Brown Macroalgae Research Articles

Detailed Chemical Prospecting of Volatile Organic Compounds Variations from Adriatic Macroalga Halopteris scoparia.

The present study aimed to isolate volatile organic compounds (VOCs) from fresh (FrHSc) and air-dried (DrHSc) Halopteris scoparia (from the Adriatic Sea) by headspace solid-phase microextraction (HS-SPME) and hydrodistillation (HD) and to analyse them by gas chromatography and mass spectrometry (GC–MS). The impact of the season of growth (May–September) and air-drying on VOC composition was studied for the first time, and the obtained data were elaborated by principal component analysis (PCA). The most abundant headspace compounds were benzaldehyde, pentadecane (a chemical marker of brown macroalgae), and pentadec-1-ene. Benzaldehyde abundance decreased after air-drying while an increment of benzyl alcohol after drying was noticed. The percentage of pentadecane and heptadecane increased after drying, while pentadec-1-ene abundance decreased. Octan-1-ol decreased from May to September. In HD-FrHSc, terpenes were the most abundant in June, July, and August, while, in May and September, unsaturated aliphatic compounds were dominant. In HD-DrHSc terpenes, unsaturated and saturated aliphatic compounds dominated. (E)-Phytol was the most abundant compound in HD-FrHSc through all months except September. Its abundance increased from May to August. Two more diterpene alcohols (isopachydictyol A and cembra-4,7,11,15-tetraen-3-ol) and sesquiterpene alcohol gleenol were also detected in high abundance. Among aliphatic compounds, the dominant was pentadec-1-ene with its peak in September, while pentadecane was present with lower abundance. PCA (based on the dominant compound analyses) showed distinct separation of the fresh and dried samples. No correlation was found between compound abundance and temperature change. The results indicate great seasonal variability of isolated VOCs, as well among fresh and dried samples, which is important for further chemical biodiversity studies.

The relative effects of interspecific and intraspecific diversity on microplastic trapping in coastal biogenic habitats

Our understanding of how anthropogenic stressors such as climate change and plastic pollution interact with biodiversity is being widened to include diversity below the species level, i.e., intraspecific variation. The emerging appreciation of the key ecological importance of intraspecific diversity and its potential loss in the Anthropocene, further highlights the need to assess the relative importance of intraspecific versus interspecific diversity. One such issue is whether a species responds as a homogenous whole to plastic pollution. Using manipulative field transplant experiments and laboratory-controlled hydrodynamic simulations, we assessed the relative effects of intraspecific and interspecific diversity on microplastic trapping in coastal biogenic habitats dominated by two key bioengineers, the brown intertidal macroalgae Fucus vesiculosus and F. guiryi. At the individual level, northern morphotypes of F. guiryi trapped more microplastics than southern individuals, and F. vesiculosus trapped more microplastics than F. guiryi. Canopy density varied among species, however, leading to reversed patterns of microplastic accumulation, with F. guiryi canopies accumulating more microplastics than those of F. vesiculosus, while no differences were observed between the canopies of F. guiryi morphotypes. We emphasize the importance of assessing the effects of intraspecific variation which, along with other crucial factors such as canopy density, flow velocity and polymer composition, modulates the extent of microplastic accumulation in coastal biogenic habitats. Our findings indicate that a realistic estimation of plastic accumulation in biogenic habitats requires an understanding of within- and between-species traits at both the individual and population levels.

Interspecies and seasonal variations in macroalgae from the Nordic region: Chemical composition and impacts on rumen fermentation and microbiome assembly

Marine macroalgae may serve as sustainable feed resources for ruminant production due to their nutritional attributes, and enteric methane (CH 4 ) mitigating potential. We aimed to characterize the anti-methanogenic properties of 12 Nordic macroalgae species (eight brown, three red, and one green). Differences in the chemical composition across two harvesting seasons and impacts of addition of macroalgae (20% dry matter basis) on in vitro rumen fermentability of maize silage (MS) and associated changes in the rumen microbiome composition were also evaluated. Green and red macroalgae contained twice as much crude protein (CP) as compared to brown macroalgae. The latter had higher mineral and total polyphenol content (TPC: 10 to 20 times). In some brown species, ash and CP contents were up to twice as high in spring than in autumn, but TPC was highest in autumn. The TPC content was inversely correlated with in vitro rumen fermentation characteristics: organic matter (OM) degradability (r = −0.85; P < 0.001), production of total gas (r = −0.79; P < 0.001), total volatile fatty acids (r = −0.78; P < 0.001) and CH 4 (r = −0.53; P < 0.03) per gram of OM. The polyphenol-rich brown species, Fucus vesiculosus and Ascophyllum nodosum , caused a significant reduction in feed degradability (∼25%) due to the suppression of cellulolytic bacteria ( Ruminococcus spp., Lacnospiraceae spp., Rikenellaceae RC9 gut group) in the rumen fluid after fermentation. Interestingly, autumn-harvested samples of those two macroalgae decreased the CH 4 production by 62.6% and 48.2%, respectively, and reduced rumen methanogenic archaea (e.g., Methanobrevibacter spp.), although the reduction was not directly correlated with TPC. Thus, Nordic macroalgae, depending upon their species-specific unique properties, could be utilized as anti-methanogenic feed additives or feeding resources for ruminants. In vivo studies are needed to establish the implications of feeding with these macroalgae on overall animal performance. • Macroalgae generally had greater protein and mineral contents in the spring. • Including 20% macroalgae with a low polyphenol content did not reduce in vitro feed degradability. • Polyphenol-rich brown algae reduced feed degradation by inhibiting cellulolytic microbes. • Brown alga, Fucus vesiculosus mitigated 62.6% of in vitro CH 4 production at 20% inclusion in feed.

Major lipophilic pigments in Atlantic seaweeds as valuable food ingredients: Analysis and assessment of quantification methods

Current trends towards the use of ingredients from natural origin in food, cosmetic and pharmaceutical industry, place macroalgae as a good reservoir of novel compounds. Among them, lipophilic major pigments such as chlorophylls and fucoxanthin, are of great interest because of their multiple applications as bioactive compounds and dyes. In this work, a mid-polarity medium was used to extract pigments from twenty-four species from North coast of Spain, including brown (Phaeophyceae) and red macroalgae (Rhodophyta). The fucoxanthin and chlorophyll a content was assessed by means of two different methods, spectrophotometric and high-performance liquid chromatography coupled to diode array detection (HPLC-DAD). The effect of dried processing on the pigment content of selected species was also evaluated. A linear relationship between the extractability of fucoxanthin and chlorophyll a was observed, being the highest content recorded among members belonging to the order Fucales and Undaria pinnatifida. This work provides good insights about the content on pigments in Spanish North Atlantic macroalgae with future commercial value in different industrial fields, as well as a critical overview of the suitability of the quantification methods and challenges related to their effect in results evaluation.

Sargassum horneri as a Prebiotic Dietary Supplement for Immunity Development in Streptococcus parauberis Infected Zebrafish Model

Sargassum horneri (SH) is a brown macroalgal species commonly found along the coast of Japan, China, and Korea. SH possesses valuable bioactive compounds that can be developed as functional food ingredients as well as pharmaceutical agents for both humans and animals. In this study, SH was tested for its potential prebiotic effect. Several solvent-assisted extracts of SH were tested on the growth of three species of probiotics (LAB) (Lactobacillus plantarum, Lactobacillus pentosus, Lactobacillus brevis) and fish pathogen bacteria (Streptococcus iniae, Streptococcus parauberis, Edwersiella tarda) both in vitro and in vivo. According to the in vitro results, Celluclast extract (SHC) and crude polysaccharide extract (SHCPs) of SH showed outstanding growth enhancing activity in all LAB species and excellent antibacterial activity against pathogenic bacteria dose-dependently. Both SHC and SHCPs induced the production of secondary metabolites from LAB. The secondary metabolites successfully reduced pathogenic bacterial growth. Furthermore, in vivo experiments revealed that co-treatment with LAB and SHC/SHCPs diminished the mortality of Streptococcus parauberis infected zebrafish by modulating iNOS, COX-2 expressions. Similarly, SH act as an anti-inflammatory agent against S. parauberis infection by hindering NF-κB pathway activation. Conclusively, the results achieved from the study suggest that S. horneri has the potential to be used as a prebiotic dietary supplement and possesses a protective effect against S. parauberis infections in the aquaculture industry.

Nutritional Assessment on Brown Macro algae Lobophora variegata from GOMBR, Tamil Nadu, India

Nutrition is very important to all living organisms and human beings obtained range of nutrition from different resources. Despite this fact, marine natural resources provide unique nutrition to human society. Based on that reason, the present study was conducted to analysis nutritional profile of brown seaweed Lobophora variegata (J.V. Lamouroux) Womersley ex. Oliveira collected from the Gulf of Mannar Biosphere, Tamil Nadu, India. The proximate composition (moisture, ash, protein, lipid, carbohydrate, and dietary fiber, mineral, amino acid , fatty acid and antioxidant activity (2-dipheny- 1 – picrylhydrazyl (DPPH) and Reducing power assays) of L.veriegata. The result indicated that the maximum concentration of protein (34.09 ± 0.95 mg/100g), carbohydrate (28.81 ± 0.07 mg/100g) and total dietary fiber (2.53 ± 0.037 mg/100g) soluble fiber (1.28 ± 0.07 mg/100g) and insoluble fiber (1.50 ± 0.07 mg/100g) recorded in the brown algae L. variegata. The mineral content of L. variegata exhibits high amount of minerals, such as Magnesium (1712.6 ± 16.75 mg/100g DW), Phosphorus (1477.3 ± 4.49 mg/100g DW), Potassium (1078.3 ± 6.23 mg/100g), Sodium (916.6 ± 4.47 mg/100g), Iron (913.6 ± 4.49 mg/100g DW), Zinc (813.6 ± 12.47 mg/100g) and Copper (427.3 ± 5.24 mg/100g DW). Fatty acid profile of docosahexaenoic acid (5.89 ± 0.021mg) and palmitic methyl ester (5.33 ±0.09 mg) were predominantly found in L. variegata. Finally the amino acids are essential (12.43±0.04 mg/g) and non essential (16.99±0.05 mg/g) respectively. DPPH scavenging of Ic50 (175.41µg /ml,) and reducing powder (186.26µg /ml) respectively. According to the current findings, brown seaweed, L. variegata, appears to be a viable marine natural resource for generating innovative nutraceutical and antioxidant products.

Fucoxanthin's Optimization from Undaria pinnatifida Using Conventional Heat Extraction, Bioactivity Assays and In Silico Studies.

Brown macroalgae are a potential source of natural pigments. Among them, Undaria pinnatifida is recognized for its high concentration of fucoxanthin (Fx), which is a pigment with a wide range of bioactivities. In this study, three independent parameters were optimized for conventional heat extraction (CHE) to maximize the recovery of Fx from Undaria pinnatifida. Optimal conditions (temperature = 45 °C, solvent = 70%, and time = 61 min) extracted 5.1 mg Fx/g dw. Later, the bioactivities of the Fx-rich extracts (antioxidant, antimicrobial, and neuroprotective) were assessed using in vitro and in silico approaches. In vitro assays indicated that Fx has a strong antioxidant capacity and even stronger antimicrobial activity against gram-positive bacteria. This data was supported in silico where Fx established a high binding affinity to DR, a Staphylococcus aureus protein, through aa ALA-8, LEU-21, and other alkane interactions. Finally, the in vitro enzymatic inhibition of AChE using Fx, was further supported using docking models that displayed Fx as having a high affinity for aa TYR72 and THR 75; therefore, the Fx extraction behavior explored in this work may reduce the costs associated with energy and solvent consumption. Moreover, this paper demonstrates the efficiency of CHE when recovering high amounts of Fx from Undaria pinnatifida. Furthermore, these findings can be applied in different industries.

Phylogeography of Colpomenia sinuosa (Ectocarpales, Phaeophyceae) along the Brazilian coast.

Colpomenia sinuosa is a cosmopolitan brown macroalgal species complex and hence a great candidate for evolutionary studies in the marine environment. Since 2009, three major C. sinuosa phylogenetic lineages, subdivided into eight subgroups, have been identified based on cox3 DNA sequences from worldwide collections. However, worldwide sampling remains limited and spotty. To date molecular data from Brazilian C. sinuosa populations have been limited to 10 specimens collected in a single locality. Nonetheless, C. sinuosa populations occur along the entire ~8,000 km Brazilian coast. Consequently, knowledge on population genetic diversity and spatial genetic structuring along most of the Brazilian coastline is nonexistent. To fulfill this gap in knowledge, we performed a phylogeographic analysis of C. sinuosa populations in Brazil. The highly variable cox3 marker was sequenced for 148 individuals collected in 12 localities in Brazil. Results identified two genetically distinct population groups (north vs. south) separated at 20.5° S latitude. Genetic diversity in northern populations is 14.6 and 15.5 times greater than southern populations in terms of haplotype and nucleotide diversity, respectively. Among northern populations, the Bahia state holds the largest genetic diversity. The southern populations had lower genetic diversity and no internal genetic sub-structure suggesting past bottlenecks followed by recent colonization from northern haplotypes. Our results do not indicate recent introductions of foreign haplotypes in Brazil and reinforce the crucial importance of historical and extant allopatric, parapatric, and sympatric processes driving marine macroalgal evolution in the Southwestern Atlantic Ocean.

Effects of temperature and light on the growth and reproduction of an endophytic pest alga Ectocarpus siliculosus (Ectocarpales) found in wild Gracilaria textorii (Gracilariales)

The genus Gracilaria is an economically important macroalgae group that has been cultivated worldwide on a commercial scale. Epiphytic algae are commonly found in both natural and cultured Gracilaria and have become one of the major concerns in the Gracilaria aquaculture. In contrast to the wide reports of epiphytic pests, the endophytic algae inGracilaria have rarely been reported. In this study, we isolated the brown filamentous endophytic macroalgae Ectocarpus siliculosus from the host wild Gracilaria textorii to investigate its growth and reproduction capability under environmental changes. We studied the effects of various temperatures and light levels on growth and reproduction for 12 days. The results revealed that the highest growth rate (26.65 ± 1.78 day−1) of the endophytic pest E. siliculosus was at 25 °C and 50 μmol photons m−2 s−1. Furthermore, the gametangium/sporangium formation and gamete/spore release of the pest E. siliculosus preferred 20 °C with medium and high light intensities. In contrast, the worst performances of growth (3.34 ± 0.49 day−1) and reproduction (0.13 ± 0.09 gametangia/sporangia) occurred at the highest temperature (25 °C) and light level (100 μmol photons m−2 s−1). Our study indicate that optimal temperature can stimulate the rapid growth of E. siliculosus, and the strategy of living inside seaweed helps E. siliculosus avoid the excessive sunlight, which is especially critical for the ones inhabiting on the intertidal rocks. The physiological characteristics of endophytic E. siliculosus may help to inform the best pest management strategies for Gracilaria aquaculture.

Effect of polysaccharides derived from brown macroalgae Sargassum dentifolium on growth performance, serum biochemical, digestive histology and enzyme activity of hybrid red tilapia

The present trial conducted to examine the impact of dietary red seaweeds, Sargassum dentifolium polysaccharides supplementation on growth induces, hematological and histological indicators of the hybrid red tilapia Oreochromis mossambicus × Oreochromis niloticus fingerlings. A total of 240 hybrid red tilapia fingerlings with an average body weight of 7.50 ± 0.01 g were divided into four experimental treatments (three replicates each). Four identical isonitrogenous isoenergetic diets except the variation of polysaccharide (SP) levels were formulated. The basal experimental diet (control diet) had no seaweed polysaccharide added (SP0). Diets 2–4 (SP1; SP2 and SP3) was formulated to contained seaweed polysaccharide at levels of 10, 20, and 30 g/kg diet, respectively. Growth performance and feed utilization efficiency of hybrid Red tilapia were significantly (P ≤ 0.05) higher in all treatments receiving SP supplemented-diets than the control diet. The red blood cells (RBCs), hemoglobin (Hb) and hematocrit (Hct, %) values differed significantly (P ≤ 0.05) between the control and fish fed various SP supplemented diets. Considering the dietary SP supplementation, a clear higher trend values of RBC was observed with increasing dietary SP inclusion. Lipase activity recorded the highest values with the fish fed diet supplemented with SP at a level of 20 g/kg-1 associated with the lower significant values amylase activity compared to other treatments. Dietary SP supplementation had no effect on total plasma protein, albumin and globulin levels. Fish fed SP2 diet had an increase in GOT, triglycerides. Fish fed SP3 recorded the lowest value of total cholesterol and LDL when compared to other diets. No abnormal or histological changes were detected in sections of liver, stomach and intestine of red tilapia fed different dietary supplemented with SP levels. The findings of current trial revealed that hybrid Red tilapia fed diets containing red seaweeds, polysaccharides for 12 weeks had enhanced performance, feed conversion ratio and hematological indices.

The effects of desiccation and salinity gradients on the PSII photochemical efficiency of an intertidal brown alga, Sargassum fusiforme from Kagoshima, Japan

SUMMARYThe responses of photochemical efficiency to desiccation and salinity gradients in an intertidal edible brown macroalga, Sargassum fusiforme (Harvey) Setchell (Sargassaceae, Fucales), were determined using a pulse amplitude modulation (PAM)‐chlorophyll fluorometer. The effective quantum yields (ΔF/Fm'; = ΦPSII) of photosystem II (PSII) dropped to zero after 360‐min aerial exposure under low irradiance (20 μmol photons m−2 s−1) and 120‐min exposure under high irradiance (700 μmol photons m−2 s−1) for this species at 20°C and 50% relative humidity. Under these conditions, ΔF/Fm' failed to recover to initial levels even after 1‐day rehydration in seawater. In general, ΔF/Fm' decreased as desiccation reduced the absolute water content (AWC, %). Nevertheless, when AWC was above ca. 20%, ΔF/Fm' was mostly restored to initial levels after 1‐day rehydration in seawater, suggesting strong tolerance to dehydration. Furthermore, S. fusiforme appeared to tolerate a broad range of salinity (i.e. 15–50 psu) during six days of culture; however, ΔF/Fm' declined when salinity was &lt;10 and 60 psu. Strong tolerance to dehydration and salinity stress likely provides S. fusiforme an advantage that allows it to flourish in the intertidal habitat.

Sargassum wightii Aqueous Extract Improved Salt Stress Tolerance in Abelmoschus esculentus by Mediating Metabolic and Ionic Rebalance

Salinity stress has hindered the growth and yield of crops globally. The demands for inducing salt stress tolerance by natural and biological sources with potent antioxidants and growth-promoting metabolites have been the main focus of the recent era. Therefore, the current research was conducted to extract salt stress tolerance-ameliorating metabolites and growth-promoting hormones from the marine brown macroalgaeSargassum wightiiGreville ex J. Agardh with maximum antioxidant potential used as a liquid fertilizer for okra (Abelmoschus esculentusL.). In the current study, the biochemical analysis showed thatSargassumaqueous extract (SAE) was rich in growth-promoting metabolites, antioxidants, and hormones. Meanwhile, overaccumulation of glycine betaine attracted the focus of the current research dealing with salt stress tolerance amelioration inA. esculentus. The plants supplemented with SAE (2% and 4%) and 0.04% ascorbic acid (AsA) alone and in combinations were subjected to sodium salt stress (NaCl; 75 mM). Results revealed that SAE efficiently promoted the vegetative and reproductive growth of plants by elevating the growth-promoting metabolites and hormones in comparison to control plants. Ionic contents (Na+, K+, Ca2+, and Mg2+) and ratios (K+/Na+, Mg2+/Na+, and Ca2+/Na+) were modulated in SAE-treated plants. SAE also increased the level of carbohydrates, proteins, lipids, carotenoids, and proline and decreased the level of hydrogen peroxide and abscisic acid in salt-treated plants compared with the control groups. Enzymatic activities of catalase, ascorbate peroxidase, and guaiacol peroxidase were also enhanced by SAE treatment upon salt stress. The SAE-mediated stress tolerance amelioration and the positive growth response ofA. esculentuswere further accelerated by AsA (0.04%) supplementation used in combination with SAE (2% and 4%). The current study revealed a novel report of the antioxidant and metabolite-rich algal extract (S. wightii) formulation along with AsA that induced salt stress tolerance and promoted the overall growth performance ofA. esculentusby rebalancing the ionic and metabolic status.

Effects of sampling and storage procedures on 16S rDNA amplicon sequencing results of kelp microbiomes.

Brown macroalgae, including the kelp Saccharina latissima, are of both ecological and increasing economic interest. Together with their microbiota, these organisms form a singular entity, the holobiont. Sampling campaigns are required to study the microbiome of algae in natural populations, but freezing samples in liquid nitrogen is complex in the field, particularly at remote locations. Here we tested two simple alternative methods for sampling the microbial diversity associated with the kelp S. latissima: silica gel conservation of tissue and swab samples preserved in DNA/RNA shield solution. We used these techniques to compare apex and meristem samples from Roscoff (Brittany, France) and evaluated their impact on the results of 16S rDNA metabarcoding experiments. Both methods were able to separate apex and meristem microbiomes, and the results were concordant with results obtained for flash-frozen samples. However, differences were observed for several rare genera and ASVs, and the detection of contaminant sequences in the silica gel-preserved samples underline the importance of including blank samples for this method. Globally, our results confirm that the silica gel technique and swabbing combined with DNA/RNA shield preservation are valid alternatives to liquid nitrogen preservation when sampling brown macroalgae in the field. However, they also underline that, regardless of the method, caution should be taken when interpreting data on rare sequences.

Nordic Blue Carbon Ecosystems: Status and Outlook

Vegetated coastal and marine habitats in the Nordic region include salt marshes, eelgrass meadows and, in particular, brown macroalgae (kelp forests and rockweed beds). Such habitats contribute to storage of organic carbon (Blue Carbon – BC) and support coastal protection, biodiversity and water quality. Protection and restoration of these habitats therefore have the potential to deliver climate change mitigation and co-benefits. Here we present the existing knowledge on Nordic BC habitats in terms of habitat area, C-stocks and sequestration rates, co-benefits, policies and management status to inspire a coherent Nordic BC roadmap. The area extent of BC habitats in the region is incompletely assessed, but available information sums up to 1,440 km2 salt marshes, 1,861 (potentially 2,735) km2 seagrass meadows, and 16,532 km2 (potentially 130,735 km2, including coarse Greenland estimates) brown macroalgae, yielding a total of 19,833 (potentially 134,910) km2. Saltmarshes and seagrass meadows have experienced major declines over the past century, while macroalgal trends are more diverse. Based on limited salt marsh data, sediment C-stocks average 3,311 g Corg m-2 (top 40-100 cm) and sequestration rates average 142 g Corg m-2 yr-1. Eelgrass C-stocks average 2,414 g Corg m-2 (top 25 cm) and initial data for sequestration rates range 5-33 g Corg m-2, quantified for one Greenland site and one short term restoration. For Nordic brown macroalgae, peer-reviewed estimates of sediment C-stock and sequestration are lacking. Overall, the review reveals substantial Nordic BC-stocks, but highlights that evidence is still insufficient to provide a robust estimate of all Nordic BC-stocks and sequestration rates. Needed are better quantification of habitat area, C-stocks and fluxes, particularly for macroalgae, as well as identification of target areas for BC management. The review also points to directives and regulations protecting Nordic marine vegetation, and local restoration initiatives with potential to increase C-sequestration but underlines that increased coordination at national and Nordic scales and across sectors is needed. We propose a Nordic BC roadmap for science and management to maximize the potential of BC habitats to mitigate climate change and support coastal protection, biodiversity and additional ecosystem functions.

Macroalgae contribution to the diet of two sea urchins in Sargassum Beds: Tripneustes depressus (Camarodonta: Toxopneustidae) and Eucidaris thouarsii (Cidaroide: Cidaridae)

Macroalgae availability is thought to be a major driver of the diet of marine herbivores. In subtropical regions, macroalgal biomass is highly seasonal and the diet of herbivores usually varies accordingly. In Sargassum beds in the Gulf of California, Tripneustes depressus and Eucidaris thouarsii dominate the invertebrate fauna and feed on macroalgae, though they represent different trophic levels. The objective of this study was to relate the availability of macroalgae with their potential contribution to the diet of both sea urchins. Macroalgae biomass and composition in Sargassum beds were analyzed in contrasting seasons (winter and summer) at four sites. Also, the food sources and the percent contribution of selected sources were determined by a mixing model analysis using stable isotope values (13C and 15N). In winter and summer, brown macroalgae attained the highest biomass, followed by red and green macroalgae. Red macroalgae showed the highest number of taxa and brown macroalgae the highest biomass. In T. depressus, the red (Gracilaria pachydermatica, Laurencia pedrochei) and brown (D. flabellata and Sargassum horridum) macroalgae made the highest contribution to their diet, consistent with the higher availability of these macroalgae in the local flora throughout the year. In E. thouarsii, mixing model indicate that the red algae Polysiphonia pacifica and G. pachydermatica were the macroalgae species with the greatest contribution to its diet.

Polyphenols of Edible Macroalgae: Estimation of In Vitro Bio-Accessibility and Cytotoxicity, Quantification by LC-MS/MS and Potential Utilization as an Antimicrobial and Functional Food Ingredient.

Macroalgae are a rich source of polyphenols, and their ingestion promotes various health benefits. However, information on factors contributing to health benefits such as antioxidants, antimicrobial properties, bioaccessibility, and cytotoxicity is less explored and often unavailable. Therefore, this study aims to investigate the above-mentioned parameters for the brown and green macroalgae Sargassum wightii and Ulva rigida, respectively, collected from the southeast coast of India. S. wightii exhibited higher antioxidant activity and moderate antimicrobial activity against major food pathogens in an agar well diffusion assay and in the broth microdilution method (MIC50 being <0.5 mg/mL for all microorganisms tested). Both macroalgae extracts exhibited significantly high bioaccessibility of polyphenols. To evaluate the safety of the extracts, in vitro cytotoxicity by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was carried out on the primary cells: mouse splenic lymphocytes. An almost complete decline in the cell viability was seen at considerably high concentration (50 mg/mL), expressing the reasonably high safety of the extracts. The extracts of both macroalgae were quantified for polyphenols, wherein fucoxanthin (9.27 ± 2.28 mg/kg DW) and phloroglucinol (17.96 ± 2.80 mg/kg DW) were found to be greater in the S. wightii apart from other phenolics, like gallic acid, quercetin, vanillin, and ferulic acid. The results signify the tremendous scope for the value addition of S. wightii through extraction and purification of polyphenols for its potential exploitation in functional foods and nutraceuticals or as an antimicrobial ingredient in active or smart packaging.

Consuming fresh macroalgae induces specific catabolic pathways, stress reactions and Type IX secretion in marine flavobacterial pioneer degraders

Macroalgae represent huge amounts of biomass worldwide, largely recycled by marine heterotrophic bacteria. We investigated the strategies of bacteria within the flavobacterial genus Zobellia to initiate the degradation of whole algal tissues, which has received little attention compared to the degradation of isolated polysaccharides. Zobellia galactanivorans DsijT has the capacity to use fresh brown macroalgae as a sole carbon source and extensively degrades algal tissues via the secretion of extracellular enzymes, even in the absence of physical contact with the algae. Co-cultures experiments with the non-degrading strain Tenacibaculum aestuarii SMK-4T showed that Z. galactanivorans can act as a pioneer that initiates algal breakdown and shares public goods with other bacteria. A comparison of eight Zobellia strains, and strong transcriptomic shifts in Z. galactanivorans cells using fresh macroalgae vs. isolated polysaccharides, revealed potential overlooked traits of pioneer bacteria. Besides brown algal polysaccharide degradation, they notably include oxidative stress resistance proteins, type IX secretion system proteins and novel uncharacterized polysaccharide utilization loci. Overall, this work highlights the relevance of studying fresh macroalga degradation to fully understand the metabolic and ecological strategies of pioneer microbial degraders, key players in macroalgal biomass remineralization.

Bioactive peptide production and determination of functional properties using crude water extracts of Ulva lactuca (Chlorophyta) and Sargassum crassifolium (Phaeophyceae) collected from Sri Lanka

ABSTRACT Bioactive peptides of marine macroalgae consist of various functional properties. Ulva lactuca and Sargassum crassifolium are economically important, abundant green and brown macroalgae species in Sri Lanka that are rich in bioactive and functional components. However, few studies have been conducted to identify these bioactive and functional components of seaweeds in the local context. The aim of this study was to determine the best method to generate bioactive peptides from crude water extracts of Ulva lactuca and S. crassifolium and determine the functional properties of their hydrolyzates. Crude proteins of U. lactuca (sample: deionized water, 1:4) and S. crassifolium (sample: deionized water, 1:3) were extracted with water, using previously developed method and then subjected to protein hydrolysis by using papain (65°C, pH 6.00–7.00), α-chymotrypsin (37°C, pH 7.00–8.00), elastase (25°C, pH 8.0–8.50), and protease (60°C, pH 6.50–8.50) enzymes (1:100) under their optimum pH and temperatures for 0, 3, 6, 9, 12, 24 hours followed by heat inactivation at 100°C for 15 min. The best enzyme treatment was selected by conducting 15% SDS PAGE. Accordingly, proteins treated with enzymes followed by heat inactivation at 100°C for 15 min were selected as the best after considering the SDS-PAGE images. These hydrolyzates were used to determine the antioxidant activity (DPPH scavenging activity assay) and metal chelating activity (ferrozine method). Apart from peptides generated by elastase, all protein hydrolyzates had strong antioxidant activity (p < 0.05), but hydrolyzates produced from both crude extracts using α-chymotrypsin exhibited low Fe2+ chelating activity (p < 0.05) while some showed metal releasing activity. Therefore, protein hydrolyzates produced from U. lactuca using papain, protease, and α-chymotrypsin, followed with heat inactivation showed strong antioxidant activity while having very low Fe2+ chelating activity than all protein hydrolyzates of S. crassifolium. Highlights Ulva lactuca and Sargassum crassifolium are promising marine algal resources found in Sri Lankan waters to produce bioactive peptides. Enzymatic hydrolysis can be carried out with different enzymes as papain, α-chymotrypsin, protease, and elastase enzymes under their optimum temperature and pH conditions to produce bioactive peptides. The crude peptides showed high DPPH radical scavenging activities but low Fe2+ chelating activity.

Differences by origin in methylome suggest eco-phenotypes in the kelp Saccharina latissima.

Most kelp species are of high ecological and economic importance worldwide, but are highly susceptible to rising ocean temperatures due to their sessile lifestyle. Due to interference with reproduction, development and growth, natural kelp forests have vanished in multiple regions after extreme summer heat waves. Furthermore, increasing temperatures are likely to decrease biomass production and, thus, reduce production security of farmed kelp. Epigenetic variation, and cytosine methylation as a heritable epigenetic trait, is a rapid means of acclimation and adaptation to environmental conditions, including temperature. While the first methylome of brown macroalgae has been recently described in the kelp Saccharina japonica, its functional relevance and contribution to environmental acclimation is currently unknown. The main objective of our study was to identify the importance of the methylome in the congener kelp species Saccharina latissima for temperature acclimation. Our study is the first to compare DNA methylation in kelp between wild populations of different latitudinal origin, and the first to investigate the effect of cultivation and rearing temperature on genome-wide cytosine methylation. Origin appears to determine many traits in kelp, but it is unknown to what extent the effects of thermal acclimation may be overruled by lab-related acclimation. Our results suggest that seaweed hatchery conditions have strong effects on the methylome and, thus, putatively on the epigenetically controlled characteristics of young kelp sporophytes. However, culture origin could best explain epigenetic differences in our samples suggesting that epigenetic mechanisms contribute to local adaptation of eco-phenotypes. Our study is a first step to understand whether DNA methylation marks (via their effect on gene regulation) may be used as biological regulators to enhance production security and kelp restoration success under rising temperatures, and highlights the importance to match hatchery conditions to origin.

Seasonal ammonium uptake kinetics of four brown macroalgae: Implications for use in integrated multi-trophic aquaculture

The combined culture of fed species (bivalves, fish) and macroalgae, known as integrated multi-trophic aquaculture (IMTA), has been suggested as a method of mitigating localised nitrogen (N) increase from aquaculture, whilst simultaneously culturing macroalgae for commercial applications. The development of IMTA requires an understanding of the N ecophysiology of candidate macroalga species. We examined seasonal variations in ammonium (NH4+) uptake kinetics, carbon to nitrogen (C:N) ratio, pigment content and soluble tissue N of four macroalgae of the phylum Ochrophyta, Ecklonia radiata, Macrocystis pyrifera, Lessonia corrugata, and Phyllospora comosa, from Tasmania, Australia. This study aimed to determine, (1) if the N physiology of the four macroalgal species was suitable for IMTA applications and (2) whether the species had seasonal variations in N ecophysiology which would influence their suitability for IMTA. Macrocystis pyrifera, L. corrugata, and E. radiata exhibited saturable NH4+ uptake kinetics, with a maximum uptake rate (Vmax) during spring, summer and autumn of 200, 45.8 and 45 μmol gDW-1 h-1 and half-saturation constants (Ks) of 361.3, 104.2 and 121 μM, respectively. Phyllospora comosa exhibited biphasic uptake patterns for three out of four months sampled. There were no noticeable seasonal patterns in pigment content or soluble tissue N for any species. C:N ratios increased from spring (October) to autumn (March) in both E. radiata (28.34 – 47.83) and P. comosa (24.99 – 51.62), indicating progressive N limitation though summer and into autumn. Results suggest that M. pyrifera and P. comosa are most suitable for IMTA due to their high NH4+ uptake potential.