CaCO3-saturated saline waters at pH values below 8.5 are characterized by two stationary equilibrium states: reversible chemical calcification/decalcification associated with acid dissociation, Ca2++HCO3-CaCO3+H+; and reversible static physical precipitation/dissolution, Ca2++CO32-CaCO3. The former reversible reaction was determined using a strong base and acid titration. The saturation state described by the pH/P-CO2-independent solubility product, [Ca2+][CO32-], may not be observed at pH below 8.5 because [Ca2+][CO32-]/([Ca2+][HCO3-]) <<1. Since proton transfer dynamics controls all reversible acid dissociation reactions in saline waters, the concentrations of calcium ion and dissolved inorganic carbon (DIC) were expressed as a function of dual variables, pH and P-CO2. The negative impact of ocean acidification on marine calcifying organisms was confirmed by applying the experimental culture data of each P-CO2/pH-dependent coral polyp skeleton weight (Wskel) to the proton transfer idea. The skeleton formation of each coral polyp was performed in microspaces beneath its aboral ectoderm. This resulted in a decalcification of 14 weight%, a normalized CaCO3 saturation state of 1.3 at P-CO2 approximate to 400ppm and pH approximate to 8.0, and serious decalcification of 45% and 2.5 at P-CO2 approximate to 1000ppm and pH approximate to 7.8.