Coral
Pillar coral, Dendrogyra cylindricus
Scientific classification
Kingdom: Animalia Phylum: Cnidaria Class: Anthozoa Ehrenberg, 1831
Extant Subclasses and Orders
Alcyonaria    Alcyonacea    Helioporacea Zoantharia    Antipatharia    Corallimorpharia    Scleractinia    Zoanthidea [1][2]  See Anthozoa for details

Corals are marine organisms from the class Anthozoa and exist as small sea anemone–like polyps, typically in colonies of many identical individuals. Marine biology is the scientific study of living Organisms in the Ocean or other marine or Brackish bodies of water A class is the Taxonomic rank in the Biological classification of organisms in Biology below phylum and above order. Anthozoa is a class within the phylum Cnidaria that contains the Sea anemones and Corals Unlike other cnidarians anthozoans do not have a medusa Sea anemones are a group of water dwelling predatory animals of the order Actiniaria; they are named after the Anemone, a terrestrial Flower In Zoology, a polyp is one of two forms of individuals found in many species of Cnidarians The two are the polyp or hydroid and the medusa. The group includes the important reef builders that are found in tropical oceans, which secrete calcium carbonate to form a hard skeleton. Coral reefs are Aragonite structures produced by living organisms found in marine waters with little to no nutrients in the water An ocean (from Greek, ''Okeanos'' (Oceanus) is a major body of saline water, and a principal component of the Hydrosphere. Calcium carbonate is a Chemical compound with the Chemical formula Ca[[Carbon C]] O 3

A coral "head", commonly perceived to be a single organism, is formed from thousands of individual but genetically identical polyps, each polyp only a few millimeters in diameter. In Zoology, a polyp is one of two forms of individuals found in many species of Cnidarians The two are the polyp or hydroid and the medusa. Over thousands of generations, the polyps lay down a skeleton that is characteristic of their species. In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. A head of coral grows by asexual reproduction of the individual polyps. Corals also breed sexually by spawning, with corals of the same species releasing gametes simultaneously over a period of one to several nights around a full moon. A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete

Although corals can catch plankton using stinging cells on their tentacles, these animals obtain most of their nutrients from symbiotic unicellular algae called zooxanthellae. Plankton consist of any drifting Organisms ( Animals Plants Archaea, or Bacteria) that inhabit the Pelagic zone of A cnidocyte, cnidoblast or nematocyte, is a type of Venomous cell unique to the Phylum Cnidaria ( Corals This article is about the biological phenomenon for other uses see Symbiosis (disambiguation The term symbiosis (from the Greek Zooxanthellae (plural ˌzoʊoʊzænˈθɛli are golden-brown intracellular Endosymbionts of various marine Animals and Protozoa, especially Anthozoans Consequently, most corals depend on sunlight and grow in clear and shallow water, typically at depths shallower than 60 m (200 ft). The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International A foot (plural feet or foot; symbol or abbreviation ft or sometimes &prime – the prime symbol) is a non-SI unit These corals can be major contributors to the physical structure of the coral reefs that develop in tropical and subtropical waters, such as the enormous Great Barrier Reef off the coast of Queensland, Australia. Coral reefs are Aragonite structures produced by living organisms found in marine waters with little to no nutrients in the water The Great Barrier Reef is the largest Coral reef system in the world composed of over 2900 individual reefs and 900 islands stretching for 2600 kilometres (1600 mi Queensland is a state of Australia, occupying the north-eastern corner of the mainland continent For a topic outline on this subject see List of basic Australia topics. Other corals do not have associated algae and can live in much deeper water, such as in the Atlantic, with the cold-water genus Lophelia surviving as deep as 3000 m. ^[3] Examples of these can be found living on the Darwin Mounds located north-west of Cape Wrath, Scotland. Describing a vast field of undersea sand mounds situated off the north west coast of Scotland. For the television series see Cape Wrath (TV series. For the Morrissey-Mullen album see Cape Wrath (album Cape Wrath Scotland ( Gaelic: Alba) is a Country in northwest Europethat occupies the northern third of the island of Great Britain. Corals have also been found off the coast of Washington State and the Aleutian Islands in Alaska. Washington ( is a state in the Pacific Northwest region of the United States. The Aleutian Islands (possibly from Chukchi aliat, " Island " are a chain of more than 300 small volcanic islands forming a Volcanic Alaska ( Аляска Alyaska) is a state in the United States of America, in the northwest of the North American continent

Phylogeny

Mushroom coral in Papua New Guinea

Main article: Anthozoa

Corals belong to the class Anthozoa and are divided into two subclasses, depending on the number of tentacles or lines of symmetry, and a series of orders corresponding to their exoskeleton, nematocyst type and mitochondrial genetic analysis. Papua New Guinea (or ˈpæpjuːə in Tok Pisin: Papua Niugini) officially the Independent State of Papua New Guinea, is a country in Oceania Anthozoa is a class within the phylum Cnidaria that contains the Sea anemones and Corals Unlike other cnidarians anthozoans do not have a medusa A class is the Taxonomic rank in the Biological classification of organisms in Biology below phylum and above order. Anthozoa is a class within the phylum Cnidaria that contains the Sea anemones and Corals Unlike other cnidarians anthozoans do not have a medusa In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. Genetic testing allows the genetic Diagnosis of vulnerabilities to inherited Diseases, and can also be used to determine a person's Ancestry. ^[1][2][4] Those with eight tentacles are called octocorallia or Alcyonaria and comprise soft corals, sea fans and sea pens. Alcyonaria (also known as Octocorallia, as they have 8-fold symmetry is a subclass of the class Anthozoa within the phylum Cnidaria. The Alcyonacea, or the soft corals are an order of Corals which do not produce Calcium carbonate skeletons and so are neither Reef -building Sea pens are colonial marine Cnidarians belonging to the order Pennatulacea. Those with more than eight in a multiple of six are called hexacorallia or Zoantharia. Zoantharia (also known as Hexacorallia, as they have 6-fold symmetry is a subclass of the class Anthozoa within the phylum Cnidaria. This group includes reef-building corals (Scleractinians), sea anemones and zoanthids. Scleractinia, also called Stony Corals, are exclusively marine animals they are very similar to Sea anemones but generate a hard skeleton Sea anemones are a group of water dwelling predatory animals of the order Actiniaria; they are named after the Anemone, a terrestrial Flower Zoanthids ( order Zoantharia) are an order of cnidarians commonly found in Coral reefs, the deep sea and many other marine environments around the

Anatomy

Anatomy of a coral polyp

While a coral head appears to be a single organism, it is actually a head of many individual, yet genetically identical, polyps. Cloning in Biology is the process of producing populations of genetically-identical individuals that occurs in nature when organisms such as Bacteria, Insects In Zoology, a polyp is one of two forms of individuals found in many species of Cnidarians The two are the polyp or hydroid and the medusa. The polyps are multicellular organisms that feed on a variety of small organisms, from microscopic plankton to small fish. Plankton consist of any drifting Organisms ( Animals Plants Archaea, or Bacteria) that inhabit the Pelagic zone of

Polyps are usually a few millimeters in diameter, and are formed by a layer of outer epithelium and inner jellylike tissue known as the mesoglea. In biology and medicine epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body Mesoglea, also known as ectoplasma, is the clear inert jellylike substance that makes up most of the bodies of Jellyfish, Comb jellies and certain primitive They are radially symmetrical with tentacles surrounding a central mouth, the only opening to the stomach or coelenteron, through which both food is ingested and waste expelled.

The stomach closes at the base of the polyp, where the epithelium produces an exoskeleton called the basal plate or calicle (L. small cup). An exoskeleton is an external Skeleton that supports and protects an animal's body in contrast to the internal Endoskeleton of for example a Human. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. This is formed by a thickened calciferous ring (annular thickening) with six supporting radial ridges (as shown below). Corals are Marine organisms from the class Anthozoa and exist as small Sea anemone –like Polyps typically in colonies of many These structures grow vertically and project into the base of the polyp. When polyps are physically stressed, they contract into the calyx so that virtually no part is exposed above the skeletal platform. This protects the organism from predators and the elements (Barnes, R. D. , 1987; Sumich, 1996). ^[5][6]

The polyp grows by extension of vertical calices which are occasionally septated to form a new, higher, basal plate. Over many generations this extension forms the large calciferous (Calcium containing) structures of corals and ultimately coral reefs. Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20

Formation of the calciferous exoskeleton involves deposition of the mineral aragonite by the polyps from calcium ions they acquire from seawater. Aragonite is a Carbonate mineral, one of the two common naturally occurring polymorphs of Calcium carbonate, Ca[[carbon C]] O 3 Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 The rate of deposition, while varying greatly between species and environmental conditions, can be as much as 10 g / m² of polyp / day (0. 3 ounce / sq yd / day). This is light dependent, with night-time production 90% lower than that during the middle of the day. ^[7]

Nematocyst discharge: A dormant nematocyst discharges response to nearby prey touching the cnidocil, the operculum flap opens and its stinging apparatus fires the barb into the prey leaving a hollow filament through which poisons are injected to immobilise the prey, then the tentacles manoeuvre the prey to the mouth. A cnidocyte, cnidoblast or nematocyte, is a type of Venomous cell unique to the Phylum Cnidaria ( Corals

The polyp's tentacles trap prey using stinging cells called nematocysts. A cnidocyte, cnidoblast or nematocyte, is a type of Venomous cell unique to the Phylum Cnidaria ( Corals These are cells modified to capture and immobilize prey, such as plankton, by injecting poisons, firing very rapidly in response to contact. These poisons are usually weak but in fire corals they are potent enough to harm humans. Fire corals are colonial marine organisms that look rather like real Coral. Nematocysts can also be found in jellyfish and sea anemones. Jellyfish are free-swimming members of the phylum Cnidaria. They have several different basic morphologies that represent several different cnidarian classes including the Sea anemones are a group of water dwelling predatory animals of the order Actiniaria; they are named after the Anemone, a terrestrial Flower The toxins injected by nematocysts immobilize or kill prey, which can then be drawn into the polyp's stomach by the tentacles through a contractile band of epithelium called the pharynx. The pharynx (plural pharynges) is the part of the Neck and Throat situated immediately Posterior to (behind the Mouth and Nasal

The polyps are interconnected by a complex and well developed system of gastrovascular canals allowing significant sharing of nutrients and symbiotes. Gastro vascular cavity, as the name indicates functions in both Digestion and Gas exchange. In soft corals these range in size from 50-500 μm in diameter and to allow transport of both metabolites and cellular components. ^[8]

Close-up of Montastrea cavernosa polyps. Tentacles are clearly visible.

Aside from feeding on plankton, many corals as well as other cnidarian groups such as sea anemones (e. Cnidaria (naɪˈdɛəriə is a phylum containing some 9000 Species of Animals found exclusively in aquatic mostly marine, environments Sea anemones are a group of water dwelling predatory animals of the order Actiniaria; they are named after the Anemone, a terrestrial Flower g. Aiptasia), form a symbiotic relationship with a class of algae, zooxanthellae, of the genus Symbiodinium. Aiptasia is a Genus of a Symbiotic Cnidarian belonging to the class Anthozoa ( Sea anemones, Corals) This article is about the biological phenomenon for other uses see Symbiosis (disambiguation The term symbiosis (from the Greek Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms Zooxanthellae (plural ˌzoʊoʊzænˈθɛli are golden-brown intracellular Endosymbionts of various marine Animals and Protozoa, especially Anthozoans Zooxanthellae (plural ˌzoʊoʊzænˈθɛli are golden-brown intracellular Endosymbionts of various marine Animals and Protozoa, especially Anthozoans The sea anemone Aiptasia, while considered a pest among coral reef aquarium hobbyists, has served as a valuable model organism in the scientific study of cnidarian-algal symbiosis. Aiptasia is a Genus of a Symbiotic Cnidarian belonging to the class Anthozoa ( Sea anemones, Corals) This article is about the biological phenomenon for other uses see Symbiosis (disambiguation The term symbiosis (from the Greek Typically a polyp will harbor one particular species of algae. Via photosynthesis, these provide energy for the coral, and aid in calcification. ^[9] The algae benefit from a safe environment, and use the carbon dioxide and nitrogenous waste produced by the polyp. Due to the strain the algae can put on the polyp, stress on the coral often triggers ejection of the algae, known on a large scale as coral bleaching, as it is the algae that contribute to the brown coloration of corals; other colors, however, are due to host coral pigments, such as GFPs (green fluorescent protein). Coral bleaching is the loss of color of Corals due to stress-induced expulsion of symbiotic Unicellular Algae or due to the loss of pigmentation within The green fluorescent protein ( GFP) is composed of 238 Amino acids (26 Ejecting the algae increases the polyps' chances of surviving stressful periods - they can regain the algae at a later time. If the stressful conditions persist, the polyps, and corals, will eventually die. ^[10]

Reproduction

Corals maintain a variety of ways to propagate and settle new areas, the two main methods being by sexual and asexual means. Corals can be both gonochoristic and hermaphroditic, each of which can utilize sexual and asexual means of reproduction. In Biology, gonochorism ( Greek offspring + disperse or unisexualism describes sexually reproducing species in which there are at A hermaphrodite is an organism having both male and female reproductive organs

Sexual

Life cycles of broadcasters and brooders.

Corals predominantly reproduce sexually, with 25% of hermatypic corals (stony corals) forming single sex (gonochoristic) colonies, whilst the rest are hermaphroditic. The Evolution of sexual reproduction is a major puzzle The first Fossilized evidence of sexually reproducing Organisms is from Eukaryotes of the Stenian Hermatypic corals, are corals that contain and depend upon Zooxanthellae (algae for nutrients In Biology, gonochorism ( Greek offspring + disperse or unisexualism describes sexually reproducing species in which there are at A hermaphrodite is an organism having both male and female reproductive organs ^[11] About 75% of all hermatypic corals "broadcast spawn" by releasing gametes - eggs and sperm - into the water to spread colonies over large distances. The gametes fuse during fertilisation to form a microscopic larvum called a planula, typically pink and elliptical in shape; a moderately sized coral colony can form several thousands of these larvae per year to overcome the huge odds against formation of a new colony. A planula is the free-swimming flattened ciliated, bilaterally symmetric Larva of a Jellyfish, a Hydrozoan Cnidarian or ^[12]

The planula swims towards light, exhibiting positive phototaxis, to surface waters where they drift and grow for a time before swimming back down to locate a surface on which it can attach and establish a new colony. Phototaxis is a kind of Taxis that occurs when a whole organism moves in response to the stimulus Light. At many stages of this process there are high failure rates, and even though millions of gametes are released by each colony very few new colonies are formed. The time from spawning to settling is usually 2 or 3 days, but can be up to 2 months. ^[13] The larva grows into a coral polyp and eventually becomes a coral head by asexual budding and growth, creating new polyps.

A male star coral, Montastraea cavernosa, releases sperm into the water.

Corals that do not broadcast spawn are called brooders, with most non-stony corals displaying this characteristic. These corals release sperm but harbour the eggs, allowing larger, negatively buoyant, planulae to form which are later released ready to settle. ^[9] The larva grows into a coral polyp and eventually becomes a coral head by asexual budding and growth to create new polyps.

Synchronous spawning is very typical on a coral reef and often, even when there are multiple species present, all the corals on the reef release gametes during the same night. Reproductive synchrony, or synchronous spawning is a term used in Evolutionary biology and behavioural ecology to describe the way in which many species In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete This synchrony is essential so that male and female gametes can meet and form planula. The cues that guide the release are complex, but over the short term involve lunar changes, sunset time, and possibly chemical signalling. ^[11] Synchronous spawning may have the result of forming coral hybrids, perhaps involved in coral speciation. Speciation is the Evolutionary process by which new biological Species arise ^[14] In some places the coral spawn can be dramatic, usually occurring at night, where the usually clear water becomes cloudy with gametes.

Corals must rely on environmental cues, varying from species to species, to determine the proper time to release gametes into the water. There are two methods corals use for sexual reproduction which differ in whether the female gametes are released:

• Broadcasters, the majority of which mass spawn, rely heavily on environmental cues, because in contrast to brooders they release both sperm and eggs into the water. The corals use long-term cues such as day length, water temperature, and/or rate of temperature change; and the short-term cue is most often the lunar cycle, with the sunset cuing the time of release. ^[11] About 75% of coral species are broadcasters, the majority of which are hermatypic, or reef-building corals. ^[11] The positively buoyant gametes float towards the surface where fertilization occurs to produce planula larvae. A planula is the free-swimming flattened ciliated, bilaterally symmetric Larva of a Jellyfish, a Hydrozoan Cnidarian or The planula larvae swim towards the surface light to enter into currents, where they remain usually for two days, but can be up to three weeks, and in one known case two months,^[13] after which they settle and metamorphose into polyps and form colonies. A planula is the free-swimming flattened ciliated, bilaterally symmetric Larva of a Jellyfish, a Hydrozoan Cnidarian or

• Brooders are most often ahermatypic (non-reef building), or some hermatypic corals which are in areas of high current or wave action. Brooders release only sperm, which is negatively buoyant, and can store unfertilized eggs for weeks, lowering the need for mass synchronous spawning events, but can still occur. ^[11] After fertilization the corals release planula larvae which are ready to settle. A planula is the free-swimming flattened ciliated, bilaterally symmetric Larva of a Jellyfish, a Hydrozoan Cnidarian or

Asexual

Calices (basal plates) of Orbicella annularis showing two methods of multiplication: gemmation (small central calicle) and division (large double calicle).

Within a head of coral the genetically identical polyps reproduce asexually to allow growth of the colony. Asexuality is a Sexual orientation that describes individuals who do not experience Sexual attraction. This is achieved either through gemmation or budding or through division, both shown in the diagrams of Orbicella annularis. Budding involves a new polyp growing from an adult, whereas division forms two polyps each as large as the original. ^[12]

• Budding expands the size of a coral colony. It occurs when a new corallite grows out from the adult polyp. As the new polyp grows it produces a coelenteron (stomach), tentacles and a mouth. The distance between the new and adult polyps grows, and with it the coenosarc (the common body of the colony; see coral anatomy). Budding can occur by means of:

• Longitudinal division begins with broadening of a polyp, which then divides the coelenteron. The mouth divides and new tentacles form. The difference with this is that each polyp must complete its missing parts of the body and exoskeleton.
• Intra-tentacular budding forms from the oral discs of a polyp, meaning that both polyps are the same size and are within the same ring of tentacles.
• Extra-tentacular budding forms from the base of a polyp, and the new polyp is smaller.
• Transversal division occurs when polyps and the exoskeleton divide transversally into two parts. This means that one has the basal disc (bottom) and the other has the oral disc (top). The two new polyps must again complete the missing parts.
• Fission occurs in some corals, especially among the family Fungiidae, where the colony is able to split into two or more colonies during the early stages of their development. Fungiidae (fən-gɪ-ɪ-daː is a family of Cnidaria that contains the mushroom corals (sometimes known as disc corals, solitary corals or plate corals

Whole colonies can reproduce asexually through fragmentation or bailout, forming another individual colony with the same genome.

• Polyp bailout occurs when a single polyp abandons the colony and re-establishes on a new substrate to create a new adult colony.

• Fragmentation, which can actually be included as a type of fission, involves individuals broken from the colony during storms, or other situations where breaking can occur. The separated individuals can start new coral colonies.

Reefs

Locations of coral reefs

Main article: Coral reef

The hermatypic, stony corals are often found in coral reefs, large calcium carbonate structures generally found in shallow, tropical water. Coral reefs are Aragonite structures produced by living organisms found in marine waters with little to no nutrients in the water Coral reefs are Aragonite structures produced by living organisms found in marine waters with little to no nutrients in the water Calcium carbonate is a Chemical compound with the Chemical formula Ca[[Carbon C]] O 3 The Tropics are centered on the Equator and limited in Latitude by the Tropic of Cancer in the northern hemisphere at approximately 23°26' (23 Reefs are built up from coral skeletons and held together by layers of calcium carbonate produced by coralline algae. Coralline algae are Red algae in the Family Corallinaceae of the order Corallinales. Reefs are extremely diverse marine ecosystems being host to over 4,000 species of fish, massive numbers of cnidarians, molluscs, crustaceans, and many other animals. An ecosystem is a natural unit consisting of all plants animals and micro-organisms( Biotic factors in an area functioning together with all of the non-living physical ( Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000 Structure of crustaceans As Arthropods crustaceans have a stiff Exoskeleton, which must be shed to allow the animal to grow ( Ecdysis or molting ^[15]

Geological history

The fossil coral Heliophyllum halli from the Devonian period, found in Canada. The Devonian is a geologic period and system of the Paleozoic era spanning from to  million years ago. Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page

Although corals first appeared in the Cambrian period,^[16] some 542 million years ago, fossils are extremely rare until the Ordovician period, 100 million years later, when Rugose and Tabulate corals became widespread. The Cambrian is a geologic period and system that began about Ma (million years ago at the end of the Proterozoic eon and ended about Ma with FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 The Rugosa Rose is also sometimes just called "Rugosa" The Rugosa, also called the Tetracoralla, are an extinct order The tabulate corals, forming the order Tabulata, are an Extinct form of Coral.

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. Limestone is a Sedimentary rock composed largely of the Mineral Calcite ( Calcium carbonate: CaCO3 Shale (also called mudstone) is a fine-grained Sedimentary rock whose original constituents were Clay minerals or Muds It is characterized by The Silurian is a geologic period and system that extends from the end of the Ordovician period about 443 Their numbers began to decline during the middle of the Silurian period and they finally became extinct at the end of the Permian period, 250 million years ago. The Permian is a geologic period and system that extends from 299 The skeletons of Tabulate corals are composed of a form of calcium carbonate known as calcite. Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3

Rugose corals became dominant by the middle of the Silurian period, and became extinct early in the Triassic period. The Triassic is a geologic period and system that extends from about 251 to 199 Ma (million years ago The Rugose corals existed in solitary and colonial forms, and like the Tabulate corals their skeletons are also composed of calcite.

The Scleractinian corals filled the niche vacated by the extinct Rugose and Tabulate corals. Scleractinia, also called Stony Corals, are exclusively marine animals they are very similar to Sea anemones but generate a hard skeleton Their fossils may be found in small numbers in rocks from the Triassic period, and become relatively common in rocks from the Jurassic and later periods. The Jurassic is a geologic period and system that extends from about Ma (million years ago to  Ma that is from the end of the Triassic to the beginning The skeletons of Scleractinian corals are composed of a form of calcium carbonate known as aragonite. Aragonite is a Carbonate mineral, one of the two common naturally occurring polymorphs of Calcium carbonate, Ca[[carbon C]] O 3 ^[17] Although they are geologically younger than the Tabulate and Rugose corals, their aragonitic skeleton is less readily preserved, and their fossil record is less complete.

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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. Like modern corals their ancestors built reefs, some of which now lie as great structures in sedimentary rocks. Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock)

These ancient reefs are not composed entirely of corals. Algae, sponges, and the remains of many echinoids, brachiopods, bivalves, gastropods, and trilobites that lived on the reefs are preserved within them. Echinoderms (Phylum Echinodermata) are a phylum of marine Animals (including Sea stars) Brachiopods (from Latin brachium, arm + New Latin -poda, foot are a small phylum of Benthic Invertebrates Also Bivalves are Molluscs belonging to the class Bivalvia. They have two-part shells and typically both valves are symmetrical along the hinge line The class Gastropoda or the gastropods, also previously known as gasteropods, or univalves, and more commonly known as Snails Trilobites ("three-lobes" are extinct Arthropods that form the class Trilobita. This makes some corals useful index fossils, enabling geologists to date the age the rocks in which they are found. Index fossils (also known as guide fossils or zone fossils are Fossils used to define and identify geologic periods (or faunal stages

Corals are not restricted to reefs, and many solitary corals may be found in rocks where reefs are not present, such as Cyclocyathus which occurs in England's Gault clay formation. England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland The Gault Clay is a formation of stiff blue Clay deposited in a calm fairly deep water marine environment during the Lower Cretaceous Period (Upper and Middle

Environmental effects

A coral reef can be an oasis for marine life.

Corals are highly sensitive to environmental changes. See also Nature The natural environment, commonly referred to simply as the environment, is a terminology that is comprised of all living and Scientists have predicted that over 50% of the coral reefs in the world may be destroyed by the year 2030;^[20] as a result they are generally protected through environmental laws. A coral reef can easily be swamped in algae if there are too many nutrients in the water. Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms A nutrient is food or chemicals that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment 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. Salinity is the Saltiness or dissolved salt content of a body of Water. In an early symptom of environmental stress, corals expel their zooxanthellae; without their symbiotic unicellular algae, coral tissues become colorless as they reveal the white of their calcium carbonate skeletons, an event known as coral bleaching. Zooxanthellae (plural ˌzoʊoʊzænˈθɛli are golden-brown intracellular Endosymbionts of various marine Animals and Protozoa, especially Anthozoans Coral bleaching is the loss of color of Corals due to stress-induced expulsion of symbiotic Unicellular Algae or due to the loss of pigmentation within ^[21]

Many governments now prohibit removal of coral from reefs to reduce damage by divers. Scuba diving is swimming underwater, or taking part in another activity while using a Scuba set. However, damage is still caused by anchors dropped by dive boats or fishermen. In places where local fishing causes reef damage, education schemes have been run to inform the population about reef protection and ecology.

The narrow niche that coral occupies, and the stony corals' reliance on calcium carbonate deposition, means they are very susceptible to changes in water pH. In Ecology, a niche (pronounced nich nēsh or nish A shorthand definition of niche is how an organism makes a living Scleractinia, also called Stony Corals, are exclusively marine animals they are very similar to Sea anemones but generate a hard skeleton Calcium carbonate is a Chemical compound with the Chemical formula Ca[[Carbon C]] O 3 pH is the measure of the acidity or alkalinity of a Solution. Ocean acidification, caused by dissolution of carbon dioxide in the water that lowers pH, is currently occurring in the surface waters of the world's oceans due to increasing atmospheric carbon dioxide. Lowered pH reduces the ability of corals to produce calcium carbonate skeletons, and at the extreme, results in the dissolution of those skeletons entirely. Without deep and early cuts in anthropogenic CO₂, scientists fear that ocean acidification may inevitably result in the severe degradation or destruction of coral species and ecosystems. ^[22]

A section through a coral, dyed to determine growth rate

A combination of temperature changes, pollution, and overuse by divers and jewelry producers has led to the destruction of many coral reefs around the world. This has increased the importance of coral biology as a discipline. In Marine science, coral biology is an academic discipline that studies various aspects of the Biology of Corals Coral reefs are a significant Climatic variations can cause temperature changes that destroy corals. For example, during the 1997-98 warming event all the hydrozoan Millepora boschmai colonies near Panamá were bleached and died within six years - this species is now thought to be extinct. Hydrozoa ( hydrozoans) are a Taxonomic class of very massive predatory animals which can be solitary or colonial and which mostly live in saltwater Panama, officially the Republic of Panama (República de Panamá) is the southernmost country of Central America. ^[23]

Uses

Live corals

Local economies near major coral reefs benefit from an abundance of fish and octopus as a food source. Reefs also provide recreational scuba diving and snorkeling tourism. Scuba diving is swimming underwater, or taking part in another activity while using a Scuba set. Snorkeling ( British spelling: snorkelling) is the practice of Swimming at the surface of a body of water while equipped with a Diving mask, a Unfortunately all these activities can also have deleterious effects, such as removal or accidental destruction of coral. Besides the recreational use, coral is also useful as a protection against hurricanes and other extreme weather.

Red shades of coral are sometimes used as a gemstone, especially in Tibet. Precious coral or red coral is the common name given to Corallium rubrum and several related species of marine Coral. Definitions of Tibet See also Definitions of Tibet Name In English The English word Tibet, like the word for Tibet in most European In vedic astrology, red coral represents Mars. Precious coral or red coral is the common name given to Corallium rubrum and several related species of marine Coral. Pure red coral is known as fire coral and is very rare because of the demand for perfect fire coral in jewelry-making. Fire corals are colonial marine organisms that look rather like real Coral.

Live corals in Papua New Guinea. Papua New Guinea (or ˈpæpjuːə in Tok Pisin: Papua Niugini) officially the Independent State of Papua New Guinea, is a country in Oceania

Ancient corals

Ancient coral reefs on land are often mined for lime or use as building blocks ("coral rag"). Coral rag is a rubbly Limestone composed of ancient Coral reef material Coral rag is an important local building material in places such as the East African coast.

Some coral species exhibit banding in their skeletons resulting from annual variations in their growth rate. A year (from Old English gēr) is the time between two recurrences of an event related to the Orbit of the Earth around the Sun In fossil and modern corals these bands allow geologists to construct year-by-year chronologies, a form of incremental dating, which can provide high-resolution records of past climatic and environmental changes when combined with geochemical analysis of each band. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. A geologist is a contributor to the Science of Geology, studying the physical structure and processes of the Earth and planets of the solar system Incremental dating techniques allow the construction of year-by-year annual chronologies which can be temporally fixed ( i Paleoclimatology (also Palaeoclimatology) is the study of Climate change taken on the scale of the entire History of Earth. The field of geochemistry involves study of the chemical composition of the Earth and other Planets chemical processes and reactions that govern the composition ^[24]

Certain species of corals form communities called microatolls. A microatoll is a small colony of Coral dead on the top as a result of exposure at Low tide. The vertical growth of microatolls is limited by average tidal height. By analyzing the various growth morphologies, microatolls can be used as a low resolution record of patterns of sea level change. Fossilized microatolls can also be dated using radioactive carbon dating to obtain a chronology of patterns of sea level change. Such methods have been used to used to reconstruct Holocene sea levels. The Holocene is a Geological epoch which began approximately 10000 years ago (about 8000 BC ^[25]

Gallery

Mushroom Coral skeleton	Brain coral, Diploria labyrinthiformis	Polyps of Eusmilia fastigiata	Staghorn coral, Acropora
Orange cup coral, Balanophyllia elegans	Brain coral spawning	Brain coral releasing eggs	Fringing coral reef off the coast of Eilat, Israel. Brain coral is a Common name given to several genera of Coral which are characterized by the Spheroid shape of their colonies, and Acropora is a genus of Coral in the phylum Cnidaria. Anatomy and Distribution Depending on the species and location Coral reefs are Aragonite structures produced by living organisms found in marine waters with little to no nutrients in the water Eilat (Hebrew אילת should not be confused with the nearby kibbutz of Eilot (Hebrew אילות For a topic outline on this subject see List of basic Israel topics.
Growing coral

References

External links

• University of Southern Mississippi - Coral Reef Resource Guide
• NOAA Ocean Service Education - Corals
• NOAA CoRIS - Coral Reef Biology