What role do zooxanthellae play in coral health?

Zooxanthellae are symbiotic algae that live in the tissues of coral polyps. Their primary role in coral health is to provide essential nutrients through the process of photosynthesis. During this process, zooxanthellae convert sunlight into energy, which they share with the coral, significantly contributing to the energy requirements of the corals. This relationship is mutually beneficial; while the corals provide the zooxanthellae with a protected environment and the compounds necessary for photosynthesis, the algae supply the corals with critical organic compounds, including glucose, glycerol, and amino acids.

The presence of zooxanthellae is crucial for the growth and overall health of coral reefs, particularly in nutrient-poor waters where many corals thrive. The energy produced by zooxanthellae helps corals to build their calcium carbonate skeletons, maintain their metabolic functions, and recover from stress. A decline in the health or abundance of zooxanthellae, often due to environmental stressors such as rising sea temperatures or ocean acidification, can lead to coral bleaching, severely affecting coral health and reef ecosystems.