Benthic bacterial production in the northern Baltic Sea measured using a modified [14C]leucine incorporation method

Abstract

Benthic bacterial production was measured with a modified [14C]leucine incorporation method in the northern Baltic Sea in 1996 and 1997. Samples were incubated and TCA extractions were done in microcentrifuge tubes. Unincorporated label was removed by repeated centrifugation. Pellets were suspended in scintillation cocktail and counted as a gel using internal standardisation, a method that gave highly comparable counts with combustion of the sample. Bacterial production varied between 0.15 and 0.8 mg Cl-1 h-1 (90 to 350 mg C m-2 d-1). The highest production was found at Stn GF2 in the Gulf of Finland and the lowest in the northern Baltic Proper. Bacterial growth rates were 0.07 to 0.84 d-1. Comparison of these results with published data from sedimentation trap measurements suggests that only a part of the benthic bacterial C demand can be explained by sedimentation.