Iridaea Cordata Research Articles

The rapid shift of intertidal macroalgal assemblage from vertical shoreline profiles in Barton Peninsula, King George Island, Antarctica during summer

Temporal variability and the vertical shoreline profile of an intertidal macroalgal assemblage were examined on the coast of Barton Peninsula, Maxwell Bay, King George Island, Antarctica. Sampling was performed during the three austral summer seasons from November 2016 to January 2019. The sampling interval for the summer shift was 1–2 months. Eighteen algal species were identified, with 75% relative coverage of the predominant red alga Iridaea cordata and endemic brown alga Phaeurus antarcticus. Temporal variation in the macroalgal assemblage showed 78.35% similarity between one month and 64.61% similarity between two months. Contour plots for visualizing macroalgal distribution were first attempted in this study, and compared to general distribution of tables and diagrams that were discontinuously expressed. The coastscape was expressed more quantitatively and continuously, and was also useful for explaining temporal changes such as summer abundance can be described as a shift from I. cordata to P. antarcticus. In addition, in terms of species composition, this study area corresponds to the middle to lower intertidal zone and shows the highest species diversity in King George Island, so it is expected to provide important information for the researches in Antarctic intertidal zones.

Bioprospecting of new Antarctic seaweed selective antitumor molecules: chemical characterization and in vitro analysis

BackgroundThe Antarctic continent exposes seaweeds to extreme environmental conditions, which may facilitate the production of novel metabolites. Algae represent a highly diverse group of little explored organisms. Thus, marine biomass has emerged as a possible source of new biologically active molecules for the treatment of diseases requiring novel therapeutic options. PurposeThe ultrasonic and Soxhlet extractions were used to evaluate chemical profiles and antitumor activities of Desmarestia anceps, Iridaea cordata, and Pyropia endiviifolia extracts using solvents of different polarity. MethodsChemical characterization of the extracts was performed using gas chromatography. The anticancer activities of the extracts were evaluated by exposing rat glioma (C6), human glioblastoma (U87), and human lung adenocarcinoma epithelial (A549) cell lines to increasing extract concentrations (10–1000 µg mL−1) for 24 and 48 h. In parallel, rat astrocyte and human lung fibroblast (MRC-5) were treated under the same conditions to represent non-transformed cell controls, and permit tumor selectivity evaluations of the extracts. ResultsAn MTT assay was used to measure cell cytotoxicity. Hexane, chloroform, and ethanol extracts reduced glioma and lung cancer cell viability. The hexane and ethanol extracts of P. endiviifolia showed the best antiproliferative effect, decreasing glioma cell viability by 40% at 10 µg mL−1, and the chloroform extract reduced lung adenocarcinoma cell viability by 50% at 46 µg mL−1 after 24 h of treatment. None of the extracts affected the viability of non-transformed cells, as was observed in tumor cells. Fatty acids, fatty alcohols, and phthalate esters were the main compounds identified in the seaweed extracts. ConclusionsAntarctic seaweeds displayed selective antitumor activity against glioma and lung cancer cells, particularly the endemic red alga P. endiviifolia. Therefore, these algae could play an important role as novel prototype molecule source for oncology drug development.

Sterols in red macroalgae from antarctica: extraction and quantification by Gas Chromatography–Mass spectrometry

Antarctica is considered a major reservoir of microorganisms and macroorganisms, including seaweed, which can biosynthesize secondary metabolites with unique structures and specific biological activities. Macroalgae are considered an interesting source of steroids, a class of metabolites involved in the control of membrane fluidity and permeability. This study reports the extraction and quantification of sterols in four red macroalgal species from Antarctica: Palmaria decipiens, Plocamium cartilagineum, Iridaea cordata, and Pyropia endiviifolia. The extraction of sterols involved alkaline hydrolysis from algal biomass. The quantification of cholesterol, brassicasterol, campesterol, stigmasterol, β-sitosterol, and fucosterol were performed by gas chromatography hyphenated with mass spectrometry (GC–MS). In general, cholesterol was the most abundant compound (216.32 to 3195.69 mg kg−1), followed by β-sitosterol (131.42 to 654.18 mg kg−1), stigmasterol (68.35 to 393.20 mg kg−1), brassicasterol (68.56 to 337.43 mg kg−1), campesterol (64.95 to 277.78 mg kg−1), and fucosterol (57.67 to 286.18 mg kg−1). Brassicasterol was not found in I. cordata, but it was identified in the other three samples. This work enriches the knowledge about the profile of steroids biosynthesized by Antarctic macroalgae and supports research to discover bioactive compounds with nutraceutical and pharmaceutical applications.

Evaluation of the Antioxidant Capacities of Antarctic Macroalgae and Their Use for Nanoparticles Production.

Macroalgae are sources of bioactive compounds that are interesting from both a chemical and a medical point of view. Although their use in biomedicine has increased significantly in recent years, tests conducted to date have been mostly related to species from temperate latitudes, with the potential application of Antarctic biodiversity being minor. The wide variety of algae species present on Antarctic coastal areas can be a source of new antioxidants. Bearing this in mind, the brown macroalgae Desmarestia antarctica (DA) and the red Iridaea cordata (IC) were selected for the preparation of aqueous extracts with the aim of analyzing their antioxidant activity. This analysis was performed by determining reducing power, total phenolic content, and 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity. Furthermore, both extracts were employed to synthesize gold and silver nanoparticles. The nanomaterials were fully characterized by means of UV-Visible spectroscopy, transmission electron microscopy, Z potential measurements, and Fourier transform infrared spectroscopy, which confirmed the formation of stable, spherical nanoparticles with mean diameters of 13.7 ± 3.1 and 17.5 ± 3.7 nm for Ag@DA and Ag@IC and 12.6 ± 1.9 and 12.3 ± 1.6 nm for Au@DA and Au@IC. Antioxidant assays were performed after the synthesis of the nanomaterials to evaluate their possible synergistic effect with the extracts. The results suggest that polysaccharides and proteins may play a key role in the process of reduction and stabilization. Finally, for the sake of comparison, the results obtained for the Antarctic macroalgae Desmarestia menziesii and Palmaria decipiens have also been considered in the present work.

Anthropogenic radionuclides in Antarctic biota – dosimetrical considerations

The article presents results of the research on artificial radionuclides (137Cs, 90Sr, 241Am) in the Antarctic environment. Samples of 12 species from the marine environment: Pygoscelis adeliae, Pygoscelis papua, Macronectes giganteus, Pagodroma nivea, Catharacta antarctica, Leptonychotes weddellii, Mirounga leonina, Harpagifer antarcticus, Chaenocephalus aceratus, Nacella concinna, Himantothallus grandifolius, Iridaea cordata (bones, feathers, soft tissues, eggs' shells of birds, bones, skin, fur of mammals, fish, mollusks’ soft tissues and shells, algae) and samples of 4 species from the terrestrial environment: Sanionia uncinata, Usnea antarctica, Usnea aurantiaco-atra, Deschampsia antarctica (mosses, lichens, grass) were investigated. Differences in the accumulation of 137Cs between marine and terrestrial ecosystem were shown, which are mostly due to conservatism of mosses and lichens and active removal of cesium by animal body. Furthermore discrepancy between mosses and lichens in the radioceasium accumulation was statistically proven with the additional use of Neutron Activation Analysis. Moreover, the internal weighted dose rates assessment was prepared using the ERICA Tool. The dose rates were relatively low, not exceeding several dozen nGy/h. Nonetheless, one species – Pagodroma nivea, was significantly outstanding due to the highest weighted dose rate it is burdened with.

Composition and structure of the marine benthic community in Terra Nova Bay, Antarctica: Responses of the benthic assemblage to disturbances.

The community structure and assemblages of marine benthic organisms were investigated in coastal areas near the Jang Bogo Antarctic Research Station in Terra Nova Bay during the 2012–2018 summer seasons. We also examined the recovery pattern of marine benthic organisms following disturbance due to the construction of the Jang Bogo Station. A total of 26 taxa were identified in the study area during the experimental period. Species number and diversity indices (richness, evenness, and diversity) were relatively low compared to data previously reported from Terra Nova Bay. Sphaerotylus antarcticus, Clavularia frankliniana, Hydractinia sp., Iridaea cordata, Fragilariopsis spp., Alcyonium antarcticum, and Metalaeospira pixelli were the dominant species in this area. Of these, the diatom Fragilariopsis spp. were the most abundant species, indicating their key role in maintaining the marine benthic community and controlling biogeochemical cycling. During the construction of the Jang Bogo Station, sediment coverage increased and diatoms declined due to the release of sediment into the coastal area. In February 2014, one month after the disturbance due to cyclone, the diatom coverage increased dramatically and thereby species number, richness index, and diversity index steadily rose from 2015 to 2018. However, non-metric multidimensional scaling ordination analysis of species similarities among sampling times showed that community structure had not completely recovered by 2018. Thus, long-term monitoring is required to elucidate the post-disturbance settlement mechanisms of marine benthic organisms at the study area in Terra Nova Bay.

Chemical Characterization and Cytotoxic Activity of Antarctic Macroalgae Extracts against Colorectal Cancer

Background/Aim: Antarctic seaweeds are considered a promising source of compounds with anticancer activity. Colorectal cancer (CRC) is one of the most incident cancers with high mortality rates worldwide. This work aimed to characterize chemically extracts of the Antarctic macroalgae Iridaea cordata, Cystosphaera jacquinotii and Desmarestia anceps and to evaluate the cytotoxic effects against human colon cancer HCT 116 cell line. Materials and Methods: The extracts were obtained by depletion using an ultrasound probe and were identified by High-Performance Liquid Chromatography (HPLC) and Gas Chromatography coupled with Mass Spectrometry (GC-MS). Cell viability was determined by MTT assay. Results: Hexanic and chloroform extracts of the I. cordata and the hexanic, chloroform and methanolic extracts of D. anceps were able to inhibit growth of colorectal cancer cells in the three different incubation times (24, 48 and 72 h). Through GC analysis, 01 compounds were identified in the hexane extract and 02 compounds in the chloroform extract of the algae I. cordata. The hexane extract of D. anceps macroalgae presented 5 compounds, chloroform extract 10 and methanolic extract 3 respectively, with special highlight to fucosterol. Carotenoid analysis by HPLC identified β-carotene in all species, while zeaxanthin was present in the spectrum of I. cordata and C. jacquinotii. Fucoxanthin and violaxanthin were confirmed in the brown seaweeds C. jacquinotii and D. anceps. Conclusion: Extracts of macroalgae I. Cordata and D. anceps may be a source of therapeutic agents against CRC.

Photosynthetic characteristics of geographically disjunct seaweeds: A case study on the early life stages of Antarctic and Subantarctic species

Propagules of geographically separated seaweeds distributed in both site of Antarctic Circumpolar Current are expected to show different light and temperature acclimation in order to cope with environmental condition in both Antarctic and Subantarctic regions. The objectives of this study were: (1) to compare the photosynthetic performance (rETRmax, Ek, and αETR) of propagules of conspecific (Iridaea cordata and Adenocystis utricularis) and congeneric (Pyropia sp. and Monostroma sp.) seaweeds from Magellan strait (Subantarctic region) and King Gorge Island (Antarctica) using in vivo chlorophyll fluorescence techniques; and (2) to determine the physiological responses (measured by rapid adjustment of photochemistry, Fv/Fm) of tetraspores of I. cordata from populations of both sites when exposed in laboratory to UV radiation. Differences in photosynthetic characteristics between propagules were observed in I. cordata and Monostroma sp. while I. cordata tetraspores from Subantarctic populations showed high light demands (Ek = 150 μmol photon m−2 s−1) when compared to those from Antarctic populations (Ek = 50 μmol photon m−2 s−1). Antarctic Monostroma sp. gametes exhibited higher Ek (300 μmol photon m−2 s−1) than those of Subantarctic populations (130 μmol photon m−2 s−1). Antarctic tetraspores of I. cordata shown low inhibition in Fv/Fm (<10%) after a 4-h exposure at 2 °C, while spores from Subantarctic population were more sensitive (>60% inhibition) under similar exposure conditions. Similar as for other cold-temperate species, these differences appear to underlie biogeographical and evolutionary elements: in I. cordata, spores from Antarctica are more tolerant to UV at low temperatures than those from Subantarctic regions, but when exposed to increased temperature the detrimental effects of stress in tetraspores from both Antarctic and Subantarctic populations were ameliorated. This differential photosynthetic response to low temperature and light among algae with Antarctic and Subantarctic disjunction is an important ecophysiological attribute that can be associated with adaptations at a genetic level reported previously for some of these populations.

Trace Metals Analysis Along the Fildes Peninsula Coastline Using Two Red Algae, Rhodymenia antarctica and Iridaea cordata, as Monitors

Two red algae, Rhodymenia antarctica and Iridaea cordata (Rhodophyta), were employed to investigate the pollution situation along Fildes Peninsula coastline, King George Island. Ten sites from east and west coastlines were investigated, and the concentrations of Cu, Pb, Zn, Cd, Cr, As and Hg were determined. The metal pollution index (MPI) was used to evaluate the overall pollution level represented by the investigated sites and for interregional comparisons. The two algae exhibited different preference to special trace metal. R. antarctica could accumulate more Cd (0.63 mg kg−1) and Hg (0.026 mg kg−1) than I. cordata (Cd 0.34 mg kg−1, Hg 0.019 mg kg−1). I. cordata could accumulate more As (15.53 mg kg−1) than R. antarctica (10.11 mg kg−1). There was no significant difference in accumulating Cu, Pb, Zn and Cr between the two algae. R. antarctica could be used to monitor Cd and Hg. I. cordata would be more appropriate for monitoring As. MPI monitored by the two algae were from 1.02 to 2.26 (R. antarctica), and 1.03 to 1.25 (I. cordata), respectively. Pollution situation of Fildes Peninsula was becoming serious, especially of the east coastline. The objective of this research was to gather the baseline information for trace metals investigation in Antarctic.

Molecular divergence between Iridaea cordata (Turner) Bory de Saint-Vincent from the Antarctic Peninsula and the Magellan Region

The distribution of the Southern Ocean (SO) biota is the result of major geological, oceanographic, and climate changes during the last 50 million years (Ma). Several groups of marine benthic organisms exhibit marked taxonomic similarities between the Antarctic Peninsula and southern South America, where families, genera, and even species are currently co-distributed in these continents. Several species of macroalgae including Gigartina skottsbergii, Plocamium cartilagineum, and Iridaea cordata are currently found on both sides of the Drake Passage. Advances in molecular techniques have allowed estimating phylogenetic relationships, levels of differentiation and divergence time estimates between populations from these continents in order to determine whether they constitute separate evolutionary units. In this study, we determine whether Iridaea cordata represents the same evolutionary unit in southern South America and the Antarctic Peninsula or if populations on the two sides of the Drake Passage represent different genetic lineages. According to our results, I. cordata populations from the Antarctic Peninsula and South America are clearly distinguishable evolutionary units with 8.31% and 3.17% mtDNA and cpDNA molecular divergence, respectively. The separation between Antarctic and South American populations of I. cordata occurred at the end of the Miocene, between 5 Ma (rbcL) and 9 Ma (COI-5P). These results are similar to those reported in G. skottsbergii on both sides of the Drake Passage. Thus, I. cordata populations on the two sides of the Drake Passage should be considered two sister species. Cryptic speciation plays an important role in the evolution of the Southern Ocean; thus, the systematics, biogeography, and biodiversity of the region require major revisions.

Antileishmanial activity of the Antarctic red algae Iridaea cordata (Gigartinaceae; Rhodophyta)

Leishmaniasis is considered a neglected disease and affects billions around the world, currently presenting few therapeutic options, which makes the development of new antileishmanial drugs urgent. Secondary metabolites from marine and terrestrial organisms are important sources of new chemical entities. Herein, the potential activity of crude extracts and fractions from the Antarctic macroalga Iridaea cordata (Turner) Bory de Saint-Vincent was studied against promastigote and intracellular amastigotes forms of Leishmania amazonensis. The cytotoxicity of the active fractions was evaluated on macrophages and 3T3 BALB/c fibroblasts. The chemical profile of volatile substances was analyzed using the GC-MS technique. The fractions IC-FE (IC50-AMA = 23.6 ± 3.4 μg mL−1; SI > 11) and IC-FF (IC50-AMA = 12.4 ± 1.2 μg mL−1; SI > 24) showed promising activity against amastigotes and higher selectivity to the parasite rather than to the mammalian host cells, when compared to the reference drug amphotericin B (IC50-AMA = 5.9 ± 0.3 μg mL−1; SI = 3.9). Their estimated LD50 in rodents are also higher than that in amphotericin B (LD50 IC-FE = 594.5 ± 25.87 mg kg−1; LD50 IC-FE = 580.1 ± 11.84 mg kg−1; LD50 amphoter = 172.20 ± 2.40 mg kg−1). The chemical profile of these fractions showed the presence of phthalates, esters, ketones, fatty acids, and carboxylic acids, which might be contributing alone or synergistically to the observed antileishmanial activity. Consequently, I. cordata might be used to identify new antileishmanial compounds.

Macroalgae Extracts From Antarctica Have Antimicrobial and Anticancer Potential.

Background: Macroalgae are sources of bioactive compounds due to the large number of secondary metabolites they synthesize. The Antarctica region is characterized by extreme weather conditions and abundant aggregations of macroalgae. However, current knowledge on their biodiversity and their potential for bio-prospecting is still fledging. This study evaluates the antimicrobial and cytotoxic activity of different extracts of four macroalgae (Cystosphaera jacquinotii, Iridaea cordata, Himantothallus grandifolius, and Pyropia endiviifolia) from the Antarctic region against cancer and non-cancer cell lines.Methods: The antimicrobial activity of macroalgae was evaluated by the broth microdilution method. Extracts were assessed against Staphylococcus aureus ATCC 19095, Enterococcus faecalis ATCC 4083, Escherichia coli ATCC29214, Pseudomonas aeruginosa ATCC 9027, Candida albicans ATCC 62342, and the clinical isolates from the human oral cavity, namely, C. albicans (3), C. parapsilosis, C. glabrata, C. lipolytica, and C. famata. Cytotoxicity against human epidermoid carcinoma (A-431) and mouse embryonic fibroblast (NIH/3T3) cell lines was evaluated with MTT colorimetric assay.Results: An ethyl acetate extract of H. grandifolius showed noticeable antifungal activity against all fungal strains tested, including fluconazole-resistant samples. Cytotoxicity investigation with a cancer cell line revealed that the ethyl acetate extract of I. cordata was highly cytotoxic against A-431 cancer cell line, increasing the inhibitory ratio to 91.1 and 95.6% after 24 and 48 h exposure, respectively, for a concentration of 500 μg mL−1. Most of the algal extracts tested showed little or no cytotoxicity against fibroblasts.Conclusion: Data suggest that macroalgae extracts from Antarctica may represent a source of therapeutic agents.HIGHLIGHTS Different macroalgae samples from Antarctica were collected and the lyophilized biomass of each macroalgae was extracted sequentially with different solventsThe antimicrobial and anticancer potential of macroalgae extracts were evaluatedEthyl acetate extract of H. grandifolius showed noticeable antifungal activity against all the fungal strains tested, including fluconazole-resistant samplesEthyl acetate extract of I. cordata was highly cytotoxic against the A-431 cancer cell lineMost of the algal extracts tested showed little or no cytotoxicity against normal cell lines

Phylogeny and bioactivity of epiphytic Gram-positive bacteria isolated from three co-occurring antarctic macroalgae.

Marine macroalgae are emerging as an untapped source of novel microbial diversity and, therefore, of new bioactive secondary metabolites. This study was aimed at assessing the diversity and antimicrobial activity of the culturable Gram-positive bacteria associated with the surface of three co-occurring Antarctic macroalgae. Specimens of Adenocystis utricularis (brown alga), Iridaea cordata (red alga) and Monostroma hariotii (green alga) were collected from the intertidal zone of King George Island, Antarctica. Gram-positive bacteria were investigated by cultivation-based methods and 16S rRNA gene sequencing, and screened for antimicrobial activity against a panel of pathogenic microorganisms. Isolates were found to belong to 12 families, with a dominance of Microbacteriaceae and Micrococcaceae. Seventeen genera of Actinobacteria and 2 of Firmicutes were cultured from the three macroalgae, containing 29 phylotypes. Three phylotypes within Actinobacteria were regarded as potentially novel species. Sixteen isolates belonging to the genera Agrococcus, Arthrobacter, Micrococcus, Pseudarthrobacter, Pseudonocardia, Sanguibacter, Staphylococcus, Streptomyces and Tessaracoccus exhibited antibiotic activity against at least one of the indicator strains. The bacterial phylotype composition was distinct among the three macroalgae species, suggesting that these macroalgae host species-specific Gram-positive associates. The results highlight the importance of Antarctic macroalgae as a rich source of Gram-positive bacterial diversity and potentially novel species, and a reservoir of bacteria producing biologically active compounds with pharmacological potential.

Macroalgae of Iridaea cordata as an efficient biosorbent to remove hazardous cationic dyes from aqueous solutions.

In the present work, Iridaea cordata (IC), a red marine macroalgae, was used as an efficient biosorbent for the removal of crystal violet (CV) and methylene blue (MB) dyes from aqueous solutions. The effects of pH (5, 7, and 9) and IC concentration (1, 3, and 5 g L-1) on the biosorption were studied through a 32 full factorial design. Under the optimal conditions (pH: 7, biosorbent concentration: 1 g L-1), biosorption kinetic studies were developed and the obtained experimental data were evaluated by pseudo-first order and pseudo-second order models. The results showed that the pseudo-second order model was in agreement with the experimental kinetic data for both dyes. Equilibrium studies were also carried out, and results exhibited good concordance with the Brunauer-Emmett-Teller isotherm. The biosorption capacities were 36.5 and 45.0 mg g-1 for CV and MB dyes, respectively. The dye removal percentages were around 75% for CV and 90% for MB. Thermodynamically, the biosorption process proved to be exothermic, spontaneous, and favorable. These results showed that IC biomass is a promising biosorbent for removal of CV and MB dyes from aqueous solutions.

Agar-degrading bacteria isolated from Antarctic macroalgae.

This study describes the taxonomic diversity of pigmented, agar-degrading bacteria isolated from the surface of macroalgae collected in King George Island, Antarctica. A total of 30 pigmented, agarolytic bacteria were isolated from the surface of the Antarctic macroalgae Adenocystis utricularis, Monostroma hariotii, Iridaea cordata, and Pantoneura plocamioides. Based on the 16S rRNA data, the agarolytic isolates were affiliated to the genera Algibacter, Arthrobacter, Brachybacterium, Cellulophaga, Citricoccus, Labedella, Microbacterium, Micrococcus, Salinibacterium, Sanguibacter, and Zobellia. Isolates phylogenetically related to Cellulophaga algicola showed the highest agarase activity in culture supernatants when tested at 4 and 37°C. This is the first investigation of pigmented agar-degrading bacteria, members of microbial communities associated with Antarctic macroalgae, and the results suggest that they represent a potential source of cold-adapted agarases of possible biotechnological interest.

Investigating essential and toxic elements in Antarctic macroalgae using a green analytical method

A systematic study for the determination of essential and toxic elements (such as As, Cd, Cu, Mn, Ni, Pb, V and Zn) in Antarctic macroalgae species (Desmarestia anceps, Iridaea cordata, Palmaria decipiens and Pyropia endiviifolia) was performed. For this purpose, a green sample preparation method combined with a high-sensitivity detection technique (inductively coupled plasma mass spectrometry) was used. By using the microwave-assisted digestion combined with ultraviolet radiation (MW-UV) method, 700 mg of macroalgae were digested using a diluted HNO3 solution (2 mol L−1). The accuracy was evaluated by analysis of certified reference materials of aquatic plant (BCR 060) and apple leaves (NIST 1515). Agreement with reference or informed values for all analytes ranged from 94 to 106%, except for As and Mo in BCR 060. The results were also compared with those obtained by the reference method, which did not present a significant difference (t test, 95% confidence level). Based on the results, analysed samples showed considerable variations in regards to the concentrations of Zn, Ni and Mn. Moreover, a relatively high concentration of As in Desmarestia anceps and Pyropia endiviifolia was observed. The results for most of the analytes in Antarctic macroalgae were in agreement with other studies that have been published in literature. In addition, the proposed method was suitable for determining toxic and essential elements in Antarctic macroalgae reducing reagent consumption and waste generation, which is in agreement with the green chemistry recommendation.

Anticancer Activity of Sulfated Polysaccharides Isolated from the Antarctic Red Seaweed Iridaea cordata

This study aimed to isolate and characterize sulfated polysaccharides (SPs) from Iridaea cordata and evaluate their anticancer activity. SPs of the Antarctic red seaweed were obtained by CaCl₂ (SP1) and ethanol precipitations (SP2) following diluted acid extraction at room temperature. Yields of SP1 and SP2 were approximately 14% and 23%, respectively, of the dry weight of red seaweed. The average molecular mass of the SP1 and SP2 was estimated about 1.84 × 10³ and 1.42 × 10³ kDa, respectively, by size-fractionation High-Performance Liquid Chromatography (HPLC). From the High-Performance Anion-Exchange Chromatography-Pulsed Amperometric Detection (HPAEC-PAD) analysis, the main monosaccharide was galactose with glucose and fucose as minor components. The sulfate content of SP2 (40.4%) was slightly higher than that of SP1 (33.8%). The FT-IR spectra also showed characteristic band of carrageenan-like sulfated polysaccharides. Taken together the SPs are thought to be carrageenan-like sulfated galactan. The polysaccharides (SPs) from I. cordata exhibited weak antitumor activity against PC-3 (prostate cancer), HeLa (cervical cancer), and HT-29 (human colon adenocarcinoma). To our knowledge, this is the first data on biological activity of the Antarctic red seaweed I. cordata.

Summer Epiphytic Diatoms from Terra Nova Bay and Cape Evans (Ross Sea, Antarctica)--A Synthesis and Final Conclusions.

Despite recent advances in polar marine biology and related fields, many aspects of the ecological interactions that are crucial for the functioning of Antarctic shallow water habitats remain poorly understood. Although epiphytic diatoms play an essential role in the Antarctic marine food web, basic information regarding their ecology, biodiversity and biogeography is largely unavailable. Here, we synthesise studies on Ross Sea epiphytic diatoms collected during 11 summer Antarctic expeditions between the years 1989/90 and 2011/12, presenting a full list of diatom taxa associated with three macroalgal species (Iridaea cordata, Phyllophora antarctica, and Plocamium cartilagineum) and their epiphytic sessile fauna. Diatom communities found during the three summer months at various depths and sampling stations differed significantly in terms of species composition, growth form structure and abundances. Densities ranged from 21 to >8000 cells mm-2, and were significantly higher on the surface of epiphytic micro-fauna than on any of the macroalgal species examined. Generally, host organisms characterized by higher morphological heterogeneity (sessile microfauna, ramified Plocamium) supported richer diatom communities than those with more uniform surfaces (Iridaea). Differences between epiphytic communities associated with different macroalgae were reflected better in species composition than in growth form structure. The latter changed significantly with season, which was related strongly to the changing ice conditions. A general trend towards an increasing number of erect forms in deeper waters and tube-dwelling diatoms in the shallowest sites (2–5 m) was also observed. This study explores further important and largely previously unknown aspects of relationships and interactions between Antarctic epiphytic diatoms and their micro- and macro-environments.

Stress tolerance of Antarctic macroalgae in the early life stages

Early life stages of macroalgae, especially from polar species, can be highly vulnerable to physical stressors, leading to important consequences for the fate of the whole population in scenarios of changing environmental variability. In the present study, tolerance to UV and temperature stress, as measured by rapid adjustment of photochemistry, Fv/Fm, and photosynthetic characteristics based on P-E curves (ETRmax, α and Ek), was assessed in the early life stages of six Antarctic macroalgal species from eulittoral (Pyropia endiviifolia, Iridaea cordata, Adenocystis utricularis and Monostroma hariotii) and sublittoral (Ascoseira mirabilis and Gigartina skottsbergii). Reproductive cells of eulittoral species showed the highest light demands (Ek >45 μmol photon m−2 s−1) when compared to those from sublittoral species (Ek 30 % inhibition in Fv/Fm in the same condition. Enhanced temperature (7 and 12 °C) improved the tolerance of I. cordata compared to 2 °C, but exacerbated the detrimental effects of UV on A. mirabilis. Results showed that photosynthetic characteristics varied among reproductive cells of different species, reflecting the vertical zonation of parental thalli. Otherwise, these differences appear to underlie biogeographical and evolutionary components. In addition, UV tolerance was modulated by temperature increase, while temperature increase, in turn, ameliorated the detrimental effects of stress treatments in some eulittoral species (I. cordata tetraspores). In sublittoral A. mirabilis gametangia, temperature exacerbated the reduction of photosynthetic efficiency.

First assessment of the rocky intertidal communities of Fildes Bay, King George Island (South Shetland Islands, Antarctica)

Studies on Antarctic intertidal fauna are comparatively scarce compared to those from the sublittoral and the deep sea. In order to contribute to filling this gap in knowledge, during the 2006 BENTART Spanish Antarctic Expedition, we conducted a quantitative and qualitative study on the fauna inhabiting the intertidal rocky platform of Fildes (=Maxwell) Bay, King George Island (South Shetlands Archipelago). This platform is dominated in its middle and lower area by the brown algae Adenocystis utricularis, which covers ca. 100 % of the rocky surface. Three quantitative samples of 20 × 20 cm were taken in the community of A. utricularis, and one additional sample of 20 × 20 cm in the tide pools community dominated by the gigartinacean rhodophyceae Iridaea cordata. In addition, qualitative samples of invertebrates that live under the boulders were also taken. Quantitative samples yielded a total of 9950 individuals belonging to 41 species. Mollusks were the most abundant group with a total of 9522 specimens belonging to 11 species, being the gastropod Eatoniella kerguelenensis regularis the most abundant with 6763 specimens. Crustaceans were represented by 295 specimens and 7 species and annelid polychaetes with 133 specimens and 20 taxa. The Shannon diversity indexes calculated for the quantitative samples of A. utricularis ranged between 0.803 and 1.030 with values of 1.577 for the I. cordata community. Our study confirms that the intertidal area of Fildes Bay hosts a surprisingly rich community in terms of abundance and biodiversity.