SEASONAL-VARIATION OF PRIMARY PRODUCTIVITY AND SKELETAL DELTA-C-13 AND DELTA-O-18 IN THE ZOOXANTHELLATE SCLERACTINIAN CORAL ACROPORA-FORMOSA

Carbon and oxygen isotopic ratios, measured along the growth axis of b ranches from colonies of the scleractinian coral Acropora formosa coll ected at 2 and 12 m depth at Yonge Reef (Northern Great Barrier Reef, Australia), were compared to metabolic rates. Measurements of primary production, respiration, temperature and irradiance were carried out i n situ twice, in winter and in summer, and skeletal isotopic analyses were performed at 2 reference points corresponding to metabolic measur ements. There was no evidence of any relationship between oxygen isoto pic ratio and productivity. Skeletal delta(13)C values and the rates o f productivity showed a statistically significant positive relationshi p as predicted by the model proposed by Goreau (1977a: Proc 3rd Int Co ral Reefs Congr 1: 395-401); delta(13)C increased as a function of inc reasing productivity. The scattering of delta(13)C observed particular ly during summer demonstrates that the relationship between delta(13)C and primary productivity is not very tight and that other internal an d external parameters probably operate to explain the delta(13)C varia bility.