Celia Murphy-Braunstein ’25, Geosciences

Celia Murphy-Braunstein ’25

Major

Geosciences

Project Title

Nitrogen Cycling in the Ocean

Presentation Link

View Celia's Presentation

Minor(s): Chinese Language

I studied the production and consumption of nitrous oxide (N₂O), a potent greenhouse gas that depletes ozone in the atmosphere, using stable isotope tracer experiments. Nitrous oxide is a looming threat due to agricultural and industrial production and is also produced in the ocean as a result of microbial pathways within the nitrogen cycle. I analyzed seawater samples collected and used in nitrogen isotope tracers incubation experiments on previous research cruises to an Oxygen Minimum Zone in the Eastern Tropical South Pacific and the Chesapeake Bay. I performed chemical analyses on the samples to measure various nitrogen compounds including nitrite and urea concentrations. I also investigated nitrogen cycling by measuring nitrate isotopes using the denitrifier method and measured ammonium isotopes through a series of reactions of bromide oxidation and via a reaction with sodium azide. We hope to construct depth distributions of nitrogen cycling rates at the sample sites to better understand environmental controls on the rates of microbial nitrogen cycling processes, for example the effect of oxygen concentrations). This internship taught me new lab techniques, deepened my understanding of marine biogeochemistry and sparked my interest in pursuing further studies in this field.