Despite recent advances in our knowledge about the nitrogen cycle in oxygen minimum zones (OMZs), one important gap still remains. The oxidation of nitrite to nitrate has rarely been investigated in general, and has only once been measured directly so far. This process, however, is the only reaction producing nitrate, thereby responsible for the formation of deep-sea nitrate reservoir. Furthermore, as the second step of nitrification, nitrite oxidation plays an important role in linking remineralisation processes to nitrogen loss processes like denitrification and anammox.

My PhD project aims to determine rates of various nitrite consuming and producing processes in oxygen minimum zones (OMZ) focusing on nitrite oxidation. Nitrite oxidation in OMZs has rarely been investigated to date and its interaction with anammox, DNRA, ammonia oxidation, denitrification and nitrate reduction still remains to be resolved. Furthermore I am investigating the molecular ecology of marine nitrite oxidizers in oxygen minimum zones, including their abundance as well as their diversity.