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The use of mesenchymal stem cells is a promising strategy for treating bone-related diseases. Therefore, the development of agents capable of inducing the differentiation of stem cells into osteoblasts is beneficial for such treatments. In this study, the effects of aqueous and organic extracts of Arthrospira platensis and Gracilaria gracilis on the induction of bone differentiation in human amniotic mesenchymal stem cells (hAMSCs) were evaluated. First, the cytotoxicity of aqueous and organic extracts at concentrations of 60, 100 and 140 μg mL-1 was measured using the MTT method. Then, the osteogenic differentiation effects of the cells were evaluated through Alizarin Red staining, alkaline phosphatase enzyme activity measurement and the expression level of Runx2, OCN and β-catenin genes. The results showed that 60 μg mL-1of aqueous and methanol extracts of the algae did not exhibit cytotoxicity. Treatment of cells with these extracts resulted in the accumulation of calcium deposits and increased alkaline phosphatase enzyme activity. Additionally, the expression of Runx2 and OCN genes increased with the influence of A. platensis aqueous and G. gracilis methanol extracts, while the β-catenin gene expression increased with the influence of A. platensis aqueous extract. In conclusion, the study suggests that A. platensis aqueous and G. gracilis methanol extracts are capable of inducing bone differentiation in hAMSCs. These findings provide new insights into osteogenesis mediated by biocompounds from algae and may contribute to the development of therapeutic agents for bone-related diseases. [ABSTRACT FROM AUTHOR]

In the economically important red macroalga Pyropia, carbohydrates and proteins contents are usually used to evaluate the nutritional status and commercial value. As main component elements of carbohydrates and proteins, C, N and S contents can be the suitable indicators. However, efficient and nondestructive estimation of these elements have not been well established in macroalgae, which is definitely needed in high-throughput phenotyping and selective breeding. In the current study, hyperspectral imaging was used to estimate the C, N and S contents in thalli of Pyropia yesoensis. Based on spectral information acquired by two hyperspectral cameras with range of 400 nm to 1700 nm, two machine learning methods, partial least squares regression (PLSR) and support vector machine regression (SVR), were performed to establish prediction models following different preprocessing methods. The result showed that SVR model following Savitzky-Golay (S-G) smoothing preprocessing performed the best for N content with excellent accuracy (RTest2 = 0.94, RMSE = 0.331, MAPE = 5.47%, RPD = 3.44). Both of PLSR and SVR models could not yet meet satisfactory prediction for C and S content with RTest2 < 0.4 and RPD < 1.5. Further validation on field samples corroborated accuracy and robustness of the optimal estimation model for N. This study demonstrates that hyperspectral imaging is effective for estimating N contents of P.yesoensis thalli. It unveils the capability of hyperspectral imaging with machine learning models for estimating macroelement contents in macroalgae thalli, and offers a convenient, non-destructive, and effective method for the phenotyping and selective breeding of macroalgae. [ABSTRACT FROM AUTHOR]

This study investigates the impact of different levels of hydroalcoholic extract of the marine red alga (Hypnea cornua) on growth performance, hematological indices, antioxidant capacity, immune response, and expression of growth-related genes in beluga sturgeon (Huso huso). A total of 120 juvenile beluga sturgeon (425.62 ± 26.32 g) were randomly divided into four treatments with three replicates and reared for 8 weeks. The fish were fed diets incorporating varying amounts of the algal extract (0 [control group], 5, 10, and 20 g kg-1). The inclusion of the dietary algal extract significantly improved final weight, weight gain, and specific growth rate (P < 0.05), while reducing the feed conversion ratio. The red blood cell count, hematocrit level, total protein level, and lysozyme activity were significantly increased (P < 0.05) in the fish group treated with 10 g algal extract kg-1 compared to the control and other treatments. The highest superoxide dismutase activity was observed in fish fed a diet with 10 g algal extract kg-1. The serum catalase activity was significantly higher in all fish treated with algal extract compared to those fed with the control diet (P < 0.05). The serum glutathione activity was markedly higher in the fish fed diets containing 10 and 20 g kg-1 compared to those fed with the control diet (P < 0.05). The malondialdehyde level was lower in the treated fish compared to those fed with the control diet (P < 0.05). The highest mRNA levels of growth hormone and insulin-like growth factor 1 were observed in the fish fed a diet containing 10 g algal extract kg-1 (P < 0.05). These findings suggest that an optimal dietary inclusion level of 11.22 g kg-1 of the marine red algal extract is recommended for improving growth performance, feed utilization, and overall well-being of beluga sturgeon. [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]

Background: The red macroalga Gracilaria parvispora is an introduced species in the Mexican Pacific. To date, there are no published studies on its sessile epibionts, including the hydrozoans and bryozoans, which are the dominant epibionts on macrophytes and of significant biological and economic interest. New information: This study provides insight into the faunal diversity of hydroids growing on G. parvispora. A total of 185 thalli from both herbarium specimens and field samples collected from five sites in La Paz Bay were revised. Each thallus size and the presence of hydroid epibionts in each thallus region were registered. Eight different hydrozoan taxa were growing on the red macroalgae, including the first recorded observation of Obelia oxydentata in the Gulf of California. The sizes of the collected thalli were mostly under 7.0 cm, the maximum number of taxa per thallus was three and the thallus region containing the highest number of epibionts was in the middle. Significant differences were observed amongst the lengths of thalli with and without epibionts. The thalli with epibionts were larger than the thalli without epibionts. Similarly, significant differences were observed amongst the months. The pair-wise test revealed that each month exhibited distinctive epibiont taxa when compared to the others. This study highlights the lack of information on these associations. Further research is needed to understand whether introduced macroalgae can bring non-native epibiont species to an area. [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 The complex interactions between epiphytic bacteria and marine macroalgae are still poorly understood, with limited knowledge about their community structure, interactions, and functions. This study focuses on comparing epiphytic prokaryotes community structure between three seaweed phyla; Chlorophyta, Rhodophyta, and Heterokontophyta in an easternmost rocky intertidal site of the Mediterranean Sea. By taking a snapshot approach and simultaneously collecting seaweed samples from the same habitat, we minimize environmental variations that could affect epiphytic bacterial assembly, thereby emphasizing host specificity. Through 16S rRNA gene amplicon sequencing, we identified that the microbial community composition was more similar within the same seaweed phylum host compared to seaweed host from other phyla. Furthermore, exclusive Amplicon Sequence Variants (ASVs) were identified for each algal phyla despite sharing higher taxonomic classifications across the other phyla. Analysis of niche breadth indices uncovers distinctive affinities and potential specialization among seaweed host phyla, with 39% of all ASVs identified as phylum specialists and 13% as generalists. Using taxonomy function prediction, we observed that the taxonomic variability does not significantly impact functional redundancy, suggesting resilience to disturbance. The study concludes that epiphytic bacteria composition is connected to host taxonomy, possibly influenced by shared morphological and chemical traits among genetically related hosts, implying a potential coevolutionary relationship between specific bacteria and their host seaweeds.

The complex interactions between epiphytic bacteria and marine macroalgae are still poorly understood, with limited knowledge about their community structure, interactions, and functions. This study focuses on comparing epiphytic prokaryotes community structure between three seaweed phyla; Chlorophyta, Rhodophyta, and Heterokontophyta in an easternmost rocky intertidal site of the Mediterranean Sea. By taking a snapshot approach and simultaneously collecting seaweed samples from the same habitat, we minimize environmental variations that could affect epiphytic bacterial assembly, thereby emphasizing host specificity. Through 16S rRNA gene amplicon sequencing, we identified that the microbial community composition was more similar within the same seaweed phylum host compared to seaweed host from other phyla. Furthermore, exclusive Amplicon Sequence Variants (ASVs) were identified for each algal phyla despite sharing higher taxonomic classifications across the other phyla. Analysis of niche breadth indices uncovers distinctive affinities and potential specialization among seaweed host phyla, with 39% of all ASVs identified as phylum specialists and 13% as generalists. Using taxonomy function prediction, we observed that the taxonomic variability does not significantly impact functional redundancy, suggesting resilience to disturbance. The study concludes that epiphytic bacteria composition is connected to host taxonomy, possibly influenced by shared morphological and chemical traits among genetically related hosts, implying a potential coevolutionary relationship between specific bacteria and their host seaweeds. [ABSTRACT FROM AUTHOR]

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]

Seasonal changes in the size of the herbal drug red alga Chondria armata (Rhodomelaceae, Ceramiales) were investigated in Kagoshima, Japan, which is near the northern distributional limit in the western Pacific. Additionally, its photosynthetic response to irradiance and temperature was examined using dissolved oxygen sensors and a pulse amplitude modulation (PAM)-chlorophyll fluorometer. This alga was observed in tidepools throughout the year; its height and weight were greatest in December and the lowest in April and May. The net photosynthesis of the photosynthesis–irradiance (P–E) curve determined at 28°C quickly saturated at 113 µmol photons m-2 s-1, with minimal inhibition even at 1000 µmol photons m-2 s-1. The gross photosynthesis of the photosynthesis–temperature (P–T) curved over 8 to 40°C, measured at 500 µmol photons m-2 s-1, peaked at 30.1°C and decreased rapidly below 20°C and above 36°C, respectively. Similarly, the effective quantum yield (ΔF/Fm') after a 3-day culture during 4–40°C at 50 µmol photons m-2 s-1 remained stable between 16°C and 32°C but decreased outside of this range. The combined effect of irradiance (200 [low] and 1000 [high] µmol photons m-2 s-1) and temperature (28, 22, and 16°C) revealed that ΔF/Fm' declined during exposure to high irradiance at all temperature treatments. However, it mostly recovered after a subsequent 12-hour period of dim-light acclimation at 28°C and 22°C. In contrast, those at 16°C could not recover, indicating the occurrence of low-temperature light stress. This alga appears to be well-adapted to the irradiance and temperature environment at the study site. However, the winter temperature appears to approach its threshold level, and the occurrence of strong light during the winter might adversely affect the abundance of this alga near its northern distributional limit. [ABSTRACT FROM AUTHOR]

A fixed off-bottom Kappaphycus striatus var. sacol farm was monitored for 12 months (June 2019 to May 2020) and the monthly incidence of disease and pests was recorded. Meteorological information in situ, from the nearest synoptic station and online data were collected to determine the relationships between temporal environmental changes and the incidence of seaweed health problems. The results showed that "ice-ice" disease (IID) was observed in dry months (i.e., from February to April 2020) and was significantly influenced by increased irradiance, salinity, sea surface temperature, and wind speed (p=0.004‒0.030). Also, the IID incidence was positively affected by reduced precipitation, storm surface run-off, water current speed, and inorganic nutrient (nitrite and ammonia) levels (p=0.002‒0.019). In comparison, epiphytic filamentous algae (EFA) were observed in wet months (i.e., from September to December 2019), with incidence varying from low to very high (≤25–100%) as the culture progressed. EFA incidence was significantly influenced by reduced salinity and increased storm surface run-off and inorganic nutrient (nitrate and ammonia) levels (p=0.006‒0.040). An intense tropical cyclone struck the farming area in December 2019, resulting in partial die-offs of farmed seaweed. Such seaweed health problems are expected to become more prevalent in the coming years as weather disturbances brought about by changing weather patterns become more frequent and intense. Hence, mitigation and preventative approaches must be fully considered to sustain the industry's growth while protecting the livelihoods of many coastal communities dependent on seaweed farming. [ABSTRACT FROM AUTHOR]

Gracilaria manilaensis is a red seaweed found in some regions of Peninsula Malaysia. In vitro studies have demonstrated that G. manilaensis has neuritogenic, neuroprotective, anticancer, antioxidant, and antimicrobial properties, suggesting that it could be developed into health supplement. However, the effects of oral consumption of G. manilaensis have not yet been evaluated in vivo. The present study evaluated the safety of sub-acute oral consumption of G. manilaensis ethanolic extract. 10, 50, 100, 250, and 500 mg kg-1G. manilaensis ethanolic extracts and distilled water (control) were administered to adult female Sprague-Dawley rats (n=3 per group) by oral gavage for 28 days. Our results showed that the G. manilaensis ethanolic extract did not induce abnormal behaviour, body weight changes, or affect the mortality rate between treatment and control groups. There were no abnormal haematological and biochemical findings, except that 500 mg kg-1G. manilaensis ethanolic extract may affect renal function, as urea levels and urea/creatinine ratio were lower when compared to other treatment groups. Gross necropsy did not reveal any abnormalities in the vital organs in all groups. There were no significant differences (p > 0.05) in the percentage relative weight of organs between treatment and control groups. In conclusion, the findings showed that daily oral consumption of G. manilaensis ethanolic extracts at 250 mg kg-1 or lower for 28 days was safe. The findings from this study provide a basis for future studies to investigate the in vivo health promoting effects of G. manilaensis. [ABSTRACT FROM AUTHOR]

Colaconema daviesii, a filamentous red alga, has been previously reported as an endophyte infesting Chondracanthus chamissoi. This study focuses on identifying the symptoms of C. daviesii infesting on haploid and diploid thalli of C. chamissoi. Co-cultivation of C. daviesii with diploid and haploid thalli of C. chamissoi was conducted under two treatments. Treatment 1 was under a 12:12 h (L:D) photoperiod for 40 days. Treatment 2 was under a 12:12 h (L:D) photoperiod for 20 days, followed by a 16:08 h (L:D) photoperiod for an additional 20 days. Parameters such as the density and coverage of C. daviesii filaments on C. chamissoi thalli were measured, as well as the growth rate and survival of C. chamissoi. Infestation occurred in both treatments and phases, with an increase in the presence of C. daviesii as the photoperiod extended. This relationship negatively affected the host in all measured parameters, with the diploid phase being more adversely affected. Infestation begins with spores under a 12:12 h (L:D) photoperiod condition, and filament development is observed on C. chamissoi thalli as the photoperiod increases. Early infestation symptoms were not evident, complicating the recognition of C. daviesii on haploid and diploid thalli of C chamissoi. The potential risk of transferring C. chamissoi contained filaments of C. daviesii through cultivation is postulated. [ABSTRACT FROM AUTHOR]

Seaweed functional traits provide insights on natural populations, their adaptations to the local environment, which can be utilized for commercial exploitation. Here, we analyzed the functional traits of Gracilaria dura from two intertidal populations in Veraval and Adri, from the coast of Gujarat, India, over a period of three months. Functional traits were measured by analyzing growth rates, respiration, primary production, antioxidant activity and the content of plant growth hormones. The weight-to-length allometric exponent ≈3 indicated that G. dura grew almost isometrically. Furthermore, frond shape was not significantly different. Fronds in Veraval, resting submerged, grew faster than the fronds in Adri, which, lay exposed in the flat bare rock during low tide. Accordingly, the simultaneous increase in antioxidant activity, O2 production and chlorophyll content in fronds from Adri suggests that stress from desiccation and UV led to the detrimental accumulation of Reactive Oxygen Species, leading to decreased growth and decreased production of growth hormones. The increased Chl-a may indicate enhanced non-photochemical quenching (NPQ) for the dissipation of excess absorbed light. These results aid in establishing the best practices for maximizing biomass yield or the yield of specific molecules. For maximized biomass yield, fronds should not be subject to emersion nor cultivated on the sea-surface. On the other hand, fronds grown subject to emersion or at the sea-surface yield less biomass but more content on molecules such as antioxidants (flavonoids, phenolics, enzymes), that fight stress from desiccation high temperatures and UV. In this case, stress should still be avoided during the initial growth, at the onset of the growth season, in order to not disrupt the production of growth hormones. The increased O2 production at Adri was initially mistakenly perceived as enhanced Net Primary Production. Only a posterior holistic perspective over the whole data allowed to conclude that it was likely the stress-induced detrimental accumulation of Reactive Oxygen Species. More robust experiments are required to establish if the differences observed between locations have led to the evolution of genetic strains specific to each habitat that may show different performances and yields when cultivated in similar environments. [ABSTRACT FROM AUTHOR]

Kappaphycus alvarezii is cultivated as a commercial source of carrageenan and salinity fluctuations adversely affect the productivity. We report on variable salinity (16, 24, 32, 40 and 48 psu) induced physio- and photo-chemical responses in K. alvarezii. Both hypo- and hyper-salinity induced higher accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA) contents in K. alvarezii. The Na+/K+ ratio was maintained at moderate-(24 and 40 psu)-salinity but ratio increased significantly at hyper-(48 psu)-salinity. Kappaphycus alvarezii exhibited 43% and 51% higher net primary productivity (NPP) at 24 and 40 psu salinity as compared with the control (32 psu) salinity. Hypo-salinity significantly increased respiration rate and hyper-salinity had no effect. There was a significant increase in sugar content at hyper-salinity and a decrease in sugar content at hypo-salinity. Phycoerythrin (PE) contents were higher at hyper-salinity, whereas chlorophyll content decreased at both hypo- and hyper-salinity. The FV/FM, FV/F0 and performance index decreased in K. alvarezii under variable salinity. The δFIP and δVIP exhibited minor changes at moderate salinity and decreased significantly at extreme salinity. The I1/I2 and I4/D2 ratios exhibited variable responses and were higher at 40 psu and 24 psu respectively. There was 113% and 86% increased accumulation of proline and 83% and 142% increased accumulation of free amino acid contents at 40 and 48 psu salinity, respectively. The activity of antioxidant enzymes varied and activity of superoxide dismutase (SOD), catalase (CAT) and guaicol peroxidase (GPOX) were significantly higher at 48 psu salinity. The results indicated modifications in the responses of photosystems (PS) and significant contributions of osmolytes and antioxidant machinery in stress acclimatization of K. alvarezii during salinity fluctuations. [ABSTRACT FROM AUTHOR]

Aedes aegypti is the main disease vector of dengue, chikungunya, and Zika. Pest control efforts to combat these diseases have focused on developing insecticides based on novel active compounds. Laurencia, a genus of red seaweeds, is an important source of brominated compounds, particularly sesquiterpenes, with antifungal, antimalarial, larvicidal, and insect-repellent properties. The objective of the study was to assess larvicidal and oviposition deterrent activity of Laurencia johnstonii against Ae. aegypti. Laurencia johnstonii ethanolic extract and fractions were evaluated against third instar Ae. aegypti larvae (New Orleans strain). All fractions exhibited larvicidal activity. The most active fraction, F2A (LC50 = 240 μg mL-1), was analyzed by GC/MS, and six sesquiterpenes were identified. The major compound, laurinterol, was isolated and identified by NMR analysis. Acetylcholinesterase (AchE) inhibition is an action mechanism employed to identify larvicidal compounds and was identified in the active fraction. Due to the chemical diversity and biological activity of Laurencia species, L. johnstonii is a notable potential source of larvicidal compounds. [ABSTRACT FROM AUTHOR]

Ocean acidification and warming caused by elevated CO2 are urgent problems facing the marine ecological environment. With the strengthening of environmental governance in China, anthropogenic inputs of terrestrial phosphorus into the coastal ocean have drastically decreased, resulting in frequent phosphorus deficiency in seawater. These environmental factors in the future may affect algal growth, photosynthesis and yield. As an important economic macroalga suitable for large-scale cultivation, Gracilariopsis lemaneiformis is also potentially affected by the coupling of ocean acidification, warming and phosphorus deficiency. In this study, G. lemaneiformis was cultured outdoors under two pCO2 levels (LC, 400 μatm; HC, 1000 μatm), two temperatures (LT, 20 ℃; HT, 24 ℃) and two phosphorus concentrations (LP, 0.1 μmol L−1; HP, 10 μmol L−1) to investigate its growth and photosynthetic performance. The results showed that LP significantly decreased the relative growth rates (RGR) and the maximum photosynthesis rate (Pm) of G. lemaneiformis both under LC and HC conditions. Under P depletion condition, the effects of warming and ocean acidification on the growth and photosynthetic performance of G. lemaneiformis showed an opposite trend, that is, HC caused a decrease in the growth, Pm, maximum relative electron transfer rate (rETRmax) and light utilization efficiency (α) from the rapid light response curve of G. lemaneiformis, and HT improved these parameters. Under LP condition, HC significantly inhibited the RGR of G. lemaneiformis in the LT group but had no significant effect on RGR in the HT group. Additionally, under LP condition, HC insignificantly affected PE and PC contents in the LT group, but significantly reduced these contents in the HT group. These findings suggest that phosphorus deficiency results in a decline in the growth of G. lemaneiformis and, under LP condition, the inhibition effect of ocean acidification on the growth of G. lemaneiformis could be mitigated by warming. This study provides scientific guidance for the field cultivation and selective breeding of G. lemaneiformis in phosphorus-deficient seawater under global climate change. [ABSTRACT FROM AUTHOR]

Antioxidants are of great interest in multiple applications, so there is a growing trend in the search for antioxidant compounds of natural origin, such as the red algae Palmaria palmata and Porphyra sp. A green ultrasound-assisted extraction method has been optimised to obtain the highest antioxidant activity, and subsequent characterisation of the antioxidant compounds present in the extracts. The antioxidant activity was determined by DPPH-RSA, FRAP and ORAC assays. The highest antioxidant activity was obtained for Porphyra sp. (DPPH: 87.64%, FRAP: 14.23 ± 0.76 µmol Fe2+ g-1 (DW) and ORAC: 106.81 ± 1.59 µmol TE g-1 (DW)) extracts with significant differences in all tests compared to P. palmata (DPPH: 78.99%; FRAP: 2.65 ± 0.14 µmol Fe2+ g-1 (DW), and ORAC: 44.78 ± 0.53 µmol TE g-1 (DW)). Subsequently, the content of pigments (phycobiliproteins, chlorophyll a and carotenoids), total polysaccharides content, total phenolic content and individual polyphenols of the optimised extracts were determined. The results suggest that the differences in antioxidant activity are mainly due to the presence of pigments and polyphenols, n particular, the polyphenols with the highest number of free hydroxyl groups in their chemical structure. [ABSTRACT FROM AUTHOR]

The pressing need for sustainable agriculture has led to increasing interest in seaweed biostimulants as a green alternative to chemical fertilizers. This study aimed to investigate and confirm the effectiveness of extracts from two cultivable red seaweeds, Kappaphycus alvarezii (KAE) and Gracilaria debilis (GDE), and a naturally harvestable brown seaweed, Sargassum cinctum (SCE), as biostimulants on maize. The chemical composition showed them to be rich in macronutrients, carotenoids, proline, micronutrients, total phenols, flavonoids, and hormones, many of which have known bioactivities in plants. Field trials were carried out over two years to assess various growth parameters, cob and yield attributes, grain quality, and the status of soil enzymes and nutrients. The findings demonstrated that all three seaweed extracts significantly enhanced plant growth, crop yield, and grain quality. The most effective dosage for maximum benefit was determined to be 7.5%, as further yield improvement was not observed beyond this point. The increases in yields were 19, 21, and 20% over their respective controls in the KAE, GDE, and SCE treatments, respectively, even at the lowest dose of 2.5%. Furthermore, the extracts had positive effects on soil properties, such as increasing enzymatic activities and nutrient availability, which contributed to improved crop nutrition. The active ingredients in the extracts, including plant growth hormones and phenolic compounds, likely influenced plant physiological processes and metabolic pathways, leading to improved shoot and root growth, yield and nutrient absorption. This study highlights the potential of seaweed biostimulants in sustainable agriculture, enhancing productivity, grain quality, soil health and profitability. [ABSTRACT FROM AUTHOR]

The paper provides an overview of all freshwater red algae species recorded to date in the territory of Bosnia and Herzegovina. Based on fieldwork and analysis of all available previously published data, it was determined that a total of 15 taxa from eight genera have been recorded to date: Bangia (1), Audoinella (3), Batrachospermum (2), Peludicola (1), Shaethia (1), Lemanea (4), Paralemanea (2) and Hildenbrandia (1). All taxa were found in clear, cold, well-oxygenated water. Bosnia and Herzegovina is very rich in different types of aquatic habitats. More than 100 sites were visited during the field research, but there are still many potential habitats where freshwater red algae can be found, which will be explored in the coming years. This work is the first step toward establishing long-term monitoring and listing of protected and threatened red algae in Bosnia and Herzegovina. [ABSTRACT FROM AUTHOR]

Background and Aims Maerl-associated communities have received considerable attention due to their uniqueness, biodiversity and functional importance. Although the impacts of human activities are well documented for maerl-associated macrofauna, the spatio-temporal variations of macroalgae have comparatively been neglected, and the drivers that influence their dynamics are poorly known. We investigate the links between maerl-associated macroalgal communities, anthropogenic pressures and environmental conditions, and hypothesize that sites under human pressure would exhibit different dynamics when compared to reference sites. Methods To better understand community variation through space and time, four subtidal maerl beds under different pressures were consistently monitored over one year in the bay of Brest, Brittany, France. Both macroalgae community monitoring and environmental data were acquired through field sampling and available models. Key Results Higher macroalgal biomass was observed within eutrophic sites, especially in summer (more than ten times higher than in the Unimpacted site), caused by free-living forms of opportunistic red macroalgae. The Dredged site also exhibited distinct macroalgal communities during summer from the Unimpacted site. Nutrient concentrations and seasonality proved to be key factors affecting the macroalgal community composition, although dredging and its effects on granulometry also had a strong influence. Over the long term, fewer than half of the species identified during historical surveys were found, indicating major temporal changes. Conclusions Human pressures have strong impacts on maerl-associated macroalgal communities. Nutrient concentrations and dredging pressure appear as the main anthropogenic factors shaping maerl-associated macroalgal communities. Additionally, our results suggest historical changes in maerl-associated macroalgal communities over 25 years in response to changes in local human pressure management. This study suggests that maerl-associated macroalgal communities could be used as indicators of anthropogenically driven changes in this habitat. [ABSTRACT FROM AUTHOR]

Ocean currents play a role in both facilitating and impeding connectivity of marine organisms' populations, serving as key drivers and potential barriers. The emergence of Taiwan around five million years ago (Mya) impacted the Kuroshio Current which later shaped the distribution of marine organisms. In this study, we examined how the Kuroshio Current influenced the distribution and population divergence of the marine red alga Dichotomaria elegans (Galaxauraceae, Nemaliales). Through phylogenetic analysis, species delimitation, and morphological comparison of Taiwanese species, we determined its phylogenetic position relative to other species within the D. marginata complex of the genus Dichotomaria. We uncovered the hidden cryptic diversity within the D. marginata complex in Taiwan and proposed the new combinations D. elegans and D. latifolia based on Galaxaura elegans and G. latifolia. Genetic analysis based on three loci (mitochondrial cox2-3 and cox1, and plastid rbcL) from 32 locations across the Philippines, Taiwan, and Japan revealed three allopatric lineages within D. elegans. The first lineage is restricted to the northern Philippines and southern Taiwan, while the second has a broader latitudinal range along the Kuroshio Current. The third lineage is found in southeast Luzon, Philippines, close to the bifurcation of the North Equatorial Current, near the start of the Kuroshio Current. The divergence of the first two lineages during the mid-Pliocene (~3.7 Mya) coincided with the emergence of Taiwan, with the current dynamics accentuating their separation. The Kuroshio Current exhibited a dual impact on the biogeography of D. elegans: promoting the dispersal of the second lineage towards higher latitudes and preventing the first lineage from moving northward. Principal component analysis showed that habitat conditions and morphologies differed between the two D. elegans lineages. This study provides insights into the cryptic diversity of Dichotomaria in Taiwan, as well as the genetic divergence, biogeographical patterns, and ecological associations of D. elegans, highlighting the interplay of island formation and currents shaping the diversification of seaweeds in the Northwest Pacific Ocean. [ABSTRACT FROM AUTHOR]

Haploid-diploid life cycles impose unique eco-evolutionary consequences, rendering commonly used proxies difficult to use (e.g. separate sexes prevent selfing). Population genetic analyses are therefore required to explore patterns of reproductive system variation. However, there are still few haploiddiploid species for which polymorphic, nuclear loci exist. This problem is particularly acute for algae. Here, we describe the development of the first microsatellite loci in a freshwater red alga. We tested 73 candidate loci against a panel of Batrachospermum gelatinosum (L.) De Candolle gametophytes that encompass much of its North American range. Ten loci consistently amplified and were characterized by clean peak architectures on a capillary sequencer with one allele per locus, as expected in a haploid gametophyte. We then explored some basic population genetic indices in gametophytes collected from one site and obtained good resolution based on the probability of identity (pid). Yet, we observed a pattern of clumped repeated genotypes throughout the stream reach sampled. The pattern of moderate genotypic richness could be due to intragametophytic selfing resulting in the complete loss of genetic diversity from a single gamete union. Future studies will need to sample more populations to determine if intragametophytic selfing is the dominant reproductive mode in this monoicous taxon. The loci developed here represent an important tool for studying freshwater red algal populations in specific as well as enhancing our understanding of reproductive system variation and the haploid-diploid life cycle of algae in general. [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]

Pollution caused by petroleum-based plastics, especially single-use food packaging, has become a global problem. In order to offer sustainable alternatives to traditional plastic, it is important to explore the use of new biodegradable plastic materials made from renewable sources. Bioplastics made from seaweed extracts, such as carrageenan and alginate, show promise as viable options. However, these phycocolloids are expensive and require a lengthy extraction process. This report presents the development of bioplastics using the entire biomass of a red seaweed (Kappaphycus sp.). The initial focus of the study was to optimize the concentration of the main ingredients, which included biomass and glycerol (plasticizer agent). The concentration range that was tested included a biomass-to-water ratio of 1:50 to 1:90 and a plasticizer concentration of 1% to 5% (v/v). Subsequently, bioplastics were created by incorporating natural dye extracts from butterfly pea flower (Clitoria ternatea), bougainvillea flower (Bougainvillea glabra), and dragon fruit peel (Hylocereus polyrhizus) using a casting method at the selected optimum concentrations. The resulting bioplastics were then characterized for their physicochemical properties (including shelf-life and biodegradability), and antimicrobial activity using standard methods. The study successfully developed bioplastics with a thickness of less than 100 µm and a moisture content below 40%. Within the tested range, the most optimal concentrations were a biomass-to-water ratio of 1:50 to 1:60 and 1% glycerol, based on factors such as tensile strength (TS), water vapor transmission rate (WVTR), elasticity, appearance, shelf-life, and biodegradability. All of the bioplastics completely degraded during a soil burial test within 13-15 days. The inclusion of brightly coloured plant extracts increased the bioplastics' antioxidant properties by more than 10% in scavenging activity. Furthermore, the dyed bioplastics had a shelf-life that was 20-30% longer. While these biomass bioplastics have lower tensile strength, elasticity, and water vapor permeation rate (<10 MPa, <30 MPa, and >2 g m-2 h-1, respectively), they show potential for applications where high tensile strength is not required, such as food packaging or wrapping. [ABSTRACT FROM AUTHOR]

The use of seaweed extracts as biostimulants is increasing worldwide to improve agricultural production, since they are natural and environmentally friendly compounds. Seaweeds biosynthesize plant hormones, including cytokinins which play an important role in plant growth and development. Cytokinin-like (CK) activity was analysed in eight species of Rhodophyta, including agarophytes (Gracilaria spp., Gelidium), and carrageenophytes (Chondracanthus, Hypnea). Comparison of CK-activity of different samples of the same species (e.g., field and cultured samples, different color and morphological variants, and reproductive phases) is described. Dried samples were extracted for 24 h at 10ºC in 100 mL 80% ethanol, filtered and rinsed with 80% ethanol. The extracts were purified using C18 Sep-Pak cartridges and Oasis MCX columns and separated into fractions by descending paper chromatography. CK-like activity was determined using the soybean callus bioassay with activity compared to kinetin standards (1, 5, 10 and 50 µg L−1). The green strain of Hypnea psedomusciformis was more active than the brown strain with most activity co-chromatographing with zeatin. Tetrasporophytes and female gametophytes of Gracilaria birdiae had CK-like activity that co-chromatographed with zeatin, and female gametophytes had an additional peak that co-chromatographed with riboside-5'-monophosphate. The highest CK-like activity (equivalent to 50 µg L−1 kinetin) occurred in G. cervicornis which co-chromatographed with isopentenyladenosine. Morphological variants of Hypnea had similar CK-like activity but the "nigrescens" variant had higher activity (equivalent to 10 µg L−1 kinetin) than the "musciformis" variant. These results indicate that Gracilaria cervicornis and Hypnea pseudomusciformis ("nigrescens" variant) have potential as biostimulants in agriculture. [ABSTRACT FROM AUTHOR]

Tropical macroalgae serve importance ecological roles on coral reefs but can supplant corals in phase shifts as shown worldwide. Thus, it is important to understand their fundamental photophysiology and effects on calcification mechanisms. We examined organic δ13C, inorganic CaCO3 δ13C and δ18O, and organic %C, %N, C:N of abundant macroalgae on Little Cayman Island (LCI) reefs across a broad light gradient (5–2,000 μmol photons m−2 s−1). We hypothesized that LCI macroalgae utilize greater CO2 in low light environments as carbon concentration mechanisms (CCMs) to take up HCO3− have high energetic costs. We proposed that calcification mechanisms are also influenced by light and Ci-use strategies. LCI macroalgae had organic δ13C values (-12‰ to -25‰) indicative of CCMs and exhibited only a 1–3‰ δ13C depletion under irradiances < 5 μmol photons m−2 s−1. Light and phyla were significant in a mixed model explaining ~ 80% of variance in organic δ13C. Organic δ13C was a weak predictor and light insignificant in explaining inorganic δ13C values of thalli carbonates. Biogenic carbonate δ13C values were taxa-specific based on cluster analysis of δ13C:δd18O ratios, an indication of diverse calcification mechanisms. LCI macroalgal photosynthesis utilized CCMs across a broad range of irradiances, thus greater CO2 availability under ocean acidification is not likely to enhance community dominance of macroalgae of concern (e.g., Lobophora sp.) due to shifts in photophysiology. The mechanisms of Ci sequestration for photosynthesis appeared to be mostly uncoupled from calcification mechanisms that were diverse across phyla, likely due to distinct macroalgal forms, sites of calcification and carbonate structure. [ABSTRACT FROM AUTHOR]

In an integrated multitrophic aquaculture (IMTA) system, seaweeds serve as extractive species that utilize excess nutrients, thereby reducing the risk of eutrophication and promoting sustainable aquaculture. However, the use of excessive fish feeds and the resultant faecal waste as nutrient streams can contribute to variations in nitrogen and phosphorus levels (e.g., primarily NH4+ and PO4−3) in the surrounding area and this may impact the physiology of the integrated seaweeds, particularly on how these species take up inorganic nutrients. In this study, the effect of different PO4−3 levels on NH4+ uptake of the three commercially important eucheumatoids Kappaphycus alvarezii, Kappaphycus striatus and Eucheuma denticulatum was examined under laboratory conditions. Seaweed thalli (n = 4) were incubated in seawater media containing 30 µM NH4+, and 0, 0.5, 1.0, 1.5, 3.0 or 5.0 µM PO4−3 for 1 h under a saturating light level of 116 ± 7.13 µmol photons m−2 s−1 inside a temperature-controlled laboratory. Species-specific responses to PO4−3 levels were observed. For K. alvarezii, maximum NH4+ uptake (17.8 ± 1.6 µmol gDW−1 h−1) was observed at 0.5 µM PO4−3 and the uptake rate declined at higher PO4−3 levels. For K. striatus, NH4+ uptake increased with increasing PO4−3 levels, with maximum N uptake (6.35 ± 0.9 µmol gDW−1 h−1) observed at 5.0 µM PO4−3. For E. denticulatum, maximum NH4+ uptake (14.6 ± 1.4 µmol gDW−1 h−1) was observed at 1.0 µM PO4−3. Our results suggest that among the three eucheumatoid species, the NH4+ uptake of K. striatus persists even at high levels of PO4−3. However, our results also showed that K. striatus had the lowest range of NH4+ uptake rates. These results should be taken into consideration when incorporating eucheumatoids in the IMTA system, where PO4−3levels significantly vary in space and time. [ABSTRACT FROM AUTHOR]

The red alga Kappaphycus alvarezii is a versatile food ingredient widely used in the food industry due to its many functional properties. The aim of this study is to substitute wheat flour with K. alvarezii powder and determine the effects it has on the physical properties and proximate composition of snack crackers. The six formulations of crackers incorporating different proportions of K. alvarezii powder were (C) 0%, (F1) 1%, (F2) 2.5%, (F3) 5%, (F4) 7.5%, and (F5) 10%. Physical analyses such as colour, water activity, and texture as well as proximate analysis of moisture, ash, crude fat, crude protein, and crude fibre content was conducted. The result showed a significant (p < 0.05) decrease in colour and water activity with the addition of K. alvarezii powder. Meanwhile, proximate analysis showed a significant (p < 0.05) increase in ash (3.77 ± 0.03%) and fibre content (2.08 ± 0.03%) with an increasing amount of K. alvarezii powder added. The crude protein, crude fat, and moisture content decreased significantly (p < 0.05) as more K. alvarezii powder was added. In conclusion, the incorporation of K. alvarezii powder in crackers showed improvement in the ash and crude fibre content and physical properties of the crackers. [ABSTRACT FROM AUTHOR]

Species of the genus Asparagopsis are rich in halogenated bioactive compounds, particularly bromoform. Its use as a feed additive in ruminant livestock drastically decreases the animal's methane production, thereby reducing the industry's environmental impact. Addressing the high demand for Asparagopsis biomass requires the understanding of the culture conditions that promote higher growth rates and bromoform content. Here we evaluated how different light quality combinations (High-Blue:Red, Medium Blue:Red, High-Blue:Green:Red, and White) and four light intensities (30, 60, 90 and 120 μmol photons m−2 s−1) affect the growth and bromoform content of the Asparagopsis taxiformis tetrasporophyte in indoor tumbling cultures at two biomass densities. We also assessed the effect of light intensity on the photosynthetic response by measuring oxygen evolution rates. Light spectra containing intermediate wavelengths promoted higher growth, regardless of biomass density. Of the different light qualities tested, white light promoted the highest bromoform content. Increasing light intensity led to a positive response in A. taxiformis growth. However, the photosynthetic parameters estimated showed that the two higher light intensity treatments were above the saturation irradiance, for both culture densities. This, along with the observed development of contamination, suggests that long-term cultures of A. taxiformis should be maintained at light intensities no higher than 60 μmol photons m−2 s−1. In addition, we found that exposing cultures to higher irradiances does not guarantee a bromoform-richer biomass. These results offer valuable insights for optimizing biomass and bioactive compound production in indoor cultures of the Asparagopsis genus. [ABSTRACT FROM AUTHOR]

A phyco-biostimulant from the brown alga Ascophyllum nodosum has been widely used in agricultural crops for decades. However, it was recently discovered that the same extract can be successfully applied in the micropropagation and field cultivation stages of eucheumatoids. The present study tested the efficacy of an alkali extract from A. nodosum (aka AMPEP) on Kappaphycus alvarezii with the aim of enhancing daily growth rate, as well as to mitigate the prevalence of ice-ice disease and macro-epiphytes, using three different seeding methods (i.e., double-looping DL, tubular-netting TN and ribbon tying RT, vis-à-vis water quality parameters. Seedlings were dipped in soluble extract powder made up to 1 g L−1 AMPEP for 1 h prior to out-planting in the sea. A total of three growth cycles, each of 45 days, from November—June (representing the dry months) were followed. The daily growth rate (% increase in fwt day−1) and prevalence (%) of ice-ice disease and macro-epiphytes were measured and correlated with the prevailing water conditions at the experimental site. The average DGR ranged from 0.10—3.8, 0.7—2.6, and 0.03—3.6% day−1 for DL, TN and RT, respectively, for AMPEP-treated K. alvarezii, while the control showed a range of average growth from -0.2—3.8, 0.2—2.6, -1.0—4.0% day−1, respectively. Negative DGRs were obtained in DL (-0.2%) and RT (-1.0%) from May—June. Using a factorial set up of ANOVA, the seeding method and growth cycle had significant interactions (p < 0.01); however, no significant interaction was found between AMPEP and the seeding method. During November—January, the three seeding methods did not influence DGR; however, a significant effect was found in January–March. Using Tukey's HSD, DL and RT were significantly different from TN, but no significant differences between RT and DL were recorded. The effects of AMPEP on DGR were only significant from May—June (p < 0.05). Growth rates, ice-ice disease and macro-epiphyte (ME) incidence correlated significantly with sea surface temperature (SST) and salinity but not with pH. This study clearly demonstrated the effects of increased temperature and salinity on Kappaphycus growth rates, ice-ice disease and macro-epiphyte incidence at certain growth cycles (months). [ABSTRACT FROM AUTHOR]

Consumption of meat and meat products may lead to health risks such as cardiovascular diseases due to the significant amount of animal fat in the formulation. Thus, various strategies have been studied to reduce saturated fat without altering the physicochemical and sensory qualities of meat products, including incorporating food additives. Kappaphycus alvarezii is a tropical red macroalga with significant fibre, carbohydrate, and mineral content. This study aims to see how replacing fat in chicken patties with seaweed gel K. alvarezii (KA) affects the physicochemical, nutritional, and sensory aspects. The chicken patties were formulated as control samples F0 (0% KA gel + 10% fat), F1 (2.5% KA gel + 7.5% fat), F2 (5% KA gel + 5% fat), and F3 (7.5% KA gel + 2.5% fat). Adding K. alvarezii significantly increased patty moisture, ash, and dietary fibre content (p < 0.05). On the other hand, increasing the level of K. alvarezii gel as a fat replacer considerably lowered the fat content (p < 0.05). Furthermore, adding K. alvarezii gel did not impact the protein content (p > 0.05). The hardness of the K. alvarezii gel-treated patties decreased significantly (p < 0.05) with no significant changes in other textural parameters (p > 0.05). When compared to the control sample (F0), the chicken patties with K. alvarezii gel seaweed exhibit lower expressible water and cooking loss (p < 0.05). The addition of seaweed gel darkened the colour of the chicken patties while decreasing the a* and b* values (p < 0.05). Compared to other formulations, F1 (2.5% KA gel + 7.5% fat) is most liked by sensory panellists (p < 0.05). In conclusion, seaweed K. alvarezii gel has the potential to be used as a fat substitute in the production of reduced-fat chicken patties. [ABSTRACT FROM AUTHOR]

Rhodolith beds, including maerl, are structurally complex perennial habitats that support a high species diversity but are threatened by numerous human activities, particularly in the Mediterranean Sea. Despite their global ecological importance, increased research efforts are needed to facilitate development of effective measures to conserve these habitats.Two areas hosting rhodolith beds are known to occur off the coast of Malta (central Mediterranean), but only one has been previously studied. Through analysis of video footage collected from 56 different stations coupled with a desk study on human activities, the present study characterized the rhodolith bed located off the southeastern coast of Malta, including its extent, rhodolith morphotype composition, associated megabiota and impacts of anthropogenic activities thereon.The bed occurred at depths of 60–95 m and covered an area of approximately 200 km2, making it the second most extensive rhodolith area reported for the Mediterranean to date. It was dominated by spherical and branched rhodoliths whose cover reached a maximum of 74% but was more often <50%, similar to other Mediterranean rhodolith beds. A total of 84 different megafaunal species were recorded, suggesting that the diversity of megafauna associated with rhodolith bed habitats has been previously underestimated. A number of human activities, including extensive vessel anchoring and officially designated areas for aquaculture, bunkering and trawling, overlap with the mapped rhodolith distribution, highlighting the risk of habitat degradation.A holistic approach to the management of all the competing activities and interests relative to the southeastern coast of Malta that gives due consideration to this newly characterized rhodolith bed and the threats it faces is therefore recommended. The legal framework and policy recommendations for better conservation of rhodolith bed habitats in the Mediterranean and European Seas are also discussed. [ABSTRACT FROM AUTHOR]

Historical vicariance events, linked to the existence of stable physical barriers to gene flow, generate concordant genetic breaks in co-distributed species while stochastic processes (e.g., costal uplift) could cause species-specific genetic breaks as a result of local strong demographic bottlenecks or extinction. In Chile, previous studies show that the area of the 30°S-33°S could correspond to a stable barrier to gene flow that have affected the genetic structure of various algae and marine invertebrates. Here we sequenced two organellar genes (COI and rbcL) in four taxonomically accepted co-distributed red seaweeds species characterized by a low dispersal potential: Mazzaella laminarioides, M. membranacea, Asterfilopsis disciplinalis, and Ahnfeltiopsis vermicularis. Our results revealed the existence of ten strongly differentiated linages in the taxa studied. Strong genetic breaks, concordant in both space and time (divergence estimated to have occurred some 2.9-12.4 million years ago), were observed between taxa distributed across the 33°S. Conversely, in the Central/South part of the Chilean coast, the localization of the genetic breaks/sub-structure observed varied widely (36°S, 38°S, 39°S, and 40°S). These results suggest that a major historical vicariance event has modeled the genetic structure of several Chilean marine organisms in the north of the Chilean coast during the mid-Miocene, while more recent stochastic events and genetic drift could be the driving forces of genetic divergence/structuration in the central-southern part of the coast. [ABSTRACT FROM AUTHOR]

Seaweed functional traits provide insights on natural populations, their adaptations to the local environment, which can be utilized for commercial exploitation. Here, we analyzed the functional traits of Gracilaria dura from two intertidal populations in Veraval and Adri, from the coast of Gujarat, India, over a period of three months. Functional traits were measured by analyzing growth rates, respiration, primary production, antioxidant activity and the content of plant growth hormones. The weight-to-length allometric exponent ≈3 indicated that G. dura grew almost isometrically. Furthermore, frond shape was not significantly different. Fronds in Veraval, resting submerged, grew faster than the fronds in Adri, which, lay exposed in the flat bare rock during low tide. Accordingly, the simultaneous increase in antioxidant activity, O2 production and chlorophyll content in fronds from Adri suggests that stress from desiccation and UV led to the detrimental accumulation of Reactive Oxygen Species, leading to decreased growth and decreased production of growth hormones. The increased Chl-a may indicate enhanced non-photochemical quenching (NPQ) for the dissipation of excess absorbed light. These results aid in establishing the best practices for maximizing biomass yield or the yield of specific molecules. For maximized biomass yield, fronds should not be subject to emersion nor cultivated on the sea-surface. On the other hand, fronds grown subject to emersion or at the sea-surface yield less biomass but more content on molecules such as antioxidants (flavonoids, phenolics, enzymes), that fight stress from desiccation high temperatures and UV. In this case, stress should still be avoided during the initial growth, at the onset of the growth season, in order to not disrupt the production of growth hormones. The increased O2 production at Adri was initially mistakenly perceived as enhanced Net Primary Production. Only a posterior holistic perspective over the whole data allowed to conclude that it was likely the stress-induced detrimental accumulation of Reactive Oxygen Species. More robust experiments are required to establish if the differences observed between locations have led to the evolution of genetic strains specific to each habitat that may show different performances and yields when cultivated in similar environments.

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]

The relative frequency of sexual versus asexual reproduction governs the distribution of genetic diversity within and among populations. Most studies on the consequences of reproductive variation focus on the mating system (i.e., selfing vs. outcrossing) of diploid‐dominant taxa (e.g., angiosperms), often ignoring asexual reproduction. Although reproductive systems are hypothesized to be correlated with life‐cycle types, variation in the relative rates of sexual and asexual reproduction remains poorly characterized across eukaryotes. This is particularly true among the three major lineages of macroalgae (green, brown, and red). The Rhodophyta are particularly interesting, as many taxa have complex haploid–diploid life cycles that influence genetic structure. Though most marine reds have separate sexes, we show that freshwater red macroalgae exhibit patterns of switching between monoicy and dioicy in sister taxa that rival those recently shown in brown macroalgae and in angiosperms. We advocate for the investigation of reproductive system evolution using freshwater reds, as this will expand the life‐cycle types for which these data exist, enabling comparative analyses broadly across eukaryotes. Unlike their marine cousins, species in the Batrachospermales have macroscopic gametophytes attached to filamentous, often microscopic sporophytes. While asexual reproduction through monospores may occur in all freshwater reds, the Compsopogonales are thought to be exclusively asexual. Understanding the evolutionary consequences of selfing and asexual reproduction will aid in our understanding of the evolutionary ecology of all algae and of eukaryotic evolution generally. [ABSTRACT FROM AUTHOR]

Species of the red algal genus Meristotheca are important natural resources that can be used directly as food for human consumption as well as raw materials for the extraction of carrageenan. Despite being harvested in Japan and Korea, a comprehensive taxonomic study of Meristotheca specimens from these two countries to elucidate their phylogenetic position is lacking. In this study, we aimed to clarify the taxonomic identities of specimens currently regarded as M. papulosa from Korea and Japan by analyzing morphological and molecular data. As the result, we recognized a new species, Meristotheca pilulaora sp. nov. from Korea and resurrected Meristotheca japonica for specimens from Japan. The two entities have long been identified as M. papulosa and exhibit similar external morphologies. They appeared independently in the concatenated phylogenetic tree of COI-5P and rbcL and could also be distinguished morphologically by the position of cystocarps (blade margins in M. pilulaora; marginal proliferations in M. japonica), spinose cystocarps (absent in M. pilulaora; present in M. japonica), and the number of cortical cell layers (two in M. pilulaora; 4–8 in M. japonica). The DNA analysis of M. pilulaora sp. nov. in local populations showed 11 COI-5P haplotypes on Jeju Island with no apparent geographical structure. High genetic diversity and occurrence of unique haplotypes in southern Jeju may provide a genetic basis for population with high thermal tolerance. These findings have strengthened our understanding of the species diversity of the genus Meristotheca and provided insights into conservation, management, and haplotype selection for the future cultivation of these economically important species. [ABSTRACT FROM AUTHOR]

Determining the relative importance of sexual and asexual reproduction is critical for determining how genetic diversity is partitioned within and among populations. Macroalgae exhibit reproductive system variability, with many species capable of both sexual and asexual reproduction. Thus, rates of fragmentation (asexual) versus sporic recruitment (sexual) must be quantified. This is critical during range expansions when shifts to uniparental reproduction are common. Chondria tumulosa is a cryptogenic red alga that was discovered forming thick mats at Manawai, in the Northwestern Hawaiian Islands, during opportunistic sampling in 2019. It reduced the biodiversity and abundance of associated coral reef organisms. To characterize the reproductive system of C. tumulosa in this atoll, we visually assessed 124 thallus clumps for reproductive structures and used five microsatellite loci to genotype 41 thalli. All thalli bearing reproductive structures (20%) and all thalli that were genotyped were tetrasporophytes. No gametophytic thalli were observed using microscopy or microsatellite genotyping, though 80% of thalli observed under the microscope were vegetative. We observed in situ thallus fragmentation supported by the presence of 17 repeated genotypes and other genetic signatures, suggesting high rates of asexual reproduction. These results suggest that C. tumulosa is partially clonal in this atoll and has the potential for spreading to other nearby atolls. Rapid establishment, thallus fragmentation and tetrasporophytic dominance are consistent with other red macroalgal invasions studied to date. Understanding the reproductive system is an important component of developing management strategies for this alga and expanding our understanding of the population genetics of partially clonal taxa. [ABSTRACT FROM AUTHOR]