Internships

Sophia Villacorta ’24

Major

Geosciences

Project Title

A Revised Pleistocene View of the Effect of Climate on North Pacific Oxygenation From Foraminifera-bound Nitrogen Isotopes

I utilized the foraminifera-bound nitrogen isotope as a climate proxy to reconstruct past changes in water-column denitrification strength in the Eastern Tropical North Pacific (ETNP). I focused on the region’s oxygen deficient zone, which is formed through a combination of slow ventilation and high biological productivity. Reconstructing this zone’s history is important for understanding climate controls on various ocean processes, including oxygen content, circulation and nutrient cycling. Under low oxygen conditions, organisms rely on nitrate for respiration, which increases the ratio of nitrogen-15 to nitrogen-14 (¹⁵N/¹⁴N) in the remaining nitrate. This nitrate is eventually consumed by organisms such as foraminifera in the surface ocean. When the resulting organic matter is buried on the seafloor, it preserves the signal of water column denitrification strength through time. I processed samples by sieving sediment material under a microscope to isolate specimens of two species of foraminifera, Neogloboquadrina dutertrei and Globorotalia menardii. I also assisted in chemically cleaning the specimens to prepare them for nitrogen isotope measurements using a mass spectrometer. I now have a solid grasp of this ocean system and how nitrogen isotopes can be used as a proxy for paleoclimate, which I hope to examine further in my senior independent research.