"are Funafuti, Nanumea, Nui, Nukufetau, Nukulaelae and Vaitupu. Funafuti is the largest atoll of the nine low reef islands and atolls that form the Tuvalu volcanic island chain. It comprises numerous islets around a central lagoon that is approximately 25.1 kilometres (15.6 mi) (N–S) by 18.4 kilometres (11.4 mi) (W-E), centred on 179°7’E and 8°30’S. On the atolls an annular reef rim surrounds the lagoon, with several natural reef channels. A standard definition of an ""atoll"" is ""an annular reef enclosing a lagoon in which there are no promontories other than reefs and islets composed of reef detritus"". The eastern"
"National Geographic Society defines lagoons as a ""shallow body of water protected from a larger body of water (usually the ocean) by sandbars, barrier islands, or coral reefs."" There are two different types of lagoons: coastal lagoons and atoll lagoons. Coral reefs are one of the most well-known marine ecosystems within the world. The largest being that of the Great Barrier Reef. These reefs are composed of large coral colonies of a variety of species living together. The corals form multiple symbiotic relationships with the organisms around them. The deep sea contains up to 95% of the space occupied by"
"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 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 changes from year to year in response to the various factors"
"enclosing a lagoon in which there are no promontories other than reefs and islets composed of reef detritus"" or ""in an exclusively morphological sense, [as] a ring-shaped ribbon reef enclosing a lagoon"". Most of the world's atolls are in the Pacific Ocean (with concentrations in the Tuamotu Islands, Caroline Islands, Marshall Islands, Coral Sea Islands, and the island groups of Kiribati, Tuvalu and Tokelau) and Indian Ocean (the Atolls of the Maldives, the Lakshadweep Islands, the Chagos Archipelago and the Outer Islands of the Seychelles). The Atlantic Ocean has no large groups of atolls, other than eight atolls east of"
"Atoll An atoll (, , , , or ), sometimes called a coral atoll, is a ring-shaped coral reef including a coral rim that encircles a lagoon partially or completely. There may be coral islands or cays on the rim. The coral of the atoll often sits atop the rim of an extinct seamount or volcano which has eroded or subsided partially beneath the water. The lagoon forms over the volcanic crater or caldera while the higher rim remains above water(s) or at shallow depths that permit the coral to grow and form the reefs. For the atoll to persist,"
"Lagoon A lagoon is a shallow body of water separated from a larger body of water by barrier islands or reefs. Lagoons are commonly divided into coastal lagoons and atoll lagoons. They have also been identified as occurring on mixed-sand and gravel coastlines. There is an overlap between bodies of water classified as coastal lagoons and bodies of water classified as estuaries. Lagoons are common coastal features around many parts of the world. Lagoons are shallow, often elongated bodies of water separated from a larger body of water by a shallow or exposed shoal, coral reef, or similar feature. Some"
"infer a region's paleoclimate. 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 the coral. Most reefs grow best in warm, shallow, clear, sunny and agitated water. Often called ""rainforests of the sea"", shallow coral reefs form some of Earth's most"
"around . At the outer edge of the reef shelf, the bottom slopes very steeply into deep water, at some locations dropping to more than within of the shore. In the lagoon, numerous coral heads present hazards to navigation. The shallow reef shelf surrounding the island on the ocean side offers no ocean-side anchorage. The channel and anchorage areas in the northern half of the lagoon are dredged, along with the pre-1971 ship turning basin. Significant saltwater wetlands called barachois exist in the southern half of the lagoon. These small lagoons off of the main lagoon are filled with seawater"
"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 the coral. Most reefs grow best in warm, shallow, clear, sunny and agitated water. Often called ""rainforests of the sea"", shallow coral reefs form some of Earth's most diverse ecosystems. They occupy"
"Pseudo-atoll A pseudo-atoll, like an atoll, is an island that encircles a lagoon, either partially or completely. A pseudo-atoll differs from an atoll as established by several authorities, such as how it is formed (not by subsidence, nor by coral). It is considered a preferable term to ""near-atoll"". There is a need for rigorous definition of ""pseudo-atoll"" before it can be accepted as a general term. Alexander Agassiz gave the term pseudo-atoll to ""any ring-shaped reefs not formed as a result of subsidence"". while Norman D. Newell and J. Keith Rigby called such reefs non-coral. and ""We conclude that almost-atoll"
"Sponge reef Sponge reefs are reefs formed by Hexactinellid sponges, which have a skeleton made of silica, and are often referred to as ""glass sponges"". Such reefs are now very rare, and found only on the western Canadian continental shelf. Although common in the late Jurassic period, sponge reefs were believed to have gone extinct during or shortly after the Cretaceous period, until the existing reefs were discovered in 1987–1988 - hence these sometimes being dubbed living fossils. The reefs serve an important ecological function as habitat, breeding and nursery areas for fish and invertebrates but are currently threatened by"
"waves overwash barrier islands. Mangroves and marsh plants can facilitate the accumulation of sediment in a lagoon. Benthic organisms may stabilize or destabilize sediments. River-mouth lagoons on mixed sand and gravel (MSG) beaches form at the river-coast interface where a typically braided, although sometimes meandering, river interacts with a coastal environment that is significantly affected by longshore drift. The lagoons which form on the MSG coastlines are common on the east coast of the South Island of New Zealand and have long been referred to as hapua by the Māori. This classification differentiates hapua from similar lagoons located on the"
"or epicontinental (as the Belize reefs or the Florida Keys). Geologically speaking, reef rocks can be classified as massive boundstones. The internal lagoon, as the name suggests, is the part of platform behind the reef. It is characterised by shallow and calm waters. Sediments are composed of reef fragments and hard parts of organisms. If the reef is epicontinental there can be also a terrigenous contribution. In some lagoons (e.g., the Florida Bay) green algae produce great volumes of carbonate mud. Rocks here are mudstones to grainstones depending on the energy of the environment. The slope is the outer part"
"Frederick Reefs Frederick Reef is in the Coral Sea Islands, over northeast of Gladstone, Queensland. The reef gets its name from ""Frederick"", which first reported sighting the reef. Frederick Reef is a small atoll with a large rock called Ridge Rock at the southern end, a sand cay called Observatory Cay, and a lighthouse at the northern end, which is the only permanently dry land, although there are a few of others cays that can be awash at high tide. The reef is around 30km2. The reefs are in a J shape that forms a semi-enclosed lagoon known as Anchorage"
"traditional owners groups agreed to cease the hunting of dugongs in the area in 2011 due to their declining numbers, partially accelerated by seagrass damage from Cyclone Yasi. Great Barrier Reef The Great Barrier Reef is the world's largest coral reef system composed of over 2,900 individual reefs and 900 islands stretching for over over an area of approximately . The reef is located in the Coral Sea, off the coast of Queensland, Australia. The Great Barrier Reef can be seen from outer space and is the world's biggest single structure made by living organisms. This reef structure is composed"
"found on many small central Pacific islands. Lizards, rats, and seabirds are common on Atafu island. The atoll attracts a wide variety of fish in large numbers. The eastern side of the lagoon is a nearly continuous thin strip of land with one small break halfway along its length. In contrast, the western side is composed of reef and several distinct islands, notably the inverted V shape of Atafu Island in the north, Alofi, which extends into the lagoon from the western reef, and the L-shaped Fenualoa in the southwest. The smaller Tamaseko Island lies in the lagoon close to"
"Reef A reef is a bar of rock, sand, coral or similar material, lying beneath the surface of water. Many reefs result from abiotic processes (i.e. deposition of sand, wave erosion planing down rock outcrops, and other natural processes), but the best known reefs are the coral reefs of tropical waters developed through biotic processes dominated by corals and coralline algae. Artificial reefs (e.g. shipwrecks) sometimes have a role in enhancing the physical complexity of featureless sand bottoms, in order to attract a diverse assemblage of organisms, especially algae, and fish. Earth's largest and most famous reef is the Great"
"submerged atoll, with just one islet (Helen Island). The atoll is 25 km long and nearly 10 km wide, with a lagoon area of 103 km² and a total area including reef flat of 163 km². A channel leads into the lagoon from near the middle of the western side of the reef. Immediately south of the channel is Round Rock, which dries. The lagoon has about 85 patch and pinnacle Reefs. When the tide is falling, the water flows out of the lagoon and over the reef in all directions until the reef is uncovered, and then flows out"
"Reef is the second largest barrier reef in the world. Amedee island is a special marine reserve of coral reef lagoon, Ilot aux Goelands is a tiny lagoon island surrounded by a large shallow reef flat. The reef has great species diversity with a high level of endemism. Many groups have been under sampled and insufficiently studied, especially when considering hard bottoms of the intermediate coral reefs and external slopes of the barrier reef. This diversity includes oceanic and continental reefs forming islands, atolls, uplifted reefs, immerged reefs, fringing reefs, barrier reefs, patch reefs and shallow or deep lagoons, is"
"site for a yet-to-be-named ray exhibit. By October, the name of the exhibit was announced to be Ray Reef. It was originally scheduled that the exhibit would open on Boxing Day 2008 (26 December 2008), however, a number of delays forced it to open on 14 January 2009. ""Ray Reef"" consists of a large lagoon pool and a smaller pool which together are home to more than 100 rays. The Ray Reef area is located under large shade cloths providing shade for guests and rays alike. The whole lagoon is divided in two by a rock wall. The smaller pool"
"its kind. The reef system has been identified as a coral and sponge reef. Scientists estimated the reef's size to be in area, and over in length, making it one of the largest reef systems in the world, comparable to the size of the island of Cyprus. Another estimate also puts the general ecoregion encompassing the reef to be as large as . The reef's area extends as far as offshore, and is estimated to lie in waters ranging from deep. The reef's existence is unusual, as reef systems do not often exist in the mouths of larger rivers like"
"buffer zone around the reefs be added to the existing groudfish trawl closures. The four reefs in the QCB, and one reef in the GB are also being considered as locations for future Marine Protected Areas (MPAs). Although MPAs may be more effective than fishery closures for long-term protection of the reefs from bottom trawling, the oil and gas industry would still pose a threat. Sponge reef Sponge reefs are reefs formed by Hexactinellid sponges, which have a skeleton made of silica, and are often referred to as ""glass sponges"". Such reefs are now very rare, and found only on"
"Page 10 Barrett Reef The cluster of rocks that is Barrett Reef (often known as ""Barrett's Reef"") is one of the most hazardous reefs in New Zealand. It lies on the western side of the entrance of Wellington Harbour, on the approaches to the city of Wellington, at coordinates . The reef is named after Richard (Dicky) Barrett (1807–1847), a whaler and trader. Its Maori name is ""Tangihanga-a-Kupe"". It is popular with recreational divers. The reef, much of which is exposed even at high tide, is located to the west of the two-kilometre-wide channel that links Cook Strait with Wellington"
"a lagoon, which often extends more than a hundred metres to the reef, then slopes steeply to deep water. The reef fronts the shore to the north of the island, making the lagoon there unsuitable for swimming and water sports, but to the south east, particularly around Muri, the lagoon is at its widest and deepest. This part of the island is the most popular with tourists for swimming, snorkelling and boating. Agricultural terraces, flats and swamps surround the central mountain area. Along the southeast coast off Muri Beach are four small coral islets within a few hundred metres of"
"suburbs and protecting the calm waters of Coxs Bay, it was the site of the city's tip for many years. This has now been capped and replaced by a 15 ha public reserve, with mangrove swamps in the streams and tidal salt marshes either side. In the 1970s, plans for a Second Harbour Crossing from the reef to Birkenhead were shelved after public outcry. Meola Reef Meola Reef, or Te Tokaroa Reef in Māori ('toka'='rock', 'roa'='long'), is a lava flow forming a reef peninsula across part of Auckland's Waitematā Harbour, New Zealand. The reef extends for over 2 kilometres across"
"meadows and patch reefs. This type of coral reef is the most common type of reef found in the Caribbean and Red Sea. Darwin believed that fringing reefs are the first kind of reefs to form around a landmass in a long-term reef growth process. Sometimes it is hard to tell the difference between fringing reefs and another type of reef called a barrier reef. One of the ways that these two types of reefs are separated is based on the depth of the lagoon in the back reef which is the area near to shore. Barrier reefs have at"
"island is circled by a broad fringing reef, which, off the western coast swings sharply away from the shore to enclose the lagoon. The precipitous sides of the central mass are scored by three shallow terraces, marking pauses in the uplift of the island; but these are not readily observed, being smothered under the dense vegetation that clothes the whole towering structure. It is a former atoll, specifically called a “Guyot”. This is an extinct volcano that has become overgrown by coral reefs to form an atoll. The flat top was once at sea level, which is why the summit"
"and reefs lie - Point Danger. He wrote: ""We now saw the breakers again they lay two Leagues from a point under which is a small Island, their situation may always be found by the peaked mountain before mentioned from them this mountain or hill, and on this account I have named Mount Warning it lies 7 or 8 Leagues inland the land is high and hilly about it, but it is conspicuous enough to be distinguished from everything else. The point off which these shoals lay I have named Point Danger."" These reefs are now named Danger Reefs and"
"commercial tour groups is regulated and limited, though there is some visitation by private yachts. Coral Sea Reserves Ramsar Site The Coral Sea Reserves Ramsar Site comprises the 17,292 km of oceanic island and reef habitats within the former Coringa-Herald National Nature Reserve and the former Lihou Reef National Nature Reserve in the Australian Coral Sea Islands Territory. The existence of the islands and cays within the two reserves has been known to navigators since the early nineteenth century. Lihou Reef was named after Captain John Lihou of HMS ""Zenobia"", who discovered the reef and its cays in 1823. The"
"eastern rim of the reef, takes up out of the main island. For the lagoon, area figures between are found. Satellite image measurement suggests that the larger figure also includes the reef flat, which is commonly not considered part of a lagoon. The barrier reef that forms the basis of Aitutaki is roughly the shape of an equilateral triangle with sides in length. The southern edge of the triangle is almost totally below the surface of the ocean, and the eastern side is composed of a string of small islands including Mangere, Akaiami, and Tekopua. The western side of the"
"cliffs with dome formationssimilar to the white domes often placed on ""capitol"" buildingsthat run from the Fremont River to Pleasant Creek on the Waterpocket Fold. The local word ""reef"" refers to any rocky barrier to land travel, just as ocean reefs are barriers to sea travel. Capitol Reef encompasses the Waterpocket Fold, a warp in the earth's crust that is 65 million years old. It is the largest exposed monocline in North America. In this fold, newer and older layers of earth folded over each other in an S-shape. This warp, probably caused by the same colliding continental plates that"
"state of constant morphological change due to the prevailing southerly sea swells and resultant northwards longshore drift. Lagoon A lagoon is a shallow body of water separated from a larger body of water by barrier islands or reefs. Lagoons are commonly divided into coastal lagoons and atoll lagoons. They have also been identified as occurring on mixed-sand and gravel coastlines. There is an overlap between bodies of water classified as coastal lagoons and bodies of water classified as estuaries. Lagoons are common coastal features around many parts of the world. Lagoons are shallow, often elongated bodies of water separated from"
"coast, while estuaries are usually drowned river valleys, elongated perpendicular to the coast. When used within the context of a distinctive portion of coral reef ecosystems, the term ""lagoon"" is synonymous with the term ""back reef"" or ""backreef"", which is more commonly used by coral reef scientists to refer to the same area. Coastal lagoons are classified as inland bodies of water. Many lagoons do not include ""lagoon"" in their common names. Albemarle and Pamlico sounds in North Carolina, Great South Bay between Long Island and the barrier beaches of Fire Island in New York, Isle of Wight Bay, which"