On the left are four records from corals in the Atlantic (Cape Verde, Florida, Dominican Republic, and Gulf of Guinea). All show the C-13 Suess effect to varying degrees. Differences between records are a result of local variations in DIC values.

Variations in the stable carbon isotopic composition of calcium carbonate sediments throughout geological time have been an invaluable aid in unraveling changes in the global carbon cycle. Generally speaking, increases in the d13C of carbonates are considered indicative of increased burial and preservation of  isotopically negative organic carbon, while decreases in the carbon isotopic ratio suggest transfer of carbon from the organic into the inorganic reservoirs.We are studing these changes in marginal platform sediments which do not seem to follow the global pattern. The figure shows the changes in the C isotopes from 4 ODP sites relative to the oceanic pattern (525).

We are studying the input of terrestrial carbon into coastal ecosystems in South Florida. The left hand figure shows the carbon isotopic composition of the particulate organic material in Biscayne Bay during September of 2006. This work is being combined with nitrogen isotopes to investigate the origin of the POM. Other work includes the investigation of the sedimentary carbon isotopic composition as well as the DIC and the records of DIC in corals and sediments.