Geology Club Seminar

Marine phytoplankton produce organic matter that is depleted in 13C relative to ambient dissolved carbon dioxide. This photosynthetic carbon isotope fractionation (εP) is recorded in marine sediments andused to resolve changes in the global carbon cycle, including variations in atmospheric CO2 levels. These applications rely on a coherent understanding of the environmental and physiological controls on P and knowledge of how this signature is recorded by different cellular constituents. While classical models for interpreting P are based on the balance between diffusion of CO2 and its fixation into biomass by the enzyme RubisCO, the details of phytoplankton carbon dynamics in reality are more complex. Phytoplankton employ a diversity of RubisCO types, and they also use carbon concentrating mechanisms (CCMs) to enhance intracellular CO2 concentrations. In this talk, I will discuss chemostat culture experiments and modeling work to characterize and rationalize the stable carbon isotope ratios of modern eukaryotic phytoplankton and to evaluate prospects for recently-proposed pCO2 proxies derived from algal biomass.