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74-669: The formation is composed of mostly reefal limestones and dolomites , the latter the result of widespread diagenesis . In many areas there is a frequent alternation of limestone and dolomite facies. Local variants to indicate the Wetterstein Formation include German : Wettersteinkalk ( Wetterstein Limestone ), Wettersteindolomit ("Wetterstein Dolomite") and combinations thereof. The Wetterstein Formation reaches

148-749: A Darwin Point is reached. One such point exists at the northwestern end of the Hawaiian Archipelago; see Evolution of Hawaiian volcanoes#Coral atoll stage . However, reefs in the Persian Gulf have adapted to temperatures of 13 °C (55 °F) in winter and 38 °C (100 °F) in summer. 37 species of scleractinian corals inhabit such an environment around Larak Island . Deep-water coral inhabits greater depths and colder temperatures at much higher latitudes, as far north as Norway. Although deep water corals can form reefs, little

222-524: A mountain range in Southern and Southcentral Europe, separating the continental Balkan Peninsula from the Adriatic Sea . They stretch from Italy in the northwest through Slovenia , Croatia , Bosnia and Herzegovina , Serbia , Montenegro , and Kosovo to Albania in the southeast. The Dinaric Alps extend for approximately 645 kilometres (401 mi) along the western Balkan Peninsula from

296-644: A continental shelf, and not around a volcanic island, Darwin's principles apply. Development stopped at the barrier reef stage, since Australia is not about to submerge. It formed the world's largest barrier reef, 300–1,000 m (980–3,280 ft) from shore, stretching for 2,000 km (1,200 mi). Healthy tropical coral reefs grow horizontally from 1 to 3 cm (0.39 to 1.18 in) per year, and grow vertically anywhere from 1 to 25 cm (0.39 to 9.84 in) per year; however, they grow only at depths shallower than 150 m (490 ft) because of their need for sunlight, and cannot grow above sea level. As

370-647: A maximum thickness of 1,000 metres (3,300 ft) with major regional thickness variations. It belongs to the tectonostratigraphical unit Austroalpine nappes . The carbonate rock of the formation is from the Middle Triassic epoch of the Ladinian stage, comparable to the German stage in which Muschelkalk rock strata were formed. The formation has provided numerous fossils of corals , sponges , bivalves , gastropods and other marine groups indicative of

444-412: A pinhead to 12 inches (30 cm) across. Reef-building or hermatypic corals live only in the photic zone (above 70 m), the depth to which sufficient sunlight penetrates the water. Coral polyps do not photosynthesize, but have a symbiotic relationship with microscopic algae ( dinoflagellates ) of the genus Symbiodinium , commonly referred to as zooxanthellae . These organisms live within

518-496: A pseudo-atoll. These can be distinguished from real atolls only by detailed investigation, possibly including core drilling. Some platform reefs of the Laccadives are U-shaped, due to wind and water flow. Atolls or atoll reefs are a more or less circular or continuous barrier reef that extends all the way around a lagoon without a central island. They are usually formed from fringing reefs around volcanic islands. Over time,

592-433: A rapidly subsiding bottom can overwhelm coral growth, killing the coral and the reef, due to what is called coral drowning . Corals that rely on zooxanthellae can die when the water becomes too deep for their symbionts to adequately photosynthesize , due to decreased light exposure. The two main variables determining the geomorphology , or shape, of coral reefs are the nature of the substrate on which they rest, and

666-488: A result of recrystallisation, fossils in the Wetterstein dolomite are harder to distinguish, and even in thin sections may be barely recognizable. Wetterstein dolomite is rarely as bituminous as typical Main Dolomite and therefore tends to be much more pure and brighter-coloured. Otherwise, there are no fundamental differences with the Wetterstein limestone. Among others, the following fossils have been described from

740-566: A shallow marine carbonate platform environment deposited at the northern end of the Tethys Ocean . The Wetterstein Formation is named after the Wetterstein Mountains in southern Germany and northwestern Austria. Alternative names for the whole formation or parts of it in stratigraphical (vertical) or facies (lateral) sense are: The Swiss stratigraphical lexicon uses Wetterstein Formation as "informal, but used name" with

814-423: A zone extending from approximately 30° N to 30° S of the equator. Tropical corals do not grow at depths of over 50 meters (160 ft). The optimum temperature for most coral reefs is 26–27 °C (79–81 °F), and few reefs exist in waters below 18 °C (64 °F). When the net production by reef building corals no longer keeps pace with relative sea level and the reef structure permanently drowns

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888-631: Is built mostly of Mesozoic limestone and dolomite deposited on top of a huge Bahama-type carbonate platform, while a few kilometers thick carbonate successions have been deformed during the Alpine orogenesis. The main tectonic phase of the Alpine orogenesis in the Dinaric Karst region took place in the Cenozoic Era ( Paleogene ) as a result of the Adriatic microplate (Adria) collision with

962-517: Is communication possible across the Karst, and roads and railways tunnel through precipitous cliffs and traverse narrow ledges above roaring torrents. A number of springs and rivers rise in the Dinaric range, including Jadro Spring noted for having been the source of water for Diocletian's Palace at Split. At the same time, the purity of these rocks is such that the rivers are crystal clear, and there

1036-578: Is constantly changing. Each reef is made up of irregular patches of algae, sessile invertebrates, and bare rock and sand. The size, shape and relative abundance of these patches change from year to year in response to the various factors that favor one type of patch over another. Growing coral, for example, produces constant change in the fine structure of reefs. On a larger scale, tropical storms may knock out large sections of reef and cause boulders on sandy areas to move. Coral reefs are estimated to cover 284,300 km (109,800 sq mi), just under 0.1% of

1110-445: Is directly attached to a shore, or borders it with an intervening narrow, shallow channel or lagoon. It is the most common reef type. Fringing reefs follow coastlines and can extend for many kilometres. They are usually less than 100 metres wide, but some are hundreds of metres wide. Fringing reefs are initially formed on the shore at the low water level and expand seawards as they grow in size. The final width depends on where

1184-523: Is known about them. The northernmost coral reef on Earth is located near Eilat , Israel . Coral reefs are rare along the west coasts of the Americas and Africa , due primarily to upwelling and strong cold coastal currents that reduce water temperatures in these areas (the Humboldt , Benguela , and Canary Currents , respectively). Corals are seldom found along the coastline of South Asia —from

1258-478: Is little soil-making residue. Water quality testing of the Jadro River , for example, indicates the low pollutant levels present. Rock faces are often bare of vegetation and glaring white, but what little soil there is may collect in the hollows and support lush lime-tolerant vegetation, or yield narrow strips of cultivation. Ruins of fortresses dot the mountainous landscape, evidence of centuries of war and

1332-418: Is often the reef's most diverse area. Coral and calcareous algae provide complex habitats and areas that offer protection, such as cracks and crevices. Invertebrates and epiphytic algae provide much of the food for other organisms. A common feature on this forereef zone is spur and groove formations that serve to transport sediment downslope. The reef flat is the sandy-bottomed flat, which can be behind

1406-926: Is part of the Austroalpine nappes . In the Semmering area of Austria, where the name Wettersteindolomit is used, the formation is unconformably overlain by the Kapellener Shale and overlies the Reifling Formation , in the Kalkkögel and Radstadt Tauern the dolomite overlies the Partnach Formation and is overlain by the Raibl Formation , while in Tyrol the formation, called Wettersteinkalk/dolomit unconformably overlies

1480-579: Is the most important corrosive force , dissolving the limestone by chemical action of its natural acidity. As it percolates down through cracks in the limestone it opens up fissures and channels, often of considerable depth, so that whole systems of underground drainage develop. During subsequent millennia these work deeper, leaving in their wake enormous waterless caverns , sinkholes and grottoes and forming underground labyrinths of channels and shafts. The roofs of some of these caverns may eventually fall in, to produce great perpendicular-sided gorges, exposing

1554-874: The Békés Zone . In the Dinarides , the formation is time-equivalent with the Grivska Formation of Bosnia . The Kopaonik Formation in its eponymous mountain range in Serbia is considered a distal, more deep water equivalent of the Wetterstein platform sediments. Dolomitization of the Wetterstein Carbonate Platform is a widespread phenomenon, especially in the Tirolic units of the Northern Calcareous Alps. At

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1628-992: The Gutenstein and Steinalm Formations and unconformably underlies the Reingraben Formation . In the Aggtelek - Rudabánya mountains of Hungary, the formation, called Wetterstein Limestone Formation overlies the Reifling and Steinalm Formations and is overlain by the Szádvárborsa Formation . In Austria the Wetterstein Dolomite correlates with the Alberg Formation of the Linz Dolomites ,

1702-540: The Julian Alps of the northeast Italy, downwards to the Šar and Korab massif , where their direction changes. The Accursed Mountains are the highest section of the entire Dinaric Alps; this section stretches from Albania to Kosovo and eastern Montenegro . Maja Jezercë , standing at 2,694 metres (8,839 ft) above the Adriatic , is the highest peak and is located in Albania. The Dinaric Alps are one of

1776-475: The Late Cretaceous (100–66 Ma), when reefs formed by a group of bivalves called rudists existed; one of the valves formed the main conical structure and the other, much smaller valve acted as a cap. Measurements of the oxygen isotopic composition of the aragonitic skeleton of coral reefs, such as Porites , can indicate changes in sea surface temperature and sea surface salinity conditions during

1850-739: The Mesoamerican Barrier Reef System and the New Caledonian Barrier Reef . Barrier reefs are also found on the coasts of Providencia , Mayotte , the Gambier Islands , on the southeast coast of Kalimantan , on parts of the coast of Sulawesi , southeastern New Guinea and the south coast of the Louisiade Archipelago . Platform reefs, variously called bank or table reefs, can form on the continental shelf , as well as in

1924-592: The Middle Cambrian (513–501 Ma ), Devonian (416–359 Ma) and Carboniferous (359–299 Ma), owing to extinct order Rugosa corals, and Late Cretaceous (100–66 Ma) and Neogene (23 Ma–present), owing to order Scleractinia corals. Not all reefs in the past were formed by corals: those in the Early Cambrian (542–513 Ma) resulted from calcareous algae and archaeocyathids (small animals with conical shape, probably related to sponges ) and in

1998-547: The Ottoman Empire failed to fully subjugate the mountainous areas of Montenegro . In the 20th century, too, the mountains provided favourable terrain for guerrilla warfare , with Yugoslav Partisans organising one of the most successful Allied resistance movements of World War II . The area remains underpopulated, and forestry and mining remain the chief economic activities in the Dinaric Alps. The people of

2072-417: The tropics where the water is agitated, but can only live within a limited depth range, starting just below low tide . Where the level of the underlying earth allows, the corals grow around the coast to form fringing reefs, and can eventually grow to become a barrier reef. Where the bottom is rising, fringing reefs can grow around the coast, but coral raised above sea level dies. If the land subsides slowly,

2146-543: The Balkans. No permanent ice caps existed, and there is little evidence of extensive glaciation . Only the highest summits of Durmitor , Orjen and Prenj have glacial valleys and moraines as low as 600 m (1,969 ft). However, in the Accursed Mountains ( Serbo-Croatian : Prokletije ), a range on the northern Albanian border that runs east to west (thus breaking the general geographic trend of

2220-544: The Clessinsperre, the type locality for the underlying Steinalm Formation, intense dolomitization has altered the microfacies characteristics of the Wetterstein Carbonate platform – typical are fore-reef carbonates, later reefal and back-reefal carbonates topped by lagoonal carbonates, making the original features hardly visible. Because, during dolomitisation , traces of fossils are largely lost as

2294-464: The Dinaric Alps are on record as being the tallest in the world, with an average male adolescent height of 185.6 cm (6 ft 1.1 in). The people of Bosnia and Herzegovina have the highest recorded average of any single country, with 183.9 cm average for men and 171.8 cm for women. The main mountain passes of the Dinaric Alps are: Major tunnels transversing the Dinaric Alps include: The famous Belgrade–Bar railway crosses

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2368-472: The Dinaric system), there is evidence of major glaciation. One geological feature of great importance to the present-day landscape of the Dinarides must be considered in more detail: that of the limestone mountains, often with their attendant faulting. They are hard and slow to erode, and often persist as steep jagged escarpments, through which steep-sided gorges and canyons are cleft by the rivers draining

2442-738: The Indian Ocean, for example, in the Maldives , the Chagos Islands , the Seychelles and around Cocos Island . The entire Maldives consist of 26 atolls. Coral reef ecosystems contain distinct zones that host different kinds of habitats. Usually, three major zones are recognized: the fore reef, reef crest, and the back reef (frequently referred to as the reef lagoon). The three zones are physically and ecologically interconnected. Reef life and oceanic processes create opportunities for

2516-676: The Serbo-Macedonian and Rhodope Massifs, and the process is still active. The Mesozoic limestone forms a very distinctive region of the Balkans , notable for features such as the Karst Plateau , which has given its name to all such terrains of limestone eroded by groundwater. The Dinarides are known for being composed of karst – limestone rocks – as is Dinara , the mountain for which they were named. The Quaternary ice ages had relatively little direct geologic influence on

2590-599: The UV radiation and allowing them to better adapt to warmer water temperatures. In the event of UV or thermal damage, if and when repair occurs, it will increase the likelihood of survival of the host and symbiont. This leads to the idea that, evolutionarily, clade A is more UV resistant and thermally resistant than the other clades. Clades B and C are found more frequently in deeper water, which may explain their higher vulnerability to increased temperatures. Terrestrial plants that receive less sunlight because they are found in

2664-605: The Wetterstein Formation: Coral reef A coral reef is an underwater ecosystem characterized by reef-building corals . Reefs are formed of colonies of coral polyps held together by calcium carbonate . Most coral reefs are built from stony corals , whose polyps cluster in groups. Coral belongs to the class Anthozoa in the animal phylum Cnidaria , which includes sea anemones and jellyfish . Unlike sea anemones, corals secrete hard carbonate exoskeletons that support and protect

2738-1038: The Wetterstein kalk/dolomite with the lower part of the Hallstatt Formation of the Northern Limestone Alps and with the Schlern Dolomite , or Schlern Formation, in the Southern Limestone Alps . In Hungary, the formation is time-equivalent with the Berva Formation of the Bükk , the Bódvavölgyi Ophiolite , Szentjánoshegy and Derenk Formations of the Aggtelek-Rudabánya range and the Csanádapáca Formation of

2812-1188: The area of France, yet they provide a home for at least 25% of all marine species , including fish , mollusks , worms , crustaceans , echinoderms , sponges , tunicates and other cnidarians . Coral reefs flourish in ocean waters that provide few nutrients. They are most commonly found at shallow depths in tropical waters, but deep water and cold water coral reefs exist on smaller scales in other areas. Shallow tropical coral reefs have declined by 50% since 1950, partly because they are sensitive to water conditions. They are under threat from excess nutrients (nitrogen and phosphorus), rising ocean heat content and acidification , overfishing (e.g., from blast fishing , cyanide fishing , spearfishing on scuba ), sunscreen use, and harmful land-use practices, including runoff and seeps (e.g., from injection wells and cesspools). Coral reefs deliver ecosystem services for tourism, fisheries and shoreline protection . The annual global economic value of coral reefs has been estimated at anywhere from US$ 30–375 billion (1997 and 2003 estimates) to US$ 2.7 trillion (a 2020 estimate) to US$ 9.9 trillion (a 2014 estimate). Though

2886-502: The coast. The fringing reefs of the Red Sea are "some of the best developed in the world" and occur along all its shores except off sandy bays. Barrier reefs are separated from a mainland or island shore by a deep channel or lagoon . They resemble the later stages of a fringing reef with its lagoon but differ from the latter mainly in size and origin. Their lagoons can be several kilometres wide and 30 to 70 metres deep. Above all,

2960-485: The coastal plains had become continental islands . As sea level rise continued, water topped most of the continental islands. The corals could then overgrow the hills, forming cays and reefs. Sea level on the Great Barrier Reef has not changed significantly in the last 6,000 years. The age of living reef structure is estimated to be between 6,000 and 8,000 years. Although the Great Barrier Reef formed along

3034-451: The coral animals. Coral that loses a large fraction of its zooxanthellae becomes white (or sometimes pastel shades in corals that are pigmented with their own proteins) and is said to be bleached , a condition which, unless corrected, can kill the coral. There are eight clades of Symbiodinium phylotypes . Most research has been conducted on clades A–D. Each clade contributes their own benefits as well as less compatible attributes to

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3108-533: The coral. Most reefs grow best in warm, shallow, clear, sunny and agitated water. Coral reefs first appeared 485 million years ago, at the dawn of the Early Ordovician , displacing the microbial and sponge reefs of the Cambrian . Sometimes called rainforests of the sea , shallow coral reefs form some of Earth's most diverse ecosystems. They occupy less than 0.1% of the world's ocean area, about half

3182-415: The corals shelter the zooxanthellae, averaging one million for every cubic centimetre of coral, and provide a constant supply of the carbon dioxide they need for photosynthesis. The varying pigments in different species of zooxanthellae give them an overall brown or golden-brown appearance and give brown corals their colors. Other pigments such as reds, blues, greens, etc. come from colored proteins made by

3256-529: The deep sea away from continental shelves , around oceanic islands and atolls . The majority of these islands are volcanic in origin. Others have tectonic origins where plate movements lifted the deep ocean floor. In The Structure and Distribution of Coral Reefs , Charles Darwin set out his theory of the formation of atoll reefs, an idea he conceived during the voyage of the Beagle . He theorized that uplift and subsidence of Earth's crust under

3330-637: The eastern tip of India ( Chennai ) to the Bangladesh and Myanmar borders —as well as along the coasts of northeastern South America and Bangladesh, due to the freshwater release from the Amazon and Ganges Rivers respectively. Significant coral reefs include: When alive, corals are colonies of small animals embedded in calcium carbonate shells. Coral heads consist of accumulations of individual animals called polyps , arranged in diverse shapes. Polyps are usually tiny, but they can range in size from

3404-479: The exchange of seawater , sediments , nutrients and marine life. Most coral reefs exist in waters less than 50 m deep. Some inhabit tropical continental shelves where cool, nutrient-rich upwelling does not occur, such as the Great Barrier Reef . Others are found in the deep ocean surrounding islands or as atolls, such as in the Maldives . The reefs surrounding islands form when islands subside into

3478-401: The floor often supports seagrass meadows which are important foraging areas for reef fish. The reef drop-off is, for its first 50 m, habitat for reef fish who find shelter on the cliff face and plankton in the water nearby. The drop-off zone applies mainly to the reefs surrounding oceanic islands and atolls. The reef face is the zone above the reef floor or the reef drop-off. This zone

3552-624: The following historical variants: Its subunits include: The Wetterstein Formation, with a total thickness of up to 1,000 metres (3,300 ft), is a major regional stratigraphic unit of the Northern Limestone Alps and Western Carpathians in Central Europe , spanning across four countries from southwestern Bavaria to northwestern Slovakia . The formation crops out to the north of the Hohe Tauern window and

3626-403: The fringing reef, barrier reef, atoll and table reef based on Stoddart, D.R. (1969). Spalding et al. list four main reef types that can be clearly illustrated – the fringing reef, barrier reef, atoll, and "bank or platform reef"—and notes that many other structures exist which do not conform easily to strict definitions, including the "patch reef". A fringing reef, also called a shore reef,

3700-463: The fringing reefs keep pace by growing upwards on a base of older, dead coral, forming a barrier reef enclosing a lagoon between the reef and the land. A barrier reef can encircle an island, and once the island sinks below sea level a roughly circular atoll of growing coral continues to keep up with the sea level, forming a central lagoon. Barrier reefs and atolls do not usually form complete circles but are broken in places by storms. Like sea level rise ,

3774-419: The growth of the coral. This technique is often used by climate scientists to infer a region's paleoclimate . Since Darwin's identification of the three classical reef formations – the fringing reef around a volcanic island becoming a barrier reef and then an atoll – scientists have identified further reef types. While some sources find only three, Thomas lists "Four major forms of large-scale coral reefs" –

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3848-559: The higher slopes. The partially submerged western Dinaric Alps form the numerous islands and harbors along the Croatian coast. The most extensive example of limestone mountains in Europe are those of the Karst of the Dinaric Alps. Here, all the characteristic features are encountered again and again as one travels through this wild and thinly populated country. Limestone is a very porous rock, yet very hard and resistant to erosion . Water

3922-548: The history of the change in sea level relative to that substrate. The approximately 20,000-year-old Great Barrier Reef offers an example of how coral reefs formed on continental shelves. Sea level was then 120 m (390 ft) lower than in the 21st century. As sea level rose, the water and the corals encroached on what had been hills of the Australian coastal plain. By 13,000 years ago, sea level had risen to 60 m (200 ft) lower than at present, and many hills of

3996-666: The island erodes away and sinks below sea level. Atolls may also be formed by the sinking of the seabed or rising of the sea level. A ring of reefs results, which enclose a lagoon. Atolls are numerous in the South Pacific, where they usually occur in mid-ocean, for example, in the Caroline Islands , the Cook Islands , French Polynesia , the Marshall Islands and Micronesia . Atolls are found in

4070-418: The main reef, containing chunks of coral. This zone may border a lagoon and serve as a protective area, or it may lie between the reef and the shore, and in this case is a flat, rocky area. Fish tend to prefer it when it is present. The reef lagoon is an entirely enclosed region, which creates an area less affected by wave action and often contains small reef patches. However, the topography of coral reefs

4144-484: The mainland. Unlike fringing and barrier reefs which extend only seaward, platform reefs grow in all directions. They are variable in size, ranging from a few hundred metres to many kilometres across. Their usual shape is oval to elongated. Parts of these reefs can reach the surface and form sandbanks and small islands around which may form fringing reefs. A lagoon may form In the middle of a platform reef. Platform reefs are typically situated within atolls, where they adopt

4218-484: The most rugged and extensive mountainous areas of Europe, alongside the Caucasus Mountains , Alps , Pyrenees , Carpathian Mountains and Scandinavian Mountains . They are formed largely of Mesozoic and Cenozoic sedimentary rocks of dolomite , limestone , sandstone and conglomerates formed by seas and lakes that once covered the area. During the Alpine earth movements that occurred 50 to 100 million years ago, immense lateral pressures folded and overthrust

4292-688: The mountainous terrain subsides to make way for the waters of the Drin River and the plains of Kosovo. The Dinarides are named after Mount Dinara (1,831 m), a prominent peak in the center of the mountain range on the border with the Dalmatian part of Croatia and Bosnia and Herzegovina. Names of the chain in local languages include Albanian : Alpet Dinarike [alpɛt dinaɾikɛ] or Dinaret ; Italian : Alpi Dinariche [alpi dinarike] ; Serbo-Croatian : Динариди , Dinaridi or Динарско горје Dinarsko gorje [dìnarskòː ɡòːrjeː] ; Slovene : Dinarsko gorstvo [dìnarskòː ɡòːrstvòː] . The Dinaric Karst region

4366-400: The name "patch reefs" and often span a diameter of just a few dozen meters. In instances where platform reefs develop along elongated structures, such as old and weathered barrier reefs, they tend to arrange themselves in a linear formation. This is the case, for example, on the east coast of the Red Sea near Jeddah . In old platform reefs, the inner part can be so heavily eroded that it forms

4440-528: The name implies, coral reefs are made up of coral skeletons from mostly intact coral colonies. As other chemical elements present in corals become incorporated into the calcium carbonate deposits, aragonite is formed. However, shell fragments and the remains of coralline algae such as the green-segmented genus Halimeda can add to the reef's ability to withstand damage from storms and other threats. Such mixtures are visible in structures such as Eniwetok Atoll . The times of maximum reef development were in

4514-415: The ocean, and atolls form when an island subsides below the surface of the sea. Alternatively, Moyle and Cech distinguish six zones, though most reefs possess only some of the zones. The reef surface is the shallowest part of the reef. It is subject to surge and tides . When waves pass over shallow areas, they shoal , as shown in the adjacent diagram. This means the water is often agitated. These are

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4588-528: The oceans formed the atolls. Darwin set out a sequence of three stages in atoll formation. A fringing reef forms around an extinct volcanic island as the island and ocean floor subside. As the subsidence continues, the fringing reef becomes a barrier reef and ultimately an atoll reef. Darwin predicted that underneath each lagoon would be a bedrock base, the remains of the original volcano. Subsequent research supported this hypothesis. Darwin's theory followed from his understanding that coral polyps thrive in

4662-426: The oceans' surface area. The Indo-Pacific region (including the Red Sea , Indian Ocean , Southeast Asia and the Pacific ) account for 91.9% of this total. Southeast Asia accounts for 32.3% of that figure, while the Pacific including Australia accounts for 40.8%. Atlantic and Caribbean coral reefs account for 7.6%. Although corals exist both in temperate and tropical waters, shallow-water reefs form only in

4736-406: The offshore outer reef edge formed in open water rather than next to a shoreline. Like an atoll, it is thought that these reefs are formed either as the seabed lowered or sea level rose. Formation takes considerably longer than for a fringing reef, thus barrier reefs are much rarer. The best known and largest example of a barrier reef is the Australian Great Barrier Reef . Other major examples are

4810-399: The open ocean, in fact anywhere where the seabed rises close enough to the surface of the ocean to enable the growth of zooxanthemic, reef-forming corals. Platform reefs are found in the southern Great Barrier Reef, the Swain and Capricorn Group on the continental shelf, about 100–200 km from the coast. Some platform reefs of the northern Mascarenes are several thousand kilometres from

4884-429: The polyps' tissues and provide organic nutrients that nourish the polyp in the form of glucose , glycerol and amino acids . Because of this relationship, coral reefs grow much faster in clear water, which admits more sunlight. Without their symbionts, coral growth would be too slow to form significant reef structures. Corals get up to 90% of their nutrients from their symbionts. In return, as an example of mutualism ,

4958-420: The precise condition under which corals flourish. The light is sufficient for photosynthesis by the symbiotic zooxanthellae, and agitated water brings plankton to feed the coral. The off-reef floor is the shallow sea floor surrounding a reef. This zone occurs next to reefs on continental shelves. Reefs around tropical islands and atolls drop abruptly to great depths and do not have such a floor. Usually sandy,

5032-453: The refuge the Dinaric Alps have provided to various armed forces. During the Roman period, the Dinarides provided shelter to the Illyrians resisting Roman conquest of the Balkans, which began with the conquest of the eastern Adriatic coast in the 3rd century BC. Rome conquered the whole of Illyria in 168 BC, but these mountains sheltered Illyrian resistance forces for many years until the area's complete subjugation by 14 AD. More recently,

5106-446: The rocks in a great arc around the old rigid block of the northeast. The main tectonic phase of the orogenesis in the area of the Dinaric Karst took place in Cenozoic Era (Paleogene) as a result of the Adriatic Microplate (Adria) collision with Europe, and the process is still active. The Dinaric Alps were thrown up in more or less parallel ranges, stretching like necklaces from the Julian Alps as far as northern Albania and Kosovo, where

5180-412: The sea bed begins to drop steeply. The surface of the fringe reef generally remains at the same height: just below the waterline. In older fringing reefs, whose outer regions pushed far out into the sea, the inner part is deepened by erosion and eventually forms a lagoon . Fringing reef lagoons can become over 100 metres wide and several metres deep. Like the fringing reef itself, they run parallel to

5254-539: The shallow water tropical coral reefs are best known, there are also deeper water reef-forming corals, which live in colder water and in temperate seas. Most coral reefs were formed after the Last Glacial Period when melting ice caused sea level to rise and flood continental shelves . Most coral reefs are less than 10,000 years old. As communities established themselves, the reefs grew upwards, pacing rising sea levels . Reefs that rose too slowly could become drowned, without sufficient light. Coral reefs are also found in

5328-1135: The surface to the water once more. The Dinaric rivers carved many canyons characteristic for Dinaric Alps, and in particular karst. Among the largest and most well known are the Neretva , the Rakitnica , the Prača , the Drina , the Sutjeska , the Vrbas , the Ugar , the Piva , the Tara , the Komarnica , the Morača , the Cem/Ciijevna , the Lim , and the Drin . Only along the Dinaric gorges

5402-424: The survival of their coral hosts. Each photosynthetic organism has a specific level of sensitivity to photodamage to compounds needed for survival, such as proteins. Rates of regeneration and replication determine the organism's ability to survive. Phylotype A is found more in the shallow waters. It is able to produce mycosporine-like amino acids that are UV resistant , using a derivative of glycerin to absorb

5476-427: The undergrowth are analogous to clades B, C, and D. Since clades B through D are found at deeper depths, they require an elevated light absorption rate to be able to synthesize as much energy. With elevated absorption rates at UV wavelengths, these phylotypes are more prone to coral bleaching versus the shallow clade A. Dinarides The Dinaric Alps ( / d ɪ ˈ n ær ɪ k / ), also Dinarides , are

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