Justin Tam ’27, Chemistry

Justin Tam ’27

Major

Chemistry

Project Title

Foraminifera-bound Nitrogen Isotope Measurements From the Arabian Sea Oxygen-deficient Zone Over the Last Glacial-interglacial Cycle

Presentation Link

View Justin's Presentation

Minor(s): Sustainable Energy
Certificate(s):  Quantitative and Computational Biology

I used nitrogen isotope measurements in planktonic foraminifera — surface-dwelling, unicellular protists — to examine the Arabian Sea oxygen-deficient zone (ODZ) and gain insights into global climate. The Arabian Sea ODZ accounts for one-third of global marine denitrification, where fixed nitrogen is lost to the atmosphere by bacterial conversion into nitrogen gas. These bacteria preferentially consume the lighter nitrogen isotope, causing heavier isotope enrichment in the remaining nitrogen pool, and the resultant isotope ratio is reflected in the organic matter within foraminifera shells. Research suggests that denitrification rates and ODZ extents have remained consistent despite climate changes between glacial and interglacial periods. I performed the preliminary steps of analysis for core samples from two sites in the Arabian Sea by removing smaller sediments via sieving and separating two species of foraminifera from the rest of the material under a microscope. One species bears a symbiont, which alters the isotope ratio in the organic matter relative to the symbiont-barren species. Observing this opened my eyes to the complexities and interconnections between climate science, biology and geochemistry. The experience has motivated me to continue exploring multidisciplinary connections in order to contextualize phenomena such as global climate variability over short and long time scales.