AME 25:207-213 (2001)  -  doi:10.3354/ame025207

Virus-like particles associated with Lyngbya majuscula (Cyanophyta; Oscillatoriacea) bloom decline in Moreton Bay, Australia

Ian Hewson1,*, Judith M. O¹Neil2, William C. Dennison1

1Marine Botany Group, Department of Botany and
2Centre for Marine Studies, University of Queensland, Brisbane, Queensland 4072, Australia
*Present address: Department of Biological Sciences, University of Southern California, 3616 Trousdale Parkway, AHF 107, Los Angeles, California 90089-0371, USA. E-mail:

ABSTRACT: Expansive blooms of the toxic cyanobacterium Lyngbya majuscula were observed in 2 shallow water regions of Moreton Bay, Australia. The rapid bloom decline (8 to <1 km2 in <7 d) prompted an investigation of the role of cyanophage viruses in the ecophysiology of L. majuscula. Virus-like particles produced by decaying L. majuscula were observed using electron microscopy. The virus-like particles were similar in morphology to viruses in the genus Cyanostyloviridae. The effect of viruses on L. majuscula photosynthesis was investigated by: (1) creating a virus concentrate using tangential-flow ultrafiltration of seawater surrounding L. majuscula; (2) inoculating L. majuscula with the concentrate; and (3) measuring photosynthetic response using a pulse-amplitude modulated fluorometer. Virus concentrate addition resulted in decreased initial fluorescence, decreased photochemical efficiency and decreased electron transport rate in rapid light curves after 5 d. Viruses present within L. majuscula filaments may play an important role in the bloom dynamics of this ecologically important cyanobacterium.

KEY WORDS: Lyngbya majuscula · Cyanophage · Virus · Lysogeny

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