Carbonate dynamics of the coral reef system at Bora Bay, Miyako Island

Abstract

Direct measurements of total inorganic carbon, total alkalinity and pH were obtained together with salinity, temperature and current velocities in a coral reef at Bora Bay, Miyako Island in the Ryukyu Islands in October 1993, March 1994 and July 1994. The 3 parameters of the carbonate system showed good internal consistency using carbonate acid dissociation coefficients from the literature, although the total alkalinity values observed in July were lower than the calculated values. Comparison of calculated values of the fugacity of CO2 in the coral reef waters and in the outer oceanic waters suggested that, particularly where water flows out of the lagoon and back to the ocean, biological activity within the reef-lagoon system may be releasing CO2 to the reef waters. However, a more careful consideration of biological inorganic and organic carbon production showed that the reef flat was a strong sink for aqueous CO2 in July. The lagoon, on the other hand, appears to be a slight source of CO2 in October and March.