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Resilience of coral reefs
The resilience of coral reefs is the biological ability of coral reefs to recover from natural disturbances such as storms and bleaching episodes.〔(Coral reef conservation program: Addressing key threats ) ''NOAA''. Retrieved 7 December 2011.〕 Resilience refers to the ability of biological or social systems to overcome pressures and stresses by maintaining key functions through resisting or adapting to change.〔Holling, C.S. (1973) ("Resilience and stability of ecological systems" ) ''Annual Review of Ecology and Systematics'', 4: 1–23.〕 Reef resistance measures how well coral reefs tolerate changes in ocean chemistry, sea level, and sea surface temperature.〔(Reef resilience toolkit model: Introduction ) ''The Nature Conservancy'' Retrieved 7 December 2011.〕 Reef resistance and resilience are important factors in coral reef recovery from the effects of ocean acidification. Natural reef resilience can be used as a recovery model for coral reefs and an opportunity for management in marine protected areas (MPAs).
== Thermal tolerance ==
Many corals rely on a symbiotic algae called zooxanthellae for nutrient uptake through photosynthesis. Corals obtain about 60-85% of their total nutrition from symbiotic zooxanthellae.〔Fujise, L., Yamashita, H., Suzuki, G., Sasaki, K., Liao, L.M., Koike, K. (2014) (Moderate thermal stress causes active and immediate expulsion of photosynthetically damaged zooxanthellae (''Symbiodinium'') from corals ) ''PLoS ONE,'' 9(12): 1-18.〕 Slight increases in sea surface temperature can cause zooxanthellae to die. Coral hosts become bleached when they lose their zooxanthellae. Difference in symbionts, determined by genetic groupings (clades A-H), may explain thermal tolerance in corals.〔Sampayo, E.M., Ridgway, T., Bongaerts, P., Hoegh-Guldberg, O. (2008) ("Bleaching susceptibility and mortality of corals are determined by fine-scale differences in symbiont type" ) ''PNAS Environmental Sciences,'' 105 (30): 10444–10449.〕 Research has shown that some corals contain thermally-resistant clades of zooxanthellae. Corals housing primarily clade D symbionts, and certain types of thermally-resistant clade C symbionts, allow corals to avoid bleaching as severely as others experiencing the same stressor.〔Berkelmans, R. and M.J.H. van Oppen (2006) ("The role of zooxanthellae in the thermal tolerance of corals: a 'nugget of hope' for coral reefs in an era of climate change" ) ''Proceedings of the Royal Society of London Series B'', 273: 2305–2312〕 Scientists remain in debate if thermal resistance in corals is due to a mixing or shifting of symbionts, or thermally resistant vs. thermally-sensitive types of zooxanthellae. Species of coral housing multiple types of zooxanthellae can withstand a 1-1.5°C change in temperature. However, few species of coral are known to house multiple types of zooxanthellae. Corals are more likely to contain clade D symbionts after multiple coral bleaching events.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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