Coral

As sessile corals (Greek Korallion ), called colony-forming cnidarians. The different groups of corals are not closely related to each other but belong to different taxa of cnidarians on. Best known are the stony corals, which have the primary role in the establishment of coral reefs. Another significant, species-rich group are the octocorals, including the soft, leather and tube corals, gorgonians and belong. The black corals are 150 species very much poorer in species. While the previously mentioned groups are flower animals, including the fire and the filigree coral to the class Hydrozoa.

In addition to the extant ( living today ) and Rugosa extinct corals are tabulata groups.

Biology / Natural Sciences

General

Corals occur exclusively in the sea, especially in the tropical belt. In view of the growth form, a distinction between soft corals and hard corals, the latter being formed by deposits of lime skeletons, created by the coral or a coral reef, as dead skeletal material is continually invaded by living tissue. Coral skeletons consist mainly of aragonite, the corals secrete from their basal disc or her ectoderm, to give the colony support. The individual skeletons are branched plant -like in general and to the ends of branches, the growth peaks, often are colorful polyps that mediate beyond the impression corals are undersea flowering plants.

( Fixed =) As with most sessile marine animals are also at coral to filter feeders, ie they feed by filtering out plankton, nutrients, and trace elements from the flow- rich seawater. Many of the corals that live near the water surface, but eat not alone by filtering plankton, but also (or even for the most part ) by endosymbionts, ie in the polyp cells embedded symbiotic algae called zooxanthellae, which also intensive cause color in the living tissue of the coral. These unicellular algae are involved with their photosynthetic metabolism seamlessly into the nutrient budget of the coral. Due to the amount of plankton, the size of the coral polyps vary greatly, therefore, a distinction between großpolypigen (LPS - Large Polyp Sclerantinia ) and small-polyp (Small Polyp Sclerantinia ), the polyp size of millimeter fractions varies up to several centimeters. Corals existed for over 400 million years ago; they help the geologists at Paläoklimarekonstruktionen (see also: Shed - age determination (biology) ).

Cold-water corals

In addition to the corals of the tropics there are also cold-water corals ( or deep sea corals), which have no zooxanthellae and live on only through the filtration of plankton. They are known only since the end of the 20th century and were in all oceans (including the Mediterranean, but not in the Black Sea, not the Baltic Sea) at depths of 40 (New England Seamount Chain) up to 3383 m ( North Atlantic ) at temperatures of 4 to 12 ° C demonstrated; but mostly they come in depths between 100 and 200 m in front under the wave of influence. Below the wave range, ie below 100-300 m and cold water corals are riffbildend and then offer as well as their relatives near the surface of a variety of wildlife habitat. About 4,000 species were detected in the cold-water coral reefs. Approximately 600 species of cold -water corals are known, 17 of which are capable of forming large reefs.

Reproduction

See:

• Propagation of the stony coral
• Propagation of octocorals

Endangering

The above-mentioned algae are very sensitive to temperature. Heats up the water too much, they start to produce toxins and are then repelled by the corals, whereupon they die immediately. The white Kalkmantel remains, hence the term coral bleaching. Due to global warming are more frequent and longer lasting to the " overheating " of the sea water. This runs an otherwise self-leveling coral bleaching, from which a coral can recover, serious and result in death. Another risk is that by the acidification of the oceans, taking a part of the anthropogenic emissions of carbon dioxide, which inhibits the formation of new carbonate shells. In addition, the discharge of sewage also appears to represent a factor for coral bleaching, since it could be increasingly observed in corresponding locations. The trigger coliform bacteria are suspected in the feces. Coral bleaching has destroyed many popular diving areas in recent years.

By deep sea fishing ( trolling and bottom trawling ) are threatened deep-sea corals; a negative influence of drilling platforms for oil or natural gas in the environment of cold-water coral reefs is not excluded. Transcontinental underwater cables for telecommunications also provide an element of threat See also: consequences of global warming

Protection

For several decades, enthusiasts like Wolf Hilbertz, Tom Goreau or the Global Coral Reef Alliance try to counteract the destruction of coral reefs. They create national parks in the seas and try artificial coral reefs to create and maintain dying reefs. Here, as the Riffball that Biorock technology, the sinking of ships, aircraft and vehicles, the variety of methods have been applied. An artificial reef of sunken tires ( Osborne Reef ) has developed in the U.S. for the ecological disaster.

Benefit

The calcareous skeletons of some axis octocorals and black corals are used for jewelery production. These terms can be shown to the prehistoric period. As a gemstone, the red precious coral is most desirable. Importantly however, the living coral as a breeding ground and nursery for many marine species. Here you can find protection from their enemies, and enough food. In the habitat of corals, there are about a quarter of all known marine fish.

Tradition, symbolism and iconography

Corals and coral branches were already used in ancient times for amulets. They were regarded as protection against diseases, lightning, and Miss growth. They were sacred in ancient Egypt of Isis in Rome and Venus. Rosaries of coral were very popular in Nachmittelalter. In Italian folklore, corals protect children against harm. Therefore, there are also many representations of the Infant Jesus with coral necklace and necklace with coral branch. In the Profanikonographie the coral necklace has become an attribute of childhood. In the story " The Leviathan " by Joseph Roth coral plays a central symbolic role.