All the plant, animals, and all other biomass is predominantly made up of carbon and are found mainly in the ocean reservoir, lithosphere and atmosphere . Also all the plants either on land or in ocean entraps the nutrients (i.e carbon, nitrogen etc.) from surroundings through photosynthesis and convert them into energy rich molecules which also get concentrated in the ocean reservoir, lithosphere and atmosphere. These three spheres are called the reservoirs as they contain 100% of the nutrients (including carbon) with in them .
When carbon dioxide CO2 is released into the atmosphere from the burning of fossil fuels, approximately 50% remains in the atmosphere, while 25% is absorbed by land plants and trees, and the other 25% is absorbed into certain areas of the ocean. The carbon dioxide is stored in the interior of the Earth in the form of carbonate rocks, such as limestone, dolomite, and chalk. Fish and other animals in the ocean breathe oxygen and give off carbon dioxide (CO2), just like land animals and hence it remains there too.
