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Climate warming in winter affects the coupling between phytoplankton and bacteria during the spring bloom: a mesocosm study (2008)
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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
DOI: 10.3354/ame01198
Language: English
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  • 2
    Online Resource
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    Effects of rising temperature on the formation and microbial degradation of marine diatom aggregates (2009)
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    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
    DOI: 10.3354/ame01273
    Language: English
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  • 3
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    Transparent exopolymer particles and dissolved organic carbon production by Emiliania huxleyi exposed to different CO2 concentrations : a mesocosm experiment (2004)
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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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