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Marine Ecology Progress Series

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MEPS 221:39-46 (2001)  -  doi:10.3354/meps221039

Microbial population dynamics and diversity during a bloom of the marine coccolithophorid Emiliania huxleyi (Haptophyta)

T. Castberg1, A. Larsen1,*, R. A. Sandaa1, C. P. D. Brussaard2, J. K. Egge3, M. Heldal1, R. Thyrhaug1, E. J. van Hannen4, G. Bratbak1

1Department of Microbiology, University of Bergen, Jahnebakken 5, 5020 Bergen, Norway
2Department of Biological Oceanography, Netherlands Institute for Sea Research, PO Box 59, 1790 AB Den Burg, Texel, The Netherlands
3Department of Fisheries and Marine Biology, University of Bergen, Bergen High Technology Centre, 5020 Bergen, Norway
4Department of Microbial Ecology, Centre for Limnology, Netherlands Institute of Ecology, PO Box 1299, 3600 BG Maarssen, The Netherlands
*Corresponding author. E-mail:

ABSTRACT: Several previous studies have shown that Emiliania huxleyi blooms and terminations have been succeeded by an increase in large virus-like particles (LVLP), strongly suggesting the bloom collapse was caused by viral lysis. However, due to methodological limitations, knowledge of how such blooms affect the rest of the microbial community is limited. In the current study we induced a bloom of E. huxleyi in seawater enclosures and applied methods enabling us to describe the algae, bacteria and virus communities with greater resolution than has been done previously. The development of the dominating algal, viral and bacterial populations in the nutrient-amended seawater enclosures was followed by flow cytometry (FCM). Light microscopy (LM), PCR denaturing gradient gel electrophoresis (PCR-DGGE) and pulsed-field gel electrophoresis (PFGE) were used to describe the changes in community composition in greater detail. The algal community was dominated by E. huxleyi until termination of the bloom by viral lysis. After bloom termination the additional algal populations present in the enclosures increased in abundance. A marked increase in viruses other than the one infecting E. huxleyi was also observed. Total bacterial number and community composition were also greatly influenced by the bloom and its collapse.

KEY WORDS: Diversity · Emiliania huxleyi · Microbial community · Viral lysis

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