Quantitative interpretation of vertical profiles of calcium and pH in the coral coelenteron
Quantitative interpretation of vertical profiles of calcium and pH in the coral coelenteron
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DOI：
10.1016/j.marchem.2018.06.001
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发表时间：
2018-08
期刊：
影响因子：
3
通讯作者：
Xiangcheng Yuan;W. Cai;C. Meile;B. Hopkinson;Qian Ding;V. Schoepf;M. Warner;Kenneth D. Hoadley;Bingzhang Chen;Sheng Liu;Hui Huang;Y. Ye;A. Grottoli
中科院分区：
文献类型：
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作者：
Xiangcheng Yuan;W. Cai;C. Meile;B. Hopkinson;Qian Ding;V. Schoepf;M. Warner;Kenneth D. Hoadley;Bingzhang Chen;Sheng Liu;Hui Huang;Y. Ye;A. Grottoli
石珊瑚（硬珊瑚）及其共生藻类是生物多样性和地质上重要的珊瑚礁栖息地的生态工程师。因此，使全生物（珊瑚+藻类）钙化并生成珊瑚礁结构的复杂且相互关联的生理过程引起了人们的极大兴趣。然而，由于钙化过程的空间尺度小以及共生体与宿主之间的紧密耦合等多种原因，钙化的机制很难研究。在这项研究中，我们探索了 pH 和 Ca2+ 微电极在限制光合作用、呼吸和钙化的速率和空间分布方面的效用。这项工作的重点是通过腔肠腔的 pH 和 Ca2+ 的垂直分布，腔肠腔是一个半隔离的改性海水隔间，适合定量解释。在两个研究物种Turbinariareniformis和Acropora millepora中，Ca2+浓度从腔肠的口部到底部以大致线性的方式下降，表明影响Ca2+浓度的主要生理过程是腔肠下方钙化的去除。相比之下，H+浓度在腔肠腔的大部分区域保持相对恒定，然后向腔肠底部急剧增加，表明来自下方钙化液的质子泵送。腔肠腔和钙化部位之间的估计 H+ 梯度比之前预测的高 10 倍以上。因此，从钙化液中输出质子所需的能量估计比之前计算的高约 3 倍。考虑光合作用、呼吸和钙化的影响，使用一维反应扩散模型来解释 pH 曲线。该模型与观察到的 pH 曲线非常吻合，有助于限制这些过程的速率和空间分布。我们的建模结果还表明，具有较深息肉的成年珊瑚可能对海洋酸化 (OA) 更敏感，因为将 H+ 从腔肠输送到周围海水的难度增加。
Scleratinian corals (hard corals) and their symbiotic algae are the ecological engineers of biodiverse and geological important coral reef habitats. The complex, linked physiological processes that enable the holobiont (coral + algae) to calcify and generate reef structures are consequently of great interest. However, the mechanism of calcification is difficult to study for several reasons including the small spatial scales of the processes and the close coupling between the symbiont and host. In this study, we explore the utility of pH and Ca2+microelectrodes for constraining the rates and spatial distribution of photosynthesis, respiration, and calcification. The work focuses on vertical profiles of pH and Ca2+through the coelenteron cavity, a semi-isolated compartment of modified seawater amenable to quantitative interpretation. In two studied species,Turbinariareniformisand Acropora millepora, Ca2+concentrations decreased in a roughly linear manner from the mouth to the base of the coelenteron, indicating the primary physiological process affecting Ca2+concentration is removal for calcification below the coelenteron. In contrast, the H+concentration remained relatively constant over much of the coelenteron cavity before it increased sharply toward the base of the coelenteron, indicative of proton-pumping from the calcification fluid below. The estimated H+gradient between the coelenteron cavity and the calcification site was >10 times higher than previously predicted. Consequently, the energy required to export protons from the calcifying fluid was estimated to be ~3 times higher than previously calculated. A one-dimensional reaction-diffusion model was used to interpret the pH profile considering the effects of photosynthesis, respiration, and calcification. This model provided a good fit to the observed pH profile and helped to constrain the rates and spatial distribution of these processes. Our modeling results also suggested that adult corals with deeper polyps may be more sensitive to ocean acidification (OA) because of enhanced difficulty to transport H+out of the coelenteron and into the surrounding seawater.