The coast known as the coastline or seashore, is the area where land meets the sea or ocean, or a line that forms the boundary between the land and the ocean or a lake. A precise line that can be called a coastline cannot be determined due to the Coastline paradox; the term coastal zone is a region where interaction of the land processes occurs. Both the terms coast and coastal are used to describe a geographic location or region. Edinburgh for example is a city on the coast of Great Britain. A pelagic coast refers to a coast which fronts the open ocean, as opposed to a more sheltered coast in a gulf or bay. A shore, on the other hand, can refer to parts of land adjoining any large body of water, including oceans and lakes; the somewhat related term "" refers to the land alongside or sloping down to a river or body of water smaller than a lake. "Bank" is used in some parts of the world to refer to an artificial ridge of earth intended to retain the water of a river or pond. While many scientific experts might agree on a common definition of the term "coast", the delineation of the extents of a coast differ according to jurisdiction, with many scientific and government authorities in various countries differing for economic and social policy reasons.
According to the UN atlas, 44% of people live within 150 kilometres of the sea. Tides determine the range over which sediment is deposited or eroded. Areas with high tidal ranges allow waves to reach farther up the shore, areas with lower tidal ranges produce deposition at a smaller elevation interval; the tidal range is influenced by the shape of the coastline. Tides do not cause erosion by themselves. Waves erode coastline. Coastlines with longer shores have more room for the waves to disperse their energy, while coasts with cliffs and short shore faces give little room for the wave energy to be dispersed. In these areas the wave energy breaking against the cliffs is higher, air and water are compressed into cracks in the rock, forcing the rock apart, breaking it down. Sediment deposited by waves comes from eroded cliff faces and is moved along the coastline by the waves; this forms an cliffed coast. Sediment deposited by rivers is the dominant influence on the amount of sediment located on a coastline.
Today riverine deposition at the coast is blocked by dams and other human regulatory devices, which remove the sediment from the stream by causing it to be deposited inland. Like the ocean which shapes them, coasts are a dynamic environment with constant change; the Earth's natural processes sea level rises and various weather phenomena, have resulted in the erosion and reshaping of coasts as well as flooding and creation of continental shelves and drowned river valleys. The coast and its adjacent areas on and off shore are an important part of a local ecosystem: the mixture of fresh water and salt water in estuaries provides many nutrients for marine life. Salt marshes and beaches support a diversity of plants and insects crucial to the food chain; the high level of biodiversity creates a high level of biological activity, which has attracted human activity for thousands of years. More and more of the world's people live in coastal regions. Many major cities have port facilities; some landlocked places have achieved port status by building canals.
The coast is a frontier that nations have defended against military invaders and illegal migrants. Fixed coastal defenses have long been erected in many nations and coastal countries have a navy and some form of coast guard. Coasts those with beaches and warm water, attract tourists. In many island nations such as those of the Mediterranean, South Pacific and Caribbean, tourism is central to the economy. Coasts offer recreational activities such as swimming, surfing and sunbathing. Growth management can be a challenge for coastal local authorities who struggle to provide the infrastructure required by new residents. Coasts face many human-induced environmental impacts; the human influence on climate change is thought to contribute to an accelerated trend in sea level rise which threatens coastal habitats. Pollution can occur from a number of sources: industrial debris. Fishing has declined due to habitat degradation, trawling and climate change. Since the growth of global fishing enterprises after the 1950s, intensive fishing has spread from a few concentrated areas to encompass nearly all fisheries.
The scraping of the ocean floor in bottom dragging is devastating to coral and other long-lived species that do not recover quickly. This destruction alters the functioning of the ecosystem and can permanently alter species composition and biodiversity. Bycatch, the capture of unintended species in the course of fishing, is returned to the ocean only to die from injuries or exposure. Bycatch represents about a quarter of all marine catch. In the case of shrimp capture, the bycatch is five times larger, it is believed that melting Arctic ice will cause sea levels to rise and flood coas
A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are made from rock, such as sand, shingle, pebbles; the particles can be biological in origin, such as mollusc shells or coralline algae. Some beaches have man-made infrastructure, such as lifeguard posts, changing rooms, showers and bars, they may have hospitality venues nearby. Wild beaches known as undeveloped or undiscovered beaches, are not developed in this manner. Wild beaches can be preserved nature. Beaches occur in areas along the coast where wave or current action deposits and reworks sediments. Although the seashore is most associated with the word beach, beaches are found by lakes and alongside large rivers. Beach may refer to: small systems where rock material moves onshore, offshore, or alongshore by the forces of waves and currents; the former are described in detail below. There are several conspicuous parts to a beach that relate to the processes that shape it; the part above water, more or less influenced by the waves at some point in the tide, is termed the beach berm.
The berm is the deposit of material comprising the active shoreline. The berm has a crest and a face—the latter being the slope leading down towards the water from the crest. At the bottom of the face, there may be a trough, further seaward one or more long shore bars: raised, underwater embankments formed where the waves first start to break; the sand deposit may extend well inland from the berm crest, where there may be evidence of one or more older crests resulting from large storm waves and beyond the influence of the normal waves. At some point the influence of the waves on the material comprising the beach stops, if the particles are small enough, winds shape the feature. Where wind is the force distributing the grains inland, the deposit behind the beach becomes a dune; these geomorphic features compose. The beach profile changes seasonally due to the change in wave energy experienced during summer and winter months. In temperate areas where summer is characterised by calmer seas and longer periods between breaking wave crests, the beach profile is higher in summer.
The gentle wave action during this season tends to transport sediment up the beach towards the berm where it is deposited and remains while the water recedes. Onshore winds carry it further inland enhancing dunes. Conversely, the beach profile is lower in the storm season due to the increased wave energy, the shorter periods between breaking wave crests. Higher energy waves breaking in quick succession tend to mobilise sediment from the shallows, keeping it in suspension where it is prone to be carried along the beach by longshore currents, or carried out to sea to form longshore bars if the longshore current meets an outflow from a river or flooding stream; the removal of sediment from the beach berm and dune thus decreases the beach profile. In tropical areas, the storm season tends to be during the summer months, with calmer weather associated with the winter season. If storms coincide with unusually high tides, or with a freak wave event such as a tidal surge or tsunami which causes significant coastal flooding, substantial quantities of material may be eroded from the coastal plain or dunes behind the berm by receding water.
This flow may alter the shape of the coastline, enlarge the mouths of rivers and create new deltas at the mouths of streams that had not been powerful enough to overcome longshore movement of sediment. The line between beach and dune is difficult to define in the field. Over any significant period of time, sediment is always being exchanged between them; the drift line is one potential demarcation. This would be the point at which significant wind movement of sand could occur, since the normal waves do not wet the sand beyond this area. However, the drift line is to move inland under assault by storm waves; the development of the beach as a popular leisure resort from the mid-19th century was the first manifestation of what is now the global tourist industry. The first seaside resorts were opened in the 18th century for the aristocracy, who began to frequent the seaside as well as the fashionable spa towns, for recreation and health. One of the earliest such seaside resorts, was Scarborough in Yorkshire during the 1720s.
The first rolling bathing machines were introduced by 1735. The opening of the resort in Brighton and its reception of royal patronage from King George IV, extended the seaside as a resort for health and pleasure to the much larger London market, the beach became a centre for upper-class pleasure and frivolity; this trend was praised and artistically elevated by the new romantic ideal of the picturesque landscape. Queen Victoria's long-standing patronage of the Isle of Wight and Ramsgate in Kent ensured that a seaside residence was considered as a fashionable possession for those wealthy enough to afford more than one home; the extension of this form of leisure to the middle and working classes began with the development of the railways in the 1840s, which offered cheap fares to fast
Kelp forests are underwater areas with a high density of kelp. They are recognized as one of dynamic ecosystems on Earth. Smaller areas of anchored kelp are called kelp beds. Kelp forests occur worldwide throughout temperate and polar coastal oceans. In 2007, kelp forests were discovered in tropical waters near Ecuador. Physically formed by brown macroalgae, kelp forests provide a unique, three-dimensional habitat for marine organisms and are a source for understanding many ecological processes. Over the last century, they have been the focus of extensive research in trophic ecology, continue to provoke important ideas that are relevant beyond this unique ecosystem. For example, kelp forests can influence coastal oceanographic patterns and provide many ecosystem services. However, the influence of humans has contributed to kelp forest degradation. Of particular concern are the effects of overfishing nearshore ecosystems, which can release herbivores from their normal population regulation and result in the overgrazing of kelp and other algae.
This can result in transitions to barren landscapes where few species persist. The implementation of marine protected areas is one management strategy useful for addressing such issues, since it may limit the impacts of fishing and buffer the ecosystem from additive effects of other environmental stressors; the term kelp refers to marine algae belonging to the order Laminariales. Though not considered a taxonomically diverse order, kelps are diverse structurally and functionally; the most recognized species are the giant kelps, although numerous other genera such as Laminaria, Lessonia and Eisenia are described. A wide range of sea life uses kelp forests including fish. In the North Pacific kelp forests rockfish, many invertebrates, such as amphipods, marine snails, bristle worms, brittle stars. Many marine mammals and birds are found, including seals, sea lions, sea otters, terns, snowy egrets, great blue herons, cormorants, as well as some shore birds. Considered an ecosystem engineer, kelp provides a physical substrate and habitat for kelp forest communities.
In algae, the body of an individual organism is known as a thallus rather than as a plant. The morphological structure of a kelp thallus is defined by three basic structural units: The holdfast is a root-like mass that anchors the thallus to the sea floor, though unlike true roots it is not responsible for absorbing and delivering nutrients to the rest of the thallus; the stipe is analogous to a plant stalk, extending vertically from the holdfast and providing a support framework for other morphological features. The fronds are leaf- or blade-like attachments extending from the stipe, sometimes along its full length, are the sites of nutrient uptake and photosynthetic activity. In addition, many kelp species have pneumatocysts, or gas-filled bladders located at the base of fronds near the stipe; these structures provide the necessary buoyancy for kelp to maintain an upright position in the water column. The environmental factors necessary for kelp to survive include hard substrate, high nutrients, light.
Productive kelp forests tend to be associated with areas of significant oceanographic upwelling, a process that delivers cool, nutrient-rich water from depth to the ocean’s mixed surface layer. Water flow and turbulence facilitate nutrient assimilation across kelp fronds throughout the water column. Water clarity affects the depth. In ideal conditions, giant kelp can grow as much as 30–60 cm vertically per day; some species, such as Nereocystis, are annuals, while others such as Eisenia are perennials, living for more than 20 years. In perennial kelp forests, maximum growth rates occur during upwelling months and die-backs correspond to reduced nutrient availability, shorter photoperiods, increased storm frequency. Kelps are associated with temperate and arctic waters worldwide. Of the more dominant genera, Laminaria is associated with both sides of the Atlantic Ocean and the coasts of China and Japan; the region with the greatest diversity of kelps is the northeastern Pacific, from north of San Francisco, California, to the Aleutian Islands, Alaska.
Although kelp forests are unknown in tropical surface waters, a few species of Laminaria have been known to occur in tropical deep waters. This general absence of kelp from the tropics is believed to be due to insufficient nutrient levels associated with warm, oligotrophic waters. One recent study spatially overlaid the requisite physical parameters for kelp with mean oceanographic conditions has produced a model predicting the existence of subsurface kelps throughout the tropics worldwide to depths of 200 m. For a hotspot in the Galapagos Islands, the local model was improved with fine-scale data and tested; this suggests that their global model might be accurate, if so, kelp forests would be prolific in tropical subsurface waters worldwide. The importance of this contribution has been ack
Mollusca is the second largest phylum of invertebrate animals. The members are known as mollusks. Around 85,000 extant species of molluscs are recognized; the number of fossil species is estimated between 100,000 additional species. Molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms. Numerous molluscs live in freshwater and terrestrial habitats, they are diverse, not just in size and in anatomical structure, but in behaviour and in habitat. The phylum is divided into 8 or 9 taxonomic classes, of which two are extinct. Cephalopod molluscs, such as squid and octopus, are among the most neurologically advanced of all invertebrates—and either the giant squid or the colossal squid is the largest known invertebrate species; the gastropods are by far the most numerous molluscs and account for 80% of the total classified species. The three most universal features defining modern molluscs are a mantle with a significant cavity used for breathing and excretion, the presence of a radula, the structure of the nervous system.
Other than these common elements, molluscs express great morphological diversity, so many textbooks base their descriptions on a "hypothetical ancestral mollusc". This has a single, "limpet-like" shell on top, made of proteins and chitin reinforced with calcium carbonate, is secreted by a mantle covering the whole upper surface; the underside of the animal consists of a single muscular "foot". Although molluscs are coelomates, the coelom tends to be small; the main body cavity is a hemocoel. The "generalized" mollusc's feeding system consists of a rasping "tongue", the radula, a complex digestive system in which exuded mucus and microscopic, muscle-powered "hairs" called cilia play various important roles; the generalized mollusc has three in bivalves. The brain, in species that have one, encircles the esophagus. Most molluscs have eyes, all have sensors to detect chemicals and touch; the simplest type of molluscan reproductive system relies on external fertilization, but more complex variations occur.
All produce eggs, from which may emerge trochophore larvae, more complex veliger larvae, or miniature adults. The coelomic cavity is reduced, they have kidney-like organs for excretion. Good evidence exists for the appearance of gastropods and bivalves in the Cambrian period, 541 to 485.4 million years ago. However, the evolutionary history both of molluscs' emergence from the ancestral Lophotrochozoa and of their diversification into the well-known living and fossil forms are still subjects of vigorous debate among scientists. Molluscs still are an important food source for anatomically modern humans. There is a risk of food poisoning from toxins which can accumulate in certain molluscs under specific conditions and because of this, many countries have regulations to reduce this risk. Molluscs have, for centuries been the source of important luxury goods, notably pearls, mother of pearl, Tyrian purple dye, sea silk, their shells have been used as money in some preindustrial societies. Mollusc species can represent hazards or pests for human activities.
The bite of the blue-ringed octopus is fatal, that of Octopus apollyon causes inflammation that can last for over a month. Stings from a few species of large tropical cone shells can kill, but their sophisticated, though produced, venoms have become important tools in neurological research. Schistosomiasis is transmitted to humans via water snail hosts, affects about 200 million people. Snails and slugs can be serious agricultural pests, accidental or deliberate introduction of some snail species into new environments has damaged some ecosystems; the words mollusc and mollusk are both derived from the French mollusque, which originated from the Latin molluscus, from mollis, soft. Molluscus was itself an adaptation of Aristotle's τὰ μαλάκια ta malákia, which he applied inter alia to cuttlefish; the scientific study of molluscs is accordingly called malacology. The name Molluscoida was used to denote a division of the animal kingdom containing the brachiopods and tunicates, the members of the three groups having been supposed to somewhat resemble the molluscs.
As it is now known these groups have no relation to molluscs, little to one another, the name Molluscoida has been abandoned. The most universal features of the body structure of molluscs are a mantle with a significant cavity used for breathing and excretion, the organization of the nervous system. Many have a calcareous shell. Molluscs have developed such a varied range of body structures, it is difficult to find synapomorphies to apply to all modern groups; the most general characteristic of molluscs is they are bilaterally symmetrical. The following are present in all modern molluscs: The dorsal part of the body wall is a mantle which secretes calcareous spicules, plates or shells, it overlaps the body with enough spare room to form a mantle cavity. The anus and genitals open into the mantle cavity. There are two pairs of main nerve cords. Other characteristics that appear in textbooks have significant exceptions: Estimates of accepted described living species of molluscs vary from 50,000 to a maximum of 120,000 species.
In 1969 David Nicol estimated the probable total number of living mollusc species at 107,000 of which were ab
Sea urchins or urchins are spiny, globular animals, echinoderms in the class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal to 5,000 metres, their tests are round and spiny from 3 to 10 cm across. Sea urchins move crawling with their tube feet, sometimes pushing themselves with their spines, they feed on algae but eat slow-moving or sessile animals. Their predators include sea otters, wolf eels, triggerfish. Like other echinoderms, urchins have fivefold symmetry as adults, but their pluteus larvae have bilateral symmetry, indicating that they belong to the Bilateria, the large group of animal phyla that includes chordates, arthropods and molluscs, they are distributed across all the oceans, all climates from tropical to polar, inhabit marine benthic habitats from rocky shores to hadal zone depths. Echinoids have a rich fossil record dating back to the Ordovician, some 450 million years ago, their closest relatives among the echinoderms are the sea cucumbers.
The animals have been studied since the 19th century as model organisms in developmental biology, as their embryos were easy to observe. Species such as the slate pencil urchin are popular in aquariums, where they are useful for controlling algae. Fossil urchins have been used as protective amulets. Sea urchins are members of the phylum Echinodermata, which includes sea stars, sea cucumbers, brittle stars, crinoids. Like other echinoderms, they have five-fold symmetry and move by means of hundreds of tiny, adhesive "tube feet"; the symmetry is not obvious in the living animal, but is visible in the dried test. The term "sea urchin" refers to the "regular echinoids", which are symmetrical and globular, includes several different taxonomic groups, with two subclasses: Euechinoidea and Cidaroidea or "slate-pencil urchins", which have thick, blunt spines, with algae and sponges growing on them; the "irregular" sea urchins are an infra-class inside the Euechinoidea, called Irregularia, include Atelostomata and Neognathostomata.
Irregular echinoids include: flattened sand dollars, sea biscuits, heart urchins. Together with sea cucumbers, they make up the subphylum Echinozoa, characterized by a globoid shape without arms or projecting rays. Sea cucumbers and the irregular echinoids have secondarily evolved diverse shapes. Although many sea cucumbers have branched tentacles surrounding their oral openings, these have originated from modified tube feet and are not homologous to the arms of the crinoids, sea stars, brittle stars. Urchins range in size from 3 to 10 cm, although the largest species can reach up to 36 cm, they have a rigid spherical body bearing moveable spines, which gives the class the name Echinoidea. The name "urchin" is an old word for hedgehog; the name is derived from Latin ericius, hedgehog. Like other echinoderms, sea urchin early larvae have bilateral symmetry, but they develop five-fold symmetry as they mature; this is most apparent in the "regular" sea urchins, which have spherical bodies with five sized parts radiating out from their central axes.
The mouth is at the anus at the top. Several sea urchins, including the sand dollars, are oval in shape, with distinct front and rear ends, giving them a degree of bilateral symmetry. In these urchins, the upper surface of the body is domed, but the underside is flat, while the sides are devoid of tube feet; this "irregular" body form has evolved to allow the animals to burrow through sand or other soft materials. Sea urchins may appear to be incapable of moving. Sometimes the most visible sign of life is the spines, which are attached to ball-and-socket joints and can point in any direction. Sea urchins have no visible eyes, legs, or means of propulsion, but can move but over hard surfaces using adhesive tube feet, working in conjunction with the spines; the internal organs are enclosed in a hard shell or test composed of fused plates of calcium carbonate covered by a thin dermis and epidermis. The test is rigid, divides into five ambulacral grooves separated by five interambulacral areas; each of these areas consists of two rows of plates, so the sea urchin test includes 20 rows of plates in total.
The plates are covered in rounded tubercles which contain the sockets to which the spines are attached by ball and socket joints. The inner surface of the test is lined by peritoneum. Sea urchins convert aqueous carbon dioxide using a catalytic process involving nickel into the calcium carbonate portion of the test. Most species have two series of spines and secondary, distributed over the surface of the body, with the shortest at the poles and the longest at the equator; the spines are hollow and cylindrical. Contraction of the muscular sheath that covers the test causes the spines to lean in one direction or another, while an inner sheath of collagen fibres can reversibly change from soft to rigid which can lock the spine i
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. 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 protect the coral. Most reefs grow best in warm, clear and agitated water. 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 the area of France, yet they provide a home for at least 25% of all marine species, including fish, worms, echinoderms, sponges and other cnidarians. Coral reefs flourish in ocean waters, they are most found at shallow depths in tropical waters, but deep water and cold water coral reefs exist on smaller scales in other areas. Coral reefs deliver ecosystem services for tourism and shoreline protection.
The annual global economic value of coral reefs is estimated between US$30–375 billion and 9.9 trillion USD. Coral reefs are fragile because they are sensitive to water conditions, they are under threat from excess nutrients, rising temperatures, oceanic acidification, sunscreen use, harmful land-use practices, including runoff and seeps. 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 pacing rising sea levels. Reefs that rose too could become drowned, without sufficient light. Coral reefs are found in 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. 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 subsidence of the Earth's crust under 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 ocean floor subsides; as the subsidence continues, the fringing reef becomes a barrier reef and 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 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, can 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 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, once the island sinks below sea level a circular atoll of growing coral continues to keep up with the sea level, forming a central lagoon. Barrier reefs and atolls do not form complete circles, but are broken in places by storms. Like sea level rise, a 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, the history of the change in sea level relative to that substrate. The 20,000-year-old Great Barrier Reef offers an example of how coral reefs formed on continental shelves. Sea level was 120 m 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 lower than at present, many hills of the coastal plains had become continental islands. As sea level rise continued, water topped most of the continental islands; the corals could overgrow the hills, forming cays and reefs. Sea level on the Great Barrier Reef has not changed in the last 6,000 years; the age of living reef structure is estimated to be between 8,000 years. Although the Great Barrier Reef formed along a continental shelf, not around a volcanic island, Darwin's principles apply. Development stopped at the barrier reef stage, it formed 300 -- 1,000 m from shore, stretching for 2,000 km. Healthy tropical coral reefs grow horizontally from 1 to 3 cm per year, grow vertically anywhere from 1 to 25 cm per year; as the name implies, coral reefs are made up of coral skeletons from intact coral colonies. As other chemical elements present in corals become incorporated into the calcium carbonate deposits, aragonite is formed. However