Seawater carbonate chemistry and calcification during an experiment with a coral Porites lutea, 2004

Using living corals collected from Okinawan coral reefs, laboratory experiments were performed to investigate the relationship between coral calcification and aragonite saturation state (W) of seawater at 25 infinity C. Calcification rate of a massive coral Porites lutea cultured in a beaker showed a linear increase with increasing Waragonite values (1.08-7.77) of seawater. The increasing trend of calcification rate (c) for W is expressed as an equation, c = aW + b (a, b: constants). When W was larger than ~4, the coral samples calcified during nighttime, indicating an evidence of dark calcification. This study strongly suggests that calcification of Porites lutea depends on W of ambient seawater. A decrease in saturation state of seawater due to increased pCO2 may decrease reef-building capacity of corals through reducing calcification rate of corals.本研究以采自冲绳珊瑚礁的活体珊瑚为实验材料，开展室内控制实验，探究珊瑚钙化作用与海水文石饱和度状态（aragonite saturation state, W）之间的关联，实验温度设定为25℃。在烧杯中培养的块状珊瑚澄黄滨珊瑚（Porites lutea），其钙化速率随海水文石饱和度数值（1.08~7.77）的升高呈线性增长趋势。该钙化速率随文石饱和度W变化的增长规律可通过公式c = aW + b（其中a、b为常数）表征。当文石饱和度W大于约4时，珊瑚样本可在夜间进行钙化，这为暗钙化现象提供了直接证据。本研究充分证实，澄黄滨珊瑚的钙化过程依赖于周围海水的文石饱和度。因二氧化碳分压（pCO2）升高导致的海水文石饱和度降低，可通过降低珊瑚钙化速率，削弱珊瑚的造礁能力。