zoosantellid

A zoosantellid is a type of single-celled organism, specifically a dinoflagellate alga, that lives in symbiosis with coral polyps. These algae are also known as zooxanthellae. The name "zoosantellid" refers to the broader taxonomic group to which these symbiotic algae belong, encompassing various genera and species within the family Zooxanthellaceae. They are crucial to the survival of reef-building corals, providing them with a significant portion of their energy through photosynthesis.

The relationship between zoosantellids and corals is mutually beneficial. The coral polyp provides the algae with a protected environment and access to sunlight, which is essential for photosynthesis. In return, the zoosantellids photosynthesize, converting sunlight into sugars and other organic compounds. These compounds are then transferred to the coral host, supplying up to 90% of the coral's energy needs. This symbiotic relationship also gives corals their vibrant colors, as the algae contain various pigments.

When corals experience environmental stress, such as elevated water temperatures or pollution, the symbiotic relationship can break down. This leads to the expulsion of the zoosantellids from the coral tissues, a phenomenon known as coral bleaching. Without their symbiotic algae, corals lose their color and their primary source of energy, making them vulnerable to starvation and disease. The ability of zoosantellid communities to adapt or recover is a key factor in coral reef resilience.