Spatial distribution of viruses , bacteria and chlorophyll a in neritic , oceanic and estuarine environments

The spatial distribution of viruses was investigated in the coastal and oceanic waters of the Southern California Bight, USA, and the brackish waters of the Gulf of Bothnia, Sweden, using the direct harvesting technique and transmission electron microscopy. The vertical and horizontal distributions of viruses were examined in relation to bacterial abundance and chlorophyll a. Total virus abundances ranged from 0.3 to 52 X log 1-l; higher concentrations of viruses were found in the upper 50 m of the water column and in coastal environments. Viruses with capsid diameters less than 60 nm dominated the virus community, were morphologically characterized as bacteriophages and were responsible for most of the observed spatial variability. Bacteria abundance alone explained 67 % of the spatial variability in virus numbers, thereby suggesting that bacteria constituted the major host organisms for viruses in these physically dlverse habitats.