Bio Geo Chemical Cycles
A dynamic stable system is created by the interaction of biotic and abiotic components of the biosphere. These interactions lead to the transfer of matter and energy between different components of biosphere.
The Carbon Cycle
Carbon is present in the atmosphere as CO2 (0.03 to 0.04 %) in the gaseous form. Oceans have large deposits of carbon as carbonates (lime stones) and various salts of bicarbonates, which dissociate to give CO2, that remains dissolved in water. Even fresh water has dissolved CO2 in it. Another important source of carbon is deep under the soil in the form of peat, coal, petroleum, oil and gas. In the living organisms, carbon is present in carbohydrates, proteins and fats. The primary withdrawal of C as CO2 from the atmosphere pool is by photosynthesis, on land as well as in water.
The replenishment is done by the processes of respiration, decomposition, combustion of fuels, and chemical reactions that give off CO2 from carbonates or limestones. Occasional eruptions of volcanoes also add to the carbon content of the atmosphere as CO2. Thus there is one major route of utilization, but several other methods for replenishing CO2 back to the atmosphere.