Zooplankton represent a vital link between phytoplankton and fish, like the endangered Delta Smelt. Human interferences (nitrates from waste water, flow alteration, invasive species introduction…) have altered the structure of the San Francisco Estuary (SFE) ecosystem. We use stable isotope analysis to improve our knowledge of the planktonic food web in the SFE and gain insights into its evolution over the past decades. We use the ratios of certain isotopes (Nitrogen, Carbon, Sulfur, etc.) in different species of zooplankton to tell us what it is feeding on as well as the trophic level it feeds in. My research focused on a number of different goals.

1) We’ve been examining the effect of Formalin vs. Frozen preservation. Since Formalin preservation is preferred by most researchers we want to see if it will affect isotope analysis. Results showed there were only small differences in the carbon isotopic composition of frozen and formalin preserved samples. A correction factor can be used.

2) After applying a correction factor to our samples, which span from 1976-2012, our results show spikes in Nitrogen concentrations in a number of species over time. The spikes may be due to influxes in Nitrogen rich waste water in those areas.


Biochemistry | Biology | Environmental Chemistry | Food Chemistry | Organic Chemistry | Other Ecology and Evolutionary Biology | Other Plant Sciences


Dr. Julien Moderan

Lab site

Romberg Tiburon Center for Environmental Studies (RTC)

Funding Acknowledgement

This material is based upon work supported by the S.D. Bechtel, Jr. Foundation and by the National Science Foundation under Grant No. 0952013. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the S.D. Bechtel, Jr. Foundation or the National Science Foundation. This project has also been made possible with support of the National Marine Sanctuary Foundation. The STAR program is administered by the Cal Poly Center for Excellence in Science and Mathematics Education (CESaME) on behalf of the California State University (CSU).



URL: https://digitalcommons.calpoly.edu/star/186


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