How do zooxanthellae and corals benefit one another?

The relationship between zooxanthellae and corals is a mutualistic symbiosis where both organisms derive significant benefits.12

Benefits to the Coral:
* Nutrient Processing: Zooxanthellae consume metabolic waste products produced by the coral, including carbon dioxide, nitrogen, phosphorus, and sulfur, which the coral would otherwise excrete.1
* Skeletal Formation: By removing carbon dioxide, the algae increase the speed at which the coral can form its calcium carbonate skeleton.1
* Nutritional Support: Corals may receive supplemental nutrients directly from the algae.1

Benefits to the Zooxanthellae:
* Resource Supply: The coral provides the algae with a steady supply of carbon dioxide and other waste materials necessary for their metabolic processes.31
* Environment: The coral host provides a stable environment, particularly in well-lit, shallow waters where the algae can utilize sunlight for photosynthesis.12

Because of this reliance, many corals are dependent on their algal partners and cannot survive in prolonged darkness, which restricts the development of coral reefs to shallow, illuminated marine environments.2