Environmental Internship Program - 2019 Booklet

BIODIVERSITY AND
CONSERVATION
Elizabeth Wallace ’20
GEOSCIENCES
Certificate: Visual Arts
PROJECT TITLE
Fish Ecology from
Otoliths (Ear Stones)
Past and Present
ORGANIZATION(S)
Sigman and Ward Labs,
Department of
Geosciences,
Princeton University
LOCATION(S)
Princeton, New Jersey
MENTOR(S)
Daniel Sigman, Dusenbury
Professor of Geological
and Geophysical
Sciences, Professor of
Geosciences; Bess Ward,
William J. Sinclair
Professor of Geosciences
and the Princeton
Environmental Institute;
Jessica Lueders-Dumont,
Postdoctoral Research
Fellow, Geosciences
I studied changes in the trophic level of four
species of commercially important fish in the
Gulf of Maine. Changes in trophic level indicate
alterations in the health and structure of the
ecosystem due to overfishing or changes in global
climate. Nitrogen isotopes in the fish’s body
provide a quantitative measurement as the ratio
of heavy-to-light isotopes increases with trophic
level. I measured the ratio of nitrogen isotopes
in the fish’s otoliths, or ear stones, which grow
throughout the fish’s life and can be preserved
over long periods of time. I compared the trends
in nitrogen isotopes of otolith samples from
the past 40 years with the stomach contents of
fish from a field-survey database. During this
internship, I learned new laboratory and dataanalysis
skills, and I gained an understanding
of how a scientific question can be explored
through experiments and data analysis. This
internship taught me skills that I will use for my
senior thesis and gave me insight into a career in
research.
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