Effects of ocean acidification on the physiological performance and carbon production of the Antarctic sea ice diatom Nitzschia sp. ICE-H

Abstract

Ocean acidification (OA) resulting from increasing atmospheric CO₂ strongly influences marine ecosystems, particularly in the polar ocean due to greater CO₂ solubility. Here, we grew the Antarctic sea ice diatom Nitzschia sp. ICE-H in a semicontinuous culture under low (~400ppm) and high (1000ppm) CO₂ levels. Elevated CO₂ resulted in a stimulated physiological response including increased growth rates, chlorophyll a contents, and nitrogen and phosphorus uptake rates. Furthermore, high CO₂ enhanced cellular particulate organic carbon production rates, indicating a greater shift from inorganic to organic carbon. However, the cultures grown in high CO₂ conditions exhibited a decrease in both extracellular and intracellular carbonic anhydrase activity, suggesting that the carbon concentrating mechanisms of Nitzschia sp. ICE-H may be suppressed by elevated CO₂. Our results revealed that OA would be beneficial to the survival of this sea ice diatom strain, with broad implications for global carbon cycles in the future ocean.

Keywords: Antarctic sea ice microalgae; Carbonic anhydrase; Nitzschia; Ocean acidification; Particulate organic carbon; Photosynthesis.