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Home , Seashell

Introduction

Marine Resources are those resources that can be found in water such as , , shells, , fish , ,and sponges. Coral polyps are tiny, soft-bodied organisms related to sea anemones and jellyfish. At their base is a hard, protective limestone called a calicle, which forms the structure of coral reefs. live in tropical waters throughout the world, generally close to the surface where the sun's rays can reach the . While corals get most of their nutrients from the byproducts of the algae's , they also have barbed, venomous tentacles they can stick out, usually at night, to grab zooplankton and even small fish. A pearl is a hard object produced within the soft tissue (specifically the mantle) of a living shelled mollusk. Just like the shell of a mollusk, a pearl is made up of carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other shapes of (baroque pearls) occur. The finest quality natural pearls have been highly valued as gemstones and objects of beauty for many centuries, and because of this, the word pearl has become a metaphor for something very rare, fine, admirable, and valuable. A seashell, also known as a sea shell, or simply as a shell, is the common name for a hard, protective outer layer, a shell, or in some cases a "", that was created by a sea creature, a marine organism. The shell is part of the body of a marine animal. In most cases a shell is an , usually that of an animal without a backbone, aninvertebrate. Seashells are most often found on .The word seashell is most often used to mean the shells of marine mollusks, i.e. mollusk shells. It can however also be used to mean the shells of a wide variety of other marine animals from various different marine .

Corals Corals are marine organisms in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important builders that inhabit tropical , which secrete to form a hard skeleton.

A coral "head," which appears to be a single organism, is a colony of myriad genetically identical polyps. Each polyp is typically only a few millimeters in diameter. Over many generations the colony secretes a skeleton that is characteristic of the species. Individual heads grow by asexual reproduction of individual polyps. Corals also breed sexually by spawning. Polyps of the same species release gametes simultaneously over a period of one to several nights around a full moon.

Although corals can catch small fish and animals such as using stinging cells on their tentacles, most corals obtain most of their energy and nutrients from photosynthetic unicellular algae called . Such corals require sunlight and grow in clear, shallow water, typically at depths shallower than 60 meters (200 ft). Corals can be major contributors to the physical structure of the coral reefs that develop in tropical and subtropical waters, such as the enormous Great Barrier Reef off the of Queensland, Australia. Other corals do not have associated algae and can live in much deeper water, with the cold-water genus Lophelia surviving as deep as 3,000 meters (9,800 ft). Examples live on the Darwin Mounds located north-west of Cape Wrath, Scotland. Corals have also been found off the coast of Washington State and the Aleutian in Alaska. Corals coordinate behavior by communicating with each other.

Coral Reefs

Coral reefs are underwater structures made from calcium carbonate secreted by corals. Corals are colonies of tiny living animals found in marine waters containing few nutrients. Most coral reefs are built from stony corals, and are formed by polyps that live together in groups. The polyps secrete a hard carbonate exoskeleton which provides support and protection for the body of each polyp. Reefs grow best in warm, shallow, clear, sunny and agitated waters.

Often called “rainforests of the sea”, coral reefs form some of the most diverse on earth. They occupy less than one tenth of one percent of the world surface, about half the area of France, yet they provide a home for twenty-five percent of all marine species, including fish, molluscs, and sponges.

Paradoxically, coral reefs flourish even though they are surrounded by ocean waters that provide few nutrients. They are most commonly found at shallow depths in tropical waters, particularly in the Pacific Ocean, but deep water and cold water corals also exist on smaller scales.

Coral reefs deliver services to tourism, fisheries and shoreline protection. The annual global economic value of coral reefs has been estimated at $30 billion. However, coral reefs are fragile ecosystems, partly because they are very sensitive to water temperature. They are under threat from climate change, , blast fishing, cyanide fishing for aquarium fish, overuse of reef resources, and harmful land-use practices. High nutrient levels such as those found in runoff from agricultural areas can harm reefs by encouraging excess algae growth.

Importance to humans

Local economies near major coral reefs benefit from an abundance of fish and other marine creatures as a food source. Reefs also provide recreational scuba diving and snorkeling tourism. Unfortunately these activities can have deleterious effects, such as accidental destruction of coral. Coral is also useful as a protection against hurricanes and other extreme weather.

Coral reefs provide many medical benefits for humans. Chemical compounds taken from corals are used in pharmaceutical medicines to fight Cancer, AIDS, severe pain and much more. Corals are also used commonly for grafting in humans. Corals have been used for thousands of years as medicine and there is still much to learn. The cure to some of the most prevalent and dangerous diseases today could very well be waiting for us in the world's coral reefs.

Live coral is highly sought after for aquaria. Given the proper ecosystem, live coral makes a stunning addition to any salt water aquarium. Soft corals are easier to maintain in captivity than hard corals.

Isididae may be usable as living bone implants and in aquatic cultivation, because of their potential to mimic valuable biological properties.

In jewelry

Coral's many colors give it appeal for necklaces and other jewelry. Intensely red coral is prized as a gemstone. It is sometimes called fire coral, but is not the same as fire coral. Red coral is very rare because of overharvesting due to the great demand for perfect specimens.

In construction

Ancient coral reefs on land provide or use as building blocks ("coral rag"). Coral rag is an important local building material in places such as the East African coast.

In climate research

The annual growth bands in bamboo corals and others allow geologists to construct year-by-year chronologies, a form of incremental dating, which underlie high-resolution records of past climatic and environmental changes using geochemical techniques. Certain species form communities called microatolls, which are colonies whose top is dead and mostly above the water line, but whose perimeter is mostly submerged and alive. Average level limits their height. By analyzing the various growth morphologies, microatolls offer a low resolution record of sea level change. Fossilized microatolls can also be dated using radioactive carbon dating. Such methods can help to reconstruct Holocene sea levels.

Deep sea bamboo corals (Isididae) may be among the first organisms to display the effects of ocean acidification. They produce growth rings similar to those of tree and can provide a view of changes in the condition in the deep sea over time

Pearl

A pearl is a hard object produced within the soft tissue (specifically the mantle) of a living shelled mollusk. Just like the shell of a mollusk, a pearl is made up of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other shapes of pearls (baroque pearls) occur. The finest quality natural pearls have been highly valued as gemstones and objects of beauty for many centuries, and because of this, the word pearl has become a metaphor for something very rare, fine, admirable, and valuable.

The most valuable pearls occur spontaneously in the wild, but they are extremely rare. Cultured or farmed pearls from pearl make up the majority of those that are currently sold. Pearls from the sea are valued more highly than freshwater pearls. Imitation or fake pearls are also widely sold in inexpensive jewelry, but the quality of their iridescence is usually very poor, and generally speaking, artificial pearls are easily distinguished from genuine pearls. Pearls have been harvested and cultivated primarily for use in jewelry, but in the past they were also stitched onto lavish clothing. Pearls have also been crushed and used in cosmetics, medicines, and in paint formulations.

Pearls that are considered to be of gemstone quality are almost always nacreous and iridescent, wild or cultured, like the interior of the shell that produces them. However, almost all species of shelled mollusks are capable of producing pearls (formerly referred to as "calcareous concretions" by some sources) of lesser shine or less spherical shape. Although these may also be legitimately referred to as "pearls" by gemological labs and also under U.S. Federal Trade Commission rules, and are formed in the same way, most of them have no value, except as curios.

Physical Properties

The unique luster of pearls depends upon the reflection, refraction, and diffraction of light from the translucent layers. The thinner and more numerous the layers in the pearl, the finer the luster. The iridescence that pearls display is caused by the overlapping of successive layers, which breaks up light falling on the surface. In addition, pearls (especially cultured freshwater pearls) can be dyed yellow, green, blue, brown, pink, purple, or black.

Value of a natural pearl

Quality natural pearls are very rare jewels. The actual value of a natural pearl is determined in the same way as it would be for other "precious" gems. The valuation factors include size, shape, quality of surface, orient and luster. Single natural pearls are often sold as a collector's item, or set as centerpieces in unique jewelry. Very few matched strands of natural pearls exist, and those that do often sell for hundreds of thousands of dollars.

Pearls in jewelry

The value of the pearls in jewelry is determined by a combination of the luster, color, size, lack of surface flaw and symmetry that are appropriate for the type of pearl under consideration. Among those attributes, luster is the most important differentiator of pearl quality according to jewelers.

All factors being equal, however, the larger the pearl the more valuable it is. Large, perfectly round pearls are rare and highly valued. Teardrop-shaped pearls are often used in pendants.

Seashell

A seashell, also known as a sea shell, or simply as a shell, is the common name for a hard, protective outer layer, a shell, or in some cases a "test", that was created by a sea creature, a marine organism. The shell is part of the body of a marine animal. In most cases a shell is an exoskeleton, usually that of an animal without a backbone, an . Seashells are most often found on beaches. The word seashell is most often used to mean the shells of marine mollusks, i.e. mollusk shells. It can however also be used to mean the shells of a wide variety of other marine animals from various different marine invertebrates.

As well as marine mollusks, many other kinds of sea animals have or even internal shells which sometimes, after death, wash up on the and may be picked up by beachcombers. These shells include remains from species in other invertebrate phyla, such as the moulted shells or exuviae of and , the shells of , shells, the tests () of sea urchins, dollars and seastars, shells, and the shells of marine worms in the familySerpulidae, which create calcareous tubes cemented onto other surfaces.

Seashells have been admired, studied and used by humans for many different purposes throughout history and pre-history.

Significance of seashells in human culture

Seashells have been used as a medium of exchange in various places, including many Indian Ocean and Pacific Ocean islands, also in North America, Africa and the Caribbean.

. The most common species of shells to be used as currency have been Cypraea moneta, the “money cowry”, and certain tusk shells or dentalium, such as those used in North Western North America for many centuries.

. It is of historic interest that the Dutch East India Company, a major force in the colonization of the Indian and Pacific Oceans, amassed a large portion of its vast fortune via trading of the species Cypraea moneta and Cypraea annulus, in exchange for commodities such as spices, exotic animals, and gemstones, all of which were considered valuable in Europe at the time. As tools

Seashells have often been used as tools, because of their strength and the variety of their shapes.

. Giant (Family Tridacnidae) have been used as bowls, and when big enough, even as bathtubs and baptismal fonts.

. , the "bailer volute", is so named because Native Australians used it to bail out their canoes.

. Many different species of bivalves have been used as scrapers, blades, clasps, and other such tools, due to their shape.

. Some marine gastropods have been used for oil lamps, the oil being poured in the aperture of the shell, and the serving as a holder for the wick.

In horticulture

Because shells are sometimes a readily available bulk source of calcium carbonate, shells such as shells are sometimes used as soil conditioners in horticulture. The shells are broken or ground into small pieces in order to have the desired effect of raising the pH and increasing the calcium content in the soil.

In religion and spirituality

Seashells have played a part in religion and spirituality, sometimes even as ritual objects.

. In Christianity, the shell is considered to be the symbol of Saint James the Great, see . . In left-handed shells of (the sacred ) are considered to be sacred to the god Vishnu. The person who finds a left-handed chank shell (one that coils to the left) is sacred to Vishnu, as well. The chank shell also plays an important role in .

As musical instruments

Seashells have been used as musical instruments, wind instruments for many hundreds if not thousands of years. Most often the shells of large sea are used, as trumpets, by cutting a hole in the of the shell, or cutting off the tip of the spire altogether. Various different kinds of large marine gastropod shells can be turned into "blowing shells".

In personal adornment Whole seashells or parts of sea shells have been used as jewelry or in other forms of adornment since prehistoric times

. Shell necklaces have been found in Stone Age graves as far inland as the Dordogne Valley in France.

. Seashells are often used whole and drilled, so that they can be threaded like , or cut into pieces of various shapes. Sometimes shells can be found that are already "drilled" by predatory snails of the family .

. Shells historically have been and still are made into, or incorporated into, necklances, pendants, beads, earrings, , brooches, rings, hair combs, belt buckles and other uses.

In architectural decoration