Distribution by Scientific Domains
Distribution within Earth and Environmental Science

Kinds of Seawater

  • artificial seawater

  • Terms modified by Seawater

  • seawater intrusion
  • seawater medium
  • seawater sample
  • seawater system
  • seawater temperature

  • Selected Abstracts

    Highly Sensitive and Selective Measurement of Bismuth in Seawater and Drug with 1,2-Phenylenedioxydiacetic Acid by Cathodic Adsorptive Stripping Voltammetry

    ELECTROANALYSIS, Issue 7 2006
    B. Gholivand
    Abstract A new method is presented for determination of bismuth based on cathodic adsorptive stripping of complex bismuth with 1,2-phenylenedioxydiacetic acid (PDA) at a hanging mercury drop electrode (HMDE). The effect of various parameters such as pH, concentration of ligand, accumulation potential and accumulation time on the selectivity and sensitivity were studied. The optimum conditions for determination of bismuth include nitric acid concentration 0.01,M, 8.0×10,4,M PDA and accumulation time 120,s, accumulation potential of ,200,mV. The limits of detection are 0.25 and 0.05,nM, and responses are linear 1,1000 and 0.1,400,nM at tacc of 60 and 120,s, respectively. Many common anions and cations do not interfere in the determination of bismuth. The method was applied to the determination of bismuth in some real samples such as sea , and spring water and drug. [source]

    Abundance and diversity of heterotrophic bacterial cells assimilating phosphate in the subtropical North Atlantic Ocean

    Krista Longnecker
    Summary Microorganisms play key roles in the cycles of carbon and nutrients in the ocean, and identifying the extent to which specific taxa contribute to these cycles will establish their ecological function. We examined the use of 33P-phosphate to identify heterotrophic bacteria actively involved in the cycling of phosphate, an essential inorganic nutrient. Seawater from the sub-tropical North Atlantic Ocean was incubated with 33P-phosphate and analysed by microautoradiography to determine the proportion and diversity of the bacterial community-assimilating phosphate. Complementary incubations using 3H-leucine and 3H-thymidine were also conducted. We found that a higher proportion of total heterotrophic bacterial cells in surface water samples assimilated phosphate compared with leucine or thymidine. Bacteria from all of the phylogenetic groups we identified by CARD-FISH were able to assimilate phosphate, although the abundances of cells within each group did not scale directly with the number found to assimilate phosphate. Furthermore, a significantly higher proportion of Alphaproteobacteria, Gammaproteobacteria and Cytophaga -like cells assimilated phosphate compared with leucine or thymidine. Our results suggest that a greater proportion of bacterial cells in surface waters are actively participating in the biogeochemical cycling of phosphorus, and possibly other elements, than is currently estimated through the use of 3H-leucine or 3H-thymidine. [source]

    Rare Earth Element Concentrations in the Natural Water Reference Materials (NRCC) NASS-5, CASS-4 and SLEW-3

    Michael G. Lawrence
    terres rares; yttrium; pré-concentration; ICP-MS; matériaux de référence du NRCC The rare earth element and yttrium concentrations of the NRCC reference materials North Atlantic Surface seawater, NASS-5; Coastal Atlantic Surface Seawater, CASS-4; and the estuarine water, SLEW-3 have been precisely determined by ICP-MS after ca. 1:8 preconcentration following a triple chelation using HDEHP (phosphoric acid 2-ethylhexyl ester -mono and di ester mixture) in heptane, and back extraction in nitric acid. We propose reference values with uncertainties for all naturally occurring lanthanides and yttrium. Les concentrations en terres rares et en yttrium des matériaux de référence suivants (du NRCC): l'eau de surface de l'Atlantique Nord NASS-5, l'eau de surface de l'Atlantique Côtier CASS-4 et l'eau d'estuaire SLEW-3 ont été déterminées précisément par ICP-MS après concentration d'un facteur 1 : 8 environ, suivie d'une triple chélation avec de l'HDEHP (mixture d'acide phosphorique 2-ethylhexyl ester - mono et di ester) dans de l'heptane et une extraction inverse en acide nitrique. Nous proposons des valeurs de référence avec leur incertitude pour toutes les terres rares naturelles et l'yttrium. [source]

    Precise/ Small Sample Size Determinations of Lithium Isotopic Compositions of Geological Reference Materials and Modern Seawater by MC-ICP-MS

    Alistair B. Jeffcoate
    composition isotopique de Li; matériaux de référence silicates; eau de mer; MC-ICP-MS; Li standard The Li isotope ratios of four international rock reference materials, USGS BHVO-2, GSJ JB-2, JG-2, JA-1 and modern seawater (Mediterranean, Pacific and North Atlantic) were determined using multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). These reference materials of natural samples were chosen to span a considerable range in Li isotope ratios and cover several different matrices in order to provide a useful benchmark for future studies. Our new analytical technique achieves significantly higher precision and reproducibility (< ± O.3%o 2s) than previous methods, with the additional advantage of requiring very low sample masses of ca. 2 ng of Li. Les rapports isotopiques du Li de 4 matériaux de référence, de provenance Internationale, BHVO-2, JB-2, JG-2, JA-1 et d'eau de mer (Méditerranée, Pacifique et Atlantique Nord) ont été déterminés par MC-ICP-MS (spectrométrie de masse avec source à plasma induit à multicollection). Ces matériaux de référence naturels ont été choisis car ils balaient un large champ des rapports isotopiques du Lithium et couvrent différentes matrices afin de fournir un point de repère utile pour les études futures. Notre nouvelle technique analytique permet d'atteindre une précision et une reproductibilité (< ± 0.3%. 2s) nettement supérieures à celles des méthodes précédemment utilisées et présente I'avantage de pouvoir travailler avec des échantillons de petite masse, , 2 ng de Li. [source]

    Calcium Isotopic Composition of Various Reference Materials and Seawater

    Dorothee Hippler
    composition isotopique du calcium; eau de mer; paléocéanographie; NIST SRM 915a A compilation of ,44/40Ca (,44/40Ca) data sets of different calcium reference materials is presented, based on measurements in three different laboratories (Institute of Geological Sciences, Bern; Centre de Géochimie de la Surface, Strasbourg; GEOMAR, Kiel) to support the establishment of a calcium isotope reference standard. Samples include a series of international and internal Ca reference materials, including NIST SRM 915a, seawater, two calcium carbonates and a CaF2 reference sample. The deviations in ,44/40Ca for selected pairs of reference samples have been defined and are consistent within statistical uncertainties in all three laboratories. Emphasis has been placed on characterising both NIST SRM 915a as an internationally available high purity Ca reference sample and seawater as representative of an important and widely available geological reservoir. The difference between ,44/40Ca of NIST SRM 915a and seawater is defined as -1.88 O.O4%o (,44/42CaNISTSRM915a/Sw= -0.94 0.07%o). The conversion of values referenced to NIST SRM 915a to seawater can be described by the simplified equation ,44/40CaSa/Sw=,44/40CaSa/NIST SRM 915a - 1.88 (,44/42CaSa/Sw=,44/42CaSa/NIST SRM 915a - 0.94). We propose the use of NIST SRM 915a as general Ca isotope reference standard, with seawater being defined as the major reservoir with respect to oceanographic studies. On présente ici une compilation de données de ,44/40Ca (,44/42Ca) obtenues sur différents matériaux de référence, à partir d'analyses effectuées dans trois laboratoires (Institute of Geological Sciences, Berne; Centre de Géochimie de la Surface, Strasbourg; GEOMAR, Kiel) dans le but de définir des matériaux standards de référence pour isotopie du calcium. Les échantillons comprenaient une série de matériaux standards, internes et internationaux, de référence pour le calcium, avec NIST SRM 915a, l'eau de mer, deux carbonates de calcium, et un échantillon de CaF2 de référence. Les déviations en ,44/40Ca pour des paires sélectionnées d'échantillons de référence ont été définies et sont en accord, compte tenu des incertitudes statistiques, entre les trois laboratoires. L'accent a été mis sur la nécessité de caractériser à la fois NIST SRM 915a, en tant que matériau de référence très pur, internationalement disponible, et l'eau de mer comme représentant d'un réservoir géologique très important et disponible partout. La différence entre les ,44/40Ca de NIST SRM 915a et de l'eau de mer est définie comme étant de -1.88 0.04%0,44/42CaNIST SRM 915a/Sw= -0.94 0.07%0). La conversion des données référencées par rapport à NIST SRM 915a à la référence -eau de mer- se fait selon l'équation simplifiée équation ,44/40CaSa/Sw=,44/40CaSa/NIST SRM 915a - 1.88 (,44/42Ca Sa/Sw=,44/42CaSa/NIST SRM 915a - 0.94). Nous proposons l'utilisation de NIST SRM 915a comme matériau standard de référence pour les isotopes de Ca, avec l'eau de mer comme réservoir majeur adapté aux études océanographiques. [source]


    Article first published online: 24 SEP 200
    Waaland, J. R. Department of Botany, University of Washington, Seattle, WA 98195 USA A new, high value product from the Turkish Towel Seaweed, Chondracanthus exasperatus, was developed recently by a Seattle company. However, Washington State has a long term moratorium on commercial seaweed harvesting from wild populations so there is renewed interest in intensive cultivation of this species. The initial phase of this research was conducted at Mukilteo, Washington. There, strategies for long term cultivation in tanks were tested, and a custom cultivation tank design was developed for pilot scale cultivation research at a site on the shore of Clam Bay near Manchester, Washington. Long term cultivation is now being tested in tanks of up to 5000 L volume supplied with natural seawater, seawater supplemented with nutrients, and seawater effluent from nearby Pacific Halibut culture tanks. Seawater from Clam Bay is naturally rich in nutrients from tidal driven upwelling and nearby commercial salmon mariculture operations. Supplemental nutrients (commercially available "f/2" enrichment) and halibut culture tank effluent have both been tested for their ability to support C. exasperatus growth with relatively low seawater turnover rates. Compared to seawater at the site, Halibut tank effluent differs in both nutrient composition and quantities. Initial results indicate that halibut tank effluent is a satisfactory source of nutrients for C. exasperatus in intensive culture and that the Turkish Towel Seaweed scrubs significant quantities of nutrients from halibut tank effluent. [source]

    Principles for Utilization of Seawater in the Flue-Gas Desulfurization Process

    Tong Yao
    The Flake-Hydro Process (SWFGD) is a flue gas desulfurization method in which sea water is used for absorption of sulfur dioxide. Shenzhen West Power Plant Unit 4 (300MW) imported this technology from Norway and installed SWFGD system. At present, the operational situation is good. All performance guarantees are secured. Shenzhen Energy Environmental Engineering Co. Ltd, also takes responsibility for monitoring and study of key techniques. [source]

    REE Compositions of Lower Ordovician Dolomites in Central and North Tarim Basin, NW China: A Potential REE Proxy for Ancient Seawater

    ZHANG Xuefeng
    Abstract: Rare earth element compositions of Lower Ordovician dolomites in the Central and Northern Tarim Basin are studied. Most dolomite samples are more or less contaminated by clay minerals. Their rare earth element compositions have been consequently changed, showing both seawater-like and non-seawater-like features. The clay contamination should be disposed before the REE data are used. Through ICP-MS and ICP-AES analyses, the REE features are well documented. The clay contamination is quantitatively determined by microscopic investigation, trace elements and REE contents. The dolomites, at least in the Tarim Basin, are thought to be pure when their total LREE contents are less than 3times10,6. Through comparison, the pure dolomites show similarities in REE patterns but differences in REE contents with co-existing pure limestone, which indicates that dolomitization may slightly change the REE compositions. Nevertheless, whatever the change is, the pure dolomites may act as a potential REE proxy for Ordovician seawater, which would be significant for ancient massive dolomite strata that lack limestone. [source]

    Comparison of Additional Costs for Several Replacement Strategies of Randomly Ageing Reinforced Concrete Pipes

    Franck Schoefs
    Some of them carry seawater and can deteriorate with time because of internal corrosion. Because of the low O2 content of aggressive water, slow corrosion is expected for such applications. If the RCPs are not periodically replaced, they will eventually fail. Replacement strategies for these pipes depend on (1) the risks associated with the failure of the water distribution network, and (2) the costs associated with replacing the pipes, including the removal of existing pipes, installation of new pipes, and associated production losses. Because of the lack of statistical data regarding RCP failure, the development of a risk-based replacement strategy is not an easy task. This article demonstrates how predictive models for the evolution of the failure of RCPs and the associated consequences of failure can be used to develop risk-based replacement strategies for RCPs. An application for the replacement strategies of a network modeled as a system consisting of 228 RCPs is presented as a case study. We focus on the assessment of the number of replaced components that governs the costs. The main objective of this article is to provide a theoretical approach for comparing replacement strategies, based on (1) the results of a reliability study, (2) the representation of the distributions of failed components (binomial distribution), and (3) the decision tree representation for replacement of RCPs. A focus on the scatter of the induced costs themselves is suggested to emphasize the financial risk. [source]

    Regulation of sperm flagellar motility activation and chemotaxis caused by egg-derived substance(s) in sea cucumber

    CYTOSKELETON, Issue 4 2009
    Masaya Morita
    Abstract The sea cucumber Holothuria atra is a broadcast spawner. Among broadcast spawners, fertilization occurs by means of an egg-derived substance(s) that induces sperm flagellar motility activation and chemotaxis. Holothuria atra sperm were quiescent in seawater, but exhibited flagellar motility activation near eggs with chorion (intact eggs). In addition, they moved in a helical motion toward intact eggs as well as a capillary filled with the water layer of the egg extracts, suggesting that an egg-derived compound(s) causes motility activation and chemotaxis. Furthermore, demembranated sperm flagella were reactivated in high pH (>7.8) solution without cAMP, and a phosphorylation assay using (,-32P)ATP showed that axonemal protein phosphorylation and dephosphorylation also occurred in a pH-dependent manner. These results suggest that the activation of sperm motility in holothurians is controlled by pH-sensitive changes in axonemal protein phosphorylation. Ca2+ concentration affected the swimming trajectory of demembranated sperm, indicating that Ca2+ -binding proteins present at the flagella may be associated with regulation of flagellar waveform. Moreover, the phosphorylation states of several axonemal proteins were Ca2+ -sensitive, indicating that Ca2+ impacts both kinase and phosphatase activities. In addition, in vivo sperm protein phosphorylation occurred after treatment with a water-soluble egg extract. Our results suggest that one or more egg-derived compounds activate motility and subsequent chemotactic behavior via Ca2+ -sensitive flagellar protein phosphorylation. Cell Motil. Cytoskeleton 2009. © 2009 Wiley-Liss, Inc. [source]

    Digestive tract ontogeny of Dicentrarchus labrax: Implication in osmoregulation

    Ivone Giffard-Mena
    The ontogeny of the digestive tract (DT) and of Na+/K+ -ATPase localization was investigated during the early postembryonic development (from yolk sac larva to juvenile) of the euryhaline teleost Dicentrarchus labrax reared at two salinities: seawater and diluted seawater. Histology, electron microscopy and immunocytochemistry were used to determine the presence and differentiation of ion transporting cells. At hatching, the DT is an undifferentiated straight tube over the yolk sac. At the mouth opening (day 5), it comprises six segments: buccopharynx, esophagus, stomach, anterior intestine, posterior intestine and rectum, well differentiated at the juvenile stage (day 72). The enterocytes displayed ultrastructural features similar to those of mitochondria-rich cells known to be involved in active ion transport. At hatching, ion transporting cells lining the intestine and the rectum exhibited a Na+/K+ -ATPase activity which increased mainly after the larva/juvenile (20 mm) metamorphic transition. The immunofluorescence intensity was dependent upon the stage of development of the gut as well as on the histological configuration of the analyzed segment. The appearance and distribution of enteric ionocytes and the implication of the DT in osmoregulation are discussed. [source]

    Does saltwater flushing reduce viability of diapausing eggs in ship ballast sediment?

    Sarah A. Bailey
    ABSTRACT Flushing of ballast tanks with seawater has been proposed to reduce the risk of invasion associated with residual ballast in ,no ballast on board' ships. The efficacy of this procedure, however, has not been determined. Using diapausing eggs isolated from ballast sediments , as well as from Lake Erie sediment , this study investigated the impact of salinity (0, 8 and 35,) and temperature (10, 20 and 30 °C) on the cumulative abundance and species richness of hatched zooplankton taxa. The rate and amount of hatching varied dramatically between sediments and across salinity,temperature regimes. Although exposure to saline water inhibited emergence of freshwater taxa during the exposure phase of all trials, mixed results were evident after diapausing eggs were returned to freshwater. The efficacy of salinity as a ballast treatment method was temperature dependent, although the direction of the effect was case-specific. Exposure of eggs to saline water was less effective at 10 and 30 °C than at 20 °C. Although flushing ballast tanks with open ocean water is expected to significantly reduce the number of active invertebrates living in residual ballast water (a potentially larger source of invaders), our results indicate that the most effective treatment conditions for reduction of diapausing egg viability is 8, salinity at 20 °C. [source]

    Voltammetry as an Alternative Tool for Trace Metal Detection in Peloid Marine Sediments

    ELECTROANALYSIS, Issue 13 2007
    Irena Ciglene
    Abstract Here was demonstrated for the first time a possible application of abrasive stripping voltammetry in the direct measurement of trace metals in anoxic, sulfidic marine sediments (peloid mud) from a small and shallow (0.2,1,m) marine lagoon in Central Dalmatia, Croatia. Trace amounts of sample compounds are transferred to the graphite electrode surface and electrochemical reduction or oxidation processes are followed by the cyclic voltammetry in seawater or 0.55,M NaCl as electrolyte. After a preelectrolysis at potentials ranging from ,1.0 to ,1.5,V (vs. SCE) a well-defined anodic stripping peak corresponding to the oxidation of metal deposits generated at deposition potentials is obtained around ,0.74,V (vs. SCE). The same samples were studied by anodic stripping voltammetry at the Hg electrode and inductively coupled plasma-mass spectrometer (ICP-MS). ICP-MS showed higher concentrations of trace metals such as Al, Fe, Mo, Mn. A relatively high concentration of reduced sulfur species (RSS) (10,3 M) is determined electrochemically in porewater of the peloid mud, indicating that the magnitude of metal enrichment in the sediments is probably controlled by precipitation with sulfide. [source]

    Mercury Detection in Seawater Using a Mercaptoacetic Acid Modified Gold Microwire Electrode

    ELECTROANALYSIS, Issue 10 2005
    Antje Widmann
    Abstract It is demonstrated here that it is possible to determine mercury in chloride containing media like seawater by anodic stripping voltammetry using a modified electrode. A gold microwire electrode is modified using mercaptoacetic acid (MAA) to eliminate the problem of calomel formation, allowing the mercury to become fully removed from the electrode surface after each scan. In a synthetic salt solution of KNO3 the sensitivity for mercury was found to be improved by the surface modification. In seawater the sensitivity was not significantly improved possibly because of complexation of the mercury by the abundant chloride; however, the MAA coating prevented the formation of calomel causing the background scan to be free of mercury. Measurements in seawater at various pH values demonstrated that mercury detection is possible at natural pH (around 8); however, best sensitivity was attained at pH,4.8 with a deposition time of 3,min. A peak for copper occurred at more negative potential but did not interfere at this pH. The calibration was linear between 0 and 37,nM mercury with a limit of detection of 1,nM mercury. [source]

    Direct Simultaneous Determination of Cu, Ni and V in Seawater Using Adsorptive Cathodic Stripping Voltammetry with Mixed Ligands

    ELECTROANALYSIS, Issue 10 2005
    A. Cobelo-García
    Abstract An analytical procedure is proposed for the direct simultaneous determination in a single scan of Cu, Ni and V in seawater by means of adsorptive cathodic stripping voltammetry (ACSV) with mixed ligands (DMG and catechol). Optimum conditions for the determination of these three elements were studied. Detection limits of the technique depended upon the reproducibility of the procedura blank, and were found to be 0.5,nM for Cu, 0.4,nM for Ni and 0.3,nM for V. The method is suitable for the analysis of estuarine, coastal and open-ocean waters, and especially to study the metal contamination in areas subject to oil spill events. [source]

    Determination of iodide in samples with complex matrices by hyphenation of capillary isotachophoresis and zone electrophoresis

    ELECTROPHORESIS, Issue 20 2007
    Pavla Pant
    Abstract A method has been developed for the determination of iodide in mineral water, seawater, cooking salt, serum, and urine based on hyphenation of capillary ITP and zone electrophoresis. A commercially available instrumentation for capillary ITP with column-switching system was used. ITP served for removal of chloride present in the analyzed samples in a ratio of 106,107:1 to iodide, zone electrophoresis was used for evaluation. Isotachophoretic separation proceeded in a capillary made of fluorinated ethylene,propylene copolymer of 0.8,mm id and 90,mm total length to the bifurcation point filled with a leading electrolyte (LE) composed of 8,mM HCl,+,16,mM ,-alanine (,-Ala),+,10% PVP,+,2.86,mM N2H4×2HCl, pH,3.2; and a terminating electrolyte composed of 8,mM H3PO4,+,16,mM ,-Ala,+,10% PVP,+,5,mM N2H4, pH,3.85 for all the matrices except seawater. For ITP of seawater the LE consisted of 50,mM HCl,+,100,mM ,-Ala,+,10% PVP +,2.86,mM N2H4×2HCl, pH,3.52. Distance of conductivity detector from the injection point and bifurcation point was 52 and 38,mm, respectively. Zone electrophoresis was performed in a capillary made of fused silica of 0.3,mm id and 160,mm total length filled with LE from isotachophoretic step. LODs reached for all matrices were 2,3×10,8,M concentration (2.5,4,,g/L) enabled monitoring of iodide in all analyzed samples with RSD 0.4,9.3%. Estimated concentrations of iodide in individual matrices were 10,6,10,8,M. [source]

    A multilayer poly(dimethylsiloxane) electrospray ionization emitter for sample injection and online mass spectrometric detection

    ELECTROPHORESIS, Issue 24 2005
    Jamie M. Iannacone
    Abstract An ESI emitter made of poly(dimethylsiloxane) interfaces on-chip sample preparation with MS detection. The unique multilayer design allows both the analyte and the spray solutions to reside on the device simultaneously in discrete microfluidic environments that are spatially separated by a polycarbonate track-etched, nanocapillary array membrane (NCAM). In direct spray mode, voltage is applied to the microchannel containing a spray solution delivered via a syringe pump. For injection, the spray potential is lowered and a voltage is applied that forward biases the membrane and permits the analyte to enter the spray channel. Once the injection is complete, the bias potential is switched off, and the spray voltage is increased to generate the ESI of the injected analyte plug. Consecutive injections of a 10,,M bovine insulin solution are reproducible and produce sample plugs with limited band broadening and high quality mass spectra. Peptide signals are observed following transport through the NCAM, even when the peptide is dissolved in solutions containing up to 20% seawater. The multilayer emitter shows great potential for performing multidimensional chemical manipulations on-chip, followed by direct ESI with negligible dead volume for online MS analysis. [source]

    Use of stable isotope-labelled cells to identify active grazers of picocyanobacteria in ocean surface waters

    Jorge Frias-Lopez
    Summary Prochlorococcus and Synechococcus are the two most abundant marine cyanobacteria. They represent a significant fraction of the total primary production of the world oceans and comprise a major fraction of the prey biomass available to phagotrophic protists. Despite relatively rapid growth rates, picocyanobacterial cell densities in open-ocean surface waters remain fairly constant, implying steady mortality due to viral infection and consumption by predators. There have been several studies on grazing by specific protists on Prochlorococcus and Synechococcus in culture, and of cell loss rates due to overall grazing in the field. However, the specific sources of mortality of these primary producers in the wild remain unknown. Here, we use a modification of the RNA stable isotope probing technique (RNA-SIP), which involves adding labelled cells to natural seawater, to identify active predators that are specifically consuming Prochlorococcus and Synechococcus in the surface waters of the Pacific Ocean. Four major groups were identified as having their 18S rRNA highly labelled: Prymnesiophyceae (Haptophyta), Dictyochophyceae (Stramenopiles), Bolidomonas (Stramenopiles) and Dinoflagellata (Alveolata). For the first three of these, the closest relative of the sequences identified was a photosynthetic organism, indicating the presence of mixotrophs among picocyanobacterial predators. We conclude that the use of RNA-SIP is a useful method to identity specific predators for picocyanobacteria in situ, and that the method could possibly be used to identify other bacterial predators important in the microbial food-web. [source]

    Diversity and expression of nitrogen fixation genes in bacterial symbionts of marine sponges

    Naglaa M. Mohamed
    Summary Marine sponges contain complex assemblages of bacterial symbionts, the roles of which remain largely unknown. We identified diverse bacterial nifH genes within sponges and found that nifH genes are expressed in sponges. This is the first demonstration of the expression of any protein-coding bacterial gene within a sponge. Two sponges Ircinia strobilina and Mycale laxissima were collected from Key Largo, Florida and had ,15N values of c. 0,1, and 3,4, respectively. The potential for nitrogen fixation by symbionts was assessed by amplification of nifH genes. Diverse nifH genes affiliated with Proteobacteria and Cyanobacteria were detected, and expression of nifH genes affiliated with those from cyanobacteria was detected. The nifH genes from surrounding seawater were similar to those of Trichodesmium and clearly different from the cyanobacterial nifH genes detected in the two sponges. This study advances understanding of the role of bacterial symbionts in sponges and suggests that provision of fixed nitrogen is a means whereby symbionts benefit sponges in nutrient-limited reef environments. Nitrogen fixation by sponge symbionts is possibly an important source of new nitrogen to the reef environment that heretofore has been neglected and warrants further investigation. [source]

    Polysaccharide hydrolysis in aggregates and free enzyme activity in aggregate-free seawater from the north-eastern Gulf of Mexico

    Kai Ziervogel
    Summary Marine snow aggregates represent hotspots of carbon remineralization in the ocean. Various aspects of bacterial dynamics have been investigated on marine snow. To date, extracellular enzymatic activities in aggregates have been measured using small substrate proxies that do not adequately reflect the complexity of biomacromolecules such as polysaccharides, proteins and lipids. To address this issue, we used six structurally distinct, fluorescently labelled polysaccharides to measure enzymatic hydrolysis on aggregates formed with a roller table and in aggregate-free (ambient) seawater from two near-coast sites, north-eastern Gulf of Mexico. A single polysaccharide was incubated in aggregates and ambient seawater. Changes in polysaccharide molecular weight were monitored over time to measure the course of enzymatic hydrolysis. All six polysaccharides were hydrolysed in aggregates, indicating a broad range of enzyme activities in aggregate-associated bacteria. Four substrates were also hydrolysed in ambient waters. Epifluorescence microscopy revealed that nearly all of the bacteria present in original waters were incorporated into aggregates. Therefore hydrolytic activities in ambient waters were presumably due to enzymes spatially disconnected from cells and aggregates. Our results show substantial enzymatic activity in cell/aggregate-free seawater, suggesting a significant role of free enzymes in hydrolytic activity in waters from the north-eastern Gulf of Mexico. [source]

    Design and testing of ,genome-proxy' microarrays to profile marine microbial communities

    Virginia I. Rich
    Summary Microarrays are useful tools for detecting and quantifying specific functional and phylogenetic genes in natural microbial communities. In order to track uncultivated microbial genotypes and their close relatives in an environmental context, we designed and implemented a ,genome-proxy' microarray that targets microbial genome fragments recovered directly from the environment. Fragments consisted of sequenced clones from large-insert genomic libraries from microbial communities in Monterey Bay, the Hawaii Ocean Time-series station ALOHA, and Antarctic coastal waters. In a prototype array, we designed probe sets to 13 of the sequenced genome fragments and to genomic regions of the cultivated cyanobacterium Prochlorococcus MED4. Each probe set consisted of multiple 70-mers, each targeting an individual open reading frame, and distributed along each ,40,160 kbp contiguous genomic region. The targeted organisms or clones, and close relatives, were hybridized to the array both as pure DNA mixtures and as additions of cells to a background of coastal seawater. This prototype array correctly identified the presence or absence of the target organisms and their relatives in laboratory mixes, with negligible cross-hybridization to organisms having , ,75% genomic identity. In addition, the array correctly identified target cells added to a background of environmental DNA, with a limit of detection of ,0.1% of the community, corresponding to ,103 cells ml,1 in these samples. Signal correlated to cell concentration with an R2 of 1.0 across six orders of magnitude. In addition, the array could track a related strain (at 86% genomic identity to that targeted) with a linearity of R2 = 0.9999 and a limit of detection of ,1% of the community. Closely related genotypes were distinguishable by differing hybridization patterns across each probe set. This array's multiple-probe, ,genome-proxy' approach and consequent ability to track both target genotypes and their close relatives is important for the array's environmental application given the recent discoveries of considerable intrapopulation diversity within marine microbial communities. [source]

    Bacterioplankton assemblages transforming dissolved organic compounds in coastal seawater

    Xiaozhen Mou
    Summary To characterize bacterioplankton functional assemblages that transform specific components of the coastal seawater dissolved organic carbon (DOC) pool, bromodeoxyuridine (BrdU) was used to label the bacterioplankton cells that were active following addition of single-DOC model compounds: two organic osmolytes [dimethylsulfoniopropionate (DMSP) and glycine betaine (GlyB)] and two aromatic monomers [para -hydroxybenzoic acid (pHBA) and vanillic acid (VanA)]. Bacterial populations were analysed based on in situ fluorescent immunodetection of BrdU incorporation followed by fluorescence-activated cell sorting (FACS). Sorted cells were then characterized by 16S rDNA-based analysis. Populations with high BrdU incorporation level (HI) developed within 8 h of introduction of 100 nM model compound. Terminal restriction fragment length polymorphisms (T-RFLP) analysis indicated that the HI populations in all four amendments were composed of bacteria from the same major taxa (phylum and subphylum levels), but the relative abundance of each differed. High-resolution clone libraries (each containing ,200 clones) showed that the HI populations in the GlyB and VanA amendments consisted of both metabolic generalists and specialists within the , -Proteobacteria (mainly members of the Roseobacter clade), , -Proteobacteria and , -Proteobacteria (mainly members of Altermonadaceae, Chromatiaceae, Oceanospirillaceae and Pseudomonadaceae). The presence of members of OM60/241, OM185, SAR11, SAR86 and SAR116 in the HI populations indicated that members of these groups can assimilate the model DOC compounds, providing some of the first glimpses into heterotrophy by members of these poorly understood environmental clusters. [source]

    Polyphyletic photosynthetic reaction centre genes in oligotrophic marine Gammaproteobacteria

    Jang-Cheon Cho
    Summary Ecological studies indicate that aerobic anoxygenic phototrophic bacteria (AAP) that use bacteriochlorophyll to support phototrophic electron transport are widely distributed in the oceans. All cultivated marine AAP are alpha-3 and alpha-4 Proteobacteria, but metagenomic evidence indicates that uncultured AAP Gammaproteobacteria are important members of ocean surface microbial communities. Here we report the description of obligately oligotrophic, marine Gammaproteobacteria that have genes for aerobic anoxygenic photosynthesis. Three strains belonging to the OM60 clade were isolated in autoclaved seawater media. Polymerase chain reaction assays for the pufM gene show that these strains contain photosynthetic reaction centre genes. DNA sequencing and phylogenetic analysis indicate that the pufM genes are polyphyletic, suggesting multiple instances of lateral gene transfer. Peptide sequences from six photosynthesis genes (pufL, pufM, pufC, pufB, pufA and puhA) were detected by proteomic analyses of strain HTCC2080 cells grown aerobically in seawater. They closely match predicted peptides from an environmental seawater bacterial artificial chromosome clone of gammaproteobacterial origin, thus identifying the OM60 clade as a significant source of gammaproteobacterial AAP genes in marine systems. The cell yield and rate of growth of HTCC2080 in autoclaved, aerobic seawater increased in the light. These findings identify the OM60 clade as a source of Gammaproteobacteria AAP genes in coastal oceans, and demonstrate that aerobic, anoxygenic photosynthetic metabolism can enhance the productivity of marine oligotrophic bacteria that also grow heterotrophically in darkness. [source]

    Limits of life in MgCl2 -containing environments: chaotropicity defines the window

    John E. Hallsworth
    Summary The biosphere of planet Earth is delineated by physico-chemical conditions that are too harsh for, or inconsistent with, life processes and maintenance of the structure and function of biomolecules. To define the window of life on Earth (and perhaps gain insights into the limits that life could tolerate elsewhere), and hence understand some of the most unusual biological activities that operate at such extremes, it is necessary to understand the causes and cellular basis of systems failure beyond these windows. Because water plays such a central role in biomolecules and bioprocesses, its availability, properties and behaviour are among the key life-limiting parameters. Saline waters dominate the Earth, with the oceans holding 96.5% of the planet's water. Saline groundwater, inland seas or saltwater lakes hold another 1%, a quantity that exceeds the world's available freshwater. About one quarter of Earth's land mass is underlain by salt, often more than 100 m thick. Evaporite deposits contain hypersaline waters within and between their salt crystals, and even contain large subterranean salt lakes, and therefore represent significant microbial habitats. Salts have a major impact on the nature and extent of the biosphere, because solutes radically influence water's availability (water activity) and exert other activities that also affect biological systems (e.g. ionic, kosmotropic, chaotropic and those that affect cell turgor), and as a consequence can be major stressors of cellular systems. Despite the stressor effects of salts, hypersaline environments can be heavily populated with salt-tolerant or -dependent microbes, the halophiles. The most common salt in hypersaline environments is NaCl, but many evaporite deposits and brines are also rich in other salts, including MgCl2 (several hundred million tonnes of bischofite, MgCl2·6H2O, occur in one formation alone). Magnesium (Mg) is the third most abundant element dissolved in seawater and is ubiquitous in the Earth's crust, and throughout the Solar System, where it exists in association with a variety of anions. Magnesium chloride is exceptionally soluble in water, so can achieve high concentrations (> 5 M) in brines. However, while NaCl-dominated hypersaline environments are habitats for a rich variety of salt-adapted microbes, there are contradictory indications of life in MgCl2 -rich environments. In this work, we have sought to obtain new insights into how MgCl2 affects cellular systems, to assess whether MgCl2 can determine the window of life, and, if so, to derive a value for this window. We have dissected two relevant cellular stress-related activities of MgCl2 solutions, namely water activity reduction and chaotropicity, and analysed signatures of life at different concentrations of MgCl2 in a natural environment, namely the 0.05,5.05 M MgCl2 gradient of the seawater : hypersaline brine interface of Discovery Basin , a large, stable brine lake almost saturated with MgCl2, located on the Mediterranean Sea floor. We document here the exceptional chaotropicity of MgCl2, and show that this property, rather than water activity reduction, inhibits life by denaturing biological macromolecules. In vitro, a test enzyme was totally inhibited by MgCl2 at concentrations below 1 M; and culture medium with MgCl2 concentrations above 1.26 M inhibited the growth of microbes in samples taken from all parts of the Discovery interface. Although DNA and rRNA from key microbial groups (sulfate reducers and methanogens) were detected along the entire MgCl2 gradient of the seawater : Discovery brine interface, mRNA, a highly labile indicator of active microbes, was recovered only from the upper part of the chemocline at MgCl2 concentrations of less than 2.3 M. We also show that the extreme chaotropicity of MgCl2 at high concentrations not only denatures macromolecules, but also preserves the more stable ones: such indicator molecules, hitherto regarded as evidence of life, may thus be misleading signatures in chaotropic environments. Thus, the chaotropicity of MgCl2 would appear to be a window-of-life-determining parameter, and the results obtained here suggest that the upper MgCl2 concentration for life, in the absence of compensating (e.g. kosmotropic) solutes, is about 2.3 M. [source]

    Key role of selective viral-induced mortality in determining marine bacterial community composition

    T. Bouvier
    Summary Viral infection is thought to play an important role in shaping bacterial community composition and diversity in aquatic ecosystems, but the strength of this interaction and the mechanisms underlying this regulation are still not well understood. The consensus is that viruses may impact the dominant bacterial strains, but there is little information as to how viruses may affect the less abundant taxa, which often comprise the bulk of the total bacterial diversity. The potential effect of viruses on the phylogenetic composition of marine bacterioplankton was assessed by incubating marine bacteria collected along a North Pacific coastal-open ocean transect in seawater that was greatly depleted of ambient viruses. The ambient communities were dominated by typical marine groups, including alphaproteobacteria and the Bacteroidetes. Incubation of these communities in virus-depleted ambient water yielded an unexpected and dramatic increase in the relative abundance of bacterial groups that are generally undetectable in the in situ assemblages, such as betaproteobacteria and Actinobacteria. Our results suggest that host susceptibility is not necessarily only proportional to its density but to other characteristics of the host, that rare marine bacterial groups may be more susceptible to viral-induced mortality, and that these rare groups may actually be the winners of competition for resources. These observations are not inconsistent with the ,phage kills the winner' hypothesis but represent an extreme and yet undocumented case of this paradigm, where the potential winners apparently never actually develop beyond a very low abundance threshold in situ. We further suggest that this mode of regulation may influence not just the distribution of single strains but of entire phylogenetic groups. [source]

    Isolation and gene quantification of heterotrophic N2 -fixing bacterioplankton in the Baltic Sea

    Kjärstin H. Boström
    Summary Cyanobacteria are regarded as the main N2 -fixing organisms in marine waters. However, recent clone libraries from various oceans show a wide distribution of the dinitrogenase reductase gene (nifH) originating from heterotrophic bacterioplankton. We isolated heterotrophic N2 -fixing bacteria from Baltic Sea bacterioplankton using low-nitrogen plates and semi-solid diazotroph medium (SSDM) tubes. Isolates were analysed for the nitrogenase (nifH) gene and active N2 fixation by nested polymerase chain reaction (PCR) and acetylene reduction respectively. A primer-probe set targeting the nifH gene from a , - proteobacterial isolate, 97% 16S rDNA similarity to Pseudomonas stutzeri, was designed for measuring in situ dynamics using quantitative real-time PCR. This nifH gene sequence was detected at two of 11 stations in a Baltic Proper transect at abundances of 3 × 104 and 0.8 × 103 copies per litre seawater respectively. Oxygen requirements of isolates were examined by cultivation in SSDM tubes where oxygen gradients were determined with microelectrodes. Growth, and thereby N2 fixation, was observed as horizontal bands formed at oxygen levels of 0,6% air saturation. The apparent microaerophilic or facultative anaerobic nature of the isolates explains why the SSDM approach is the most appropriate isolation method. Our study illustrates how combined isolation, functional analyses and in situ quantification yielded insights into the oxygen requirements of heterotrophic N2 -fixing bacterioplankton isolates, which were confirmed to be present in situ. [source]

    Distribution, phylogenetic diversity and physiological characteristics of epsilon- Proteobacteria in a deep-sea hydrothermal field

    Satoshi Nakagawa
    Summary Epsilon- Proteobacteria is increasingly recognized as an ecologically significant group of bacteria, particularly in deep-sea hydrothermal environments. In this study, we studied the spatial distribution, diversity and physiological characteristics of the epsilon- Proteobacteria in various microbial habitats in the vicinity of a deep-sea hydrothermal vent occurring in the Iheya North field in the Mid-Okinawa Trough, by using culture-dependent and -independent approaches. The habitats studied were inside and outside hydrothermal plume, and annelid polychaete tubes. In addition, we deployed colonization devices near the vent emission. The polychaete tubes harboured physiologically and phylogenetically diverse microbial community. The in situ samplers were predominantly colonized by epsilon -Proteobacteria. Energy metabolism of epsilon- Proteobacteria isolates was highly versatile. Tree topology generated from the metabolic traits was significantly different (P = 0.000) from that of 16S rRNA tree, indicating current 16S rRNA gene-based analyses do not provide sufficient information to infer the physiological characteristics of epsilon- Proteobacteria. Nevertheless, culturability of epsilon- Proteobacteria in various microbial habitats differed among the phylogenetic subgroups. Members of Sulfurimonas were characterized by the robust culturability, and the other phylogenetic subgroups appeared to lose culturability in seawater, probably because of the sensitivity to oxygen. These results provide new insight into the ecophysiological characteristics of the deep-sea hydrothermal vent epsilon- Proteobacteria, which has never been assessed by comparative analysis of the 16S rRNA genes. [source]

    Bacterial diversity in the bacterioneuston (sea surface microlayer): the bacterioneuston through the looking glass

    Mark P. Franklin
    Summary The bacterioneuston is defined as the community of bacteria present within the neuston or sea surface microlayer. Bacteria within this layer were sampled using a membrane filter technique and bacterial diversity was compared with that in the underlying pelagic coastal seawater using molecular ecological techniques. 16S rRNA gene libraries of , 500 clones were constructed from both bacterioneuston and the pelagic water samples and representative clones from each library were sequenced for comparison of bacterial diversity. The bacterioneuston was found to have a significantly lower bacterial diversity than the pelagic seawater, with only nine clone types (ecotaxa) as opposed to 46 ecotaxa in the pelagic seawater library. Surprisingly, the bacterioneuston clone library was dominated by 16S rRNA gene sequences affiliated to two groups of organisms, Vibrio spp. which accounted for over 68% of clones and Pseudoalteromonas spp. accounting for 21% of the library. The dominance of these two 16S rRNA gene sequence types within the bacterioneuston clone library was confirmed in a subsequent gene probing experiment. 16S rRNA gene probes specific for these groups of bacteria were designed and used to probe new libraries of 1000 clones from both the bacterioneuston and pelagic seawater DNA samples. This revealed that 57% of clones from the bacterioneuston library hybridized to a Vibrio sp.-specific 16S rRNA gene probe and 32% hybridized to a Pseudoalteromonas sp.-specific 16S rRNA gene probe. In contrast, the pelagic seawater library resulted in only 13% and 8% of 16S rRNA gene clones hybridizing to the Vibrio sp. and Pseudoalteromonas sp. probes respectively. Results from this study suggest that the bacterioneuston contains a distinct population of bacteria and warrants further detailed study at the molecular level. [source]

    Biogeography of bacteria associated with the marine sponge Cymbastela concentrica

    Michael W. Taylor
    Summary Recent debate regarding microbial biogeography has focused largely on free-living microbes, yet those microbes associated with host organisms are also of interest from a biogeographical perspective. Marine eukaryotes and associated bacteria should provide ideal systems in which to consider microbial biogeography, as (i) bacteria in seawater should be able to disperse among individuals of the same host species, yet (ii) potential for adaptation to particular hosts (and thus speciation) also exists. We used 16S rDNA-DGGE (denaturing gradient gel electrophoresis) to examine geographic variability in bacterial community composition in the marine sponge Cymbastela concentrica. Denaturing gradient gel electrophoresis banding patterns (and phylogenetic analysis of excised DGGE bands) indicated different communities in Cymbastela concentrica from tropical versus temperate Australia. In contrast, communities were very similar over a 500-km portion of the sponge's temperate range. Variation in bacterial community composition was also considered with respect to ocean current patterns. We speculate that the divergent communities in different parts of the sponge's range provide evidence of endemism attributed to host association, although variation in environmental factors such as light and temperature could also explain the observed results. Interestingly, bacterial communities in seawater varied much less between tropical and temperate locations than did those in C. concentrica, supporting the concept of widespread dispersal among these free-living microbes. [source]

    Characterization of a Vibrio cholerae phage isolated from the coastal water of Peru

    Miguel Talledo
    Summary A Vibrio cholerae bacteriophage, family Myoviridae, was isolated from seawater collected from the coastal water of Lima, Peru. Genome size was estimated to be 29 kbp. The temperate phage was specific to V. cholerae and infected 12/13 V. cholerae O1 strains and half of the four non-O1/non-O139 strains tested in this study. Vibrio cholerae O139 strains were resistant to infection and highest infection rates were obtained in low nutrient media amended with NaCl or prepared using seawater as diluent. [source]