Viral dynamics in two trophically different areas in the Central Adriatic Sea

To understand the activity of marine viruses, experiments on viral production, viral decay and the percentage of lytic and lysogenic bacterial cells among the total number of bacterial cells were carried out seasonally at two stations in the Adriatic Sea with different trophic conditions. Additionally, we are providing an insight on the enrichment with dissolved and particulate organic matter by viral lysis in the studied area. Viral production was higher at the coastal station than at the open-sea station. Viral decay rates were also higher at the coastal sea station than at the open-sea station, and accounted for approximately 40% of viral production at both investigated stations. The percentage of lysogenic infection was lower than that of lytical infection, which indicates the prevalence of the lytic cycle at both stations. Viruses had a significant influence on bacterial mortality through high daily removal of the bacterial standing stock at the coastal and open-sea station. The viruses contributed to the restoration of dissolved organic carbon, nitrogen and phosphorus in the microbial loop by lysing the bacterial cells at the studied stations. All the above suggest that viruses are important in the microbial food web and an important factor in the control of bacterial populations within the study area.