The abundances of the different compartments of the microbial loop (i.e., viruses, heterotrophic bacteria, heterotrophic nanoflagellates,
and pigmented nanoflagellates), total (TPP) and excreted (EPP) primary production, bacterial production (BP), viral
lytic activity (LA), and bacterivory by nanoflagellates (FG) were measured on June 15 and 16, 1998, in a moderate-altitude oligomesotrophic
lake (Lac Pavin, France), at 5 and 10 m depths. At both depths, losses of the bacterial community by viral lysis
(LA5 m = 1.7 x 106 cells.1-1.h-1, LA10 m = 2.0 x 106 cells.1-1.h-1) were, on average, lower than those due to the grazing activity
of flagellates (FG5 m = 10.3 x 106 cells.1-1.h-1 , FG10 m = 8.4 x 106 cells.1-1.h-1). A carbon budget exercise indicated that, for the
sampling period and depths, 17.8 % of C from TPP (= 38.1 % of EPP) was used by bacteria. On the other hand, 52.7 % of BP
(= 2.15 % of TPP) was grazed by nanoflagellates, while 11.0 % of BP (= 0.45 % of TPP) was lysed by viruses.