Separation of kinetic and metabolic isotope effects in carbon-13 records preserved in reef coral skeletons

The stable isotopic signatures of Jamaica and Zanzibar coral skeletons, col lected over depth and light gradients, are strongly affected by kinetic iso tope effects associated with the calcification process. These kinetic effec ts mask delta(13)C metabolic signals of Light availability/photosynthesis. A simple data transformation, based on oxygen isotopic variation in the ske leton, has been developed to correct for the presence of these disequilibri um kinetic influences. The resulting transformed skeletal delta(13)C data s how significant correlation with associated tissue delta(13)C and with dept h/light attenuation. These relationships demonstrate the value of the trans formation and suggest that transformed skeletal delta(13)C data faithfully record the carbon isotope effect associated with photosynthesis, in which i ncreased photosynthesis leads to skeleton enriched in the heavy isotope of carbon. Possible applications of these transformations include improved mod eling of carbon fluxes in corals and more accurate reconstruction of insola tion, depth, water clarity and cloudiness. The C-13 transformation presente d will also allow for better identification of periods of metabolic stress in corals, when growth rate effects on delta(13)C might normally obscure th e C-13 metabolic signal. Copyright (C) 2000 Elsevier Science.