Abundance of viruses in deep oceanic waters

Vertical distributions of bacteria and viruses were investigated in the oceanic stations located in subarctic (Stn A) and subtropical (Stn B) areas of the Pacific using the direct count technique and transmission electron microscopy. Small DAPI-positive, virus-like particles (VLP) were found to be distributed throughout the water column down to 5000 m at both of the stations. The abundance of VLP ranged from 38 x 10(5) ml(-1) at 50 m depth to 0.6 x 10(5) ml(-1) at 5000 m depth at Stn A. The ratio of VLP to bacteria-like particle (BLP) ranged from 1.1 to 7.4 at Stn A and 1.0 to 8.7 at Stn B in the entire water column. The maximum ratio was recorded at Stn B from the deepest sample, collected at a depth of 5000 m. The electron microscopic investigation indicated that the major proportion of VLP were probably viruses.