Process understanding of photosynthetic fluxes underlying ocean acidification responses in the coccolithophore Emiliania huxleyi

Abstract

Emiliania huxleyi, the most abundant coccolithophore in the modern ocean, has been found to be very sensitive towards ocean acidification (OA): Under increased partial pressures of carbon dioxide (pCO2), the species' photosynthesis is stimulated, whereas its calcification and growth are impaired. Many studies investigated integrated responses to OA, i.e., cellular changes in growth and elemental composition were measured. In order to understand the cellular processes governing these integrated responses, real-time measurements of cellular oxygen (O2), CO2 and HCO3- fluxes need to be applied. In this thesis carbonate-chemistry dependent flux regulations of E. huxleyi were investigated using different real-time measurements (14C tracer methods and membrane-inlet mass spectrometry). Next to the cellular processes causing OA effects, their chemical drivers and modulation by light were assessed. Furthermore, the fluxes of the diploid, calcifying and the haploid, non-calcifying life-cycle stage were compared, which allowed drawing conclusions about the function of calcification.