Coral

For other uses, see Coral (disambiguation).
Orders
Scleractinia

Corals are gastrovascular marine cnidarians (phylum Cnidaria; class Anthozoa) existing as small sea anemone-like polyps, typically forming colonies of many individuals. The group includes the important reef builders known as hermatypic corals, found in tropical oceans, and belonging to the subclass Zoantharia of order Scleractinia (formerly Madreporaria). The latter are also known as stony corals in as much as the living tissue thinly covers a skeleton composed of calcium carbonate. A coral "head" is formed of many individual polyps, each polyp only a few millimetres in diameter. The colony of polyps functions essentially as a single organism by sharing nutrients via a well developed gastrovascular network, and the polyps are clones, each having the same genetic structure. Each polyp generation grows on the skeletal remains of previous generations, forming a structure that has a shape characteristic of the species, but subject to environmental influences.

The hermatypic corals obtain much of their nutrient requirement from symbiotic unicellular algae called zooxanthellae, and so are dependent upon growing in sunlight. As a result, these corals are usually found not far beneath the surface, although in clear waters corals can grow at depths of 60 m (200 ft). Other corals, notably the cold-water genus Lophelia, do not have associated algae, and can live in much deeper water, with recent finds as deep as 3000 m. Corals breed by spawning, with many corals of the same species in a region releasing gametes simultaneously over a period of one to several nights around a full moon.

Corals are major contributors to the physical structure of coral reefs that develop only in tropical and subtropical waters. Some corals exist in cold waters, such as off the coast of Norway (north to at least 69° 14.24' N) and the Darwin Mounds off western Scotland. The most extensive development of extant coral reef is the Great Barrier Reef off the coast of Queensland, Australia. Indonesia is home to 581 of the world's 793 known coral reef-building coral species.

Coral types

There are several other types of corals, notably the octocorals (subclass Octocorallia) and corals classified in other orders of subclass Zoantharia: to wit, the black corals (order Antipatharia) and the soft corals (order Zoanthinaria). Extinct corals include rugose corals and tabulate coral. These two groups went extinct at the end of the Paleozoic. Most other anthozoans would be treated under the common name of "sea anemone".

Geological history

Fossil coral Heliophyllum halli from the Devonian of Canada.

Although corals first appeared in the Cambrian period, some 570 million years ago, they are extremely rare as fossils until the Ordovician period, when Rugose and Tabulate corals became widespread.

Tabulate corals occur in the limestones and calcareous shales of the Ordovician and Silurian periods, and often form low cushions or branching masses alongside Rugose corals. Their numbers began to decline during the middle of the Silurian period and they finally became extinct at the end of the Permian period. The skeletons of Tabulate corals are composed of a form of calcium carbonate known as calcite.

Rugose corals became dominant by the middle of the Silurian period, and became extinct early in the Triassic period. The Rugose corals may be either solitary or colonial, and like the Tabulate corals their skeletons are also composed of calcite. The finest details of their skeletal structures are often well preserved, and such fossils may be cut and polished.

Coral skeletons in a zoological display

Scleractinian corals diversified during the Mesozoic and Cenozoic eras and are at the height of their development today. Their fossils may be found in small numbers in rocks from the Triassic period, and they are relatively common fossils in rocks from the Jurassic and Cretaceous periods as well as the Caenozoic era. The skeletons of Scleractinian corals are composed of a form of calcium carbonate known as aragonite. Although they are geologically younger than the Tabulate and Rugose corals, the aragonite skeleton Scleractinian corals does not tend to preserve well, so it is often easier to find fossils of the more ancient Tabulate and Rugose corals.

At certain times in the geological past corals were very abundant, just as modern corals are in the warm clear tropical waters of certain parts of the world today. And like modern corals their fossil ancestors built reefs beneath the ancient seas. Some of these reefs now lie as great structures in the midst of sedimentary rocks. Such reefs can be found in the rocks of many parts of the world including those of the Ordovician period of Vermont, the Silurian period of the Michigan Basin and in many parts of Europe, the Devonian period of Canada and the Ardennes in Belgium, and the Cretaceous period of South America and Denmark. Reefs from both the Silurian and Carboniferous periods have been recorded as far north as Siberia, and as far south as Australia.

Brain coral off the coast of Belize

However, these ancient reefs are not composed entirely of corals. Algae and sponges, as well as the fossilized remains of many echinoids, brachiopods, bivalves, gastropods, and trilobites that lived on the reefs help to build them. These fossil reefs are prime locations to look for fossils of many different types, besides the corals themselves.

Corals are not restricted to just reefs, many solitary corals may be found in rocks where reefs are not present (such as Cyclocyathus which occurs in the Cretaceous period Gault clay formation of England).

As well as being important rock builders, some corals are useful as zone (or index) fossils, enabling geologists to date the age the rocks in which they are found, particularly those found in the limestones of the Carboniferous period.

Environmental effects on coral

A coral reef can be an oasis of marine life.

Coral can be sensitive to environmental changes, and as a result are generally protected through environmental laws. A coral reef can easily be swamped in algae if there are too many nutrients in the water. Coral will also die if the water temperature changes by more than a degree or two beyond its normal range or if the salinity of the water drops. In an early symptom of environmental stress, corals expel their zooxanthellae; without their symbiotic unicellular algae, coral tissues are colorless, revealing the white of their calcium carbonate skeletons, an event known as 'coral bleaching'.

A combination of temperature changes, pollution, and overuse has led to the destruction of many coral reefs around the world. This has increased the importance of coral biology as a subject of study. Climatic variations, such as El Niño, can cause the temperature changes that destroy corals.

Some coral species exhibit banding in their skeletons resulting from annual variations in their growth rate. In fossil and modern corals these bands allow geologists to construct year-by-year chronologies, a kind of incremental dating, which combined with geochemical analysis of each band, can provide high-resolution records of paleoclimatic and paleoenvironamental change.

Uses

Living corals underwater are more colorful than dead coral

Coral reefs are a great source of tourism for scuba diving or snorkelling, however this has conservational implications due to damage from removal or destruction of coral.

Ancient coral reefs on land are often mined for limestone. An example of this is the quarrying of Portland limestone from the Isle of Portland.

Reddish coral is sometimes used as a gemstone especially in Tibet. Pure red coral is known as 'fire coral' and it is very rare because of the demand for perfect fire coral for jewellery-making purposes.


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Pure red coral is known as 'fire coral' and it is very rare because of the demand for perfect fire coral for jewellery-making purposes. The Dakota is built at Warren Truck Assembly in Warren, Michigan. Reddish coral is sometimes used as a gemstone especially in Tibet. Two 4.7 L V8 engines are available as well. An example of this is the quarrying of Portland limestone from the Isle of Portland. There are one V6 and two V8 engines available: The standard engine is a 3.7 L PowerTech V6 (specs below). Ancient coral reefs on land are often mined for limestone. This model is 3.7 in longer and 2.7 in wider, and features a new front and rear suspension, and rack-and-pinion steering.

Coral reefs are a great source of tourism for scuba diving or snorkelling, however this has conservational implications due to damage from removal or destruction of coral. The redesigned 2005 Dakota shares its platform with the new Dodge Durango SUV. In fossil and modern corals these bands allow geologists to construct year-by-year chronologies, a kind of incremental dating, which combined with geochemical analysis of each band, can provide high-resolution records of paleoclimatic and paleoenvironamental change. Engines:. Some coral species exhibit banding in their skeletons resulting from annual variations in their growth rate. 2004 was the end of the old OHV V6 and the big R/T V8. Climatic variations, such as El Niño, can cause the temperature changes that destroy corals. Most buyers ordered the V6 or V8 engines, which were considerably more powerful and, in the case of the V6, which was made standard for 2003, nearly as fuel-efficient with a manual transmission.

This has increased the importance of coral biology as a subject of study. 2002 was the final year for the four-cylinder engine in the Dakota, as Chrysler was ending production of the former AMC design. A combination of temperature changes, pollution, and overuse has led to the destruction of many coral reefs around the world. The smaller V8 was replaced by a new high-tech V8 as well. In an early symptom of environmental stress, corals expel their zooxanthellae; without their symbiotic unicellular algae, coral tissues are colorless, revealing the white of their calcium carbonate skeletons, an event known as 'coral bleaching'. Four-door "Quad-Cab" models were added for 2000 with a slightly shorter bed, 63.1 in (160.2 cm), but riding on the Club Cab's 130.9 in (332.5 cm) wheelbase. Coral will also die if the water temperature changes by more than a degree or two beyond its normal range or if the salinity of the water drops. 1998 saw the introduction of the R/T model with the big 5.9 L 250 hp (186 kW) Magnum V8.

A coral reef can easily be swamped in algae if there are too many nutrients in the water. It inherited the semi truck look of the larger Ram but remained largely the same underneath. Coral can be sensitive to environmental changes, and as a result are generally protected through environmental laws. The second-generation Dakota was built from 1997 through 2004. As well as being important rock builders, some corals are useful as zone (or index) fossils, enabling geologists to date the age the rocks in which they are found, particularly those found in the limestones of the Carboniferous period. Engines:. Corals are not restricted to just reefs, many solitary corals may be found in rocks where reefs are not present (such as Cyclocyathus which occurs in the Cretaceous period Gault clay formation of England). It was the only major change for 1996, and would be carried over as the base engine in the new, larger 1997 model.

These fossil reefs are prime locations to look for fossils of many different types, besides the corals themselves. In 1996, the first generation's final year, the K-based 2.5 L I4 engine was out of production and had been considered vastly underpowered compared to the competition, so Dodge borrowed the Jeep 2.5 L I4 (rated at 120 hp) and installed it as the base engine in the Dakota. Algae and sponges, as well as the fossilized remains of many echinoids, brachiopods, bivalves, gastropods, and trilobites that lived on the reefs help to build them. Both of the V-configuration engines were updated to Magnum specs the next year, providing a tremendous power boost. However, these ancient reefs are not composed entirely of corals. This engine produced 170 hp (127 kW). Reefs from both the Silurian and Carboniferous periods have been recorded as far north as Siberia, and as far south as Australia. For 1991, the front of the Dakota received a more aerodynamic grille and hood, and Dodge added the 5.2 L V8 as an option, inspired by the earlier Shelby Dakota option.

Such reefs can be found in the rocks of many parts of the world including those of the Ordovician period of Vermont, the Silurian period of the Michigan Basin and in many parts of Europe, the Devonian period of Canada and the Ardennes in Belgium, and the Cretaceous period of South America and Denmark. This model allowed the Dakota to boast capacity for six passengers, although the rear seat was best suited for children and shorter adults. Some of these reefs now lie as great structures in the midst of sedimentary rocks. An extended "Club Cab" model was added for 1990, still with two doors. And like modern corals their fossil ancestors built reefs beneath the ancient seas. Another important addition that year was Carroll Shelby's V8-powered Shelby Dakota, his first rear wheel drive vehicle in two decades. At certain times in the geological past corals were very abundant, just as modern corals are in the warm clear tropical waters of certain parts of the world today. Just 2,482 were sold that first year.

Although they are geologically younger than the Tabulate and Rugose corals, the aragonite skeleton Scleractinian corals does not tend to preserve well, so it is often easier to find fossils of the more ancient Tabulate and Rugose corals. The first convertible pickup since the Ford Model T, it featured a fixed roll bar and complicated manual top. The skeletons of Scleractinian corals are composed of a form of calcium carbonate known as aragonite. 1989 saw the unusual Dakota convertible. Their fossils may be found in small numbers in rocks from the Triassic period, and they are relatively common fossils in rocks from the Jurassic and Cretaceous periods as well as the Caenozoic era. Fuel injection was added to the 3.9 L V6 for 1988 but the output remained the same. Scleractinian corals diversified during the Mesozoic and Cenozoic eras and are at the height of their development today. Both 6.5 ft (2 m) and 8 ft (2.4 m) beds were offered.

The finest details of their skeletal structures are often well preserved, and such fossils may be cut and polished. Four wheel drive was available only with the V6. The Rugose corals may be either solitary or colonial, and like the Tabulate corals their skeletons are also composed of calcite. Straight-4 and V6 engines were offered along with either a 5-speed manual or 4-speed automatic transmission. Rugose corals became dominant by the middle of the Silurian period, and became extinct early in the Triassic period. The first generation of the Dakota was produced from 1987 through 1996. The skeletons of Tabulate corals are composed of a form of calcium carbonate known as calcite. .

Their numbers began to decline during the middle of the Silurian period and they finally became extinct at the end of the Permian period. One notable feature was the Dakota's rack and pinion steering, a first in work trucks. Tabulate corals occur in the limestones and calcareous shales of the Ordovician and Silurian periods, and often form low cushions or branching masses alongside Rugose corals. The Dakota has also long been the only midsize pickup with an optional V8 engine. Although corals first appeared in the Cambrian period, some 570 million years ago, they are extremely rare as fossils until the Ordovician period, when Rugose and Tabulate corals became widespread. It is a conventional design with body-on-frame construction and leaf spring/live axle rear end. Most other anthozoans would be treated under the common name of "sea anemone". The Dakota has always been sized above the compact (Ford Ranger, Chevrolet S-10) and below the full-sized (Ford F-150, Chevrolet Silverado) pickups and Dodge's own Ram.

These two groups went extinct at the end of the Paleozoic. The Dakota was nominated for the North American Truck of the Year award for 2000. Extinct corals include rugose corals and tabulate coral. It was introduced in 1987 alongside the redesigned Dodge Ram 50. There are several other types of corals, notably the octocorals (subclass Octocorallia) and corals classified in other orders of subclass Zoantharia: to wit, the black corals (order Antipatharia) and the soft corals (order Zoanthinaria). The Dakota is a midsize pickup truck from DaimlerChrysler's Dodge brand. . 2005 - 4.7 L HO PowerTech V8, 260 hp (194 kW) at 5200 rpm and 310 ft·lbf (420 N·m) at 5200 rpm.

Indonesia is home to 581 of the world's 793 known coral reef-building coral species. 2005 - 4.7 L PowerTech V8, 230 hp (172 kW) at 4400 rpm and 290 ft·lbf (393 N·m) at 3600 rpm. The most extensive development of extant coral reef is the Great Barrier Reef off the coast of Queensland, Australia. 2005 - 3.7 L PowerTech V6, 210 hp (157 kW) at 5200 rpm and 235 ft·lbf (319 N·m) at 4000 rpm. Some corals exist in cold waters, such as off the coast of Norway (north to at least 69° 14.24' N) and the Darwin Mounds off western Scotland. 2004 - 3.7 L PowerTech V6, 210 hp (157 kW). Corals are major contributors to the physical structure of coral reefs that develop only in tropical and subtropical waters. 2000-2004 - 4.7 L PowerTech V8, 230 hp (175 kW).

Corals breed by spawning, with many corals of the same species in a region releasing gametes simultaneously over a period of one to several nights around a full moon. 1998-2003 - 5.9 L Magnum V8, 250 hp (186 kW). Other corals, notably the cold-water genus Lophelia, do not have associated algae, and can live in much deeper water, with recent finds as deep as 3000 m. 1997-1999 - 5.2 L Magnum V8, 230 hp (172 kW). As a result, these corals are usually found not far beneath the surface, although in clear waters corals can grow at depths of 60 m (200 ft). 1997-2003 - 3.9 L Magnum V6, 175 hp (131 kW). The hermatypic corals obtain much of their nutrient requirement from symbiotic unicellular algae called zooxanthellae, and so are dependent upon growing in sunlight. 1997-2002 - 2.5 L AMC I4, 120 hp (90 kW).

Each polyp generation grows on the skeletal remains of previous generations, forming a structure that has a shape characteristic of the species, but subject to environmental influences. 1996 - 2.5 L AMC I4, 120 hp (90 kW). The colony of polyps functions essentially as a single organism by sharing nutrients via a well developed gastrovascular network, and the polyps are clones, each having the same genetic structure. 1994-1996 - 5.2 L Magnum V8, 220 hp (164 kW). A coral "head" is formed of many individual polyps, each polyp only a few millimetres in diameter. 1994-1996 - 3.9 L Magnum V6, 175 hp (131 kW). The latter are also known as stony corals in as much as the living tissue thinly covers a skeleton composed of calcium carbonate. 1991-1993 - 5.2 L Magnum V8, 230 hp (172 kW).

The group includes the important reef builders known as hermatypic corals, found in tropical oceans, and belonging to the subclass Zoantharia of order Scleractinia (formerly Madreporaria). 1992-1993 - 3.9 L Magnum V6, 180 hp (134 kW). Corals are gastrovascular marine cnidarians (phylum Cnidaria; class Anthozoa) existing as small sea anemone-like polyps, typically forming colonies of many individuals. 1991 - 5.2 L LA V8, 170 hp (127 kW). 1989-1995 - 2.5 L K I4, 99 hp (74 kW). 1987-1991 - 3.9 L LA V6, 125 hp (93 kW).

1987-1988 - 2.2 L K I4, SOHC, 96 hp (72 kW).

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