The transport of aquatic viruses to particles can be described in terms of diffusive transport from solution. Such transport is influenced by motion of the water relative to the particle. Because transport rate is determined purely by physical factors it is independent of whether the particle is a host or non-host organism. The low viral diffusivity relative to that for dissolved nutrients makes transport enhancement from organism swimming more important for viruses. The virus contact rate with bacteria is relatively unaffected by such motions because of small bacterial sizes. Transport rates for phytoplankton and protozoa can increase over an order of magnitude when swimming motions are considered. Although larger organisms have much higher transport rates per individual, their far lower concentrations In sea water should make small organisms the preferred targets for viruses. Rates of host-virus interactions in culture are closely related to predictions from transport theory. There is a fairly close relationship between bacterial populations and virus disappearance rates in the marine environment, suggesting that non-host organisms are a major cause of viral mortality at the higher ionic strengths typical of sea water. Other factors, such as UV radiation, must also be included when estimating viral mortality in seacvater.

Viruses are an important component in the functioning of marine ecosystems. They are especially vulnerable at the stage when they are free particles seeking a new host. A major factor in viral mortality during this phase IS the presence of ultraviolet (UV) radiation. UV radiation penetrates only a short distance into the water column because of a very high attenuation coefficient. Processes that move viruses to the surface change their UV exposure. We have modelled the mortality of viruses subject to UV radiation by means of a Lagrangian Monte-Carlo type model that incorporates viral movements within the mixed layer. For viruses with a given UV-induced surface mortality, mixed-layer depth and UV attenuation coefficient are important factors in their water column mortality. Other more subtle factors can also affect viral mortality: nature of the diurnal thermocline; type of mixing; and the time of day that they are released into the water. Viruses not subject to mlxing have their mortahty rate enhanced by internal wave motion, although the absolute mortality rates may remain low. Increased UV irradiance associated with atmospheric ozone depletion could significantly change viral mortality in polar environments. UV-induced mortality can be comparable to that from biological factors such as virucidal bacteria.

No abstract

Viruses are an important component in the functioning of marine ecosystems. They are especially vulnerable at the stage when they are free particles seeking a new host. A major factor in viral mortality during this phase IS the presence of ultraviolet (UV) radiation. UV radiation penetrates only a short distance into the water column because of a very high attenuation coefficient. Processes that move viruses to the surface change their UV exposure. We have modelled the mortality of viruses subject to UV radiation by means of a Lagrangian Monte-Carlo type model that incorporates viral movements within the mixed layer. For viruses with a given UV-induced surface mortality, mixed-layer depth and UV attenuation coefficient are important factors in their water column mortality. Other more subtle factors can also affect viral mortality: nature of the diurnal thermocline; type of mixing; and the time of day that they are released into the water. Viruses not subject to mlxing have their mortahty rate enhanced by internal wave motion, although the absolute mortality rates may remain low. Increased UV irradiance associated with atmospheric ozone depletion could significantly change viral mortality in polar environments. UV-induced mortality can be comparable to that from biological factors such as virucidal bacteria.

No abstract