Import and decomposition of dissolved organic carbon in pre dams of drinking water reservoirs Dissolved organic carbon (DOC) depicts a key component in the aquatic carbon cycle as well as for drinking water production from surface waters. DOC concentrations increased in water bodies of the northern hemisphere in the last decades posing ecological consequences and water quality problems. Within the pelagic zone of lakes and reservoirs the DOC pool is greatly affected by biological activity as DOC is simultaneously produced and decomposed. This thesis aimed for a conceptual understanding of organic carbon cycling and DOC quality changes under differing hydrological and trophic conditions. Further the occurrence of aquatic priming was investigated which has been proposed as a potential process facilitating the microbial decomposition of stable allochthonous DOC within the pelagic zone. To study organic carbon cycling under different hydrological conditions quantitative and qualitative investigations were carried out in three pre dams of drinking water reservoirs exhibiting a gradient in DOC concentrations and trophic…