- Ocean acidification (OA) enhances growth of Thalassiosira weissflogii only at limiting low light levels.
- The energy saved from down-regulation of CCMs under OA rather than “CO2 fertilization aids in the enhancement under low levels of light energy supply.
- Coastal diatoms can benefit from OA, especially under cloudy weather or conditions of low solar exposures.
Diatom responses to ocean acidification have been documented with variable and controversial results. We grew the coastal diatom Thalassiosira weissflogii under 410 (LC, pH 8.13) vs 1000 μatm (HC, pH 7.83) pCO2 and at different levels of light (80, 140, 220 μmol photons m−2 s−1), and found that light level alters physiological responses to OA. CO2 concentrating mechanisms (CCMs) were down-regulated in the HC-grown cells across all the light levels, as reflected by lowered activity of the periplasmic carbonic anhydrase and decreased photosynthetic affinity for CO2 or dissolved inorganic carbon. The specific growth rate was, however, enhanced significantly by 9.2% only at the limiting low light level. These results indicate that rather than CO2 “fertilization”, the energy saved from down-regulation of CCMs promoted the growth rate of the diatom when light availability is low, in parallel with enhanced respiration under OA to cope with the acidic stress by providing extra energy.
Qu L., Campbell D. A. & Gao K., 2021. Ocean acidification interacts with growth light to suppress CO2 acquisition efficiency and enhance mitochondrial respiration in a coastal diatom. Marine Pollution Bulletin 163: 112008. doi: 10.1016/j.marpolbul.2021.112008. Article (subscription required).