Photosynthesis by tiny marine plants (phytoplankton) in the sunlit surface waters turns the carbon into organic matter. Many organisms use carbon to make calcium carbonate, a building material of shells and skeletons
The photosynthesis by the aquatic plants, atmospheric carbon dioxide dissolved in the oceanic water, the decomposed and degraded matter of animals and plants can increase the concentration of the carbon dioxide in the oceanic water. This carbon dioxide can be useful to develop the coral reef the hard skeleton structure composed of calcium carbonate by the colonies of the coral polyps.
