Morphology, phylogenetic position, and ecophysiological features of the coccolithophore Chrysotila dentata (Prymnesiophyceae) isolated from the Bohai Sea, China

Coccolithophores are cosmopolitan, major calcifying protists that have significant roles in marine carbon cycling. Although the influence of temperature and irradiance fluctuation on coccolithophore physiology have been extensively studied, little is known about these effects on coastal coccolithophore species, including their cell morphology, coccolith formation, life cycle, and photoacclimation. We carried out indoor experiments to investigate the photo-physiological response of Chrysotila dentata at two temperatures (13 °C and 25 °C) and varied light irradiance. Using a geometric model, coccolith volume and mass of C. dentata were estimated. At low temperature (13 °C) and low irradiance (100 μmol photons m−2 s−1) cell size and coccolith calcite mass increased, which was further verified using a geometric model. The ratio of calcification to total carbon fixation rate and certain pigments (chlorophyll a, fucoxanthin and β-carotene concentrations) increased at high temperature (25 °C). Cells had variable C and N quotas (apparent diel cycling of C:N ratio) when cells were forming new coccoliths. Our findings help to better understand environmental controls on coccolith carbonate production and interaction with organic carbon production in C. dentata.