Coral Bleaching: Potential Mechanisms and Observed Adaptations :: Sea Coral Corals Ecosystem Papers

Coral Bleaching probable Mechanisms and Observed AdaptationsCoral reefs are the most biologically diverse nautical ecosystems. Driving this diversity are cnidarian corals which are obligate mutualistic symbioses surrounded by coral animals and dinoflagellate algae of the genus symbiodinium. These algae are commonly called zooxanthellae. This symbiosis among heterotrophic innkeepers and photosynthetic symbionts allows coral to thrive in nutrient sad seas and deposit calcium carbonate to build reefs (Toller et al. 2001, 348).Coral bleaching occurs when there is a loss of zooxanthellae from their coral host. This is accompanied by loss of a corals blueprint color that may or may non be noticeable to the human eye. Bleaching can lead to coral death when prolonged, although links amongst bleaching and subsequent coral recovery or death are not well known. Causes of bleaching have been observed to include salinity, exposure to air, and sedimentation. The primary reasons c ited to relieve oneself most instances of coral bleaching are increased sea temperatures and solar radiation. These dickens factors have been observed to cause the most damage in combining (Fitt et al. 2001, 51).The two figures of bleaching that result from organism damage or disturbance are algal-stress bleaching and animal-stress bleaching. Algal-stress bleaching is characterized by expulsion of individual zooxanthellae from a host carrell. Animal-stress bleaching is characterized by host cell detachment, which is expulsion of zooxanthellae from the coral animal along with the host cell they occupy. Radiation and temperature induced animal-stress bleaching and host cell detachment have not been observed in the field at current sea temperatures. This fictitious character of bleaching has only been observed under laboratory conditions (Fitt et al. 2001, 55). A third type of bleaching, physiological bleaching, occurs in an unstressed coral-zooxanthellae holobiont as a meth od of withdraw excess zooxanthellae from host cells. Zooxanthellae density within host cells varies eonally in this manner. Maximum zooxanthellae density is observed to occur during the coolest season with the lowest solar radiation. The minimum density is observed to occur at the end of the warmest season with the highest solar radiation (Fitt et al. 2001, 54).The temperature at which coral bleaching occurs has been observed to be from 30 to 34 degrees Celsius (Ralph et al. 2001, 163). Solar radiation exacerbates bleaching in this temperature range and can withal cause bleaching at normal temperatures when at sufficient intensity.