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

ABSTRACT

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.

KEYWORDS:

• C:N ratio
• Calcification
• Chrysotila dentata
• Geometric model
• Holococcolith
• Photosynthesis
• Pigment

Acknowledgements

We thank Drs. Wenzhe Xu and Liying Peng for their helpful comments on the manuscript. We also appreciate the help of Minjuan Jia with the carbon and pigment measurements.

Additional information

Funding

This research was supported by the National Nature Science Foundation of China grants (41876134, 41676112 and 41276124), the University Innovation Team Training Program for Tianjin (TD12-5003), the Tianjin 131 Innovation Team Program (20180314), National Natural Science Foundation of Tianjin (17JCZDJC40000); and the Changjiang Scholar Program of Chinese Ministry of Education to Jun Sun.