Manganese Cycling in the Subtoxic Zone in the Black Sea

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OCE-0221500Elemental profiles in the suboxic zone of the Black Sea suggest that the upward flux of sulfide may be oxidized by manganese oxides rather than oxygen and that ammonia reacts with nitrate to produce N2. In addition, the profiles suggest that Mn(II) oxidation occurs anaerobically, possibly coupled to denitrification. However, the occurrence of the proposed reactions remains controversial. A scientist from Scripps Institute of Oceanography, in collaboration with scientists from the University of Washington, the University of Delaware, Monterey Bay Aquarium Research Institute, Russia and Ukraine, plans to carry out field work in the suboxic zone of the Black Sea, as well as laboratory culture experiments to test the hypothesis that Mn species act as a catalyst for oxidation of sulfide and ammonia and reduction of nitrate and nitrite. The PI also will assess the microbial and abiogenic reaction rates of the oxidation of Mn (II) and reduction of Mn (III, IV) and assess how oxygen affects these processes. In the laboratory, the distribution of bacteria and the genes involved in Mn(II) oxidation throughout the vertical and horizontal transects of the Black Sea also will be determined. Lastly, the PI will ascertain the importance of lateral inputs versus in-situ processes in controlling the suboxic zone of the Black Sea.