Seawater carbonate chemistry and community calcification during Miyako Island (Japan) coral reef studies, 1994

This effect is caused by the increase of CO3 content and carbonate saturation degree in seawater. If photosynthesis use molecular carbon dioxide, the second effect occurs when the calcification rate is more than approximately 1.6 times larger than that of photosynthesis. Time series model experiments indicate that photosynthesis and calcification potentially enhance each other and that organic and inorganic carbon is produced more efficiently in the coexisting system than in the isolated reactions.These coexisting effects on production enhancement of photosynthesis and calcification are expected to appear not only in the internal pool of organisms but also in a reef environment which is isolated from the outer ocean during low tide.

According to the measurements on the fringing type Shiraho Reef in the Ryukyu Islands, the diurnal change of water properties (pH, total alkalinity, total carbon dioxide and carbonate saturation degree) were conspicuous. This environment offers an appropriate condition for the appearance of these coexisting effects. The photosynthetic enhancement of calcification and the respiratory inducement of decalcification were observed during day-time and night-time slack-water periods, respectively.

These coexisting effects, especially the photosynthetic enhancement of calcification, appear to play important roles for fluorishing coral reef communities.