oceans and seas are the heritage of humanity, because they lived not only the majority of all known (and unknown) to science species of living beings.In addition, only in the gloomy depths of the sea water at times you can see these paintings, whose beauty often able to simply overwhelm even the most indifferent person.Look at the coral reef, and you will see that nature is many times greater than the creation of any talented artist.
What is it?
coral reefs called coral colonies that form sometimes really huge education, similar in size with rocks.
note that these corals, which can form reefs are Scleractinia, belong to the class Anthozoa, type Cnidaria.Single individuals form enormous colonies of polyps, and lime colony older individuals provide support for the development and growth of young animals.Contrary to popular belief, polyps are found at all depths, and not just in the shallows.So, beautiful black coral lives at such a depth, which does not penetrate no ray of sunshine.
But the real coral reef can be formed only by the species that live in shallow tropical seas.
Which reefs are there?
There are three main varieties: fringing, barrier and atolls.As you might guess, bordering variety found in the shallow waters near the coast.The most impressive formations are barrier reefs, which are similar to the breakwater.They are located along the coast of the mainland or larger islands.As a rule, they are very important.Firstly, there are millions of species of shelter living beings, and secondly, given the important role education plays in shaping the climate of the region, preventing the ocean currents.
biggest and well known is the Great Barrier Reef, which stretches for 2,000 kilometers, forming the eastern edge of the Australian continent.Others are not so significant and greater than its "relatives" are located along the coast of the Bahamas, as well as in the western Atlantic.
atolls - are small ring-shaped island.Their coast is protected by coral reefs, which form a natural barrier that prevents the strong tides and ocean currents to wash away the fertile layer of the land surface.Where did come from the reefs, what is the mechanism of their formation?
emergence of coral reefs
Since most polyps requires relatively shallow water, ideal for them is the presence of small and flat base, preferably located near the coast.However, many scientists believe that the conditions under which the formation of colonies of polyps, which varied.
So many atolls all signs had to be on top of the old volcano, but not everywhere traces of really high lava formations that could fully confirm this theory.The famous scientist Charles Darwin, traveling at no less famous ship "Beagle", engaged not only in the formation of the evolutionary view of the development of mankind.Along the way, he managed to make a lot of discoveries, one of which was an explanation of how the world came coral reefs.
«Reef" theory of Darwin
Suppose that arose in ancient volcano gradually increased due to the lava, which fell into the environment as a result of many eruptions.As soon as the surface of the ocean will be about 20 meters, there will be optimal conditions for the settlement of the top of the seamount corals.They begin to quickly build a colony, gradually completely altering the primary relief arising after the eruptions.
When the young coral reef reaches a critical mass, the volcano, the upper part of which had already been virtually destroyed, gradually begins to sink back to the ocean.As dive corals begin to grow more intense, and because the reef starts to become more massive, while remaining about the same level relative to the surface of the water.
Dynamic theory of the formation of
Near the reef starts to accumulate sand, most of which - a coral skeletons themselves, milled erosion and some kinds of sea creatures.Shallows becoming more riff eventually begins to protrude above the ocean surface, gradually forming the atoll.The dynamic model suggests that the rise of the colony of polyps above the water is due to the constant changes in the level of the World Ocean.
Many geologists and geographers of the time immediately became interested in this theory.If it is true, then every major coral reef had to carry the at least some remnants of volcanic core.
truthfully whether volcanic theory of the origin of reefs?
To verify this, in 1904 on the island of Funafuti in the Pacific was organized by the test drilling.Alas, the then existing technology have led to a depth of 352 meters, after which the work has been stopped and before the expected core scientists reach and could not.
In 1952, the Americans with the same aim to begin drilling in the Marshall Islands.At a depth of about 1.5 kilometers, scientists have found a layer of volcanic basalt.It has been proven that the reef was formed over 60 million years ago, when the colony of polyps settled on the top of an extinct volcano.Darwin once again proved to be right.
As varied reefs during periods of declining global sea level
known that the amplitude of oscillation of the ocean in different periods of reaching one hundred meters.The current level of stabilized only six thousand years ago.Scientists believe that 15,000 years ago the sea level was at least 100-150 meters below the present.Thus, all the coral reefs that were formed at that time, now there are 200-250 meters below the modern edge.After this mark polyps colony formation becomes impossible.
In addition, many of them former coral reefs (the photo is in the article), which were formed in more ancient times, and are at the present land.They were formed in those days, when the sea level was highest, and the ice caps at the poles of the earth did not exist.Note that between the ice ages polyps do not actually form a more or less significant colonies, as the water level too quickly changed.
particularly revealing in this respect, Egypt.Coral reefs in the Red Sea are sometimes at great depths, which are millions of years ago, there were the usual small sea bottom.
main components of a coral reef
To understand how specifically arranged colony of polyps, for example, consider the coast of Jamaica.At any photos of classic atoll first visible rising steeply from the depths of sand spit.Dark stripes are parallel atoll - it marks the destruction of coral that occurred in different geological periods due to changes in sea level.
Mariners this zone is determined by the breaker: even at night the noise of the surf, which is distributed long before the coast, warning of a reef.After the protected area begins the plateau on which the corals are opened at low tide.Oddly, but in the waters of the lagoon depth increases sharply, the colony of polyps in this area is not so developed, at low tide they remain under water.Land near the shore, which constantly opens at low tide, called the littoral.There is little coral.
largest and branching corals grow on the outer edges, which look into the open ocean.The greatest concentration of marine life is observed in the littoral area.By the way, anyone at all can be found by visiting the coral reef?Underwater Egypt and other popular tourist destinations so rich that you will run up your eyes!Yes, in the richness of the fauna of these places can not refuse.
underwater world of coral reefs
Scientists say only one Great Barrier Reef (which we have already discussed) inhabits almost two thousand species of fish!Can you imagine how many lives of worms, sponges and other invertebrates?
most colorful inhabitants are a wonderful coral reef fish - a parrot.The name they got for a specific type of "beak", which is a modified jaw plate.The jaws of these "parrots" are so strong that they can easily tear and grind the whole blocks of coral.
Since polyps are not too high in calories, these fish have to constantly eat.During the year one population can destroy several tonnes of coral.Digested their remnants are ejected to the outside environment in the form of sand.Yes, yes, "parrots" play an important role in shaping the amazingly beautiful beaches of pure white coral sand.
recognizable and colorful inhabitants of these places are hundreds of species of sea urchins.Their natural enemies - starfish - sometimes become perpetrators of the destruction of the reefs themselves.Thus, the star of the Crown of Thorns, who arrived on the Australian coast from another hemisphere, have destroyed almost 10% of the Barrier Reef!Because of this, oceanographers and fishery biologists around the world declared it a real war: the stars are caught and destroyed.
Past events do provide a certain effect, but because to date the underwater world of Australia is beginning to recover.
