoglobulin (Ig) and mucus lysozyme in the group fed on PAM 6 were significantly higher than the control group (p < 0.05). The serum total Ig in the group fed on SIM 6 was significantly higher with respect to the control group (p < 0.05). No significant differences were recorded in the contents of the alternative complement pathway hemolytic activity (ACH50) and serum lysozyme among all treatment groups (p > 0.05). There was no significant difference in the contents of protease, lipase, and amylase among all treatments (p > 0.05). At the end of the experiment, the insulin-like growth factor I (IGF-I), lysozyme (LZ), and interleukin-1β (IL-1β) in liver organ in PAM 6 were significantly higher than other treatments (p < 0.05). The results obtained in the present study showed that P. australis as a partial replacement for fishmeal in the diet of Asian sea bass juveniles is beneficial for its immune system and growth performance stimulatory effects. [ABSTRACT FROM AUTHOR]

The massive arrival of Sargassum biomass on the Caribbean coast is a potential raw material source that needs an assessment of its quality and preservation state. Thus, the present study aimed to investigate how pelagic Sargassum changes its chemical composition due to sample transportation, morphotype (S. natans I, S. natans VIII, and S. fluitans III), and exposure to open-air conditions during two months of outdoor conditions using Fourier Transform Infra-Red (IR) spectroscopy and chemometric analysis. The results demonstrate that cold transportation to the lab before flash-freezing caused sample degradation, characterized by mannitol consumption and the formation of anaerobic metabolism products. Multivariate analyses showed that the IR spectral zone with differences between S. natans and S. fluitans were in the same IR spectral regions related to sample degradation. In the two flash-freezing treatments, S. fluitans had the highest IR peak absorbance of mannitol and a lower absorbance for the carboxylic acids IR peak. Between S. natans morphotypes, S. natans I had the highest modification caused by the cold transportation to the lab. The decomposition under prolonged time (up to eight weeks) in open-air conditions demonstrated an increased absorbance on the IR bands of carboxylic acids in the first four weeks. In the sixth and eighth weeks, the IR signals of calcium carbonate increased more than those from organic matter. This study provides a better understanding of the importance of preserving the collected samples and how the decomposition dynamics of Sargassum species may impact the extraction of key compounds, e.g., alginate and mannitol. [ABSTRACT FROM AUTHOR]

Effective monitoring of non-indigenous seaweeds and combatting their effects relies on a solid confirmation of the non-indigenous status of the respective species. We critically analysed the status of presumed non-indigenous seaweed species reported from the Mediterranean Sea, the Northeast Atlantic Ocean and Macaronesia, resulting in a list of 140 species whose non-indigenous nature is undisputed. For an additional 87 species it is unclear if they are native or non-indigenous (cryptogenic species) or their identity requires confirmation (data deficient species). We discuss the factors underlying both taxonomic and biogeographic uncertainties and outline recommendations to reduce uncertainty about the non-indigenous status of seaweeds. Our dataset consisted of over 19,000 distribution records, half of which can be attributed to only five species (Sargassum muticum, Bonnemaisonia hamifera, Asparagopsis armata, Caulerpa cylindracea and Colpomenia peregrina), while 56 species (40%) are recorded no more than once or twice. In addition, our analyses revealed considerable variation in the diversity of non-indigenous species between the geographic regions. The Eastern Mediterranean Sea is home to the largest fraction of non-indigenous seaweed species, the majority of which have a Red Sea or Indo-Pacific origin and have entered the Mediterranean Sea mostly via the Suez Canal. Non-indigenous seaweeds with native ranges situated in the Northwest Pacific make up a large fraction of the total in the Western Mediterranean Sea, Lusitania and Northern Europe, followed by non-indigenous species with a presumed Australasian origin. Uncertainty remains, however, regarding the native range of a substantial fraction of non-indigenous seaweeds in the study area. In so far as analyses of first detections can serve as a proxy for the introduction rate of non-indigenous seaweeds, these do not reveal a decrease in the introduction rate, indicating that the current measures and policies are insufficient to battle the introduction and spread of non-indigenous species in the study area. Non-indigenous seaweed species in the Northeast Atlantic Ocean, the Mediterranean Sea and Macaronesia are critically reanalysed. > 19,000 distribution records revealed considerable variation in diversity of non-indigenous seaweed species in the study area. Taxonomic and biogeographic uncertainties hamper a critical evaluation of the non-indigenous status of many seaweed species. [ABSTRACT FROM AUTHOR]

Brown algal male gametes show chemotaxis to the sex pheromone that is released from female gametes. The chemotactic behavior of the male gametes is controlled by the changes in the beating of two flagella known as the anterior and posterior flagellum. Our previous study using Mutimo cylindricus showed that the sex pheromone induced an increment in both the deflection angle of the anterior flagellum and sustained unilateral bend of the posterior flagellum, but the mechanisms regulating these two flagellar waveforms were not fully revealed. In this study, we analyzed the changes in swimming path and flagellar waveforms with a high‐speed recording system under different calcium conditions. The extracellular Ca2+ concentration at 10−3 M caused an increment in the deflection angle of the anterior flagellum only when ionomycin was absent. No sustained unilateral bend of the posterior flagellum was induced either in the absence or presence of ionomycin in extracellular Ca2+ concentrations below 10−2 M. Real‐time Ca2+ imaging revealed that there is a spot near the basal part of anterior flagellum showing higher Ca2+ than in the other parts of the cell. The intensity of the spot slightly decreased when male gametes were treated with the sex pheromone. These results suggest that Ca2+‐dependent changes in the anterior and posterior flagellum are regulated by distinct mechanisms and that the increase in the anterior flagellar deflection angle and sustained unilateral bend of the posterior flagellum may not be primarily induced by the Ca2+ concentration. [ABSTRACT FROM AUTHOR]

Genetic connectivity of kelp populations can provide essential information for estimating their dispersal capability and related perspectives on persistence. We examined population genetic variability to identify connectivity and potential drivers shaping population genetic clusters of Ecklonia cava, a foundation kelp species in the northwest Pacific region. Using microsatellite markers, we analyzed 11 local populations along the Korean coastline from Jeju Island to Ulleungdo. We found that entire study populations were segregated into two genetic groups, inner (south coast populations) and outer (Jeju Island and Ulleungdo) coastal regions, in accordance with current patterns around South Korea and geographical topography. Genetic similarity between the furthest populations (Jeju Island and Ulleungdo) suggest that the dispersal range of E. cava could be largely expanded by the prevalent current. Inter-population genetic structure in the perspectives of isolation-by-distance (IBD) and isolation-by-environment (IBE) revealed that distance and turbidity gradient were both contributors to the gene flow of E. cava. However, different results appeared for a few populations, suggesting that effects of these factors could vary depending on geographic range of populations and surrounding oceanographic conditions. This study suggests that gene flow of E. cava could be driven by multiple seascape factors (ocean currents, coastal topography, distance and sediments) and the interplay among them at a regional scale, which is applicable to other kelp species with diverse scales. [ABSTRACT FROM AUTHOR]

The sub-Antarctic Magellan Ecoregion is a unique biogeographic area located at the southern tip of South America, which has exceptional marine flora and high endemism. Along the coastline, the ochrophytes Macrocystis pyrifera and Lessonia flavicans form vital underwater forests that serve as critical habitats, providing shelter, food and breeding grounds for a diverse marine organisms. These algal species are also important components used in the food industry and biomedicine, due to their high lipid, amino acid and fiber content. In this study, we investigated the intra-thallus variation of fatty acids among the different morphological structures (fronds, stipes and holdfast) of M. pyrifera and L. flavicans collected in Rinconada Bulnes during spring, 2021. The stipes of M. pyrifera (3.73 ± 1.73%) and the fronds of L. flavicans (3.35 ± 0.97%) both exhibited high lipid content. Saturated fatty acids were highest in the holdfast of M. pyrifera (37.82 ± 0.06%) followed by the fronds of L. flavicans (34.30 ± 0.10%). Notably, monounsaturated fatty acids showed higher levels en the holdfast of L. flavicans (46.45 ± 0.19%) followed by the stipes of M. pyrifera (43.04 ± 0.08%). The fronds of both M. pyrifera (32.38 ± 0.26%) and L. flavicans (28.89 ± 0.23%) showed high levels of polyunsaturated fatty acids. These findings provide valuable insight into the intra-thallus variation of fatty acids in different morphological structures of M. pyrifera and L. flavicans, highlighting their potential nutritional and biomedical importance as the most representative kelps in the Magellan region. [ABSTRACT FROM AUTHOR]

We found that an innovative nursery approach, where Lessonia corrugata seeded spools were cultivated by spinning to increase the water motion relative to non-spinning spools, had higher growth in both the nursery and at-sea stages. Using this method, we compared the at-sea growth of sporophytes cultivated on spinning spools at different depths (1 m, 3 m, 5 m) and seasons (timing of out-planting). Finally, we compared the at-sea growth of sporophytes cultivated on spinning spools vs. non-spinning sporophytes at 3-m depth. In the nursery, sporophytes on spinning spools developed significantly faster than those on non-spinning spools: blade length was 4.6 and 2.5 cm, and holdfast area was 0.10 and 0.03 cm2 for spinning and non-spinning spools, respectively. At-sea L. corrugata in spring had significantly greater biomass production at 3 m and 5 m (3.0 kg m−1 and 2.4 kg m−1, respectively) and up to 96% survival. In summer, 100% of deployed kelps died at all depths. Growth was faster at 5 m (0.3 ± 0.06 kg m−1) in autumn and at 3 and 5 m (1.1 ± 0.1 kg m−1 and 0.8 ± 0.1 kg m−1, respectively) in winter. At sea, sporophytes from the spinning spools grew significantly 60% larger, and survival was ~ 3 times greater over 3 months than sporophytes from non-spinning. Overall, this study shows that spinning seeded spools in the nursery improves the growth at sea, spring is the best season for out-planting L. corrugata, and 3 or 5 m depth is best for production. [ABSTRACT FROM AUTHOR]

Alginate fractions from the pelagic Sargassum fluitans (Børgesen) Børgesen and kelp, Ecklonia maxima (Osbeck) Papenfuss sourced from the coastal waters of Ghana and South Africa respectively, were extracted by a simple sequential protocol different from the conventional methods. A total of six different phycocolloids were obtained, with two extracted under ambient conditions (fractions 1A) and the remaining four under hot conditions (fractions 2A and 3A) using ethanol and CaCl2, respectively, for precipitation. These extracts were assessed for variations in their physicochemical properties, tyrosinase inhibition, antioxidation and anticoagulation activities. Molecular weights of the extracts were ~ 58–1506 kDa with their yields ranging between 4.8 to 11.1%. A sequential reduction (up to tenfold) was observed in their total phenolic compounds, proteins and sulphate contents. 1H-NMR analysis of their uronic acid block structure revealed M/G ratios less than 1 for all extracts with dominant FGG and FGGG units depicting guluronic acid rich alginate fractions. Extracts from S. fluitans, notably, showed distinct antioxidation activity comparable to the well-known antioxidants like ascorbic acid. For tyrosinase inhibition, the highest was from S. fluitans fraction 1A (~ 37.1 ± 4.38%). The variations in properties of extracts reported herein, elucidates the possibility of obtaining series of relatively desirable alginate fractions from E. maxima and Ghanaian sourced S. fluitans via this modified extraction process. [ABSTRACT FROM AUTHOR]

Bioactive compounds were extracted from the brown seaweed Ecklonia stolonifera using subcritical water hydrolysis, a green extraction technique to valorize raw biomass. The reaction temperature for the hydrolysis ranged between 120 °C and 220 °C and the products were compared with those obtained by methanol extraction. Reaction temperature played a significant role in the release of active compounds such as sugars, phenolics, flavonoids, and antioxidants. The optimum extraction temperature was found to be 195 °C; at this temperature, the yield of reducing sugars was 61.83 ± 1.63 mg glucose, the total phenolic compound content was 26.02 ± 0.05 mg phloroglucinol, and the total flavonoid compound content was 8.40 ± 0.18 mg quercetin g−1 of E. stolonifera sample on a dry weight basis. Six different phenolic compounds were identified by high performance liquid chromatography (HPLC), of which gallic acid was the most abundant. Hydrolysates obtained using subcritical water extraction possessed strong antioxidant and antimicrobial activities. The results of this study will be useful for further valorizing brown seaweeds in applications with potential benefits for humans. [ABSTRACT FROM AUTHOR]

The effects of steam- or warm water treatments of the brown seaweed Saccharina latissima on iodine content and nutrient and sensory profiles were investigated. Warm freshwater or seawater treatments reduced the dry weight iodine content by 73% and 59%, respectively. Steam treatment was less efficient and only reduced the iodine content by 26%. Freshwater treatment resulted in a greater reduction in total solids and loss of water-soluble components, mainly reducing the content of ash and carbohydrates. Seawater treatment had a small effect on total solid content but altered the mineral profile leading to an increase in sodium and decrease in potassium content. The sensory profiles reflected the observed differences in composition as it revealed a significantly higher saltiness of the seawater-treated sample compared to other treatments, as well as a higher umami intensity compared to the freshwater-treated sample. The latter was characterized by low scores across all sensory attributes, indicating greater loss of flavour-active compounds. Further, including seawater-treated S. latissima at relatively low levels (0.5% and 1%) significantly altered the flavour of a commercial spinach soup compared to the same preparation without seaweed. Therefore, warm water treatment using seawater could be an alternative method for lowering the iodine content in brown seaweed while limiting nutrient loss and maintaining its flavour potential for applications in the food industry. [ABSTRACT FROM AUTHOR]

Marine environmental monitoring is essential to ensure that heavy-metal (HM) concentrations remain within safe limits. Most seawater analyses currently consider sediment or water samples, but this approach does not apply to rocky substrates, where water samples can only indicate immediate contamination. We used two common Mediterranean algae species, Cystoseira compressa and Ericaria mediterranea, as bioindicators living in the intertidal zone on rocky substrates along the seacoast. HM concentrations were assessed over a one-year period in the perennial base crust and in the seasonal frond, considering marine sites characterised by different contamination risks. Both algae showed that HMs accumulate mainly in the perennial base rather than in the seasonal frond. Furthermore, the algae species always showed a different order of bioaccumulation factors: Cd > Ni > Pb > Cr > Cu > Mn > Zn for the frond and Pb > Cr > Ni > Cd > Mn > Cu > Zn for the base. Our study shows that C. compressa and E. mediterranea accumulate HM consistently with the types of sites analysed and differentially with respect to the part of the thallus. These results demonstrate that these algae can be effectively used as reliable bioindicators to assess the presence of HM in marine environments with rocky substrates, providing both short- and long-term monitoring. [ABSTRACT FROM AUTHOR]

Culturing kelps for commercial, conservation, and scientific purposes is becoming increasingly widespread. However, kelp aquaculture methods are typically designed for ocean‐based farms, and these methods may not be applicable for smaller scale cultivation efforts common in research and restoration. Growing kelps in closed, recirculating culture systems may address many of these constraints, yet closed system approaches have remained largely undescribed. Extensive declines of the bull kelp (Nereocystis luetkeana), an ecologically important canopy species in the Northeast Pacific, have received widespread attention and prompted numerous research and conservation initiatives. Here, we detail two approaches for cultivating N. luetkeana sporophytes in closed recirculating systems. Nereocystis luetkeana were reared as attached thalli in custom seaweed growth flumes and also free‐floating in tumble culture tanks. Careful control of stocking density, water motion, aeration, and nutrient levels allowed for rapid growth and normal morphogenesis of laboratory‐grown kelp. Culture systems reached up to 3 kg · m−3, and individual thalli attained lengths of up to 6 m before the trials were terminated. Our results demonstrate the potential of recirculating, closed culture systems to overcome limitations associated with traditional culture methods. Recirculating systems enable the precise control of culture conditions, improving biosecurity and facilitating cultivar development and other research. Kelps can be grown away from the ocean or outside their native ranges, and seasonal or annual species can be produced year‐round without seasonal constraints. [ABSTRACT FROM AUTHOR]

Fleshy macroalgae dominate the hard bottom, shallow waters along the Western Antarctic Peninsula (WAP). Although there are numerous reports on their ecology, geographic distribution, and to a lesser extent, vertical (depth) distribution in the northern portions of the WAP, much less is known farther south along the central portion of the WAP. Here we provide the first report of the vertical distributions of brown and red fleshy macroalgae in this region based on scuba-derived collections at 14 study sites between southern Anvers Island (64.8°S, 64.4°W) in the north and central Marguerite Bay (68.7°S, 67.5°W) in the south. Although several overstory brown macroalgal species that can be common along the northern WAP including Desmarestia anceps and Cystosphaera jacquinotii are mostly absent from the central WAP, the vertical distributions of the brown macroalgae Desmarestia menziesii and Himantothallus grandifolius are similar to the northern WAP even though their percent cover is much lower. Likewise, the vertical distribution of the 14 most widespread red macroalgae, where they occur, mirrored those known from the northern part of the WAP even though macroalgal cover, biomass, and total species richness declined markedly to the south across this region due to increasing sea ice concentrations. [ABSTRACT FROM AUTHOR]

Macroalgae are an important component of marine ecosystems. Small-sized macroalgae are easily ignored by traditional monitoring leading to an underestimation of macroalgae biodiversity. In the present study, 18S rDNA metabarcoding and traditional identification methods were used to reveal the species composition and spatial–temporal distribution of macroalgae along the coast of Weizhou Island. Nine macroalgal species were identified by visual inspection in the field and 39 by DNA metabarcoding. About 80% of the macroalgae identified by visual inspection belonged to Phaeophyceae. However, 5.6% of the macroalgae identified by DNA metabarcoding belonged to Phaeophyceae, and most were Ulvophyceae (60.4%). Most small-sized macroalgae were missed by traditional surveys but can be detected by DNA metabarcoding. Significant temporal variations in the macroalgal community were reflected in the diversity indices obtained by the two methods in four sampling dates (P < 0.01). DNA metabarcoding data presented more complex temporal variations in macroalgal community, with Ulvophyceae being the dominant species in four sampling dates, and the results by visual inspection showed that Phaeophyceae were gradually replaced by Ulvophyceae with increasing temperature. The dominant species accounted for more than 50% of the total species and for more than 80% of the total abundance. Both identification methods verified that water temperature and NO2−–N are important environmental factors influencing the structure of macroalgal community. Our results suggest that the combination of DNA metabarcoding and traditional monitoring can complement each other to enhance our understanding of the biodiversity and the ecological role of macroalgae in marine ecosystems. [ABSTRACT FROM AUTHOR]

The Andaman Sea-Malacca Strait is an area with high maritime complexity and rich seaweed biodiversity. The brown seaweed Sargassum plagiophyllum C.Agardh occurs abundantly in the intertidal in the area. However, its population genetics has not been studied. Here, we used the nuclear Internal Transcribed Spacer 2 of the ribosomal cistron ITS2 and the mitochondrial cytochrome c oxidase subunit 1 gene cox1 as genetic markers to determine the population genetic structure along the entire west coast of Thailand. A total of 351 individuals from the ten populations were genotyped. Nine different cox1 haplotypes and 17 different ITS2 ribotypes were found. Generally, S. plagiophyllum populations were found to have low genetic diversity. Two lineages were found based on ITS2 and two cryptic diversities were inferred from cox1 data. Most individuals belonged to the one single ribotype and haplotype. Ocean currents are believed to influence the S. plagiophyllum distributions and connectivity between populations. Higher phosphate concentrations during the northeast monsoon season could promote its growth and propagation. Our study suggested that the temporal and spatial transformation of the marine environment in the Andaman Sea influences the distribution, biomass, and population genetic structure of S. plagiophyllum, our results are beneficial for the management of seaweed resources. [ABSTRACT FROM AUTHOR]

This work centered on the valorization of brown macroalgae by sequentially extracting multiple value-added compounds using emerging green extraction techniques. Supercritical fluid extraction (SFE) was used to extract lipids (up to 8%) from Padina tetrastromatica and Turbinaria conoides biomass, which was found to be rich in polyunsaturated fatty acids with multiple potential nutraceutical applications. Using the subcritical water (ScW) technique, 48 wt % sodium alginate and 11 wt % protein were then recovered from the SFE residual biomass. The alginate derived from ScW contained mannuronic (M) and guluronic acids (G) with M/G ratio greater than 1, fulfilling WHO and FAO guidelines for the nutraceutical and pharmaceutical industries. Alginate extracted using ScW exhibited up to 80% in vitro 2,2-diphenyl-1-picrylhydrazyl scavenging activity and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity. Thus, an integrated method has been designed to valorize biomass by extracting commercially relevant valuable compounds from macroalgae utilizing green and sustainable technologies, which could be used to scale-up extraction of these compounds by a variety of industrial sectors. [ABSTRACT FROM AUTHOR]

The Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus that primarily affects people in Asia and seriously threatens public health. Considering the rising occurrence rates and lack of targeted antiviral treatments, it is essential to comprehend and tackle obstacles related to JEV in order to lessen its influence on world health. This investigation explores compounds derived from marine brown algae (Phaeophyceae) as potential inhibitors of JEV RNA-dependent RNA polymerase (RdRp), a critical enzyme in the virus's replication cycle. Employing the computational virtual screen approach, four compounds, i.e., CMNPD16749, CMNPD2606, CMNPD27817, and CMNPD23662, with favorable binding energies ranging from −15.7 Kcal/mol to −13.9 kcal/mol were identified. Subsequently, through molecular docking analysis, the interactions responsible for the binding stability between the target protein and hit molecules compared to the reference molecule Galidesvir were studied. Further, through extensive molecular dynamic (MD) simulation studies at 200 ns, it was confirmed that each docked complex showed acceptable dynamic stability compared to the reference molecule. These findings were further validated using MM/PBSA free binding energy calculations, PCA analysis and free energy landscape construction. These computational findings suggested that the brown algae-derived compounds may act as an antiviral drug against JEV infection and lay a crucial foundation for future experimental studies against JEV. [ABSTRACT FROM AUTHOR]

Background The unprecedented influence of human activities on natural ecosystems in the 21st century has resulted in increasingly frequent large-scale changes in ecological communities. This has heightened interest in understanding such changes and effective means to manage them. Accurate interpretation of state changes is challenging because of difficulties translating theory to empirical study, and most theory emphasizes systems near equilibrium, which may not be relevant in rapidly changing environments. Scope We review concepts of long-transient stages and phase shifts between stable community states, both smooth, continuous and discontinuous shifts, and the relationships among them. Three principal challenges emerge when applying these concepts. The first is how to interpret observed change in communities – distinguishing multiple stable states from long transients, or reversible shifts in the phase portrait of single attractor systems. The second is how to quantify the magnitudes of three sources of variability that cause switches between community states: (1) 'noise' in species' abundances, (2) 'wiggle' in system parameters and (3) trends in parameters that affect the topography of the basin of attraction. The third challenge is how variability of the system shapes evidence used to interpret community changes. We outline a novel approach using critical length scales to potentially address these challenges. These concepts are highlighted by a review of recent examples involving macroalgae as key players in marine benthic ecosystems. Conclusions Real-world examples show three or more stable configurations of ecological communities may exist for a given set of parameters, and transient stages may persist for long periods necessitating their respective consideration. The characteristic length scale (CLS) is a useful metric that uniquely identifies a community 'basin of attraction', enabling phase shifts to be distinguished from long transients. Variabilities of CLSs and time series data may likewise provide proactive management measures to mitigate phase shifts and loss of ecosystem services. Continued challenges remain in distinguishing continuous from discontinuous phase shifts because their respective dynamics lack unique signatures. [ABSTRACT FROM AUTHOR]