<P> CO + H O → H CO → H + HCO </P> <P> Ca + 2HCO → CaCO + CO + H O </P> <P> While this process does manage to fix a large amount of carbon, two units of alkalinity are sequestered for every unit of sequestered carbon, thereby lowering the pH of surface water and raising atmospheric CO . The formation and sinking of CaCO drives a surface to deep alkalinity gradient which serves to raise the partial pressure of dissolved CO in surface waters and actually raise atmospheric levels . In addition, the sequestration of CaCO serves to lower overall oceanic alkalinity and again raise atmospheric levels . </P> <P> The vast majority of carbon incorporated in organic and inorganic biological matter is formed at the sea surface and then must sink to the ocean floor . A single phytoplankton cell has a sinking rate around 1 m per day and with 4000 m as the average depth of the ocean, it can take over ten years for these cells to reach the ocean floor . However, through processes such as coagulation and expulsion in predator fecal pellets, these cells form aggregates . These aggregates, known as marine snow, have sinking rates orders of magnitude greater than individual cells and complete their journey to the deep in a matter of days . </P>

The physical and biological pumps are oceanic components of the global