AME 73:171-183 (2014)  -  DOI: https://doi.org/10.3354/ame01713

ABSTRACT: Viral infection is considered a significant factor affecting the dynamics of diatoms in marine environments. Two different diatom viruses—the single-stranded DNA virus CtenDNAV and the single-stranded RNA virus CtenRNAV, that both infect and lyse the marine planktonic diatom Chaetoceros tenuissimus Meunier—have been isolated from western Japan. To understand the ecological relationship explaining how they share the same host species in nature and how the host population survives, basic host growth and physiology of viral infections should be examined. We evaluated the relationship between host growth rates and viral infections with respect to water temperature within the range of 10 to 30°C. The maximum growth rates of 2 different strains of C. tenuissimus were 3.4 to 3.5 divisions d^-1, which were obtained at 25 to 30°C. The viral infection tests showed that the decline in the host population due to CtenDNAV was faster at higher water temperatures. The susceptibilities of the host strains to CtenRNAV (but not to CtenDNAV) were diverse, and varied with water temperature. The results indicate that successful CtenDNAV proliferation occurs during seasons with higher water temperature that are more suitable for host growth. However, CtenRNAV proliferation does not necessarily correlate with temperature-dependent host growth. The host populations grow in the water column during the course of a year, and the different temperature-dependent viral proliferations allow the 2 viruses to coexist in a narrow spatial region. Additionally, the viral infections seem to be accelerated during the host stationary growth phase, but not during the logarithmic growth phase, which might contribute to host population survival in nature.

KEY WORDS: Diatom · CtenDNAV · CtenRNAV · Virus · Niche partitioning