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  • 1
    Keywords: Hochschulschrift ; Aufsatzsammlung
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (288 Seiten = 17 MB) , Illustrationen, Graphen
    Edition: Online-Ausgabe
    Language: English
    Note: Zusammenfassung in deutscher und englischer Sprache
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 46 (2003), S. 0 
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Observations that the majority of silica dissolution occurs within the upper 200 m of the ocean, and that sedimentation rates of diatom frustules generally do not decrease significantly with depth, suggested reduced dissolution rates of diatoms embedded within sinking aggregates. To investigate this hypothesis, silica dissolution rates of aggregated diatom cells were compared to those of dispersed cells during conditions mimicking sedimentation below the euphotic zone. Changes in the concentrations of biogenic silica, silicic acid, cell numbers, chlorophyll a and transparent exopolymer particles (TEP) were monitored within aggregates and in the surrounding seawater (SSW) during two 42-day experiments. Whereas the concentration of dispersed diatoms decreased over the course of the experiment, the amount of aggregated cells remained roughly constant after an initial increase. Initially only 6% of cells were aggregated and at the end of the experiment more than 60% of cells were enclosed within aggregates. These data imply lower dissolution rates for aggregated cells. However, fluxes of silica between the different pools could not be constrained reliably enough to unequivocally prove reduced dissolution for aggregated cells.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2023-03-03
    Keywords: CTD; Date/Time of event; DEPTH, water; Elevation of event; Event label; Latitude of event; Littorina; Longitude of event; MSN; Multiple opening/closing net; PEX86; PEX86_10; PEX86_11; PEX86_12; PEX86_13; PEX86_14; PEX86_15; PEX86_16; PEX86_17; PEX86_18; PEX86_19; PEX86_20; PEX86_21; PEX86_22; PEX86_23; PEX86_24; PEX86_25; PEX86_26; PEX86_27; PEX86_28; PEX86_29; PEX86_3; PEX86_30; PEX86_31; PEX86_32; PEX86_33; PEX86_4; PEX86_5; PEX86_6; PEX86_7; PEX86_8; PEX86_9; Temperature, water
    Type: Dataset
    Format: text/tab-separated-values, 390 data points
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  • 4
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    Inter Research
    In:  Marine Ecology Progress Series, 219 . pp. 1-10.
    Publication Date: 2018-05-28
    Description: The carbon and nitrogen content of transparent exopolymer particles (TEP) was determined and related to the concentration of TEP as quantified by a colorimetrical method. TEP were produced in the laboratory from dissolved precursors by laminar or turbulent shear. Dissolved precursors were obtained by 0.2 µm filtration from diatom cultures, with or without nutrient reduction, and from natural diatom populations. The relationship between carbon and TEP was significant, linear and species-specific. Carbon concentration of TEP derived from this relationship concurred with previous findings. Shortage of silicic acid or nitrate in the culture media had no effect on the carbon content of TEP. Molar C:N ratios of TEP were above the Redfield ratio, with a mean value of 26. It is suggested that the nitrogen fraction of TEP can be explained by adsorption of dissolved organic nitrogen (DON) onto TEP. Based on the newly established relationship, concentrations of TEP-derived carbon (TEP-C) were calculated for the Baltic Sea, the coastal Pacific, the North East Atlantic and the Northern Adriatic Sea.
    Type: Article , PeerReviewed
    Format: text
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  • 5
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    ASLO (Association for the Sciences of Limnology and Oceanography)
    In:  Limnology and Oceanography, 47 (3). pp. 753-761.
    Publication Date: 2014-01-30
    Description: Flows of the major biogeochemical elements (C, N, P, Si) and of transparent exopolymer particles (TEP) were traced during a bloom of a natural assemblage of marine diatoms in a mesocosm (l m(3)) to determine whether the exudation and subsequent gelation of carbon-rich phytoplankton exopolymers can account for the formation and potential export of carbon in excess of that predicted by Redfield ratios. Exponential growth of the phytoplankton community in the mesocosm extended for 10 d until nitrate concentration fell below detection and concentrations of dissolved inorganic and particulate organic nitrogen and phosphorus remained stable. Tight covariation of particulate organic elements occurred as long as nutrients were replete. But, after nitrate depletion, decoupling of carbon dynamics from that of nitrogen and phosphorus was observed, with a large flow of carbon into TEP An uptake of 72% more dissolved inorganic carbon (DIC) than inferred from nitrate supply and Redfield stoichiometry (referred to as carbon overconsumption) occurred during the study, largely during the postbloom phase, and was almost entirely traced to the particulate organic matter (POM) pool. Marine snow (aggregates 〉0.5 mm) appeared at the onset of nitrate depletion and coincided with rapid increase in TEP concentrations. Elemental composition of marine snow differed from the Redfield ratio by an enrichment in carbon and a depletion in phosphorus relative to nitrogen. It is suggested that sinking of TEP-rich marine snow could be a possible mechanism for export of carbon above calculations that are based on the Redfield stoichiometry.
    Type: Article , PeerReviewed
    Format: text
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  • 6
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    Elsevier
    In:  FEMS Microbiology Ecology, 46 (3). pp. 247-255.
    Publication Date: 2020-03-20
    Description: Observations that the majority of silica dissolution occurs within the upper 200 m of the ocean, and that sedimentation rates of diatom frustules generally do not decrease significantly with depth, suggested reduced dissolution rates of diatoms embedded within sinking aggregates. To investigate this hypothesis, silica dissolution rates of aggregated diatom cells were compared to those of dispersed cells during conditions mimicking sedimentation below the euphotic zone. Changes in the concentrations of biogenic silica, silicic acid, cell numbers, chlorophyll a and transparent exopolymer particles (TEP) were monitored within aggregates and in the surrounding seawater (SSW) during two 42-day experiments. Whereas the concentration of dispersed diatoms decreased over the course of the experiment, the amount of aggregated cells remained roughly constant after an initial increase. Initially only 6% of cells were aggregated and at the end of the experiment more than 60% of cells were enclosed within aggregates. These data imply lower dissolution rates for aggregated cells. However, fluxes of silica between the different pools could not be constrained reliably enough to unequivocally prove reduced dissolution for aggregated cells.
    Type: Article , PeerReviewed
    Format: text
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  • 7
    Publication Date: 2023-11-07
    Type: Thesis , NonPeerReviewed
    Format: text
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  • 8
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 9
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    In:  EPIC3Marine ecology-progress series, 236, pp. 1-12
    Publication Date: 2019-07-17
    Description: Transparent exopolymer particles (TEP) exist abundantly in oceans and lakes and have been found to play an important role for sedimentation and biochemical cycling of matter. But the origin of these particles and the factors regulating their formation are not well understood. This study examined several strains of algae and bacteria with respect to their production of TEP or TEP-precursors. The formation rate of TEP in batch cultures of algae varied widely between species, and interspecies variability between diatoms was as large as that between species belonging to different classes or even divisions. Species, growth phase and environmental factors acted in concert in determining the accumulation of TEP in algal cultures and no general rules or patterns could be derived. The concentration of TEP during the growth phase of algal batch cultures, mesocosm or natural phytoplankton blooms was a significant function of chl. a, confirming the significance of phytoplankton for the formation of TEP. Experiments with three bacterial strains and a natural bacteria population indicated, that bacteria are also able to generate TEP, but the role of bacterial derived TEP for in situ TEP concentrations remains unclear.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 10
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    In:  EPIC3Fems microbiology ecology, 46, pp. 247-255, ISSN: 0168-6496
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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