Study Of The Decay Of Cyanophage PP In Field Samples

The decay of virioplankton is the important process of virioplankton population dynamics. Besides the solar-UV, other factors can also lead to the decay of virioplankton. In this thesis, experiment was carried out to study the decay rate of cyanophage PP caused by some environmental factors, including non-UV radiation in sunlight, particle materials, heat-labile substances, water temperature. The results indicated that the decay rate of cyanophage PP by the non-UV radiation part of sunlight at noon was 3.8 %·h^-1, the decay rate of cyanophage PP was swiftly attenuated to less than 1.0 %·h^-1 with the attenuation of light intensity; the decay rate of cyanophage PP in field sample was steadily 2.5 %·h^-1 in dark condition, among which more than 2.0 %·h^-1 contributed to particle materials, and 2.17 %·h^-1 contributed to heat-labile substances. The result demonstrated that both particles and heat-labile substances are responsible for the dark decay of cyanophage PP. The dark decay rate in field sample varied at different temperatures, the dark decay rate was 8.75 %·h^-1 at 35℃, which was 2.5 times greater than the decay rate at 28℃. The result demonstrated that the dark decay of cyanophage PP was strictly adjusted by water temperature in field samples.Since cyanophage PP was proved to be extremely sensitive to solar-UV (the decay rate caused by solar-UV was 60⁸0 %·h^-1), it can conclude that: in daytime, solar-UV is the dominant factor for the decay of cyanophage PP in surface water, while non-UV radiation in the sunlight, cooperated by dark decay factors, might work in deeper water column; at night, dark decay leaded to the slow decline of titer of cyanophage PP, however, high water temperature might greatly increase the speed of dark decay. The results may help to explain the dynamics of the titer of cyanophage PP in natural conditions, which fluctuated rapidly in the daytime and slightly declined at night.