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  • Artikel  (4)
  • Frontiers  (2)
  • Blackwell Publishing Ltd  (1)
  • Wiley-Blackwell  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 46 (2003), S. 0 
    ISSN: 1574-6941
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Publikationsdatum: 2015-01-28
    Beschreibung: Although the north-western coast of Western Australia is highly vulnerable to tropical cyclones and tsunamis, little is known about the geological imprint of historic and prehistoric extreme wave events in this particular area. Despite a number of site-specific difficulties such as post-depositional changes and the preservation potential of event deposits, both tropical cyclones and tsunamis may be inferred from the geomorphology and the stratigraphy of beach ridge sequences, washover fans, and coastal lagoons or marshes. A further challenge is the differentiation between tsunami and storm deposits in the geological record, particularly where modern deposits and/or historical reports on the event are not available. This study presents a high resolution sedimentary record of washover events from the Ashburton River delta (Western Australia) spanning approximately the last 150 years. A detailed characterization of event deposits is provided, and a robust chronostratigraphy for the investigated washover sequence is established based on multi-proxy sediment analyses and optically stimulated luminescence dating. Combining sedimentological, geochemical and high-resolution optically stimulated luminescence data, event layers are assigned to known historical events and tropical cyclone deposits are separated from tsunami deposits. For the first time, the 1883 Krakatoa and 1977 Sumba tsunamis are inferred from sedimentary records of northwest Australia. It is demonstrated that optically stimulated luminescence applied in coastal sedimentary archives with favourable luminescence characteristics can provide accurate chronostratigraphies even on a decadal time scale. The results contribute to the data pool of tropical cyclone and tsunami deposits in Holocene stratigraphies; however, they also demonstrate how short-lived sediment archives may be in dynamic sedimentary environments. This article is protected by copyright. All rights reserved.
    Print ISSN: 0037-0746
    Digitale ISSN: 1365-3091
    Thema: Geologie und Paläontologie
    Publiziert von Wiley-Blackwell
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Publikationsdatum: 2018-02-16
    Beschreibung: Carbohydrates represent an important fraction of labile and semi-labile marine organic matter that is mainly comprised of exopolymeric substances derived from phytoplankton exudation and decay. This study investigates the composition of total combined carbohydrates (tCCHO; 〉 1 kDa) and the community development of free-living (0.2 - 3 μm) and particle-associated (3 - 10 μm) bacterioplankton during a spring phytoplankton bloom in the southern North Sea. Furthermore, rates were determined for the extracellular enzymatic hydrolysis that catalyzes the initial step in bacterial organic matter remineralization. Concentrations of tCCHO greatly increased during bloom development, while the composition showed only minor changes over time. The combined concentration of glucose, galactose, fucose, rhamnose, galactosamine, glucosamine and glucuronic acid in tCCHO was a significant factor shaping the community composition of the particle-associated bacteria. The richness of particle-associated bacteria greatly increased in the post‐bloom phase. At the same time, the increase in extracellular β‐glucosidase activity was sufficient to explain the observed decrease in tCCHO, indicating the efficient utilization of carbohydrates by the bacterioplankton community during the post-bloom phase. Our results suggest that carbohydrate concentration and composition are important factors in the multifactorial environmental control of bacterioplankton succession and the enzymatic hydrolysis of organic matter during phytoplankton blooms.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    facet.materialart.
    Unbekannt
    Frontiers
    In:  EPIC3Frontiers in Marine Science, Frontiers, 4(166), pp. 1-14, ISSN: 2296-7745
    Publikationsdatum: 2017-07-03
    Beschreibung: Gel particles—a class of abundant transparent organic particles—have increasingly gathered attention in marine research. Field studies on the bacterial colonization of marine gels however are still scarce. So far, most studies on respective particles have focused on the upper ocean, while little is known on their occurrence in the deep sea. Here, we report on the vertical distribution of the two most common gel particle types, which are polysaccharide-containing transparent exopolymer particles (TEP) and proteinaceous Coomassie stainable particles (CSP), as well as numbers of bacteria attached to gel particles throughout the water column, from the surface ocean down to the bathypelagial (〈 3,000 m). Our study was conducted in the Arctic Fram Strait during northern hemispheres' summer in 2015. Besides data on the bacterial colonization of the two gel particle types (TEP and CSP), we present bacterial densities on different gel particle size classes according to 12 different sampling depths at four sampling locations. Gel particles were frequently abundant at all sampled depths, and their concentrations decreased from the euphotic zone to the dark ocean. They were colonized by bacteria at all sampled water depths with risen importance at the deepest water layers, where fractions of bacteria attached to gel particles (%) increased within the total bacterial community. Due to the omnipresent bacterial colonization of gel particles at all sampled depths in our study, we presume that euphotic production of this type of organic matter may affect microbial species distribution within the whole water column in the Fram Strait, down to the deep sea. Our results raise the question if changes in the bacterial community composition and functioning on gel particles occur over depth, which may affect microbial respiration and remineralization rates of respective particles in different water layers.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , peerRev
    Standort Signatur Einschränkungen Verfügbarkeit
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