Based on the CSRD obtained by AMS the contribution of fossil OC (F14C=0; [%]) used for bacterial membrane lipid synthesis (IPL-FA) was calculated using an isotope mass balance. For the estimation two endmembers were used:1) Fossil carbon (F14C=0) – OC derived from the local bedrock2) Recently synthesized carbon (F14C~1) – OC derived from primary production in the water column. Detailed F14C-values were taken from surface DIC age model, depending on the year of sediment deposition (based on Pb+Cs age model).