Durvillaea Antarctica Research Articles

Morphological and physiological differences between two morphotypes of Durvillaea antarctica (Phaeophyceae) from the sub-Antarctic ecoregion of Magallanes, Chile

The coastal marine ecosystems of the sub-Antarctic ecoregion of Magallanes in southern Chile are strongly characterized by environmental heterogeneity with a unique and high biodiversity of benthic macroalgae. The kelp Durvillaea antarctica (Phaeophyceae) is abundant in the intertidal in this region. Two morphotypes, one with elongated-cylindrical (“morphotype EC”) and one with laminar (“morphotype L”) blades, have been collected from a wave-protected site at the Strait of Magellan and the wave-exposed shores of the isolated Otway Sound. Morphometric and physiological (by chlorophyll fluorescence) analyses showed significant differences between the two morphotypes regarding the morphology, the maximum electron transport rates (ETRmax), and the chlorophyll c concentration. These morphological and physiological differences can be linked to their hydrodynamic environment. The presence of two different species in the region of Magallanes based on the measured parameters is discussed. This study may be useful for future genetic and biotechnological investigations and draws attention to D. antarctica as a species of commercial value among the marine resources of Chile.

Nutritional properties of dishes prepared with sub-Antarctic macroalgae—an opportunity for healthy eating

In order to promote the use of sub-Antarctic macroalgae as food, three species of seaweeds, Macrocystis pyrifera, Pyropia columbina, and Durvillaea antarctica, were used as ingredients in a variety of dishes such as cochayuyo bread, cochayuyo hamburgers, cochayuyo fettuccine, huiro fritters, huiro breadsticks, and luche-parsley pesto. Subsequently, the nutritional value of each of the dishes was analyzed. The chemical composition, including carbohydrates, proteins, lipids, sodium, and the fatty acid (FA) content, was examined. In general, the prepared food varieties demonstrated low lipid contents (4.1 to 8.5% dry weight, dw), moderate concentrations of protein (6.9 to 12.7% dw), and highly variable contents of total dietary fiber (1.3 to 18.9% dw). The fatty acid patterns were different for all prepared dishes, and the FA profile exhibited a beneficial contribution of polyunsaturated fatty acids (PUFAs), with a preponderance of linoleic acid and α-linolenic. The chemical composition of the dishes was compared to that of similar and commonly consumed food like white bread, hamburgers, fettuccine made of dough enriched with eggs, fritters, breadsticks, and green pesto. The results suggest that macroalgae can be used as an ingredient in prepared food where they may contribute successfully to a more balanced diet and to maintain the organoleptic characteristics in commercially attractive prepared food like cochayuyo bread, cochayuyo hamburger, cochayuyo fettuccine, huiro breadsticks, and luche-parsley pesto.

Hot-air drying characteristics and energetic requirement of the edible brown seaweedDurvillaea antarctica

The drying characteristics of edible seaweed Durvillaea antarctica subjected to hot-air drying at 40, 50, 60, 70, and 80°C were investigated. Desorption isotherm was performed to estimate the equilibrium moisture content. Ten mathematical models were applied on the drying kinetics. The effect of drying temperatures on the proximate composition in this seaweed was also evaluated. Drying process resulted in an apparent increase of the ash and crude protein contents as compared to fresh sample. Midilli-Kucuk model presented the best-fit quality on drying curves. An effective diffusional coefficient from 0.74 × 10−9 to 2.37 × 10−9 m2 s−1 was determined. At last, the energy consumption and efficiency value at 80°C were 13.54 kWh kg−1 and 34.57%, respectively. Furthermore, it is possible to estimate the hot-air drying conditions and obtain a dehydrated product as alternative to solar drying. Practical applications Durvillaea antarctica is a brown seaweed, which has proving to be very significant in terms of its nutritional value and bioactive compounds, which can benefit human health. For this reason, it is expected that its commercialization and consumption will increase strongly. Usually, D. antarctica requires of a drying process due to large amount of water that contain in its fresh state. Traditionally, it is dried under the sun but this operation can cause losses of material, degradation of nutritional values and poor quality on this seaweed. The use of a convective dryer with controlled conditions can be a good alternative to explore for this seaweed. Several mathematical modeling have been widely used for analysis of drying of various marine products such as seaweed to determine the best operation conditions and to understand the water transfer mechanisms from seaweed to surrounding air.

Reproductive biology of Durvillaea antarctica (Chamisso) Hariot in the sub-Antartic ecoregion of Magallanes (51–56° S)

Durvillaea antarctica (Chamisso) Hariot is a large kelp commonly found on the exposed rocky shores of the Chilean coastline. It is endemic to the Southern Hemisphere and is used for direct consumption in the human diet and for alginate extraction; it is commonly known as “cochayuyo” (word from Chilean indigenous population “Mapudungun” language). The species occurs in the sub-Antarctic region and is found from Coquimbo (30° S) to Cape Horn (56° S). This study investigates and describes the seasonal reproductive strategies of D. antarctica located in the far south of the Chilean coast, in the region of the Magallanes (51–56° S), Chile, during the period of a year. Samples were taken in quadrants of 10 m2 parallel to the coastline in the intertidal zone of three locations during consecutive seasons. Both the phenological stages and the different states of maturity in individuals were determined. These findings were used to describe the main characteristics of the reproductive cycle and the spatial heterogeneity that may exist between the reproductive processes within each studied area. The results indicate that in all three studied localities of D. antarctica reproductive individuals are present throughout the year. The largest amount of reproductive individuals tends to exist in autumn and winter, with the numbers subsequently decreasing in spring and summer. In all studied localities, it was possible to identify male and female non-reproductive individuals. The largest number of male and female plants in the studied populations was found from autumn to winter; however, there were shifts in the proportions during these periods that lead to an increase in male over female fronds. In all localities, both male and female individuals in different stages of maturity were found, with the level of maturity depending on locality and season. Mature fronds were found more frequently during autumn and winter although the measures of maturity vary between different localities. Based on these results we conclude that D. antarctica is a species with present reproductive individuals throughout the year, similar to populations of this species described for other sub-Antarctic latitude. It is possible that there could be a cryptic species in the region, presenting morphological and reproductive variability that did not agree well with the circumscription of the species. Therefore, studies of ecophysiological and molecular aspects are needed to clarify the taxonomic status of this species in the sub-Antarctic region of Magallanes.

Transport of drifting fucoid algae: Nearshore transport and potential for long distance dispersal

Processes responsible for transporting detached macroalgae through the nearshore environment and offshore to where long distance dispersal (LDD) can occur have rarely been examined. Here, we test the influence of nearshore winds, tidal currents and position of release (low, mid or high tidal zone) on the dispersal of drifting fucoid algae were tested. “Drift sets” (tagged Hormosira banksii, Durvillaea antarctica, Cystophora torulosa and GPS drifters) were tracked over single tidal cycles. Wind direction had the greatest effect on movement of drift sets, but interacted with tidal direction. Overall, offshore winds and outgoing tides were most favourable for LDD, but their effect differed between species. Approximately 90% of H. banksii, D. antarctica and GPS-tracked drifters were beach-cast after one tidal cycle during onshore winds, while 19% were beach-cast during offshore winds. In contrast, 50–75% of C. torulosa were beach-cast after one tide, regardless of wind direction. Displacement of drifters was affected by tidal zone of release, but interacted with wind and tidal direction. Drifting velocities varied between drifter types, with surface drifters travelling further and faster than the benthic-drifting species. Analysis of 20years of wind data found seasonal differences in the percentage of hourly winds, with greater periods of south-westerly and north-westerly winds, and fewer onshore north-easterly winds, during autumn and winter periods. Conditions for successful offshore dispersal from the major algal dominated peninsulas of southern New Zealand are, therefore, more likely to occur if detachment of algae occurs during outgoing tides in autumn and winter.

Ecological tipping points for an invasive kelp in rocky reef algal communities

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 587:93-104 (2018) - DOI: https://doi.org/10.3354/meps12429 Ecological tipping points for an invasive kelp in rocky reef algal communities David R. Schiel1,*, Stacie A. Lilley1, Paul M. South2 1Marine Ecology Research Group, School of Biological Sciences, University of Canterbury, Christchurch, New Zealand 2Cawthron Institute, Nelson, New Zealand *Corresponding author: david.schiel@canterbury.ac.nz ABSTRACT: Invasive species are affecting coastal ecosystems worldwide and there are many potential mechanisms that allow their spread into native communities. To investigate this phenomenon, we used an experiment in which the canopy of the southern bull kelp Durvillaea antarctica was removed in 2 seasons and community development was followed over 3 yr. The invasive kelp Undaria pinnatifida recruited almost exclusively into plots from which the natural canopy had been removed. We examined, through a series of regression tree models and change point analyses, the gradients of community responses that allowed the successful recruitment of this invasive species. Analyses revealed a range of coinciding conditions, especially a decline in fucoid cover below 20% and an increase in turf cover above 80%, that facilitated Undaria recruitment. The abundance of molluscan grazers and cover of subcanopy algae had lesser effects on Undaria recruitment. In an ecological sense, there was a clear tipping point in the interaction between canopy loss and the subsequent expansion of coralline turf that allowed communities to switch from dominance by native species to seasonal dominance of Undaria. This study illustrates the complex nature of disturbance thresholds and interactions within the native communities that can facilitate the spread and recruitment success of Undaria. KEY WORDS: Tipping point · Threshold · Rocky reef · Native algae · Invasive algae · Regression tree Full text in pdf format PreviousNextCite this article as: Schiel DR, Lilley SA, South PM (2018) Ecological tipping points for an invasive kelp in rocky reef algal communities. Mar Ecol Prog Ser 587:93-104. https://doi.org/10.3354/meps12429 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 587. Online publication date: January 25, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Extraction, Structural Characterization, and Potential Antioxidant Activity of the Polysaccharides from Four Seaweeds.

Four seaweed polysaccharides were extracted from Sarcodia ceylonensis, Ulva lactuca L., Gracilaria lemaneiformis, and Durvillaea antarctica, respectively, by microwave-assisted extraction. The effect of three significant variables (extraction time, extraction temperature, and the ratio of water to raw material) on the process for extracting polysaccharides was investigated, along with the optimization of the extraction using the response surface method (RSM) with a Box–Behnken design. The polysaccharide structure, monosaccharide composition, degree of sulfation, and molecular weight (MW) distribution were analyzed by infrared (IR) spectrometry, gas chromatography (GC), and high-performance gel permeation chromatography (HPGPC). IR spectrometry showed that Sarcodia ceylonensis polysaccharide (SCP), Ulva lactuca L. polysaccharide (ULLP), and Durvillaea antarctica polysaccharide (DAP) were all sulfated polysaccharides and, except Gracilaria lemaneiformis polysaccharide (GLP), all belong to β-pyranosidic polysaccharides. The average molecular weight (MW) of SCP, ULLP, GLP, and DAP was 466, 404, 591, and 482 kDa, respectively. The quantitative and comparative results with external standards indicated that the main monosaccharide in SCP and ULLP was mannose; and GLP and DAP were mainly composed of galactose and glucose, respectively. Then the in vitro antioxidant activity of all of the polysaccharides was evaluated using different assays—2,2–azino –bis (3-ethylbenzthiazoline-6- sulfonate) (ABTS), hydroxyl radical, nitrite scavenging capacity, and reducing power—and the relationship between their antioxidant activity and chemical characteristics were also examined. ULLP presented the highest ABTS radical scavenging activity; ULLP, SCP and DAP also showed a strong effect on the ABTS radical scavenging activity. SCP and ULLP exhibited excellent hydroxyl radical scavenging activities, about 83.33% ± 2.31% and 80.07% ± 2.17%, respectively, at 4 mg/mL. The reducing power of DAP was relatively more pronounced than that of the three other polysaccharides. However, the nitrite scavenging activities of the four seaweed polysaccharides were weaker than other antioxidant activity (ABTS), hydroxyl radical scavenging capacity, and reducing power. In addition, GLP exhibited lower activities than the other three samples in all of the tests for the antioxidant activity.

The variable routes of rafting: stranding dynamics of floating bull kelp Durvillaea antarctica (Fucales, Phaeophyceae) on beaches in the SE Pacific.

Dispersal on floating seaweeds depends on availability, viability, and trajectories of the rafts. In the southern hemisphere, the bull kelp Durvillaea antarctica is one of the most common floating seaweeds, but phylogeographic studies had shown low connectivity between populations from continental Chile, which could be due to limitations in local supply and dispersal of floating kelps. To test this hypothesis, the spatiotemporal dynamics of kelp strandings were examined in four biogeographic districts along the Chilean coast (28°-42°S). We determined the biomass and demography of stranded individuals on 33 beaches for three subsequent years (2013, 2014, 2015) to examine whether rafting is restricted to certain districts and seasons (winter or summer). Stranded kelps were found on all beaches. Most kelps had only one stipe (one individual), although we also frequently found coalesced holdfasts with mature males and females, which would facilitate successful rafting dispersal, gamete release, and reproduction upon arrival. High biomasses of stranded kelps occurred in the northern-central (30°S-33°S) and southernmost districts (37°S-42°S), and lower biomasses in the northernmost (28°S-30°S) and southern-central districts (33°S-37°S). The highest percentages and sizes of epibionts (Lepas spp.), indicative of prolonged floating periods, were found on stranded kelps in the northernmost and southernmost districts. Based on these results, we conclude that rafting dispersal can vary regionally, being more common in the northernmost and southernmost districts,depending on intrinsic (seaweed biology) and extrinsic factors (shore morphology and oceanography) that affect local supply of kelps and regional hydrodynamics.

Latitudinal and seasonal effects on short-term acclimation of floating kelp species from the South-East Pacific

Floating seaweeds are important dispersal vehicles for many organisms in cold-temperate waters between latitudes 30° and 60°. Molecular studies suggested that long-distance rafting of seaweeds is more prevalent at the polar edges of their distribution but knowledge about their physiological status at high latitudes is limited. Seasonal short-term field experiments were conducted along a latitudinal gradient (30°, 37° and 54°S) with floating kelps Macrocystis pyrifera and Durvillaea antarctica. Kelps were tethered at the sea surface for 14d during austral winter and summer to examine their acclimation potential in floating conditions. Biomass changes, reproductive status and physiological traits (chlorophyll a fluorescence, pigments, phlorotannins and antioxidant capacity) were evaluated after 7d and 14d of floating. Biomass changes (positive or negative) depended on species and latitude: at low latitudes (Coquimbo) both species lost biomass during both seasons while at mid latitudes (Concepción) they grew during summer but not in winter. Species-specific responses were observed at high latitudes (Pta. Arenas) with floating M. pyrifera growing in summer and D. antarctica in winter. Both species were able to maintain reproductive status mainly in winter, but at mid latitudes M. pyrifera also showed high reproductive activity during summer. Physiological adjustment was detected for both species at day 7 and upheld until the end of the experiment (14d). Latitudinal changes in photosynthetic variables (maximum quantum yield and pigments) were more evident in summer conditions, M. pyrifera showing decreases in Fv/Fm and pigment levels at low and high latitudes while in D. antarctica these variables increased with latitude. Phlorotannin contents varied with latitude but showed an opposing pattern in the two kelp species, with high concentrations at low latitudes for M. pyrifera and at high latitudes for D. antarctica. The floating kelps maintained high antioxidant capacity during the experiments. The short-term acclimation responses support the hypothesis of long-distance dispersal at high latitudes for both floating kelp species. The acclimation potential differed between the two species depending on the season, especially at mid and high latitudes. Summer conditions were favorable for floating M. pyrifera at high latitudes and for both species at mid latitudes in which a combination of increasing radiation and moderate temperature can stimulate growth. The results confirm that kelp rafting is favored at mid/high latitudes but suggest that in polar waters (>60°) low temperatures and light limitations might suppress growth of floating seaweeds.

Microscopic and infrared spectroscopic comparison of the underwater adhesives produced by germlings of the brown seaweed species Durvillaea antarctica and Hormosira banksii.

Adhesives from marine organisms are often the source of inspiration for the development of glues able to create durable bonds in wet environments. In this work, we investigated the adhesive secretions produced by germlings of two large seaweed species from the South Pacific, Durvillaea antarctica, also named 'the strongest kelp in the word', and its close relative Hormosira banksii The comparative analysis was based on optical and scanning electron microscopy imaging as well as Fourier transform infrared (FTIR) spectroscopy and principal component analysis (PCA). For both species, the egg surface presents peripheral vesicles which are released soon after fertilization to discharge a primary adhesive. This is characterized by peaks representative of carbohydrate molecules. A secondary protein-based adhesive is then secreted in the early developmental stages of the germlings. Energy dispersive X-ray, FTIR and PCA indicate that D. antarctica secretions also contain sulfated moieties, and become cross-linked with time, both conferring strong adhesive and cohesive properties. On the other hand, H. banksii secretions are complemented by the putative adhesive phlorotannins, and are characterized by a simple mechanism in which all constituents are released with the same rate and with no apparent cross-linking. It is also noted that the release of adhesive materials appears to be faster and more copious in D. antarctica than in H. banksii Overall, this study highlights that both quantity and quality of the adhesives matter in explaining the superior attachment ability of D. antarctica.

No sex-related dispersal limitation in a dioecious, oceanic long-distance traveller: the bull kelp Durvillaea antarctica

Abstract Dispersal of dioecious floating seaweeds could be limited due to biological constraints. This study examined for benthic and floating populations (stranded individuals) of the rafting kelp Durvillaea antarctica whether male and female individuals cohabit within one holdfast. As a previous study had indicated colour differences between sexes, we also examined whether these colour differences are consistent and possibly related to pigment and phlorotannin concentrations. Our large-scale survey of rafted holdfasts and a small-scale survey of benthic holdfasts at two sites found that reproductive males and females do travel together in coalesced holdfasts, although this proportion is relatively low (5–17%). There were no sex-specific differences in pigment and phlorotannin concentrations, but there were significant differences between the two benthic populations. There was no relationship between the colouration of thalli and the concentration of pigments but there was a slight colour difference between vegetative and reproductive sexual stages. Based on these results we conclude that biological conditions are not the cause for the lack of genetic connectivity between D. antarctica populations from central Chile. Instead, we suggest that ecological processes, such as density-blocking and physical factors (i.e. currents and winds), limit the potential for successful rafting dispersal.

Do native subtidal grazers eat the invasive kelp Undaria pinnatifida?

Key to understanding the impacts of invasive macroalgae on local food webs is determining the extent to which native herbivores consume the invasive macroalga. We used multiple-choice feeding assays to ascertain the relative feeding preferences of four subtidal grazers (the amphipod Aora typica, the isopod Batedotea elongata and the gastropods Cookia sulcata and Haliotis iris) for the invasive macroalga Undaria pinnatifida and six native macroalgae (Macrocystis pyrifera, Durvillaea antarctica, Carpophyllum flexuosum, Cystophora scalaris, Marginariella boryana and Ulva spp.) that are all abundant along the Otago coast of southern New Zealand. Multiple-choice feeding assays were run under laboratory conditions during the austral autumn (April and June) of 2013. The relative abundances of the macroalgae in the field were also determined. All of the grazers ate U. pinnatifida at rates comparable to most of the native macroalgae, except for B. elongata, which barely consumed it. This indicates that U. pinnatifida, which was shown to be more abundant than native macroalgae in subtidal habitats, has the potential to contribute organic matter to the local food web and may be an undesirable food for some group of grazers. We suggest that U. pinnatifida could potentially alter existing trophic relationships.

Characterization of copper (II) biosorption by brown algae Durvillaea antarctica dead biomass

In this study we analyze the Cu(II) biosorption characteristics of the dead biomass of the Chilean brown macroalgae Durvillaea antarctica as a function of initial metal ion concentration and pH. We determined an equilibrium time of 120 min and a maximum biosorption performance at pH 5.0. The isotherms data at optimum pH best fitted with the Dubinin–Radushkevish model, showing a maximum capacity for Cu(II) biosorption of 1.44 mmol g−1. A quantitative analysis by potentiometric titrations was performed to determine different acid–base properties of the biomass surface and a FTIR analysis was performed to identify the key functional groups present on the biomass. We found characteristic peaks corresponding mainly to amine, carboxylate, hydroxyl and sulphonate moieties. A time course FTIR analysis of interaction between the biomass and Cu(II) in aqueous solution was performed to estimate sequential steps of functional groups interactions, and a SEM analysis was performed to observe the textural properties of D. antarctica biomass surface. The value of the total cation exchange capacity supports an ion exchange mechanism for the adsorption of Cu(II) by the biomass, characterized as an physisorption phenomena in a multilayer heterogeneous system.

Ocean acidification induces changes in algal palatability and herbivore feeding behavior and performance.

The effects of global stressors on a species may be mediated by the stressors' impact on coexisting taxa. For instance, herbivore-algae interactions may change due to alterations in algal nutritional quality resulting from high CO2 levels associated with ocean acidification (OA). We approached this issue by assessing the indirect effects of OA on the trophic interactions between the amphipod Orchestoidea tuberculata and the brown alga Durvillaea antarctica, two prominent species of the South-east Pacific coast. We predicted that amphipod feeding behavior and performance (growth rate) will be affected by changes in the palatability of the algae exposed to high levels (1000 ppm) of CO2. We exposed algae to current and predicted (OA) atmospheric CO2 levels and then measured their nutritive quality and amphipod preference in choice trials. We also assessed consumption rates separately in no-choice trials, and measured amphipod absorption efficiency and growth rates. Protein and organic contents of the algae decreased in acidified conditions and amphipods showed low preference for these algae. However, in the no-choice trials we recorded higher grazing rates on algae exposed to OA. Although amphipod absorption efficiency was lower on these algae, growth rates did not differ between treatments, which suggests the occurrence of compensatory feeding. Our results suggest that changes in algal nutritional value in response to OA induce changes in algal palatability and these in turn affect consumers' food preference and performance. Indirect effects of global stressors like OA can be equally or more important than the direct effects predicted in the literature.

Herbivore-Alga Interaction Strength Influences Spatial Heterogeneity in a Kelp-Dominated Intertidal Community.

There is a general consensus that marine herbivores can affect algal species composition and abundance, but little empirical work exists on the role of herbivores as modifiers of the spatial structure of resource assemblages. Here, we test the consumption/bulldozing effects of the molluscan grazer Enoplochiton niger and its influence on the spatial structure of a low intertidal community dominated by the bull kelp Durvillaea antarctica and the kelp Lessonia spicata. Through field experiments conducted at a rocky intertidal shore in north-central Chile (~30°-32°S), the edge of the grazer and algae geographic distributions, we estimated the strength and variability of consumptive effects of the grazer on different functional group of algae. We also used data from abundance field surveys to evaluate spatial co-occurrence patterns of the study species. Exclusion-enclosure experiments showed that E. niger maintained primary space available by preventing algal colonization, even of large brown algae species. The grazing activity of E. niger also reduced spatial heterogeneity of the ephemeral algal species, increasing bare space availability and variability through time in similar ways to those observed for the collective effect with other grazers. Overall, our result suggests that E. niger can be considered an important modifier of the spatial structure of the large brown algae-dominated community. Effects of E. niger on resource variability seem to be directly related to its foraging patterns, large body size, and population densities, which are all relevant factors for management and conservation of the large brown algae community. Our study thus highlights the importance of considering functional roles and identity of generalist consumers on spatial structure of the entire landscape.

Comparison of different extraction techniques for obtaining extracts from brown seaweeds and their potential effects as angiotensin I-converting enzyme (ACE) inhibitors

An extraction protocol was developed to maximize the amount of extracts obtained from three brown seaweeds, Lessonia nigrescens (in two stages of development), Macrocystis pyrifera, and Durvillaea antarctica, and to evaluate them as natural inhibitors of the angiotensin I-converting enzyme (ACE). Two extraction methods were used, an enzymatic method (cellulase and α-amylase) and a conventional method (maceration). The extracts were analyzed to determine the extraction yield (%), the total phenolic and carbohydrate concentrations, and the ACE inhibition. Juvenile L. nigrescens extracts obtained by α-amylase exhibited the highest extraction yield (37.72 ± 4.13 %), the highest ACE inhibition (95.61 ± 0.33 %), and the lowest IC50 (10.10 ± 1.55 μg PGE mg−1 seaweed) among the studied extracts. Extraction by maceration produced extracts with chemical characteristics that were less favorable for inhibiting ACE than the enzymatic extraction. The presence of phlorotannins and carbohydrates in these brown seaweeds after enzymatic extraction could be responsible for the superior ACE inhibitory activity of the extracts. Thus, these molecules could be considered as potential phytopharmaceuticals for the development of new ACE inhibitors.

Morphological convergence in the inter-holdfast coalescence process among kelp and kelp-like seaweeds (Lessonia, Macrocystis, Durvillaea)

:In brown macroalgae, intraspecific holdfast coalescence has only been studied in two species of Lessonia (Lessonia spicata and Lessonia berteroana). In both species coalescence followed the same general pattern: once the connection between holdfasts was established, the contact areas showed significant cellular morphological modifications. Typical epidermal cells became polygonal and similar to cortical cells. In addition, coalescence involved the de novo formation of secondary plasmodesmata, establishing a direct cytoplasm connection within neighbouring cells, where dense materials, vacuoles and organelles can be observed. In the present study, we demonstrate intraspecific holdfast coalescence in two additional kelp species, Lessonia trabeculata and Macrocystis pyrifera, as well as in the kelp-like seaweed, Durvillaea antarctica. The process of holdfast fusions in these species is similar to that described previously and suggests that this is a generalized phenomenon among kelp and kelp-like brown algae. In addition, the formation of cytoplasmic connections between genetically different brown algal individuals is shown for the first time.

Assemblage and understory carbon production of native and invasive canopy-forming macroalgae

Carbon flow is essential to the function of all ecosystems, yet there is little mechanistic understanding of how non-indigenous macroalgae alter rates of carbon fixation in marine ecosystems. The spread of fast-growing non-indigenous species, such as the annual kelp Undaria pinnatifida (Harvey) Suringer, can potentially change trophic links through variable photosynthetic parameters relative to indigenous species. Here we use in situ photorespirometry to compare rates of net primary productivity (NPP) of assemblages dominated by U. pinnatifida and two native canopy-forming species, Cystophora torulosa and Durvillaea antarctica. The three assemblages had different light-use dynamics across a full light range, with the indigenous macroalgae showing no sign of saturated NPP at high irradiance, but with U. pinnatifida showing saturated NPP beyond 1000μmolm−2s−1. Using incident irradiance collected over a full year, we show small differences in modeled average daily NPP during spring between U. pinnatifida assemblages (8g C m−2day−1) and those dominated by C. torulosa (7g C m−2day−1), whereas D. antarctica assemblages were the most productive (10g C m−2day−1). The proportion of NPP provided by the sub-canopy component of assemblages varied between the canopy-forming species, where D. antarctica had a low sub-canopy contribution compared to stands dominated by U. pinnatifida or C. torulosa. High biomass turnover associated with the annual life history of U. pinnatifida has the potential to increase carbon export to surrounding ecosystems compared to perennial fucoid species. Therefore, U. pinnatifida may have a positive effect on carbon flow, fixing similar quantities of carbon in a 6-month period as the native C. torulosa in a year. It appears that U. pinnatifida has the potential to contribute a great deal of carbon and alter the biomass export regime as it spreads across shallow coastal habitats.

Impacts of local and global stressors in intertidal habitats: Influence of altered nutrient, sediment and temperature levels on the early life history of three habitat-forming macroalgae

As human pressure in coastal areas increases, it is important to understand how key functional components of nearshore ecosystems respond to combinations of global climate changes and local non-climatic stressors. Stressors originating at local scales such as elevated nutrient concentrations and sediment loads are known to contribute to the regression of large habitat-forming macroalgae in temperate rocky reefs. How the persistence of algal beds will be affected by combinations of altered nutrient and sediment regimes and increased temperatures under future global change scenarios is still unclear. We used a series of laboratory experiments to test short- (48h) and long-term (eight weeks) effects of different combinations of nutrient, sediment and temperature on the early life stages of the habitat-forming fucoids Hormosira banksii, Cystophora torulosa, and Durvillaea antarctica. A light coating of sediment affected the post-settlement survival of H. banksii and C. torulosa germlings within 48h and reduced growth and survival of all species over eight weeks. Temperatures 3°C higher than ambient levels during the reproductive season of each species caused increased mortality of the germlings of the three fucoids after eight weeks, but these effects were only evident in the absence of sediment. The cold-adapted D. antarctica was particularly susceptible to temperature increase, with reduced germling survival in warmer waters after 48h. In the absence of sediment, nutrient enrichment stimulated the growth of H. banksii and C. torulosa, but caused a decline in the survival and growth of D. antarctica. This was probably due to the poor adaptation of D. antarctica to laboratory conditions. This study contributes to a better understanding of the impacts of altered physical conditions on important habitat-forming species. Our results highlight mechanisms that may well apply in natural contexts, and they reinforce the need for appropriate management of local stressors in order to mitigate the impacts of altered climate conditions.

Genetic analyses of rafted macroalgae reveal regional oceanographic connectivity patterns

AbstractAimThis study examines beach‐cast rafts of Durvillaea antarctica (bull kelp) along New Zealand's east coast to determine spatial variation in beach‐cast haplotype assemblages. By using genetic markers, the geographical origins of rafted D. antarctica samples can be determined, allowing for the examination of dispersal pathways, distances rafted, and potential barriers to dispersal.LocationAn approximately 1000 km stretch of New Zealand's eastern coastline.Methods686 samples of beach‐cast D. antarctica rafts were collected and sequenced for cytochrome c oxidase subunit 1 in order to infer geographical origins and dispersal dynamics of rafted specimens. Results were examined using principal components analysis (PCA) in order to determine spatial groupings. Analysis of molecular variance (AMOVA) was used to determine statistical support for the detected spatial groups.ResultsHierarchical AMOVA revealed three major regional genetic assemblages, which probably reflect broad oceanographic features. In particular, the north–south genetic partitioning in rafted kelp assemblages either side of the Cape Campbell region in central New Zealand closely corresponds to an oceanographically mediated disjunction previously observed in a number of larval‐dispersed marine invertebrate taxa.Main conclusionsFindings from this study suggest that passively drifting kelp rafts and planktonic invertebrate larvae may be similarly constrained by oceanographic features, and demonstrate how the phylogenetic structure present in populations of D. antarctica provide a framework with which to map dispersal patterns.