pH homeostasis during coral calcification in a free ocean CO2 enrichment (FOCE) experiment, Heron Island reef flat, Great Barrier Reef
pH homeostasis during coral calcification in a free ocean CO2 enrichment (FOCE) experiment, Heron Island reef flat, Great Barrier Reef
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DOI：
10.1073/pnas.1505586112
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发表时间：
2015-10-27
影响因子：
11.1
通讯作者：
McCulloch, Malcolm
中科院分区：
文献类型：
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作者：
Georgiou, Lucy;Falter, James;McCulloch, Malcolm
据报告，对在自由海洋碳富集 (FOCE) 实验中生长的柱状滨珊瑚进行了地球化学分析（Delta B-11 和 Sr/Ca），该实验在赫伦岛礁滩（大堡礁）上进行，为期 6 个月，从 2010 年 6 月到 12 月初。FOCE 实验旨在模拟预计到本世纪末将发生的二氧化碳驱动酸化的影响（情景 RCP4.5），同时保持珊瑚在原位条件下暴露于环境的自然变化。骨骼生长分析（通过延伸率和骨骼密度测量）显示，低 pH FOCE 处理（Delta pH = 低于环境值约 0.05 至 -0.25 个单位）和当前对照（Delta pH = 0）之间的钙化速率或钙化液 pH (pH(cf)) 没有系统差异；后者源自珊瑚骨骼的硼同位素成分（δ B-11）。此外，无论季节或处理如何，单个小块沿其主要顶端生长轴（+/- 0.02 pH(cf) 单位）都表现出接近恒定的 delta B-11 成分。因此，在苍鹭岛礁滩的高度动态条件下，P. cylindrica 上调了其钙化液的 pH 值（pH(cf) 类似于 8.4-8.6），每个小块具有接近恒定的 pHcf 值，独立于礁滩水域的大的自然季节波动（pH 类似于 7.7 到类似于 8.3）或叠加的 FOCE 处理。这种新发现的钙化过程中 pH 稳态现象表明，生活在高度动态环境中的珊瑚对其钙化液的碳酸盐化学具有强烈的生理控制作用，这意味着在研究范围内对海洋酸化具有高度的适应能力。
Geochemical analyses (delta B-11 and Sr/Ca) are reported for the coral Porites cylindrica grown within a free ocean carbon enrichment (FOCE) experiment, conducted on the Heron Island reef flat (Great Barrier Reef) for a 6-mo period from June to early December 2010. The FOCE experiment was designed to simulate the effects of CO2-driven acidification predicted to occur by the end of this century (scenario RCP4.5) while simultaneously maintaining the exposure of corals to natural variations in their environment under in situ conditions. Analyses of skeletal growth (measured from extension rates and skeletal density) showed no systematic differences between low-pH FOCE treatments (Delta pH = similar to-0.05 to -0.25 units below ambient) and present day controls (Delta pH = 0) for calcification rates or the pH of the calcifying fluid (pH(cf)); the latter was derived from boron isotopic compositions (delta B-11) of the coral skeleton. Furthermore, individual nubbins exhibited near constant delta B-11 compositions along their primary apical growth axes (+/- 0.02 pH(cf) units) regardless of the season or treatment. Thus, under the highly dynamic conditions of the Heron Island reef flat, P. cylindrica up-regulated the pH of its calcifying fluid (pH(cf) similar to 8.4-8.6), with each nubbin having near-constant pHcf values independent of the large natural seasonal fluctuations of the reef flat waters (pH similar to 7.7 to similar to 8.3) or the superimposed FOCE treatments. This newly discovered phenomenon of pH homeostasis during calcification indicates that coral living in highly dynamic environments exert strong physiological controls on the carbonate chemistry of their calcifying fluid, implying a high degree of resilience to ocean acidification within the investigated ranges.