Zooxanthellae: Symbiotic coral algae
What are Zooxanthellae?
Zooxanthellae are single-celled algae that live symbiotically with corals, clams and anemones. That was a mouthful and a bit nerdy, so let’s take a little bit deeper at each of the important terms there:
Single-celled: Living things are made of cells. You are made of cells, but millions of tiny cells make up each and every organ in your body. Single-celled organisms, like an amoeba or zooxanthellae are much simpler in structure. Each and every cell is a unique organism, and the cells do not group together to form something larger. The seaweed that washes up on the beach is an example of a macroalgae that is made from a bunch of algal cells all grouping together to form the larger plant-like seaweed. Zooxanthellae, by comparison, are tiny algae made up from just one cell.
Algae: Algae are like plants, in that they take light energy from the sun and carbon dioxide to create food called glucose by the process of photosynthesis. Algae are unlike plants in that they do not have flowers, roots, stems or leaves. In the case of zooxanthellae, each algal cell is a unique organism, as mentioned above.
Symbiotic with corals: In the algae world, Zooxanthellae are unique because they have a special relationship with their host corals. A symbiosis is a reciprocal relationship between two organisms where each organism provides a benefit to the other. In the case of zooxanthellae and corals, the corals are thought to provide a safe home and carbon dixoide while zooxanthellae provide oxygen, food/nourishment and help remove waste.
In addition to providing corals with nourishment, the zooxanthellae are also responsible for the variations in color that make some species of coral so popular in the saltwater aquarium hobby.
Coral bleaching occurs when a coral, generally under stress, expels most of the symbiotic zooxanthellae from its body.
Zooxanthellae also go by another name in scientific circles–the scientific name is symbiodinium.
The National Oceanic and Atmospheric Administration (NOAA) has an interesting article you can find here, for more information.
Odd to think that the reason you spent hundreds of dollars on a lighting system for your saltwater aquarium was because of these single-celled organisms, but it’s true.