In the biogeochefmical cycles of the ocean, a multitude of processes are catalyzed by Bacteria and Archaea, and the fufnctioning of these cycles in the Barents sea do not differ qualitatively from those at lower latitudes. The carbon cycle may well serve as an example of the biogeochemical cycles (Figure 2.4.1). The heterotrophic procaryotes, denoted bacteria for simplicity, are the major degraders of dissolved organic carbon (DOC), which is their principle source of energy and carbon. At high latitudes, DOC accumulates in the photic zone during the productive season, and the concentration decreases in September/October due to the combination of bacterial degradation and physical mixing processes (Børsheim and Myklestad 1997; Børsheim 2000).
