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.

硅藻对海洋酸化的反应已被证明具有可变且有争议的结果。我们在410（LC，pH 8.13）vs 1000μatm（HC，pH 7.83）pCO ₂和不同光水平（80，140，220μmol光子m ^-2  s ^-1）下生长了沿海硅藻Thalassiosira weissflogii光照水平会改变对OA的生理反应。在所有光照水平下，HC生长的细胞中的CO ₂浓缩机制（CCM）均下调，这反映为周质碳酸酐酶活性降低和对CO _2的光合亲和力降低或溶解的无机碳。然而，仅在有限的弱光水平下，比生长速度才显着提高了9.2％。这些结果表明，当光利用率低时，从CCM下调节省的能量而不是CO _2的“受精”促进了硅藻的生长速率，同时在OA下增强呼吸以通过提供额外的酸来应对酸性胁迫。能源。