New data are presented on the dynamics of total bacterioplankton numbers (BN) and dark CO 2-fixation (DCF) in 1989-1993. During this period, both BN and DCF have been much higher than in the preceding years. Summer averages of DCF and BN for the period 1985-1988 were 0.49 μg C l-1 d-1 and 0.54 × 10 6 cells ml-1 , and for 1989-1993 they were 2.4 μg C l-1 d-1 and 1.02 × 10 6 cells ml-1 , respectively. The summer 1992 averages of BN, 2.26 × 10 6 cells ml-1 in epilimnion and 1.16 × 10 6 cells ml-1

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... n hypolimnion are the highest values recorded since the beginning of bacterioplankton investigations in Lake Ladoga in 1977. The increase of DCF and BN has been accompanied with a considerable decrease (from 9 down to 6.3-8.3 mg l-1) of total organic carbon levels in Lake Ladoga.