Eur. J. Chem. volume 1, issue 4, P246-251 2010 DOI: 10.5155/eurjchem.1.4.246-251.156
Kazuhiko Ichikawa
Abstract: KEYWORDSThe CaCO3-oversaturated weakly basic water at around pH=8 was proved by the novel simple equations (e.g. log [Ca 2+ ] = -2pH -logPCO2 + 9.94) derived from material energetics and protoncontrolled mechanism for coupling among proton/hydroxide production/consumption reactions (e.g. CaCO3 + H + ↔ HCO3 -+ Ca 2+ ) in equilibrium with atmospheric carbon dioxide. The cyclic/oscillating variation between pH=8.3 and 8.0 for marine calcifying organisminhabited paleo and preindustrial seawaters was elucidated by applying the improved protoncontrolled mechanism to biochemical reactions in cytoplasts or host tissues of marine calcifying phytoplanktons and phytosymbiont-bearing corals/zooplanktons. It was revealed that photosynthesis enhances biogenic calcification and vice versa, as the thicker growth of CaCO3-made outer casings causes proton production and photosynthesis continuously needs protons to produce CO2(aq) from major HCO3 -. The correlation between calcification and photosynthesis creates a number of stationary states with respect to oscillating pH variation. Marine biogenic calcification reaction releases no CO2 to atmosphere and is no positive feedback to rising atmospheric PCO2 levels.Acid attack Calcifying organism Phytosymbiont Proton mechanism CaCO3-oversaturated water pH Seawater pH

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