Once the algae leave, the coral loses its color or becomes "bleached," and is more susceptible to disease.
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They have a symbiotic relationship with the algae. When the coral expels the algae it becomes bleached or "completely white". This is called coral bleaching. The coral then become more vulnerable to disease and death.
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The eye is able to detect a visual stimulus when the photons (light packets) cause a photopigment molecule, primarily rhodopsin, to come apart. Rhodopsin, which is usually pink, becomes bleached in the process. At high levels of light, photopigments are broken apart faster than can be regenerated. Because a low number of photopigments have been regenerated, the eyes are not sensitive to light.
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The polyps of Favites complanata expand and extend their tentacles to catch plankton, but much of the nutritional requirements of this coral are met by the zooxanthellae housed within its tissues. These symbiotic unicellular dinoflagellates use photosynthesis to create organic molecules. In adverse conditions, such as when the coral is stressed by high temperatures, the zooxanthellae may be expelled and the coral becomes bleached and white. Bleaching occurs in this species when the water temperature rises above .
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Variations outside the normal range of these parameters may make the corals less able to grow and reproduce successfully. Of themselves these variations may be insufficient to kill the corals, but they make them more susceptible to disease organisms. The main factor that causes stress to the corals is climate change, with an increase in sea temperatures, particularly affecting shallow-water corals in the tropics. One of the consequences of heat stress is that the coral expels its zooxanthellae and becomes bleached.
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Hipposideros cervinus is a medium-sized hipposiderid with two lateral leaflets on its nose leaf. Noseleaf is greyish pink, ears triangular. Pups are dark gray in coloration, maturing to a dark brown in adults which often becomes bleached over time, turning a bright orange colour due to the ammonia from droppings in communal roosts. The nose-leaf distinguishes the species by its squarish outline which is broader at the lower part, below the nostrils, where small leaflets extend from either side of this structure.
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A Podzol with a characteristic eluvial (bleached, ash-colored) horizon and intensely coloured illuvial horizons. The photo was taken in the Feldberg area, Southern Black Forest, Germany. Podzolization (or Podsolization) is complex soil formation process by which dissolved organic matter and ions of iron and aluminium, released through weathering of various minerals, form organo-mineral complexes (chelates) and are moved from the upper parts of the soil profile and deposit in the deeper parts of soil. Through this process, the eluvial horizon becomes bleached and of ash-grey colour.
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This type of soil, the topsoil of which becomes bleached as a result of continual waterlogging, is often formed on sand-rich material over dense, sandy-loamy to silty-clayey subsoil - also called Sandkerf in German - in cool, moist climatic zones. As a result of frequent waterlogging throughout the seasons at low temperatures, minerals like iron and magnesium are released and deposited in sandy topsoils to the sides. Where the soil is saturated all-year round it turns into bog stagnogley and, eventually, into bog. Examples, known as missen occur in the Black Forest in Germany.
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