A Abundance and production of viruses and their relationship with bacteria in the Middle Adriatic

Viral and bacterial communities were studied at two different areas (coastal and open sea) in the Middle Adriatic during the summer period 2008. Viral number was obtained by epifluorescent microscopy and viral production rates were determined from first-order regressions of viral abundance versus time for triplicate incubations. Viral turnover rates were estimated by dividing viral production rates by viral abundance. Abundance of bacteria was obtained by flow cytometer. Relationship between viruses and bacteria was calculated from virus to bacteria ratio (VBR). Viral abundance (2, 77 - 6, 31 x 106 VLP ml-1) and production (2, 28 - 6, 26 x 106 VLP ml-1 h-1) in the coastal sea area were lower than in the open sea area where viral abundance ranged from 2, 75 to 8, 39 x 106 VLP ml-1 and viral production from 4, 14 to 7, 27 x 106 VLP ml-1 h-1. Viral turnover rates at coastal sea ranged from 1, 41 to 2, 00 h and from 0, 39 to 0, 70 h at open sea. VBR in the coastal sea area ranged from 5, 49 to 7, 54 and in the open sea area from 7, 44 to 36, 46. Domination of the viruses over bacteria was evident in both observed areas, but it was greater in oligotrophic open sea suggesting that the viruses were more important factor in controlling bacterial abundance in the open than in the coastal sea area.