A model of photosynthesis and photo-protection based on reaction center damage and repair

Phytoplankton photosynthesis under the rapidly fluctuating irradiance which results from turbulent mixingthrough the vertical light gradient is poorly understood. Ship-based measurements often apply the fast repetitionrate fluorescence (FRRF) technique in situ or in vivo to gauge the physiological state of the phytoplanktoncommunity and infer some of the physical properties of the water column (such as mixing time scales). We describethe development and validation of a model of photosynthetic electron turnover at photosystemII with considerationof downstream limitation, based on the redox state of photosystem II. We also include empirical formulations forslower processes such as photo-protection (from nonphotochemical quenching) and photo-inhibition. Byconfronting the simple model with laboratory data for Dunaliella tertiolecta, we were able to refine the model sothat it faithfully produced rates of photosynthetic electron transfer determined by FRR fluorescence. Further, wewere able to validate the model estimates of linear photosynthetic electron transfer rates against completelyindependent measurements obtained using 14C-bicarbonate assimilation in photosynthesis-light curves