Rebecca Cho ’26, Geosciences

Rebecca Cho ’26

Major

Geosciences

Project Title

Developing Analytical Method for Biomineral-bound Organic Matter Isotopic Composition With nanoEA

Presentation Link

View Rebecca's Presentation

Minor(s): Environmental Studies

Metabolic rate is critical to the survival, reproduction and environmental interactions of marine organisms. Recent literature has proposed the application of the carbon isotopic composition (δ13C) of fish ear stone (“otolith”) calcium carbonate to infer its metabolic rate. The preservation of fish otoliths additionally enables the study of the diets and life history of both extant and extinct fishes. However, inorganic carbonate, although a major form of carbon in otoliths, is affected by both environmental seawater and metabolism — the latter of which generates great uncertainty in existing δ13C measurements. My project aims to use δ13C of organic matter in the fish otoliths that is derived from diet alone to reconstruct the fish’s metabolism. I focused on developing the methods for organic matter δ13C analysis with a novel instrument, “nanoEA”, laying the foundation for future applications with fish otoliths. I prepared organic and biomineral standards for experiments alongside the instrumental modifications, learned to use nanoEA for analysis and ran several tests to develop protocols for biomineral analysis. This experience gave me the opportunity to explore my interests across anatomy, physiology and marine biogeochemistry while cultivating research skills for my junior independent work.