Nitrogen Isotope and N2/Ar Biogeochemistry of the Peru Suboxic Zone

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The suboxic intermediate waters of the world's oceans, though constituting only a small fraction of total oceanic volume (0.1%), play a vital role in the ocean's nitrogen cycle and its biogeochemical and isotopic signatures. Suboxic conditions are required to activate the microbial processes that convert nitrogen to N2 gas. Because of this, suboxic waters act as a predominant sink, removing nitrogen from the biosphere. An ocean chemist from the University of Massachusetts at Dartmouth is working in collaboration with scientists from GEOMAR/Kiel University to complete an extensive field study of the Eastern Tropical South Pacific Ocean off the coast of Peru, one of the three major open ocean suboxic zones. Water samples, collected from a series of transects off the Peruvian margin, would undergo isotopic and gas ratio analyses to assess the following: (1) insights on the net impact of the Peru suboxic zone on oceanic nitrogen and nitrogen isotope budgets and (2) the relationship between the intensity of the nitrogen sink and the nitrogen isotope signal preserved in margin sediments. Results from this research would provide the science community with a greater understanding of the relationship between the oceanic nitrogen cycle and suboxic waters. As regards broader impacts, this research would refine the interpretation of paleo-records with respect to past interactions between the oceanic nitrogen cycle and climate variability and contribute to numerical modeling studies of the global oceanic cycle. This study represents a collaborative effort between U.S., German, and Peruvian scientists. One graduate student would be supported and trained as part of this project.