2004, Max Planck Institute for Marine Microbiology
Jørgensen, Bo Barker
The sea floor is a site of high biological activity where the organic material produced in the water column by planktonic algae is deposited and degraded. Oxygen is present only in the upper few millimeters or centimeters of the sea floor. In the zone below which is free of oxygen (anaerobic zone) other oxidants like nitrate, sulfate and insoluble oxides of iron or manganese function as electon acceptors for alternative respiratory processes of diverse anaerobic microorganisms. If their metabolic products like ammonia, hydrogen sulfide or more soluble metal ions diffuse into the oxic zone, they serve as an energy source for chemolithotrophic microorganisms. All these reactions in the sea floor thus form a cascade of redox processes which is initiated by deposited organic material and which is essentialy linked to the global turnover of oxygen, nitrogen, iron, manganese, sulfur and other elements. The diversity and physiological potential of many microorganisms that catalyze these redox reactions are still unknown. The major task of the Department of Biogeochemistry is to elucidate the processes, the involved microorganisms, the control of their activity and their and interactions with the abiotic habitat.