Dictyota Dichotoma Research Articles

Fucoxanthin and Phenolic Contents of Six Dictyotales From the Tunisian Coasts With an Emphasis for a Green Extraction Using a Supercritical CO2 Method

Dictyotales, a common taxonomic group of brown seaweeds found in warm and temperate waters, are known for their richness in bioactive metabolites. In this study, six species of Dictyotales (Dictyopteris polypodioides, Dictyota dichotoma, Dictyota fasciola, Dictyota spiralis, Padina pavonica, and Taonia atomaria) collected from the Tunisian coasts were investigated for their antioxidant potentials, based on their contents of high added-value bioactive metabolites such as fucoxanthin and polyphenols. Fucoxanthin and polyphenols were analyzed quantitatively by high-performance liquid chromatography (HPLC) and UV spectrophotometer, respectively. The antioxidant property of extracts was also determined based on their ability to scavenge 2,2-Diphenyl-1-picrylhydrazyl (DPPH’s) free radical. Thus, the highest concentrations of fucoxanthin were obtained from T. atomaria and D. polypodioides (5.53 ± 1.2 and 3.43 ± 1.3 mg⋅g–1 dry weight, respectively), while the lowest amount was from D. spiralis (0.23 ± 0.1 m mg⋅g–1 dry weight). Dictyota dichotoma and T. atomaria gave the highest total phenol content (19.3 ± 0.4 and 15.2 ± 1.1 mg GAE⋅g–1 dry weight, respectively). In the second step, supercritical carbon dioxide (ScCO2) was used as a green and environmentally safe technique for the extraction of fucoxanthin from the most abundant species D. polypodioides. The extraction of fucoxanthin by ScCO2 allowed an extraction yield ranging from 0.50 ± 0.04% to 1.32 ± 0.02%, with 60°C temperature and 50-MPa pressure as the best extraction conditions. The maximum fucoxanthin and polyphenol recovery in the extract attained 15 and 64%, respectively. The results strengthen the possible use of Dictyotales from the Mediterranean Sea as a promising source of natural ingredients of health and economic interests contributing to Blue Growth in the region.

Bioactive Phenolic Metabolites from Adriatic Brown Algae Dictyota dichotoma and Padina pavonica (Dictyotaceae).

In this study, the influences of temperature (20, 40 and 60 °C) and extraction solvents (water, ethanol) on the ultrasound-assisted extraction of phenolics from the Adriatic macroalgae Dictyota dichotoma and Padina pavonica were studied. The extracts were analysed for major phenolic sub-groups (total phenolics, flavonoids and tannins) using spectrometric methods, while the individual phenolics were detected by HPLC. The antioxidant activities were evaluated using three methods: Ferric Reducing/Antioxidant Power (FRAP), scavenging of the stabile 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and Oxygen Radical Antioxidant Capacity (ORAC). The aim of the study was also to find the connection between the chemical composition of the extracts and their biological activity. Therefore, principal component analysis (PCA), which permits simple representation of different sample data and better visualisation of their correlations, was used. Higher extraction yields of the total phenolics, flavonoids and tannins were obtained using an alcoholic solvent, while a general conclusion about the applied temperature was not established. These extracts also showed good antioxidant activity, especially D. dichotoma extracts, with high reducing capacity (690–792 mM TE) and ORAC values (38.7–40.8 mM TE in 400-fold diluted extracts). The PCA pointed out the significant influence of flavonoids and tannins on the investigated properties. The results of this investigation could be interesting for future studies dealing with the application of these two algae in foods, cosmetics and pharmaceuticals.

Study of Composition and Composition of Macro Algae Habitat in the Intertidal Zone Water of Sibu Island, Nort Oba District Tidore Islands City Nort Maluku

Macro algae is a part of marine plants whose whole body is called the "thallus". Macro algae are widespread in tropical and sub-tropical waters. The purpose of this study was to determine the composition of the macro algae species, the width of the micro-habitat niches, and the overlapping of the micro-habitat niches in the intertidal zone of the waters of Sibu Island, Oba Utara District, Tidore Islands City. The data was collected using survey method using belt transects and squares measuring 1x1 m2 which are placed systematically in zigzags along the tansek belt. In this study, 20 species of macro algae were found in the waters of the island of Sibu, consisting of Halimeda macroloba, Halimeada opuntia forma chordata, Halimeda incrassata, Halimeda opuntia forma renschii, Chaetamorpha sp, Eucheuma cottonii, Sargassum duplicatum, S.polycestum, Turbina ornata, T. conoides, Padina boergesenii, Dictyota dichotoma, Amphiroa fragilissima, Acanthopora spicifera, Eucheuma denticulatum, E. spinosum, Glacilaria salicornia, Hypnea nidulans, Galaxaura apiculata. The results of the analysis of the width of the recesses showed that the macro algae species with the largest recess width were Eucheuma denticulatum with a value of 0.905, while Galaxura apiculata had the narrowest recess widths with a value of 0.200. Furthermore, based on the results of overlapping analysis of microhabitat niches, it shows that the overlap of microbaitate niches is quite large by Sargassum polycestum against Galaxaura apiculata with a value of 0.337, while the lowest was carried out by Halimeda macroloba against Galaxaura apiculata, Halimeda opuntia forma chordata against Galaxaura apiculata with a value of 0.337, while the lowest was carried out by Halimeda macroloba against Galaxaura apiculata, Halimeda opuntia forma chordata against Galaxaura apiculata, Eucheuma spinosum against Galaxaura apiculata with a value of 0.000.

Spatial-temporal changes of macrophytobenthos in the coastal zone of the Reserve “Karan’sky” (Sevastopol City, Black Sea)

For the first time, a comparative analysis of the specific diversity, changes in the biomass of macrophytobenthos in the reserve “Karan’sky” coastal zone from 1964 to 2016 was performed on the basis of a landscape approach. A landscape map of the underwater coastal slope has been drawn up, three bottom natural complexes (BNC) have been identified. The BNC of psephite deposits dominated by C. crinita and Tr. barbata (up to 89.7–78.6% of the total biomass of macrophytes) is the main one. This complex is characterized by high floristic diversity and maximum values of the biomass of macrophytobenthos. The BNC of psephite deposits with C. crinita and Tr. barbata to predominate and with pebble-gravel deposits with broken shells alternate, where Ph. crispa is the dominant species, is characterized by high floristic diversity and a decreased proportion of C. crinite and Tr. barbata, the contribution of Ph. crispa to the total biomass of macrophytes is 14.4%. The BNC of psammitic deposits with Ph. crispa to predominate and with separately randomly located blocks, where Nereia filiformis and Zanardinia typus predominate, is characterized by low floristic diversity, the predominance of Phyllophora crispa (74.3% of the total biomass of macrophytes), and the preservation of perennial species. For more than 50 years, there was a reorganization and degradation of the plant component in all BNC (depth 0.5–10 m), which was probably due to the intensification of anthropogenic activity in the coastal zone. Eudesme virescens, Dictyota dichotoma, Feldmania irrgularis, Dasya baillouviana and Rhodochorton purpureum, which live in clean, open areas of the coast, have disappeared from the bottom vegetation, and macrophytes (Cladophora laetevirens, Ectocarpus siliculosus and C. virgatum), typical for eutrophic waters, have appeared in the duodenum. The biomass of epiphytes has increased (from 0.1 to 42.6% of the total biomass of macrophytes), and the role of dominant species has decreased: C. crinita, Tr. barbata (from 99.9 to 78.6%) and Ph. crispa (from 52.9 to 14.4% of the total biomass of macrophytes). The organization of the “Karan’sky” Reserve contributed to the preservation and partial restoration of the unique natural complex of marine flora and bottom vegetation, which is confirmed by the increased floristic diversity of algaeindicators of clean waters and the increased proportion of the Red Data Book species.

Anti-glycation effects of brown algae extracts and its phenolic compounds

In this study, 50% (v/v) ethanolic extracts from 12 brown algae species were investigated for their antiglycation effects. Three glycation models, namely (bovine serum albumin with fructose [Fru-BSA], glyoxal [BSA-GO], and methylglyoxal [BSA-MGO]) were used for screening. Ecklonia cava (Ec), Leathesia difformis (Ld), and Dictyota dichotoma (Dd) exhibited the highest levels of advanced glycation end-product (AGE) inhibition in the Fru-BSA model. Ec exhibited the highest levels of advanced glycation end-product (AGE) inhibition in the BSA-MGO and BSA-GO models. Further, Ec extract exhibited the highest total antioxidant activity and phenolic content. The phenolic compounds in the extracts were identified using high-performance liquid chromatography. The AGE inhibition effects of the identified phenolic compounds (dieckol, phlorofucofuroeckol-A, gallic acid, catechin, and quercetin) were measured to evaluate the predominant AGE inhibitor among the phenolic compounds. Among the standard phenolic compounds, phlorofucofuroeckol-A and dieckol exhibited lower IC50 values in the BSA-GO and BSA-MGO models. Pearson's correlation analyses showed that dieckol, phlorofucofuroeckol-A, and quercetin in the extracts were positively correlated with BSA-MGO (r > 0.90, p < 0.001) and BSA-GO (r > 0.84, p < 0.001), whereas no significant correlation was observed between other phenolic compounds (gallic acid and catethin) and AGE inhibition effects. The findings of this study suggest that Ec extract is a suitable natural source of antiglycation agents, and that dieckol is its predominant AGE inhibitor.

Characteristic Volatile Composition of Seven Seaweeds from the Yellow Sea of China.

Plant volatile organic compounds (VOCs) represent a relatively wide class of secondary metabolites. The VOC profiles of seven seaweeds (Grateloupia filicina, Polysiphonia senticulosa, Callithamnion corymbosum, Sargassum thunbergii, Dictyota dichotoma, Enteromorpha prolifera and Ulva lactuca) from the Yellow Sea of China were investigated using multifiber headspace solid phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME/GC–MS), among them, the VOCs of three red algae Grateloupia filicina, Polysiphonia senticulosa, and Callithamnion corymbosum were first reported. Principal component analysis (PCA) was used to disclose characteristic categories and molecules of VOCs and network pharmacology was performed to predict potential biomedical utilization of candidate seaweeds. Aldehyde was found to be the most abundant VOC category in the present study and (E)-β-ionone was the only compound found to exist in all seven seaweeds. The chemical diversity of aldehydes in E. prolifera suggest its potential application in chemotaxonomy and hinted that divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber is more suitable for aldehyde extraction. VOCs in D. dichotoma were characterized as sesquiterpenes and diterpenes and the most relevant pharmacological pathway was the neuroactive ligand–receptor interaction pathway, which suggests that D. dichotoma may have certain preventive and therapeutic values in cancer, especially in lung cancer, in addition to neuropsychiatric diseases.

Depth-related plasticity in the diet composition of Pseudechinus magellanicus (Echinoidea, Temnopleuridae) in nearshore environments off central Patagonia, Argentina

Pseudechinus magellanicus is one of the most abundant sea urchins in southern South America, but many aspects of its feeding ecology in nearshore environments remain unknown. Here, we aimed to analyze the variability of the diet composition along a coastal depth gradient from intertidal tidepools to upper circalittoral zones and examine the relation between seaweed availability and the diet composition at intertidal tidepools. A total of 118 food items, including seaweeds and animal components, were identified. The diet composition showed a large variation between the different coastal habitats present along the depth gradient studied. In tidepools, articulate coralline seaweeds (Corallina spp.), mussel shell fragments and small crustaceans were frequent in the gut contents, suggesting that this species behaves like a general omnivore but can also act as a mussel bioeroder when consuming epizoic algae and microeuendolithic organisms. In intertidal tidepools, the species showed a negative preference toward typical species of late successional stages such as Dictyota dichotoma, Adenocystis utricularis, Codium fragile and Chondria macrocarpa. Sea urchins from kelp forests showed higher dietary diversity than those from intertidal and deeper subtidal habitats, but with prevalence of kelps. At upper circalittoral soft bottoms, diverse detrital items as benthic diatoms, cyanobacteria and drifted algae were observed in gut contents, usually associated with fine sediments, indicating that P. magellanicus captures drifted algae and behaves like a biofilm feeder. This trophic plasticity may allow this species to occupy contrasting habitats and may also contribute to explain its wide distribution in southern South America.

In vitro antifungal activity screening of beach-cast seaweeds collected in Yucatan, Mexico

The use of natural products in fungal disease control is an approach to reduce the negative impact of synthetic fungicides in agriculture and the environment. Although there are many alternatives, beach-cast seaweeds are a natural source of novel compounds that can be useful against fungal phytopathogens. In this study, aqueous extracts (AEs) of five species of beach-cast seaweeds, Agardhiella subulata, Bryothamnion triquetrum, Codium isthmocladum, Dictyota dichotoma, and Halymenia floresii, collected in Yucatan, Mexico, were tested against Fusarium oxysporum, Colletotrichum gloeosporioides, and Pseudocercospora fijiensis by dilution assays. From these, only H. floresii AE showed antifungal activity against P. fijiensis (13.7 mg mL−1). Furthermore, the protein fraction isolated from this AE was also active against P. fijiensis at 0.625 μg mL−1. The chromatographic profile of H. floresii AE with antifungal activity showed three major peaks at retention times (tR) 1.6, 23.0, and 23.9 min, respectively. Analysis of solids in H. floresii AE after lyophilization revealed a possibly sulfated polysaccharide (carrageenan) derivative. The toxicity analysis on Artemia salina showed that this aqueous extract is safe.

Characterization of sodium alginate extracted from brown seaweeds growing on Veraval coast, Gujarat

Marine environment is a major potential source of functional materials, including polysaccharides, vitamins, enzymes, oils, antioxidants and peptides. All these materials are extracted from different marine living organisms including microbes, plants and animals. Among these seaweeds or marine macroalgae are one of the important sources and they are a part of staple diet from time immemorial in the orient as they are nutritionally rich materials. Those species that adapted to these pressures will expand their living boundaries and higher potential of row material availability in industry like pharmaceutical market, textile, fertilizer and for animal and human consumption. The present study concerns about the specific brown seaweeds, which is suitable material for alginate and growing abundantly at seacoast of Gujarat. Out of many species of seaweeds growing on the coastline of Veraval, four species viz., Sargassum tenerrimum, Dictyota dichotoma, Spathoglossum asperum, Iyengaria stellata were selected for alginate extraction. The focus of this study is to utilize natural resources as alternatives and sustainability of human health to use sodium alginate as novel polymer and which is also biodegradable. It may be associated to other biologically active molecules and has a wide range of physicochemical and biochemical properties. Because of amazing properties, alginate and its salts are used in drug delivery system.

Characterization of Native Alginates of Common Alginophytes from the Red Sea Coast of Sudan

The objective of this investigation was to investigate the content, viscosity, and major functional groups of the native alginates extracted from 4 alginophytes collected from the Red Sea coast of Sudan in order to evaluate the quality of the polymer for potential applications. The content of the polymer ranged from 7.99±2.60% to 19.1±1.62% based on dry weight in the 4 seaweeds. The peak characteristics of the major functional groups of alginates were identified between 3469.70 cm-1 to 451.31 cm-1. These peaks specify the presence of hydroxyl (OH), carbonyl (C=O), and carboxyl (COOH) groups, respectively. The M/G ratios of the alginate extracted from the Sudanese brown macroalgae are ≤ 1 indicating that the proportion of guluronic acid is slightly greater than the mannuronic acid. The alginate with highest viscosity was that of Padina pavonica (Linnaeus) Thivy (190.7±1.14 mPa.s) followed by Dictyota dichotoma (Hudson) J.V.Lamouroux (146.96±1.2 mPa.s), Turbinaria ornata (Turner) J.Agardh (140.1±1.14 mPa.s), and Hormophysa cuneiformis (J.F.Gmelin) P.C.Silva (109±0.6 mPa.s). The values of the parameters of the native alginates extracted from the Sudanese macroalgae are comparatively in conformity with values reported for some species from similar geographical regions. These values indicated that the present biopolymer is of a potential with regard to pharmaceutical and industrial applications.

Brown Algal Model Organisms.

Model organisms are extensively used in research as accessible and convenient systems for studying a particular area or question in biology. Traditionally, only a limited number of organisms have been studied in detail, but modern genomic tools are enabling researchers to extend beyond the set of classical model organisms to include novel species from less-studied phylogenetic groups. This review focuses on model species for an important group of multicellular organisms, the brown algae. The development of genetic and genomic tools for the filamentous brown alga Ectocarpus has led to it emerging as a general model system for this group, but additional models, such as Fucus or Dictyota dichotoma, remain of interest for specific biological questions. In addition, Saccharina japonica has emerged as a model system to directly address applied questions related to algal aquaculture. We discuss the past, present, and future of brown algal model organisms in relation to the opportunities and challenges in brown algal research.

Iodine and fluorine concentrations in seaweeds of the Arabian Gulf identified by morphology and DNA barcodes

Abstract Even though seaweeds have been recognized as key players in the ocean-to-atmosphere transfer of iodine in other parts of the world, there is a complete lack of knowledge about iodine accumulation in seaweeds of the Arabian Gulf. Similarly, very little is known about fluorine in seaweeds, anywhere in the world. Given that the Arabian Gulf is of particular interest due to being an extreme environment, featuring some of the highest temperatures and salinities observed in any marine water body worldwide, this study endeavoured to conduct a preliminary survey of iodine and fluorine levels in 11 of the most common seaweed species in the region, supported by morphological and molecular (DNA barcode)-based identification. Iodine was determined by inductively-coupled plasma-mass spectrometry, while ion chromatography was employed for analysis of fluoride. Species surveyed included Iyengaria stellata, Padina boergesenii, Chondria sp. Dictyota dichotoma, Colpomenia sinuosa, Feldmannia indica, Codium papillatum, Sargassum ilicifolium, S. ilicifolium var. acaraeocarpum, Sargassum asperifolium and Sargassum aquifolium. The findings of S. ilicifolium and S. ilicifolium var. acaraeocarpum reported here are new records both for Kuwait and the Arabian Gulf. P. boergesenii and D. dichotoma are new records for Kuwait.

Bio-functionalized Gold Nanoparticles: A Potent Probe for Profound Antibacterial Efficiency through Drug Delivery System

In the present manuscript, we reported extracellular biosynthesis of gold nanoparticles through extract of leaves from Dictyota dichotoma. Biosynthesized nanoparticles were characterized using UV– Vis spectroscopy, HRTEM, EDX and FTIR spectroscopy. The polyshaped gold nanoparticles of size 8±21 nm were synthesized. The antibacterial activities were observed by the agar well diffusion method for the action of Streptomycin and Gentamycin and their formulation with biocapped gold nanoparticles. The profound efficacies were supported by the increase in fold area of inhibition against the tested bacteria. The appropriate cause of this divergence has also been discussed due to suitable binding of biogenic gold nanoparticles with drugs and supports these findings to overcome the conflict of previously reported data.

Exploring the Role of Macroalgal Surface Metabolites on the Settlement of the Benthic Dinoflagellate Ostreopsis cf. ovata

Macroalgae constitute one of the preferred substrates of the benthic dinoflagellate Ostreopsis cf. ovata. Across the Mediterranean Sea, this toxic microalga has been shown to thrive on the surface of various species of macroalgae, including Chlorophyta, Rhodophyta and Phaeophyceae. Interestingly, some Dictyotaceae are characterized by a low abundance of cells of O. cf. ovata on their surface. Based on the antifouling properties of some specialized metabolites produced by seaweeds, macroalgal metabolites have been proposed to contribute to the settlement and development of O. cf. ovata. To address this question, the composition of the surface of four Dictyotaceae, Dictyota dichotoma, Dictyota spiralis, Taonia atomaria and Padina pavonica was investigated through an integrative approach combining the analysis of their eukaryotic diversity (18S rRNA gene metabarcoding), their surface metabolome (untargeted LC-MS-based metabolomics) as well as the bioactivity of their surface extracts on O. cf. ovata. Altogether, the data suggest an influence of the macroalgal surface chemistry on the growth of the dinoflagellate, with D. dichotoma being the most bioactive. Some metabolites are proposed to be involved in the observed bioactivity. Other biotic factors are also likely to be entailed in the control of the O. cf. ovata population and they may even prevail on the influence of the macroalgal surface chemistry.

Multidrug-resistant antibacterial activity and active compound analysis several types of seaweed from Karimunjawa, Jepara

Pathogenic bacteria that recently infect humans have been undergone an evolution. The evolution of treatment measures is not in accordance with the dose. Several cases in hospitals have found multi-type bacterial drug resistance. These cases affected much death of the patient. Therefore, this study explores the seaweed from the Karimunjawa Islands, Jepara as the potential sources of new antibacterial active compounds. The study is conducted in the laboratory and used the experimental design of sampling, extraction, resistance test, antibacterial extract test, and analysis of extract active compounds. There are three types of seaweed sampled: S. crassifolium, Padina australis and Dictyota dichotoma. Each extraction is carried out with diethyl ether, methanol, ethanol and chloroform solvents. This study used pathogenic bacterial isolates: Pseudomonas aeruginosa, Staphylococcus epidermidis, Staphylococcus aureus and Escherichia coli which are tested with 13 antibiotics. The resistance test showed the value of multiple antibiotic resistance index (mar) of 0.84; 0.76; 0.48 and 0.34. Antibiotics with a high percentage resistance value (100%) are from groups of lipopeptides (colistine sulfate) and (3-lactams groups (ampicillin). The seaweeds extract tested for antibacterial activity at different concentrations. The results showed that different types and concentrations of extracts had different antibacterial activity values (p <0.05). The extract with high antibacterial activity is an extract from seaweed S crassifolium with methanol solvent. The extract contained phenol 12 mg/g, flavonoid 1.6%, tannin 0.63%, fucoxanthin 0.59 mg/g, carotenoid 165.9 g/g, chlorophyll-a 0.92 mg/g and chlorophyll-b 0.28 mg/g.

Extracts of the Brown Alga Dictyota dichotoma (Hudson) J.V. Lamouroux Alleviate Salt Stress in Rice (Oryza sativa L.) During Germination

Algal extracts provide a safe regime for enhancing crop productivity under stressful conditions. The present study evaluated the efficiency of aqueous and ethanolic extracts of the brown alga Dictyota dichotoma in alleviation of salt stress on germination of rice seeds. Firstly, seeds were germinated using the aqueous extract of D. dichotoma at concentrations of 0, 5, 10, 20, and 50 g L−1, prepared either at room temperature (RTE) or by boiling (BLE). The % germination of rice increased from 84% in non-treated seeds to 100% when treated with 20 g L−1 BLE, although this treatment caused reduced uniformity of germination. Embryo growth was maximum at 20 g L−1 of both extracts with superiority of BLE over RTE. In the second experiment, the effect of 20 g L−1 aqueous and ethanolic extracts relative to a balanced nutrient supply on germination of seeds treated with 0, 40, 90, and 170 mM NaCl was investigated. Salinity reduced % germination with delayed onset but high uniformity of germination, whereas algal amendments counterbalanced the effect of salinity to a greater extent relative to the nutrient supply. Upon withdrawal of salt stress, seeds promptly recovered, with more efficient recovery of seeds exposed to 170 mM than from 90 mM NaCl. The lower recovery of salt-treated seeds compared with the control seed germination suggests that rice suffered from the toxic ion effect of salinity on embryo rather than from the osmotic effect. Extracts of D. dichotoma can enhance and also alleviate salinity stress on rice seed germination.

Bioremediation of Ammonium and Phosphates and their Effect on the Macroalgae Dictyota dichotoma (Hudson) Lamouroux Native to the Red Sea Coast, Egypt

IN LABORATORY experiments for eleven days, the effect of dissolved ammonium and phosphate on the absorption, growth, and nutritional content of Dictyota dichotoma was examined to determine their potential application as a nutrient biofilter. Five combinations of phosphates and ammonium concentration (0.8/8, 2/20, 4/40, 6/60, and 8/80μmol/L) were added to Sterile seawater. Molar phosphorus/ nitrogen ratio was 1:10. Over a 24hrs period, 69.2–99.9% of the available ammonium and 90.7–100% of the available phosphate were taken up by D. dichotoma. The highest specific growth rate was 9.3± 0.2% day-1 at 6/60μmol/L while the lowest was 5.11± 0.3% day-1 at 0μmol/L. On the other hand at 8/80μmol/L the biomass was decreased in the second day of treatment. Total soluble carbohydrate, total soluble protein, and total lipids of the tested D. dichotoma were significantly increased with the increase of PO4-3/NH4+ concentration and greater than their respective initial content. The highest averages of total soluble carbohydrate (TSC) (9.79± 0.45% dry wt.), total soluble protein (TSP) (16.3± 0.32% dry wt.) and total lipid (8± 0.30% dry wt.) were observed at the concentration of 6μmol/L for PO4-3 and 60μmol/L for NH4+. Based on these results, D. dichotoma has a strong absorption capacity for ammonium & phosphates, and as bioremediator in eutrophic environments can be a promising applicant.

The aqueous extract and powder of the brown alga Dictyota dichotoma (Hudson) differentially alleviate the impact of abiotic stress on rice (Oryza sativa L.).

Algal supplements can improve crop productivity and afford protection against abiotic stress by virtue of their rich content of plant nutrients and bioactive compounds. The present work investigates the relative efficiency of the biomass and extract of the brown alga Dictyota dichotoma in protection of rice against salinity and water stress. Rice (Oryza sativa L.) cv. Sakha 101 was grown on a silty clay soil amended with the aqueous extract and powder of D. dichotoma under NaCl and PEG 6000 stress at water potential of - 0.492MPa. Abiotic stress, particularly water stress, reduced rice growth and concentrations of K+ and protein but increased soluble sugars, starch, proline and Na+ concentrations of plant tissues, with counterbalancing effect of algal amendment. The benefit of algal amendment was greater for algal extract than algal powder and under water stress than salt stress. Algal amendment and abiotic stress promoted catalase and peroxidase activities in rice leaves with variable effect on polyphenol oxidase. The benefit of D. dichotoma to rice can be related to macro- and micro-nutrients, growth hormones, phenolics, flavonoids, sterols, vitamins and fucoidan. The production of toxic intermediates as a result of fermentation of the algal biomass in the paddy soil might reduce the benefit of algal amendment. Although rice is salt-sensitive, it is more resistant to salt stress than to drought stress. The ability of rice to retain Na+ in the root is pivotal for stress resistance, but the role of K+ partitioning is less evident.

Long-term response of Dictyota dichotoma var. intricata (C. Agardh) Greville (Phaeophyceae) to ocean acidification: Insights from high pCO2 vents

The ocean acidification may severely affect macroalgal communities of the shallowest coastal habitats where they play relevant structural and functional roles. In this paper were investigated the physiological traits of two populations of Dictyota dichotoma var. intricata, living at two different pH for several generations to assess the reasons of the algae reduced abundance at current (8.1) compared to low pH (6.7). Besides, through transplant experiments, the two populations were analysed for the stress response and reversibility of physiological performance at different pH. The long-term acclimation to high pCO2/low pH favours an ecotype characterised by low energetic costs, higher photochemical efficiency and more resistance to the oxidative stress, compared to individuals living at current pH. These traits promoted the growth and reproduction of the community living at pH 6.7, favouring a lower macroalgal diversity, but a higher ecological success under ocean acidification. The similar behaviour observed between Dictyota living at pH 6.7 and transplanted thalli from pH 6.7 to 8.1, suggested a high tolerance to pH changes in the short-term. On the contrary, adaptive responses may have favoured molecular adjustments on the long-term, as showed by the significant differences between the wild populations at pH 8.1 and 6.7. The overall data indicate that both plasticity and adaptive mechanisms may be the reasons for the success of the brown seaweeds under future high pCO2/low pH. The plasticity due to photochemistry adjustments is likely involved in the early response to environmental changes. Conversely, modifications in the photosynthetic biochemical machinery suggest that more complex adaptive mechanisms occurred in the current population of Dictyota living at pH 6.7. Further studies on population genetics will reveal if any differentiation is taking place at the population level or a local adaptation has already occurred in Dictyota and other brown algae under chronic low pH.

Species identification of stranded seaweeds on eastern seashores of Thailand and utilization as a sole carbon source for single cell oils synthesized by oleaginous yeasts

Abstract. Chantarasiri A. 2020. Species identification of stranded seaweeds on eastern seashores of Thailand and utilization as a sole carbon source for single-cell oils synthesized by oleaginous yeasts. Biodiversitas 21: 2353-2361. Many stranded seaweeds are left to decompose on the seashore. This study aimed to identify and utilize the stranded seaweeds collected from seashores in Rayong Province on the east coast of Thailand. Seaweeds were identified as Dictyota dichotoma strain A and Padina australis strain B based on their distinctive morphology and 18S rDNA sequence analyses. The most abundant seaweed, D. dichotoma strain A, was analyzed for chemical compositions following AOAC standard methods. This seaweed was considered a low-cost carbon source for the cultivation of three oleaginous yeasts without any other nutrient supplements. All oleaginous yeasts utilized the carbon source from Dictyota medium for growth and accumulation of single-cell oils (SCOs). The oleaginous yeast, Cryptococcus albidus strain TISTR 5103 accumulated SCOs at 51% (w/w). The resulting SCOs from oleaginous yeasts comprise many fatty acids with 10 to 22 carbon atoms. This study is the first to identify stranded seaweeds in Rayong Province using morphological and genetic techniques. Results showed the potential application of stranded seaweeds as a low-cost carbon source for SCO biosynthesis of oleaginous yeasts.