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  • 2000-2004  (63)
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  • 1
    Online Resource
    Online Resource
    Transparent exopolymer particles and dissolved organic carbon production by Emiliania huxleyi exposed to different CO2 concentrations : a mesocosm experiment (2004)
    Associated volumes
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    In: Aquatic microbial ecology, Oldendorf, Luhe : Inter-Research, 1995, 34(2004), 1, Seite 93-104, 1616-1564
    In: volume:34
    In: year:2004
    In: number:1
    In: pages:93-104
    Description / Table of Contents: The role of transparent exopolymer particles (TEP) and dissolved organic carbon (DOC) for organic carbon partitioning under different CO2 conditions was examined during a mesocosm experiment with the coccolithophorid Emiliania huxleyi. We designed 9 outdoor enclosures (~11 m3) to simulate CO2 concentrations of estimated ŒYear 2100£ (~710 ppm CO2), Œpresent (~410 ppm CO2) and Œglacial (~190 ppm CO2) environments, and fertilized these with nitrate and phosphate to favor bloom development. Our results showed fundamentally different TEP and DOC dynamics during the bloom. In all mesocosms, TEP concentration increased after nutrient exhaustion and accumulated steadily until the end of the study. TEP concentration was closely related to the abundance of E. huxleyi and accounted for an increase in POC concentration of 35 ± 2% after the onset of nutrient limitation. The production of TEP normalized to the cell abundance of E. huxleyi was highest in the Year 2100 treatment. In contrast, DOC concentration exhibited considerable short-term fluctuations throughout the study. In all mesocosms, DOC was neither related to the abundance of E. huxleyi nor to TEP concentration. A statistically significant effect of the CO2 treatment on DOC concentration was not determined. However, during the course of the bloom, DOC concentration increased in 2 of the 3 Year 2100 mesocosms and in 1 of the present mesocosms, but in none of the glacial mesocosms. It is suggested that the observed differences between TEP and DOC were determined by their different bioavailability and that a rapid response of the microbial food web may have obscured CO2 effects on DOC production by autotrophic cells.
    Type of Medium: Online Resource
    Pages: Ill., graph. Darst
    ISSN: 1616-1564
    DOI: 10.3354/ame034093
    Language: English
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  • 2
    Electronic Resource
    Electronic Resource
    Polysaccharide aggregation as a potential sink of marine dissolved organic carbon (2004)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 428 (2004), S. 929-932 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The formation and sinking of biogenic particles mediate vertical mass fluxes and drive elemental cycling in the ocean. Whereas marine sciences have focused primarily on particle production by phytoplankton growth, particle formation by the assembly of organic macromolecules has almost been ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature02453
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The role of aggregation for the dissolution of diatom frustules (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 46 (2003), S. 0 
    Details
    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
    URL: http://dx.doi.org/10.1016/S0168-6496(03)00199-5
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  • 4
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    Carbon and nitrogen content of transparent exopolymer particles (TEP) in relation to their Alcian Blue adsorption (2001)
    Inter Research
    In:  Marine Ecology Progress Series, 219 . pp. 1-10.
    Details
    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
    DOI: 10.3354/meps219001
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  • 5
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    Distribution of transparent exopolymer particles (TEP) in the northeast Atlantic Ocean and their potential significance for aggregation processes (2004)
    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 51 (1). pp. 83-92.
    Details
    Publication Date: 2016-11-01
    Description: The abundance of transparent exopolymer particles (TEP) was determined in the northeast Atlantic Ocean (40–55°N, ∼20°W) during several cruises from June to November 1996. An accumulation of TEP in the water column was observed at bloom and post-bloom sites along a 20°W transect in June/July (maximum concentration: 124 μg Gum Xanthan equivalents (Xeq.) l−1), but concentrations were uniformly low (mean concentration: 28.5±10.2 μg Xeq. l−1) during autumn at the BIOTRANS site (47°N, 20°W). TEP concentrations in the open northeast Atlantic were considerably lower than previously published values from coastal sites. However, during June/July TEP:Chl a (weight/weight) ratios were comparable to values at coastal seas. It is suggested that phytoplankton production modulates TEP concentration in the open ocean as it does in coastal systems. TEP contributed significantly to the organic carbon pool as derived from the ratio TEP-C:POC, in summer (mean percentage: 17±7.5; w/w), as well as in autumn (mean percentage: 18±11, w/w). The potential influence of TEP on particle coagulation rates in the northeast Atlantic was assessed from estimates of their influence on particle stickiness and on particle volume concentrations. This indicated that TEP may be essential for initiating particle aggregation at low biomass concentrations, typical for open ocean sites.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1016/j.dsr.2003.09.001
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Direct relationship between CO2 uptake and transparent exopolymer particles production in natural phytoplankton (2002)
    Oxford Univ. Press
    In:  Journal of Plankton Research, 24 (1). pp. 49-53.
    Details
    Publication Date: 2018-06-01
    Description: Incubation experiments with natural phytoplankton revealed a relationship between CO2 concentration and the production of transparent exopolymer particles (TEP), with TEP production being linearly related to theoretical CO2 uptake rates.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1093/plankt/24.1.49
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Abundance and variability of microorganisms and transparent exopolymer particles across the ice-water interface of melting first-year sea ice in the Laptev Sea (Arctic) (2001)
    Springer
    In:  Marine Biology, 138 (1). pp. 173-185.
    Details
    Publication Date: 2018-06-07
    Description: The distribution and abundance of transparent exopolymer particles (TEP) was determined in and below pack ice of the Laptev Sea from July to September 1995. Samples were collected from the lowermost 10 cm of ice floes and at 10 cm below the ice–water interface. Abundance of bacteria, protists and TEP was determined, and the sea ice–water boundary layer was characterized using temperature, salinity and molecular viscous shear stress. TEP, with a distinct size distribution signal, were found in highest concentrations inside the sea ice, ranging from not detectable to 16 cm2 l−1 (median: 2.9 cm2 l−1). In the water, concentrations were one order of magnitude lower, ranged from below detection to 2.7 cm2 l−1 (median: 0.2 cm2 l−1) and decreased after the middle of August, whereas abundances of autotrophic flagellates (AF), diatoms, heterotrophic flagellates (HF) and ciliates increased. The abundance of TEP decreased with its size in all samples following a power law relationship. The relation of TEP to the microbial community differed between the sea ice and water, being positively correlated with bacteria and diatoms in the ice and negatively correlated with HF in the sea water. The presence of a pycnocline significantly influenced the abundance of organisms, diatom composition and TEP concentrations. Pennate diatoms dominated by Nitzschia frigida were most abundant inside the ice. Though bacteria have the potential to produce exopolymeric substances (EPS), the results of this study indicate that the majority of TEP at the ice–water interface in first-year Arctic summer pack ice are produced by diatoms.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s002270000396
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  • 8
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    The role of transparent exopolymer particles (TEP) in the increase in apparent particle stickiness (alpha) during the decline of a diatom bloom (2000)
    Oxford Univ. Press
    In:  Journal of Plankton Research, 22 (3). pp. 485-497.
    Details
    Publication Date: 2018-05-30
    Description: The termination of diatom spring blooms in temperate waters has been connected with the formation and subsequent rapid sedimentation of aggregates. According to coagulation theory, the rate of aggregate formation depends on the probability of particle collision and on the efficiency with which two particles adhere once they have collided (stickiness). During this study, the variation in particle stickiness was determined over the decline of a diatom bloom using the Couette Chamber assay with low shear (G = 0.86 s–1). A mixed diatom population, dominated by Skeletonema costatum, was sampled during the spring bloom in the Baltic Sea and incubated in the laboratory for 18 days. Measurements of diatom species composition, transparent exopolymer particles (TEP) and bulk particle abundance, as well as chemical and biological variables, were conducted in order to reveal the determinants of coagulation efficiency. The investigation showed that an increase in TEP concentration relative to conventional particles at the decline of the bloom significantly enhanced apparent coagulation efficiencies. High proportions of TEP led to apparent values of stickiness 〉1, which indicates that collision rates can be substantially underestimated when the stickiness parameter α is calculated on the basis of conventional particle counting only, e.g. with the Coulter Counter. A new stickiness parameter, α′, was therefore estimated based on the combined volume fractions of TEP and conventional particles. The problems of stickiness measurements are discussed and the role of TEP in coagulation processes is emphasized.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1093/plankt/22.3.485
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  • 9
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    The effect of different CO2 concentrations on bacterial abundance and activity in the course of a diatom bloom (2004)
    In:  [Talk] In: Abstract VAM, 2004, Braunschweig, Germany .
    Details
    Publication Date: 2012-02-23
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 10
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    Modeling the formation of transparent exopolymer particles during a bloom of the coccolithophorid Emiliania huxleyi (2004)
    In:  [Talk] In: ASLO/TOS Ocean Research Conference 2004, 15.-20.02.2004, Honolulu, USA .
    Details
    Publication Date: 2019-08-09
    Description: A simple two-size-class aggregation model is developed to describe the time-dependent carbon content of dissolved polysaccharides (PCHO) and of transparent exopolymer particles (TEP) during the bloom. A conservative estimate for the effective collision kernel is obtained from the Smoluchowski equation under the assumption that the growth of aggregates is controlled by a Brownian process near the scaling regime. In the model, PCHO are assumed to represent a fraction of the photosynthetic carbon, which is not used for net algal growth. Time dependence of chlorophyll a and of cellular carbon during the bloom is modelled in terms of algal growth and sinking of single and aggregated algal cells. The aggregation of exopolysaccharides into TEP may have important implications for the organic carbon cycle in the ocean, as TEP promote the aggregation of algae during a bloom.
    Type: Conference or Workshop Item , NonPeerReviewed
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