Occurrence of the planktonic bloom-forming marine diatom Chaetoceros tenuissimus Meunier and its infectious viruses in western Japan

The genus Chaetoceros is among the most species-rich marine planktonic diatoms. Most Chaetoceros are considered important primary producers in various marine environments, but because of their small size, we know little about their ecology and distribution. Therefore, from 2008 to 2012, we examined the occurrence of C. tenuissimus Meunier, one of the smallest members in the genus, and its infectious viruses in western Japanese coastal waters. Using real-time quantitative PCR, we found that C. tenuissimus was widely detected throughout our study sites, with a maximum concentration of 2.4 x 10(7) cells/l in May 2012. Sediment analysis revealed that C. tenuissimus resting-stage cells were present at potentially high levels, despite its infectious viruses being detected in the same region. The present study suggests that C. tenuissimus remains highly productive even when surrounded by its infectious viruses. This tolerance to viral infection, along with the diatom's fast growth rate, suggests that C. tenuissimus might play an important role in maintaining the growth of important filter feeders.