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Sep 30, 2018

Coral Bleaching

Coral Bleaching
Coral Bleaching

About Coral Bleaching

Coral reefs are found in shallow tropical waters with circumtropical islands along the coast of the islands and continents. The reef substrate is mainly made of live and dead calcareous carbonate from the scalactinic coral. Many other modifiers, vertebrae, and plants live close to the scalactinian coral, with tight resource coupling and recycling, allow highly high productivity and biodiversity of coral rocks, such as the 'tropical rainforests of the oceans' Is known in. .

Corals are very nutritious to live in poor water and there are some areas of water temperature, salinity, UV radiation, ambiguity and tolerance of nutrient amounts.

Scalactinians make skeletal calcium carbonate, indexed by coral water. When coral polyp dies, it is included in the skeleton reef framework.

Scleractinial corals are in Fillium Sinarias, and they receive their nutrients and energy resources in two ways. They use the traditional cnidarian tactics to capture small planticonic organisms with their nematocyst capped tankclues as well as a responsible symbiotic relationship with a single cell algae, which is known as Zooxenthale. Zooxanthellae Phylum Dinoflagellata has various tax-related autorophic microalgaes.

Zooxanthellae live symbiotically within coral polyp tissues and assist the coral in nutritious production through its photosynthetic activities. These activities provide energy with fixed carbon compounds for energy, increase calibration, and mediator elements provide mediators in nutrients. In turn the Host Coral Polip provides its zooxoxhethe to live with a safe environment, and provides a steady supply of carbon dioxide for its photosynthesis processes. The symbiotic relationship allows slow-growing corals to compete with fast-growing multicellular algae because the tight coupling of resources and the fact is that corals can feed through photosynthesis and through prognosis until night.

Coral tissue is not really the beautiful color of the coral reef, but it is rather obvious. Coral receives its color from Zoxanthheel living within its tissue.

Coral Reef ecosystems worldwide have been under unprecedented deterioration in the past few decades. Anthropogenic and natural phenomena are involved in the impact of coral reefs. Recently, the quick coral reef fall is mostly related to the anthropological effects (overexploitation, overfishing, increased sediment and nutrient overload.) Natural disturbances that damage coral rocks include violent storms, floods, high and low temperatures, extremes of el Nino Oscillation (Inso) events, suburban exposure, violent outbreaks and epizootics.

Coral Reef Bleaching is a common stress reaction of coral for various disturbances mentioned above. In the early 1980s, the frequency and widespread distribution of bleaching incidents of reported coral reefs increased. Large scale bleaching, which includes major coral mold areas and as a result, the mass coral mortality has raised concerns about global warming, or events related to global events including climate change and ozone depletion, including UV radiation. This paper examines the reasons for coral reef bleaching and addresses the effect of global climate change on coral reefs.

There are approximately 400 species of coral on the Great Barrier Reef, and most of them have a symbiotic relationship with zoxenthhely algae - a micro plant that lives inside coral tissue, which provides corals for up to 90% of the energy requirements.

Like most plants, zoxenthele photosynthesis - use sunlight to change water and carbon dioxide to carbohydrate (sugar) to feed your corals and sugars. This allows corals to grow faster than feeding on Planckton for food. Most of the coral skeleton is white - it is the zoxenthhele living inside the coral polyps tissue that looks at the rocks, brown, purple and other colors coral which we see on the rock.

Zooxanthellae ("feels like jelly"!) Are furious about the conditions of their living. They can not survive in cold water, this is the reason that coral reefs are found mainly in tropical (although some corals that can survive in cold dark waters - for example outside of Scotland and Norway - with them There is no connection with Zoxenthhele and with the Great Barrier Reef we grow very slowly to create a Reef system).

Unfortunately zooxanthellae do not like hot water. If the temperature of the ocean gets very hot, then algae develops heat-stress, and closes the production of carbohydrate. However, it starts to produce toxic waste products that leave the coral to poison until it rejects the zooxoxhente - it spreads in open water. When this happens, the coral becomes white, and it is known as "coral bleaching".

Bleached coral is not necessary. If the temperature of the ocean falls drastically, the coral will survive and within a few months, its zooxoxhetale will be fully recovered.

However, if the temperature of the sea is very long (it is impossible to normalize how high and how long it is possible because it depends on many variations, such as the special stress of zoxanthele, coral species and its geographical location etc.) Polyps may not be able to feed in the manner and eventually die, except for dead, white, calcium-carbonate skeleton.

The dead coral will eventually cover with other types of algae, which changes the species of fish and other animal species on the rock. The number of algae-eaten species (such as surgeon, fish, sea urchins) on the rock may increase, while coral species and even local extinction, along with coral dependent species (like butterfly) may also fall.

Bleaching can also occur (mainly on insulating rocks), especially when heavy rainfall (for example during cyclone), when sharp declines in salinity cause tension in algae. And other animals, such as anemones and clams, nadibrains and jellyfish, some of which also have a symbiotic relationship with zooxenthale, can also bleach.

There was severe bleaching worldwide in 1998 and 2006, which was warmer than the average sea temperature associated with El NiƱo events. These broad incidents are known as "mass bleaching". By 1979 only 3 large-scale bleaching incidents were recorded worldwide. In 2002 alone, large-scale bleaching programs of 400 events were recorded (UNEP) and large scale bleaching took place in every coral reef area of ​​the world by 2008.

The worst bleaching ever recorded with Great Barrier Reef (GBR) in 1998 and 2002. In 2002, 55% of corals on GBR were affected (GBRMPA). Between 1871-2005, the temperature of the water increased to 0.4 degree Celsius with GBR, and it has been predicted to increase 1.1-1.2 degree Celsius by 2050. Scientists are concerned that the rock will experience more and more serious episodes of bleaching large scale.

There are several factors that affect resistance and recovery from coral bleaching, and some rocks can be cured within a decade or two, others can never be cured. More emphasis is placed on a rock - for example, the effects of storm damage, pollutants, methods of destructive fishing, ocean acidification - low resistance and flexibility are likely to be bleaching.

The Great Barrier Reef Marine Park Authority has predicted the low risk of bleaching with the GBR for the summer of 2009-2010, although the conditions are in line with a weak El Nino phenomenon, and it is linked to the high potential of bleaching in the past.

What are the causes of coral bleaching ?

Since coral reef bleaching is a general reaction to stress, it can be induced alone or by various factors in combination. Therefore, it is difficult to clearly identify the reasons for bleaching incidents. The following stress has been implicated in coral reef bleaching incidents.


Coral species live within relatively narrow temperature margins, and unusually low and high sea temperatures can induce coral bleaching. Bleaching incidents occur during sudden temperature drops with severe waste episodes (5 to 10 days to -3 ° C to -5 ° C), seasonal cold wind outbreaks Bleaching is often reported by excessive water temperatures. During the summer season, a small positive anomaly of 1-2 degrees Celsius for 5-10 weeks usually inspires bleaching.

Inorganic nutrients

Due to coral reef bleaching, the increase in the fundamental nutrient concentrations (such as ammonia and nitrate) actually increases the density of zoxenthhele 2-3 times. Although the eutrophication zooxhenthale does not involve directly in damage, but it can have secondary adverse effects, such as reducing coral resistance and more sensitivity to diseases.


The loss of zooxenthale is in contact with coral when there is high concentration of various chemical contaminants such as q, herbicide and oil. Since the high concentrations of xenobiotics are required to induce zenocytale loss, bleaching from such sources is usually very localized and / or transient.


Relatively few examples of coral bleaching are completely connected to sediments. It is possible but has not been shown that sediment loading can make zooxanthellate species more likely to bleach.

Fresh water

Rapid weakness of rock water from the storm and runoff generated from the storm has been shown due to coral reef bleaching. Generally, such bleaching incidents are rare and limited to relatively small, adjacent areas.

What are the impacts of Coral reef bleaching  Globally ?

Due to coral reef bleaching, many of the Tanves are related to local environmental degradation and rock overexploitation. Of the stresses mentioned above, only the potential global factors in sea water temperature and solar radiation are driving changes and extremes. Global warming with the ENSO events, the temperature of sea water varies. Due to the lack of ozone, the amount of UVR reaches the Earth's surface, and possibly coral bleaching phenomena.

Sea temperature and solar radiation (especially UV radiation), either in different or in combination, have received considerable mass tension on the scale. In most cases, wherever the coral reef bleaching was reported, it was done during the summer season or at the end of the long warming period.

Coral bleaching occurred during low wind velocity, clear sky, calm ocean and low unrest, when conditions are in favor of high penetration of localized heating and short wave length (UV) radiation. At high temperatures, less oxygen is conducted than water. Potentially stressful high sea temperatures and UV radiation flows can cause Coral Reef bleaching globally, with estimated greenhouse warming and thin ozone layer.

Since the reef building corals live near their upper thermal tolerance limit, in few weeks, the temperature of the sea (.5 -1.5 ° C) in some weeks or more (3-4 ° C) increase in coral dysfunction and death Causes During the Caribbean-wide bleaching events that occurred during 1986-88, unusually high sea temperatures have been reported, due to the global warming effect on the coral reef in the region.

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