Undersea Paradise: The Great Barrier Reef
Posted on: July 24, 2021.

What is a “Reef”?

It is a ridge of jagged rock, or a shoal of rock, coral, or sand, just above or below the surface of a natural body of water such as the sea or ocean. Reefs form naturally, are relatively stable, and do not float.

What is a “Coral”?

Corals are neither plants—as they appear to be—nor a singular organism. They differ in shape, size, and color—orange, yellow, green, blue, red and purple—resulting in a spectacular underwater phenomenon.

Corals are, in fact, not plants but animals—”marine invertebrates”—and colonial organisms—hundreds to thousands of tiny creatures—called “polyps”, bonded by calcium carbonate “limestone” shells.

Subsequently, those with the stony skeletons are called “hard corals”, while those without are called “soft corals”—jelly-like and flexible, thus often mistaken to be plants.

How do corals form a reef?

Along the edges of islands or continents, submerged rocks or other hard surfaces provide a “substrate” for coral larvae to attach—this is when, and where, a coral reef begins to form.

Reef-building coral species inhabit tropical oceans and secrete calcium carbonate which gives them their hard exoskeleton. Coral reefs are known as “rainforests of the sea”, for their appearance.

Reefs—typically one formed of corals—take on one of three major characteristic structures—fringe reefs, barrier reefs, and atolls—as the corals grow and expand.

What is a “Barrier Reef”?

It is a specific kind of coral reef that typically runs close and almost parallel to a shore, and separated from it by a channel of deep water, or say, a lagoon—forming, in effect, a natural, geological “barrier”.

However, a barrier reef is connected to such a lagoon—and the shore of the island or continent beyond—by several channels that pierce it at random intervals along its length.

New Caledonian Barrier Reef in the South Pacific Ocean is the world’s longest continuous and third-largest, while Mesoamerican Barrier Reef off Belize, Central America, in the Caribbean Sea, is the second-largest.

And now, the “Great Barrier Reef” (GBR)…

It is located in the Coral Sea—part of the South Pacific Ocean—off the coast of Queensland, Australia, and includes more than 2,900 individual reefs and 900 islands.

Occupying an area of 3.44 lakh square kilometres in the Coral Sea—and spanning a length of more than 2,300 kilometres—these collectively form the Great Barrier Reef, which is…
… the world’s biggest marine ecosystem,
… largest coral reef system in world,
… the largest living structure on Earth,
… one of the “Seven Natural Wonders of the World”,
… the world’s first coral reef ecosystem to become a UNESCO “World Heritage Site” in 1981,
… and the only object on Earth visible from outer space!

The GBR’s vast expanse supports an immense variety of life—animals, plants, algae, and microorganisms too small for the naked eye to see—encompassing a rather extraordinary biodiversity.

The GBR is home to
… one of the world’s most important dugong “sea cow” populations
… six of the world’s seven species of marine turtle
… 1,625 species of fish
… 450 species of hard coral
… lesser-known species like mollusks, sponges, marine algae, soft coral and sea pens

The interconnectedness of these species and their habitats makes the Great Barrier Reef and its surrounding areas one of the most complex natural systems on Earth.

In the progress of evolution
… coral reefs originated 50 crore years ago,
… the Great Barrier Reef originated 5 lakh years ago,
… and last changed about 8,000 years ago!

Australia’s Great Barrier Reef Marine Park Authority (GBRMPA) protectively manages much of this Marine Protected Area (MPA) in the Coral Sea.



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