Responses of elemental content and macromolecule of the coccolithophore Emiliania huxleyi to reduced phosphorus availability and ocean acidification depend on light intensity

• Main Authors: Zhang, Yong, Ma, Shuai, Chen, Hanbing, Li, Jiabing, Li, Zhengke, Xu, Kui, Huang, Ruiping, Zhang, Hong, Han, Yonghe, Sun, Jun
• Format: Text
• Language: English
• Published: 2023
• Subjects: Ocean acidification
• Online Access: https://doi.org/10.5194/egusphere-2022-947; https://egusphere.copernicus.org/preprints/2022/egusphere-2022-947/

Global climate change leads to simultaneous changes in multiple environmental drivers in the marine realm. Although physiological characterization of coccolithophores has been studied under climate change, there is limited knowledge on the biochemical responses of this biogeochemically important phytoplankton group to changing multiple environmental drivers. Here, we investigate the interactive effects of reduced phosphorus availability (4 to 0.4 µ mol L −1 ) , elevated pCO 2 concentrations (426 to 946 µ atm), and increasing light intensity (40 to 300 µ mol photons m −2 s −1 ) on elemental content and macromolecules of the cosmopolitan coccolithophore Emiliania huxleyi . Reduced phosphorus availability reduces particulate organic nitrogen (PON) and protein contents per cell under 40 µ mol photons m −2 s −1 but not under 300 µ mol photons m −2 s −1 . Reduced phosphorus availability and elevated pCO 2 concentrations act synergistically to increase particulate organic carbon (POC) and carbohydrate contents per cell under 300 µ mol photons m −2 s −1 but not under 40 µ mol photons m −2 s −1 . Reduced phosphorus availability, elevated pCO 2 concentrations, and increasing light intensity act synergistically to increase the allocation of POC to carbohydrates. Under elevated pCO 2 concentrations and increasing light intensity, enhanced carbon fixation could increase carbon storage in the phosphorus-limited regions of the oceans where E. huxleyi dominates the phytoplankton assemblages. In each type of light intensity, elemental-carbon-to-phosphorus ( C:P ) and nitrogen-to-phosphorus ( N:P ) ratios decrease with increasing growth rate. These results suggest that coccolithophores could reallocate chemical elements and energy to synthesize macromolecules efficiently, which allows them to regulate their elemental content and growth rate to acclimate to changing environmental conditions.