Реферат: Coral Reefs Essay Research Paper The most

Coral Reefs Essay, Research Paper

The most beautiful and well engrossed houses in the whole world belong to a

huge variety of tropical fish. These houses are underwater vertebrates that have

caught the attention of many human beings for a spectacular amount of time.

Coral reefs are not only pretty, actually quite beautiful, and they present a great

deal of human interest; but, they also render an enormous amount of shelter for an

abundant number of different fish. Corals, one of the largest vertebrates in the

world, also have a unique way of reproducing.

Corals are small, marine animals that remain in one place throughout their adult

lives and produce a hard skeleton made of calcium carbonate (CaCO 3), or

limestone. The skeletal material, which can be either internal or external, is also

called coral. After the coral animal dies, the skeleton remains. Many species of

corals grow in colonies that continue to enlarge year after year. Other species are

solitary; that is, they live alone. Collectively, several different species of corals

can form enormous colonies that are called coral reefs, coral islands, and coral

atolls (Young CD-ROM).

According to Elizabeth and others, there are basically three kinds of coral reefs:

fringing reefs, barrier reefs, and atolls. Fringing reefs are reefs that grow in

shallow water near the coast’s shore or are separated from the shore by a narrow

stretch of water. Several zones, characterized by depth, structure, and plant and

animal life make up fringing reefs. These regions are composed of the reef’s crest

(the part of the reef waves break over, the region with medium energy, and the

spur and groove), or buttress zone. This place of coral growth includes rows of

coral with sandy passages between each row. Barrier reefs are separated from

land by a lagoon. They grow parallel to the coast and are large and continuous.

These barrier reefs also contain regions of coral formation that include zones

found in fringing reefs, along with patch reefs, or small reefs, back reefs, or the

shore ward side of the reef, and bank reefs, which appear on the bottom of the

ocean’s irregularities. Atolls, the third type of coral reef, are annular reefs that

develop near or at the surface of the water when islands that are surrounded by

reefs subside. Atolls are circular, or sub-circular and they separate a central

lagoon. Deep sea atolls that rise from deep sea and those found on the continental

shelf are two types of atolls. (http://www.mcgill.pvt.k12.al.us/coral.htm)

One of the greatest colonies of coral reefs in the world is the Great Barrier

Reef. The Great Barrier Reef, the coral formation running for some twelve

hundred and fifty miles off the coast of Northeastern Australia is regarded as one

of the natural wonders of the world. Over the millennium the reef has evolved into

an enormous habitat which supports a spectacular and varied array of marine life.

The tropical waters abound with sea creatures of all types and sizes including

sharks and giant clams. The variety and beauty of the reefs? life make it a popular

tourist attraction (Young CD-ROM).

Many fish also acquire homes in coral reefs. Some examples of these fish

include, the lemon – yellow masked butterfly fish and the royal purple

Pseudochromis fridmani, also known as the orchid dottyback (Doublet 49-50).

Some more examples of these fish and a description of them are as follows:

Brittle stars, Tube worms, Cowries, moray eels, and sting rays. Brittle stars

are a unique and beautiful creature of the coral reef. Their long feathery arms and

small disc shaped bodies are delicate and fragile. Unlike their regular sea star

friends, brittle stars move quite quickly, and will rapidly head for shelter when

exposed to the light. They also have an interesting habit of breaking off parts or

all of their arms at the slightest provocation, hence their name. The mouth is in the

center of the central disc, which leads to a stomach bag. Brittle stars feed by

filtering mud and sand, removing and digesting decaying organic matter in the

process. Tube worms belong to the Sedentaria order of tube-making worms. The

tubes themselves can be used to identify the species of worm as they are so unique

in character. This tube worm has its anterior segments projected into the water,

forming a complex breathing and food catching apparatus. These feathery like

extensions are long gill plumes arranged into distinct spirals, which have often

been likened to flowers (a coral reef covered with tube worms would look like a

spring garden). They are sensitive to the slightest shadow or movement in the

water, and withdraw quickly into their tube, shutting their operculum behind them.

They feed on plankton and suspended sediment from the water. Cowries are

mollusks whose shells are prized amongst shell collectors. Once polished and

lacquered, the shells can look very beautiful. There are many types of cowries and

they all have varying colors and patterns on their shells. Moray eels are strange

creatures that hunt by night, and hide in crevices by day. They are not dangerous,

but may bite when provoked or frightened. This particular species of moray eel is

not found in northern New South Wales waters, but there are many of its relatives

found here. Coral reefs are the marine equivalent of tropical rain forests in terms

of species diversity and richness, and there are so many to see. Besides the ones

mentioned here, there are sea cucumbers, sea urchins, shrimps, many species of

spectacular fish, sharks and stingrays (http://www.tip.net.au/~sef/amanda/crother.htm)

Corals and coral fish are also being used as an anti-cancer mechanism. Dr.

Patrick Colin has worked in the coral reef environment since 1968. His

dissertation from the University of Miami was on the association of small gobies

with sponges and corals. He says, “While my focus has been on reef fishes, I

became interested in most everything concerned with coral reefs and other shallow

water tropical environments.” In 1978 he published a field guide to Caribbean

invertebrates and plants and recently he collaborated with Charles Arneson on

another field guide, “Tropical Pacific Invertebrates.” Since 1991 he has had the

contract to make marine collections for the US National Cancer Institute. The

collecting work began while living in Chuuk (Truk) and then in 1995 he and his

wife, Lori Bell, decided to move the operation to Palau where they established the

Coral Reef Research Foundation (CRRF). In 1991 the US National Cancer

Institute (NCI) put out to bid their contract to collect marine invertebrates and

marine plants from the Indo-Pacific region for anti-cancer screening. After nearly a

year, including lengthy negotiations, we were awarded this contract. Our original

base of operations in 1992 was in Chuuk (Truk) in the Federated States of

Micronesia, where we leased an unfinished cement building from the Chuuk State

Government as our laboratory. In 1995 we relocated our base to Palau, a move we

have not regretted at all. Basing in an area of high species diversity allows us to

collect a high percentage of local species over the long term while making a series

of short (3-4 week) collections in other countries each year. So far we have

worked in 14 different countries for the NCI. In Palau we do other research in

addition to the NCI work as time allows. In 1997 we won a renewal contract, so

we will be doing this work until at least 2002. We have a staff of seven in Palau.

Right now we collect about 700 samples per year for the NCI. A sample ideally

consists of 1.0 – 1.5 kilogram wet weight of a single species, plus a series of

preserved voucher specimens, photographs and full collection data. Most come

from countries other than Palau, since we have already sampled a high percentage

of a larger fauna here. Samples for screening are frozen and shipped frozen all the

way to Frederick, Maryland where the NCI labs are located


As this report mentioned earlier corals are living creatures and therefore they

have to reproduce also. The adult coral, which is stationary in this stage of life, is

called a polyp. Polyps reproduce in two different ways. One is by means of eggs

that, when fertilized by sperm, develop into tiny, swimming larval organisms

called planulae. Planulae eventually settle on the bottom of the ocean, on a rock,

or on another coral and develop into polyps. Each polyp builds a limestone

skeleton attached to the surface on which the polyp has landed. After the coral

establishes itself, the upper part of the body becomes dome-shaped and develops a

stomach and mouth. Tentacles form around the mouth and are used to draw in

food from the surrounding waters. The tentacles are armed with specialized

stinging structures, called nematocysts, that paralyze tiny prey. Small marine

organisms are the major food of corals.

A polyp can also reproduce by a process known as budding, in which offshoots

called buds grow out from the body and remain attached to it. The buds become

polyps, which in turn send out more buds. In some kinds of corals the buds may

break away to become separate individuals. The largest of the solitary polyps

grows to a diameter of about 10 inches (25 centimeters). The polyps of the

colonial species that form coral reefs range from 0.04 to 1.2 inches (0.1 to 3

centimeters) in diameter.

Vast coral colonies are built by budding, the animals being connected by their

extensive skeletal network. Nutrients are passed from individuals on the outside of

the colony to those on the inside (Young CD-ROM).

Fringing reefs also follow the coastline, but they extend up to the beach at

some points. Atolls have no relationship to any visible land. They are circular in

form, surrounding a central lagoon of calm water. Atolls are often associated with

the rims of extinct underwater volcanoes. Bikini in the South Pacific is a

well-known atoll that was used in nuclear weapons testing by the United States.

Coral reefs create underwater habitats that are essential for many species of marine

organisms. Certain species of fish spend their life among the corals, using them as

a refuge from predators.

Because of the permanence of their skeletons, corals are common in the fossil

record, the remains of long-dead plants and animals. More than 6,000 extinct

species of corals have been described. Corals belong to the phylum Coelenterata

(also called Cnidaria) and are related to jellyfishes. Most species are in the class

Anthozoa. The class has more than 6,000 living species, including the sea

cucumbers, sea anemones, and sea pansies, which are not corals. A few corals are

in the class Hydrozoa.

By the 1990s coral reefs off the coasts of more than 20 countries were being

ravaged by coral bleaching, pollution, freighter traffic, and the venomous,

coral-eating starfish known as the crown of thorns. Bleaching is thought to be

caused by rising water temperatures, which the coral cannot withstand. Oil spills

and chemical pollution are a major threat to coral. Long-term damage occurs

when stands of coral are knocked down by freighters or boat anchors. Over

harvesting of fish has resulted in the loss of coral-protecting sea urchins, leaving

the coral open to the crown of thorns (Young CD-ROM).

So now as one can see corals and coral reefs are more complex than anyone

would make them out to be. Now anyone could plainly see why humans are

interested in corals, this report is just scratching the surface of all the information

on corals in the world. One should now take more respect for corals and not just

think they are a lot of rocky material, but realize that they are living creatures.

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