On the stable carbon and oxygen isotopic composition of some shallow water,ahermatypic, scleractinian coral skeletons

The δC¹³ and δO¹⁸ values of skeletons of shallow water, ahermatypic scleractinian corals from Jamaica show an excellent correlation over a wide range of isotopic composition. Within individual specimens there are large differences in the isotopic composition of separate skeletal elements. Some of these ahermatypes are enriched in O¹⁸ relative to equilibrium precipitates of calcium carbonate from Jamaican sea water. Therefore our data do not support a two-reservoir mixing model for calcification if one of these reservoirs consists of dissolved marine (inorganic) bicarbonate. As some of these ahermatypic species are enriched in both C¹³ and O¹⁸ relative to hermatypic corals from the same reefs, calcification models based on withdrawal of metabolic CO₂ by photosynthesizing zooxanthellae must also be modified.