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1.
Food Chem ; 455: 139926, 2024 Oct 15.
Artículo en Inglés | MEDLINE | ID: mdl-38833868

RESUMEN

Brown seaweed Ecklonia radiata harbors valuable polyphenols, notably phlorotannins, prized for their health benefits. This study optimized phlorotannin extraction via conventional solvent extraction and ultrasound-assisted extraction methods, utilizing variable concentrations of ethanol. Employing fractional factorial designs, key variables were identified. Steepest ascent/descent method and central composite rotatable designs refined optimal conditions, enhancing phlorotannin and polyphenol yields, and antioxidant capacities. Under optimized conditions, phlorotannin contents reached 2.366 ± 0.01 and 2.596 ± 0.04 PGE mg/g, total polyphenol contents peaked at 10.223 ± 0.03 and 10.836 ± 0.02 GAE mg/g. Robust antioxidant activity was observed: DPPH and OH radical scavenging capacities measured 27.891 ± 0.06 and 17.441 ± 0.08 TE mg/g, and 37.498 ± 1.12 and 49.391 ± 0.82 TE mg/g, respectively. Reducing power capacities surged to 9.016 ± 0.02 and 28.110 ± 0.10 TE mg/g. Liquid chromatography-mass spectrometry (LC-MS) and high-performance liquid chromatography (HPLC) analyses revealed enriched antioxidant compounds. Variations in polyphenol profiles were noted, potentially influencing antioxidant capacity nuances. This study illuminated the potential of E. radiata potential as a polyphenol source and offers optimized extraction methods poised to benefit various industries.


Asunto(s)
Antioxidantes , Polifenoles , Algas Marinas , Polifenoles/química , Polifenoles/aislamiento & purificación , Polifenoles/análisis , Antioxidantes/química , Antioxidantes/aislamiento & purificación , Algas Marinas/química , Cromatografía Líquida de Alta Presión , Extractos Vegetales/química , Extractos Vegetales/aislamiento & purificación , Fraccionamiento Químico/métodos , Phaeophyceae/química , Zygophyllaceae/química , Espectrometría de Masas
2.
Mol Ecol ; 33(5): e17267, 2024 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-38230446

RESUMEN

The range-expansion of tropical herbivores due to ocean warming can profoundly alter temperate reef communities by overgrazing the seaweed forests that underpin them. Such ecological interactions may be mediated by changes to seaweed-associated microbiota in response to warming, but empirical evidence demonstrating this is rare. We experimentally simulated ocean warming and marine heatwaves (MHWs) to quantify effects on two dominant temperate seaweed species and their microbiota, as well as grazing by a tropical herbivore. The kelp Ecklonia radiata's microbiota in sustained warming and MHW treatments was enriched with microorganisms associated with seaweed disease and tissue degradation. In contrast, the fucoid Sargassum linearifolium's microbiota was unaffected by temperature. Consumption by the tropical sea-urchin Tripneustes gratilla was greater on Ecklonia where the microbiota had been altered by higher temperatures, while Sargassum's consumption was unaffected. Elemental traits (carbon, nitrogen), chemical defences (phenolics) and tissue bleaching of both seaweeds were generally unaffected by temperature. Effects of warming and MHWs on seaweed holobionts (host plus its microbiota) are likely species-specific. The effect of increased temperature on Ecklonia's microbiota and subsequent increased consumption suggest that changes to kelp microbiota may underpin kelp-herbivore interactions, providing novel insights into potential mechanisms driving change in species' interactions in warming oceans.


Asunto(s)
Kelp , Microbiota , Algas Marinas , Kelp/fisiología , Ecosistema , Cambio Climático , Océanos y Mares
3.
Ann Bot ; 133(1): 153-168, 2024 Mar 08.
Artículo en Inglés | MEDLINE | ID: mdl-37665952

RESUMEN

BACKGROUND AND AIMS: Kelp forests underpin temperate marine ecosystems but are declining due to ocean warming, causing loss of associated ecosystem services. Projections suggest significant future decline but often only consider the persistence of adult sporophytes. Kelps have a biphasic life cycle, and the haploid gametophyte can be more thermally tolerant than the sporophyte. Therefore, projections may be altered when considering the thermal tolerance of gametophytes. METHODS: We undertook thermal tolerance experiments to quantify the effect of temperature on gametophyte survival, relative growth rate (RGR) and sex ratio for three genetically distinct populations of Ecklonia radiata gametophytes from comparatively high, mid- and low latitudes (43°, 33° and 30°S). We then used these data to project the likely consequences of climate-induced thermal change on gametophyte persistence and performance across its eastern Australian range, using generalized additive and linear models. KEY RESULTS: All populations were adapted to local temperatures and their thermal maximum was 2-3 °C above current maximum in situ temperatures. The lowest latitude population was most thermally tolerant (~70 % survival up to 27 °C), while survival and RGR decreased beyond 25.5 and 20.5 °C for the mid- and low-latitude populations, respectively. Sex ratios were skewed towards females with increased temperature in the low- and high-latitude populations. Spatially explicit model projections under future ocean warming (2050-centred) revealed a minimal decline in survival (0-30 %) across populations, relative to present-day predictions. RGRs were also projected to decline minimally (0-2 % d-1). CONCLUSIONS: Our results contrast with projections for the sporophyte stage of E. radiata, which suggest a 257-km range contraction concurrent with loss of the low-latitude population by 2100. Thermal adaptation in E. radiata gametophytes suggests this life stage is likely resilient to future ocean warming and is unlikely to be a bottleneck for the future persistence of kelp.


Asunto(s)
Kelp , Animales , Cambio Climático , Ecosistema , Células Germinativas de las Plantas , Australia , Temperatura
4.
J Phycol ; 59(5): 838-855, 2023 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-37432133

RESUMEN

Sea urchins can cause extensive damage to kelp forests, and their overgrazing can create extensive barren areas, leading to a loss of biodiversity. Barrens may persist when the recruitment of kelp, which occurs through the microscopic haploid gametophyte stage, is suppressed. However, the ecology of kelp gametophytes is poorly understood, and here we investigate if grazing by juvenile urchins on kelp gametophytes can suppress kelp recruitment and if this is exacerbated by climate change. We compared grazing of Ecklonia radiata gametophytes by two species of juvenile urchins, the tropical Tripneustes gratilla and the temperate Centrostephanus rodgersii, at winter (19°C), summer (23°C), and ocean warming (26°C) temperatures for the low-latitude range edge of E. radiata, which is vulnerable to ocean warming. We examined the rate of recovery of gametophytes following grazing and determined whether they survived and formed sporophytes after ingestion by sea urchins. Both T. gratilla and C. rodgersii grazed E. radiata gametophytes, reducing their abundance compared to no grazing controls. Surprisingly, temperature did not influence grazing rates, but gametophytes did not recover from grazing in the ocean warming (26°C) treatment. Gametophytes survived ingestion by both species of sea urchin and formed sporophytes after ingestion by T. gratilla, but not C. rodgersii. These results suggest complex grazer-gametophyte interactions, in which both negative (reduced abundance and poor recovery with warming) and positive (facilitated recruitment) effects are possible. Small grazers may play a more important role in kelp ecosystem function than previously thought and should be considered in our understanding of alternate stable states.


Asunto(s)
Ecosistema , Kelp , Animales , Células Germinativas de las Plantas , Océanos y Mares , Bosques
5.
Mar Drugs ; 21(4)2023 Mar 24.
Artículo en Inglés | MEDLINE | ID: mdl-37103342

RESUMEN

Human colorectal cancer (CRC) is a recurrent, deadly malignant tumour with a high incidence. The incidence of CRC is of increasing alarm in highly developed countries, as well as in middle to low-income countries, posing a significant global health challenge. Therefore, novel management and prevention strategies are vital in reducing the morbidity and mortality of CRC. Fucoidans from South African seaweeds were hot water extracted and structurally characterised using FTIR, NMR and TGA. The fucoidans were chemically characterised to analyse their composition. In addition, the anti-cancer properties of the fucoidans on human HCT116 colorectal cells were investigated. The effect of fucoidans on HCT116 cell viability was explored using the resazurin assay. Thereafter, the anti-colony formation potential of fucoidans was explored. The potency of fucoidans on the 2D and 3D migration of HCT116 cells was investigated by wound healing assay and spheroid migration assays, respectively. Lastly, the anti-cell adhesion potential of fucoidans on HCT116 cells was also investigated. Our study found that Ecklonia sp. Fucoidans had a higher carbohydrate content and lower sulphate content than Sargassum elegans and commercial Fucus vesiculosus fucoidans. The fucoidans prevented 2D and 3D migration of HCT116 colorectal cancer cells to 80% at a fucoidan concentration of 100 µg/mL. This concentration of fucoidans also significantly inhibited HCT116 cell adhesion by 40%. Moreover, some fucoidan extracts hindered long-term colony formation by HCT116 cancer cells. In summary, the characterised fucoidan extracts demonstrated promising anti-cancer activities in vitro, and this warrants their further analyses in pre-clinical and clinical studies.


Asunto(s)
Neoplasias Colorrectales , Fucus , Algas Marinas , Humanos , Línea Celular Tumoral , Sudáfrica , Algas Marinas/química , Polisacáridos/farmacología , Polisacáridos/química , Neoplasias Colorrectales/tratamiento farmacológico , Fucus/química
6.
J Phycol ; 58(6): 760-772, 2022 12.
Artículo en Inglés | MEDLINE | ID: mdl-36054376

RESUMEN

Cystophora is the second largest genus of fucoids worldwide and, like many other forest-forming macroalgae, is increasingly threatened by a range of anthropogenic impacts including ocean warming. Yet, limited ecological information is available from the warm portion of their range (SW Western Australia), where severe range contractions are predicted to occur. Here, we provide the first insights on the abundance, diversity, productivity, and stand structure of Cystophora forests in this region. Forests were ubiquitous over more than 800 km of coastline and dominated sheltered and moderately-exposed reefs. Stand biomass and productivity were similar or greater than that of kelp forests in the temperate reef communities examined, suggesting that Cystophora spp. play a similarly important ecological role. The stand structure of Cystophora forests was, however, different than those of kelp forests, with most stands featuring an abundant bank of sub-canopy juveniles and only a few plants forming the canopy layer. Stand productivity followed an opposite seasonal pattern than that of kelps, with maximal growth in late autumn through early winter and net biomass loss in summer. Annually, stands contributed between 2.2 and 5.7 kg · m-2 (fresh biomass) to reef productivity depending on the dominant stand species. We propose that Cystophora forests play an important and unique role in supporting subtidal temperate diversity and productivity throughout temperate Australia, and urge a better understanding of their ecology and responses to anthropogenic threats.


Asunto(s)
Kelp , Algas Marinas , Bosques , Kelp/fisiología , Biomasa , Australia , Ecosistema
7.
J Fish Biol ; 100(4): 935-943, 2022 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-35229283

RESUMEN

Habitat associations can be critical predictors of larger-scale organism distributions and range shifts. Here the authors consider how a critical habitat, kelp (Ecklonia radiata) and prey (mysid crustacean swarms), can influence small- and large-scale distribution on the iconic common (weedy) seadragon (Phyllopteryx taeniolatus:Syngnathidae). P. taeniolatus are charismatic fish endemic to the temperate reefs of southern Australia, reported to range from Geraldton, Western Australia (28.7667°S, 114.6167°E) around southern Australia to Port Stephens, New South Wales (32.614369°S, 152.325676°E). The authors test a previously developed model of seadragon habitat preferences to predict P. taeniolatus occurrence within four sites from Sydney to the northern limit of their range in eastern Australia. They determined that P. taeniolatus associations with Ecklonia and mysid shrimp can be extrapolated across multiple sites to predict the occurrence of individual P. taeniolatus within a location/site. For instance, the authors demonstrated a significant positive relationship between the density of mysid swarms and the density of P. taeniolatus, evident across all sites despite large differences in the density of mysid swarms among sites. The findings are the first to model P. taeniolatus habitat associations across multiple sites to the northern limit of their range and have applications in protecting P. taeniolatus populations and how they may respond under climate change scenarios, such as poleward kelp retractions.


Asunto(s)
Kelp , Smegmamorpha , Animales , Cambio Climático , Ecosistema , Alimentos Marinos
8.
Mar Pollut Bull ; 175: 113368, 2022 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-35114545

RESUMEN

Outlet infrastructure and hypersaline discharge from large-scale desalination operations have the potential to impact marine environments. Here, we present the results of a six-year M-BACI assessment of the impacts of desalination discharge outlet construction and hypersaline effluent on the cover of habitat-forming species on temperate reefs. The construction of the desalination outlet caused a decrease in the cover of Ecklonia radiata (kelp) and an increase in the cover of algal turfs up to 55 m from the outlet. Following the commencement of discharging of hypersaline brine, the impact to E. radiata and algal turfs persisted, but decreased in spatial extent to be less than 25 m from the outlet. Hypersaline discharge was also associated with a significant decline in the cover of sponges in outlet compared to reference sites. Overall, our results demonstrate that the water security benefits from large-scale desalination may sometimes be appropriately balanced against the associated ecological consequences.


Asunto(s)
Arrecifes de Coral , Ecosistema , Kelp , Salinidad , Purificación del Agua
9.
J Phycol ; 58(1): 92-104, 2022 02.
Artículo en Inglés | MEDLINE | ID: mdl-34612512

RESUMEN

The kelp, Ecklonia radiata, is an abundant subtidal ecosystem engineer in southern Australia. Density-dependent changes in the abiotic environment engineered by Ecklonia may feedback to affect reproduction and subsequent recruitment. Here, we examined: 1) how the reproductive capacity of Ecklonia individuals in the field (zoospores released · mm-2 reproductive tissue) varied with adult density and time, and 2) how the recruitment of microscopic gametophytes and sporophytes was influenced by zoospore density at two times. Zoospore production did not vary with adult density, with only one month out of ten sampled over a 2-y period showing a significant effect of density. However, zoospore production varied hugely over time, being generally highest in mid-autumn and lowest in mid-late summer. There were strong effects of initial zoospore density on gametophyte and sporophyte recruitment with both a minimum and an optimum zoospore density for sporophyte recruitment, but these varied in time. Almost no sporophytes developed when initial zoospore density was <6.5 · mm-2 in spring or <0.5 · mm-2 in winter with optimum densities of 90-355 · mm-2 in spring and 21-261 · mm-2 in winter, which resulted in relatively high recruitment of 4-7 sporophytes · mm-2 . Sporophyte recruitment declined at initial zoospore densities >335 · mm-2 in spring and >261 · mm-2 in winter and was zero at very high zoospore densities. These findings suggest that although adult Ecklonia density does not affect per-capita zoospore production, because there is a minimum zoospore density for sporophyte production, a decline in population-level output could feedback to impact recruitment.


Asunto(s)
Kelp , Phaeophyceae , Ecosistema , Reproducción , Estaciones del Año
10.
J Fish Biol ; 100(1): 175-183, 2022 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-34697812

RESUMEN

The weedy seadragon (Phyllopteryx taeniolatus: Syngnathidae) is an iconic fish endemic to the southern coastal waters of Australia. The authors of this study analysed the habitat preferences and factors influencing microhabitat selection by P. taeniolatus in a population from Kurnell, NSW, Australia. Using field surveys and the resource selection probability function, the authors determined that P. taeniolatus significantly preferred kelp (Ecklonia radiata)-dominated habitat and avoided rock-dominated habitat. They showed P. taeniolatus preferred habitat of between 40% and 80% coverage of Ecklonia, while avoiding areas of <20% cover. Furthermore, across all habitats, mysid prey availability significantly influenced P. taeniolatus habitat selection. The strong dependence of P. taeniolatus on Ecklonia habitat shown in this study was previously untested and highlights that reductions in Ecklonia cover under climate change, or impacts from increasing urbanisation, may render seadragon populations vulnerable to declines.


Asunto(s)
Kelp , Smegmamorpha , Animales , Ecosistema , Peces , Urbanización
11.
J Phycol ; 58(1): 22-35, 2022 02.
Artículo en Inglés | MEDLINE | ID: mdl-34800039

RESUMEN

Marine heatwaves (MHWs), discrete periods of extreme warm water temperatures superimposed onto persistent ocean warming, have increased in frequency and significantly disrupted marine ecosystems. While field observations on the ecological consequences of MHWs are growing, a mechanistic understanding of their direct effects is rare. We conducted an outdoor tank experiment testing how different thermal stressor profiles impacted the ecophysiological performance of three dominant forest-forming seaweeds. Four thermal scenarios were tested: contemporary summer temperature (22°C), low persistent warming (24°C), a discrete MHW (22-27°C), and temperature variability followed by a MHW (22-24°C, 22-27°C). The physiological performance of seaweeds was strongly related to thermal profile and varied among species, with the highest temperature not always having the strongest effect. MHWs were highly detrimental for the fucoid Phyllospora comosa, whereas the laminarian kelp Ecklonia radiata showed sensitivity to extended thermal stress and demonstrated a cumulative temperature threshold. The fucoid Sargassum linearifolium showed resilience, albeit with signs of decline with bleached and degraded fronds, under all conditions, with stronger decline under stable control and warming conditions. The varying responses of these three co-occurring forest-forming seaweeds under different temperature scenarios suggests that the impact of ocean warming on near shore ecosystems may be complex and will depend on the specific thermal profile of rising water temperatures relative to the vulnerability of different species.


Asunto(s)
Kelp , Phaeophyceae , Algas Marinas , Ecosistema , Bosques , Kelp/fisiología , Temperatura
12.
Pharmaceutics ; 13(11)2021 Nov 22.
Artículo en Inglés | MEDLINE | ID: mdl-34834394

RESUMEN

Although there are chemotherapeutic efforts in place for Type 2 diabetes mellitus (T2DM), there is a need for novel strategies (including natural products) to manage T2DM. Fucoidan, a sulphated polysaccharide was extracted from Ecklonia radiata. The integrity of the fucoidan was confirmed by structural analysis techniques such as FT-IR, NMR and TGA. In addition, the fucoidan was chemically characterised and tested for cell toxicity. The fucoidan was investigated with regards to its potential to inhibit α-amylase and α-glucosidase. The fucoidan was not cytotoxic and inhibited α-glucosidase (IC50 19 µg/mL) more strongly than the standard commercial drug acarbose (IC50 332 µg/mL). However, the fucoidan lacked potency against α-amylase. On the other hand, acarbose was a more potent inhibitor of α-amylase (IC50 of 109 µg/mL) than α-glucosidase. Due to side effects associated with the use of acarbose, a combination approach using acarbose and fucoidan was investigated. The combination showed synergistic inhibition (>70%) of α-glucosidase compared to when the drugs were used alone. The medicinal implication of this synergism is that a regimen with a reduced acarbose dose may be used, thus minimising side effects to the patient, while achieving the desired therapeutic effect for managing T2DM.

13.
Mar Environ Res ; 172: 105508, 2021 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-34710739

RESUMEN

Temperate reefs are being tropicalized worldwide. In temperate Western Australia, a marine heatwave led to a regime shift from kelp (Ecklonia radiata) dominated to canopy-free reefs, together with an increase in tropical herbivorous fishes that contribute to keeping low kelp abundances and even prevent kelp reestablishment in northern regions. However, whether tropical herbivorous fishes prefer kelps over other seaweeds and/or whether this preference changes with latitude remains untested. Multiple-choice experiments (young kelp vs. other seaweeds) with tropical, subtropical and temperate herbivorous fishes show shifting species-specific preferences and fish-to-fish interference shifting with latitude (assays replicated in two regions four degrees of latitude apart). Against expectations, only the temperate Kyphosus sydneyanus preferred kelp over other seaweeds, but only in the lower latitude region. Siganus fuscescens, the most abundant tropical herbivore in both regions, preferred grazing on turf, suggesting that tropical fish might reduce kelp recruitment by consuming microscopic sporophytes in turf matrix.


Asunto(s)
Kelp , Algas Marinas , Animales , Arrecifes de Coral , Ecosistema , Peces , Herbivoria
14.
Mar Environ Res ; 171: 105450, 2021 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-34543878

RESUMEN

Ecosystem engineering kelp forms habitat and influences associated communities by altering abiotic conditions. These conditions can also affect the engineer's own demographic rates but the mechanisms underpinning these feedbacks are not well known. Here, we tested the interactive effects of three abiotic factors engineered by the Australasian kelp Ecklonia radiata (light, water flow and scour) on the early survivorship and growth of its outplanted microscopic recruits. After six weeks, recruit survivorship was high in the absence of scour and low light (2-3 times higher than when scour was present) and under low water flow-ambient light conditions. Growth of sporophytes was strongly related to light, with recruits under ambient light approximately four times larger after six weeks. Overall, reduced scour (for survivorship) and ambient light (for growth) appear crucial for maximising E. radiata recruitment suggesting a healthy forest can provide microenvironments to enhance survivorship while gaps in the canopy enhance growth.


Asunto(s)
Kelp , Phaeophyceae , Ecosistema , Bosques , Agua
15.
Glob Chang Biol ; 27(21): 5547-5563, 2021 11.
Artículo en Inglés | MEDLINE | ID: mdl-34382288

RESUMEN

Macroalgal-dominated habitats are rapidly gaining recognition as important contributors to marine carbon cycles and sequestration. Despite this recognition, relatively little is known about the production and fate of carbon originating from these highly productive ecosystems, or how anthropogenic- and climate-related stressors affect the role of macroalgae in marine carbon cycles. Here, we examine the impact of increasing turbidity on carbon storage, fixation and loss in southern hemisphere kelp forests. We quantified net primary production (NPP) and biomass accumulation (BA), and estimated carbon release via detritus and dissolved organic carbon (DOC) across a large-scale turbidity gradient. We show that increased turbidity, resulting in a 63% reduction in light, can result in a 95% reduction in kelp productivity. When averaged annually, estimates of NPP and BA per plant at high-light sites were nearly six and two times greater than those at low-light sites, respectively. Furthermore, the quantity of carbon fixed annually by kelp forests was up to 4.7 times greater than that stored as average annual standing stock. At low-light sites, the majority of C goes directly into tissue growth and is subsequently eroded. In contrast, excess production at high-light sites accounts for up to 39% of the total carbon fixed and is likely released as DOC. Turbidity is expected to increase in response to climate change and our results suggest this will have significant impacts on the capacity of kelp forests to contribute to carbon sequestration pathways. In addition to demonstrating that turbidity significantly reduces the quantity of carbon fixed by kelp forests, and subsequently released as detritus, our results highlight the negative impacts of turbidity on a large source of previously unaccounted for carbon.


Asunto(s)
Kelp , Biomasa , Ciclo del Carbono , Ecosistema , Bosques
16.
Mar Environ Res ; 170: 105439, 2021 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-34365122

RESUMEN

Kelps are ecosystem engineers, which collectively form forests that provide a variety of important ecosystem services for humans and other organisms. Kelp forests are threatened by multiple local and global stressors, one of the most notable is herbivory. Overabundant sea; urchins can consume kelp, leading to a phase shift from productive forests to unproductive; rocky barrens. Reducing sea urchin densities by directly removing them can reverse this; phase shift. However, maintaining low densities of sea urchins, is logistically and financially; challenging. Following a review of herbivore exclusion methods to date, we tested the efficacy of three different methods for excluding sea urchins from kelp in the laboratory: flexible fences; electricity; and copper anti-fouling paint. The results from the laboratory; experiment showed that flexible fencing was the most successful method for excluding sea urchins. To test the efficacy of this method in the field, sea urchins were removed from 1m2 patches in barrens and intact kelp beds, and the effectiveness of flexible fences of two different heights (30 cm and 60 cm) at excluding sea urchins were tested. The results from the field study demonstrated that flexible fences of both heights were effective at maintaining low sea urchin densities in barrens but not in intact kelp beds, relative to unmanipulated; rocky barrens. These findings suggest that flexible fencing could be an important tool in restoring kelp in barrens, however the costs of fencing are likely to place limits on the scale at which this management strategy can be implemented.


Asunto(s)
Kelp , Animales , Ecosistema , Cadena Alimentaria , Bosques , Humanos , Erizos de Mar
17.
FEMS Microbiol Ecol ; 97(7)2021 07 02.
Artículo en Inglés | MEDLINE | ID: mdl-34156064

RESUMEN

Epiphytic microbial communities often have a close relationship with their eukaryotic host, assisting with defence, health, disease prevention and nutrient transfer. Shifts in the structure of microbial communities could therefore have negative effects on the individual host and indirectly impact the surrounding ecosystem, particularly for major habitat-forming hosts, such as kelps in temperate rocky shores. Thus, an understanding of the structure and dynamics of host-associated microbial communities is essential for monitoring and assessing ecosystem changes. Here, samples were taken from the ecologically important kelp, Ecklonia radiata, over a 17-month period, from six different sites in two distinct geographic regions (East and West coasts of Australia), separated by ∼3,300 kms, to understand variation in the kelp bacterial community and its potential environmental drivers. Differences were observed between kelp bacterial communities between the largely disconnected geographical regions. In contrast, within each region and over time the bacterial communities were considerably more stable, despite substantial seasonal changes in environmental conditions.


Asunto(s)
Kelp , Microbiota , Australia , Bacterias/genética , Ecosistema
18.
Mar Environ Res ; 166: 105267, 2021 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-33601331

RESUMEN

Canopy forming macroalgae are declining globally due to climate change and the identification of refuges for these habitats is crucial for their conservation. This is particularly pertinent in ocean warming hotspots where significant range contractions of kelp have occurred and are projected to continue. We developed a stacked urchin-kelp species distribution model (SDM) to predict climate refugia for kelp (Ecklonia radiata) in an ocean warming hotspot, south-eastern Australia. The optimal stacked-SDM incorporated biotic and abiotic explanatory covariates and was validated using an independent dataset. Density of the urchin Centrostephanus rodgersii, summer bottom temperature and photosynthetically available radiation at the seabed were significant predictors of kelp cover, highlighting the physiological and ecological influence of these variables on the distribution of kelp. Our optimal stacked-SDM predicted three spatially distinct refuge areas, where kelp occurs in deeper waters than surrounding seascapes. The presence of kelp at two of these refuge areas was confirmed using independent data. The identification of these refuge areas is crucial for conservation, as they are likely to facilitate the persistence of ecologically and economically important kelp forests as waters warm in shallow areas and kelp retreat to depth under climate change. Furthermore, identification of refugia will enable proactive spatial planning that prioritises new locations for protection to ensure that key kelp habitats can persist in a future of increasing stress.


Asunto(s)
Kelp , Animales , Cambio Climático , Ecosistema , Océanos y Mares , Refugio de Fauna , Australia del Sur
19.
J Phycol ; 57(1): 311-323, 2021 02.
Artículo en Inglés | MEDLINE | ID: mdl-33150586

RESUMEN

Ecklonia radiata is the main foundation species in Australian temperate reefs, yet little has been published on its reproduction and how this may change across its depth range (1-50+ m). In this study, we examined differences in sporophyte morphology and zoospore production during a reproductive season and across four depths (7, 15, 25, and 40 m). Additionally, we examined differences in germination rate, survival, and morphological traits of gametophytes obtained from these four depths, cultured under the same light and temperature conditions. Multivariate morphology of sporophytes differed significantly between deep (~40 m) and shallow sites (7 and 15 m), but individual morphological traits were not significantly different across depths. Total spore production was similar across depths but the peak of zoospore release was observed in February at 15 m of depth (6,154 zoospores · mm-2 of tissue) and the minimum observed in January at 7, 25, and 40 m (1,141, 987, and 214 zoospores · mm-2 of tissue, respectively). The source depth of zoospores did not have an influence in the germination rate or the survival of gametophytes, and only gametophytes sourced from 40 m sites presented significantly less surface area and number of branches. Overall, these results indicate that E. radiata's reproductive performance does not change across its depth range and that kelp beds reproducing in deeper areas may contribute to the replenishment of their shallow counterparts. We propose that deep kelps may constitute a mechanism of resilience against climate change and anthropogenic disturbances.


Asunto(s)
Kelp , Australia , Cambio Climático , Reproducción , Estaciones del Año
20.
Ann Bot ; 125(2): 235-246, 2020 02 03.
Artículo en Inglés | MEDLINE | ID: mdl-31424534

RESUMEN

BACKGROUND AND AIMS: Coastal protection from erosion and flooding is a significant ecosystem service provided by vegetated marine systems. Kelp beds are a dominant habitat-forming species on temperate reefs worldwide. While they are valued as hotspots of biodiversity, there is a paucity of information that supports their use in nature-based coastal defence. This includes the effectiveness of kelp beds in attenuating waves approaching the shore and how this influences sediment transport. METHODS: Wave loggers were deployed at paired kelp bed and control (urchin barren) treatments at four sites in Port Phillip Bay, Australia. The significant wave height offshore (exposed side) to onshore (sheltered side) of the treatment were compared to determine wave attenuation. KEY RESULTS: At three sites, the wave attenuation of kelp beds was significantly less than that of the control. This result was consistent across the environmental conditions recorded in this study. At the fourth site, on average there was no significant difference in wave transmission between kelp and control. However, wave attenuation at kelp beds was 10 % greater than the control during periods of northerly winds. We highlight the importance of disentangling the effects of the reef substratum and kelp when evaluating the efficacy of kelp at providing coastal protection. CONCLUSIONS: We have highlighted a significant gap in the research on ecosystem services provided by kelp beds. A greater understanding is needed on which kelp species are able to provide coastal protection, and under what conditions. Such future research is essential for providing managers and policy makers with actionable information on sustainable and cost-effective solutions for coastal defence when faced with a changing climate.


Asunto(s)
Kelp , Australia , Bahías , Biodiversidad , Ecosistema
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