What is the use of carbon dioxide for marine animals?

Marine animals:

The animals that can live in the ocean in salty water are known as marine animals, for example- fishes, mollusks, etc

The uses of carbon dioxide for marine animals:

1. The presence of excess carbon dioxide leads to ocean acidification.
2. However, certain shell-building creatures like shrimps, lobsters, and crabs utilize carbon dioxide in the form of dissolved inorganic carbon to build more shells.