Cells were incubated for 3 days at in-situ temperature and in the dark. Incubations were analysed for bacterial abundances by flow cytometry after nucleic acid staining with Sybr Green I (Invitrogen). For determination of LAP activities, L-leucyl-4-methylcoumarinyl-7-amide was added to final concentrations of 50 µmo/L. The initial abundance of free-living bacteria was 2.0 x 10**5 cells/ml, representing about 20% of the total bacterioplankton community.