Title: 13C and 18O isotopic disequilibrium in biological carbonates: I. Patterns
Abstract: Biological carbonates frequently precipitate out of 18O and 13C equilibrium with ambient waters. Two patterns of isotopic disequilibrium are particularly common. “Kinetic” disequilibria, so designated because they apparently result from kinetic isotope effects during CO2 hydration and hydroxylation, involve simultaneous depletions of 18O and 13C as large as 4%. and 10 to 15%., respectively. Rapid skeletogenesis favors strong kinetic effects, and approximately linear correlations between skeletal δ18O and δ13C are common in carbonates showing mainly the kinetic pattern. “Metabolic” effects involve additional positive or negative modulation of skeletal δ13C, reflecting changes in the δ13C of dissolved inorganic carbon, caused mainly by photosynthesis and respiration. Kinetic isotope disequilibria tend to be fairly consistent in rapidly growing parts of photosynthetic corals, and time dependent isotopic variations therefore reflect changes in environmental conditions. δ18O variations from Galápagos corals yield meaningful clues regarding seawater temperature, while δ13C variations reflect changes in photosynthesis, modulated by cloudiness.
Publication Year: 1989
Publication Date: 1989-01-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 989
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