Data from: Elevated pCO2 affects tissue biomass composition, but not calcification, in a reef coral under two light regimes

Ocean acidification (OA) is predicted to reduce reef coral calcification rates and threaten the long-term growth of coral reefs under climate change. Reduced coral growth at elevated pCO2 may be buffered by sufficiently high irradiances, however, the interactive effects of OA and irradiance on other fundamental aspects of coral physiology, such as the composition and energetics of coral biomass, remain largely unexplored. This study tested the effects of two light treatments (7.5 vs. 15.7 mol photons m-2 d-1) at ambient- or elevated-pCO2 (435 vs. 961 μatm) on calcification, photopigment and symbiont densities, biomass reserves (lipids, carbohydrates, proteins), and biomass energy content (kJ) of the reef coral Pocillopora acuta from Kāne‘ohe Bay, Hawai‘i. While pCO2 and light had no effect on either area- or biomass-normalized calcification, tissue lipids gdw-1 and kJ gdw-1 were reduced 15% and 14% at high pCO2, and carbohydrate content increased 15% under high light. The combination of high light and high pCO2 reduced protein biomass (per unit area) by ~ 20%. Thus, under ecologically relevant irradiances, P. acuta in Kāne‘ohe Bay does not exhibit OA-driven reductions in calcification reported for other corals; however, reductions in tissue lipids, energy content, and protein biomass suggest OA induced an energetic deficit and compensatory catabolism of tissue biomass. The null effects of OA on calcification at two irradiances support a growing body of work concluding some reef corals may be able to employ compensatory physiological mechanisms that maintain present-day levels of calcification under OA. However, negative effects of OA on P. acuta biomass composition and energy content may impact the long-term performance and scope for growth of this species in a high pCO2 world.

海洋酸化（Ocean Acidification，OA）被预测会在气候变化背景下降低造礁珊瑚的钙化速率，并威胁珊瑚礁的长期存续。在升高的二氧化碳分压（pCO₂）条件下，珊瑚生长的减缓可通过足够高的辐照度得到缓冲；然而，海洋酸化与辐照度对珊瑚生理学核心方面的交互效应——例如珊瑚生物量的组成与能量学特征——仍未得到充分探究。本研究针对来自夏威夷卡内奥赫湾的鹿角杯形珊瑚（Pocillopora acuta），测试了两种光照处理（7.5 与 15.7 mol 光子·m⁻²·d⁻¹）结合环境或升高的pCO₂（435 与 961 微大气压（μatm））对其钙化速率、光色素与共生体密度、生物量储备（脂质、碳水化合物、蛋白质）以及生物量能量含量（kJ）的影响。研究结果显示，pCO₂与光照对标准化至面积或生物量的钙化速率均无显著影响，但高pCO₂条件下的单位干重组织脂质与单位干重能量含量（kJ·gdw⁻¹）分别降低了15%与14%；高光条件下的碳水化合物含量则提升了15%。高光与高pCO₂的联合处理可使单位面积的蛋白质生物量降低约20%。因此，在生态相关的辐照度条件下，卡内奥赫湾的鹿角杯形珊瑚并未出现其他造礁珊瑚中报道的、由海洋酸化驱动的钙化速率降低现象；但组织脂质、能量含量与蛋白质生物量的降低表明，海洋酸化诱导了能量赤字与组织生物量的补偿性分解代谢。海洋酸化在两种辐照度下对钙化速率无显著影响的结果，支持了日益增多的研究结论：部分造礁珊瑚可借助补偿性生理机制，维持海洋酸化背景下当前的钙化速率水平。然而，海洋酸化对鹿角杯形珊瑚生物量组成与能量含量的负面影响，可能会影响该物种在高pCO₂世界中的长期生存表现与生长潜力。