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  • 1
    In: Aquatic microbial ecology, Oldendorf, Luhe : Inter-Research, 1995, 51(2008), 2, Seite 105-115, 1616-1564
    In: volume:51
    In: year:2008
    In: number:2
    In: pages:105-115
    Description / Table of Contents: The response of the phytoplankton and bacterial spring succession to the predicted warming of sea surface temperature in temperate climate zones during winter was studied using an indoor-mesocosm approach. The mesocosms were filled with winter water from the Kiel Fjord, Baltic Sea. Two of them were started at ~2ʿC and the temperature was subsequently increased according to the decadal temperature profile of the fjord (Delta T 0ʿC, baseline treatment). The other mesocosms were run at 3 elevated temperatures with differences of Delta T +2, +4 and +6°C. All mesocosms were exposed to the same light conditions. Timing of peak phytoplankton primary production (PP) during the experimental spring bloom was not significantly influenced by increasing temperatures, whereas the peak of bacterial secondary production (BSP) was accelerated by about 2 d per °C. This suggests that, in case of warming, the spring peak of bacterial degradation of organic matter (in terms of BSP) would occur earlier in the year. Furthermore, the lag time between the peaks of PP and BSP (about 16 d for Delta T 0°C) would diminish progressively at elevated temperatures. The average ratio between BSP and PP increased significantly from 0.37 in the coldest mesocosms to 0.63 in the warmest ones. Community respiration and the contribution of picoplankton (〈3 Mym fraction) to this also increased at elevated temperatures. Our results lead to the prediction that climate warming during the winter/ early spring in temperate climate zones will favor bacterial degradation of organic matter by tightening the coupling between phytoplankton and bacteria. However, if PP is reduced by warming, as in our experiments, this will not necessarily lead to increased recycling of organic matter (and CO2).
    Type of Medium: Online Resource
    ISSN: 1616-1564
    Language: English
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  • 2
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: Online-Ressource (151 Seiten = 17 MB) , Illustrationen, Graphen
    Language: English
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  • 3
    Keywords: Hochschulschrift
    Description / Table of Contents: Abstract ; Zs.-Fassung
    Type of Medium: Online Resource
    Pages: Online-Ressource (IV, 127 Bl. = 1.86 MB, Text) , Ill., graph. Darst.
    Edition: [Electronic ed.]
    DDC: 577.7
    Language: English
    Note: Kiel, Univ., Diss., 2006
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  • 4
    Keywords: Hochschulschrift ; Phytoplankton ; Klimaänderung
    Description / Table of Contents: Global warming has already and is continuing to impact the global oceans. Half of the global primary production is performed by phytoplankton in the oceans and heterotrophic marine bacteria channel a substantial amount of primary organic carbon through the microbial loop. Understanding the influence of climate change on these important processes is therefore essential for an assessment of the vulnerability of the carbon cycle and possible feedbacks. This thesis reports results from investigations on the temperature dependent coupling between phytoplankton and bacterioplankton, with respect to additional effects of light intensity and inorganic nutrient concentrations. During four consecutive years, mesocosm experiments with natural Kiel Fjord winter plankton communities investigated the influences of increasing water temperatures of up to ?T +6ʿC and different light intensities between 16 and 100% of natural incident light. In an additional microcosm experiment with a single algal species and the natural bacterial community, two inorganic nutrient concentrations were used, in order to evaluate the combined effects of temperature and substrate on the algal-bacterial coupling. Summarising the results from all experiments it can be concluded, that increasing temperatures generally led to an increased heterotrophic bacterial organic substrate utilisation relative to primary production. In combination with a further brightening, the supplemental promotion of primary production would increase the absolute amounts of cycled organic matter. Future increasing P-limitation in coastal waters would lead not only to an enhanced absolute amount of cycled carbon, but additionally to an increased relative amount of remineralised organic carbon through the microbial loop. An enhanced organic matter transfer through the microbial loop has the potential to alter the whole structure and functioning of the marine food web and the biological sequestration of carbon to depth. Additionally, a substantial rise of CO2 emissions through enhanced respiration represents a positive feedback loop to the global climate change problem.
    Type of Medium: Online Resource
    Pages: Online-Ressource (pdf-Datei: 199 S., 1,7 MB)
    DDC: 578.77622
    Language: English
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