Dijkman, N. A. AWI, ndijkman@awi-bremerhaven.de
Kroon, B. A. AWI, bkroon@awi-bremerhaven.de

Photosynthesis versus irradiance (P-I) curves and derived empirical parameters are commonly used to characterize the physiological state of algae and to calculate primary production rates. However, during the P-I measurement itself photochemical changes take place in response to the incident light intensity. Our work aims to define these changes at a fundamental level, such that it becomes possible to predict the response of different algae to any type of light exposure. To investigate some of the changes during a P-I curve we exposed the diatom Thalassiosira weisflogii to a series of increasing light intensities . Absorption- and fluorescence spectra, fluorescence measurements and pigment analysis were used to examine light-harvesting capacity, function of photosystem II and electron transfer rates. The light-harvesting capacity did not change, but the transfer of absorbed energy to the reaction center decreased by 50%. The quantum yield of charge separation decreased gradually with increasing light intensities. Electron transfer rates from QA to QB initially decreased, but reversed as light intensity further increased. The conversion of diadinoxanthin into diatoxanthin and its concomitant increase in heat dissipation only partly explains the observed changes.
Day: Tuesday, Feb. 2
Time: Poster
Location: Sweeney Center
Code: SS41TU0657S