Intracellular calcification of coccolithophores generates CO2 and consumes additional energy for acquisition of calcium and bicarbonate ions; therefore, it may correlate with photoprotective processes by influencing the energetics. To address this hypothesis, a calcifying Emiliania huxleyi strain (CS-369) was grown semi-continuously at reduced (0.1 mM, LCa) and ambient Ca2+ concentrations (10 mM, HCa) for 150 d (>200 generations). The HCa-grown cells had higher photosynthetic and calcification rates and higher contents of Chl a and carotenoids compared with the naked (bearing no coccoliths) LCa-grown cells. When exposed to stressfull levels of photosynthetically active radiation (PAR), LCa-grown cells displayed lower photochemical yield and less efficient non-photochemical quenching (NPQ). When the LCa- or HCa-grown cells were inversely shifted to their counterpart medium, LCa to HCa transfer increased photosynthetic carbon fixation (P), calcification rate (C), the C/P ratio, NPQ and pigment contents, whereas those shifted from HCa to LCa exhibited the opposite effects. Increased NPQ, carotenoids and quantum yield were clearly linked with increased or sustained calcification in E. huxleyi. The calcification must have played a role in dissipating excessive energy or as an additional drainage of electrons absorbed by the photosynthetic antennae. This phenomenon was further supported by testing two non-calcifying strains, which showed insignificant changes in photosynthetic carbon fixation and NPQ when transferred to LCa conditions

In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Lavigne and Gattuso, 2011) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation by seacarb is 2013-11-29.

Supplement to: Xu, Kai; Gao, Kunshan (2012): Reduced Calcification Decreases Photoprotective Capability in the Coccolithophorid Emiliania huxleyi. Plant and Cell Physiology, 53(7), 1267-1274