Calcification does not stimulate photosynthesis in the zooxanthellate scleractinian coral Stylophora pistillata

The interaction between photosynthesis and calcification remains poorly known in zooxanthellate scleractinian corals. We tested whether calcification is a significant source of CO 2 for photosynthesis in Stylophora pistillata . Rates of net photosynthesis, respiration, and calcification were measured on colonies incubated in synthetic seawater (SSW) controlled with respect to the inorganic carbon system and containing standard (11.40 mmol kg −1 ) and low (2.85 mmol kg −1 ) calcium concentrations. Net photosynthesis and respiration are not significantly different in standard and low‐Ca 2+ SSW despite a rate of calcification 2.0–2.4 times lower in Ca 2+ −depleted SSW. Additional experiments carried out on the noncalcifying zooxanthellate Anthozoa Anemonia viridis demonstrate that a low calcium concentration has no direct effect on rates of photosynthesis and respiration. It is suggested that calcification is not a significant source of photosynthetic CO 2 and that photosynthesis stimulates calcification rather than the opposite.