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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 ...
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 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 ]
Slight increases in sea surface temperature can cause zooxanthellae to die. Coral hosts become bleached when they lose their zooxanthellae. Differences in symbionts, determined by genetic groupings (clades A-H), may explain thermal tolerance in corals. [5] Research has shown that some corals contain thermally-resistant clades of zooxanthellae.
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 ]
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.
Astrangia poculata, the northern star coral, is a temperate stony coral, widely documented along the eastern coast of the United States. The coral can live with and without zooxanthellae (algal symbionts), making it an ideal model organism to study microbial community