THE DISTRIBUTION DYNAMICS OF CYANOBACTERIA AND CYANOPHAGES IN THE NORTH PACIFIC OCEAN

Cyanobacteria of the genera Synechococcus and Prochlorococcus are abundant primary producers in the oceans and contribute significantly to global primary production. They are infected by various cyanophage families, which are considered one of the major factors influencing their mortality. The major goal of this study is to gain insight into the impact of different cyanophage groups on the cyanobacterial community in the North Pacific Ocean. Quantification of several phage groups was performed using the single molecule polony method, previously developed in our laboratory. We assessed the abundances of the cyanobacteria Prochlorococcus and Synechococcus, total virus-like particles (VLPs), as well as three different cyanophage groups on a cruise along a transect from Oregon to Hawai’i. No correlation was found between the abundances of VLPs and cyanophages, with VLPs being most abundant in the productive coastal waters off Oregon, while cyanophages were more abundant in the oligotrophic waters of the North Pacific Ocean. The abundances of the three cyanophage groups: T7-like clade B, T7-like clade A and TIM5-like cyanophages, correlated with each other. Furthermore, cyanophage abundances correlated significantly with abundances of the cyanobacteria Prochlorococcus but not Synechococcus. The T7-like clade B cyanophages were at least an order of magnitude more abundant than clade A and TIM5-like cyanophages across the transect, suggesting drastic differences in their impact on their cyanobacterial hosts. The abundance of T4-like cyanophages have yet to be determined. Our methodology enabled us to determine, for the first time, the differential distributions and abundances of specific phage families that infect a particular host taxon in the North Pacific Ocean.