OCE-9618626 ABSTRACT OCE-9618626 The isotopic composition of organic carbon in marine organic matter in the modern ocean and in the sedimentary record has been an object of study for a number of years. Variations in the carbon-13/carbon-12 ratio have variously been interpreted as arising from changes (or differences) in temperature, the amount of dissolved carbon dioxide in seawater, growth rate and productivity of phytoplankton, among other possibilities. The phenomenon is not only a major feature of present-day ocean chemistry but, moreover, may be of use for understanding historical variations in global carbon dioxide through isotopic studies of the sedimentary record. In this study the principal investigator will conduct a series of laboratory experiments and field comparisons to test the strength of a mathematical model for carbon isotope fractionation resulting from uptake by phytoplankton. In collaboration with colleagues at the Alfred Wegener Institut in Bremerhaven, Germany, and the Monterey Bay Aquarium Research Institute, he will study the effects of several processes on carbon isotope fractionation by phytoplankton species. If successful, this work could lead to a new predictive tool for understanding the carbon isotope chemistry of the present-day ocean and perhaps provide a key to understanding paleoclimate through analysis of marine sediment cores.
