What are barrier coral reefs near. See what "RIF" is in other dictionaries. Significance of corals and coral reefs
What are Coral reefs? Coral reefs are an amazing form of life that occurs only in the warm seas of our planet. They need intense sun to grow and develop. all year round. They are very sensitive to cold. Therefore, they occur only in areas around and between two tropical circles and only in places where there are warm ocean currents.
In addition to plenty of sunlight and warm water, corals also need shallow water to thrive. They appear at a depth of about 40 meters. If you see them deeper, then this will be an exception. They often form colonies near volcanic islands.
When volcanoes die out and begin to sink, the coral reef retains its integrity and even continues to grow in height.
Sometimes coral rings that form around volcanic islands emerge above the surface of the ocean and so-called atolls are formed.
Corals accumulate not only around volcanic islands, but also around seamounts that are below the surface of the water or close to it. They are also found around continental coasts, but need the right conditions.
How are they formed and how do they affect the environment? These strange creatures extract calcium carbonate from sea water. Then they turn it into a varovik.
It forms a hard coral part. Over hundreds and even thousands of years, this calcium carbonate forms a coral reef. The formed reef is very attractive to hundreds of large and small fish that compete with each other for the most enticing territories.
It's no secret that the biodiversity of coral reefs is the same, and sometimes even greater, than that of tropical forests.
It is believed that corals are painted in 300 or 400 colors. Such a variety of colors and shades has seriously affected the marine animals that live among the reefs.
Fish and other sea creatures try to be inconspicuous, either to easily capture prey or to hide more effectively from predators.
Where are corals found? Corals are heat loving creatures. Widespread in tropical waters where warm ocean currents pass. They thrive best at temperatures between 25°C and 30°C.
The largest coral reef on the planet, which extends for a distance of 2030 kilometers along the northeast coast (state).
Near northern and western Australia there are also coral reefs, although not as large. The countries of Southeast and South Asia also boast a large variety of corals.
There is a very large variety of corals on the continent of North America and especially in the Caribbean. Unfortunately, they are seriously threatened by the rapid pace of development of the tourism industry.
The Caribbean has the second largest coral reef on the planet. North America also has the most remote coral reef. It is located in shallow water around .
The reason for the existence of coral reefs at a great distance from the tropics that passes here warm current. The only continent where there are no corals and coral reefs is Europe, because it is the most distant from the tropics.
Very attractive with their incomparable beauty of the coral islands and reefs that are scattered in the water of the southern part of the South Pacific. probably the most beautiful place on the planet with beautiful coral reefs.
Why are corals and reefs such a powerful engine of the tourism industry? Corals with their beauty are very valuable among divers and underwater adventure lovers.
Indeed, one dive among the waters of the Great Barrier Reef, for example, cannot be compared with anything else.
An interesting fact is that in places where there are coral reefs near the coast, large ocean waves break inside the sea and thus in the shallow water of the coast there is always clean and calm water with a characteristic azure color.
In addition, in places where coral reefs, under the influence of sea waves, old corals are broken into a very fine powder, which is gradually layered along the shore. As a result, white and fine sand are almost unchanged across the coral islands.
Who is the main enemy of corals? The most detrimental impact of the welfare of coral reefs is represented by people from their activities. The emissions they emit into the atmosphere through industrial development, and more specifically carbon dioxide, are very harmful to corals.
In principle, these creatures absorb carbon dioxide from the water, but when it exceeds certain limits, the corals begin to die and cannot absorb it.
On the contrary - the whole system is confused and they even separate additional quantities in the water, and from there into the atmosphere.
Due to poorly treated sewage, many coral reefs have already died. Such an example is found in the Caribbean.
The reason is found in the rapid development of tourism in this region. The blackest and ominous forecasts show that coral reefs will disappear completely by the 50s and 60s of the 21st century.
Many people do not pay serious attention to this, but in the end, life on our planet is interconnected and someday, if the harmful influence of man on nature is not stopped, it will take revenge on him.
In recent decades, we have seen massive bleaching of coral reefs. This should serve as a sign to people that something is wrong with the system and it is time for a change.
The content of the article
CORAL REEFS, organogenic limestone structures located near sea level or at shallow depths in the coastal zone of tropical seas or in shallow warm seas. They are massive deposits of calcite (limestone) formed from the skeletal remains of some colonial marine organisms - plants and animals - among which madrepore corals and coralline algae stand out. In addition to these two dominant groups of reef-forming organisms, the proportion of other animal and plant species, such as mollusks, sponges, foraminifera, and some green algae, is also significant in the composition of reefs.
Major reef builders the best way develop at depths of no more than 50 m, in clear water of normal salinity with a temperature of at least 20 ° C, abundantly saturated with dissolved gases and the smallest organisms (plankton) that serve them as food. A slight growth of reef corals can occur up to a depth of penetration of sunlight - up to a maximum of 185 m, but almost no limestone is formed below 120 m. The rather wide distribution of reefs within tropical and subtropical shallow waters is interrupted where cold currents pass (for example, along the western coast of South America) or turbidity of the water prevents their growth.
Structure.
The modern coral reef can be considered as a well-organized biogeocenosis. It is unlikely that corals would be able to build reefs if there were not extremely favorable conditions, because corals are very fragile and have a large surface area, which is affected by waves that tend to break and crush them. However, coralline algae, which form a calcareous crust, grow abundantly on the surface of corals and in the spaces between them, especially where the wave action is strongest and the water is most saturated with dissolved gases. They form a continuous, smooth, extremely dense and durable coating, excellent for cementing corals.
Best of all, corals and algae grow along the periphery of the reef and on its outer slopes. On the reef platform, a small water column, warming up, becomes depleted in gases; in addition, silt accumulates there. At low tide, the reef surface is exposed, which is deadly for corals. Some types of corals and algae (especially green algae Halimeda) under such conditions produce less lime. In addition, on the reef platform, waves raise silty sandy sediments from the bottom, consisting of finely crushed limestones and organic remains. Abrupt changes in temperature lead to the dissolution and precipitation of calcium carbonate, which fills and compacts the interior of the reef. The accumulation of debris and coral sand often continues above sea level, forming coral islands. A significant part of the coral sand is sometimes made up of foraminifera shells. In the relatively shallow, calm waters of the lagoons, the growth of some coral and algae species also lead to lime accumulation. At the bottom of individual lagoons, a large number of destroyed algae skeletons accumulate Halimeda. In other lagoons, fantastically beautiful underwater forests of branching "coral trees" and columns called coral heads grow. However, usually lagoons are not filled with clastic material, since, in all likelihood, finer material is carried out to the open sea by tidal currents.
Types.
There are three main types of interconnected coral reefs: fringing, barrier and atolls.
Fringing, or coastal, reefs
usually located along a recently exposed (drained) or stable coast. Such a reef is a terrace-like platform at sea level or somewhat below it, extending from the shore and often ending in an elevated edge, strongly indented by channels, from which the reef slope drops rather steeply into the water, and then abruptly breaks off to great depths. Corals grow fastest on the outer slope of the reef and very slowly on the shallow platform.
barrier reefs
like borders. They often surround individual islands, but are located at some distance from the coast, separated from it by a strait or a calm, medium-deep lagoon. The largest and best known is the Great Barrier Reef, a complex reef system stretching over 1,600 km along the east coast of Australia.
atolls
- These are usually ring-shaped reefs surrounding lagoons, inside of which there are no land areas. They are ring-shaped with an inner shallow lagoon; annular with one or more ring breaks through which tidal waters enter the lagoon; in the form of a half ring, a quarter ring or annular, flooded during high tides; or in the form of giant rings, consisting of individual small atoll-like reefs, fringing huge lagoons.
transitional forms.
Three types of reefs give rise to many transitional forms. A fringing reef near one part of the shore may further merge into a barrier reef, and their boundary is difficult to distinguish. Some islands could actually be considered atolls, if it were not for the presence of one or more dissected massifs of volcanic rocks in the center of the reef ring. Submerged (submerged) reefs serve as indicators of submerged platforms located near the water surface, which promote coral growth, but are more likely to be submerged atolls or islands.
Origin of coral reefs.
A coral reef can form in any tropical or subtropical water where the depth, temperature, and salinity allow reef-building organisms to thrive. Thus, the genesis of fringing reefs in shallow waters surrounding islands and continents is fairly obvious. However, the specific forms of atolls and barrier reefs have given rise to endless discussions and reasoning about their origin. There are many hypotheses, but none of them is recognized as completely satisfactory in explaining the conflicting geological facts.
Charles Darwin was the first to note that if a barrier reef did not surround a high island, it would be a real atoll. His observations on several coral reefs, and especially on the Cocos (Keeling) Islands (southwest of Sumatra), suggested that fringing reefs, barrier reefs, and atolls may represent different stages of the same process. He argued that if the entire coral structure was sinking at a speed not exceeding the growth rate of corals, then a barrier reef would form from the fringing reef, and if further subsidence continued until the island inside it was under water, then from the barrier reef reef would form an atoll. The atolls are characterized by a calmer water regime, and the former barrier reef in such conditions receives less dissolved gases and less abundant food for corals in the form of plankton, hiding from the ocean waves behind it. This shortage will result in slower growth of reef-forming corals on the inside of the atoll, and thus a lagoon is formed. To explain the huge number of atolls, Darwin assumed that large swaths of the seafloor had subsided in the recent past. When this theory, later called the immersion theory, was first published, it was widely accepted and was seen as a triumph of deduction.
However, this theory of Darwin was not long accepted as true, and a series of alternative hypotheses was put forward to replace it. K. Semper and H. Guppy believed that reefs grow on rising grounds. Other researchers (including J. Reine, J. Murray, W. Wharton, and F. Wood-Jones) thought that atolls were formed by coral growth on submerged banks, an idea revived this century in J. Hoffmeister's antecedent platform theory. and G. Ladd, who, after a long and careful study of the raised reefs of the Fiji Islands, prove that modern reefs grow on pre-existing underwater platforms. The origin of banks, or platforms (small underwater plateaus), was explained in its own way in each theory. Semper, Murray, and Wharton believed that lagoons formed as a result of the dissolution of limestone in marine environments or within flat limestone islands. S. McNeil revived this idea and put forward a number of evidence in its favor, obtained as a result of the study of uplifted coral islands. Older versions of these theories, other than those proposed by Hoffmeister, Ladd, and McNeil, developed until the concept of changing sea levels was widely accepted.
In 1910, R. Daly suggested that the effect of sea level rise, which occurred as a result of the melting of the Pleistocene ice sheets, is similar to the result of sinking earth's crust. Based on this assumption, he developed the theory of glacial control, which dominated all subsequent discourse on the genesis of atolls. He assumed that during low sea levels, the leveling of the islands occurred everywhere, but when the sea level rose again, these flat banks became the foundations of the atolls. In a series of articles culminating in a book The problem of coral reefs (The Coral Reef Problem, 1928), W. Davis combined the theories of Darwin's sinking and Daly's glacial control and put forward a more plausible theory, confirmed by many geological facts.
From the very beginning of research, in order to find out what is under the coral reefs, the idea arose to drill the entire thickness of the coral structure. E. Belcher was the first who tried to implement it in 1840 on the Khao Atoll on the Tuamotu Islands. At a depth of 14 m, which the primitive drill managed to pass, he found nothing but corals. In 1896-1898, a group funded by the Royal Scientific Society and the government of New South Wales (Australia) made a series of determined attempts to drill a well to the foundation of Funafuti atoll (Tuvalu). In this way, it was possible to reach a depth of 340 m in a homogeneous layer of coral limestones. This borehole, penetrating far below the maximum depths of possible growth of reef-building organisms, was considered by some researchers as sufficient proof of the subsidence theory. Other scientists believed that since the drilling was carried out on the periphery of the reef, the hole passed only a layer of detrital material that crumbled and accumulated on the outer slope of the island. They refused to consider the borehole as definitive evidence of subsidence. But later it was confirmed by Japanese scientists who drilled a 432 m deep well on the uplifted atoll of Kito-Daito-Shima in the eastern part of the Ryukyu Islands. This well also did not reach the underlying bedrock of the atoll.
Seismic data from the atomic bomb test at Bikini Atoll in 1946 also indicate that the limestone extends to great depths. In 1947, several wells were drilled in Bikini, one of which, at a depth of 779 m, penetrated exclusively limestone and reached Early Miocene deposits, which are approx. 25 million years. A study of the reflection of seismic waves, carried out by the expedition of the second research vessel Challenger in 1951, showed that the limestones on the Funafuti and Nukufetau atolls (Tuvalu Islands) have a thickness of approx. 600 m and possibly lie on volcanic rocks. And finally, in 1954, two boreholes on Eniwetok Atoll (Marshall Islands) penetrated Eocene limestones (about 50 million years old), which at depths of 1266 and 1405 m are in contact with bedrock basalts - rocks of volcanic origin. Judging by the thickness of limestone deposits, the formation of the Funafuti and Nukufetau atolls is explained by the gradual lowering of the coral structure below sea level (or significant fluctuations in sea level). Basalts under the Eniwetok Atoll testify to the volcanic genesis of its base. Thus, it is highly likely that the most common way atolls formed was through the subsidence of volcanic islands.
Interesting discoveries on the seabed a large number flat-topped seamounts (called guyots), similar to deeply submerged atolls. Shallow corals were recovered from at least one of them.
Finally, it appears from a review of the fossil reef literature that reef formation occurred mainly during those geologic epochs when weak crustal subsidence (or slow sea level rise) predominated. During geological periods characterized by the uplift of coral structures or their rapid subsidence, reefs hardly developed.
Coral reefs are the equivalent of underwater forests. Twenty-five percent of all marine life lives in coral reefs. The combination of plant life and colorful marine fish makes these sites a favorite diving spot for scuba divers. Large coral reefs, such as the Great Barrier Reef, are actually made up of many smaller reefs that are connected into a single ecosystem.
Reed Bank
This reef is located in the Philippines, its area is 8.866 square kilometers. This wonder of nature is located in the South China Sea.
Chagos Archipelago
The Chagos Archipelago in the Maldives covers an area of 12,000 sq. km. It is the second largest atoll in the world.
Saia de Mala
Saia de Mala in Indian Ocean covers an area of 40,000 square kilometers. These are the largest flooded banks in the world. This ridge connects the Seychelles and Mauritius along the Mascarene Plateau. Along with its coral reefs, the marine habitat includes pastures for green turtles and breeding grounds for blue whales. 
Zongsha Islands
Located in the South China Sea. This atoll is 80 kilometers long and covers an area of 6,448 square kilometers. This atoll is a disputed territory between the People's Republic of China, Taiwan and the Philippines. 
Reef Andros
Andros is a barrier reef in the Bahamas that stretches for more than 200 kilometers. The island lies along the edge of an oceanic crevice known as Ocean's Tongue. The reef widens down along the crevice to a depth of 6,000 feet instead of lying flat along the ocean floor. 
Florida reef
This is a reef system around the coast of Florida that extends from the Atlantic Ocean into the Gulf of Mexico near Key West. This reef system is approximately 7,000 years old and is 322 kilometers long. 
mesoamerican reef
The Mesoamerican Barrier Reef System extends along the east coast of Central America. From its northern point - the Yucatan Peninsula in Mexico, to the southern coast of Honduras, the reef reaches a total of 943 kilometers. 
Barrier reef of New Caledonia
This coral reef is almost 1,500 kilometers long and is located near the former French colony of New Caledonia in pacific ocean. Some parts of the reef have been damaged by nickel mining, but overall the health of this reef is quite normal. 
red sea reef
Coral reef of the Red Sea from the coasts of Egypt, Israel and Saudi Arabia approximately 5,000 - 7,000 years. Ten percent of the 1,200 species found on this reef live in this area alone. The Red Sea coral reef includes the Dahab Blue Hole, one of the most popular and dangerous dive sites in the world. 
Great Barrier Reef
The largest and most famous coral reef is the Great Barrier Reef. Over 2,500 kilometers long, it covers an area of 348,000 square kilometers and is home to more than 400 marine species. It is also one of Australia's most prominent tourist attractions. Unfortunately, the reef is under threat from pollution and fishing. 
The oceans and seas are the property of mankind, since not only most of all species of living beings known (and unknown) to science live in them. In addition, only in the gloomy depths of sea waters can one sometimes see such pictures, the beauty of which can sometimes simply stun even the most indifferent person. Look at the coral reef and you will see that nature is many times superior to the creation of any talented artist.
What it is?
Coral reefs are called colonies of corals, which sometimes form really gigantic formations, similar in size to rocks.
Note that the true corals that can form reefs are Scleractinia, belonging to the class Anthozoa, phylum Cnidaria. Single individuals form giant colonies of polyps, and the calcareous colonies of older individuals provide support for the development and growth of young animals. Contrary to popular belief, polyps are found at all depths, not just in shallow water. So, the most beautiful black coral lives at such a depth that not a single sunbeam penetrates.
But a real coral reef can only be formed by those species that live in the shallow waters of tropical seas.
What reefs exist?
There are three main varieties: fringing, barrier and atolls. As you might guess, the fringing variety is found in shallow water near the coast. The most impressive formations are barrier reefs, which look like a breakwater. They are located along the coast of the continents or large islands. As a rule, they are very important. Firstly, millions of species of living beings find refuge there, and secondly, these formations play an important role in shaping the climate of the region, preventing ocean currents.
The largest and most famous is the Great Barrier Reef, which stretches for 2000 km, forming the eastern edge of the Australian mainland. Other not so significant and large "relatives" are located along the coast of the Bahamas, as well as in the western part of the Atlantic.
Atolls are small ring-shaped islands. Their coast is protected by coral reefs, which form a natural barrier that prevents strong tides and ocean currents from washing away the fertile layer from the land surface. Where do reefs come from, what is the mechanism of their formation?
The emergence of coral reefs
Since most polyps require a relatively shallow water environment, it is ideal for them to have a small and flat base, preferably close to the coast. However, many scientists believe that the conditions under which the formation of a colony of polyps is possible are much more diverse.
So, many atolls, by all indications, should have arisen on the tops of old volcanoes, but traces of really high lava formations that could fully confirm this theory have not been found everywhere. The famous scientist Charles Darwin, traveling on the no less famous Beagle ship, was engaged not only in the formation of an evolutionary view of the development of mankind. Along the way, he managed to make many discoveries, one of which was the explanation of how the world of coral reefs arose.
"Reef" theory of Ch. Darwin
Suppose that a volcano that arose in antiquity gradually increased due to lava, which fell into the external environment as a result of numerous eruptions. As soon as about 20 meters remain to the surface of the ocean, there will be optimal conditions to populate the top of the seamount with corals. They begin to rapidly build up the colony, gradually completely modifying the primary relief that arose after the eruptions.
When a young coral reef reaches the volcano, the upper part of which by that time had already practically collapsed, begins to gradually sink back into the ocean. As you dive, the corals begin to grow more intensively, and therefore the reef begins to become even more massive, remaining approximately at the same level in relation to the surface of the water.
Dynamic formation theory
Sand begins to accumulate near the reef, most of which is the skeletons of the corals themselves, ground up by erosion and some types of sea creatures. There are more and more shallows, the reef eventually begins to protrude above the surface of the ocean, gradually forming an atoll. suggests that the rise of a colony of polyps above the surface of the water is due to a constant change in the level of the World Ocean.
Many geologists and geographers of that time immediately became interested in this theory. If it is correct, then every large coral reef must have carried at least some remnants of the volcanic core.
Is the volcanic theory of the origin of reefs true?
To test this, in 1904, test drilling was organized on the island of Funafuti. Alas, the technologies that existed at that time made it possible to reach a depth of only 352 meters, after which the work was stopped, and scientists could not reach the alleged core.
In 1952, the Americans began drilling in the Marshall Islands for the same purpose. At a depth of about 1.5 kilometers, scientists found a layer of volcanic basalt. It has been proven that the coral reef was formed over 60 million years ago when a colony of polyps settled on top of an extinct volcano. Darwin was right once again.
How did reefs change during periods of sea level decline?
It is known that the ocean different periods reached one hundred meters. The current level stabilized only six thousand years ago. Scientists believe that 15 thousand years ago, the ocean level was at least 100-150 meters lower than today. Thus, all the coral reefs that formed at that time are now 200-250 meters below the modern edge. After this mark, the formation of polyp colonies becomes impossible.
In addition, often former coral reefs (there is a photo in the article), which were formed in even more ancient periods, are also found on the current land. They formed at a time when the ocean level was at its highest, and there were no ice caps at the Earth's poles yet. Note that between the ice ages, the polyps actually did not form any significant colonies, since the water level changed too quickly.
Egypt is especially indicative in this regard. Coral reefs in the Red Sea are sometimes found at great depths, which a few million years ago were the bottom of ordinary shallow seas.
The main components of a coral reef
To understand how a polyp colony is specifically arranged, for example, consider the coast of Jamaica. In any photo of a classic atoll, a sandbar rising steeply from the depths is first visible. The dark stripes running parallel to the atoll are traces of coral destruction that occurred at different times due to ocean level fluctuations.
Sailors determine this zone by breakers: even at night, the sound of the surf, which is heard long before the shore appears, warns of the presence of reefs. After the protected zone, a plateau begins, on which the corals open at low tide. Oddly enough, but in the water area of the lagoon, the depth increases sharply, the colonies of polyps in this area are not so developed, at low tide they continue to remain under water. The area near the coast, which is constantly open at low tide, is called the littoral. There are few corals.
The largest and most branched corals grow on the outer edges that face the open ocean. The highest concentration of marine life is observed in the littoral region. By the way, who can you meet when visiting a coral reef? The underwater world of Egypt and other popular tourist countries is so rich that your eyes will run wide! Yes, you can’t deny the richness of the fauna to these places.
The underwater world of coral reefs
As scientists say, only one Great Barrier Reef (which we have already talked about) is home to almost two thousand species of fish! Can you imagine how many worms, sponges and other invertebrates live there?
The most colorful inhabitants are amazing coral reef fish - parrots. They got their name 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 off and grind entire blocks of coral.
Since polyps are not very high in calories, these fish have to constantly eat. In a year, one population can destroy several tons of corals. Their digested remains are released into the external environment in the form of sand. Yes, yes, "parrots" play an important role in the formation of amazingly beautiful beaches of white coral sand.
Recognizable and colorful inhabitants of these places are also hundreds of species. Their natural enemies - - sometimes become the culprits of the destruction of the reefs themselves. So, the star Crown of Thorns, which arrived on the Australian coast from another hemisphere, has already destroyed almost 10% of the entire Barrier Reef! Because of this, oceanologists and ichthyologists around the world have declared a real war on her: the stars are caught and destroyed.
The measures taken still give a certain effect, and therefore, today the underwater world of Australia is beginning to recover.
Coral reefs are large underwater formations consisting of the skeletons of coral polyps, which are marine invertebrates. A squad of reef-building coral polyps called stony or stony corals extract calcium carbonate from seawater and create a hard, durable exoskeleton to protect their soft, baggy bodies.
Each individual coral is called a polyp. The new coral polyps live on the calcium carbonate exoskeletons of their ancestors, and after death they add another exoskeleton to the existing structure. Over the centuries, the coral reef grows with each new polyp and over time becomes a large and visible structure underwater.
Corals can be seen everywhere from the Aleutian Islands off the coast of Alaska to warm tropical waters. caribbean. The largest coral reefs can be seen in the clear, shallow subtropical and tropical ocean waters, where they grow rapidly. The length of the largest of the coral reef systems, the Great Barrier Reef of Australia, exceeds 2,400 kilometers.
coral life
According to the non-profit environmental organization Coral Reef Alliance (CORAL), there are hundreds of species of corals in the world. Corals come in many shapes and colors, from round and curled brain corals (brain corals), which resemble the human brain, to tall, elegant eight-pointed Muricea corals (sea whips) and sea fans (sea fans), which look like intricate, brightly colored corals. trees or plants.
Pictured: Stunning new coral species in Polynesia.
Corals belong to the type of cnidarians (Cnidaria). This group also includes jellyfish, anemones, Portuguese man o' war and other marine animals. Although each individual animal is considered a polyp, corals are often described as colonies of thousands of polyps.
Corals feed in two different ways: some species can catch small marine organisms such as fish and plankton using stinging tentacles on the outer edges of their bodies. However, according to the Agency for Protection environment United States (US Environmental Protection Agency (EPA)) most corals maintain a symbiotic (mutually beneficial) relationship with marine algae known as zooxanthellae (zooxanthellae).
These algae live inside the body of the coral polyp and, through photosynthesis, produce food for themselves and for the polyp. The polyps, in turn, provide the algae with a home and carbon dioxide. In addition, zooxanthellae give corals their vibrant colors - most coral polyp bodies are transparent and colorless.
Some coral species, such as brain corals, are hermaphrodites and produce both eggs and sperm at the same time. They breed in mass coral spawning, which in some species occurs only once a year on a certain night.
Other species, such as the elkhorn coral, are dioecious and form all-female or all-male colonies. Among these coral colonies, all polyps in one particular colony produce only sperm. To continue the breeding process, they rely on a neighboring colony that produces only eggs.
Photo of corals taken on a reef behind Ofu Island, home of the American Samoa National Park.
coral reef world
Most of the significant coral reefs that exist today began to form 5,000-10,000 years ago, according to CORAL. These formations mainly exist in warm, shallow waters, where sufficient sunlight penetrates, which is necessary for algae, which provide food for coral polyps.
Coral reefs cover less than 1 percent of the ocean floor - collectively they would cover an area of approximately 285,000 square kilometers, close to the size of the state of Nevada. However, they are among the most productive and diverse ecosystems on earth.
Approximately 25 percent of all known marine species depend on coral reefs for food, habitat and reproduction. Corals are sometimes referred to as the "rainforests of the sea" because of their biodiversity. They are home to over 4,000 fish species, 700 coral species, and many thousands of other plants and animals.
However, according to experts, their lives are in imminent danger.
Coral reefs in danger
According to scientists at the Hopkins Marine Station at Stanford University, coral reefs are vital marine environment habitat on which many species of ocean animals depend. In addition, they provide people with direct economic benefits of approximately 30 billion annually through food, fisheries and tourism.
However, coral reefs are threatened by several dangers at once. The first danger is the growing acidification of the ocean environment, caused by the fact that the oceans absorb a huge amount of carbon dioxide(CO2) released into the atmosphere from the combustion of fossil fuels. This limits the ability of corals to produce the calcium carbonate exoskeletons they depend on for their habitat.
Water pollution also negatively affects corals. Agricultural pesticides and fertilizers, oil and gasoline, sewage discharges and soil spills from eroded land into the ocean are disrupting the delicate relationship that exists between the plants, corals and other animals that make up the reef ecosystem.
As ocean temperatures rise due to global warming, coral polyps are rejecting the zooxanthellae they depend on for food. As soon as the zooxanthellae disappear, the corals also lose their bright colors, and all that remains of them is a white exoskeleton. This process is called coral bleaching. According to the non-profit environmental organization Coral Reef Alliance (CORAL), corals that have undergone bleaching usually die off.
In addition, fishing activities such as cyanide fishing (which uses cyanide to make fish easier to catch), explosive fishing, and overfishing with trawlers can destroy thousands of years of coral in minutes. reef.
“Overfishing, ocean acidification and ocean pollution are slowly killing coral reefs,” said Roger Bradbury, an environmentalist at the Australian national university(Australian National University), located in Canberra (Canberra), in an interview with the New York Times. “Each of these factors individually is quite capable of causing the destruction of coral reefs around the world, but in combination this destruction is guaranteed.”
