India Ingemi ’24


Molecular Biology

Project Title

Fish Ecology From Ear Stones (Otoliths) and Coral Skeletal Material Past and Present

Presentation Link

View India's Presentation

My goal was to determine the nitrogen isotopic baseline (δN 15 / δN 14 ratio) in the Caribbean and Pacific Ocean across the Miocene, Pliocene, and Modern epochs. I accomplished this by performing nitrogen isotope analysis on otoliths, or ear bones, from myctophids, a family of fish that live in the ocean below the zone where sunlight can reach. Otoliths contain small amounts of protein that serve as great indicators of a fish’s δN 15 / δN 14 ratio. Measuring the nitrogen content of the otoliths involved a 7-day long procedure: I first cleaned the samples using chemical reduction and oxidation to remove nonorganic bound matter, then I oxidized the organic material using persulfate and sodium hydroxide, before pH adjusting and sparging the samples, and finally performed N2O nitrogen isotope ratio spectroscopy. I found it fascinating how so much paleontological history can be garnered by comparing the δN 15 / δN 14 ratio of modern and fossil myctophid otoliths; for example, this method helps to narrow the estimated time frame of the formation of the Isthmus of Panama. Additionally, I gained valuable lab skills, including how to use a mass spectrometer and centrifuge, which are greatly applicable to my future career.

Internship Year


Project Category

Climate and Environmental Science


Sigman Research Laboratory and The Ward Lab, Department of Geosciences, Princeton University - Princeton, New Jersey


Daniel Sigman, Dusenbury Professor of Geological and Geophysical Sciences, Professor of Geosciences; Bess Ward, William J. Sinclair Professor of Geosciences and the High Meadows Environmental Institute; Jessica Lueders-Dumont, Postdoctoral Research Fellow, Geosciences