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Results | Food Web and its Function | Interesting Isotopic Studies

Food web isotope study using fingernails

During the 2000, 2003, and 2006 Open House exhibitions at the USGS office in Menlo Park (California, USA), team members of the Isotope Tracers Project analyzed fingernails of visitors for carbon and nitrogen stable isotope ratios in "real time", using two mass spectrometers. 

The purpose of this exhibit was to demonstrate the usefulness of isotope techniques for determining differences in diets between individuals. It was also a lot of fun for both team members and visitors. This technique is often used for isotopic studies of food webs -- which is a method for determining who is eating what.  This kind of information can be very useful for understanding how toxic materials, including mercury, become bioaccumulated in animals high on the food chain.

In 2000, we had 150 visitors over the weekend who contributed fingernail samples.  In 2003, we had 3 times more visitors than expected -- 456.  In 2006, we had even more visitors – 501. Since the number of visitors exceeded the number of samples we could analyze during the weekend, the samples took a few additional days to analyze, and the results were eventually posted here for the visitors to see.

This web page provides links to the results, including plots of fingernail data, explanations of how to interpret the results, and examples of other applications of isotopes for food web studies.

The posters and handouts prepared for the 2003 Open House are available below.  Many of the posters prepared for the 2006 Open House are the same as for 2003. The new ones will be posted by mid June. 

Introductory poster  (High Res PDF, 3.8m)
Poster with the  isotope data for fingernails of visitors  (High Res PDF, 86K)
Simple explanation of stable isotopes  (High Res PDF, 315K)
More detailed explanation of food webs and samples (High Res PDF, 3.2m)
Examples of other stable isotopes diet studies  (High Res PDF, 1.1m)
Handout from Open house 2003 (front side, High Res PDF, 157K and back side, High Res PDF, 181K

Fingernail results

Interpreting your data

Comparing 2006 with 2003

Where you fall on the food chain


Results | Food Web and its Function | Interesting Isotopic Studies

Please contact Carol Kendall ( for questions and comments regarding this page. 
This web page constructed by Carol Kendall -- with a
LOT of help from colleagues Steve Silva, May Lam, Bryan Bemis, Dan Doctor, and Scott Wankel.

This page was last changed in June 2006. 
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