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Thomas Wernberg - One of the best experts on this subject based on the ideXlab platform.
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Biology and Ecology of the Globally Significant Kelp Ecklonia Radiata
Oceanography and Marine Biology, 2019Co-Authors: Thomas Wernberg, Melinda A. Coleman, Craig R. Johnson, Russell C. Babcock, Sahira Y. Bell, John J. Bolton, Sean D. Connell, Catriona L. Hurd, Ezequiel M. Marzinelli, Nick T. ShearsAbstract:Ecklonia Radiata is a globally widespread kelp, dominating temperate reefs throughout the southern hemisphere. Throughout much of its range it is the only laminarian kelp and hence plays a key role in facilitating biodiversity and driving food webs, and underpins immense ecological and socioeconomic values. This review synthesises the growing literature on E. Radiata from its phylogeny and distribution through to its biology, ecology and recent changes. It provides an assessment of the state of knowledge and identifies gaps in our understanding of this important species. Despite being tolerant to a wide range of abiotic conditions, recent environmental change has caused direct and indirect loss of E. Radiata forests, with extensive areas transitioning to turf and urchin barrens. Ongoing climate change may require application of multi-faceted and novel strategies to increase resistance and resilience to future conditions. By integrating variation across space, time and environmental change, this review provides a synthesis of the current status and possible future trajectories of E. Radiata forests.
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Appendix A. Photograph of the study species Ecklonia Radiata.
2016Co-Authors: Thibaut De Bettignies, Thomas Wernberg, Paul S. Lavery, Mathew A. Vanderklift, Jim R. Gunson, Graham Symonds, Neil CollierAbstract:Photograph of the study species Ecklonia Radiata
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Appendix C. Relationship between modelled and measured drag for Ecklonia Radiata.
2016Co-Authors: Thibaut De Bettignies, Thomas Wernberg, Paul S. Lavery, Mathew A. Vanderklift, Jim R. Gunson, Graham Symonds, Neil CollierAbstract:Relationship between modelled and measured drag for Ecklonia Radiata
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physiological responses of Ecklonia Radiata laminariales to a latitudinal gradient in ocean temperature 1
Journal of Phycology, 2009Co-Authors: Peter A Staehr, Thomas WernbergAbstract:We tested the ability of sporophytes of a small kelp, Ecklonia Radiata (C. Agardh) J. Agardh, to adjust their photosynthesis, respiration, and cellular processes to increasingly warm ocean climates along a latitudinal gradient in ocean temperature (∼4°C). Tissue concentrations of pigment and nutrients decreased with increasing ocean temperature. Concurrently, a number of gradual changes in the metabolic balance of E. Radiata took place along the latitudinal gradient. Warm-acclimatized kelps had 50% lower photosynthetic rates and 90% lower respiration rates at the optimum temperature than did cool-acclimatized kelps. A reduction in temperature sensitivity was also observed as a reduction in Q10 -values from cool- to warm-acclimatized kelps for gross photosynthesis (Q10 : 3.35 to 1.45) and respiration (Q10 : 3.82 to 1.65). Respiration rates were more sensitive to increasing experimental temperatures (10% higher Q10 -values) than photosynthesis and had a higher optimum temperature, irrespective of sampling location. To maintain a positive carbon balance, E. Radiata increased the critical light demand (Ec ) exponentially with increasing experimental temperature. The temperature dependency of Ec was, however, weakened with increasing ocean temperature, such that the critical light demand was relaxed in kelp acclimated to higher ocean temperatures. Nevertheless, calculations of critical depth limits suggested that direct effects of future temperature increases are unlikely to be as strong as effects of reduced water clarity, another globally increasing problem in coastal areas.
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Spatial variation in juvenile and adult Ecklonia Radiata (Laminariales) sporophytes
Aquatic Botany, 2009Co-Authors: Thomas WernbergAbstract:Juvenile and adult sporophytes of Ecklonia Radiata were counted on in-shore and off-shore reefs at Marmion (Perth, Western Australia), across spatial scales of kilometres, 10s of metres and metres. The position on in-shore reefs vs. off-shore reefs did not influence recruit and adult kelp density. There was considerable site-to-site (kilometres) variation in densities of recruits but not adults. The majority of variation in both recruit and adult densities was found between quadrats separated by a few metres. There was no relationship between abundance of recruits and abundance of adult sporophytes at any of the spatial levels of investigation, suggesting a decoupling of recruitment and canopy processes. The results emphasise the patchy nature of kelp canopy distribution and suggest that relatively small-scale processes, acting on scales of a few metres, are of primary importance in generating heterogeneity in the canopy of these kelps.
Gary A Kendrick - One of the best experts on this subject based on the ideXlab platform.
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canopy understorey relationships are mediated by reef topography in Ecklonia Radiata kelp beds
European Journal of Phycology, 2008Co-Authors: Benjamin D Toohey, Gary A KendrickAbstract:There is a growing body of literature that demonstrates that distributions of macroalgal species are heavily influenced by local-scale processes, such as species competition and small-scale variability in the physical environment. Macroalgal assemblages on shallow temperate reefs in Australia are structured by the presence or absence of kelp canopies. Here we test if the negative influence of a canopy of Ecklonia Radiata differs among reefs with different topographies. Reefs, with complex topography have higher irradiance and greater water motion than topographically simple, horizontal reefs and these physical differences may affect the extent that the canopy shades the understorey. In this study, we quantified the relationship between understorey assemblage structure and the density of the kelp canopy on reefs of different topographies. We also measured sub-canopy irradiance on each reef type and kelp morphology. The kelp canopy had a greater effect on the understorey on reefs with simple, planar topogra...
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Canopy–understorey relationships are mediated by reef topography in Ecklonia Radiata kelp beds
European Journal of Phycology, 2008Co-Authors: Benjamin D Toohey, Gary A KendrickAbstract:There is a growing body of literature that demonstrates that distributions of macroalgal species are heavily influenced by local-scale processes, such as species competition and small-scale variability in the physical environment. Macroalgal assemblages on shallow temperate reefs in Australia are structured by the presence or absence of kelp canopies. Here we test if the negative influence of a canopy of Ecklonia Radiata differs among reefs with different topographies. Reefs, with complex topography have higher irradiance and greater water motion than topographically simple, horizontal reefs and these physical differences may affect the extent that the canopy shades the understorey. In this study, we quantified the relationship between understorey assemblage structure and the density of the kelp canopy on reefs of different topographies. We also measured sub-canopy irradiance on each reef type and kelp morphology. The kelp canopy had a greater effect on the understorey on reefs with simple, planar topogra...
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Survival of juvenile Ecklonia Radiata sporophytes after canopy loss
Journal of Experimental Marine Biology and Ecology, 2007Co-Authors: Benjamin D Toohey, Gary A KendrickAbstract:Abstract The understorey beneath a canopy of the kelp Ecklonia Radiata often contains juvenile sporophytes of the same species. When canopy disturbance occurs, these juvenile sporophytes are exposed to new environmental conditions. If these juvenile sporophytes survive these new conditions, then they become a ready source of kelps to rapidly form a new canopy. This study investigated the potential of pre-existing juvenile sporophytes of E. Radiata to survive post-disturbance conditions and contribute to the rapid formation of a new canopy. The potential of canopy recovery by recruitment of kelp from zoospores was also investigated. These processes were studied at different times during the summer and on reefs ranging in topographic complexity from simple, flat reefs to highly complex, rugose reefs. By tagging juvenile sporophytes after the adult kelp canopy was removed and monitoring them through time, it was demonstrated that most juveniles (> 50%) survived the change in conditions after canopy loss, with some juveniles going on to become members of a new canopy. Approximately 6–47% of tagged sporophytes died within 3–4 days after canopy removal possibly due to excessive photoinhibition and photostress as demonstrated by changes in photosynthetic performance (decreased alpha values) of juveniles. The potential contribution of juvenile sporophytes to the rapid formation of a new canopy appears to be dependent on the timing of canopy removal with late summer–autumn canopy loss favouring faster recovery. Topographically complex reefs had less short-term (7 days) survival of juvenile sporophytes than topographically simple reefs; however this difference was not carried through to the long-term (6 months) abundance of adult kelp in experimental clearings, which was greater on topographically complex reefs. Clearly, juvenile sporophytes in arrested development under existing canopies of the small kelp E. Radiata are important for the rapid recovery of the kelp canopy once adults are lost through physical disturbance.
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Disturbance and reef topography maintain high local diversity in Ecklonia Radiata kelp forests
Oikos, 2007Co-Authors: Benjamin D Toohey, Gary A Kendrick, Euan S. HarveyAbstract:Disturbance of competitive-dominant plant and algae canopies often lead to increased diversity of the assemblage. Kelp forests, particularly those of temperate Western Australia, are habitats with high alpha diversity. This study investigated the roles of broad-scale canopy loss and local scale reef topography on structuring the kelp-dominated macroalgal forests in Western Australia. Eighteen 314 m 2 circular areas were cleared of their Ecklonia Radiata canopy and eighteen controls were established across three locations. The patterns of macroalgal recolonisation in replicate clearances were observed over a 34 month period. Macroalgal species richness initially increased after canopy removal with a turf of filamentous and foliose macroalgae dominating cleared areas for up to seven months. A dense Sargassum canopy dominated cleared areas from 11 to 22 months. By 34 months, partial recovery of the kelp canopy into cleared areas had occurred. Some cleared areas did not follow this trajectory but remained dominated by turfing, foliose and filamentous algae. As kelp canopies developed, the initial high species diversity declined but still remained elevated relative to undisturbed controls, even after 34 months. More complex reef topography was associated with greater variability in the algal assemblage between replicate quadrats suggesting colonising algae had a greater choice of microhabitats available to them on topographically complex reefs. Shading by canopies of either Sargassum spp. and E. Radiata are proposed to highly influence the abundance of algae through competitive exclusion that is relaxed by disturbance of the canopy. Disturbance of the canopy in E. Radiata kelp forests created a mosaic of different patch types (turf, Sargassum-dominated, kelp-dominated). These patch types were both transient and stable over the 34 months of this study, and are a potential contemporary process that maintains high species diversity in temperate kelp-dominated reefs.
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Modification of the physical environment by an Ecklonia Radiata (Laminariales) canopy and implications for associated foliose algae
Aquatic Ecology, 2005Co-Authors: Thomas Wernberg, Gary A Kendrick, Benjamin D TooheyAbstract:Macroalgal canopies modify their surrounding environment and thereby influence the structure of associated algal assemblages. Canopies can modify many factors that can be hard to separate and, consequently, the importance of individual factors often remains unknown. Experiments were carried out to test the hypotheses that Ecklonia Radiata canopies modify light, sediment cover and water motion, and that each of these physical factors separately influence the assemblage of associated foliose algae. We measured light, sediment cover and water motion across six naturally occurring E. Radiata densities and found a reduction in light and sediment cover as kelp density increased. The outcome for water motion was inconclusive. We also manipulated each of these three factors, while controlling for the two others, to determine the separate effects of light, sediment cover and water motion on the assemblage of foliose algae. Reduction in light had a strong effect on the foliose assemblage, reducing species richness and biomass. Reduction in sediment cover and water motion did not cause separate effects at the level of the assemblage, but the biomass of individual species of foliose algae indicated both positive and negative effects. We conclude that E. Radiata canopies at Marmion, Western Australia, modify at least two factors of their physical environment, light and sediment cover. However, only light is modified to an extent where it has effects at the assemblage-level because, in contrast to the effects of sediment cover and water motion, the direction of responses are consistent among individual species of algae.
Peter D. Steinberg - One of the best experts on this subject based on the ideXlab platform.
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Novel ssDNA viruses detected in the virome of bleached, habitat-forming kelp Ecklonia Radiata
Frontiers in Marine Science, 2018Co-Authors: Douglas T. Beattie, Tim Lachnit, Elizabeth A. Dinsdale, Torsten Thomas, Peter D. SteinbergAbstract:Kelp forests provide essential habitats for organisms in temperate rocky shores. Loss of kelp forests has occurred over large areas in a number of temperate regions, including in Australia, where the dominant kelp Ecklonia Radiata has been lost from substantial areas of the shoreline. Loss of E. Radiata has been associated with environmental stressors, including increased temperature and anthropogenic contaminants, as well as biological factors such as herbivory. Disease may also play a role, but there is little information on the role of disease in the loss of kelp from coastal ecosystems or on the potential role of pathogenic microorganisms, such as viruses. E. Radiata across much of its distribution in Australia can develop a “bleached” phenotype, which may be a disease. To investigate whether the phenotype was associated with a potential viral agent, we shotgun sequenced viral particles that were isolated from kelp with normal (healthy) and bleached phenotypes. Each virome consisted of ~380,000 reads, of which ~25 % were similar to known viruses. All samples were dominated by bacteriophages, but novel ssDNA virus sequences were detected that were almost exclusively in viromes from the bleached kelp phenotype. These ssDNA viruses are covered by eleven contigs that contained complete capsids and characteristic rep genes that were 30 – 60 % similar to those of circular, Rep-encoding ssDNA viruses (CRESS-DNA viruses). CRESS-DNA viruses have not previously been described from macroalgae, and the rep genes were similar to CRESS-DNA viruses from marine water samples, snails, crabs, anemones, but also dragonflies. This raises the interesting possibility that the kelp could be a vector of the CRESS-DNA viruses to other organisms that are associated with the bleached state.
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Novel ssDNA Viruses Detected in the Virome of Bleached, Habitat-Forming Kelp Ecklonia Radiata
Frontiers Media S.A., 2018Co-Authors: Douglas T. Beattie, Peter D. Steinberg, Tim Lachnit, Elizabeth A. Dinsdale, Torsten ThomasAbstract:Kelp forests provide essential habitats for organisms in temperate rocky shores. Loss of kelp forests has occurred over large areas in a number of temperate regions, including in Australia, where the dominant kelp Ecklonia Radiata has been lost from substantial areas of the shoreline. Loss of E. Radiata has been associated with environmental stressors, including increased temperature and anthropogenic contaminants, as well as biological factors, such as herbivory. Disease may also play a role, but there is little information on the role of disease in the loss of kelp from coastal ecosystems or on the potential role of pathogenic microorganisms, such as viruses. E. Radiata across much of its distribution in Australia can develop a “bleached” phenotype, which may be a disease. To investigate whether the phenotype was associated with a potential viral agent, we shotgun sequenced viral particles that were isolated from kelp with normal (healthy) and bleached phenotypes. Each virome consisted of ~380,000 reads, of which ~25% were similar to known viruses. All samples were dominated by bacteriophages, but novel ssDNA virus sequences were detected that were almost exclusively in viromes from the bleached kelp phenotype. These ssDNA viruses are covered by 11 contigs that contained complete capsids and characteristic rep genes that were 30–60% similar to those of circular, Rep-encoding ssDNA viruses (CRESS-DNA viruses). CRESS-DNA viruses have not previously been described from macroalgae, and the rep genes were similar to CRESS-DNA viruses from marine water samples, snails, crabs, anemones, but also dragonflies. This raises the interesting possibility that the kelp could be a vector of the CRESS-DNA viruses to other organisms that are associated with the bleached state
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Phlorotannins versus other factors affecting epiphyte abundance on the kelp Ecklonia Radiata.
Oecologia, 1997Co-Authors: J. G. Jennings, Peter D. SteinbergAbstract:We examined factors affecting the abundance and distribution of epiphytes (fouling) on the sublittoral kelp Ecklonia Radiata. We first assessed the importance of phlorotannins as chemical defences against epiphytes by (a) correlating epiphyte loads on different parts of the thallus with the phlorotannin content of those tissues, and (b) experimentally testing the effects of variation in phlorotannin concentration against the settlement and growth of gametes of Ulva lactuca, a common epiphyte in the system. Tissue phlorotannin content was, at best, only weakly related to epiphyte loads, with r2 values typically 10 mg l−1, which is 5 orders of magnitude greater than levels of phlorotannins in the water column around beds of E. Radiata, and 1–3 orders of magnitude greater than estimated levels in the boundary layer at the surface of the plant. We concluded that phlorotannins have a negligible impact on patterns of epiphytism on E. Radiata, and proceeded to investigate other factors influencing the distribution and abundance of epiphytes. In our samples the relative age of different parts of the thallus was strongly correlated with epiphyte abundance, with epiphyte densities greatest on the oldest tissue and least on the youngest. Distal parts of the thalli also had greater epiphyte loads than basal parts. Field experiments in which kelp tissue was suspended at two heights in an E. Radiata forest for varying lengths of time confirmed the importance of the length of time that the tissue was in the water, and its height in the water column, to the development of an epiphyte community. Comparison of epiphyte loads on tissue from primary (smooth) and secondary (rough) laminae in these experiments indicated that surface rugosity also affected fouling. Macroherbivores were rare on E. Radiata, and abundances of mesofauna and epiphytes were positively related, suggesting that grazers were not important determinants of patterns of epiphyte abundance. Although phlorotannins have been previously suggested to play an important role as defences against epiphytes, we suggest that water-soluble compounds such as phlorotannins are less likely to be effective defences against epiphytes than non-polar metabolites, which can adhere to the surface of the producing organism.
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Seasonal variation in the relationship between growth rate and phlorotannin production in the kelp Ecklonia Radiata.
Oecologia, 1995Co-Authors: Peter D. SteinbergAbstract:Most theories for the evolution of plant chemical defences assume that defences are costly. In order to investigate the potential cost of phlorotannin production in the brown alga (kelp) Ecklonia Radiata, I measured the correlation between changes in phlorotannin levels and growth rates for E. Radiata in two seasons, spring and autumn. In spring, when both phlorotannin levels and growth rates in E. Radiata were highest, there was a significant negative relationship between changes in phlorotannin levels and growth, consistent with a cost of phlorotannin production. No relationship was evident in autumn, indicating that moderate levels of phlorotannins and growth could be maintained simultaneously. These and related results suggest that the cost of defence will vary as a function of (1) endogenous patterns of growth or metabolite production and (2) variation in available resources. Evidence for a cost of phlorotannins in E. Radiata adds to the paradox of the maintenance of high levels of phlorotannins in Australasian brown algae.
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In situ exudation of phlorotannins by the sublittoral kelp Ecklonia Radiata
Marine Biology, 1994Co-Authors: J. G. Jennings, Peter D. SteinbergAbstract:Exudation of phlorotannins (polyphenolics) was measured in situ from the sublittoral kelp Ecklonia Radiata at two locations near Sydney, New South Wales, Australia during 1992–1993. Minimally disruptive techniques were used in which individual plants were enclosed within clear plastic bags in order to concentrate exudates. Rates of exudation from E. Radiata were low relative to most previous studies, with a mean rate (averaged across four seasons and two sites) of 5.5 μg g (dry wt)-1 h-1. Exudation was greatest in summer and least in winter at one site, but there were no seasonal differences at a second, more protected site. There was no measurable diurnal variation in exudation rates. Exudation after a period of heavy storms was not significantly different from exudation during calm weather, but severe physical damage to the kelp did increase exudation. Our results suggest that exudation of phlorotannins in temperate Australian waters may be less ecologically important than has been suggested for coastal systems in the Northern Hemisphere.
Victoria A Fairhead - One of the best experts on this subject based on the ideXlab platform.
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Seasonal and depth related variation in the photosynthesis–irradiance response of Ecklonia Radiata (Phaeophyta, Laminariales) at West Island, South Australia
Marine Biology, 2004Co-Authors: Victoria A Fairhead, Anthony C. CheshireAbstract:The photosynthesis–irradiance response of Ecklonia Radiata (C. Agardh) J. Agardh, a common kelp in the temperate southern hemisphere, was investigated in situ throughout the year and across a depth profile at West Island, South Australia. Temperature and irradiance environment altered throughout the year, varying at 3 m between 14–20°C and 279–705 μmol photons m^−2 s^−1. Photosynthetic capacity ( P _m) varied throughout the year between 177–278 μmol O_2 g^−1 dry wt h^−1 at 3 m and 133–348 μmol O_2 g^−1 dry wt h^−1 at 10 m. The irradiance required for sub-saturation of photosynthesis ( E _k) varied between 97–152 and 81–142 μmol photons m^−2 s^−1 for 3 m and 10 m respectively, and the respiration rate varied between 15–36 and 13–20 μmol O_2 g^−1 dry wt h^−1 for 3 m and 10 m. A clear seasonal change in photokinetic parameters was detected and provided strong evidence for a seasonal acclimation response. During winter an increase in the efficiency of light utilisation at low irradiance (α) was accompanied by a decrease in both E _k and that required for photosynthetic compensation. P _m also increased during the winter and autumn months and respiratory requirements decreased. These changes enable E. Radiata to display an optimal photosynthetic performance throughout the year despite significant changes in the surrounding environment.
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Rates of primary productivity and growth in Ecklonia Radiata measured at different depths, over an annual cycle, at West Island, South Australia
Marine Biology, 2004Co-Authors: Victoria A Fairhead, Anthony C. CheshireAbstract:The pattern of growth (biomass accumulation) in Ecklonia Radiata throughout the year and across a depth profile was investigated using the traditional “hole-punch” method, and the information presented in context with concurrently measured in situ net productivity rates. The rate of net daily productivity showed a lack of consistent seasonal variability, remaining constant throughout the year at two of the four depths measured (3 m and 12 m), and becoming higher during winter at another (5 m). Throughout the year, rates of net daily productivity differed significantly across the depth profile. Net daily productivity rates averaged 0.017 g C g^−1 dwt day^−1 and 0.005 g C g^−1 dwt day^−1 at a depth of 3 m (1,394 μmol O_2 g^−1 dwt day^−1) and 10 m (382 μmol O_2 g^−1 dwt day^−1) respectively. In contrast, the biomass accumulation rate of E. Radiata was highly seasonal, with low rates of growth occurring in autumn (0.002 g dwt g^−1 dwt day^−1 at both 3 and 10 m) and summer (0.007 and 0.004 g dwt g^−1 dwt day^−1 at 3 and 10 m respectively) and higher rates in spring (0.016 and 0.007 g dwt g^−1 dwt day^−1 at 3 and 10 m respectively) and winter (0.015 and 0.008 g dwt g^−1 dwt day^−1 at 3 and 10 m respectively). The proportion of assimilated carbon used for biomass accumulation varied throughout the year, between 5% and 41% at 3 m and between 28% and 128% at 10 m. The rates of biomass accumulation at all depths represented only a small proportion of the amount of carbon assimilated annually.
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Rates of primary productivity and growth in Ecklonia Radiata measured at different depths, over an annual cycle, at West Island, South Australia
Marine Biology, 2004Co-Authors: Victoria A Fairhead, Anthony C. CheshireAbstract:The pattern of growth (biomass accumulation) in Ecklonia Radiata throughout the year and across a depth profile was investigated using the traditional “hole-punch” method, and the information presented in context with concurrently measured in situ net productivity rates. The rate of net daily productivity showed a lack of consistent seasonal variability, remaining constant throughout the year at two of the four depths measured (3 m and 12 m), and becoming higher during winter at another (5 m). Throughout the year, rates of net daily productivity differed significantly across the depth profile. Net daily productivity rates averaged 0.017 g C g^−1 dwt day^−1 and 0.005 g C g^−1 dwt day^−1 at a depth of 3 m (1,394 μmol O_2 g^−1 dwt day^−1) and 10 m (382 μmol O_2 g^−1 dwt day^−1) respectively. In contrast, the biomass accumulation rate of E. Radiata was highly seasonal, with low rates of growth occurring in autumn (0.002 g dwt g^−1 dwt day^−1 at both 3 and 10 m) and summer (0.007 and 0.004 g dwt g^−1 dwt day^−1 at 3 and 10 m respectively) and higher rates in spring (0.016 and 0.007 g dwt g^−1 dwt day^−1 at 3 and 10 m respectively) and winter (0.015 and 0.008 g dwt g^−1 dwt day^−1 at 3 and 10 m respectively). The proportion of assimilated carbon used for biomass accumulation varied throughout the year, between 5% and 41% at 3 m and between 28% and 128% at 10 m. The rates of biomass accumulation at all depths represented only a small proportion of the amount of carbon assimilated annually.
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seasonal and depth related variation in the photosynthesis irradiance response of Ecklonia Radiata phaeophyta laminariales at west island south australia
Marine Biology, 2004Co-Authors: Victoria A Fairhead, Anthony CheshireAbstract:The photosynthesis–irradiance response of Ecklonia Radiata (C. Agardh) J. Agardh, a common kelp in the temperate southern hemisphere, was investigated in situ throughout the year and across a depth profile at West Island, South Australia. Temperature and irradiance environment altered throughout the year, varying at 3 m between 14–20°C and 279–705 μmol photons m−2 s−1. Photosynthetic capacity (Pm) varied throughout the year between 177–278 μmol O2 g−1 dry wt h−1 at 3 m and 133–348 μmol O2 g−1 dry wt h−1 at 10 m. The irradiance required for sub-saturation of photosynthesis (Ek) varied between 97–152 and 81–142 μmol photons m−2 s−1 for 3 m and 10 m respectively, and the respiration rate varied between 15–36 and 13–20 μmol O2 g−1 dry wt h−1 for 3 m and 10 m. A clear seasonal change in photokinetic parameters was detected and provided strong evidence for a seasonal acclimation response. During winter an increase in the efficiency of light utilisation at low irradiance (α) was accompanied by a decrease in both Ek and that required for photosynthetic compensation. Pm also increased during the winter and autumn months and respiratory requirements decreased. These changes enable E. Radiata to display an optimal photosynthetic performance throughout the year despite significant changes in the surrounding environment.
Wei Zhang - One of the best experts on this subject based on the ideXlab platform.
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Ecklonia Radiata extract containing eckol protects neuronal cells against Aβ1-42 evoked toxicity and reduces aggregate density.
Food & function, 2020Co-Authors: Srijan Shrestha, Wei Zhang, Alexander J. Begbie, Tara L. Pukala, Scott D. SmidAbstract:Brown seaweed (Phaeophyceae) polyphenolics such as phlorotannins are ascribed various biological activities, including neuroprotection. Of these seaweeds, Ecklonia Radiata (E. Radiata) is found abundantly along South Australian coastal regions; however it has not been explored for various biological activities relative to any component phlorotannins previously ascribed neuroprotective capacity. In the present study, we evaluated neuroprotective activity against the neurotoxic amyloid β protein (Aβ1-42) of an ethanol extract of E. Radiata compared with various additional solvent-solubilised fractions in a neuronal PC-12 cell line. The ethyl acetate fraction comprising 62% phlorotannins demonstrated the most efficacious neuroprotective activity, inhibiting neurotoxicity at all Aβ1-42 concentrations. In addition, this fraction demonstrated a significant reduction in Aβ aggregate density, but did not alter overall aggregate morphology. Centrifugal partitioning chromatography was used to isolate the major component, eckol, in high yield and liquid chromatography-mass spectrometry was used to characterize the major components of the ethyl acetate fraction. Our results demonstrate that the prevalence of eckol-type phlorotannins are associated with neuroprotective bioactivity of E. Radiata, suggestive of potential nutraceutical and biopharmaceutical uses of this brown seaweed phlorotannin in dementia.
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Impact of Ecklonia Radiata extracts on the neuroprotective activities against amyloid beta (Aβ1-42) toxicity and aggregation
Journal of Functional Foods, 2020Co-Authors: Mousa Alghazwi, Suvimol Charoensiddhi, Scott D. Smid, Wei ZhangAbstract:Abstract The impact of extract composition on the neuroprotective activities of Ecklonia Radiata was investigated in multiple neuroprotective assays in vitro. A total of six fractions (crude extract (CE), phlorotannin (PT), polysaccharide (PS), free sugar (FS), low molecular weight (LM), and high molecular weight (HM)) prepared from E. Radiata were used to determine their effects against Aβ1-42 and oxidative stress in neuronal cell line PC-12. Only three fractions (CE, PS, and HM) demonstrated cytotoxicity in at least the highest concentration (100 μg/mL) tested in PC-12 cells. All fractions inhibited apoptosis induced by Aβ1-42 and enhanced neurite outgrowth activity. With the exception of HM, other fractions inhibited the aggregation of Aβ1-42 and demonstrated antioxidant activity against the toxicity induced by hydrogen peroxide. This study highlights the potential of using brown seaweed E. Radiata components for improving neuroprotective activities. Such extracts could be potentially used as functional food or dietary supplements to support neurological function.
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Process and economic feasibility for the production of functional food from the brown alga Ecklonia Radiata
Algal Research, 2018Co-Authors: Suvimol Charoensiddhi, Michael A. Conlon, Christopher M. M. Franco, Andrew J. Lorbeer, Wei ZhangAbstract:Abstract This article provides a case-study for the simulated industrial-scale production of high-value functional food products from the brown seaweed Ecklonia Radiata. Three process scenarios at a batch processing scale of 2000 kg seaweed were assessed for their economic feasibility: Scenario 1: Enzyme-assisted production of a crude seaweed extract; Scenario 2: Scenario 1, followed by fractionation based on different molecular weights (MW); Scenario 3: Ethanolic extraction, followed by enzyme-assisted extraction and separation into high and low MW fractions. Scenario 2 demonstrated greater profitability, with a payback time of 1.6 years and a net present value (NPV) twice that of Scenario 1 (2.1 years and US$ 45.03M). Scenario 3 was not economically feasible, with a negative NPV and payback time that was three times longer than Scenario 1. To improve profitability, Scenario 4 was assessed, which integrated Scenario 1 (at the batch processing scale of 500 kg seaweed) with formulation of the extract as a functional ingredient into a juice-based beverage. This process was more profitable than Scenario 1, with a payback time and NPV of 1.1 years and US$ 89.43M, respectively.
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sequential extraction and characterization of fucoidans and alginates from Ecklonia Radiata macrocystis pyrifera durvillaea potatorum and seirococcus axillaris
Journal of Applied Phycology, 2017Co-Authors: Andrew J. Lorbeer, Suvimol Charoensiddhi, Christopher M. M. Franco, Jelle Lahnstein, Vincent Bulone, Claire Lars, Wei ZhangAbstract: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.
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Polysaccharide and phlorotannin-enriched extracts of the brown seaweed Ecklonia Radiata influence human gut microbiota and fermentation in vitro
Journal of Applied Phycology, 2017Co-Authors: Suvimol Charoensiddhi, Michael A. Conlon, Michelle S. Vuaran, Christopher M. M. Franco, Wei ZhangAbstract:This study aimed to understand the prebiotic potential and contribution of four extract fractions from the brown seaweed Ecklonia Radiata. Four seaweed fractions were tested for their digestibility and prebiotic effects using an in vitro anaerobic fermentation system containing human faecal inocula. After 24 h fermentation, three seaweed fractions, except the phlorotannin-enriched fraction (PF), significantly increased (P < 0.05) total short chain fatty acid (SCFA) production (68.9–97.3 μmol mL−1) compared to the negative controls comprising either of a blank (36.3 μmol mL−1) or cellulose (39.7 μmol mL−1). The low molecular weight (MW) polysaccharide-enriched fraction (LPF) stimulated the growth of beneficial bacteria including Bifidobacterium, Lactobacillus, and Clostridium coccoides. The high MW polysaccharide-enriched fraction (HPF) showed the greatest potential for improving gut health as this fraction was not digestible by enzymes present in the small intestine, and induced significantly higher butyric acid production (8.2 μmol mL−1) than the positive control, inulin (2.3 μmol mL−1). These findings further demonstrate that E. Radiata-derived polysaccharides have the potential to be used as dietary supplements with gut health benefits, worthy of further in vivo studies.
