COLLABORATIVE RESEARCH: Laboratory Validation of Alkenone-Specific Hydrogen Isotopic Composition as a Robust, Quantitative Proxy for Paleosalinity Determination
F.G. Prahl (Oregon State University) and B.N. Popp (University of Hawaii)
Knowledge of past ocean salinity and temperature is essential for assessment of basic oceanographic processes such as surface water circulation and deep water formation. Such processes are integral to the redistribution of heat on the Earths surface and consequently to the dynamics of global climate change. In this project, the PIs propose to conduct calibration experiments on a novel paleosalinity indicator, the compound specific hydrogen isotopic (D/H) composition of unique biomarker molecules that are biosynthesized by the phytoplankton species Emiliania huxleyi and Isochrysis galbana. The central hypothesis is that the D/H of such biomarkers is controlled fundamentally by the isotopic composition of the water in which the source organism grows. Here, the D/H of compounds biosynthesized in batch culture experiments under varying laboratory-controlled experimental conditions will be analyzed in order to evaluate the extent that D/H values can vary as a function of physiological growth factors such as nutrient and light availability and actual salinity change as well as between species. The laboratory results from this proxy will then be used to examine the Holocene evolution of the Black Sea to determine whether a salinity threshold impacted phytoplankton ecology of surface waters and caused the well-documented mid-Holocene shift in the depositional characteristics of Black Sea sediments. Results of these experiments will be integrated directly into classroom teaching, allowing transfer of cutting edge, topical information to undergraduate science and non-science majors and to graduate students specializing in oceanography and geology. An undergraduate student from the Honors College at Oregon State University will benefit educationally from this project. The University of Hawaii is a designated EPSCoR institution and a federally recognized minority-serving institution, thus students from underrepresented groups are likely to be benefit from education activities stemming from the results of this research.
