Symbiotic Zooxanthellae

Home of Symbiotic Zooxanthellae

 

Symbiotic zooxanthellae need sunlight to perform its main job, photosynthesis. This need determines where symbiotic zooxanthellae are hosted within the coral. Most often, symbiotic zooxanthellae are found underneath the skin of coral- this is the area of corals that have the most access to sunlight. Originally, symbiotic zooxanthellae are literally absorbed (or ingested) by the coral’s polyp.

 

Symbiotic Zooxanthellae  Colony Grows in Host

 

However once inside the host organism, symbiotic zooxanthellae do not get fully digested. The ingestion through the water column is purely the means into the coral. Once inside, the symbiotic zooxanthellae quickly expand its colony through budding- splitting apart and becoming two separate algae.

The Relationship between Corals and Symbiotic Zooxanthellae

Symbiotic zooxanthellae are labeled as such because of the symbiotic relationship the algae forms with its host coral. It is a mutually beneficial relationship, with the symbiotic zooxanthellae undergoing photosynthesis which provide the coral with nutrients and energy, and the coral providing excellent protection for symbiotic zooxanthellae from predators and other environmental disturbances. The process of photosynthesis produces almost all of the energy levels required for a coral’s survival (over 90%), yielding carbon compounds that the coral uses to create its calcium skeletons. The symbiotic zooxanthellae cannot run rampant in a coral however. The coral is able to control overpopulation of symbiotic zooxanthellae by limiting its access to daylight and expelling superfluous algae cells.

Environmental Dangers to Symbiotic Zooxanthellae

Sometimes environmental stress can trigger the shedding of symbiotic zooxanthellae, although this process is not one that is beneficial to the host organism. Known as “coral bleaching” occurs, the number of symbiotic zooxanthellae decline rapidly, and the coral loses its coloring and takes on a glassy, white appearance. Such disturbances to the levels of symbiotic zooxanthellae can include overexposure to air during low tides or increased temperature of ocean water (i.e. global warming).

Without Symbiotic Zooxanthellae

 

Without symbiotic zooxanthellae, most coral will certainly die from nutrient insufficiency. In artificial environments, strict observance of water temperature should be maintained to prevent coral bleaching from occurring. Even slight changes in temperature (such as 1-2 degrees Celsius) from week to week could cause symbiotic zooxanthellae to be expelled from its host organism.