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Isolation of viruses responsible for the demise of an Emiliania huxleyi bloom in the English Channel

Published online by Cambridge University Press:  30 September 2002

William H. Wilson
Affiliation:
Marine Biological Association, Citadel Hill, Plymouth, PL1 2PB
Glen A. Tarran
Affiliation:
Plymouth Marine Laboratory, Prospect Place, Plymouth, PL1 3DH
Declan Schroeder
Affiliation:
Marine Biological Association, Citadel Hill, Plymouth, PL1 2PB
Michael Cox
Affiliation:
Department of Biological Sciences, University of Warwick, Coventry, CV4 7AL
Joanne Oke
Affiliation:
Marine Biological Association, Citadel Hill, Plymouth, PL1 2PB
Gillian Malin
Affiliation:
School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ

Abstract

This study used analytical flow cytometry (AFC) to monitor the abundance of phytoplankton, coccoliths, bacteria and viruses in a transect that crossed a high reflectance area in the western English Channel. The high reflectance area, observed by satellite, was caused by the demise of an Emiliania huxleyi bloom. Water samples were collected from depth profiles at four stations, one station outside and three stations inside the high reflectance area. Plots of transect data revealed very obvious differences between Station 1, outside, and Stations 2–4, inside the high reflectance area. Inside, concentrations of viruses were higher; E. huxleyi cells were lower; coccoliths were higher; bacteria were higher and virus:bacteria ratio was lower than at Station 1, outside the high reflectance area. This data can simply be interpreted as virus-induced lysis of E. huxleyi cells in the bloom causing large concentrations of coccoliths to detach, resulting in the high reflectance observed by satellite imagery. This interpretation was supported by the isolation of two viruses, EhV84 and EhV86, from the high reflectance area that lysed cultures of E. huxleyi host strain CCMP1516. Basic characterization revealed that they were lytic viruses approximately 170 nm–190 nm in diameter with an icosahedral symmetry. Taken together, transect and isolation data suggest that viruses were the major contributor to the demise of the E. huxleyi population in the high reflectance area. Close coupling between microalgae, bacteria and viruses contributed to a large organic carbon input. Consequent cycling influenced the succession of an E. huxleyi-dominated population to a more characteristic mixed summer phytoplankton community.

Type
Research Article
Copyright
2002 Marine Biological Association of the United Kingdom

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