Study Of Temporal And Spatial Distribution Of Cyanophage PP

Investigation was carried out to study the distribution of cyanophage PP in several freshwater lakes of different trophic status. We also analyzed the relationship between the distribution of cyanophage PP and several environmental factors. We also studied the dynamics of daily titer fluctuation of cyanophage PP by mathematic model. The results are as follow:Cyanophage PP widely distributed in mesotrophic and eutrophic lakes (e.g. Donghu lake of Wuhan), but was not observed in oliotrophic lake(e.g. Liangzi lake of Wuhan).Temporately, cyanophage PP tended to exist in warm seasons: its titer would reach its maximum in September, and was almost zero in winter.Several environmental factors could influence the distribution of cyanophage PP. Although there was no significant correlation between trophic status and the titer of cyanophage PP, there existed a significant positive correlation between the titer of cyanophage PP and Chl a concentration. The result implies that trophic status may influence the distribution of cyanophage PP by influencing the living condition of the host cell, rather than by influencing the density of the host cell. In fact, our data proved that although there existed a threshold concentration of host cell for the maintenance of cyanophage PP's population, there was no significant correlation between the titer of cyanophage PP and its host's cell density. In the year-round investigation, we also found out that the density of host cell was much greater than the titer of cyanophage PP, which was unusual to other reported PHS and needed to be studied further.The result of analysis on the daily fluctuation of cyanophage PP indicated that although the titer greatly changed in a day, it tended to recover its original value at the end of the day. By establishing a mathematic model, we found out that there were at least two key factors that may contribute to the phenomena. One was that the PHS worked differently from day to night. The other is that cyanophage PP was hyper-sensitive to the UV components of sun radiation (the decay rate of cyanophage PP by sun radiation would be as high as 0.62h^-1 ). Above all, it was suggested that sun radiation can be the key factor to influence the fluctuation of cyanophage PP's titer.