Viruses are abundant and dynamic members of marine environments. The persistence of viral communities in aquatic systems requires the daily destruction of a significant proportion of the bacterial and phytoplankton populations. While the destruction of host cells by viruses has several implications for aquatic systems, one of the most important effects is on nutrient cycling.
Over the last several years we have obtained estimates of viral turnover rates and viral production for a variety of environments. We have used these estimates to infer the remobilization of nutrients in marine systems attributed to viral lysis. For example, viral lysis of bacterioplankton in the western Gulf of Mexico was estimated to liberate 0.12 to 0.55 µg C / L / d in offshore waters and 0.72 to 5.2 µg C / L / d in coastal waters. Similarly, viral mediated carbon release in the Straight of Georgia, British Columbia, ranged from 1.4 to 7.0 µg C / L / d, with the highest estimates associated with strong tidal mixing. Viruses also play an important role in the remobilization of organic nutrients and trace elements. For example, in the Strait of Georgia viral lysis was estimated to result in the remobilization of 0.3 to 1.7 ug / L / d of organic nitrogen, 0.03 to 0.14 ug / L / d of organic phosphorus and 0.06 to 0.33 ng / L / d of organically complexed iron.
We have incorporated estimates of viral mediated carbon turnover into a model of carbon cycling in aquatic systems. Results from the model suggest that 12 % to 25 % of photosythetically fixed organic carbon is ultimately recycled through the viral loop: i.e., released into the environment by host-cell lysis. Results from a variety of environments imply that viruses are important drivers of carbon and nutrient recycling in marine systems.