Isolation of a widespread giant virus implicated in cryptophyte bloom collapse

Photosynthetic cryptophytes are ubiquitous protists that are major participants in the freshwater phytoplankton bloom at the onset of spring. Mortality due to change in environmental conditions and grazing have been recognized as key factors contributing to bloom collapse. In contrast, the role of viral outbreaks as factors terminating phytoplankton blooms remains unknown from freshwaters. Here, we isolated and characterised a cryptophyte virus contributing to the annual collapse of a natural cryptophyte spring bloom population. This viral isolate is also representative for a clade of abundant giant viruses (phylum <i>Nucleocytoviricota</i>) found in freshwaters all over the world.