Ichtyotoxic activity of extracts from Mexican marine macroalgae

Seventy-three species of macroalgae from the Mexican Pacific, Atlantic and Caribbean coast were screened for ichtyotoxic activity. Ethanolic, acetonic and aqueous extracts were prepared and tested against the fish Carassius auratus. The extracts were classified on the basis of their effects as: toxic if the fish died in two hours or less; moderately toxic, if the organism behaved abnormally but death did notoccur, and non-toxic if the fish did not display any change. 79% species were ichtyotoxic to some degree. Extracts of 39 species were toxic, with at least one extract with lethal effects, 19 were moderately toxic and 15 species were non-toxic. Only the extracts ofDictyota bartayresiana, Dictyota cervicornis,Lobophora variegata, Bryothamnion triquetrum and Laurencia obtusa were toxic in all three solvents. The acetone and ethanol extracts were more active, and therefore are more suitable for extraction of toxic substances. This revised version was published online in August 2006 with corrections to the Cover Date.     

Fungal community associated with marine macroalgae from Antarctica

Filamentous fungi and yeasts associated with the marine algae Adenocystis utricularis, Desmarestia anceps, and Palmaria decipiens from Antarctica were studied. A total of 75 fungal isolates, represented by 27 filamentous fungi and 48 yeasts, were isolated from the three algal species and identified by morphological, physiological, and sequence analyses of the internal transcribed spacer region and D1/D2 variable domains of the large-subunit rRNA gene. The filamentous fungi and yeasts obtained were identified as belonging to the genera Geomyces, Antarctomyces, Oidiodendron, Penicillium, Phaeosphaeria, Aureobasidium, Cryptococcus, Leucosporidium, Metschnikowia, and Rhodotorula. The prevalent species were the filamentous fungus Geomyces pannorum and the yeast Metschnikowia australis. Two fungal species isolated in our study, Antarctomyces psychrotrophicus and M. australis, are endemic to Antarctica. This work is the first study of fungi associated with Antarctic marine macroalgae, and contributes to the taxonomy and ecology of the marine fungi living in polar environments. These fungal species may have an important role in the ecosystem and in organic matter recycling.     

Allelochemistry in marine macroalgae

Allelochemistry refers to the effect of an organic compound released from one organism upon an organism separated from its source. When the donor and receptor are plants (or microorganisms placed in the plant kingdom), allelopathy is described whether the effect is harmful or beneficial. In the aquatic environment, water disperses any water‐soluble allelochemical from its point of release, and rapid dilution along with lack of contact between competing organisms reduces potential encounter. This review centers on macroalgae as the source of allelochemicals. In all examples, the releasor organism is a macroalga, but receptor organisms include algae, invertebrates, fish, and microbes. Direct evidence in the sea is scanty, and there is a need for appropriate experiments in the laboratory and field. The compounds that are released by macrolagae (e.g., polyphenolics, halogenated phenols, and terpenoids) may be fortuitous byproducts of metabolism. But where they alter colonization, growth, or reproduction in a target organism, it is conceivable that they influence community structure as is known for terrestrial systems. The potential for allelochemistry is maximized in sites where water is poorly mixed, allowing released algal products to concentrate (e.g., tide pools and backbays) and where the receptor organism is adjacent to the releasor (e.g., surfaces of thalli and seaweed farms). In combination with restricting environmental conditions (e.g., critical temperature, light, salinity, pH, or oxygen), the effect of allelopathy can be synergistic. Combinations of allelochemicals, each at a concentration too low to be physiologically effective, could have a pronounced impact.     

A new screening for hemagglutinins from Vietnamese marine macroalgae

Aqueous extracts from 42 species of Vietnamese marine macroalgae, including 17 Chlorophyta, 22 Rhodophyta, and three Phaeophyta species, were examined for hemagglutination activity using native and enzyme-treated different animal and human erythrocytes. All extracts agglutinated at least one type of erythrocytes tested. Strong activity was detected in extracts from four Chlorophyta (Caulerpa serulata var. boryana, Caulerpa sertularioides f. longipes, Halimeda velasquezii, and Halimeda discoidea) and two Rhodophyta species (Gelidiella acerosa and Titanophora pulchra) with enzyme-treated rabbit and horse erythrocytes. The hemagglutinins of some active species were examined for sugar-binding specificity, pH, temperature stability, and divalent cation independency using ammonium sulfate precipitates prepared from their extracts. In a hemagglutination–inhibition test with various monosaccharides and glycoproteins, none of the hemagglutinins had affinity for monosaccharides. The activity of the hemagglutinins was inhibited by some glycoproteins tested. The inhibition profiles with glycoproteins were different depending on hemagglutinin species, suggesting the presence of lectins specific for complex N-glycans, high mannose N-glycans or O-glycans. On the other hand, the activities of almost all algal hemagglutinins were stable over a wide range of pH and temperature, and independent of the presence of divalent cations, except Gelidiopsis scoparia hemagglutinin, its activity was dependent on the presence of divalent cations. These results suggest that Vietnamese marine macroalgae may be good sources of useful lectins for many biological applications.     

Agglutinins from marine macroalgae of the southeastern United States

Protein extracts from 22 species of marine macroalgae from Florida and North Carolina were compared for their abilities to agglutinate sheep and rabbit erythrocytes. Protein extracts from 21 algal species agglutinated rabbit erythrocytes compared to 19 for sheep erythrocytes. However, agglutination by brown algal extracts was variable. The agglutination produced by protein extracts from Dictyota dichotoma could be blocked by addition of polyvinylpyrrolidone. Protein extracts from North Carolina macroalgae were also tested against five bacterial species. Three of these agglutinated bacterial cells. Ulva curvata and Bryopsis plumosa agglutinated all five species. Protein extracts from five species of Florida algae were tested for their effects on mitogenesis in mouse splenocytes and human lymphocytes. Gracilaria tikvahiae HBOI Strain G-5, Ulva rigida and Gracilaria verrucosa HBOI Strain G-16S stimulated mitogenesis in mouse splenocytes, while Gracilaria tikvahiae HBOI Strain G-16stimulated mitogenesis in human lymphocytes.     

Temperature requirements for growth and survival of macroalgae from Disko Island (Greenland)

The temperature requirements for growth and upper temperature tolerance were determined in 16 macroalgal species collected on Disko Island (Greenland). The upper survival temperatures were examined in 1°C steps, and growth measured at 5°C intervals between 0 and 20°C using a refined method, where the fresh weight was determined weekly or fortnightly over a period of 5 or 6 weeks. To express temperature-growth responses, growth rates of temperature-acclimated plants were taken. Two groups with different temperature requirements were identified: (1) A stenothermal group includingAcrosiphonia arcta, Acrosiphonia sonderi, Urospora penicilliformis, Devaleraea ramentacea, Desmarestia aculeata, Pilayella littoralis, growing between 0 and (10 to) 15 (or 20)°C with optima between 0 and 10°C. The upper survival temperatures in these species and inChromastrum secundatum, Chromastrum virgatulum, Chordaria flagelliformis were between 17 and 23°C (duration of experiment: 2 weeks). (2) A eurythermal group includingEnteromorpha clathrata, Enteromorpha intestinalis andPolysiphonia urceolata growing between 0 and 20°C with growth optima at 10 or 15°C. The upper survival temperatures in these species and inChaetomorpha tortuosa, Bangia atropurpurea andEudesme virescens were between 24 and 31°C. These algal species showed little adaptation to the Arctic temperatures. In contrast, algae from the first group exhibited a relatively high adaptation to low temperatures — approaching the low temperature requirements of Antarctic algae. The results are discussed in relation to the geographic distribution of individual species.     

New records of temperate and sub-Antarctic marine benthic macroalgae from Antarctica

 During visits to several localities on the South Shetland Islands and the Antarctic Peninsula in summer 1994 we made collections of marine benthic algae. Among the algae we collected were three new records for Antarctica [Petalonia fascia (OF Müller) Kuntze; Enteromorpha intestinalis (L.) Nees; Rhodymenia subantarctica Ricker] and seven other species [Scytosiphon simplicissimus (Clemente) Cremades; Chordaria linearis (Hooker et Harvey) Cotton; Halopteris obovata (Hooker et Harvey) Sauvageau; Acrosiphonia arcta (Dillwyn) J. Agardh; Enteromorpha compressa (L.) Nees; Bangia atropurpurea (Roth) C. Agardh; Porphyra plocamiestris Ricker] that had been reported on only one or two previous occasions (or, in one case, three). The ten species detailed in this paper fall into two groups: four species previously known from sub-Antarctic islands and/or locations in southern South America, and six species having a wider distribution in temperate regions. We discuss the possibility that the less accessible subtidal habitats of some species may have prevented earlier discovery. Other species may be comparatively recent adventives, most likely introduced with shipping. In view of possible global climate changes, species of this latter group are regarded as suitable organisms for monitoring changes of water temperature. Received: 12 December 1995/Accepted: 14 April 1996     

Responses of marine macroalgae to hydrogen-peroxide stress

In this study, we determined the antioxidative potential of 15 marine macroalgae by measuring the photosynthetic efficiency under artificial oxidative stress after a 30-min exposure to a series of ascending H₂O₂ concentrations. Species exhibiting high maximum quantum yields (F_v/F_m values) were regarded as not susceptible towards H₂O₂ stress. In addition to the short-term stress experiments, the antioxidative defense systems (enzymatic and non-enzymatic) of selected algal species under longer exposure times to H₂O₂ were investigated.Species with striking photosynthetic activity under H₂O₂ stress were Chaetomorpha melagonium (Chlorophyta), showing 40% reduced F_v/F_m as compared to the control after 8 days of exposure to 20 mM H₂O₂. In Fucus distichus (Phaeophyta) F_v/F_m decreased to 50% of the control under the same exposure conditions. Polysiphonia arctica (Rhodophyta) exhibited highest F_v/F_m values with a reduction of only 25%, therefore possessing the highest antioxidative potential of the investigated species.In P. arctica the activities of the antioxidative enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), as well as the pool size of the antioxidant ascorbic acid were investigated. When exposed to different H₂O₂ concentrations (0-2 mM) over 6 days, the intrinsic activities of SOD and GR were stimulated. In a kinetic study over 8 days, the activity of antioxidative enzymes APX and CAT as well as ascorbic acid content were recorded. APX activity was much higher in H₂O₂-treated thalli at the end of the experiment than in the control, also CAT activity increased significantly with increasing H₂O₂ stress. In parallel, ascorbic acid content was reduced under high H₂O₂ concentrations. Furthermore, by using GC-MS techniques in P. arctica bromophenolic compounds with antioxidative properties were identified.This study shows that the measurement of the in vivo fluorescence of photosystem II is a suitable tool to determine the effect of oxidative stress on macroalgae. From these studies it is obvious that different algal species have varying strategies against oxidative stress which correlate with zonation on the shore.     

The characteristics of bio-oil produced from the pyrolysis of three marine macroalgae

The pyrolysis of two brown macroalgae (Undaria pinnatifida and Laminaria japonica) and one red macroalgae (Porphyra tenera) was investigated for the production of bio-oil within the temperature range of 300-600°C. Macroalgae differ from lignocellulosic land biomass in their constitutional compounds and high N, S and ash contents. The maximum production of bio-oil was achieved at 500°C, with yields between 37.5 and 47.4 wt.%. The main compounds in bio-oils vary between macroalgae and are greatly different from those of land biomass, especially in the presence of many nitrogen-containing compounds. Of the gaseous products, CO(2) was dominant, while C(1)-C(4) hydrocarbons gradually increasing at 400°C and above. The pretreatment of macroalgae by acid washing effectively reduced the ash content. The pyrolysis of macroalgae offers a new opportunity for feedstock production; however, the utilization of bio-oil as a fuel product needs further assessment.     

Hydrogen and volatile fatty acids production from marine macroalgae by anaerobic fermentation

Hydrogen and volatile fatty acids (VFAs) were coproduced from marine macroalgae by anaerobic fermentation using a microbial community. The hydrogen and VFAs production were characterized based on inoculum heat-treatment, methanogen inhibitor addition, operating temperature, and in-situ extraction of VFAs. Maximum hydrogen of 179 mL/g-VS and VFAs concentration of 9.8 g/L were produced from 35 g/L of S. japonica within 5 days of anaerobic fermentation. Hydrogen and VFAs yields were well-correlated with carbohydrate content of substrate. Inoculum heat-treatment significantly improved hydrogen production while the VFAs productivity was affected adversely. The addition of methanogen inhibitors also enhanced the hydrogen production, but the effect on VFAs production was dependent on the type of inhibitor used. Low temperature (25°C) was found to be favorable for high hydrogen and VFAs yield, while high temperature (40°C) and programmed-temperature (35 ~ 45°C) were more favorable for hydrogen and VFAs productivity. Clostridium sp. content was found to be the most abundant at 25°C. An extractive fermentation with anion-exchange resin was tested to recover the VFAs and to control the pH during the anaerobic fermentation.     

Recombinant viruses as transformation vectors of marine macroalgae

The large dsDNA viruses that are known to infect eukaryotic algae show promise as genetic vectors for algal biotechnology. The large size (150–330 kbp) of these viral genomes may permit insertion of large sequences of foreign DNA. The viruses infecting filamentous marine brown algae appear to be integrated into the genomes of their hosts, and may provide integration mechanisms that can be used for directing insertion of foreign genes into algal chromosomes.     

Vanadium an essential element for some marine macroalgae

In some marine algae cultivated axenically in the artificial medium ASP6 F2 (pH 8.3) vanadium at 1–100 g l^-1 increases the fresh weight. In the multicellular brown algaFucus spiralis 10 g V I^-1 enhances the fresh weight by about 400% while in the green algaEnteromorpha compressa the yield is increased by 90%. Red algae do not respond to vanadium. InFucus morphological effects are displayed in more frequent branching and/or broader blades. No significant increase in the chlorophyll content could be demonstrated at the early stage at which these morphological effects first appeared. Later the chlorophyll content increased.     

Red List of marine macroalgae of the Wadden Sea

This list forms part of the Report on the RED LISTS OF BIOTOPES, FLORA AND FAUNA OF THE TRILATERAL WADDEN SEA AREA. For basic information concerning, for example, function of these lists, species taken into account, structure of the lists and abbreviations used, see also the general introduction to the Red Lists.     

中国青岛沿岸潮间带海藻中的可培养真菌多样性（英文）

从中国青岛沿岸潮间带采集9种海藻,包括3种褐藻、4种绿藻和2种红藻,通过传统培养方法共分离获得92株真菌。根据形态学特征和真菌转录间隔区(ITS)r DNA序列分析对所得菌株进行鉴定,结果显示:92株真菌隶属子囊菌门56种,担子菌门1种及接合菌门1种;优势属为枝顶孢属、曲霉属、枝孢属、青霉属和帚霉属;无性型真菌40种,占总菌株数量的75%;绿藻门刺松藻的真菌多样性最高,其次为褐藻门鼠尾藻,红藻门珊瑚藻的真菌多样性最低。本研究首次对中国沿岸潮间带海藻中的真菌多样性进行报道,为进一步研究藻生真菌生态功能提供参考。     

Alternative methods of photosynthetic carbon assimilation in marine macroalgae

Two green macroalgae, Codium decorticatum and Udotea flabellum, differ photosynthetically. Codium had high O₂-sensitive, and Udotea low O₂-insensitive, CO₂ compensation points; Codium showed a Warburg effect at seawater dissolved inorganic carbon levels and had photorespiratory CO₂ release, whereas Udotea did not. Seawater dissolved inorganic carbon levels did not saturate photosynthesis. For Codium, but not Udotea, the Warburg effect was increased by ethoxyzolamide, a carbonic anhydrase inhibitor, at high but not low pH. Isolated chloroplasts from both macroalgae showed a Warburg effect that was ethoxyzolamide-insensitive. In both macroalgae, chloroplastic and extrachloroplastic carbonic anhydrase activity was present. P-enolpyruvate carboxykinase (PEPCK) carboxylating activity in Udotea extracts was equivalent to that of ribulose bisphosphate carboxylase, and enzyme activities for C₄ acid metabolism and P-enolpyruvate regeneration were sufficient to operate a limited C₄-like system. In Udotea, malate and aspartate were early-labeled photosynthetic products that turned over within 60 seconds. Photorespiratory compounds were much less labeled in Udotea. Low dark fixation rates ruled out Crassulacean acid metabolism. A limited C₄-like system, based on PEPCK, is hypothesized to be the mechanism reducing photorespiration in Udotea. Codium showed no evidence of photosynthetic C₄ acid metabolism. Marine macroalgae, like terrestrial angiosperms, seem to have diverse photosynthetic modes.     

Antioxidant activity of mycosporine-like amino acids isolated from three red macroalgae and one marine lichen

Several standard in vitro assays were performed in order to determine the potential antioxidant capabilities of purified aqueous extracts of the mycosporine-like amino acids (MAAs), porphyra-334 plus shinorine (P-334 + SH), isolated from the red alga Porphyra rosengurttii, asterina-330 plus palythine (AS-330 + PNE), from the red alga Gelidium corneum, shinorine (SH), from the red alga Ahnfeltiopsis devoniensis, and mycosporine -glycine (M-Gly), isolated from the marine lichen Lichina pygmaea. The scavenging potential of hydrosoluble radicals (ABTS⁺ decolorization method), the antioxidant activity in lipid medium (β-carotene/ linoleate bleaching method) and the scavenging capacity of superoxide radicals (pyrogallol autooxidation assay) were evaluated. In terms of scavenging of hydrosoluble radicals, the antioxidant activity of all MAAs studied was dose-dependent and it increased with the alkalinity of the medium (pH 6 to 8.5). M-Gly presented the highest activity in all pH tested; at pH 8.5 its IC₅₀ was 8-fold that of L-ascorbic acid (L-ASC) followed by AS-330 + PNE while P-334 + SH and SH showed scarce activity of scavenging of hydrosoluble free radicals. AS-330 + PNE showed high activity for inhibition of β-carotene oxidation relative to vitamin E and superoxide radical scavenging whilst the activity of P-334 +SH and SH were moderate. According to these results, the potential of MAAs in photoprotection can be considered high due to a double function: (1) UV chemical screening with high efficiency for UVB and UVA regions of the solar spectrum, and (2) their antioxidant capacity.     

Clonal architecture in marine macroalgae: ecological and evolutionary perspectives

The study of the ecological and evolutionary consequences of clonal growth in vascular plants has been widely addressed; however, marine macroalgae, which are interesting modular organisms that combine simple morphologies and complex life cycles, have been almost ignored. This paper presents a review and analysis of the ecological and evolutionary consequences of clonality in marine macroalgae, including three main subjects: (1) modular construction (modules and ramets); (2) life cycle and evolutionary perspectives, and (3) ecological perspectives of clonality in marine macroalge. The biological emergent attributes of clonality are present in marine macroalgae e.g. high longevity of the genet by the continual renewal of modules, and variable morphological plasticity of ramets and modules in relation to environmental conditions. However, experimental work is still needed to solve questions such as the effect of crowding on survival rates and use of resources, as well as its effect on sexual or asexual patterns of reproduction. I expect that the study of the evolutionary consequences of the combined presence of alternation of generations and clonal growth in marine macroalgae will make important contributions to clonal plant theory.     

Molecular detection of epiphytic Acaryochloris spp. on marine macroalgae

A molecular method for detecting the epiphyte community on marine macroalgae was developed by using PCR-denaturing gradient gel electrophoresis. Selective amplification of 16S rRNA gene fragments from either cyanobacteria or algal plastids improved the detection of minor epiphytes. Two phylotypes of Acaryochloris, a chlorophyll d-containing cyanobacterium, were found not only on red macroalgae but also on green and brown macroalgae.     

Using marine macroalgae for carbon sequestration: a critical appraisal

There has been a good deal of interest in the potential of marine vegetation as a sink for anthropogenic C emissions (“Blue Carbon”). Marine primary producers contribute at least 50% of the world’s carbon fixation and may account for as much as 71% of all carbon storage. In this paper, we analyse the current rate of harvesting of both commercially grown and wild-grown macroalgae, as well as their capacity for photosynthetically driven CO₂ assimilation and growth. We suggest that CO₂ acquisition by marine macroalgae can represent a considerable sink for anthropogenic CO₂ emissions and that harvesting and appropriate use of macroalgal primary production could play a significant role in C sequestration and amelioration of greenhouse gas emissions.