Carbon Cycle

The cycling of carbon takes place in oceans and other aquatic ecosystems as well as in terrestrial environments. The world's oceans contain about 50% more carbon than does the atmosphere. The oceans are able to absorb some of the carbon dioxide currently being released by the burning of fossil fuels, thus offsetting global warming. However, the oceans cannot do this as quickly as the carbon dioxide is being released to the atmosphere, and this time lag is resulting in increasing concentrations in the atmosphere.

In aquatic environments, carbon cycling is more complex because carbon interacts with water. When carbon dioxide is released by cellular respiration, it combines with water to form carbonic acid and bicarbonate. Therefore, in aquatic environments most inorganic carbon is in the form of bicarbonate rather than carbon dioxide. Carbon dioxide from the atmosphere readily diffuses into water, and it is quickly converted to bicarbonate.