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Zooxanthellae (/ ˌ z oʊ ə z æ n ˈ θ ɛ l iː /; sg. zooxanthella) is a colloquial term for single-celled dinoflagellates that are able to live in symbiosis with diverse marine invertebrates including demosponges, corals, jellyfish, and nudibranchs.
Coral can survive short-term disturbances, but if the conditions that lead to the expulsion of the zooxanthellae persist, the coral's chances of survival diminish. In order to recover from bleaching, the zooxanthellae have to re-enter the tissues of the coral polyps and restart photosynthesis to sustain the coral as a whole and the ecosystem ...
Coral bleaching is the result of the loss of vital zooxanthellae; any of the stressors can cause bleaching. [14] The corals expel their symbionts because they are trying to get rid of any foreign bodies that might be causing them stress. Corals can survive up to a week without the zooxanthellae, but it is difficult. [15]
There is a symbiotic relationship between coral polyps and the photosynthesising algae called zooxanthellae, without which, neither would survive. When sea surface temperatures exceed approximately 29 °C or more, even for a couple of days, the relationship between the coral and its zooxanthellae becomes unbalanced. [ 5 ]
Symbiotic Symbiodiniaceae are sometimes colloquially referred to as Zooxanthellae, though the latter term can be interpreted to include other families of symbiotic algae as well. [7] While many Symbiodiniaceae species are endosymbionts, others are free living in the water column or sediment.
An increase of about 1 or 2 °C can cause the collapse of the relationship between coral and zooxanthellae, possibly leading to bleaching. [15] The average sea surface temperature in the Great Barrier Reef is predicted to increase between 1 and 3 °C by 2100. [ 6 ]
SST coupled with high irradiance (light intensity), triggers the loss of zooxanthellae, a symbiotic single cell algae that gives the coral its color and the coral's dinoflagellate pigmentation, which turns the coral white when it is expelled, which can kill the coral. Zooxanthellae provide up to 90% of their hosts' energy supply. [56]
The corallites are small and tightly-packed and give the coral a porous appearance. The polyps each have six tentacles and are generally retracted during the day. This coral is yellow, yellowish-green, pale grey or pale brown, a colour given to it by the dinoflagellate zooxanthellae, microscopic algae that live symbiotically within the coral's ...