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Encyclopedia > Reef
Pamalican island with surrounding reef, Sulu Sea, Philippines.
Pamalican island with surrounding reef, Sulu Sea, Philippines.
A reef surrounding an islet.

In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water yet shallow enough to be a hazard to ships. Many reefs result from abiotic processes—deposition of sand, wave erosion planning 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 calcareous algae. Reef can mean: Reef, a shallow or underwater obstacle, such as a coral reef. ... The main beach on the southern shore of Pamalican. ... The Sulu Sea is a large sea in the southwestern area of the Philippines. ... A reef sticking out of the water. ... A reef sticking out of the water. ... Mōkōlea Rock in Kailua Bay, O‘ahu, Hawai‘i, 2. ... Rock redirects here. ... Sand bars in the Mississippi River at Arkansas and Mississippi A bar is a linear shoaling landform feature within a body of water. ... For online phenomenon of shipping, see Shipping (fandom). ... This article or section does not adequately cite its references or sources. ... Part of a coral reef. ... The tropics are the geographic region of the Earth centered on the equator and limited in latitude by the two tropics: the Tropic of Cancer in the north and the Tropic of Capricorn in the southern hemisphere. ... Look up biotic in Wiktionary, the free dictionary. ... Extant Subclasses and Orders Alcyonaria    Alcyonacea    Helioporacea Zoantharia    Antipatharia    Corallimorpharia    Scleractinia    Zoanthidea [1][2]  See Anthozoa for details For other uses, see Coral (disambiguation). ... Calcareous formed from or containing a high proportion of Calcium carbonate. ... Osborne (talk) 20:17, 5 December 2007 (UTC):For the programming language, see algae (programming language) Laurencia, a marine red alga from Hawaii. ...


Reefs can be created artificially either by special construction or through deliberately sinking ships, but one can argue that these "reefs" are not real ones, as it is seldom the case that an artificial obstruction would be created that is a hazard to shipping. These structures are usually created to enhance physical complexity on generally featureless sand bottoms in order to attract a diverse assemblage of organisms, especially fish. Thus, "artificial reef" is a misnomer, though firmly established as the term used for man-made underwater habitat structures. For other uses, see Fish (disambiguation). ... Construction in place of an artificial reef from hollow tile blocks Ship about to be scuttled to act as an Artificial Reef An artificial reef is a man-made, underwater structure, typically built for the purpose of promoting marine life in areas of generally featureless bottom. ...

Contents

Biotic reef types

There are a number of biotic reef types, including oyster reefs, but the most massive and widely distributed are tropical coral reefs. Although corals are major contributors to the framework and bulk material comprising a coral reef, the organisms most responsible for reef growth against the constant assault from ocean waves are calcarous algae, especially, although not entirely, species of coralline algae. For other uses, see Oyster (disambiguation). ... Some of the biodiversity of a coral reef, in this case the Great Barrier Reef, Australia. ... Genera 39 genera Coralline algae are red algae in the Family Corallinaceae characteriuzed by a thallus covered with calcareous deposits. ...


Geologic reef definition

Geologists define reefs and related terms (for example, bioherm, biostrome, carbonate mound) using the factors of depositional relief, internal structure, and biotic composition. There is no consensus on one universally applicable definition. A useful definition distinguishes reefs from mounds as follows. Both are considered to be varieties of organosedimentary buildups: sedimentary features, built by the interaction of organisms and their environment, that have synoptic relief and whose biotic composition differs from that found on and beneath the surrounding sea floor. Reefs are held up by a macroscopic skeletal framework. Coral reefs are an excellent example of this kind. Corals and calcareous algae grow on top of one another and form a three-dimensional framework that is modified in various ways by other organisms and inorganic processes. By contrast, mounds lack a macroscopic skeletal framework. Mounds are built by microorganisms or by organisms that don't grow a skeletal framework. A microbial mound might be built exclusively or primarily by cyanobacteria. Excellent examples of biostromes formed by cyanobacteria occur in the Great Salt Lake of Utah (USA), and in Shark Bay, Western Australia.


Cyanobacteria do not have skeletons and individuals are microscopic. Cyanobacteria encourage the precipitation or accumulation of calcium carbonate and can produce compositionally distinct sediment bodies that have relief on the seafloor. Cyanobacterial mounds were most abundant before the evolution of shelly macroscopic organisms, but they still exist today (stromatolites are microbial mounds with a laminated internal structure). Bryozoans and crinoids, common contributors to marine sediments during the Mississippian (for example), produced a very different kind of mound. Bryozoans are small and the skeletons of crinoids disintegrate. However, bryozoan and crinoid meadows can persist over time and produce compositionally distinct bodies of sediment with depositional relief.


Geologic reef structures

Ancient reefs buried within stratigraphic sections are of considerable interest to geologists because they provide paleo-environmental information about the location in Earth's history. In addition, reef structures within a sequence of sedimentary rocks provide a discontinuity which may serve as a trap or conduit for fossil fuels or mineralizing fluids to form petroleum or ore deposits. Corals, including some major extinct groups Rugosa and Tabulata, have been important reef builders through much of the Phanerozoic since the Ordovician period. However, other organism groups, such as calcifying algae, especially members of the red algae Rhodophyta, and mollusks (especially the rudist bivalves during the Cretaceous period) have created massive structures at various times. During the Cambrian period, the conical or tubular skeletons of Archaeocyatha,an extinct group of uncertain affinities (possibly sponges), built reefs. Other groups, such as the Bryozoa have been important interstitial organisms, living between the framework builders. The corals which build reefs today, the Scleractinia, arose after the Permian-Triassic extinction that wiped out the earlier rugose corals (as well as many other groups), and became increasingly important reef builders throughout the Mesozoic Era. They may have arisen from a rugose coral ancestor. Rugose corals built their skeletons of calcite and have a different symmetry from that of the scleractinian corals, whose skeletons are aragonite. However, there are some unusual examples of well preserved aragonitic rugose corals in the late Permian. In addition, calcite has been reported in the initial post-larval calcification in a few scleractinian corals. Nevertheless, scleractinian corals (which arose in the middle Triassic) may have arisen from a non-calcifying ancestor independent of the rugosan corals (which disappeared in the late Permian). Stratigraphy, a branch of geology, studies rock layers and layering (stratification). ... The Geologist by Carl Spitzweg 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 (see planetary geology). ... Geological time put in a diagram called a geological clock, showing the relative lengths of the eons of the Earths history. ... Two types of sedimentary rock: limey shale overlaid by limestone. ... Fossil fuels or mineral fuels are fossil source fuels, this is, hydrocarbons found within the top layer of the earth’s crust. ... Petro redirects here. ... For other uses, see Ore (disambiguation). ... Suborders Columnariina† Cystiphyllina† Streptelasmatina† The Rugosa, also called the Tetracoralla, are an extinct order of coral that were abundant in Middle Ordovician to Late Permian seas. ... The tabulate corals, forming the order Tabulata, are an extinct form of coral. ... During the Phanerozoic the biodiversity shows a steady but not monotonic increase from near zero to several thousands of genera. ... Artist impression of the Ordovician Sea. ... Red algae Classes Florideophyceae Bangiophyceae Cyanidiophyceae The red algae are a large group of mostly multicellular, marine algae, including many notable seaweeds. ... Rudists are a group of bivalves that peaked in abundance and diversity during the late Mesozoic era, particularly in the Cretaceous period, at the end of which they became extinct. ... // The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i. ... For other uses, see Cambrian (disambiguation). ... The Archeocyatha, also called Archaeocyathids, were sessile, reef-building marine organisms that lived during the Lower Cambrian period (500-600 million years ago). ... Classes Stenolaemata Gymnolaemata Phylactolaemata Bryozoans are tiny colonial animals that generally build stony skeletons of calcium carbonate, superficially similar to coral. ... Families Suborder Astrocoeiina   Acroporidae   Astrocoeniidae   Pocilloporiidae Suborder Caryophylliina   Caryophylliidae Suborder Dendrophylliina   Dendrophylliidae Suborder Faviina   Astrangiidae   Faviidae   Meandrinidae   Mirulinidae   Mussidae   Oculinidae   Pectiniidae   Trachyphyllidae Suborder Fungiina   Agariciidae   Fungiidae   Poritidae   Siderastreidae   Thamnasteriidae Scleractinia, also called Stony star corals, are exclusively marine animals; they are very similar to sea anemones but generate a hard... The Permian is a geologic period that extends from about 299. ... The Triassic is a geologic period that extends from about 251 ± 0. ... The Mesozoic Era is one of three geologic eras of the Phanerozoic eon. ... Doubly refracting Calcite from Iceberg claim, Dixon, New Mexico. ... Aragonite Aragonite is a polymorph of the mineral calcite, both having the chemical composition CaCO3. ... The Permian is a geologic period that extends from about 299. ...


External links

This article is about the US organization called The Nature Conservancy. ...

  Results from FactBites:
 
Reef - Wikipedia, the free encyclopedia (315 words)
Reefs can be created artificially either by special construction or through deliberately sinking ships, but one can argue that these "reefs" are not real ones, as it is seldom the case that an artificial obstruction would be created that is a hazard to shipping.
Thus, "artificial reef" is a misnomer, though firmly established as the term used for man-made underwater habitat structures.
In addition, reef structures within a sequence of sedimentary rocks provide a discontinuity which may serve as a trap or conduit for fossil fuels or mineralizing fluids to form petroleum or ore deposits.
Coral reef - Wikipedia, the free encyclopedia (3604 words)
Coral reefs are either restricted or absent from along the west coast of the Americas, as well as the west coast of Africa.
Coral reefs are home to a variety of tropical or reef fishes, such as the colorful parrotfishes, angelfishes, damselfishes and butterflyfishes.
Reefs are also home to a large variety of other organisms, including sponges, Cnidarians (which includes some types of corals and jellyfish), worms, crustaceans (including shrimp, spiny lobsters and crabs), mollusks (including cephalopods), echinoderms (including starfish, sea stars, sea urchins and sea cucumbers), sea squirts, sea turtles and sea snakes.
  More results at FactBites »

 
 

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