BACTERIAL POPULATION-DYNAMICS IN A MEROMICTIC LAKE

Polyclonal antibodies against nine different bacteria isolated from La ke Saelenvannet in western Norway were produced, and the population dy namics of these strains in the lake were monitored through two spring seasons by immunofluorescence staining. The total counts of bacteria v aried over time and space from 1.5 x 10(6) to 1.5 x 10(7) cells ml(-1) . The counts of specific bacteria were in the range of 10(3) to 10(4) cells ml(-1) or less; in sum, they generally made up less than 1% of t he bacterial community. Some populations showed significant changes in abundance, with blooms lasting 1 to 3 weeks, The rate of change (incr ease and decrease) in abundance during blooms was estimated to be 0.2 to 0.6 day(-1). The average virus-to-bacteria ratio was 50, and there was a significant correlation between the abundances of virus and bact eria. Both protozoan grazing and lytic virus infection were assessed a s possible mechanisms driving the variations in bacterial population d ensity.