Carbon dioxide is slightly soluble and is absorbed into bodies of water
such as the ocean and lakes. It is not overly soluble as evidenced by what
happens when a can of carbonated soda such as Coke is opened. Some of the
dissolved carbon dioxide remains in the water, the warmer the water the
less carbon dioxide remains in the water.
Some carbon dioxide is used by algae and phytoplankton through the
process of photosynthesis.
In other marine ecosystems, some organisms such as coral and those
with shells take up carbon dioxide from the water and convert it into calcium
carbonate. As the shelled organisms die, bits and pieces of the shells
fall to the bottom of the oceans and accumulate as sediments. The carbonate
sediments are constantly being formed and redissolved in the depths of
the oceans. Over long periods of time, the sediments may be raised up as
dry land or into mountains. This type of sedimentary rock is called limestone.
The carbonates can redissolve releasing carbon dioxide back to the air
or water.
