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  • 1
    Online Resource
    Online Resource
    ARCHEMHAB : interactions and feedback mechanisms between hydrography, geochemical signatures and microbial ecology, with a focus on HAB species diversity, biogeography and dynamics : Cruise No. MSM 21/3 - July 25 - August 10, 2012 - Nuuk (Greenland) - Reykjavik (Iceland) (2016)
    Bremen : DFG-Senatskommission für Ozeanographie c/o MARUM - Zentrum für Marine Umweltwissenschaften, Universität Bremen
    Details Availability
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (49 Seiten)
    Series Statement: Maria S. Merian-Berichte MSM 21/3
    URL: https://doi.org/10.2312/cr_msm21_3
    DOI: 10.2312/cr_msm21_3
    Language: English
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    GEOMAR CATALOGUE
    Link to Library Catalog
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  • 2
    Electronic Resource
    Electronic Resource
    Growth kinetics and nitrogen-nutrition of the marine diatom Phaeodactylum tricornutum in continuous dialysis culture (1991)
    Springer
    Journal of applied phycology 3 (1991), S. 1-10 
    Details
    ISSN: 1573-5176
    Keywords: dialysis culture ; continuous growth ; nitrogen metabolism ; diatoms ; Phaeodactylum tricornutum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The growth kinetics and nitrogen (N)-nutrition of the marine pennate diatom Phaeodactylum tricornutum Bohlin were determined in continuous dialysis culture at different cell densities. Inflow nutrient medium was supplied as natural unenriched estuarine seawater to a dialysis culture system with a high ratio of membrane surface area/culture volume (Am/Vc). Under the experimental conditions, the supply of inorganic macronutrients (NO 3 − + NO 4 − and PO 4 −3 ) by diffusion (Nd) was markedly greater than that provided by the dilution (FfCN) of the culture (Nd ≫ FfCN), thereby establishing an inverse relationship between the cell density and the dilution rate (D). This continuous dialysis system allows for the maintenance of prolonged growth (〉 two weeks) at various cell densities (1.4 to 27.2 × 109 cells 1−1) within a range of dilution rates between 0.30 to 1.08 d−1. In high cell density cultures, where the extracellular medium was characterized as nutrient deficient, a lower growth rate (μe) was exhibited than in cultures with lower cell densities. The growth rate (μe) remained equivalent to the dilution rate (D) throughout the culture cycle, indicating that equilibrated growth was achieved. High cell density cultures yielded higher productivity (P), relative to that of cultures grown at lower cell densities, in terms of cell-N and −C produced per unit time. However, cell quotas of both N and C declined with increasing cell concentrations. Denser cultures were characterized by an enhanced N-conversion efficiency (YN) and a higher cellular N/C atomic ratio. The nutritional response of this diatom in dense cultures reveals an efficient use of N-nutrients, presumably as a result of cellular nutrient adaptation to oligotrophic conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00003914
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    Paper (German National Licenses)
    Fulltext
  • 3
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    Cruise report FS POSEIDON Cruise No. 352 [POS352], 8.6.-5.7.2007: NORCOHAB (North Sea Coast Harmful Algal Bloom Study) (2007)
    Alfred Wegener Institute for Polar and Marine Research, Section Ecological Chemistry
    In:  Alfred Wegener Institute for Polar and Marine Research, Section Ecological Chemistry, Bremerhaven, 36 pp.
    Details
    Publication Date: 2015-02-19
    Description: The overall objective of the NORCOHAB cruise was to study the coastal oceanographic processes and mechanisms underlying the dynamics of key toxic bloom species and the biogeographical distribution of their toxins in the water column of different North Sea coastal waters. The cruise was endorsed by SCOR-IOC Programme GEOHAB (Global Ecology and Oceanography of Harmful Algal Blooms), under the auspices of the Core Research Project on HABS in Fjords and Coastal Embayments. Following the prescribed format of GEOHAB research the studies were international, multidisciplinary and comparative with the ultimate aim of modeling dynamics and behavior.We assessed and compared key genotypic and phenotypic properties of HAB species in relation to grazing and toxic and allelochemical interactions in Scottish and Norwegian/Danish (Skagerrak) coastal areas. For the first time, on board measurements of known phycotoxins collected directly from the plankton were subjected to analysis by high resolution tandem mass-spectrometry coupled with liquid chromatography (LC-MS/MS). These measurements included domoic acid and a large variety of lipophilic toxins associated with marine plankton. We also performed grazing experiments with protists and copepods on selected key toxin algal species in on-board incubations. The following main goals of the cruise programme were successfully addressed: 1) the phenotypic and genotypic characteristics of populations of selected HAB species were compared, including that of a new dinoflagellate identified as the proximal source of azaspiracid poisoning (AZP) in the North Sea; 2) the toxin profile and content of HAB species and toxin transfer and metabolism to the next trophic level were assessed and compared; and 3) insights into the relative importance of grazing by both metazoa and protists as a potential “top down” regulatory mechanism for population dynamics of HAB species was achieved.
    Type: Report , NonPeerReviewed
    Format: text
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    OceanRep: Report - Cruise Report
  • 4
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    Transcriptomic response of the toxic prymnesiophyte Prymnesium parvum (N. Carter) to phosphorus and nitrogen starvation (2012)
    Elsevier
    Details
    Publication Date: 2023-02-15
    Description: The ichthyotoxic and mixotrophic prymnesiophyte Prymnesium parvum is known to produce dense virtually monospecific blooms in marine coastal, brackish, and inshore waters. Fish-killing Pyrmnesium blooms are often associated with macronutrient imbalanced conditions based upon shifts in ambient nitrogen (N):phosphorus (P) ratios. We therefore investigated nutrient-dependent cellular acclimation mechanisms of this microalga based upon construction of a normalized expressed sequence tag (EST) library. We then profiled the transcriptome of P. parvum under nutrient-replete conditions as well as under nitrogen (N) and phosphorus (P) limitation via microarray analyses. Twenty-three genes putatively involved in acclimation to low nutrient levels were identified, among them three phosphate transporters, which were highly upregulated under P-starvation. In contrast, the expression of genes involved in transport and acquisition of ammonium or nitrate/nitrite was unaltered in N-starved cells. We propose that genes upregulated under P- or N-starvation lend themselves as potential tools to monitor nutrient limitation effects at the cellular level and indirectly the potential for initiation and maintenance of toxic blooms of P. parvum.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Growth- and nutrient-dependent gene expression in the toxigenic marine dinoflagellate Alexandrium minutum (2011)
    Elsevier
    Details
    Publication Date: 2023-02-16
    Description: The toxigenic marine dinoflagellate Alexandrium minutum forms toxic blooms causing paralytic shellfish poisoning (PSP), primarily in coastal waters, throughout the world. We examined effects on physiology and gene expression patterns associated with growth and nutrient starvation in a toxic strain of A. minutum. Bloom-relevant factors, including growth rate, intracellular toxin content, allelochemical activity and nutrient status were investigated in A. minutum cultures grown under different environmental regimes. Allelochemical activity of A. minutum cultures, quantified with a cryptomonad Rhodomonas bioassay, increased with age but was independent of nutrient status. The phenotypic data were integrated and compared with gene expression in cell samples taken at selected points along the growth curve. We observed 489 genes consistently differentially expressed between exponentially growing and growth-limited cultures. The expression pattern of stationary-phase cultures was characterized by conspicuous down-regulation of translation-associated genes, up-regulation of sequences involved in intracellular signalling and some indications of increased activity of selfish genetic elements such as transposons. Treatment-specific patterns included five genes regulated in parallel in all nutrient-limited cultures. The conspicuous decrease in photosynthetic performance identified in N-starved cultures was paralleled by down-regulation of chloroplast-associated genes. The particular gene expression patterns we identified as specifically linked with exponential growth, cessation of growth or nutrient limitation may be suitable biomarkers for indicating the beginning of growth limitation in field- or mesocosm studies.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Data files of figures 1, 2 and 3 (2011)
    PANGAEA
    In:  Supplement to: Ma, Haiyan; Krock, Bernd; Tillmann, Urban; Cembella, Allan (2010): Towards characterization of lytic compound(s) produced by Alexandrium tamarense. Proceedings of the 13th International Conference on Harmful Algae, Ed. Ho, K. et al., International Society for the Study of Harmful Algae and Intergovernmental Oceanographic Commission of UNESCO, Hong Kong, 2008, China, 142-146, hdl:10013/epic.36232.d001
    Details
    Publication Date: 2023-01-13
    Description: We investigated optimal conditions for characterization of bioactivity of lytic compound(s) excreted by Alexandrium tamarense based on a cell-bioassay system. Allelochemical response of the cryptophyte Rhodomonas salina indicated the presence oflytic compound(s) in a reliable and reproducible way and allows for quantification of this lytic effect. The parameters tested were the incubation time of putatively lytic extracts or fractions with the target organism R. salina, different techniques for cell harvest from A. tamarense cultures and the optimal harvest time. A three hour incubation time was found to be optimal to yield a rapid response while accurately estimating effective concentration (ECso) values. Harvest of A. tamarense cultures by filtration resulted in loss of lytic activity in most cases and centrifugation was most efficient in terms of recovery of lytic activity. Maximum yield of extracellular lytic activity of A. tamarense cultures was achieved in the stationary phase. Such optimized bioassay guided fractionation techniques are a valuable asset in the isolation and eventual stmctural elucidation of the unknown lytic substances.
    Type: Dataset
    Format: application/zip, 368.1 kBytes
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    DATA PANGAEA
  • 7
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    Files related to figures 1 to 13 (2011)
    PANGAEA
    In:  Supplement to: Ma, Haiyan; Krock, Bernd; Tillmann, Urban; Cembella, Allan (2009): Preliminary characterization of extracellular allelochemicals of the toxic marine dinoflagellate Alexandrium tamarense using a Rhodomonas salina bioassay. Marine Drugs, 7(4), 497-522, https://doi.org/10.3390/md7040497
    Details
    Publication Date: 2023-01-13
    Description: Members of the marine dinoflagellate genus Alexandrium are known to exude allelochemicals, unrelated to well-known neurotoxins (PSP-toxins, spirolides), with negative effects on other phytoplankton and marine grazers. Physico/chemical characterization of extracellular lytic compounds of A. tamarense, quantified by Rhodomonas salina bioassay, showed that the lytic activity, and hence presumably the compounds were stable over wide ranges of temperatures and pH and were refractory to bacterial degradation. Two distinct lytic fractions were collected by reversed-phase solid-phase extraction. The more hydrophilic fraction accounted for about 2% of the whole lytic activity of the A. tamarense culture supernatant, while the less hydrophilic one accounted for about 98% of activity. Although temporal stability of the compounds is high, substantial losses were evident during purification. Lytic activity was best removed from aqueous phase with chloroform-methanol (3:1). A “pseudo-loss” of lytic activity in undisturbed and low-concentrated samples and high activity of an emulsion between aqueous and n-hexane phase after liquid-liquid partition are strong evidence for the presence of amphipathic compounds. Lytic activity in the early fraction of gel permeation chromatography and lack of activity after 5 kD ultrafiltration indicate that the lytic agents form large aggregates or macromolecular complexes.
    Type: Dataset
    Format: application/zip, 843.6 kBytes
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    DATA PANGAEA
  • 8
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    Files of figures 2, 3 and table (2011)
    PANGAEA
    In:  Supplement to: Ma, Haiyan; Krock, Bernd; Tillmann, Urban; Bickmeyer, Ulf; Graeve, Martin; Cembella, Allan (2011): Mode of action of membrane-disruptive lytic compounds from the marine dinoflagellate Alexandrium tamarense. Toxicon, 58(3), 247-258, https://doi.org/10.1016/j.toxicon.2011.06.004
    Details
    Publication Date: 2023-01-13
    Description: Certain allelochemicals of the marine dinoflagellate Alexandrium tamarense cause lysis of a broad spectrum of target protist cells but the lytic mechanism is poorly defined. We first hypothesized that membrane sterols serve as molecular targets of these lytic compounds, and that differences in sterol composition among donor and target cells may cause insensitivity of Alexandrium and sensitivity of targets to lytic compounds. We investigated Ca2+ influx after application of lytic fractions to a model cell line PC12 derived from a pheochromocytoma of the rat adrenal medulla to establish how the lytic compounds affect ion flux associated with lysis of target membranes. The lytic compounds increased permeability of the cell membrane for Ca2+ ions even during blockade of Ca2+ channels with cadmium. Results of a liposome assay suggested that the lytic compounds did not lyse such target membranes non-specifically by means of detergent-like activity. Analysis of sterol composition of isolates of A. tamarense and of five target protistan species showed that both lytic and non-lytic A. tamarense strains contain cholesterol and dinosterol as major sterols, whereas none of the other tested species contain dinosterol. Adding sterols and phosphatidylcholine to a lysis bioassay with the cryptophyte Rhodomonas salina for evaluation of competitive binding indicated that the lytic compounds possessed apparent high affinity for free sterols and phosphatidylcholine. Lysis of protistan target cells was dose-dependently reduced by adding various sterols or phosphatidylcholine. For three tested sterols, the lytic compounds showed highest affinity towards cholesterol followed by ergosterol and brassicasterol. Cholesterol comprised a higher percentage of total sterols in plasma membrane fractions of A. tamarense than in corresponding whole cell fractions. We conclude therefore that although the molecular targets of the lytic compounds are likely to involve sterol components of membranes, A. tamarense must have a complex self-protective mechanism that still needs to be addressed.
    Type: Dataset
    Format: application/zip, 164.3 kBytes
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    DATA PANGAEA
  • 9
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    Operational taxonomic units and taxonomy of a phytoplankton community during Maria S. Merian cruise MSM21/3 - Greenland (ARCHEMHAB) (2017)
    PANGAEA
    In:  Supplement to: Elferink, Stephanie; Neuhaus, Stefan; Wohlrab, Sylke; Toebe, Kerstin; Voß, Daniela; Gottschling, Marc; Lundholm, Nina; Krock, Bernd; Koch, Boris P; Zielinski, Oliver; Cembella, Allan; John, Uwe (2017): Molecular diversity patterns among various phytoplankton size-fractions in West Greenland in late summer. Deep Sea Research Part I: Oceanographic Research Papers, 121, 54-69, https://doi.org/10.1016/j.dsr.2016.11.002
    Details
    Publication Date: 2023-07-11
    Description: Arctic regions have experienced pronounced biological and biophysical transformations as a result of global change processes over the last several decades. Current hypotheses propose an elevated impact of those environmental changes on the biodiversity, community composition and metabolic processes of species. The effects on ecosystem function and services, particularly when invasive or toxigenic harmful species become dominant, can be expressed over a wide range of temporal and spatial scales in plankton communities. Our study focused on the comparison of molecular biodiversity of three size-fractions (micro-, nano-, picoplankton) in the coastal pelagic zone of West Greenland and their association with environmental parameters. Molecular diversity was assessed via parallel amplicon sequencing the 28S rRNA hypervariable D1/D2 region. We showed that biodiversity distribution within the area of Uummannaq Fjord, Vaigat Strait and Disko Bay differed markedly within and among size-fractions. In general, we observed a higher diversity within the picoplankton size fraction compared to the nano- and microplankton. In multidimensional scaling analysis, community composition of all three size fractions correlated with cell size, silicate and phosphate, chlorophyll a (chl a) and dinophysistoxin (DTX). Individually, each size fraction community composition also correlated with other different environmental parameters, i.e. temperature and nitrate. We observed a more homogeneous community of the picoplankton across all stations compared to the larger size classes, despite different prevailing environmental conditions of the sampling areas. This suggests that habitat niche occupation for larger-celled species may lead to higher functional trait plasticity expressed as an enhanced range of phenotypes, whereas smaller organisms may compensate for lower potential plasticity with higher diversity. The presence of recently identified toxigenic harmful algal bloom (HAB) species (such as Alexandrium fundyense and A. ostenfeldii) in the area points out the potential risk for this vulnerable ecosystem in a changing world.
    Type: Dataset
    Format: application/zip, 3 datasets
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    DATA PANGAEA
  • 10
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    Continuous thermosalinograph oceanography along HEINCKE cruise track HE358 (2016)
    PANGAEA
    In:  Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven
    Details
    Publication Date: 2024-01-12
    Keywords: AWI_PhyOce; CT; DATE/TIME; DEPTH, water; HE358; HE358-track; Heincke; LATITUDE; LONGITUDE; Physical Oceanography @ AWI; Salinity; Temperature, water; Thermosalinograph; TSG; Underway cruise track measurements
    Type: Dataset
    Format: text/tab-separated-values, 6836 data points
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