Coral bleaching

Bleaching of coral stone blocks is referred to as coral bleaching, which can lead to subsequent death of the coral.

Corals are living organisms. They are among the cnidarians and settle in symbiosis with zooxanthellae, a type of algae, on a limestone layer that grows from year to year. If the zooxanthellae expelled by the coral, the coral colony loses its colors. This phenomenon can be localized, but also occur over a large area and is called coral bleaching. It occurs at high water temperatures.

Coral bleaching is not new and was already observed in the 1970s. At that time, however, the incident occurred only temporary and localized, after heavy rains or prolonged low water. But a decade later, it was observed worldwide. During the El Niño in 1998 coral bleaching in the Indian Ocean and the western Pacific occurred particularly strong. A large surface area, the temperature of the water was higher than months 1 to 3 ° C above the average. In the Maldives bleached at that time near the water surface 98% of the corals. Through the Global Warming is expected to be an increased incidence of coral bleaching.

Warming of the oceans

Corals live in a symbiotic relationship with zooxanthellae. The zooxanthellae provide the corals energy through photosynthesis. However, the zooxanthellae are sensitive to heat: If the water is too warm, these algae begin to produce toxins in the heat stress. This stresses the coral, because if they absorb these toxins, they die. Therefore, they come from the algae and it remains the white Kalkmantel in the cnidarians live. Without the zooxanthellae, the coral can hardly survive on their own. Because their growth is highly dependent on their plant symbionts. Return the zooxanthellae over a period of about eight weeks - this period is species specific - not back, die from the coral and are overgrown by algae.

It is increasingly common due to global warming in a persistent overheating of the oceans. Therefore the corals can not recover as usual in the past, quickly again. Additional factors, such as water pollution, overfishing and disease slow down the recovery. Whole reefs fall victim to coral bleaching and die off over a large area. The increased water temperature not only leads to coral bleaching, but also reduces the reproductive capacity of the coral that survived so far without prejudice.

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When corals die, species diversity is low and entire ecosystems can collapse: Some coral species may disappear and they need with them fish that depend of them as a food source or as a place to raise their young.

Fishermen lose their food source; Diving tourism as a source of income disappears as well as the protection from ocean waves.

Pay

The U.S. State Department in 2005 the value of the reefs in dollars per year is calculated and came to a " tourist " value of the Great Barrier Reef of $ 1.5 billion. The reefs off the Florida coast are $ 2.5 billion and in the Caribbean about 140 billion dollars worth.

In addition to the rainforests of the coral reefs are considered the most biologically diverse habitats in the world. So far, about 60,000 different species have been discovered in this habitat. However, there are more than 400,000 species suspected in the reefs, so here live more than a quarter of all known marine fish. The size of all reefs is estimated at 600,000 km ². For over 225 million years, there are coral reefs and are among the oldest ecosystems in the world.

The two most coral bleaching, 1998 and 2002, were approximately 50 to 60 % of all reefs of coral bleaching affected and died about 5%.

Rescue attempts

On artificial reefs such as sunken ships, airplanes, car tires or steel constructs new coral is trying to locate.

The artificial reef made ​​of car tires has been in the U.S. even developed into an environmental fiasco: The tires torn from their roots and destroyed healthy reefs. The artificial reefs in the Biorock technology, however, are very promising: The Licensed procedure was developed by the architect Wolf Hilbertz. The scientist Tom Goreau 1990 he founded the non-profit Global Coral Reef Alliance.

Furthermore, here is the very dedicated Reef Ball Foundation to call. The organization was founded by Todd Barber, after he developed a patented process in 1993, with which one could use Riffbälle ( concrete structures) to Riffneubildung and for coastal protection.

Some states have established national parks in their coastal seas and banned all coral- damaging activities there.