Evidence of microalgal isotopic fractionation through enrichment of depleted uranium.

Resulting from the nuclear fuel cycle, large amounts of depleted uranium (DU) tails are piling up, waiting for possible use or final disposal. To date, the recovery of the residual 235U isotope contained in DU has been conducted only marginally by physical processes. Relative isotope abundances are often mediated by biological processes, and the biologically driven U isotopic fractionation has been previously identified in reducing bacteria. Our results indicate that the cells of two microalgal strains (freshwater Chlamydomonas sp. (ChlGS) and marine Tetraselmis mediterranea (TmmRU)) took up DU from the exposure solutions, inducing U isotopic fractionation with a preference for the fissile 235U isotope over 238U. The n(235U)/n(238U) isotopic fractionation magnitudes (δ235) were 23.6 ± 12.5‰ and 370.4 ± 103.9‰, respectively. These results open up new perspectives on the re-enrichment of DU tailings, offering a potential biological alternative to obtain reprocessed natural-equivalent uranium. Additionally, the findings present implications for identifying biological signatures in the geologic records.

[Effects of Nutrient Addition on the Growth and Competition of Bloom Forming Cyanobacterium Chrysosporum ovalisporum: An In-situ Experiment].

An in-situ mesocosm experiment was conducted to study the growth dynamic of Chrysosporum ovalisporum and the other phytoplankton organisms under accelerated eutrophication conditions by using 39 buckets (100 L) in Lake Dishui, Shanghai. The results showed that the growth of both filamentous cyanobacteria (C. ovalisporum) and green algae were promoted with nutrient enrichment. The increase in the algal biomass rate in N plus P addition treatments was significantly higher than in treatments with N or P alone (P<0.05). Although the increasing biomass rate with P addition alone was higher than with N alone, there was no statistically significant difference (P>0.05). The relevant abundance of C. ovalisporum showed a significantly decreasing trend with N addition treatments and N plus P additions treatments (P<0.05), although it was slightly increased with the treatments with P alone (P>0.05). Nutrient addition could significantly improve the growth of small sized algae organisms (Chroococcus spp., Coelastrum spp., Chlorella spp., Tetraedron spp., and Scenedesmus spp.) rather than C. ovalisporum in all treatments (P<0.05). The small sized green algae overcoming C. ovalisporum indicated that small sized algae were more favored by hyper-eutrophicated, high water temperature and relatively undisturbed conditions. This is because small sized algal organisms have higher metabolic and growth rates compared to other sized algae, especially in stationary water regimens and high, light density conditions. We foresee that the small sized algae, Chlorophyte, dominating the small hyper-eutrophic aquatic system may be a potential succession pattern in the high water temperature seasons.

A study of the chemical diversity of macroalgae from South Eastern Australia.

Macroalgae are a rich source of biologically active chemical diversity for pharmaceutical and agrichemical discovery. However, the ability to understand the complexities of their chemical diversity will dictate whether these natural products have a place in modern discovery paradigms. In this study, we examined the relationship between secondary metabolite production and biological activity for a cohort of 127 macroalgae samples collected from various locations across South Eastern Australia. Approximately 20% of the macroalgae samples showed high levels of chemical diversity and productivity, which also correlated strongly with bioactivity. These "talented" species represent sustainable sources of metabolites that may be readily harvested for large-scale production. At a taxonomic level, significant differences in metabolite production and diversity were observed between Chlorophyta, Rhodophyta and Phaeophyta. For each talented species, the cometabolite pattern was unique to that species, with closely related species within the same genus displaying very different profiles. Despite over 50years of investigation, we estimate that more than two-thirds of the chemical diversity of macroalgae remains unknown to science. By understanding the physicochemical properties and distribution patterns of metabolites, it is possible to make reasoned judgements about sustainable sourcing of macroalgae for biodiscovery.

Polar Lipids Analysis of Cultured Phytoplankton Reveals Significant Inter-taxa Changes, Low Influence of Growth Stage, and Usefulness in Chemotaxonomy.

The high lipid diversity of microalgae has been used to taxonomically differentiate phytoplankton taxa at the class level. However, important lipids such as phospholipids (PL) and betaine lipids (BL) with potential chemotaxonomy application in phytoplankton ecology have been scarcely studied. The chemotaxonomy value of PL and BL depends on their intraspecific extent of variation as microalgae respond to external changing factors. To determine such effects, lipid class changes occurring at different growth stages in 15 microalgae from ten different classes were analyzed. BL occurred in 14 species and were the less affected lipids by growth stage with diacylglyceryl-hydroxymethyl-N,N,N-trimethyl-b-alanine (DGTA) showing the highest stability. PL were more influenced by growth stage with phosphatidylcholine (PC), phosphatidylglycerol (PG), and phosphatidyletanolamine (PE) declining towards older culture stages in some species. Glycolipids were the more common lipids, and no evident age-related variability pattern could be associated to taxonomic diversity. Selecting BL and PL as descriptor variables optimally distinguished microalgae taxonomic variability at all growth stages. Principal coordinate analysis arranged species through a main tendency from diacylglyceryl-hydroxymethyl-N,N,N-trimethyl-b-alanine (DGCC) containing species (mainly dinoflagellates and haptophytes) to DGTA or PC containing species (mainly cryptophytes). Two diatom classes with similar fatty acid profiles could be distinguished from their respective content in DGTA (Bacillariophyceae) or DGCC (Mediophyceae). In green lineage classes (Trebouxiophyceae, Porphyridophyceae, and Chlorodendrophyceae), PC was a better descriptor than BL. BL and PL explained a higher proportion of microalgae taxonomic variation than did fatty acids and played a complementary role as lipid markers.

CO2 and inorganic nutrient enrichment affect the performance of a calcifying green alga and its noncalcifying epiphyte.

Ocean acidification studies in the past decade have greatly improved our knowledge of how calcifying organisms respond to increased surface ocean CO2 levels. It has become evident that, for many organisms, nutrient availability is an important factor that influences their physiological responses and competitive interactions with other species. Therefore, we tested how simulated ocean acidification and eutrophication (nitrate and phosphate enrichment) interact to affect the physiology and ecology of a calcifying chlorophyte macroalga (Halimeda opuntia (L.) J.V. Lamouroux) and its common noncalcifying epiphyte (Dictyota sp.) in a 4-week fully crossed multifactorial experiment. Inorganic nutrient enrichment (+NP) had a strong influence on all responses measured with the exception of net calcification. Elevated CO2 alone significantly decreased electron transport rates of the photosynthetic apparatus and resulted in phosphorus limitation in both species, but had no effect on oxygen production or respiration. The combination of CO2 and +NP significantly increased electron transport rates in both species. While +NP alone stimulated H. opuntia growth rates, Dictyota growth was significantly stimulated by nutrient enrichment only at elevated CO2, which led to the highest biomass ratios of Dictyota to Halimeda. Our results suggest that inorganic nutrient enrichment alone stimulates several aspects of H. opuntia physiology, but nutrient enrichment at a CO2 concentration predicted for the end of the century benefits Dictyota sp. and hinders its calcifying basibiont H. opuntia.

[Phytoplankton community structure and assessment of water quality in the middle and lower reaches of Fenhe River].

To understand the distribution of phytoplankton and the water quality in the middle and lower reaches of Fenhe River, 18 sampling sites were selected for specimen collection, species identification and data analysis. The results showed that: (1) There were 298 species of phytoplankton under the membership of 8 divisions and 96 genera, among which, Bacillariophyta was the dominant division, with a total of 127 species of 27 genera, followed by Chlorophyta, with 104 species of 41 genera, and Cyanophyta, with 45 species of 20 genera. Only 22 species of 8 genera belonged to Euglenophyta, Cryptophyta, Pyrrophyta, Chrysophyta and Xanthophyta. The number of species in wet season was higher than that in dry season at all sites. Dominant species included Cyclotella meneghiniana, Synedra acus, Navicula cryptocephala, Nitzschia palea of Bacillariophyta, Chlorella vulgaris of Chlorophyta, Oscillatoria tenuis, O. amphibia of Cyanophyta, most of which were indicator species of alpha- and beta-mesosaprobic type. Cell density was higher in wet season and lower in dry season. (2) Shannon-Wieaver species diversity index ranged from 1 to 3 basically. Margalef species richness index ranged from 0.5 to 2. Pielou evenness index ranged 0.3-0.8. (3) During the wet season, most dominant species of Chlorophyta and Euglenophyta had higher correlation with chemical oxygen demand (COD), conductivity and ammonia nitrogen. The dominant species of Cyanophyta were greatly influenced by the contents of water temperature and chromium (Cr). The distribution of dominant species of Bacillariophyta was complicatedly related with environmental factors. During the dry season, there was a higher correlation between the members of Cyanophyta and ammonia nitrogen, total phosphorus, COD. The species of Chlorophyta and Euglenophyta were mainly influenced by the dissolved oxygen and total phosphorus. The bacillariophytes were mainly related with total phosphorus, dissolved oxygen, pH and cadmium (Cd). In conclusion, the water was moderately to heavily contaminated in middle and lower reaches of Fenhe River and the water quality was eutrophic.

Optimisation of the critical medium components for better growth of Picochlorum sp. and the role of stressful environments for higher lipid production.

BACKGROUND: Coastal countries that suffer from a scarcity of water, such as Tunisia, have to cultivate marine microalgae on non-arable land in order to produce feedstock and overcome their demands of nutrition and energy. In this framework, a green microalga, CTM 20019, was isolated, identified as Picochlorum sp. and tested for its lipid production. RESULTS: The dry weight of Picochlorum sp. is composed of 163 g kg(-1) lipids, 225 g kg(-1) total sugars, 440 g kg(-1) proteins and 112 g kg(-1) ash rich in potassium, calcium, iron, magnesium and zinc. Gas chromatography-mass spectrometry analysis showed that the main fatty acids were palmitic acid (29%), linolenic acid (26.5%), linoleic acid (23.5%), hexadecatrienoic acid (11%) and hexadecadienoic acid (8.5%). As it is known that culture conditions greatly influence the composition of microalgae, the experiments were designed to optimise the composition of the medium in order to increase Picochlorum sp. growth from OD680nm = 0.53 to OD680nm = 2.2 and lipid accumulation from 163 g kg(-1) to 190 g kg(-1) . The highest lipid contents of 570 and 585 g kg(-1) were achieved under phosphate starvation and sodium carbonate supplementation, respectively. Under these conditions, the fatty acid profile is dominated by mono-unsaturated and polyunsaturated acids, and is therefore suitable for aqua-culture feeding. However, under high salinity, growth and lipid synthesis are inhibited, and the fatty acids are saturate, and the product is therefore suitable for biodiesel. CONCLUSION: This high lipid content rich in essential fatty acids, omega-6 and omega-3, endorses this wild strain of Picochlorum sp. as a promising feedstock for aqua-culture and human nutrition or for the production of biodiesel. © 2013 Society of Chemical Industry.

[Influence of decomposition of Cladophora sp. on phosphorus concentrations and forms in the overlying water].

Sediments were sampled in the dominated zone of Cladophora sp. in Rongcheng Swan Lake, and cultivated with algae in the laboratory to reveal the influence of Cladophora decomposition on concentrations and forms of phosphorus in the overlying water. Concentrations of total phosphorus (TP), dissolved total phosphorus (DTP), soluble reactive phosphorus (SRP), particulate phosphorus (PP) and dissolved organic phosphorus (DOP) in overlying water were investigated, and some physicochemical parameters, such as dissolved oxygen (DO), pH and conductivity were monitored during the experiment. In addition, the influence of algae decomposition on P release from sediments was analyzed. Due to the decomposition of Cladophora, DO concentration in the overlying water declined remarkably and reached the anoxic condition (0-0.17 mg x L(-1)). The pH value of different treatments also decreased, and treatments with algae reduced by about 1 unit. Concentrations of TP and different P forms all increased obviously, and the increasing extent was larger with the adding algae amount. TP concentrations of different treatments varied from 0.04 mg x L(-1) to 1.34 mg x L(-1). DOP and PP were the main P forms in the overlying water in algae without sediments treatments, but SRP concentrations became much higher in algae with sediments treatments. The result showed that P forms released from decomposing Cladophora were mainly DOP and PP, and the Cladophora decomposition could also promote the sediments to release P into the overlying water.

Interactions between pH and nutrients on benthic algae in streams and consequences for ecological status assessment and species richness patterns.

Eutrophication and acidification are among the major stressors on freshwater ecosystems in northern Europe and North America, but possible consequences of interactions between pH and nutrients on ecological status assessment and species richness patterns have not previously been assessed. Using data from 52 river sites throughout Norway, we investigated the combined effects of pH and nutrients on benthic algae assemblages, specifically 1) taxa-specific couplings between nutrient and acidity traits, 2) the degree of consistency between different biotic indices, separately for nutrients and acid conditions, 3) the impact of pH on nutrient indices and phosphorus on indices of acid conditions, and 4) the impact of pH and phosphorus supply on diatom and non-diatom taxon richness. We found that 1) acid-tolerant taxa are generally associated with nutrient-poor conditions, with only a few exceptions; this is probably more a consequence of habitat availability than reflecting true ecological niches; 2) correlation coefficients between nutrient indices and TP, as well as acid conditions indices and pH were barely affected when the confounding factor was removed; 3) the association of acid-tolerant taxa with nutrient-poor conditions means that the lowest possible nutrient index at a site, as indicated by benthic algae, is lower at acid than at circumneutral sites. Although this may be an artifact of the datasets from which taxa-specific indicator values were derived, it could lead to a drift in nutrient indices with recovery from acidification; 4) the response of non-diatom taxon richness follows a complex pattern with a synergistic interaction between nutrient supply and pH. In contrast, diatom richness follows a simple additive pattern; this suggests structural differences between diatoms and non-diatom benthic algae in their response to nutrient supply and pH; diatom taxon richness tended to increase with nutrient supply, while non-diatom richness decreased.

Mangrove microbial diversity and the impact of trophic contamination.

Mangroves are threatened ecosystems that provide numerous ecosystem services, especially through their wide biodiversity, and their bioremediation capacity is a challenging question in tropical areas. In a mangrove in Mayotte, we studied the potential role of microbial biofilm communities in removing nutrient loads from pre-treated wastewater. Microbial community samples were collected from tree roots, sediments, water, and from a colonization device, and their structure and dynamics were compared in two areas: one exposed to sewage and the other not. The samples from the colonization devices accurately reflected the natural communities in terms of diversity. Communities in the zone exposed to sewage were characterized by more green algae and diatoms, higher bacteria densities, as well as different compositions. In the area exposed to sewage, the higher cell densities associated with specific diversity patterns highlighted adapted communities that may play a significant role in the fate of nutrients.

Algal diversity in flowing waters at an acidic mine drainage "barrens" in central Pennsylvania, USA.

Microscopic investigations were undertaken to decipher the diversity in the lotic algal communities from acidic waters (pH 2.4-3.2) flowing overland in sheets and channels at an acid mine drainage (AMD) barrens near Kylertown, PA, USA. Microscopic observations, supplemented with taxonomic keys, aided in identification of the dominant algae, and measurement of carbon from adjacent soils was undertaken. The unicellular protist Euglena sp. was most abundant in slower flowing waters (i.e., pool near point of emergence and surficial flow sheets), while Ulothrix sp. was most abundant in faster flowing water from the central stream channel. A diverse range of unicellular microalgae such as Chlorella, Cylindrocystis, Botryococcus, and Navicula and several filamentous forms identified as Microspora, Cladophora, and Binuclearia were also recorded. The observed high algal diversity may be related to the long duration of AMD flow at this site which has led to the development of adapted algal communities. The comparatively higher carbon content in soil materials adjacent to slower flowing water sampling locations provides evidence for the important role of algae as primary producers in this extreme environment.

Isolation of a new strain of Picochlorum sp and characterization of its potential biotechnological applications.

Selection of new autochthon strains is necessary, and for the moment the best strategy, to find microalgae well adapted to the local climatological conditions able to simultaneously produce several compounds of biotechnological interest and grow at high rates. We describe the isolation and characterization of a new microalgal strain isolated from the marshlands of the Odiel River in the Southwest of Spain. The new microalga belongs to the genus Picochlorum, as deduced from the analysis of its 18S rRNA encoding gene, is able to grow at a high growth rate and thrive with adverse conditions. It has an appreciable constitutive level of lutein (3.5 mg g(-1) DW) and zeaxanthin (0.4 mg g(-1) DW) which is increased to 1.8 mg g(-1) DW at high light intensities. This strain is also characterized by a very low level of linolenic acid (3.8% of total fatty acids) and no polyunsaturated fatty acids with four or more double bonds. Although the total lipid content is not particularly high, 23% of the dry weight, its fatty acid profile makes of Picochlorum sp HM1 a promising candidate for biodiesel production, and the high content in the carotenoids lutein and zeaxanthin indicates that the microalga could also be a good source for natural eye vitamin supplements, which could be obtained as co-products.

Fatty acids as chemotaxonomic markers of marine macrophytes from Rio de Janeiro state, Brazil.

The distribution of fatty acids in 13 species of macroalgae (Chlorophyta, Ochrophyta and Rhodophyta) and 1 seagrass (Spartina sp), collected on the Rio de Janeiro state coast was determined. The results were evaluated in search of correlations between the taxonomic and phylogenetic position of these macrophytes. Statistical analyses showed the effectiveness as taxonomic and phylogenetic markers of the distribution of the methyl fatty acid esters in these macrophytes.

Influence of CO2 on growth and hydrocarbon production in Botryococcus braunii.

Botryococcus braunii is a green colonial fresh water microalga and it is recognized as one of the renewable resources for production of liquid hydrocarbons. CFTRI-Bb-1 and CFTRI-Bb-2 have been reported for the first time and their performance with regard to growth and biochemical profile is presented here. The present study focused on effect of carbon dioxide (CO2) on biomass, hydrocarbon, carbohydrate production, fatty acid profile, and carotenoid content in various species of B. braunii (LB-572, SAG 30.81, MCRC-Bb, N-836, CFTRI-Bb-1, and CFTRI-Bb-2) at 0.5, 1.0, and 2.0% (v/v) levels using a two-tier flask. CO2 at 2.0% (v/v) level enhanced growth of the organism, and a two-fold increase in biomass and carotenoid contents was observed in all the B. braunii strains studied compared with control culture (without CO2 supplementation). At 1% and 2% (v/v) CO2 concentrations, palmitic acid and oleic acid levels increased by 2.5 to 3 folds in one of the strains of B. braunii (LB-572). Hydrocarbon content was found to be above 20% at 2% CO2 level in the B. braunii LB-572, CFTRI-Bb-2, CFTRI-Bb-1, and N-836 strains, whereas it was less than 20% in the SAG 30.81 and MCRC-Bb strains compared with control culture. This culture methodology will provide information on CO2 requirement for growth of algae and metabolite production. B. braunii spp. can be grown at the tested levels of CO2 concentration without much influence on culture pH.

Removal of low molecular weight phenols from olive oil mill wastewater using microalgae.

The treatment of olive oil mill wastewater (OMW) with two phenol resistant algae, Ankistrodesmus braunii and Scenedesmus quadricauda, showed a limited reduction of phenol content after 5 d of treatment, irrespective of algal concentration. Otherwise, cultures of both algae, grown in the dark, degraded over 50% of the low molecular weight phenols contained in OMW, but they were not completely removed, but were biotransformed into other non-identified, aromatic compounds.

Haematococcus astaxanthin: applications for human health and nutrition.

The carotenoid pigment astaxanthin has important applications in the nutraceutical, cosmetics, food and feed industries. Haematococcus pluvialis is the richest source of natural astaxanthin and is now cultivated at industrial scale. Astaxanthin is a strong coloring agent and a potent antioxidant - its strong antioxidant activity points to its potential to target several health conditions. This article covers the antioxidant, UV-light protection, anti-inflammatory and other properties of astaxanthin and its possible role in many human health problems. The research reviewed supports the assumption that protecting body tissues from oxidative damage with daily ingestion of natural astaxanthin might be a practical and beneficial strategy in health management.