Proton-controlled mechanism for coupling among proton production/consumption reactions in CaCO3-oversaturated waters or calcifying organism-inhabited seawaters

Abstract

The CaCO₃-oversaturated weakly basic water at around pH=8 was proved by the novel simple equations (e.g. log [Ca²⁺] = -2pH -logP_CO2 + 9.94) derived from material energetics and proton-controlled mechanism for coupling among proton/hydroxide production/consumption reactions (e.g. CaCO₃ + H⁺↔HCO₃^- + Ca²⁺) in equilibrium with atmospheric carbon dioxide. The cyclic/oscillating variation between pH=8.3 and 8.0 for marine calcifying organism-inhabited paleo and preindustrial seawaters was elucidated by applying the improved proton-controlled mechanismto biochemical reactions in cytoplasts or host tissues of marine calcifying phytoplanktons and phytosymbiont-bearing corals/zooplanktons. It was revealed that photosynthesis enhances biogenic calcificationand 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 P_CO2 levels.