Durvillaea Potatorum Research Articles

Insights into the in vitro biological properties of Australian beach‐cast brown seaweed phenolics

AbstractFive Australian seaweed species, Phyllosphora comosa, Ecklonia radiata, Durvillaea potatorum, Sargassum fallax, and Cystophora siliquosa, thrive along the country's shorelines. Some of these seaweeds have recognized health benefits but have not been fully investigated in terms of their bioactive components and mechanisms of action. We employed ultrasonication with 70% methanol to extract phenolic compounds from these seaweeds and investigated a range of bioactivities for these extracts, including anti‐inflammatory activity exploring urease inhibition, nitric oxide scavenging activity, protein denaturation inhibition, and protease inhibition. Anti‐diabetic activities were investigated using α‐amylase and α‐glucosidase inhibition assays. Anti‐proliferative and anti‐mitotic activities were evaluated using yeast‐cell and green‐gram models, respectively. Our findings showed that C. siliquosa inhibited nitric oxide, urease, and protease activities, with S. fallax, P. comosa, and E. radiata exhibiting substantial inhibition of protein denaturation. E. radiata displayed inhibitory effects on both α‐amylase and α‐glucosidase, whereas P. comosa targeted only the α‐glucosidase enzyme, indicating different mechanisms of anti‐diabetic activity. In these anti‐mitotic assays, C. siliquosa exhibited low cell viability and a significant anti‐proliferative effect, particularly within 24 h, while E. radiata demonstrated notable inhibition at 48 h. LC‐ESI‐QTOF‐MS/MS investigation identified 48 phenolic compounds, including 19 phenolic acids, 20 flavonoids, and 9 other polyphenols. The presence of these compounds in extracts correlated with observed biological activities. These results support the potential health benefits of these seaweeds and link this activity to the presence of bioactive phenolics.

Applications of seaweed extracts in agriculture: An Australian perspective

AbstractSociety depends on food production. However, agricultural productivity is greatly challenged by extreme climate events and volatility. Seaweed extracts (SWE) have a key role in food production and their use is central to improving agricultural productivity by increasing crop tolerance to stress, improving the efficiency of plant nutrient use, and by contributing to sustainable farm practices. The benefits of SWE to crops have previously been reviewed in the context of the northern hemisphere, but not since 2015 in Australia – specific to its crops and unique stressors. This review is focused on the scientific progress since 2015 and insights from Australian research related to: (i) SWE-stimulated plant responses, (ii) field research on SWE, (iii) optimising the use of SWE in agriculture. The review considers the effects of SWE (made from Durvillaea potatorum and Ascophyllum nodosum) in the field, across crops, seasons, regions, and farming systems in Australia, and research conducted in the laboratory under controlled conditions on model and crop plants at the molecular, cellular, and physiological levels. The results from the review highlight the role of SWE in plant priming responses in laboratory experiments and its association with improved plant tolerance in the field. The review discusses the field effects related to production and fruit quality. The uniqueness of the Australian research is the inclusion of the same SWE in laboratory and field research, and the characterisation of plant responses under challenged and un-challenged conditions. This information provides deeper insights into the actions of SWE and enables growers and agronomists to optimize their field application in Australian agriculture.

Australian brown seaweeds as a source of essential dietary minerals

Seaweeds are rich in essential dietary minerals, often lacking in terrestrial plant foods, with interest in Australian seaweeds rapidly increasing. We screened six Australian brown seaweeds with commercial potential for dietary mineral composition: Cystophora torulosa, Caulocystis uvifera, Durvillaea potatorum, Ecklonia radiata, Hormosira banksii and Phyllospora comosa. Spatial replicates of each species were collected from three non-urbanised sites remote from pollution sources and processed for human consumption. Dried samples were analysed by inductively coupled plasma mass spectrometry (ICP-MS) for 12 essential dietary minerals. Overall dietary mineral composition differed significantly amongst all species, except between sargassaceous species C. torulosa and C. uvifera; but concentrations of individual elements varied in complex ways. All species investigated had high concentrations of dietary minerals essential for optimal human health if consumed in realistic quantities (e.g. 10 g day−1 DW) as part of balanced diets, including the most common dietary minerals deficient in humans (iodine, iron, zinc, magnesium, calcium and selenium): iodine (888 ± 100 mg kg−1 DW) and zinc were highest in P. comosa; iron and calcium were highest in C. torulosa, but calcium was also high in E. radiata, H. banksii and D. potatorum; magnesium was highest in H. banksii, D. potatorum and P. comosa; selenium concentrations exceeded those previously reported for seaweeds for all species, except D. potatorum. The best nutritional outcomes may be achieved by regularly consumption of a diversity of seaweed species. However, further investigation into ways to reduce iodine content in some species may be required to maximise health benefits from regular consumption of these Australian seaweeds.

Effect of Seaweed Extracts on Growth and Yield of China Aster cv. Arka Archana under Prayagraj Agro Climatic Conditions

The objective of this study was to assess the effect of seaweed extracts on the growth and yield of China aster (cv. Arka Archana). Thirteen different treatments,along with control were employed in order to investigate their effects. The treatments consisted of two concentrations (2ML/L and 4ML/L) of Ascophyllum nodosum seaweed extract, two concentrations (2ML/L and 4ML/L) of Durvillaea potatorum seaweed extract, and application intervals of 5, 10, and 15 days.To ensure accuracy and reliability, each treatment in the study was replicated three times using a randomized block design (RBD).Various growth parameters, including plant height (cm), number of leaves, number of branches, plant spread (cm), were examined to assess the plant's growth progress. The yield parameter was assessed by examining flower yield per plant, flower yield per plot, and flower yield per hectare.Among the different treatments, treatment T9 (2ML/L Ascophyllum nodosum applied at 15 days interval) demonstrated the highest values for various parameters, including plant height (53.41 cm), number of leaves (172.78), number of branches (25.40), plant spread (53.33 cm), flower yield per plant (367.15 g), flower yield per plot (2202.92 g), and flower yield per hectare (23.13 t). Conversely, the control group (water spray) exhibited the lowest values across all parameters. These findings led to the conclusion that foliar applications of 2ML/L Ascophyllum nodosum at 15 days interval have the potential to significantly enhance flower yield, making it a promising option for improving overall productivity.

The biostimulant effect of an extract from Durvillaea potatorum and Ascophyllum nodosum is associated with the priming of reactive oxygen species in strawberry in south-eastern Australia

AbstractStrawberry is an important horticultural crop in Victoria, Australia. Grey mould caused by Botrytis cinerea reduces marketable yield and post-harvest quality of strawberry fruit in the region. We conducted two field experiments in Victoria (Coldstream and Warburton) to evaluate the effectiveness of a commercial seaweed extract from Durvillaea potatorum and Ascophyllum nodosum (Seasol®) on the yield, revenue, and post-harvest rot of strawberry fruit. We applied the extract to strawberry crops (cv. Albion) monthly as a combined drench (10 L ha-1) and foliar spray (1:400), with water as a control. Application of the seaweed extract significantly increased strawberry fruit yields by 8-10% and revenue by AU$0.37-0.59 per plant. Furthermore, the extract significantly reduced the incidence and severity of post-harvest rots in strawberry fruit by 52-87%, respectively. The extract did not affect the firmness, soluble solids concentration (SSC), titratable acidity, or SSC:acid of strawberry fruit. In a separate laboratory experiment, we found that growing strawberry in the seaweed extract (1:400) increased the concentration of peroxidase by 50% and doubled H2O2 in roots soon after treatment. Increases in reactive oxygen species are an indicator of a suite of pathways associated with resistance and tolerance of biotic and abiotic stresses. Overall, the results demonstrate that the seaweed extract can act as a commercially-viable biostimulant for strawberry fruit production in south-eastern Australia.

Effect of seaweed extract on avocado root growth, yield and post-harvest quality in far north Queensland, Australia

Seaweed extracts are proven to increase productivity in many agricultural crops, but there is limited research on their use in avocado production. Therefore, we evaluated the effectiveness of a seaweed extract from Durvillaea potatorum and Ascophyllum nodosum on avocado yield, revenue and post-harvest fruit quality in a series of field experiments in Australia, and on seedling root growth in a pot experiment. The field experiments were conducted on commercial farms across three different locations in northern Queensland over four years and utilised avocado trees with different ages, cultivars (Hass and Shepard) and inoculum pressures from Phytophthora cinnamomi. Results showed that the application of the seaweed extract by fertigation significantly improved avocado yield (kg fruit per tree) by 38%, fruit firmness by 4% (skin) and 22% (flesh) and fruit skin colour by 1° (hue), and an upgraded visual ripeness score. The increases in yield were associated with greater number of fruits per tree (up to 42%) indicating the liquid seaweed extract improved fruit set and retention per tree. Regular soil application of the seaweed extract to young trees (cv. Hass) in pots increased the root fresh weight by 22%. Overall, the regular application of the seaweed extract to avocado trees was found to be practical and economically viable for improving fruit production and post-harvest quality in Australian orchards.

Comparative metabolomic profiling of Arabidopsis thaliana roots and leaves reveals complex response mechanisms induced by a seaweed extract.

Seaweed extracts are a prominent class of biostimulants that enhance plant health and tolerance to biotic and abiotic stresses due to their unique bioactive components. However, the mechanisms of action of biostimulants are still unknown. Here, we have used a metabolomic approach, a UHPLC-MS method, to uncover the mechanisms induced following application to Arabidopsis thaliana of a seaweed extract derived from Durvillaea potatorum and Ascophyllum nodosum. We have identified, following the application of the extract, key metabolites and systemic responses in roots and leaves across 3 timepoints (0, 3, 5 days). Significant alterations in metabolite accumulation or reduction were found for those belonging to broad groups of compounds such as lipids, amino acids, and phytohormones; and secondary metabolites such as phenylpropanoids, glucosinolates, and organic acids. Strong accumulations of TCA cycle and N-containing and defensive metabolites such as glucosinolates were also found revealing the enhancement of carbon and nitrogen metabolism and defence systems. Our study has demonstrated that application of seaweed extract dramatically altered the metabolomic profiles of Arabidopsis and revealed differences in roots and leaves that varied across the timepoints tested. We also show clear evidence of systemic responses that were initiated in the roots and resulted in metabolic alterations in the leaves. Collectively, our results suggest that this seaweed extract promotes plant growth and activates defence systems by altering various physiological processes at the individual metabolite level.

Seaweed Extract-Stimulated Priming in Arabidopsis thaliana and Solanum lycopersicum.

Plant priming is an induced physiological state where plants are protected from biotic and abiotic stresses. Whether seaweed extracts promote priming is largely unknown as is the mechanism by which priming may occur. In this study, we examined the effect of a seaweed extract (SWE) on two distinct stages of plant priming (priming phase and post-challenge primed state) by characterising (i) plant gene expression responses using qRT-PCR and (ii) signal transduction responses by evaluating reactive oxygen species (ROS) production. The SWE is made from the brown algae Ascophyllum nodosum and Durvillaea potatorum. The priming phase was examined using both Arabidopsis thaliana and Solanum lycopersicum. At this stage, the SWE up-regulated key priming-related genes, such as those related to systemic acquired resistance (SAR) and activated the production of ROS. These responses were found to be temporal (lasting 3 days). The post-challenge primed state was examined using A. thaliana challenged with a root pathogen. Similarly, defence response-related genes, such as PR1 and NPR1, were up-regulated and ROS production was activated (lasting 5 days). This study found that SWE induces plant priming-like responses by (i) up-regulating genes associated with plant defence responses and (ii) increasing production of ROS associated with signalling responses.

Effect of seaweed extract application on wine grape yield in Australia

Seaweed extracts are agricultural biostimulants that have been shown to increase the productivity of many crops. The aim of this study was to determine the effect of a seaweed extract from the brown algae Durvillaea potatorum and Ascophyllum nodosum as a soil treatment on the yield of wine grapes grown in Australian production and climate conditions. This study used a series of seven field experiments (2012–2017), across five locations, in three Australian states and four cultivars, and analysed data using a linear mixed model approach. The analysis revealed that recurring soil applications of the seaweed extract significantly increased wine grape yield by an average of 14.7% across multiple growing years that experienced climate extremes. Partial budget analysis showed that the use of the seaweed extract increased profits depending on the grape cultivar. This study is the most extensive investigation of its type in Australian viticulture to understand the effect of a soil-applied seaweed extract on wine grape production.

The effect of seaweed extract on tomato plant growth, productivity and soil

This study investigated the effects of seaweed extract (SWE) made from the brown algae Durvillaea potatorum and Ascophyllum nodosum on plants and soil. The application of SWE to soil growing tomato plants showed dual effects. SWE comprehensively improved tomato plant growth (flower clusters, flower number, fruit number, root length, root and shoot dry weight, SPAD) and increased plant productivity (yield and quality). Similarly, SWE application effected soil biology at the soil root zone by increasing total bacterial count and available soil nitrogen and impacting bacterial community diversity with an increase in certain bacterial families linked to soil health. A broader understanding of the effects of SWE on the plant-soil ecosystem may offer breakthrough approaches for sustainable food production.

Ion-exchange purification and structural characterization of five sulfated fucoidans from brown algae.

Fucoidans are a diverse class of sulfated polysaccharides integral to the cell wall of brown algae, and due to their various bioactivities, they are potential drugs. Standardized work with fucoidans is required for structure–function studies, but remains challenging since available fucoidan preparations are often contaminated with other algal compounds. Additionally, fucoidans are structurally diverse depending on species and season, urging the need for standardized purification protocols. Here, we use ion-exchange chromatography to purify different fucoidans and found a high structural diversity between fucoidans. Ion-exchange chromatography efficiently removes the polysaccharides alginate and laminarin and other contaminants such as proteins and phlorotannins across a broad range of fucoidans from major brown algal orders including Ectocarpales, Laminariales and Fucales. By monomer composition, linkage analysis and NMR characterization, we identified galacturonic acid, glucuronic acid and O-acetylation as new structural features of certain fucoidans and provided a novel structure of fucoidan from Durvillaea potatorum with α-1,3-linked fucose backbone and β-1,6 and β-1,3 galactose branches. This study emphasizes the use of standardized ion-exchange chromatography to obtain defined fucoidans for subsequent molecular studies.

Phaeophyceaean (Brown Algal) Extracts Activate Plant Defense Systems in Arabidopsis thaliana Challenged With Phytophthora cinnamomi.

Seaweed extracts are important sources of plant biostimulants that boost agricultural productivity to meet current world demand. The ability of seaweed extracts based on either of the Phaeophyceaean species Ascophyllum nodosum or Durvillaea potatorum to enhance plant growth or suppress plant disease have recently been shown. However, very limited information is available on the mechanisms of suppression of plant disease by such extracts. In addition, there is no information on the ability of a combination of extracts from A. nodosum and D. potatorum to suppress a plant pathogen or to induce plant defense. The present study has explored the transcriptome, using RNA-seq, of Arabidopsis thaliana following treatment with extracts from the two species, or a mixture of both, prior to inoculation with the root pathogen Phytophthora cinnamomi. Following inoculation, five time points (0−24 h post-inoculation) that represented early stages in the interaction of the pathogen with its host were assessed for each treatment and compared with their respective water controls. Wide scale transcriptome reprogramming occurred predominantly related to phytohormone biosynthesis and signaling, changes in metabolic processes and cell wall biosynthesis, there was a broad induction of proteolysis pathways, a respiratory burst and numerous defense-related responses were induced. The induction by each seaweed extract of defense-related genes coincident with the time of inoculation showed that the plants were primed for defense prior to infection. Each seaweed extract acted differently in inducing plant defense-related genes. However, major systemic acquired resistance (SAR)-related genes as well as salicylic acid-regulated marker genes (PR1, PR5, and NPR1) and auxin associated genes were found to be commonly up-regulated compared with the controls following treatment with each seaweed extract. Moreover, each seaweed extract suppressed P. cinnamomi growth within the roots of inoculated A. thaliana by the early induction of defense pathways and likely through ROS-based signaling pathways that were linked to production of ROS. Collectively, the RNA-seq transcriptome analysis revealed the induction by seaweed extracts of suites of genes that are associated with direct or indirect plant defense in addition to responses that require cellular energy to maintain plant growth during biotic stress.

Optimisation of biorefinery production of alginate, fucoidan and laminarin from brown seaweed Durvillaea potatorum

Conventional alginate extraction from brown seaweed uses alkaline conditions to produce soluble sodium alginate as a single product. The objective of this study was to develop and optimise a seaweed biorefinery process to extract polysaccharides of alginate, fucoidan and laminarin from an Australian seaweed species Durvillaea potatorum (giant bull kelp). The addition of acid extraction as the first step and its optimisation have enabled the production of three polysaccharide products of fucoidan and laminarin (F/L), acidic extractable alginate (acid-A1), and alkaline extractable alginate (alkaline-A2). The two alginates have distinctively different biochemical properties compared to the conventional extracted alginate. The optimised acid extraction conditions (0.05 M HCl at 60 °C for 3 h) produced a higher yield (43.57%, w/w) of total polysaccharides (acid-A1, alkaline-A2, and F/L) than that of the conventional processing for single alginate product (38.97%, w/w). This novel biorefinery process yielded polysaccharides with different molecular weight, depending upon the extraction conditions. The molecular weight distribution of acid-A1 was in the size range of 250–500 kDa (93.6%) and <1 kDa (5.9%), alkaline-A2 was in the size range of 250–500 kDa (91.8%) and <1 kDa (8.1%) and F/L was in the size range of 750–1000 kDa (44.3%), 1–250 kDa (48.5%) and <1 kDa (8.8%). The M/G ratio, viscosity and pH solubility range properties of the two alginate products are distinctively different, as well as different from the conventional extracted alginate. The results establish a new biorefinery process incorporating an acid extraction step before alkaline extraction, thereby producing multiple valuable polysaccharide products from a single seaweed feedstock D. potatorum.

Distribution models predict large contractions of habitat‐forming seaweeds in response to ocean warming

AbstractAimUnderstanding the relative importance of climatic and non‐climatic distribution drivers for co‐occurring, functionally similar species is required to assess potential consequences of climate change. This understanding is, however, lacking for most ecosystems. We address this knowledge gap and forecast changes in distribution for habitat‐forming seaweeds in one of the world's most species‐rich temperate reef ecosystems.LocationThe Great Southern Reef. The full extent of Australia's temperate coastline.MethodsWe assessed relationships between climatic and non‐climatic environmental data known to influence seaweed, and the presence of 15 habitat‐forming seaweeds. Distributional data (herbarium records) were analysed with MAXENT and generalized linear and additive models, to construct species distribution models at 0.2° spatial resolution, and project possible distribution shifts under the RCP 6.0 (medium) and 2.6 (conservative) emissions scenarios of ocean warming for 2100.ResultsSummer temperatures, and to a lesser extent winter temperatures, were the strongest distribution predictors for temperate habitat‐forming seaweeds in Australia. Projections for 2100 predicted major poleward shifts for 13 of the 15 species, on average losing 78% (range: 36%–100%) of their current distributions under RCP 6.0 and 62% (range: 27%–100%) under RCP 2.6. The giant kelp (Macrocystis pyrifera) and three prominent fucoids (Durvillaea potatorum, Xiphophora chondrophylla and Phyllospora comosa) were predicted to become extinct from Australia under RCP 6.0. Many species currently distributed up the west and east coasts, including the dominant kelp Ecklonia radiata (71% and 49% estimated loss for RPC 6.0 and 2.6, respectively), were predicted to become restricted to the south coast.Main conclusionsIn close accordance with emerging observations in Australia and globally, our study predicted major range contractions of temperate seaweeds in coming decades. These changes will likely have significant impacts on marine biodiversity and ecosystem functioning because large seaweeds are foundation species for 100s of habitat‐associated plants and animals, many of which are socio‐economically important and endemic to southern Australia.

Is Australian seaweed worth eating? Nutritional and sensorial properties of wild-harvested Australian versus commercially available seaweeds

This study aimed to determine the nutritional composition, perceived quality and palatability of nine Australian seaweeds (wild-harvested species not yet exploited for human consumption; Laurencia filiformis, Codium galeatum, Cystophora polycystidea, Cystophora torulosa, Phyllotricha decipiens, Durvillaea potatorum, Hormosira banksii, Phyllospora comosa, Ecklonia radiata), and compare them to four of the commonest commercially available species (Pyropia tenera, Sargassum fusiforme, Saccharina angustata, Undaria pinnatifida). Nutritional value varied amongst species and inconsistently with time. Four Australian species had higher total lipids than all commercial products in this study and amongst the highest values reported in the literature for seaweeds. Moreover, nine out of 13 species had an omega-6 and omega-3 fatty acid ratio favourable for human health (≤ ~ 1). Eicosapentaenoic acid (EPA) was present in higher concentrations than docosahexaenoic acid (DHA) in all species. Highest DHA concentrations were found in Australian species, whilst EPA was very much higher in Pyropia tenera (nori) than all other species. Crude-fibre and protein contents were high for most Australian and commercially available species on a dry weight basis. A subset of Australian and commercially available seaweeds was prepared and cooked as soup or salad for sensorial (organoleptic) evaluation. There were no significant differences in consumer acceptance of any seaweeds when prepared in the soup, but acceptance of the salad dishes differed significantly, influenced primarily by a preferred texture of commercial hijiki (S. fusiforme) over the Australian species. This study identifies specific Australian seaweeds that may be viable as commercial foods. Regular consumption of 10 g (dwt) of a mixture of the seaweeds tested in this study may improve human health by contributing health-promoting fatty acids, fibre and protein to an omnivorous diet, with higher levels of consumption required for vegetarians and vegans to meet daily requirements of favourable fatty acids and protein from non-animal sources. However, further research must also examine potentially toxic effects of regularly consuming seaweeds in these quantities.

Aboriginal uses of seaweeds in temperate Australia: an archival assessment

Global demand for seaweed has increased dramatically over recent decades and the potential for seaweed aquaculture to address issues around food security and climate-change mitigation are being recognised. Australia is a global hotspot for seaweed biodiversity with a rich, diverse Indigenous history dating back 65,000 years, including an extensive traditional knowledge of Australian natural resources. In our present review of archival literature, we explored the contemporary and historical uses and cultural significance of seaweeds to Indigenous Australians. We found records of seaweed use by Indigenous Saltwater Australians (Australian Aboriginal peoples from coastal areas across the nation who are the Traditional Owners/Guardians and custodians of the lands and waters characterised by saltwater environment) for a variety of purposes including cultural activities, ceremonial activities, medicinal uses, clothing, cultural history, food, fishing, shelter and domestic uses. Species-specific records were rarely recorded (and/or accurately translated) in the archival literature, with the exception of the use of the fucoid bull kelp, Durvillaea potatorum, which was prevalent. Our research is a step forward in the important task of recovering and conserving Indigenous Australian knowledge and customary traditions surrounding coastal resource use. Unlocking this knowledge creates opportunities for the continuance and revitalization of traditional customary practises that may enable innovative Indigenous business activities and product creation, based around food, sustainable natural-fibre technologies and health. Such research also has the potential to enhance a developing Australian seaweed industry by guiding species selection, preparation, use and sustainable resource management. We recommend our findings are used to inform the direction and locations of further research conducted in conjunction with Indigenous coastal communities in Australia’s temperate regions, to explore in more detail the Indigenous Australian’s historical heritage associated with coastal seaweed resources and their uses.

Increased growth response of strawberry roots to a commercial extract from Durvillaea potatorum and Ascophyllum nodosum

The withdrawal of soil fumigants like methyl bromide is forcing strawberry growers to consider supplementary and alternative ways of producing crops. In addition to controlling soil-borne pests, soil fumigation causes an increased growth response in strawberry roots, and the use of biostimulants may offer an alternative to replace this response. We tested the hypothesis that treatment with a commercial extract (Seasol®) from the seaweeds Duvillaea potatorum and Ascophyllum nodosum can increase root growth, and transplant (runner) and fruit yields of strawberry. From 2014 to 2016, we conducted three field trials on strawberry farms in the nursery sector at Toolangi and in the fruiting sector at Coldstream in Victoria, Australia. We applied the seaweed extract as a monthly drench (10 L ha−1) to two cultivars of strawberry (‘Albion’ and ‘Fortuna’), compared with an untreated control. In the nursery sector, use of the extract significantly increased the density of secondary roots (feeder roots) on harvested runners by up to 22%. Treatment with the extract also significantly increased yields of marketable runners by 8–19%. In the fruit sector, use of the extract significantly increased the root length density (root length per volume of soil) of strawberry plants by 38% and marketable fruit yields by 8%. Root length density at final harvest and marketable fruit yield of strawberry were highly correlated (r = 0.94). This relationship provides an insight into the mode of action of seaweed extracts and is discussed. Overall, the results show the potential benefits of the integrated use of seaweed extracts in strawberry production across the nursery and fruit sectors, and their promise for supplementing or replacing the increased growth response provided by soil fumigants.

A morphological and phylogenetic investigation into divergence among sympatric Australian southern bull kelps (Durvillaea potatorum and D. amatheiae sp. nov.)

Genetic analyses can reveal a wealth of hitherto undiscovered cryptic biodiversity. For co-occurring and morphologically similar species, the combination of molecular, ecological and morphological analyses provides an excellent opportunity for understanding some of the processes that can lead to divergence and speciation.The Australian endemic brown macroalga Durvillaea potatorum (Phaeophyceae) was examined with a combination of genetic and morphological approaches to confirm the presence of two separate species and to infer the processes that led to their divergence. A total of 331 individuals from 11 sites around coastal Tasmania were collected and measured in situ for a range of morphological and ecological characteristics. Tissue samples were also collected for each individual to allow genetic analyses using mitochondrial (COI) and nuclear (28S) markers. Genetic analyses confirmed the presence of two deeply divergent clades. The significant morphological differentiation, despite high levels of intra-lineage variability, further supported their recognition as distinct species.We describe a new species, D. amatheiae sp. nov., which is characterised by a narrower and proportionately shorter stipe, shorter total length, and higher number of stipitate lateral blades and branches than D. potatorum (sensu stricto). The occurrence of both species in sympatry along Tasmania’s eastern and western coasts, as well as their contrasting patterns of haplotype diversity, supports a hypothesis of geographical isolation, allopatric speciation and subsequent secondary contact in response to sea level and ocean current change throughout the Pleistocene glaciation cycles. This research contributes to resolving the phylogenetic relationships, taxonomy and evolution of the ecologically keystone kelp genus Durvillaea.

Sequential extraction and characterization of fucoidans and alginates from Ecklonia radiata, Macrocystis pyrifera, Durvillaea potatorum, and Seirococcus axillaris

In a previous study, we optimized the acidic treatment of brown algae to facilitate the efficient sequential extraction of fucoidans and alginates, using a sample of the brown alga Ecklonia radiata. Here, we applied the optimized process to other brown algae feedstocks from South Australia, in order to assess their potential for valorization and to determine whether the process was effective when using different feedstocks. The starting materials included samples of Macrocystis pyrifera, Durvillaea potatorum, Seirococcus axillaris, and two more samples of E. radiata collected from different sites and at different periods. The initial feedstock sample (as used for optimization) was also included for comparison. In terms of product yields, the sequential process appeared to perform similarly for all feedstocks (30–40 % of total available fucoidans and 80–94 % of total available alginates), with the exception of Seirococcus axillaris (5.5 and 74 %, respectively). The remainder of the fucoidans either resisted extraction or were hydrolyzed by the acid treatment. The fucoidan extracts had sulfate contents of 10 to 30 % by weight and fucose contents of 12–30 % by weight and exhibited antioxidant potential, to which the presence of phlorotannins contributed. The quality of the alginates varied, with M. pyrifera yielding the most viscous (599 mPa s) and colorless alginates, while the alginates from S. axillaris had the lowest mannuronic to guluronic acid ratio (0.54), indicating the strongest gel-forming capability.

Quantification of plant growth biostimulants, phloroglucinol and eckol, in four commercial seaweed liquid fertilizers and some by-products

Kelp species such as Ecklonia maxima are widely used as sources of liquid fertilizer for many economically important crops. Phloroglucinol and eckol are active biomolecules isolated from the brown seaweed Ecklonia maxima. They have shown root and growth promoting activity in some crop species. Currently there are many seaweed liquid products available in the markets that are sold as plant biostimulants. In some of these products auxins, cytokinins, polyamines, gibberellins, abscisic acid and brassinosteroids have been quantified and their role in plant growth and development has been well established. But, the presence and quantification of phloroglucinol and eckol in these products have not been determined yet. This would be useful for quality control of the products. In this study, four commercially available seaweed liquid fertilizers were analyzed for phloroglucinol and eckol content using High Performance Liquid Chromatography (HPLC). Additionally, a seaweed dry cake product (‘Plant it’ manufactured by Kelpak® from Ecklonia maxima) and Kelpak® cell wall paste by-product were also assessed for phloroglucinol and eckol content. The liquid seaweed products evaluated in this study were prepared from the seaweeds Ascophyllum nodosum, Durvillaea potatorum and Ecklonia maxima. HPLC analysis of these products showed that eckol content was greater than the known plant growth regulator phloroglucinol in three products. The amount of eckol detected in all the samples ranged from 96 to 860μgL−1. A higher quantity of both phloroglucinol and eckol was recorded for Kelpak® in comparison to the other products. The higher levels of these two plant growth promoting biomolecules in the Kelpak® samples can be attributed to the use of cold cellular-burst technology. More studies are necessary to determine the optimum levels of phloroglucinol and eckol required for plant growth in different liquid seaweed fertilizers.