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3256897 
Journal Article 
Microelectrode characterization of coral daytime interior pH and carbonate chemistry 
Cai, W; Ma, Y; Hopkinson, BM; Grottoli, AG; Warner, ME; Ding, Q; Hu, X; Yuan, X; Schoepf, V; Xu, Hui; Han, C; Melman, TF; Hoadley, KD; Pettay, D; Matsui, Y; Baumann, JH; Levas, S; Ying, Ye; Wang, Y 
2016 
1 
Nature Communications
EISSN: 2041-1723 
Nature Publishing Group 
7 
11144 
English 
27041668 
WOS:000373531100001 
Reliably predicting how coral calcification may respond to ocean acidification and warming depends on our understanding of coral calcification mechanisms. However, the concentration and speciation of dissolved inorganic carbon (DIC) inside corals remain unclear, as only pH has been measured while a necessary second parameter to constrain carbonate chemistry has been missing. Here we report the first carbonate ion concentration ([CO3(2-)]) measurements together with pH inside corals during the light period. We observe sharp increases in [CO3(2-)] and pH from the gastric cavity to the calcifying fluid, confirming the existence of a proton (H(+)) pumping mechanism. We also show that corals can achieve a high aragonite saturation state (Ωarag) in the calcifying fluid by elevating pH while at the same time keeping [DIC] low. Such a mechanism may require less H(+)-pumping and energy for upregulating pH compared with the high [DIC] scenario and thus may allow corals to be more resistant to climate change related stressors. 
carbonic acid; proton; carbonic acid derivative; acidification; anion; aragonite; calcification; carbonate; climate change; coral; dissolved inorganic carbon; electrode; pH; saturation; acidification; Acropora millepora; active transport; Article; climate change; coral; diffusion; greenhouse effect; microelectrode; nonhuman; Orbicella faveolata; pH; photosynthesis; species differentiation; Turbinaria reniformis; animal; Anthozoa; chemistry; pH; Anthozoa; Animals; Anthozoa; Carbonates; Hydrogen-Ion Concentration; Microelectrodes