Abstract
To understand the ecological role of cyanophage and its effect on nutrients cycling in the coastal marine environment, it is critical to understand cyanophage infectivity and the interactions that occur between the phage and its host, marine cyanobacterial picoplankton (Synechococcus sp.). We previously isolated a new virulent cyanophage (strain S-KM1), and here have investigated its seasonal infectivity of cyanophage, phycoerythrin-rich Synechococcus sp. (strain KFM001) in Kagoshima Bay. We found that the phage titers ranged from undetectable to 7.5×103/ml in autumn, and began to increase about one week after the onset of the Synechococcus autumn bloom. During the autumn months, the phage numbers oscillated in a fashion that mirrored levels of host abundance, showing a lag of about one week. We calculated that from 0.0055% to 2.1% of the host population per day was lysed by the phage during a Synechococcus bloom in autumn. This suggests that lytic phages have a noticeable effect on regulating the densities of marine Synechococcus populations.
