Answer: Carbonic acid
Step-by-step explanation: The carbon dioxide when get dissolved in the water is known as carbonic acid. This carbon dioxide from the water is used by the pytoplanktons to perform the process of photosynthesis.
This is a very weak acid which is formed when the carbon dioxide gets dissolved in the water. The carbon dioxide in the environment goes inside the ocean that is used by the organisms and oxygen is released into the environment and inside water.