The marine biota also redistribute carbon: marine organisms grow organic tissue and calcareous shells in surface waters, which, after their death, sink to deeper waters, where they are returned to the dissolved
inorganic carbon reservoir by dissolution and microbial decomposition.
In seawater, CO2 interacts with water molecules to form carbonic acid, which reacts very quickly with the large
reservoir of dissolved
inorganic carbon — bicarbonate and carbonate ions — in the ocean.