Wolf-Gladrow, D. A.. Alfred Wegener Institute for Polar and Marine Research, dwolf@awi-bremerhaven.de
Burkhardt, S. A.. Alfred Wegener Institute for Polar and, sburkhardt@awi-bremerhaven.de
Riebesell, U. Alfred Wegener Institute for Polar and Marine Research, uriebesell@awi-bremerhaven.de

Stable carbon isotopic composition of microalgae can potentially serve as an indicator for the environmental conditions under which the algae grew. Factors suggested to influence isotope fractionation of microalgae include CO2 concentration, growth rate, cell geometry, the carbon source (CO2 and/or HCO3-), and the operation of a carbon concentrating mechanism (CCM). Models on carbon isotope fractionation presently available have treated the algal cell as a single compartment with uniform internal carbon concentrations. However, it is expected that strong gradients in inorganic carbon concentrations are maintained between the bulk of the cytoplasm and the actual sites of carboxylation (e.g., in the chloroplasts or pyrenoids). The objective of this study is to examine the possible effect of energy-driven gradients in internal carbon concentrations on isotope fractionation in microalgae. We have therefore developed a kinematic model simulating a cell with an inner compartment in which higher carbon concentrations are maintained by a CCM. Model results show that isotope fractionation increases with increasing carbon transport into the inner cell compartment even when carbon influx and efflux of the whole cell remain constant. This implies that understanding carbon isotope fractionation in microalgae ultimately requires knowledge of the intracellular carbon fluxes.
Day: Monday, Feb. 1
Time: 02:45 - 03:00pm
Location: Eldorado Hotel
Code: SS32MO0245E