Physiological responses of a coccolithophore to multiple environmental drivers

Ocean acidification is known to affect primary producers differentially in terms of species and environmental conditions, with controversial results obtained under different experimental setups. In this work we examined the physiological performances of the coccolithophore Gephyrocapsa oceanica that had been acclimated to 1000 paten CO2 for similar to 400 generations, and then exposed to multiple drivers, light intensity, light fluctuating frequency, temperature and UV radiation. Here, we show that increasing light intensity resulted in higher nonphotochemical quenching and the effective absorption cross-section of PSII. The effective photochemical efficiency (Fv'/Fm') decreased with increased levels of light, which was counterbalanced by fluctuating light regimes. The greenhouse condition acts synergistically with decreasing fluctuating light frequency to increase the Fv'/Fm' and photosynthetic carbon fixation rate. Our data suggest that the coccolithophorid would be more stressed with increased exposures to solar UV irradiances, though its photosynthetic carbon fixation could be enhanced under the greenhouse condition.