VIRAL AND BACTERIAL DYNAMICS IN ARCTIC SEA-ICE DURING THE SPRING ALGAL BLOOM NEAR RESOLUTE, NWT, CANADA

High virus counts were found in Arctic sea ice samples taken during th e spring ice algal bloom near Resolute, Northwest Territories, Canada. Viral abundances in the sea ice ranged from 3.7 x 10(11) viruses m(-2 ) (or 9.0 x 10(6) ml(-1)) to 4.9 x 10(12) m(-2) (1.3 x 10(8) ml(-1)) w hich is 10- to 100-fold greater than the concentration of viruses in t he underlying water column (1.1 x 10(6) ml(-1)). This increase in vira l abundance corresponds with the 10- to 100-fold increase in bacterial abundance in sea ice as compared with the water column. Bacterial abu ndances ranged from 6.1 x 10(9) bacteria m(-2) (1.5 x 10(5) ml(-1)) to 4.2 x 10(11) m(-2) (1.0 x 10(7) ml(-1)) from early to late spring res pectively. The virus-to-bacteria ratios (VBR) were among the highest r eported in natural samples. The greatest viral abundances occurred in the 0.5 to 1.5 cm layer of the ice profile, where the bacteria were mo st active. The VBR generally decreased during the spring although viru ses were increasing in abundance. The disequilibrium between phage and bacterial growth and abundance maxima during the spring bloom is sugg ested to be due to (1) a change in the makeup of the bacterial communi ty, such that phage-resistant bacteria proliferated later in the sprin g, or (2) an increase in viral lytic activity with higher bacterial ce ll-specific growth rates; both viral lytic activity and bacterial grow th rates declined later in the spring as the bacterial population reac hed its peak.