The physiological mechanisms that regulate coral calcification and how these processes are effected by environmental change are still unclear. However, geochemical signals in the coral's calcium carbonate skeleton provide us with a means to track changes in the corals Internal carbonate chemistry. This thesis provides evidence that corals grown in situ under C02 manipulation experiments and on natural reefs poses a high degree of regulation. However, abrupt increases In SST can disrupt the physico-chemical response and impede calcification. Long-term data indicate a strong effect of rising SST and lowering of seawater pH on tho corals regulatory mechanisms.