Why and how do oceans absorb carbondioxide?
Ocean is the largest carbon sink on earth. It occupies nearly 70% of the earth’s surface. As such, the atmosphere comes into contact with the vast extent of ocean’s surface. The atmospheric CO enters the ocean through steady exchange at surface. This is a physico-chemical process. The difference in partial pressure of the CO between seawater and air facilitate gaseous exchange. The diffusion takes place until the partial pressures across the air-water interface are equilibrated. The following two processes ensure the continuous exchange at the air-sea interface, though occasional supersaturation at the surface film is not ruled out.
The seawater contains millions of tiny, microscopic photosynthetic phytoplankton which utilizes CO during photosynthesis. They convert the CO into sugars and other carbon compounds which ultimately enters the food web. The biological pump transfers carbon dioxide from the surface of the ocean to the deep sea.
Unlike other gases, CO reacts with seawater to form dissolved inorganic carbon, ionic and non-ionic species like dissolved free Carbon dioxide (CO), Carbonic Acid (HCO), Bicarbonate (HCO) and Carbonate (CO). The carbonate system is the unique phenomenon of marine ecosystem. The pH of seawater is regulated by the bicarbonate and carbonate concentrations. Marine organisms combine calcium and carbonate ions in the calcification process and manufacture calcareous material. As the organisms die, the skeletal material sinks and buried in sediments.
Dr. MURUGAN ANNAPPAN
Marine Ecology and Conservation Lab
V.O. Chidambaram College, Tuticorin
Tamil Nadu
Courtesy: The Hindu
