δ 13 C PDB compositions for 39 samples of dissolved organic carbon (DOC) from the Gulf of Mexico-Caribbean Sea-Atlantic Ocean system, the South Pacific and Ross Sea are reported. Deep water values are similar with a mean of −21.8%. attesting to the homogeneity of the oceanic DOC pool. In Antarctic waters, a 5%. difference between DOC and particulate organic carbon (POC), with POC having values similar to modern plankton ( δ 13 C PDB approx −27%.) supports the idea of the transient nature of POC as compared to DOC. Total, lipid, acid hydrolyzed, amino acid and residue fractions of POC are about 5, 3, 7, 5 and 3%. respectively, more negative in 2000 m water as compared to surface water samples from the Gulf of Mexico.