Bacterial utilization of different DOC size classes and demand for inorganic nutrients in the Northern Adriatic Sea

Bacterial utilization of different molecular sizes of dissolved organic carbon (DOC) was investigated in the northern Adriatic sea. DOC classes were separated using a cascade ultrafiltration system (10 and 1 kDa molecular weight cutoff). The lowest bacterial growth efficiency and DOC utilization rate were in all experiments observed in the 1-10 kDa fraction. Based on these results the above fraction seems to cycle slower compared to other fractions. Nutrient addition (P+N) to bacterial cultures increased DOC utilization rates suggesting a nutritional limitation of the substrate.