Map of Plankton produced by the NASA. Red indicates the higher concentration, blue the lower. Plankton is important component of the food chain and a CO2 regulator. Plankton contains small amount of Calcium Carbonate (CaCO3). When they die (and if they are not eaten by other animals) they sink and remove CO2 out of the atmosphere for a certain period of time. See Phytoplankton.
in detail see also: Phytoplankton XlnkS6F5