Abstract
Radioactive Ca45 is used as a tracer in experiments performed on pieces of healthy colonies of 6 West Indian and 4 Indo-Pacific stony corals, and 1 coralline alga. Different parts of a colony deposit calcium at different rates. In darkness lime is deposited 2-3 times faster than in light, in forms where zooanthellae are present; where these have been removed there is a lowering of the rate. The calcium uptake is also reduced in the presence of Diamox, a specific carbonic anhydrase inhibitor.