Dynamics of bacteria, phytoplankton and extracellular carbohydrates during blooms of the coccolithophore Emiliania huxleyi
The composition of bacterial and phytoplankton communities during phytoplankton blooms, and their interactions, are important properties of the microbial food web, which can potentially have a strong impact on the fate of organic matter and hence carbon cycling in the world’s oceans. During late spr...
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| Other Authors: | , , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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Ghent University. Faculty of Sciences
2011
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| Online Access: | https://biblio.ugent.be/publication/1919906 http://hdl.handle.net/1854/LU-1919906 https://biblio.ugent.be/publication/1919906/file/4335689 |
| Summary: | The composition of bacterial and phytoplankton communities during phytoplankton blooms, and their interactions, are important properties of the microbial food web, which can potentially have a strong impact on the fate of organic matter and hence carbon cycling in the world’s oceans. During late spring (May-June 2006-2008) we investigated the relationship between the community structures of phytoplankton (pigment-based) and free-living and particle-associated bacterioplankton (denaturant gradient gel electrophoresis), and environmental constraints during natural coccolithophore blooms along the North East Atlantic continental margin (Bay of Biscay). The alternation between diatom and coccolithophore blooms (mainly Emiliania huxleyi) of similar biomass was partly driven by changes in nutrient stoichiometry (N:P and dSi:N). High concentrations of transparent exopolymer particles (TEP) were associated with stratified, coccolithophore-rich water masses. Free-living and particle-associated bacterial communities had different typical representatives but showed a considerable overlap in composition. Furthermore, the structure of the bacterial communities was significantly correlated to the abundance of phytoplankton groups and water column stratification. At selected stations, we assessed the relationship of dimethyl sulphide (DMS) and dimethylsulphonioproprionate (DMSP) concentrations and the fate of phytoplankton in terms of cell lysis rates and microzooplankton grazing. Coccolithophores constituted an important source of particulate DMSP, and cell lysis enhanced the release of dissolved DMSP. Finally, we assessed the role of bacterial activity and life cycle stage of the coccolithophore E. huxleyi on the dynamics of dissolved carbohydrates and TEP by measuring their production and composition during the stationary growth phase of batch cultures, and by tracing the fate of photosynthetically fixed carbon by stable isotope probing in non-axenic calcifying E. huxleyi cultures using liquid chromatographic separation of ... |
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