Morphological and compositional changes in the skeletons of new coral recruits reared in acidified seawater: Insights into the biomineralization response to ocean acidification
Morphological and compositional changes in the skeletons of new coral recruits reared in acidified seawater: Insights into the biomineralization response to ocean acidification
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DOI：
10.1029/2009gc002411
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发表时间：
2009-07-24
影响因子：
3.5
通讯作者：
Rose, Kathryn A.
中科院分区：
文献类型：
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作者：
Cohen, Anne L.;McCorkle, Daniel C.;Rose, Kathryn A.
我们将大西洋常见的球状珊瑚（法维亚珊瑚，Favia fragum）的初级珊瑚虫（新繁殖个体）在25℃的海水中培养8天，海水的文石饱和度从环境水平（Ω = 3.71）到严重不饱和（Ω = 0.22）不等。所有珊瑚都有文石沉积，即使是在严重不饱和海水中培养的珊瑚也是如此。然而，与在环境条件下生长的珊瑚相比，在处理水箱中培养的珊瑚在钙化开始和初级珊瑚单体随后的生长方面都出现了显著延迟。此外，我们观察到用于构建骨骼的文石晶体在大小、形状、取向和成分上逐渐发生变化。随着酸化程度的增加，紧密排列的细文石针束被高度多面的菱形无序聚集体所取代。通过二次离子质谱（SIMS）离子微探针测量的晶体锶/钙比值增加了13%，镁/钙比值降低了45%。通过将这些元素比值的变化与瑞利分馏计算结果进行比较，我们表明观察到的晶体形态和成分变化与珊瑚从每“批”钙化液中沉淀的文石量减少>80%是一致的。这表明，尽管珊瑚将隔离的钙化腔室内的流体饱和度维持在远高于外部海水的水平，但随着外部海水饱和度的降低，其仍会系统性地显著降低。酸化处理中的珊瑚无法达到驱动晶体快速生长的钙化液过饱和水平，这可能反映了可用于钙化所需的质子泵的能量有限。如果是这样，那么海洋酸化对热带珊瑚生态系统的未来影响可能取决于个体或物种克服这一限制并达到确保快速生长所需的钙化液过饱和水平的能力。
We reared primary polyps (new recruits) of the common Atlantic golf ball coral Favia fragum for 8 days at 25 degrees C in seawater with aragonite saturation states ranging from ambient (Omega = 3.71) to strongly undersaturated (Omega = 0.22). Aragonite was accreted by all corals, even those reared in strongly undersaturated seawater. However, significant delays, in both the initiation of calcification and subsequent growth of the primary corallite, occurred in corals reared in treatment tanks relative to those grown at ambient conditions. In addition, we observed progressive changes in the size, shape, orientation, and composition of the aragonite crystals used to build the skeleton. With increasing acidification, densely packed bundles of fine aragonite needles gave way to a disordered aggregate of highly faceted rhombs. The Sr/Ca ratios of the crystals, measured by SIMS ion microprobe, increased by 13%, and Mg/Ca ratios decreased by 45%. By comparing these variations in elemental ratios with results from Rayleigh fractionation calculations, we show that the observed changes in crystal morphology and composition are consistent with a > 80% decrease in the amount of aragonite precipitated by the corals from each "batch'' of calcifying fluid. This suggests that the saturation state of fluid within the isolated calcifying compartment, while maintained by the coral at levels well above that of the external seawater, decreased systematically and significantly as the saturation state of the external seawater decreased. The inability of the corals in acidified treatments to achieve the levels of calcifying fluid supersaturation that drive rapid crystal growth could reflect a limit in the amount of energy available for the proton pumping required for calcification. If so, then the future impact of ocean acidification on tropical coral ecosystems may depend on the ability of individuals or species to overcome this limitation and achieve the levels of calcifying fluid supersaturation required to ensure rapid growth.