Hello, zooxanthellae is coral's companion. The relationship between them is that corals provide living environment for zooxanthellae, and provide coral metabolites such as nitrogen and phosphorus, while zooxanthellae provides 90% of the energy generated by photosynthesis to corals.

Chrysophyta is a unicellular algae with a very small volume and a diameter of only microns. Usually, there are 30,000 golden algae in every cubic millimeter of coral. Most of them are autotrophs, which will provide the host with translocation-type reduced carbides, such as glucose, glycerol, amino acids and other products of photosynthesis, among which up to 90% of the energy of corals is provided by zooxanthellae.

Coral can absorb calcium and carbon dioxide in seawater during its growth, and then secrete limestone to become its own living shell. Coral is the secretion of coral and constitutes the supporting structure of coral.