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

Marin Ordulj,Nada Krstulović,Slaven Jozić,Mladen Šolić,Danijela Šantić

doi:10.1186/s10152-017-0502-2

Marin Ordulj, Nada Krstulović + Show 3 more

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https://doi.org/10.1186/s10152-017-0502-2

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Abstract

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.

Highlights

Viruses are the most abundant and ubiquitous component of marine microbial plankton, and the major cause of bacterial mortality, since bacteria are thought to be their main hosts [1,2,3,4,5]
Bacterial production was higher at the coastal rather than at the open sea station (0.19 ± 0.12 × 104 and 0.12 ± 0.03 × 104 cells mL−1 h− 1, respectively)
Since the investigated sites are located in the central Adriatic area, which is characterized by the different trophic conditions of the coastal and open sea waters [24, Table 2 Sampling depth and month, viral production, viral decay, viral turnover time, burst size (BS), percentage of lysogenic cells, percentage of lytically infected cells and virus-mediated mortality (VMM) at the investigated coastal and open-sea station

Summary

Introduction

Viruses are the most abundant and ubiquitous component of marine microbial plankton, and the major cause of bacterial mortality, since bacteria are thought to be their main hosts [1,2,3,4,5]. Viral abundance exceeds the abundance of their bacterial host by approximately 25 times, but this value may vary, generally from 3 to 100, due to different environmental conditions [3, 6]. In nutrientrich and more productive environments, the difference is expected to be greater in favour of viral abundance [6]. Viruses lyse 10–50% of bacterial standing stock per day on average [5]. This value can be even higher, depending mostly on the host density and productivity, and on environmental conditions, such as temperature, salinity and UV radiation [3, 4, 6, 7].

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