Production and decay of viruses in aquatic environments

The quantitative significance of aquatic viruses in coastal and in lake water was investigated. The number of viruses in marine surface waters was found to change on a diurnal basis along with changes in number of bacteria and bacterial activity. By inhibiting the production of viruses, we were able to measure viral decay rates up to 1.1 h-' in marine systems, and up to 0.6 h-' in a freshwater lake, for the majority of the viral population. A minor fraction (4 to 40 %) of the viral population was found to have decay rates lower than 0.05 h-' The fraction of bacteria containing mature virus particles ranged from 2 to 16 % , and the number of viruses released from these bacteria was on average about 50 [range 10 to 300). From these results we eshmate that phages may lyse 2 to 24 % of the bacterial population per hour. Phages may thus be a major cause of bacterial mortality in aquatic ecosystems and may have a significant impact on the carbon and nutrient flow in aquatic food webs.