EESS Fall Seminar Series, Karen Casciotti, Assistant Professor, Environmental Earth System Science, Stanford University
EESS Fall Seminar Series, Karen Casciotti, Assistant Professor, Environmental Earth System Science, Stanford University, "Stable isotopic tracers of marine nitrogen biogeochemistry", Abstract: The availability of bioavailable nitrogen (N) is one factor that controls primary productivity, nitrous oxide production, and carbon uptake in the oceans. The inventory of bioavailable N is controlled in part by processes occurring in oceanic oxygen deficient zones (ODZs) that convert bioavailable N to gaseous N2. In this study, we use natural abundance stable isotope distributions of nitrate and nitrite to understand how bioavailable N is cycled and lost in oceanic oxygen deficient zones. Our data suggest that a large percentage of nitrite produced within the oxygen deficient zone is reoxidized to nitrate rather than being reduced to N2gas. This result leads to questions about the physiology and metabolism of nitrite-oxidizing bacteria, and how physical, chemical, and biological processes work together to control the amount of bioavailable N available to marine organisms.