Zooxanthellae

Importance of Zooxanthellae to Coral Reefs

 

Almost every single type of coral contains its own colony of zooxanthellae. One of the main reasons that zooxanthellae are so critical to reef systems is that their photosynthetic process directly provides the energy used in building the coral skeletons that in turn create coral reefs. When zooxanthellae undergo photosynthesis, the energy that is created is then consumed by the coral animal, which in turn uses the nutritional elements to build their skeletons.

 

Zooxanthellae Populations

 

Because the zooxanthellae need sunlight to kick start photosynthesis, zooxanthellae are almost exclusively found in the skin of sea animals where they are able to access the most amount of light. It only takes a small number of zooxanthellae to originally permeate the body of a sea animal to quickly populate its tissue. The reproduction process of zooxanthellae is asexual, and reproduces by simply splitting in half in a process known as division. When zooxanthellae split in half, the entire population of the colony instantly doubles.

Zooxanthellae Reproduction

The reproduction process of zooxanthellae is asexual, and reproduces by simply splitting in half in a process known as division. When zooxanthellae split in half, the entire population of the colony instantly doubles.

Disruptions to the Zooxanthellae / Coral Relationship

Although most zooxanthellae spent their entire lifespan with the host organism, the process can be disrupted. Unfortunately, when coral becomes stressed its zooxanthellae rapidly exit the tissue, creating an imbalance in the previously existing symbiotic relationship. This process is known as “bleaching” and can be fatal for the coral since its main energy source is no longer available. Bleaching can be caused by a variety of conditions, including changes in temperature and bacterial infections. Bleaching is one of the newest byproducts of global warming- rising temperatures throughout the world’s oceans are causing this process to occur ever more frequently. 

Zooxanthellae Presence in Other Animals

When the zooxanthellae are not residing underneath the tissue of corals, they are usually found floating loosely in warm tropical ocean waters. Other types of sea animals that contain zooxanthellae include clams, nudibranches, flatworms, octocorals, sea anemones, hydrocorals, mollusks, zoanthids, sponges, and jellyfish.