Oceanic biological nitrogen fixation: Sensitivity to changes in dissolved oxygen
Nitrogen (N2) fixation is a key control on the oceanic nitrogen inventory. In many oceanic regions, growth of phytoplankton is N limited because oceanic N2 cannot make up for the removal of fixed inorganic nitrogen (NH4+, NO2-, and NO3-) by anaerobic microbial processes. Oxygen minimum zone (OMZ) waters play a crucial role in regulating the availability of nutrients, nitrogen (N) in particular. Within this project we investigate in close collaboration with Dr. Marcel Kuypers’ group at the MPI Bremen the effects of oxygen concentration on nutrient regeneration, N-loss as N2-production, and N2-fixation in OMZ Waters. Rate measurements for various N-cycling processes are performed via incubation experiments with stable isotope-labeled substrates, and the microorganisms involved will be identified using molecular biological techniques.