Calcification rate of massive Porites spp. and Porites rus in the experiment of Moorea

This study tested the hypothesis that the response of corals to temperature and pCO2 is consistent between taxa. Juvenile massive Porites spp. and branches of P. rus from the back reef of Moorea were incubated for 1 month under combinations of temperature (29.3 °C and 25.6 °C) and pCO2 (41.6 Pa and 81.5 Pa) at an irradiance of 599 µmol quanta/m/s. Using microcosms and CO2 gas mixing technology, treatments were created in a partly nested design (tanks) with two between-plot factors (temperature and pCO2), and one within-plot factor (taxon); calcification was used as a dependent variable. pCO2 and temperature independently affected calcification, but the response differed between taxa. Massive Porites spp. was largely unaffected by the treatments, but P. rus grew 50% faster at 29.3 °C compared with 25.6 °C, and 28% slower at 81.5 Pa vs. 41.6 Pa CO2. A compilation of studies placed the present results in a broader context and tested the hypothesis that calcification for individual coral genera is independent of pH, [HCO3]-, and [CO3]2-. Unlike recent reviews, this analysis was restricted to studies reporting calcification in units that could be converted to nmol CaCO3/cm**2/h. The compilation revealed a high degree of variation in calcification as a function of pH, [HCO3]-, and [CO3]2-, and supported three conclusions: (1) studies of the effects of ocean acidification on corals need to pay closer attention to reducing variance in experimental outcomes to achieve stronger synthetic capacity, (2) coral genera respond in dissimilar ways to pH, [HCO3]-, and [CO3]2-, and (3) calcification of massive Porites spp. is relatively resistant to short exposures of increased pCO2, similar to that expected within 100 y.

本研究验证了“不同珊瑚类群对温度与二氧化碳分压（pCO₂）的响应模式一致”这一假说。实验以采自茉莉雅岛（Moorea）礁坪后区的幼年块状微孔珊瑚（Porites spp.）与玫瑰微孔珊瑚（Porites rus）分枝为材料，在辐照度为599 μmol量子·m⁻²·s⁻¹的条件下，设置温度（29.3 ℃与25.6 ℃）和pCO₂（41.6 Pa与81.5 Pa）的组合处理，开展为期1个月的培养实验。本研究采用微宇宙（microcosms）系统与二氧化碳混气技术，通过部分嵌套设计（培养槽）构建实验处理体系，包含2个区组间因子（温度、pCO₂）与1个区组内因子（类群），以钙化作用作为因变量。结果显示，pCO₂与温度分别独立影响珊瑚钙化，但不同类群的响应模式存在显著差异。块状微孔珊瑚（Porites spp.）基本不受实验处理的影响，而玫瑰微孔珊瑚（Porites rus）在29.3 ℃条件下的生长速率较25.6 ℃时提升50%，在81.5 Pa pCO₂条件下较41.6 Pa时降低28%。本研究整合多项已发表研究，将本次实验结果置于更广泛的研究框架中，并验证了“单个珊瑚属的钙化作用与pH、碳酸氢根离子([HCO₃⁻])、碳酸根离子([CO₃²⁻])无关”这一假说。与近期相关综述不同，本次分析仅纳入采用可转换为纳摩尔碳酸钙·厘米⁻²·小时⁻¹单位报告钙化作用的研究。整合分析结果显示，钙化作用随pH、[HCO₃⁻]与[CO₃²⁻]的变化呈现高度变异，并支持三项结论：（1）海洋酸化对珊瑚影响的相关研究需更注重降低实验结果的方差，以提升更强的综合推演能力；（2）不同珊瑚属对pH、[HCO₃⁻]与[CO₃²⁻]的响应模式存在显著差异；（3）块状微孔珊瑚属（Porites spp.）的钙化作用对短期升高的pCO₂（即未来100年预计的二氧化碳分压水平）具有相对较强的抵抗力。