Growth rhythms recorded in stable isotopes and density bands in the reef coral Porites lobata (Cebu,Philippines)

Growth rhythms in the reef coral Porites lobata are revealed by X-radiography and stable carbon and oxygen isotopic analysis. High density increments were deposited during warm temperatures in summer and low density increments during winter. The seasonal temperature variations are reflected in the oxygen isotope ratios. The coral carbonate shows a constant depletion in ¹⁸O of –2.7%₀ relative to calcite in equilibrium with the ambient seawater. The mean annual growth rate of the specimen studied was 1.3±0.3 cm/year.