In oceanography, the depth where carbonate ions under saturation in the water column or in the sediment pore and the water interface is large enough so that the rate of calcium carbonate (CaCO₃) sedimentation is totally compensated for by the rate of calcium carbonate dissolution, reaches the carbonate compensation depth (CCD). Alternately stated, the CCD is the depth at which calcareous skeletons of marine animals accumulate at the same rate at which they dissolve. Depending on the mineral structure of CaCO₃, the CCD is called calcite

Stalactites in Cueva Nerja Cave, Spain. © Y. Shopov. Reproduced by permission.

compensation depth (trigonal structure) or aragonite compensation depth (rhombic structure), respectively.

Foraminifera, coccolithophorids, pteropods, and a few other benthic and planktic organisms build calcium carbonate shells or skeletons. Upon death or reproduction, the shells are discarded and sink to the sea-floor. Within the water column...