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  • GEOMAR Catalogue / E-Books  (3)
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  • 1
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (102 Blatt = 7 MB) , Illustrationen, Diagramme, Karten
    Language: English
    Note: Zusammenfassung in deutscher und englischer Sprache
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  • 2
    In: Aquatic microbial ecology, Oldendorf, Luhe : Inter-Research, 1995, 54(2009), 3, Seite 305-318, 1616-1564
    In: volume:54
    In: year:2009
    In: number:3
    In: pages:305-318
    Description / Table of Contents: Effects of elevated temperature on the formation and subsequent degradation of diatom aggregates were studied in a laboratory experiment with a natural plankton community from the Kiel Fjord (Baltic Sea). Aggregates were derived from diatom blooms that developed in indoor mesocosms at 2.5 and 8.5°C corresponding to the 1993 to 2002 mean winter in situ temperature of the Western Baltic Sea and the projected sea surface temperature during winter in 2100, respectively. Formation and degradation of diatom aggregates at these 2 temperatures in the dark were promoted with roller tanks over a period of 11 d. Comparison of the 2 temperature settings revealed an enhanced aggregation potential of diatom cells at elevated temperature, which was likely induced by an increased concentration of transparent exopolymer particles (TEP). The enhanced aggregation potential led to a significantly higher proportion of particulate organic matter in aggregates at 8.5°C Moreover, the elevated temperature favoured the growth of bacteria, bacterial biomass production, and the activities of sugar- and protein-degrading extracellular enzymes in aggregates. Stimulating effects of rising temperature on growth and metabolism of the bacterial community resulted in an earlier onset of aggregate degradation and silica dissolution. Remineralization of carbon in aggregates at elevated temperature was partially compensated by the formation of carbon-rich TEP during dark incubation. Hence, our results suggest that increasing temperature will affect both formation and degradation of diatom aggregates. We conclude that the vertical export of organic matter through aggregates may change in the future, depending on the magnitude and vertical depth penetration of warming in the ocean.
    Type of Medium: Online Resource
    Pages: graph. Darst
    ISSN: 1616-1564
    Language: English
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  • 3
    Keywords: Hochschulschrift
    Description / Table of Contents: Bacteria, Organic matter, Extracellular enzymes, Degradation, Carbon cycle, Global Change. - Anthropogenic emissions have increased the concentration of carbon dioxide (CO2) during the last 200 years. Since radiative forcing by greenhouse gases plays an essential role in maintaining the Earth's temperature, increasing emissions resulted in an observed warming of the atmosphere and the ocean. Furthermore, the absorption of excess atmospheric CO2 by the ocean has increased the acidity of seawater at global scale. The experimental simulation of changes in seawater temperature and CO2 projected for the near future led to a substantial acceleration of organic matter degradation. Higher degradation rates were primarily induced by temperature and pH effects on bacterial extracellular enzymes that increased rates of polymer hydrolysis. Effects of changing ocean temperature and pH on bacterial activity and the consequences for the cycling of organic matter are highly relevant for marine organic carbon fluxes and the ocean-atmosphere CO2 exchange.
    Type of Medium: Online Resource
    Pages: Online-Ressource (PDF-Datei: 201 S., 2,7 MB)
    DDC: 577.7144
    Language: English
    Note: Bremen, Univ., Diss., 2009
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