Pathway of Movement
The aerobic respiration of organisms, volcanic eruptions, the weathering of carbonate rocks, and the burning of carbon-containing compounds found in wood, grasses, and fossil fuels add carbon dioxide to the troposphere.
Aerobic respiration in the cells of oxygen-using producers, consumers, and decomposers breaks down glucose and other complex organic compounds and converts the carbon back to CO2, which is released into the troposphere and in water for reuse by producers.
Carbon dioxide is removed from the troposphere by terrestrial and aquatic producers, which use photosynthesis to convert it into complex carbohydrates such as glucose (C6H12O6).
This linkage between photosynthesis in producers and aerobic respiration in producers, consumers, and decomposers circulates carbon in the biosphere.
Fossil fuels are buried deposits of dead plant matter and bacteria that have been compressed between layers of sediment; they are also carbon-containing, so when burned these fuels release CO2 back into the troposphere for recycling.
Some of the atmosphere’s carbon dioxide dissolves in ocean water, and the ocean’s photosynthesizing producers remove some.
Some ocean organisms build their shells and skeletons by using dissolved CO2 molecules in seawater to form carbonate compounds such as calcium carbonate (CaCO3). When these organisms die, tiny particles of their shells and bone drift slowly to the ocean depths. There they are buried for eons in deep bottom sediments, where under immense pressure they are converted into limestone rock.