The effect of seawater calcium concentrations on the growth and skeletal composition of a scleractinian coral: Acropora Squamosa.

These corals were grown in seawater spiked with CaCl₂. Growth rate increased greatly with a moderate (25%) increase in Ca²⁺ concentration but this increase was less marked at still higher Ca²⁺ levels. The growth rate declined at concentrations above a 50% increase. This suggests that Ca²⁺ may limit growth at concentrations near seawater. The Sr²⁺/Ca²⁺ ratio in the new growth proved to reflect that in solution. The same trend was followed to some extent by Mg but Na showed no variation at all. This demonstrates clearly that some elemental variation in seawater is likely to be reflected in the composition of scleractinian corals. -from Author