2010 JISAO Research Internship
Learning about the ITCZ by researching the biological processes of sediments
I am currently a student at Texas Southern University in Houston, Texas. My Summer working with JISAO, the UW School of Oceanography, and Julian Sachs' research team was one of great learning experiences and fun. I worked with The Purification of Lipid Biomarkers through RP-HPLC and its Application to Paleoclimate Research. The work I did was a contribution to the development of research concerning rainfall reconstructions from molecular and isotopic changes in tropical pacific lake, bog, and ocean sediments, specifically in the intertropical convergence zone (ITCZ). Biomarkers are indicators of biological processes and states, they are also referred to as biosignatures, and they need to be purified in order to be properly studied. Dinosterol is an exclusive biomarker produced by dinoflagellate algae that has the potential to track changes in the salinity of the water that's used by dinoflagellates living in the water during its biosynthesis.
I used HPLC (High Performance Liquid Chromatography) to purify compounds (lipids) while separating samples into fractions containing portions of the peak of the compound. Studies show that fractionation, which is the variation in equilibrium distribution in isotopes, takes place during Normal Phase HPLC2. In my research I determined how much isotopic fractionation of cholesterol occurs across a RP-HPLC purified peak. What are the implications, or aspects of the process that can impact results associated with using RP-HPLC? The isotopic fractionation across a cholesterol RP-HPLC peak has a range of 580 0/00, therefore small losses can lead to large isotopic biases. RP-HPLC may induce large isotopic biasing even when the entire measurable peak is recombined.
Clipperton Island lies about 1,100 km SW of Mexico at the northern edge of the present ITCZ. Temperature and rainfall there are controlled by the seasonal migration of the ITCZ. By contributing isotope measurements of dinosterol to an existing Clipperton Island sediment record I was able to determine the dD values of RP-HPLC purified dinosterol with depth in a Clipperton Island sediment core, and how reproducible the dD values of RP-HPLC purified dinosterol of the Clipperton Island samples were. Clipperton Island dinosterol dD data show isotopically enriched values prior to 1850AD, and therefore suggest significant hydrological changes and potentially higher salinities during that time period. Also the results show that the data is reproducible.
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