Corals are marine organisms in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans, which secrete calcium carbonate to form a hard skeleton.
A coral "head", which appears to be a single organism, is a colony of myriad genetically identical polyps. Each polyp is typically only a few millimeters in diameter. Over many generations, the colony secretes a skeleton that is characteristic of the species. Individual heads grow by asexual reproduction of individual polyps. Corals also breed sexually by spawning. Polyps of the same species release gametes simultaneously over a period of one to several nights around a full moon.
Although corals can catch small fish and animals, such as plankton, using stinging cells on their tentacles, most corals obtain the majority of their energy and nutrients from photosynthetic unicellular algae called zooxanthellae. Such corals require sunlight and grow in clear, shallow water, typically at depths shallower than . 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. Other corals do not have associated algae and can live in much deeper water, with the cold-water genus ''Lophelia'' surviving as deep as . Examples live on the Darwin Mounds located north-west of Cape Wrath, Scotland. Corals have also been found off the coast of the U.S. in Washington state and the Aleutian Islands in Alaska.
While a coral head appears to be a single organism, it is actually a group of many individual, yet genetically identical, polyps. The polyps are multicellular organisms. 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. They are radially symmetrical, with tentacles surrounding a central mouth, the only opening to the stomach or coelenteron, through which 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). The calicle is formed by a thickened calcareous ring (annular thickening) with six supporting radial ridges (as shown below). These structures grow vertically and project into the base of the polyp. When a polyp is physically stressed, its tentacles contract into the calyx so that virtually no part is exposed above the skeletal platform. This protects the organism from predators and the elements.
The polyp grows by extension of vertical calices which occasionally septate to form a new, higher, basal plate. Over many generations, this extension forms the large calcareous structures of corals and ultimately coral reefs.
Formation of the calcareous exoskeleton involves deposition of the mineral aragonite by the polyps from calcium and carbonate ions they acquire from seawater. The rate of deposition, while varying greatly across 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.
Nematocysts are stinging cells at the tips of the calices that carry poison, which they rapidly release in response to contact with another organism. The tentacles also bear a contractile band of epithelium called the pharynx. Jellyfish and sea anemones also carry nematocysts.
The polyps interconnect by a complex and well-developed system of gastrovascular canals, allowing significant sharing of nutrients and symbiotes. In soft corals, these range in size from in diameter, and allow transport of both metabolites and cellular components.
Many corals, as well as other cnidarian groups such as sea anemones (e.g. Aiptasia), form a symbiotic relationship with a class of algae, zooxanthellae, of the genus ''Symbiodinium''. ''Aiptasia'', while considered a pest among coral reef aquarium hobbyists, serves as a valuable model organism in the study of cnidarian-algal symbiosis. Typically, a polyp harbors one species of algae. Via photosynthesis, these provide energy for the coral, and aid in calcification. The algae benefit from a safe environment, and consume 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 drives them to eject the algae. Mass ejections are known as coral bleaching, because the algae contribute to coral's brown coloration; other colors, however, are due to host coral pigments, such as green fluorescent proteins (GFPs). Ejection increases the polyp's chances of surviving short-term stress—they can regain algae at a later time. If the stressful conditions persist, the polyp eventually dies.
These poisons are usually too weak to harm humans. An exception is fire coral.
Planulae exhibits positive phototaxis, swimming towards light to reach surface waters, where they drift and grow before descending to seek a hard surface to which it can attach and establish a new colony. They also exhibit positive sonotaxis, moving towards sounds that emanate from the reef and away from open water. High failure rates afflict many stages of this process, and even though millions of gametes are released by each colony, very few new colonies form. The time from spawning to settling is usually two to three days, but can be up to two months. The larva grows into a polyp and eventually becomes a coral head by asexual budding and growth.
Synchronous spawning is very typical on the coral reef, and often, even when multiple species are present, all corals spawn on the same night. This synchrony is essential so male and female gametes can meet. Corals must rely on environmental cues, varying from species to species, to determine the proper time to release gametes into the water. The cues involve lunar changes, sunset time, and possibly chemical signalling. Synchronous spawning may form hybrids and is perhaps involved in coral speciation. In some places, the spawn can be visually dramatic, clouding the usually clear water with gametes, typically at night.
Corals use two methods 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 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. The short-term cue is most often the lunar cycle, with sunset cuing the release. About 75% of coral species are broadcasters, the majority of which are hermatypic, or reef-building corals. The positively buoyant gametes float towards the surface, where fertilization produces planula larvae. The 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, after which they settle and metamorphose into polyps and form colonies.
Brooders are most often ahermatypic (not reef-building) in areas of high current or wave action. Brooders release only sperm, which is negatively buoyant, and can harbor unfertilized eggs for weeks, lowering the need for mass synchronous spawning events, which do sometimes occur. After fertilization, the corals release planula larvae which are ready to settle.
Within a coral head, the genetically identical polyps reproduce asexually, either via gemmation (budding) or division, both shown in the photo of ''Orbicella annularis''. Budding involves a new polyp growing from an adult, whereas division forms two polyps each as large as the original.
Asexual reproduction has several benefits for these sessile colonial organisms:
Whole colonies can reproduce asexually through fragmentation or bailout, forming another individual colony with the same genotype.
In the Caribbean alone, 50 species of uniquely structured hard coral exist. Well-known types include: Brain coral grow to in width.
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, 250 million years ago. 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 existed in solitary and colonial forms, and are also composed of calcite.
The scleractinian corals filled the niche vacated by the extinct rugose and tabulate species. Their fossils may be found in small numbers in rocks from the Triassic period, and become common in the Jurassic and later periods. Scleractinian skeletons are composed of a form of calcium carbonate known as aragonite. 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.
At certain times in the geological past, corals were very abundant. Like modern corals, these ancestors built reefs, some of which now lie as great structures in sedimentary rocks.
Fossils of fellow reef-dwellers algae, sponges, and the remains of many echinoids, brachiopods, bivalves, gastropods, and trilobites appear along with coral fossils. This makes some corals useful index fossils, enabling geologists to date the age the rocks in which they are found.
Coral fossils are not restricted to reef remnants, and many solitary corals may be found elsewhere, such as ''Cyclocyathus'', which occurs in England's Gault clay formation.
A Petoskey stone is a rock and a fossil, often pebble-shaped, that is composed of a fossilized coral, ''Hexagonaria percarinata''. They are found predominantly in Michigan's Upper Peninsula, and the northwestern portion of Michigan's Lower Peninsula.
Seaweed/algae can destroy a coral reef. In the Caribbean and tropical Pacific, direct contact between ~40 to 70% of common seaweeds and coral causes bleaching and death to the coral via transfer of lipid–soluble metabolites. Seaweed and algae proliferate given adequate nutrients and limited grazing by herbivores. Corals die if surrounding water temperature changes by more than a degree or two beyond their normal range or if water salinity drops. In an early symptom of environmental stress, corals expel their zooxanthellae; without their symbiotic algae, coral tissues become colorless as they reveal the white of their calcium carbonate skeletons, an event known as coral bleaching.
Many governments now prohibit removal of coral from reefs, and use education to inform their populations about reef protection and ecology. However, many other human activities damage reefs, including runoff, mooring, fishing, diving, mining and construction.
Coral's narrow niche and the stony corals' reliance on calcium carbonate deposition makes them susceptible to changes in water pH. The increase in atmospheric carbon dioxide has caused enough dissolution of carbon dioxide to lower the ocean's pH, in a process known as ocean acidification. Lowered pH reduces corals' ability to produce calcium carbonate, and at the extreme, can dissolve their skeletons. Without deep and immediate cuts in anthropogenic , many scientists fear acidification will severely degrade or destroy coral ecosystems.
Coral reefs provide medical benefits for humans. Chemical compounds taken from corals are used in medicine for cancer, AIDS, pain, and other uses. Coral skeletons are also commonly used for bone grafting in humans.
Live coral is highly sought after for aquaria. Given the proper ecosystem, live coral makes a stunning addition to any saltwater aquarium. Soft corals are easier to maintain in captivity than hard corals. Aquariums with corals are used by hobbyists in both tropical countries, as well as in countries in colder climates, where corals do not occur in the wild (sea). To eliminate destruction of corals in their indigenous regions, projects have been started to grow corals in colder countries, too. One such project is the KoralenKAS, which has been executed in practice by EcoDeco BV.
''Isididae'' may be usable as living bone implants and in aquatic cultivation, because of their potential to mimic valuable biological properties.
Certain species form communities called microatolls, which are colonies whose top is dead and mostly above the water line, but whose perimeter is mostly submerged and alive. Average tide level limits their height. By analyzing the various growth morphologies, microatolls offer a low resolution record of sea level change. Fossilized microatolls can also be dated using radioactive carbon dating. Such methods can help to reconstruct Holocene sea levels.
Deep sea bamboo corals (''Isididae'') may be among the first organisms to display the effects of ocean acidification. They produce growth rings similar to those of tree, and can provide a view of changes in the condition in the deep sea over time.
Category:Anthozoa Category:Incremental dating Category:Coral reefs
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This text is licensed under the Creative Commons CC-BY-SA License. This text was originally published on Wikipedia and was developed by the Wikipedia community.
name | Jools Holland |
---|---|
background | solo_singer |
birth name | Julian Miles Holland |
birth date | January 24, 1958 |
birth place | Blackheath, London, England |
instrument | Piano, keyboard, guitar |
genre | Boogie-woogie, jazz, blues, R&B; |
occupation | Musician, composer, television presenter, bandleader |
years active | 1974–present |
associated acts | Squeeze Rhythm & Blues Orchestra |
website | Official site }} |
Julian Miles "Jools" Holland OBE, DL (born 24 January 1958) is an English pianist, bandleader, singer, composer, and television presenter. He was a founder of the band Squeeze (1974-1980 & 1985-1990) and his work has involved him with many artists including Sting, Eric Clapton, George Harrison, The Who, David Gilmour, Magazine and Bono.
Holland is a published author and appears on television shows besides his own and contributes to radio shows. In 2004, he collaborated with Tom Jones on an album of traditional R&B; music. He currently hosts ''Later... with Jools Holland'', a music-based show aired on BBC2, on which his annual show the Hootenanny, is based.
Holland played as a session musician before finding fame, and his first studio session was with Wayne County & the Electric Chairs in 1976 on their track "F*ck Off."
Holland was a founding member of the British pop band Squeeze, formed in March 1974, in which he played keyboards until 1981 and helped the band to achieve millions of record sales, before pursuing his solo career.
Holland began issuing solo records in 1978, his first EP being ''Boogie Woogie '78''. He continued his solo career through the early 1980s, releasing an album and several singles between 1981 and 1984. He branched out into TV, co-presenting the Newcastle-based TV music show ''The Tube'' with Paula Yates. Holland achieved notoriety by inadvertently using the phrase "groovy fuckers" in a live, early evening TV trailer for the show, causing it to be suspended for six weeks. He referred to this in his sitcom "The Groovy Fellers" with Rowland Rivron.
thumb|right|Holland at the Tsunami Relief concert in Cardiff's Millennium Stadium, 22 January 2005In 1983 Holland played an extended piano solo on The The's re-recording of "Uncertain Smile" for the album ''Soul Mining''. In 1985, Squeeze (which had continued in Holland's absence through to 1982) unexpectedly regrouped including Jools Holland as their keyboard player. Holland remained in the band until 1990, at which point, he again departed Squeeze on amicable terms to resume his solo career as a musician and a TV host.
In 1987, Holland formed The ''Jools Holland Big Band'' which consisted of himself and Gilson Lavis from Squeeze. This gradually became his 18-piece Rhythm & Blues Orchestra.
Between 1988 and 1990 he performed and co-hosted along with David Sanborn during the two seasons of the music performance program Sunday Night on NBC late-night television. Since 1992 he has presented the eclectic music program ''Later... with Jools Holland'', plus an annual New Year's Eve "Hootenanny".
In 1996 Holland signed a record deal with Warner Bros. Records and his records are now marketed through Rhino Records.
Holland has a touring band, The Rhythm And Blues Orchestra, which often includes singers Sam Brown and Ruby Turner. In January 2005 Holland and his band performed with Eric Clapton as the headline act of the Tsunami Relief Cardiff. He also headlined the Skegness SO Festival in July 2010.
Holland was an interviewer for The Beatles Anthology TV project, and appeared in the 1997 film ''Spiceworld'' as a musical director.
He received an OBE in 2003 in the Queen's Birthday Honours list, for services to the British music industry as a television presenter and musician. In September 2006 Holland was appointed a Deputy Lieutenant for Kent. He is also known for his charity work: in June 2006 he performed in Southend for HIV/AIDS charity Mildmay, and in early 2007 he performed at Wells and Rochester Cathedrals to raise money for maintaining cathedral buildings. He is also patron of the Drake Music Project and has raised many thousands of pounds for the charity.
Jools Holland was appointed an Honorary Fellow of Canterbury Christ Church University at a ceremony held at Canterbury Cathedral on 30 January 2009.
On 29 August 2005 Holland married Christabel McEwen, his girlfriend of 15 years (between 1983 and 1995 she had been married to Edward Lambton, 7th Earl of Durham, but they divorced). The wedding, at St James's Church, Cooling near Rochester, was attended by many celebrities, including Ringo Starr, Robbie Coltrane, Stephen Fry, Lenny Henry, Noel Gallagher, Dawn French and Jennifer Saunders.
Holland is also a patron for The Milton Rooms, a new Arts centre in Malton, North Yorkshire, along with Bill Nighy, Imelda Staunton and Kathy Burke.
Category:1958 births Category:Living people Category:Boogie-woogie pianists Category:English rock pianists Category:English television presenters Category:Officers of the Order of the British Empire Category:Bandleaders Category:Squeeze (band) members Category:I.R.S. Records artists Category:People from Blackheath, London Category:BBC Radio 2 presenters Category:Deputy Lieutenants of Kent Category:British people of Irish descent Category:English people of Irish descent
cy:Jools Holland de:Jools Holland es:Jools Holland fr:Jools Holland nl:Jools Holland pl:Jools Holland pt:Jools Holland fi:Jools HollandThis text is licensed under the Creative Commons CC-BY-SA License. This text was originally published on Wikipedia and was developed by the Wikipedia community.
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